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Resistance to water uptake : a comparison of ponderosa pine and Douglas-fir seedlings and an investigation… Standish, J. T. 1983

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RESISTANCE TO WATER UPTAKE: A COMPARISON OF PONDEROSA PINE AND DOUGLAS-FIR SEEDLINGS and AN INVESTIGATION INTO THE EFFECTS OF PLANTING by 3.T. Standish B.S.F., The U n i v e r s i t y of B r i t i s h Columbia, 1977 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of S o i l Science We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1983 C) -John Thomas Sta n d i s h , 1983 In presenting t h i s 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 a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or pub l i c a t i o n of t h i 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. J.T. S t a n d i s h Department of S o i l S c i e n c e  The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date 29 September 1983 E-6 (2/79) ABSTRACT Resistance to water uptake i n ponderosa pine (Pinus ponderosa Laws.) and coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) seedlings was studied in a controlled environment using an Ohm's Law analogy to liquid phase water flow for calculating resistance from measurements of soil and needle water potential and, uptake rate. This study compares resistance in ponderosa pine to similarly measured resistance in Douglas-fir from another study. Resistance to water uptake in planted Douglas-fir seedlings was also investigated. Ponderosa pine shows virtually constant needle water potential through the range of s o i l water potential where uptake occurs. A modified Weibull function was found to give good overall results for predicting uptake as a function of s o i l water potential using nonlinear regression techniques. Generally, uptake rates are high compared to Douglas-fir at s o i l water potentials greater than about -0.5 MPa but decrease more rapidly as the s o i l dries. Resistance to water uptake appears to be more or less constant and much less than i n Douglas-fir at soil water potentials greater than -1.5 MPa. At lower s o i l water potentials resistance increases rapidly; at -2.0 MPa, resistances for the two species are about equal. The increase in resistance below -1.5 MPa of soil water potential in ponderosa pine may be largely a result of increases in plant and soil-root contact resistance. - i i i -Resistance in planted Douglas-fir seedlings was studied using three experimental treatments. The control treatment consisted of seedlings which had grown in pots for about 15 months. Planting was simulated by c a r e f u l l y l i f t i n g and re-potting a randomly selected group of seedlings. Half of the planted seedlings were randomly a l l o c a t e d to the t h i r d treatment which consisted of subjecting seedlings to v i b r a t i o n . Planted seedlings showed considerably greater (by about six times) resistance than controls. Planted and vibrated seedlings, however, were s t a t i s t i c a l l y i d e n t i c a l to the control seedlings. Because of s i m i l a r i t y i n s o i l p hysical properties among treatments, i t i s doubtful that decreased s o i l resistance i n planted and vibrated seedlings could t o t a l l y account for t h e i r lower resistance compared to planted seedlings. Therefore i t i s i n f e r r e d that reduced s o i l - r o o t contact resistance i s responsible for the lower t o t a l resistance. - iv -TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS iv LIST OF TABLES vi LIST OF FIGURES v i i ACKNOWLEDGEMENTS ' ix INTRODUCTION 1 CHAPTER 1: RESISTANCE TO WATER UPTAKE IN PONDEROSA PINE 5 COMPARED TO DOUGLAS-FIR Introduction 6 Methods and Materials 7 Seedlings and Soil 8 Experimental Environment 10 Soil Water Potential 11 Needle Water Potential 13 Uptake 15 Resistance 17 Comparison of Resistance 18 Results 19 Discussion 34 Summary and Conclusions 41 - V -Page CHAPTER 2: RESISTANCE TO WATER UPTAKE IN PLANTED 43 DOUGLAS-FIR SEEDLINGS Introduction 44 Methods and Materials 45 Results 51 Discussion 64 Summary and Conclusions 68 CONCLUSIONS 70 LITERATURE CITED 76 APPENDIX I: Spectral Irradiance in the Experimental 86 Environment APPENDIX II: Statistical Summary for Regression of Needle 89 Water Potential as a Function of Soil Water Potential for Ponderosa Pine APPENDIX III: Calculations for Uptake and Resistance for 91 Ponderosa Pine APPENDIX IV: Observed Uptake Rates in Ponderosa Pine 100 Compared to Average Uptake Curves APPENDIX V: Uptake and Needle Water Potential Data for 103 Ponderosa Pine APPENDIX VI: Data for Douglas-Fir Experiment 107 APPENDIX VII: Statistical Summaries for Resistance in 112 Douglas-Fir Seedlings APPENDIX VIII: Stomatal Resistance Measurements and Estimated 116 Maximum Transpiration Rates APPENDIX IX: Seedling and Water Pathway Dimensions 119 APPENDIX X: Soil Physical Properties 123 APPENDIX XI: Estimates of Soil Resistance 126 - vi -L I S T OF TABLES Page Table 1: Soil Properties Table 2: Summary of Average Seedling and Water Flow Pathway Dimensions for Ponderosa Pine Seedlings Table 3: Average Coefficients for Uptake Equations Table ki Kruskal-Wallis Test for Differences in Resistance to Water Uptake for Douglas-Fir (F) and Ponderosa Pine (Py) Table 5: Soil Characteristics and Water Pathway Dimensions for Ponderosa Pine and Douglas-Fir Table 6: Seedling and Water Pathway Dimensions for Douglas-Fir Seedlings 18 23 34 39 51 - v i i -L I S T OF F I G U R E S Page Figure 1 Needle Water P o t e n t i a l vs S o i l Water Poten t i a l for Ponderosa Pine Figure 2 Water P o t e n t i a l Difference vs S o i l Water P o t e n t i a l for Ponderosa Pine Figure 3 Uptake in Ponderosa Pine per Unit Root Area as a Function of S o i l Water P o t e n t i a l - Regression Model I Figure 4 Uptake in Ponderosa Pine per Unit Root Area as a Function of S o i l Water P o t e n t i a l - Regression Model II (Modified Weibull Function) Figure 5 Average Residuals for Uptake Equation Model I Figure 6 Average Residuals for Uptake Equation Model II Figure 7 Resistance to Uptake per Unit Root Area for Ponderosa Pine (Uptake Model I) Figure 8 Resistance to Uptake per Unit Root Area for Ponderosa Pine (Uptake Model II) Figure 9 Resistance to Uptake per Unit Root Area for Ponderosa Pine (Uptake Model I I ) , Douglas-fir on S i l t Loam and Douglas-fir on Loamy Sand Figure 10 Needle Water P o t e n t i a l vs S o i l Water Pot e n t i a l for Control Douglas-fir Seedlings Figure 11 Needle Water P o t e n t i a l vs S o i l Water Poten t i a l for Planted Douglas-fir Seedlings 20 22 24 25 27 28 30 31 33 52 53 - v i i i -Page Figure 12 Needle Water Potential vs Soil Water Potential for Planted and Vibrated Douglas-fir Seedlings Figure 13 Uptake Rate for Control Douglas-fir Seedlings Figure 14 Uptake Rate for Planted Douglas-fir Seedlings Figure 15 Uptake Rate for Planted and Virbrated Douglas-fir Seedlings Figure 16 Resistance to Uptake for Control Douglas-fir Seedlings Figure 17 Resistance to Uptake for Planted Douglas-fir Seedlings Figure 18 Resistance to Uptake for Planted and Vibrated Douglas-fir Seedlings 54 56 57 58 60 61 62 - i x -ACKNOWLEDGEMENT I owe a debt of g r a t i t u d e to Dr. T.M. B a l l a r d ( P r o f e s s o r , Department of S o i l Science and Fac u l t y of F o r e s t r y ) for h i s guidance and encouragement during my graduate s t u d i e s and f o r h i s patience and h e l p f u l advice i n producing t h i s t h e s i s . Dr. T.A. Black ( P r o f e s s o r , Department of S o i l Science) deserves s p e c i a l thanks, not only f o r h i s sound t e c h n i c a l and e d i t o r i a l advice, but als o f o r many e n t h u s i a s t i c and s t i m u l a t i n g d i s c u s -s i o n s . The support and encouragement of the other members of my commit-tee, Dr. L.M. L a v k u l i c h (Professor and Department Head, Department of S o i l Science) and Dr. C A . Rowles (Professor Emeritus, Department of S o i l S cience), i s al s o g r a t e f u l l y acknowledged. The b r e v i t y r e q u i r e d i n t h i s acknowledgement p r o h i b i t s s i n g l i n g out a l l of the f a c u l t y members and students who provided encouragement, h e l p f u l advice and many s t i m u l a t i n g ideas during my graduate program; however, a few i n d i v i d u l a s need to be mentioned. F.M. K e i l l i h e r (Ph.D. candidate, Department of S o i l Science) provided i n v a l u a b l e advice and t e c h n i c a l a s s i s t a n c e . Dr. M.W. Sondheim (now with the B.C. M i n i s t r y of Environ-ment), Dr. J.P. Demaerschalk (P r o f e s s o r , F a c u l t y of F o r e s t r y ) , Dr. A. Y Kozak ( P r o f e s s o r and As s o c i a t e Dean, Fac u l t y of F o r e s t r y ) , and Dr. M. Greig (UBC Computing Centre) gave extremely h e l p f u l advice on s t a t i s t i -c a l matters. - X Thanks are extended to Dr. W. Herman (Pacific Soil Analysis Inc.) and M. Goldstein (Soilcon Laboratories Ltd.) for their assistance and provision of laboratory facilities. I also must thank Westwords for very prompt and efficient word proces-sing services and N. Cukor, V. Kwong and N. Smith of Talisman Graphics for producing the final figures. The B.C. Ministry of Forests provided tree seed and seedlings and their Research Branch provided assistance and advice in the early stages of my studies. In particular, I express my appreciation to R.L. Schmidt (former Director, Research Branch) and Dr. T.E. Baker (Manager, Ecology and Earth Sciences, Research Branch). Finally, I offer many thanks to my family, Sheila, Matthew, Jack and Emily for thier patience, encouragement and moral support. Research for this thesis was partially supported by a grant from the Natural Sciences and Engineering Research Council of Canada. - 1 -INTRODUCTION The importance of water to plants has been long recognized and scientif-ic enquiry into plant water relations began over two hundred and f i f ty years ago (Hales, 1727). Water is important physiologically as a major constituent of protoplasm, as a solvent for gases, minerals and growth substances, and as a chemical reagent (e.g., in photosynthesis and in hydrolysis of starch to sugar); i t also maintains c e l l turgidity which is important for c e l l enlargement and growth, opening and closure of stomata, and in leaf movement (Bidwell, 1974; Salisbury and Ross, 1969). Ecological ly, water is important in partioning energy into sensible and latent heat, thus affecting s o i l , plant and ambient air temperatures (Gates, 1980; Oke, 1978). At a much broader scale, the distribution of vegetation over geographic areas or regions is also affected by the avai labi l i ty of water, as i l lustrated in various vegeta-tion and ecological mapping and c lass i f icat ion schemes (e.g. see Burger, 1972; Damman, 1979; Franklin and Dyrness, 1973; Holdridge, 1947; Krajina, 1969; Merriam, 1898; Pfister et al., 1977; Pojar, 1983; Walter, 1973). Moisture has been widely recognized as a major environmental variable affecting seedling survival and growth (Waring, 1970; Greaves, Hermann and Cieary, 1978). Hinckley et al. (1978), in their l i terature review of water status in forest trees, point out that the growth is generally limited by either an excess or a scarcity of water. - 2 -The water balance of a plant depends on the r e l a t i v e rates of uptake from the s o i l and loss to the atmosphere by evaporation. The rate of water flow from the s o i l to the root and through the plant t i s s u e s to the l e a f , under steady state conditions, can be expressed by a simple model based on an analogy to Ohm's Law for the flow of e l e c t r i c a l current. This model for water flow was proposed by van den Honert (1948) and has since been widely used by many authors including Cowan (1965), H i i l e l (1971 and 1980) J a r v i s (1975), Rose (1966), Rutter (1975) and Slatyer (1967). Liquid phase water flow i s mainly a passive process (Kramer, 1969; Kramer and Kozlowski, 1979) which i s proportional to a decreasing water p o t e n t i a l gradient from the s o i l , through the roots, into the xylem and to the leaves and inversely proportional to resistance along the same pathway. At steady state, flow i s equal through a l l segments of the s o i l - p l a n t system and the t o t a l resistance from the s o i l to the leaves can be expressed, again using an e l e c t r i c a l analogue, as the sum of the component resistances ( s o i l , root, xylem and leaf) linked in serie s (Hinckley et al., 1978). Resistance to water flow through xylem t i s s u e from the roots to the leaves i s apparently r e l a t i v e l y small (Boyer, 1971; Herkelrath et al., 1977a; T i n k l i n and Weather ley, 1966). However, there i s some evidence that resistance increases with decreasing flow and, at very low flow rates, xylem resistance may be s i g n i f i c a n t (Oarvis, 1975; Richter, 1976). - 3 -Although resistance to flow in the bulk soil can become large as the soil dries, many authors indicate that the major source of resistance to liquid phase water flow is in the root, probably at the endodermis, or at the contact zone between the soil and the roots (Andrews and Newman, 1969; Herkelrath et al., 1977a, 1977b; Newman, 1969a, 1969b; Nnyamah et al., 1978). Large plant resistance in the root has been suggested in several studies of plants growing in solutions (Boyer, 1969; Stoker and Weatherley, 1971; Tinklin and Weatherley, 1966; Tomar and O'Toole, 1982). For plants growing in soil at normal rooting densities, soil resistance appears to be relatively small compared to root or soil-root contact resistance (Dosskey, 1978; Herkelrath et al., 1977a; Newman, 1969b; Nnyamah et al., 1978; Reicosky and Ritchie, 1976). Several authors (Dosskey and Ballard, 1980; Faiz, 1973; Faiz and Weatherley, 1978; Oarvis, 1975; Nnyamah et al., 1978) indicate that soil-root contact is a major source of total resistance. This thesis arose from a keen interest in the relation between various forest site classifications and prescriptions for tree species selection with regard to seedling water requirements. Given the problems in studying water relations from a holistic ecological viewpoint (Elston and Monteith, 1975), it seems