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The soil water regime and growth of uneven-age interior Douglas-fir (Pseudotsuga menziesii var. glauca)… Korol, Ronda Lee 1985

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THE SOIL WATER REGIME AND GROWTH OF UNEVEN-AGE INTERIOR DOUGLAS-FIR (PSEUDOTSUGA MENZIESII VAR. GLAUCA) STANDS BY RONDA LEE KOROL A t h e s i s submitted i n p a r t i a l f u l f i l m e n t o f the requirements f o r the Degree of Master of Sc ience i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF FORESTRY We accept t h i s t h e s i s as conforming to the r e q u i r e d s tandard UNIVERSITY OF BRITISH COLUMBIA November 1985 © RONDA LEE KOROL, 1985 In presenting this thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of th i s thesis for scho l a r l y purposes may be granted by the Head of my Department by his or her representatives. It i s understood that copying or publication of thi s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. DEPARTMENT OF FORESTRY UNIVERSITY OF BRITISH COLUMBIA 2075 Wesbrook Mall Vancouver, B.C., Canada V6T 1W5 Date: November 27, 1985 ABSTRACT A study was initiated in 1984 to investigate the soil water regime and growth in uneven-age interior Douglas-fir stands. Eleven 10 m x 10 m microclimate plots covering a wide range of canopy coverages and twenty-two 25 m x 25 m inventory plots were estab-lished in the IDFa and IDFD biogeoclimatic subzones in the Kamloops area. On one microclimate plot windspeed, relative humidity, air temp-erature, solar irradiance, net radiation and soil temperature were meas-ured. Relative humidity, solar irradiance and air temperature were measured on six additional plots, while on a l l eleven plots snow water equivalence, root zone water storage and rainfall were measured. The inventory plots, which had stand densities ranging from 96 to 2,784 trees h a - 1 , were located near the microclimate plots on areas partially logged between five and thirty years ago. There were a total of 956 trees on these plots. One hundred trees were randomly selected for stem analysis by falling and removing cross-sectional discs at ground level, breast height, base of the crown and midway through the crown. An addi-tional 700 increment cores were taken and analyzed. Diameter at breast height was recorded for a l l the trees in a l l plots, while height and bark width was measured on 30% of the total number of trees. The number and age of the regeneration were obtained and a l l plots were mapped. Four permanent sample plots established by Balco Industries Ltd. were also remeasured. From the data obtained from the microclimate plots, the snow water equivalent depths, soil water matric potentials and courses of the soil water storage over the growing season were analyzed. The growing season (ii) evapotranspiration and tr a n s p i r a t i o n rates, determined by the water balance method for each of the canopy coverages, were analyzed. It was found that although growing season evapotranspiration rates were roughly s i m i l a r for d i f f e r e n t canopy coverages, growing season t r a n s p i r a t i o n rate varied considerably. As stand density increased, growing season t r a n s p i r a t i o n rate tended to decrease. This was f e l t to be due to the large contribution of the grass component to the t r a n s p i r a t i o n at low canopy coverages. Canopy resistance increased with increasing vapour pressure d e f i c i t . Sites with higher s o i l water matric potentials had higher t r a n s p i r a t i o n rates. Gross Interception loss for a 100% canopy coverage was about 37% of the t o t a l r a i n f a l l . Both the breast height diameter and height growth rate decreased with increasing stand density. The r a t i o of the diameter to height was used successfully as a variable i n the l o c a l volume equation and decreased with increasing stand density. The highest growth rates (9 -11 m3 h a - 1 y e a r - 1 ) were found at stand densities of 901 - 1200 trees ha , and stand volumes of 225 to 300 m ha . At lower stand d e n s i t i e s , the annual volume growth rates tended to increase with increasing stand volumes. At stand densities of > 1500 trees h a - 1 , which had stand volumes of between 96 and 240 m ha , annual volume growth rate decreased with increasing stand volume. Furthermore, i t was found that there was a wide range of annual volume growth rates that can be obtained for a given stand volume. This v a r i a t i o n was due to d i f f e r e n t stand d e n s i t i e s . Stand diameter d i s t r i b u t i o n s which favoured annual volume growth rates had q-values (5 cm diameter classes) of between 1.28 and 1.29. ( i i i ) There was a positive correlation between annual volume growth rate and growing season transpiration for stands > 35% canopy coverage. At lower canopy coverages, the poor correlation was thought to be due to the large grass component. The reduction i n the annual volume growth rates of stand with densities > 1500 trees h a - 1 appeared to be due to increased between-tree competition and not solely to lower transpiration rates because of interception loss. ( i v ) TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS v LIST OF TABLES v i i i LIST OF FIGURES i x LIST OF SYMBOLS . x i v ACKNOWLEDGEMENTS x v i i 1. INTRODUCTION 1 2. THEORY 6 2.1 Forest Evapotranspiration 7 2.2 Relationship Between Growth and Transpiration 15 2.3 Uneven-age Stand Management 18 3. STUDY AREA 26 3.1 Location 27 3.2 Climate 29 3.3 Geology and S o i l s 29 3.4 Vegetation 35 3.5 Logging History 36 4. EXPERIMENTAL METHODS 40 4.1 Forest Water Balance 41 4.1.1 F i e l d Measurements 41 4.1.2 A n a l y t i c a l Methods 44 4.1.2.1 Net Radiation 44 4.1.2.2 Estimation of Evapotranspiration Using Water Balance Analysis 45 4.2 Volume Growth 48 4.2.1 F i e l d Measurements 48 4.2.1.1 Inventory Plots 48 A. Data C o l l e c t i o n for Core Analysis . . 48 B. Data C o l l e c t i o n for Stem Analysis . . 49 4.2.1.2 Permanent Sample Plots 49 4.2.2 A n a l y t i c a l Methods 51 4.2.2.1 Development of Local Volume Equation . . 51 4.2.2.2 Stand Growth 53 (v) TABLE OF CONTENTS ( cont inued) Page 5. RESULTS AND DISCUSSION 55 5.1 Water Balance Analysis 56 5.1.1 I n i t i a l Soil Water Storage at the Beginning of the Growing Season 56 5.1.2 Soil Water Storage Distribution in the Root Zone 60 5.1.3 Course of Soil Water Storage over the Growing Season 64 5.1.4 Evapotranspiration and Transpiration Rates Over the Growing Season 70 5.1.5 Factors Affecting Evapotranspiration and Transpiration 78 5.2 Relationships Derived from the Stem Analysis Trees . . . 91 5.2.1 Relationships Between Diameter, Age and Stand Density 91 5.2.2 Relationsips Between Height, Age and Stand Density 94 5.2.3 Relationships Between Diameter-to-Height Ratio and Stand Density 96 5.2.4 The Local Volume Equation . . . . 103 5.2.5 Relationship Between Form Factor, Tree Diameter and Stand Density 104 5.2.6 Reliability of the Local Volume Equation . . . . 106 5.3 Average Annual Volume Growth Relationships 109 5.3.1 Relationship Between Average Yearly Volume Growth and Stand Density and Volume 109 5.3.2 Relationship Between Average Annual Volume Growth and Stand Structure 118 5.3.3 Relationship Between Annual Volume Growth and Total Growing Season Transpiration 121 6. SUMMARY AND CONCLUSIONS 125 6.1 Conclusions 125 6.2 Management Implications 129 7. LITERATURE CITED 133 (vi) TABLE OF CONTENTS (continued) Page APPENDIX 1. Natural Regeneration Under a F a l l e r Selection Method 140 APPENDIX 2. Analysis of Fish-eye Lens Photographs to to Determine Canopy Coverage 143 APPENDIX 3. F o l i a r Analysis of the Lac Le Jeune and Knouff 12 km Sites . . . 149 APPENDIX 4. Analysis of average volume growth by diameter class for a l l inventory plots i n three stand density classes for the 1978-1983 season. 153 APPENDIX 5. The a, q and k c o e f f i c i e n t s , number of trees and stand volumes prior to logging, immediately following logging, and currently in the stand . . . 156 APPENDIX 6. Basal areas corresponding to the different stand volumes for the different density classes in 1983 163 ( v i i ) L I S T OF TABLES Page Table 1: S o i l c h a r a c t e r i s t i c s of the m i c r o c l i m a t e p l o t s 31 Table 2 . Summary of t rees sampled on the i n v e n t o r y p l o t s (on per p l o t [1/16 ha] b a s i s ) 50 Table 3 . V a r i a b l e s i n f l u e n c i n g the i n i t i a l s o i l water content 61 Table 4: Changes i n the s o i l water storage from May 3 to October 5, 1984 65 Table 5: E v a p o t r a n s p i r a t i o n ra tes over the growing season (mm d a y - 1 ) 72 Table 6: T r a n s p i r a t i o n ra tes over the growing season (mm d a y - 1 ) . 76 Table 7: Comparison of the t o t a l growing season evapo-t r a n s p i r a t i o n and t r a n s p i r a t i o n ra tes 77 Table 8: R a t i o of LE to [ s / ( s + y ) ] ( R n " G ) • ( A l s o shown are m e t e o r o l o g i c a l v a r i a b l e s used i n the c a l c u l a t i o n of the a v a i l a b l e e n e r g y . ) 79 Table 9: Average vapour pressure d e f i c i t s f o r d i f f e r e n t , . time i n t e r v a l s . . 85 Table 10: Average age and diameter at breast he ight f o r the d i f f e r e n t stand d e n s i t y c l a s s e s 92 Table 11: Cumulat ive average height growth r a t e f o r stands at d i f f e r e n t d e n s i t i e s . 98 Table 12: L o c a l volume t a b l e . 105 Table 13: T o t a l stand volume and d e n s i t y before l o g g i n g , immediately f o l l o w i n g l o g g i n g and i n 1983 110 Table 14: Cumulat ive t o t a l stand volume from time of l o g l a s t l o g g i n g to 1983 I l l Table 15: Course of annual volume growth 'from l o g g i n g to 1983 112 Table 16: Summary of the permanent p l o t a n a l y s i s 115 Table 17: Stand s t r u c t u r e c h a r a c t e r i s t i c s f o r d i f f e r e n t s tand d e n s i t i e s and growth r a t e s . . 119 ( v i i i ) L I S T OF FIGURES Page F i g u r e 1: R e l a t i o n s h i p s between the water balance and e v a p o t r a n s p i r a t i o n components f o r a f o r e s t e d , p a r t i a l l y f o r e s t e d and grass s i t e . Only t r e e s at l e a s t two metres i n he ight are cons idered part of the canopy. As the c o n t r i b u t i o n of the grass component i s much h igher than that of the t ree component f o r s i t e s w i t h l e s s than 5% canopy coverage, these s i t e s are cons idered " g r a s s " s i t e s 8 F igure 2: Map of study a r e a . The number l o c a t e d next the d i f f e r e n t symbols i n d i c a t e s the number of a c t u a l p l o t s at that s i t e . 28 F i g u r e 3: S o i l water r e t e n t i o n curves f o r the Lac Le Jeune s i t e . . . 32 F i g u r e 4: S o i l water r e t e n t i o n curves f o r the Knouff 12 km s i t e 33 F i g u r e 5: S o i l water r e t e n t i o n curves f o r the H e f f l e y s i t e . . . . 34 F i g u r e 6: R e l a t i o n s h i p between canopy coverage and s tand d e n s i t y 37 F i g u r e 7: C a l i b r a t i o n of the neutron probes . Probe A i s from the B . C . M i n i s t r y of Environment w h i l e Probe B i s from A g r i c u l t u r e Canada 43 F i g u r e 8: Course of the snow water e q u i v a l e n t depths on the p l o t s at the Knouff 12 km s i t e from January to June 1984 57 F i g u r e 9: Course of the snow water e q u i v a l e n t depths on the p l o t s at the Lac Le Jeune s i t e from January to June 1984 58 F i g u r e 10: Course of the snow water e q u i v a l e n t depths f o r the H e f f l e y , Knouff 14 km and R e c r e a t i o n Area p l o t s from January to June 1984 59 F i g u r e 11: D i s t r i b u t i o n of the s o i l water content f o r three p l o t s l o c a t e d at the Knouff 12 km s i t e on three d i f f e r e n t days 62 ( i x ) LIST OF FIGURES (continued) Page F i g u r e 12: D i s t r i b u t i o n of the s o i l water content f o r three p l o t s l o c a t e d at the Lac Le Jeune s i t e on three d i f f e r e n t days 63 F i g u r e 13: The r a i n f a l l events and course of root zone s o i l water storage f o r the p l o t s at the Knouff 12 km s i t e 66 F i g u r e 14: The r a i n f a l l events and course of root zone s o i l water storage for the p l o t s at the Lac Le Jeune s i t e 67 F i g u r e 15: The r a i n f a l l events and course of root zone s o i l water storage for the H e f f l e y p l o t 68 F i g u r e 16: The r a i n f a l l events and course of root zone s o i l water s torage f o r the R e c r e a t i o n Area and Knouff 14 km p l o t s 69 F i g u r e 17: Course of the s o l a r i r r a d i a n c e over the 1984 growing season. These values were c a l c u l a t e d as an average f o r the d a y l i g h t hours ( d a y l i g h t hours (N) are i n Table 8) 71 F i g u r e 18: The r e l a t i o n s h i p between the r a i n f a l l r e a c h i n g the ground ( P n ) and r a i n f a l l above the canopy (P) for d i f f e r e n t canopy coverages 74 F i g u r e 19: Changes i n P n / P (c) w i t h canopy coverage 75 F i g u r e 20: R e l a t i o n s h i p of the e v a p o t r a n s p i r a t i o n ra tes to s o i l water storage and a v a i l a b l e energy (R n - G ) . A v a i l a b l e energy was c a l c u l a t e d as the average f o r the d a y l i g h t hours 80 F i g u r e 21: The time course of E and T, the a v a i l a b l e energy and vapour pressure d e f i c i t s f o r three p l o t s at the Knouff 12 km s i t e over the 1984 growing season. 82 F i g u r e 22: The time course of E and T, the a v a i l a b l e energy and vapour pressure d e f i c i t s f o r three p l o t s at the Lac Le Jeune s i t e over the 1984 growing season. 83 F i g u r e 23: D a i l y t races of vapour pressure d e f i c i t s f o r three d i f f e r e n t days 84 (x) LIST OF FIGURES (continued) Page F i g u r e 24: R e l a t i o n s h i p s between t r a n s p i r a t i o n and vapour pressure d e f i c i t s f o r d i f f e r e n t canopy coverages and s o i l water matr i c p o t e n t i a l s grea ter than - 0 . 5 MPa 87 F i g u r e 25: R e l a t i o n s h i p s between t r a n s p i r a t i o n and vapour pressure d e f i c i t s f o r d i f f e r e n t canopy coverages and s o i l water m a t r i c p o t e n t i a l s l e s s than - 0 . 5 MPa 88 F i g u r e 26: R e l a t i o n s h i p s between canopy r e s i s t a n c e (dry ) and vapour pressure d e f i c i t f o r d i f f e r e n t canopy coverages and s o i l water m a t r i c p o t e n t i a l s g r e a t e r than - 0 . 5 MPa 89 F i g u r e 27: R e l a t i o n s h i p s between canopy r e s i s t a n c e (dry) and vapour pressure d e f i c i t s f o r d i f f e r e n t canopy coverages and s o i l water m a t r i c p o t e n t i a l s l e s s than - 0 . 5 MPa 90 F i g u r e 28: R e l a t i o n s h i p s between diameter at breast h e i g h t (d) and age f o r three d i f f e r e n t stand d e n s i t i e s . Each l i n e i s the average diameter growth of f o u r t rees which were greater than 125 years o l d 93 F i g u r e 29: R e l a t i o n s h i p of the p r o p o r t i o n a l i t y constant (m) to stand d e n s i t y . 95 F i g u r e 30: R e l a t i o n s h i p s between t o t a l he ight and age f o r three d i f f e r e n t stand d e n s i t i e s . Each l i n e i s an average of the he ight growth of four t rees which were greater than 125 years o l d . F i g u r e 31: R e l a t i o n s h i p s between the cumulat ive he ight growth and stand d e n s i t y . 99 F i g u r e 32: R e l a t i o n s h i p s between he ight and diameter at breast he ight f o r three d i f f e r e n t stand d e n s i t i e s . . . 100 F i g u r e 33: R e l a t i o n s h i p s between he ight and diameter at breast he ight f o r three d i f f e r e n t stand d e n s i t i e s . . . 101 F i g u r e 34: R e l a t i o n s h i p between the d/H r a t i o and stand d e n s i t y . The l i n e drawn i s from Equat ion (54) . . . 102 ( x i ) LIST OF FIGURES (continued) Page F i g u r e 35: R e l a t i o n s h i p between the form f a c t o r and stand d e n s i t y f o r s e v e r a l values of diameter at breast h e i g h t 107 F i g u r e 36: Comparison of p r e d i c t e d versus a c t u a l volumes of t rees 5 , 10 and 20 years ago. The s o l i d l i n e represents a 1:1 r e l a t i o n s h i p . The dashed l i n e represents the average r e l a t i o n s h i p of the p r e d i c t e d and a c t u a l volumes f o r a l l three t ime p e r i o d s . The a c t u a l equat ions f o r the p r e d i c t e d (Vp) 5, 10 and 20 years ago, as d e r i v e d from the a c t u a l volume ( V a ) are V p = 0.013 m 3 + 0.909 V a ; V p = 0.005 m 3 + 0.924 V a ; and V p = 0.007 m 3 + 0.895 V a , r e s p e c t i v e l y 108 F igure 37: The time course of the volume growth ra te as r e l a t e d to stand d e n s i t y . The 301 - 600 and 601 - 900 l i n e s represent an average of two p l o t s each w h i l e the 901 - 1200 l i n e represents an average of three p l o t s . Only one p l o t i s i n c l u d e d i n the 2701 - 3000 l i n e . . 113 F i g u r e 38: The r e l a t i o n s h i p of t o t a l stand volume to annual volume growth f o r the d i f f e r e n t d e n s i t y c l a s s e s . Both the i n v e n t o r y and permanent sample p l o t s are i n c l u d e d . 117 F i g u r e 39: The r e l a t i o n s h i p between annual volume growth and t o t a l growing season t r a n s p i r a t i o n . The e r r o r bars shown are f o r a 25 cm d t ree w i t h an approximate he ight of 29 m [Equation ( 5 2 ) ] , and assume that the e r r o r s i n diameter and h e i g h t were 0.1 mm and 0 .5 m, r e s p e c t i v e l y , f o r a one year growth p e r i o d on the permanent sample p l o t s and 0.1 mm and 0.1 m, r e s p e c t i v e l y , f o r a f i v e year growth p e r i o d on the i n v e n t o r y p l o t s . The form f a c t o r was determined to be 1.2 [Equat ion (62)] Open symbols i n d i c a t e p l o t s l o c a t e d next to a m i c r o c l i m a t e s t a t i o n , w h i l e the c l o s e d symbols i n d i c a t e that T was i n t e r p o l a t e d from the m i c r o -c l i m a t e p l o t s which had s i m i l a r s o i l c h a r a c t e r -i s t i c s ( from Table 7 ) . P l o t s marked w i t h a P are permanent sample p l o t s w h i l e the remainder are i n v e n t o r y p l o t s 123 ( x i i ) LIST OF FIGURES (continued) Page F i g u r e 40: R e l a t i o n s h i p between annual volume growth and t o t a l stand volume i n t e r p r e t e d f o r management purposes . M a i n t a i n i n g t h i s stand i n Zone A w i t h 900 to 1200 t r e e s ha w o u l d be cons idered o p t i m a l . The c u t t i n g c y c l e would be ten y e a r s . In cases where, a 20 year c u t t i n g c y c l e i s d e s i r e d , stands should be mainta ined w i t h between 800 - 1300 t rees h a - 1 and w i t h stand volumes represented by Zone B. Logging i n Zone C should be done w i t h c a u t i o n i f there are > 1500 t r e e s h a - 1 on the s t a n d , as stem c o l l a p s e would l i k e l y be a problem. Logging down to Zone D would be unacceptab le , p a r t i c u l a r l y i f < 400 t rees h a - 1 remain a f t e r l o g g i n g . This i s due to both r e g e n e r a t i o n problems and low annual volume growth r a t e s . In a l l cases , uneven-age s tand diameter d i s t r i b u t i o n s w i t h some l a r g e r r e s i d u a l t rees should be mainta ined 131 ( x i i i ) LIST OF SYMBOLS Symbol A basal area m D drainage rate mm day" 1 D vapour pressure d e f i c i t kPa E evapotranspiration rate mm day E(j dry evaporation rate mm day E 0 free evaporation rate mm day E s s o i l evaporation rate mm day E w wet evaporation rate mm day F c o n i c a l form factor dimensionless F j f r a c t i o n of the period leaves are dry dimensionless F w f r a c t i o n of the period leaves are wet dimensionless G s o i l heat f l u x density W m - 2 H sensible heat f l u x density W m - 2 H height m I gross interception loss mm d a y - 1 I t gross tree interception loss mm d a y - 1 Ig gross grass interception loss mm d a y - 1 L l atent heat of vaporization J k g - 1 L length m M rate of canopy energy storage W m N number of trees trees N daylength hours P above canopy rate of p r e c i p i t a t i o n mm d a y - 1 (xiv) Symbol P n below canopy rate of p r e c i p i t a t i o n mm day - 1 R rate of runoff mm day - 1 RH r e l a t i v e humidity % R n net r a d i a t i o n flux density W m S t s o l a r irradiance W m T . t o t a l t r a n s p i r a t i o n rate mm day - 1 T a a i r temperature °K Tfi dry leaf t r a n s p i r a t i o n rate mm day - 1 Tg grass t r a n s p i r a t i o n rate mm day - 1 Tj; tree t r a n s p i r a t i o n rate mm day - 1 U windspeed m s - 1 V volume of tree m V c volume of cone m W s o i l water storage ram a solar absorption c o e f f i c i e n t of vegetation dimensionless a rate of change in number of trees in successive diameter classes cm - 1 c tree throughfall c o e f f i c i e n t dimensionless Cp s p e c i f i c heat of moist a i r J k g - 1 °C~ 1 d diameter (at breast height unless otherwise noted) cm or m e a * saturation vapour pressure of the a i r kPa g age years h diameter class i n t e r v a l cm (xv) Symbol r c d r c t A Y £a e v 9 P a number of trees per hectare per diameter i n t e r v a l sunshine hours r a t i o of trees in successive diameter classes (5 cm classes i n t h i s t hesis) aerodynamic resistance canopy resistance as defined by Equation (13) dry canopy resistance canopy resistance as defined by Equation (21) slope of saturation vapour curve r a t i o of \ . a x to Egq for vegetation with dry leaves change i n associated parameter psychrometric constant emissivity of the atmosphere emissivity of the vegetation volumetric s o i l water content density of moist a i r Stefan-Boltzmann constant s o i l water matric p o t e n t i a l trees ha 1 cm"1 hours dimensionless s m~ 1 s m s m s m _ - 1 kPa "C" 1 dimensionless dimensionless kPa ° C _ 1 dimensionless dimensionless 3 - 3 m m -3 kg m MJ m - 2 d" 1 MPa (xvi) ACK NOWLEDGEMENTS There are several people for whose assistance I am very g r a t e f u l . Of p a r t i c u l a r importance were the help and guidance of my major supervisor, Dr. T.A. Black, and the l o g i s t i c a l support and suggestions of Mr. Trevor Jeanes, Vice-President of Balco Industries Ltd. Additional people who provided valuable assistance from Balco Industries are Randall Chan, Douglas G i l e s , Kenneth MacAulay, Patrick Linge, Dennis Crabtree and Keith Brown. People whom I would l i k e to thank for their advice throughout the study and assistance in reviewing the work are Dr. Peter Marshall of U.B.C, Dr. Kenneth M i t c h e l l , Dr. Wayne Johnstone, Dr. Dave Spittlehouse and Mr. Alan Vyse of B.C. Ministry of Forests, and B i l l Colter of Crown Forest Products. F i e l d equipment was provided by Rod Davis, B.C. Ministry of Environment, Bruce Clark and Dr. Jack Cheng, B.C. Ministry of Forests, and Dr. A l Van Ryswyk, Agriculture Canada. Rocky Hudson, B.C.F.S., supplied equipment and some assistance for data c o l l e c t i o n . Bob M i t c h e l l , B.C. M i n i s t r y of Forests, assisted in the s i t e s e l e c t i o n . Other f i e l d assistants include Renata Piedmont and Rene Thomson. Dr. Roy Strang, Forest Research Council, provided monetary support. F i n a l l y I would l i k e to acknowledge my husband, Jerry, for his understanding and support and also assistance with the graphics. I w i l l always be g r a t e f u l to Maureen Browning who typed the manuscript. ( x v i i ) 1 1. INTRODUCTION 2 1- INTRODUCTION Uneven-age stands c h a r a c t e r i z e the i n t e r i o r D o u g l a s - f i r (IDF) b i o g e o c l i m a t i c zone as a r e s u l t of past l o g g i n g p r a c t i c e s , the frequency and s i z e of n a t u r a l f i r e s , and the shade t o l e r a n c e of i n t e r i o r D o u g l a s - f i r (Pseudotsuga m e n z i e s s i i var g lauca [Bessin] F r a n c o ) . A l l f o r e s t stands i n the d r i e r IDF subzones are c u r r e n t l y r e q u i r e d to have some form of p a r t i a l l o g g i n g as o u t l i n e d i n the Kamloops s i l v i c u l t u r e guide ( B . C . F . S . 