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Initial effects of clearcutting on the flow of chemicals through a forest-watershed ecosystem in south-western… Feller, M. C. (Michael Charles) 1975

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INITIAL EFFECTS OF CLEARCUTTING ON THE FLOW OF CHEMICALS THROUGH A FOREST-WATERSHED ECOSYSTEM IN SOUTHWESTERN BRITISH COLUMBIA by MICHAEL CHARLES FELLER B. Sc. Hons., University of Melbourne (Australia), 1968 M. Sc.(Chem.) University of Melbourne (Australia), 1969 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY (Forest Ecology) in the Faculty of Forestry accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Spring,^ 1975 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly pur-poses may be granted by the Head of my Department or by his representatives. It i s understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Faculty of Forestry The University of B r i t i s h Columbia, Vancouver, B.C. V6T 1W5, Canada. Date £ / II J7<j i ABSTRACT A literature survey indicated that l i t t l e was known about the effects of commercial clearcutting on stream and watershed solution chemistry. To investigate these effects, five small watersheds were studied in the University of B.C. Research Forest. Three of the watersheds were equiped with weirs, stream height recorders, and soil-air-water thermographs. Soil pits were dug in the three calibrated watersheds and equiped with surface runoff collectors and hanging water column tension lysimeters. Samples of - precipitation above the forest, throughfall (through forest and slash), surface runoff, forest floor leachate, mineral s o i l leachate near the bottom of the rooting zone, groundwater, and streamwater - were collected at regular intervals and analyzed for pH, e l e c t r i c a l conductivity, alkalinity as bicarbonate, K, Na, Mg, Ca, Fe, Mn, A l , C l , P, N, S, and Si for periods of up to three years prior to clear-cutting and two years after clearcutting. Streamwater was also analyzed for dissolved oxygen and suspended sediment. Sampling was carried out for periods of up to three years prior to clearcutting and up to two years following clear-cutting . The streams were characterized by high discharges from late autumn u n t i l early summer and low discharges from May un t i l October, with almost no contri-bution from snowmelt runoff. Response to precipitation was f a i r l y rapid and i t was hypothesized that stormflow arose mainly from flow of water through macrochannels in the s o i l . Visual observations and chemical data were con-sistent with this hypothesis. Evapotranspiration from the gauged watersheds was estimated to be about 85 cm per year by subtracting streamflow outputs from precipitation inputs i i and 65 cm per year using t h e o r e t i c a l methods. The discrepancy between these two values was a t t r i b u t e d to an unmeasured leakage of water, p a r t i c u l a r l y from the untreated c o n t r o l watershed which rendered too low the streamflow out-puts. There was an increase of 30.8 cm i n runoff from one watershed, and 27.6 cm from another during the f i r s t s i x months of the dormant season im-mediately following c l e a r c u t t i n g . During t h i s period runoff from the con-t r o l watershed was 141.5 cm. Stream temperatures underwent annual cycles with winter minima close to 0°C and summer maxima close to 17°C. Diurnal temperature f l u c t u a t i o n s were s l i g h t and u s u a l l y l e s s than a few degrees. C l e a r c u t t i n g caused an increase i n both maximum and minimum stream temperatures during the f i r s t dormant sea-son following c l e a r c u t t i n g . The few measurements which were made of suspended sediment, together with v i s u a l observations, i n d i c a t e d that concentrations were us u a l l y n e g l i g i b l e i n the streams. Dissolved oxygen concentrations i n streams were u s u a l l y close to 100% sa-t u r a t i o n and underwent annual cycles with maximum values i n winter and minimum values i n l a t e summer and e a r l y autumn. C l e a r c u t t i n g had l i t t l e e f f e c t on d i s -solved oxygen values during the cooler wetter months but caused very pronounced decreases during summer and e a r l y autumn. This was a t t r i b u t e d to the b i o l o g i -c a l and chemical oxygen demands of decaying slash i n the streams. Stream chemistry exhibited l i t t l e d i u r n a l v a r i a t i o n but considerable v a r i a t i o n with discharge. Sodium, calcium, magnesium, dissol v e d s i l i c a , and bicarbonate concentrations, and e l e c t r i c a l c onductivity and pH decreased with i n c r e a s i n g discharge, whereas potassium and n i t r a t e concentrations exhibited some increases and some decreases. Chloride and sulphate concentrations were generally not s i g n i f i c a n t l y r e l a t e d to discharge. i i i In the undisturbed ecosystems, chemical concentrations, pH, and e l e c t r i -c a l c o n d u c t i v i t y throughout the systems were generally highest i n l a t e summer and e a r l y autumn and lowest i n winter and e a r l y spring. This was a t t r i b u t e d to seasonal c y c l e s of g e o l o g i c a l and b i o l o g i c a l a c t i v i t y with accumulation of weathering and decomposition products occurring during dry, warm summers. These were flushed through the system i n autumn, with solutions becoming pro-g r e s s i v e l y more d i l u t e throughout the winter u n t i l the onset of warmer wea-ther. N i t r a t e concentrations tended to be higher i n winter than i n summer which was a t t r i b u t e d to greater nitrogen uptake by organisms i n summer. The most abundant ions i n p r e c i p i t a t i o n and t h r o u g h f a l l were hydrogen, sulphate, and c h l o r i d e , while calcium, bicarbonate, and sulphate were domi-nant i n a l l the other types of water samples. There was a general increase i n chemical concentrations to maximum values i n f o r e s t f l o o r leachate f o l -lowed by a decrease to minimum values i n groundwater, and a s l i g h t increase again i n streamwater. The lowest pH values were i n thr o u g h f a l l (4.0-4.5) followed by a steady increase through the system to maximum values i n stream-water (6.5-7.0). C l e a r c u t t i n g increased the pH of water reaching the f o r e s t f l o o r and surface runoff but decreased the pH of mineral s o i l leachate, groundwater, and streamwater. I t g e n e r a l l y decreased chemical concentrations i n water reaching the f o r e s t f l o o r and i n surface runoff, and, to a le s s e r extent, i n f o r e s t f l o o r and mineral s o i l leachates, but i t increased concentrations i n groundwater and, to a l e s s e r extent, i n streamwater. A most notable i n -crease throughout the system was i n the concentration of potassium which was a t t r i b u t e d to the r e l a t i v e ease with which potassium i s leached from decaying vegetation. Increases i n n i t r a t e concentrations were p a r t i c u l a r l y high i n groundwater. iv Streamwater concentrations of potassium, iron, calcium, dissolved oxy-gen, and probably manganese, were significantly affected by clearcutting; concentrations of a l l these chemicals increased, except dissolved oxygen which decreased. Slight increases in magnesium, nitrate, sulphate, and chloride concentrations, and e l e c t r i c a l conductivity, and decreases in pH and bicarbonate concentrations were also observed. A l l changes were most noticeable during the low flow periods of late summer and early autumn. There were no obvious effects on sodium, aluminium, ammonium, dissolved s i l i c a , and phosphate concentrations. In terms of chemical budgets, there was a general net loss of calcium, sodium, magnesium, potassium, and sulphur from a l l the watersheds, in their undisturbed state, while nitrogen was accumulated and phosphorus underwent very l i t t l e change. The chloride balance changed from year to year with losses one year and gains the next. Chemical outputs increased relative to inputs with increasing precipitation so that net losses were greater in win-ter than in summer. Chemical budgets and stream chemistry at Haney were compared to the results of other studies, particularly one in the nearby Seymour watershed (Zeman, 1973). At Haney, clearcutting significantly increased potassium losses and decreased nitrogen gains in one watershed and significantly increased potas-sium, sodium, magnesium, and chloride losses i n another watershed. From the nutrient viewpoint, i t appears that clearcutting has not im-paired the mechanisms for nutrient retention in the ecosystems of the type present in the study area. This may not be the case for a l l ecosystems in coastal B.C., or for other forestry practices, such as slashburning. V The study has pointed out the need f o r furth e r work to quantify the ro l e of macrochannels i n s o i l s with respect to hydrologic and chemical be-haviour of watersheds. I t has also pointed out the danger of extrapolating to l a r g e r ecosystems the r e s u l t s of lysimeter studies. Chemical analysis of groundwater may o f f e r a more accurate means of estimating chemical losses from s o i l s than do lysimeters. v i TABLE OF CONTENTS ABSTRACT Page TABLE OF CONTENTS vi LIST OF TABLES v m LIST OF FIGURES xi ACKNOWLEDGEMENTS X l l CHAPTER 1 INTRODUCTION Ecological effects of clearcutting Effects on the s o i l Effects on l i v i n g organisms Effects on streams and aquatic ecosystems Objectives of the thesis CHAPTER 2 DESCRIPTION OF THE STUDY AREA Location Climate Geology, landforms, and soils Vegetation Watershed description CHAPTER 3 EXPERIMENTAL METHODS Field instrumentation and sampling techniques Chemical analyses CHAPTER 4 STREAM BEHAVIOUR Stream hydrology Stream and s o i l temperature Suspended sediment 2 3 12 25 40 41 41 41 46 48 55 58 58 66 71 71 83 88 Dissolved oxygen pH E l e c t r i c a l conductivity Ions and dissolved s i l i c a Chemical budgets General discussion Summary CHAPTER 5 SOLUTION CHEMISTRY OF THE ENTIRE FOREST-WATERSHED ECOSYSTEM pH E l e c t r i c a l conductivity Cations Anions and dissolved s i l i c a General discussion Summary CHAPTER 6 CONCLUSIONS LITERATURE CITED APPENDICES I Stage-discharge calibration of weirs A, B, and C II Descriptions of s o i l profiles III Soil profile physical and chemical properties IV Mathematical relationships between discharges at weirs A, B, and C V Annual average chemical composition of streams A, B, and C VI Examples of potentiometric bicarbonate concentrations VII Lysimeter tensions and volumes of solution collected VIII Contents of slash throughfall collectors IX Tree volumes and slash loadings in the study area X S t a t i s t i c a l comparison of chemical concentrations in streams, and chemical losses from watersheds, before and after clearcutting XI Monthly average chemical concentrations in throughfall after clearcutting XII Chemical analyses of" groundwater at Haney XIII Monthly chemical .budgets for the different watersheds XIV Relationships between monthly chemical loads and amount of precipitation and discharge XV Scienti f i c names of the major plant species present in the watersheds at Haney V l l l LIST OF TABLES Table Page 2.1 Annual average precipitation for the three guaged 41 watersheds at Haney 2.2 Precipitation at Haney during the study period 44 2.3 Climatological data for two weather stations at Haney 45 2.4 Relative distribution of the major tree species i n 48 watersheds A, B, and C 2.5 Physical characteristics of the watersheds at Haney 55 2.6 Relative watershed areas and stream discharges 56 3.1 Detection limits of chemicals by the analytical 66 methods used. 3.2 Precision of the chemical analyses 66 4.1 Precipitation and runoff for the watersheds at Haney 78 4.2 Estimates of evapotranspiration for Haney 79 4.3 Measured and predicted values of stream discharge 83 following clearcutting 4.4 Suspended sediment concentrations i n streams leaving 88 the watershed . 4.5 Average pH values of streams before and after clear- 115 cutting 4.6 E l e c t r i c a l conductivities of stations B and C and four 122 tributaries 4.7 E l e c t r i c a l conductivity of subsurface seepage water i n 123 Polystichum - Thuja plicata ecosystems of different ages in the U.B.C. Research Forest 4.8 Ionic sums from streamwater analyses 126 4.9 Average e l e c t r i c a l conductivities of streams before 128 and after clearcutting 4.10 Seasonal variation of cation concentrations i n 132 streamwater in temperate regions 4.11 Variation of cation concentrations i n streams i n 134 temperate regions with increasing stream discharge 4.12 Average concentrations of cations in streamwater 135 before and after clearcutting 4.13 Seasonal variation of dissolved s i l i c a and anion 155 concentrations in streamwater in temperate regions 4.14 Variation of dissolved s i l i c a and anion concentrations 157 in streamwater in temperate regions with increasing ' stream discharge IX Table Page 4.15 Average concentrations of d i s s o l v e d s i l i c a and anions 159 i n streams before and a f t e r c l e a r c u t t i n g 4.16 Annual chemical budgets 179 4.17 Estimated maximum e r r o r s i n chemical budget c a l c u l a t i o n s 181 4.18 Annual chemical budgets of undisturbed f o r e s t - watershed 185 ecosystems i n humid temperate regions 4.19 Streamwater chemistry during a 24-hour period, 5-6 189 November, 1973 4.20 Streamwater chemistry during a 24-hour period, 24-25 191 June, 1972 4.21 Cation concentrations i n s i m i l a r streams i n the 193 C h i l l i w a c k V a l l e y area, November, 1972 4.22 Maximum measured concentrations of selected chemicals 197 i n streamwater and permissible l i m i t s f o r human con-sumption and other uses 5.1 Means and standard deviations of chemical parameters ob- 204 tained from a n a l y s i s of a s i n g l e c o l l e c t i o n of samples c o l l e c t e d on two dates, one before and one a f t e r c l e a r -c u t t i n g 5.2 Means and standard deviations of chemical parameters 205 obtained from a n a l y s i s of one c o l l e c t i o n of samples from the same biogeocoenosis 5.3 Average pH values of waters i n an undisturbed f o r e s t 207 ecosystem a t Haney - watershed B 5.4 Average pH values of ecosystem waters before and a f t e r 210 c l e a r c u t t i n g - watershed B 5.5 Average e l e c t r i c a l c o n d u c t i v i t i e s of waters i n an un- 211 disturbed f o r e s t ecosystem at Haney - watershed B 5.6 Average e l e c t r i c a l c o n d u c t i v i t i e s of ecosystem waters 214 before and a f t e r c l e a r c u t t i n g - watershed B 5.7 Average c a t i o n concentrations of waters i n an undis- 216 turbed f o r e s t ecosystem at Haney - watershed B 5.8 Ratios of c a t i o n concentrations i n water at d i f f e r e n t 217 l e v e l s i n a f o r e s t ecosystem i n Germany 5.9 Relat i v e abundance of the major cations i n s o l u t i o n at d i f f e r e n t l e v e l s i n the ecosystem 221 Table Page 5.10 Average c a t i o n concentrations i n ecosystem waters 232 before and a f t e r c l e a r c u t t i n g - watershed B 5.11 Average anion and d i s s o l v e d s i l i c a concentrations of 235 waters i n an undisturbed f o r e s t ecosystem at Haney -watershed B 5.12 Relative abundance of the major anions i n s o l u t i o n at 236 d i f f e r e n t l e v e l s i n the ecosystem 5.13 Ratios of anion-element concentrations i n water at 239 d i f f e r e n t l e v e l s i n a f o r e s t ecosystem i n Germany 5.14 Average anion and di s s o l v e d s i l i c a concentrations i n 249 ecosystem waters before and a f t e r c l e a r c u t t i n g -watershed B 5.15 Average chemical composition of groundwater and 254 streamwater at Haney x i LIST OF FIGURES Figure Page 2.1 Location of the study area 42 2.2 Isohyetal map of the watersheds 43 2.3 Forest cover 50 2.4 Biogeocoenoses of the watersheds 53 2.5 Location of clearcuts and major roads 57 3.1 The research area at Haney 60 3.2 A surface runoff collector 63 3.3 A tension lysimeter, type 1 63 3.4 A tension lysimeter, type 2 63 4.1 Mean daily discharges at the weirs at Haney 72 4.2 Response,of stream discharge to precipitation during an 73 October storm 4.3 Response of stream discharge to precipitation during a 74 January storm 4.4 Macrochannels exposed in the faces of s o i l pits 77 4.5 Weekly maximum and minimum stream temperatures 80 4.6 Streamwater temperatures during a typical summer's day 81 and a typical winter's day 4.7 Streamwater temperature during the passage of an arctic 82 front 4.8 . Relationships between maximum streamwater temperatures 84 in streams A and B and those of stream C 4.9 Relationships between minimum streamwater temperatures 85 in streams A and B and those of stream C 4.10 Weekly maximum and minimum s o i l temperatures 86 4.11 Yarding techniques for the watersheds at Haney 91 4.12 Stream channels before and after clearcutting 92 4.13 Dissolved oxygen concentrations - streams A, B, and C 96 4.14 Dissolved oxygen percent saturation - streams A, B, and 96 C 4.15 Diurnal variation in streamwater dissolved oxygen and 98 pH - late autumn 4.16 Diurnal variation in streamwater dissolved oxygen and 101 pH - early summer X l l Figure Page 4.17 Relationships between streamwater dissolved oxygen 104 concentrations and discharge 4.18 Relationships between streamwater dissolved oxygen 105 percent saturations and discharge 4.19 Streamwater dissolved oxygen during a storm event 106 4.20 Dissolved oxygen concentrations - streams D and E 109 4.21 Dissolved oxygen percent saturation - streams D and E 109 4.22 Streamwater pH - streams A, B, and C 112 4.23 Relationships between streamwater pH and discharge 113 4.24 Streamwater pH during a storm event 114 4.25 Streamwater pH - streams D and E 115 4.26 Streamwater ele c t r i c a l conductivity - streams A, B, and 118 C 4.27 Relationships between streamwater e l e c t r i c a l conductiv- 119 i t y and discharge 4.28 Streamwater ele c t r i c a l conductivity during a storm event 120 4.29 Relationships between el e c t r i c a l conductivity and the 124 sum of potassium, sodium, magnesium, and calcium concen-trations 4.30 Relationships between el e c t r i c a l conductivity and the 125 sum of bicarbonate, sulphate, and chloride concentra-tions 4.31 Streamwater potassium concentrations - streams A, B, and 129 C 4.32 Relationships between streamwater potassium concentra- 130 tions and discharge 4.33 Streamwater cation concentrations during a storm event 131 4.34 Streamwater potassium concentrations - streams D and E 137 4.35 Streamwater sodium concentrations — streams A, B, and C 139 4.36 Relationships between streamwater sodium concentrations 140 and discharge 4.37 Streamwater magnesium and calcium concentrations - 142 streams A, B, and C 4.38 Relationships between streamwater magnesium concentra- 144 tions and discharge 4.39 Relationships between streamwater calcium concentrations 145 and discharge 4.40 Streamwater calcium concentrations - streams D and E 146 X l l l Figure Page 4.41 Streamwater i r o n and manganese concentrations - streams 2.49 D and E 4.42 Streamwater ammonium concentrations - streams A, B, and 151 C 4.43 Streamwater n i t r a t e concentrations - streams A, B, and C 151 4.44 Relationships between streamwater ammonium concentra- 153 tio n s and discharge 4.45 Relationships between streamwater n i t r a t e concentrations 154 and discharge 4.46 Streamwater bicarbonate concentrations - streams A, B, 163 and C 4.47 Streamwater diss o l v e d s i l i c a and anion concentrations 164 during a storm event 4.48 Relationships between streamwater bicarbonate concentra- • 165 ti o n s and discharge 4.49 Streamwater bicarbonate concentrations - streams D and E 167 4.50 Streamwater diss o l v e d s i l i c a concentrations - streams A, 169 B, and C 4.51 Relationships between streamwater d i s s o l v e d s i l i c a con- 170 centrations and discharge 4.52 Streamwater sulphate concentrations - streams A, B, and 172 C 4.53 Relationships between streamwater sulphate concentra- 173 ti o n s and discharge 4.54 Streamwater c h l o r i d e concentrations - streams A, B, and 175 4.55 Relationships between streamwater ch l o r i d e concentra- 177 t i o n s and discharge 5.1 pH of ecosystem solutions 208 5.2 E l e c t r i c a l c o n d u c t i v i t y of ecosystem s o l u t i o n s 212 5.3 Potassium concentrations i n ecosystem s o l u t i o n s 223 5.4 Sodium concentrations i n ecosystem s o l u t i o n s 224 5.5 Magnesium concentrations i n ecosystem s o l u t i o n s 225 5.6 Calcium concentrations i n ecosystem s o l u t i o n s 226 5.7 Iron concentrations i n ecosystem s o l u t i o n s 227 5.8 Manganese concentrations i n ecosystem solutions 228 5.9 Ammonium concentrations i n ecosystem solutions 229 5.10 Chloride concentrations i n ecosystem s o l u t i o n s 241 Figure Page 5.11 Phosphate concentrations i n ecosystem solutions 242 5.12 Nitrate concentrations in ecosystem solutions 243 5.13 Sulphate concentrations in ecosystem solutions 244 5.14 Bicarbonate concentrations i n ecosystem solutions 245 5.15 Dissolved s i l i c a concentrations in ecosystem solutions 246 XV ACKNOWLEDGEMENTS I would like to express my gratitude to the people from whom I have received considerable support during the course of this thesis. I am deeply indebted to Dr. J.P. Kimmins who not only enabled me to begin a career i n forestry, but also provided much guidance, encourage-ment, and financial support, without which the present study could never have been completed. I am also indebted to the members of my research committee, Drs. T.M. Ballard, B.C. Goodell, P.G. Haddock, J.H.G. Smith and R.P. Willing-ton, for advice and assistance during different phases of this project. Mr. J . Walters and the staff of the University of B r i t i s h Columbia Re-search Forest often went out of their way to l e t me use their f a c i l i -t ies, for which I am grateful. I also wish to thank Drs. T.A. Black (Department of Soil Science), A. Kozak, V.J. Krajina (Department of Botany), and L.M. Lavkulich (Department of S o i l Science) for their use-fu l comments. I would particularly like to thank my colleague, K. Klinka, for many hours of useful and stimulating discussion and for letting me use some of his s o i l and vegetation data. I must also thank K.M. Tsze for assistance with f i e l d work and l a -boratory analyses and H.D. Schell for assistance with laboratory analyses. In addition, I am indebted to L. Keir, K. Hejjas, and D. Roff for carry-ing out the computer programming, and to Penny Lewis, T r i c i a Rankin, and Jean Williamson for typing most of the thesis'. xvi I am g r a t e f u l f o r the f i n a n c i a l support supplied by a National Re-search Council Bursary, by the Resource Science Centre at the U n i v e r s i t y o f B r i t i s h Columbia, and by a K i l l a m Predoctoral Fellowship. 1 CHAPTER 1. INTRODUCTION In coastal B.C. the most common method of harvesting forests for tim-ber consists of clearcutting. Areas up to several thousand acres i n extent have been cut progressively, but most have now been lmited to a maximum of about 200 acres (80 hectares) (Cameron, 1972) . Both s i l v i c u l t u r a l and short-term economic constraints i n the coastal region favour the use of clearcutting over any alternative harvesting method, and foresters have traditionally accepted clearcutting as the most approp-riate harvesting method. The general public, however, i s becoming increas-ingly concerned about clearcutting. With an increasing concern over the goals of society and the type of environment created by technology, and a greater awareness of the forest as a national inheritance, people are demanding high quality management of their forests. Clearcutting i s widely considered to make the land ugly, to degrade i t by lowering i t s productivity, and to lower the value of some of the forest's products, such as water and recreation. Many people con-sider that, in the long run, forests and trees may be more important to man and his well being as a part of the human environment than as a source of raw materials. Some foresters, particularly those i n the U.S. where public criticism of forestry has a longer history than i n B.C., are advocating better and more aesthetic practices (e.g. Duncan, 1971; Hopkins, 1970; Jeffrey et al., 1970; Ruckelshaus, 1971; Spurr and Arnold, 1971; Wilson, 1970). Others have responded to the criticism by using economic and s i l v i c u l t u r a l 2 arguments to support t h e i r case f o r c l e a r c u t t i n g and by denying that c l e a r -c u t t i n g degrades the land (e.g. Brooks, 1971; D u f f i e l d and Davis, 1971; Har-k i n , 1972; U.S. Senate, 1971). Both sides i n t h i s debate are hampered by a lack o f data. C l e a r c u t t i n g imposes changes on a f o r e s t ecosystem that extend f a r beyond the mere sudden removal of the dominant vegetation. These changes may be e i t h e r subtle or dramatic and have varying e c o l o g i c a l and s o c i a l s i g -n i f i c a n c e . R e l i a b l e data p e r t a i n i n g to these changes would help to c l a r -i f y aspects of the c l e a r c u t t i n g controversy. I t i s the o v e r a l l aim of t h i s t h e s i s to provide such data for. c e r t a i n aspects of the t o p i c . The approach used was as f o l l o w s : The f i r s t step was to review the l i t e r a t u r e p e r t a i n i n g to the e c o l o g i c a l e f f e c t s of c l e a r c u t t i n g i n order t o determine which e f f e c t s were worthy, of study. The next step was t o study some of these e f f e c t s about which l i t t l e was known. When the l i t e r a t u r e was f i r s t reviewed i n 1970, the e f f e c t s of c l e a r c u t t i n g on streamwater chemistry, and watershed n u t r i e n t c y c l i n g were not known, but r e s u l t s of the e a r l i e r Hubbard Brook experiments (e.g. Bormann et at. , 1968; Likens et al., 1969) suggested that these e f f e c t s might be very s i g n i f i c a n t . Consequently, i t was decided to study these e f f e c t s . Review o f the Literature^" , E c o l o g i c a l e f f e c t s o f c l e a r c u t t i n g A f o r e s t c o n s i s t s not only of trees but of the t o t a l assemblage of l i v i n g organisms.(trees, a l l other p l a n t s , animals, and microbes) as w e l l Review concluded September, 1974. 3 as the t o t a l p h y s i c a l environment ( s o i l , a i r , and water) i n which the o r -ganisms l i v e . A l l these l i v i n g and n o n - l i v i n g components i n t e r a c t with each other, forming a very complex system c a l l e d an ecosystem (Tansley, 1935). Due to the great d i v e r s i t y within and between ecosystems, i t i s usu a l l y very d i f f i c u l t to generalize about the e f f e c t s of c l e a r c u t t i n g and each c l e a r c u t area should be considered separately. The e f f e c t s of c l e a r c u t t i n g on ecosystems w i l l depend on many f a c t o r s such as the type and condition of the s o i l and the f o r e s t f l o o r , the topography, climate, p l a n t and animal communities present, the type of equipment used, and the season o f the year when c l e a r c u t t i n g took place. For any one e f f e c t of c l e a r c u t t i n g on a p a r t i c u l a r f o r e s t ecosystem i t i s usu a l l y p o s s i b l e to f i n d the opposite e f f e c t on another f o r e s t ecosystem. (1) E f f e c t s on the s o i l (a) S o i l erosion - Dyrness (1967) and Rice et al, (1972) have reviewed the l i t e r a t u r e p e r t a i n i n g to erosion of f o r e s t s o i l s . Extensive c l e a r c u t t i n g on slopes i s l i k e l y to increase s o i l surface erosion and surface runoff (Bethlahmy, 1967; Curry, 1973; Dyrness, 1967; Fr o e h l i c h , 1973; Rice et al., 1972; Sherry, 1954; Swanston, 1971a; Tackle, 1962; W i l l i n g t o n , 1968). This i s the r e s u l t of lower i n f i l t r a t i o n r ates which may be due t o : 1, A decrease i n s o i l p o r o s i t y when s o i l p a r t i c l e s are splashed or washed i n t o pores by r a i n or snowmelt. This may be enhanced by the r e -moval o f any vegetative cover or organic debris, exposing mineral s o i l to the d i r e c t impact of raindrops. 4 2. The induction of hydrophobicity i n s o i l s . Coarse textured s o i l s throughout Alaska and the western U.S. frequently e x h i b i t hydrophobicity during dry summer periods (DeBano et al. , 1967; Foggin and DeBano, 1971; Jamieson, 1969; Krammes and Debano, 1965; Meeuwig, 1971). DeByle (1973) observed water repellency i n the decomposing l i t t e r under larch-Douglas-f i r f o r e s t s i n Montana and found i t to be more common on the warmer southern aspects. By exposing the s o i l surface to more heat through r e -moval of vegetative cover and by depositing more decomposing material on the s o i l surface, i n the form of s l a s h , c l e a r c u t t i n g my f a c i l i t a t e the formation of hydrophobic s o i l s . 3, An increase i n the amount of exposed bedrock r e s u l t i n g i n l o c a l concentration of runoff. These h y d r o l o g i c a l e f f e c t s are not u n i v e r s a l , however. Some studies have found that c l e a r c u t t i n g has l i t t l e e f f e c t on i n f i l t r a t i o n capacity (e.g. Dyrness et al. , 1957; L u l l and Reinhart, 1972) and i t i s c l e a r that the degree of s o i l disturbance, and hence the degree of s o i l surface erosion, w i l l depend to a large extent on the harvesting tech-nique used, with high lead systems causing l e s s disturbance than t r a c t o r logging (Dyrness, 1972; Rice et al. , 1972). ' C l e a r c u t t i n g causes a progressive d e t e r i o r a t i o n of the root sys-tems responsible f o r s o i l s t a b i l i t y on steep slopes. This, together with the increase i n s o i l water content following vegetation removal, may i n -duce mass movements o f s o i l (Bishop and Stevens, 1964; C r o f t and Adams, 1950; Fredriksen, 1970; O'Loughlin, 1974; Rice and Krammes, 1971; Swan-ston, 1971a,b), O'Loughlin (1972) studying mass movements of s o i l i n southwestern B.C., found that l a n d s l i d e s not associated with roads were 5 mainly on long uniform slopes with gradients of more than 30° underlain by poorly drained podzols. Large l a n d s l i d e s were more frequent on c l e a r c u t s than on undisturbed slopes. He concluded t h a t : "Current f o r e s t c u t t i n g and road b u i l d i n g p r a c t i c e s on the steep slopes of B r i t i s h Columbia's Coast Mountains are not compatible with sensible mountainland management which f o s t e r s p r o t e c t i o n of the s o i l resource", and recommended that there be no c l e a r c u t t i n g on a) slopes greater than 35°, b) f o r e s t s over 1000 m i n a l t i t u d e , c) f o r e s t s adjacent to mountain streams, and d) f o r e s t s on poorly drained slopes and i n large drainage depressions subject to p e r i o -d i c s a t u r a t i o n . There i s general agreement among a l l workers i n the f i e l d of s o i l erosion, that, o f a l l man's a c t i v i t i e s i n f o r e s t s , road b u i l d i n g i s the major cause of erosion. (b) S o i l moisture r e l a t i o n s - The removal of vegetation decreases evapo— t r a n s p i r a t i o n and i n t e r c e p t i o n water losses to the atmosphere tending to increase s o i l moisture l e v e l s (Cochran, 1969; J e f f r e y , 1970; P a t r i c , 1973), In B.C., Baker (1968) and Knight (1964) have both found increases i n s o i l moisture l e v e l s a f t e r c l e a r c u t t i n g . Baker (1968) found that moisture l e v -e l s of c l e a r c u t and burned s o i l s i n southeastern B.C. were higher than those of undisturbed s o i l s during the growing season whereas the reverse was true during the r e s t of the year. Knight (1964) obtained s i m i l a r r e -s u l t s the f i r s t year a f t e r logging. However, i n subsequent years he found les s a v a i l a b l e moisture i n the surface horizons of s o i l s under c l e a r c u t s than i n undisturbed s o i l s . This he a t t r i b u t e d to the r a p i d invasion of shallow rooting t r a n s p i r i n g herbs and shrubs and the added exposure due to stand removal which increased evaporation i n the c l e a r c u t compared t o . the undisturbed f o r e s t . 6 S o i l moisture increases following c l e a r c u t t i n g may r e s u l t i n a r i s e o f the s o i l water table which can r e s u l t i n f l o o d i n g of the surface i n wet s i t e s (Bay, 1967; Heikurainen and PaivMnen, 1970; T r o u s d e l l and Hoover, 1955). This has been observed i n the spruce-subalpine f i r f o r -ests of A l b e r t a (Jarvis et at., 1966; Lees, 1960; Lees, 1970). Con-ver s e l y , the water table may be lowered i f c l e a r c u t t i n g exposes a large area of mineral s o i l . This was observed following burning of s i t e s with a t h i c k moss cover i n Sweden (Ahlgren and Ahlgren, 1960). In the undis-turbed condition the s o i l did not freeze completely i n winter so that the spring thaw was absorbed i n t o the ground keeping the water table high. Burning, which exposed mineral s o i l , r e s u l t e d i n complete f r e e z i n g of the s o i l i n winter permitting water from the spring thaw to run o f f the s i t e . Removal o f the surface organic s o i l and s o i l compaction have been shown to increase the depth and persistence of s o i l f r e e z i n g (Thorud and Duncan, 1972) which may r e s u l t i n more surface runoff (Dunne and Black, 1971), (c) S o i l microclimate - C l e a r c u t t i n g , as p r a c t i s e d i n c o a s t a l B.C., seems u n l i k e l y to a f f e c t macroclimate s i g n i f i c a n t l y . Only i n s p e c i a l circum-stances with very extensive c l e a r c u t t i n g might a s l i g h t decrease i n nearby p r e c i p i t a t i o n occur (Golding, 1970). The removal of trees u s u a l l y causes changes i n the climate near the s o i l surface, however. 1. Temperature extremes may be greater. Although Cochran (1969) stated that surface temperature extremes increase with the s i z e of the c l e a r c u t , Powell (1971), i n a l i t e r a t u r e review of the e f f e c t s of c l e a r -c u t t i n g on c l i m a t i c f a c t o r s , found that the i n f l u e n c e o f the f o r e s t on most c l i m a t i c parameters r a r e l y extends more than 2-3 times the height 7 of the trees i n t o a c l e a r c u t , so the c l i m a t i c conditions i n the open w i l l remain p r a c t i c a l l y constant with i n c r e a s i n g s i z e of the c l e a r c u t , once i t s diameter exceeds 4-6 times the height of the t r e e s . Lower temperature minima give r i s e to more intense and e a r l i e r f r o s t s which can cause f r o s t heaving of seedlings or s o i l slumping on steep h i l l s i d e s (Cochran, 1969; Hale, 1950; J a r v i s et al. , "1966; Pierce et al., 1958; Remezov and Pogrebnyak, 1969, ch. 6 and 8; Waldron, 1966; Zasada and Gregory, 1969). Increased s o i l temperatures during the warmer months may, on p a r t i c u l a r l y hot s i t e s such as south-facing slopes, be so high as to prevent germintion or to k i l l seedlings (Issac, 1938; Isaac and Hop-kins, 1937). However, i n colder regions, increased temperatures may be b e n e f i c i a l to p l a n t growth (Ahlgren and Ahlgren, 1960; Lutz, 1956). In permafrost regions increased s o i l temperatures can cause a downward r e -t r e a t o f the permafrost layer, i n c r e a s i n g the p o t e n t i a l p r o d u c t i v i t y of a s i t e by making a greater amount of s o i l a v a i l a b l e to p l a n t r o o t s . Fur-thermore, increased s o i l temperature increases the rate o f chemical wea-thering and b i o l o g i c a l a c t i v i t y , thus i n c r e a s i n g the r a t e of n u t r i e n t release to the s o i l (Likens et al., 1970). 2. Tree canopies s i g n i f i c a n t l y reduce i n c i d e n t short-wave r a d i a -t i o n (although long-wave r a d i a t i o n i s depleted very l i t t l e ) (Reifsnyder and L u l l , 1965) and i n c i d e n t s o l a r r a d i a t i o n under f o r e s t canopies i s often l e s s than 10% of that i n nearby clea r c u t s (Vezina and Pech, 1964). Thus, c l e a r c u t t i n g favours the growth of the more shade i n t o l e r a n t species c h a r a c t e r i s t i c of a f o r e s t ' s e a r l i e r successional stages. 8 3, Forests s i g n i f i c a n t l y reduce wind v e l o c i t i e s r e l a t i v e to those i n open areas. Thus, wind v e l o c i t i e s i n cl e a r c u t s are increased and intense turbulence may develop (Kittredge, 1962; Powell, 1971; Remezov and Pogre-bnyak, 1969, ch. 8) . 4. Vegetation removal u s u a l l y decreases i n t e r c e p t i o n losses of pre-c i p i t a t i o n r e s u l t i n g i n an increase i n the amount of p r e c i p i t a t i o n reach-ing the s o i l surface (Jeffrey, 1970; Powell, 1971; Remezov and Pogrebnyak, 1969, ch. 8). This may have l i t t l e or no e f f e c t , may be b e n e f i c i a l by supplying more moisture f o r plant growth, or may be detrimental i f increased s o i l erosion occurs. Detrimental e f f e c t s are more l i k e l y i n areas subject to high i n t e n s i t y r a i n f a l l whereas b e n e f i c i a l e f f e c t s are more l i k e l y i n areas of low i n t e n s i t y r a i n f a l l . Increased snow accumulation occurs on cl e a r c u t s not only due to reduced i n t e r c e p t i o n but a l s o to wind e f f e c t s which r e d i s t r i b u t e snow i n cle a r i n g s i n f o r e s t s (Powell, 1971). ' (d) Chemical p r o p e r t i e s - As discussed above, c l e a r c u t t i n g has the f o l -lowing e f f e c t s : 1. I t exposes the s o i l surface to more heat and moisture which ac-celerat e s s o i l m i c r o b i a l a c t i v i t y , r e s u l t i n g i n greater rates of organic matter decomposition and concomitant increases i n the supply of a v a i l a b l e chemical n u t r i e n t s . 2. By exposing any mineral s o i l , at the surface to greater tempera-ture extremes and inc r e a s i n g s o i l moisture l e v e l s , c l e a r c u t t i n g may i n -crease the rate of chemical weathering or inorganic substrata. 3. By removing vegetation, i t decreases n u t r i e n t uptake from the s o i l . 9 4. By decreasing evapotranspiration and i n t e r c e p t i o n losses, i t may increase the amount of water passing through the s o i l . A l l these f a c t o r s i n d i c a t e that c l e a r c u t t i n g w i l l increase the flow of n u t r i e n t chemicals down through the s o i l , as was suggested by Nye and Greenland (1960) and Ovington (1962). This aspect o f c l e a r c u t t i n g has been r e c e i v i n g i n c r e a s i n g a t t e n t i o n and has been w e l l documented by Cole and co-workers i n Washington (Cole and Gessel, 1965; Cole et at., 1973; Gessel and Cole, 1965). These authors used tension lysimeters to show that c u t t i n g a 43-year-old D o u g l a s - f i r p l a n t a t i o n on g r a v e l l y sandy loam podzols d i d increase the amount of chem-i c a l s passing through the s o i l although the increase was very s l i g h t be-low the r o o t i n g zone (36 inches), Nutrient fluxes were greatest during the wetter winter months and phosphorus and calcium losses were increased t o a greater extent than nitrogen and potassium los s e s . Curry (1973), i n a review o f world l i t e r a t u r e on the e f f e c t s of c l e a r -c u t t i n g on s o i l p r o d u c t i v i t y , quoted several other workers who have a l s o found that c l e a r c u t t i n g can increase the flow o f chemicals down the s o i l pedon. Remezov and Pogrebnyak (1969, ch. 7 and 8) i n d i c a t e d that s i m i l a r r e s u l t s occur a f t e r c l e a r c u t t i n g . o r p a r t i a l c u t t i n g i n Russia. F i r s o v a (1965) found t h a t c l e a r c u t t i n g on sod p o d z o l i c s o i l s i n the Russian Tran-su r a l s l e d to a change not so much i n the t o t a l quantity as i n the r e l a -t i v e q u a n t i t i e s of water soluble chemicals i n the s o i l . At Hubbard Brook Experimental Forest i n the northeastern U.S., vegetation removal g r e a t l y stimulated the a c t i v i t y of n i t r i f y i n g b a c t e r i a leading to a large increase i n n i t r a t e ion concentration i n s o i l leaching waters accompanied by large increases i n c a t i o n concentrations (Likens et at., 1970; Bormann et at., 10 1968). Although the i n i t i a l r e s u l t s at Hubbard Brook were f o r a very a t y p i -c a l f o r e s t treatment, recent studies of regular commercial c l e a r c u t t i n g i n the same f o r e s t area have produced very s i m i l a r r e s u l t s (Hornbeck et at., 1973; P i e r c e et al. , 1972). C l e a r c u t t i n g i n Sweden has also been shown to enhance n i t r i f i c a t i o n i n s o i l s (Popovic, 1974), The increased flow of chemicals may cause an increase i n s o i l pH. In-creased s o i l pH, two years a f t e r c l e a r c u t t i n g i n c o a s t a l Washington, has been recorded by G r i e r (1972). The increased chemical a v a i l a b i l i t y f o l l owing c l e a r c u t t i n g may be b e n e f i c i a l i f there i s l i v i n g vegetation present to withdraw the n u t r i e n t s from the s o i l before they are leached away. Indeed, r a p i d growth of e a r l y successional species following c l e a r c u t t i n g tends to minimize n u t r i e n t losses by vigorous uptake and accumulation of the a v a i l a b l e n u t r i e n t s i n s o i l (Marks and Bormann, 1972). But i f the logging operations have des-^ troyed much of the l e s s e r vegetation or retarded regeneration then s i g n i f i -cant l o s s of n u t r i e n t s from the s o i l may occur. This l o s s w i l l be most dramatic i n areas characterized by heavy r a i n s and s o i l s with a low c a t i o n exchange capacity (Cole, 1963; Nye and Greenland,. 1960) or a high base satu r a t i o n (Grier, 1972). Pierce et-al. (1972) considered that the f o l l o w -i n g types of s o i l s are e s p e c i a l l y vulnerable to excessive n u t r i e n t losses a f t e r c l e a r c u t t i n g : a) shallow to bedrock s o i l s ; b) s o i l s which have t h i n layers o f unincorporated humus ov e r l y i n g mineral horizons; c) coarse s k e l e t a l s o i l s on steep t e r r a i n . An increased n u t r i e n t a v a i l a b i l i t y w i l l not n e c e s s a r i l y b e n e f i t p l a n t s , however, since plants have been shown-to sometimes take up exces-sive q u a n t i t i e s of n u t r i e n t s without showing a corresponding increase i n 11 growth (Baker and Phelps, 1969; Wells, 1971). The n u t r i e n t s which are rendered a v a i l a b l e may not be the f a c t o r s which are l i m i t i n g growth. S i t e f e r t i l i t y may require a sustained release of n u t r i e n t s over a long p e r i o d rather than sudden flushes of a v a i l a b i l i t y . E a r l y successional species which come i n soon a f t e r c l e a r c u t t i n g i n B.C. often include species such as Ceanothus or Atnus which have root nodules containing n i t r o g e n - f i x i n g b a c t e r i a . The n u t r i e n t - r i c h l i t t e r and through-f a l l from such species enriches the s o i l i n nitrogen as well as other nu-t r i e n t s , helping to o f f s e t any n u t r i e n t losses f o l l o w i n g c l e a r c u t t i n g (Franklin et al., 1968; Tarrant and Trappe, 1971; Tarrant et al., 1968; Tarrant et al., 1969; Zavitkovski and Newton, 1968). As yet, there appears to be no published work which d i r e c t l y measures the e f f e c t s of c l e a r c u t t i n g on the supply of chemicals to the s o i l by min-e r a l weathering. However, the Hubbard Brook workers, by observing changes i n sodium budgets of a watershed and a t t r i b u t i n g net sodium losses s o l e l y to chemical weathering, have c a l c u l a t e d that devegetation of t h e i r water-shed by c u t t i n g and herbicides increased the rate of chemical weathering of the minerals about three f o l d (Johnson et al., 1968; Likens et al. , 1970). Commercial c l e a r c u t t i n g was expected to cause a s i m i l a r but smaller increase (Bormann et al. , 1968) . In general, c l e a r c u t t i n g tends to increase the amount of chemicals moving i n s o l u t i o n through the s o i l , although to varying degrees depending on a v a r i e t y of meteorological, b i o l o g i c a l , and chemical f a c t o r s . C l e a r — c u t t i n g removes one component o f a multicomponent p l a n t community. I f the other components are not too s e r i o u s l y disturbed by the logging operations, 12 they w i l l be able to u t i l i z e any increased n u t r i e n t supplies i n the s o i l and the b i o l o g i c a l n u t r i e n t c y c l e on the s i t e w i l l remain i n operation. The degree to which c l e a r c u t t i n g leads to leaching losses of nutrients from the ecosystem w i l l depend to a considerable extent on the degree t o which the various components of the system have been disturbed. (2) E f f e c t s on l i v i n g organisms (a) Tree pathogens: disease and i n s e c t s - C l e a r c u t t i n g mature f o r e s t s i s considered by Cerezke (1971) to have an immediate devastating e f f e c t . upon many i n s e c t populations since t h e i r food source i s eliminated and t h e i r h a b i t a t destroyed or a l t e r e d . The s l a s h l e f t by c l e a r c u t t i n g i s u n l i k e l y t o cause i n s e c t pest outbreaks, as i l l u s t r a t e d by Graham and Knight (1965) who stated i n t h e i r f o r e s t entomology text (p. 173): "The general con-sensus of opinion i s that hardwood s l a s h i s almost never a breeding place f o r i n s e c t s that attack l i v i n g trees.. Even coniferous s l a s h i s not so serious a menace as has been sometimes stated. There are instances, how-ever, when i t presents important problems. As long as logging i s going on and f r e s h s l a s h i s c o n t i n u a l l y being supplied by successive operations the i n s e c t s breeding i n t h i s m a t e r i a l w i l l f i n d adequate feeding places f o r each generation. When logging operations end i n a l o c a l i t y , then the s l a s h i n s e c t s , because of a s c a r c i t y of food, may attack standing t r e e s . . . . Such outbreaks are u s u a l l y sporadic and seldom, occasion great l o s s e s . " Insects which have o c c a s i o n a l l y become serious pests a f t e r c l e a r c u t t i n g include the bark beetles (Graham and Knight, p. 330, 1965; Graham, p. 220, 1963) . Injurious logging p r a c t i c e s which scar or break the roots of r e s i d u a l trees predispose these trees to damage from i n s e c t s , p a r t i c u l a r l y from 13 bark beetles, ambrosia beetles, and root-eating weevils (Graham and Knight, p. 230, 1965). Sometimes the opening of a stand by c l e a r c u t t i n g may sub-j e c t trees to the e f f e c t s of d e s i c c a t i o n and heating of the s o i l with sub-sequent root i n j u r y and s u s c e p t i b i l i t y to bark-mining i n s e c t s (Graham, p. 220, 1963). Wi n d f a l l of "edge" trees commonly follows c l e a r c u t t i n g i n v i r -g i n f o r e s t s . The windthrown trees can provide i d e a l breeding s i t e s f o r c e r t a i n beetles, such as the Engelmann spruce beetle i n the ol d spruce-subalpine f i r f o r e s t s i n the i n t e r i o r of B.C. (Alexander, 1964; Graham and Knight, p. 340, 1965). Cerezke (1971), i n a recent l i t e r a t u r e review of the e f f e c t s of c l e a r -c u t t i n g on i n s e c t pests i n A l b e r t a , concluded that c l e a r c u t t i n g r a r e l y bene-f i t s i n s e c t populations but that i n s e c t s are favoured i f s i n g l e species f o r e s t s are developed on cl e a r c u t areas. Graham and Knight (p. 229, 1965) l i s t e d s e v e r a l i n s e c t species which, once almost unknown, have become se r -ious pests i n man-made pure stands. Cerezke (1971) l i s t e d several more. Stark (1973) disagreed, however, claiming that man-made pure stands are not n e c e s s a r i l y more prone to i n s e c t attack than na t u r a l stands. C l e a r c u t t i n g appears to have s i m i l a r e f f e c t s on f o r e s t diseases as i t has on i n s e c t pests. Thus, although s l a s h provides a substrate neces-sary f o r the development of f r u i t i n g bodies of many fungal diseases, such as those which cause damping o f f , root r o t s , stem and f o l i a g e r u s t s , and bark cankers, such diseases probably seldom cause serious m o r t a l i t y i n na-t u r a l l y regenerated areas but are more l i k e l y t o cause serious m o r t a l i t y i n a r t i f i c i a l regeneration of monocultures (Boyce, p. 515, 1961; Loman, 1971). Damping o f f diseases i n seedlings appear i n e v i t a b l e a f t e r c l e a r -c u t t i n g , although of v a r i a b l e importance (Loman, 1971). 