inevitable to shift to what Gates (1980), in the introductory chapter of his text, called "a reductionist approach". More specifically, differences in resistance to water uptake arising from cultural practices, such as planting, and between contrast-_ 4 _ ing species offered t r a c t a b l e subjects for research. This also presented a l o g i c a l extension of work conducted by Dosskey (1978). The objectives of t h i s t hesis are to compare the magnitude and pattern of resistance to water uptake in ponderosa pine (Pinus ponderosa Laws.) to Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menzxesii) and to investigate the e f f e c t of planting on resistance i n Douglas-fir seedlings. A study of resistance i n ponderosa pine i n comparison to r e s u l t s obtained by Dosskey (1978) for Douglas-fir i s presented i n Chapter 1 and resistance to water uptake in planted Douglas-fir seedlings i s the subject of Chapter 2. A summary of the findings from both studies along with an overview of t h e i r s i g n i f i c a n c e i s given at the end of the t h e s i s . Both of the studies employ many si m i l a r methods. For example, r e s i s t -ance was calculated using the Ohm's Law analogy to water flow based on measurements of s o i l water p o t e n t i a l , needle water p o t e n t i a l and uptake. Seedlings were grown under si m i l a r greenhouse conditions and the experiments were conducted i n a s i m i l a r c o n t r o l l e d environment i n the same growth chamber. In the i n t e r e s t of brevity, s i m i l a r d e t a i l s of experimental strategy, methods and materials are presented only once ( i n Chapter 1); however, departures made in the experiments described in Chapter 2 are e x p l i c i t l y stated. - 5 -C H A P T E R 1 R E S I S T A N C E TO WATER U P T A K E I N PONDEROSA P I N E C O M P A R E D TO D O U G L A S - F I R - 6 -INTRODUCTION Ponderosa pine (Pinus ponderosa Laws.) i s a widely distributed commer-c i a l l y important tree species in western North America occurring from southern B r i t i s h Columbia east to North Dakota, south to Trans-Pecos, Texas and west to southern C a l i f o r n i a and Mexico (Fowells, 1965). In B r i t i s h Columbia, i t i s confined to the southern i n t e r i o r , south of about Clinton, at elevations mostly below 900 metres above sea level (Krajina et al., 1982). Although i t s commercial importance i s r e l a t i v e -l y small on a province wide basis, i t assumes particular importance as one of a few species, or sometimes the only native species, which can survive and produce timber on drier s i t e s in the i n t e r i o r regions. Much has been written on the morphological adaptations to drought and s i l v i c s of the species (for example, see Barrett, 1979; Curtis and Lynch, 1957; Fowells, 1965; Krajina, 1969; Mirov, 1967; Waring, 1970) and some aspects of water relations have been studied by Cleary (1971), Lopushinsky (1969) and Lopushinsky and Klock (1974). Because of i t s widely recognized a b i l i t y to survive and grow under dry conditions, i t i s interesting to speculate on what characteristics might be responsible for maintaining a favourable water balance under adverse conditions. Lopushinsky (1969) and Lopushinsky and Klock (1974) i d e n t i f i e d r e l a t i v e -l y rapid stomatal closure as an important adaptation. As an extension of these sort of studies, investigation of resistance to l i q u i d phase water flow from the s o i l to the foliage and comparison with results from - 7 -other species seem logical. Studies conducted by Dosskey (1978) and reported in part by Dosskey and Ballard (1980) on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) provide a basis for comparison. METHODS AND MATERIALS Resistance to water uptake was calculated based on an Ohm's Law analogy to water flow proposed by van den Honert (1948): Af soil-root A¥root-leaf Ay leaf-air [1] °1 = R soil-root = R root-leaf = R leaf-air where q is the rate of water flow and AY and R are, respectively, the water potential difference and the resistance to flow along a particular pathway. In this study, only liquid phase water flow from the bulk soil to the needle was measured. Also, flow was measured as the transpiration rate at steady state in a controlled environment so it is equated to the uptake rate, U. Therefore, equation 1 can be simplified and solved for R: ^s - * N [2] R = T J Ys is the bulk soil water potential and ^ is needle water potential. Equation 2 provided the basis for calculating resistance in this study. - 8 -Seedlings and Soil Thirty grams of ponderosa pine seed, seedlot registration number Py 82E 5/B3/3002/0.50, were obtained from the British Columbia Ministry of Forests Seed Centre at Duncan, B.C. The seeds had been collected from natural stands in the southern interior region of British Columbia (in the general vicinity of Penticton, B.C.) at an elevation of about 500 m above sea level. Seeds were sown in coarse sand and gravel flats in a heated greenhouse on February 10, 1980 and young seedlings were transplanted to 11.4 cm (4-1/2") square, tapered pots on March 11 and 12, 1980. The seedlings were grown for over a year under natural illumination supplemented by a bank of fluorescent lights until the time of experimentation. Periodi-cally monitored daytime greenhouse temperatures generally ranged between 20° and 25°C and relative humidity was 80% plus or minus about 5%. Day-time irradiance was estimated to be about 20 to 25% of full sunlight (but was of course greater on clear, sunny days). Photoperiod was kept at 8 hours or greater, when necessary to correspond to the natural photoperiod. This was gradually increased prior to experimentation so that i t equalled the 15 hour photoperiod used in the experimental environment a week before the experimental runs were conducted in May 1981. Seedlings were watered daily, or less, as required to keep soils near field capacity and were fertilized regularly with full strength modified Hoagland's solution (see Dosskey, 1978, Appendix II). - 9 -Soil was obtained from the B horizon of a Sunshine soil series on the University of B.C. Endowment Lands, dried and sieved to remove particles greater than 2 mm. Seedlings were potted with a pre-weighed mass of soil packed to equal volumes. Average total soil volume was about 360 cm^  and soil bulk density was 998 kg*m"3. A summary of some soil properties is presented in Table 1. Table 1 Soil Properties Texture % Sand* % S i l t * % Clay* % 0Mb p H C Ksd Loamy Sand 79 17 4 5.6 6.3 96 cm day~1 ^Based on 2 mm and smaller fraction, by hydrometer method bWalkley-Black method c1:5 soil:water S a t u r a t e d hydraulic conductivity constant head permeameter method By December of 1980, 182 seedlings were growing and about 70% of them had developed secondary needles. Over the next several months seedlings with abnormally high or low leaf area or soil volume were culled. Seedlings which had not shed their primary leaves prior to experimenta-tion were also culled, leaving 128 seedlings. Seventy-eight of these were randomly selected for use in the experiments. Soil psychrometers were then inserted into each of the pots at a point 1 cm from the root collar in the manner described by Dosskey (1978). The lead wires were coiled several times around inside the pot to avoid development of large thermal gradients in the first one-half metre. - 10 -Drainage holes in the pots were taped over and the seedlings sealed in plastic bags as described by Dosskey (1978). Seedlings were ventilated for ten minutes every day to allow for soil atmosphere exchange. Seedlings were then watered from below and lightly sprinkled from above to bring them to field capacity and were placed in the growth chamber three days prior to experimentation to allow them to become acclimatized to the experimental environment. Soils were again watered to field capacity at the beginning of the experiment and subsequent irrigation was withheld. Measurements of needle water potential, uptake and soil water potential were taken over a period of eleven days during May 1981. Experimental Environment The experiment was conducted in a Percival P-C-78 growth chamber (#67-26) with lighting provided by a bank of fluorescent and incande-scent lights. The spectral irradiance at mid-crown level is shown in Appendix I. Photon flux density within the visible spectrum at mid-crown level ranged from 490 to 540 Mmol-m~2«s -^, corresponding to about 25% of sunlight at full solar noon during mid-summer. The maximum variation observed was about 20% and values were lowest near the front and near the corners of the growth chamber. These locations were avoided during the experiment and seedling positions were randomly rotated three times daily to eliminate bias associated with location. - 11 -In order to reduce boundary layer resistance and variation in tempera-ture, humidity and carbon dioxide concentrations, the growth chamber was ventilated at an average velocity of 0.33 m«s"^ (measured with a hot wire anemometer at mid-crown level in the centre of the growth chamber). Average velocity at mid-crown level varied from 0.33 to 1.3 m-s"^  and was greatest near the ends; turbulence varied from 0.35 to 0.76 and was greater at the ends and at the front centre. Temperature was controlled at 20 ±1°C during light periods and 15 ±1°C during dark periods. Relatively high soil temperatures, similar to those observed by Dosskey (1978), were measured in this study, probably due to the greenhouse effect of the plastic bags enclosing the seedlings (Dosskey, 1978). Soil temperatures of 25°C were common and occasionally reached 29°C in very dry soil (soil water potentials of -2.7 MPa and lower). Relative humidity was controlled at 65 ±5% during light period and 85 ±5% for the dark period. Both temperature and relative humidity were monitored with a hygrothermograph which was regularly checked and calibrated by measurements with an Assmann psychrometer. Soil Water Potential Soil water potential was measured with Wescor PCT-55-05 thermocouple - 12 -psychrometers. The psychrometric mode of measurment was used because of its speed and reliability. Psychrometers were calibrated in distilled water and in sealed vials suspended over a 0.5 molal sodium chloride solution and were checked by immersion in distilled water after the experiment was completed. The two point calibration is adequate since some preliminary measurements confirmed the linearity of output over the range of soil water potentials studied. After allowing ample time for equilibration, six readings were taken for each psychrometer over the 0.5 molal solution. Psychrometers showing variation of more than ±0.5 UV, amounting to ±0.1 MPa or less in soil water potential at a potential of about -2.2 MPa, were not used. Measurements were taken three times daily beginning four hours after the start of the light period at about four hour intervals in conjunction with uptake measurements. Measurements for determining the soil water potential-needle water potential relationship were taken at 7-1/2 to 10 hours after the beginning of the light period. Actual times of measure-ments within this period were systematically varied. Variability in soil water potential within a pot was investigated in a manner similar to that of Dosskey (1978). In addition, measurements were compared with those from soil samples which were rapidly trans-ferred to Wescor C-51 and C-52 sample chambers. Results were also similar; up to ±0.3 MPa difference was found within a pot. The greatest - 13 -variation seemed to be at lower soil water potentials (less than about -2.0 MPa) suggesting that variable contact between the psychrometer cup and thermal gradients within the pot are important factors contributing to variability. Needle Water Potential Needle water potential was measured with Wescor C-51 and C-52 thermo-couple psychrometer sample chambers. Sample chambers were calibrated using 0, 0.05, 0.2, 0.5514 and 0.9 molal sodium chloride solutions and exhibited strong linearity in the range of water potential from -0.23 to -4.16 MPa. Accuracy of measurements was within ±0.025 MPa at equilib-rium. Sample chamber holders were coated with paraffin to minimize water adsorption to the holder surface (Boyer, 1967). Large (0.95 x 0.48 cm) sample chamber holders were used to accommodate the large, bulk needle samples used in the experiment. One needle from each of three randomly selected fasicles (from a randomly selected seedling) was removed, brushed with xylene, blotted dry, cut into sections and inserted in the sample chamber. Since a complete sample of even one needle was much too large to f i t in the sample chamber holder, middle, distal and proximal subsamples of each needle were used. Several segments, about 0.5 cm in length, for each - 14 -subsample location and each needle were included in the bulk sample. The xylene treatment was used to speed the equilibration time in the sample chamber (Dosskey, 1978; Dosskey and Ballard, 1980; Neumann and Thurtell, 1972). Several different techniques were tried and practiced in order to mini-mize the time between xylene treatment and cutting and insertion in the sample chamber. Using a pair of sharp surgical scissors for cutting the needle sections speeded the sampling process considerably. Comparisons of razor cut and scissor cut needles showed no detectable difference in water potential. After a considerable amount of practice the sampling process could be completed within 60 seconds. Sample chambers were checked for contamination after each measurement using procedures given by Wescor (1979) and were cleaned and recalibrated with distilled water and a 0.5 molal sodium chloride solution when necessary. When no contamination was apparent, the sample chambers were cleaned and recalibrated every other day. Several different sample equilibration times, varying from 15 minutes to 5 hours were investigated and 20 minutes was found to be a suitable period. Water potential at 20 minutes was found to be within less than 0.2 MPa of that at periods of 2 hours or more. The relationship between soil and needle water potential was determined from linear regression analysis. A grand total of 47 paired