1979). This i s p a r t l y to prevent the h i g h ground surface temperatures which would r e s u l t from a c l e a r c u t . The c u t t i n g method should r e l y on n a t u r a l regenera t ion as p l a n t a t i o n success i s very low ( C l a r k 1962). Widespread use of diameter l i m i t and s e l e c t i o n l o g g i n g systems has s l o w l y changed to a f a l l e r ' s s e l e c t i o n system of management. This system i s used p r i m a r i l y to encourage regenera t ion but has the added advantage of enhancing the m u l t i p l e resource uses of t h i s land base (Johnstone 1984). Both the shelterwood (even-age) or s e l e c t i o n (uneven-age) r e g e n e r a t i o n systems would be s u c c e s s f u l o b t a i n i n g n a t u r a l r e g e n e r a t i o n ( K o s t l e r 1956); however the l a t t e r i s the ' p r e f e r r e d management system' ( B . C . M . F . 1981) i n the Kamloops a r e a . T h e r e f o r e , t h i s t h e s i s w i l l dea l w i t h uneven-age s t a n d s . Shading , u s u a l l y i n the form of canopy coverage, can create f a v o u r -able c o n d i t i o n s f o r n a t u r a l r e g e n e r a t i o n (Helgerson et a l . 1982; Smith 1979) . S o i l temperature , p a r t i c u l a r l y at the s u r f a c e , i s a f f e c t e d by the amount of shade ( C h i l d s et_ al_. 1985; Marquis 1979; McDonald 1976; W i l l i a m s o n 1973; Roeser 1924). Isaac (1937) found t h a t , as a general r u l e , s o i l sur face temperatures , on a sunny day, cou ld be 15-20°C h igher on f u l l y exposed s u r f a c e s , and 8-10°C h igher under a brush canopy than 3 the corresponding a i r temperature . He found i t was approximate ly equal to the a i r temperature under a c l o s e d f o r e s t canopy. S ta thers (1983), i n a study of a steep ( 3 0 ° ) , south f a c i n g s lope on Vancouver I s l a n d , B . C . , found that the daytime s o i l sur face temperatures d u r i n g the summer remained above 50°C f o r seven h o u r s , and above 30°C f o r nine hours on a c l e a r c u t . On areas which were shaded w i t h shade c a r d s , s o i l sur face temperatures never exceeded 50°C, and there were only s i x hours when they were greater than 30°C. In Oregon, C h i l d s et_ a l . (1985) showed that a shelterwood system s i g n i f i c a n t l y amel iora ted seasonal s o i l temperature c o n d i t i o n s and suggested that i t may be an a p p r o p r i a t e technique where h i g h s o i l temperatures l i m i t r e f o r e s t a t i o n success . I n s o l a t i o n damage to s e e d l i n g c o n i f e r s occurs at 64°C w i t h exposure p e r i o d s of l e s s than one hour (Maguire 1955), but death from s e e d l i n g d e s s i c a t i o n or cambial damage can occur at lower temperatures of longer " d u r a t i o n ( B a l l a r d 1981; Smith 1951). Shading a l s o i n f l u e n c e s shoot and root growth. Increased shading i n c r e a s e s root growth and decreases root r e s p i r a t i o n and shoot growth (Krauch 1956), reduc ing the shoot to root r a t i o , t r a n s p i r a t i o n a l l e a f s u r f a c e area and subsequent mois ture l o s s , thus i n c r e a s i n g drought r e s i s t a n c e (Ryker and P o t t e r 1970). Too much canopy c l o s u r e , however, i n c r e a s e s the s o i l moisture and root c o m p e t i t i o n and decreases the p h o t o s y n t h e t i c photon f l u x d e n s i t y i n c i d e n t on the p l a n t . Optimal shade f o r D o u g l a s - f i r occured between 50% ( W i l l i a m s o n 1973) and 65% (Strothman 1972) canopy c l o s u r e i n the Oregon Cascades and nor thern C a l i f o r n i a , r e s p e c t i v e l y . 4 A f a v o u r a b l e seedbed i s a l so r e q u i r e d f o r s u c c e s s f u l i n t e r i o r D o u g l a s - f i r s e e d l i n g e s t a b l i s h m e n t . The most f a v o u r a b l e seedbed would c o n s i s t of approximate ly 25% m i n e r a l s o i l ( B a l l a r d 1981; S e i d a l 1979; W i l l i a m s o n 1973; Smith 1951), a loose g r a n u l a r s t r u c t u r e , a l i g h t e r c o l o u r to reduce s o l a r r a d i a t i o n a b s o r p t i o n (Krauch 1956; Roeser 1924), and a loose l i t t e r l a y e r which would r e t a i n the s o i l sur face mois ture (Krauch 1956). S e l e c t i o n l o g g i n g w i l l g e n e r a l l y m e c h a n i c a l l y d i s t u r b the s o i l s u f f i c i e n t l y f o r seedbed p r e p a r a t i o n . In a problem a n a l y s i s by C l a r k (1962) on the B i g Bar Sus ta ined Y i e l d U n i t i n i n t e r i o r B r i t i s h Columbia , i t was found that 91% of the t o t a l number of s e e d l i n g s e s t a b l i s h e d occurred where seedbed and shade requirements were adequate. I n a p r e l i m i n a r y examinat ion of the study area by the a u t h o r , i t was found that s o i l sur face temperatures were reduced s i g n i f i c a n t l y under d i f f e r e n t canopy coverages , and s e e d l i n g es tab l i shment was adequate (Appendix 1 ) . Whereas s o i l sur face temperatures tend to be the major f a c t o r i n f l u e n c i n g s e e d l i n g e s t a b l i s h m e n t , s o i l moisture may be the major f a c t o r i n f l u e n c i n g the growth of the r e s i d u a l stems (Watts 1983; M i t c h e l l and Green 1981). S e l e c t i o n l o g g i n g may be caus ing changes i n the water regime which cou ld a f f e c t the t r a n s p i r a t i o n r a t e of the f o r e s t s t a n d . These changes w i l l i n f l u e n c e the growth ra te of the r e s i d u a l stems. Al though increased growth r a t e s on the i n d i v i d u a l t rees are not uncommon f o l l o w i n g a p a r t i a l l o g g i n g , the c u t t i n g l e v e l and r e s i d u a l stand volumes necessary f o r o p t i m a l growth are unknown. Consequent ly , the o b j e c t i v e s of t h i s t h e s i s a r e : 1. To i n v e s t i g a t e how p a r t i a l l o g g i n g I n f l u e n c e s the s o i l water regime of uneven-aged i n t e r i o r D o u g l a s - f i r s tands . 5 2 . To determine the changes i n the volume growth of r e s i d u a l stems i n these stands as a r e s u l t of d i f f e r e n t s tand s t r u c t u r e s and d e n s i t i e s . In order to meet these o b j e c t i v e s , there were two s t u d i e s under taken . The f i r s t , c a r r i e d out at two w i d e l y separated s i t e s , p r i m a r i l y d e a l t w i t h the water balance i n stands having a wide range of s tand d e n s i t i e s . T h i s r e q u i r e d the i n s t a l l a t i o n of s i x weather s t a t i o n s and e leven s o i l mois ture sampling ( m i c r o c l i m a t e ) p l o t s . The second study d e a l t w i t h the long term (5-30 years ) growth ra tes of twenty-two 1/16 ha i n v e n t o r y p l o t s u s i n g stem a n a l y s i s and increment core measurements. These p l o t s and four a d d i t i o n a l p r e v i o u s l y e s t a b l i s h e d permanent sample p l o t s were l o c a t e d near the m i c r o c l i m a t e p l o t s . 6 2 . THEORY 7 2. THEORY 2.1 Forest Evapotranspiration Forest evapotranspiration is an important component of the water balance equation: where AW, P, E, D, and R are, respectively, the rate of change i n the s o i l water storage i n the root zone, and the rates of p r e c i p i t a t i o n , evapotranspiration, drainage and runoff which occurred during the time i n t e r v a l , At. Evapotranspiration rate can be defined as where T t i s the tree t r a n s p i r a t i o n rate, I t and Ig are the rates of gross interception loss from the tree and grass cover, respectively, Tg i s the grass t r a n s p i r a t i o n rate, and E s is the evaporation rate from the s o i l . Under a f u l l y closed canopy, the la s t three terms of (2) are usually small when compared to the f i r s t two terms, because only a r e l a t i v e l y small f r a c t i o n of solar r a d i a t i o n reaches the forest f l o o r . As the canopy becomes less dense, Tg becomes greater. In t h i s thesis, T = T t + Tg , Ig w i l l be assumed to be n e g l i g i b l e , so that I « I t , and E s w i l l also be assumed to be n e g l i g i b l e . The variables i n (1) and (2) are i l l u s t r a t e d i n F i g . 1. The energy transfer required for the evapotranspiration of water i s the latent heat flux density, LE, (the latent heat of vaporization, L, multiplied by E) and i s an important component of the forest energy balance: P + E + D + R - AW/At = 0 (1) E = T t + I t +.Tg + tg + E, s (2) ro . AW/At T D AW/At T D AW/At TD FORESTED (>85% Canopy Coverage) PARTIALLY FORESTED (5-85% Canopy Coverage) GRASS (0-5% Canopy Coverage) Figure 1: Relationships between the water balance and evapotranspiration components for a forested, p a r t i a l l y forested and grass s i t e . Only trees at least two metres i n height are considered part of the canopy. As the contribution of the grass component i s much higher than that of the tree component for sites with less than 5% canopy coverage, these sites are considered "grass" si t e s . R n - H - L E - G - M = 0 9 (3) where R^, H, and G are the net ra d i a t i o n , sensible and s o i l heat flux d e n s i t i e s , respectively, and M i s the rate of canopy energy storage. The exchange of sensible and latent heat between the atmosphere and the forest stand i s f a c i l i t a t e d by turbulence within and above the canopy (Campbell 1977). Selection logging to d i f f e r e n t stand structures and densities not only a l t e r s the microclimate [ i . e . , changing the terms i n (3)], but may influence evapotranspiration enough to s i g n i f i c a n t l y change the water balance. Penman (1948) combined the surface energy balance equation (3) and the eddy d i f f u s i o n equations of sensible and latent heat to produce the well-known Penman evaporation equation. Monteith (1965) introduced the physiologically-based canopy resistance into the equation to give the Penman-Monteith equation for c a l c u l a t i n g the tr a n s p i r a t i o n rate assuming the canopy is dry (T^) as follows pc D s(R n - G) + - j E -T d = ±— (4) C d ^ L ( s + Y ( l + — ) ) where R n - G i s the available energy f l u x density, and p, Cp, y> L, and s are, respectively, the density of a i r , s p e c i f i c heat of a i r , the psychrometric constant, the latent heat of vaporization, and the slope of the saturation vapour pressure curve evaluated at the a i r 10 temperature. The aerodynamic resistance, r a , i s the eddy d i f f u s i o n resistance between the canopy and the measurement height above the stand. The canopy resistance for a canopy with dry leaves ( r C ( j ) i s given by where LAI^ and rs± are the leaf area index and stomatal resistance of the i t h layer of the canopy. Since E i s the sum of the evaporation and t r a n s p i r a t i o n rates, evaporation w i l l be eliminated by correcting for the gross interception loss from the trees. Evaporation losses due to gross i n t e r c e p t i o n under a 100% canopy coverage can be over 20% of the growing season r a i n f a l l (Spittlehouse and Black 1981). Giles et a l . (1985) found 8% and 30% of the growing season r a i n f a l l was loss under a 60% and 100% canopy coverage, re s p e c t i v e l y . When the leaves are wet, the average rate of evapotranspiration can be written as the sum of the evaporation rate from a completely wet canopy and the dry canopy t r a n s p i r a t i o n rate ( E w and T d, r e s p e c t i v e l y ) weighted by the f r a c t i o n of the period the leaves are wet and dry ( F w and F j , respectively) as follows n red -. J 1 G r s i (5) LAIi E = F w E w + F d T d (6) The f r a c t i o n of the period the leaves are wet i s given by F w = I/F^ (7) 11 where I i s the rate of gross interception loss over the entire period. The f r a c t i o n of the period the leaves are dry i s given by F d = 1 - F w (8) The evaporation rate from leaves when completely wet, i s pc D s(R - G) + — L _ n E w = IS ( 9 ) L(s + Y ) Substituting (7) and (8) into (6) gives E = T d + 1(1 - T d/E w) (10) Substituting (9) and (4) into (10) gives , s ( R n - G) + pc pD/r a ^ _ s + Y ^ ^ L(s + Y(l + s + Y ( l + r a r a so that PCpD s(R n - G) + _ E = - _ (12) L(s + Yd + [1 - J - ] ) ) ^ Therefore, an equation for E which would take into account periods when leaves are wet for part of the time can be written as s(R n - G) + — pc pD E = ^ (13) L ( s + Y ( l +-T")) 12 where the combined wet and dry canopy resistance ( r c ) i s r c = (1 - I / E ) r c d (14) Equation (14) i s Thorn and Oliver's (1977) equation (25). The average t r a n s p i r a t i o n rate for a canopy for which there i s gross interception losses i s , neglecting s o i l evaporation, T = E - I (15) Equation (10) can be substituted into equation (15) to give T d T = T d - I _ 1 _ (16) Ew Sub s t i t u t i n g (9) and (4) into (16) gives pcDD s(R n - G) —f- I(s + y) X = : - (17) L(s + Y ( i + - £ ! )) s + Y ( l + - £ ! ) or pcDD s(R n - G) + -f- - LI(s + y) T = ~ (18) r c d L[s + y ( l + - T 2 - ) ] The canopy resistance of the canopy (while i t i s dry) during a period i n 13 which the leaves are wet part of the time i s obtained using (18) rewritten as r r c d <, P°o D LT(s + y(l + -£2-)) = s(Rn - G) + — 2 LI(s + Y) d9 ) so that pc DD r s , ( R n " G) i j r c d = — E - + r a ._( J L - - - 1 - 1 - 1 (19a) C d YLT a L Y LT T T Note that this reduces to equation (2) of Tan and Black (197 6) when 1 = 0 and T = E, i . e . pc DD s (R n - G) r c d - ^ + r a [ - ( - - 2 — - 1 ) - 1] (20) If a canopy resistance ( r c t ) was defined as follows pepD s(R n - G) + -f-T = (21) L[s + y(l r a for a period during which r a i n occurred, then r c t would be ' c f ^ + r . (22) The r e l a t i o n s h i p between r c d and r c t obtained by subtracting (22) from (19a) i s 14 s + y Y (23) P r i e s t l e y and Taylor (1972) demonstrated that for a smooth dry-leafed vegetative surface (e.g. a g r i c u l t u r a l crop), with adequate water, t r a n s p i r a t i o n i s well correlated with the f i r s t , or r a d i a t i v e term, of the Penman-Monteith equation, so that i t could be expressed as where a i s an experimentally determined constant. This approach has been shown to work quite well for extremely rough surfaces (e.g. forests) on a daytime or 24 hour basis (Spittlehouse and Black 1981; Shuttleworth and Calder 1978; McNaughton and Black 1973). Over shorter time periods (e.g., one hour), Tan and Black (1976) showed that the t r a n s p i r a t i o n from dry-leafed forest stands can be estimated to a good approximation by Note that pc p/(LY) = (Rv Ta)~ where R v i s the gas content for water vapour and T a i s the a i r temperature. Equation (18) reduces to this equation when 1 = 0 and r a approaches zero, as i s the case f o r f o r e s t s , and the contribution of the r a d i a t i v e term becomes small. In this case, t r a n s p i r a t i o n i s primarily a function of D and r c . Stomatal resistance of forest canopies i s a function of photosyn-t h e t i c photon (0.4 - 0.7 vim) f l u x density, s o i l water p o t e n t i a l (4 S) T d = a[s/(s + Y ) ] ( R n - G)/L (24) T d = [ p c p / ( L Y ) ] [ D / r c d ] (25) 15 (or predawn l e a f water p o t e n t i a l ) and vapour pressure d e f i c i t (McNaughton and J a r v i s 1983). Tan et_ a l . (1978) found t h a t , d u r i n g the dayt ime, s tomatal r e s i s t a n c e was r e l a t e d to s o i l water p o t e n t i a l and D i n D o u g l a s - f i r t rees on Vancouver I s l a n d . They showed that E i n c r e a s e d w i t h i n c r e a s i n g D, r e a c h i n g a maximum value and t h e r e a f t e r d e c l i n i n g , as a r e s u l t of r s i n c r e a s i n g markedly w i t h D. They a l so found that the va lue of D at maximum t r a n s p i r a t i o n i n c r e a s e d w i t h i n c r e a s i n g i( , s . 2 .2 R e l a t i o n s h i p Between Growth and T r a n s p i r a t i o n I t has been recognized f o r many years t h a t , f o r many p l a n t s , growth i s c o r r e l a t e d w i t h t r a n s p i r a t i o n . Boyer (1976) suggested that t h i s e m p i r i c a l r e l a t i o n s h i p can be used to es t imate growth. De Wit (1958) was the f i r s t to f o r m a l i z e t h i s e m p i r i c a l r e l a t i o n s h i p as Y = mT (26) where Y i s the ra te of crop dry matter y i e l d and m i s an e x p e r i m e n t a l l y determined c o n s t a n t . This equat ion worked w e l l f o r a g r i c u l t u r a l crops at mid to n o r t h e r n l a t i t u d e s ( e . g . W a l l i s et^ a l . (1983) f o r hay crops i n the B . C . Peace R i v e r r e g i o n ) . In a r i d c o n d i t i o n s where moisture was l i m i t e d , (26) d i d not work w e l l . For t h i s case , de Wit (1958) found that dry matter y i e l d ra te was b e t t e r determined as Y = n T / E Q (27) 16 where n i s an e x p e r i m e n t a l l y determined constant and E 0 i s the f ree water e v a p o r a t i o n r a t e . Equat ion (27) s ta tes that Y i s approximately i n v e r s e l y p r o p o r t i o n a l to s tomata l r e s i s t a n c e . This i s because the l a t t e r i s approximate ly p r o p o r t i o n a l to E 0 / T i n a r i d c o n d i t i o n s where E Q tends to be p r o p o r t i o n a l to D. Assuming aerodynamic and boundary l a y e r r e s i s t a n c e s are s m a l l , l e a f t r a n s p i r a t i o n i s equal to ( R v T a ) ~ ^ D / r g ) and the net p h o t o s y n t h e s i s i s equal to ( c a - C i ) / r s , where c a and c^ are the c o n c e n t r a t i o n s of atmospheric and i n t e r n a l ( l e a f ) carbon d i o x i d e , r e s p e c t i v e l y . Consequent ly , the r a t i o of y i e l d to t r a n s p i r a t i o n would be B i e r h u i z e n and S l a t y e r (1965) suggested that where the c ^ / c a r a t i o was c o n s t a n t , ra te of dry matter y i e l d c o u l d be expressed as where D/T i s p r o p o r t i o n a l to s tomata l r e s i s t a n c e , and the c o n s t a n t , k , was s i m i l i a r to de W i t ' s c o n s t a n t , n . Wong et a l . (1981) found that the c i / c a r a t l ° w a s constant i n s e v e r a l p l a n t s . Tanner (1981) a p p l i e d e q u a t i o n (29) to a potato l ea f and es t imated the y i e l d f o r an e n t i r e crop by summing t h i s f o r the l e a f area index (LAI) of the c r o p , and i n c l u d i n g the e f f e c t of growth and maintenance r e s p i r a t i o n . Y/T = c a ( l - C i / c a ) R v T a / D (28) Y = kT/D (29) 17 In f o r e s t r y , several workers have shown a good c o r r e l a t i o n between growing season water d e f i c i t s , or t r a n s p i r a t i o n , and growth. Forest s i t e indices on Vancouver Island were shown to correlate well with growing season water d e f i c i t s and t r a n s p i r a t i o n , while basal area annual increments were found to be correlated to s o i l water d e f i c i t s (Giles et a l . 1985). Spittlehouse (1983) also found good a c o r r e l a t i o n between tree growth and t r a n s p i r a t i o n , and suggested that a water balance model could be used to i n d i c a t e s i t e p r o d u c t i v i t y . Jarvis et a l . (1983) developed an evapotranspiration growth model for Sitka spruce i n which a growth index, which was a function of s o i l water d e f i c i t , was found to be well correlated with annual volume growth. Leaf area index, which has been found to be l i n e a r l y related to estimated s o i l water d e f i c i t s , i s c l o s e l y related to stand productivity (Gohlz 1982; Schroeder et_ a l . 