14 Loman (1971), i n a recent literature review of the effects of clear-cutting on tree diseases i n Albertan forests, concluded that extensive clearcuts eliminate a l l forest diseases associated with mature forests. Thus, heartwood stains i n spruce (Loman, 1961) and decay i n even-aged stands of pine, spruce, and Douglas-fir are eliminated (Boyce, p. 378, 1961; Loman, 1971). Similarly, total clearcutting can remove a l l sources of dwarf mis-tletoe infection (Boyce, p. 335, 1961; Loman, 1971; Parmeter, 1973; Smith and Baranyay, 1971). Clearcutting can remove the infection sources of stem canker on lodgepole pine which a f f l i c t s immature trees (Loman, 1971). Fungi which decay slash are promoted, of course (Loman, 1971). Injuries i n f l i c t e d on trees during clearcutting operations may allow decay organisms to enter the injured trees (Boyce, p. 374, 1961). Thin-barked species such as western hemlock, sitka spruce, and true f i r s are particularly vulnerable (Wright and Isaac, 1956). After a stand i s opened up, sunscald may occur on the residual trees with decay infection often following (Boyce, p. 374, 1961). In general, however, diseases arising from clearcutting appear to be relatively unimportant. It appears that i t i s not clearcutting alone, but clearcutting together with subsequent s i l v i c u l t u r a l treatments, which w i l l determine the importance of attacks by tree diseases on trees. Boyce (p. 374, 1961) concluded that: "It i s unlikely i n most forest types that the infection of l i v i n g trees by fungi from slash w i l l be serious enough to warrant the increased expense of disposing of large c u l l material on cut-over areas, since generally the fungi causing most of the decay i n li v i n g trees are not abundant even on large slash." . Parmeter (1973) has arrived 15 at a s i m i l a r conclusion, as had Childs (1939), f o r the west coast S i t k a spruce, western hemlock, and Douglas-fir f o r e s t s . (b) S o i l micro- and meso-organisms - Changes i n s o i l temperatures, mois-ture r e l a t i o n s , and n u t r i e n t a v a i l a b i l i t y may induce changes i n numbers and species composition of s o i l organisms, as has been well documented i n Russia and Europe. Abundant evidence i s presented i n Sukachev's "Fundamentals of Forest Biogeocoenology" i l l u s t r a t i n g how c l e a r c u t t i n g can change both species num-bers and species composition of s o i l m i c r o b i a l populations (Egorova et al., 1964). Egorova (1970b) found that c l e a r c u t t i n g oak f o r e s t s i n Russia caused an increase i n the population of spore-forming b a c t e r i a i n the l i t t e r l a y e r but a decrease i n the populations of non-spore-forming b a c t e r i a , microscopic f u n g i , and actinomycetes. In the mineral s o i l , c l e a r c u t t i n g caused a de-crease i n anaerobic m i c r o b i a l a c t i v i t y but an increase i n a c t i v i t y of non-spore- forming b a c t e r i a , aerobic cellulose-decomposing b a c t e r i a , actinomy-cetes, and microscopic f u n g i . However, as oak regeneration grew up, the s o i l m i c r o f l o r a gradually reverted to t h e i r p r e - c l e a r c u t t i n g composition. The a c t i v i t y of the m i c r o f l o r a was determined p r i m a r i l y by s o i l moisture. In aspen stands Egorova (1970a) found that c l e a r c u t t i n g increased pop-u l a t i o n s of b a c t e r i a and actinomycetes and s i g n i f i c a n t l y a f f e c t e d the microscopic fungal populations. In c e n t r a l Europe, Gretschy (1949) found that arthropod abundance f e l l t o h a l f the o r i g i n a l value soon a f t e r c l e a r c u t t i n g with the types and proportions of species remaining unchanged. Three years a f t e r 16 c u t t i n g , the abundance had decreased s t i l l more and the species composition had changed as w e l l . Moritz (1965) found that c l e a r c u t t i n g caused no change i n the species composition of O r i b a t i d s although abundance r e l a t i o n s changed, with some of the l e s s numerous pre-logging species becoming dom-inants . In the northeastern U.S., one study found higher nematode populations on c l e a r c u t than on forested areas (Shigo and Yelenosky, 1960) and the Hub-bard Brook study (Likens et al., 1969; Pierce et al., 1972; Smith et al., 1968 suggests that c l e a r c u t t i n g the deciduous hardwood f o r e s t s of that r e -gion increases the abundance of n i t r i f y i n g b a c t e r i a and probably decreases the abundance of sulphur-oxidizing b a c t e r i a . I t was considered (Smith et al., 1968) that the increased abundance of n i t r i f y i n g b a c t e r i a was probably due to one or more of: enhanced a v a i l a b i l i t y of ammonium ions r e s u l t i n g from increased heterotrophic a c t i v i t y ; e l i m i n a t i o n of n u t r i e n t uptake by vegetation, and removal of d i r e c t e f f e c t s such as i n h i b i t i o n of chemauto-trophs by substances produced by the vegetation. A decrease i n abundance of sulphur-oxidizing b a c t e r i a was considered most l i k e l y due to high n i -t r a t e concentrations being t o x i c to these b a c t e r i a (Likens et al., 1970). C l e a r c u t t i n g has been found to have l i t t l e or no deleterious e f f e c t s on mycorrhizal fungi or on the formation of mycorrhizae (Wilde, 1968). Vlug (1972) found that c l e a r c u t t i n g i n the U n i v e r s i t y of B.C. Research Forest, near Haney, severely reduced the population d e n s i t i e s of a l l a r t h r o -pods and of both Collembola and A c a r i although recovery was s i g n i f i c a n t a f t e r only two years. D i f f e r e n t taxa were a f f e c t e d by logging i n a v a r i e t y of ways. 17 Micro- and meso-organisms are p r i m a r i l y responsible f o r the mineral-i z a t i o n of n u t r i e n t s and t h e i r r e t u r n to the s o i l and, consequently, they are d i r e c t l y involved i n s o i l p r o d u c t i v i t y . C l e a r c u t t i n g has quite v a r i a b l e e f f e c t s on populations of these organisms. None of these e f f e c t s , however, has been shown to i n t e r f e r e with r e f o r e s t a t i o n of cleared areas and micro-b i a l populations u s u a l l y return to the p r e - c u t t i n g balance as the new f o r -est develops (Egorova et ali, 1964). In some cases, c l e a r c u t t i n g has l e d t o a marked increase i n m i c r o b i a l a c t i v i t y with concomitant increases i n n u t r i e n t a v a i l a b i l i t y . However, the Hubbard Brook study has shown that increased abundance of microbes w i l l not n e c e s s a r i l y increase long-term s o i l p r o d u c t i v i t y because increases i n numbers of n i t r i f y i n g b a c t e r i a r e -s u l t e d i n considerable l o s s of n u t r i e n t s from the s o i l (Likens et at., 1970; Pierce et at., 1972). (c) Vertebrates 1. Large animals - Animals depend on vegetation f o r food and cover and are thus a f f e c t e d by tree removal i n various ways. C l e a r c u t t i n g r a r e l y causes d i r e c t l o s s of w i l d l i f e . I t i s thought to have three major e f f e c t s on p o t e n t i a l forage p l a n t s : a s h i f t i n p l a n t composition favouring grasses, herbs, and shrubs c h a r a c t e r i s t i c of e a r l y successional stages, an increase i n n u t r i e n t q u a l i t y , and an increase i n dry-matter production (Basile and Jensen, 1971; Taber, 1973; T e l f e r , 1972). However, t h i s does not always oc-cur as some studies have found that n u t r i e n t q u a l i t y of forage i s sometimes higher i n mature f o r e s t (Brown, 1961; Gates, 1968). In a recent review, Taber (1973) concluded that the e f f e c t of c l e a r c u t t i n g c o a s t a l Douglas-fir f o r e s t s i s to cause a slow r i s e i n n u t r i e n t q u a l i t y of the succeeding vege-t a t i o n over a period of about ten years. He a l s o concluded that although 18 the dietaxy q u a l i t y of forage r i s e s a f t e r c l e a r c u t t i n g , the extent of the r i s e and i t s r e l a t i o n to time, s i t e , and s i l v i c u l t u r a l treatments are s t i l l not completely understood. The increased q u a l i t y and quantity of food has been frequently used as evidence that c l e a r c u t t i n g b e n e f i t s animals (e.g. Hooven 1973a; Regelin et al., 1974; Resler, 1974). There i s much evidence to suggest that a n i -mals such as deer, moose, and elk, which are adapted to e a r l y successional stages do i n f a c t b e n e f i t from c l e a r c u t t i n g (Hooven, 1973a; Resler, 1972; T e l f e r , 1972). However, a n a l y s i s of the l i t e r a t u r e by Taber (1973) and Pengelly (1972) i n d i c a t e d that, while t h i s may be true i n some cases, i t -cannot be accepted as a g e n e r a l i z a t i o n . Taber (1973) pointed out that the seasonal home ranges of deer and w a p i t i are r e l a t i v e l y small so that a c l e a r c u t i s l i k e l y to a t t r a c t only those animals i n whose home range i t l i e s . Pengelly (1972) questioned the accuracy of published data, wonder-ing whether more animals can be seen i n a c l e a r c u t only because they are more r e a d i l y v i s i b l e and whether or not they were the same animals which formerly l i v e d unobserved i n the v i c i n i t y . He also pointed out that food may not always be the l i m i t i n g f a c t o r f o r animal populations. Where i t i s not the l i m i t i n g f a c t o r , then forage production may be at the expense of cover and freedom from harassment. Behavioural l i m i t s of an animal may take over long before food shortages occur and w h i t e - t a i l e d deer, f o r ex-ample, frequently s e l e c t cover i n preference to food. Also, increased snow accumulation on c l e a r c u t s may s t r e s s animals i n winter (Pengelly, 1972). Pengelly i s supported by one of the p r i n c i p a l deer researchers who has stated t h a t : " c l e a r c u t t i n g has been considered one of the best ways to improve deer h a b i t a t .... Beyond the knowledge that c l e a r c u t t i n g should 19 produce good hab i t a t , very l i t t l e i s known about the influences of f o r e s t p r a c t i c e s on deer ecology. Much i s assumed, but few f a c t s are a v a i l a b l e to back up the assumptions." (Crouch, 1969). I t i s g e n e r a l l y considered (Hooven, 1973a; Pengelly, 1972; Resler, 1972; Taber, 1973) that small c l e a r c u t s , by providing more ecotone, are more b e n e f i c i a l to w i l d l i f e than are large c l e a r c u t s . While there i s argument about the merits of c l e a r c u t t i n g for animals such as deer and elk, i t appears that animals such as martens, f i s h e r s , and wolverines, which are adapted to mature f o r e s t s , almost always s u f f e r from c l e a r c u t t i n g (Ahlgren and Ahlgren, 1960; Grakov, 1972; Lutz, 1956). Caribou, which depend to a considerable extent on tree lichens f o r winter food (Lutz, 1956; Cowan and Guiget, ) w i l l probably s u f f e r i f c l e a r -c u t t i n g removes the v a l l e y bottom f o r e s t s and associated l i c h e n s . 2. Small mammals - These depend f o r food upon seeds, herbs, or i n -sects, and f o r cover upon the vegetation c l o s e to the surface and the l i t t e r l a y e r . C l e a r c u t t i n g a f f e c t s both t h e i r food supply and cover i n v a r i a b l e ways and w i l l thus have v a r i a b l e e f f e c t s on t h e i r populations. In Washington and Oregon, populations of red backed vo l e s , s q u i r r e l s , lagomorphs, and chipmunks de c l i n e a f t e r - c l e a r c u t t i n g . Shrew populations also decrease i f s l a s h i s l e f t on the c l e a r c u t s , but increase on older c l e a r c u t s with dense shrubby vegetation. However, mountain beaver, deer mice, and several types of voles increase a f t e r c l e a r c u t t i n g (Hooven, 1973a,b) . Porcupine (Resler, 1972) and pocket gophers (Barnes, 1971; Resler, 1972) are a l s o reported to be favoured by c l e a r c u t t i n g . The reasons f o r these changes are not a l l known since the p a r t i c u l a r requirements of many small mammal species are unknown and i t i s d i f f i c u l t 20 to evaluate t h e i r f o r e s t h a b i t a t requirements. The d i f f i c u l t y i s furt h e r increased because many populations of small mammals appear c y c l i c or vary sharply from year to year f o r unknown reasons (Hooven, 1973b). Very low temperatures decrease the overwintering s u r v i v a l r a t e of small mammals so that c l e a r c u t t i n g , by exposing the s o i l surface to lower tempera-tures i n winter, may, during snowless winters, lower the s u r v i v a l rate of some animals (Hooven, 1973b). Hooven (1973b) concluded t h a t : " a f t e r c l e a r c u t t i n g , regardless of the change-of species composition and d e n s i t i e s , the small mammal biomass r e -mains comparable to that of the uncut f o r e s t and exerts.the same detrimental e f f e c t upon regeneration". 3. B i r d s - Because some b i r d species evolved to l i v e i n mature f o r -ests while others depend on disturbed s i t e s and e a r l y successional stages, c l e a r c u t t i n g a f f e c t s b i r d populations i n d i f f e r e n t ways. Hagar (1960), studying c l e a r c u t s i n Douglas-fir f o r e s t s i n northwes-tern C a l i f o r n i a , found that logging a l t e r e d the composition of the b i r d population and l e d to a temporary decline i n o v e r a l l numbers. Former num-bers were regained w i t h i n a year a f t e r c u t t i n g although the species compo-s i t i o n was d i f f e r e n t . A f t e r a comprehensive d i s c u s s i o n of the r e l a t i o n s h i p s between b i r d s , f o r e s t s , and f o r e s t management i n A u s t r a l i a , Cowley (1971) concluded that c l e a r c u t t i n g does not destory b i r d h a b i t a t but simply changes i t to the advantage of some species and to the disadvantage of others. In conclusion, a l l that can accurately be said about the e f f e c t of c l e a r c u t t i n g on w i l d l i f e i s that: "some c l e a r c u t logging b e n e f i t s some species of w i l d l i f e i n some areas some of the time" (Pengelly, 1972). 21 (d) Vegetation - C l e a r c u t t i n g favours the growth of grasses, herbs, and shrubs by r e v e r t i n g the ecosystem back to an e a r l i e r successional stage. The degree of s i t e disturbance caused by c l e a r c u t t i n g operations i s l i k e l y t o determine the p a r t i c u l a r s e r a i stage to which the ecosystem i s reverted, with the more severe types of disturbance favouring the e a r l i e r stages (Kimmins, 1972). Thus, Dyrness (1966 and 1973) found that the de-gree of disturbance and s l a s h d i s p o s a l had more influence on the composition of the subsequent pioneer vegetation than d i d the species composition of the undisturbed f o r e s t ; some pre-logging species could s t i l l be found a f t e r logging, however. On r i c h e r s i t e s , growth of pioneer species may be so great that succession i s delayed due to the severe competition faced by t r e e seedlings. Salmonberry and red alder i n c o a s t a l B.C. are examples of pioneer species which may take over a s i t e (Franklin and DeBell, 1973; Isaac, 1940). When the tree species desired by f o r e s t e r s experiences such competition and cannot grow s u c c e s s f u l l y , then the y i e l d of the s i t e , from the f o r e s t e r ' s p o i n t of view, i s lowered. The f o l l o w i n g review of the e f f e c t s of c l e a r c u t t i n g on trees w i l l be l i m i t e d to the trees of the lower e l e v a t i o n f o r e s t s of south c o a s t a l B.C. These f o r e s t s l i e i n Krajina's Coastal Douglas-fir and Coastal Western Hem-lock biogeoclimatic zones of B.C. (Krajina, 1959, 1965 and 1969; K r a j i n a and Brooke, 1970) and contain mainly S i t k a spruce, D o u g l a s - f i r , western hemlock, and western red cedar, with l e s s e r amounts of grand f i r , western white pine, red alder, b i g l e a f maple, and other deciduous species. Douglas-f i r and western hemlock are the most important commercial species and are the only two which w i l l be considered i n d e t a i l . 22 1. Douglas-fir - Coastal Douglas-fir requires moderate temperatures and mesic s o i l s . I t i s intermediate i n shade tolerance but demands more l i g h t than most of i t s a s s o c i a t e s . I t prefers mineral s o i l seedbeds and new seedlings b e n e f i t from l i g h t shade. Once esta b l i s h e d , however, i t grows best i n f u l l s unlight (Fowells, 1965; Williamson, 1973). In the x e r i c to mesic s i t e s of the Coastal Douglas-fir zone and the x e r i c s i t e s of the Coastal Western Hemlock zone, Douglas-fir i s rather shade t o l e r a n t (Krajina, 1969) so that c l e a r c u t t i n g , p a r t i c u l a r l y followed by s l a s h d i s p o s a l , would probably not provide the optimum conditions f o r Douglas-fir regeneration. F a i l u r e of Douglas-fir regeneration on c l e a r c u t s of the more severe s i t e s has been noted (Franklin, 1963; F r a n k l i n and DeBell, 1973; Isaac, 1938; Isaac, 1963) and although most f o r e s t e r s p r e s c r i b e c l e a r -c u t t i n g for o l d growth Douglas-fir f o r e s t s (D e l l and Green, 1968; D u f f i e l d and Davis, 1971; Gilmour, 1970; Smith, 1962) several workers have advocated the use of shelterwood cuttings (Franklin, 1963; F r a n k l i n and DeBell, 1973; Garman, 1955; Starker, 1970; Wylie, 1960). Smith (1971), with reference to Washington and Oregon, has stated t h a t : "In most instances the o p t i -mum environment f o r young Douglas-firs i s found underneath p a r t i a l shade.... complete exposure i s u s u a l l y detrimental to regeneration of Douglas-fir on many s i t e s . " He considered that shelterwood c u t t i n g , rather than c l e a r -c u t t i n g , most c l o s e l y imitated the n a t u r a l processes leading to the eco-l o g i c a l optimum f o r Douglas-fir on each s i t e . However, p l a n t i n g seedlings can often overcome the disadvantages caused to Douglas-fir regeneration by c l e a r c u t t i n g . In the U.S., shelterwood c u t t i n g appears t o be very slowly r e p l a c i n g c l e a r c u t t i n g of D o u g l a s - f i r , f o r s i l v i c u l t u r a l reasons among others (Williamson, 1973). 23 In Krajina's Coastal Douglas-fir and Coastal Western Hemlock zones, there i s some p l a n t i n g of S i t k a spruce i n the low elevation wetter s i t e s and western hemlock i n the higher e l e v a t i o n s i t e s , but the great majority of the f o r e s t s i n these zones i s managed f o r D o u g l a s - f i r . D o u g l a s - f i r i s a pioneer species on a l l of the moist s i t e s except fo r a few with r i c h s o i l s derived from b a s a l t or d i o r i t e , on which i t i s more p e r s i s t e n t (Krajina, 1969). C l e a r c u t t i n g i s v i r t u a l l y the only pre-s c r i b e d c u t t i n g method and u s u a l l y succeeds i n promoting Douglas-fir i n i t i a l l y a t the'expense of i t s more shade t o l e r a n t t r e e competitors, but these u s u a l l y restock the c l e a r c u t area i n due course (Franklin and DeBell, 1973; Mueller-Dombois, I960; Osborn, 1968; Williamson, 1973). On the wetter, but n u t r i t i o n a l l y poorer s i t e s where western hemlock has a competitive advantage (Krajina, 1969), c l e a r c u t t i n g may favour Douglas-f i r i n i t i a l l y . Western hemlock, however, may eventually take over such s i t e s with the r e s u l t that any investment i n p l a n t i n g Douglas-fir or i n s l a s h treatment w i l l be l o s t . C l e a r c u t t i n g i s not always b e n e f i c i a l to western hemlock, as discussed below, so that i t s growth might be retarded f o r some time although i t w i l l eventually dominate (V.J. K r a j i n a , Depart-ment of Botany, U n i v e r s i t y of B.C.: Personal communication). With regard t o Douglas-fir regeneration, i t has been stated (Franklin and DeBell, 1973) t h a t : "Almost a l l c l e a r c u t t i n g and p a r t i a l c u t t i n g meth-ods, excepting only true s e l e c t i o n techniques, have proved b i o l o g i c a l l y s u i t -able f o r regeneration of f o r e s t s of Douglas-fir .... On the majority of f o r e s t s i t e s , these large c l e a r c u t t i n g s have been remarkably s u c c e s s f u l . They are i n no way b i o l o g i c a l l y e s s e n t i a l f o r regenerating even-aged stands of Douglas-fir, however." 24 2. Western hemlock - Western hemlock i s becoming an i n c r e a s i n g l y important commercial species. I t i s very shade t o l e r a n t and regenerates both on mineral s o i l and organic seedbeds (Bernsten, 1955; Fowells, 1965; Harmon, 1963). I t i s d i f f i c u l t to e s t a b l i s h a r t i f i c i a l l y and regenera-t i o n from c l e a r c u t t i n g i s not always s u c c e s s f u l , t h i s being a t t r i b u t e d to d e s i c c a t i o n i n summer or f r o s t heaving i n winter (Osborn, 1968; Ruth, 1968; Soos and Walters, 1963). P a r t i a l shading of seedlings i s considered de-s i r a b l e since sun-scorching may occur under severe conditions (Fowells, 1965; Harmon, 1963; Soos and Walters, 1963). K e l l e r (1973) found that western hemlock advanced regeneration i n f o r e s t s i s adapted to low l i g h t i n t e n s i t i e s and exposure of these trees to sunlight as, f o r example, by c l e a r c u t t i n g , often causes i n j u r y or death from scorching. I t s low demand f o r nu t r i e n t s and i t s a b i l i t y to t o l e r a t e shade render hemlock s u i t a b l e f o r many forms of management. In f a c t , i t has been suc-c e s s f u l l y regenerated by a l l c u t t i n g methods (Franklin and DeBell, 1973; Ruth and H a r r i s , 1973). Due t o i t s shallow-rooted nature and i t s se n s i -t i v i t y to exposure, i t b e n e f i t s from mixtures with Dou g l a s - f i r , S i t k a spruce, or amabilis f i r (Anderson, 1956, K r a j i n a , 1954) and shelterwood c u t t i n g has often been advocated (Fowells, 1965; Herman, 1962; Osborn, 1967; Ruth and H a r r i s , 1973; Williamson, 1966), i n some cases with hemlock occupying the lower story and Do u g l a s - f i r , amabilis f i r , or S i t k a spruce the upper story i n two story mixed f o r e s t s (Osborn, 1968; Wylie, 1960). I t i s commonly i n f e c t e d with dwarf mistletoe i n which case the only c u t t i n g system which appears t o prevent serious attacks on regeneration i s c l e a r c u t t i n g (Buckland and Marples, 1952; -Ruth and Har r i s , 1973). I t i s a l s o very susceptible to logging i n j u r y with decay s e t t i n g i n r a p i d l y , which favours c l e a r c u t t i n g oyer p a r t i a l c u t t i n g methods (Shea, 1960). 25 The s i l v i c a l c h a r a c t e r i s t i c s and regeneration requirements of both Douglas-fir and western hemlock suggest using a c u t t i n g method which pro-duces even-aged stands, i . e . c l e a r c u t t i n g , seed-tree, or shelterwood cut-t i n g methods. Any of these methods may be used depending on s i t e and/or requirements. In summary, from a s i l v i c u l t u r a l standpoint, excluding ec-onomic arguments, c l e a r c u t t i n g often appears to be the best harvesting method, but not always. (3) E f f e c t s on streams and aquatic ecosystems (a) Streamflow - By reducing evapotranspiration and canopy i n t e r c e p t i o n losses, t r e e removal u s u a l l y causes increased streamflow and may a l s o de-crease the response time of a stream to p r e c i p i t a t i o n , the e f f e c t s being most pronounced during the growing season (Anderson and Hobba, 1959; G i l -mour, 1971; Hewlett and Hibbert, 1967; Hewlett and Melvey, 1970; Hornbeck, 1973; Hornbeck et al. , 1970; L u l l and Reinhart, 1972; Nakano, 1967; P a t r i c , 1973; Rothacher, 1971; Sopper and Lynch, .1970). Hibbert (1967), summariz-ing the r e s u l t s of many watershed c u t t i n g experiments, found that the r e -sponse of streamflow to c l e a r c u t t i n g v a r i e d g r e a t l y and was u s u a l l y unpre-d i c t a b l e . However, f o r humid regions, the increase i n streamflow a f t e r c l e a r c u t t i n g was p r o p o r t i o n a l to the percentage of the watershed area cut with an apparent upper l i m i t of y i e l d increase about 4.5 mm per year f o r each percent reduction i n f o r e s t cover. The seasonal d i s t r i b u t i o n of streamflow response to c l e a r c u t t i n g was v a r i a b l e . The response i n stream-flow appeared almost immediately or some time l a t e r , depending on climate, s o i l s , topography, and other f a c t o r s . Snowmelt i s also a f f e c t e d by c l e a r c u t t i n g . In general, the removal of vegetation causes an increase i n the snowpack followed by more r a p i d 26 melting i n the spring (Anderson, 1967; Bay, 1958; Berndt, 1965; Berndt and Swank, 1970; Goodell, 1958; Hornbeck, 1973; L u l l and Reinhart, 1972; Roth-acher, 1965). This may be modified by aspect (Haupt, 1972) and the extent and o r i e n t a t i o n of the cutover areas, as well as by climate (Anderson, 1971; L u l l and Reinhart, 1972; Satterlund and Haupt, 1972)- Anderson and Glea-son (1960) found that, by absorbing s o l a r r a d i a t i o n , slash increased the melting r a t e of snow compared to areas i n which s l a s h had been removed by burning. The e f f e c t of snowmelt on peak flows i s v a r i a b l e although i t ap-pears that c l e a r c u t t i n g may increase peak flows i n the e a r l y part of the snowmelt season but reduce them i n the l a t t e r part ( L u l l and Reinhart, 1972). Increased f l o o d flows may be detrimental to f i s h through scouring of spawning beds. However, increased low flows i n summer may be b e n e f i c i a l to f i s h by i n c r e a s i n g the space a v a i l a b l e to them i n streams (Chapman, 1962). (b) Sediment load - Increased flows of water from land to streams, to-gether with l o s s of p r o t e c t i v e vegetative cover, may increase removal of s o i l from t e r r e s t r i a l to aquatic ecosystems, as w e l l as a c c e l e r a t i n g stream-bed and bank erosion. This increases sediment loads i n streams, as has been frequently observed a f t e r logging (Anderson, 1954; Anderson, 1971; Burns, 1972; Megahan and Kidd, 1972; Narver, 1972; Reinhart and Eschner, 1962; Swanston, 1971). The break-up of logging-caused debris jams with subsequent f l o o d surges i s another major source of sediment (Curry, 1973; F r o e h l i c h , 1971). I t appears that most of the stream sediment associated with c l e a r -c u t t i n g o r i g i n a t e s from road construction (Anderson, 1954; Anderson, 1971; Brown and Krygier, 1971; D i l s , 1957; Fredriksen, 1965; Fredriksen, 1970; 27 Megahan, 1972; Megahan and Kidd, 1972; Packer, 1967; Reinhart and Eschner, 1962; Swanston, 1971b). In coastal Oregon, Brown and Krygier (1971) found that clearcutting produced l i t t l e or no change i n sediment concentrations i n streams whereas road construction and slashburning both produced s i g n i f i -cant increases. Well controlled clearcutting may cause no significant i n -crease i n stream sediment concentrations (Jeffrey and Goodell, 1970; Leaf, 1966; Reinhart and Eschner, 1962). Thus, stream sediment load i s closely correlated with the quality of timber harvesting practices and roads and log-ging skid t r a i l s are the main sources of sediment. The degree of stream sedimentation depends on the type of logging but tends to increase with increasing slopes, and the duration of sedimentation depends on the rate of revegetation, other factors being equal (Dyrness, 1967; Rice et al. , 1972) . Cordone and Kelley (1961), Chapman (1962), Gibbons and Salo (1973), and Phi l l i p s (1971) have reviewed the effects of sediment on aquatic l i f e . High sediment levels may have detrimental effects on adult fi s h , develop-ment of eggs and alevins, production of aquatic plants and f i s h food organ-isms. High turbidity levels may: prevent adults from spawning or cause death where concentrations are high and exposure prolonged; destroy spawn-ing beds; smother eggs reducing their supply of oxygen and interfering with the removal of potentially.toxic metabolites; prevent fry from emerging into the stream; decrease the abundance of fi s h food organisms; and i n -duce changes i n the species composition of fish communities. It has re-cently been shown (Bustard, 1973) that f i s h i n coastal B.C. streams pre-fer clean gravel to sedimented gravel streambeds. 28 These e f f e c t s may be p a r t i c u l a r l y s i g n i f i c a n t since many of the small streams flowing through forested areas c o n s t i t u t e the spawning areas f o r f i s h . (c) Logging debris - C l e a r c u t t i n g nearly always deposits debris i n streams although t h i s can be minimized by taking simple precautions (Burwell, 1971; Rothwell, 1971; U.S. Department of the I n t e r i o r , 1970). Debris deposited i n f i s h bearing streams can i n t e r f e r e with migration of adults and juven-i l e f i s h , temporarily reduce pool habitat, reduce oxygen concentrations i n surface and i n t r a g r a v e l water, and can impair the q u a l i t y of spawning gravel (Narver, 1971). In a d d i t i o n , debris l e f t i n stream channels during spring peak flows may cause scouring and d i v e r s i o n , i n c r e a s i n g stream sedimentation and decreasing f i s h populations (Elser, 1968; Narver, 1971). S e r v i z i et dl. (1971) found that high bark concentrations i n streams i n southern B.C. allowed abundant growth of a filamentous b a c t e r i a on f r e s h l y decaying bark. T h i s b a c t e r i a caused severe m o r t a l i t y of f i s h embryos and a l e v i n s due to s u f f o c a t i o n . On the other hand, debris accumulations may provide good winter cover f o r coho and t r o u t , and may thus provide favourable f i s h h abitat, providing the accumulations are s t a b l e and are not flushed away by freshets (Bustard, 1973; Hartman, 1968). By covering a stream, debris may prevent excessive r i s e s i n stream temperatures during summer (Levno and Rothacher, 1969). (d) Stream temperature — The removal of vegetation, p a r t i c u l a r l y stream-bank vegetation, from watersheds u s u a l l y causes a r i s e i n stream tempera-ture during the summer (Brown, 1969; Brown and Krygier, 1970; Brown et dl., 1971; Burns, 1972; Gray and Edgington, 1969; Greene, 1950, H a l l , 1967; Levno and Rothacher, 1967; Meehan et dl. , 1969; Narver, 1972; Patton, 1973; 29 Swift and Baker, 1973; Swift and Messer, 1971; Titcomb, 1926) and a de-crease during winter (Greene, 1950). The magnitude of the temperature i n -crease depends on the s i z e of the stream, being greater f o r small streams, other f a c t o r s being equal. Downstream e f f e c t s are complex, depending on a i r temperatures, stream cover, and temperature and s i z e of t r i b u t a r y streams (Brown et al., 1971; Gray and Edgington, 1969; Greene, 1950; Levno and Rothacher,. 1967). The r e t e n t i o n of streamside vegetation, even shrubs on small streams, tends to minimize any temperature changes following c l e a r -c u t t i n g (Brown, 1969; Brown and Krygier, 1970; Brown et al., 1971; Burns, 1972; Lantz, 1971; Reinhart et al., 1963; Swift and Baker, 1973). Chapman (1962) and Lantz (1971a) have reviewed the influences of wa-t e r temperature on f i s h . Increased or decreased temperatures during the early stages of embryonic development can modify several p h y s i c a l charac-t e r i s t i c s of f i s h . Increased temperatures may cause gaseous nitrogen to come out of s o l u t i o n , supersaturating the water with nitrogen and causing symptoms i n f i s h s i m i l a r to the "bends" i n man. Increased temperature a l s o increases the v i r u l e n c e of many f i s h diseases, increases the t o x i c i t y of many chemicals to f i s h , lowers the amount of oxygen d i s s o l v e d i n streams, and enhances the decay of organic material present, f u r t h e r decreasing d i s -solved oxygen l e v e l s . Behavioural and p h y s i o l o g i c a l changes i n f i s h may occur which prevent them from migrating i n t o t h e i r spawning r i v e r s . De-creased winter temperatures may extend the incubation period f o r autumn-or winter-spawning f i s h , i n c r e a s i n g the l i k e l i h o o d of exposure of embryos to severe f l o o d or unfavourable i n t r a g r a v e l water conditions. Extension of f r y emergence beyond normal periods may increase losses to predators and decrease i n i t i a l growth. 30 Although the e f f e c t s of c l e a r c u t t i n g were not separated from those of slashburning, H a l l and Lantz (1969) i n Oregon found that c l e a r c u t t i n g and slashburning a small watershed s i g n i f i c a n t l y reduced the number of reside n t f i s h i n the stream, but had l i t t l e i n i t i a l e f f e c t on numbers of coho salmon. On Vancouver Island, steelhead numbers have been found to be greater i n sections of a stream flowing through f o r e s t rather than i n sec-tions flowing through c l e a r c u t s (Narver, 1972). Increased summer stream temperatures can be b e n e f i c i a l to f i s h i n some instances. Cold streams, shaded by dense f o r e s t canopies, are not optimum t r o u t h a b i t a t (White and Brynildson, 1967). Thus, increased stream temper-atures may speed up the l a t e stages of embryonic development, r e s u l t i n g i n e a r l i e r emergence (Narver, 1972). Increased temperatures may a l s o increase the production of b a c t e r i a , algae, and the i n s e c t s upon which f i s h feed (Burns, 1972; Krammes and Burns, 1973). F i s h growth, however, i s rather complicated, depending on the balance between food production and environ-mental c o n d i t i o n s . For example, increased stream temperatures w i l l decrease f i s h growth i f food production remains the same or i s lowered (Brett et at., 1969). (e) Inorganic n u t r i e n t chemicals - When c l e a r c u t t i n g increases the flow of chemicals through the s o i l , as discussed above, increased chemical concentra-ti o n s i n streams can be expected. This has now been w e l l documented, par-t i c u l a r l y from the numerous papers d e s c r i b i n g experiments at Hubbard Brook Ce.g. Bormannet al,, 1968, Hornbeck et at., 1973; Likens et at., 1970; Pierce et at., 1972), and b r i e f reviews of t h i s f i e l d have r e c e n t l y appeared (Gibbons and Salo, 1973; Rothacher, 1970; Tarrant, 1970). 31 Fredriksen (1971), i n Oregon, found that c l e a r c u t t i n g l e d to a s l i g h t increase i n chemical concentrations i n streamwater whereas slashburning caused a much greater increase. Another study i n Oregon (Brown et at., 1973) found increased potassium and n i t r a t e concentrations and unchanged phosphorus concentrations i n a stream following c l e a r c u t t i n g and burning, but the e f f e c t s of c l e a r c u t t i n g were not separated from those of burning. In the same study another watershed which was 25% patch cut and had only one of i t s three c l e a r c u t u n i t s slashburned, showed no change i n concen-t r a t i o n s or y i e l d s of n i t r a t e , potassium, or phosphorus a f t e r logging. The Hubbard Brook workers (Likens et at., 1970; Pierce et at., 1972) have found n u t r i e n t chemical concentrations and y i e l d s to be greatest the second year a f t e r c u t t i n g and to extend f o r a t l e a s t three years following c l e a r c u t t i n g , despite vegetation regrowth. Fredriksen et at. (1973) found s i m i l a r delays i n peak concentrations and y i e l d s and considered that where revegetation i s r a p i d , as on the Oregon coast, increased chemical concentra-tions i n streams following c l e a r c u t t i n g may not p e r s i s t f o r more than seven years. However, t h e i r data show streamwater n i t r a t e concentrations, f o l -lowing c l e a r c u t t i n g and burning i n the H.J. Andrews experimental f o r e s t i n Oregon, to be s t i l l above pre-logging l e v e l s s i x years a f t e r completion of c l e a r c u t t i n g . The Hubbard Brook workers (Pierce et at. , 1972) found that c l e a r c u t s made during the summer months had greater t o t a l loss of chemical n u t r i e n t s i n streams than d i d autumn c l e a r c u t t i n g s . This was a t t r i b u t e d to the ex-tended exposure of the s i t e f o l l owing a summer c l e a r c u t t i n g since, regard-l e s s of c u t t i n g time, vegetation d i d not become established u n t i l the f o l -lowing growing season. Another study at Hubbard Brook (Hornbeck et at.s 32 1973) compared streamwater chemical concentrations and yields in a stream from a clearcut watershed to another which had one-third of i t s area clear-cut i n strips. Both cutting treatments increased chemical concentrations i n streamwater but the s t r i p cutting did this to a lesser extent. The Hubbard Brook workers have generally shown that, for the ecosys-tems they studied, clearcutting caused decreases i n pH, and increases in the concentrations of a l l the major ions except ammonium, sulphate, and bicarbonate ions. Nitrate increases were the most spectacular due to the enhanced activity of n i t r i f y i n g bacteria, as discussed above. Sulphate concentrations decreased after cutting, which has been attributed (1) to an increase i n the volume of water discharged, and (2) to either the elim-ination of sulphate producing sources within the system due to the toxicity of high nitrate concentrations to sulphur-oxidizing bacteria, and/or i n -creased reduction of sulphate to sulphide under the more anaerobic condi-tions prevailing i n the s o i l after cutting (Hornbeck et at., 1973; Likens et at., 1970). It was also found that nitrate concentrations i n stream-water after clearcutting peaked earlier in autumn. Clearcutting, followed by burning i n Oregon, increased streamwater nitrate concentrations but to a lesser extent than at Hubbard Brook and caused no apparent change in the seasonal distribution of streamwater nitrate concentrations (Brown et at., 1973; Fredriksen, .1971). Partial clearcutting, in strips at Hubbard Brook (Hornbeck et at., 1973), or patches i n Oregon (Brown et at., 1973) as well as shelterwood cutting i n Oregon (Fredriksen et at., 1973) have been shown to cause smaller changes i n streamwater chemistry than extensive clearcutting. This i s partly due to the fact that smaller proportions of the watersheds were affected by 33 c u t t i n g and p a r t l y because the area that was l e f t unlogged could reduce the e f f e c t s of the logging on streams. Thus, p l a n t roots could take up n u t r i e n t s leached out of the logged areas, and p r o t e c t i o n of the cut areas from excess heat by a surrounding f o r e s t could reduce the rate of decom-p o s i t i o n of s l a s h and hence the a v a i l a b i l i t y of n u t r i e n t s on the cutover areas (Hornbeck et al., 1973). In Sweden, c l e a r c u t t i n g has a l s o been found to increase nitrogen and potassium concentrations i n streamwater (Wiklander, 1974). In contrast t o the previous studies, Verry (1973) found no change i n concentrations of chemicals i n a stream f o l l o w i n g c l e a r c u t t i n g of a l l as-pen i n a mixed aspen-black spruce bog watershed. He considered that t h i s might be due to slow decay rates caused by a cool climate, n u t r i e n t uptake by vigorous regeneration, shading of the s o i l surface by the regeneration, a high s o i l c a t i o n exchange capacity, absorption of excess n u t r i e n t s by the bog and i t s organisms, or the low r e l i e f of the watershed. A study of c l e a r c u t and h i g h l y disturbed watersheds a t Coweeta, i n the eastern U.S., found th a t n u t r i e n t f l u x e s i n streams flowing from h i g h l y disturbed watersheds were not very d i f f e r e n t to the f l u x e s from an undis-turbed watershed nearby (Johnson and Swank, 1971 and 1973). However, the stream chemistry was only studied some t h i r t y years a f t e r the various t r e a t -ments began so the i n i t i a l e f f e c t s of the c u t t i n g on stream chemistry are unknown. Ions r e a d i l y attach themselves t o f i n e sediment p a r t i c l e s so t h a t l o s s of s o i l from an area may increase chemical losses from that area (Grissinger and McDowell, 1970) . Although Kennedy (1965) found th a t the r a t i o of ad-sorbed cations to those i n s o l u t i o n can be greater than one, watershed 34 studies at. Coweeta have found that over 98% of the amounts of each of c a l -cium, magnesium, potassium, and sodium i n streams was i n d i s s o l v e d form (Johnson and Swank, 1971 and 1973). Streams a l s o remove chemicals which are i n immobile forms within s e d i -ment p a r t i c l e s . At Hubbard Brook i t was found that s o l u t i o n losses, how-ever, accounted f o r more than 94% of the annual losses i n streams of a l l the common elements except potassium and s i l i c o n , where the f i g u r e was about 80%, and aluminium, where the f i g u r e was 72% (Bormann et al., 1969). Fred-r i k s e n et al. (1973) considered that chemical losses v i a s o i l erosion are important i n watersheds with steep slopes and Fredriksen (1971) found tha t more than h a l f the amount of nitrogen l o s t from a watershed following c l e a r -c u t t i n g and slashburning was organic nitrogen contained i n sediment. C r i s p (1966) studied n u t r i e n t losses i n d i s s o l v e d and p a r t i c u l a t e forms i n a stream dr a i n i n g a peaty watershed used f o r sheep grazing. From h i s data i t can be c a l c u l a t e d that losses i n d i s s o l v e d form accounted f o r 99% of the sodium, 92% of the calcium, 81% of the potassium, 47% of the phosphorus, and 17% of the nitrogen l o s t annually. These studies suggest that lo s s of the non-metallic n u t r i e n t elements from a watershed may be s i g n i f i c a n t i f the stream flowing from the watershed contains much organic sediment. When sedimented stream water reaches lakes or areas of r e l a t i v e l y s t i l l water, the sediment w i l l be deposited. The chemicals bound to or contained i n sediment p a r t i c l e s may e i t h e r remain immobilized i n these deposits or be released to the surrounding water. T h i s , combined with the d i s s o l v e d chemicals, can enhance eutrophication. A small f l u x of chemicals i n streams f o l l o w i n g c l e a r c u t t i n g may be h i g h l y b e n e f i c i a l to the p r o d u c t i v i t y of aqua-t i c ecosystems, e s p e c i a l l y o l i g o t r o p h i c ones, but large fluxes moving i n t o 35 richer systems may lead to vigorous growth of algae and algal blooms, this growth being enhanced by increased stream temperatures following clear-cutting (Likens et al., 1970; Pierce et al., 1972; Werner, 1973). Hansmann and Phinney (1973) observed changes i n the microflora of a coastal Oregon stream following clearcutting and slashburning. Changes i n numbers and species composition of the microflora communities as well as algal blooms following logging were observed. They concluded that: filamentous algal blooms are common i n streams influenced by the removal of the vege-tation from the surrounding watershed." This algal growth may reduce light penetration causing the disappear-ance of benthic plants. When the algae and any other plants decay, dissolved oxygen levels may be lowered causing, in severe cases, the death of other aquatic organisms and/or changes i n the species composition of aquatic com-munities (Hynes, 1969; Werner, 1973). Loss of chemical nutrients i n streamwater may have important conse-quences for watershed s o i l productivity (Likens et al., 1970; Pierce et al. 1972). Such losses have generally been ignored i n the past with the emphasis on nutrient loss via timber removal (e.g. Ovington, 1962; Rennie, 1955). To the writer's knowledge, the f i r s t comparison of nutrient losses in streams to nutrient losses through timber removal has only recently ap-peared. This work, again from Hubbard Brook, found that, as a result of clearcutting one-third of a watershed in strips, the amount of nitrate-nitrogen removed i n timber was about the same as that removed i n stream-water the f i r s t two years after cutting, whereas calcium losses were slightly greater, i n streamwater (Hornbeck et'al., 1973). The authors indicated that chemical losses i n streamwater after clearcutting the entire watershed are 36 l i k e l y to be more than three times the losses from clearcutting one-third of the watershed. Although nutrient losses were small i n comparison to the totals present in the s o i l , the significance of such losses i s s t i l l unknown (Hornbeck et al., 1973; Pierce et al., 1972). However, i t i s pos-sible that the significance far exceeds the actual proportions since the losses are l i k e l y to be of the biologically active nutrients (Pierce et al., 1972) . I n i t i a l results from Hubbard Brook, i n which complete removal of veg-etation i n a watershed by cutting and herbicides caused nitrate concentra-tions i n streamwater leaving the watershed to continuously exceed the U.S. recommended concentration for drinking water, suggested that clearcutting might similarly impair the chemical quality of streamwater for human con-sumption (Likens et al., 1970). However, this has not been confirmed by more recent studies of commerical clearcutting operations both at Hubbard Brook (Hornbeck et al., 1973; Pierce et al., 1972), and i n Oregon (Brown et al., 1973; Fredriksen, 1971), although i n one Oregon study (Fredriksen, 1971) ammonia and manganese concentrations i n streamwater exceeded the U.S. maximum permissible concentrations for drinking water for a twelve day per-iod immediately following slashburning. (f) Dissolved organic chemicals - Soluble tannins and lignin-like sub-stances which produce yellow and brown colours i n water can be leached out of bark (Narver, 1971; Servizi et al., 1971). This leachate from slash has been found to range from non-toxic to slightly toxic for young salmon and trout (Narver, 1971; Pease, 1974; Servizi et al., 1971) but Narver (1971) considered that toxic,levels would be reached only where a large accumulation of debris collects i n a very small stream. In such a stream, anaerobic 37 b a c t e r i a l decomposition of organic material may also occur, producting t o x i c hydrogen sulphide. (g) Dissolved oxygen - C l e a r c u t t i n g operations which deposit s l a s h i n a stream tend to lower the amount of oxygen di s s o l v e d i n that stream. This i s due to the consumption of oxygen by aquatic organisms which are decompos-ing the s l a s h m a t e r i a l and to the leaching of soluble organic substances from the s l a s h . Many of these substances, which include the wood sugars, exert a considerable chemical oxygen demand as w e l l as a b i o l o g i c a l oxygen demand' (Hall and Lantz, 1969; Narver, 1971; S e r v i z i et al., 1971; U.S. De-partment of the I n t e r i o r , 1970). I f sl a s h i s kept out of streams, on the other hand, d i s s o l v e d oxygen l e v e l s may be l i t t l e a f f e c t e d by c l e a r c u t t i n g i f stream temperatures do not r i s e s i g n i f i c a n t l y (Burns, 1972; Krammes and Burns, 1973; U.S. Department of the I n t e r i o r , 1970). When sl a s h materials are covered with a layer of sediment, as i s sometimes the case a f t e r l o g -ging operations, decomposition of the s l a s h w i l l be slow and w i l l occur a n a e r o b i c a l l y . The products of t h i s process w i l l decompose furth e r using up more oxygen i n the water, producing the end products: hydrogen sulphide, ammonia, methane, carbon dioxide, and hydrogen, which slowly d i f f u s e up through the o v e r l y i n g sediment ( S e r v i z i et al., 1971). The amount of oxygen d i s s o l v e d i n streamwater increases as stream-flow increases and as water temperature decreases. Thus, by in c r e a s i n g water temperatures, c l e a r c u t t i n g may further lower d i s s o l v e d oxygen l e v e l s . Depletion of streamwater oxygen by decomposer organisms w i l l be greatest i n the summer when streamwater temperatures are high and streamflow i s low. Thus, se v e r a l s y n e r g i s t i c processes operate i n summer to lower the amount of oxygen d i s s o l v e d i n streamwater. Although c l e a r c u t t i n g increases 38 streamflow which tends to increase oxygen l e v e l s , temperature increases and s l a s h deposition appear more important so that the general e f f e c t of c l e a r c u t t i n g i s to decrease oxygen l e v e l s i n the summer. The occurrence of freshets i n autumn, however, w i l l bring d i s s o l v e d oxygen l e v e l s back to near s a t u r a t i o n . The e f f e c t s of d i s s o l v e d oxygen l e v e l s on f i s h l i f e and development have been discussed by Narver (1971) and H a l l and Lantz (1969). Dissolved oxygen plays an important r o l e i n both the long-term and short-term s u r v i v a l of f i s h . The oxygen d i s s o l v e d i n the i n t r a g r a v e l water of a stream i s supplied both by interchange from the stream and by ground-water, but i t appears that interchange from the stream i s the main source (Narver, 1971). Debris and sediment from c l e a r c u t t i n g operations can cause a s u b s t a n t i a l decrease i n t h i s r a t e of interchange by covering the gravel, as w e l l as by exerting a high oxygen demand (Hall and Lantz, 1969; Narver, 1971; Pease, 1974). A large decrease below sat u r a t i o n i n the oxygen d i s s o l v e d i n the i n t r a -g r avel water can cause a reduction of f r y s i z e , slow growth, a delay i n hatching, and, i n severe cases, can lower the success of incubation of eggs or cause m o r t a l i t y of f r y . Thus, the s u r v i v a l , growth, and general f i t n e s s of young salmonids i s d i r e c t l y r e l a t e d to i n t r a g r a v e l d i s s o l v e d oxygen l e v e l s . S i m i l a r l y , the success of salmonids i s strongly influenced by the amount of oxygen d i s s o l v e d i n the surface waters i n which the f i s h l i v e a f t e r emerg-i n g frcm 'the g r a v e l . Growth and food conversion depend on t h i s oxygen and death or l o s s of weight can occur i f the concentration of d i s s o l v e d oxygen drops to about 2 m g / l i t r e . D a i l y f l u c t u a t i o n s i n d i s s o l v e d oxygen of 6 mg/ l i t r e or more can g r e a t l y reduce salmonid appetite and growth (Narver, 1971). 