measurements of soil and needle water potential were made; four or more individual seedlings were measured on each day and were fitted to a simple linear regression model: [3] y N = a 0 + b! V s where a Q is the intercept and b-| the regression coefficient. Uptake Seedlings were weighed two times daily at four hour intervals using a beam balance with an accuracy of ±0.01 g and uptake was calculated as the average of the two four hour periods. Because of the destructive sampling of seedlings for needle water potential, uptake was determined from a separate group of 14 seedlings. Measurements of soil water potential were taken with each weighing and the three readings were averaged for determining the relationship between the average daily uptake rate and soil water potential for each seedling. Water uptake rate as a function of soil water potential was then deter-mined using nonlinear regression analysis to provide a range of continuous uptake values over the range of soil water potential where appreciable uptake occurs. A general model for uptake (U) can be expressed as: - 16 -[4] U = a + F(f s ) where "a" represents an asymptote which should approximately equal the evaporation rate from the bag surrounding each pot (Dosskey, 1978). The value of "a" was estimated from the average of measurements from seven pots containing no seedlings and was found to be r e l a t i v e l y small. This value was subtracted from the measured weight loss to ar r i v e at a true uptake value (exclusive of evaporation). Uptake for each of the 14 seedlings was then computed using the BMD-PAR nonlinear regression program (Ralston, 1983) at the U.B.C. Computing Centre. Two regression models were used: ( V c > 2 [5] U = ab MODEL I [6] U = a -b(*s-c)d 1-e MODEL II Where a, b, c and d are c o e f f i c i e n t s whose value varies from seedling to seedling and "e" i s the base of the natural logarithms. Model I was used by Dosskey (1978) i n h i s studies of Douglas-fir, western hemlock (Tsuga heterophylla (Raf.) Sarg.) and mountain hemlock (Tsuga mertensiana (Bong.) Carr.) seedlings and f i t t e d his uptake data well (Dosskey, 1978; Dosskey and Ba l l a r d , 1980). Model II i s a modified Weibull function which has been used i n r e l i a b i l i t y and l i f e t e s t i n g i n engineering and, more recently, i n fo r e s t mensuration applications including growth curves (Weibull, 1951; Yang et a l . , 1978). - 17 -Coefficients for each seedling were computed for each regression model and an average curve for each model was derived by averaging the coefficients. Uptake values for each seedling for both models and the average for each model were generated for fixed (0.1 MPa) intervals of soil water potential. Resistance Resistance to water uptake was calculated from equation 2 for soil water potential values of -0.1 to -2.4 MPa at 0.1 MPa intervals using the values of needle water potential and uptake derived from regression equations 3, 5 and 6. Because resistance values can be difficult to interpret and compare for seedlings with different water pathway dimen-sions, these were estimated and all analyses were conducted on unit root area basis. Water Pathway Dimensions Needle surface area, root surface area and the average pathlength for water movement from the bulk soil to a root surface were estimated and calculated according to the procedures used by Dosskey (1978) (also see Dosskey and Ballard, 1980) and are summarized in Table 2. One exception was that root density was determined in a dry state. Dry densities were then converted to fresh densities based on fresh:dry density ratios later determined from several seedlings from the population. - 18 -Table 2 Summary of Average Seedling and Water Flow Pathway Dimensions for Ponderosa Pine Seedlings Root Area (cm2) Needle Area 3 (cm2) Needle:Root Area R a t i o d Oven-Dry Root: Shoot Ratio Z b (cm) Average 116 44.9 0.40 1.8 0.19 C o e f f i c i e n t of V a r i a t i o n 23% 23% 23% 24% 13% a0ne sided area assuming a f l a t needle; t h i s assumption r e s u l t s in an underestimate of actual one sided needle area and the needle:root area r a t i o i s the calculated average distance that water must move through the s o i l to a root surface Comparison of Resistance Although the experimental environment and methods used i n t h i s study were nearly i d e n t i c a l to those used by Dosskey (1978), several obstacles to rigorous comparison of the r e s u l t s of the studies e x i s t . The sampling and c a l c u l a t i o n techniques i n both studies, necessitated by the destructive sampling of f o l i a g e for needle water p o t e n t i a l measurements, precludes any purely rigorous a n a l y s i s . Generated data for Douglas-fir on loamy sand textured s o i l i s not published on a unit root area basis (although the average curve and generated data points for i n d i v i d u a l seedlings on s i l t loam are). - 19 -The generated data violate assumptions of normality and homogeneity of variance which must be at least approximated in order to use parametric statistical tests such as analysis of variance or covariance. These shortcomings were not rectifiable by any commonly used data transforma-tions. In order to surmount these problems, the Kruskal-Wallis test, a non-parametric test suggested by Sokal and Rohlf (1981) in lieu of analysis of variance, was employed to test for significant differences between resistance for ponderosa pine and Douglas-fir on silt-loam. textured soil. RESULTS Needle Water Potential A plot of needle water potential against soil water potential shown in Figure 1 shows a linear, almost horizontal trend. Regression analysis of the data failed to produce a statistically significant regression coefficient indicating that needle water potential can be regarded as constant under the experimental conditions and over the range of soil water potential studied. Mean needle water potential is -2.2 MPa and the 95% confidence interval is from -2.3 to -2.1 MPa. It should be noted that the linear relationship shown in Figure 1 is not - 20 -Soil Water Potential Ok) (MPa) -3.0 i -2.0 i -1.0 o / / / / / / / / / / / / / / ^ / • • • • • • • m a = s • • / • • / J • / • • / * • • / • • • / • / / / Figure 1 NEEDLE WATER POTENTIAL vs SOIL WATER POTENTIAL FOR PONDEROSA PINE (Error Bars Represent the 95% Confidence interval) - 21 -d i r e c t l y comparable to r e l a t i o n s h i p s such as those shown by Cowan (1965) and Slatyer (1967) which show the d a i l y course of needle water p o t e n t i a l over several days of a drying period under natural conditions. For the purpose of such comparisons, needle water potential i n Figure 1 can be regarded as a s e r i e s of needle water po t e n t i a l measurements taken near mid-day over a drying period of several days. The data shown i n Figure 1 aLso suggest that the r e l a t i o n s h i p between needle water p o t e n t i a l and s o i l water p o t e n t i a l may not be l i n e a r at r e l a t i v e l y high s o i l water potentials (greater than about -0.1 MPa). This hypothesis was not v e r i f i a b l e by regression a n a l y s i s . However, further studies with a greater number of observations at high s o i l water pot e n t i a l s might, in f a c t , show a nonlinear r e l a t i o n s h i p over a small range near the upper extreme of s o i l water p o t e n t i a l . Since needle water p o t e n t i a l i s v i r t u a l l y constant in t h i s experiment, the water p o t e n t i a l difference between the s o i l and needles i s a l i n e a r function of s o i l water p o t e n t i a l . This r e l a t i o n s h i p i s shown in Figure 2. Uptake Uptake rates were predicted for each seedling and an average regression equation was derived using both regression models (equations 5 and 6). Values for the average c o e f f i c i e n t s for both models are shown i n Table - 22 -Soil Water Potential (0s) (MPa) Figure 2 WATER POTENTIAL DIFFERENCE vs SOIL WATER POTENTIAL FOR PONDEROSA PINE - 23 -3. No s t a t i s t i c s such as standard deviations for the c o e f f i c i e n t s or residual sums of squares are presented because these are not determinable for an average equation. Figures 3 and 4 show the generated uptake values for each seedling and the average curves for Models I and I I . Table 3 Average C o e f f i c i e n t s for Uptake Equations Model a b c d I 3.99 1.49 -2.11 n/a II 8.52 1.65 2.07 -2.20 Both models give good f i t for most i n d i v i d u a l seedlings. On the basis of generally smaller root mean square residuals (analogous to standard errors) and standard deviations for the c o e f f i c i e n t s , Model I appears to give more precise predictions. However, in many cases, l i m i t s had to be imposed on some of the c o e f f i c i e n t s in order to permit convergence of i t e r a t i v e c a l c u l a t i o n process and, for several seedlings, increment halvings occurred during the l a s t few i t e r a t i o n s . For these reasons, the magnitude of the standard deviations of the c o e f f i c i e n t s i s not a consistently r e l i a b l e indicator of precision (Ralston, 1983). One advantage of Model II i s that i t i s easier to attach some p h y s i c a l l y meaningful i n t e r p r e t a t i o n to some of the c o e f f i c i e n t s . For example, the c o e f f i c i e n t "a" represents the maximum asymptotic uptake rate and "c" i s related to the s o i l water po t e n t i a l where uptake becomes zero (i.e. UPTAKE IN PONDEROSA PINE PER UNIT ROOT AREA AS A FUNCTION OF SOIL WATER POTENTIAL - REGRESSION MODEL I -2.0 -1.0 Soil Water Potential (MPa) 0 Figure 4 UPTAKE IN PONDEROSA PINE PER UNIT ROOT AREA AS A FUNCTION OF SOIL WATER POTENTIAL - REGRESSION MODEL 11 - 26 -where s o i l water p o t e n t i a l i s equal to needle water p o t e n t i a l ) . These features are also h e l p f u l because most computer programs for nonlinear regression require an i n i t i a l estimate for each c o e f f i c i e n t . The c o e f f i c i e n t s "b" and "d" are not so e a s i l y interpretable but e f f e c t , respectively, the scale and shape of the curve (Yang et al., 1978). Average curves for both models exhibit bias as shown by a plot of the average residuals in Figures 5 and 6. Examination of the residuals for curves of i n d i v i d u a l seedlings confirms the trends shown for the plotted average r e s i d u a l s . Model I c o n s i s t e n t l y overpredicts uptake between s o i l water potentials of -1.5 and -2.8 MPa; Model II tends to consis-t e n t l y overpredict uptake between -1.2 and -1.8 MPa but underpredicts between -2.0 and -2.2 MPa. The uptake values plotted in Figures 3 and 4 for i n d i v i d u a l seedlings show considerable v a r i a b i l i t y which can be a t t r i b u t e d to p h y s i o l o g i c a l v a r i a b i l i t y among seedlings, environmental v a r i a b i l i t y i n the growth chamber and v a r i a b i l i t y in the degree of mycorrhizal i n f e c t i o n among seedlings. No ectomycorrhizal development was observable at the end of the experiment and the degree of environmental v a r i a t i o n appears to be too low to account for the observed v a r i a b i l i t y . Therefore, i t appears that p h y s i o l o g i c a l differences between i n d i v i d u a l seedlings i s the most s i g n i f i c a n t source of v a r i a b i l i t y in uptake. - 27 -- 4 'E - 3 | CO • - 2 CO E - 1 _W CO - 0 •o - - 1 CO cu DC - - 2 d) O ) - - 3 CC V . Q - - 4 > < -3.0 -2.0 -1.0 0 Soil Water Potential (MPa) Figure 5 AVERAGE RESIDUALS FOR UPTAKE EQUATION MODEL I ( +=underprediction, — = overprediction ) - 28 -—| i i i i | i i i i | i r -3.0 -2.0 -1.0 Soil Water Potential (MPa) Figure 6 AVERAGE RESIDUALS FOR UPTAKE EQUATION MODEL 11 ( + = underprediction, — = overprediction) - 29 -Resistance to Water Uptake Average seedling resistance, on a unit root area basis, calculated from equation 2 i s shown for both uptake regression models in Figures 7 and 8. Resistance based on uptake Model I (Figure 7) shows a s l i g h t increase as s o i l water p o t e n t i a l decreases from -0.1 to -1.2 MPa and then decreases u n t i l i t approaches zero at a s o i l water p o t e n t i a l of about -2.4 MPa. This behaviour i s in agreement with the bias indicated for uptake, as shown in Figure 5, and therefore appears to be an a r t i f a c t of the resistance c a l c u l a t i o n process. Resistance based on uptake Model II (Figure 8) shows a much d i f f e r e n t pattern. Resistance decreases between s o i l water po t e n t i a l s of -0.1 and -1.1 MPa and then increases r e l a t i v e l y r a p i d l y . At a s o i l water poten-t i a l of -2.0 MPa, resistance has increased by nearly an order of magni-tude and becomes i n f i n i t e l y large at -2.2 MPa. The i n i t i a l decrease i n resistance shown at higher s o i l water potentials appears to be a res u l t of bias i n the uptake equation (see Figure 6); s i m i l a r l y resistance i s s l i g h t l y overestimated at s o i l water potentials below -1.9 MPa. How-ever, the steep r i s e i n resistance between -1.1 and -1.8 MPa i s not a re s u l t of bias i n predicted uptake; i n f a c t , uptake i s generally over-estimated i n that range, which would r e s u l t i n underestimates of resistance. - 30 -h 3.0 a> o c ^  Soil Water Potential (MPa) Figure 7 RESISTANCE TO UPTAKE PER UNIT ROOT AREA FOR PONDEROSA PINE ( Uptake Model I) (Error Bars are Approximate) - 31 --2.0 -1.0 0.0 Soil Water Potential (MPa) Figure 8 RESISTANCE TO UPTAKE PER UNIT ROOT AREA FOR PONDEROSA PINE ( Uptake Model 11) (Error Bars are Approximate) - 32 -Comparison of Ponderosa Pine to Douglas-fir The results of this study compared to Dosskey's study of Douglas-fir (Dosskey, 1978), conducted under similar environmental conditions and using similar techniques, indicate that both ponderosa pine and Douglas-fir regulate needle water potential equally well; plots of needle water potential against soil water potential for both species show a nearly horizontal line. Uptake rates in ponderosa pine are greater than in Douglas-fir at high soil water potentials, but rates decrease more rapidly in ponderosa pine as the soil dries. A comparison of resistance to water uptake