1982; Grier and Running 1977). Emmingham and Waring (1977) found a very high c o r r e l a t i o n between a photosynthetic index (which combined the influence of a i r and s o i l temperatures and available s o i l moisture on photosynthesis) and forest p r o d u c t i v i t y . Reductions i n the t r a n s p i r a t i o n rate due to higher stoma-t a l resistances and low s o i l water po t e n t i a l s , as found by Tan et_ a l . (1978), would be expected to r e s u l t i n a proportional reduction of the photosynthetic rate and, therefore, the growth rate. P r i c e et_ a l . (1985), however, found that unless D i s high, and l i g h t i s not l i m i t i n g , photosynthesis in coastal Douglas-fir was not generally l i m i t e d by stomatal resistance, although a reduction i n t r a n s p i r a t i o n may have occurred. In this study s o i l water p o t e n t i a l might be expected to vary with stand density as a r e s u l t of differences i n snow through-f a l l and melt, r a i n f a l l i n t e r c e p t i o n loss and t r a n s p i r a t i o n rate. 18 2.3 Uneven-age Stand Management Gibbs (1978) d e f i n e d uneven-age s i l v i c u l t u r e and management as the " m a n i p u l a t i o n of a f o r e s t f o r a continuous h i g h - f o r e s t c o v e r , r e c u r r i n g r e g e n e r a t i o n of a d e s i r a b l e s p e c i e s , and the o r d e r l y growth and development of t rees through a range of age or diameter c l a s s e s to p r o v i d e a sus ta ined y i e l d of f o r e s t p r o d u c t s . Managed uneven-age f o r e s t s are c h a r a c t e r -i z e d by t rees of many ages, or s i z e s , i n t e r m i n g l e d s i n g l y or i n groups. Trees are harvested s i n g l y or i n very s m a l l groups and the process of r e g e n e r a t i o n of the d e s i r a b l e spec ies occurs e i t h e r c o n t i n u o u s l y or at each h a r v e s t . Each harvest u s u a l l y i n c l u d e s t h i n n i n g and c u l t u r a l treatments to promote growth and m a i n t a i n or enhance stand s t r u c t u r e . " The advantages of the s e l e c t i o n method, as i n d i c a t e d i n the i n t r o d u c -t i o n , i n c l u d e ensur ing the n a t u r a l r e g e n e r a t i o n of a t o l e r a n t species and e x c e l l e n t s i t e p r o t e c t i o n , w i t h l i t t l e or no exposure to i n s o l a t i o n or wind ( D a n i e l et_ a l . 1979). Johnstone (1984) suggests that i n order to apply the f a l l e r ' s s e l e c t i o n method i t i s necessary to ( i ) m a i n t a i n an evenly d i s t r i b u t e d f o r e s t cover , ( i i ) remove poor q u a l i t y t r e e s , and ( i i i ) improve s p a c i n g . The three major aspects of the s t r u c t u r e of an uneven-age stand are volume, diameter d i s t r i b u t i o n and spec ies compos i t ion (Davies 1966). As t ree spec ies other than i n t e r i o r D o u g l a s - f i r are only a minor component ( l e s s than 10%) of the uneven-age stands i n the I D F a and IDF^ subzone i n the i n t e r i o r of B . C . , on ly the f i r s t two w i l l be d i s c u s s e d , together w i t h t h e i r i n t e r r e l a t i o n s h i p s . Volume growth p r e d i c t i o n s have been developed i n B . C . f o r s e v e r a l t ree s p e c i e s , but u n f o r t u n a t e l y , are only a v a i l a b l e f o r pure even-age stands and g e n e r a l l y i n v o l v e s i t e index or p r o d u c t i v i t y as a f u n c t i o n of age. Meyer et_ aT. (1952) s ta tes that "under t h i s concept of (uneven-age) management the a c t u a l age of any g iven t ree or group of t rees i s of l i t t l e or no 19 p r a c t i c a l importance . Volume per acre cannot be expressed as a f u n c t i o n of age, and the use of the r o t a t i o n as the b a s i s f o r r e g u l a t i o n i s no longer v a l i d . S i m i l a r l y , y i e l d t a b l e s based on stand age are meaningless because s i t e index cannot be obta ined from dominant t ree c h a r a c t e r i s t i c s as determined f o r even-age s t a n d s . An e n t i r e l y d i f f e r e n t ph i losophy of management based on d i f f e r e n t concepts and c h a r a c t e r i s t i c s must be e v o l v e d . " Walker (1956) f u r t h e r concluded that "the a d a p t a t i o n of net y i e l d t a b l e data from even-age stands to uneven-age f o r e s t c o n d i t i o n s i s m i s l e a d i n g , i n a c c u r a t e , and a waste of t i m e . " Growth of uneven-age stands i s r e l a t e d to the c u t t i n g c y c l e . The g e n e r a l aim of management i s to m a i n t a i n maximum growth ra tes by c u t t i n g before the current growth r a t e s d i m i n i s h s i g n i f i c a n t l y . Davies (1966) d e f i n e s the volume of growing stock at three d i f f e r e n t l e v e l s : 1. The volume j u s t a f t e r a c y c l i c c u t . 2. The volume j u s t before a c y c l i c c u t . 3 . The average volume midway through the c u t t i n g c y c l e . The t h i r d i s u s e f u l i n d e s c r i b i n g the average growing-s tock l e v e l of a f o r e s t u n i t as a whole . In order to m a i n t a i n a s u s t a i n e d y i e l d , the c u t t i n g c y c l e should correspond to the time r e q u i r e d to r e g a i n the volume removed i n the i n i t i a l cut and i n c l u d e any adjustments made i n the growing s t o c k . r Growth i n a p a r t i c u l a r stand w i l l vary from year to year due to c l i m a t i c and changing growth c o n d i t i o n s . The growth r a t e s of d i f f e r e n t diameter c l a s s e s w i l l a l s o v a r y . A balance of these b i o l o g i c a l f a c t o r s i s necessary to o p t i m i z e the t o t a l growth r a t e of a s t a n d . T h e r e f o r e , i t may be necessary to i n c r e a s e or reduce the growing s tock to encourage a b e t t e r s i z e d i s t r i b u t i o n . Too low a reserve growing s t o c k , or r e s i d u a l number of stems, would not f u l l y u t i l i z e the s i t e p r o d u c t i v t y , 20 w h i l e too h igh a growing stock would reduce the stand value and volume growth through o v e r s t o c k i n g . I t i s a l s o necessary to m a i n t a i n a d e s i r a b l e diameter d i s t r i b u t i o n which w i l l support the c o n t i n u i n g stand e n t r i e s . De L i o c o u r t (1898) determined that a balanced s u s t a i n a b l e diameter d i s t r i b u t i o n was c h a r a c t e r i z e d by an i n v e r s e J-shape curve w i t h a constant r a t i o , q , of t rees i n s u c c e s s i v e diameter c l a s s e s . In order to determine the a c t u a l , or d e s i r e d , diameter d i s t r i b u t i o n , i t Is necessary to know the d e s i r e d q - v a l u e , r e s i d u a l b a s a l a r e a , and the maximum tree s i z e (Marquis 1978). Moser (1976) descr ibed the diameter d i s t r i b u t i o n u s i n g a n e g a t i v e e x p o n e n t i a l f u n c t i o n : N = k e " a d (30) where N i s the number of t rees per hectare per diameter c l a s s i n t e r v a l f o r diameter (at breast h e i g h t ) c l a s s d , and k and a are c o e f f i c i e n t s c h a r a c t e r i z i n g a g iven d i s t r i b u t i o n . The c o e f f i c i e n t a determines the r a t e at which the number of t rees change between success ive diameter c l a s s e s . In p r a c t i c e , i t can be c a l c u l a t e d from N and d measurements as f o l l o w s : [ ln(N j /N 2 ) ] a = (31) d2 ~ d l where and N 2 are the number of stems i n success ive diameter c l a s s e s , d^ and d2- The r a t i o of N 1 / N 2 i s the v a l u e of q f o r a stand w i t h a diameter c l a s s i n t e r v a l of dz ~ d\, or h . I f q i s known and cons tant , 21 a can be c a l c u l a t e d from an approximate r e l a t i o n s h i p between a and q, f o r q < 1 .3 . This r e l a t i o n s h i p i s found by t a k i n g the d e r i v a t i v e of (30) w i t h respect to d as f o l l o w s : dN = - a k e ~ a d d d (32) D i v i d i n g (32) by (30) g i v e s dN N o - N i « —£ L « —ah N N 2 (33) so tha t a « (q •- l ) / h for q < 1.3 (34) i • The c o e f f i c i e n t k i s the number of t rees per hectare per diameter c l a s s i n t e r v a l as d approaches z e r o . When the a c t u a l or d e s i r e d b a s a l a r e a , A, i s known, k can be c a l c u l a t e d as f o l l o w s : 2 2. k = - ( 4 A / i r ) [ { — + ^ ( a d 2 + 1) }e" a d2 - (iL + (ad l + l ) } e " a d l ] _ 1 (35) where d^ and d 2 are the s m a l l e s t and l a r g e s t diameter c l a s s e s . In cases where d^ approaches zero and d 2 = d and i s r e p r e s e n t a t i v e of the l a r g e s t d e s i r a b l e or a c t u a l t ree on the s t a n d , (35) reduces to r 2 A 1 2 , - a d r 1 k = (4A/ir) [~~7 - — + ~T(ad + 1) e a a ] (36) a° a a 3 Researchers have demonstrated an e m p i r i c a l r e l a t i o n s h i p showing a p o s i t i v e c o r r e l a t i o n between a and k (Meyer et a l . 1961). The va lue of q and a w i l l vary depending on the ra te of diameter growth and the growing space r e q u i r e d f o r each c l a s s and the l a r g e s t d e s i r a b l e diameter f o r the crop t r e e s . Values of q (5 cm diameter c l a s s i n t e r v a l s ) g e n e r a l l y range from 1.1 to 2 (Meyer 1952), w i t h the lower the q value the h igher the growing space u t i l i z e d by l a r g e r , more v a l u a b l e t r e e s . Maintenance a l s o i n c r e a s e s w i t h low q va lues due to the number of s m a l l stems which develop and should be removed. Growing space occupied by s u r p l u s s m a l l stems can only be u t i l i z e d at the expense of the l a r g e r stems. Al though t h i s e m p i r i c a l approach i s u s e f u l f o r d e s c r i b i n g a d e s i r a b l e diameter d i s t r i b u t i o n , b i o l o g i c a l f a c t o r s should be used to determine the a c t u a l diameter d i s t r i b u t i o n (Davies 1966; Leak and P h i l l i p 1977). The f l a t t e r the c u r v e , the more economica l ly favourable i t i s . This diameter d i s t r i b u t i o n , however, i s l e s s l i k e l y to be b i o l o -g i c a l l y s u s t a i n a b l e f o r long per iods of t ime, due to m o r t a l i t y i n the younger, s m a l l e r diameter c l a s s e s . The growth ra tes of the d i f f e r e n t diameter c l a s s e s w i l l vary w i t h the l a r g e r t rees growing at a f a s t e r ra te than the s m a l l e r t r e e s . A d e f i c i e n c y i n one diameter c l a s s may be compensated by f a v o u r i n g the growth ra tes of the t rees i n the next s m a l l e r diameter c l a s s . The diameter d i s t r i b u t i o n can have a s i g n i f i -cant impact on gross volume i n c r e a s e or p o s s i b l e s u s t a i n e d gross y i e l d of a stand (Meyer 1952). C u r r e n t l y , the m a j o r i t y of the uneven-age stands i n i n t e r i o r B . C . are u n s t r u c t u r e d and, as such, have an unbalanced diameter d i s t r i b u t i o n w i t h an abundance of some diameter c l a s s e s and a r e d u c t i o n or absence of 23 o t h e r s . Any growth p r o j e c t i o n s based on the past m o r t a l i t y rates of these stands may be u n r e l i a b l e f o r e v a l u a t i n g d i f f e r e n t stand s t r u c t u r e s or long term p r o j e c t i o n s (Johnstone 1984). Monsurud (1984) has developed he ight growth and s i t e index curves f o r i n t e r i o r D o u g l a s - f i r i n the Rocky Mountains , u s i n g uneven-age s t a n d s . He found no changes i n he ight growth w i t h s t o c k i n g , and no s i g n i f i c a n t d i f f e r e n c e i n these curves and ones developed from even-age stands i n the same a r e a . The sample s i t e t rees s e l e c t e d were the dominant t r e e s , w i t h no observable damage, w e l l developed and hea l thy crowns, no s igns of s u p p r e s s i o n , and r e g u l a r r a d i a l growth s ince e s t a b l i s h m e n t . Al though the t rees grew i n uneven-age s t a n d s , they were e s s e n t i a l l y open-grown w i t h l i t t l e c o m p e t i t i o n e v i d e n t . These s i t e t rees w i l l provide an i n d i c a t i o n of r e l a t i v e ( e . g . , good, f a i r , poor) s i t e p r o d u c t i v i t y , but cannot be used to p r o j e c t a c t u a l volume growth f o r a g iven stand s t r u c t u r e and d e n s i t y . Langsaeter (1941) hypothes ized that f o r an even-age stand the t o t a l y e a r l y volume growth per hectare remains constant over a range of t o t a l stand volumes. Y e a r l y height growth i s a l s o assumed to be r e l a t i v e l y constant over t h i s range of stand volumes. An increase i n y e a r l y volume growth per hectare w i t h i n c r e a s i n g s t o c k i n g w i l l be observed only when s t o c k i n g i s low and there i s u n f i l l e d growing space. Opt imal stand growth occurs between 60% of f u l l s t o c k i n g and f u l l s t o c k i n g . This g e n e r a l r u l e i s a l s o b e l i e v e d to be a p p l i c a b l e to uneven-age stands (Smith 1962). Walker (1956) d e f i n e s f u l l s t o c k i n g of an uneven-age stand as the s t o c k i n g at which the " f u l l p r o d u c t i v e c a p a c i t y " of the s i t e i s u t i l i z e d w i t h a minimum of suppress ion and m o r t a l i t y . While i n t h i s opt imal 24 range , t h i n n i n g does not increase the t o t a l p r o d u c t i o n , but r a t h e r r e d i s t r i b u t e s the growth on fewer stems. Once a c r i t i c a l point i s reached and the stands become o v e r s t o c k e d , t o t a l stand growth decreases due to c o m p e t i t i o n . This c r i t i c a l s t o c k i n g l e v e l v a r i e s w i t h s i t e c h a r a c t e r i s t i c s . There have been some s t u d i e s , however, i n which t o t a l stand p r o d u c t i v i t y d i d i n c r e a s e above that i n d i c a t e d w i t h o p t i m a l s t o c k i n g l e v e l s . B a r r e t t (1973) found that l o g g i n g o l d growth ponderosa pine (Pinus ponderosa Laws) to leave on ly the advanced r e g e n e r a t i o n r e s u l t e d i n a t h r e e - f o l d volume growth ra te i n c r e a s e over that of the o l d growth o v e r s t o r y . The growth ra te of s a p l i n g s was s t i l l r i s i n g r a p i d l y e ight years a f t e r t h i n n i n g and the author es t imated that i t would have a growth rate f i v e to s i x times that of the o r i g i n a l o v e r s t o r y . In another study by Tiramer and Weetman (1969) , on b lack spruce ( P i c e a  m a r i a n a ) , i t was suggested that t o t a l p r o d u c t i o n would be greater than that which would occur f o l l o w i n g t h i n n i n g due to an improved thermal environment . Al though these examples are on predominant ly even-age s t a n d s , they i l l u s t r a t e i n s t a n c e s where volume growth was increased w i t h stand m a n i p u l a t i o n . For a g iven c u t t i n g c y c l e and s i t e q u a l i t y , there i s an optimum stand s t r u c t u r e and d e n s i t y which w i l l r e s u l t i n the maximum product ive c a p a c i t y and net r e t u r n (Davies 1966). The p r o d u c t i v e c a p a c i t y of the s i t e can only be f u l l y r e a l i z e d w i t h the es tab l i shment and maintenance of the d e s i r a b l e growing stock at these l e v e l s . I t i s g e n e r a l l y accepted that the u n s t r u c t u r e d uneven-age stands i n the southern i n t e r -i o r of B . C . are not c u r r e n t l y at t h i s l e v e l . T h e r e f o r e , an increase volume growth i n these stands could be achieved by the b a l a n c i n g of the age classes. This would re s u l t in a better u t i l i z a t i o n of the growing area, both s p a t i a l l y and over time (Knuchel 1953). Trees are able to occupy a l l of the s t r a t a , and mature trees are not harvested merely as a function of age, but may be allowed to achieve addi t i o n a l volume growth (Daniel et a l . 1979; Smith 1962). 26 3. STUDY AREA 3. STUDY AREA 3.1 Location of Study Plots The study area i s near Kamloops, B r i t i s h Columbia. There were two major s i t e s established for the water balance study. The f i r s t was located near the Knouff Lake Road at the 12 km marker, in the I D F ^ subzone, had a predominantly southern exposure, and included f i v e micro-climate plots representing f i v e d i f f e r e n t degrees of canopy closure. The second study s i t e was located off the Lac Le Jeune Road i n the IDF a subzone, included three microclimate plots with d i f f e r e n t canopy closures and had a northern exposure. Both sites were r e l a t i v e l y f l a t (< 3° slope). There were three other microclimate plots established, two off the Todd Mountain Road in the Heffley drainage (Recreation area and Heffley p l o t s ) , and one off the Knouff Lake Road (Knouff 14 km p l o t ) . These plots had moderate slopes (<15°) and were primarily south facing. A l l microclimate plots were 10 m x 10 m i n s i z e , with a 25 m wide buffer zone. The inventory and permanent sample plots used for growth analysis were located adjacent to the microclimate plots at the Knouff Lake Road s i t e s , and Heffley drainage, and near Lac Le Jeune. Additional invent-ory plots were located near McQueen Lake, Red Lake, Anderson Lake, Pinantan Lake and Orchard Lake. The elevation ranges from 1006 m to 1280 m, topography i s gently to moderate, and a l l aspects are repre-sented. There were twenty-two inventory plots 25 m x 25 m i n s i z e , and four permanent sample plots (Figure 2). Each permanent sample plot consisted of ten c i r c u l a r subplots, f i v e i n a control area and f i v e i n a logged area. The control area subplots were 0.01 ha i n size and the 28 y / "^Orchard Lake Road >. . Orchard Lake Kamloops Lake \ Red Lake Road i \ ' K n o u f f Lake McOuean Lake J T o d d "V—v _ I M o u n t a i n ,* C\" — ' | Road H e f f l e y Lake 'Lac D u b o i s fs-f/l ' Road Paul Lake Road Paul Lake ££\>p I n a n t a n Lake V . HWY 1 ' ' N . . ^ Lac La Juene Road; KAMLOOPS CITY LIMITS Lac La Juene Anderson Lake RoadC"^ / f HWY 5 Stump Lake KEY • EXPERIMENT 1: M i c r o c l i m a t e P l o t O EXPERIMENT 2: I n v e n t o r y P l o t A PERMANENT SAMPLE PLOT Figure 2: Map of study area. The number located next the d i f f e r e n t symbols indicates the number of actual plots at that s i t e . 29 logged subplots were 0.02 ha i n s i z e . Subplots were located l i n e a r l y 30 m apart along a compass heading. 3.2 Climate In the IDF a subzone, annual r a i n f a l l varies from 315 mm to 429 mm, with an average of 376 mm, and annual snowfall ranges from 110 cm to 170 cm, averaging 144 cm. The annual r a i n f a l l i s higher for the IDF^i, ranging from 376 mm to 465 mm with an average of 428 mm. Annual snowfall ranges from 140 cm to 287 cm, averaging 183 cm a year. Mean annual temperatures are 5°C and 4°C with a mean annual minima of 3°C and 2°C and a mean annual maxima of 6°C and 5°C for the IDF a and IDF^i, r e s p e c t i v e l y . The IDF a has a f r o s t free period averaging 90 days (between 60 and 116 days), and f i v e months with a s o i l moisture d e f i c i t , while the IDF^i has an average f r o s t free period averaging 75 days (between 52 and 106 days), and four months with a s o i l moisture d e f i c i t ( M i t c h e l l and Greene 1981). 3.3 Geology and Soils The s o i l s are orthic or e u t r i c brunisols. The parent material is morainal and the bedrock geology i s primarily volcanic with some fine to medium sedimentary material ( M i t c h e l l and Greene 1981). S o i l texture ranges from a gravelly loamy sand to a gravelly sandy loam and drainage i s generally good. Rooting depth i s approximately 80 cm. A detailed description of the s o i l c h a r a c t e r i s t i c s for the micro-climate plots was done. The inventory and permanent sample plots, however, have s i m i l i a r s o i l c h a r a c t e r i s t i c s . The organic layer on a l l 30 p l o t s i s very sha l low w i t h a F and H l a y e r of approximate ly 1 cm. An o v e r l y i n g L l a y e r of approximate ly 2 cm i s common. The p a r t i c l e d e n s i t y q and the bulk d e n s i t y of the organic l a y e r was found to be 1.88 Mg m , and 0.53 Mg m~ , r e s p e c t i v e l y , which r e s u l t e d i n a p o r o s i t y of 72%. A d d i t i o n a l o r g a n i c matter i n the form of r e s i d u a l l o g g i n g s l a s h i s s c a t t e r e d around the p l o t s to a depth of 30 cm. The s o i l t e x t u r e of the Lac Le Jeune s i t e was a g r a v e l l y sandy loam w i t h an impermeable l a y e r at 1 m, w h i l e the s o i l t ex ture of the Knouff 12 km s i t e was a g r a v e l l y loamy sand. The coarse fragment (> 10 mm) content was determined f o r the 0 - 50 cm and 50 - 100 cm depths from 50 cm x 50 cm x 100 cm deep s o i l p i t s , two at the Lac Le Jeune s i t e , three at the Knouff 12 km s i t e , and one each at the H e f f l e y , Knouff 14 km and R e c r e a t i o n area p l o t s . Values ranged from 0% to 25% by volume f o r the e n t i r e s o i l p i t (Table 1 ) . The d e n s i t y of the coarse fragment was determined to be 2.64 Mg m . The bulk d e n s i t y of the f i n e s (< 10 mm), as determined by the e x c a v a t i o n method (Blake 1965), was 1.49 Mg m~ 3 and 2.19 Mg m~ 3 at the Lac Le Jeune s i t e , and 1.39 Mg m - 3 and 2.25 Mg m~ 3 at the Knouff 12 km s i t e , f o r the 0 - 25 cm and 25 - 50 cm depths , r e s p e c t i v e l y (Table 1 ) . The R e c r e a t i o n area and Knouff 14 km p l o t s were assumed to have approximate ly the same v a l u e s . The bulk d e n s i t y of H e f f l e y p l o t was c a l c u l a t e d s e p a r a t e l y because t h i s p l o t conta ined no coarse fragments . For the H e f f l e y p l o t the f i n e bulk d e n s i t y at the 0 - 25 cm depth was 1.46 Mg m - 3 and at the 25 - 50 cm depth , 2.12 Mg m - 3 (Table 1 ) . S o i l water r e t e n t i o n curves were obta ined f o r the Lac Le Jeune, Knouff 12 km and H e f f l e y s i t e s ( F i g s . 