39 In general, i t appears that r e t e n t i o n of s t r i p s of vegetation along stream banks may s i g n i f i c a n t l y reduce the impact of c l e a r c u t t i n g on aqua-t i c ecosystems. Apart from the stream temperature c o n t r o l provided by vegetation, the f o r e s t f l o o r beneath the vegetation may f i l t e r out any sediment being c a r r i e d by overland water flow and plant roots may take up excess chemical n u t r i e n t s being leached out of the c l e a r c u t area (Brown, 1969; Fredriksen et al., 1973; Hornbeck et al., 1973; Swift and Baker, 1973). Streamside b u f f e r s t r i p s can also p r o t e c t stream bank habitat f o r f i s h (Bustard, 1973; Narver, 1972) and maintain t e r r e s t r i a l input.of food i n t o streams (Chapman and Demory, 1963; Warren et al., 1964). Streamside buf-f e r s t r i p s w i l l not, however, prevent stream sedimentation caused by l o g -ging operations remote from the stream, as sediment may enter a stream v i a side channels (T.W. Chamberlin, Canada Department of the Environment, F i s h -e r i e s Service: Personal communication). Burns (1970) has reviewed the benefits to be obtained by leaving s t r i p s of vegetation beside streams. The timing of logging operations i s a l s o important. From the f i s h e r -i e s viewpoint, slash or sediment i n streams i s p a r t i c u l a r l y harmful i n spring when eggs are incubating and f r y are emerging (Hall and Lantz, 1969). Winter logging, as i n the i n t e r i o r of B.C., although causing l e s s s o i l d i s -turbance, may s t i l l cause heavy sedimentation of streams from roads and landings, and can deposit much debris i n stream channels since these chan-nels may not be seen i n winter and heavy overnight snowfall may cover slash, leaving i t to be exposed only a f t e r spring melt (T.W. Chamberlin, Canada Department of the Environment, F i s h e r i e s Service: Personal communication). Reviews of the l i t e r a t u r e p e r t a i n i n g to some of the e c o l o g i c a l e f f e c t s of c l e a r c u t t i n g have r e c e n t l y appeared i n "Report of the President's Advisory Panel on Timber and the Environment", U.S. Government P r i n t i n g O f f i c e , 1973. Objectives of the Thesis When the literature was reviewed early i n 1970, the results from the earlier Hubbard Brook experiments (Bormann et al., 1968; Likens et at., 1969; Smith et dl., 1968) suggested that forest clearcutting might increase chemical fluxes i n streams which might have significant implications for the quality of the streamwater as well as for the productivity of terres-t r i a l forest ecosystems. The review also indicated that knowledge of the effects of logging on streams on the west coast of North America was limited to those parameters, such as sediment load and temperature, which directly affected f i s h populations, but that l i t t l e was known about stream chemistry. Consequently, this study was undertaken to attempt to answer the f o l -lowing questions: (1) What i s the chemical behaviour of small streams flowing through re l a -tively undisturbed forest watersheds i n the Coastal Western Hemlock biogeoclimatic zone of B.C.? (2) How i s this behaviour affected by clearcutting? (3) What additional effects are imposed by broadcast slashburning? (4) Are any changes i n streamwater chemistry similar to changes i n solu-tion chemistry elsewhere i n the ecosystem? Due to time constraints of the study and because the completion of clearcutting operations was unavoidably delayed six months, the study of the effects of broadcast slashburning had to be abandoned and only the i n i -t i a l effects of clearcutting on forest and stream biogeochemistry could be considered. The objectives of the thesis are therefore limited to (1), (2) and (4) above. 41 CHAPTER 2. DESCRIPTION OF THE STUDY AREA (1) Location Five watersheds were studied in the University of B.C. Research Forest, approximately 60 km east of Vancouver, B.C. (Figure 2.1). Three (watersheds, A, B, and C) were equipped with stream gauging devices and located between 140 and 450 m above sea lev e l . The other two (watersheds D and E) were located between 315 and 400 m above sea level. (2) Climate The study area has a Cfb climate (Koppen, 1936), which i s described as marine warm temperate rainy (mesothermal). It has no distinct dry season, with the driest summer month receiving more than 3 cm of rain. Summer i s the driest season, however, and more than 70% of the total precipitation f a l l s in the 6 months between September and A p r i l . Average annual precipitation varies from 220 cm at the lower southern end of the area to 270 cm at the higher northern end, nearly a l l of which i s the form of rain (Figure 2.2). Snow occasionally accumulates to depths of 30 cm during the winter months but i t rarely remains for more than 1-2 weeks. Average annual precipitation for the watersheds i s given in Table 2.1, and precipitation during the study period i s given i n Table 2.2. Table 2.1 Annual average precipitation for the 3 gauged watersheds at Haney (based on 16 years data) Watershed A 226 cm Watershed B 238 cm Watershed C 254 cm Watershed B + C 247 cm R n to H f o O k cr H -0 3 0 H i rt i (0 ft 6 »< pj R (H Kilometres 5 to "Administration" P (219.1) 44 The values in Table 2.1 are based on annual precipitation of 219 cm for the University of B.C. Research Forest "Administration" weather station and calculated from the isohyetal map of the area (Figure 2.2). Table 2.2 Precipitation at Haney during the study period 1958-1974 1970 (16 years) average 1971 1972 1973 1974 January 29.1 50.2 21.3 17.8 40.6 February 22.9 33.0 30.4 13.1 30.5 March 20.1 31.1 42.0 16.6 25.8 •*• Study Apri l 16.4 9.6 18.3 4.4 terminated May 9.5 5.9 6.4 8.1 June 8.8 15.2 9.1 13.9 July 7.1 5.8 21.9 4.7 August 8.0 Study 3.9 6.3 4.2 commenced September 15.6 -»• 17.1 15.1 25.9 9.2 October 24.1 16.5 27.8 7.6 23.7 November 26.2 22.8 34.4 24.9 31.7 December 31.3 38.3 15.3 52.0 29.2 Year 219.1 247.3 266.1 176.6 A l l values are in cms for the University of B.C. Research Forest "Administration" weather station. Summers are cool with an average daily mean temperature for the warmest month of about 17°C. The average daily mean temperature for the coldest month is close to 0°C. Fog and mist are common. Due to the relatively mild climate 45 the soils are seldom frozen, and then only b r i e f l y and superficially. Temperature and r a i n f a l l data for two weather stations close to the study area are given i n Table 2.3, and the location of the weather stations i s shown i n Figure 2.2. Table 2.3 Climatological data for two weather stations at Haney. Average values for a 16 year period between 1958 and 1974. Administration (elevation 145 m) Spur 17 (elevation 375 m) maximum temp. (°C) minimum temp. (°C) precipitation (cm) maximum temp. (°C) minimum precipitation temp. (°C) (cm) January 3.9 -1.1 29.1 -0.5 -3.2 31.8 February 7.4 1.1 22.9 1.8 -2.6 23.3 March 9.3 1.5 20.1 2.0 -3.3 21.4 April 12.4 3.8 16.4 9.2 1.2 17.4 May 17.3 6.9 9.5 15.7 7.6 10.6 June 19.9 10.2 8.8 16.7 9.6 10.7 July 22.8 11.7 7.1 21.9 13.4 8.1 August 22.0 11.1 8.0 19.0 11.4 8.6 September 18.1 9.4 15.6 18.5 13.5 17.1 October 13.3 6.2 24.1 8.7 6.8 26.4 November 8.2 2.1 26.2 2.0 0.1 27.0 December 4.9 0.3 31.3 2.3 1.4 32.3 Mean annual total 219.1 Mean annual total 234.7* The table was calculated from climatological records published in the Annual Reports of the University of B.C. Research Forest and on f i l e at the University of B.C. Research Forest. 46 *E. Hetherington (Forestry Service, Environment Canada: Personal communication) measured p r e c i p i t a t i o n at the U n i v e r s i t y of B.C. Research Forest using h i s own network of c o l l e c t o r s and concluded that the p r e c i p i t a t i o n c o l l e c -t o r at Spur 17 was u n d e r c o l l e c t i n g p r e c i p i t a t i o n by 8%. Thus, the mean annual t o t a l of 234.7 cm should be 253.5 cm. (3) Geology, landforms, and s o i l s The bedrock c o n s i s t s predominantly of a c i d igneous rocks - d i o r i t e , grano-d i o r i t e , quartz d i o r i t e , and some granite syenite and monzonite - with some i s o l a t e d masses of v o l c a n i c and sedimentary rocks. The most common rock type i n the study area i s quartz d i o r i t e which contains more b i o t i t e than hornblende (Roddick, 1965). Outcrops and exposures of the quartz d i o r i t e d i s p l a y smooth, s u p e r f i c i a l l y weathered surfaces r e l a t i v e l y f r e e of. open j o i n t s , suggesting that the bedrock i s generally impermeable. Most of the area was covered by i c e during the Pleistocene, being a f f e c t e d by at l e a s t three (Seymour, Semiamu, and Vashon) and p o s s i b l y four (Sumas) major g l a c i a t i o n s (Armstrong, 1956) . The material deposited by an advancing g l a c i e r was overridden by the i c e to give r i s e to the present basal t i l l . T his basal t i l l i s grey i n colour, h i g h l y compacted and impermeable to water. When i t occurs i t u s u a l l y determines the lower l i m i t of root penetration and only very r a r e l y do roots penetrate i t v i a cracks. M a t e r i a l deposited l a t e r and during r e t r e a t of the g l a c i e r i s a b l a t i o n t i l l . T his t i l l , which forms the present s o i l mantle, was reworked i n places by the meltwaters of the receding g l a c i e r s , p a r t i c u l a r l y i n the southern part of the study area, and i s mixed i n places with colluvium. The southern h a l f of watershed A belongs to Lacate's (1965) land a s s o c i a t i o n C, described as a f l a t to gently r o l l i n g complex of g l a c i o - f l u v i a l outwash and 47 sub-stratified d r i f t deposits. Outwash sand and gravel terraces and deltas are the common landforms and the s o i l materials are usually quite deep and of variable texture. Although the s o i l i s generally permeable, tree rooting i s restricted on some terraces by discontinuous iron pans and cemented layers. Temporary perched water tables occur above these layers for short periods during the year. Except for terrace scarps and the occasional bedrock knoll, the topography i s f l a t to gently sloping (0-20%). The northern half of watershed A and a l l of watersheds B, C, D, and E belong to Lacate's land association B, described as h i l l y to gently r o l l i n g , granitic-cored uplands and valleys. Gravelly sandy loam colluvium overlying unweathered basal t i l l and/or bedrock i s the most common structural pattern of the terrain. In gullies and low-lying areas, reworked t i l l and poorly sorted sands and gravels mantle basal t i l l . Patches of talus and varved lacustrine clays and s i l t s are minor inclusions. An organic cap often covers exposed bedrock. In deep gullies a deep muck i s often present. • Soils in watershed A are humo-ferric podzols (Canada Soil Survey Committee, 1970) derived mainly from glacial outwash and colluvial materials. Close to the stream they are described as very moist to wet deep soils of variable texture (Lacate, 1965) . Away from the stream they are dry to slightly moist, shallow, coarse textured (sandy loam to loamy sand) s o i l s . Soils in watersheds B and C are predominantly humo-ferric podzols with small areas of humic gleysols in a l l u v i a l f l a t s in the valley bottom, and some l i t h i c f o l i s o l s on bedrock outcrops. Adjacent to stream channels they are described (Lacate, 1965) as dry to slightly moist, deep, coarse textured s o i l s , and elsewhere as dry to slightly moist, shallow, coarse textured s o i l s . Textures were found to be predominantly sandy loam and loamy sand. 48 A d e t a i l e d s o i l survey or c l a s s i f i c a t i o n of the U n i v e r s i t y of B.C. Research Forest was not a v a i l a b l e , but nineteen s o i l p i t s were dug i n the watersheds. P r o f i l e d e s c r i p t i o n s are given i n Appendix II and s o i l p h y s i c a l and chemical data are given i n Appendix I I I . (4) Vegetation The watersheds l i e i n the dry subzone of the Coastal Western Hemlock biogeoclimatic zone of B.C. (Krajina, 1959, 1965, and 1969) and are covered mostly by the coniferous species Tsuga heterophylla* (western hemlock), Thuja plioata (western red cedar), and Pseudotsuga menziesii (Douglas-fir) with some Alnus rubra (red a l d e r ) , Populus trichocarpa (black cottonwood), Acer maorophyllum ( b i g l e a f maple) and Betula papyrifera (western white birch) i n the occasional opening or wet s i t e . The r e l a t i v e abundance of the major tr e e species i s given i n Table 2.4. Understory vegetation i s v a r i e d and w i l l be described under biogeocoenoses. Table 2.4 R e l a t i v e d i s t r i b u t i o n of the major tree species i n • watersheds A, B, and C. Percentage Percentage by volume Watershed Species by numbers prism cruii A Hemlock 37 41 Cedar 28 22 Douglas-fir 35 37 B Hemlock 79 82 Cedar 15 12 Douglas-fir 6 6 C Hemlock 50 - • Cedar 36 -Douglas-fir 5 -B i r c h 9 - ' * A l l l a t i n names are from Taylor (1966) and S c h o f i e l d (1968). Complete s c i e n t i f i c names are given i n Appendix XV. 49 (a) Forest cover - Forest cover i s shown in Figure 2.3; the units are described below. Names of the units are descriptive and have been used only for the purposes of this study. Watershed A 1. T a l l Forest: Covers 14.2 ha (61% of watershed A) and was entirely clearcut (Figure 2.5). This unit consists predominantly of western hemlock and western red cedar with some Douglas-fir and very small amounts of red alder and bigleaf maple. The trees grew up after a f i r e in 1868 and are mostly 70-90 years old. Understory vegetation i s described under biogeocoenoses. 2. Plantation, 1961: Covers 7.0 ha (31% of watershed A). The T a l l Forest on this area was clearcut in 1957, pa r t i a l l y scarified, then planted with Douglas-fir and western hemlock i n 1961. I t now contains much red alder, Rubus leuaodermis} Gaultheria shallon3 and grasses. Sections of i t near the creek which were not scarified contain remnants of the original stand as well as a l l -aged Douglas-fir, western hemlock, western red cedar and red alder regeneration growing above a dense tangle of Rubus speatabilis3 Ttevidium aquilinum, Rubus ursinus, and Gaultheria shallon. 3. Field and Forest: Covers 1.9 ha (8% of watershed A) and consists of several grass-covered fields surrounded by small stands of the T a l l Forest. The fields were created by clearing the forest and planting grass in 1913 (J. Walters, U.B.C. Research Forest: Personal Communication). Watershed B 1. T a l l Forest: Covers 16.3 ha (55% of watershed B), 13.1 of which were clearcut (Figure 2.5). I t was the same cover type as i n watershed A. 4. Plantation, 1958: Covers 4.8 ha (20% of watershed B). The T a l l Forest on this unit was logged i n 1958, slashburned i n the autumn of 1960, then -5JL Figure 2.3 Forest cover Legend 1. Mature f o r e s t 2. P l a n t a t i o n , 1961 3. F i e l d and Forest 4. P l a n t a t i o n , 1958 5. Immature Forest 6. P l a n t a t i o n , 1959 7. Swamp 8. P l a n t a t i o n , 1964 Scale (metres) — J — 200 1~ 400 600 51 immediately planted with Douglas-fir. I t now consists of densely stocked Douglas-fir and western hemlock with some red alder. Where the tree canopy i s very dense there i s no understory vegetation; elsewhere, Pteridium aquitinum3 Gaultheria shallon, Rubus spectabiUs 3 Rubus ursinus3 Vacoinium parvifolium3 Vacoinium ovalifolium3 Polystichum munitum, Linnaea borealis3 HyZocomium splendenSy and Eurhynchium oreganum are the major understory species. 5. Immature Forest: Covers 0.6 ha (2% of watershed B). This unit was logged by railway in the 1920's and now consists predominantly of immature western hemlock, western red cedar, western white birch, and Douglas-fir with considerable quantities of red alder and Ace? civcinatum (vine maple). Understory vegetation i s described under biogeocoenoses. 6. Plantation, 1959: Covers 2.3 ha (10% of watershed B). The Ta l l Forest on this unit was logged in 1956, slashburned in 1958, then planted with Douglas-f i r i n the autumn of 1959. Its vegetation i s identical to that of unit 4 except that BZechnum spioant i s more prominant as an understory species. Watershed C 5. Immature Forest: Covers 39.1 ha (89% of watershed C) and i s described above. 6. Plantation, 1959: Covers 3.4 ha (8% of watershed C) and i s described above. 7. Swamp: Covers 1.5 ha (3% of watershed C) and occurs only i n slight depressions. Tree cover i s sparse, usually confined to western red cedar and the occasional western hemlock growing on decaying logs. Lesser vegetation i s described below under Lysichiturn-western red cedar biogeocoenoses. Watershed D • 1. T a l l Forest: Covers 6.9 ha (80% of watershed D), 1.7 of which were clearcut (Figure 2.5). Its vegetation i s described above. 52 8. P l a n t a t i o n , 1964: Covers 1.7 ha (20% of watershed D). The T a l l Forest of t h i s u n i t was logged i n 1964 and spring 1965, then planted with Douglas-fir seedlings i n spring 1966. Other tree species now present include western hemlock and red alder. Understory species are mainly Pteridium aquilinum, Rubus spectdbilis s Rubus ursinus, Vacoinium parvifolium, and Gaultheria shallon. Watershed E 1. T a l l Forest: Covers 10.4 ha (100% of watershed E ) , 2.8 of which were c l e a r c u t ( F i g . 2.5) . I t s vegetation i s described above, (b) Biogeocoenoses The U n i v e r s i t y of B.C. Research Forest was e c o l o g i c a l l y c l a s s i f i e d i n t o biogeocoenoses (Krajina, 1965 and 1969) by K. K l i n k a . This involved a considera-t i o n o f s o i l s , landforms, and vegetation. Only the vegetation component o f the biogeocoenoses w i l l be b r i e f l y described here. For more d e t a i l e d information the Ph.D. t h e s i s of K. K l i n k a (yet to be completed) should be consulted. Biogeocoenoses are shown i n Figure 2.4 as arranged i n t o f i v e main groups. The major plant species found i n each group are given below. Tree species are l i s t e d i n order of importance. Group 1. Gaultheria-Douglas f i r : These biogeocoenoses are found on ridge tops and dry spurs. The overstory i s quite open and c o n s i s t s of D o u g l a s - f i r , western red cedar, and western hemlock. Understory plants include Gaultheria shallon, Vacoinium parvifolium, Mahonia nervosa, Pteridium qquilinum, Rubus ursinuSj and the mosses Hylocomiun splendens, Eurhynchium oreganum, Plagiothecium undulatum, Rhytidiadelphus loreus3 and some Sphagnum sp. i n depressions. Group 2. Moss-Western Hemlock: These biogeocoenoses are found on the gentler slopes where there i s l i t t l e influence of subsurface seepage water. The overstory i s rather dense and c o n s i s t s of western hemlock, Do u g l a s - f i r , and 54 western red cedar. Understory plants include Vaccinium parvi folium, Polystichum muntium, Vaccinium alaskaense, Gaultheria shallon, Dryopteris austriaca, Rubus spectabilis, Rubus ursinus, Trientalis latifolia, and the mosses Hylocomium splendens, Eurhynchium oreganum, Plagiothecium undulatum, Rhytidiadelphus loreus, and Isothecium stoloniferum. Group 3. Polystichum-Western Red Cedar: These biogeocoenoses usually occur on the lower slopes where subsurface seepage water is important. The overstory i s moderately dense and consists of western red cedar, Douglas-fir, and western hemlock, with small amounts of bigleaf maple and red alder. Understory plants include Acer circinatum, Sambucus pubens, Vaccinium parvifolium, Vaccinium alaskaense, Menziesia ferruginea, Rubus spectabilis, Pteridium aquilinum, Polystichum munitum, Blechnum spicant, Athyrium filix-femina, Dryopteris austriaca, Comus canadensis, Gaultheria shallon, Tiarella trifoliata, Linnaea borealis, and the mosses Hylocomium splendens, Rhytidiadelphus loreus, Rhizomnium glabrescens, Rhizomnium nudum, Plagiothecium undulatum, Isothecium stoloniferum, Dicranum fuscescens, Dicranum scoparium, Eurhynchium oreganum, and Hypnum circinale. Group 4 . Stream Edge Biogeocoenoses: These biogeocoenoses occur only in valley bottoms near streams. The overstory i s moderately dense and consists of western hemlock, western red cedar, and Douglas-fir, with an occasional red alder and black Cottonwood. Understory plants include Acer circinatum, Menziesia ferruginea, Vaccinium alaskaense, Vaccinium parvifolium, Oplopanax horridus, Rubus spectabilis, Athyrium filix-femina, Dryopteris austriaca, Polystichum munitum, Blechnum spicant, Gymnocarpium dryopteris, Tiarella trifoliata, Lactuca muralis, Gaultheria shallon, and the mosses Hylocomium splendens, Eurhynchium oreganum, Rhytidiadelphus loreus, Rhizomnium glabrescens, Rhizomnium nudum, and Plagiothecium undulatum. 55 Group 5. Lysichitum-Western Red Cedar: These biogeocoenoses occur in wet depressions within areas which are f l a t or only gently sloping. The overstory i s relatively open and dominated by western red cedar with lesser amounts of western hemlock and Douglas-fir. Understory plants include Vacoinium aZaskaense, Rubus spectabilis 3 Dryopteris austriaca, Athyrium fiZix-femina, Btechnum spicant3 Lysichitum americanum, Tiarella trifoZiata, and the mosses Rhizomnium punctatum, Eurhynchium stokesii, and Sphagnum sp. (5) Watershed description Physical characteristics of the five watersheds are given in Table 2.5. Table 2.6 indicates that the two streams, D and E, despite considerably smaller watershed areas and shorter channel lengths, have only slightly lower discharges than the stream leaving watershed A, which probably reflects their shallower s o i l s . Discharges for streams D and E were measured at the end of a road culvert through which the two streams pass downstream of their confluence. Table 2.5 Physical characteristics of the watersheds at Haney Drainage Elevation (m) Channel length (m) density Average Average stream watershed A 145 310 670 275 40.9 N-»-S upper lower 7° 3° upper lower B 235 330 610 872 61.8 N-+S 515° 12° C 295 455 855 460 29.9 NNE+SSW 3° 7° D 315 390 275 - - NNE+SSW 43j° 19° E 315 400 290 _ — ESE+WNW 5h° 14° 56 Table 2.6 Relative watershed areas and stream discharges Watershed A B C D E Watershed area (ha) 23.1 24.0 44.0 8.6 10.4 v combined Stream discharge (25/9/73 - 2 p.m.) 1.5 6.1 3.6 2.4 Stream discharge (30/10/73 - 1 p.m.) 12.9 49.4 28.4 20.7 A l l discharges are i n l i t r e s / s e c . The l o c a t i o n of clearcuts and major roads within the watersheds i s given i n Figure 2.5. 58 CHAPTER 3. EXPERIMENTAL METHODS (1) F i e l d instrumentation and sampling techniques (a) Streamwater - Sharp-crested 120° V-notch weirs were constructed on the creeks d r a i n i n g two small watersheds. The e n t i r e drainage of the smaller of the two watersheds was included i n the experiment. On the l a r g e r watershed, only the lower region was included i n the treatment part of the experimental design, while the upper region acted as an untreated c o n t r o l . I t was separated from the lower treatment area by a rectangular broad-crested weir. A l l three weirs were equipped with instrument s h e l t e r s housing s t i l l i n g w e l l s , Richards-type water l e v e l recorders, and thermographs. The weir i n the smaller watershed (weir A) and the rectangular weir i n the l a r g e r watershed (weir C) were equipped with Lambrecht type 258 remote recording 3-point thermographs each of which measured water temperature (within 3 m of the weir o u t l e t ) , a i r temperature at the organic-mineral s o i l i n t e r f a c e (7 cm below the surface at weir A and 18 cm below the surface at weir C ) . The V-notch weir i n the l a r g e r watershed (weir B) was equipped with a Weathermeasure remote recording 2-point thermograph which measured water temperature (within 3 m of the weir outlet) and s o i l temperature at the organic-mineral s o i l i n t e r f a c e (16 cm below the s u r f a c e ) . A l l water l e v e l recorders and thermographs had spring-wound clocks and 7-day charts and were r e g u l a r l y c a l i b r a t e d (approximately once a fortnight) and adjusted as necessary. The height-discharge r e l a t i o n s h i p s of the three weirs were determined f o r low and intermediate flows by using a bucket and stopwatch technique. For the rectangular weir these measurements were f a c i l i t a t e d by b u i l d i n g a small dam 59 upstream of the weir t o d i v e r t the water i n t o a pipe. At intermediate flows not a l l of the water could be accommodated i n t h i s pipe. The height of t h i s overflow i n the weir was measured and the overflow discharge determined from the low flow c a l i b r a t i o n curve. This discharge was added to that obtained f o r the water flowing through the pipe to obtain the o v e r a l l discharge f o r the stream at intermediate flows. For high flows through the rectangular weir, a Kempten OTT u n i v e r s a l -current meter, model 10.002, was used to determine discharge. High flows through the two V-notch weirs were determined d i r e c t l y from the t h e o r e t i c a l weir c a l i b r a t i o n curve by assuming that the c l o s e s i m i l a r i t y between the .measured and t h e o r e t i c a l c a l i b r a t i o n curves f o r low and intermediate flows would a l s o be r e f l e c t e d at the high flows. Stage-discharge curves are given i n Appendix I . Samples of streamwater f o r chemical a n a l y s i s were c o l l e c t e d once a week (occasionally more frequently) immediately upstream of the ponds behind the weirs. Samples were c o l l e c t e d i n polyethylene b o t t l e s . At the beginning of the study these were washed with warm d i l u t e hydrochloric a c i d , hot water, and deionized water between samplings. The a c i d r i n s e was found to be unnecessary and was discontinued l a t e r i n the study. (b) P r e c i p i t a t i o n - Incident p r e c i p i t a t i o n was c o l l e c t e d i n simple polyethylene systems, each c o n s i s t i n g of a funnel containing a plug of spun f i b r e g l a s s ( " f i l t e r f i b r e " ) connected to a narrow necked polyethylene container (capacity 1 l i t r e ) v i a a rubber stopper. The system was clamped to a supporting rod such that the top o f the funnel was 40-70 cm above the s o i l surface and above any nearby vegetation. There was a t o t a l of four p r e c i p i t a t i o n c o l l e c t o r s , each placed i n open areas at the lower and upper ends of each of the two treated areas (Figure 3.1). 61 Snow was collected from the ground near the precipitation collectors by using the l i d of a wide necked 1 l i t r e polyethylene container to scoop the snow into the container. (c) Throughfall - Throughfall precipitation was collected in polyethylene systems identical to those for incident precipitation except that the collectors had a larger capacity (4.7 litr e s ) and rested on the s o i l surface. There was a total of 42 throughfall collectors, 38 of which were located in the study watersheds (2 near each of the 19 s o i l pits) and 4 of which were located i n a forest stand close to the southern end of the watersheds (Figure 3.1). The 34 collectors associated with the 17 s o i l pits i n the treatment areas were removed just prior to clearcutting. Throughfall through slash was collected by placing appropriate pieces of slash i n the funnels of the polyethylene systems described above. To avoid errors due to contamination when setting up the collectors (when being set up, the slash pieces were wet and were collected and broken up by hand), a l l samples were discarded after the f i r s t week of rain. There were 13 such collectors, a l l located at the edge of the slash near weir B (Figure 3.1). Slash pieces in the funnels are described i n Appendix VIII. A l l throughfall and incident precipitation systems were cleaned regularly, especially during warm periods when algae tended to develop i n the water. . Samples were collected once a fortnight or whenever possible during dry periods. (d) Soils and s o i l water - The watersheds above weirs A and B were str a t i f i e d into biogeocoenoses by f i e l d examination by Mr. Karel Klinka. One or more sites were selected within each different biogeocoenosis as being representative of that biogeocoenosis. A s o i l p i t was dug on each s i t e , the 62 s o i l p r o f i l e was described using standard methods (U.S. Department of A g r i -culture S o i l Survey S t a f f , 1962), and samples of each horizon were taken fo r a n a l y s i s . Care was taken not to d i s t u r b the s o i l upslope of the p i t . A t o t a l of 19 s o i l p i t s were dug, 8 i n watershed A, 9 i n watershed B, and 2 (numbers 9 and 10) outside the treatment areas (Figure 3.1). F i f t e e n of the 19 s o i l p i t s were each equipped with a surface runoff c o l l e c t o r (Figure 3.2) and 2 tension lysimeters (Figure 3.3) which were i n s t a l l e d i n the s o i l on the upslope side of the p i t , one a t the organic-mineral s o i l i n t e r f a c e and the other i n the mineral s o i l 70 cm below i t s surface, or as clo s e to t h i s depth as p o s s i b l e i n shallow s o i l s . Surface runoff c o l -l e c t o r s were placed i n p o s i t i o n s judged most l i k e l y to e x h i b i t surface runoff. Two of the remaining four s o i l p i t s were located i n shallow organic s o i l s o v e r l y i n g bedrock and each was equipped with only a surface runoff c o l l e c t o r and an organic l a y e r lysimeter. Another p i t , with a frequently high water ta b l e , had no mineral s o i l lysimeter but had the bottom p a r t of the p i t covered to prevent contamination of the groundwater which was c o l -l e c t e d whenever p o s s i b l e . The l a s t p i t was located on a f l a t a l l u v i a l s i t e with a high water table and therefore functioned as a w e l l . I t was covered t o prevent contamination of groundwater which was sampled weekly. Surface runoff c o l l e c t o r s were constructed out of p l e x i g l a s as shown i n Figure 3.2. The upper p l e x i g l a s sheet was t o prevent c o l l e c t i o n : i O f through-f a l l . The c o l l e c t o r was i n s e r t e d i n t o the organic layer so that the bottom p l e x i g l a s sheet was 1 cm below the surface and the o u t l e t was the lowest p a r t of the c o l l e c t o r . Polyethylene tubing connected the o u t l e t to a 4.7 l i t r e polyethylene storage container. The tension lysimeters used i n t h i s study were of two types. One type, Figure 3.2 A surface runoff collector outlet Figure 3.3 A tension lysimeter, type 1. Figure 3.4 A tension lysimeter, type 2. sidewalls alundum disc 1^1 | - I—ring spacer radial spacer plexiglas basal cone sidewalls s i l i c o n carbide cotton screen .perforated plexiglas (4 mm diameter holes) to storage container as i n Figure 3.3 stopcock rubber stopper air hole • storage container 64 which was constructed from plexiglas and circular porous alundum discs (10.2 cm in diameter, 1.3 cm thick), was similar to that described by Cole (1968) but with the addition of sidewalls cut from plexiglas pipe (Figure 3.3). These walls were 5 cm t a l l for the lysimeters in the organic layer and 7.5 cm t a l l for the lysimeters in the mineral s o i l . The other type was a modified version of that used by Bourgeois and Lavkulich (1972b). I t had identical dimensions to those of the f i r s t type but u t i l i z e d a 1 cm thick layer of 320 g r i t s i l i c o n carbide powder instead of an alundum disc. Details are shown in Figure 3.4. The cotton screen prevented movement of si l i c o n carbide through the outlet and into the storage container. The apparatus was f i l l e d with water before adding the si l i c o n carbide to exclude any a i r pockets. Flexible polyethylene tubing led from the outlets of a l l lysimeters down to 4.7 l i t r e storage containers via 3-way stopcocks, as shown i n Figure 3.3. The stopcocks allowed the lysimeters to be switched off and fac i l i t a t e d any repairs. When the polyethylene tubing was f u l l of water i t acted as a hanging water column which provided the necessary tension to the lysimeter plate. Tensions of 90 cm of water, or as close to this as possible, were applied, 90 cm being a compromise between the shallow nature of the soils and the tension of the water in the s o i l at f i e l d capacity. The alundum disc lysimeters were found to have air intrusion values of 150-190 cm of water, and the si l i c o n carbide lysimeters, a i r intrusion values of 175-200 cm. (e) Tree and slash volumes 1. Standing trees - The volume of standing timber was estimated from a standard prism (BAF 30) cruise by the author i n 1971 using a random sampling pattern (26 points for 30.5 ha. of. forest). 65 2. Slash - The loading of f i n e s l a s h (pieces l e s s than 1.3 cm i n diameter) was estimated by randomly l o c a t i n g 24 c i r c u l a r p l o t s o f one square metre (radius 56.4 cm) each throughout the logged area. A l l the material within each p l o t which o r i g i n a t e d from the s l a s h and which was l e s s than 1.3 cm i n diameter was placed i n t o a polythene bag. The material i n the bags was a i r - d r i e d and weighed weekly u n t i l there was no furth e r change i n weight. Slash materials greater than 1.3 cm i n diameter were sampled using the l i n e i n t e r s e c t method of Warren and Olsen (1964) as modified by Van Wagner (1968). Twenty-eight 30-metre sections of sample l i n e were run i n three d i f f e r e n t d i r e c t i o n s , each, of the three l i n e s being at an angle of 60° to the others. The f i r s t d i r e c t i o n was randomly chosen. The diameter of each piece of slash i n t e r s e c t e d by the l i n e was measured to the nearest 0.2 cm. The weight of s l a s h i n kg per square metre was determined from the formula 2 2 61SEd w = adapted from Van Wagner (1968) L where: S i s the mean s p e c i f i c g r a v i t y of the wood (calculated as the weighted mean of the s p e c i f i c g r a v i t i e s of D o u g l a s - f i r , western hemlock, and western red cedar (Canadian Forestry Branch, 1951). In the c a l c u l a t i o n s , bark was assumed to have the same s p e c i f i c g r a v i t y as wood, which probably leads to a s l i g h t underestimate of s l a s h loading since, i n the case of both western hemlock and western red cedar, the bark s p e c i f i c g r a v i t y i s greater than the wood s p e c i f i c g r a v i t y (Smith and Kozak, 1971). d i s the piece diameter, measured i n inches, and L i s the length of the sample l i n e , measured i n f e e t . Results of the tree and sla s h volume surveys are given i n Appendix IX. 66 (2) Chemical analyses (a) Water - Dissolved oxygen concentrations were measured i n the streams at the time of sample c o l l e c t i o n . Water samples c o l l e c t e d i n the f i e l d were brought to the laboratory and bicarbonate concentrations, pH, and conductiv-i t y were measured as soon as p o s s i b l e , u s u a l l y within four hours of c o l -l e c t i o n . The samples were then stored at 0°C f o r a period of up to s i x weeks, p r i o r to being analyzed f o r cations and anions. Detection l i m i t s of a l l chemicals analyzed are given i n Table 3.1 and p r e c i s i o n of the an-alyses i s given i n Table 3.2 Table 3.1 Detection l i m i t s of chemicals by the a n a l y t i c a l methods • used. + K .003 2+ Mn .003 N 0 3 .09 + Na .0005 A l 3 + .5 S 0 4 1.0 2+ Mg .0003 + NH . 4 .01 s i o 2 .2 o 2 + Ca .01 C l ~ .2 HC0~ .2 _ 3+ Fe .005 A l l H 2 P ° 4 values are .06 i n mg/litre Table 3.2 P r e c i s i o n of the chemical analyses • + K ±.01 A l 3 + ±•5 s i o 2 ±.05 + Na ±.02 + NH. 4 ±.01 HC0~ ±.1 Mg 2 + ±.005 C l ~ ±.05 pH ±.1 C a 2 + ±.1 H 2 P ° 4 ±.002 cond. ±.5 - 2+ Fe ±.02 N 0 3 ±.04 2+ Mn ±.01 s ° 4 ±1.0 A l l concentrations are i n m g / l i t r e . Conductivity i s i n micromho/cm at 25°C. 67 Dissolved oxygen i n streamwater was measured using a YSI model 54 oxygen meter. The instrument was c a l i b r a t e d i n the ambient a i r before each measurement and a l l measurements were corrected f o r streamwater temperature and atmospheric pressure. Conductivity was measured using a Radiometer type CDM 2e conductivity meter with a CDC 104 conduc t i v i t y c e l l . A l l measurements were corrected to 25°C. pH was measured using an Orion model 404 s p e c i f i c ion meter with standard glass and s i l v e r / s i l v e r c h l o r i d e reference electrodes. Bicarbonate ion was determined by t i t r a t i n g a 25 ml a l i q u o t of the sample with a standard .0005 M hydrochloric acid s o l u t i o n to an endpoint of pH 4.5, using the Orion model 404 s p e c i f i c ion meter (Black et at., p. 945, 1965). Cation concentrations (potassium, sodium, magnesium, calcium, i r o n , manganese, and aluminium) were measured on a Varian Techtron AA5 atomic absorption spectrophotometer using an air-acetylene flame f o r potassium, sodium, magnesium, i r o n , and manganese, and a nitrous oxide-acetylene flame f o r calcium and aluminium. Standard solutions containing a l l the cations were prepared from commercial standards (Fisher S c i e n t i f i c Company). Ammonium io n , d i s s o l v e d s i l i c a , and anion concentrations (Chloride, phosphate, n i t r a t e and sulphate) were measured on a Technicon autoanalyzer II using the following standard c o l o r i m e t r i c methods: Ammonium - The method u t i l i z e s the Berthelot r e a c t i o n i n which a blue coloured compound (absorption maximum 630 my) forms when a s o l u t i o n containing ammonium ions i s added to sodium phenoxide, followed by addition of sodium hypochlorite (Technicon I n d u s t r i a l Systems, 1971a). Chloride - Chloride l i b e r a t e s thiocyanate 1 from mercuric thiocyanate which forms coloured f e r r i c thiocyanate (absorption maximum 480 my)in the presence of 68 fer r i c ions (Technicon Industrial Systems, 1971b) . Phosphate - Phosphate in acid solution i s used to form molybdophosphoric acid which i s then reduced to the molybdenum blue complex (absorption maximum 885 my) by reaction with ascorbic acid (Technicon Industrial Systems, 1971c). Nitrate (Plus ni t r i t e) - Nitrate i s reduced to n i t r i t e by hydrazine and a copper catalyst in alkaline solution. N i t r i t e then reacts with sulphanilamide and N-(1-naphthyl) ethylene diamine dihydrochloride in acid solution to form an azo dye (absorption maximum 520 my) (Johnson, 1972). Sulphate - An excess of barium chloride i s added to an acidified solution containing sulphate, forming barium sulphate. An equimolar (to barium) solution of methylthymol blue i s added to form a blue coloured chelate with the excess barium i n alkaline solution. The amount of uncomplexed methylthymol blue (absorption maximum 460 my) i s determined (Technicon Industrial Systems, 1971d). S i l i c a - The method i s based on the reduction of a silicomolybdate in acid solution to heteropoly blue (absorption maximum 660 my) by ascorbic acid (Technicon Industrial Systems, 1973). (b) Mineral s o i l - Mineral s o i l samples were air-dried, crushed, then sieved to determine the percentage (by weight) of particles less than 2 mm i n diameter. Subsequent analyses were performed on this (less than 2 mm) fraction. Rock samples were identified by Dr. G. Richards of the Geology Department at the University of B.C. .. So i l texture was obtained from a textural triangle (U.S. Department of Agriculture Survey Staff, 1962) after determining the particle size distribution by the Bouyoucos hydrometer sedimentation method (Day, 1950). S o i l pH was determined in 1:1 soil:water and in 1:2 soil:0.01 M CaCl2 suspensions (Black et al. , p. 914, 1965). 69 T o t a l carbon was determined by decomposition i n a Leco induction furnace followed by gasometric analysis of the carbon dioxide formed (Black et al. , p. 1346, 1965) i n a method developed by the (University of B.C.) Department of S o i l Science (1974). T o t a l nitrogen was determined by di g e s t i n g the sample with sulphuric a c i d followed by a c o l o r i m e t r i c determination of the ammonium ions formed using the phenol-hypochlorite method (Beecher and Whitten, 1970). Iron and aluminium were each determined by two methods: 1) by an o x a l i c acid-ammonium oxalate e x t r a c t i o n (McKeague and Day, 1966); 2) by a sodium pyrophosphate e x t r a c t i o n (Bascomb, 1968). In both methods, the supernatant l i q u i d was analyzed f o r i r o n and aluminium by atomic absorption spectro-photometry a f t e r c e n t r i f u g i n g the r e a c t i o n mixture. Cation exchange capacity was determined by a pH 7, IM ammonium acetate leaching of the s o i l , followed by a micro-Kjeldahl determination of the ad-sorbed ammonium ions. Atomic absorption spectrophotometric a n a l y s i s of the leachate was performed to give exchangeable c a t i o n (sodium, potassium, magnes-ium, and calcium) concentrations (Black et al. p. 891, 1965). (c) Organic LFH layers —' ' Bulk density was determined by c u t t i n g out a core of the organic l a y e r (3-4 cores per s o i l p i t ) , measuring i t s volume (by noting the volume of water required to f i l l the r e s u l t i n g hole l i n e d with a t h i n p l a s t i c sheet) and measuring i t s weight a f t e r oven-drying at 105°C. LFH samples were crushed and pulv e r i z e d and subjected to the.following analyses: Ash content and organic matter content were determined by a dry ashing procedure developed i n the (University o f B.C.) Department of S o i l Science 70 (1974). The percentage of organic matter was taken as (100 — % ash). Total cations were determined by atomic absorption spectrophotometric analysis of a solution prepared by dissolving the ash obtained above i n d i -lute HC1. Sodium, potassium, magnesium, calcium, iron, manganese, and aluminium ions were determined. Total sulphur was determined turbidimetrically as barium sulphate after dry ashing the sample in the presence of an alcoholic solution of MgfNO^^ and dissolving the ash i n warm, dilute HCl (Black et al., p. 102, 1965; Jackson, p. 337, 1958). Total phosphorus was determined colorimetrically by the vanadomolybdo phosphoric yellow colour method (Jackson, p. 334, 1958) after dry ashing the sample i n the presence of an alcoholic solution of MgCNO^^ a n < ! dis-solving the ash i n warm, dilute HCl. Total carbon was estimated from the loss i n weight after ashing, as described above under "ash content", and dividing the percentage of organic matter by the conventional "Van Bemmelen factor" of 1.724 (Black et dl., p. 1367, 1965). Total nitrogen was determined by the phenol-hypochlorite method, as described above for the mineral s o i l . P_H was determined i n 1:4 organic matter:water and 1:8 organic matter: 0.01 M CaCl 2 slurries (Black et dl., p. 914, 1965). Extractable Iron and aluminium were determined by the sodium pyro-phosphate method, as described above for the mineral s o i l . Exchangeable cations and cation exchange capacity were determined by the pH 7 ammonium acetate method, as described above for the mineral s o i l . 71 CHAPTER 4. STREAM BEHAVIOUR 1. Stream Hydrology Instantaneous discharges of streams A, B, and C have ranged from 0.2 to 250 l i t r e s / s e c , 0.7 to 1200 l i t r e s / s e c , and 0.2 to 550 l i t r e s / s e c . r e -s p e c t i v e l y , during the study period. The stream hydrographs (Figure 4.1) were characterized by high d i s -charges from October or November u n t i l A p r i l followed by a decline u n t i l a low was reached i n May and sustained u n t i l the following autumn. Sus-tained low flows during the winter period only occurred when the c o l d a r c -t i c a i r mass moved south over the Coast Mountains to i n f l u e n c e the Lower Mainland. Frozen streams and water l e v e l recorders rendered water l e v e l measurements inaccurate during such periods which occurred for a t o t a l of 31 days during the three winters of measurement. Manual measurement of the height of water flowing over the weirs permitted f a i r l y accurate deter-mination of d a i l y discharges during these periods, however. Occasional summer storms caused high discharges. For example, i n July, 1972, a storm deposited 12.9 cm of r a i n i n 24 hours (the greatest amount of p r e c i p i t a t i o n f a l l i n g i n 24 hours during the 3-1/2 years of study) on-to s o i l s which had been wetted by 8.3 cm of r a i n the preceding four days. This r e s u l t e d i n peak discharges of 250, 1220,.and 550 l i t r e s / s e c . f o r streams A, B, and C r e s p e c t i v e l y . In a d d i t i o n to the o v e r a l l seasonal trends, the stream hydrographs were characterized by r a p i d r i s e s and f a l l s i n response to i n d i v i d u a l p r e c i p i t a -t i o n events (Figures 4.2 and 4.3). This r a p i d response i s probably r e l a t e d to the ease with which water can t r a v e l through s o i l s and also to the s h a l -low nature of the s o i l s . H -•X) c H CD MERN DRILY DISCHARGE (LITRES/SEC) MEAN DRILY DISCHARGE (LITRES/SEC) MERN DRILY DISCHARGE (LITRES/SEC) cn o o cn o o o o no CO cn •• o o o CO cn o — — — — (V) o ro cn —J o o cn CD cn CD Li X) CO Q a 3 « X ) cn o •21 3 12 X) s CD 3 & . H -M << & h1-W O D 4 0) H i Q (D cn pj ci-ci-3" CD K <D H -H cn P) r r EC ••01 3 CD N3 73 Figure 4.2 Response of stream discharge to p r e c i p i t a t i o n during an October storm Hourly p r e c i p i t a t i o n (cm) 1.-5-, l.CH 0.5" ,n-i rThrpTTf 600 1200 1800 12th I k . 1 I I 600 1200 1800 13th 1 October, 1973 74 Figure 4.3 Response of stream discharge to p r e c i p i t a t i o n during a January storm Hourly p r e c i p i t a t i o n (cm) 1.0-0.5 600 1200 1800 23rd 600 1200 1800 24th January, 1974 75 Stormflow at Haney The source of stormflow at Haney appears to be complex and i s not r e a d i l y explained by any one current theory. In f a c t , the source of stormflow i s gener a l l y a subject of considerable debate among hydro l o g i s t s at present. For a long time, d i r e c t surface runoff was considered to be the major source of stormflow (Horton, 1945). This theory has been replaced, however, by one i n which subsurface seepage water i s the major source (Kirkby and Chorley, 1967). A proponent of t h i s theory, Hewlett, has advanced the v a r i a b l e source area concept (Hewlett, 1961; Hewlett and Hibbert, 1967). This considers both surface and subsurface flow, generated by an expanding and shrinking zone surrounding the perennial channel, as the major c o n t r i b u t i o n to stormflow. The zone expands i n response to r a i n f a l l by lengthening of the surface channel net-work and by expansion of the subsurface zones of water saturation. However, Dunne and Black (1970a, b) have r e c e n t l y found that most of the storm runoff i n watersheds i n Vermont was produced from surface runoff which o r i g i n a t e d on a small proportion of the watershed. This surface runoff only occurred when the water table rose to the s o i l surface. Few hydrologic studies have been made of the s o i l s i n mountainous south-western B.C. Plamondon (1972), working i n Seymour watershed near Vancouver, found that d i r e c t surface runoff does occur, but only over short distances; microtopography prevents i t from occurring on a l a r g e r s c a l e . De V r i e s and Chow (1973) , also working i n Seymour watershed, considered that the hydrologic behaviour of the s o i l was dominated by macrochannels (large open channels i n the s o i l caused by decay of roots or animal burrows). During a r a i n f a l l event, a large proportion of the water was conducted down-ward through these channels, the openings to which were located near the sur-face of the H horizon i n the f o r e s t f l o o r . Watershed hydr o l o g i s t s have tended to neglect the p o t e n t i a l s i g n i f i c a n c e of macrochannels, despite widespread evidence f o r t h e i r existence ( e.g. 76 Aubertin, 1971; Jones, 1971). At Haney, surface runoff, of the type described by Plamondon (1972), has been observed. In a d d i t i o n , c l o s e examination of faces i n the s o i l p i t s dug revealed an abundance of macrochannels (Figure 4.4). Water has been observed pouring r a p i d l y out of some of these macrochannels during heavy r a i n s . Furthermore, the water table has been observed to r i s e and f a l l very q u i c k l y i n response to r a i n f a l l , sometimes r i s i n g and f a l l i n g more than 50 cm within two days. This suggests that the water t r a v e l s r a p i d l y down through the s o i l to the groundwater zone and then q u i c k l y out of t h i s zone. Assuming that the bed-rock and basal t i l l are r e l a t i v e l y watertight, the groundwater must move i n t o the streams. These observations suggest that i n the watersheds at Haney, subsurface flow of water through macrochannel networks makes a s i g n i f i c a n t c o n t r i b u t i o n to stream stormflow. Other sources of storm runoff cannot be excluded, however. Dunne and Black's elevated water table surface runoff mechanism i s l i k e l y to operate when the s o i l s are very wet, and d i r e c t surface runoff from areas im-mediately adjacent to stream channels i s also l i k e l y to contribute to storm-flow. Water budgets and evapotranspiration Isohyetal maps (Figure 2.2) were drawn i n order to determine the amount of p r e c i p i t a t i o n f a l l i n g on each watershed. Table 4.1 summarizes the p r e c i p i -t a t i o n and stream runoff data f o r the two water years of measurement. The estimated annual evapotranspiration (ET) using simple water- budgets i s about 80-85 cm (Table 4.1). This does not agree very well with other es-timates of ET f o r the watersheds and nearby areas (Table 4.2). This may be p a r t l y explained by errors i n c a l c u l a t i n g water volumes. The estimated maximum possible e r r o r s involved i n c a l c u l a t i n g p r e c i p i t a t i o n inputs are 10%and i n streamflow outputs, 30-35%. Unrecorded leakage of water from the watersheds may also explain the r e s u l t s . In t h i s respect, the base of weir C does not Figure 4.4 Macrochannels exposed i n the faces of s o i l p i t s p i t no. 3 r e s t on completely impervious m a t e r i a l s . In a d d i t i o n , a very small amount of leakage i s known to occur at weir B. Table 4.1 P r e c i p i t a t i o n and runoff f o r the watersheds at Haney. watershed water year P R (P-R) Oct. 1 - Sept. 30 (cm) (cm) (cm) A 1971 - 1972 267 170 97 1972 - 1973 182 101 81 B + C 1971 - 1972 292 212 80 1972 - 1973 199 124* 75* C 1972 - 1973** 204 104 100 P = incoming p r e c i p i t a t i o n , as measured at the U.B.C. Research Forest "Administration" s t a t i o n and corrected, to give the p r e c i p i t a t i o n a c t u a l l y f a l l i n g on the watersheds, using the data obtained from the i s o h y e t a l maps. R = runoff as c a l c u l a t e d from weir discharge records. Discharge from weir B o r i g i n a t e s from watershed B plus watershed C. (P-R) = an estimate of evapotranspiration assuming that the bedrock and basal t i l l of the watershed are watertight and that there i s no leakage through or around the weirs. * These values may be a f f e c t e d by c l e a r c u t t i n g which took place during the l a s t four months of the 1972-1973 water year. ** Weir C commenced operation half-way through the 1971-1972 water year so that data f o r t h i s period are not a v a i l a b l e . 79 Table 4.2 Estimates of evapotranspiration f o r Haney Method 1. 2. 3. 4. . watershed A 1971- 1972 water year 97 64 56 1972- 1973 water year 81 65 watershed B + C 1971- 1972 water year 80 63 61 56 1972- 1973 water year 75 64 watershed C 1972-1973 water year- 100 65 A l l values are i n cms. 1. Estimated from water budgets i n the present study (Table 4.1). 