for ponderosa pine (based on uptake Model II) and Douglas-fir on s i l t loam and loamy sand soil (from Dosskey, 1978) is shown in Figure 9. The curve for Douglas-fir on loamy sand is an approximation derived from dividing resistance values per seedling by the average seedling root area. Because very few observa-tions could be made at soil water potentials greater than -0.5 MPa in both studies, values in that range are not included in the species comparison. Resistance for Douglas-fir on si l t loam was compared to that for ponderosa pine at soil water potential values of -0.6, -1.0 and -2.0 MPa using the Kruskal-Wallis test. A summary of the statistical analysis is presented in Table 4. The results show a very highly significant difference between the two - 33 --2.0 -10 0.0 Soil Water Potential (MPa) Figure 9 RESISTANCE TO UPTAKE PER UNIT ROOT AREA FOR PONDEROSA PINE ( Uptake Model 11) DOUGLAS-FIR ON SILT LOAM AND DOUGLAS-FIR ON LOAMY SAND (Curves for Douglas-Fir from Dosskey, 1978) - 34 -species at s o i l water po t e n t i a l s of -0.6 and -1.0 MPa. The differ e n c e indicated at -2.0 MPa i s not considered to be p h y s i o l o g i c a l l y s i g n i f i c a n t because estimates of resistance based on uptake Model I for ponderosa pine are a r t i f i c i a l l y low. Table 4 Kruskal-Wallis Test for Differences i n Resistance to.Water Uptake for Douglas-fir (F) and Ponderosa Pine (Py) S o i l Water Chi-Square Chi-Square Po t e n t i a l (MPa) F vs Py Model I F vs Py Model II -0.6 8.06* 12.00** -1.0 8.76* 17.02** -2.0 15.75** 2.29 n.s. n.s. Not s i g n i f i c a n t l y d i f f e r e n t * S i g n i f i c a n t l y d i f f e r e n t at = 0.005 * * S i g n i f i c a n t i y d i f f e r e n t at = 0.001 Comparison of resistance to water uptake, as shown in Figure 9, and the r e s u l t s of the Kruskal-Wallis t e s t i n d i c a t e that resistance for ponderosa pine on loamy sand i s s i g n i f i c a n t l y lower than for Douglas-fir on s i l t loam at higher s o i l water p o t e n t i a l s . As s o i l water po t e n t i a l approaches -2.0 MPa,' resistance increases more rapidly i n ponderosa pine and becomes approximately equal for both species. DISCUSSION The observed constancy of needle water po t e n t i a l and r e l a t i v e l y rapid - 35 -decrease in uptake as soil water potential decreases generally agree with the findings of Lopushinsky (1969) and Lopushinsky and Klock (1974) that ponderosa pine is relatively sensitive to decreasing soil water potential compared to Douglas-fir and that leaf water potential should decrease slowly as soil water potential decreases. The shape of the uptake curves from this study compared to the curve for Douglas-fir on loamy sand soil from Dosskey (1978) bear the same general relationship as the transpiration curves for the same species shown by Lopushinsky and Klock (1974); that is, transpiration (or, in this study, uptake) falls rapidly in ponderosa pine compared to Douglas-fir. Transpiration in ponderosa pine was shown to be about 3% of the maximum rate at a soil water potential of -2.0 MPa compared to about 20% of maximum for Douglas-fir (Lopushinsky and Klock, 1974). This agrees closely with uptake predicted with Model II at a soil water potential of -2.0 MPa in this study, which is about 3% of the maximum uptake rate. Model I predicts an uptake rate of about 30% of the maxi-mum rate at the same soil water potential. However, both models predict greater uptake rates than would be expected from Lopushinsky and Klock (1974) at higher soil water potentials. The estimated maximum transpiration rate (1.7 x 10~^ mg*s~ -cnr^) based on measurement of the stomatal resistance of a well watered seedling, agrees closely with the maximum rate predicted by the average uptake curve for Model II (about 2.0 x 10~3mg's"^ •cm~2). The maximum rate predicted by the average curve for Model I (about 5.0 x - 36 -10"3mg*s~ 'cm-^) i s nearly three times greater. Based on these comparisons, as well as the comparison of predicted to observed uptake for i n d i v i d u a l seedlings, Model I seems to be a r e l a t i v e l y poor model. In p a r t i c u l a r , i t s overly high predictions at low s o i l water p o t e n t i a l s make r e s u l t i n g estimates of resistance to water uptake questionable. This overprediction may be, at least i n part, a r e s u l t of underestimates of the evaporation rate (the intercept "a" in equation 4). Dosskey (1978) encountered t h i s problem in using the same regression model. However, the large r e l a t i v e errors that occur as both the water po t e n t i a l gradient and uptake rate approach zero i s probably the major source of d i f f i c u l t y in predicting resistance at low s o i l water p o t e n t i a l s . There are probably several reasons why uptake f a l l s less r a p i d l y than t r a n s p i r a t i o n i n the study by Lopushinsky and Klock (1974). Very few (only f i v e ) observations were made at s o i l water potentials greater than -0.3 MPa in t h i s study; therefore, estimates of uptake and resistance at the upper extreme are probably only rough approximations. Differences i n experimental conditions, such as the r e l a t i v e l y high s o i l temperatures in t h i s study, may account for some discrepancies. Also, the rate of decrease i n t r a n s p i r a t i o n as s o i l water p o t e n t i a l decreases s l i g h t l y (for example from -0.1 to 0.2 MPa) w i l l depend on s o i l properties such as conductivity, volume of s o i l and i t s degree of e x p l o i t a t i o n by roots (Rutter, 1967). F i n a l l y , p h y s i o l o g i c a l differences between the seedlings in the two studies may be s i g n i f i c a n t . - 37 -Predictions of uptake based on Model I I seem reasonable, at le a s t for s o i l water po t e n t i a l s below about -0.5 MPa, and are judged to be more r e a l i s t i c than predictions from Model I. The major l i m i t a t i o n to f i t t i n g Model II to the data i s probably the d i f f i c u l t y of getting observations at the upper extreme of s o i l water p o t e n t i a l . This model avoids the problem of obtaining precise estimates of the water p o t e n t i a l gradient and the uptake rate by forcing the uptake curve to zero when the water po t e n t i a l d i f f e r e n c e approaches zero. This strategy probably produces some d i s t o r t i o n s at other parts of the curve which are apparent i n the plot of average res i d u a l s shown in Figure 6. However, use of t h i s model seems j u s t i f i a b l e at le a s t from a pragmatic viewpoint since i t seem to produce more r e a l i s t i c predictons of average uptake rates. Since the difference i n resistance shown between the curves i n Figures 7 and 8 are a function of t h e i r respective uptake models i t follows that resistance to water uptake based on Model I (Figure 7) shows a s l i g h t increase as s o i l water p o t e n t i a l decreases to intermediate values and then decreases to nearly zero at about ^ s = -2.2 MPa. With regard to the e x i s t i n g knowledge of the species t h i s does not make sense. Even i f the s l i g h t decrease i n resistance as Vs decreases from -1.2 to -1.8 MPa can be explained as a r e l a t i v e l y minor a r t i f a c t of the c a l c u l a t i o n s , the subsequent drop i n resistance below ^ s = -1.8 MPa seems unreasonable. Resistance based on Model I I i s reasonable in t h i s respect. The decrease i n resistance as s o i l water potential decreases down to about -1.1 MPa i s also an a r t i f a c t of c a l c u l a t i o n s ( r e s u l t i n g from overpredic-tions of uptake) but the subsequent r i s e i s not. - 38 -S t a t i s t i c a l l y rigorous parametric t e s t s (such as analysis of variance or covariance) of differences in resistance between ponderosa pine and Douglas-fir cannot be properly applied to t h i s study because too many of the underlying assumptions of such t e s t s are too severely v i o l a t e d . However, the differences in the patterns of uptake, the magnitude of differences in resistance and the r e s u l t s of the Kruskal-Wallis t e s t together suggest a meaningful difference in resistance between the two species. The experimental conditions for t h i s study and the study of Douglas-fir were p r a c t i c a l l y i d e n t i c a l (see Dosskey, 1978). S o i l s and water pathway dimensions for the two species on loamy sand s o i l are compared i n Table 5. Table 5 i n d i c a t e s that s o i l conditions are very s i m i l a r . The s o i l in t h i s study has 5% less sand, 5% more s i l t and 3.2% more organic matter which might r e s u l t i n s l i g h t l y increased water retention and higher unsaturated conductivity. However, t h i s may be o f f s e t by i t s lower bulk density. Therefore, i t seems reasonable to say that the s o i l s are comparable. The average distance which water must move in the s o i l to a root surface i s about three times greater for ponderosa pine. If differences in s o i l resistance were lar g e l y responsible for the differences between the two species, i t would be expected that resistance to water uptake would be much greater for ponderosa pine. Since t h i s i s not the case, i t i s suggested that differences in s o i l s between the two species are not a major factor contributing to the - 39 -observed differences i n resistance to water uptake ( p a r t i c u l a r l y in view of the differences shown when ponderosa pine i s compared to Douglas-fir on s i l t loam). Table 5 S o i l C h a r a c t e r i s t i c s and Water Pathway Dimensions for Ponderosa Pine and D o u g l a s - f i r d Parameter Ponderosa Pine D o u g l a s - f i r a S o i l Texture % sand 0 % s i l t 0 % c l a y 0 loamy sand 79 17 4 loamy sand 84 12 4 S o i l Bulk Density (kg.m-3) 998 1,120 % Organic Matter 0 5.6 2.4 Average Z (cm) e 0.19 0.064 aFrom Dosskey (1978) °Based on 2 mm and smaller f r a c t i o n , by hydrometer method cWalkley-Black method ^1:5 soii:water C a l c u l a t e d average distance that water must move from the s o i l to a root surface A complete and thorough error analysis incorporating a l l the sampling and non-sampling er r o r s associated with prediction of uptake and the measurement of s o i l water p o t e n t i a l i s not possible. A rough approxima-tio n of a "worst case" upper l i m i t for combined sampling and non-sampling errors of about ±50% i s s t i l l not large enough to account for the differences found. - 40 -The observed differences in uptake and resistance may reflect different adaptive strategies of drought avoidance and tolerance. Low resistance to water uptake at high soil water potentials facilitates the high rates of uptake observed in this and other studies of ponderosa pine and other pine species. The relatively rapid decrease in uptake as the soil dries is probably at least partly a result of the greater sensitivity of stomata to decreasing soil water potential. In contrast, uptake in Douglas-fir falls much more gradually as the soil dries. Rapid stomatal closure is probably an important drought avoidance mechanism for ponderosa pine, which often grows on dry sites and in relatively dry climatic regions where the major source of growing season soil water is usually from snowmelt and spring rainfall. Coastal Douglas-fir is mainly a successional species; an avoidance strategy such as rapid stomatal closure in response to decreasing soil water potential would probably not be useful because any soil water conserved might be depleted by competing vegetation and maintenance of transpiration may be necessary to avoid excessive leaf temperatures (Bunce et al., 1977; Duhme, 1974; Passioura, 1976). The rapid increase in resistance to water uptake between soil water potentials of -1.5 and -2.0 MPa is a result of increasing plant, soil and soil-root contact resistance. Comparison with Douglas-fir studied by Dosskey (1978) under similar conditions and growing in similar soil suggests that some physiological and morphological factors might be responsible. It might be that differences in root morphology and the - 41 -degree of mycorrhizal development are i n d i r e c t l y responsible. Dosskey (1978) noted that the roots of Douglas-fir had developed a large number of f i n e l a t e r a l root hairs and that there was a s l i g h t degree of mycorrhizal development on some roots; neither of these c h a r a c t e r i s t i c s were present i n ponderosa pine. These root c h a r a c t e r i s t i c s could be responsible for a more gradual increase i n s o i l - r o o t contact resistance i n Douglas-fir. SUMMARY AND CONCLUSIONS Resistance to water uptake in ponderosa pine seedlings was calculated based on independent estimates of needle water p o t e n t i a l and uptake determined as a function of decreasing s o i l water p o t e n t i a l i n a con t r o l l e d environment. Linear regression analysis based on 47 observations was used to estimate needle water p o t e n t i a l , which was found to be v i r t u a l l y constant over the range of observed s o i l water p o t e n t i a l . Uptake rates were estimated using nonlinear regression analysis based on two d i f f e r e n t models. A modified Weibull function provided the most s a t i s f a c t o r y o v e r a l l p r e d i c t i o n s . Curves were f i t t e d for 14 seedlings based on a t o t a l of 92 observations i n the range of s o i l water p o t e n t i a l where uptake occurs. Predicted uptake values were then generated and plotted for fixed values of s o i l water potential and an average curve for the species was determined. - 42 -Average seedling resistance to water uptake was calculated and plotted based on predicted needle water potential and generated average uptake values for regular, fixed intervals of soil water potential. The results were then compared to results from a similar study of Douglas-f i r conducted by Dosskey (1978). Compared to Douglas-fir, resistance to water uptake in ponderosa pine seedlings differs, both in magnitude and in its pattern of change as soil water potential decreases. Both species seem to regulate needle water potential equally well, maintaining nearly constant water potential over