3 , 4 and 5) from u n d i s t u r b e d s o i l samples (7.6 cm diameter x 7.6 cm l e n g t h ) taken at the s u r f a c e and at Table 1: S o l i characteristics of the microclimate plots. f of Canopy Average (X) S o i l Bulk density of fines (pg m" ) Coarse fragments (0% volume) Average available s o i l water content (mm) at s o i l water matric potentials Site Plots Texture 0-25 cm 25-50 cm 0-50 cm 50-100 cm -0.01 MPa -0.1 MPa -1.5 MPa Lac Le Jeune 3 1 0 50 100 Sandy loams 1.49 2.19 11.6 15.3 240 168 96 Knouff 12 km 5 0 10 25 50 100 Loamy sands 1.39 2.25 12.0 13.9 136 104 72 Knouff 14 km 1 10 Loamy sands * * 20.4 30.6 Recreation Area 1 35 Loamy sands * * 20.2 23.6 not obtained Heffley Creek 1 20 Loamy sands 1.46 2.12 0 0 264 208 120 "These plots were assumed to have similar values as the Knouff 12 km s i t e , because coarse fragment content and s o i l texture were si m i l a r . The Heffley plot s o i l characteristics were analyzed separately due to lack of coarse fragments. Figure 3: S o i l water retention curves for the Lac Le Jeune s i t e . I I I I I I I -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 SOIL WATER POTENTIAL (MPa) Figure 4: S o i l water retention curves for the Knouff 12 km s i t e . Figure 5: S o i l water retention curves for the Heffley s i t e . depths of 10 cm, 25 cm, and 60 cm. The available water storage capacity [the water held between s o i l water matric potentials of -0.01 MPa ( f i e l d capacity) and -1.5 MPa (w i l t i n g point)] was much higher for the Heffley and Lac Le Jeune si t e s than for the Knouff 12 km s i t e (Table 1). At s o i l water matric potentials (\|,s) of -0.01 MPa, -0.1 MPa and -1.5 MPa, the Heffley plot has an average of 33%, 26%, and 15% s o i l water content by volume, while the Lac Le Jeune s i t e averages 30%, 21% and 12%, resp e c t i v e l y , for the entire root zone. For these same s o i l water matric potentials, the Knouff 12 km s i t e averages only 17%, 13% and 9%, resp e c t i v e l y . 3.4 Vegetation Coniferous tree species include i n t e r i o r Douglas-fir, ponderosa pine, lodgepole pine (Pinus contorta Dougl.), and on s i t e s i n the IDFbi, spruce (Picea spp.). Understory vegetation consists of a poorly developed shrub layer dominated by spirea (Spirea b e t u l i f o l i a ) , snowberry (Symphoricarpos albus), and serviceberry (Almelanchier  a l n i f l o l i a ) . The herb layer i s well developed with pinegrass (Calamagrostis rebescens) dominating, and a major twinflower (Linnaea  b o r e a l i s ) component. Wild strawberry (Fragaria vesca), oregon grape (Mahonia nervosa), and wild rose (Rosa woodsii) are frequently found on some s i t e s . The Knouff 12 km s i t e has f i v e microclimate plots of averaging 100%, 50%, 25% 10% and 0% (±10%) canopy coverage, while the Lac Le Jeune s i t e has three microclimate plots averaging 100%, 50% and 0% canopy coverages. The ad d i t i o n a l three microclimate plots have canopy coverages averaging 10%, 20% and 35%. Canopy coverages were determined i n i t i a l l y with a spherical densiometer (Forest densiometer, Arlington, V i r g i n i a ) and l a t e r v e r i f i e d by analyzing photographs taken with a fish-eye lens ( K e l l i h e r 1985) (Appendix 2). Canopy coverage i s defined as the f r a c t i o n of the hemispherical s o l i d angle at two metres above the ground that i s occupied by trees (boles, branches, f o l i a g e ) . The two metre height was selected to include only those trees large enough to have a s i g n i f i c a n t impact on the microclimate, p a r t i c u l a r l y regarding snow thr o u g h f a l l . The density of the inventory plots varied from 96 trees per hectare to 2,784 trees per hectare. The stand densities corresponding to the above canopy coverages are shown i n Figure 6. A f o l i a r analysis of the nutrient content of the conifer needles was done on the Lac Le Jeune and Knouff 12 km s i t e s from a sample composite of the plots located at each s i t e , and r e p l i c a t e d twice. The results indicate that the Lac Le Jeune s i t e i s richer i n a v a i l a b l e nutrients than the Knouff 12 km s i t e (Appendix 3). It i s u n l i k e l y that f e r t i l i z a t i o n would improve stand growth, due to the extreme s o i l moisture d e f i c i t . A f e r t i l i z e r screening t r i a l done on i n t e r i o r Douglas-fir by Weetman and Fournier (1981) showed no s i g n i f i c a n t growth response to f e r t i l i z a t i o n , however, a p r e - f e r t i l i z a t i o n nutrient analysis was not done. 3.5 Logging History The f i r s t major logging in the Kamloops area occurred in the 1940's with the advent of World War I I . In the 1960's the B.C. Forest Service decided that only mature trees could be f e l l e d and, basing maturity on diameter s i z e , i n i t i a t e d diameter l i m i t logging. The assumption that the larger trees were the older tees was not always correct. These 37 F i g u r e 6: R e l a t i o n s h i p between canopy coverage and stand d e n s i t y . 38 trees could possess better genotypes, inhabit the more favourable micro-s i t e s , and/or be more open grown. In combination with this and a stand structure consisting of large areas of even-size diameter d i s t r i b u t i o n s and missing diameter classes, diameter l i m i t logging often resulted i n either dense pockets of residual stems of variable quality or small cl e a r c u t s . By the early 1970's these stands were in very poor shape and i t was evident that a better type of logging was necessary (Clark 1983, personal communication). The s e l e c t i o n method was f i r s t implemented as a "mark to cut" in the mid 1970's. The forester would select and mark each tree to be f e l l e d . The r e s i d u a l trees would then provide the necessary shade for natural regeneration and put on a d d i t i o n a l volume which could be harvested at the next stand entry. Furthermore, the bet-ter stems were l e f t to provide a seed source for the next crop. Some s i t e s , however, had stands in such poor condition that even the "better" stems are of low vigour. Over time the stand quality should have improved. However, because the cost of marking each i n d i v i d u a l tree to be f e l l e d on a l l the cutting permits was p r o h i b i t i v e , f a l l e r ' s s e l e c t i o n evolved. F a l l e r ' s s e l e c t i o n began in the late 1970's. Instead of foresters marking each tree to be f e l l e d , the f a l l e r selects the trees to f a l l . Each f a l l e r i s instructed as to the type of tree to f a l l and the spacing to be l e f t on the stand and works under close supervision of a woods foreman. Again, the better trees are l e f t , and stems are taken from a wide range of diameter classes. This would be a true s e l e c t i o n system except that trees below the u t i l i z a t i o n s p e c i f i c a t i o n s of the B.C. Forest Service cannot be f e l l e d economically as part of a commercial 39 logging operation. F a l l i n g these smaller stems would be c l a s s i f i e d as "damage to immature stems" and r e s u l t i n f i n e s . This prevents optimal stand structures and densities from being obtained, as large areas may be overstocked with small stems that cannot be thinned at the time of logging. When funds are a v a i l a b l e , however, these trees can be thinned i n a separate stand entry for juvenile spacing. EXPERIMENTAL METHODS 41 4. EXPERIMENTAL METHODS 4-1 Forest Water Balance 4.1.1 F i e l d Measurements The main weather station was located at the Knouff 12 km s i t e . With the exception of a r e l a t i v e humidity (RH) sensor and some of the thermistors, a l l the weather station instruments, which were connected to a Campbell S c i e n t i f i c CR21 data logger, were located at the grass (0% canopy coverage) p l o t . On this p l o t , hourly measurements of solar irradiance ( S t ) , net rad i a t i o n , and s o i l heat flux density were obtained by e l e c t r o n i c a l l y integrating the voltage output from, respect-i v e l y , a Kipp solarimeter, Swissteco S - l net radiometer, and three s o i l heat f l u x plates connected in s e r i e s . R a i n f a l l (P) and windspeed (U) were measured by counting the pulses from a Sierra Misco tipping bucket r a i n gauge and a Met-One anemometer, res p e c t i v e l y . The instruments were located with minimal obstruction by any trees on the horizon. Relative humidity was integrated every two hours from a Phys-Chem sulphonated polystyrene sensor located at the 50% canopy coverage plot and recorded on the data logger. S o i l and a i r temperatures were obtained on a l l five plots (0%, 10%, 25%, 50%, and 100% canopy coverages) by expanding the capacity of the CR21 data logger with a stepping switch (Clare relay, 26 position) connected to two channels. This configuration enabled s o i l temperature at 40 positions to be monitored. A l l data were recorded with a cassette recorder powered by a 6 V Gel c e l l . Cassettes had to be changed weekly. Data were read from the cassette by a Campbell C2000 microcomputer and transferred to the Amdahl V/8 computer at U.B.C. In addition to the data recorded with the data logger, each microclimate plot at the Knouff 12 km s i t e had a hygrothermograph to 42 record a i r temperature and r e l a t i v e humidity, and storage r a i n gauges to measure below-canopy r a i n f a l l . The Lac Le Jeune s i t e had a hygro-thermograph located on the grass plot and storage r a i n gauges on each of the three plots (0%, 50%, 100% canopy coverage). S o i l surface temperatures were taken throughout the daytime, with an i n f r a r e d thermometer, every two weeks on a l l eleven microclimate p l o t s . The net ra d i a t i o n and s o i l heat f l u x density measurements were taken for four weeks i n August. A l l other growing season measurements were taken from May to October. Winter measurements of snow depth and water equivalant depths were taken every two weeks with a snow auger. Four snow samples were taken and the results averaged for each pl o t . S o i l water content was measured on a l l eleven plots approximately every two weeks with a neutron probe (Campbell P a c i f i c Nuclear Model 503). The measurement depths were at 15 cm i n t e r v a l s from the surface to the 75 cm depth. Except for the plots at the Knouff 12 km s i t e , three aluminium access tubes (50 mm outer diameter and 12 mm wall thickness) were i n s t a l l e d i n a triangular configuration approximately one metre apart. The grass and completely forested (100% canopy cover-age) plots at the Knouff 12 km s i t e have four access tubes arranged i n a square, while the other three p a r t i a l l y forested plots have f i v e access tubes arranged as two adjacent t r i a n g l e s . A l l tubes are one metre apart. There were two neutron probes used over the 1984 growing season. Probe A (B.C. Ministry of Environment) was used u n t i l July 5 and c a l i b r a t e d once, while probe B (Agriculture Canada, Kamloops) was used for the remainder of the summer and c a l i b r a t e d twice by gravimetric s o i l samples taken one metre away from a c a l i b r a t i o n access tube (Figure 7). 43 F i g u r e 7: C a l i b r a t i o n of the neutron probes. Probe A i s from the B . C . M i n i s t r y of Environment while Probe B i s from A g r i c u l t u r e Canada. 44 The 0 - 5 cm and 5 - 10 cm s o i l depths were sampled gra v i m e t r i c a l l y each time the neutron probe was used. The hygrothermographs were c a l i b r a t e d p r i o r to use at the Balco Reforestation Centre lab. The sulphonated polystyrene sensor and hair hygrometers were ca l i b r a t e d p e r i o d i c a l l y with an Assmann psychrometer at both Knouff 12 km and Lac Le Jeune s i t e s . A l l other instruments were ca l i b r a t e d at the U.B.C. Biometeorology lab. 4.1.2 A n a l y t i c a l Methods 4.1.2.1 Net Radiation Net r a d i a t i o n for the daytime was calculated as R n = aS t + L* (37) where S t i s the solar irradiance, L* i s the net longwave i r r a d i -ance, a i s the solar absorption c o e f f i c i e n t and assumed to be 0.88 for a forest cover (Giles et_ a l . 1985; Ja r v i s et_ a l . 1976). The net longwave irradiance was calculated as L* = e v ( e a - l)oT a' +(0.1 + 0.9 n/N) (38) where e v i s the emissivity of the vegetation [assumed to be 0.96 (Giles et a l . 1985) in this study], a i s the Stefan-Boltzmann constant, T a i s the mean daytime a i r temperature i n Kelvins, n i s the number of hours of sunshine, N i s the daylength, and e a i s the emissivity of the atmosphere. The l a t t e r i s given to a good approximation by a l i n e a r i z e d 45 version of the Idso-Jackson (1969) equation given by Campbell (1977) e a = 0.72 + 0. 005T a (39) where T a i s i n °C. The net rad i a t i o n was assumed to be the same for a l l p l o t s . The measurements required to calculate RJJ were obtained over a grass cover, except for the a i r temperature which was obtained from a p a r t i a l l y forested plot. Due to the s e n s i t i v i t y of R N to the absorption c o e f f i c i e n t , which would be less for a grass cover than for a forest cover, there may be an over estimate of ^ to the 0%, 10% and 25% canopy coverage p l o t s . Longwave radiation from the edges of the grass plots would tend to compensate for the lower absorption c o e f f i c i e n t and higher surface temperature of the p l o t s . Also, the d a i l y courses of S t indicated that the Weathermeasure actinograph was obstructed for the f i r s t and la s t two hours of each day r e s u l t i n g i n an underestimate of approximately 20%. The d a i l y S t measurements were mu l t i p l i e d by 1.25 to compensate for this underestimate. 4.1.2.2 Estimation of Evapotranspiration Using Water Balance  Ana l y s i s . There was no noticeable runoff observed on the s i t e s , and s o i l drainage was assumed to be n e g l i g i b l e since the s o i l water content remained below that corresponding to a s o i l water matric p o t e n t i a l of -0.1 MPa for the majority of the growing season. At this p o t e n t i a l i n most s o i l s , drainage becomes n e g l i g i b l e because of a marked 46 decrease i n the unsaturated hydraulic conductivity (Baver e_t_ al^. 1972). Under these conditions (1) reduces to E = P - AW/ At (40) where AW/At was calculated over seven or fourteen day i n t e r v a l s using K w f i n a l " w i n i t i a l ) / ( t f i n a l " t i n i t i a l ) ( m m d a y - 1 ) ] . The forest root zone water balance which excludes interception loss from the tree canopy can be written as T + Ig + E s = P n - AW/At (41) where P n > the net p r e c i p i t a t i o n , i s the sum of the throughfall and stemflow (the l a t t e r was observed to be very small and was neglected). Net p r e c i p i t a t i o n was measured at one or two week i n t e r v a l s on a l l p l o t s , except for Heffley, Knouff 14 km and Recreation Area p l o t s . In those cases, P n was estimated from P n = cP (42) Th e o r e t i c a l l y , this p r o p o r t i o n a l i t y should only hold for low p r e c i p i t a t i o n rates (Rutter et al_. 1971), where c i s i d e n t i f i e d as the free throughfall c o e f f i c i e n t . Assuming that Ig + E s i s much less than T, equation (41) becomes T « P n - ZW/ At (43) 47 This would only be true at higher canopy coverages where the grass component i s small. Otherwise Tg would not be n e g l i g i b l e . The growing season evapotranspiration or t r a n s p i r a t i o n was the sum of the d a i l y E or T values from June 1 to October 6. To test the s e n s i t i v i t y of the E to net r a d i a t i o n , the P r i e s t l e y - T a y l o r model for evapotranspiration was used. In this approach, the c o e f f i c i e n t a was calculated using equation (24) where s and y are, respectively, 0.11 kPa°C _ 1 and 0.660 kPa°C _ 1 at an a i r temperature of 15°C, and L i s 2,450 J k g - 1 . There was reasonable agreement between R n measured on the grass plot at Knouff 12 km and R n calculated using (37). The s o i l heat flux (G) was measured to be 3% of the net r a d i a t i o n . This r e l a t i o n s h i p was used when c a l c u l a t i n g a v a i l a b l e energy (R n - G) using so l a r irradiance and temperature. To see i f the v a r i a t i o n i n T i s more c l o s e l y linked with changes i n the vapour pressure d e f i c i t s , the canopy resistance of the dry leaves was calculated using equation (25) where pep was assumed to be 1200 J m C° at 15°C, r a was assumed to be 5 s m for a forested s i t e (Jarvis ejt a_l. 1976), and D was determined from measurements of RH, taken at the 50% canopy coverage p l o t , using D = (1 - RH)e a*, where e a*, the saturation vapour pressure of the a i r , was calculated as . follows (Tetens 1930) [7.5 T a / ( T a + 237.3)1 e a * = (0.6108)10 (44) 48 4-2 Volume Growth 4.2.1 F i e l d Measurements 4.2.1.1. Inventory Plots A l l inventory plots were marked and each tree over 7.5 cm d (diam-eter at breast height) (coreable size) had d and species recorded, and was numbered with spray paint. Additionally a l l stumps had diameters recorded and were numbered. The location of the trees, stumps, and regeneration (< 7.5 cm d) were mapped. The age of the regeneration was determined by counting the branch whorls and some destructive sampling to count the rings. A. Data collection for core analysis One of the sets of four adjacent plots (see Fig. 2) was completely inventoried, including a l l tree heights, d, and an increment core taken from each tree with a d > 7.5 cm. From this set of four plots which contained 313 trees (n), the last five years of growth was analyzed to determine the number (N) of trees to be cored on each of the remaining plots using N = tn-1' (45) where tn-\ is the appropriate t-statistic for the 95% confidence level and n-1 degrees of freedom (1.96), S x is the standard deviation of the last five years radial growth, and E is the sampling error (5% of the mean). The value of N was found to be 698 (Sx = 0.0593 cm y r - 1 ; x = 0.0898 cm y r - 1 ) . There were 961 numbered trees from a l l the plots; 49 therefore, about 70% of the trees on each plot were cored. For each of the trees, bark width was measured i n s i x d i f f e r e n t locations at breast height and these values were averaged. B. Data c o l l e c t i o n for stem analysis Equation (45) was also used to determine the number of trees required for stem analysis, except the standard deviation of the d to height r a t i o (cm ra-1) was used instead of growth. It was determined that 231 trees were necessary for stem analysis ( S x = 0.0984 cm y r _ 1 ; x = 0.2591 cm y r _ 1 ) . Since this number could not r e a l i s t i c a l l y be obtained, only 100 of the 961 trees (or about 10% of the trees for each plo t ) were f e l l e d for stem analysis ( M i t c h e l l 1985, personal communication; Kozak 1985, personal communication). The 100 trees selected for stem analysis had a minimum of four discs taken: one at the base of the tree, one at 1.3 m, one at the base of the crown, and the l a s t midway through the crown, as suggested by M i t c h e l l (1984, personal communications). The number of discs were determined by taking tea discs at i n t e r v a l s of one-tenth t o t a l tree height on four trees and p l o t t i n g the tree form. It was found that the four discs could adequately describe the tree form. The t o t a l number of trees, number of trees cored, and the number of trees sampled for stem analysis i n each of the 22 inventory plots are i n Table 2. 4.2.1.2 Permanent Sample Plots Permanent sample plots, o r i g i n a l l y established by Balco Industries Ltd. i n 1980 and 1982, were remeasured according to the B.C. Ministry of Forests, Inventory Branch s p e c i f i c a t i o n s . This included recording d Table 2. Summary of trees sampled on the inventory plots (on per plot [1/16 ha] b a s i s ) . Total Total Number Number of number number t o t a l of trees trees for Number Plot of trees of regen. number for stem increment of No. Location >5 cm dbh <5 cm dbh of stumps analysis cores heights 1 Anderson Lake 54 93 20 6 39 16 2 Heffley Creek A 65 767 12 7 47 65 3 Heffley Creek B 68 508 10 7 49 68 4 Heffley Creek C 29 317 4 3 21 29 5 Heffley Creek D 29 941 4 3 21 29 6 Heffley Creek E 41 369 6 4 30 21 7 Heffley Creek F 43 202 7 4 31 23 8 Heffley Creek G 61 217 10 4 27 24 9 Heffley Creek H 19 217 2 2 14 14 10 Knouff 14 A 6 33 17 1 4 4 11 Knouff 14 B 13 41 12 1 10 6 12 Knouff 14 C 13 37 21 1 10 8 13 Knouff 14 D 61 62 6 6 45 26 14 McQueen 174 0 5 18 126 28 15 Orchard Lake A 18 91 13 2 13 12 16 Orchard Lake B 102 57 8 11 74 21 17 Orchard Lake C 15 33 12 2 11 12 18 Orchard Lake D 30 49 12 3 22 13 19 Orchard Lake E 24 114 9 3 18 13 20 Pinantan 20 3 17 2 15 12 21 Red Lake 20 576 3 2 15 12 22 Knouff 19 80 221 17 8 45 18 TOTALS 961 4,899 227 100 700 494 51 and species for a l l marked trees, and remeasuring the heights of the previously recorded trees, and age and height of selected regeneration. 4.2.2 Analytical Methods A stand table was developed for each of the 22 inventory plots by 5 cm d classes, including regeneration. The coefficients a, q, and k were determined for the diameter distribution currently on each plot [eq. (30) and (31)]. Analysis of the height to age, height to diameter, and diameter to age relationships were done for each density class. The density classes were selected from height and diameter relationships to be 10 - 300, 301 - 600, 601 - 900, 901 - 1200, 1201 - 1500, 1501 - 1800, 1801 - 2100, 2101 - 2400, 2401 - 2700, and 2701 - 3000 trees per hectare. 4.2.2.1 Development of a Local Volume Equation The volume (V) of the stem analysis sample trees was determined by using Sraalian's equation (Husch et_ a l . 1972) n V = J ^ ( d l i 2 + d 2 i 2 ) L i / 8 (46) where d]^ and d£i are the top and bottom diameters of log section i with a length, L^. Although Smalain's equation has been shown to overestimate tree volume by approximately nine percent, other methods (Huber's and Newton's equations) require the additional measurement of the cross-sectional area at the middle of each log section (Young et a l . 