2. Calculated from data supplied by Dr. T.A. Black and the formula S ET + _ + R^ where y I s the psychrometric constant, S i s the slope of the satu r a t i o n vapour pressure curve at the monthly mean temperature, and R^ i s the net r a d i a t i o n (McNaughton and Black, 1973). 3. Estimated from data of Zeman (1969) using a simple water budget f o r the M i l i t z a Lake basin at Haney. 4. Ca l c u l a t e d by J . Cheng (Graduate Student, F a c u l t y of For e s t r y , U n i v e r s i t y of B.C.: Personal communication) using Hamon's method (Hamon, 1963) f o r an area near watershed A. E f f e c t s of c l e a r c u t t i n g on streamflow C l e a r c u t t i n g i s expected to increase the water y i e l d from watersheds with the most pronounced increases during the growing season when i n t e r -ception and t r a n s p i r a t i o n by vegetation i s greatest (e.g. Hibbert, 1967). 80 Figure 4.5 Weekly maximum and minimum stream temperatures ^ weekly maximum a i r temperature - weir A 71 I I I I 1 I I I I I 1 i 1 I I 1 I I I I 1 1 1 I I I 1 I ! 1 weekly minimum a i r temperature - weir A I 1 I I 1 I 1 1 1 1 I 1 1 1 I I 1 I I I 1 I I | | | | | 1 1 |- | | " S O N D J F M R B J j q s O M D J F M f l M J J f l S O M D J F H B '^ 7' • H71 I H73 | |«174 Figure 4.6 Streamwater temperatures during a t y p i c a l summer's day and a t y p i c a l winter's day Temperature (°C) 5-, -i 1 \ 1 1 — > 4 8 12 16 20 '24 2nd July, 1972 82 Figure 4.7 Streamwater temperature during the passage of an arctic front Temperature (°C) 4 8 12 16 20 3rd January, 1973 At Haney, increases have been observed during the f i r s t dormant season following clearcutting (Table 4.3}. Slightly greater increases from water-shed A than from watershed B have occurred and can be attributed to the fact that a greater percentage of watershed A than watershed B was clear-cut (61% versus 55%). These increases are probably mainly due to decreased interception losses. In October, the runoff was less than expected for both clearcut water-sheds. This may have been due to increased interception by slash and trees which had not then been yarded. Lower temperatures and more complete yard-ing in later months would have reduced interception and contributed to the general increase i n water yields. 83 Table 4.3 Measured and predicted values of stream discharge following c l e a r c u t t i n g . watershed A (cm) watershed B (cm) Oct. 1973 8.9 14.2 -5.3 17.0 25.7 -8.7 Nov. 1973 22.7 18.6 4.1 36.7 34.5 2.2 Dec. 1973 27.1 18.2 8.9 59.2 33.8 25.4 Jan. 1974 30.9 24.0 6.9 50.8 45.5 5.4 Feb. 1974 31.4 23.4 8.0 44.4 44.4 0.0 Mar. 1974 26.5 18.3 8.2 37.1 33.8 3.3 t o t a l increase 30.8 t o t a l increase 27.6 For t h i s 6-month period, t o t a l discharge from watershed C was 141.5 cm. Predicted values r e f e r to the discharges expected, had the watersheds remained undisturbed, and were determined from the regression equations: 1) D A = .0641 + .7421 D c r e l a t i n g t o t a l d a i l y discharges at weir A / ° A » to those at the c o n t r o l weir C, D^, and 2) D g = .0124 + 1.1740 D c r e l a t i n g t o t a l d a i l y discharges at weir B,Dg, to those at the c o n t r o l weir C, D^ (Appendix IV). 2. Stream and s o i l temperature a) Stream temperature The streams i n t h e i r undisturbed watersheds were protected by a moder-a t e l y dense shrub and tree canopy. This, together with many f a l l e n trees (Figure 4.12) shaded them i n summer preventing temperatures from r i s i n g much above 15°C despite a i r temperatures of close to 30°C. In winter the streams were r a r e l y covered by snow so that when a i r temperatures remained below f r e e z i n g f o r several days, the stream temperatures dropped, sometimes to below zero, and the stream surface began to i c e over. Complete i c i n g over was never observed, however, due mainly to stream turbulence and the l i m i t e d duration of below f r e e z i n g temperatures. The stream i n watershed B tended to be cooler than that i n watershed A throughout the year, probably mainly due to i t s s l i g h t l y higher a l t i t u d e . 84 Figure 4.8 Relationships between maxiinura streanwater temperatures In screams a. and I end those at stream C Weakly uxlma atream temperatures i A versus C c BEFORE ClEfiRCUTTIHG fi RRER aCRSCUTTIHC 2^-cc <OC3~ 4 Regression aquation T - 1.709 + .9388 X (r - 0.97) » * O.D 2.0 -i 1 r 4.0 6.0 B.C STREAM C f C ) ttraan temperaturesi ft versus C — I — 12.0 ^ ICO 18.0 , BEFORE aEBROjniNC 8 Rf TEH CLEARCUTTING «fc*= CD t—R IU9r«.fioa squttlon T - -0.0066 • 1.056 X (r . 0.97) 0.0 2.0 6.0 STREAM C ^ C l " — | — 12.0 -1 M.O 16.0 -1 IB.O 85 86 Figure 4.10 Weekly maximum and minimum soil temperatures o soil near weir A * soil near weir B * soil near weir C WEEKLY MAXIMUM S O I L TEMPERATURES ^ weekly maximum a i r temperature - weir A J fi S 0 N O J F H R H J J R S O N D J F H R M J J R S O N O J f H f l c l e a r c u t t i n g -watershed B S"l WEEKLY HINIHUH S O I L TEMPERATURES c l e a r -cu t t i ng water-shed A J R S O H O J F M R H J J f l S O N D J F H f i M J J f i S O N D J F H f i I 971 117 X 1173 I 117/r 87 This a l t i t u d i n a l temperature gradient i s a l s o i l l u s t r a t e d by the lower water temperatures recorded at weir C compared to those recorded downstream at weir B (Figure 4.5). T y p i c a l d a i l y temperature behaviour f o r winter and summer i s shown i n Figure 4.6. D a i l y f l u c t u a t i o n s depended very much on cloud cover, being great-est when there were no clouds. This i s expected i n view of the f a c t that stream temperature depends mainly on incoming s o l a r r a d i a t i o n (Brown, 1969). D a i l y f l u c t u a t i o n s tended to be greatest during cloudless days i n summer. During winter, d a i l y f l u c t u a t i o n s were u s u a l l y quite small (less that 1°C) except during the passage of an a r c t i c f r o n t over the region when stream temperatures followed a i r temperatures, r i s i n g or f a l l i n g by several degrees (Figure 4.7). The streams at Haney appear to have s i m i l a r temperature regimes to those at Hubbard Brook (Likens et at., 1970) and to those i n the H.J. Andrews Experi-mental Forest i n Oregon (Rothacher et at., 1967) except that the Haney streams are s l i g h t l y cooler i n the summer. E f f e c t s of c l e a r c u t t i n g on stream temperature C l e a r c u t t i n g i s expected t o cause an increase i n stream temperatures during the summer and a decrease during winter, these changes decreasing with time as vegetation grows back, as discussed i n Chapter 1. The streams have not yet been monitored during a post-treatment summer. Data are a v a i l a b l e f o r an autumn and winter a f t e r c u t t i n g , however. During t h i s period, maximum and minimum stream temperatures below both c l e a r c u t s have tended to be higher than usual (Figures 4.8 and 4.9). This can be a t t r i b u t e d to ah increase i n the amount of s o l a r r a d i a t i o n reaching the streams, and to an increase i n the energy stored i n the s o i l which increases the temperature of s o i l water, and to adsorption of energy by sla s h i n the streams. b) S o i l temperature S o i l temperatures follow stream temperatures c l o s e l y (Figure 4.10). Lower temperatures measured at s t a t i o n s B and C are probably mainly due to higher a l t i t u d e s , but, i n summer, a l s o p a r t l y due t o greater depths of i n s u l a t i n g duff above the temperature probes, r e l a t i v e to s t a t i o n A. 88 3. Suspended sediment The streams at a l l three weirs were usually very clear, and samples taken during periods of steady flow, both high and low, contained no measurable sus-pended sediment (Table 4.4). Although very few analyses of suspended sediment were carried out, i t appears that significant concentrations only occur during the early part of a storm event when the stream i s ris i n g . Concentrations tended to increase with discharge, peaking before the stream peaked, then de-clined rapidly to zero, well before the stream had dropped to base flow levels (Table 4.4). Concentrations fluctuated widely, however, and consistent trends could not be seen from the limited data collected. Most of the stream sediment, both before and after clearcutting, was organic, the mineral particles of the s o i l generally being too large to be carried great distances over short time periods. Due to the relatively gentle topography of the watersheds and the location of roads away from streams, suspended sediment concentrations were expected to be low, both before and after clearcutting. In addition, relatively low stream gradients and the presence of many pools caused by small debris jams which help to f i l t e r out sediment, also favoured low sediment concentrations. Table 4.4 Suspended sediment concentrations i n streams leaving the watersheds. Stream Time and date Before clearcutting Discharge(litres/sec) Suspended sediment concentration(mg/1) A 2.45 p.m. 12/7/72 249 peak discharge 107.0 B 3.00 p.m. 12/7/72 1223 of the largest 29.5 C 3.15 p.m. 12/7/72 553 recorded storm 12.0 A 11.15 a.m. 24/8/72 0.6 steady 0.0 B 11.30 a.m. 24/8/72 1.7 summer 0.0 c 11.50 a.m. 24/8/72 1.2 base flow 0.0 A 5:00 p.m. 12/1/73 17 steady 0.0 B 5.15 p.m. 12/1/73 78 winter 0.0 C 5.30 p.m. 12/1/73 39 base flow 0.0 cont. 89 Table 4.4 cont. 5 Time and date Suspended sediment Stream During and a f t e r Discharg e ( l i t r e s / s e c ) concentration (mg/1) Cl e a r c u t t i n g October storm A ( p a r t i a l l y 2.00 p.m. 12/10/73 4 r i s i n g 20.2 clearcut) 4.30 p.m. 13/10/73 91 f a l l i n g 1.3 11.30 a.m. 15/10/73 9 f a l l i n g 0.6 B ( f u l l y 1.30 p.m. 12/10/73 43 r i s i n g 35.2 clearcut) 6.15 p.m. 12/10/73 78 r i s i n g 24.2 5.30 p.m. 13/10/73 173 f a l l i n g 1.3 12.30 p.m. 15/10/73 33 f a l l i n g 0.8 C (undisturbed) 4.00 p.m. 12/10/73 40 r i s i n g 7.5 5.45 p.m. 13/10/73 105 f a l l i n g 1.9 11.45 a.m. 15/10/73 17 f a l l i n g 0.2 November storm A ( p a r t i a l l y 11.00 a.m. 27/11/73 38 r i s i n g 0.0 clearcut) 2.00 p.m. 27/11/73 61 r i s i n g 0.0 7.15 p.m. 27/11/73 120 r i s i n g 12.7 11.00 p.m. 27/11/73 131 peak .0.6 2.30 a.m. 28/11/73 118 f a l l i n g 0.4 1.30 p.m. 28/11/73 78 f a l l i n g 0.0 4.00 p.m. 28/11/73 67 f a l l i n g 0.0 1.30 p.m. 29/11/73 33 f a l l i n g 0.0 B ( f u l l y 11.15 a.m. 27/11/73 144 r i s i n g 0.0 clearcut) 2.30 p.m. 27/11/73 273 r i s i n g 2.3 8.00 p.m. 27/11/73 689 r i s i n g 1.6 11.30 p.m. 27/11/73 694 peak 3.6 3.00 a.m. 28/11/73 561 f a l l i n g 0.0 2.00 p.m. 28/11/73 290 f a l l i n g 0.0 4.30 p.m. 28/11/73 245 f a l l i n g 0.0 2.00 p.m. 29/11/73 100 f a l l i n g 0.0 C (undisturbed) 12.15 p.m. 27/11/73 105 r i s i n g 0.0 2.45 p.m. 27/11/73 155 r i s i n g 9.3 7.45 p.m. 27/11/73 271 r i s i n g 10.3 11.15 p.m. 27/11/73 290 peak 8.8 3.15 a.m. 28/11/73 258 f a l l i n g 0.4 2.15 p.m. 28/11/73 145 f a l l i n g 0.0 4.15 p.m. 28/11/73 114 f a l l i n g 0.0 2.15 p.m. 29/11/73 55 f a l l i n g 0.0 Streamwater was analyzed f o r suspended sediment during the f i r s t major storm a f t e r c l e a r c u t t i n g (October 12-14, 1973 i n Table 4.4). Shortly a f t e r the streams began to r i s e , high concentrations were found, but these r a p i d l y • 90 declined. Suspended sediment concentrations i n streams leaving the c l e a r c u t watersheds during a l a t e r storm (November 27-29, 1973 i n Table 4.4) were lower than during the October storm, despite comparable discharges. This i s probably due to the tendency of the f i r s t major autumn storm to f l u s h out debris which has accumulated near the streams during t h e i r low flow period i n l a t e summer. Subsequent increases i n streamflow, unless they are greater than a l l the pre-ceding ones, thus encounter l e s s debris to wash away. The l i m i t e d measurements made, together with v i s u a l observations, suggest that c l e a r c u t t i n g has caused no major change i n suspended sediment concentra- . ti o n s with the p o s s i b l e exception of the f i r s t major storms f o l l o w i n g c l e a r -c u t t i n g . This can be a t t r i b u t e d to the r e l a t i v e l y gentle topography, the ab-sence of prolonged intense r a i n f a l l , and to the lack of road construction near streams. Although several s k i d roads were used, e s p e c i a l l y i n the upper p o r t i o n of watershed A, these were generally p a r a l l e l to land contours and not very steep. Most of watersheds A and B were yarded using a high lead spar system (Figure 4.11). Although yarding across the streams occurred (Figure 4.11), landings were located close to the height of land so that nearly a l l yarding was u p h i l l . Such logging operations are known to minimize stream sedimentation (Lantz, 1971b; U.S. Department of t h e , I n t e r i o r , 1970). Low suspended sediment concentrations following c l e a r c u t t i n g may also be due to the f a c t that many of the f i n e p a r t i c l e s deposited i n the streams by logging operations have remained trapped behind logging debris (Figure 4.12). The Hubbard Brook study (Likens et al. , 1970) found that f o r e s t c u t t i n g and h e r b i c i d e a p p l i c a t i o n caused no obvious d i f f e r e n c e s i n t u r b i d i t y (and hence suspended sediment) of stream water and that measurements of t u r b i d i t y were of l i t t l e value i n assessing the changes i n the q u a l i t y of streamwater from f o r e s t -ed and deforested watersheds. Although the watershed ecosystems at Haney are d i f f e r e n t from those at Hubbard Brook and the commercial c l e a r c u t t i n g s at Haney and the Hubbard Brook tree c u t t i n g treatment were quite d i f f e r e n t , i t seems that F i g u r e 4.12 stream channels before and a f t e r c l e a r c u t t i n g A . Before c l e a r c u t t i n g Stream B Stream B 94 95 the Hubbard Brook conclusions apply j u s t as well to the watersheds at Haney. Fredricksen (1971) observed s i g n i f i c a n t increases i n suspended sediment concentrations i n a stream following logging i n Oregon. The watersheds he was studying are much steeper than those at Haney, however, and t h e i r s o i l s are quite d i f f e r e n t . These f a c t o r s , together with the use of slashburning, which followed c l e a r c u t t i n g i n the Oregon study and which tends to increase the p o s s i b i l i t y of erosion more than does c l e a r c u t t i n g alone (Dyrness, 1967; Rice et al. , 1972; Swanston and Dyrness, 1973), suggests that the logging at Haney would have l e s s impact on stream sediment concentrations than d i d the logging i n Oregon. Fredricksen (1970) also noted that, following c l e a r c u t t i n g , most of the f i n e sediment and nearly a l l the coarse sediment remained i n the stream channel trapped behind logging d e b r i s , as was probably the case i n the present study (Figure 4.12). 4. Dissolved oxygen  Seasonal behaviour The stream water at Haney was u s u a l l y between 90% and 110% saturated (Figure 4.14). Values below saturation were most common during the lowest flow periods i n l a t e summer and e a r l y autumn when stream temperatures were also at a maximum. However, values below 65% sat u r a t i o n have not been measured. Supersaturation of d i s s o l v e d oxygen i n stream water has been frequently observed i n many parts of the world (e.g. Likens et al. , 1970 and references therein; Lindroth, 1957), i n c l u d i n g a t r i b u t a r y of the P i t t r i v e r , several km. north of the study area (Harvey and Cooper, 1962). This may be due to turbulence i n which gas bubbles are pushed to various depths i n streams, where they give o f f some of t h e i r gases to the water, due to increased hydrostatic pressures, before r i s i n g to the surface (Lindroth, 1957). I t may also depend on the a l t i t u d i n a l stream temperature gradient (Likens et al. , 1970), i n which case streamwater temperatures may be e q u i l i b r a t i n g with a i r temperatures more r a p i d l y than are d i s s o l v e d oxygen concentrations with stream water temperatures. 96 16 § 12 g 101 y s i o CJ i Figure 4.13 Dissolved oxygen concentrations - stream A, B, and C DISSOLVED OXYGEN CONCENTRATION fl = STREAM fl B = STREAM B C = STREAM C c l e a r c u t t i n g A 160 j 140 •• 120 • 100 80 j in in i II in II II nun iHiiuiiiiiniiiiimmi mini nun mini mm ii i i i i i i m i i i i i n i i timi i i i i i i i i i i i n i i i i i i i i i i i i n i i i O N D J F M R M J J f l S O N D J F M f l M J J R S O N D J F M R M J J f l S O N D J F M f l Figure 4.14 Dissolved oxygen percent saturation - streams A, B, and C DISSOLVED OXYGEN PERCENT SATURATION fl = STREAM fl B = 5TRERM B C = STREAM C 60 c l e a r c u t t i n g -A I 1 c l e a r c u t t i n g -B nmiiiiHiiiii nun mini nun mini nun ii iiiiniiniuniitniiimmn4mintmnmntMmiiiiiiiiiiiiiiiiw O N D J F M f l M J J f i S O N D J F M f l M J J H S O N D J F M f i M J J R S O N D J F M R 1970 1971 1972 1973 1974 97 As can be seen from Figures 4.15 and 4.16, the time of sampling can a f -f e c t the measured concentrations and degrees of s a t u r a t i o n . Weekly sampling u s u a l l y occurred between 10 a.m. and 4 p.m. - the time when concentrations and degree of s a t u r a t i o n tended to be highest. Dissolved oxygen concentrations and degrees of saturation tended to be lower during the night and higher during the day (Figures 4.15 and 4.16). This suggests that there was some, a l b e i t s l i g h t , production of oxygen i n the streams by photosynthetic processes (Minckley, 1963, Schmassmann,1951; Wiken, 1936). The absence of a pronounced d i u r n a l v a r i a t i o n i n pH values (Figures 4.15 and 4.16) which would occur i f photosynthetic organisms took up d i s s o l v e d CC^ during d a y l i g h t hours, increas-ing the streamwater pH, further suggests that photosynthetic oxygen production i n the streams was only rather s l i g h t (Livingstone, 1963; Minckley, 1963). This i s also supported by the absence of high d i s s o l v e d oxygen concentrations i n e a r l y summer when stream flows and temperatures are high and when photosyn-t h e t i c a c t i v i t y should also be high (Minckley, 1963). The d i s s o l v e d oxygen behaviour of the streams at Haney i s almost i d e n t i c a l to that a t Hubbard Brook (Likens et al. , 1970). Weisel and Newell (1970), studying streams i n western Montana, found that d i s s o l v e d oxygen concentrations exhibited a pattern s i m i l a r to those at Haney, but they found that the degree of oxygen saturation was highest during the low flow summer months which they a t t r i b u t e d to photosynthetic production of oxygen within the streams. Moreover, they found no nocturnal decrease i n oxygen l e v e l s , and they observed maximum d i s s o l v e d oxygen concentrations i n the morning and minimum concentrations i n the evening due to changes i n water temperature. In a d d i t i o n , they found that d i s s o l v e d oxygen depended more on stream temperature than on discharge. Their study streams, however, flowed through highly d i s -turbed watersheds at elevations above 1000 m. where spring snowmelt accounted f o r most of the peak stream runoff, and temperature extremes were greater than those at Haney. Thus, these Montana streams are not r e a l l y comparable to those 98 Figure 4.15(a) Diurnal v a r i a t i o n i n streamwater disso l v e d oxygen and pH - l a t e autumn STREAM A Discharge - steady at 3.8 l i t r e s / s e c Dissolved oxygen % saturation 86 , 84 J 80 76 74 A l l readings ±3% ~i 1 1 r ~l r 1 1 1 1 Dissolved oxygen concentration (mg/1) 9.5 9.2 J 8.8 8.4H 8.0 A l l readings ±.2 mg/1 -i 1 1 1 1 r i 1 1 1 r pH 6.71 6.6 6.5. A l l readings ±.1 pH un i t T 1 1 ; 1 T 1 1 1 1 1 1 1 1 Stream temperature (°C) 5.2 4.8 4.4 4.0 i 1 -i r 1800 November 5 i r 2400 — i 1 1 600 1200 November 6 1973 9 9 Figure 4.15(b) Diurnal v a r i a t i o n i n streamwater d i s s o l v e d oxygen - l a t e autumn STREAM B o Discharge - steady at 12.4 l i t r e s / s e c Dissolved oxygen % saturation 100-r 96H 92-88-A l l points ±4% ~i 1 1 r -i 1 1 1 1 — — i 1 Dissolved oxygen concentration (mg/1) 12.4, 12.0-11.6-11.2J 10.8. T 1 1 1 r A l l points ±.2 mg/1 T— 1 1 1 1— 1 1 pH 6.8 6.6-1 6.4 A l l points ±.1 pH un i t T 1 1 1 1 1 1 ~\ 1 1 1 r Stream temperature (°C) 4.2 -, 3.8H 3.4 i — ; — i 1 r 1800 November 5 — | — ; i 1 1— — i r 1 1 2400 600 1200 November 6 1973 100 Figure 4.15(c) Diurnal v a r i a t i o n i n streamwater d i s s o l v e d oxygen - l a t e autumn STREAM C Discharge - steady at 7.2 l i t r e s / s e c Dissolved oxygen % sa t u r a t i o n 100 n 96 H 92 88 J 84 T 1 1 1 r A l l points ±4% i r r Dissolved oxygen concentration (mg/1) 12.8' 12.4-.12.0-11.6-11.2 A l l points ±.2 mg/1 1 1 1 1 r "I i i 1 1 1 - T — — I pH 6.9-, 6.7H -* *-A l l points ±.1 pH u n i t T i i 1—•—r " i I — i r— 1 r Stream temperature (°C) 3.4-, 3.0-] 2.6 ~i 1 1 1 r 1800 • November 5 24'00 ~i 1— '— i 1 1 — — i 600 1200 November 6 1973 101 Figure 4.16(a) . Diurnal v a r i a t i o n i n streamwater d i s s o l v e d oxygen and pH - e a r l y summer STREAM A Dissolved oxygen % saturation 96^ 94 92 -| 90 88 A l l points ±4% ~i 1 1 1 r 1 1 1 1 1 1 Dissolved oxygen concentration (mg/1) 10.0' 9.8 9.6 9.4 9.2 A l l points ±.2 mg/1 ~i 1 1 1 r - i 1 1 1 —I 1 i pH 7.0-1 6.9 6.8 11 points ±.1 pH u n i t T 1 1 1 r T 1 1 1 1 1 Stream discharge ( l i t r e s / s e c ) .1.4, 1.0. T 1 1 1 1 1 1 i — : — i 1 1 r Stream temperature (^C) 11.1" 10.91 10.7 -T r 1800 June 24 1 r 2400 " i 1 r 600 June 25 T 1 1 1200 1972 102 Figure 4.16(b) Diurnal v a r i a t i o n i n streamwater disso l v e d oxygen and pH - ea r l y summer STREAM B Dissolved oxygen % saturation 108 - i 104 A 100 J 96 A i r A l l points ±4% i 1 1 1 1 r Dissolved oxygen concentration (mg/1) 11.2 _, 10.8 -10.4 -10.0 A l l points ±.2 mg/1 ~t 1 1 r -i 1 1—:—r 1 r pH 7.0 -, 6.9 i 1 1 r T— 1 1 r A l l points ±.1 pH un i t ~i r Stream discharge ( l i t r e s / s e c ) 10.0 ~] 5.0 A 2.0 T 1 1 1 r "i 1 1 1 1 1 r Stream temperature (°C) 10.4 -, 10.0 H 9.6 1 1 1 r~ 1 1 1 1 1 1—:—i 1 r i4c 1800 June 24 2 00 600 June 25 1200 1972 I n s u f f i c i e n t measurements were made of di s s o l v e d oxygen and pH on stream C to permit d i u r n a l trends to become apparent. 103 at Haney. Variation with discharge Dissolved oxygen concentrations and, to a lesser extent, degrees of satura-tion, increased with discharge (Figures 4.17, 4.18, and 4.19). However, the relationship may be complicated by temperature effects, since the lowest flows occurred during late summer when stream temperatures were highest. Variation between streams Dissolved oxygen concentrations i n stream A tended to be lower than those in streams B and C (Figure 4.13). This may be partly due to the fact that, although the average stream gradients are similar, immediately upstream of the sampling points, stream A had a very low gradient with l i t t l e turbulence whereas immediately upstream of sampling points B and C, the stream dropped more rapidly with considerable turbulence. It may also be partly due to the fact that stream A tended to be slightly warmer than streams B and C as dis-cussed above, and is also smaller, making i t s dissolved oxygen concentrations more easily lowered by inputs of organic materials. Effects of clearcutting It i s too soon to detect any significant effect of clearcutting on dis-solved oxygen levels in streams A and B as the effects are only l i k e l y to be significant during the summer and early autumn. This i s indicated by the be-haviour of dissolved oxygen i n streams D and E following clearcutting (Figures 4.20 and 4.21). During the cooler and wetter months, dissolved oxygen concen-trations in these streams remained close to 100% saturation, even after clear-cutting, whereas during the warmer and drier months, dissolved oxygen concen-trations dropped spectacularly following clearcutting, often to less than 5 mg/litre and 50% saturation. Dissolved oxygen concentrations also exhibited much greater fluctuations in response to discharge after clearcutting than be-fore (Figures 4.20 and 4.21). Clearcutting appears to have lowered the s t a b i l i t y of the stream ecosystem with respect to dissolved oxygen. Figure 4.17 Relationships between streamwater dissolved oxygen concentrations and discharge. DISSOLVED OXYGEN VERSUS DISCHARGE. STREAM A . BLfonE C I E W C U T I I K ; I fifTER CLLRBCUrilNG Y = 9.570 + 2.1341ogX (r = .75) — i — 1 3 . 0 —1 1 1 9 . 5 3 6 . 0 3 2 . 5 3 9 . 0 0I5CHARGE [LITRES/SEC) DISSOLVED OXYGEN VERSUS DISCHARGE. STREAM B . BEFORE CIEFBCUTUKS I RFTEH CLERKajTUHS s.s —I 4 5 . 5 Y = 10.56 + 1.3481ogX (r = .55) a.o • i ^ 1 1 1 1 * 6 . 0 5 2 . 0 7 8 . 0 1 0 4 . 0 1 3 0 . 0 1 5 6 0 DISCHARGE (LITRES/SEC) DISSOLVED OXYGEN VERSUS DISCHARGE. STREAM C . 2 0 8 . 0 2 3 4 . 0 - 1 ' 2E0 0 . 0 Y = 10.80 + 1.1421ogX (r = .58) — t — n .o ~ i — 2 3 . 0 1 3 . 0 4 4 . 0 S R . . O 6 0 0 DISCHARGE (LITRES/SEC) ' — r — 8 8 . 0 B 9 . 0 —1 1)0 Regressions are for "before clearcutting" data only. 105 Figure 4.18. Relationships between streamwater dissolved oxygen percent saturations and discharge. D I S S O L V E D OXYGEN PERCENT SATURATION VERSUS D I S C H A R G E . STREAM A . BEFORE ClEflRCUniW I WICR CltWEUITlNS Y = 95.9124 - 6.2468C-) (r = .47) X 1 1 1 1 1 1 1 1— 6.3 13.0 19.5 25.0 32.5 39.0 "S.5 52.0 DISCHARGE ( L I T R t S / S E C ) D I S S O L V E D OXYGEN PERCENT SATURATION VERSUS D I S C H A R G E . STREAM 8 . BEFORE aEPRCJTTING I RFTER O-ERSCUTTING —1 182.0 —I 234.0 UJ 7B.0 104.0 130.0 155.0 DISCHARGE ( L I T R E S / S E C ! 280.0 D1SSOLVE0 OXYGEN PERCENT SATURATION VERSUS D I S C H A R G E . STREAM C — I — u.o 0.0 —1 1 1— 1— 33.0 14.(1 W B 66.0 DISCHARGE (L U R L S / S E C ! — l — ea.o — l — 03.0 110.0 Regression i s for "before clearcutting" data only, relationships were found for streams B and C. No significant 106 Figure 4.19(a) Streamwater d i s s o l v e d oxygen during a storm event (27-29 November, 1973) STREAM A Dissolved oxygen concentration (mg/1) Figure 4.19(b) Streamwater d i s s o l v e d oxygen during a storm event (27-29 November, 1973) STREAM B Dissolved oxygen concentration (mg/1) 13.5" 13.0 12.5 A l l points ±.2 mg/1 T r ~ i r Dissolved oxygen % sa t u r a t i o n 105-95 -i r A l l points ±4% -i r Stream discharge ( l i t r e s / s e c ) 1000-i 500 J 100 10-1 0 -| r Stream temperature (°C) 4.5 108 Figure 4.19(c) Streamwater d i s s o l v e d oxygen during a storm event (27-29 November, 1973) STREAM C Dissolved oxygen concentration (mg/1) 15.0-14.04 13.0- T T r A l l points ±.2 mg/1 Dissolved oxygen % saturation 105 n 95 H -* A l l points ±4% - i r-Stream discharge ( l i t r e s / s e c ) 300-100-Stream temperature (°c) 4.0 -3.0 • 109 20 T | 1 6 -E 1 2 -81 CE CH LU CJ ZZL o 4 -c D E Figure 4.20 Dissolved oxvqen concentrations - streams'D and E DISSOLVED OXYGEN CONCENTRATION STREAM C STREAM D F e l , l i n 9 Y a r p 9 STREAM E | I Q liiiiiimtuiMtiiifiiiicsiifimiiIIIIIPIf«ini«itmi<tiiniitiitiiimitiniMHIIHIIIMMtiimimiii 11111111111111111111 Q N D J F M R M J J R S O N D J F M H M J J R S O N D J F M f l M J J f l S O N D J F M R 140 j 120 •• 100 80 •• 60 •• 40 • 20 • 0 Figure 4.21 Dissolved oxygen percent saturation - streams D and E DISSOLVED OXYGEN PERCENT SATURATION C = STREAM C D = STREAM D E = STRERM E , Q N D J F M H M J J R S O N D J F M R M J J R S O N D J F M R M J J R S Q N D J F M R 1970 1971 1972 1973 1974 110 The odour of hydrogen sulphide frequently detected near streams D and E a f t e r c l e a r c u t t i n g suggested the occurrence of anaerobic decomposition of the slash deposited i n the streams. Such decomposition i s i n d i c a t i v e of consider-able b i o l o g i c a l and chemical oxygen demands with r e s u l t i n g low d i s s o l v e d oxygen concentrations. S i m i l a r low d i s s o l v e d oxygen concentrations a f t e r logging have been ob-served i n the Alsea basin i n Oregon by H a l l and Lantz (1969). They found that removal of s l a s h from streams r a i s e d the l e v e l s of the surface water d i s s o l v e d oxygen but had l i t t l e e f f e c t on i n t r a g r a v e l d i s s o l v e d oxygen. The low d i s s o l v e d oxygen concentrations were found to cause high m o r t a l i t y of salmon and t r o u t . Small cutthroat t r o u t were observed i n streams D and E p r i o r to c l e a r -c u t t i n g but none have been observed since. Although there i s no conclusive evidence that t h e i r absence i s a function of reduced oxygen l e v e l s , the concen-t r a t i o n of d i s s o l v e d oxygen i n streams D and E i n the summer and e a r l y autumn has been c o n s i s t e n t l y lower than 6 m g / l i t r e (the l e v e l required f o r good growth and general well-being of t r o u t and salmon, National Technical Advisory Commit-tee t o the Secretary of the I n t e r i o r , 1972) so i t i s l i k e l y that the f i s h pop-u l a t i o n s i n these streams have suffere d from the observed oxygen reduction. Streams A, B, and C supported no anadromous f i s h but there was a popula-t i o n of resident cutthroat t r o u t , 5 to 15 cm. i n length. F i s h surverys of these streams were made before and a f t e r c l e a r c u t t i n g , by Dr. T.G. Northcote of the Zoology Department, U.B.C, but the data have not yet been processed. The f o r e s t c u t t i n g and h e r b i c i d e a p p l i c a t i o n experiment at Hubbard Brook (Likens et al., 1970) r e s u l t e d i n greater stream discharges which helped to maintain high d i s s o l v e d oxygen concentrations during the summer months. In the Hubbard Brook experiment, a d e l i b e r a t e attempt was made to keep slash out of streams. T h i s , together with considerable stream turbulence, i s considered to have maintained high l e v e l s of d i s s o l v e d oxygen (G.E. Likens: Personal communi-ca t i o n ) . A f t e r commercial c l e a r c u t t i n g , where large amounts of s l a s h i n e v i t a b l y I l l end up in streams, i t seems that, despite increased flows, the biological and chemical oxygen demand of the decaying slash w i l l lower dissolved oxygen concentrations i n streams. 5. pH Seasonal behaviour The streams at Haney were characterized by neutral to s l i g h t l y acidic water, with pH usually ranging from 6.5 to 7.2. Although weekly fluctuations were considerable, a trend towards higher pH i n the summer and lower pH i n the winter was discernable (Figure 4.22). Similar trends have been found at Hubbard Brook (Fisher et al., 1968; Likens et at., 1970).and in western Montana (Weisel and Newell, 1970) where they have generally been attributed to variations in discharge, pH decreasing with increasing discharge (Johnson et at., 1969). The decrease i n pH i n autumn was probably due mainly to dilution by more acidic throughfall and s o i l waters. However, i t may have been partly due to increased l i t t e r f a l l which deposits large amounts of organic material in the streams. Leached constituents and the decomposition products of leaf l i t t e r have been shown to significantly affect streamwater pH in autumn (Minckley, 1963; Slack and Feltz, 1968) and may do so to some extent at Haney. The streams there were surrounded by deciduous species such as Rubus spectabilis, Alnus rubra, Oplopanax horridus, and Vaccinium sp. and large amounts of leaf l i t t e r have been observed on and in the streams during autumn. Variation with discharge pH decreased with increasing discharge (Figures 4.23 and 4.24) as i t did in streams i n Oregon (Rothacher et al., 1967), Utah (Johnston and Doty, 1972), and New Hampshire (Johnson et at., 1969), accounting for the weekly fluctuations. Variation between streams There were no significant differences i n pH values between streams (Fig-ure 4.22) . 8T 7.6-7.2-6.8-6.4-Figure 4.22 Streamwater pH - streams A, B, and C H A = S T R E A M fl B = S T R E A M B •C. = S T R E A M C P c l e a r c u t t i n g -c l e a r c u t t i n g -B 1 1 g ti11nu1111111111iiii111 i i i i i i i i i i i i i i i i i i i i i i i i i n l i i i i i i i m i n i m i n m i n i m i i i i i i i i i l i n m n i ONDJFMRMJJflSONDJFMflMJJflSO'NDJFMflMJJflSONDJFMfl 1970 1971 1972 19.73 1974 Figure 4.23. Relationships between streamwater pH and discharge. PH pH VERSUS DISCHARGE. STREAM H . etfjit au;ru!ii.», 0 WTER CLERft'uniNG 6.973 - 0.24521ogX (r = .60)-— i — 6.S I 13.0 ~1 1 1 1 19.5 25.0 32.5 39.0 DISCHARGE ILITRES/SEC! —I «.5 —I 52.0 t 65.0 0.0 PH' pH VERSUS DI5CHARGE. STREAM B . BEFORE a.E?fiamiiit; 0 RFTER CURSOJTT1SG Y = 7.101 - 0.27421ogX (r = .67) T - —n 1 1 1 78.0 104.0 130.0 1S6.0 DISCHARGE (LITRES/SEC) pH VERSUS DISCHARGE. STREAM C -1 182.0 -1 208.0 -1 1 234.0 260.0 0.0 26.0 52.0 Y = 7.019 - 0.27451ogX (r = .80) i i i 1 1 1— 0.0 II.0 22.0 33.0 <M.0 Vill GC.O DISCHARGE (LITRES/SEXI 77.0 en.o no o n o . o Regressions are for "before clearcutting" data only. 114 Figure 4.24 Streamwater pH during a storm event (27-29 November, 1973) STREAM A pH 6.41 T 1 1 1 1 1 1 j 1 1 r 27 28 29 STREAM C (undisturbed) A l l points ±.1 pH unit Figure 4.25. Streamwater pH - streams D and E 8 7.5 7 6 . 5 -6 -5 . 5 -G = STREAM C D = STREAM D E = STREAM E P H F e l l i n g Yarding iii aiiiai igjffgifiijfg iiiiiii iitiBfftiiiitfiifiififiiii ifinjitimi ifiiifiiiini iiifiiniitit iiftffjiniiniiiitiniifti minim ONDJFMflMJJflSONDJFMflMJJflSONDJFMflMJJflSONDJFMfl 1970- 1971 1972 1973 1974 116 E f f e c t s of c l e a r c u t t i n g C l e a r c u t t i n g has lowered streamwater pH s l i g h t l y (Figures 4.22 and 4.25; Table 4.5). These decreases were generally s t a t i s t i c a l l y s i g n i f i c a n t (Appendix X). The decreases r e s u l t from a combination of the following f a c t o r s : 1. Increased stream discharges following c l e a r c u t t i n g . 2. Leaching of i o n i z a b l e organic acids from the sl a s h . 3. Increased carbon dioxide production r e s u l t i n g from enhanced a c t i v i t y of decomposer organisms. Table 4.5 Average pH values of streams before and a f t e r c l e a r c u t t i n g . before a f t e r before a f t e r Stream A Control (C) 6.7(.2) 6.6(.l) 6.4(.l) 6.5(.l) Stream B Control (C) 6.7(.2) 6.7(.2) 6.4(.2) 6.6(.2) before after(1) after(2) before a f t e r (1) after(2) Stream D Control (C) 6.7(.2) 7.0(.2) 6.4(.3) 6.8(.2) 6.6(.2) 6.9(.2) Stream E Control (C) 6.8(.2) 7.0(.2) 6.5(.3) 6.8(.2) 6.8(.2) 6.9(.2) Standard deviations are given i n parentheses. Values are for the periods: A - November 1, 1972 to A p r i l 1, 1973 before c l e a r c u t t i n g November 1, 1973 to A p r i l 1, 1974 a f t e r c l e a r c u t t i n g B - October 1, 1972 to A p r i l 1, 1973 before c l e a r c u t t i n g October 1, 1973 to A p r i l 1, 1974 a f t e r c l e a r c u t t i n g D,E - A p r i l 1, 1971 to November 1, 1971 before c l e a r c u t t i n g A p r i l 1, 1972 to November 1, 1972 a f t e r c l e a r c u t t i n g - year 1 A p r i l 1, 1973 to November 1, 1973 a f t e r c l e a r c u t t i n g - year 2 A s i m i l a r decrease i n streamwater pH was observed i n the Hubbard Brook study following f o r e s t c u t t i n g and herbicide a p p l i c a t i o n (Likens et al. , 1970). 6. E l e c t r i c a l c o n d u c t i v i t y Seasonal behaviour E l e c t r i c a l c o n d u c t i v i t y of the streamwatdr underwent pronounced seasonal f l u c t u a t i o n s with minimum values i n winter and maximum values i n l a t e summer and e a r l y autumn. The values f l u c t u a t e d from 10 to 30 around a mean of 20 micromhos/cm at 25°C. 117 S i m i l a r seasonal behaviour i n e l e c t r i c a l c o n d u c t i v i t y has been found f o r streams i n c o a s t a l Oregon (Rothacher et al. , 1967) and c o a s t a l C a l i f o r n i a (Kopperdahl et al. ,. 1971) . In both cases only values f o r t o t a l d i s s o l v e d s o l -i d s were reported, but e l e c t r i c a l c o n d u c t i v i t y i s c l o s e l y r e l a t e d t o , and v a r i e s d i r e c t l y with, t o t a l d i s s o l v e d s o l i d s concentrations (Hem, 1970). The streams at Hubbard Brook and nearby areas seem to have rather uniform e l e c t r i -c a l c o n d u c t i v i t i e s which undergo l i t t l e d a i l y or seasonal v a r i a t i o n (Bormann et al., 1969; Likens et al., 1970). Pierce et al. (1972) quote ranges of of e l e c t r i c a l c o n d u c t i v i t y measured i n seven d i f f e r e n t streams i n New Hampshire over an eight month period. For s i x of the streams the range was l e s s than 9 micromhos/cm; f o r the seventh i t was 26 micromhos/cm. V a r i a t i o n with discharge E l e c t r i c a l c o n d u c t i v i t y decreased with increasing discharge (Figures 4.27 and 4.28); a condition that has been established f o r many streams ( K e l l e r , 1970a; Livingstone, 1963; Stottlemyer and Ralston, 1970). Within a s i n g l e storm event, the e l e c t r i c a l c o n d u c t i v i t y f o r a given d i s -charge i s higher on the r i s i n g limb of the hydrograph than on the f a l l i n g limb, with the minimum co n d u c t i v i t y occurring a f t e r the stream has peaked (Figure 4.28). This may be due to the tendency of the e a r l i e r port-ion of waters con-t r i b u t i n g to stream stormflow to f l u s h chemicals from the ecosystem, becoming enriched i n them r e l a t i v e to the l a t e r p o r t i o n . In a d d i t i o n , the l a t e r p o r t i o n may have r e l a t i v e l y greater contributions from low-conductivity ground water and r e l a t i v e l y smaller contributions from high-conductivity surface runoff and t h r o u g h f a l l . McColl (1972; 1973a) studied the chemistry of water passing through the f o r e s t f l o o r and mineral s o i l A horizon of a Douglas-fir f o r e s t i n western Washington. His data ind i c a t e d that, regardless of flow r a t e , there was a general d e c l i n e i n e l e c t r i c a l c o n d u c t i v i t y across a storm f r o n t with the e a r l i e r p o r t i o n of the storm f r o n t water having a higher c o n d u c t i v i t y than the Figure 4.26 Streamwater e l e c t r i c a l conductivity - streams A, B, and C CH LU Q_ D JZ o Ct LO CM cr 40 T 32-24-16-8 0 B C ELECTRICAL CONDUCT IVIU. S T R E A M A S T R E A M B S T R E A M C clearcutting-c l e a r c u t t i n g -J J f' J'»^ 11: r i T i f r) 111 J J r r i i f > f f 11 i <) J1111111J: 11 < J f 1111111 > 11 J J i f 11 r i J 1111 J 11 f t f 11 f 111 a 11 j j ; i > 11111 r > j 11 [ 1111 (11 T 111 J 1111) r i ONDJFMRMJJflSONDJFMflMJJflSONDJFMRMJJRSONDJFMR 1970 1971 1972 1973 1974 co 119 Figure 4.27 Relationship's between streamwater e l e c t r i c a l conductivity and discharge. o u 5 -i n o.o ELECTRICAL CUNli'oCnviTT VERSUS DISCHARGE. STREAM fl . tira:!. CLtfrcuiTiNS I fif ICR CLlBiXUIIIdS 5.2981ogX .75) 19.S 25.0 37.5 39.0 DISCHARGE (LITRES/SEC) 6.5 13.0 ELECTRICRL CONDUCTIVITY VERSUS DISCHARGE . stfORE atflRcaniw: t RFTES aESfiOJTlKG 58.5 —1 £5.0 STREAM 8 Y = 24.81 - 4.7881ogX (r = .75) (0 u •H U 4J O <0 rH W 78.0 104.0 130.0 156.0 0ISCHASGE (LITRES/SEC) 208.0 250.0 ELECTRICAL CONDUCTIVITY VERSUS DISCHARGE. STREAM C Y = 26.57 - 5.9811ogX (r = .76) - 1 — u .o i i 1 1— 3J.0 44 0 0 f.fi.O DISCHARGE ILI IRES/SEC) 77.0 -1 60.0 Regressions are for "before clearcutting." data only. 120 Figure 4.28 Streamwater e l e c t r i c a l conductivity' during a storm event (27-29 November, 1973) Conductivity (micromhos/cm at 25°C) 17.0-1 STREAM A cond Discharge (litres/sec) ,-150 Conductivity (micromhos/cm at 25°C) 17. CH 16.5-16. a STREAM B 15.5-15. a 14.5-14.04 27 28 Discharge (litres/sec) 1000 -h500 Conductivity (micromhos/cm at 25°C) 15.5T 29 STREAM C (undisturbed) Discharge (litres/sec) r500 300 hlOO A l l points ±.5 micromhos/cm at 25°C 121 l a t e r p o r t i o n . Windsor (1969) studied phosphorus, i r o n , aluminium, and s i l i c o n i n t h r o u g h f a l l , stemflow, f o r e s t f l o o r leachates, and s i x mineral s o i l leachates at d i f f e r e n t depths i n the same area as McColl. He found that at each l e v e l of the ecosystem sampled, phosphorus, i r o n , and aluminium concentrations were highest at the s t a r t of moisture flow at that l e v e l and decreased with time. Th i s r e f l e c t e d an i n i t i a l f l u s h i n g away of the chemicals which had b u i l t up i n a leachable form during dry periods. S i l i c o n concentrations also tended to decrease with time as moisture flow continued, but f l u c t u a t e d somewhat, un-l i k e the other compounds. Some of t h i s s o i l water, plus t h r o u g h f a l l and stem-flow, would contribute to stream stormflow so both of these studies support the idea that the e a r l i e r p o r t i o n of the water c o n t r i b u t i n g to stream storm-flow i s enriched i n chemicals, and hence has a higher e l e c t r i c a l c o n d u c t i v i t y , than the l a t e r p o r t i o n . V a r i a t i o n between streams In the undisturbed s t a t e , stream C generally had a higher e l e c t r i c a l con-d u c t i v i t y than stream A, with stream B the lowest (Figure 4.26). Since B and C are the same stream with s t a t i o n B downstream from s t a t i o n C, and the d i s s o l v e d content of streamwater tends to increase from source to mouth (Livingstone, 1963), B was expected t o have a higher e l e c t r i c a l c o n d u c t i v i t y than C. Between sampling s t a t i o n s B and C are four t r i b u t a r i e s , two of which had e l e c t r i c a l c o n d u c t i v i t i e s greater than that of B, and one of the others had an e l e c t r i c a l c o n d u c t i v i t y comparable to that of B (Table 4.6). This a l s o suggests that s t a t i o n B should have had a greater e l e c t r i c a l c o n d u c t i v i t y than i t d i d . The f a c t that s t a t i o n B u s u a l l y had a lower e l e c t r i c a l c o n d u c t i v i t y than s t a -t i o n C may be due to inflow of subsurface s o i l seepage waters. Watershed B had a more mature f o r e s t cover than d i d watershed C so that s o i l drainage waters i n watershed B may have contained l e s s d i s s o l v e d substances than d i d s o i l drainage 122 Table 4.6. E l e c t r i c a l conductivity of stations B and C and.four.tributaries. I (.. sampling station E l e c t r i c a l conductivity (Vtmho/cm at 25°C) -25/4/73 17/5/73 \ ] V weir C 4\ weir B tributary 20.2 21.3 1 34.8 35.7 2 21.4 23.4 l \ , 3 17.4 17.9 2 4 weir C 20.2 21.0 21.0 23.1 weir B waters in watershed C. This i s supported by: 1) observations of water seeping from the s o i l in streambanks into the streams; 2) analysis of s o i l seepage waters in watershed B which showed that they usually had significantly lower e l e c t r i c a l conductivities than did the streamwater, as discussed in the following chapter; and 3) unpublished data of Klinka (Table 4.7) which show, for the same bio-geocoenosis in the U.B.C. Research Forest, a decline in s o i l ground-water e l e c t r i c a l conductivity as the surface vegetation becomes more mature. Another possible explanation for the relatively low el e c t r i c a l conductiv-i t y of station B i s that ions may be lost from solution by adsorption onto small particles of organic or mineral materials, or by uptake by aquatic organ-isms. Visual observations suggest that there were no obvious differences be-tween the stream bed of watershed B and that of watershed C. However, the d i f f e r -ences in e l e c t r i c a l conductivities were only slight and could be due to unde-tectable visual differences in the composition of the streambeds. 123 Table 4.7 E l e c t r i c a l c o n d u c t i v i t y of subsurface s o i l seepage water i n Poly-stichum - Thuja p l i c a t a ecosystems of d i f f e r e n t ages i n the U.B.C. Research Forest.* Present cover mean e l e c t r i c a l ymho/cm at 25°C conduct i v i t y (no. of samples) mature f o r e s t 21.0 (12) immature f o r e s t 31.8 (4) undisturbed cut-over and plant a t i o n s ( l i t t l e exposure of mineral s o i l ) 41.9 (4) disturbed cut-over and plan t a -t i o n s (much exposure of mineral s o i l ) 37.4 (6) * Unpublished data of K. Klinka, Graduate Student, Faculty of Fore s t r y , U n i v e r s i t y of B r i t i s h Columbia. Differences i n maturity of vegetative cover or i n ge o l o g i c a l weathering inputs may account f o r the higher e l e c t r i c a l c o n d u c t i v i t y of stream A r e l a t i v e to stream B. E l e c t r i c a l c o n d u c t i v i t y and sums of ions E l e c t r i c a l c o n d u c t i v i t y was c l o s e l y r e l a t e d to the sum o f the concentra-t i o n s of the four major cations i n the streamwater: - calcium, sodium, magnesium, and potassium (Figure 4.29) - as w e l l as that of the three major anions -bicarbonate, sulphate, and c h l o r i d e (Figure 4.30). This i n d i c a t e s that reason-able estimates of t o t a l cations or t o t a l anions i n the streamwater may be ob-tained from measurements of e l e c t r i c a l c o n d u c t i v i t y alone. However, as i n d i c a t e d i n Table 4.8, the c a t i o n i c sum i s i n v a r i a b l y l e s s than the anionic sum i n d i c a t i n g that the analyses are e i t h e r underestimating cations or overestimating anions. With respect to the cations, the presence of s i l i c a t e , phosphate, sulphate, and aluminium can lower the concentrations of calcium and magnesium determined by atomic absorption spectrophotometry 124 Figure 4.29. Relationships between e l e c t r i c a l conductivity and the sum of potassium, sodium, magnesium and calcium concentrations. m CM ELECTRICAL CONDUCTIVITY RELATED TO THE SUM OF THE 4 MAJOR CUT IONS. STREAM A. . BEFOJE CU'.fflluniNG i nno) UFWiT.umuG CJ o X 3T. Y • 10.17 « J.420X (r - .77) O r - " -CK t— CJ I 1 1 1 1 1 1 1 1 1 0.5 . 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 SO NA*K'MG«CA CONCENTRATIONS IMG/L) ELECTRICAL CONDUCTIVITY RELATED TO THE SUM OF THE A MAJOR CATIONS. STREAM B. . BEFORE CLEFKCUT11N5 I AFTER CLEfiRCUTTJNG . C J S -in CM o X sr. a T " 8.144 • 4.216X (r - .79) CJr--I I 1 1 1 1 1 1 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4 0 NA*K-»MG+CA CONCENTRATIONS (MG/L) - 1 — 4.5 ~1 5.0 ELECTRICAL CONDUCTIVITY RELATED TO THE SUM OF THE 4 MAJOR CATIONS. STREAM C. in CM CJ X a;" 5.04'i « 4.74MC (r • .91) I I 1 1 1 1 1 1 1 "•0 0.5 1.0 1.5 2.0 2.5 1.11 j.S 4.0 4 5 NA-fK + Hd+CA CONCENTRnriONS ING/L) 125 Figure 4.30. Relationships between e l e c t r i c a l c o n d u c t i v i t y and the sum of bicarbonate, sulphate, and ch l o r i d e concentrations. • in CM 3C™ CJ X o CJ _ J do CJr-' i—i c j ELECTR1CRL CONDUCTIVITY RELATED TO THE SUM OF THE 3 MAJOR ANIONS. STREAM fl. . BEFORE CIEBRCUTUNG ' I AFTER CLtRNCUITlNG If - 9.239 + 1.020X lr - .82) 1 1 1 1 1 1 1 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 HC03*S04+CL CONCENTRATIONS IMG/LI 20.0 ~I 22.5 25.0 in CM £ O g CJ CJr-or CJ ELECTRICAL CONDUCTIVITY RELATED TO THE SUM OF THE 3 MAJOR ANIONS. STREAM B. . BEFORE CLEARCUTTING I RfTfJ) CLEflHOimNG 1— 2.5 Y - 8.739 + 1.087X (r - .83) -1 1 1 1 1 1 — 5.0 7.5 10.0 12.5 1S.0 17.5 HC03»S04-CL CONCENTRATIONS IMG/L) 0.0 - 1 — 20.0 -1 22.5 25.0 in CJ O 5* c i g ELECTRICAL CONDUCTIVITY RELATED TO THE SUM OF THE 3 MAJOR ANIONS. STRERM C. '» - 5.995 • 1.280X (r - .95) ~~1 2.S 1 HC03*SCM "T " 1 10.0 IP.5 15.1) >CL CONCENTRATIONS IMG/L) 0.0 17.5 —1 20.0 22.' I 2!i.O 126 Table 4.8 Ionic sums from streamwater analyses Sample C a t i o n i c sum (meq/1) Anionic sum (meq/1) Ionic sum (meq/1) + 2+ + fNa + Mg + K + [Cl + HC0 3 + SO^ + estimated from 2 + 3 + 2 + - - , c o n d u c t i v i t y Ca" + Fe + M n + N0 3 + H W 4 J ( 1 9 6 1 ) + 3+ + NH. + A l + H (from 4 pH)] stream A 6/7/72 .179 .225 .216 ti B 1  .154 .212 .210 II C M .178 .243 .224 H A 7/9/72 .219 .275 .249 it B fl .204 .253 .247 H C If .265 .309 .301 H A 25/1/73 .113 .185 .178 •i B ft .102 .149 .165 H C tl .102 .141 .165 •i A 25/4/73 .165 .186 .203 II B II .142 .192 .202 II C II .146 .196 .210 H A 28/11/73 .099 .139 .161 it B II .088 .120 .143 II C II .076 .121 .130 (David, 1960). Phosphate, s i l i c a t e , and aluminium ions were present i n s o l u -t i o n i n extremely low and r a r e l y detectable concentrations. Although consider-able q u a n t i t i e s of s i l i c o n were present i n s o l u t i o n , i t e x i s t s mainly i n non i o n i c form, as discussed below. Some sulphate i s present but i t occurs i n very low concentrations. Water samples were analyzed f o r calcium and magnesium i n the present of lanthanum or strontium c h l o r i d e s to a s c e r t a i n i f interference was responsible f o r low c a t i o n values. This method f a i l e d to increase the c a t i o n values and since even the purest lanthanum and strontium;chlorides obtained s t i l l contained s u f f i c i e n t calcium and magnesium to i n t e r f e r e with the analyses, the method was not used. Calcium was always determined using a n i t r o u s oxide-acetylene flame as t h i s was found to c o n s i s t e n t l y give readings which were about 10-20% higher than those obtained from the cooler a i r - a c e t y l e n e flame. The detection l i m i t f o r aluminium was 0.5 mg/1 so that concentrations of t h i s magnitude may have been present although they would have contributed l i t t l e 127 to the i o n i c sum since aluminium i s l i k e l y to occur as various polynuclear aluminium hydroxide complexes at the pH of the solutions CHem, 1970). In general, then, i t i s considered that the cat i o n analyses were quite accurate. Of the anions, bicarbonate accounted f o r about 30 - 50% of the anionic sum and sulphate, about 20 - 30%. As discussed below, bicarbonate analyses are known to overestimate the concentration of bicarbonate present by 20 - 40%. The a n a l y t i c a l method .for sulphate had low r e s o l u t i o n and the concentrations measured were close to the detection l i m i t . Thus, i t i s f e l t that the sulphate concentrations recorded may also be too high. The other major anion was c h l o r -i d e , which accounted f o r 10 - 20% of the anionic sum. Chloride analyses were i n i t i a l l y performed using two separate methods. Agreement between the two methods was quite good (always within 10%) so i t i s f e l t that c h l o r i d e analyses are reasonably accurate. The estimated i o n i c sums were obtained from the empirical equation: E l e c t r i c a l c o n d u c t i v i t y = 100 x (half the sum of anions and cations) which can y i e l d inaccurate r e s u l t s (Logan, 1961). Thus, despite the f a c t that the anionic sums were closer to these estimated sums than were the c a t i o n i c sums, the anionic sums are considered to be i n c o r r e c t due to overestimated bicarbonate and s u l -phate concentrations. E f f e c t s of c l e a r c u t t i n g C l e a r c u t t i n g has caused s l i g h t , b u t generally s t a t i s t i c a l l y i n s i g n i f i c a n t (Appendix X) increases i n the e l e c t r i c a l c o n d u c t i v i t i e s of streams A, B, D, and E (Table 4.9). The increases have been observed both years following c l e a r -c u t t i n g i n the case of streams D and E. For the other streams, the order of e l e c t r i c a l c o n d u c t i v i t y has been changed from C>A>B to A>B>C. 128 Table 4.9 Average e l e c t r i c a l cutting conductivities of streams before and after clear-before after . before after Stream A Control(C) 19.1(1.8) 18.1(2.2) 17.8(1.4) 15.8(2.6) Stream B Control(C) 18.8(2.9) 19.3(3.6) 17.8(3.7) 17.7(4.5) before after(1) after (2) before after(1) after (2) Stream D Control(C) 24.5(8.0) 24.1(5.4) 22.7 (6.6) 20.5(5.7) 25.0(6.8) Stream E 23.7(4.8) Control(C) 34.9(15.0) 24.1(5.4) 31.8(11.6) 20.5(5.7) 36.8(11.6) 23.7(4.8) A l l values are in micromho/cm at 25°C. Standard deviations are given i n parentheses. Values are for the periods: A - November 1, 1972 to April 1, 1973 before clearcutting November 1, 1973 to April 1, 1974 after clearcutting B - October 1, 1972 to April 1, 1973 before clearcutting October 1, 1973 to April 1, 1974 after clearcutting D,E - April 1, 1971 to November 1, 1971 before clearcutting April 1, 1972 to November 1, 1972 after clearcutting - year 1 April 1, 1973 to November 1, 1973 after clearcutting - year 2 Increases in el e c t r i c a l conductivity are expected i f clearcutting increases the concentration of dissolved ions in stream water, as has been found in studies from Hubbard Brook, both following forest cutting and herbicide application (Likens et al., 1970) and commercial clearcutting (Pierce et al., 1972). In-creases in the concentration of total dissolved solids (and hence in el e c t r i c a l conductivity) have also been observed following clearcutting in Oregon (Fredrik-sen, 1971). 