a relatively wide range of soil water potentials. Uptake rates are comparatively large for ponderosa pine at higher soil water potentials but decrease much more rapidly as the soil dries. Resistance to uptake is lower for ponderosa pine until soil water potential reaches about -2.0 MPa. Resistance starts increasing at a soil water potential of about -1.0 MPa and rises rapidly between -1.5 and -2.0 MPa. The relatively low resistance to water uptake at higher soil water potentials agrees with the observed high transpiration rates at high soil water potentials reported in the literature for ponderosa pine and other pine species. The rapid increase in resistance as soil water potential drops from about -1.5 to -2.0 MPa probably reflects increasing soil and soil-root contact resistance, as well as plant resistance. - 43 -CHAPTER 2 RESISTANCE TO WATER UPTAKE IN PLANTED DOUGLAS-FIR SEEDLINGS - ¥ f -INTRODUCTION Coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var menziesii) has long been and continues to be a major timber producing species in B r i t i s h Columbia and the P a c i f i c Northwest of the United States. Douglas-fir has probably received as much (or more) study of i t s physiology and ecology as any species i n B.C. Many past studies of i t s water r e l a t i o n s have centred on s i t e and s o i l c h a r a c t e r i s t i c s or plant water status; however, understanding of seedling water r e l a t i o n s requires some knowledge, not only of s o i l and plant water status, but of resistance to flow along various segments of the water flow pathway. This sort of information i s d i f f i c u l t to gather because many plant and environmental variables can confound i n t e r p r e t a t i o n s . Dosskey (1978) revealed some s i g n i f i c a n t insights into species and s o i l c h a r a c t e r i s t i c s r e l a t e d to resistance to l i q u i d phase water flow i n the s o i l - p l a n t system. An i n t e r e s t i n g inference a r i s i n g from his studies was that s o i l - r o o t contact resistance may be a major source of resistance i n the water pathway. S i g n i f i c a n t contact resistance has also been i n f e r r e d by a number of authors such as Herkelrath et al. (1977a, 1977b), Nnyamah et al. (1978) and was i d e n t i f i e d by Faiz (1973) as a major source of resistance to water flow. Given the pot e n t i a l s i g n i f i c a n c e of contact resistance i t i s l o g i c a l to speculate that i t could be an important factor influencing the s u r v i v a l and growth of planted Douglas-fir seedlings. - 45 -The objective of this experiment is to investigate the relative magni-tude of resistance to water uptake in planted Douglas-fir seedlings and to see i f soil-root contact effects could be contributing to increased total resistance. METHODS AND MATERIALS Many of the methods employed in this experiment have been described and discussed in the previous chapter reporting the results of a study on ponderosa pine and will not be repeated here. The greenhouse and experimental environments, general properties of soils, instruments used for measuring uptake and soil and needle water potential and watering and fertilization procedures are the same in both experiments. Six-hundred, one year old bareroot Douglas-fir seedlings, seedlot 92G/B2/2890/0.145, were obtained from the B.C. Ministry of Forests' Green Timbers Nursery in Surrey, B.C. on February 8, 1980 and stored in a sealed vinyl lined paper seedling bag in a sheltered location at ambient outdoor temperatures. On February 11, the seedlings were planted in 11.4 cm square, tapered pots using preweighed volumes of soil packed to equal volumes. Seedling roots were thoroughly washed to remove the nursery soil and roots in excess of about 10 cm in length were pruned prior to potting. Seedlings were grown in the greenhouse for 15 months prior to experimentation. - 46 -Average soil bulk density was 995 kg-nr^ and average soil volume about 370 cm^ . Other general soil properties are described in Table 1 in the previous chapter. Effect of Needle Removal! on Uptake Seedlings were of sufficient needle area to suppose that removing a few needles would not appreciably affect water balance. For example, removal of 10 needles would constitute a needle area reduction of only about one or two percent. A nested factorial experiment to investigate the effects of removing 3 or 10 needles on water uptake rates was run in the growth chamber during January of 1981. Nine seedlings were randomly selected and assigned to treatments. Treatment factors were defined as three levels for the number of needles removed (0, 3 and 10) combined with two qualitative levels of soil water potential (-0.3 to -0.6 MPa and -1.4 to -2.2 MPa). Soil water potential was monitored continually throughout the experiment using Wescor PCT-55-05 soil psychrometers. The results of analysis of variance conducted showed no significant effect of removal of 3 or 10 needles on uptake rates (at a <0.25). Measurement of Needle Water Potential Since up to 10 needles could be removed without producing a detectable change in water uptake, this opened the possibility of making repeated - 47 -measurements of needle water potential on an individual seedling. Fur-thermore, the same seedling could be used for measuring uptake so that the awkward statistical procedures for calculating resistance used in the previously described experiment on ponderosa pine could be avoided. Exploratory experiments were conducted during February of 1981 to determine a suitable sample holder size, sampling procedure and equili-bration time for a single needle sample in the Wescor C-51 and C-52 thermocouple psychrometer sample chambers. Using the .64 x .08 cm (1/4 x 1/32 inch) sample holder, a 30 minute equilibration time resulted in water potential measurements that were usually within ±0.1 MPa of the value at two hours. Occasionally the difference was as much as ±0.2 MPa. Paired measurements of needle water potential from the same seedling at the same time were then taken for single needle samples and bulk samples of 10 needles. The results were analyzed using a t-test for paired observations. Water potential measured for single needles averaged 0.078 MPa lower than for bulk samples but the difference was not statistically significant (at <*<0.20). Investigations into variability in water potential among needles on the same seedling sampled at the same time revealed that needle water poten-tia l estimates could vary up to about 20% (about ±0.2 to ±0.3 MPa). However this variability was reduced to ±0.15 MPa by restricting sampling to needles of the same age and comparable crown position. - 48 -In the ensuing experiment, needles were s e l e c t e d from the mid-point of a l a t e r a l twig near mid-crown l e v e l . The needle was t r e a t e d with xylene, b l o t t e d dry, cut i n t o t h i r d s using a razor blade, i n s e r t e d i n the sample chamber and allowed to e q u i l i b r a t e f o r 30 minutes before water p o t e n t i a l measurements were taken. A needle could be sampled, t r e a t e d and sealed i n the sample chamber w i t h i n 30 seconds. Experimental Conditions and Procedures Seedlings were weighed and concurrent measurements of s o i l water poten-t i a l were taken three times d a i l y at four hour i n t e r v a l s beginning at four hours a f t e r the s t a r t of the l i g h t p e r i o d . Needle water p o t e n t i a l measurements were made between 7-1/2 and 10 hours a f t e r the beginning of the l i g h t p e riod and the time of measurement was s y s t e m a t i c a l i y a l t e r e d . Seedlings were s e l e c t e d i n random order for measurements and t h e i r l o c a t i o n i n the growth chamber was changed randomly three times d a i l y a f t e r each weighing. Uptake was c a l c u l a t e d as the average f o r two four-hour periods and s o i l water p o t e n t i a l was averaged f o r the three d a i l y readings. Resistance was c a l c u l a t e d from water p o t e n t i a l and uptake values using equation 2 (Chapter 1). V a r i a b i l i t y i n s o i l water p o t e n t i a l was found to be comparable to that i n the ponderosa pine experiments (Chapter 1). S o i l temperatures were l e s s than i n the ponderosa pine experiment, - 49 -probably because the Douglas-fir seedlings were t a l l e r and the s o i l surface was fart h e r below the bank of l i g h t s i n the growth chamber. Temperatures were generally 25 to 26°C but occasionally reached 27°C in dry s o i l s with s o i l water po t e n t i a l s of less than -2.0 MPa. Treatments F i f t e e n seedlings were randomly selected and allocated to one of three treatments: c o n t r o l , planted and planted and vibrated. Ten of the seedlings were c a r e f u l l y l i f t e d from th e i r pots, replanted and the o r i g i n a l s o i l repacked to i t s previous volume. Root exposure time was kept to a minimum (about one minute) and roots were kept moist by misting. Immediately a f t e r planting s o i l s were watered to f i e l d capacity. Five of the planted seedlings were randomly selected and subjected to vib r a t i o n for 30 minutes on a vortex mixer. Keeping s o i l water content high (at about f i e l d capacity) apparently helped to keep compaction minimal while s t i l l allowing v i b r a t i o n to move s o i l p a r t i c l e s . Mean bulk de n s i t i e s sampled at the end of the experiment for c o n t r o l , planted, and planted and vibrated treatments were 995, 1020 and 984 kg'm"^, re s p e c t i v e l y . Allowing for sampling error, they can be regarded as equal. S o i l psychrometers were then inserted i n each pot i n the manner - 50 -described in the previous chapter and seedlings were watered and placed in the growth chamber for a three day equilibration period before the experiment began. Measurements were made over a period of six days in April 1981. Experimental Design and Data Analysis The experiment was set up as a nested analysis of variance, mixed effects model. Five seedlings were allocated to each treatment and six replicate measurements were taken for each seedling. Treatment effects were considered fixed and both seedlings and replicates were treated as random effects. Because individual seedlings depleted soil water at different rates and depletion was especially slow for planted seedlings, covariance analysis was used to analyze the data. Before the fina l analysis, the data were analyzed for normality and homogeneity of variance by plotting and by Bartlett's test (Sokal and Rohlf, 1981). In order to meet the assump-tions of analysis of variance and covariance data were transformed using base-10 logarithms. Data were then analyzed using the UBC ANOVAR (Greig and Osterlin, 1978) program at the University of B.C. Computing Centre. - 51 -Seedling and Water Pathway Dimensions Seedling and water pathway dimensions were determined using methods described by Dosskey (1978) and are summarized in Table 6. Table 6 Seedling and Water Pathway Dimensions for Douglas-fir Seedlings3 (Measured at the end of the Experiment) Root Area Needle Area0 Needle:Root Oven Dry Root: Treatment (cm2) (cm2) Area Ratio Shoot Ratio (cm) Control 246 111 .46 .60 0.14 (21%) (17%) (15%) (28%) (19%) Planted 290 101 .37 .62 0.12 (23%) (13%) (32%) (34%) (20%) Planted and 301 130 .44 .57 0.14 Vibrated (28%) (30%) (18%) (70%) (28%) dNumbers in parentheses are coefficients of variation °0n e-sided needle area CZ is the calculated average distance that water must move through the soil to a root surface RESULTS Needle Water Potential Plots of needle water potential against soil water potential for each of the three treatments are shown in Figures 10, 11 and 12. In these figures, different symbols represent five individual seedlings and the Figure 10 NEEDLE WATER POTENTIAL vs SOIL WATER POTENTIAL FOR CONTROL DOUGLAS-FIR SEEDLINGS ( The different symbols respresent individual seedlings. Line is from Dosskey, 1978 ) - 53 --3.0 _ i Soil Water Potential (i/'s) in MPa -1.0 L _ / / / / / / / / / / / / L-1.0 -2.0 ca CL 2 ca +-« c CD o CL i_ CD o •o co o z -3.0 Figure 11 NEEDLE WATER POTENTIAL vs SOIL WATER POTENTIAL FOR PLANTED DOUGLAS-FIR SEEDLINGS ( The different symbols represent individual seedlings. Line is from Dosskey, 1,978 ) - 54 -Soil Water Potential OAs) in MPa -1.0 Figure 12 NEEDLE WATER POTENTIAL vs SOIL WATER POTENTIAL FOR PLANTED AND VIBRATED DOUGLAS-FIR SEEDLINGS ( The different symbols represent individual seedlings. Line is from Dosskey, 1978 ) - 55 -s o l i d l i n e shown i s the least squares f i t t e d l i n e derived by Dosskey (1978) in his study of Douglas-fir on loamy sand. Because of d i f f e r -ences in the sampling methods between t h i s study and Dosskey's, a rigorous comparison of r e s u l t s i s not appropriate. However, looking at a l l the i n d i v i d u a l data points, there i s general agreement between the data from t h i s study and the regression l i n e s from Dosskey (1978) for the control (Figure 10) and the planted and vibrated (Figure 11) t r e a t -ments. Needle water po t e n t i a l for the planted treatment i s more d i f f i c u l t to compare, p a r t l y because i t was not possible for the seedlings in t h i s treatment to reduce s o i l water po t e n t i a l below about -1.0 MPa. There-fore, a l i n e a r trend, even i f i t did e x i s t , cannot be c l e a r l y shown. Looking at the data points for i n d i v i d u a l seedlings, a trend toward increasing needle water p o t e n t i a l as s o i l water po t e n t i a l decreases i s suggested, at least for some of the seedlings. This may be a r e s u l t of increased stomatal closure in response to water stress. Some yellowing, browning and hooking of needle t i p s was observed on several seedlings when s o i l water po t e n t i a l s were near -0.5 MPa. Uptake Figures 13, 14 and 15 show the uptake values at d i f f e r e n t s o i l water potentials for the three treatments along with the uptake regression curve developed by Dosskey (1978) for Douglas-fir on loamy sand. Con-- 56 -(The different symbols represent individual seedlings. Curve is from Dosskey, 1978) - 0.3 6) • E Soil Water Potential (MPa) Figure 