52 1967). Since successive volumes are subtracted from each other to determine growth rates, error i n the l a t t e r w i l l be small. A l o c a l volume equation using multiple regression was developed from the measured volume of the 100 sample trees (Schumacher and H a l l 1933) log V = log a + b log d + c log H (47) where a, b and c are experimentally determined c o e f f i c i e n t s , H i s height, and d i s taken at breast height. In a l o c a l volume equation H i s i m p l i c t l y expressed as a function of d and a constant proportional r e l a t i o n s h i p is assumed between H and d. This was not the case i n the uneven-age stands studied. In these stands, the diameter to height r a t i o varied considerably with stand density. I t was found that this r a t i o remained f a i r l y constant for d i f f e r e n t sized stems i n the same density class (see RESULTS). Therefore, this r a t i o was used to account for the v a r i a t i o n i n the form factor due to density and replaced the l a s t variable i n (47), so that i t was rewritten as log V = a + b log d + c log d/H (48) This equation was tested to determine i t s accuracy i n estimating tree volume 5, 10 and 20 years ago from increment cores taken at breast height. The volumes were calculated assuming the same d/H r a t i o as currently on the stands and were compared to actual volumes determined from stem analysis and Smalian's equation. The diameters of the tree 5, 10 and 20 years ago, at d i f f e r e n t i n t e r v a l s along the stem were obtained 53 from the d i s c s removed. The t ree he ight at each time was determined by us ing where h t i s the he ight 5, 10 or 20 years ago ( t ) , h c i s the current age of the t ree when i t was the h e i g h t of the p o s i t i o n where the d i s c neares t the tree top was removed ( h ^ ) . 4 . 2 . 2 . 2 Stand Growth The increment cores were measured on the Addo-X t ree r i n g a n a l y z e r i n f i v e year i n t e r v a l s s i n c e the time of the l a s t l o g g i n g . The one core taken from each was c o r r e c t e d t o equal the r a d i u s of the t ree ( M i t c h e l l 1984, p e r s o n a l communicat ion) . Growth was c a l c u l a t e d f o r each f i v e year i n t e r v a l as the d i f f e r e n c e between the volume per hectare on the stand at the b e g i n n i n g and end of each i n t e r v a l . S ince the l o c a l volume equat ions r e q u i r e d d o u t s i d e bark , the bark w i d t h was determined as a p r o p o r t i o n of the outer bark d i a m e t e r , and the cores c o r r e c t e d to i n c l u d e bark w i d t h . The growth ra te of each p l o t f o r each f i v e year p e r i o d , r e f l e c t i n g the e f f e c t s of a g i v e n stand volume, and stand d e n s i t y was used as one growth datum p o i n t . The i n i t i a l s tand c o n d i t i o n s p r i o r to l o g g i n g and immediate ly f o l l o w i n g l o g g i n g were a l s o a n a l y z e d . The a , q , and k c o e f f i c i e n t s and volume f o r each p l o t at the time of l o g g i n g was es t imated from the stump diameters converted to d (DemaTchalk 1984), and the diameters of h t " h c " (8c ~ g L > t / ( h c " h L ) (49) h e i g h t of the t r e e , g c i s the current age of the t r e e , g^ i s the 54 the residual trees at the time of the l a s t logging were determined. The same variables were determined for the stand immediately following logging. The permanent sample plot growth was determined as the difference i n the volume per hectare currently on the stand and at the time of plot establishment. The f i v e subplots both i n the c o n t r o l l e d and the logged s i t e s were combined and analyzed as one 0.05 ha control and one 0.10 ha logged plot for each permanent sample p l o t . RESULTS AND DISCUSSION RESULTS AND DISCUSSION 5.1 Water Balance Analysis 5.1.1 I n i t i a l Soil Water Content at the Beginning of the Growing S e a s o n A major factor influencing the i n i t i a l growing season root zone s o i l water content was the s o i l recharge due to the spring snowmelt. The snow melted off the south facing lower elevation Knouff 12 km and Heffley s i t e s f i r s t (Figs. 8 and 9). The snow was o f f the 0% and 100% canopy coverage plots by A p r i l 1. It was off the p a r t i a l l y forested plots by A p r i l 15, with the exception of the Knouff 12 km 50% canopy coverage p l o t . The snow was off this plot by A p r i l 1, very l i k e l y due to the large amount of logging slash present. The slash absorbs short-wave rad i a t i o n beneath the snow's surface, which melts the snow from below (Oke 1978). The higher elevation south facing Recreation Area and Knouff 14 km plots retained t h e i r snow u n t i l A p r i l 30. The north facing Lac Le Jeune 100% canopy coverage plot l o s t i t s snow by A p r i l 1, probably due to a low i n i t i a l snow cover, while the 50% and 0% canopy coverage plots retained their snow for an ad d i t i o n a l month ( F i g . 10). The maximum snow water equivalent depth was consistently higher on lower canopy coverages, with the highest values on both 0% canopy coverage plots (140 mm at Lac Le Jeune and 110 mm at Knouff 12 km). The lowest values were observed on both 100% canopy coverage plots (50 mm on each). While the Lac Le Jeune 0% canopy coverage plots had 30 mm greater snow water equivalent depth than the Knouff 12 km 0% canopy coverage p l o t , both of the 50% canopy coverage plots and both of 100% canopy coverage plots had s i m i l a r maximum snow water equivalents depths. 57 JAN FEB MAR APR Figure 8: Course of the snow water equivalent depths on the p lo ts at the Knouff 12 km s i t e from January to June 1984. 58 F i g u r e 9: Course of the snow water equivalent depths on the p l o t s at the Lac Le Jeune s i t e from January to June 1984. 59 Figure 10: Course of the snow water equivalent depths for the Heffley, Knouff 14 km and Recreation Area plots from January to June 1984. The i n i t i a l s o i l water storage (W) for a rooting depth of 80 cm varied from 252 mm to 92 mm for the eleven microclimate plots (Table 3). The three Lac Le Jeune plots had approximately twice as much i n i t i a l W as the Knouff 12 km p l o t s . The Lac Le Jeune 0% canopy cover-age plot had the highest i n i t i a l W. The Knouff 12 km 0% canopy coverag plot had the second highest snow water equivalent but the lowest i n i t i a W of a l l the p l o t s . This was partly due to the snow melting e a r l i e r than on the other p a r t i a l l y forested p l o t s . This appeared to r e s u l t from warm days and very cold nights, causing the snow to melt but preventing the ground from thawing to enable i n f i l t r a t i o n of the water. These findings indicate that the i n i t i a l W was the res u l t of the i n t e r -action of the maximum snow water equivalent, duration of snow cover, s o i l temperatures at the time of snow melt and the a b i l i t y of the s o i l to r e t a i n water. An ad d i t i o n a l factor i s the root zone s o i l water storage i n the previous autumn prior to snowfall; however, these data were not av a i l a b l e i n th i s study. 5.1.2 S o i l Water Content D i s t r i b u t i o n i n the Root Zone The volumetric s o i l water content (6) tends to be highest for the 0-7.5 cm s o i l depth, and over the growing season the s o i l tends to dry from the top down. Figs. 11 and 12 show how 9 varies with s o i l depth throughout the root zone for the 0%, 50% and 100% canopy coverage plots at the Knouff 12 km and Lac Le Jeune s i t e s , r e spectively, on June 15, July 13, and August 19, 1984. The Lac Le Jeune plots had a f a i r l y uniform d i s t r i b u t i o n of water on June 15, but by August 19 the plots were noticeably d r i e r at the 10-40 cm depth. These plots remained Table 3. Variables influencing the i n i t i a l s o i l water content. I n i t i a l Maximum Date S o i l temperature s o i l root zone Canopy snow water at which no (°C) at the 5 cm water content coverage Elevation equivalence snow remained depth at the time (9) Plot Name (%) (m) (mm) on plot of snowmelt (mm) Lac Le Jeune 0% 140 May 3 +0.5 252 50% 1069 70 May 3 +1.5 215 100% 50 A p r i l 1 +0.5 220 Heffley 20% 878 75 A p r i l 15 0.5 234 Knouff 14 km 10% 980 105 May 3 0.5 169 Recreation Area 35% 912 95 May 3 0.5 146 Knouff 12 km 0% 110 A p r i l 1 -1.5 94 10% 878 100 A p r i l 15 0 122 25% 95 A p r i l 15 0.5 143 50% 65 A p r i l 1 0.5 118 100% 50 A p r i l 1 0.5 115 June 15, 1984 J u l y 13, 1984 August 19, 1984 VOLUMETRIC WATER CONTENT (%) Figure 11: Distribution of the s o l i water content for three plots located at the Knouff 12 km site on three different days. June 15, 1984 J u l y 13, 1984 August 19, 1984 15 -VOLUMETRIC WATER CONTENT (%) Figure 12: Distribution of the s o i l water content for three plots located at the Lac Le Jeune site on three different days. wetter at the lower depths p a r t l y because of the presence of an impermeable layer at the 1 m depth, which retarded drainage. The 0% canopy coverage (grass) plot at the Lac Le Jeune s i t e was the wettest of a l l the p l o t s . The Knouff 12 km plots had the most between-plot v a r i a t i o n on June 15, but had s i m i l a r s o i l water content p r o f i l e s by August 19. The Knouff 12 km 0% canopy coverage plot was the d r i e s t plot throughout the summer. The 0% canopy coverage plots at both s i t e s generally remained d r i e r i n the approximately top 40 cm of s o i l , while the p a r t i a l l y forested plots were d r i e r at the lower depths. This appeared to be due to the observed presence of grass roots only i n the upper depths of the s o i l i n the grass plots and tree roots i n both the upper and lower depths i n the p a r t i a l l y forested p l o t s . 5.1.3 Course of Root Zone S o i l Water Storage The t o t a l reduction i n the s o i l water storage from May 3 to October 4, 1984, ranged from 123 mm to 40 mm (Table 4). These values give a preliminary i n d i c a t i o n of the s o i l water which i s transpired by the trees. F i g s . 13, 14, 15 and 16 i l l u s t r a t e the course of the s o i l water storage and r a i n f a l l events. P r e c i p i t a t i o n was approximately 90 mm over the summer on a l l p l o t s . The horizontal l i n e s on the graphs i n these figures indicate the s o i l water storage i n the root zone (assumed to be 80 cm deep) at s o i l water matric potentials of -0.01 MPa ( f i e l d c a p a c i t y ) , -0.1 MPa and -1.5 MPa ( w i l t i n g p o i n t ) , and assume a uniform d i s t r i b u t i o n of the water content i n the s o i l p r o f i l e . Since no s o i l water retention data were obtained for the Recreation Area or Knouff 14 km plots i l l u s t r a t e d i n F i g . 16, these two plots are not discussed i n Table 4: Changes i n the s o i l water storage from May 3 to October 5, 1984. P l o t A8 (mm) Lac Le Jeune Grass (0% canopy coverage) 123 P a r t i a l l y f o r e s t e d (50% canopy coverage) 87 Fores ted (100% canopy coverage) 92 Knouff 12 km Grass (0% canopy coverage) 40 P a r t i a l l y f o r e s t e d (10% canopy coverage) 46 (25% canopy coverage) 48 (50% canopy coverage) 50 Fores ted (100% canopy coverage) 64 H e f f l e y (20% canopy coverage) 110 Knouff 14 km (10% canopy coverage) 73 R e c r e a t i o n Area (35% canopy coverage) 42 66 O 10055 MAY JUN JUL AUG SEP (1984) Figure 13: The r a i n f a l l events and course of root zone s o i l water storage for the plots at the Knouff 12 km site. 67 (1984) 14- The r a i n f a l l events and course of root zone soi storage for the plots at the Lac Le Jeune site. 68 Figure 15: The r a i n f a l l events and course of root zone s o i l water storage for the Heffley plot. 69 Figure 16: The r a i n f a l l events and course of root zone s o i l water storage for the Recreation Area and Knouff 14 km plots. terms of s o i l water matric p o t e n t i a l . However, on the basis of their s o i l texture, t h e i r retention properties are probably s i m i l a r to the s o i l s at the Knouff 12 km s i t e . Only two plots were at f i e l d capacity i n early May, when 6 was f i r s t measured. The Lac Le Jeune 0% canopy coverage plot remained at this l e v e l for a short time (about 1 week), while the Knouff 12 km 25% canopy coverage plot remained at f i e l d capacity u n t i l the end of June. The l a t t e r plot, however, had standing water nearby. There was a decline i n the s o i l water storage of a l l the plots corresponding to the Increase i n solar irradiance i n spring ( F i g . 17). This was also the time of bud break, which occurred on June 15 on the south facing lower elevation plots, and about one week l a t e r at the Lac Le Jeune s i t e . By the middle of July a l l plots had s o i l water storages corresponding to average s o i l water matric potentials less than -0.1 MPa. At this time, only the Knouff 12 km 0%, 50% and 100% canopy coverage plots had s o i l water storages corresponding to average matric potentials of less than -1.5 MPa (permanent w i l t i n g p o i n t ) . A l l plots had an increase i n root zone s o i l water storage i n mid-August, as a r e s u l t of an increase i n r a i n f a l l and the decline of solar irradiance at this time of year. This was also the time of bud set. 5.1.4 Evapotranspiration and Transpiration Rates Over the Growing Season Table 5 l i s t s the calculated evapotranspiration rates for the 11 microclimate plots for 1-4 week periods during the 1984 growing season (June 1 to October 4). The highest evapotranspiration rates occurred on a l l plots from June 23 to July 13. As expected, the plots which had the Figure 17: Course of the solar irradiance over the 1984 growing season. These values were calculated as an average for the daylight hours (daylight hours (N) are in Table 8). Table 5 ; E v a p o t r a n s p i r a t i o n ra tes over the growing season (mm day l ) Knouff 12 km P l o t s Canopy Coverage 0% 10% 25% 50% 100% June 1 June 7 0.81 0.83 0.35 0.88 0.80 June 8 - June 15 1.08 1.26 1.38 1.26 1.34 June 16 - June 22* 1.22 0.61 0.56 0.55 0.89 June 23 - J u l y 13 2.12 2.33 2.19 2.50 2.40 J u l y 14 - J u l y 24 0.85 0.43 0.31 0.42 0.45 J u l y 25 - Aug. 19* 0.84 0.91 0.94 0.65 0.64 A u g . 20 Oct . 4 1.09 1.27 1.58 1.64 1.61 Lac Le Jeune P l o t s H A T F Canopy Coverage 0% 50% 100% June 1 - June 22 1.90 1.44 1.86 June 23 - June 27* 2.57 2.20 1.97 June 28 - J u l y - 13* 1.39 1.21 0.99 J u l y 14 - Aug. 18 1.61 0.98 0.78 A u g . 19 - Oct . 4 1.43 2.38 2.85 DATE Knouff 14 H e f f l e y R e c r e a t i o n Area (10%) (20%) (35%) June 1 June 7 0.69 0.95 0.47 June 8 - June 15 1.09 0.55 0.72 June 16 - June 22* 0.68 1.41 0.69 June 23 - J u l y 13 2.47 2.68 1.18 J u l y 14 - J u l y 24 0.64 1.06 0.57 J u l y 25 - Aug. 19* 1.06 0.61 1.28 A u g . 20 - O c t . 4 1.07 1.76 1.24 * P e r i o d s of no recorded r a i n f a l l . highest i n i t i a l s o i l water storages also had the highest evapotranspir-ation rates during the growing seasion. Drainage during the growing season was small because s o i l water matric potentials were generally <-0.01 MPa. Consequently, as indicated e a r l i e r , neglecting drainage would cause only a small error i n the calculated values of E. The r a i n f a l l reaching the ground (P n) (mainly throughfall) for a given canopy closure was a constant proportion (c) of the above canopy p r e c i p i t a t i o n as indicated by the slopes of the l i n e s i n F i g . 18. This r e l a t i o n s h i p appeared to be constant for both large and small r a i n f a l l events. The standard deviation of c increased with increasing canopy coverage. The constant c decreased from 0.98 to 0.63 as canopy coverages increased from 10% to 100% ( F i g . 19). Table 6 l i s t s the calculated t r a n s p i r a t i o n rates for each plot and time i n t e r v a l during the 1984 growing season. Transpiration rates for the forested plots were lower than E, except for time in t e r v a l s during which there was no r a i n f a l l . In this case there was no interception loss due to a forest cover, so that E = T. During time in t e r v a l s of no r a i n f a l l , T was higher on the low canopy coverage plots than on the high canopy coverage plots. Table 7 l i s t s the t o t a l growing season E and T for each pl o t . The canopy coverage plots at the Knouff 12 km s i t e had a t o t a l E ranging from 129 mm to 138 mm. The three plots at the Lac Le Jeune s i t e had a t o t a l E ranging from 168 mm to 178 mm. Generally the t o t a l E on the Knouff 12 km and Lac Le Jeune s i t e s exhibited l i t t l e v a r i a t i o n with canopy coverage or stand density. The t o t a l T for the growing season, however, varied considerably with canopy coverage. The t o t a l T on the completely forested plots on both the Knouff 12 km and Lac Le Jeune 74 Figure 18: The relationship between the r a i n f a l l reaching the ground (P n) and r a i n f a l l above the canopy (P) for different canopy coverages. 75 Figure 19: Changes i n Pn/P (c) with canopy coverage. Table 6: T r a n s p i r a t i o n r a t e s over the growing season (mm day ) . Knouff Lake P l o t s DATE Canopy Coverage 0% 10% 25% 50% 100% June 1 - June 7 0.81 0.69 0.45 0.63 0.45 June 8 - June 15 1.08 1.16 1.34 1.20 1.07 June 16 - June 22* 1.22 0.61 0.56 0.55 0.89 June 23 - J u l y 13 2.12 2.31 2.14 2.20 2.01 J u l y 14 - J u l y 24 0.85 0.41 0.27 0.30 0.31 J u l y 25 - Aug. 19* 0.84 0.91 0.94 0.65 0.64 A u g . 20 - Oct . 4 1.09 1.24 1.37 1.38 0.98 Lac Le Jeune P l o t s Canopy Coverage 0% 50% 100% June 1 -• June 22 1.90 1.10 1.08 June 23 - June 27* 2.57 2.20 1.97 June 28 -• J u l y 13* 1.39 1.21 0.99 J u l y 14 - Aug. 18 1.61 0.90 0.68 A u g . 19 -• Oct . 4 1.43 2.24 1.97 DATE Knouff '. L4 H e f f l e y R e c r e a t i o n Area (10%) (20%) (35%) June 1 - June 7 0.68 0.93 0.39 June 8 - June 15 1.07 0.54 0.60 June 16 - June 22* 0.67 1.36 0.63 June 23 - J u l y 13 2.42 2.63 1.08 J u l y 14 - J u l y 24 0.63 1.04 0.52 J u l y 25 - Aug. 19* 1.06 0.59 1.17 Aug. 20 - Oct . 4 1.05 1.73 1.14 * P e r i o d s of no recorded r a i n f a l l . Table 7: Comparison of the t o t a l growing season evapotranspiration and t r a n s p i r a t i o n rates. PLOT IE (mm) ET (mm) (Canopy Coverage) Knouff 12 km 0% 129 129 10% 132 129 25% 134 128 50% 138 122 100% 138 107 Knouff 14 km 10% 134 132 Heffley 20% 153 147 Recreation Area 35% 113 102 Lac Le Jeune 0% 179 179 50% 168 153 100% 178 132 78 s i t e s was less than on the p a r t i a l l y forested p l o t s . The 25% canopy coverage plot had the highest t o t a l T at the Knouff 12 km s i t e , while the highest t o t a l T occurred on the grass plot at the Lac Le Jeune s i t e . These results support the suggestions of Calder (1979) that grass w i l l transpire more than a coniferous fo r e s t ; however, the evaporation of r a i n f a l l intercepted by the forest can compensate for the lower T, r e s u l t i n g in s i m i l a r E. The errors i n the E and T c a l c u l a t i o n s are due to uncertainties i n the neutron probe measurements of s o i l water content and the measurements of P. Calibrations of the neutron probe with gravimetric s o i l samples indicated a possible error of 7%, while the largest possible error associated with the P measurements was estimated to be 9% and occurred under completely forested plots. Consequently, the root mean square (RMS) error in E i s 11.4%, i . e . ( 9 2 + 7 2 ) 0 * 5 . 5.1.5 Factors Affecting Evapotranspiration and Transpiration Rates The values of the r a t i o of LE to s/(s + y)^n (daytime basis) were found to be quite low, ranging from 0.15 to 0.33 (Table 8). These values appear to be too low to be estimates of the P r i e s t l e y - T a y l o r a defined by L E m a x = a ( s / ( s + y ) R n . Generally, values of a range from 0.6 and 1.1 for coniferous forests (Giles et a l . 1985; Spittlehouse and Black 1983; McNaughton and Black 1981). These low a values indicate the E and T are probably s o i l l i m i t e d . In this case E or T would be expected to increase with increasing root zone water content regardless of available energy. Although E appears to be s o i l l i m i t e d , i t does not appear to increase with increasing W ( F i g . 20). The data i n this figure are s t r a t i f i e d according to the available energy. In cases in which E Table 8: Ratio of LE to [s/(s + Y)](Rn_ ~ ^) • (Also shown are meteorological variables used i n the c a l c u l a t i o n of the available energy.) TIME INTERVAL T a n N R n G S t L* L E 1 LE (°C) (hrs) (hrs) (W m - 2) (W m - 2) (W m - 2) (W m - 2) (W m - 2) [s/(s + y ) ] ( R n - G) June 1 - June 7 10.50 5.77 14.7 296.15 10.25 377.93 -36.43 30.62 0.15 June 8 - June 15 9.28 9.09 14.7 246.32 7.39 340.14 -53.00 58.33 0.39 June 16 - June 22 14.87 10.66 14.8 322.71 9.68 431.68 -57.11 26.74 0.14 June 23 - July 13 15.85 8.39 15.0 416.91 12.51 462.96 -46.04 116.66 0.46 July 14 - July 24 19.82 10.85 15.1 424.22 12.73 478.29 -54.07 14.58 0.06 July 25 - Aug. 19 22.27 9.91 14.8 363.65 10.91 412.91 -49.26 31.60 0.14 Aug. 20 - Oct. 4 10.01 8.21 13.5 318.35 9.55 370.37 -52.02 67.08 0.35 June 1 - June 22 11.55 8.51 14.7 384.93 11.55 372.50 -49.35 53.47 0.39 June 23 - June 27 15.84 8.39 15.0 439.90 13.20 393.96 -45.70 106.94 0.43 June 28 - July 13 15.84 8.39 15.0 455.14 13.65 393.96 -45.70 58.82 0.23 July 14 - Aug. 18 21.00 10.50 15.0 449.07 13.47 424.60 -52.00 43.75 0.18 Aug. 19 - Oct. 4 10.01 8.21 13.5 359.26 10.78 364.37 -52.02 108.89 0.56 LE was calculated for the 50% canopy coverage p l o t s . 80 R n - 6 ( w m 2 ) o E < CL (/) z < cn 2.5-2 -1.5-1-O CL. > 0 5-— • • * • • (S) % l b ® <§) <§)<§) e> 7>t7) *° c o o e>e> ° O O o 4 0 4 . 4 - • 3 0 8 . 8 - ® 3 3 1 . 3 - ® 41 1.5 - O 50 100 150 200 250 ROOT ZONE (80 cm) WATER STORAGE (mm) Figure 20: Relationship of the evapotranspiration rates to s o i l water storage and a v a i l a b l e energy (R n - G). Available energy was calculated as an average for the daylight hours. 