7. Ions and dissolved s i l i c a 1) Potassium  Seasonal behaviour In the undisturbed watersheds, potassium concentrations in stream water average about .1 mg/litre and, unlike a l l the other major ions, showed no pro-nounced seasonal trends, although concentrations were slightly higher during late summer and early autumn (Figure 4.31). This i s similar to results obtained elsewhere(Table 4.10). 129 C1/9W) NQIlbcJlN33NQ3 130 Figure 4.32 Relationships between streamwater potassium concentrations and discharge. POTASSIUM CONCENTRATION VERSUS DISCHARGE. . BEfiHE CUrBCurn.tG • flf TEH CLEPRCUITIHG STREAM A Y = .1465 + .0645 (-) .. (r = .49) - 1 — 13.0 T -1 1 13.5 25.0 3 2 . 5 39.0 DISCHARGE (UTRES/SEC1 POTASSIUM CONCENTRATION VERSUS DISCHARGE. STREAM B . BEFORE O E S R C U n i W • WTES OERSQiniHS E.5 45.5 £2.0 Y = .0859 + .0438(-) (r = .33) • • • * . • 65.0 0.0 2S.0 52.0 73.0 104.0 130.0 1SS.0 DISCHARGE (UTRES/SECJ POTASSIUM CONCENTRATION VERSUS DI5CHARGE. STREAK C — i 182.0 209.0 —I 250.0 y °'0 • "~a n^ o 3 3 ^ 2Ta s v o uTa rTo eTo vTa na a DISCHARGE IUTKE5/SEC) 0 " 0 ARegressions are for "before clearcutting" data only. No s i g -nificant relationship was found for stream C. 131 Figure 4.33 Streamwater ca t i o n concentrations during a storm event (27-29 November, 1973) Concentration (mg/1) 1.1-1 1.0 A STREAM A Concentration (mg/1) 1.2 Concentration (mg/1) 1.2-1.0. 0.8-0 ^ STREAM B Discharge ( l i t r e s / s e c ) 150 50 10 Discharge ( l i t r e s / s e c ) 1000 I- 500 STREAM C (undisturbed) Discharge ( l i t r e s / s e c ) 500 A l l N H 4 concentrations £.01 mg/1 132 Variation with discharge Potassium concentrations generally tended to decrease with increasing discharge (Figure 4.32) although, for an individual storm event, the concen-trations clearly increased with increasing discharge (Figure 4.33). This apparent discrepancy might be due to potassium concentrations being lower at higher discharges for steady flows, although exhibiting increases with i n -creasing discharge during storm events. This i s supported by the observation that potassium concentrations in streamwater during wet winters generally tend to be lower than those during dry summers. Table 4.10 Seasonal variation of cation concentrations in streamwater in tem-perate regions Location K Na Mg Ca Reference Haney relatively constant but slight i n -crease in late summer-early autumn early autumn maximum, winter mini-mum early autumn maximum, winter mini-mum early autumn maximum, winter mini-mum This study Seymour watershed, Vancouver relatively constant higher in summer, lower in winter higher in summer, lower in winter higher in summer, lower in winter Zeman, 1973 H.J. Andrews Experimental Forest, coastal Oregon relatively constant late summer maximum, winter-spring mini-mum late summer maximum, winter-spring mini-mum late summer maximum, winter-spring mini-mum Rothacher et al., 1967; Fredricksen, 1972 Coastal California relatively constant but lower in winter higher in autumn, lower in winter higher in autumn, lower in winter higher in autumn, lower in winter Steele, 1968 Sagahen Ck. Eastern California — • early autumn maximum, spring snow-melt minimum early summer maximum, spring snow-melt minimum early summer maximum, spring snow-melt minimum Johnson and Needham, 1966 Ohio relatively constant - - - Taylor et al. 1971 Table 4.10 cont. 133 Location K Na Mg Ca Reference Maryland r e l a t i v e l y constant but maximum i n autumn autumn maxi-mum, l a t e winter m i n i -mum autumn maxi-mum, early summer mini-mum autumn maxi-mum, early -spring mini-mum Cleaves et al., 1970 Hubbard Brook, New Hampshire r e l a t i v e l y constant but s l i g h t de-crease i n summer and increase i n autumn autumn maxi-mum, spring minimum r e l a t i v e l y constant but s l i g h t r i s e i n autumn s l i g h t i n -crease i n autumn, and decrease i n spring Johnson et al., 1969; Likens et al., 1967 and 1970 Coweeta, North Ca r o l i n a 1. Forested watershed autumn maxi-mum, winter minimum autumn maxi-mum, winter minimum early autumn maximum,win-te r minimum autumn maxi-mum, winter minimum Johnson and Swank, 1973 2. Grass S shrub watershed l a t e winter maximum,late summer mini-mum v a r i a b l e l a t e winter maximum,late summer mini-mum v a r i a b l e A g r i c u l t u r a l watersheds, Norfolk, B r i t a i n autumn maxi-mum, spring minimum l a t e summer-autumn maxi-mum, l a t e winter-spring minimum r e l a t i v e l y constant winter maxi-mum , summer minimum Edwards, 1973a Finland autumn maxi-mum, winter minimum - autumn maxi-mum, winter minimum autumn maxi-mum, winter minimum V i r o , 1953 Variation between streams In the undisturbed condition, potassium concentrations were usually highest in stream A which may be due to one or more of the following factors: 1. There may be slight chemical and mineralogical differences between the soils and bed-rock of the different watersheds; 2. Although the watersheds have the same overall aspect, a substantial portion of watershed A consists of southwesterly facing slopes where decomposition and mineralization may be more rapid than on cooler exposures, which are more common in watershed B. Also s o i l temperatures will be higher in the lower elevation watershed A; 3. Differences in maturity of the forest ecosystems may cause differences in the amounts of chemical nutrients lost to streams. ' Higher calcium and magnesium concentrations in stream C suggest that factors 2 and, particularly, 3, are of lesser importance. Table 4.11 V a r i a t i o n of cation concentrations i n streams i n temperate regions .with increasing stream discharge Location K Na Mg Ca Reference Haney some increases some decreases decreases decreases decreases This study Seymour watershed, Vancouver no s i g n i f i c a n t r e l a t i o n s h i p no s i g n i f i c a n t r e l a t i o n s h i p no s i g n i f i c a n t r e l a t i o n s h i p no s i g n i f i c a n t r e l a t i o n s h i p L.J. Zeman, Faculty of Forestry, University of B r i t i s h Columbia: Personal communication H.J. Andrews Experimental Forest, coastal Oregon decreases Fredriksen, 1972 Coastal C a l i f o r n i a decreases decreases decreases decreases Steele, 1968 Sagahen Ck., Eastern C a l i f o r n i a • - decreases decreases decreases Johnson and Needham, 1966 Western Montana K-Na combined increase decreases decreases Weisel and Newell, 1970 Northern Utah does not decrease decreases decreases decreases Johnston and Doty, 1972 Ohio no s i g n i f i c a n t r e l a t i o n s h i p - - Taylor et at,, 1971 Maryland increases decreases s l i g h t l y increases increases Cleaves et al._ 1970 Hubbard Brook, New Hampshire increases s l i g h t l y decreases decreases s l i g h t l y no s i g n i f i c a n t r e l a t i o n s h i p Johnson et al.3 1969 Coweeta, * North Carolina increases no s i g n i f i c a n t r e l a t i o n s h i p increases no s i g n i f i c a n t r e l a t i o n s h i p Johnson and Swank, 1973 Switzerland no s i g n i f i c a n t r e l a t i o n s h i p decreases no s i g n i f i c a n t r e l a t i o n s h i p decreases K e l l e r , 1970a, b Bog and peat moorland, B r i t a i n i n i t i a l l y decreases, then increases no s i g n i f i c a n t r e l a t i o n s h i p decreases C r i s p , 1966 A g r i c u l t u r a l watersheds, Norfolk, B r i t a i n increases decreases decreases no s i g n i f i c a n t r e l a t i o n s h i p Edwards, 1973a, b Japan increases - no s i g n i f i c a n t r e l a t i o n s h i p decreases Iwatsubo and Tsutsumi, 1968 Johnson and Swank considered the concentrations of a l l four cations to be inde-pendent of discharge. However, data presented in t h e i r paper indicate that t h i s i a not the case for potar.sium ami magnesium concentrations, both of which appear to increase with increasing discharge. 135 E f f e c t s of c l e a r c u t t i n g C l e a r c u t t i n g has had a more dramatic e f f e c t on potassium concentrations than on those of any other ion . Following c l e a r c u t t i n g , potassium concentra-t i o n s i n streams A and B rose sharply during autumn and have remained abnormally high throughout the winter (Figure 4.31, Table 4.12). Potassium concentrations i n streams D and E have been abnormally high f o r two years following c l e a r -c u t t i n g (Figure 4.34, Table 4.12). In a l l four streams the increases have been hi g h l y s i g n i f i c a n t s t a t i s t i c a l l y (Appendix X). Table 4.12 Average concentrations of cations i n streamwater before and a f t e r c l e a r c u t t i n g . 1. Stream A before a f t e r control(C) before a f t e r 2. Stream B before a f t e r control(C) before a f t e r 3. Stream D before after(1) after(2) Stream E before after(1) after(2) control(C) before a f t e r ( 1 ) after(2) K • 15(.02) .29(.05) .09(.04) .08(.02) .09(.02) .27(.19) .09(.04) .08(.02) .10(.06) .30(.16) .20(.08) .1M.06) .27(.08) .26(.10) .06(.05) .09(.03) .08(.04) Na 1.02(.21) 1.03(.ll) .80(.25) .79(.14) ,88(.30) .93(.21) ,89(.30) .87 (.21) 1.02(.36) 1.03(.30) 1.14(.29) 1.36(.45) 1.44(.43) 1.67(.37) 1.18(.26) 1.09(.33) 1.23(.28) Mg .27(.03) .23 (.02) .25(.04) .2K.04) .28(.06) .27 (.09) .27(.06) .25(.09) .42(.19) .37(.13) .52(.20) .63(.30) .59(.24) .86(.39) .36(.09) . 3 K . 0 9 ) .42(.14) Ca 1.3(.2) 1.2(.2) 1.3(.3) 1.3(.3) 1.4(.3) 1.3(.3) 1.5(.5) 1.5(.6) 1.5(.6) 1.6(.6) 2.2(.9) 2.K.9) 2.7(1.3) 3.6(1.6) 1.6(.4) 1.7(.7) 2.2(.7) NH, .OK.01) 0 •02(.03) 0 ,01(.02) 0 ,02(.03) 0 ,03(.05) 0 .03(.03) 0 ,02(.03) 0 A l l concentrations are i n mg/l i t r e Standard deviations given i n parentheses cont. 136 Stream A November 1, 1972 to Apr i l 1, 1973 before clearcutting November 1, 1973 to Apr i l 1, 1974 after clearcutting Stream B October 1, 1972 to Apr i l 1, 1973 before clearcutting October 1, 1973 to Apr i l 1, 1974 after clearcutting Streams D & E Apr i l 1, 1971 to November 1, 1971 before clearcutting Apr i l 1, 1972 to November 1, 1972 after clearcutting (year 1) Apr i l 1, 1973 to November 1, 1973 after clearcutting (year 2) Potassium is not a structural component of plant tissue (Gilbert, 1957) so that i t can be easi ly leached from l iv ing or decomposing plant material. This i s i l lus t ra ted by studies of nutrient enrichment of rain passing through forest canopies. These show that, of a l l the major cations, potassium concen-trations undergo the greatest increases (Abee and Lavender, 1972; Eaton et al. 3 1973; Gorham, 1961). In addition, Slack (1964) found that accumulation of leaf l i t t e r in pools caused greater increases in potassium concentrations than in those of any of the other major cations. At Hubbard Brook decomposing forest l i t t e r released potassium ions at a greater rate than that for any of the other major cations (Gosz et al.3 1973). Furthermore, the forest cutting and herbi-cide application treatment at Hubbard Brook increased potassium concentrations in streamwater to a greater extent than for the other major cations (Likens et al. j 1970). Greatly increased potassium concentrations in streams have been noted after clearcutting in the H.J. Andrews Experimental Forest in Oregon, although calcium concentrations were increased to a greater extent (Fredriksen, 1971), and also after clearcutting and slashburhing in the Alsea basin in Oregon (Brown et al. 3 1973). Thus, in the l ight of the above studies, the- increase in potassium concen-trations in the streams following clearcutting i s expected. It i s most l i ke ly due to leaching by water of potassium from vegetation within the watershed. The large amount of slash in and above the streams (Figure 4.11) i s l i ke ly to provide the source for much of this potassium although increased potassium con-centrations in so i l waters have also been noted. F i g u r e 4.34 S t reamwater po ta s s i um c o n c e n t r a t i o n s - s t reams D and E ONDJFMRMJJflSQNDJFMflMJJflSONDJFMflMJJflSQNDJFMfl 1970 1971 1972 1973 1974 OJ ~0 138 2) Sodium  Seasonal behaviour Sodium concentrations showed pronounced seasonal v a r i a t i o n s with maxima during e a r l y autumn and minima during winter (Figure 4.35). This agrees with that found i n other studies (Table 4.10). V a r i a t i o n with discharge Despite large v a r i a t i o n s , sodium concentrations tended to decrease with increasing discharge (Figures 4.33 and 4.36). This also agrees well with that found i n other studies (Table 4.11). V a r i a t i o n between streams Both before and a f t e r c l e a r c u t t i n g , sodium concentrations tended to be highest i n stream A and s i m i l a r i n streams B and C. This i s l i k e l y to be due to the same reasons discussed above f o r potassium. Sodium concentrations i n the streams have always been higher than those of the other major a l k a l i - m e t a l , potassium. This i s u s u a l l y the case (Hem, 1970) and i s due to one or more of the following f a c t o r s : 1. Sodium i s u s u a l l y more abundant than potassium i n igneous rocks (Hem, 1970). Such rocks form the bedrock i n the watersheds at Haney. 2. Sodium i s more r e a d i l y l i b e r a t e d from s i l i c a t e minerals than i s potassium (Hem, 1970). 3. Once l i b e r a t e d , potassium has a strong tendency to be reincorporated i n t o weathering products, e s p e c i a l l y c e r t a i n c l a y minerals (Hem, 1970; Johnson et al., 1968). 4. B i o t a may u t i l i z e a higher proportion of the a v a i l a b l e potassium than of the a v a i l a b l e sodium (Johnson et al., 1968; Likens et al.,1967). 5. Once i n s o l u t i o n , potassium tends to be adsorbed on surfaces of p a r t i c l e s more r e a d i l y than i s sodium (Bear, 1964). E f f e c t s of c l e a r c u t t i n g There has been l i t t l e e f f e c t of c l e a r c u t t i n g on sodium concentrations Figure 4.35 Streamwater sodium concentrations - streams A, B, and C 2 T 6-fl B C STREAM fl STREAM B STREAM C 2-1 8-4 -SODIUM c l e a r c u t t m g -B n Im i i i i i i n i i n i m i n i m m i i i i i i i i i i i i i i i i i i i i i i i n i i i i i i i i i i i m i n i i i i i i i u m " t i n i m i i i m i n i i i i i u i n ONDJFMflMJJflSONDJFMflMJJRSON'DJFMflMJJflSONDJFMfl 1970 1971 1972 1973 1974 140 Figure 4.36 Relationships between sreamwater sodium concentrations and discharge. P SODIUM CONCENTRATION VERSUS DISCHARGE. STREAM A "1 . 8CFCRE CUrHCt;:!:*} Regressions are for "before clearcutting" data only. 141 (Figure 4.35, Table 4.12), and no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s were found (Appendix X). Although the f o r e s t c u t t i n g and herbicide a p p l i c a t i o n experiment at Hubbard Brook r e s u l t e d i n increased sodium concentrations i n streamwater, the percentage increase f o r sodium was the lowest of a l l the major cations (Likens et al. j 1970). S i m i l a r l y , the c l e a r c u t t i n g and slashburning experiment i n the H.J. Andrews Experimental Forest i n Oregon also produced increases i n sodium concentrations which were proportionately l e s s than the increases i n the concen-t r a t i o n s of the other major cations (Fredriksen, 1971). Thus, sodium i n the streams at Haney has behaved i n a s i m i l a r fashion to that found i n these other studies. 3) Magnesium and calcium  Seasonal behaviour Both ions exhibited i d e n t i c a l seasonal behaviour with maximum concentra-t i o n s i n e a r l y autumn and minimum concentrations i n winter (Figure 4.37). This agrees w e l l with the r e s u l t s of other studies (Table 4.10). The apparent anomalous seasonal behaviour of calcium reported by Edwards (1973a) f o r watersheds i n B r i t a i n may be due to inaccurate calcium analyses or to the s o l u b i l i t y r e l a t i o n s h i p s of the two main calcium sources - calcium car-bonate and calcium sulphate. With increasing discharge, bicarbonate concentra-t i o n s decrease whereas sulphate concentrations increase, having opposite e f f e c t s on the s o l u b i l i t i e s of the calcium s a l t s . Where the source of calcium i s almost e n t i r e l y calcium carbonate, as i n limestone country i n Kentucky, i t has been found that calcium concentrations decrease as discharge increases and apparently depend more on discharge than on temperature or season ( T h r a i l k i l l , 1972). However, the s i t u a t i o n i n that study, where streams were i n a warmer climate and i n contact with an abundance of calcium i s very d i f f e r e n t to that at Haney. In the former case, p h y s i c a l and chemical p r o p e r t i e s of the streams are quite l i k e l y to c o n t r o l calcium 142 CD 1 T 8 Figure 4.37 streamwater magnesium and calcium MAGNESIUM fl = STREAM fl concentrations - streams A, B, and C cle a r c u t t m g -A CL CH UJ <_J O CJ HIIHIIIIIIl I l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l " fl i n i M i i i i m i m i i M i m i i "" '".II n•• Q C - . , n , r u p ONDJFMflMJJflSONDJFMflhJJRSONDJFMflMJJRSONDJFMfl CALCIUM 4 T | 3 . 2 t § 2 . 4 £ 1 . 6 UJ o CJ • ° fl = STREAM A B = STREAM B C = STREAM C O CJ 0 C c l e a r c u t t i n j t A cl e a r c u t t i n g -1 m i l l I " ' " 1 1 1 1 , r - M n 1 9 7 1 1972 1973 1974 t | i l l i n i u m 1  1970 143 concentrations i n streamwater, whereas, at Haney, calcium concentrations i n streamwater would be more dependant on seasonally induced changes i n b i o l o g i c a l decomposition and mineral weathering. V a r i a t i o n with discharge The concentrations of both ions tended to decrease with increasing d i s -charge (Figures 4.33, 4.38 and 4.39), generally agreeing with the r e s u l t s of other studies (Table 4.11). V a r i a t i o n between streams In the undisturbed streams calcium was the dominant cation with magnesium being the t h i r d most important a f t e r sodium (Appendix V). This i s the usual order of cations i n streams i n humid temperate regions (Hem, 1970; Livingstone, 1963). When concentrations were high (late summer - e a r l y autumn) both calcium and magnesium concentrations were highest i n stream C but when concentrations were low (winter), they were lowest i n stream C (Figure 4.38) . Differences i n bedrock and s o i l chemistry or i n weathering rates may account f o r higher concen-t r a t i o n s i n stream C during summer and e a r l y autumn, whereas greater b i o l o g i c a l a c t i v i t y i n the warmer, lower e l e v a t i o n watersheds A and B during the winter may account f o r the winter behaviour. Watershed C was noticeably colder and had l a r g e r and more prolonged snowpacks than the other two watersheds. E f f e c t s of c l e a r c u t t i n g C l e a r c u t t i n g has had no pronounced e f f e c t on calcium or magnesium concen-t r a t i o n s i n streams A and B (Figure 4.37, Table 4.12). I t has, however, caused s l i g h t , but s t a t i s t i c a l l y i n s i g n i f i c a n t , increases i n magnesium concentrations and s t a t i s t i c a l l y s i g n i f i c a n t increases i n calcium concentrations i n streams D and E (Appendix X). Results from streams D and E (Figure 4.40) i n d i c a t e that almost an e n t i r e growing season following c l e a r c u t t i n g was necessary before changes i n calcium concentrations became apparent. S i m i l a r r e s u l t s have been noted near Hubbard 144 Figure 4.38 Relationships between streamwater magnesium concentrations and discharge. MAGNESIUM CGNCEN1RATICN VERSUS DISCHARGE . BEfCUE. CLFWCUHING 0 BFIH CLFRRLUIIINC SISEAM A .4243 - 0.14301ogX (r = .72) — i — 6.5 1 3 . 0 1 9 . 5 2 B . 0 3 2 . 5 3 9 . 0 DISCHARGE ILITRE5/5EC) MAGNESIUM CONCENTRATION VERSUS DISCHARGE . BEFORE Q.ERRCUT7 ING 0 UTTER O E R R O i r T l H S ~ l 4 5 . 5 6S.0 STREAM B Y = 0.4007 - .094161ogX (r = .76) 52.0 7B.0 1 0 4 . 0 1 3 0 . 0 156.0 „ DISCHARGE (LITRES/SEC) MAGNESIUM CONCENTRATION VERSUS DISCHARGE. STREAM C 2 6 0 . 0 Y - .4508 - .12971ogX (r = .66) o.o 11.0 33.0 4-1.0 5 0 0 66.0 DISCHARGE III IRES/SEC) - 1 77.0 Bfl.O . 110.0 Regressions are for "before clearcutting" data only. 145 Figure 4.39 Relationships between streamwater calcium concentrations and discharge. CALCIUM CONCENTRATION VERSUS DISCHARGE. 'STREMM 9 . 9EFOK riEWCUTTING I flFIEH CLt.iiJUIII.% T 1 1 1 1 1 1 1 1 1 1 0.0 S.S 1 3 . 0 19.5 2 6 . 3 3 2 . 5 3 9 . 0 45.5 52.0 58.3 65.0 DISCHARGE (LITRES/SEC) C A L C I U M CONCENTRATION VERSUS DISCHARGE. STREAM B . BEFORE CLEARCUTTING I AFTER CLEARCUTTING Y = 2.104 - 0.55671ogX (r = .77) Regressions are for "before clearcutting" data only. Figure 4.40 Streamwater calcium concentrations - streams D and E 8 T 6-4-2-0 C D E CALCIUM S T R E R M C S T R E A M D S T R E R M E F e l l i n g Yarding III miii iiiiiii IIIIII iiii III iimi IIIIIII mill IIIIIIIIM ONDJFMRMJJflSONDJFMRMJJflSONDJFMflMJJFlSONDJFMR 1970 1971 1972 1973 1974 147 Brook (Pierce et al., 1972) where potassium concentrations increased almost immediately a f t e r an October c l e a r c u t t i n g whereas no noticeable increases i n magnesium or calcium concentrations occurred u n t i l the following summer. I t was considered that the season of c u t t i n g could influence the amount of chemi-c a l s l o s t from land to streams, with greater losses from summer c l e a r c u t t i n g s than from autumn c l e a r c u t t i n g s due to prolonged s i t e exposure. I f t h i s i s so then one would expect a greater increase i n losses from watershed B than from watershed A since B was c l e a r c u t i n summer whereas A was c l e a r c u t i n autumn. In t h i s respect i t i s noteworthy that magnesium concentrations i n stream B tended to be higher i n i t i a l l y f o l l o wing c l e a r c u t t i n g than those i n A u n l i k e the values before c l e a r c u t t i n g . No d i s t i n c t trends can be seen i n calcium values. 4) Iron, manganese, and aluminium During more than three years of sampling streams A, B, and C, measurable concentrations of i r o n have been found only four times whereas measurable con-centrations of manganese and aluminium have not yet been found. A n a l y t i c a l detection l i m i t s are given i n Table 3.1. These elements are u s u a l l y present i n very low concentrations i n streams i n humid temperate regions (e.g. Hem, 1970; Livingstone, 1963). Iron and manganese In streamwater clos e to neutral pH, any i r o n present would e x i s t mainly as p a r t i c u l a t e Fe(0H) 3 or as an organic complex which may also be p a r t i c u l a t e . Manganese behaves i n a s i m i l a r fashion (Hem, 1970). Thus, concentrations of the uncomplexed soluble ions of these metals i n unpolluted streams are l i k e l y to be quite low, as has been found by Hem (1970), Livingstone (1963), Perhac (1972), Rothacher et al., (1967), Weisel and Newell (1970), and many others. S i g n i f i c a n t concentrations of i r o n and manganese have been reported i n streams following l e a f f a l l during low flow periods i n autumn (Slack, 1964; Slack and F e l t z , 1968). The more intense the colour of the water, the higher were the 148 iron and manganese concentrations. This colouration might have been due to the presence of various carboxylic acids which exist in water as a col l o i d a l sol to which cations may be either complexed or adsorbed (Lamar and Goerlitz, 1966). The presence of such compounds may allow significant concentrations of iron and manganese ions to occur i n a dissolved form in solution. In this re-spect, i t i s noteworthy that measurable iron and manganese concentrations were found in streams D and E only during low flow periods i n autumn when the streams were slightly coloured (Figure 4.41). Decreases in iron and manganese concen-trations with increasing discharge, as has been observed elsewhere (Buscemi, 1969), may be partly responsible for the absence of detectable iron and man-ganese concentrations during the rest of the year. Aluminium The detection limit for aluminium by the analytical method used i n this study i s 0.5 mg/1. Because of pH dependent solubility relationships, this i s greater than the concentrations of aluminium usually found in water of near-neutral pH. Only at very low pH values do aluminium concentrations appear to increase significantly (Hem, 1970) . At Hubbard Brook, aluminium concentrations in undisturbed streams were less than 0.5 mg/1 nearly a l l the time (Likens et al.3 1970). Aluminium concentrations also increased with increasing discharge (Johnson et al., 1969). Effects of clearcutting  Iron and manganese Neither of these ions has yet been detected i n streams A or B following clearcutting. This i s expected in view of their low concentrations i n natural waters and their tendency to increase in concentration only during the low flow periods of late summer and early autumn. Detectable concentrations have been found in streams D and E during this time of the year. Although manganese concentrations were not determined prior to clearcutting, iron concentrations were and they show a s t a t i s t i c a l l y significant increase following clearcutting CONCENTRATION (MG/L) CONCENTRATION (MG/L) CD CD CD CD (V) CD CO CD 4^ O ID 11 ZD O — 1 — o DO — H _ ro — 1 — 0 1 — 1 — — 1 m a 11 11 LT> U) —1 —1 70 70 m m x> XI m o w 8 C l 1 1 0 O — i m I C Q " m o O I o cn — 1 — cn — 1 — ro — 1 — cn —H— CO m m 0 11 11 3 in to —1 —i 70 70 m m t—• n -D cn r* M m a A C rr 3 0> 3. 3 P 1—1 a n O 0 3 0 CD 3 H ft 0 u l to rr »1 jams 0 (» O. w 1X1 150 (Figure 4.41; Appendix X). Fredriksen (1971) found increases in both iron and manganese concentrations following clearcutting and slashburning in Oregon but the iron increases were only very slight. Aluminium Detectable aluminium concentrations have yet to be found in any of the streams at Haney. Even in streams which are many times more concentrated than those at Haney, such as streams in the Chilliwack valley area of B.C. whose ele c t r i c a l conductivities were up to 440 micromhos/cm at 25°C, failed to ex-hib i t measurable concentrations of aluminium. However, following the forest cutting and herbicide application treatment at Hubbard Brook, aluminium con-centrations increased from around 0.2 mg/1 to between 1 and 3 mg/1, these con-centrations being greatest during autumn. Thus, i t appears that i f increased concentrations of iron and manganese are to occur following clearcutting, they w i l l not be observed u n t i l late sum-mer or early autumn and are not l i k e l y to be very high. Aluminium concentra-tions are l i k e l y to remain below detectable levels following clearcutting. 5) Ammonium and nitrate The analytical method for nitrate actually measured n i t r i t e as well as nitrate, but since n i t r i t e i s usually present in only very small amounts (Feth, 1961; Hem, 1970; Livingstone, 1963) the analytical results can be as-sumed to closely approximate nitrate concentrations. Seasonal behaviour Weekly fluctuations in the concentrations of ammonium and nitrate ions appear to be greater than seasonal fluctuations so that clear seasonal trends are not apparent. Ammonium concentrations tended to be lower during the grow-ing season and higher during the rest of the year (Figure 4.42) and this i s similar behaviour to that found by Zeman (1973) for Seymour watershed. Nitrate trends were more apparent with concentrations tending to be higher in winter and lower in summer (Figure 4.43). CONCENTRATION (MG/L) CONCENTRATION (MG/L) 152 The low ammonium and r e l a t i v e l y high n i t r a t e concentrations may be a r e -s u l t of high d i s s o l v e d oxygen concentrations i n the streams which f a c i l i t a t e o x idation of ammonium to n i t r a t e . The decrease i n n i t r a t e concentrations during the summer when d i s s o l v e d oxygen concentrations also decreased, and the absence of a corresponding increase i n ammonium concentrations suggest that the decrease i n n i t r a t e was caused by increased b i o l o g i c a l uptake of nitrogen com-pounds which occurs during the growing season, as has been postulated f o r Hub-bard Brook (Johnson et al., 1969; Likens et al., 1970) and elsewhere (Feth, 1966) . Increases i n n i t r a t e concentrations i n C a l i f o r n i a n streams during e a r l y winter have been a t t r i b u t e d to leaching by r a i n of nitrogenous decomposition products from decaying vegetation (Feth, 1961). Such products would accumulate during the dry periods of l a t e summer at Haney and i t i s l i k e l y that winter r a i n s would f l u s h them away. N i t r a t e concentrations decreased throughout spring as b i o l o g i c a l a c t i v i t y increased, unlike the s i t u a t i o n at Hubbard Brook where n i t r a t e concentrations reached a maximum during spring. There, however, n i t r a t e i s stored i n the winter snowpack and concentrated by evaporation throughout the winter so the spring snowmelt runoff can supply much n i t r a t e to streams (Likens et al., 1970). Buscemi (1969) found a s i m i l a r increase i n n i -t r a t e concentrations i n streams i n Idaho during the spring snowmelt period, and higher n i t r a t e concentrations during the spring snowmelt period have been meas-ured i n streams i n the Chilliwack v a l l e y area. Due to the absence of a prolong-ed winter snowpack at Haney, there would be no such c o n t r i b u t i o n of n i t r a t e to the streams. V a r i a t i o n with discharge N i t r a t e and ammonium concentrations were generally not s i g n i f i c a n t l y r e l a t e d to discharge although some decreases i n t h e i r concentrations with i n c r e a s i n g discharge were observed (Figures 4.44 and 4.45). During a storm event, n i t r a t e concentrations increased with increasing discharge i n stream A (Figure 4.47). The v a r i a b l e behaviour of n i t r a t e i s s i m i l a r to that found elsewhere (Table 4.14), and may be explained i n the same way as potassium's behaviour, discussed above Figure 4.44 Relationships between streamwater ammonium concentrations and discharge. 'AMMONIUM, CONCENTRATION VERSUS DISCHARGE. STREftl A . EEFORE ClEfKCUIIING • BflER CLEPRCU1TING — V 1 • " 1 1 — • I " 1 1 S.5 13.0 19.5 26.0 32.5 39.0 DISCHARGE (LITRES/SEC) AMMONIUM CONCENTRATION VERSUS DISCHARGE. STREAM 8 . BEFORE CLERRCUTIMG • AFTER CLEflRCunjNG 1 Y = .009891 + .0655(77) (r = .55) I I 1 I I I I 78.0 1 0 1 . 0 1 3 0 . 0 156.0 102.0 203.0 234.0 DISCHARGE (LITRES/SEC) AMMONIUM CONCENTRATION VERSUS DISCHARGE. STREAM C i r i , , , ! , , ! o.o l l .o 72.0 .13.0 4.1 n v,.n r.c.o 77.o nn.o 19.0 no o nisCHrwcE. iLMRts/seci No significant relationships were found for streams A and C. Regression i s for "before clearcutting" data only. 154 Figure 4.45 Relationships between streamwater n i t r a t e concentrations and discharge. NITRATE CONCENTRATION VERSUS DISCHARGE! STREAM A . ecro;c curticuniiic I BflCR CIEHSCUTT1NG i i i i i 1 1 1 — 6.5 13.0 IS.5 2 5 . 0 3 2 . 5 3 9 . 0 45.5 S2.0 DISCHARGE (LITRES/SEC) NITRATE CONCENTRATION VERSUS DISCHARGE. STREAM 8 . BEFORE CIERRCUTTING I UTTER a t f a D J T T l N G 0-0 26.0 52.0 18.0 104.0 1311.0 155.0 182.0 208 0 DISCHARGE (LITRES/SEC) NITRATE CONCENTRATION VERSUS DISCHARGE. STREAM C — i 1 1 1 1 1 , — 22.0 33.0 -WO ' ,5.0 GCi.O 77.0 80 0 DISCHARGE (LITRES/SEC) No s i g n i f i c a n t r e l a t i o n s h i p s were found. 155 (P.132). The behaviour of ammonium is similar to that found elsewhere (Fisher et al. , 1968; Keller, 1970a). Variation between watersheds In the undisturbed watersheds, nitrate concentrations were usually highest in stream A and similar in streams B and C, probably due to the reasons discuss-ed above for higher potassium concentrations in stream A. There were no obvious differences in ammonium concentrations between streams. Effects of clearcutting Clearcutting has had no significant effect on ammonium concentrations (Table 4.12) whereas nitrate concentrations have been increased (Table 4.15) , this increase being s t a t i s t i c a l l y significant (P<0.05) in the case of stream A. In view of the time lag of more than half a year noted by Likens et al., (1970) and Pierce et al.i[1912) for nitrate increases to become apparent, i t may s t i l l be too soon to observe any major increases. Table 4.13 Seasonal variation of dissolved s i l i c a and anion concentrations in streamwater in temperate regions Location Nitrate Sulphate Chloride Bicarbonate Dissolved s i l i c a Reference Haney higher in winter, lower in summer higher in autumn, lower in winter autumn max-imum, spring -early sum-mer minimum late summer early aut-umn maximum winter mini mum higher in early aut-umn , lower in winter and early spring This study Seymour watershed, Vancouver low but maximum i n late sum-mer rxses xn autumn to January maximum, March minimum summer maximum, spring minimum variable late summer early aut-umn maximum late spring minimum Zeman (1973) cont. Table 4.13 cont. Location N i t r a t e Sulphate Chloride Bicarbonate Dissolved s i l i c a Reference Alsea basin coastal Oregon autumn maximum, summer minimum Brown et al., 1973 H.J. An-drews Ex-perimental Forest, c o a s t a l Oregon autumn maximum, summer minimum l a t e summer early aut-umn maximum winter-spring min-imum l a t e r win-te r - s p r i n g maximum, summer minimum Fredrik-sen, 1971 and 1972 Coastal C a l i f o r -nia 1. r e l a t i v e l y constant but higher i n l a t e autumn Baldwin, 1971 Coastal C a l i f o r -nia 2. higher i n autumn, lower i n winter higher i n autumn, lower i n winter higher i n autumn, lower i n winter Steele, 1968 Sagahen Ck., Eastern C a l i f o r -nia autumn maximum, spring minimum Johnson and Needham, 1966 Ohio - - r e l a t i v e l y constant - - Taylor et al., 1971 Maryland autumn maximum, summer minimum r e l a t i v e l y constant l a t e summer early aut-umn maximum l a t e winter minimum autumn maximum, l a t e winter minimum Cleaves et al., 1970 Hubbard Brook, New Hampshire spring maxi-mum, summer-autumn mini-mum before c u t t i n g ; autumn maxi-mum, spring minimum a f t e r c u t t i n g - autumn - maximum, • spring minimum r e l a t i v e l y constant l a t e summer early aut-umn maximum winter-spring minimum l a t e summer ear l y aut-umn maximum spring minimum Fisher et al., 1968; Likens et al., 1970 Review of r e s u l t s obtained throughout the U.S. higher i n winter, lower i n summer Cleaves et al., 1970 A g r i c u l t u r -a l water-sheds, Norfolk, B r i t a i n l a t e autumn maximum, summer minimum autumn maximum, summer minimum r e l a t i v e l y constant v a r i a b l e autumn maximum, winter-spring minimum Edwards, 1973a Finland winter maximum, spring minimum (for nitrogen) autumn maximum, summer minimum r e l a t i v e l y constant but higher i n autumn large f l u c -tuations but highest in spring V i r o , 1953 157 Table 4.14 V a r i a t i o n of di s s o l v e d s i l i c a and anion concentrations i n streamwater i n temperate.regions with increasing stream discharge Location N i t r a t e Sulphate Chloride Bicarbonate Dissolved s i l i c a Reference Haney some increases some decreases no s i g n i f i -cant r e l a -t i o n s h i p no s i g n i f i -cant r e l a -t i onship decreases decreases This study H.J. An-drews Ex-perimental Forest, Coastal Oregon decreases decreases Fredriksen, 1971 and 1972 Western C a l i f o r n i a some increases, some decreases Baldwin, 1971 Coastal C a l i f o r n i a decreases decreases decreases no s i g n i f i -cant r e l a -t i o n s h i p Steele, 1968 Sagahen Ck. Eastern C a l i f o r n i a — — — decreases — Johnson and Needham, 1966 Western Montana increases some increases, some decreases decreases decreases Weisel and Newell, 1970 Northern Utah no s i g n i f i -cant r e l a -t i o n s h i p - — decreases — Johnston and Doty, 1972 Ohio no s i g n i f i -cant r e l a -t i onship - - - • - Taylor et al., 1971 Maryland increases some increases, some decreases decreases decreases Cleaves et al., 1970 Hubbard Brook, New Hampshire increases decreases s l i g h t l y no s i g n i f i -cant r e l a -t i o n s h i p decreases (inferred from de-creases i n pH) decreases Johnson et al., 1969 Switzerland decreases decreases increases but not s i g n i f i c a n t s t a t i s t i c -a l l y decreases no s i g n i f i -cant r e l a -t i o n s h i p K e l l e r , 1970a and b A g r i c u l t u r -a l water-sheds, Norfolk, B r i t a i n increases increases decreases Edwards, 1973a and b 158 The Hubbard Brook workers have found greatly increased n i t r a t e concen-t r a t i o n s following c l e a r c u t t i n g i n New Hampshire with concentrations being greater the second year a f t e r c u t t i n g than the f i r s t (Hornbeck et al., 1973; Pierce et al. , 1972). Although n i t r a t e concentrations were not measured i n streams D and E before c l e a r c u t t i n g , a noticeable increase i n these concentra-tions occurred i n both streams the second year a f t e r c l e a r c u t t i n g (Table 4.15). Several studies i n c o a s t a l Oregon have also recorded increased n i t r a t e con-centrations i n streams following a v a r i e t y of commerical logging treatments i n -cluding c l e a r c u t t i n g (Brown et al., 1973; Fredriksen, 1971; Fredriksen et al., 1973). Invariably however, the increases were much less d r a s t i c than those found i n New Hampshire. C l e a r c u t t i n g i n New Hampshire was also found to a l t e r the seasonal v a r i a t i o n of n i t r a t e concentrations with maximum concentrations occurring i n early autumn instead of i n spring, as before c u t t i n g , and minimum concentrations occurring i n l a t e spring instead of i n l a t e summer-early autumn (Likens et al., 1970; Pierce et al., 1972). No changes i n the seasonal v a r i a t i o n of n i t r a t e concentrations i n streamwater were found i n the Oregon studies. Fredriksen et al. (1973) have proposed that the greater increases i n n i t r a t e concentrations i n streams following c l e a r c u t t i n g i n New Hamsphire, compared to those i n Oregon, aire due to a l e s s favourable climate causing l e s s decomposition o f f o r e s t l i t t e r i n New Hampshire. This allows a greater b u i l d up of l i t t e r , , and hence n u t r i e n t s , than i n Oregon. Thus, r e l a t i v e l y more nutrients can be released from the New Hampshire l i t t e r once c l e a r c u t t i n g has provided a more favourable microclimate f o r decomposition. The s o i l s i n the H.J. Andrews Ex-perimental Forest i n Oregon have very t h i n f o r e s t f l o o r s ranging up to only 2.5 cm i n thickness (Rothacher et al., 1967), whereas those at Hubbard Brook vary from 3 to 18 cm i n thickness with an average of about 8 cm (Hart et al., 1962). The s o i l s at Haney (Appendix II) are more s i m i l a r to those at Hubbard 159 Table 4.15 Average concentrations of dissolved s i l i c a and anions in streamwater before and after clearcutting. Cl N0_ S0„ HCO„ SiO„ 3 4 3 2 1. Stream A before .97(.23) .40(.21) 1.9(.6) 7.1(1.1) 5.7(1.2) after .97(.20) .68 (.17) 1.6(.6) 5.6(.9) 5.0(1.1) control(C) before .77(.22) .20(.32) 1.8(.8) 6.6(1.2) 4.5(.7) after .76(.21) .09(.07) 1.4(.5) 6.2(1.3) 4.0(.9) 2. Stream B before .80(.37) .18(.33) 2.K.8) 6.7(1.6) 4.5(1.3) after .96(.31) .11(.10) 2.0(.8) 5.8(1.5) 4.0(1.3) control(C) before .83(.34) .18(.30) 1.9(.8) 7.4(2.3) 4.5(1.1) after .85(.25) .08(.08) 1.7(.7) 6.9(2.3) 4.0(1.3) 3. Stream D before .64(.32) - - -after(l) .79(.30) .14(.14) 2.2(.5) 8.1(6.1) after(2) .76(.16) .29(.56) 2.9(.9) 10.4(4.4) 5.2(1.5) Stream E before .81 (.41) - - - -after(l) 1.04(.40) .22(.26) 3.0(.7) 12.2(9.4) 4.3(2.6) after(2) 1.12(.19) .36(.71) 4.4(.9) 15.4(7.1) 7.6(1.8) control(C) before .80(.13) -after(l) .73(.34) .19(.22) 1.9(.6) 8.1(5.8) 4.4(2.2) after(2) .79(.21) .14(.20) 2.2(.8) 11.0(3.5) 5.9(1.7) A l l concentrations are i n mg/litre * Standard deviations are given i n parentheses Values are for the same periods as i n table 4.12 (p. ) Brook, particularly with respect to forest floor depth. In view of the behaviour of streams D and E after clearcutting, i t i s li k e l y that the streams at Haney w i l l respond to clearcutting more like those in 160 Oregon than those at Hubbard Brook. This suggests that the explanation given by Fredriksen et al. (1973) for streamwater nitrate behaviour i s not completely correct. The large increases in nitrate concentrations in streams found in New Hampshire may be associated with the predominantly deciduous forest cover. The l i t t e r from deciduous hardwoods is relatively rich, promoting bacterial activity, and in particular, the activity of n i t r i f y i n g bacteria. A more favourable microclimate following clearcutting, together with an increased energy source and decreased inhibition of chemoautotrophic bacteria by vegetation in New Hampshire stimulated the n i t r i f y i n g bacteria which were present in sufficient quantities to produce large amounts of nitrate which were ultimately washed into streams. The Oregon watersheds were characterized by a predominantly coniferous forest cover whose l i t t e r i s l i k e l y to be more acidic and not as rich as that found in deciduous forests (Rodin and Bazilevich, 1965). Such l i t t e r conditions would not promote n i t r i f y i n g bacteria to the same extent as the hardwood forest l i t t e r . A lower population of n i t r i f y i n g bacteria in the Oregon s o i l s , i f i t occurred, could explain the lower nitrate concentrations in streams observed there. In addition, nutrient fluxes in the Hubbard Brook hardwood forest ecosystems are probably greater than those in the Oregon ecosystems where the soils may have fewer available nutrients and, due to the coniferous vegetation, fewer nutrients would be circulating. Interruption of the nutrient cycle would then allow a relatively greater loss of nutrients from the Hubbard Brook ecosystems than from those in Oregon. Furthermore, the solution percolating through s o i l in New Hampshire i s a weak sulphuric-nitric acid mixture which has a stronger leaching potential, as discussed in the following chapter, than the carbonic acid solution which percolates through coastal Oregon, Washington, and Br i t i s h Columbia ecosystems. No increases in ammonium concentrations were found after forest cutting 161 and herbicide application at Hubbard Brook (Likens et at., 1970) although i n -creases were detected after clearcutting and slashburning in Oregon (Fredrik-sen, 1971). In the Oregon study, ammonium concentrations immediately follow-ing burning were significant but for the rest of the time they were quite low and one year later they were negligible. The increased ammonium concentrations in Oregon relative to those at Hubbard Brook following forest removal may be related to the slashburning treatment in Oregon or may be due to more anaerobic conditions in the Oregon stream which would inhibit the oxidation of ammonium to nitrate, although the latter seems rather unlikely. The absence of abnormally high nitrate and ammonium concentrations i n streams D and E following clearcutting, relative to those i n undisturbed streams, suggests that clearcutting w i l l not drastically affect the concentrations of either of these ions in streams at Haney. 6) Bicarbonate The analytical method used determined alkalinity and not bicarbonate. At the pH of the samples, the predominant carbon species contributing to alkalin-i t y w i l l be the bicarbonate ion. However, bicarbonate concentrations calculated from the t i t r a t i o n results w i l l be too high for two reasons. F i r s t l y , although contributions of orthophosphate ions and aluminium hydroxide complexes are li k e l y to be negligible, undissociated carbonic acid together with lesser amounts of organic and s i l i c i c acids are present in solution and w i l l contrib-ute to al k a l i n i t y (Hem, 1970). Secondly, the analytical method involved a ti t r a t i o n to a fixed endpoint of pH 4.5 according to the recommended procedure. This, however, neglects the effects of ionic strength and the reagents used (Barnes, 1964). Several accurate potentiometric titrations were carried out and yielded endpoints varying from pH 4.9 to pH 5.7. The bicarbonate concen-trations from these accurate titrations ranged from 60 to 80% of the concentra-tions obtained from the standard procedure (Appendix VI). Due to time limita-tions and to be able to compare the results of this study to those of others, .162 the standard a n a l y t i c a l method was used for bicarbonate analyses. Even allowing f o r a reduction of about 30% i n the bicarbonate values given, bicarbonate was s t i l l the most common anion present i n streams at Haney (Appendix V). Although s i l i c a concentrations are sometimes higher, most of the s i l i c a i s probably not present i n anionic form, as discussed below. B i -carbonate i s u s u a l l y the most abundant anion i n f r e s h waters (Gorham, 1961; Hem, 1970). Seasonal behaviour Bicarbonate concentrations followed the seasonal trends of most of the other ions i n that concentrations peaked during the low flow periods of l a t e summer and e a r l y autumn then declined to minimum values during the winter (Figure 4.46). The amount of bicarbonate i n streamwater depends l a r g e l y on the stream-water pH and the amount of b i o l o g i c a l a c t i v i t y . Carbon dioxide from the a t -mosphere and b i o l o g i c a l a c t i v i t y d i s s o l v e s i n water y i e l d i n g a v a r i e t y of species depending on the pH of the s o l u t i o n . Increased b i o l o g i c a l a c t i v i t y and increased streamwater pH i n summer both tend to increase the amount of bicarbonate i n s o l u t i o n . Low carbon dioxide production from decreased b i o -l o g i c a l a c t i v i t y and large contributions of more a c i d i c t h r o u g h f a l l and s o i l water to streams i n winter both act to lower bicarbonate concentrations. This seasonal behaviour of bicarbonate agrees w e l l with that found i n other studies (Table 4.13). V a r i a t i o n with discharge Bicarbonate concentrations tended to decrease with increasing discharge (Figures 4.47 and 4.48). This w i l l be due p a r t l y to d i l u t i o n and p a r t l y to decreases i n pH with increasing discharge. This behaviour i s i d e n t i c a l to that found i n other studies (Table 4.14). V a r i a t i o n between streams Bicarbonate concentrations were s i m i l a r i n streams A, B, and C although Figure 4.46 Streamwater bicarbonate concentrations - streams A, B, and C 20 T 16-12-8-4 ALKALINITY AS R B C STREAM A STREAM B STREAM C BICARBONATE c l e a r c u t t i n g -c l e a r c u t t i n g -> B Q l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l N ONDJFMRMJJRSONDJFMflMJJflSONDJFMRMJJflSONDJFMfl 1970 1971 1972 1973 1974 164 Figure 4.47 Streamwater dissolved s i l i c a and anion concentrations during a storm event (27-29 November, 1973) STREAM A Concentration (mg/1) 5.0 Concentration (mg/1) 5.0 Si02 28 STREAM B 27 I 28 A l l N 0 3 concentrations <0.09 mg/1 Discharge (litres/sec) 150 50 H o Discharge (litres/sec) r1000 . r 500 Concentration (mg/1) 5.0 \ 4.0 3.0 -I 2.0 1.0 H STREAM C Discharge (litres/sec) r500 f-300 100 27 28 ' 29 A l l N O 3 concentrations <0.09 mg/1 For the three streams a l l H 2 P 0 4 concentrations <0.01 mg/1 Figure 4.48 Relationships between streamwater bicarbonate concentrations and discharge. • ALKflLINMT AS BICARBONATE Y&R5U5 DISCHARGE. . B E F C K E C I . E F I « : . U M I S S • BFTER CLCPRCuniNG STREAM A Y = 11.98 - 4.1651ogX (r = .87) 6 . 5 -1 13.0 —1 1 1 1 1 9 . 5 ? 5 . 0 3 2 . 5 3 9 . 0 DISCHARGE (LITRES/SEC) ALKALINITY AS BICARBONATE VERSUS DISCHARGE. . BEFORE ClEflRCUniNG f RFTER CLEBRCUrTING STREAM B Y = 12.02 - 3.5361ogX (r = .88) 7 8 . 0 1 0 4 . 0 DISCHARGE 1 3 0 . 0 1 5 6 . 0 (LITRES/SEC) 208.0 234.0 ALKALINITY AS BICARBONATE VERSUS DISCHARGE. STREAM C Regressions are for "before clearcutting" data only. 166 maximum concentrations in C tended to be higher than those in A and B (Figure 4.46). Effects of clearcutting Clearcutting has i n i t i a l l y decreased bicarbonate concentrations (Table 4.15), this decrease being s t a t i s t i c a l l y significant (P<0.10) for stream A only (Appendix X). This i s probably associated with the decreased pH follow-ing clearcutting. During the warmer months, biological activity i s l i k e l y to be enhanced by the more favourable microclimate and the increased abundance of material for decomposition. The resulting increased carbon dioxide production would have the opposite effect on bicarbonate concentrations to that of de-creased streamwater pH. The net result of this i s not yet completely clear. However, i t i s noteworthy that, despite lower pH values in streams D and E following clearcutting, rather high bicarbonate concentrations have been measured during the summer whereas winter concentrations are similar to those in streams A, B, and C (Figure 4.49). Forest cutting and herbicide application at Hubbard Brook decreased streamwater bicarbonate concentrations due to a decrease in pH (Likens et dl.3 1970). On the other hand, clearcutting in Oregon tended to increase bicarbon-ate concentrations, but no changes in pH were observed (Fredriksen, 1971). 