13 UPTAKE RATE FOR CONTROL DOUGLAS-FIR SEEDLINGS - 57 (The different symbols represent individual seedlings. Curve is from Dosskey, 1978) Soil Water Potential (MPa) Figure 14 UPTAKE RATE FOR PLANTED DOUGLAS-FIR SEEDLINGS - 58 - 8 (The different symbols represent individual seedlings. Curve is from Dosskey, 1978) 0.4 0.3 . A a h0.2 co cn E »^  CD *-< CO CC CD J£ CO a 13 • h0.1 © e •3.0 -2.0 -1.0 Soil Water Potential (MPa) Figure 1 5 UPTAKE RATE FOR PLANTED AND VIRBRATED DOUGLAS-FIR SEEDLINGS - 59 -s i d e r i n g differences in seediing s i z e , there i s a reasonable degree of agreement between observed uptake rates and predicted rates from Dosskey (1978) for the control (Figure 13) and planted and vibrated (Figure 15) seedlings i n the range of s o i l water po t e n t i a l from about -0.5 to -2.0 MPa. Uptake i s obviously less in the planted seedlings (Figure 14) than in the other two treatments and i s considerably less than would be pre-dicted from regression (Dosskey, 1978). These low uptake rates agree with the above observations on needle water potential and seem to con-firm that the seedlings were in fact s u f f e r i n g from water s t r e s s . Resistance to Water Uptake Observed resistance for the three treatments along with the resistance curves for Douglas-fir on loamy sand from Dosskey (1978) are shown in Figures 16, 17 and 18. Resistance for the control (Figure 16) and the planted and vibrated (Figure 18) seedlings i s s i m i l a r and both t r e a t -ments show general agreement with the resistance curves. Resistance for the planted and vibrated seedlings appears to be somewhat lower but t h i s i s probably partly a r e s u l t of differences in seedling dimensions. Resistance for the planted seedlings shown in Figure 17 i s c l e a r l y greater than for the other treatments. Also a trend of much more steeply r i s i n g resistance for one or two i n d i v i d u a l seedlings as s o i l - 60 -h 1 0 0 o o» • o r - 1 0 h i I I | I I I l l I l I l 2:0 -1.0 0 Soil Water Potential (MPa) I I I l l l i l I •3.0 "i 1 1 1 r Figure 16 RESISTANCE TO UPTAKE FOR CONTROL DOUGLAS-FIR SEEDLINGS. (Thie different symbols represent individual seedlings. Curve is from Dosskey,1978) (Error bar represents 95% confidence interval for resistance, shown at mean value fortes) - 61 --3.0 -2'.0 -1.0 0 Soil Water Potential (MPa) Figure 17 RESISTANCE TO UPTAKE FOR PLANTED DOUGLAS-FIR SEEDLINGS (The different symbols represent individual seedlings. Curve is from Dosskey ,1978) (Error bar represents 95% confidence interval for resistance, shown at main value for^s) - 62 -O MOO ~ r-10 'co CO CO 0. r -« ^ CU o c CO CO CO CU CC | I I I I I I I I l | I l I l I I l I l | -3.0 -2.0 -1.0 Soil Water Potential (MPa) Figure 18 RESISTANCE TO UPTAKE FOR PLANTED AND VIBRATED DOUGLAS-FIR SEEDLINGS (The different symbols represent individual seedlings. Curve is from Dosskey, 1978) (Error bar represents 95% confidence interval for resistance, shown at mean value forV's) - 63 -water po t e n t i a l decreases between about -0.1 and - 1 . 0 MPa i s apparent. For the other two treatments, resistance appears to be nearly constant, at least down to s o i l water po t e n t i a l s of about - 1 . 0 MPa. As the s o i l gets d r i e r , resistance appears to increase more slowly than for the planted seedlings. Covariance analysis of resistance data on a seedling, unit needle area and unit root area basis showed a very highly s i g n i f i c a n t treatment e f f e c t . Treatment means were tested and showed resistance i n planted seedlings to be s i g n i f i c a n t l y d i f f e r e n t from control and the planted and vibrated seedlings (cc = 0 . 0 5 ) . However, the planted and vibrated seedlings are not s i g n i f i c a n t l y d i f f e r e n t from the c o n t r o l . Results were s i m i l a r regardless of whether data were analyzed on a seedling, unit needle area or unit root area basis. Details of the s t a t i s t i c a l analyses are in Appendix VII. The analyses also showed a very highly s i g n i f i c a n t variance component a t t r i b u t a b l e to v a r i a t i o n among seedlings within a treatment. The c o e f f i c i e n t of i n t r a c l a s s c o r r e l a t i o n (Sokal and Rohlf, 1981) for seedlings within a treatment i s 0 . 9 2 which can be interpreted as showing that 92% of the v a r i a t i o n within a treatment i s accounted for by d i f f e r -ences between i n d i v i d u a l seedlings and only 8% i s a t t r i b u t a b l e to v a r i a b i l i t y within an i n d i v i d u a l seedling. S i g n i f i c a n t v a r i a b i l i t y between i n d i v i d u a l seedlings may r e s u l t from ph y s i o l o g i c a l d i f f e r e n c e s , v a r i a b i l i t y i n the growth chamber environment - 6k -or differences i n extent of mycorrhizal development. Environmental d i f -ferences i n the growth chamber appear to be r e l a t i v e l y minor; also, the e f f e c t s of any differences were accounted by randomly changing the loca-ti o n of seedlings during the experiment. Seedling roots were examined for ectomycorrhizal development at the end of the experiment and development appeared to be minor and s i m i l a r between treatments and i n d i v i d u a l seedlings. However, even some apparently minor differences i n the extent of development might be a source of v a r i a t i o n between seedlings. P h y s i o l o g i c a l differences between seedlings, however, are probably the major source of v a r i a b i l i t y . DISCUSSION Analysis of resistance data shows that planted seedlings have a much higher resistance to water uptake than seedlings which have been growing na t u r a l l y in the s o i l . I t i s speculated that roots of such n a t u r a l l y growing seedlings can e s t a b l i s h intimate contact with the s o i l r e s u l t i n g i n reduced s o i l - r o o t contact resistance compared to planted seedlings. The r e s u l t s of v i b r a t i n g planted seedlings seem to confirm t h i s hypothesis. Mean resistance for planted seedlings i s about six times greater than for planted and vibrated seedlings. Other possible explanations are that v i b r a t i o n somehow a f f e c t s the seedlings themselves so as to lower t h e i r resistance or that v i b r a t i o n a l t e r s s o i l density and pore geometry r e s u l t i n g i n reduced s o i l r e s i s t -- 65 -ance. The former p o s s i b i l i t y , that v i b r a t i o n could act to lower plant resistance independently from e f f e c t s on the s o i l , cannot be substanti-ated by any e x i s t i n g evidence. However changes in s o i l density and pore geometry could lower s o i l resistance which might account for the reduced t o t a l resistance. Examination of the resistance data shown i n Figure 17 for planted seedlings suggests that resistance for i n d i v i d u a l seedlings i s more or l e s s constant or may be increasing for one or two of the seedlings as the s o i l d r i e s . C a l c u l a t i o n s by Gardner (1960) suggest that s o i l resistance i s small compared to t o t a l resistance at s o i l water potentials greater than -0.5 MPa i n Pachappa sandy loam and Newman (1969) concluded that s o i l resistance should be r e l a t i v e l y small at s o i l water po t e n t i a l s of -0.7 MPa under conditions of normal rooting density. Nnyamah et al. (1978) found that resistance in a gravelly sandy loam s o i l remained r e l a t i v e l y small at s o i l water po t e n t i a l s of about -1.0 MPa or greater. Dosskey and Ballard (1980) i n f e r r e d that s o i l resistance could account for no more than 3% of t o t a l resistance i n Douglas-fir seedlings growing i n s i l t loam and s i l t y clay s o i l s . Inasmuch as these findings are applicable to t h i s experiment, s o i l resistance would seem to be too small to account for the observed differences between treatments. Laboratory analyses conducted at the end of the experiment show the s o i l s to be v i r t u a l l y i d e n t i c a l i n bulk density, water retention c h a r a c t e r i s t i c and saturated hydraulic conductivity. Unsaturated - 66 -hydraulic conductivity was estimated according to the method given by Jackson (1972). These estimates indicate that bulk s o i l resistance would increase by about three to four orders of magnitude as s o i l water pote n t i a l f a l l s from -0.06 to -0.5 MPa. The resistance data shown i n Figures 16, 17 and 18 show no correspondingly sharp increase in t o t a l resistance. Even though the calculated c o n d u c t i v i t i e s are only rough approximations, they may provide some in s i g h t into the contribution of s o i l resistance to t o t a l r e s i s tance. S o i l resistance based on the conductivity c a l c u l a t i o n s and the c a l c u l a t e d average pathlength for water flow from the s o i l to the root surface could account for a maximum of about 2% or l e s s of t o t a l resistance at a s o i l water po t e n t i a l of -1.5 MPa. The calculated average pathlength for water flow from the s o i l to a root surface for c o n t r o l , planted and vibrated and planted seedlings are 0.14, 0.14 and 0.12 cm, r e s p e c t i v e l y . Given the errors inherent in these c a l c u l a t i o n s , the pathlengths should be regarded as equal and cannot explain differences in resistance between treatments. In view of the above evidence, i t appears to be u n l i k e l y that differences between treatments can be accounted for only by differences i n s o i l resistance or by e f f e c t s of v i b r a t i o n on seedling physiology. It i s therefore i n f e r r e d that differences between treatments may be a r e s u l t of differences in s o i l - r o o t contact resistance. S i g n i f i c a n t contact resistance i n Douglas-fir and other plant species has been - 67 -inf e r r e d i n several studies (Dosskey and B a l l a r d , 1980; Herkelrath et al., 1977a, 1977b; Nnyamah et al., 1978) and Fa i z (1973) i d e n t i f i e d i t as a major component of t o t a l resistance i n sunflower (Helianthus annuus L.). The s i g n i f i c a n t variance component among seedlings i s noteworthy for several reasons. It confirms observations made by Dosskey (1978) and Dosskey and Ballard (1980) that considerable v a r i a t i o n can occur between apparently s i m i l a r seedlings growing under s i m i l a r , controlled environ-mental conditions. Such information may also be useful in designing future experiments. With reference to t h i s experiment, the large variance component between seedlings implies that experimental errors associated with measurements of water p o t e n t i a l and uptake and sampling errors associated with the sampling of sing l e needles for detemination of water p o t e n t i a l are r e l a t i v e l y i n s i g n i f i c a n t . Although extrapolation from the co n t r o l l e d experimental conditions to f i e l d conditions i s problematic, the findings of t h i s study have important s i l v i c u l t u r a l i mplications. High contact resistance i n planted bareroot seedlings may s i g n i f i c a n t l y a f f e c t s u r v i v a l and early growth. In f i e l d p r a c t i c e , considerably less care i s taken in planting compared to the c a r e f u l planting and packing of the s o i l practiced i n t h i s study. Therefore high contact resistance and, i n some cases, increased s o i l resistance can be expected i n f i e l d planted seedlings. - 68 -In addition to c a r e f u l stock handling and planting, c u l t u r a l measures to promote rapid root growth and encourage mycorrhizal development are p o t e n t i a l p r a c t i c a l solutions to the problem. SUMMARY AND CONCLUSIONS Resistance to water uptake in planted, planted and vibrated, and control Douglas-fir seedlings in loamy sand textured s o i l was compared. Re s i s t -ance was calculated from d i r e c t measurements of s o i l water p o t e n t i a l , needle water p o t e n t i a l and uptake on i n d i v i d u a l seedlings i n a con-t r o l l e d environment. The experimental design used was a nested analysis of variance and the data was analyzed with covariance analysis to allow f o r differences in the range of s o i l water p o t e n t i a l encountered between treatments and i n d i v i d u a l seedlings. Data were analyzed on a seedling, unit needle area and unit root area basis. Uptake rates, needle water p o t e n t i a l and resistance values for the con-t r o l seedlings were c l o s e l y comparable with those presented by Dosskey (1978) i n a s i m i l a r study in which d i f f e r e n t techniques were used. Results of the covariance analysis show a very highly s i g n i f i c a n t difference between treatments; resistance for planted seedlings i s about six times greater than for control or planted and vibrated seedlings. The l a t t e r two treatments are s t a t i s t i c a l l y i d e n t i c a l . The analysis also indicates that v a r i a b i l i t y among i n d i v i d u a l seedlings i s very highly s i g n i f i c a n t . - 69 -Increased resistance to water uptake in planted seedlings appears to be a result of greater soil-root contact and soil resistance. Because of the d i f f i c u l t y in obtaining precise estimates of unsaturated conductiv-ity for the soils, the relative contributions of contact and s o i l resistance cannot be precisely determined. However, because of the similarity of so i l properties, such as texture, bulk density and water retention characteristic, among treatments i t seems unlikeiy that s o i l resistance alone could account for the observed difference in total resistance. - 70 -CONCLUSIONS Resistance to Liquid phase water uptake in ponderosa pine seedlings and in planted Douglas-fir seedlings was studied using potted seedlings growing in a c o n t r o l l e d environment. Measurements of needle water and s o i l water p o t e n t i a l were taken under steady state conditions using Wescor C-51 and C-52 thermocouple psychrometer sample chambers and PCT-55-05 s o i l psychrometers. Transpiration was measured gravim e t r i c a l -l y and used as a measure of uptake since, at steady state, they are equal. Resistance was then calculated based on the