81 i s l i m i t e d by the available energy and not s o i l water content, E would increase with increasing available energy. This i s not the case as the period with the highest average available energy (412 W m ) has the lowest E. This suggests that the vapour pressure d e f i c i t may be playing a major role i n the evapotranspiration process. The time courses of E and T, av a i l a b l e energy and the average day-time D are shown i n F i g . 21 for the Knouff 14 km s i t e , and i n F i g . 22 for the Lac Le Jeune s i t e . There i s a poor c o r r e l a t i o n between E and T of the forested plots and R n - G of. a l l the p l o t s . There does, how-ever, appear to be a strong negative c o r r e l a t i o n between E and T of the forested plots and vapour pressure d e f i c i t . The grass plots do not appear to have a consistent r e l a t i o n s h i p with either vapour pressure d e f i c i t or available energy. The average daytime D i s the arithmetic average of the 10:00 and 14:00 hour values (Tanner 1981). Figure 23 shows three d a i l y traces of D. The highest hourly average value of D, i n t h i s figure, occurred on August 18, 1984 and was 2.1 kPa. Table 9 l i s t s the average daytime D for each time i n t e r v a l . Although Spittlehouse (1981) recorded greater vapour pressure d e f i c i t s on Vancouver Island, he was able to relate E to R n - G and s o i l water storage. The s o i l water contents during much of the growing season i n his study, however, were greater than those found i n this study. The s e n s i t i v i t y of t r a n s p i r a t i o n to vapour pres-sure d e f i c i t s , i n the i n t e r i o r of B.C. may be due to extended periods of low s o i l water matric potentials and possibly due to greater s e n s i t i v i t y of the stomata of i n t e r i o r Douglas-fir compared to those of coastal Douglas-fir. 82 o 3-1 • 0 2.0 £ 1.5-o '.0 0.5-0 -•T 400 6 * 300 -° 200 « c 100 0% 50% 100% i JUN JUL AUG SEP Figure 21: The time course of E and T, the available energy and vapour pressure deficits for three plots at the Knouff 12 km site over the 1984 growing season. 83 3 -•o 0 3-1 0 2 . 0 -£ 1 .5 a '-° 0 . 5 -0-rT 400-E 3 300 o 200 i c 100 0 0% 50% 100% i JUN JUL AUG SEP Figure 22: The time course of E and T, the available energy and vapour pressure deficits for three plots at the Lac Le Jeune site over the 1984 growing season. 84 2.5 2^ A JUNE 3, 1984 O JULY 6, 1984 • AUGUST 5, 1984 1.5 / / f JO- \ .0 H 0.5 H • P •' A-A 0 10 15 TIME (hours) 20 25 Figure 23: Daily traces of vapour pressure deficits for three different days. Table 9: Average daytime (10:00 and 14:00 hours) vapour pressure d e f i c i t s for d i f f e r e n t time i n t e r v a l s . Time i n t e r v a l D S x (kPa) (kPa) Knouff 12 km s i t e June 1 - June 7 June 8 - June 15 June 16 - June 22 June 23 - July 13 July 14 - July 24 July 25 - Aug. 18 Aug. 19 - Oct. 4 0.39 0.04 0.31 0.17 1.39 0.11 1.11 0.39 1.97 0.30 1.43 0.22 0.88 0.23 Lac Le Jeune s i t e June 1 - June 22 June 23 - June 27 June 28 - July 13 July 14 - Aug. 18 Aug. 19 - Oct. 4 1.40 0.17 1.00 0.19 1.53 0.41 1.83 0.30 0.88 0.23 86 F i g s . 24 and 25 show T plotted as a function of D, for s o i l water matric potentials greater than -0.5 MPa, and less than -0.5 MPa, res p e c t i v e l y . In both cases, T increased with increasing D, peaking at a D of approximately 1.1 kPa. After t h i s point, there i s a rapid decline i n T. For low values of D (less than 0.88 kPa), canopy coverage and s o i l water matric p o t e n t i a l did not appear to influence T, which was si m i l a r for a l l p l o t s . At higher values of D, however, the grass plots had the highest T, and as the forest cover increased, T tended to decrease, p a r t i c u l a r l y at values of D higher than 1.2 kPa. The plots with low water contents ( F i g . 25) had much lower T, e s p e c i a l l y at high values of D. The grass covered plots did not respond to s o i l water matric p o t e n t i a l as much as the forested p l o t s ; however, there was a reduction i n T on these plots at the end of the summer, probably due to a reduction i n the grass leaf area due to grazing and the senescence of grass on the south facing slopes. Figures 26 and 27 show the r e l a t i o n s h i p between r c c j and D for s o i l water matric potentials (^s) >-0.5 MPa and <-0.5 MPa, respective-l y , for a range of canopy coverages. At the higher range of i | / s , r c d remained r e l a t i v e l y low, increasing s l i g h t l y at higher values of D. When tys was less than -0.5 MPa, however, there was a large increase i n r C ( j at higher D. The grass plots had the lowest r c d , regardless of ij / s . The resistance tended to increase with increasing canopy coverage. Therefore, D appeared to have a d e f i n i t e c o n t r o l l i n g influence on tr a n s p i r a t i o n , p a r t i c u l a r l y on the forested plots and with low s o i l water matric p o t e n t i a l s . When D was low, T was low, as would be expected. When D increased to above 1.2 kPa, canopy resistance 87 Figure 24: Relationships between transpiration and vapour pressure deficits for different canopy coverages and s o i l water matric potentials greater than -0.5 MPa. 88 2.5-1 1 " l 1 1 r 0 0.5 1 1.5 2 VAPOUR PRESSURE DEFICIT (kPa) Figure 25: Relationships between transpiration and vapour pressure deficits for different canopy coverages and s o i l water matric potentials less than -0.5 MPa. 89 800 CANOPY COVERAGE E „w, 600 cr UJ o Z 400 CO CO UJ ce >-Q_ o z < 200-o IOS • D 25* • 507. -A K>0* • • _ _ J3 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 VAPOUR PRESSURE DEFICIT (kPa) Figure 26: Relationships between canopy resistance (dry) and the vapour pressure deficit for different canopy coverages and s o i l water matric potential greater than -0.5 MPa. 90 2500 £ in Q co co LU cr >-CL O z < CJ 2000 1500-1000 500-CANOPY COVERAGE • o% O 1055 Q 25% • 5055 A 1007. T i i i i ••r 0 0.5 1 1.5 2 VAPOUR PRESSURE DEFICIT (kPa) Figure 27: Relationships between canopy resistance (dry) and the vapour pressure deficits for different canopy coverages and so i l water matric potential less than -0.5 MPa. 91 increased, p a r t i c u l a r l y on the forested s i t e s , with low s o i l water matric p o t e n t i a l s . The higher the canopy coverage and the higher the D, the higher was the value of r C ( j , and subsequently, the lower the t r a n s p i r -a t i o n r a t e s . The high values of r C ( j found for the grass p l o t s , which corresponded to the high values of D occurring at the end of the summer, was probably a r e s u l t of lower leaf area indices and the higher stomatal resistances of senescing leaves. As s o i l water matric p o t e n t i a l increased, the s e n s i t i v i t y of T to D decreased, which i s i n agreement with Tan and Black (1976). Consequently, the higher t r a n s p i r a t i o n rates occurred on the plots which had the higher a v a i l a b l e s o i l water content. Transpiration (the sum of T t and Tg) decreased with an increased stand density. In contrast with these r e s u l t s , Black et a l . (1980) found that the T of thinned and unthinned stands were s i m i l a r , while Whitehead et a l . (1985) found that T was higher on an unthinned stand than on a thinned stand. In the former case, t r a n s p i r a t i o n from an understory s a l a l component compensated for any reduction i n the tree t r a n s p i r a t i o n of the thinned plots, r e s u l t i n g i n s i m i l a r t o t a l plot t r a n s p i r a t i o n s . In the l a t t e r case, s o i l was not l i m i t i n g so plots with the larger number of trees, and higher LAI's had higher t r a n s p i r a t i o n rates. 5.2 Relationships Derived From the Stem Analysis Trees 5.2.1 Relationships Between Diameter, Age and Stand Density The diameter growth at breast height decreased with increasing stand density, as would be expected (Table 10 and F i g . 28). The curves i n F i g . 28 were f i t t e d using the equation d = m(g - 10)°- 6 (50) 92 Table 10: Average age and diameter at breast height for the d i f f e r e n t stand density classes. Density class d (cm) age (years) (trees h a - 1 ) mean range mean range 0 - 300 12.2 6.2 - 24.1 50 22 - 120 301 - 600 16.3 5.8 - 35.4 ' 58 30 - 102 601 - 900 20.1 5.4 - 51.2 82 33 - 150 901 - 1200 15.1 5.5 - 47.0 105 35 - 210 1501 - 1800 11.9 6.6 - 21.6 51 35 - 73 2701 - 3000 10.0 5.7 - 19.5 76 50 - 147 93 AGE (years) F i g u r e 28: R e l a t i o n s h i p s between diameter at breast height (d) and age f o r three d i f f e r e n t stand d e n s i t i e s . Each l i n e i s the average diameter growth of four trees which were greater than 125 years o l d . 94 where d i s the diameter (cm) at breast height, ra is an experimental c o e f f i c i e n t (given i n F i g . 28) s p e c i f i c to each density class and g i s age (years) from germination. The constant, 10 years, corresponds to the approximate time required for the trees to reach breast height. An equation to calculate age from d and stand density (S) was determined as follows. The values of m i n F i g . 28 were plotted against S and the curve f i t t e d i s as follows ra = 40.5 S - 0 - 5 (51) where S i s i n trees h a - 1 ( F i g . 29). Substituting (51) into (50) gives d = 40.5 S _ 0 - 5 ( g - 1 0 ) 0 - 6 (52) By rearranging (52), age can be expressed as g = 10 + 0.00207 dl.67 s0.83 ( 5 3 ) This equation i s only v a l i d i f d i s taken at breast height. Although t h i s equation was successfully used for the 100 trees sampled for stem analyses i t should be used with caution for trees greater than 140 years of age. 5.2.2 Relationships Between Height, Age and Stand Density Height (H) i s generally believed to be mainly a function of s i t e environment rather than stand density. This, however, was not the case i n the stands studied, as indicated by the height growth of the stem Figure 29: R e l a t i o n s h i p of the p r o p o r t i o n a l i t y constant (m) to s d e n s i t y . 96 a n a l y s i s trees ( F i g . 30) . At 100 years of age, t rees growing at a low stand d e n s i t y (300-600 trees h a - 1 ) were approximate ly 48% t a l l e r than t rees growing at a moderate stand d e n s i t y (900-1200 t r e e s h a - 1 ) , and approximate ly 82% t a l l e r than t rees growing at a h i g h stand d e n s i t y (2700-3000 t r e e s h a - 1 ) . The cumulat ive he ight growth, d e f i n e d as the c u r r e n t he ight of the t ree d i v i d e d by the c u r r e n t age, ranged from 0.26 m y e a r - 1 f o r a stand d e n s i t y of <300 t r e s s h a - 1 to 0.12 m y e a r - 1 f o r a stand d e n s i t y of 2700 - 3000 trees h a - 1 (Table 11 and F i g . 3 1 ) . I n c o n t r a s t to these r e s u l t s , Monserud (1984) found no change i n the he ight growth ra te w i t h stand d e n s i t y , on the t rees he s e l e c t e d f o r s tudy i n e i t h e r an even-age or uneven-age s t a n d . The sample t rees he s e l e c t e d f o r s t u d y , however, were dominants i n an open stand w i t h c o n s i s t e n t even r a d i a l growth and no s igns of s u p p r e s s i o n . 5.2.3 The Relationship Between Diameter-to-Height Ratio and Stand Density Diameter at breast he ight i n c r e a s e d l i n e a r l y i n p r o p o r t i o n to height ( F i g s . 32 and 33) . As the stand d e n s i t y i n c r e a s e d , the r a t i o of d to H ( i . e . the r e c i p r o c a l of the s lope of the l i n e s i n F i g s . 32 and 33) decreased. Except f o r immediate ly adjacent d e n s i t y c l a s s e s , the r a t i o s were s t a t i s t i c a l l y s i g n i f i c a n t l y d i f f e r e n t . F i g . 34 shows that the r a t i o of d to H decreased s l o w l y w i t h i n c r e a s i n g stand d e n s i t y . The equat ion that best descr ibes the r e l a t i o n s h i p between d/H and S i s 97 AGE (years) Figure 30: R e l a t i o n s h i p s between t o t a l height and age f o r three d i f f e r -ent stand d e n s i t i e s . Each l i n e i s an average of the height growth of four trees which were greater than 125 years o l d . 98 Table 11: Cumulative average height growth rate for stands at d i f f e r e n t d e n s i t i e s . Cumulative average Density class Height (m) age (years) height growth rate (trees h a - 1 ) (m year" *) mean range mean range mean 0 - 300 12.92 5.35 - 20 .90 50 22 - 120 0.26 0.06 301 - 600 14.19 4.70 - 25 .74 58 30 - 102 0.21 0.08 601 - 900 14.74 8.00 - 36 .00 82 33 - 150 0.18 0.06 901 - 1200 15.75 8.70 - 28 .95 105 35 - 210 0.15 0.04 1501 - 1800 8.62 5.90 - 16 .20 51 35 - 73 0.17 0.02 2701 - 3000 9.15 4.95 - 14 .70 76 50 - 147 0.12 0.03 99 0.30-1 Figure 31: R e l a t i o n s h i p s between the cumulative height growth and stand d e n s i t y . 100 Figure 32: Rela t ionships between height and diameter at breast height f o r three d i f f e r e n t stand d e n s i t i e s . DIAMETER (cm) Figure 33: Relationships between height and diameter at breast height for three d i f f e r e n t stand d e n s i t i e s . 102 Figure 34: Relationship between the d/H ratio and stand density. The line drawn is from Equation (54). 103 d/H = 0.0341S - 0 . 1 4 0 (54) where d/H i s i n m m . This equation i s shown as the l i n e i n Fi g . 34. 5.2.4 The Local Volume Equation A li n e a r logarithmic equation to describe current i n d i v i d u a l tree volume (V) as a function of d and d/H was determined for the stem analysis trees to be where V, d and H are in cubic metres, centimetres and metres, respec-t i v e l y . The regression equation r e l a t i n g estimated volume, using (55) to actual volume (V a) i s V = 0.008 m3 + 0.951 V a ( r 2 = 0.986, n = 100, SE =0.00697 m ). The 5% underestimate i s due p a r t l y to a negative bias introduced by using a log function. This equation, when expressed as a power function, becomes l o g V = - 3 . 9 8 3 + 2.603 l o g d - 0.5556 l o g d/H (55) V = 0.000104 d 2 . 04 7 H 0 . 5 5 6 (56) Eliminating H i n (56) using (54) gives V in terms of d and S as V = 0.0000525 d 2 . 6 0 3 c 0 . 0 7 8 (57) When both d and H are expressed i n metres, (56) becomes V = 1.29 d 2- 0 4 7 H 0 - 5 5 6 (58) 104 and (57) becomes V = 8.44 d 2.603 <, 0.078 (59) Using equation (55), a local volume table was developed (Table 12). It should be noted that a time factor is not included in this table. Although, for a given diameter at breast height, volume increases with increasing stand density, trees growing at a higher stand density are actually growing slower. For example, (53) shows that a tree with a breast height diameter of 10 cm, growing at a stand density of 2850 trees ha - 1 would be about three times older than a tree with the same diameter growing at a stand density of 450 stems ha - 1. 5.2.5 Relationship Between Form Factor, Tree Diameter and Stand Density The form factor (F) is defined as where V is the volume of a tree and V c , the volume of a cone with the same height as the tree and a base diameter equal to the tree diameter at breast height, is given by F = V/V c (60) V c = (rr/12) d2H (61) Substituting (59) and (61) into (60) gives F = 4.93 d 0 . 0 < 4 7 H _ 0 . ^ (62) Table 12: Local volume table. VOLUME ( r ) d/H Ratio 1 (cm/m) D (cm) 1.63 1.50 1.38 1.29 1.21* 1.14 1.10* 1.075* 1.065* 1.06 5 0.005 0.006 0.006 0.006 0.006 0.006 0.006 0.006 0.007 0.007 10 0.032 0.033 0.035 0.036 0.037 0.390 0.039 0.039 0.039 0.041 15 0.091 0.096 0.100 0.104 0.108 0.111 0.114 0.115 0.116 0.116 20 0.193 0.202 0.212 0.220 0.228 0.236 0.240 0.243 0.244 0.245 25 0.345 0.361 0.378 0.393 0.407 0.420 0.420 0.435 0.438 0.439 30 0.555 0.580 0.608 0.630 0.655 0.676 0.690 0.698 0.703 0.705 35 0.828 0.867 0.908 0.943 0.977 1.01 1.03 1.04 1.05 1.05 40 1.170 1.23 1.29 1.34 1.38 1.43 1.46 1.48 1.49 1.49 45 1.59 1.67 1.75 1.82 1.88 1.95 1.98 2.01 2.02 — 50 2.09 2.19 2.30 2.39 2.47 2.56 2.61 2.64 2.65 — 55 2.69 2.81 2.94 3.06 3.16 3.27 3.34 3.39 — — 60 3.37 3.53 3.70 3.84 3.97 4.11 4.19 4.25 — — 65 4.15 4.35 4.55 4.72 4.90 5.06 5.16 — — — 70 5.04 5.27 5.52 5.73 5.94 6.14 6.27 — — — 75 6.03 6.31 6.61 6.85 7.11 7.35 — — — — 80 7.13 7.46 7.82 8.11 8.41 8.69 — -T — — 85 8.34 8.73 9.14 9.51 9.84 — — — — 90 9.53 10.23 10.72 10.96 11.48 — — — — 95 11.55 11.75 12.30 12.59 — — — — — 100 12.59 13.18 14.13 — — — — 150 450 750 1050 1350 1650 1950 2250 2550 2850 Midpoint of Density Class (trees ha" 1) lThe d/H ratios l i s t e d are from actual data and not determined from equation (54). an (*) were l i n e a r l y interpolated from the actual data points i n Figure 34. Ratios marked with 106 where d and H are i n meters . S u b s t i t u t i n g (54) i n t o (62) g ives F = 1.10 d-0 . 397 s-0. 062 ( f i 3 ) where d i s i n meters . From t h i s equat ion i t can be seen that f o r a constant d , F decreases s l o w l y w i t h i n c r e a s i n g S, and the t rees become more c o n i c a l i n shape ( F i g . 35 ) . T h i s f i g u r e a l s o shows t h a t , f o r a constant S, the form f a c t o r decreases s i g n i f i c a n t l y w i t h i n c r e a s i n g t ree d iameter . 5.2.6 Relia b i l i t y of the Local Volume Equation E s t i m a t i o n of t ree volumes u s i n g the l o c a l volume equat ion (55) were compared to a c t u a l volumes of t rees 5, 10 and 20 years ago, as determined from S m a l i a n ' s equat ion (46) . Because the d to H r a t i o was found to decrease s l o w l y w i t h i n c r e a s i n g stand d e n s i t y , the current d to H r a t i o was assumed to have remained approximate ly constant over the previous 20 y e a r s . T h e r e f o r e , the only v a r i a b l e changing i n (55) was the t ree diameter at breast h e i g h t . F i g . 36 shows the est imated volume versus the a c t u a l volume on the t rees 5, 10, and 20 years ago. Equat ion (55) es t imated the volume of the t rees 5, 10 and 20 years ago w i t h i n 9%, 8% and 10%, r e s p e c t i v e l y ( r 2 = 0 .967, 0.984 and 0 .983 , r e s p e c t i v e l y ) . This i n d i c a t e s that the l o c a l volume equat ion can es t imate the past volume of a t ree i n the i n v e n t o r y p l o t s w i t h acceptable accuracy . 107 1.5-cr O i— o cr O 0.5-! I 500 1000 1500 2000 2500 STAND DENSITY (trees ha" 1) i 1 3000 3500 Figure 35: Relationship between the form factor and stand density several values of diameter at breast height. 108 ACTUAL VOLUME (m 3) F igure 36: Comparison of predic ted versus a c t u a l volumes of trees 5, 10 and 20 years ago. The s o l i d l i n e represents a 1:1 r e l a t i o n s h i p . The dashed l i n e represents the average r e l a t i o n s h i p s of the predic ted and a c t u a l volumes for a l l three time p e r i o d s . The a c t u a l equations for the p r e d i c t e d volumes (V p ) 5, 10 and 20 years ago, as derived from the a c t u a l volume ( V a ) are V p - 0.013 m 3 + 0 .909V a ; V p - 0.005 m3 + 0 .924V a ; and V p = 0.007 m 3 + 0 .895V a , r e s p e c t i v e l y . 109 5.3 Average Annual Stand Volume Growth 5.3.1. Relationship of Average Annual Stand Growth to Stand Density and Volume Table 13 shows the stand density and t o t a l stand volume before logging, immediately following logging and i n 1983 for each of the 21 inventory p l o t s . (Plot 22, located i n the IDF-Montane Spruce t r a n s i -t i o n , was found to be more representative of the l a t t e r and was e l i m i n -ated.) Stand densities immediately following logging ranged from 80 to 2552 trees ha and t o t a l stand volumes ranged from 2 to 243 m ha . In 1983 stand densities were between 96 and 2784 trees h a - 1 , while stand volumes ranged from 9 to 477 m ha . Table 14 shows the cumulative stand volumes since the time of logging. In three cases, the volume harvested had been regained. Plots 3 and 8 had regained th e i r harvested volume by 1968 (15 years after logging), while plot 4 regained i t s harvested volume by 1983 (30 years after logging). Table 15 shows the average annual volume growth rates (for f i v e year periods) of each plot since the l a s t logging (Appendix 4). The growth rates ranged from 0.2 to 11.0 m3 h a - 1 y e a r - 1 , with the lowest values occurring on plots with less than 300 trees h a - 1 and the highest values on the 901 - 1200 trees h a - 1 density p l o t s . Plots in the 2701 -3000 trees h a - 1 density class had s l i g h t l y lower o v e r a l l growth rates than plots in the 301 - 600 trees h a - 1 density c l a s s . F i g . 37 shows the time course of the average annual growth rates, as related to density c l a s s , for the eight plots logged i n 1953. From this figure, i t can be seen that the highest average annual growth rates occurred on plots i n the 901 - 1200 density class and ranged from 6.0 to 9.7 m3 ha" 1 y e a r - 1 average values for three p l o t s . The highest stand density class (2701 -Table 13: T o t a l stand volume and dens i ty before l o g g i n g , immediately f o l l o w i n g l o g g i n g and i n 1983 P l o t Las t Before l o g g i n g F o l l o w i n g l o g g i n g 1983 number l o g g i n g Volume Dens i ty Volume D e n s i t y Volume D e n s i t y (year) (m 3 h a - 1 ) ( t r e e s h a - * ) (md ha~ l ) ( t r e e s ha l ) (m 3 h a _ l ) ( t r e e s h a - 1 ) < 300 t rees h a - 1 9 1968 19 352 2 288 24 304 10 1968 375 352 10 80 23 96 11 1968 391 400 3 176 17 208 12 1968 487 560 2 208 9 224 15 1978 65 480 28 272 39 288 17 1978 416 256 68 224 87 240 301 - 600 t rees h a - 1 4 1953 181 528 67 414 194 464 5 1953 267 464 25 280 140 464 18 1978 225 656 39 480 48 480 19 1978 282 528 103 384 124 384 20 1968 312 592 9 320 19 320 21 1978 132 368 43 320 61 320 601 - 900 t rees h a - 1 1 1978 477 1200 273 864 274 864 6 1953 261 752 81 304 236 656 7 1953 348 800 89 . 