7) Dissolved s i l i c a  Seasonal variation Although the i n i t i a l s i l i c a concentrations were widely scattered and are f e l t to be inaccurate due to inconsistent analytical procedures associated with the tendency of dissolved s i l i c a to settle to the bottom of sample con-tainers, concentrations tended to be lower in winter and early spring and higher i n early autumn (Figure 4.50). This seasonal behaviour agrees well with that found in other studies (Table 4.13). Most of the s i l i c a dissolved in streamwater comes originally from weather-ing of mineral particles and w i l l be present predominantly in the form of Figure 4.49 Streamwater bicarbonate concentrations - streams D and E 40 T 32 •• 24-16-8-flLKRLINITY RS BICARBONATE 0 c D E STREAM C STREAM D STREAM E F e l l i n g Yarding i " I IIIHIMIIIIIIIIIMIIIIIIIIIHnilllllllHIilllllllHIIIMIinnMllllllMHHMUIIIIiHIIIIIIIHHIIIMIIIIIIIIHIIIIIIIllllllll ONDJFMflMJJflSQNDJFMflMJJRSONDJFMRMJJflSQNDJFMR 1970 1971 1972 1973 1974 168 s i l i c i c acid at the pH of the streams, rather than as s i l i c a t e anions (Hem, 1970). Weathering of minerals i s l i k e l y to be most active in the warmer months when the weathering products w i l l accumulate during dry periods. These products w i l l be flushed away by the autumn rains, accounting for increased concentra-tions during early autumn. Variation with discharge Dissolved s i l i c a concentrations decreased with increasing discharge (Figures 4.47 and 4.51) which agrees with results from some other studies (Table 4.14). The variable relationships reported between dissolved s i l i c a concentrations and discharge may be due to concentrations increasing with i n -creasing discharge following rains after periods of active weathering in warm-er months and concentrations decreasing with increasing discharge during the colder months as precipitation dilutes the streamwaters. Variation between streams Dissolved s i l i c a concentrations tended to be highest in stream A and similar in streams B and C (Figure 4.50). This suggests a greater amount of weathering in watershed A. The warmer temperatures in watershed A together with the exposure of much mineral s o i l to the atmosphere in the 1961 planta-tion which covers 31% of watershed A (Figure 2.3) are l i k e l y to be major con-tributing factors to the higher quantities of s i l i c a in stream A. Effects of clearcutting Clearcutting has had v i r t u a l l y no effect on dissolved s i l i c a concentra-tions i n streams A and B (Table 4.15; Appendix X). Increases are only expected i f mineral weathering rates are increased, and this- i s only l i k e l y to occur during the warmer months. Data has, so far, only been collected for the colder months following clearcutting, so i t i s s t i l l too early to draw any conclusions. In addition to changes in weathering rates, changes in pH can also affect the concentrations of s i l i c a in solution. At the relatively low temperatures Figure 4.50 Streamwater dissolved s i l i c a concentrations - streams A, B, and C 15T 12.5-10 7.5-5-2.5-DISSOLVED SILICA R = S T R E A M R B - S T R E A M B C - S T R E A M C clearcutting-clearcutting-B Q 1 1111 [ I i E1111111111 i 11 ) 11111 r 111111 i 111111 ] i 111M111111111111L11L111U111111111T M L1111 i i 11111 i I i I i i 11L L11L1 i 11111111T f i ONDJFMRMJJflSONDJFMRMJJRSONDJFMRMJJflSONDJFMR 1970 1971 1972 1973 1974 Figure 4.51 Relationships between streamwater dissolved s i l i c a concentrations and discharge. 0 I S S 0 L V E 0 S I L I C A VERSUS D I S C H A R G E . STREAM A . BtfoHC c i E w c u r n n c • wIEH c u t t c u r r m s . BEFORE OEflRGinilC Regressions are for "before clearcutting" data only. 171 commonly encountered i n the watersheds the s o l i d which i s f i r s t formed from weathering i s amorphous s i l i c a whose s o l u b i l i t y i s i n v e r s e l y r e l a t e d to pH between pH3 and 7 (Marshall, 1964). Thus, a decrease i n streamwater pH fo l l o w -ing c l e a r c u t t i n g may furt h e r increase the amount of s i l i c a going i n t o s o l u t i o n . Increases i n d i s s o l v e d s i l i c a concentrations were observed a f t e r f o r e s t c u t t i n g and herbicide a p p l i c a t i o n at Hubbard Brook but i t was more than a year before the increases became d i s t i n c t (Likens et al., 1970). In view of t h i s , i t may be that, i f any s i g n i f i c a n t increases i n s i l i c a concentrations are to occur, i t w i l l be some time before they are manifest. This time l a g may be associated with increasing exposure of the s o i l surface caused by decay of p r o t e c t i v e s l a s h or may be due to the necessity f o r a considerable amount of extra weathering products to accumulate before changes i n stream s i l i c a con-centrations become noticeable. 8) Sulphate Sulphur i n aqueous s o l u t i o n which has a high d i s s o l v e d oxygen content and near-neutral pH values w i l l occur almost e n t i r e l y as sulphate anions (Hem, 1970). Seasonal behaviour Sulphate concentrations f l u c t u a t e d considerably so that no c l e a r season-a l trends were apparent. However, concentrations tended to be higher i n au-tumn and lower i n winter (Figure 4.52) , which agrees well with the r e s u l t s of other studies (Table 4.13). The observed f l u c t u a t i o n s were probably due to poor r e s o l u t i o n i n the a n a l y t i c a l technique as well as to the f a c t that the measured concentrations are close to the detection l i m i t of the a n a l y t i c a l method used. The concentra-t i o n data presented are probably too high, as discussed above (P. 127). V a r i a t i o n with discharge Sulphate concentrations generally were not s i g n i f i c a n t l y r e l a t e d to discharge, although some increases with increasing discharge were observed (Figures 4.47 and 4.53). The v a r i a b l e behaviour of sulphate concentrations Figure 4.52 Streamwater sulphate concentrations - streams A, B, and C 4 1 c = 3-2 • 1 -SULPHATE R = S T R E A M fl B = S T R E A M B S T R E A M C clearcutting-. A . clearcutting-, a , Q I I I I I M M n i l M I I I I I I I M l ' l l l l H M M I I t l l l l l l l l l M l l l l l l l l l H l l i n i l l l i n H i n i l l l M l l l l l l i l l 4 M l l i n ONDJFMflMJJflSONDJFMRMJJflSONDJFMflMJJflSONDJFMfl 1970 1971 1972 1973 1974 Figure 4.53 Relationships between streamwater sulphate concentrations and discharge. SULPHATE CONCENTRATION VERSUS Olf-OinRGC. STREAM A . FEfiVf C'. r!l-CUtt!)«G c uniF curjcjrtjNG 1 1 1 1 1 1 : 1 1 1 1 6.5 13.0 19.5 25.0 32.5 39.0 45.5 52.0 58.5 65.0 DISCHARGE (LITRES/SEC) SULPHATE CONCENTRATION VERSUS DISCHARGE. STREAM B . BEFORE CIEPRCUTTISC • RfTER C L E f l S C u m . i S I I 1 1 1 1 1 1 1 26.0 52.0 18.0 104.0 130.0 156.0 182.0 203.0 234.0 0 I S C H R R G E (LITRES/SEC) SULPHATE CONCENTRATION VERSUS DISCHARGE. STREAM C -1 : i i 1 1 1 1 — 11.0 22.0 3) 0 . u p v. n i.s n 17 0 O l S C t i t ^ G K t L U K t S / S t C ! No s i g n i f i c a n t r e l a t i o n s h i p s were found. 174 with discharge reported in other studies (Table 4.14) may depend on the amount of sulphate in precipitation, with high sulphate concentrations in precipita-tion causing increases in sulphate concentrations as streams rise and low con-centrations in precipitation causing decreases. Sulphate concentrations in precipitation at Haney are relatively high, as discussed in chapter five. Variation between streams There are no obvious differences in sulphate concentrations between the three streams (Figure 4.52). This may reflect the over-riding influence of concentrations in precipitation on streamwater concentrations. Effects of clearcutting Clearcutting has caused slight but s t a t i s t i c a l l y insignificant increases in sulphate concentrations in both streams A and B (Tabel 4.15, Appendix X). Forest cutting and herbicide application at Hubbard Brook decreased sulphate concentrations in streamwater (Likens et aZ.,,1970) as did commercial clearcutting (Pierce et al. s 1972). The decrease in sulphate concentrations was explained by large increases in nitrate concentrations in the s o i l which are toxic to sulphur oxidizing bacteria. Since i t i s unlikely that there w i l l be such a large increase in nitrate concentrations at Haney, (as discussed above), decreases in sulphate concentrations in streams are equally unlikely. Although sulphate concentrations were not measured in streams D and E prior to clearcutting, no abnormally high or low post-logging concentrations have been observed. This suggests that any changes in sulphate concentrations, as a result of clearcutting, w i l l be rather small. 9) Chloride  Seasonal behaviour Chloride concentrations exhibited pronounced seasonal trends with maximum values in autumn and minimum values in spring and early summer (Figure 4.54). These trends d i f f e r from those found by most other workers although they are similar to those found by Zeman (1973) in a stream 60 km. from the Haney Figure 4.54 Streamwater chloride concentrations - streams A, B, and C 4 T 2.90 -2.18-1 .45 .727-0 fl B C S T R E A M A S T R E A M B S T R E A M C CHLORIDE clearcutting-A clearcutting-B I 1 1 1 1 l l l l l l l l t l f t t I J f t l - f l l l l l i f f l t l l l I I I I I I I J l l l l l I t l l l l l l l t l t t i l l i l l f l l l l f l l t < - l < t < l l l l l l I I I I I I I f f l l t l f I I I I I I I I f l l l t l < < < < - * t 4 1 < 4 l i ONDJFMflMJJflSONDJFMflMJJflSONDJFMflMJJflSONDJFMfl 1970 1971 1972 1973 1974 176 watersheds (Table 4.13). Igneous rocks, such as those which form the bedrock of the watersheds, contain l i t t l e chloride. Due to the biological inactivity of chloride and i t s lack of reactivity in s o i l s , i t i s l i k e l y that most of the chloride in the streamwater comes from precipitation (Hem, 1970; Junge and Werby, 1958). During the dry summer i t has been proposed that most chloride i s deposited in particulate form, to be washed away by the autumn rains (Juang and Johnson, 1967). This would explain the seasonal trends observed at Haney. Variation with discharge Chloride concentrations appear to be independent of discharge at Haney (Figures 4.47 and 4.55) in agreement with the findings of most other workers (Table 4.14). This may be partly due to the variable nature of chloride con-centrations in precipitation, which are higher when the prevailing winds come directly from the sea. It may also be partly due to the inert nature of chloride ions which tend to pass through an ecosystem without many reactions. Variation between streams There were no obvious differences in chloride concentrations between the three streams (Figure 4.54). This i s expected i f the source of most of the chloride i s precipitation. Effects of clearcutting Clearcutting has caused a very slight increase in chloride concentrations in stream A but pronounced increases in streams B, D, and E, which were st a t i s -t i c a l l y significant (P<0.01) in the case of stream E (Table 4.15; Appendix X). The effect of clearcutting on chloride concentrations was not studied in Oregon. At Hubbard Brook, however, forest cutting and herbicide application increased chloride concentrations, the increase being greatest the f i r s t year after cutting (Likens et at., 1970), as has been found in the present study for stream D. This suggests that any increases in chloride concentrations in stream A may be most noticeable in the autumn of 1974. Figure 4.55 Relationships between streamwater chloride concentrations and discharge. 177 0C 3 o §2-• C H L O R I D E CONCENTRATION VERSUS D I S C H A R G E . 0 WTLR t L C W t t i t T I n S STREAM A — I — 6 . S 0 . 0 1 3 . 0 1 9 . 5 26.0 J2.5 39 0 DISCHARGE ( L I T R E S / S E C ) CHLORIDE CONCENTRATION VERSUS D I S C H A R G E . STRESM 3 o BfUR cuft jo irr i i i s — i — 3 8 . 5 - 1 6 5 . 0 OJt 2 S . 0 5 2 . 0 3 O — I 1 T 1 — — 1B.0 104.0 130.0 iss.o DISCHARGE ( L I T R E S / S E C J CHLORIDE CONCENTRATION V E R S U S D I S C H A R G E . STREAM C 1 8 2 . 0 —TT 2 0 4 . 0 2 3 4 . 0 2 6 0 . 0 -1 1 1 — 1 1 1 11.0 2 2 . 0 1 3 . 0 +4.0 5 5 0 66 0 D I S C H A R G E I L J I R E S / S E C ) ' —I 110.0 No significant relationships were found. 178 10) Phosphate Phosphate concentrations have remained undetected v i r t u a l l y throughout the entire sampling period. Phosphate in unpolluted streams is usually found at extremely low concentrations, this being attributed to the u t i l i z a t i o n of phosphorus by aquatic vegetation and the adsorption of phosphate ions by metal oxides, especially f e r r i c hydroxide (Hem, 1970). Any phosphorus present i n streamwater at Haney, however, would exist predominantly as dihydrogen ortho-phosphate anions (H2P0^) in view of the pH of the solutions (Hem, 1970) . Although phosphate concentrations have been reported to decrease with increasing discharge [and to be lower in spring and higher in autumn (Edwards, 1973a and b; Johnston and Doty, 1972)J, concentrations in streams at Haney have been too low to permit such observations. Effects of clearcutting Phosphate concentrations in a l l streams have remained too low to permit any meaningful conclusions to be drawn. Brown et at., (1973) found no changes in phosphate concentrations follow-ing clearcutting and slashburning in the Alsea basin i n Oregon. Although Fredriksen (1971) also observed no changes in stream phosphate concentrations following clearcutting, he did observe an increase following slashburning. The concentrations measured in both these studies are close to the detection li m i t of the analytical method used in this study and consequently any such changes would be d i f f i c u l t to detect at Haney. 8. Chemical budgets Monthly chemical inputs of selected nutrient chemicals were determined for each watershed by multiplying monthly amounts of precipitation by monthly average chemical concentrations in precipitation. Outputs were determined by multiplying volumes of water discharged in streams per month by monthly average chemical concentrations in streamwater. Net gains or losses were determined by subtracting outputs from inputs. Detailed monthly budgets are given in 179 Appendix XIII. Annual budgets are summaried i n Table 4.16. There was a net loss of calcium, sodium, and magnesium from a l l water-sheds and potassium and sulphur from a l l watersheds except watershed C. Net losses of potassium and sulphur from watershed C are l i k e l y , however, since the amount of water discharged from watershed C was probably underestimated by about 30% (P.76 ). A l l watersheds accumulated nitrogen but neither gained nor l o s t phosphorus, as the very low phosphorus inputs equalled the outputs. The c h l o r i d e balance changed from year to year with net losses one year and net gains the second. Table 4.16 Annual chemical budgets (kg/ha) K Na Mg Ca C l N S P watershed A 1. water year 1971/72 -0.8 -10.7 -3.0 -15.9 -1.5 • - - • -2. water year 1972/73 -0.9 -6.3 -2.1 -10.6 +0.6 +2.6 -0.6 0.0 3.* f i r s t s i x months a f t e r c l e a r c u t t i n g -3.7 -10.1 -2.7 -14.7 -4.6 + 1.6 -3.3 0.0 watershed B 1. water year 1972/73 -1.4 -8.3 -3.7 -17.3 -4.0 +3.3 -7.5 0.0 2.* f i r s t s i x months a f t e r c l e a r c u t t i n g -8.0 -17.2 -5.5 -24.3 -13.2 +3.3 -10.8 0.0 watershed B + C 1. water year 1971/72 -0.1 -10.5 -3.6 -18.6 -0.8 - - -2. water year 1972/73 -0.5 -5.2. -2.6 -13.7 +0.7 +3.4 -2.4 0.0 3.* f i r s t s i x months a f t e r c l e a r c u t t i n g -3.1 -10.7 -3.4 -19.3 -4.8 +3.9 -5.0 0.0 watershed C 1. water year 1972/73 +0.1 -3.5 -1.8 -11.8 +3.3 +3.5 +0.5 0.0 2.* f i r s t s i x months a f t e r c l e a r c u t t i n g -0.4 -5.6 -2.2 -16.5 -0.1 +4.2 -1.8 0.0 Water years are from October 1st to September 30th. Potassium, sodium, magnesium, calcium, and chlorine budgets were determined from concentrations of t h e i r r e spective ions. Nitrogen was determined from the sum of n i t r a t e - n i t r o g e n and ammonium-nitrogen budgets. Sulphur was determined from concentrations of sulphate-sulphur. Phosphorus was determined from concentrations of phosphate-phosphorus. *These chemical budgets are for a six-month period only. 180 Estimated errors i n budget c a l c u l a t i o n s Contamination of p r e c i p i t a t i o n presented a large uncertainty i n budget c a l c u l a t i o n s . However, i t was considered that pH and potassium concentra-t i o n measurements were good i n d i c e s of the p u r i t y of samples. When ei t h e r of these measurements were abnormally high the samples were r e j e c t e d . This minimized the c o n t r i b u t i o n of contaminated samples to budgets. The estimated maximum e r r o r s i n the budget c a l c u l a t i o n s are given i n Table 4.17. These er r o r s were rather large and were greater f o r output -than f o r input - c a l c u l a t i o n s . E r r o r s i n water volume c a l c u l a t i o n s were us u a l l y greater than errors i n chemical concentration measurements. S u l -phur, nitrogen, and calcium budgets, i n that order, were considered to be the l e a s t accurate. I t should be stressed that the estimated maximum e r r o r s were derived from subjective estimates of the maximum errors p o s s i b l e f o r each step i n the c a l c u l a t i o n s . The estimated maximum e r r o r s represent an extreme s i t u a t i o n where a l l e r r o r s were considered t o act i n the same d i -r e c t i o n , Thus, i t i s u n l i k e l y that the r e a l e r r o r s would be as great. R e l a t i v e l y high e r r o r s are involved i n budget c a l c u l a t i o n s f o r water-shed B. These a r i s e mainly from the necessity of c a l c u l a t i n g volumes of water flowing over two weirs, rather than j u s t one. Thus, the experimental design used produces r e s u l t s which are much l e s s accurate than those ob-tained from a design which uses e n t i r e watersheds only. I f weir C i s underestimating streamflow by about 30%, as seems l i k e l y , then chemical losses from watershed C would a l s o be underestimated by about 30%. Increasing chemical losses from watershed C by 30% would produce chemical budgets more s i m i l a r to those found f o r watershed A and B + C). I t would a l s o reduce chemical losses from watershed B producing budgets which would a l s o be more s i m i l a r to those found f o r watersheds A and (B + C). Table 4.17 Estimated maximum errors i n chemcial budget calculations a) Inputs (to a l l watersheds) Total Error (%) in K Na Mg Ca Cl H^PC^-P NC^ -N NH^ -N s o 4 " s 1. Volume estimation 10 10 10 10 10 10 10 10 - 10 2. concentration measurement 14 8 9 2 5 9 10 8 10 - 45 cumulative total 25 19 20 38 20 21 19 21 40 60 b) Outputs i . Watersheds A and (B + C) Error (%) i n K Na Mg Ca Cl H2P04-P NO -N NH -N 4 Total N SO -s 4 1. weir calibration 6 6 6 6 6 6 6 6 6 2. mean daily height estimation 23 23 23 23 23 23 23 23 - 23 3. concentration measurement 14 8 9 25 9 10 8 10 - 45 cumulative total 48 40 42 62 42 43 40 43 83 89 i i . Watershed B 1. weir B discharge 30 30 30 30 30 30 30 30 ' - 30 2. weir C discharge 34 34 34 34 34 34 34 34 - 34 3. concentration measurement 14 8 9 25 9 10 8 10 - 45 cumulative total 88 78 80 106 80 82 78 82 160 139 i i i . Watershed C 1. weir calibration 10 10 10 10 10 10 10 10 — 10 2. mean daily height estimation 23 23 23 23 23 23 23 23 - 23 3. concentration measurement 14 8 9 25 9 10 8 10 - 45 54 46 47 69 47 49 46 49 95 96 O Budgets (Overall % error = % error in input + % error in output) i . Watersheds A and B + C 73 59 62 100 62 64 59 64 123 149 i i . Watershed B 113 97 100 144 100 103 97 103 200 199 i i i . Watershed C 79 65 67 107 67 • 70 65 70 135 156 182 Work at Hubbard Brook (Likens et al. 3 1967) and Coweeta (Johnson and Swank, 1971) has established that weekly sampling i s sufficiently frequent to produce accurate nutrient budgets. The absence of large daily variations in chemical concentrations in streamwater at Haney, discussed below (P.189 ) suggested that weekly sampling was also sufficient at Haney. Loss of chemicals bound to solid particles in streamwater was considered to be unimportant at Haney in view of the low suspended sediment concentrations measured in the streams. This was found to be the case at Coweeta where less than 2% of each of sodium, potassium, magnesium, and calcium was lost in solid form (Johnson and Swank, 1973). At Hubbard Brook, less than 6% of each of calcium, magnesium, sodium, nitrogen, and sulphur but 18% of potassium (Bormann et al.3 1969) and most of the phosphorus (Hobbie and Likens, 1973) was lost in solid form. Seasonal trends in chemical budgets A l l the chemicals considered exhibited similar behaviour with outputs i n -creased relative to inputs throughout winter and early spring, and inputs i n -creased relative to outputs throughout summer and autumn. Of these chemicals, potassium, chloride, and sulphate exhibited frequent monthly gains during sum-mer and autumn. Net monthly losses were usually observed throughout the year for sodium, magnesium, and calcium, whereas the watersheds gained both ammonium and nitrate nitrogen v i r t u a l l y every month although the gains were lower during the summer. Continual gains in nitrogen are probably due to biological uptake with a net incorporation of nitrogen in the forest biomass. Some nitro-gen may also be lost by conversion to gaseous forms (Wollum and Davey, 1973). Potassium behaved erra t i c a l l y , unlike the other metallic cations. The gains almost balanced the losses although there was considerable monthly fluc-tuation between gains and losses. Also, in the 1972/73 water year, losses were greater than in the 1971/72 water year, despite less precipitation. Such atypical behaviour by potassium has been attributed to the fact 183 that i t s mineralogical and biological roles are different from those of the other metallic cations (Likens et al. 3 1967). Chemical weathering does not completely release potassium as some ions remain in clay structures. Hence, clay particles in the s o i l may act as a reservoir of chemically bound potassium. Also, a higher percentage of available potassium compared to the other cations may be taken up by organisms so that biomass accumulation, which was occurring in the watersheds as evidenced by the relatively large width of recent tree growth rings, may allow biota to be a reservoir for potassium. The seasonal trends i n chemical budgets at Haney are v i r t u a l l y identical to those found at Hubbard Brook for sodium, magnesium, and calcium (Likens et al., 1967), chloride (Juang and Johnson, 1967), and sulphate, nitrate, and ammonium (Fisher et al.3 1968). These trends, however, are different to those found at Seymour where chemical inputs increased relative to outputs during the winter but decreased relative to outputs during the summer (Zeman, 1973). This i s probably due to greater contributions of snowmelt runoff during summer to the stream at Seymour compared to Haney and Hubbard Brook. At Seymour, stream discharge exceeded precipitation during summer (Zeman, 1973), unlike the situation at Hubbard Brook (Likens et al., 1967), and Haney.. Relationships between chemical loads and water quantities In general, the inputs and outputs of a l l chemicals increased with volume of water. S t a t i s t i c a l l y significant relationships were found in most cases but the relationships were invariably better between chemical outputs and volume of water discharged than between chemical inputs and volume of precipi-tation (Appendix XIV). This can be attributed to the highly variable nature of chemical concentrations in precipitation which depend on the amount of i n -dustrial a i r pollution and the direction of the prevailing winds. These two factors frequently change and thus affect the monthly chemical inputs. Logarithmic relationships between chemical loads and water volumes were SJ found to be invariably more accurate than linear relationships, as has been 184 found elsewhere (e.g. Zeman, 1973). Annual chemical budgets f o r forest-watershed ecosystems ' Despite the p o s s i b i l i t y of large errors i n chemical budget c a l c u l a t i o n s , the budgets f o r the Haney watersheds are quite s i m i l a r to budgets f o r water-sheds elsewhere i n humid temperate regions (Table 4.18). They are p a r t i c u l a r -l y s i m i l a r to those f o r Hubbard Brook. From Table 4.18, c e r t a i n trends i n annual chemical budgets of undisturbed forest-watershed ecosystems are apparent: 1. There i s a consistent l o s s of magnesium, calcium, and u s u a l l y sodium. 2. There i s a consistent gain of nitrogen. 3. Net gains or losses of phosphorus are i n v a r i a b l y very small. 4. C h l o r i d e , sulphur, and potassium may be gained or l o s t but these gains or losses are quite small. The only exception i s the large c h l o r i d e l o s s from Seymour (Zeman, 1973). Results from Haney were consistent with each of these trends. Comparing the Haney watersheds to nearby Jamieson Ck. at Seymour, i t can be seen that losses of a l l chemicals, except sulphur, were greater, and n i t r o -gen accumulation l e s s , at Seymour. This was probably due to a combination of the following f a c t o r s : 1. A i r p o l l u t i o n from Vancouver and surrounding i n d u s t r i a l areas, has in c r e a s -ed chemical inputs i n p r e c i p i t a t i o n at Haney, r e l a t i v e to Seymour. 2. The f o r e s t s at Haney are r e l a t i v e l y young and s t i l l accumulating biomass. They are l i k e l y to be accumulating greater amounts of biomass, and hence chemi-c a l s , than the very o l d f o r e s t s at Seymour. 3. Greater p r e c i p i t a t i o n at Seymour (316 cm f o r the 1972/73 water year, com-pared to 177 cm at Haney) and lower evapotranspiration (40 cm compared to about 65 cm at Haney) causes considerably greater q u a n t i t i e s of water to. pass through the Seymour watershed. This i s l i k e l y to increase the amount of chemi-c a l s leached away r e l a t i v e to Haney. This i s supported by s t a t i s t i c a l l y 185 Table 4.18 Annual chemical budgets of undisturbed forest-watershed ecosystems i n humid temperate regions (kg/ha). Area K Na Mg Ca . C l N S P Reference Haney - 1971/72 -0.5 -10.6 -3.3 -17.3 -1.2 _ _ _ This study average of water-sheds A 1972/73 -0.7 -5.8 -2.4 -12.2 +0.7 +3.0 -1.5 0.0 and (B+C) Jamieson Creek, Calculated Seymour 1970/71 -1.7 -12.4 -6.6 -34.4 -15.0 +0.1 -0.8 -0.1 from data water- i n Zeman shed , (1973) Vancouver Hubbard 1963/64 +0.7 -4.9 -1.9 -5.0 - - - C a l c u l a t e d Brook, 1964/65 +0.7 -2.4 -0.7 -1.1 - +1.8 +0.2 - from data New 1965/66 - - - - -1.4 +4.0 -1.5 - i n F i s h e r Hamp- 1966/67 -1 -6 -3 -8 +2 +5 -3 - et al. .,1968; sh i r e 1967/68 -2 -7 -3 -9 0 +5 -3 - Hobbie and 1968/69 - - - - - - - +0.1 Likens, 1973; Juang and Johnson,1967; Likens et al. 1967; Likens et al.,1970. Coweeta, 1969/71 -2. 2 -4.3 -1.8 -0.8 — — - - Johnson and North annual Swank, 1973. Car o l i n a average Oak Ridge 1969/ Swank and Tennessee 70 +1.6 +1.1 -46.7 -58.6 - — — — Elwood, 1971 Maryland 1966/68 -0.3 -1.4 -0.7 +0.2 +1.9 - +4.6 - Calculated annual from data i n average Cleaves et al.3 1970. H.J. An- 1969/70 -1.0 -32.5 -12.0 -46.0 - +0.5 - - Fredriksen, drews Ex- 1972. perimen- 1970/71 -2.1 -23.4 -11.1 -48.0 - +0.5 - -0.3 t a l For-est , Oregon Beech f o r e s t area near Wellington, New Zealand +1 -8 -10 -17 0 +2.6 +2 +0.2 M i l l e r , 1968 Finla n d -2.1 -3.6 -3.0 -10.0 +0.2 +4.0 -3.3 +0.2 V i r o , 1953 Japan +0.4 -1.0 +3.8 - • +4.9 - +0.4 Iwatsubo and Tsutsumi,1968 186 s i g n i f i c a n t r e l a t i o n s h i p s between net losses and amount of p r e c i p i t a t i o n f o r watersheds A and (B+C) which showed increases i n net losses of a l l chemicals except nitrogen as the amount of p r e c i p i t a t i o n increases (Appendix XIV). The most outstanding d i f f e r e n c e s between Haney and Seymour are the much greater c h l o r i d e losses at Seymour. These may be a function of the c l o s e r proximity of Seymour to the sea causing i t to catch greater q u a n t i t i e s of windblown s a l t aerosols (Clayton, 1972; Juang and Johnson, 1967). E f f e c t s of c l e a r c u t t i n g In the s i x month period following c l e a r c u t t i n g , there has been a net l o s s of a l l chemicals, except nitrogen, from each of the watersheds. This was ex-pected i n view of the f a c t that net losses i n the undisturbed watersheds usua l -l y occurred during winter and spring. The net losses following c l e a r c u t t i n g were greater than i n the e n t i r e 1972/73 water year. This can be a t t r i b u t e d to the heavy p r e c i p i t a t i o n following c l e a r c u t t i n g which, i n s i x months, has ex-ceeded that f o r the 1972/73 water year. By comparing chemical budgets of watershed A to those of the undisturbed watershed C (Table 4.16), i t was found that potassium losses were g r e a t l y i n -creased ( s i g n i f i c a n t at P<0.01) and nitrogen gains decreased ( s i g n i f i c a n t at P<0.01, and due to changes i n n i t r a t e but not ammonium budgets) following c l e a r c u t t i n g (Appendix X). For watershed (B+C), however, potassium, sodium, magnesium and c h l o r i d e losses were s i g n i f i c a n t l y increased (P<0.01) and n i t r a t e , but not t o t a l nitrogen, gains were s i g n i f i c a n t l y decreased (P<0.05) by c l e a r -c u t t i n g (Appendix X). As the s l a s h i n watershed B had time to s t a r t decom-posing during l a t e summer and e a r l y autumn i n 1973, unlike the sl a s h i n water-shed A, and as s i t e exposure i n watershed B has been more prolonged, e s p e c i a l l y during a warm period, p o s t - c l e a r c u t t i n g chemical losses from watershed B were expected to be greater than those from watershed A. Phosphorus inputs and outputs were extremely low and have not been a f f e c t -ed by c l e a r c u t t i n g . At Hubbard Brook, f o r e s t c u t t i n g and herbicide a p p l i c a t i o n 187 has increased phosphorus losses from a watershed, but the losses are s t i l l very small (0.1 kg/ha/yr) and most of the losses were i n p a r t i c u l a t e form (Hobbie and Likens, 1973). Such losses could not be detected at Haney. Nitrogen has s t i l l been accumulated i n each watershed following c l e a r -c u t t i n g but t o a l e s s e r extent than i n the undisturbed watershed C. Although i t i s too soon to draw d e f i n i t e conclusions, i t appears that c l e a r c u t t i n g has s i g n i f i c a n t l y a f f e c t e d c e r t a i n chemical budgets at Haney, p r i m a r i l y due to increased amounts of runoff i n the case of sodium, mag-nesium and c h l o r i d e as the concentrations of these chemicals were not s i g -n i f i c a n t l y a f f e c t e d by c l e a r c u t t i n g . Stream Chemistry - General Discussion 1. Undisturbed watersheds a. Comparison with Zeman's data f o r the nearby Seymour watershed The streams studied at Haney e x h i b i t generally s i m i l a r chemical be-haviour to those studied elsewhere. Although i n s u f f i c i e n t data were pre-sented by Zeman (1973) t o permit f u l l comparison of the streams a t Haney with Jamieson Creek i n the nearby Seymour watershed, i t seems that t h e i r chemical behaviour i s rather s i m i l a r . Chemical concentrations i n the streams at Haney are s l i g h t l y greater than those i n Jamieson Creek although mag-nesium and c h l o r i d e concentrations at Haney are lower than at Seymour. The major mechanism c o n t r o l l i n g streamwater chemistry i n southwestern B.C., and elsewhere i n the humid temperate regions of the world, i s mineral weathering (Gibbs, 1970; Gorham, 1961). However, where weathering supplies only small amounts of chemicals t o streams, then the c o n t r i b u t i o n of pre-c i p i t a t i o n t o streamwater chemistry can be s i g n i f i c a n t . The g e o l o g i c a l survey of the area (Roddick, 1965) i n d i c a t e s that the bedrock at Haney and Seymour are quite s i m i l a r , although the Haney bedrock 188 contains relatively more biotite and potash feldspar while the Seymour bedrock contains relatively more quartz and hornblende. These differences in composition, together with the fact that biotite weathers more rapidly than hornblende, suggest that mineral weathering w i l l release greater quan-t i t i e s of chemicals at Haney than at Seymour. Rates of weathering may also be important. A higher weathering rate in the low elevation watersheds at Haney compared to that in the higher elevation Seymour watershed may also help to explain differences in stream chemistry. Differences i n precipitation chemistry may also contribute to differences i n stream chemistry. Higher chloride concentrations i n the stream at Seymour may refle c t the closer proximity of Seymour to the sea with the precipitation at Sey-mour being richer i n chloride. A comparison of precipitation data sup-ports this conclusion. b. Seasonal behaviour Most of the chemical parameters measured exhibited prounounced seasonal variations with maximum values i n late summer to early autumn and minimum values from winter to early spring. Major exceptions were nitrate and dissolyed oxy-gen concentrations which had maximum values in winter and minimum values i n summer. The seasonal pattern i n concentrations, however, suggests that the stream chemistry was dominated by annual cycles. These involved bidlogical and geological breakdown in the warmer part of the year with accumulation* of chemi-cals during dry periods, followed by the flushing of these chemicals into streams by the autumn rains. This was followed by a period of relative bio-logical and geological inactivity u n t i l temperatures rose again the following spring. During that time, there was l i t t l e addition to the supply of chemicals available for movement into streamwater. At the same time, the lack of biologi-189 c a l a c t i v i t y allowed movement of nitrogen compounds in t o streamwater. During the warmer p a r t o f the year, however, b i o l o g i c a l uptake allowed l i t t l e move-ment of nitrogen out of the t e r r e s t r i a l ecosystem, c. V a r i a t i o n with discharge Decreases i n pH, and sodium, calcium, magnesium, di s s o l v e d s i l i c a , and bicarbonate concentrations were observed with i n c r e a s i n g discharge. Potas-ium concentrations tended to generally decrease with i n c r e a s i n g discharge although they tended to increase with discharge during storm events. Chem-i c a l s which increase i n concentration with increasing discharge have been assumed to o r i g i n a t e l a r g e l y from surface runoff or p r e c i p i t a t i o n , unlike those showing the opposite behaviour which have been assumed to o r i g i n a t e l a r g e l y from seepage of water through the s o i l (e.g. Buscemi, 1969; Weisel and Newell, 1970). This w i l l be discussed i n more d e t a i l i n the following chapter. Table 4.19 Streamwater chemistry during a 24-hour period, 5-6 November, 1973 Parameter Stream A Stream B Stream C mean max. min. mean max. min. mean max. min. potassium .31 .32 .29 .18 .20 .17 .06 .06 .05 sodium 1.32 1.32 1.30 1.14 1.15 1.12 1.13 1.15 1.11 magnesium .30 .30 .29 .32 .33 .32 .31 .32 .31 calcium 1.1 1.2 1.0 1.5 1.6 1.3 2.0 2.1 2.0 c h l o r i d e 1.2 1.4 1.1 1.1 1.2 1-1 1.0 1.0 .9 sulphate 2.5 . 2.5 2.0 2.5 2.5 2.5 2.5 2.5 2.5 s i l i c a 5.1 5.5 4.5 4.8 5.0 4.5 5.3 5.5 5.1 bicarbonate 8.1 8.5 7.6 7.9 8.1 7.6 9.4 9.7 9.0 e l e c t r i c a l c o n d u c t i v i t y 20.4 20.3 20.6 20.7 20.9 20.5 21.4 21.6 21.2 discharge 3.8 3.8 3.8 12.4 12.4 12.4 7.2 7.2 7.2 Ten samples were c o l l e c t e d per stream with a sampling i n t e r v a l of 2-1/2 hours. A l l concentrations are i n m g / l i t r e , c o n d u c t i v i t y i s i n micromho/cm at 25°C, and discharge i s i n l i t r e s / s e c . Iron, manganese, aluminium, ammonium, phosphate, and n i t r a t e concen-t r a t i o n s were a l l close to or below t h e i r respective detection l i m i t s . 190 With relatively constant discharge, chemical concentrations in the streams were quite constant throughout^ the day (Tables 4.19 and 4.20); the slight differences observed may be due more to analytical error than to real differences. Concentrations thus appeared to depend more on season and discharge than on time of day. Similar results have been reported by Cleaves et al. (1970) for a small stream in Maryland. 2. Effects of clearcutting on stream chemistry a. Results of this study Streams A and B have been studied for a period of only six months af-ter clearcutting. During this period only potassium concentrations have been significantly changed. Slight changes in other parameters have been noted above. Neither of the two clearcut watersheds has yet been subjected to a long warm period when slash decomposition and mineral weathering i s most active. At the end of March, 1974, the termination of data collection for this thesis, the foliage on the slash in watershed A was s t i l l green. As discussed in the following chapter, maximum carbonic acid concentrations, and hence leaching potential, of the s o i l water w i l l occur during the f i r s t autumns following clearcutting. Thus, maximum release of chemicals from the slash and s o i l s should not yet have occurred but w i l l probably occur during the summers of 1974 and 1975. The chemicals released should have the greatest effect on stream concentrations during the late summer-early autumn periods of 1974 and 1975 i n view of the results of other studies and observations of streams D and E. Dissolved oxygen concentrations are expected to decrease s i g n i f i -cantly during the coming summers with greater decreases in stream A due mainly to i t s smaller size. b. Results of other studies There have been relatively few studies investigating the effects of clear-cutting on streamwater chemistry and most of these have a number of shortcomings. 191 Table 4.20 Streamwater chemistry during a 24 hour period, 24-25 June, 1972. Stream A Stream B Stream C Parameter mean max. min. mean max. min. mean max. min. potassium .16 .17 .16 .10 .20 .09 .07 .07 .07 sodium 1.40 1.42 1.39 ' 1.24 1.26 1.23 1.22 1.23 1.20 magnesium .38 .39 .38 .39 .40 .39 .41 .41 .40 calcium 1.9 . 1.9 1.8 2.1 2.1 2.1 2.5 2.6 2.5 ammonium .01 .02 .01 .01 .04 <.01 .01 .02 .01 sulphate .6 .7 .5 1.0 1.5 1.0 1.0 1.5 1.0 n i t r a t e .26 .29 .22 .21 .27 .18 .25 .33 .20 s i l i c a 6.9 7.6 6.6 5.4 5.6 5.2 5.6 5.6 5.4 e l e c t r i c a l c o n d u c t i v i t y 22.5 22.9 22.1 22.7 23.0 22.4 24.0 24.6 23.4 discharge 1.1 1.4 1.1 5.9 9.0 3.0 3.8 4.2 3.2 Thi r t e e n samples were c o l l e c t e d f o r each of streams A and B with a sampling i n t e r v a l of 2 hours and four samples were c o l l e c t e d f o r stream C with a sampling i n t e r v a l of eight hours. A l l concentrations are i n m g / l i t r e , c o n d u c t i v i t y i s i n micromho/cm at 25°C, and discharge i s i n l i t r e s / s e c . Iron, aluminium, and phosphate concentrations were a l l close to or below t h e i r respective detection l i m i t s , and manganese, bicarbonate, and c h l o r i d e analyses were not performed. The f i r s t , and most comprehensive work, i n v e s t i g a t i n g the e f f e c t s of c l e a r c u t t i n g on stream chemistry i s that c a r r i e d out at Hubbard Brook. The study of the e f f e c t s of complete vegetation removal on stream chemistry (Likens et al., 1970) i n d i c a t e d what might happen to streams following c l e a r c u t t i n g . Recent papers from Hubbard Brook (Hornbeck et al., 1973; Pierc e et al.', 1972) have reported the e f f e c t s of commercial c l e a r c u t t i n g on stream chemistry. The f i r s t of these (Pierce et al., 1972) was rather l i m i t e d i n that only calcium, n i t r a t e , sulphate, and con d u c t i v i t y data were presented, un l i k e the more com-prehensive paper which followed (Hornbeck et al., 1973). In both cases, the chemistry of a stream was studied before as w e l l as a f t e r c l e a r c u t t i n g . This avoids the nec e s s i t y of assuming that chemical concentrations i n a stream i n a cl e a r c u t watershed would have been the same as those i n a stream i n a nearby uncut watershed, had the f i r s t watershed not been cut. Pierce et al. (1972) do use t h i s assumption, however, i n part of t h e i r paper, and i t i s also used 192 i n several of the other papers. This assumption i s considered to be generally i n v a l i d , as discussed below. The second study was c a r r i e d out at Coweeta by Johnson and Swank (1973). Calcium, magnesium, sodium, and potassium concentrations were monitored i n four watersheds, one of which contained undisturbed f o r e s t , and the other three of which had complex treatment h i s t o r i e s dating back to 1942. Because monitoring was begun almost t h i r t y years a f t e r the s t a r t of the various treatments, there i s no pretreatment data and the conclusions are based on the assumption stated above so that i t was considered that: "Comparison of r e s u l t s among the four catchments i s p r i m a r i l y a contrast i n management h i s t o r i e s . " (Johnson and Swank, 1973: p. 77). This statement i s f e l t to be i n c o r r e c t since the chemistry of the streams at Coweeta i s l i k e l y to be c o n t r o l l e d by bedrock and s o i l chemistry (Gibbs, 1970; Gorham, 1961) and even s l i g h t d i f f e r e n c e s i n geology between the four watersheds could cause s i g n i f i c a n t d i f f e r e n c e s i n streamwater c a t i o n concentrations. I t i s noteworthy that the s o i l s i n the four watersheds are r e s i d u a l and derived from a heterogeneous bedrock which i s b a s i c a l l y gneiss but includes g r a n i t e , d i o r i t e , mica gneiss and mica s c h i s t . Under such conditions d i f f e r e n c e s i n stream chemistry between the watersheds would seem i n e v i t a b l e . The chemistry of streams flowing through apparently s i m i l a r watersheds i n the C h i l l i w a c k v a l l e y area of B.C. over the same bedrock has been found to be quite d i f f e r e n t . Differences between streams 1 and 2 and between streams 3, 4, and 5 (Table 4.21) are obvious. S i m i l a r , but l e s s spectacular d i f f e r e n c e s have been found f o r streams at Haney. This f u r t h e r points out the weakness of the assumption that one stream w i l l e x h i b i t i d e n t i c a l chemical concentrations to another i f both have s i m i l a r bedrock and f o r e s t cover. The t h i r d study was c a r r i e d out by Brown et al. (1973) i n the Alsea Basin i n c o a s t a l Oregon. Streams were sampled p r i o r to logging and found to have quite d i f f e r e n t n i t r a t e concentrations, with the highest n i t r a t e concen-193 Table 4.21 Cation concentrations i n s i m i l a r streams i n the Chilliwack v a l l e y area. November 1972. Bedrock K Na Mg Ca cond. Stream < mg/1 > ymho/cm at 25°C G r a n i t i c (Mainly 1 .4 .6 .3 1.3 16 granodiorite 2 1.0 1.1 .9 3.8 39 Volcanics (Basic 3 .6 1.3 1.2 12 79 v o l c a n i c s , t u f f , 4 .2 1.2 1.9 13 124 and agglomerate) 5 .1 .6 1.3 10 93 Streams 1 and 2 are comparable i n s i z e , and were sampled within 15 minutes of each other. They flow p a r a l l e l to one another through undisturbed f o r -est, down the same h i l l s i d e , approximately 2 km apart, i n t o C h i lliwack Lake. Both t h e i r watersheds l i e within the same g e o l o g i c a l u n i t . Streams 3, 4, and 5 are also comparable i n size but smaller than 1 and 2. They were sampled within 20 minutes of each other and flow p a r a l l e l to one another, down the same h i l l s i d e , a l l within a distance of 2 km, i n t o Foley Creek. A l l three watersheds l i e within the same g e o l o g i c a l u n i t . t r a t i o n s occurring i n the watersheds with abundant Alnus rubra. C l e a r c u t t i n g was followed by slashburning so the study cannot d i f f e r e n t i a t e between the e f f e c t s of c l e a r c u t t i n g and those of slashburning. Data f o r only three chemi-c a l s - potassium, n i t r a t e , and phosphate - are reported. Of these, potassium concentrations increased i n i t i a l l y but soon declined to pretreatment l e v e l s ; n i t r a t e concentrations were increased s i g n i f i c a n t l y f o r the two years of post-treatment data, and phosphate concentrations remained low and unchanged. In the same study, a stream flowing from another watershed which was 25% c l e a r -cut i n three u n i t s , one of which was slashburned, showed no s i g n i f i c a n t changes i n chemical concentrations. The f o u r t h study was c a r r i e d out by Fredriksen (1971) i n the H.J. Andrews Experimental Forest, also i n c o a s t a l Oregon. I n t e r p r e t a t i o n of the r e s u l t s of t h i s study i s d i f f i c u l t f o r two reasons. F i r s t l y , there are no pretreatment chemical data f o r the streams, g i v i n g r i s e to the problems discussed above. Secondly, c l e a r c u t t i n g extended over a period of four years and proceeded se q u e n t i a l l y from the ridge tops and the head of the watershed down to the 194 stream channels (R.L. Fredriksen: personal communication). The s t r i p s of f o r -est which remained f o r some time between the c l e a r c u t and the stream are l i k e l y to have e f f e c t i v e l y removed any excess chemicals moving through the s o i l to the stream, thus reducing the magnitude of the changes i n stream chemistry. Thus, the g r e a t l y increased chemical concentrations following slashburning might be p a r t l y due to the f i n a l removal of the " n u t r i e n t - f i l t e r i n g " stream edge f o r e s t . Such a c u t t i n g sequence might have a d i f f e r e n t e f f e c t on stream chemistry than one which removes stream edge f o r e s t f i r s t . As the watershed has an area of 96 hectares, a one year c u t t i n g period would have been reasonable. The c l e a r c u t t i n g treatment appeared to increase chemical concentrations i n streamwater, p a r t i c u l a r l y magnesium, calcium, n i t r a t e , and bicarbonate con-centrations , but the greatest increase was observed following slashburning. N i t r a t e concentrations were s t i l l abnormally high s i x years a f t e r burning, although they appear to be gradually returning to pretreatment l e v e l s (Fred-r i k s e n et al., 1973). In the same study another watershed was 25% c l e a r c u t i n three u n i t s , each of which was slashburned. The only chemical data f o r t h i s watershed were t o t a l d i s s o l v e d s o l i d s concentrations which also increased a f t e r c u t t i n g and even more so a f t e r burning. Fredriksen et al. (1973) presented r e s u l t s of two other studies i n Oregon , which also found increases i n n i t r a t e concentrations following d i f f e r e n t t r e a t -ments - p a r t i a l (25%) c l e a r c u t t i n g and slashburning, shelterwood c u t t i n g , and complete c l e a r c u t t i n g . Invariably the increases were much l e s s than those found i n New Hampshire. The f i f t h major study was c a r r i e d out by Verry (1972) i n low r e l i e f aspen-black spruce bog watersheds i n Minnesota. Despite rather l i m i t e d pretreatment sampling (only three samples were c o l l e c t e d per year f o r three years), c l e a r -c u t t i n g the aspen, ^which constituted 80% of a watershed, appears to have caused no change i n stream chemistry. Verry considered that t h i s might be due to the following f a c t o r s : slow decay rates caused by a cool climate or 195 shading of the s o i l surface by vigorous regeneration; nutrient uptake by the vigorous regeneration; l i t t l e leaching from the s o i l due to low r e l i e f or high s o i l cation exchange capacities; or absorption of excess nutrients by the bog and i t s organisms. From these studies i t can be concluded only that clearcutting tends to increase concentrations and fluxes of chemicals i n some streams to varying degrees for varying periods of time. The variable response of different forest-watershed ecosystems to clearcutting suggests the need for monitoring programmes i n a wider variety of ecosystems and j u s t i f i e s the present study. Apart from work i n New Hampshire and Oregon, there i s l i t t l e quantitative data available for assessing nutrient losses from watersheds. Such data are also important in determining under what ecological conditions nutrient losses to streams w i l l be important and, hence, under what conditions special management practices would be required to avoid these losses. 3. Comparison with stream chemistry i n the Chilliwack valley The question arises as to how representative the streams at Haney are of streams i n coastal B.C. In order to obtain data for streams flowing through different types of ecosystems, a number of streams i n the Chilliwack valley area of southwestern B.C. were sampled occasionally during 1972 and 1973. The wide variety of vegetation types, soils, and bedrock i n the area permits samp-ling of a large variety of forest-watershed ecosystems. In general, the streams at Haney were chemically similar to Chilliwack streams flowing over granitic bedrock, but significantly less concentrated than Chilliwack streams flowing over other types of bedrock. In addition, many of the Chilliwack streams are fed by snow and their discharge patterns are dominated by snowmelt runoff with maximum streamflows i n midsummer and minimum flows in winter or early autumn. The el e c t r i c a l conductivity of such streams i s highest during the low flow winter period and lowest during the high flow summer period (J. Vickerson, Department of Geography, University of 196 B r i t i s h Columbia: Personal communication). The concentrations of most of the i n d i v i d u a l chemical constituents seem to behave i n a s i m i l a r way. Such behavi-our i s quite d i f f e r e n t to the streams at Haney where snowmelt runoff i s unim-portant. 