Ohm's Law r e l a t i o n -ship shown in equation 2 (Chapter 1). Because sampling for needle water po t e n t i a l i s destructive and upsets seedling water balance, i n d i r e c t methods were used to obtain independent estimates of uptake and needle water p o t e n t i a l as a function of s o i l water p o t e n t i a l for the study of ponderosa pine. Continuous values of uptake and resistance were then generated from the observed regression r e l a t i o n s h i p s . In the study of planted Douglas-fir, i t was found that removal of a small number of needles (up to 10), comprising about 1% of the t o t a l needle area, had no detectable e f f e c t on seedling water balance. Therefore, in t h i s experiment, measurements of uptake and water p o t e n t i a l were taken from the same seedlings. Seedlings in both experiments were grown in a loamy sand textured s o i l i n a heated greenhouse for a period of about 15 months prior to the experimental runs in the growth chamber. On completion of the experi-ments, seedling and water pathway dimensions were determined. - 71 -Resistance to water uptake in ponderosa pine, on a unit root area basis, was estimated using two d i f f e r e n t nonlinear regression models. The f i r s t model was i d e n t i c a l to that used by Dosskey (1978) i n his study of Douglas-fir, western hemlock and mountain hemlock. It f i t t e d data points for i n d i v i d u a l seedlings well and gave reasonable predictions of resistance at s o i l water po t e n t i a l s of about -1.5 MPa or higher. However, uptake was c o n s i s t e n t l y overpredicted at lower s o i l water po t e n t i a l s , r e s u l t i n g i n a r t i f i c i a l l y low, decreasing estimates of resistance. The second model, a modified Weibull function, gave better o v e r a l l r e s u l t s although r e s u l t i n g resistance estimates are a r t i f i c i a l l y s l i g h t l y low at s o i l water po t e n t i a l s between about -1.1 to -0.2 MPa. The main advantage of t h i s model i s that i t can be constrained within r e a l i s t i c l i m i t s at the extremes of the s o i l water po t e n t i a l range where uptake occurs. This i s useful because l i m i t a t i o n s of the experimental techniques l i m i t the accuracy and number of observations that can be made at these extremes. Results of the study of ponderosa pine were compared to those reported for Douglas-fir by Dosskey (1978). Needle water po t e n t i a l i n ponderosa pine appears to remain v i r t u a l l y constant as the s o i l d r i e s . Generally, uptake rates are r e l a t i v e l y high at high s o i l water potentials but decrease more rap i d l y as the s o i l d r i e s . At s o i l water potentials above about -1.5 MPa, resistance to water uptake in ponderosa pine seems to be less than i n Douglas-fir. However, resistance i n ponderosa pine (based - 72 -on the second uptake model) increases rapidly at s o i l water po t e n t i a l s below -1.5 MPa. These observations are in agreement with other comparisons of these species concerning t r a n s p i r a t i o n as a function of decreasing s o i l water po t e n t i a l (Lopushinsky and Klock, 1974). The r e l a t i v e l y rapid decline i n uptake for ponderosa pine may r e f l e c t the greater s e n s i t i v i t y of stomata to decreasing a v a i l a b i l i t y of water (Lopushinsky, 1969; Lopushinsky and Klock, 1974). The source of ra p i d l y increasing resistance to water uptake predicted from the second uptake model at s o i l water potentials below -1.5 MPa i s d i f f i c u l t to i s o l a t e . Increasing plant resistance or contact resistance at the s o i l - r o o t i n t e r f a c e appear to be the most l i k e l y sources. Differences observed in resistance to water uptake between Douglas-fir and ponderosa pine do not seem to be explainable by differences in s o i l r esistance. The differences observed between the species may r e f l e c t broad d i f f e r -ences i n e c o l o g i c a l s t r a t e g i e s . Coastal Douglas-fir grows mainly as a pioneer tree species in southwestern B r i t i s h Columbia. Maintaining t r a n s p i r a t i o n as the s o i l d ries may be necessary in order to avoid excessive needle temperatures (as suggested by Duhme (1974) for other early successional species); furthermore, conserving s o i l water may not be advantageous since any water conserved would l i k e l y be depleted by competing shrubs or other vegetation. Ponderosa pine occurs mainly i n - 73 -dry i n t e r i o r regions or in dry s i t e s in more moist climates. Under these conditions, moist s o i l conditions, probably occurring mainly i n the spring, are exploited by maintaining open stomata and therefore high rates of t r a n s p i r a t i o n and photosynthesis. S o i l moisture i s r a p i d l y depleted as the growing season progresses and water i s then conserved. Several morphological and p h y s i o l o g i c a l adaptations noted for ponderosa pine and other pines f a c i l i t a t e t h i s drought avoidance strategy i n c l u d i n g : s e n s i t i v i t y of stomata to decreasing a v a i l a b i l i t y of s o i l water (Lopushinsky, 1969, 1973; Lopushinsky and Klock, 1974), rapid establishment of a deep taproot (Curtis and Lynch, 1957), and needles with a thick c u t i c u l a r layer (Mirov, 1967). In the study of resistance to water uptake in planted Douglas-fir seedlings, three experimental treatments were compared: c o n t r o l , planted, and planted and vibrated. Planted seedlings show a marked increase i n resistance to water uptake while planted and vibrated seedlings were s t a t i s t i c a l l y i d e n t i c a l to the control seedlings. I t therefore appears that the increased resistance in planted seedlings i s a r e s u l t of increased s o i l and s o i l - r o o t contact resistance. On the basis of the s i m i l a r i t y among treatments i n s o i l physical properties (such as texture, bulk density and water retention c h a r a c t e r i s t i c ) , rough approximations of unsaturated hydraulic conductivity, estimates of s o i l resistance and other evidence in the l i t e r a t u r e (see Dosskey and B a l l a r d , 1980; Faiz, 1973; Faiz and Weatherley, 1978; Herkelrath et al., 1977a; Newman, 1969b; 3arvis, 1975; Nnyamah et al., 1978; Reicosky and R i t c h i e , 1976), i t i s concluded that s o i l - r o o t contact resistance i s an - 74 -important source of the increased t o t a l resistance. Comparing the data on needle water p o t e n t i a l , uptake rates and r e s i s t -ance to uptake from c o n t r o l and the planted and vibrated seedlings from t h i s experiment to the curves generated by Dosskey (1978) using i n d i r e c t techniques for estimation, there i s a remarkable degree of s i m i l a r i t y . The differences that are apparent could be l a r g e l y explained by d i f f e r -ences in the seedling populations, differences in seedling dimensions and sampling error. S t a t i s t i c a l analysis of the experimental data shows a s i g n i f i c a n t v a r i -ance component among i n d i v i d u a l seedlings; the variance maintains i t s s t a t i s t i c a l s i g n i f i c a n c e whether the data i s analyzed on a seedling, unit needle area or unit root area basis and therefore i s not a t t r i b u t a b l e to d i f f e r e n c e s in seedling dimensions. Calculated water pathway dimensions also do not appear d i f f e r e n t enough to account for the observed v a r i a b i l i t y . This seems to confirm the observations of Dosskey (1978) and Dosskey and B a l l a r d (1980) that p h y s i o l o g i c a l v a r i a b i l i t y among Douglas-fir seedlings was the major source v a r i a b i l i t y i n predicted uptake rates. The increased resistance to water uptake in planted seedlings has some important s i l v i c u l t u r a l implications. Careful handling of seedlings in the f i e l d , although i t s importance i s recognized, may not be s u f f i c i e n t to ensure s a t i s f a c t o r y s u r v i v a l or early growth of planted bareroot seedlings. The seedlings in t h i s experiment were planted with a great - 75 -deal more care than would be feasible in operational f i e l d planting but they s t i l l show a significant increase in resistance. Nursery practices which promote early and vigorous root growth and other cultural measures such as inoculation with mycorrhizal fungi may be important, particu-l a r l y when seedlings are planted in dry sites or they encounter warm dry weather during or immediately following planting. - 76 -L I T E R A T U R E C I T E D Andrews, R.E. and E.I. Newman. 1969. Resistance to water flow in s o i l and plant: I I I . Evidence from experiments with wheat. 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A s t a t i s t i c a l d i s t r i b u t i o n function of wide a p p l i c a b i l i t y . 3. Appl. Mech. 18:293-296. Wescor. 1979. Instruction Manual. C-51 sample chamber psychrometer. Wescor, Inc. Logan, Utah. 15 p. Yang, R.C., A. Kozak and 3.H.G. Smith. 1978. The pot e n t i a l of Weibull-type functions as f l e x i b l e growth curves. Can. 3. For. Res. 8(4):424-431. - 86 -APPENDIX I Spectral Irradiance in the Experimental Environment - 87 -1020 -, ~ - 823 A .30 .41 .52 .63 .74 W a v e l e n g t h (ftm) Figure IA SPECIAL IRRADIANCE IN THE GROWTH CHAMBER (Source: F.M. Kelliher, University of B.C., Dept. Soil Science) (Measured at 54cm below lights, sampled at 1nm intervals) - 88 -.30 .41 .52 .63 .74 .85 Wavelength (^ im) Figure IB SPECTRAL IRRADIANCE ON A CLEAR DAY (NOVEMBER 11, 1981) AT LOGAN , UTAH (Sampled at 1 nm Intervals) (Source: LI-COR .INC.) - 89 -APPENDIX II S t a t i s t i c a l Summary for Regression of Needle Water Poten t i a l as a Function of S o i l Water Po t e n t i a l for Ponderosa Pine - 90 -ANOVA Source d.f. SS MS F Regression 1 0.028617 0.028617 0.29194 n.s. Residual 45 4.4111 0.098025 Total 46 4.3973 Regression i s not s i g n i f i c a n t at 11 = 0.05 Standard error of the regression c o e f f i c i e n t = 0.038534 95% confidence i n t e r v a l for the regression co e f f i c i e n t = -0.05675 to 0.09839 Standard error of the sample mean = 0.04567 95% confidence interval for the sample mean = -2.31 to -2.13 MPa - 91 -APPENDIX III Calculations f o r Uptake and Resistance for Ponderosa Pine > ui & u M - 00 *1 01 Ul * u o o o o o o o o o o o o o o o -^ 8 8 73 0 73 TJ O O C 73 O O m C >-H >-H O H CO > Z Z r - m s e c Z O TJ 1/1 "D H H -H Z Z — > G3 H 7; (/> C/l -1 m O > O > Z > - Z o r u i o o -n C n o r *fc m 73 > l/> -1 Ul »-H > m i/i < O J I H m rn > J J C -n Z > TJ m O O M 73 m m » % > Z — o ui m m TJ TJ TJ TJ l/l H 1/1 1/1 l/l - M c c c w C_ II II II II I C. • ll 13 U * TJ > l / l • C/l « t-i -«• I ^ •—- C_ fO • C_ * ^ 01 —• CO • z + x *~o *-*-~C IO o o r - r o o o o o o to TJ TJ o o o o c -> O O it II - - O H - - m Z ro — z a M j i m m - - 73 X _» —. > m —i i / i rn ) m > ) > -n < * CO z 1 H O : — i / i o H Ul m i w > -n o co > o ca > ^ ^ —^ co ca cn _L J - — > J> > Ul Ul Ul 73 73 73 w w w ir n II II II n c/l t/l t/l O CO > c c c CO CO C0 2 2 3 J> J> > O CO > 73 73 73 W \ £. ^ n i / i to i / i o o c c c o Z 3 2 3 —I O CO J> CJ t-H II II II O Z l / l l / l i / i o c c c c m s 3 3 r -n co > II + + + — o ca > -r~ r r~ u Z j> i/i -* l/l X •n 73 C > l/l l/l i/i O CO J> - 73 >-< 73 O m 2 ca c c c CO CO CD Ci m z m > 73 > > i> 2 2 3 > J> > • > H 2 r~ 2 O - 73 O ca > 73 73 73 — I— m m o > Ul o 2 c Ul l/l O O O O O O — l/l rn CO r - - C CO - TJ 73 m > U — 2 CO J> l/l 73 H •n w CO > CO ' i—i - 73 > ^v- H Z O 73 N) C O cn J> l/l • -Ul ~ C > 03 w X O X 2 Z CO - - m < w o a > z r n 73 TJ - r— 73 CO > Ci - d 2 > > —* Ci CO O *-> - 73 cn X O > CO -s z m m w C 33 > I O i/i • 2 73 *w o c » Z o J3 l/l • H •n X > m C O m w H 2 -0 O o - m > > l/l m o X < 73 m II O m l/l ^ irt -n — O 73 C I O -n - m > 2 A 2 — n Q CO w o •fc. -n m V l/i c o o . C TJ z z <-< a s -< H m m Ci X T I l/l Z -n o —1 T I 73 l/l »-< Ul Ci -rt -n *-* ( O O O m 73 73 Z 2 •H J> O l/l 73 H J> m —1 r - l/l m O O c I - Ul O > C -1 ro —1 T) Z r z o -i 3 -n TJ O TJ 73 r 73 m O l / l tn m 73 m > a TJ Z 73 O >- l/l 7] m m 73 i / i > > O Z O r> m § 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ooooooooooooooooooooooooooo oooooooooooooooooooooooooooo ) O O O O Q O O O O O O O O O O O O O O O O O O O O O O O O O ) O O O O O O O O O O O O O O O O O O O O O O O O O O O O Q O ) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - 26 -32 33 •EXTENS •EXTENS 34 35 36 C C c C OUTPUT : WRITING RES AND UPTK FOR 14 SEEDLINGS AND FOR AVERAGE C AVERAGE IS » 15 C WRITES RES AND UPTK FOR 3 SEEDLINGS (OR AVERAGE FOR #15) PER PAGE C DO 400 M = 1 , 1 5 , 3 WR ITE (6 ,40S )M ,M+1.M+2 ION* OTHER COMPILERS MAY NOT ALLOW EXPRESSIONS IN OUTPUT L I S T S ION* OTHER COMPILERS MAY NOT ALLOW EXPRESSIONS IN OUTPUT L I S T S 405 FDRMAT(2X, ' S E E D L I N G * " , 1 2 , BX . ' S E E D L I N G # ' . I 2 , 8 X , ' S E E D L I N G * ' . I 2 ) C THANK YOU FOR THE EXTENSIONS ON FORMAT WRITE STATEMENT #405 C C 37 38 39 41 42 43 W R I T E ( 6 , 4 1 5 ) 415 F O R M A T ( 3 X , ' R E S ' , 7 X , ' U P T K ' 6 X , ' R E S ' , 7 X , ' U P T K ' , 6 X , ' R E S ' . 7 X . ' U P T K ' ) DO 500 N = 1 , 2 4 , 1 W R I T E ( 6 , 5 0 5 ) R E S ( M . N ) ,UPTK(M,N) ,RES(M+1 ,N) ,UPTK(M+1 , N) , RES (M+2, N) , U XPTK(M+2,N) 505 F0RMAT (3 ( F 10.4,-F IO. 4) ) 5O0 CONTINUE 4 0 0 CONTINUE STOP END 6 4 . 0 0 0 6 5 . 0 0 0 6 6 . 0 0 0 6 7 . 0 0 0 6 8 . 0 0 0 6 9 . 0 0 0 7 0 . 0 0 0 71 .000 7 2 . 0 0 0 7 3 . 0 0 0 7 4 . 0 0 0 7 5 . 0 0 0 7 6 . 0 0 0 7 7 . 0 0 0 7 8 . 0 0 0 7 9 . 0 0 0 8 0 . 0 0 0 81 . 000 8 2 . 0 0 0 83 . 000 8 4 . 0 0 0 8 5 . 0 0 0 8 6 . 0 0 0 8 7 . 0 0 0 88 . 000 89 . 000 9 0 . 0 0 0 91 . 000 9 2 . 0 0 0 /E O . 3 9 8 7 8 4 SEEDL ING RES 0 . 2 6 7 3 . 3 2 4 7 . 3 8 6 8 . 4 5 1 9 . 5 1 7 4 . 5 8 0 5 . 6 3 7 9 . 6 8 6 3 . 7224 . 7 4 3 3 0 . 7 4 7 1 0 . 7 3 2 6 0 . 6 9 9 7 0 . 6 4 9 5 O . 5844 0 . 5 0 7 4 0 . 4 2 2 6 O . 3341 O . 2462 O . 1629 0 . 0 8 7 4 0 . 0 2 2 3 - O . O 3 0 8 - 0 . 0 7 1 5 XECUTE 2E 01 1 UPTK 7 . 8 3 5 5 O . 1 4 9 3 3 0 1 E SEEDL ING # RES O . 1 5 7 3 1492 . 9086 . 9856 . 2 9 1 6 . 765 1 .3627 . 0535 1.8154 .1 .6324 1 .4930 1 . 3 8 9 0 1 .3144 1 .2652 1 .2387 1 .2335 1 .2495 1 .2873 1.3491 1.4381 1 .5593 1 .7197 1.9291 2 . 