608 261 688 901 - 1200 t rees h a " 1 2 1953 477 1200 179 864 416 1040 3 1953 328 1232 243 976 477 1088 8 1953 343 826 207 812 448 972 13 1968 240 1072 76 896 105 976 1501 - 1800 t rees h a - 1 16 1978 309 1760 181 1632 200 1632 2701 - 3000 trees h a - 1 14 1953 235 2864 97 2752 160 2784 I l l Table 14: Cumulat ive t o t a l stand volume from time of l a s t l o g g i n g to 1983. Volume (m h a " 1 ) Year P l o t L a s t number l o g g i n g 1953 1958 1963 1968 1973 1978 1983 < 300 t rees h a - 1 9 1968 — — — 2 8 15 24 10 1968 — — — 10 11 13 23 11 1968 — — — 3 5 8 17 12 1968 — — — 2 3 4 9 15 1978 — — — — 28 29 17 1978 — — —— 68 87 301 - 600 t rees h a " 1 4 1953 67 82 103 123 146 168 194 5 1953 25 37 61 76 100 119 140 18 1978 — — — — — 39 48 19 1978 — — — — 103 124 20 1968 — — — 9 12 15 19 21 1978 • —— 43 61 601 -900 t rees h a - 1 1 1978 — — — — — 237 274 6 1953 81 100 124 146 174 202 236 7 1953 89 113 140 166 197 227 261 901 - 1200 t rees h a - 1 2 1953 179 211 254 309 352 383 416 3 1953 243 298 346 382 419 448 477 8 1953 207 256 311 349 388 418 448 13 1968 — — — — ~" 76 100 125 153 1501 - 1800 t rees h a " • 1 16 1978 181 200 2701 - 3000 trees h a " • 1 14 97 113 127 137 149 154 160 112 Table 15: Course of annual volume growth from logging to 1983. Average yearly volume growth (m ha ) Plot Last 1953- 1958- 1963- 1968- 1973- 1978 number logging 1958 1963 1968 1973 1978 1983 < 300 trees h a - 1 ,9 1968 — . — — 1.2 1.4 1.8 10 1968 — — — 0.2 0.4 2.0 11 1968 — — — 0.4 0.6 1.8 12 1968 — — — 0.2 0.2 1.0 15 1978 — — — — — 2.2 17 1978 —— — —— —— —— 3.8 301 - 600 trees h a - 1 4 1953 3.0 4.2 4.0 4.6 4.4 5.2 5 1953 2.4 4.8 3.0 4.8 3.8 4.2 18 1978 — — — — — 1.8 19 1978 — — — — — 4.2 20 1968 — — — 0.6 0.6 0.8 21 1978 — — — —— 3.6 601 -900 trees h a - 1 1 1978 — — — — — 7.4 6 1953 3.8 4.8 4.4 4.6 5.6 6.8 7 1953 4.8 5.4 5.2 6.2 6.0 6.8 901 - 1200 trees ha~ 1 2 1953 6.4 8.6 10.9 8.6 6.2 6.6 3 1953 11.0 9.6 7.2 7.4 5.8 5.8 8 1953 9.8 11.0 7.6 7.8 6.0 6.0 13 1968 4.80 5.0 5.6 1501 - 1800 trees ha' -1 16 1978 3.8 2701 - 3000 trees ha' -1 14 1953 3.2 2.8 2.0 2.4 1.0 1.2 113 O o o U l 10 8 I L . r L_. trees ha 301-600 -1 601-900 901-1200 2701-3000 .ZlT o > _J < < 2 -1953 1958 1963 1968 1973 TIME (year) — i — 1978 1 983 F i g u r e 37: The time course of the volume growth rate as re la ted to stand d e n s i t y . The 301 - 600 and 601 - 900 l i n e s represent an average of two plo ts each, while the 901 - 1200 l i n e represents an average of three p l o t s . Only one plot i s inc luded i n the 2701 - 3000 l i n e . 114 3000 t rees h a - 1 ) had the lowest average annual growth r a t e s which were 3 1 l between 1.0 and 3.8 m h a - year . They were h i g h e s t immediately f o l l o w i n g l o g g i n g and decreased w i t h t ime . P l o t s w i t h stand d e n s i t i e s of l e s s than 900 t rees h a - 1 tended to have i n c r e a s i n g growth ra tes w i t h time s i n c e the l a s t l o g g i n g , w h i l e the p l o t s In the 901 - 1200 d e n s i t y c l a s s tended to i n c r e a s e f o r approximate ly 10 to 15 years a f t e r l o g g i n g , t h e r e a f t e r d e c l i n i n g . The growth ra tes per hectare c a l c u l a t e d from the stem a n a l y s i s t rees (= 10% of the t o t a l number of t r e e s ) agreed, except f o r one i n s t a n c e , w i t h i n 8% of the va lues c a l c u l a t e d from core a n a l y s i s ( « 70% of the t o t a l number of t r e e s ) . The e x c e p t i o n o c c u r r e d on the 901 - 1200 d e n s i t y p l o t s d u r i n g the 1958 - 1963 time p e r i o d . I n t h i s case, the annual growth ra tes c a l c u l a t e d from the stem a n a l y s i s t rees were 16% h i g h e r than those c a l c u l a t e d from the core a n a l y s i s t r e e s . Table 16 shows the growth ra tes and changes i n stand d e n s i t y , the d/H r a t i o and volume of the permanent sample p l o t s s i n c e e s t a b l i s h m e n t . The annual growth r a t e s were between 1 and 10 m ha year . The h i g h e s t growth ra te was at a stand d e n s i t y of 1100 t rees h a - 1 , w h i l e the lowest growth ra te was at a stand d e n s i t y of 2755 t rees h a - 1 . These p l o t s showed the same r e l a t i o n s h i p between annual volume growth rates and stand d e n s i t y as the 21 i n v e n t o r y p l o t s . The d/H r a t i o s (used i n the l o c a l volume equat ion) of the treatment p l o t s were n o t , as y e t , r e p r e s e n t a t i v e of t h e i r d e n s i t y c l a s s . They were, however, i n c r e a s i n g s i n c e treatment ( t h i n n i n g ) had o c c u r r e d . The t r e e m o r t a l i t y s ince p l o t es tab l i shment on the c o n t r o l p l o t s appeared to be due to c o m p e t i t i o n , w h i l e the m o r t a l i t y which occurred on the treatment p l o t s was observed to be due to stem c o l l a p s e . From a sample of 100 t rees which were observed to have stem c o l l a p s e , i n the g e n e r a l v i c i n i t y of the permanent Table 16: Summary of the permanent plot a n a l y s i s . Plot Time of density (trees ha ) Establishment d/H Volume (cm m - 1) (m3 h a - 1 ) density (trees h a -1983 d/H ^(cm m"1) Volume (m 3 h a - 1 ) Growth (m 3 h a - 1 y _ 1 ) A Knutsford (1980)* Control 2280 1.07 241 2240 1.05 250 3 Treatment 1100 1.06 140 1050 1.08 170 10 B Knouff (1982)* Control 1440 1.19 438 1440 1.12 442 4 Treatment 700 1.19 208 700 1.21 214 6 C Sugarloaf (1982)* Control 2755 1.06 155 2521 1.06 156 1 Treatment 888 1.08 107 836 1.10 114 7 D Lac Le Jeune (1982)* Control 1987 1.12 170 1987 1.12 172 2 Treatment 880 1.13 88 880 1.16 96 8 *Year of i n i t i a l plot establishment. 116 sample p l o t s , 85% had d/H r a t i o s of less than 1.0 cm m - 1, which suggests a density of ~ 1500 trees h a - 1 before thinning. This indicates that heavy thinning of such stands can r e s u l t i n serious losses due to stem collapse. Figure 38 shows the r e l a t i o n s h i p of annual volume growth to stand volume for d i f f e r e n t stand densities and includes both the inventory and permanent sample p l o t s . In plots with stand densities greater than 1500 trees h a - 1 , annual volume growth rate tended to decrease with increasing 3 — 1 stand volume. In these p l o t s , stand volume did not exceed 170 m ha This was probably caused by the presence of a large number of small trees and increased competition between trees. In the plot i n the 2701 - 3000 trees h a - 1 density c l a s s , there were approximately 320 trees h a - 1 which were observed to be dead. A l l these trees had diameters at breast height of < 6 cm. In plots with stands less than 900 trees h a - 1 , annual volume growth rate tended to increase with increasing stand volume; however, the t o t a l stand volumes did not exceed 275 m h a - 1 . Plots with stand densities of 901 - 1200 trees h a - 1 had stand volumes between 105 and 477 m ha . Annual volume growth rate increased with increasing 3 1 stand volume u n t i l the stand volume reached approximately 275 m h a - , thereafter volume growth rates decreased. Clark (1952) calculated the average annual growth rate for a 20 year period to be 1.83 m3 h a - 1 y e a r - 1 for an i n t e r i o r Douglas-fir stand i n the Kamloops area with f a l l e r ' s s e l e c t i o n logging. Johnstone (1984) suggested that t h i s low growth rate was due to the i n t e n s i t y of the o r i g i n a l logging, p a r t i c u l a r l y since the large diameter classes (> 75 cm) were removed. This growth rate i s s i m i l a r to ones found i n t h i s study on stands with a low number of trees and a low t o t a l stand volume. 117 12- i 500 TOTAL STAND VOLUME ( m 3 ha" 1 ) F i g u r e 38: The r e l a t i o n s h i p of t o t a l stand volume to annual volume growth for the d i f f e r e n t densi ty c l a s s e s . Both the inventory and permanent sample p lo ts are i n c l u d e d . 118 As indicated by the data obtained from the permanent sample plots, tree growth after a p a r t i a l logging more than compensated for the fewer number of trees, i . e . the treatment (logged) plots had much higher growth rates than the control (unlogged) p l o t s . This indicates that p a r t i a l logging of uneven-age stands can surpass the volume growth rates of unlogged stands. This i s i n agreement with the post-thining f i n d -ings, i n even-age stands of Barrett (1973) on Ponderosa pine, and Williamson and Curtis (1984) and Berg and B e l l (1979) on Douglas-fir. This i s in contrast, however, with Langsaeter (1941), who hypothesized that a broad range of stand volumes w i l l result i n the same per hectare growth rates. 5.3.2 Relationship Between Average Annual Volume Growth and Stand Structure The a, q and k c o e f f i c i e n t s for each of the inventory plots immedi-ately after logging and currently on the stand are summarized i n Table 17. The values of a and k in this table are the arithmetic mean of the a and k values (found i n Appendix 5) for plots which met the following c r i t e r i a : ( i ) occurred i n the appropriate stand density class and ( i i ) occurred i n the appropriate range of annual yearly volume growth rates (from Table 15). As only the a values immediately following logging and currently on the stand are known, only the annual volume growth rates for the f i v e years immediately following logging and for the 1978 - 1983 time period were included. The values of q were calculated from equation (31) using the arithmetic mean a values. The range of annual volume growth rates corresponding to a given density class are from Table 14, while the diameter of the largest tree i s found in Appendix 5. Table 17: Stand structure c h a r a c t e r i s t i c s for d i f f e r e n t stand densities and growth rates. Average yearly Density volume Stand largest class (trees h a - ) growth (m3 h a - 1 y _ 1 ) volume (m3 h a - 1 ) a 3 (cm" 1) k 3 (trees ha 1 cm *) tree (d cm < 300 < 1 2 - 10 0 1 0 15 1 - 2 2 - 15 0.0275 1.15 32 20 2 - 4 28 - 68 0.0390 1.21 70 30 301 - 600 < 1 0 - 19 0.0743 1.45 83 20 2 - 4 25 - 67 0.0241 1.13 91 30 4 - 6 103 - 168 0.0509 1.29 170 70 601 - 900 3 _ 5 81 - 89 0.0296 1.16 92 50 6 - 8 202 - 237 0.0510 1.29 222 70 901 - 1200, 4.8 _ 7 76 - 179 0.0888 1.46 435 35 9 - 11 207 - 243 0.0495 1.28 304 50 5 - 7 6 383 - 448 0.0446 1.48 410 70 1501 - 1800 3. 8 181 0.1002 1.65 1242 40 2701 - 3000 1 _ 3.2 97--154 0.1230 1.85 1539 30 From Table 15. 2From Table 14. Arithmetic mean of values in Appendix 5. ^Calculated from arithmetic a and k values and Equation (30). 5Frora stand table in Appendix 5. ^As the average growth rates over time tended to have approximately a b e l l shape curve n 1 1 ( F i g . 37), the average growth rates of 5 - 7 m ha year ocurred at two d i f f e r e n t stand volumes. 120 The stands had highly i r r e g u l a r diameter d i s t r i b u t i o n s with missing diameter classes, and there were some larger diameter classes with more trees than found i n smaller diameter classes (Appendix 5). Because of t h i s , the a, q (5 cm d classes) and k c o e f f i c i e n t s are approximate and represent an average for the p l o t . The k c o e f f i c i e n t , which i s strongly influenced by the number of trees i n the smaller diameter classes, tended to increase with stand density, as would be expected. The a and q c o e f f i c i e n t s also increased with stand density, i n d i c a t i n g that the proportion of trees in the smaller diameter class increased. The values of a which corresponded to the highest growth rates for each of the three stand density classes between 300 - 1200 trees h a - 1 , ranged from 0.0495 to 0.0510 cm - 1. The corresponding q values ranged from 1.28 to 1.29. This indicates that there was a high proportion of trees i n the larger diameter classes which tended to grow at a faster rate than those i n the smaller diameter classes (Daniel et a_l. 1979). At stand densities > 1500 trees h a - 1 , high a, q and k c o e f f i c i e n t s combined with the largest tree on the plot being r e l a t i v e l y small (30 -40 cm d) were observed for stands with a large number of small trees and a low t o t a l stand volume. The growth rates of the trees on these plots were slower than trees grown at lower stand densities due to the reduction in both height and basal area growth rates. As previously mentioned, the highest stand volume and annual volume growth rates occurred on the plots in the 901 - 1200 trees h a - 1 density class ( F i g . 18). On the plots i n this class with low stand volumes (76 - 179 m3 h a - 1 ) [corresponding to low growth rates (1 - 5 m3 h a - 1 y e a r - 1 ) ] , the diameter at breast height of the largest tree was r e l a -t i v e l y small (35 cm), and the a, q and k values were r e l a t i v e l y high (0.0888 cm , 1.56 and 435 trees ha cm" , r e s p e c t i v e l y ) , indi c a t i n g a large proportion of small diameter trees. As stand volumes increased to 207 - 243 m3 h a - 1 (and annual volume growth increased to 9 - 11 m 3 h a - 1 y e a r - 1 ) , the largest diameter tree (at breast height) on the stand increased to 50 cm, while the a, q and k c o e f f i c i e n t s decreased, i n d i c -ating a higher proportion of large trees. When stand volumes reached approximately 380 m ha , (and annual volume growth rates decreased), the largest diameter tree at breast height continued to increase (70 cm). With the presence of more larger diameter trees, the a, q and k c o e f f i c i e n t s decreased. However, due to the i n f l u x of small stems (approximately 120 trees h a - 1 ) , the decrease in the c o e f f i c i e n t s was small. P r i o r to logging, the a, q and k c o e f f i c i e n t s tended to be low (Appendix 5). On one t h i r d of the plots, q was less than 1, r e s u l t i n g i n negative a values. For the remainder of the p l o t s , the a, q and k c o e f f i c i e n t s ranged from 0.0084 to 0.0578 cm - 1, 1.05 to 1.62, and 12 to 527, r e s p e c t i v e l y . The average a, q and k values prior to logging, Immediately following logging, and currently on the stands were, respectively, 0.0108 cm - 1, 1.06, 120 tree h a - 1 cm - 1; 0.0629 cm - 1, 1.21, 212 trees h a - 1 cm - 1; 0.0566 cm - 1, 1.30, and 257 trees h a - 1 cm - 1. This indicates that the o v e r a l l stand structure was improved af t e r logging, with an increase in the number of small stems. 5 . 3 .3 R e l a t i o n s h i p of Annual Volume Growth and T o t a l Growing Season T r a n s p i r a t i o n The r e l a t i o n s h i p between annual volume growth rate on the inventory plots for the 1978 - 1983 time period (Table 15) and t o t a l growing 122 season t r a n s p i r a t i o n i n 1984 i s shown i n F i g . 39 f o r d i f f e r e n t canopy coverages . I t was assumed that the r e l a t i v e d i f f e r e n c e s i n growing season t r a n s p i r a t i o n between p l o t s i n 1984 was r e p r e s e n t a t i v e of those over the 1978 to 1983 time p e r i o d . This assumption was t e s t e d by p l o t t i n g the growth ra tes (Table 16) and growing season t r a n s p i r a t i o n f o r 1984 on the permanent sample p l o t s ( F i g . 3 9 ) . Al though the accuracy of the annual growth ra te of these p l o t s was l e s s than that f o r the i n v e n t o r y p l o t s , the agreement i n the genera l t rend supports the p r e v i -ous assumption. G i l e s et a l . (1985), i n a t r a n s e c t study of c o a s t a l D o u g l a s - f i r , found that the long term growth r a t e to s o i l water d e f i c i t r e l a t i o n s h i p f o l l o w e d the same t rend as that found over a two year p e r i o d . F i g . 39 shows that the r e l a t i o n s h i p between growth and t r a n s p i r a -t i o n had a r e l a t i v e l y h i g h c o r r e l a t i o n f o r the 35 - 65% and 85 - 100% canopy coverages (r = 0.892 and 0 .890, r e s p e c t i v e l y ) . The growing season t r a n s p i r a t i o n combined both the c o n t r i b u t i o n of the grass and t ree components. In the case of the 35 - 65% canopy coverage range, the p r o p o r t i o n of t ree t r a n s p i r a t i o n to t o t a l t r a n s p i r a t i o n would be expected to remain roughly constant so that an i n c r e a s e i n T w i l l correspond to an i n c r e a s e i n growth, as i n d i c a t e d by the d a t a . The h i g h c o r r e l a t i o n between growth and t r a n s p i r a t i o n f o r the canopy coverages of > 85% would be expected as the c o n t r i b u t i o n of Tg to T would be n e g l i g i b l e , so that T t * T . At h igh canopy coverages , there i s a r e d u c t i o n i n T t due to gross i n t e r c e p t i o n l o s s . T h i s r e d u c t i o n i n the growth r a t e , however, i s much h i g h e r than expected from j u s t a lower T . T h i s i n d i c a t e s that much lower growth r a t e s on p l o t s w i t h a canopy coverage of > 85% are due m a i n l y to between t ree c o m p e t i t i o n . 123 12 O D . C o o _J < 3 8 6-4 -CANOPY COVERAGE A 5-15% O 20-30% • 35-655: O 85-100% • [J • LTD; p It O . O P o 1 0 0 110 120 1 3 0 1 4 0 150 160 170 GROWING SEASON TRANSPIRATION (mm) F i g u r e 39: The r e l a t i o n s h i p between annual volume growth and t o t a l growing season t r a n s p i r a t i o n . The e r r o r bars shown are f o r a 25 cm d tree w i t h an approximate he ight of 29 m [Equat ion ( 5 2 ) ] , and assume that the e r r o r s i n diameter and he ight were 0.1 mm and 0.5 m, r e s p e c t i v e l y , f o r a one year growth p e r i o d on the permanent sample p l o t s and 0.1 mm and 0.1 m, r e s p e c t i v e l y , f o r a f i v e year growth p e r i o d on the i n v e n t o r y p l o t s . The form f a c t o r was determined to be 1.2 [Equat ion ( 6 2 ) ] . Open symbols i n d i c a t e p l o t s l o c a t e d next to a m i c r o c l i m a t e s t a t i o n , w h i l e the c l o s e d symbols i n d i c a t e tha t T was i n t e r p o l a t e d from the m i c r o c l i m a t e p l o t s which had s i m i l a r s o i l c h a r a c t e r i s t i c s (from Table 7 ) . P l o t s marked w i t h a P are permanent sample p l o t s w h i l e the remainder are i n v e n t o r y p l o t s . Keyes and Grier (1981) found that a reduction i n above-ground biomass production of dense stands was due to an increase i n below-ground biomass production, p a r t i c u l a r l y i n the growth of the fine roots. At canopy coverages of < 30%, a poor r e l a t i o n s h i p between growth rate and t r a n s p i r a t i o n was observed, with a large range of growth rates for si m i l a r values of T (Fig. 39). This was probably due to av a i l a b l e growing space which i s not occupied by trees and, subsequently, the large contribution of the grass component to t o t a l t r a n s p i r a t i o n . Plots which had higher volume growth rates also had higher s o i l water contents and, therefore, higher s o i l water matric p o t e n t i a l s . These plots also had lower calculated values of canopy resistance, a r e f l e c t i o n of the higher t r a n s p i r a t i o n rates on these plots (Figs. 26 and 27). SUMMARY AND CONCLUSIONS 126 6. SUMMARY AND CONCLUSIONS 6.1 Conclusions 1. Canopy coverages of between 25% and 65% r e s u l t e d In the h i g h e s t va lues of the s o i l water s torage at the beg inning of the growing season, p a r t i c u l a r l y on s o u t h - f a c i n g s l o p e s , by i n c r e a s i n g the d u r a t i o n of snow c o v e r . At lower canopy coverages on southern s l o p e s , snowmelt tended to occur before the ground thawed and, consequent ly , runof f o c c u r r e d . At h igher canopy coverages , r e g a r d l e s s of aspec t , the maximum snow water e q u i v a l e n t depth was reduced s u f f i c i e n t l y to cause s i g n i f i c a n t r e d u c t i o n s i n s o i l water s torage at the beginning of the growing season. 2 . Root zone s o i l water s torage decreased most r a p i d l y from mid-June to mid-August i n 1984. The m a j o r i t y of the s o u t h - f a c i n g p l o t s , which had lower i n i t i a l s o i l water s t o r a g e s , tended to have s o i l water m a t r i c p o t e n t i a l s of between - 0 . 1 and - 1 . 5 MPa f o r most of the 1984 growing season. The n o r t h - f a c i n g s lopes ( e . g . Lac Le Juene) had h i g h e r snow water e q u i v a l e n t depths and remained wet ter throughout the 1984 growing season. The grass p l o t s tended to be d r i e r at the top of the root zone , w h i l e the p a r t i a l l y f o r e s t e d and f o r e s t e d p l o t s tended to be d r i e r at d e p t h . 3 . The r a i n f a l l r e a c h i n g the ground was an approximate ly constant p r o p o r t i o n of the above-canopy r a i n f a l l and was 98%, 95%, 85% and 63% f o r canopy coverages of 10%, 25%, 50% and 100%, r e s p e c t i v e l y . 4 . The growing season e v a p o t r a n s p i r a t i o n r a t e s were s i m i l a r f o r d i f f e r e n t canopy coverage p l o t s l o c a t e d at the same s i t e . The growing season t r a n s p i r a t i o n , however, v a r i e d c o n s i d e r a b l y f o r 127 d i f f e r e n t canopy coverages. Plots with coverages of less than 25% had the highest growing season t r a n s p i r a t i o n folowed by the 50% and 100% canopy coverage plots, r e s pectively. The Lac Le Jeune plots had the highest growing season t r a n s p i r a t i o n , regardless of canopy coverage. Transpiration was found to be s o i l l i m i t e d ; however, i t was found to be more sensitive to vapour pressure d e f i c i t s than to available energy. This s e n s i t i v i t y may be due to extended periods of low s o i l water matric potentials and, possibly, a p h y s i o l o g i c a l adaptation of the i n t e r i o r Douglas-fir species. Canopy resistance increased s l i g h t l y with increasing vapour pres-sure d e f i c i t s at high s o i l water matric p o t e n t i a l s , but dramatic-a l l y at low s o i l water matric p o t e n t i a l s . This resulted in a much greater decline i n tra n s p i r a t i o n with increasing vapour pressure d e f i c i t s , when the vapour pressure d e f i c i t was high and the s o i l water matric p o t e n t i a l was low. Furthermore, higher canopy cover-ages had higher canopy resistances at high vapour pressure d e f i c i t s r e s u l t i n g i n lower t r a n s p i r a t i o n rates. This r e f l e c t s the increase i n the proportion of the t o t a l t r a n s p i r a t i o n o r i g i n a t i n g from the trees as the trees are more s e n s i t i v e than grass to vapour pressure d e f i c i t s . Both the diameter (breast height) and height growth rates decreased with increasing stand density. Diameter at breast height was found to be proportional to (age minus 10 y e a r s ) 0 , 6 , while the r e l a -tionship of diameter to height was found to be l i n e a r . The r a t i o of breast height diameter-to-height for a given density class was found to be a good indicator of form factor and was used 128 i n the l o c a l volume equation. This equation was found to estimate current tree volumes and also tree volumes 5, 10 and 20 years ago with acceptable accuracy. 