4. C l e a r c u t t i n g and streamwater p o l l u t i o n The e f f e c t of c l e a r c u t t i n g on highly concentrated streamwater i s not c l e a r . The g e o l o g i c a l c o n t r i b u t i o n of chemicals to such streams i n the undisturbed state may be so great as to e f f e c t i v e l y mask any increments caused by logging. However, i f the chemical concentrations i n a stream are already very high then even s l i g h t increases may take the concentrations above recommended maximum l e v e l s f o r human use. En f a c t , some Chilliwack streams n a t u r a l l y have concen-t r a t i o n s of i r o n which are above permissible l e v e l s (Table 4.22). Thus, i n -creases induced by logging, which are modest r e l a t i v e to natural l e v e l s , are not n e c e s s a r i l y without s i g n i f i c a n c e . At Haney, c l e a r c u t t i n g has r a i s e d the l e v e l s of only manganese and i r o n above permissible l e v e l s . Permissible ammonia l e v e l s might also be exceeded wit h i n the next two years, but i t i s u n l i k e l y that permissible l e v e l s f o r any of the other common chemicals w i l l be exceeded. In the case of di s s o l v e d oxy-gen, however, the U.S. standards (National Technical Advisory Committee to the Secretary of the I n t e r i o r , 1972) state that the monthly mean concentration must be greater than or equal to 4 mg/1 with no i n d i v i d u a l sample l e s s than 3 mg/1. These standards were not met by stream D the f i r s t autumn following c l e a r c u t t i n g nor by stream E the second autumn following c l e a r c u t t i n g . I t i s l i k e l y that they w i l l not be met by stream A i n the f i r s t autumns following c l e a r c u t t i n g . Stream B i s l a r g e r and i s l i k e l y to continue to meet the standards. C r i t e r i a f o r i n d u s t r i a l use, such as the, two given i n Table 4.22 are often more s t r i n g e n t than those f o r human consumption, so that impairment of water q u a l i t y f o r such uses i s r e l a t i v e l y easy. C l e a r c u t t i n g at Haney has impaired the q u a l i t y of streamwater f o r a v a r i e t y 197 Table 4.22 Maximum measured concentrations of selected chemicals in stream-water and permissible limits for human consumption and other uses NH3 Fe Mn NO 3 + N ° 2 S 0 4 = < - mg/1itre- — > Recommended permissible limits 1. Human consumption a) B.C. Health Branch (1969) .6 .3 .05 45 500 b) U.S. (National Technical Advisory Committee to the Secretary of the Interior, 1972) .6 .3 .05 45 250 c) World Health Organization for Europe (Davis et a1.3 1971) - .1 .1 50 250 2. U.S. dairy industry (American trace .1- .1-Water Works Association, 1971) only .03 .03. 25 60 3. U.S. food canning and freezing industry (American Water Works Association, 1971) .5 .2 .2 12.4 — Chilliwack basin undisturbed watersheds (38)* .25** .95** .02 1.2 23.5 below clearcuts (12) .08 .22 .05 1.3 22 Haney undisturbed watersheds ( 6) .11 .11 .00 1.4 4.5 below clearcuts ( 4) .27 .25 .16*** 6.6 6 The number of streams sampled are given in parentheses. The Chilliwack streams were only sampled a maximum of three times. Although the highest iron and ammonia concentrations were found in undisturbed streams, these streams cannot be compared to those sampled below clearcuts due to the large differences in soils and bedrock geology between watersheds. For example, the stream with the highest iron concentration flows through an area known to be mineralized. Manganese concentrations in streams D and E at Haney remained continuously above B.C. and U.S. permissible limits for human consumption for several weeks in early autumn both years following clearcutting. 198 of uses, this impairment being most serious in late summer and early autumn and is probably unimportant for the rest of the year. Impairment i s l i k e l y to de-pend on the size of the stream and on the percentage of the watershed cut. Thus, i t i s l i k e l y to be more important for stream A than stream B. / Summary 1. The streams at Haney were characterized by high discharges from late au-tumn u n t i l early summer and low discharges from May un t i l October with almost no contribution from snowmelt runoff. Response to precipitation was f a i r l y rapid and stormflow probably arose mainly from flow of water through macro-channels in the s o i l with lesser contributions from surface runoff. Instan-taneous discharges of streams A, B, and C have varied from 0.2 to 250 1/sec., 0.7 to 1200 1/sec, and 0.2 to 550 1/sec. respectively. 2. Evapotranspiration was estimated to be about 85 cm per year from simple water balances and 65 cm per year by theoretical methods, suggesting some un-measured leakage of water from the watersheds, particularly watershed C. Slight increases in stream runoff have been found during the f i r s t dormant season following clearcutting. 3. Stream temperatures underwent annual cycles with winter minima close to 0°C and summer maxima around 17°C. Diurnal temperature fluctuations .were usually slight except on cloudless summer days,when the temperature changes could be up to several degrees. ^ 4. Few analyses have been made for suspended sediment but those which have been made, together with visual observations, indicated that suspended sedi-ment concentrations were usually negligible. Concentrations reached a maxi-mum during the rising stage of the streams in response to the f i r s t major storms in autumn after prolonged periods of low flows. Clearcutting may have caused increases in suspended sediment concentrations during the f i r s t major 199 storms following treatment but has subsequently had l i t t l e significant effect on these concentrations. 5. Dissolved oxygen concentrations in the streams were usually close to 100% saturation and underwent annual cycles with maximum values i n winter and minimum values in late summer and early autumn. Dissolved oxygen concentra-tions and degree of saturation tended to increase with increasing discharge and decreasing temperature. Slight diurnal fluctuations, with higher values during the day indicated that there was slight production of oxygen in the streams by photosynthetic processes. Clearcutting had l i t t l e effect on dissolved oxygen values during the cooler wetter months but caused very significant decreases during summer and early autumn. This was attributed to the biological and chemical oxygen de-mands of the decaying slash in the streams. 6. The major cation in Haney streamwater was calcium and the major anion was bicarbonate. The streams at Haney characteristically exhibited annual cycles of hydrogen ion (pH), sodium, magnesium, calcium, chloride, nitrate, dissolved s i l i c a , and bicarbonate concentrations and e l e c t r i c a l conductivity. With the exception of hydrogen ion and nitrate, maximum values of a l l these chemical parameters occurred during late summer and early autumn and minimum values occurred during winter and early spring. This was probably due to accumulation of weathering and decomposition products during dry and warm summer periods followed by the flushing of these products into streams during early autumn. Leaf f a l l i n autumn may also have contributed chemicals to streams. Hydrogen ion and nitrate concentrations exhibited the opposite behaviour with maximum values in winter and minimum values in summer. Hydrogen ion be-haviour was explained by greater contributions of the relatively acidic through-f a l l and s o i l water to streams during winter. Nitrate behaviour was probably a response to biological activity. Relatively high biological activity during 200 the warmer months meant significant nitrogen uptake, but l i t t l e activity during the colder months meant less uptake and greater amounts of nitrogen available for flushing into streams. Potassium and sulphate concentrations were relatively uniformly dis-tributed throughout the year although they tended to be higher in late sum-mer and early autumn. Iron, manganese, aluminium, ammonium, and phosphate concentrations were very low and usually undetectable although, after clearcutting, iron and man-ganese concentrations rose above the detection limits i n summer peaking during early autumn then dropping below the detection limits again later i n autumn. 7. There was l i t t l e diurnal variation of chemical concentrations but much greater variation with discharge. Sodium, calcium, magnesium, dissolved s i l i c a , and bicarbonate concentrations, pH, and el e c t r i c a l conductivity de-creased with increasing discharge whereas potassium concentrations exhibited some increases and some decreases. Chloride, nitrate, and sulphate concentra-tions were not significantly related to discharge although nitrate and sulphate concentrations increased with discharge during a storm event. The other chemicals were present in such low concentrations as to render any relationship meaningless. 8. Differences in chemical concentrations between streams A, B, and C were attributed mainly to geological factors - chemical and mineralogical d i f f e r -ences in bedrock and differences in mineral weathering rates between the water-sheds. Biological factors involving differences in maturity of the different forest ecosystems, were considered less important. 9. So far, the effects of clearcutting on stream chemistry have been studied for only the f i r s t dormant season following treatment. The most significant effects on stream chemistry are expected during the f i r s t several late summer-early autumn periods following clearcutting for two reasons: a) Maximum release and accumulation of chemicals from the decomposing slash and weathered minerals w i l l occur during the dry, warm periods i n the f i r s t summers following clear-cutting; b) Maximum carbon dioxide production w i l l accompany maximum biological 201 a c t i v i t y during the summer. Thus, water moving through the system as a result of the f i r s t autumn rains w i l l have maximum carbonic acid concentrations, and hence maximum leaching potential. 10. Clearcutting has significantly affected potassium, iron, calcium, and dissolved oxygen concentrations, and probably also manganese concentrations in streamwater at Haney, with potassium, iron, calcium, and manganese concentra-tions increasing, and dissolved oxygen concentrations decreasing. Slight i n -creases in magnesium, nitrate, sulphate, and chloride concentrations have also been observed, the changes being most noticeable in streams D and E during the low flow periods of late summer and early autumn. Slight decreases in bicar-bonate concentrations and pH also occurred. There have been no obvious effects on sodium, aluminium, ammonium, dissolved s i l i c a , and phosphate concentrations. 11. The increases i n iron and manganese concentrations have impaired the quality of the streamwater for certain uses but this impairment was only im-portant in late summer and early autumn. 12. Other streams in coastal B.C. which are expected to react, chemically, to clearcutting in a fashion similar to those at Haney would be those which have the following features: a) Watersheds underlain by granitic bedrock similar to that at Haney. b) Watersheds which have similar h i l l y topography and shallow soils con-taining an abundance of macrochannels. c) Watersheds at low elevations where snowmelt runoff i s not important. 13. A literature review on the effects of clearcutting on stream chemistry indicated that a variety of results have been found i n the few studies carried out to date. More such studies are considered necessary to determine under what ecological conditions chemical losses to streams w i l l be important. 14. Calculation of nutrient budgets indicated that there was a general net loss of calcium, sodium, magnesium, potassium, and sulphur from the watersheds. Nitrogen was accumulated by the watersheds whereas phosphorus was neither 202 gained nor lost. The chloride balance changed from year to year with net loss-es one year and net gains the next. Maximum estimated errors in budget calculations ranged from 53 to 191% and were mainly due to water volume estimations. Sulphur and nitrogen budgets were regarded as the least reliable. With increasing precipitation, chemical outputs increased relative to i n -puts so that net losses were greater in winter than in summer and greater in a wet year than in a dry year. Potassium exhibited less consistent behaviour than the other chemicals. This was attributed to i t s different mineralogical and biological role. S t a t i s t i c a l l y significant relationships were found for a l l major chemi-cals between output load and volume of water discharged and, to a lesser ex-tent, between input load and volume of precipitation, on a monthly basis. Logarithmic regression equations between loads and water volumes were found to be invariably more accurate than linear relationships. Annual chemical budgets at Haney were consistent with the results of other studies. The much greater net losses observed at nearby Jamieson Ck. in Sey-mour watershed were attributed to: 1. Greater inputs at Haney due to a i r pollu-tion; 2. Greater biomass and nutrient accumulation at Haney; 3. Greater flows of water through the Seymour watershed. Clearcutting has significantly increased potassium losses and decreased nitrogen gains in watershed A, and significantly increased potassium, sodium, magnesium, and chloride losses in watershed (B+C). Having examined the chemical behaviour of the streams, and how this be-haviour was affected by clearcutting, the next step was to examine the chemi-cal behaviour of solutions elsewhere in the forest-watershed ecosystem and to try to determine how this affected streamwater chemistry. This is done in the following chapter. 203 CHAPTER '5: SOLUTION CHEMISTRY OF THE ENTIRE FOREST WATERSHED ECOSYSTEM In this part of the study, the chemistry of water at different stages in i t s passage through a forest was monitored, with the overall aim of relating this to streamwater chemistry. I n i t i a l l y i t was hoped to concentrate on s o i l solutions but i t became apparent that interpretation of the chemistry of surface runoff and s o i l solutions required a knowledge of the chemistry of water arriving at the forest floor. Consequently, throughfall was collected, but commencing at a later date than the other solutions. Only two months of pre-clearcutting throughfall data i s available. Samples were collected of the following stages: 1. Precipitation above the forest. 2. Throughfall, beneath the forest and beneath slash. 3. Surface runoff. 4. Forest floor leachate. 5. Mineral s o i l leachate, near the bottom of the rooting zone. 6. Groundwater. 7. Streamwater. Stages 2 to 6 were sampled in or near s o i l p i t s . These s o i l pits were located in different biogeocoenoses with the aim of comparing the solution chemistry of different biogeocoenoses. However, data from the few replicate pits indicated that differences within a biogeocoenosis were as great as differences between biogeocoenoses. Standard deviations were used to indicate the v a r i a b i l i t y in the concentration measurements. For a particular type of solution (e.g. surface runoff) for a particular chemical (e.g. chloride), the means in Tables 5.1 and 5.2 (e.g. 1.88 and 1.62 for the subhygric Polystichum biogeocoenosis) are often similar, as are the respective standard deviations (e.g. .63 and .80). This indicates that the v a r i a b i l i t y i n chemical concentration measurements within one biogeocoenosis (Table 5.2) is often as great, or even greater, than the v a r i a b i l i t y in the measurements when data from a l l the biogeocoenoses are considered together (Table 5.1). I t i s f e l t that there were too few s o i l pits to permit any meaningful comparison between biogeocoenoses. 204 Table 5.1: Means and standard deviations of chemical parameters obtained from analysis of a single collection of samples collected on two dates, one before and one after clearcutting. No. of Collectors K N a M * C * C 1 »2 r o 4 Precipitation 25/4/73 (4) .08 (.03) .48 (.01) .08 (.01) .4 (.1) .70 (.14) 0 5/3/74 (4) .08 (.01) .25 (.02) .04 (.01) .3 (.1) .41 (.03) 0 Throughfall 15/3/73 (38) .46 (.43) .52 (.17) .14 (.08) .6 (.3) .88 (.36) .04 (.06) 5/3/74 (13) .35 (.44) .21 (.02) .13 1.13) .6 (1.0) .45 (.04) .05 (.08) Surface runoff - watershed B 10/5/73 (7) .84 (.37) .58 (.09) .40 (.13) 1.9 (.9) 1.88 (.63) .07 (.12) 26/3/74 (6) .60 (.59) .20 (.08) .12 (.06) .6 (.3) .76 (.48) .10 (.10) - control 10/5/73 (2) 1.66 (1.27) .95 (.47) .76 (.54) 3.1 (.9) 3.47 (2.58) .30 (.13) 26/3/74 (2) .12 (.11) .27 (.13) .10 (.06) .6 (.1) .75 (.35) .01 (.02) Forest floor leachate - watershed B 10/5/73 (8) 1.30 (.85) .89 (.32) 1.S2 (.93) 2.5 (1.7) 2.93 (1.60) .06 (.09) 26/3/74 (8) .62 (.37) .25 (.OS) .27 (.19) .7 (.5) .90 (.36) .04 (.03) - control 10/5/73 (2) 1.24 (.08) 1.39 (.55) 3.18 (1.75) 3.9 (1.9) 2.75 (.28) .35 (.50) 26/3/74 (2). .28 (.05) .40 (.25) .66 (.10) 1.0 (.1) 1.10 (.42) .18 (.23) Mineral so i l leachate - watershed B 10/5/73 (5) .38 (.36) .80 (.30) .48 (.29) .9 (.9) 1.18 (.66) 0 26/3/74 (5) .51 (.35) .53 (.26) .18 (.09) .6 (.2) .52 (.10) 0 - control 10/5/73 (2) .18 (.07) .77 (.32) .61 (.01) 2.4 (2.0) 1.97 (1.66) 0 26/3/74 (2) .16 (.12) .62 (.46) .32 (.10) 2.0 (1.4) 1.37 (1.17) 0 No. of Collectors SiO, Cond. pH Precipitation 25/4/73 5/3/74 (4) (4) .71 (.15) .85 (.06) .02 .11 (.02) (.02) .3 0 (.5) .2 ( 0 ) 0 .4 .5 (.4) (.4) 16.1 10.5 (1.2) (1.2) 4.6 4.7 (.1) (.1) Throughfall 15/3/73 5/3/74 «8) (13) .56 (.25) .13 (.17) .03 0 (.02) 3.8 1.0 J2.0) (.4) 0 0 .2 4.5 (.4) (4.9) 27.6 10.4 (12.8) (6.6) 4.4 5.8 (.2) (.6) Surface runoff - watershed B 10/5/73 26/3/74 (7) ,21 (.27) (6) .01 (.02) - control .09 .10 (.08) (.13) 2.4 (1.4) 1.0 .3 (.6) (.6) 1.0 1.2 (.8) (1.0) 32.8 13.7 (7.7) (7.9) 4.7 4.9 (.2) (.4) 10/5/73 26/3/74 (2) <2> .20 (.28) .04 (.06) .02 0 (.03) 2.0 (.7) .8 (.4) 0 .5 0 (.7) 61.7 16.1 (35.2) (7.2) 4.3 4.6 (.3) (.2) Forest floor leachate - watershed B 10/5/73 26/3/74 (8) (8) .10 (.19) .01 (.03) - control .05 (.09) 0 2.8 (1.2) 4.0 .9 (1.7) (.7) 6.0 3.1 (6.1) (3.0) 46.5 1S.1 (21.2) (5.8) 5.5(1.0) 5.3 (.7) 10/5/73 26/3/74 (2) (2) .04 (.06) .02 (.03) .03 0 (.04) 3.3 (.4) 6.5 .3 (1.5) (.1) IS.6(10.0) 4.0 (1.9) 56.6 17.9 (23.6) (5.4) 6.6 S.6 (.6) (.4) Mineral s o i l leachate - watershed B 10/5/73 26/3/74 (5) (5) .10 (.22) .40 (.57) - control .02 0 (.04) 3.1 (1.4) 3.7 2.8 (1.4) (.7) 3.9 2.7 (1.0) (1.4) 19.1 15.3 (11.8) (4.9) 6.1 5.6 (.2) (.6) 10/5/73 26/3/74 (2) (2) 0 0 0 0 3.3 (3.2) 4.1 2.5 (2.0) (1.6) 6.S 5.7 X.6) (2.2) 31.0 24.0 (18.2) (17.5) 6.4 6.3 (0 ) (.1) Concentrations are in mg/litre. Electrical conductivity ia in micromho/cm at 25°C. Standard deviations are given in parentheses. 205 Table 5,2i Means and standard deviations of chemical parameters obtained from analysis of one collection of samples from the same biogeocoenosis. 1) Subhygric Polystichum biogeocoenosis * (4 soil pits - numbers 1, 9, 18 and 19). NO. of Collectors K Na Mg Ca Cl H2P04 N03 Throughfall (8) .61 (.26) .77 (.23) .23 (.08) 1.0 (.5) 1.57 (.69) .09 (.15) 1.44 (.38) Surface runoff (4) .92 (.20) .57 (.12) .38 (.19) 2.2(1.3) 1.62 (.80) .22 (.08) .34 (.23) Forest floor leachate (4) 1.09 (.27) .93 (.23) 2.01 (.75) 2.5 (.9) 2.55 (.45) .04 (.07) 0 Mineral soil leachate (4) .21 (.00) .63 (.10) .59 (.34) .8 (.6) .86 (.27) 0 .07 (.04) 2) Lithic Gaultheria biogeocoenosis (3 s o i l pits - numbers 13, 14 and 15). Throughfall (6) .58 (.16) .72 (.08) .24 (.05) 1.0 (.2) 1.39 (.21) 0 1.84 (.31) Surface runoff (3) .70 (.47) .58 (.07) .41 (.09) 2.0 (.8) 2.05 (.56) 0 .22 (.38) Forest floor leachate (3) 1.07 (.58) .85 (.07) 1.12 (.82) 1.6 (.7) 2.50 (.54) .06 (.10) 0 1) Subhygric Polystichum biogeocoenosis * (4 soi l pits - numbers 1, 9, 18 and 19). No. of Collectors NH. 4 Si0 2 H2C03 Cond. pH Throughfall (8) .03 (.02) .1 (.1) 0 38.4 (9.1) 4.3 (.1) Surface runoff (4) .11 (.11) .9 (.3) 1.1 (1.0) 32.0 (12.6) 4.8 (.3) Forest floor leachate (4) 0 5.0 (1.5) 9.9 (6.6) 43.5 (4.4) 6.1 (1.0) Mineral soil leachate (4) 0 3.4 (.7) 7.2 (4.2) 18.1 (6.9) 6.5 (.3) 2) Lithic Gaultheria biogeocoenosis (3 soil pits - numbers 13, 14 and 15). Throughfall (6) .03 (.03) .1 (.1) 0 39.4 (2.2) 4.3 (.1) Surface runoff (3) .03 (.02) 1.1 (.8) .5 (.5) 35.4 (3.2) 4.6 (.2) Forest floor leachate (3) .01 (.01) 3.0 (1.6) 3.5 (4.2) 40.3 (2.1) 5.1 (.9) Concentrations are in mg/litre. Electrical conductivity is in microraho/cm at 25°C. A l l samples vere collected on 10th Hay, 1973, Standard deviations are given in parentheses. * Names of biogeocoenoses are from Klinka (Graduate student, Faculty of Forestry, University of B. C , Personal Communication). 206 For this chapter, the data have been treated in the following way: 1. Precipitation - There were no consistent, but rather, random di f f e r -ences between the four collectors. A l l measurements have been averaged on a monthly basis. 2. Throughfall - Measurements have been averaged for each collection. 3. Surface runoff, forest floor leachate, and mineral s o i l leachate -Measurements for each have been averaged for each collection. 4. Groundwater - This was collected from two s o i l p i t s . As these pits are i n quite different ecological situations, data from them are considered separately. Data on the effects of clearcutting are confined to watershed B because lysimeters and surface runoff collectors could not be reinstalled in watershed A u n t i l late February, 1974, just two months before this study terminated. 1. pH, Variation through the ecosystem Precipitation at Haney usually had a pH of about 4.5. Passage through the forest canopy lowered this s l i g h t l y , to about 4.4. This increased i n surface runoff and forest floor leachate waters, and even more so in mineral s o i l leach-ates. Maximum pH values were always measured i n streamwater (Table 5.3). This i s very similar behavior to that found by Mayer (1971) for a beech forest ecosystem i n Germany. Cleaves et al, (1970), studying a forested water-shed i n Maryland, found the pH of the A horizon leachate to be about the same as that of precipitation. They observed an increase i n pH i n groundwater and a further increase in streamwater. Windsor (1969), working at Cedar River in western Washington, observed an increase in pH from throughfall to forest floor leachate. The solution pH remained constant for the f i r s t 5 cm of mineral s o i l but then increased with increasing depth i n the s o i l . Thus, the observations at Haney are consistent with the results of these other studies. 207 Table 5.3: Average pH values of waters in an undisturbed forest ecosystem at Haney - watershed B. pH PERIOD OF SAMPLING Precipitation 4.5 (.2) AUG 1, 1972 - AUG 1, 1973 Throughfall 4.4 (.1) APR 1, 1973 - APR 1, 1974 Surface runoff 4.8 (.5) AUG 1, 1972 - AUG 1, 1973 Forest floor leachate 5.4 (.9) AUG 1, 1972 - AUG 1, 1973 Mineral s o i l leachate 6.2 (.4) AUG 1, 1972 - AUG 1, 1973 Groundwater (pit 17 (pit 12 6.0 6.3 (.5) (.2) SEP If 1972 - AUG 1, 1973 Streamwater (stream B) 6.8 (.2) JUN 1, 1972 - JUN 1, 1973 (Standard deviations are given in parentheses.) The pH of lysimeter leachates was found to generally be greater than that of the s o i l . This has been observed elsewhere (Shilova and Korovkina, 1961; Windsor, 1969) and has been attributed by Windsor (1969) to "uptake of bases into solution" from the s o i l . This should be more correctly stated as being due to replacement of hydrogen ions in solution by metallic cations from the s o i l exchange complex. Adsorption of organic acids into s o i l particles or weathering of s i l i c a t e minerals, which uses up hydrogen ions (Hem, 1970), may also account for the higher pH of the solution. Seasonal variation The pH of precipitation and throughfall was relatively constant with l i t t l e significant variation, although values tended to be slightly higher during sum-mer (Figure 5.1). The pH of precipitation was closer to that of the University of B. C. campus than to that of Seymour watershed (Zeman, 1973). This suggests that the precipitation at Haney i s influenced by industrial a i r pollution which i s expected since there i s much industrial activity west of Haney, in the direc-tion of the prevailing winds. There i s much less industrial activity upwind of Seymour. H<< -uiu- aiaarea h* - n nd - t a i u o i m g I I *« ' I liH I OLU 1 u r .: 1 1 1 1 r r 1 1 1 j r 1 1 1 1 1 r r • 1 1 j r o • 1 s 1 r r 1 1 i i r 1 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I j I I I I I 1 1 | 1 1 1 1 g 8 CTHSlGitM - SWJimOS W1SIM3J JO *• 803 209 Seasonal trends i n the pH of surface runoff were not completely clear. However, the values tended to be higher i n late winter and lower in autumn and spring (Figure 5.1). The pH of forest floor leachate displayed no clear sea-sonal trends (Figure 5.1) although McColl (1972) found the pH of forest floor leachates at Cedar River to undergo similar seasonal fluctuations to those described above for surface runoff. The pH of mineral s o i l leachate tended to be lowest i n late winter and early spring and highest in summer and autumn (Figure 5.1). This trend was more pronounced i n groundwater and was identical to that for streamwater, with maximum values i n late summer and minimum values in winter (Figure 5.1). During the warmer months increased biological activity produces carbon dioxide which dissolves i n water,yielding an acidic solution. On this basis solution pH should be lower in summer and higher i n winter which appears to be the case for water near the s o i l surface. The large fluctuations observed may be related to climate with warmer periods allowing increased biological activity and colder periods restricting such activity. The pH of water flowing through the s o i l as a result of heavy rains i s l i k e l y to be different to that resulting from light rains, being closer to the value for the rain i t s e l f . In this re-spect, McColl (1972) has recorded decreases i n the pH of a mineral s o i l A horizon leachate with increases in the rate of flow of water through the s o i l . This illustrates the tendency of the pH of the s o i l solution to approximate that of water higher up the s o i l pedon as increased amounts of water pass through the system. I t appears that the effects of water quantity, aided by loss of hydrogen ions from solution to the s o i l exchange complex, could overcome those of bio-logical activity lower i n the s o i l pedon explaining the seasonal trends i n pH of mineral s o i l leachate, groundwater, and ultimately streamwater. 210 E f f e c t s of c l e a r c u t t i n g C l e a r c u t t i n g has caused an increase i n the pH of water reaching the s o i l surface as t h r o u g h f a l l and water near the s o i l surface, but s l i g h t decreases i n mineral s o i l leachate and streamwater (Table 5.4) . The most s i g n i f i c a n t e f f e c t has been on t h r o u g h f a l l pH were the s u b s t i t u t i o n of slash f o r l i v i n g trees has caused a considerable increase i n pH. These e f f e c t s of c l e a r c u t t i n g w i l l be discussed i n more d e t a i l below, under "cations". Table 5.4: Average pH values of ecosystem waters before and a f t e r c l e a r c u t t i n g watershed B. 1. P r e c i p i t a t i o n Mineral s o i l leachate before 4.6 (.1) before 6.1 (.4) a f t e r 4.7 (.1) a f t e r 5.7 (.5) 2. Throughfall a f t e r 5.6 (.1) c o n t r o l - before - a f t e r 6.2 6.3 (.6) (.1) c o n t r o l - a f t e r 4.6 (.1) 6. Groundwater 3. Surface runoff before 5.0 (.6) ( p i t 17) before a f t e r 5.9 5. 5 (.6) (.1) a f t e r 5.1 (.5) ( p i t 12) before 6.3 (.2) c o n t r o l - before 4.5 (.2) a f t e r 6.1 (.2) a f t e r 4.5 (.3) 7. Streamwater (B) 4. Forest f l o o r leachate before 6.7 (.2) before 5.2 (.8) a f t e r 6.4 (.1) a f t e r 5.4 (.7) c o n t r o l - before 6.6 (.1) c o n t r o l - before* 6.5 (.1) - a f t e r 6.5 (.1) - a f t e r 5.5 (.5) Values are f o r the periods -November 1, 1972 - A p r i l 1, 1973 before c l e a r c u t t i n g , and November 1, 1973 - A p r i l 1, 1974 a f t e r c l e a r c u t t i n g . Standard deviations are given i n parentheses. *This i s an average of two samples only, and i s u n r e l i a b l e . 2. E l e c t r i c a l c o n d u c t i v i t y  V a r i a t i o n through the ecosystem The e l e c t r i c a l c o n d u c t i v i t y of p r e c i p i t a t i o n was u s u a l l y rather low. I t increased g r e a t l y a f t e r the s o l u t i o n passed through the f o r e s t canopy, due to leaching of ions from the vegetation. There was l i t t l e change from t h r o u g h f a l l to surface runoff but, after passing through the forest floor, s t i l l more ions have been added to the solution raising the e l e c t r i c a l conductivity further. A steady decline then occurred as the solution moved down through the mineral s o i l to groundwater, caused by loss of ions to the s o i l exchange complex. Groundwater had a similar e l e c t r i c a l conductivity to precipitation. The elec-t r i c a l conductivity of streamwater was higher than that of groundwater probably due to inputs of concentrated throughfall and surface runoff, as well as to leaching of ions from organic material by the streamwater. These changes are indicated in Table 5.5. Table 5.5: Average e l e c t r i c a l conductivities of waters in an undisturbed forest ecosystem at Haney - watershed B. Pre cipitation 17.0 (5.6) Throughfall 36.0 (16.5) Surface runoff 34.8 (29.0) Forest floor leachate 50.2 (34.9) Mineral s o i l leachate 27.8 (19.4) Groundwater - p i t 17 15.2 (7.3) - p i t 12 18.5 (2.0) Streamwater (B) 20.0 (3.1) Values are i n microho/cm at 25°C. Standard deviations are given in parentheses. Values are for the same time periods given i n Table 5.3. Very few comparable studies have been reported. However, the elect r i c a l conductivity of forest floor leachate has been found to exceed that of precipi-tation at Cedar River (Grier and Cole, 1972). Seasonal variation The el e c t r i c a l conductivities of precipitation, throughfall, surface run-off, and s o i l solutions a l l exhibited the same seasonal trends as streamwater, 212 tiqytf 1.1 * . CLECTRICflL CWOUCIIVITT OF CCCSrSTOl SOLUTION5 - VRTCRSCD 8 precipitation a. -throughfall »- —aurfaea runoff ....... foraat flour laachata » . - . ^ Blnaral sail lcachae* — i t ruwtUr i i i 11 i i i i i i i i i i r i i i i i i i i i i i i i i i i i i I J r i i i J J a i i • i j r i t * J J i i i i • j r i • i j j • i i i i J r i i 1 , 7 4 I I M71 I I1T3 | M1» h. aUactrlcaJ. conductivity of orounduatar OBUWMITW - PIT 12 - ELECTRICAL CSNOUCTIVITT H 1 1—I 1 r-t a • a K M H 1 h • 1.71 o J f n a aowowira - PIT n - aecniica. c o a c r i v i i t 213 with maximum values in early autumn and minimum values in late winter (Figure 5.2). This seasonal behavior reflects an accumulation of decomposition and weathering products during the summer followed by a flushing of these products through the system by the autumn rains. Throughout autumn and winter, the solutions became progressively more dilute as fewer and fewer ions were l e f t behind to be leached away. With the onset of warmer weather in spring, and the resulting increase i n biological and geological activity, the amount of ions in -the solution began to increase again. Identical seasonal behavior i n s o i l solutions has been observed at Cedar River in western Washington (Grier and Cole, 1972; McColl, 1972; 1973 b). There, the most important factors i n determining the amount of ions moving in solution through the s o i l were: a i r temperature, the length of the drying period between storm fronts, and the quantity of precipitation f a l l i n g . Higher elec-t r i c a l conductivities of s o i l solutions were expected for increased air tempera-tures and drying periods, and smaller quantities of precipitation. Changes in these three parameters can explain minor fluctuations i n concentrations and elect r i c a l conductivities. Effects of clearcutting Precipitation following clearcutting has had a lower elec t r i c a l conducti-vity than that before clearcutting but throughfall e l e c t r i c a l conductivity has been significantly lowered by clearcutting, so that i t i s only slightly higher than that of precipitation i t s e l f (Table 5.6). During the dormant season, precipitation apparently leached more ions from l i v i n g vegetation than from dead vegetation. During the growing season when the dead vegetation i s decaying precipitation may leach more ions from this vegetation than from l i v i n g vegeta-tion. However, this has not yet been determined. Surface runoff and forest floor leachates also exhibited significantly decreased elec t r i c a l conductivities after clearcutting (Table 5.6). This sug-gests that the high elec t r i c a l conductivity of surface runoff in the undisturbed 214 Table 5.6: Average el e c t r i c a l conductivities of ecosystem waters before and after clearcutting — watershed B. 1. Precipitation 5. Mineral s o i l leachate before 16.0 (5.0) before 20.5 (11.0) after 10.7 (1.8) after 19.6 (8.6) control - before 31.7 (18.3) Throughfall - after 34.0 (24.8) after 11.0 (3.2) control - after 22.3 (3.8) 6. Groundwater (pit 17) before 15.8 (8.8) Surface runoff after 20.1 (4.0) before 28.2 (25.2) after 15.2 (11.7) (pit 12) before 17.9 (2.2) control - before 31.8 (15.0) after 18.6 (5.3) - after 44.7 (83.7) 7. Streamwater (B) Forest floor leachate ^ before 17.9 (1.9) before 35.3 (16.1) after 16.2 (2.3) after 18.9 (8.3) control(C)-before 18.1 (2.2) control - before 43.7 (12.2) -after 15.8 (2.6) - after 33.0 (24.5) Values are in micromho/cm at 25° C. Standard deviations are given in parentheses. A l l values are for the same time periods given i n Table 5.4. forest i s primarily due to leaching of ions from the above-ground vegetation. The situation i n the forest floor i s more complicated and i s discussed below. The e l e c t r i c a l conductivities of surface runoff from some of the collec-tors have been consistently lower than that of precipitation following clear-cutting. These collectors were collecting from areas characterized by heavily disturbed s o i l surfaces with much exposure of mineral s o i l . I t thus appears that the precipitation water lost ions to particles at the s o i l surface, probably by adsorption reactions, before being collected as surface runoff. Three of the seven surface runoff collectors i n watershed B behaved i n this fashion and made significant contributions to the lowered conductivity. Following clearcutting there has been very l i t t l e change i n the el e c t r i c a l conductivity of the s o i l solution as i t passed through the mineral s o i l . If anything, there has been a slight decrease relative to the control (Table 5.6). 215 The relatively large increases at the groundwater level (Table 5.6) might be attributed to the influence of macrochannels which would conduct more concentrated solutions from near the s o i l surface. Disturbances of the s o i l surface by logging operations may have opened up more macrochannels allowing greater amounts of concentrated solution to travel more quickly to the groundwater level than occurred in the undisturbed forest. Another possible explanation - that of contamination of groundwater by logging operations - i s unlikely because s o i l pit.17, from which groundwater was sampled, has remained continuously covered and was not disturbed at a l l by the logging. The other s o i l p i t from which groundwater was collected was f i l l e d with slash after logging. Although i t was subsequently cleaned and washed out, the possib i l i t y of contamination cannot be completely excluded. The elect r i c a l conductivity of streamwater has increased only s l i g h t l y , as discussed in Chapter 4. 3. Cations Variation through the ecosystem The concentrations of a l l cations i n precipitation were quite low and were usually lower than streamwater concentrations (Table 5.7) . However, potassium concentrations were occasionally higher in precipitation. Compared to precipitation at Seymour (Zeman, 1973), sodium, calcium and magnesium concentra-tions were similar whereas potassium and ammonium concentrations were higher at Haney. After passing through the forest canopy, the concentrations of most cations in solution were increased, particularly potassium and manganese. Concentra-tions in surface runoff were similar to those in throughfall, except for calcium which was increased again (Table 5.7). Increases in a l l cations, except ammonium, were found after the water.had passed through the forest floor (Table 5.7). I t i s at this stage that maximum concentrations were usually found. Then, a l l cation concentrations decreased as Table 5.7: Average cation concentrations of waters in an undisturbed forest ecosystem at Haney -watershed B. K Na Mg Ca Fe Mn Al NH ;4 Precipitation .06 (.06) .30 (.16) .06 (.02) .2 (.1) 0 0 0 .09 (.13) Throughfall 1.11 (.90) .64 (.25) .30 (.31) 1.0 (.8) .01 (.01) .19 (.18) 0 .03 (.03) Surface runo ff 1.21 (1.55) .56 (.33) .39 (.43) 1.8 (1.9) .02 (.03) .17 (.21) 0 .26 (.59) Forest floor leachate 1.65 (1.62) 1.04 (.65) 1.82 (1.85) 2,9 (2.1) .39 (.34) .26 (.75) .6 (.7) .05 (.12) Mineral s o i l leachate .35 (.37) .84 (.37) .65 (.46) 1.8 (1.8) .01 (.02) .01 (.03) 0 .05 (.12) Groundwater • - p i t 17 .05 (.03) .79 (.23) .16 (.02) 1.2 (1.2) .01 (.02) 0 0 .01 (.02) - p i t 12 .09 (.07) .87 (.27) .25 (.04) 1.3 (.2) 0 .01 (.02) 0 .02 (.03) Streamwater (B) .09 (.02) 1.02 (.30) .31 (.06) 1.5 (.4) 0 0 0 .02 (.02) Values are in mg/litre. Standard deviations are given in parenthesis. Values are for the same time periods given in Table 5.3. 217 the water moved through the mineral s o i l to the groundwater stage (Table 5.7). Sodium decreases were relatively less than the others which may be due to greater weathering inputs of sodium relative to the other cations, or to the low a b i l i t y of sodium to replace ions on the s o i l exchange complex. The general decrease in cations in solution i s probably due to adsorption of ions by the • s o i l exchange complex. While there was l i t t l e change i n the concentrations of the four minor cations, the concentrations of the four major cations increased again in stream-water. This i s consistent with the similar increase i n elec t r i c a l conductivity and i s probably due to the same reasons as for conductivity, discussed above. The chemical behavior of water flowing through a beech forest - acid braunerde s o i l ecosystem in Germany i s similar to that at Haney (Mayer, 1971). Data extracted from Mayer's paper show a build up of cations i n throughfall followed by a decrease i n potassium, calcium, and iron concentrations as water moves down the s o i l profile (Table 5.8). Sodium, magnesium, aluminium, and iron concentrations apparently increase as the water moves down through the mineral s o i l , but no explanation for this behavior was given. Table 5.8: Ratios of cation concentrations in water at different levels i n a forest ecosystem i n Germany. Na K Ca Mg Al Fe Mn Precipitation 1 1 1 1 1 1 1 Throughfall 3.9 46.2 5.9 4.8 1.3 3.2 49.5 Forest floor leachate 2.1 24.1 3.5 3.0 2.5 2.7 32.4 Mineral s o i l leachate - 50 cm depth 2.6 3.3 3.3 3.2 7.1 .2 52.4 - 100 cm depth 3.6 2.4 3.4 4.0 10.1 .2 58 Calculated from data i n Mayer (1971) by dividing amounts of ions collected (in kg/ha) by the relative amount of water collected at each stage. 218 Bourgeois and Lavkulich (1972 a) collected leachates from the mineral horizons of two soils at Haney which are also present i n the study area. They found decreases in cation (sodium, potassium, calcium, magnesium) concentrations with depth although sodium concentrations sometimes increased (Bourgeois, 1969). Cleaves et al. (1970) measured chemical concentrations of precipitation, A horizon leachate, groundwater, and streamwater in Maryland. Sodium concentra-tions increased steadily through the system. Potassium and magnesium concentra-tions were highest in the A horizon leachate and lower i n the groundwater than i n streamwater. Calcium concentrations were highest in streamwater, followed by the A horizon leachate. A study of lysimeter leachates from various depths in fine textured podzols in Russia (Shilova and Korovkina, 1961) found a decrease i n calcium concentra-tions with depth, but increases in magnesium and sodium + potassium concentra-tions. From data presented in the paper, i t can be seen that groundwater had higher calcium concentrations than mineral s o i l leachates, but comparable mag-nesium and sodium + potassium concentrations. These results are consistent with the presence of macrochannels but they are also consistent with local d i f f e r -ences i n s o i l mineralogy. At Cedar River, a lysimeter study found potassium and calcium concentra-tions to decrease with depth i n the s o i l while magnesium concentrations increased (Cole, 1963; Cole et al., 1961). Another lysimeter study at Cedar River, of a clearcut area, found a steady decrease i n potassium concentrations with depth but decreases i n calcium, magnesium, and sodium concentrations from the forest floor to the A horizon, followed by increases i n the C horizon (Grier, 1972). In the same area, iron and aluminium concentrations tended to be highest in forest floor leachates, and decreased with depth in the surface 3 cm of mineral s o i l although there were some fluctuations depending on the time of measurement and the form of the element measured (Windsor, 1969). 219 At Hubbard Brook, cation concentrations are higher i n t h r o u g h f a l l than i n p r e c i p i t a t i o n (Eaton et al., 1973) and calcium concentrations appear s l i g h t l y higher i n t h r o u g h f a l l than i n streamwater (Eaton et a l . , 1973; Pierce et al., 1972). A study o f the chemistry of p r e c i p i t a t i o n , t h r o u g h f a l l , surface runoff, mineral s o i l s o l u t i o n , and streamwater i n Japan found cation concentrations to increase through the system to maxima i n s o i l s o lutions then decline i n stream-water although streamwater concentrations were higher than p r e c i p i t a t i o n con-centrations (Iwatsubo and Tsutsumi, 1968). Gorham (1961) presented the r e s u l t s of studies which showed that lysimeter leachates were more concentrated than groundwater and exhibited d i f f e r e n t propor-t i o n s of ions present. Thus, the l i t e r a t u r e i n d i c a t e s that there are g r e a t l y varying trends i n cation concentrations at d i f f e r e n t l e v e l s i n a f o r e s t ecosystem. Consistent trends are r a r e . In the present study, the trends were not smooth but subject to wide f l u c t u a t i o n s . These n a t u r a l f l u c t u a t i o n s can be a t t r i b u t e d to a number of f a c t o r s . 1. C l i m a t i c influences - Long warm periods allow an accumulation of chemicals which can be flushed away by subsequent r a i n s . The longer and warmer the period and the l e s s intense the r a i n f a l l , the greater are l i k e l y to be the concentrations of chemicals i n water moving through the system. 2. Movement of water i n the s o i l - Mineral s o i l lysimeters may c o l l e c t water from lower i n the s o i l p r o f i l e i f the water p o t e n t i a l gradients i n the s o i l are favourable. In a d d i t i o n , the presence or absence of macrochannels and t h e i r l o c a t i o n i n the s o i l p r o f i l e with respect to i n s t a l l e d lysimeters can be very important. Terry and McCants (1970) found that leaching of ions was more extensive i n s o i l s with a l a r g e r volume of macropores. They con-sidered that most of the leaching was occurring i n the macropores. Lysimeters 220 which only collect water percolating through the s o i l matrix and avoid col-lecting macrochannel water may significantly underestimate chemical fluxes. 3. Characteristics of different ions - Cations i n solution can replace cations adsorbed on the s o i l exchange complex. The ease of replacement of different cations from the s o i l i s K < Na < Mg < Ca (Bear, 1964). The replacing a b i l i t y of cations in solution depends on several factors such as the type of exchange material in the s o i l , the exchange capacity and nature of the ions i n solution, the concentration of the solution, and the relative proportions of exchangeable ions in solution. However, i n the Haney area, the order i s A l ^ + , H +> Ca 2 +> Mg2+> K +> Na+ (L. M. Lavkulich, Department of Soil Science, University of B. C: Personal communication). In soils with a low base satura-tion, loss of cations from solution to the s o i l exchange complex i s more l i k e l y than the reverse process. The varying results i n the literature may be a func-tion of variations i n these chemical properties of s o i l s . The soils at Haney have a low base saturation (Appendix III) so that loss of cations from solution was expected, and observed. Sodium concentrations should undergo the least changes with depth, and hydrogen ion concentrations, the most. This has also been observed. 4. Geological influences - Local changes i n s o i l mineralogy may pro-foundly influence the composition of s o i l water. Easily weathered or chemically rich mineral particles low in the s o i l profile may account for increased chemical concentrations in the s o i l solution at greater depths. In the undisturbed ecosystems at Haney, calcium i s the most abundant cation at a l l levels except in precipitation and throughfall where hydrogen ions are more abundant (Table 5.9). Vegetation adds considerable quantities of hydrogen and potassium ions to solution. As the solution percolates through the forest floor, ions are added to solution, magnesium and sodium to a greater extent than potassium, but hydrogen ions are lost from solution suggesting replacement of 221 Table 5.9: Relative abundance of the major cations in solution at different levels in the ecosystem. Before clearcutting After clearcutting Precipitation H > Ca > Na > Mg > K H > Ca > Na > Mg > K Throughfall H > Ca > K > Na > Mg Ca > K > Mg > Na > H Surface runoff Ca > H > K > Mg > Na Ca> K > Na > Mg > H Forest floor leachate Ca > Mg > Na > K > H Ca > K > Mg > Na > H Mineral s o i l leachate Ca > Mg > Na > K > H Ca> Na > Mg > K > H Groundwater Ca > Na > Mg > K > H Ca > Na > Mg > K > H Streamwater Ca > Na > Mg > K > H Ca > Na > Mg > K > H Relative abundances were determined from concentrations expressed as equivalents. Hydrogen ion concentrations were calculated from pH values. metallic cations on the forest floor exchange complex by hydrogen ions. While passing through the mineral s o i l , ions are lost from solution but magnesium to a greater extent than sodium. The relative abundance of cations i n groundwater i s the same as that i n streamwater. The s o i l analyses (Appendix III) indicate that the relative abundance of exchangeable metallic cations i n the forest floor i s Ca> Mg > K> Na. This, together with the fact that sodium i s more easily replaced than potassium, as discussed above, i s consistent with the cation composition of the forest floor leachates. In the mineral s o i l , the order i s Ca) Mg > K > Na (Appendix I I I ) . This i s consistent with the observed greater losses of magnesium, relative to sodium, from solution. In mineral s o i l leachates from similar soils at Haney, the data of Bourgeios and Lavkulich (1972 a) show the order of cation abundance as Ca^ Na y Mg > K which i s similar to that found i n the present study. Differences may be due to different sampling periods, s o i l mineralogy, or analytical techniques. The order of cation abundance i n groundwater from sandy podzols in Russia was found 222 to be Ca> Mg > Na K (Vazhenin et al,, 1972), which i s also very similar to that found in the present study. Manganese, iron, aluminium, and ammonium concentrations have remained quite low throughout the study. Appreciable concentrations of iron and manga-nese were only observed during summer and autumn at the surface runoff and forest floor leachate levels. Manganese was also found i n throughfall, again mainly during summer and autumn. Small quantities of iron and manganese were leached from vegetation and concentrations increased to maximum values in sur-face runoff and forest floor leachates, but rapidly decreased i n the mineral s o i l . Windsor (1969) found similar behavior for iron. High manganese concen-trations are favoured by fine textured soils and anaerobic conditions (Cheng and Ouellette, 1971) and are not expected in the coarse textured soils at Haney. Ammonium has sometimes occurred in significant concentrations in precipi-tation. It reached maximum concentrations at the surface runoff level, declin-ing rapidly with passage of the solution through the s o i l , as has also been found by Cole (1963). Relatively high concentrations of manganese and ammonium have been found in groundwater from p i t 12. The s o i l i n the bottom of this p i t i s below the water table for most of the year so that anaerobic conditions prevail. These conditions would retard oxidation of ammonium to nitrate, favouring ammonium ions. They are also known to favour high manganese concentrations (Cheng, 1973). Seasonal variation At a l l levels in the undisturbed ecosystem, cation concentrations in solution tended to be highest i n autumn and lowest in late winter (Figures 5.3 -5.9). . • ' , Similar seasonal behavior in s o i l leachates has been observed at Cedar River although secondary peaks were observed in spring (Cole, 1963> Grier and Cole, 1972). Although Bourgeois and Lavkulich (1972 a) collected leachates from 223 ri**ra 1.1 • . POTOSSIUI COKCEMRBTItWS III CCDSTSTOl MLUTIarS - WTER5KD 0 g i i j r • i • j ) i s i < o j f i I >J J • i g > i J r N < i j j • s I i D j F i a SrOIKMIIOl - PIT 12 - POHSSIUrl SOUIIMItn - PIT 17 - P0TB5SI* KUDOS - « m - niwcmsa witoot - si IM - uiwomoio 2 2 5 «. KOCStUI DXCfNIRflTIDfrS (* taKTSTCK SOUJIIOtS - WTtRSrtO B _ pcaelpltAtloa » » thtourhfall »1 • tMicfaci runoff ----- (or*»S floor l»*ch*t» » - - i l M r i l aotl l«*c luca • lUttmatar _ b. tUgauisa eoaccBtntiau In groundwater SRDutownrDi - PIT 12 - reocsui ODUWJWTCH - P I T 17 - HRGrCSHJI Figure 5.7 a. IRON CONCENTRATIONS IN ECOSYSTEM SOLUTIONS - WATERSHED B OQ o ' - a CD 21 O cc°'' U J C J o •. C j a a a ' ••• p r e c i p i t a t i o n -* throughfall -0 surface runoff forest f l o o r leachate ^ a mineral s o i l leachate - streamwater clearcutting I 1 i 1 1 1 1 1 1 1 1 1 I - f - A I N I 1-t-l 1 1 1 — \ , 0 N D H 7 0 J F N fl H J J fl H 7 I S 0 N D J F H A M J J fl S | m i | Significant iron concentrations i n groundwater were rarely detected. O N D J F M R N i t I I M r i J J A 1*173 S 0 N 0 J F K A j I W r i g u r e 5.8 a . H f l N G R N E S E C O N C E N T R A T I O N S I N E C O S Y S T E H S O L U T I O N S — W A T E R S H E D B 228 a' 4 a * CD O £ ° r— C J o • p r e c i p i t a t i o n K t h r o u g h f a l l O s u r f a c e r u n o f f f o r e s t f l o o r l e a c h a t e . - - j t m i n e r a l s o i l l e a c h a t e s t r e a m w a t e r O K D J F M R - H J J R S 0 N D J F H H M J J H S O H D J F M H M J J H S 0 H O IS70 | 1171 | m j . | 1173 b . M a n g a n e s e c o n c e n t r a t i o n s i n g r o u n d w a t e r G R O U N D W A T E R - P I T 12 - M A N G A N E S E CO clearcutting f44 H 1 r-M J J M 7 J F H H 7 * Significant manganese concentrations in groundwater from p i t 17 were rarely detected. rifiirc 3.9 a. RrWHlUH CflrlCEKrRflllOHS IN KOSISTtH SOLUM Oft - VHTW3C0 9 2 2 9 precipitation I throuihtall ) aurfac* runoff for*at floor l«*ch*e« 1 nlnaral soil laachata klua eoocamuationa In cjrour.dwatar GsowownrER - PIT 12 - (WUKJUH h I-' »— z (JO - 1 H h H h A, ' , " 1 1 1 " I H7» SROKwnra - PIT n - maiiw r ft. H 1 h A „?i ,J ' " ' ' I ' r 'I 1 J . „ . J « » " « 0 4 r N « 230 two soi l s at Haney for four months only, they found higher concentrations i n September and October and lower concentrations i n November and December, as in the present study. Although there was considerable variation between cations, studies of leachates from Russian podzols usually found increases in cation concentrations i n autumn and sometimes i n spring (Shilova and Korovkina, 1961; Smirnova and Glebova, 1958). Smirnova and Glebova (1958) attributed this to leaching of chemicals from added l i t t e r : . In a Japanese study, seasonal fluctuations of cation concentrations were greater i n throughfall than i n streamwater and increased i n autumn and winter i n precipitation, throughfall, surface runoff, and s o i l water when precipitation was lowest and l i t t e r f a l l most active (Iwatsubo and Tsutsumi, 1968). In a German beech forest, maximum cation concentrations in precipitation were observed i n autumn, whereas sodium concentrations were found to peak i n early winter for forest floor leachate and i n spring for mineral s o i l leachate (Mayer, 1971). This three to four month difference was attributed to the time i t took for water to travel through the mineral s o i l . However, i t seems rather unlikely that i t would take such a long time for water to travel the 50 cm from forest floor to mineral s o i l lysimeters. Unfortunately no data pertaining to the seasonal behaviour of any other ions, nor to volumes of leachate collected, are given so that few conclusions can be drawn from the isolated results pre-sented. Movement of iron, manganese, and aluminium i s more complicated, depending on a variety of factors such as redox reactions, amount of soluble organic matter present, pH, and concentration of the solution, but maximum concentrations are usually observed i n autumn and spring (Bloomfield, 1953 a, b; Delong and Schnitzer, 1955; Smirnova and Glebova, 1958). Maximum ammonium concentrations in s o i l solutions occurred in winter (Figure 5.9) which may be related to water-logging of the s o i l . 