9. The coni c a l form factor was found to decrease slowly with increas-ing stand density and rapidly with increasing diameter. Trees with a diameter at breast height of 40 cm at stand densities of 1000 and 2000 trees h a - 1 had conical form factors of about 1.1 and 1.0, respectively. 10. The highest annual volume growth rate of 9 to 11 m ha year-occurred at stand densities ranging from 901 - 1200 trees h a - 1 with o — 1 t o t a l stand volumes of between 200 to 300 m ha . At higher stand volumes, there was a reduction i n annual growth rate, probably due to between-tree competition. At lower stand d e n s i t i e s , lower growth rates appeared to be due to u n f i l l e d growing space; however, the annual growth rates increased with increasing stand volume. At stand densities of greater than 1500 trees h a - 1 , which corresponded 3 1 to stand volumes ranging from 97 to 240 m h a - , growth rates decreased with increasing stand volumes. This was due to very slow diameter and height growth rates causing the stand to consist of primarily small diameter trees. M o r t a l i t y was observed at these high stand d e n s i t i e s . 11. Values of q (5 cm diameter classes) ranging from 1.28 to 1.29 for stand de n s i t i e s of less than 1200 t r e e s - 1 had the highest growth rate. Corresponding a and k values ranged from 0.0495 to 0.0510 cm - 1 and 170 to 304 trees h a - 1 cm - 1, res p e c t i v e l y . This stand diameter d i s t r i b u t i o n could only be maintained on stands of < 1500 129 trees h a - 1 . At higher stand densities the a, q, and k c o e f f i c i e n t s were much higher due to the largest diameter tree being r e l a t i v e l y small. 12. Based on the calculated a, q and k values p r i o r to and after a p a r t i a l logging, i t was found that, i n general, the stands studied appeared to have better o v e r a l l diameter d i s t r i b u t i o n a f t e r a p a r t i a l logging. However, in some cases there were missing diameter classes and, i n other cases, the t o t a l r e s idual stand volumes were lower than necessary for favourable annual growth rates. 13. At canopy coverages of > 35% (or stand densities of > 600 trees h a - 1 ) , there was a l i n e a r c o r r e l a t i o n between growing season trans-p i r a t i o n and annual volume growth. At lower canopy coverages, the poor c o r r e l a t i o n observed between growing season tr a n s p i r a t i o n and annual volume growth was attributed to the high contribution of the grass to the t o t a l t r a n s p i r a t i o n . At canopy coverages of > 85% (> 1500 trees h a - 1 ) , the reduction i n annual volume growth is much higher than would be predicted from the reduction i n tr a n s p i r a t i o n due to gross interception l o s s . In this case, the lower annual volume growth rates appeared to be primarily due to between tree competition. 6.2 Management Implications Primary objectives of a management plan which would optimize annual growth rates would be to ( i ) reduce gross interception loss of both the r a i n f a l l and snowfall to increase s o i l water content and growing season tr a n s p i r a t i o n , ( i i ) maximize the proportion of t o t a l t r a n s p i r a t i o n which 130 o r i g i n a t e s from the t r e e s , ( i i i ) reduce between-tree c o m p e t i t i o n , and ( i v ) m a i n t a i n a favourab le tree diameter d i s t r i b u t i o n . F i g u r e 40 shows the average of the h i g h e s t annual growth ra tes versus stand volumes and i n c l u d e s a l l study p l o t s (see F i g . 38 ) . I n order to be i n Zone A, which has the h ighes t growth r a t e s , the stand should have between 900 and 1200 t rees h a - 1 . The f i g u r e suggests that at these stand d e n s i t i e s , stand volumes should be reduced to approximate ly 250 m h a . Assuming the stand w i l l grow about 10 m h a - 1 y e a r - 1 and a ten-year c u t t i n g c y c l e i s d e s i r a b l e , r e - e n t r y i n t o the stand should occur at a stand volume of 350 m ha . I f a 20 year c u t t i n g c y c l e i s d e s i r e d , F i g . 40 suggests that stands should be mainta ined w i t h i n the range of stand volumes shown by Zone B ( » 220 -380 m ha ) , which should have an average volume growth r a t e of 8 m h a - 1 y e a r - 1 f o r the 20 years p e r i o d . To o b t a i n these growth r a t e s , s tand d e n s i t y should be between 800 and 1300 t rees h a -Both the management scenar ios i l l u s t r a t e d by Zones A and B assume that the o r i g i n a l s tand d e n s i t y i s < 1500 t rees h a - 1 (or a diameter to he ight r a t i o of 1.0 cm m - 1 ) . I f the o r i g i n a l stand has > 1500 t rees h a - 1 (Zone C, between 100 to 220 m 3 h a - 1 ) , the f i r s t en t ry i n t o the stand should be done w i t h c a u t i o n . The r i s k of stem c o l l a p s e i s very h i g h at these s tand d e n s i t i e s and s e v e r a l s tand e n t r i e s may be necessary to create the d e s i r e d stem diameter d i s t r i b u t i o n . In t h i s case , the t r e e s should be th inned to a s p a c i n g of twice the canopy w i d t h (approx imate ly 65% canopy coverage or a spac ing of » 3 m x 3 m). The s tand should be th inned aga in once canopy c l o s u r e o c c u r s . T h i s would r e q u i r e frequent e n t r i e s i n t o the s t a n d s ; however, i t would reduce the m o r t a l i t y of the next crop of t r e e s . C 3 i 12 Figure AO: Relationship between annual volume growth and t o t a l stand volume interpreted for management purposes. Maintaining the stand i n Zone A with 900 to 1200 trees h a - 1 would be considered optimal. The c u t t i n g cycle would be ten years. In cases where a 20 year c u t t i n g cycle i s desired, stands should be maintained with between 800 - 1300 trees h a - 1 and with stand volumes represented .by Zone B. Logging i n Zone C should be done with caution i f there are > 1500 trees h a - 1 on the stand, as stem c o l l a p s e would l i k e l y be a problem. Logging down to Zone D would be unacceptable, p a r t i c u l a r l y i f < 400 trees h a - 1 remain a f t e r logging. This is due to both regeneration problems and low annual volume growth rates. In a l l cases, uneven-age stand diameter d i s t r i b u t i o n s , with some larger r e s i d u a l trees, should be maintained. 132 The f i n a l zone i n F i g . 40 i s D. Logging to a t o t a l stand volume of < 100 m3 h a - 1 , p a r t i c u l a r l y on fewer than 400 trees h a - 1 , should be avoided. Natural regeneration may become a problem at these low l e v e l s . Also there would be a large grass component r e s u l t i n g i n low annual volume growth rates. In a l l cases, i t would be important to maintain a favourable stem diameter d i s t r i b u t i o n , even i f juvenile spacing was required. This figure allows a rough estimate of the stand volumes and densities which are necessary to maintain certain rates of annual volume growth, based on growth rates determined from a l l study p l o t s . F i g . 39 suggests, however, that stands which have higher s o i l water matric potentials and, e s s e n t i a l l y , higher growing season t r a n s p i r a t i o n rates w i l l have a higher annual volume growth rates. Therefore, stands which have higher a v a i l a b l e s o i l water content may have ( i ) higher annual volume growth rates, ( i i ) maximum growth rates that occur at higher or lower stand volumes, or ( i i i ) a combination of ( i ) and ( i i ) . 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O l i v e r . 1977. On Penman's equat ion f o r e s t i m a t i n g r e g i o n a l e v a p o r a t i o n . Quar t . J . R . M e t . Soc. 103:345-357. Timmer, V . R . and G . F . Weetman. 1969. Humus temperatures and snow cover c o n d i t i o n s under upland b l a c k spruce i n n o r t h e r n Quebec. Pulp and Paper Research I n s t i t u t e of Canada. Woodlands Paper No. 11. 28 pp. Walker , N . 1956. Growing stock volumes i n unmanaged and managed f o r e s t s . J . F o r . 54:378-383. W a l l i s , C . H . , T . A . B l a c k , 0 . Hertzman and V . J . W a l t o n . 1983. A p p l i c a t i o n of a water balance model to e s t i m a t i n g key growth i n the Peace R i v e r R e g i o n . Atmosphere-Ocean 21:326-343. Wat t s , S . B . 1983. F r o e s t r y Handbook of B r i t i s h Columbia . F o u r t h E d i t i o n . Pub. by F o r e s t r y Undergraduates S o c i e t y , F a c u l t y of F o r e s t r y , U n v i e r s i t y of B r i t i s h Columbia , Vancouver, B . C . Weetman, G . F . and R . M . F o u r n i e r . 1981. Fores t f e r t i l i z a t i o n sc reen ing t r i a l s , I n t e r i o r of B r i t i s h Columbia , 1980: Lodgepole p i n e , D o u g l a s - f i r and white s p r u c e . Res . Branch , B . C . M . F . , U n i v e r s i t y of B r i t i s h Columbia , Vancouver, B . C . Whitehead, D. P . G . J a r v i s and R . H . War ing . 1984. Stomatal conductance, t r a n s p i r a t i o n , and r e s i s t a n c e to water uptake i n a Pinus s y l v e s t r i s spac ing exper iment . Can. J . F o r . Res . 14:692-700. W i l l i a m s o n , R. L . 1973. R e s u l t s of shelterwood h a r v e s t i n g of Douglas -f i r i n the Cascades of western Oregon. U . S . D . A . F o r . S e r v . Res . Paper PNW-161. 11 PP-W i l l i a m s o n , R . L . and R .O. C u r t i s . 1984. L e v e l s - o f - g r o w i n g - s t o c k c o o p e r a t i v e study i n D o u g l a s - f i r : Report No. 7. - P r e l i m i n a r y r e s u l t s , Stampede Creek, and some comparisons w i t h I ron Creek and H a s k i n s . Res . Pap. PNW-323, 42 pp. Wong, S . C , I . R . Cowan and G.D. Farquhar . 1979. Stomatal conductance c o r r e l a t e s w i t h p h o t o s y n t h e t i c c a p a c i t y . Nature 282:424-426. Young, J . A . , D.W. H e d r i c k , and R . F . K e n i s t o n . 1967. Fores t cover and l o g g i n g . J . F o r . 65:807-813. APPENDIX 1: NATURAL REGENERATION UNDER A FALLER SELECTION METHOD 141 APPENDIX 1: NATURAL REGENERATION UNDER A FALLER SELECTION METHOD Figure Al-1 shows the amount of regeneration which occurred at di f f e r e n t stand d e n s i t i e s . This figure includes the results of the regeneration surveys on a l l inventory and microclimate p l o t s . At stand densities of between 400 and 1300 trees ha" 1 (or canopy coverages ranging from 10% to 75%) natural regeneration appears to be adequate. At lower stand densities s o i l surface temperatures, which can be as high as 75°C at 1:00 p.m., prevent regeneration success. At higher stand d e n s i t i e s , between-tree competition i n h i b i t s regeneration establishment. 142 20000-1 15000 10000 5000-500 1000 1 1500 2000 2500 3000 STAND DENSITY (trees h a " ' ) Figure A l - 1 : The r e l a t i o n s h i p between the number of regeneration established and the t o t a l number of trees per hectare. 143 APPENDIX 2: ANALYSIS OF FISH EYE LENS PHOTOGRAPHS TO DETERMINE CANOPY COVERAGE 144 APPENDIX 2: ANALYSIS OF FISH EYE LENS PHOTOGRAPHS TO DETERMINE CANOPY COVERAGES The f i s h eye lens photographs were taken with a Soligar f i s h eye lens which was attached to a Minolta XG with a 52 mm inner diameter convertor, using Kodak PX-135 panochromatic f i l m #25 ASA. Prints had a 68 mm diameter c i r c u l a r f i e l d . The grid used for analysis of the prints was divided into 27 equal sectors as shown in F i g . A2-1. The canopy coverage was determined for each sector and the average was used for the t o t a l canopy coverage of the p l o t . Figs. A2-2 through A2-4 i l l u s t r a t e canopy coverages of 10%, 50% and 100%, respectively. 143 Figure A.2-1: Grid for analysis of f i s h eye lens photographs with a diameter of 68 mm. 146 Figure A2-2: Example of 10% canopy coverage. Figure A2-3: Example of 50% canopy coverage. 148 Figure A2-4: Example of a forested plot (>85% canopy coverage). APPENDIX 3: FOLIAR ANALYSIS OF THE LAC LE JEUNE AND KNOUFF 12 km SITES 150 APPENDIX 3 : FOLIAR ANALYSIS OF THE LAC LE JEUNE AND KNOUFF 12 km SITES A f o l i a r analysis was done on trees from the Knouff 12 km and Lac Le Jeune s i t e s . Table A3-1 l i s t s the average results along with suggested minimum values. Unfortunately, no c r i t i c a l values were found s p e c i f i c a l l y for i n t e r i o r Douglas-fir. The c r i t i c a l values l i s t e d i n Table A3-1 are from coastal Douglas-fir and screening t r i a l s done i n Europe. Therefore, these results must be used with caution, and should only serve as a guide. It i s doubtful that f e r t i l i z a t i o n would increase volume growth of i n t e r i o r Douglas-fir stands due to the prolonged water d e f i c i t s . 151 Table A 3 - 1 : F o l i a r a n a l y s i s r e s u l t s . Knouff Lac Le Suggestei # C o n c e n t r a t i o n 12 km Jeune minimum 1 N% 0.943 1.115 l a 2 P% 0.195 0.256 0 . 1 4 b 3 K% 0.710 0.960 0 . 5 b 4 Ca% 0.406 0.385 0 . 1 b 5 Mg% 0.097 0.148 0 . 1 b 6 A l % 0.006 0.005 7 Mn ppm 523 660 0 . 1 b 8 Fe ppm 40 33 10 d 9 Zn ppm 20 31 10 Cu ppm 1 2 .5 2 . 6 a 11 Fe ppm 42.5 36.9 50 c 12 Cu ppm 3.2 4.2 2 . 6 a 13 A c t i v e Fe ppm 25 25 50 c 14 B ppm 16.3 18.2 10 c 15 S% 0.1 0.104 16 N/S 9.6 10.69 14 .6 C (: a M o r r i s o n (1984) b E v e r a r d (1973) c B a l l a r d (1979) d S t o n e (1968) 152 LITERATURE CITED B a l l a r d , T . M . 1979. Development of i n t e r i m o p e r a t i o n a l g u i d e l i n e s f o r f o r e s t f e r t i l i z a t i o n i n the Kamloops Fores t D i s t r i c t . U n p u b l . Contrac t Research Report to B . C . F o r . S e r v . 86 pp. E v e r a r d , J . 1973. F o l i a r a n a l y s i s sampling methods i n t e r p r e t a t i o n and a p p l i c a t i o n of r e s u l t s . Q . J . F o r . 67 :51-66. M o r r i s o n , I . K . 1974. M i n e r a l n u t r i t i o n of c o n i f e r s w i t h s p e c i a l re ference to n u t r i e n t s ta tus i n t e r p r e t a t i o n : A review of the l i t e r a t u r e . Can. F o r . Serv . P u b l . No. 1343. S tone , E . L . 1968. Microelement n u t r i t i o n of f o r e s t t r e e s : a r e v i e w . I n : Begnston, G . M . , Fores t F e r t i l i z a t i o n Theory and P r a c t i c e . TVA, Muscle S h o a l s , Alabama, pp.132-175 . 153 APPENDIX 4: ANALYSIS OF AVERAGE VOLUME GROWTH BY DIAMETER CLASS FOR ALL INVENTORY PLOTS IN THREE STAND DENSITY CLASSES FOR THE 1978-1983 TIME INTERVAL. 154 APPENDIX 4: ANALYSIS OF AVERAGE VOLUME GROWTH BY DIAMETER CLASS FOR ALL INVENTORY PLOTS IN THREE STAND DENSITY CLASSES FOR THE 1978-1983 TIME INTERVAL. Analysis of the yearly diameter (at breast height) growth for the 1978 - 1983 period was done for a l l Inventory plots i n the 300 - 600, 900 - 1200 and 2700 - 3000 trees h a - 1 density classes. Six plots were included i n the lowest density c l a s s , four i n the middle density class and one i n the highest density c l a s s . The volume growth of trees i n the 5 - 15, 15 - 25, 25 - 35, 35 - 45 and 45 - 55 cm diameter classes were analyzed separately for each density c l a s s . The number of trees i n each diameter class was determined from the stand table i n Appendix 5. Tree volumes were calculated from Equation (57). Table A4-1 i l l u s t r a t e s the annual volume growth rates which would occur, given the diameter growth and number of trees for each 10 cm diameter class as indicated from the inventory p l o t s , and summed for a l l trees on the p l o t . Table A4-1: Analysis of average volume growth by diameter class for a l l inventory plots in three stand density classes for the 1978 - 1983 time i n t e r v a l . Mid point of Number 1 year Volume (m~3 ha" 1) Tota l diameter of diameter volume class trees increment 1983 1982 difference (m 3 h a - 1 y e a r - 1 ) (cm) (cm) 300 - 600 trees ha" 1 10 200 0.171 0.035 0.034 0.001 0.2 20 150 0.226 0.210 0.204 0.006 0.9 30 100 0.322 0.603 0.586 0.017 1.7 40 50 0.289 1.263 1.240 0.023 1.2 50 25 0.265 2.247 2.216 0.031 0.8 Total 525 4.8 900 - 1200. trees ha" 1 10 325 0.130 0.038 0.036 0.002 0.6 20 250 0.175 0.226 0.221 0.005 1.3 30 200 0.276 0.650 0.634 0.016 3.2 40 150 0.243 1.363 1.341 0.022 3.3 50 100 0.210 2.424 2.398 0.026 2.6 Total 1025 11.0 2700 - 3000 trees h a - 1 10 2100 0.045 0.0395 0.390 0.005 1.1 20 600 0.075 0.239 0.237 0.002 1.2 30 50 0.128 0.689 0.681 0.008 0.4 Total 2750 2.2 APPENDIX 5: THE a, q AND k COEFFICIENTS, NUMBER OF TREES AND STAND VOLUMES PRIOR TO LOGGING, IMMEDIATELY FOLLOWING LOGGING AND CURRENTLY ON THE STAND. 157 APPENDIX 5: THE a, q AND k COEFFICIENTS, NUMBER OF TREES AND STAND VOLUMES PRIOR TO LOGGING, IMMEDIATELY FOLLOWING LOGGING AND CURRENTLY ON THE STAND. Included i n this appendix i s the 1984 stand table for the inventory plots (Table A5-1). The more commonly found diameter d i s t r i b u t i o n s are i l l u s t rated i n Figs. A5-1 through A5 —3. Table A5—2 l i s t s the stand structure c h a r a c t e r i s t i c s prior to logging, following logging and currently on the stand. TABLE A5~l: Stand table for the Inventory plots by d (cm) classes, 1984. Trees ha"'  d classes (cm) Totals <5.0 Plot Regener- 5.1- 10.1- 15.1- 20. 1- 25.1- 30.1- 35.1- 40.1- 45.1- 50.1- 55.1- 60.1- 65.1- cm A l l number ation <5.0 10 15 20 25 30 35 40 45 50 55 60 65 70 d trees 1 1488 48 416 160 208 32 0 16 16 0 0 0 0 0 0 896 2384 2 13272 96 208 112 128 48 144 176 96 16 16 0 0 0 0 1040 13312 3 8128 48 256 128 192 96 96 80 80 64 32 0 16 0 0 1072 9200 4 5072 0 144 64 64 32 32 48 16 0 16 0 0 0 16 432 5504 5 15056 0 112 64 80 32 16 16 48 0 32 0 0 0 0 400 15456 6 6336 64 304 64 32 96 32 16 0 0 16 0 16 0 16 656 6992 7 3472 112 240 112 32 48 32 48 32 0 16 16 0 0 0 688 4160 8 3472 64 240 96 64 32 32 48 64 48 32 0 0 0 16 672 4144 9 3232 16 32 32 16 32 48 32 16 64 0 16 16 0 0 320 3552 10 528 16 16 16 16 16 16 0 0 0 0 0 0 0 0 96 624 11 656 32 64 48 16 48 0 0 0 0 0 0 0 0 0 208 864 12 592 172 80 16 48 0 0 0 0 0 0 0 0 0 0 224 816 13 992 208 432 208 48 64 0 0 0 0 0 0 0 0 0 960 1952 14 0* 624 768 1184 160 16 32 0 0 0 0 0 0 0 0 2784 2784 15 1456 16 96 80 32 16 32 0 0 0 0 0 0 0 0 272 1728 16 912 250 250 640 352 304 64 0 0 16 0 0 0 0 . 0 1632 2544 17 528 0 48 32 48 48 16 32 0 .0 0 0 0 0 0 224 752 18 736 64 128 192 48 0 0 0 0 0 0 0 0 0 0 480 1216 19 1824 48 112 32 48 32 64 16 32 0 0 0 0 0 0 384 2208 20 48 96 112 64 16 32 0 0 0 0 0 0 0 0 0 320 368 21 9216 32 48 64 32 80 64 0 0 0 0 0 0 0 0 320 9536 The plot numbers are the same as ln Table 2. *A11 the small trees ln this plot were dead. TABLE A5-2: Stand c h a r a c t e r i s t i c s prior to logging, Immediately following logging, and currently on the stand. Number Number Number Plot Year of trees Vc ilume a q k of trees Volume a q k of trees Volume a q k number logged ha" 1 (m 5 ha" 1) (cm" 1) ha" 1 (m 3 h a - 1 ) (cm" 1) ha" 1 (m 3 h a - 1 ) (cm" 1) 1 1978 1200 477 0.0116 1.05 144 864 237 0.0536 1.26 137 864 274 0.0536 1.26 536 2 1953 1232 329 0.0384 1.05 235 928 179 0.0576 1.11 285 1040 416 0.0421 1.49 357 3 1953 1216 334 0.0499 1.12 527 1072 243 0.0528 1.12 380 1028 477 0.0693 1.43 512 4 1953 528 181 0.0366 1.06 208 414 67 0.0520 1.14 215 464 194 0.0549 1.29 249 5 1953 464 267 -0.0019 0.95 104 2 80 25 0 1 .00 0 464 140 0.0486 1.17 182 6 1953 752 261 . 0.0183 1.11 96 304 81 0.0278 1.17 106 656 236 0.0497 1.15 219 7 1953 800 348 0.0084 1.05 61 608 89 0.0313 1.13 77 688 261 0.0478 1.17 178 8 1953 926 343 0.0275 1.20 63 816 207 0.0575 1.20 227 976 448 0.0347 1.43 91 9 1968 352 19 0 1.00 0 288 2 0 1.00 0 304 24 0 1.00 0 10 1968 352 375 -0.322 0.75 12 80 10 0 1.00 0 96 23 0 1.00 0 11 1968 400 391 -0.0081 0.75 30 176 3 0 1.00 0 208 17 0 1.00 0 12 1958 560 487 0 1.00 0 208 2 0.1099 1.50 144 224 9 0.1099 1.50 144 13 1968 1072 240 0.0139 1.15 110 896 76 0.1040 1.43 362 976 105 0.1199 1.80 584 14 1953 2864 235 0.0578 1.62 513 2752 97 0.1522 1.75 1539 2784 160 0.1522 1.75 1539 15 1978 480 65 -0.0085 0.85 29 272 28 0.0347 1.20 45 288 39 0.0549 1.14 83 16 1978 1760 309 0.0301 1.28 122 1632 181 0.2041 1.60 442 1632 200 0.2041 1.60 442 17 1978 416 256 -0.0231 0. 95 51 224 68 0.0231 1.11 40 240 87 0.0231 1.11 40 18 1978 656 225 0.0231 1.14 81 480 39 0.0924 1.33 161 480 48 0.0924 1.33 161 19 1978 528 282 -0.0173 0.99 46 384 103 0.0485 1.10 78 384 124 0.0485 1.10 78 20 1978 592 312 -0.0173 0.95 40 320 9 0.0549 1.50 83 320 19 0.0599 1.50 83 21 1978 368 132 0.0183 1.20 48 320 43 0.0283 1.10 58 320 61 0.0203 1.101 58 The plot numbers are the same as In Table 2. A l l values are for 5 cm diameter classes and only Include trees greater than 5.0 cm at breast height. vO 160 80-i DIAMETER CLASS (cm) Figure A5-1: Example of the diameter d i s t r i b u t i o n found on 18% of the inventory p l o t s . 161 Figure A5-2: Example of the diameter d i s t r i b u t i o n found on 45% of the inventory p l o t s . 1200-1 1000-DIAMETER C L A S S (cm) Figure A 5 - 3 : Example of the diameter d i s t r i b u t i o n found on 37% of inventory p l o t s . 163 APPENDIX 6: BASAL AREAS CORRESPONDING TO THE DIFFERENT STAND VOLUMES FOR THE DIFFERENT DENSITY CLASSES IN 1983 Table A6-1 shows the basal areas and stand volumes on the 21 inventory plots in 1983. TABLE A6-1: Basal areas which correspond to the d i f f e r e n t density classes In 1983. Plot Volume Basal area number (m 3 ha" (m 2 h a - 1 ) < 300 trees ha" 1 9 24 8 10 23 9 11 17 6 12 9 3 15 29 14 17 . 87 17 301 - 600 trees h a - 1 4 194 28 5 140 24 18 48 7 19 124 14 20 19 3 21 61 8 601 - 900 trees h a - 1 1 274 24 6 236 23 7 261 22 901 - 1200 trees h a - 1 2 416 46 3 477 41 8 448 43 13 153 14 1501 - 1800 trees h a - 1 16 200 35 2701 - 3000 trees h a - 1 14 160 33 

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