231 In general, then, maximum cation concentrations in s o i l solutions have been observed in autumn with an occasional secondary peak in spring. This i s similar behaviour to that observed for streamwater and i s probably caused by the same factors (see P. 1 8 8 ). In addition, chemical inputs from leaching of fresh l i t t e r may also be important. Significant quantities of fresh l i t t e r have sometimes been observed at Haney i n spring, as a result of windy storms. These may be responsible for the peaks in spring. Effects of clearcutting There has been l i t t l e change in precipitation chemistry from one year to the next, but the replacement of l i v i n g trees with slash has caused significant changes in throughfall chemistry (Table 5.10). Potassium concentrations were much higher, magnesium concentrations slightly higher, sodium concentrations much lower, and calcium concentrations unchanged, in slash throughfall. Changes in pH show that hydrogen ion concentrations were much lower i n slash throughfall also, probably due to less leaching of organic acids from the dead vegetation. Most of the change in el e c t r i c a l conductivity of these solutions i s probably due to changes i n hydrogen ion-anion pair concentrations, i n view of the relatively smaller changes i n metallic cation concentrations. At the surface runoff level, cation concentrations have been lower f o l -lowing clearcutting, with the exception of potassium concentrations which have been higher, and hydrogen ion concentrations which have been approximately the same. A possible explanation for this decrease has been given above under "electrical conductivity". At the forest floor leachate level, cation concentrations have probably been slightly lower following clearcutting, again with the exception of potas-sium (higher) and hydrogen ions (approximately the same). However, due to the limited number of pretreatment control samples, interpretation of the forest floor leachate results i s not easy. Table 5.10i Average cation concentrations in ecosystem waters before and after clearcutting - watershed fl. 232 Kg Ca 1 . Precipitation before .04 after .03 2. Throughfall after control - after 3. Surface runoff before after control - before - after 4. Forest floor leachate before after control - before - after 5. Mineral so i l leachate before .37 after .69 control - before .15 - after .23 6. Groundwater (pit 17) before after (pit 12) before .09 after .34 7. Stream B before .09 after .18 Control(C)-before .09 -after .08 (.03) (.02) 1.13 (1.07) .40 (.20) 1.00 (1.5S) 1.18 (1.0C) .56 (.26) .28 (.28) 1.06 (.72) 1.36 (1.05) 1.01 (.21) 1.01 (1.35) (.38) (.56) (.05) (.08) .03 (.03) .36 (.03) (.09) (.14) (.02) (.05) (.04) (.02) .27 (.19) .26 (.09) .20 (.03) .43 (.12) .05 .04 .13 .11 (.02) (.02) (.03) (.03) .2 .1 .5 .4 (.1) (.1) (.1) (.1) .47 (.36) .32 (.38) 1.7 (2.6) .24 (.17) .11 (.08) .4 (.2) .57 (.24) .34 (.24) 1.5 (.9) .42 (.24) .21 (.21) 1.1 (.7) .70 (.25) .83 (1.15) 2.3 (1.6) .33 (.18) .35 (.33) .9 (.6) 1.18 (.45) 2.22 (.62) 3.1 (.3) .65 (.50) 1.41 (1.48) 1.6 (1.0) .74 (.32) .53 (.39) 1.2 (1.2) .83 (.44) .28 (.17) .9 (.5) .75 (.30) .58 (.17) 2.8 (2.5) .89 (.49) .52 (.27) 3.7 (3.6) .79 (.29) .17 (.02) 1.1 (1.2) .95 (.24) .28 (.08) 1.2 (.3) .77 (.26) .23 (.03) 1.2 (-2) .97 (.32) .23 (.08) 1.3 (.5) .80 (.25) .26 (.04) 1.3 (.2) .85 (.13) .23 (.04) 1.2 (.2) .80 (.25) .25 (.04) 1.3 (.3) .79 (.14) .21 (.04) 1.3 (.3) Fe Mn Al NH4 1. precipitation before 0 0 0 .15 (.16) after 0 0 0 .09 (.05) 2. Throughfall after « . 03 (.01) 0 .02 (.03) control - after "0 .ITJ (.03) 0 ,04 (.02) 3. Surface runoff before .02 (.03) .12 (.20) 0 .52 (.90) after .03 (.07) .03 (.04) .1 (.3) .13 (.27) control - before .01 (.02) .17 (.12) 0 .12 (.16) - after .02 (.03) .15 (.14) 0 .05 (.06) 4 . Forest floor leachate before .20 (.13) .05 (.04) .2 (.3) .09 (.18) after .18 (.19) .02 (.03) .3 (.5) .19 (.42) control - before .38 (.08) .21 (.21) .4 (.1) 0 - after .34 (.36) .24 (.38) .3 (.6) .03 (.05) 5. Mineral soil leachate before 0 .02 (.02) 0 .06 (.12) after 0 .01 (.02) 0 .04 (.07) control - before .03 (.03) 0 0 .01 (.02) - after .02 (.04) 0 0 0 6. Groundwater (pit 17) before 0 0 0 .02 (.03) after 0 0 0 .01 (.02) (pit 12) before 0 .02 (.03) 0 .03 (.04) after 0 0 0 .01 (.03) 7. Stream B before 0 0 0 .01 (.02) after 0 0 0 0 Control(C)-before 0 0 " 0 .02 (.03) -after 0 0 0 0 Values are in mg/litre. Standard deviations arc given in parent!). M l values aro for tho same time periods given in Table 5.4, 233 At the mineral s o i l leachate l e v e l , potassium and hydrogen ion concen-t r a t i o n s have been higher, sodium concentrations almost unchanged, and magnes-ium and calcium concentrations s l i g h t l y lower a f t e r c l e a r c u t t i n g . At t h i s l e v e l lower c a t i o n concentrations following c l e a r c u t t i n g are l i k e l y to be due to one or more of the f o l l o w i n g : a) Increased volumes of water flowing through the s o i l (see Appendix V I I ) ; b) The f a c t that samples have only been c o l l e c t e d during the dormant season and not during the b i o l o g i c a l l y a c t i v e period; c) A d i s r u p t i o n of the pathways of water flow through the s o i l , as discussed below. At the groundwater l e v e l the concentrations of a l l the major cations have been increased by c l e a r c u t t i n g (Table 5.10; Figures 5.3-5.8). Observations tend to exclude the p o s s i b i l i t y of contamination, as discussed above under " e l e c t r i c a l c o n d u c t i v i t y " . Analyses of groundwater from p i t s 18 and 19 (Appendix XII A) as well as from elsewhere i n the U n i v e r s i t y of B.C. Research Forest (Appendix XII B) are generally consistent with those from p i t s 12 and 17. Cation concentrations i n groundwater from p i t 18 are s i m i l a r to those from p i t 17 whereas those from p i t 19 are somewhat lower. Cation concentrations i n groundwater have been increased by c l e a r c u t t i n g elsewhere at Haney (Appendix XII B) and i n Sweden (Wiklander, 1974) . The absence of any abnormal chemical properties at lower depths i n the s o i l s at Haney (Appendix III) and the generally observed decrease i n c a t i o n concentrations i n s o l u t i o n with increasing depth of the mineral s o i l suggest that groundwater chemical concentrations should be lower than those i n mineral s o i l leachates. That t h i s has not been found can be explained by increased flow of water through macrochannels due t o surface s o i l disturbances caused by logging operations. Water from near the s o i l surface i s r e l a t i v e l y r i c h i n chemicals and has l e s s opportunity to lose them flowing through macrochannels than i t does p e r c o l a t i n g through the mineral s o i l where i t comes in t o contact with a l a r g e r surface area of s o i l p a r t i c l e s f o r longer periods of time. Thus, groundwater o r i g i n a t i n g l a r g e l y from macrochannel flow should be more concentrated than mineral s o i l leachates. The small diameter of the lysimeter p l a t e s (10 cm) 2 3 4 decreases the probability of their intersection of macrochannels. The v a r i a b i l -i t y in concentrations in groundwater between pits 17, 18, and 19 (Appendix XII A) can be explained by differences i n quantities of water flowing through macrochan-nels. In this regard, i t i s noteworthy that the s o i l upslope of p i t 19 was only very slightly disturbed by logging operations and retained most of i t s original, moss cover after logging. This lack of disturbance indicates l i t t l e or no alteration to pathways of water flow in the soils present, unlike the situation upslope of pits 17 and 18. Changes in streamwater cation concentrations following clearcutting have occurred as discussed in Chapter 4, but are less pronounced than in groundwater. This may be due to: a) dilution from upstream i n the case of stream Bj b) reac-tions occurring i n the stream which result i n loss of ions from solution (e.g. biological uptake or physical adsorption); or c) the possi b i l i t y that the i n -creased concentrations in groundwater are localized effects which do not occur throughout the entire watershed. The latter point i s suggested by the chemical composition of groundwater from p i t 19. The only significant effect clearcutting has had on the relative abundances of the major cations present i s to increase the relative importance of potassium and magnesium from the throughfall to the mineral s o i l levels (Table 5.9). 4. Anions and dissolved s i l i c a Variation through the ecosystem Anion concentrations in precipitation were variable but low, nearly always lower than in streamwater (Table 5.11). Chloride, nitrate, sulphate, and b i -carbonate concentrations were higher than, whereas phosphate and dissolved s i l i c a concentrations were similar t°r those found by Zeman (1973) at Seymour. After passing through the forest canopy, anion concentrations increased with the exception of bicarbonate, whose concentrations decreased, probably due to a decrease i n pH (Table 5.11). Table 5.11: Average anion and forest ecosystem , Cl Precipitation .6 (.2) Throughfall 1.7 (1.0) Surface runoff 1.7 (1.5) Forest floor leachate 2.7 (1.8) Mineral s o i l leachate 1.6 (1.0) Groundwater - p i t 17 .9 (.2) - p i t 12 .7 (.2) Streamwater (D) .8 (.3) dissolved s i l i c a concentrations of waters it Haney - watershed B. H 2P0 4 N03 so4 .01 (.03) .68 (.54) 1.3 (.9) .13 (.13) 1.04 (1.29) 4.9 (4.0) ,35 (.84) .58 (2.38) ' 6.0 (5.8) .10 (.16) .18 (.39) 13.9 (12.9) .03 (.13) .30 (1.02) 5.0 (3.7) 0 .07 (.13) 1.7 (.5) .02 (.06) .21 (.22) 2.2 (.8) .01 (.06) .23 (.29) 2.1 (.7) in an undisturbed HCO, SiO .3 (.4) .1 (.1) .2 (.2) .1 (.2) 1.3 (2.0) .5 (.6) 6.0 (6.1) 3.7 (2.3) 5.0 (2.5) 3.2 (1.8) 4.7 (3.3) 2.8 (1.1) 6.5 (1.3) 4.0 (1.5) 7.8 (2.2) 4.7 (1.6) Values are i n mg/litre. Standard deviations are given in parenthesis. Values are for the same time periods given in Table 5.3. Table 5.12: Relative abundance of the major anions in solution at different levels in the ecosystem. Precipitation Throughfall Surface runoff Forest floor leachate Mineral s o i l leachate Groundwater Streamwater Before clearcutting SO4 > Cl > NO3 > HCO3 > H2PO4 S 0 4 > Cl > N0 3 > IICO3 > H 2 P0 4 S 0 4 > Cl > HCO3 > N0 3 > H 2 P0 4 S 0 4 > IICO3 > Cl > N0 3 > H 2 P0 4 S 0 4 > H C 0 3 > Cl > N 0 3 > H 2 P0 4 HCO3 > S 0 4 > Cl> NO3 > H 2 P0 4 HC0 3 > S 0 4 > Cl> NO3 > H 2 P0 4 After clearcutting SO4 > Cl> NO3 > HCO3 > H2PO4 HC0 3 > S0 4 > Cl > H 2 P0 4 > N0 3 S 0 4 > HC0 3 > Cl > N0 3 > H 2 P0 4 S 0 4 > HC0 3 > Cl> N 0 3 > H 2 P0 4 so 4 > 11CO3 } c i > No 3 y H 2 P O 4 NO3 > S 0 4 > Cl > HC0 3> H 2 P0 4 HC0 3 > S 0 4 > Cl> H0 3 > H 2 P0 4 Relative abundances were determined from concentrations expressed as equivalents. 237 As the solution travelled over and through the forest floor, there was a further increase in a l l concentrations except those of phosphate and nitrate which decreased (Table 5.11). This decrease i s probably due to the high bio-logical demand for these two nutrients. While passing through the mineral s o i l to groundwater, there was a general decrease in most concentrations (Table 5.11). The large decrease in phosphate concentrations was probably due to fixation by iron and aluminium (John, 1971). Nitrate concentrations, however, fluctuated somewhat and smooth trends have not been found. Streamwater anion and dissolved s i l i c a concentrations were usually higher than groundwater concentrations (Table 5.11) reflecting trends in cation concentrations. The absence of large amounts of pyrite or any evaporite rocks from which sulphate could form (Hem, 1970), suggests that the major sulphate supply to the system i s in precipitation, as i s the case for chloride (Gambell and Fisher, 1966; Junge and Werby, 1958). The very close similarity i n the behaviour of chloride and sulphate throughout the system i s consistent with this. Increases in chloride and sulphate concentrations at the forest floor leachate level, however, suggest that there was some input from decomposing vegetation. Decreases i n sulphate and chloride, as well as in nitrate and bicarbonate, concentrations as water travelled through the mineral s o i l are probably due to adsorption reac-tions whereby the anions are immobilized as the cations with which they are associated become adsorbed to the s o i l exchange complex. Some adsorption of anions to the s o i l anion exchange complex may also have occurred. Despite the inaccuracy of the bicarbonate and sulphate analyses, as dis-cussed in Chapter 4, these were probably the most abundant anions in solution throughout the s o i l profile and in streamwater in the undisturbed ecosystem. Phosphate was the least abundant of the anions throughout the ecosystem (Table 5.12). Calculations of anion-cation balances showed a large excess of cations 238 over anions i n p r e c i p i t a t i o n and a s l i g h t excess of cations over anions i n t h r o u g h f a l l . The anion d e f i c i t may be explained by the presence of carbonate ions, f o r which no analyses were carred out. P r e c i p i t a t i o n at Haney was thus a weak mixture of carbonic, sulphuric, and hydrochloric a c i d s . A f t e r p e r c o l a t i n g through the f o r e s t f l o o r , loss of hydrogen ions and gain of carbon dioxide con-verted the s o l u t i o n to a weaker mixture of sulphuric and carbonic acids which then leached the mineral s o i l . As was the case with the cations, the order of anion abundances f o r streamwater was not reached u n t i l the groundwater l e v e l . Bourgeois and Lavkulich (1972a) a l s o observed decreases i n n i t r a t e and sulphate concentrations with depth i n the mineral s o i l at Haney. As i n the present study, they reported considerable f l u c t u a t i o n i n n i t r a t e concentrations and found n i t r a t e to be more abundant i n s o l u t i o n than ammonium. Studies i n western Washington (Cole, 1963; Cole et at., 1961) a l s o found nitrogen concen-t r a t i o n s to decrease with depth i n the s o i l , but found nitrogen to e x i s t pre-dominantly as ammonium. At Cedar River i n western Washington, phosphorus concentrations decreased r a p i d l y with depth i n the mineral s o i l due to p r e c i p i t a t i o n as i r o n and aluminium compounds. Phosphorus release was c o n t r o l l e d b i o l o g i c a l l y i n the f o r e s t f l o o r and by s o l u b i l i t y i n the mineral s o i l (Windsor, 1969). Cleaves et at., (1970) found trends i n bicarbonate, c h l o r i d e , and sulphate concentrations throughout a forested ecosystem i n Maryland which were s i m i l a r to those i n the present study. Mayer (1971) i n Germany also found trends i n nitrogen, phosphorus and sulphur concentrations throughout an ecosystem s i m i l a r to those i n the present study (Table 5.13). Chloride concentrations tended to increase with depth i n the s o i l , however. In Japanese coniferous and broadleaved f o r e s t s , phosphorus concentrations f l u c t u a t e d considerably throughout the ecosystems whereas n i t r a t e concentrations were highest i n t h r o u g h f a l l , d e c l i n i n g through s o i l s o l u t i o n and streamwater to values lower than i n p r e c i p i t a t i o n (Iwatsubo and Tsutsumi, 1968). 239 Table 5.13: Ratios of anion-elenent concentrations in water at different levels in a forest ecosystem in Germany. N P Cl S Precipitation 1 1 1 1 Throughfall 1.4 .6 .5 8.3 Forest floor leachate 3.6 11.7 2.6 2.4 Mineral s o i l leachate - 50 cm depth .7 .1 5.9 1.4 - 100 cm depth .8 .1 4.8 2.4 Calculated from data in Mayer (1971), as for Table 5.8. In fine textured Russian podzols, no consistent trends were found in bicarbonate, sulphate, or chloride concentrations i n solution with depth i n the s o i l (Shilova and Korovkina, 1961). The order of abundance of anions in ground-water in Russian podzols was HC03 S0 4 ") Cl (Shilova and Korovkina, 1961; Vazhenin et a l . , 1972) - identical to that i n the present study. Of a l l the major ions, chloride appears unique in that i t s concentration i n streamwater underwent very l i t t l e change. Higher chloride concentrations in streamwater relative to those i n precipitation are usually observed (e.g. Juang and Johnson, 1967; Zeman, 1973) and may be attributed to increasing concentration i n runoff by evaporation and transpiration, and inputs from dry fallout, weather-ing, and decomposition processes. Chloride concentrations fluctuated more widely in precipitation than they did in streamwater (Figure 5.12). As precipitation forms the major source of chloride, this suggests that chloride concentrations in streamwater are buffered against changes i n discharge and precipitation periodicity. Considerable fluctuations in chloride concentrations occurred through the s o i l p r o f i l e , becoming slight only at the groundwater level (Figure 5.12). Juang and Johnson (1967) considered that the buffering action of chloride was probably due to chloride retention and exchange by colloids in the s o i l . Data from this study suggest that the whole s o i l column above the water table i s necessary for this buffering action to become complete. 240 Dissolved s i l i c a concentrations at Cedar River increased to maximum values in the top few cm of mineral s o i l then decreased at greater depths (Windsor, 1969). These decreases were attributed to accumulation of s i l i c a i n the B horizon and uptake of s i l i c a by plant roots. Kurtz and Melsted (1973) considered that the f i n a l concentrations of salts i n s o i l water are controlled to some ex-tent by weathering of primary s i l i c a t e minerals. They considered that low s i l -ica concentration in s o i l water accelerate primary s i l i c a t e weathering and that metallic cations may be in equilibrium with the clay minerals, thus stabilizing the clays, while the primary minerals continue to weather. This might help to ex-plain the occasional higher ion concentrations in mineral s o i l leachates (with lower dissolved s i l i c a concentrations) than i n forest floor leachates found in a number of s o i l p i t s . Seasonal variation Anion and dissolved s i l i c a concentrations fluctuated considerably. This may reflect the real situation or may reflect analytical problems. Anion con-centrations were generally closer to their respective detection limits than were cation concentrations. Consequently, anion analyses were generally less accur-ate. Despite t h i s , anion and dissolved s i l i c a concentrations tended to be highest in autumn or late summer and lowest i n winter or spring for the s o i l solutions (Figures 5.10-5.15). In general, changes in anion concentrations i n s o i l solutions corresponded to those i n streamwater, probably for the same reasons, as discussed i n Chapter 4. There were a few exceptions, however. For example, bicarbonate concentra-tions in groundwater fluctuated considerably but maximum concentrations occurred i n spring (Figure 5.14), as has been found in Russian podzols (ShiJova and Korovkina, 1961). These fluctuations may be due to climatically-controlled changes i n biological activity. I t i s noteworthy that Bourgeois and Lavkulich (1972 a) also found considerable fluctuations in bicarbonate concentrations in 242 Figure 5.11 4 . P H O S P H I T E CONCENTRATIONS IN E C 0 5 Y S T E H SOLUTIONS - VTITERSHEO 8 p r e c i p i t a t i o n H » t h r o u g h f a l l q 0 surface runoff . - f o r e s t f l o o r leachate ^ . . . . ^ j mineral s o i l leachate _____ streamwater c l e a r c u t t i n g < 1 1 I 1 i 1 1 1 1 1 I 1 I I I I I 1 I 1 1 1 1 0 N 0 m o J F H fl M J J fl S 0 N 0 J F K I fl H J J B i<na b. Phosphate concentrations i n groundwater GROUNOyRTEfl - PIT 12 - PHOSPHATE a Significant phosphate^concentrations in groundwater from p i t 17 were rarely detected. t o U l «. aiowaowflTc uajn.iiitTn c»coirem ims w cxjcniui somrittis - W T O G * O e 246 riqur* 4.11 OlSttLVQD StltXR CWCDlTHBTtWrS III tCn5T5TC« 50UJTIDIT5 - WTCRSKfl B 247 soils at Haney. In addition, although nitrate concentrations were highest in autumn, they were lower in summer than in winter (Figure 5.12). Concentrations i n precipitation tended to fluctuate randomly. In through-f a l l they were higher in early autumn, probably due to an accumulation of dust particles on vegetation and of leachable chemicals i n foliage and bark during the preceding dry period. Bourgeois and Lavkulich (1972 a) observed higher nitrate and sulphate concentrations in autumn than in winter in mineral s o i l leachates from Haney whereas chloride and phosphate concentrations were higher i n winter. As most of the chloride i n streamwater comes from precipitation, fluctuations i n chloride concentrations in s o i l solutions may reflect fluctuations in chloride concentra-tions i n precipitation. There i s some similarity between changes i n chloride concentrations in precipitation and those in s o i l solutions in the present study (Figure 5.10). This might explain differences between the results of the present study and those of Bourgeois and Lavkulich. Elsewhere, chloride concentrations in s o i l solutions are higher i n autumn (Shilova and Korovkina, 1961). In western Washington, nitrogen and phosphorus concentrations in s o i l solu-tions peaked i n spring and autumn (Cole, 1963; Windsor, 1969). High precipita-tion, as i n winter, lowered the concentrations. Maximum s i l i c a concentrations in s o i l solutions also occurred in summer and autumn (Windsor, 1969). In Japan, phosphorus concentrations in surface runoff and s o i l solution fluctuated considerably through the year whereas nitrate concentrations were highest in winter and autumn when there was l i t t l e precipitation (Iwatsubo and Tsutsumi, 1968). In general, there i s good agreement between the results of this study and those of other studies. Effects of clearcutting There has been a decrease i n chloride concentration i n precipitation after 2 4 8 clearcutting but, otherwise, changes are only slight (Table 5.14). In through-f a l l , however, increases in phosphate and bicarbonate and decreases i n chloride, sulphate, and nitrate concentrations have been observed (Table 5.14). Bicarbon-ate increases were probably associated with increases in pH. High phosphate concentrations were only measured in two collectors under Douglas-fir slash. These were sufficiently high to significantly raise the average value. Through-f a l l phosphate concentrations might have been much lower than indicated, in view of the low proportion of Douglas-fir slash present, or the poss i b i l i t y of con-tamination. An overall decrease i n anion concentrations i s expected in view of the decrease i n cation concentrations discussed above. At the surface runoff level, decreases i n a l l concentrations, except b i -carbonate, were recorded (Table 5.14). Bicarbonate concentrations remained es-sentially unchanged. These changes following clearcutting reflect the changes in throughfall, with qualifications for phosphate, as discussed above. At the forest floor leachate level, interpretation of the results i s rendered d i f f i c u l t by the limited number of "control - before clearcutting" samples. However, i t does appear as i f there has been a general decrease in concentrations, again with the exceptions of phosphate and bicarbonate (Table 5.14). At the mineral s o i l level decreases in a l l concentrations except nitrate (which increased) were recorded (Table 5.14). However, the decreases were gen-erally less pronounced than those higher up the s o i l p r o f i l e . At the groundwater level, increases in chloride, and particularly in nitrate concentrations have occurred (Table 5.14; Figures 5.10 and 5.12). There has been l i t t l e change in the other concentrations except bicarbonate, which decreased. The behavior of bicarbonate, relative to the other anions, paralleled the be-havior of hydrogen ion, relative to the other cations, throughout the ecosystem. The concentration of hydrogen ions in solution thus appeared to be the dominant Table 5.14: Average anion and dissolved s i l i c a concentrations i n ecosystem waters before and after clearcutting - watershed B. 1. P r e c i p i t a t i o n before .6 af t e r .2 2. Throughfall a f t e r .5 control - af t e r .9 3. Surface runoff before 1.4 a f t e r .8 control - before 1.5 - a f t e r 1.3 4. Forest f l o o r leachate before 2.1 a f t e r 1.3 control - before 2.1 aft e r 2.0 5. Mineral s o i l leachate before 1.3 af t e r 1.2 control - before 1.5 af t e r 2.0 6 . Groundwater (pit.17) before .9 a f t e r 1.1 (pit 12) before .8 a f t e r 1.0 7. Stream B before .9 a f t e r .8 Control(C)-before ,8 - a f t e r .8 C l H 2P0 4 N0 3 (.5) .01 (.04) .78 (.60) (.2) 0 .59 (.23) (.1) .21 (.22) .10 (.07) (.3) .05 (,08) .44 (.13) (1.0) .54(1.21) .41 (1.17) (.6) .17 (.18) .15 (.41) (.9) .24 (.24) .09 (.15) (.9) .12 (.12) .10 (.22) (1.0) ,06 (.11) .13 (.16) (.7) .25 (.36) .09 (.14) (.3) .13 (.18) .18 ( 0 ) (1.7) .19 (.24) .05 (.05) (.8) .07 (.21) .15 (.26) (.9) .02 (.06) .84 (1.54) (.8) 0 .08 (.20) (2.1) .01 (.02) .01 (.03) (.3) 0 .12 (.15) (.4) 0 3.44 (1.83) (.3) .01 (.02) .22 (.30) (.4) .01 (.02) .74 (.99) (.3) 0 .20 (.35) (.2) 0 .14 (.10) (.2) 0 .20 (.32) (.2) 0 ,09 (.07) s o 4 HC03 S i 0 2 .9 (.6) .4 (.4) .1 (.1) .6 (.7) .6 (.4) 0 1.0 (.5) 3.8 (.4) 0 2.3 (1.0) .2 (.1) 0 5.2 (6.9) 2.1 (2.7) .6 (.7) 2.7 (2.6) 2.0 (1.2) .4 (.8) 4.6 (1.9) .5 (.5) .3 (.2) 3.7 (3.0) .5 (.6) .2 (.2) 9.4 (3.6) 3.4 (3.9) 2.2 (1.7) 4.3 (2.9) 3.8 (3.0) 1.0 (1.1) 0 10.2 (3.1) 6.0 (1.9) 7.0 (7.1) 5.0 (6.2) .7 (1.0) 4.0 (3.3) 3.9 (2.4) 3.2 (1.7) 3.6 (2.3) 2.8 (1.3) 2.8 (1.3) 5.6 (4.7) 6.1 (2.1) 3.2 (2.0) 6.4 (6.9) 5.7 (1.4) 3.5 (2.2) 1.5 (.6) 4.6 (4.0) 2.4 (1.3) 1.7 (.4) 2.5 (.5) 2.8 (1.3) 2.2 (.9) 5.9 (1.2) 3.4 (1.5) 2.1 (.9) 4.9 (1.2) 3.4 (1.3) 2.2 (.7) 6.2 (1.0) 4.7 (1.1) 1.6 (.4) 5.5 (.9) 4.2 (.9) 1,8 (.8) 6.6 (1.2) 4.5 (.7) 1.4 (.5) 6.2 (1.3) 4.0 (.9) Values are i n mg/litre. Standard errors are given i n parentheses. A l l values are for the same time periods given i n Table 5.4. 250 f a c t o r c o n t r o l l i n g bicarbonate concentration. The large increases i n n i t r a t e concentrations suggest enhanced n i t r i f i c a -t i o n or leaching o f nitrogen compounds from decomposing vegetation near the s o i l surface. N i t r a t e was the major anion accompanying the increased amounts of cations found i n groundwater. High n i t r a t e concentrations i n groundwater were found i n p i t 17 but not i n p i t s 18 or 19 (Appendix XII A). Although the LFH l a y e r i n p i t 17 contained more nitrogen and had a lower C/N r a t i o than i n the other two p i t s , the d i f f e r e n c e s were not very great (Appendix I I I ) . As discussed above, d i f f e r e n c e s between the p i t s were probably due to l o c a l i z e d e f f e c t s of c l e a r c u t t i n g on the pathways of water flow through the s o i l , as w e l l as on microclimate which a f f e c t s decomposition and n i t r i f i c a t i o n r a t e s . In the case of n i t r a t e , however, the exposure of groundwater to the atmosphere i n a p i t may have enhanced oxi d a t i o n of ammonium to n i t r a t e with greater amounts of n i t r a t e being measured i n those s o l u t i o n s which once contained more ammonium. I t i s noteworthy that a Swedish study (Wiklander, 1974) found considerably higher n i t r a t e concentrations i n groundwater from c l e a r c u t , than from undisturbed, f o r e s t lands. At the streamwater l e v e l , s l i g h t increases i n n i t r a t e and decreases i n bicarbonate concentrations followed c l e a r c u t t i n g (Table 5.14). Concentrations of the other species remained e s s e n t i a l l y unchanged. This generally r e f l e c t e d changes i n groundwater chemistry but on a much l e s s pronounced scale, as was the case f o r c a t i o n concentrations, as discussed above. The only major e f f e c t s c l e a r c u t t i n g has had on the r e l a t i v e abundances of the anions, have been an increase i n the importance of bicarbonate a t the t h r o u g h f a l l and surface runoff l e v e l s , and an increase i n the importance of n i t r a t e at the groundwater l e v e l (Table 5.12). 5. General d i s c u s s i o n The flow of d i s s o l v e d ions through a f o r e s t ecosystem I t i s well known that p r e c i p i t a t i o n washes chemicals out of vegetation (e.g. Ovington, 1962). Less w e l l known i s what happens to these chemicals as the s o l u t i o n t r a v e l s through the s o i l and i n t o streams. 251 Several rather sweeping statements have appeared in past works. For example, Gorham (1961) considered that solutions from mineral s o i l lysimeters were more concentrated than groundwater which tended to be more concentrated than streamwater. In addition, Livingstone (1963) considered that groundwater, because of i t s long-standing intimate contact with rocks and mineral s o i l , was chemically more concentrated than surface runoff. Other workers (e.g. Weisel and Newell, 1970) considered that surface runoff was more concentrated than streamwater. Others (e.g. Steele, 1968) have assumed that stream base flow chemistry i s identical to groundwater chemistry. Thus, several theories con-cerningbroad trends in solution chemistry as water passes through an ecosystem, have arisen. A more detailed explanation of solution chemistry was developed by Nye and Greenland (1960). They considered that the major anions in solution were not retained to any extent by the s o i l and remained i n solution. To maintain electroneutrality, cations were required. Thus, leaching of cations through the s o i l depended on the amount of anions present. This theory has now been refined by workers at Cedar River (e.g. Cole and Gessel, 1974; Cole et al., 1973; McColl, 1972; 1973 b) and at Hubbard Brook (Likens et al., 1970). A description of the current theory follows. Changes in the chemistry of s o i l solutions depend mainly on transfers by leaching. This leaching depends on a series of relationships between the biolog-i c a l and physical components of the system. F i r s t l y , through biological decompo-sition and mineral weathering, elements are changed into readily leachable forms. These forms may be immobilized by biological uptake or adsorption reactions, however. Secondly, to remove cations from an exchange site in the s o i l , other cations must be present in solution. These cations in solution are necessarily accompanied by anions. They may be adsorbed by the s o i l exchange complex which would leave excess anions in solution unless other cations were lost from the 252 exchange complex, or unless the excess anions were also adsorbed by the s o i l . Now, in soils which do not contain appreciable amounts of iron and aluminium oxides, as i n the soils of cold temperate Canada, anion adsorption w i l l occur to a lesser extent that cation adsorption (Kurtz and Melsted, 1973). This i s also suggested by a study of exchangeable anions in some soils of southwestern B. C. (Breckner, 1969). In this study, the amount of exchangeable chloride, sulphate, and phosphate i n Humo-ferric podzols, similar to those at Haney, was found to be between 0 and 5 meg/100 gm s o i l . The anions are, therefore, rela-tively mobile and act to maintain high cation levels i n s o i l solutions. As water percolates through s o i l i t does lose ions, however, through adsorption or biological uptake (e.g. plant roots) reactions. The chemical composition of a s o i l solution depends on a complex series of equilibrium, adsorption, displace-ment, immobilization, weathering, and decomposition reactions. Leaching of ions through s o i l depends, then, to some extent on the genera-tion of a supply of mobile anions. In some lower elevation soils of western Washington these anions are predominantly bicarbonate. At higher elevations, the anions of organic acids may be important (Johnson et al,, 1974). In the soils beneath deciduous forests i n the northeastern U.S., nitrate and sulphate appear important. In a l l cases the anions are generated together with hydrogen ions and occur as acids. The degree of ionization of these acids depends on their strength. Thus, sulphuric and n i t r i c acids are strong and are v i r t u a l l y com-pletely ionized under the conditions prevailing i n s o i l s . The organic and carbonic acids of the west coast soils are relatively weak so that the quantity of anions present, and the relative abundance of different anions, depends to a large extent on the pH of the s o i l solution, and hence, of the s o i l . The hydro-gen cations have a very strong replacing a b i l i t y and can readily replace other cations adsorbed to the s o i l . The mobile anions can then drag cations through the s o i l . 253 The data collected i n this study are entirely consistent with this theory. As the solution passed through the forest floor and mineral s o i l , there was an increase i n metallic cations relative to hydrogen ions. Loss of hydrogen ions caused greater ionization of the carbonic acid present which increased the im-portance of bicarbonate. The solution reaching the s o i l surface was a mixture of carbonic, sulphuric, and hydrochloric acids. After passing through the s o i l , the solution became more dilute and bicarbonate became the most important anion. Changes i n chemistry between s o i l waters and streamwater were probably due to processes occuring in the streams, as discussed above. In the undisturbed state, groundwater was less concentrated than streamwater. Data collected by K. Klinka (Table 5.15) support this result. Thus, the results obtained, together with those of Cleaves et al. (1970) invalidate the broad generalizations made by Gorham (1961), Livingstone (1963), and Steele (1968), discussed above. Their theories may be valid for some s i t u -ations but certainly not for a l l . Ecosystem solution chemistry and stream stormflow The behavior of chemical concentrations as stream discharge increases has been used by several authors to determine the origin of the water contributing to stormflow. For example, Livingstone (1963) considered that groundwater was more concentrated than surface runoff. Hence, decreases in concentrations with increasing discharge implied significant contributions of surface runoff to stormflow. Other workers, however (e.g. Buscemi, 1969; Weisel and Newell, 1970), considered that surface runoff was more concentrated than s o i l solutions. In-creases i n the concentrations of certain chemicals with increasing discharge also implied contributions of surface runoff to stormflow. Cleaves et a l . (1970) found that those chemicals whose concentrations increased with increasing dis-charge also exhibited high concentrations in (LFH .+ A horizon) leachates sug-gesting a significant contribution of this water to stormflow. Surface runoff, 254 Table 5.15: Average chemical composition of groundwater and streamwater at Haney., No. of Samples pH Cond. Ca Mg K Na Fe NH4 Groundwater 44 5.8 18.0 .8 .2 .3 .9 .1 .2 Streamwater 24 6.9 20.7 1.7 .4 .1 1.2 0 0 N 0 3 Cl H 2 P0 4 so 4 sio 2 HC0 3 Groundwater .4 1.4 0 3.1 2.0 4.4 Streamwater .3 1.2 0 3.0 5.3 8.6 Concentrations are in mg/litre. Electr i c a l conductivity i s in micromho/cm at 25°C. Groundwater data i s from K. Klinka (Graduate student. Faculty of Forestry, University of 3. C.) and was collected from a number of undisturbed biogeocoenoses with soils of mesotrophic or better nutrient status, during the summers of 1972 and 1973. Streamwater data i s from undisturbed streams A, B,and C during the same time periods. however, was notsampled. None of these studies, with the par t i a l exception of . that by Cleaves et al., sampled water at different stages i n i t s passage through an ecosystem for extended periods of time. Consequently, the various theories are backed up by few facts. At Haney, potassium and sulphate concentrations i n streamwater increased with increasing discharge whereas the concentrations of a l l other ions decreased (Figures 4.33 and 4.47). This i s similar behaviour to that found by other workers. If appreciable quantities of throughfall, surface runoff, forest floor leachate, or even mineral s o i l leachate contributed to stormflow, then potassium and sul-phate concentrations would have increased as the stream rose, but so too would the concentrations of most of the other ions. .This leaves only contributions from precipitation and groundwater. As virtually the entire stream channel of 255 each stream was covered by vegetation, very l i t t l e precipitation would have reached the stream without coming into contact with vegetation, thereby becoming throughfall. Thus, by a process of elimination, i t seems as i f major contribu-tions to stream stormflow were made by groundwater. This i s consistent with flow of water through macrochannels discussed in Chapter 4. Increases in potas-sium concentrations with increasing discharge might have been due to processes within the stream i t s e l f . For example, potassium was leached from vegetation more readily than any of the other major ions, as discussed above. As a rising stream came into contact with more streambank vegetation, or l i t t e r deposited near or in the stream, relatively large quantities of potassium could have been leached into the stream, accounting for the rise i n potassium concentrations. The increase in sulphate concentrations was less pronounced than that for potassium (Figures 4.33 and 4.47) and might have been: a) an artifact caused by analytical errors; b) due to contributions from forest floor leachates which are particularly high i n sulphate (Table 5.11); or c) due to processes within the stream i t s e l f . Effects of clearcutting Clearcutting causes a number of changes which are l i k e l y to increase the flux of chemicals through the s o i l and into streams. Increases i n concentra-tions, however, may not always be detected due to increased quantities of water flowing through the s o i l and to the possibility of ions being lost from solution to the s o i l exchange complex or to organisms. Destruction of vegetation causes a decrease i n chemical uptake by plant roots. Increased biological decomposition and mineral weathering add more chemicals to solution, A third important effect of clearcutting i s on biologi-cal activity. In soils under deciduous forests at Hubbard Brook, clearcutting increases the numbers of n i t r i f y i n g bacteria which then produce more n i t r i c acid. The hydrogen ions from this n i t r i c acid replace metallic cations from 256 the s o i l exchange complex which are then dragged through the s o i l by the mobile nitrate ions (Likens et a l . 1970). At Cedar River in western Washington, accelerated activity of decomposer organisms produces more carbon dioxide which dissolves in water yielding carbonic acid. This carbonic acid functions in an analogous way to the n i t r i c acid just described. The only significant study on the effects of clearcutting on the flow of chemicals through soils appears to be the Cedar River study. There, clearcut-ting was found to greatly increase the amounts and concentrations of potassium, calcium, and nitrogen passing through the forest floor but to cause only a slight increase in the amounts passing beyond the rooting zone in the mineral s o i l (Gessel and Cole, 1965). Due to the increase i n the amount of water passing through, nitrogen and potassium concentrations were actually lower in the mineral s o i l leachate after clearcutting, whereas calcium concentrations were vir t u a l l y unchanged. The absence of large increases in the flow of chemi-cals beyond the rooting zone has been attributed by Cole et al. (1973) to reac-tions involving the bicarbonate ion. Increased carbon dioxide production was stated (Cole and Gessel, 1974; Cole et al., 1973) to increase carbon dioxide and bicarbonate concentrations, and the pH of the solution near the s o i l surface. (However, increased carbon dioxide concentrations should decrease the pH of the solution due to increased hydrogen ion concentrations. Some decreases in pH have been observed i n the present study but, as they have been recorded during the dormant season, they are probably due to increased leaching of organic acids rather than increased carbon dioxide production.) Now, for the surface reaction to result in an increase in the flow of chemicals lower i n the s o i l , the products from the reaction must leach through the soil, to the deeper layer. The absence of such leaching at Cedar River was attributed to the capacity of the s o i l to buffer increases in bicarbonate and changes in pH. Upon moving down the s o i l p r o f i l e , a more acidic condition was 257 encountered by the s o i l solution causing loss of H+ HCO3 ion pairs through formation of H2CO3, This lowered the leaching potential of the s o i l solution and allowed metallic cations associated with bicarbonate ions to replace hydro-gen ions i n the s o i l exchange complex. Now, a solution percolating through the s o i l normally encounters less acidic conditions with depth. This would cause increased dissociation of H2CO3 to H + and HCO3. Only a large increase in the pH of the forest floor, as was stated to occur at Cedar River (Cole et al., 1973), would decrease the number of H + HCO3 ion pairs in solution. This mechanism i s unlikely to operate at Haney, because the pH of the forest floor leachates has been vir t u a l l y unchanged by clearcutting and has remained less than that of the mineral s o i l leachate (Table 5.4). At Haney, flow of water through macrochannels in the s o i l i s considered more important than percolation of water through the s o i l matrix, particularly with regard to increased chemical concentrations i n groundwater, as discussed above. Increased chemical concentrations in groundwater following clearcutting have also been found by Klinka at Haney (Appendix XII B) and by Vazhenin et al. (1972) i n Russian podzols. Summary 1. The chemistry of water was monitored at the following stages of i t s passage through a forest-watershed ecosystem: precipitation, throughfall, sur-face runoff, forest floor leachate, mineral s o i l leachate near the bottom of the rooting zone, groundwater, and streamwater, 2 , In the undisturbed ecosystem, pH was lowest for throughfall then i n -creased steadily throughout the system to streamwater. Seasonal trends in pH were obvious only i n mineral s o i l leachates, groundwater, and streamwater where maximum values occurred in late summer and early autumn and minimum values oc-curred i n winter. Clearcutting increased the pH of throughfall and surface run-off but decreased the pH of mineral s o i l leachate, groundwater and streamwater. 258 3. As water passed through the undisturbed ecosystem, i t s electrical conductivity increased to a maximum value in forest floor leachate then decreased to a minimum value in groundwater followed by a slight increase again in stream-water. Throughout the ecosystem a l l solutions had maximum elect r i c a l conductiv-i t i e s in early autumn with minima in later winter. Clearcutting decreased the electr i c a l conductivity of throughfall, surface runoff, and probably forest floor leachate and mineral s o i l leachate, but increased the electrical conductivity of groundwater and, to a lesser extent, streamwater. 4. As water passed through the undisturbed ecosystem, the concentrations of dissolved chemicals generally paralleled the behaviour of electrical conduc-t i v i t y with maximum values i n forest floor leachates and minimum values in groundwater. As was the case for electrical conductivity, concentrations were generally highest in late summer - early autumn and lowest in winter. However, anion concentrations exhibited greater fluctuations than cation concentrations and bicarbonate concentrations were highest in spring. 5. Clearcutting caused an increase i n potassium concentrations throughout the ecosystem. Clearcutting generally caused a decrease in concentrations from throughfall to mineral s o i l leachates, a large increase i n groundwater, and a lesser increase in streamwater. Nitrate concentrations were greatly increased in groundwater. 6. The most abundant ions measured in precipitation and throughfall were hydrogen, sulphate, and chloride ions. In surface runoff, s o i l solutions, and streamwater, the most abundant ions were calcium, bicarbonate, and sulphate. The only significant effects of clearcutting on the relative abundances of ions in solution were an increase i n the abundance of - potassium throughout the system, bicarbonate i n throughfall and surface runoff, and nitrate in ground-water - and a decrease in the abundance of bicarbonate in groundwater. 7. In the undisturbed ecosystem, the increase in chemical concentrations to the forest floor leachate stage was attributed to leaching of chemicals from 259 l i v i n g and decaying vegetation, together with mineral weathering inputs. The decrease as water percolated through the mineral s o i l was attributed to loss of ions to the s o i l exchange complex. Slight increases as the solution moved from s o i l to stream were attributed to reactions occurring within the stream i t s e l f . 8. In the undisturbed ecosystem, the seasonal behaviour of chemicals i n solution was attributed to an accumulation of decomposition and weathering products in the s o i l and a build-up of dry fallout on, and leachable chemicals i n , standing vegetation during the dry summer, followed by a flushing of these accumulated chemicals through the system by the autumn rains. The solutions became progressively more dilute throughout winter but became more concentrated with the onset of the warmer weather which enhanced biological and geological activity i n spring. 9. Increased potassium concentrations following clearcutting were att r i b -uted to the relative ease with which potassium was leached from decaying vege-tation. Decreases i n chemicals in surface runoff, forest.floor leachates, and mineral s o i l leachates were attributed to a) increased amounts of water flowing through the system, b) decreased amounts of chemicals i n throughfall, c) the fact that samples have been collected only during the dormant season following clearcutting, and d) a disruption of the pathways of water flow through the s o i l . 10. Significantly increased concentrations i n groundwater following clear-cutting were attributed to increased flow of concentrated surface solutions through macrochannels i n the s o i l by-passing the ion-adsorbing s o i l matrix. Lesser increases i n the streamwater of stream B were considered due to a) dilution from upstream waters, b) biological and chemical uptake reactions occurring with-i n the stream i t s e l f , and c) the possibility that increased concentrations i n groundwater were localized effects which may not occur throughout the entire clearcut. 11, Chemical analyses of ecosystem waters were consistent with flow of 260 water through macrochannels in the s o i l , this flow becoming more important after clearcutting. The analyses were also consistent with groundwater making a major contribution to stream stormflow, 12. The carbonic acid dissociation theory developed by Cole et a l . (1973) to explain the absence of pronounced increases in the flow of chemicals through the mineral s o i l after clearcutting, i s considered not to apply to the soils at Haney. 261 CHAPTER 6. CONCLUSIONS 1. The streams at Haney are characterized by low concentrations of dissolved chemicals compared to streams elsewhere. They exhibit no abnormal or out-standing chemical behaviour. 2. The division of a watershed into upper and lower portions, as exemplified by watersheds B and C, can lead to relatively large uncertainties in the results of hydrologic or watershed chemical studies obtained for the lower portion (watershed B ) . Such an experimental design i s not recommended as the use of entire watersheds only leads to more accurate results. 3. I t i s s