2 0 1 2 . 1654 . 1730 . 1798 . 1856 . 1904 . 1939 . 1960 . 1964 . 1951 . 1918 . 1865 . 1791 . 1694 . 1574 . 1431 . 1265 . 1076 0 . 0 8 6 4 0 . 0 6 3 2 0 . 0 3 8 O 0 .01 10 - 0 . 0 1 7 5 - 0 . 0 4 7 4 2 UPTK 13 .3196 12 .0712 10 .9777 10 .0178 9 .1734 8 .4293 7 .7723 1913 .6768 2205 8154 4556 1357 8512 5984 3738 1746 9983 3 .8426 3 .7058 3 . 5862 3 .4825 3 . 3935 3 .318 1 !111933E 01 SEEDLING # RES O .1524 . 1710 . 1902 . 2095 .2285 . 2467 .2636 .2786 . 2910 .3002 . 3056 .3067 . 3028 . 2935 .2786 . 2579 .2313 . 1989 .1611 . 1 184 .07 13 .0206 - 0 . 0 3 2 6 - 0 . 0 8 7 5 3 UPTK 13 .7456 11 .6756 9 .9851 8 . 5 9 7 6 7 .4534 6 . 5 0 5 6 5 .7171 5 .0584 4 . 5 0 6 2 4 . 0 4 1 6 3 .6497 3 . 3 1 8 3 3 . 0 3 7 5 2 . 7 9 9 5 2 . 5 9 7 8 2 . 4 2 7 0 2 . 2 8 2 9 2 .1621 2 . 0 6 1 6 1.9792 1.9131 1.8617 1.8242 1.7996 SEEDLING 4 SEEDLING RES UPTK RES 0 . 0 3 1 7 66 . 1764 0 . 2953 O . 0 3 9 3 50 .8324 0 . 3559 0 . 0 4 8 2 39 .4092 0 .4206 O .OS84 30 .837 1 0 .4873 O . 0 6 9 9 24 . 3540 0 .5534 0 . 0 8 2 7 19 .4128 0 .6156 0 . 0 9 6 5 15 . 6179 0 .6706 0 .1111 12 .6817 0 . 7 1 5 0 0 . 1262 10 . 3933 0 . 7458 0 .1411 8 .5971 0 .7604 0 . 1554 7 . 1774 0 . 7570 0 . 1683 6 .0478 0 .7352 O . 1788 5 . 1434 0 . 6953 O . 1861 4 . 4 1 5 0 0 . 6 3 9 0 O . 1892 3 . 8249 0 .5691 0 . 1871 3 .3445 0 . 4890 0 . 1789 2 .9517 0 . 4030 O . 1636 2 .6292 0 .3152 0 . 1405 2 . 3637 0 . 2297 O . 1092 2 . 1448 0 , 1503 0 . 0694 1 .9643 0 .0798 O .0212 1 .8157 0. .0201 -0 .0351 1 . 6939 - 0 . .0275 - o .0987 1 . 5950 -o. 0 6 3 0 SEEDLING H 7 SEEDLING RES UPTK RES O. .0993 21 .0886 0 . 1339 O . 1091 18 . 2993 0 . 1880 0 . 1 190 15 . 9583 0 . 2562 0. . 1288 13 .9861 0 . 3391 0 . 1382 12 .3189 0 . 4355 0 . 1472 10. .9045 0 . 5427 O. . 1554 9 .7007 0 . 6558 0 . 1625 8 . 6729 0 . 7682 O. 1683 7 . 7926 0 . 8717 O. 1724 7 . 0366 0 . 9575 O. 1747 6 . 3857 1 . 0171 0. 1747 • 5. 8239 1 . 0436 O. 1723 5 . 3381 1 . 0327 0. 1671 4 . 9172 0 . 9835 0. 1590 4 . 5520 0 . 8988 0. 1478 4 . 2351 0 . 7849 O . 1333 3 . 9598 0 . 6509 o . 1 156 3 . 7209 0 . 5074 0. 0945 3 . 5139 0 . 3650 o . 0702 3 . 3350 0 . 2334 0 . 0429 3 . 1809 0 . 1 199 0. 0 1 2 6 3 . 0491 0 . 0 2 9 0 - o . 0 2 0 3 2 . 9374 - 0 . 0376 - 0 . 0554 2. 8439 - 0 . 08 10 SEEDLING #10 SEEDLING RES UPTK RES 0 . O680 3 0 . 8154 0 . 2219 0 . 0767 26 . 0399 0 . 2052 0 . 0858 22 . 1349 0 . 1923 0. 0952 18 . 9269 0.' 1827 0 . 1046 16 . 2798 0 . 1759 0. 1 140 14 . 0859 0 . 1715 5 SEEDLING # 6 UPTK RES UPTK 7 . 0 9 3 2 0 . 1799 11 .6430 5 . 6 1 0 2 0 . 1677 1 1 .9095 4 . 5 1 4 3 0 . 1578 12 .0360 3 . 6 9 5 5 0 . 1499 12 .0181 3 . 0 7 7 6 0 . 1436 1 1 .8563 2 . 6 0 7 5 0 . 1389 1 1 .5565 2 . 2476 0 . 1354 1 1 . 1292 1 . 9 7 0 9 0 .1331 10 .5892 1 . 7583 0 . 1317 9 .9547 1 . 5 9 5 8 0 .1312 9 . 2460 1 . 4 7 3 5 0 . 1315 8 .4848 1 .3841 0 . 1323 7 .6929 1 . 3 2 2 8 0 . 1335 6 .8913 1 . 2 8 6 0 0 . . 1347 6 .0993 1 . 2 7 2 0 0 . 1357 5 .3336 1 . 2 8 0 0 0 . . 1358 4 .6080 1 . 3 103 0 . . 1342 3 .9335 1 . 3 6 4 6 0 . . 1296 3 .3174 1 . 4 4 5 9 0 . 1202 2 .7643 1 . 5 5 8 5 0 . 1029 2 . 2758 1 .7091 0 . 0736 1 .8512 1 . 9 0 6 7 0 . 0258 1 ,4877 2 . 1641 - 0 . 0504 1 .1813 2 . 4 9 8 9 -o. 1699 0 .9267 8 SEEDLING # 9 UPTK RES UPTK 15 . 6 4 2 3 0 . 1343 15 .5963 10 . 6 2 2 8 0 . 1476 13 .5283 7 .41 10 O. 1610 1 1 .7932 5 . 3 1 1 5 0 . 1743 10. 3321 3 . 9 1 0 6 0 . 1872 9. 0974 2 . 9 5 7 9 0 . 1994 8. 0502 2 . 2983 0 . 2105 7 . 1593 1 . . 8 3 4 6 0 . 2202 6 . 3988 1 . 5044 0 . 2282 5. 7477 1 . 2673 0 . 2339 5 . 1887 1 . 0 9 6 8 0 . 2370 4 . 7075 0. .9751 0 . 2371 4 . 2922 0 8 9 0 5 0 . 2338 3. 9332 0 . . 8 3 5 6 0 . 2269 3. 6223 0. . 8054 0 . 2159 3 . 3526 0 . 7975 0 . 2007 3. 1 186 0 . 8112 0 . 181 1 2 . 9154 0 . 8477 0 . 1570 2 . 7390 0 . 9 1 0 0 0 . 1284 2 . 5862 1 . 0 0 3 6 0 . 0954 2 . 4542 1 . 1370 0 . 0582 2 . 3405 1 . 3233 0 . 0171 2 . 2433 1 . 5822 -o. 0275 2. 1609 1 . 9434 -o. 0 7 5 3 2. 0919 1 SEEDLING #12 UPTK RES UPTK 9. 4377 0 . 1824 1 1 . 4835 Q 73 18 0 . 1655 12. 0628 9 . 8738 0 . 1513 . 12. 5509 9 . 8568 0 . 1392 12. 9346 9 . 6 8 1 6 0 . 1290 13. 2035 9 . 3566 0 . 1202 13. 3499 O.1229 12 . 2598 0 . 1694 8 .8972 0 . 1 127 13 . 3697 O.1313 10 . 7338 0 . 1693 8 . 3243 0 . 1063 13 .2623 0.1387 9 . 4533 0 .17 11 7 .6631 0 . 1006 13 .0308 0.1449 8 . 3750 0 . 1748 6 .9410 0 .0957 12 .6817 0.1495 7 . 4636 0 . 1803 6 . 1859 0 .0913 12 .2247 0.1521 6 . 6908 0 . 1876 5 . 4243 0 .0872 1 1 .6722 0.1524 6 .0336 0 . 1965 4 .6800 0 .0833 1 1 .0388 0.1501 5 .4731 0 .2068 3 .9729 0 .0795 10 . 3406 0 . 1449 4 . 9942 0 .2181 3 .3184 0 .0754 9 .5945 0.1365 4 . 5842 0 . 2295 2 .7272 0 .0710 8 .8 177 0.1247 4 . 2327 0 . 2394 2 . 2053 0 .0658 8 .0268 0.1094 3 . 93 14 0 . 245 1 1 . 7546 0 .0594 7 . 2374 0.0904 3 .6731 0 . 24 18 1 .3735 0 .0514 6 .4636 0.0679 3 .4522 0 .2214 1 .0580 0 .0410 5 .7178 0.0418 3 . 2638 0 . 1700 0 .8018 0 .0272 5 .0099 0.0124 3 . 1039 0 .0643 0 .5979 O .0088 4 . 3480 -0.0200 2 .9694 -0 . 1357 0 .4387 -0 .0159 3 . 7376 -0.0551 2 .8575 -0 . 497 1 0 .3167 -0 .0495 3 . 1825 SEEDLING , S<13 SEEDLING #14 SEEDLING #15 RES UPTK RES UPTK RES UPTK O.0680 30 .8227 0 . 1518 13 . 7956 0 . 1036 20 .2146 0.0784 25 . 472 1 0 . 1648 12 . 1 163 0. . 1 156 17 .2715 0.0896 21 . 1916 0 . 1776 10 .6901 0. 1276 14 .8758 0.1015 17 . 7488 0. 1901 9 . 4747 0. . 1394 12. .9156 O.1138 14 . 9651 0. 2019 8 . 4359 0. 1507 1 1 . 3039 0.1264 12 . 7026 0. 2127 7 . 5453 0. 1609 9. 9731 0.1389 10. 8546 0. 2223 6 . 7795 0. 1699 8. 8697 0.1509 9 . 3377 0. 2303 6. 1 192 0. 1772 7. 9520 0.1622 8 . 0868 0. 2363 5 . 5484 0. 1825 7 . 1866 0.172 1 7 . 0504 0. 2401 5 . 0539 0. 1853 6 . 5472 0.1803 6 . 188 1 0. 2412 4 . 6244 0. 1855 6. 0127 O.1861 5 . 4677 0. 2394 4 . 2507 0. 1823 5. 5662 0.1891 4 . 8636 0. 2343 3 . 9251 0. 1770 5 . 1945 0.1887 4 . 3553 0. 2257 3 . 6410 0. 1682 4. 8866 0.1844 3 . 9263 0. 2133 3 . 3928 0. 1562 4 . 6339 0.1757 3 . 5633 0. 1971 3 . 1760 0. 14 13 4 . 4297 0.1622 3 . 2556 0. 1768 2 . 9866 0. 1237 4 . 2686 0.1436 2 . 9944 0. 1524 2 . 8214 .0. 1037 4 . 1465 0.1198 • 2. 7727 0. 1241 2 . 6774 0. 0818 4 . 0603 0.0906 2 . 5846 0. 0918 2 . 5524 0. 0584 4 . 0079 0.0562 2. 4254 0. 0558 2 . 4443 0. 0342 3. 9881 0.0168 2 . 29 13 0. 0163 2 . 3515 0. 0096 4. 0003 -0.0273 2. 1792 -0. 0262 2 . 2725 -o. 0147 4 . 0448 -0.0754 2 . 0865 -0. 0714 2 . 2062 -o. 0382 4 . 1228 CORE USAGE OBJECT CODE= 2096 BYTES,ARRAY AREA= 3348 BYTES,TOTAL AREA AVAILABLE' 102400 BYTES DIAGNOSTICS NUMBER OF ERRORS' 0, NUMBER OF WARNINGS' 0, NUMBER OF EXTENSIONS' 2 COMPILE TIME= 0.071 SEC,EXECUTION TIME' 0.113 SEC, WATFIV - JUL 1973 V1L4 19:08:08 THURSDAY /STOP Execution terminated 19:08:08 T=0.197 RC=1 $0.18 $SIGN0FF /COMPILE C FOR SEEDLINGS 1 TO 1 5 : #15 REFERS 10 AVERAGE COEFF IC I ENTS 5. .000 C PROGRAM PRINTS CALCULATED UPTAKE AND RESISTANCE FOR EACH SEEDL ING 6 000 C 7 000 C UPTAKE PREDICTED FROM A MODIFIED WEIBULL PROBABIL ITY FUNCTION 8 OOO C 9 OOO C 10 .000 c REMEMBER TO DECLARE INTEGERS M S N FOR FORMATTED OUTPUT 1 1 . .000 1 INTEGER I , J . K , L . M . N 12. .000 2 REAL SPS I (24 ) ,NPS I (24 ) ,DPS I ( 2 4 ) ,UPTK( 15 . 2 4 ) , R E S ( 1 5 , 2 4 ) , A ( 1 5 ) . B ( 1 5 ) 13. OOO X , C ( 1 5 ) , A B A R , B B A R , C B A R . S U M A , S U M B . S U M C 14 . 000 3 REAL D 15. .000 4 ABAR=0 16. .000 5 BBAR=0 17 .000 6 CBAR=0 18 .000 7 SUMA'O 19 ooo 8 SUM8=0 20 .000 9 SUMC=0 21 ooo 1 0 D=-2.2 22 ooo c 23 ooo c ABAR, BBAR, AND CBAR ARE AVERAGE COEFF IC IENTS 24 . ooo c SUMA, SUMB, SUMC ACCUMULATE COEFF IC IENTS FOR CALCULATING AVERAGES 2 5 . .000 1 1 R E A D ( 5 , 1 ) ( A ( K ) , B ( K ) . C ( K ) , K - = 1 . 1 4 ) 26 .000 1 2 1 F 0 R M A T ( 3 F 1 O . 5 ) " 27 .000 c 28 000 c CALCULATING AVERAGES OF COEFF IC IENTS 29 . .000 c 30 .000 1 3 DO 300 L= 1 . 14 31 ooo 14 SUMA=SUMA+A(L) 32 . .000 1 5 SUMB=SUMB+B(L) 3 3 . ooo 1 6 SUMC=SUMC+C(L) 34 000 1 7 300 CONTINUE 3 5 . 000 c 36 .000 c 37 .000 1 8 ABAR=SUMA/14 38 ooo 1 9 BBAR=SUMB/14 39 . 000 2 0 CBAR=SUMC/14 40 .000 2 1 A(15)=ABAR 4 1 ooo 2 2 B(15)=BBAR 42 .000 2 3 C(15)=CBAR 43 .000 c 44 .ooo c 45 .000 c PRINTING AVERAGE C O E F F I C I E N T S A . B . SC 46 .000 c AVERAGE C O E F F I C I E N T S A . B , SC 47 .000 24 PR INT, A ( 1 5 ) , B ( 1 5 ) , C ( 1 5 ) 48 . 000 c AVERAGE C O E F F E C I E N T S A . B . & C 49 .ooo c 50 ooo c 51 .000 c LOOP 200 INDEXES SEEDLINGS 1 TO 14 52 ooo c LOOP 100 GENERATES SOIL WATER POTENTIAL VALUES 53 . 000 2 5 DO 200 1 = 1 . 1 5 . 1 54 . 000 2 6 DO 10O J = 1 . 2 2 , 1 55 . 000 2 7 S P S K J ) = J * ( - 0 . 1 ) 56 ooo 28 NPSI ( J ) = - 2 . 1 9 2 6 1 + ( 0 . 0 2 0 8 2 0 1 * S P S I ( J ) ) 57 .000 29 DPSI ( J ) = S P S I ( J ) - N P S I ( J ) 58 . 000 3 0 U P T K ( I , J ) = A ( I ) » < 1 - ( E X P ( - B ( I ) * ( < S P S I ( J ) - D ) » * C ( I ) ) ) ) ) 59 . 000 31 IF ( U P T K ( I , J ) . G T . 0 . 0 0 0 1 ) GO TO 22 6 0 . 000 32 U P T K ( I , J ) = 0 61 . 000 33 R E S ( I . J ) = 0 62 .ooo 34 GO TO 33 63 .ooo 35 22 CONTINUE 36 RES(I,d)=DPSI(J)/UPTK(I, d) 37 33 CONTINUE 38 ' 100 CONTINUE 39 200 CONTINUE c c c c c c c c c c c c c c c 40 41 EXTENSION' EXTENSION' 42 C C C PROGRAM PRINTS CALCULATED UPTAKE AND RESISTANCE FOR EACH SEEDLING FOR 14 SEEDLINGS AND FOR AVERAGE: AVERAGE IS # 15 OUTPUT UPTAKE AND RESISTANCE FOR SEEDLINGS 1 TO 15: #15 REFERS TO AVERAGE COEFFICIENTS OUTPUT: WRITING RES AND UPTK FOR 14 SEEDLINGS AND FOR AVERAGE AVERAGE IS # 15 ^ WRITES RES AND UPTK FOR 3 SEEDLINGS (OR AVERAGE FOR #15) PER PAGE DO 400 M=1,15,3 WRITE(6,405)M,M+1. M+2 ' OTHER COMPILERS MAY NOT ALLOW EXPRESSIONS IN OUTPUT LISTS • OTHER COMPILERS MAY NOT ALLOW EXPRESSIONS IN OUTPUT LISTS 405 F0RMAT(2X, 'SEEDLING #' ,I 2.8X, 'SEEDLING #' ,I 2.8X, 'SEEDLING #'.I2) THANK YOU FOR THE EXTENSIONS ON FORMAT WRITE STATEMENT #405 43 44 WRITE(6,415) „, . 4 15 FORMAT(3X,'RES',7X,'UPTK',6X,'RES',7X,'UPTK',6X,'RES',7X. UPTK ) DO 500 N=1,22,1 WRITE(6,505)RES(M,N),UPTK(M,N),RES(M+1,N).uPTK(M+1,N),RES(M+2.N),U XPTK(M+2,N) 505 FORMAT(3(F10.4.F10.4)) 49 50 51 500 CONTINUE 400 CONTINUE STOP END 64 .000 65.000 66 .000 67 .000 68.000 69 . OOO 70.000 71.000 72.000 73.000 74 .000 75.000 76.000 77.000 78 .000 79.000 80.000 81.000 82 .000 83.000 84 . OOO 85.000 86.000 87.000 88.000 89.000 90.000 91.000 92.000 93.000 94.000 95.000 CO 96.000 ~-> 97.000 98 .000 99.000 100.000 '101 .000 102.000 103.000 104 .000 105.000 I I /EXECUTE 0.8520613E 01 SEEDLING # 1 RES UPTK 0. 3613 5 7983 0. 3467 5 7591 0. 3324 5 7127 0. 3183 5 6576 0. 3045 5 5923 0. 2910 5 5151 0 2779 5 4238 0. 2651 5 3162 0 2527 5 1895 O 2407 5 0405 O 2293 4 8658 O.1647898E 01 O. SEEDLING # 2 RES UPTK 0. 197 1 10 6302 0. 1891 10 5584 0. 1813 10 4733 0. 1736 10 3722 0. 1661 10 2525 0. 1587' 10 1 109 0. 1516 9 9437 0. 1446 9 7464 0. 1378 9 5140 0. 1313 9 2409 0. 1250 8 9206 39E 01 SEEDLING # 3 ES UPTK 0. 2466 8 4958 0. 2381 8 3870 0. 2297 8 2654 0. 22 15 8 1295 0. 2135 7 9777 0. 2056 7 8080 0. 1978 7 6184 0. 1903 7 4065 0 1829 7 1698 0. 1757 6 9055 0 1688 6 6102 0 2 183 4 . 6 6 1 2 0 1191 8 . 5456 0 1620 6 .2805 0 2 0 8 0 4 . 4 2 2 4 0 1 1 34 8 . 1077 0 1555 5 .9125 0 1983 4 1443 0 1082 7 . 5 9 8 0 0 1 194 5 .5017 o 1894 3 82 17 0 1033 7 .0064 0 1.135 5 0434 0 1815 3 4488 0 0990 6 . 3227 0 138 1 4 .5321 o 1748 3 0 1 9 8 0 0954 5 . 5363 0 1333 3 9620 0 1700 2 5295 0 0927 4 .6374 0 1293 3 3268 0 1683 1 9 7 3 9 0 0918 3 . 6 1 8 8 0 I2S8 2 6 194 0 1732 1 3524 0 0945 2 . 4 7 9 3 0 1278 1 8326 0 2023 0 6739 0 1 103 1 . 2356 0 142 1 0 9595 o OOOO O OOOO 0 OOOO 0 OOOO 0 OOOO 0 OOOO SEEDL ING # 4 SEEDLING # 5 SEEDLING # 6 RES UPTK RES UPTK RES UPTK 0 54 19 3 8655 0 2992 7 OOOO 0 1790 1 1 7047 0 5201 3 8394 0 2853 7 OOOO 0 17 11 1 1 6707 0 4986 3 8085 0 2713 7 OOOO 0 1634 1 1 6220 0 4 7 7 5 3 7717 0 2573 7 OOOO 0 1559 1 1 5533 O 4568 3 7282 0 2433 7 OOOO 0 I486 1 1 4578 0 4 3 6 6 3 6 7 6 7 0 2293 7 OOOO 0 14 17 1 1 3270 O 4168 3 6 159 0 2 153 7 OOOO 0 1352 1 1 1509 0 3 9 7 6 3 544 1 0 2013 6 9999 0 129 1 10 9178 0 3 7 9 0 3 4597 0 1874 6 9988 0 1235 10 6145 0 36 1 1 3 3603 0 1737 6 987 1 0 1 186 10 2272 O 3439 3 2438 0 1612 6 9179 0 1 145 9 7421 0 3275 3 1075 0 1527 6 6 6 4 0 0 1113 9 1469 0 31 19 2 9483 0 1521 6 0454 0 1091 8 4325 0 2974 2 7629 0 1649 4 9821 0 1082 7 5955 0 284 1 2 5478 0 1998 3 6236 0 1090 6 6405 0 2722 2 2992 0 2748 2 2774 0 112 1 5 5831 O 2623 2 0 1 3 2 0 4363 1 2101 0 1 186 4 4522 0 2 5 5 0 1 6863 0 8215 0 5236 0 1306 3 2931 0 2524 1 3159 1 9530 0 1701 0 1532 2 1687 o 2598 0 9016 6 9042 0 0339 0 2016 1 1619 o 3034 0 4493 64 1445 0 002 1 0 3577 0 381 1 0 OOOO 0 OOOO 0 OOOO 0 OOOO 0 OOOO 0 OOOO SEEDL ING # 7 SEEDLING # 8 SEEDLING # 9 RES UPTK RES UPTK RES UPTK 0 . 2155 9 7218 0 54 19 3 8655 , 0 2457 8 5266 O . 2066 9 667 1 0 5201 3 8394 b 2346 8 5096 0 . 1978 9 599 1 0 4986 3 8085 0 2238 8 4833 O . 1893 9 5 149 0 4775 3 77 17 0 2 133 8 4436 O. 1810 9 4 1 10 0 4568 3 7282 0 203 1 8 3847 0 . 1729 9 2835 0 4366 3 6767 0 1934 8 2995 0 . 1651 9 1278 0 4 168 3 6159 0 1843 8 1790 0 . 1577 8 9384 0 3976 3 544 1 0 1 759 8 0124 O . 1506 8 7094 0 3790 3 4597 0 1684 7 7880 0 . 1439 8 4 3 4 0 0 361 1 3 3603 0 16 19 7 4930 0 . 1376 8 1050 0 3439 3 2438 0 . 1568 7 1 153 0 . 1319 7 7 145 0 3275 3 1075 0 . 153 1 6 6451 O. 1268 7 2546 0 3119 2 9483 0 . 15 14 6 0765 0 . 1223 6 7 177 0 2974 2 7629 0 15 19 5 4 101 0 . 1 187 6 0 9 6 8 0 284 1 2 5478 0 . 1555 4 6553 0 . 1 162 5 3 8 7 0 0 2722 2 2992 0 . 1633 3 8323 o . 115 1 4. 5869 0 2623 2 0132 0 . 1776 2 9728 o . 1 162 3. 7005 0 2550 1 6863 0 . 2028 2 12 10 0 . 1212 2 . 7414 0 . 2524 1 3159 0 . 2495 1 3313 0 . 1346 1 . 7399 0 . 2598 0 9016 0 . 3515 0 6665 0 . 1795 0 . 7597 0 . 3034 0 4493 0 . 698 1 0 1953 0 . OOOO 0 . OOOO 0 . OOOO 0 OOOO 0 . OOOO 0 OOOO SEEDL ING #10 SEEDLING #11 SEEDLING #12 RES UPTK RES UPTK RES UPTK 0 . 2 178 9 .6165 0 . 2619 7 .9985 0 . 1 74S 12 -OOOO 0 . 2076 9 . 6 165 0 . 2497 7 .9962 0. 1664 12 .OOOO 0 . 197S 9 .6165 0 . 2376 7 .9909 0. . 1582 12 .OOOO 0 . 1873 9 .6165 0 . 2257 7 .9796 0. 1501 12 .OOOO 0 .1771 9 .6164 0 . 2 1 4 0 7 .9569 0. 14 19 1 1 . 9 9 9 9 O . 1669 9 .6164 0 . 2028 7 .9137 0. 1338 1 1 .9991 0 . 1S67 9 . 6 1 6 0 0 . 1923 7 .8367 0. 1257 1 1 . 9 9 4 2 0 . 1466 9 .6114 0 . 1828 7 .7075 0. 1 177 1 1 . 9 7 2 0 0 . 1369 9 .5814 0 . 1748 7 .5035 0. 1 103 1 1 . 8 9 4 2 0 . 1284 9 .4533 0 . 1685 7 .2002 0. 1039 1 1 . 6 7 8 7 0 . 1229 9 .0758 0 . 1646 6 .7753 0 . 0996 1 1 . 1988 0 . 1230 8 . 2700 0 . 1637 6 . 2 1 5 0 0 . 0986 10 . 3 2 3 0 O . 1320 6 . 9 6 9 0 0 . 1666 5 .5192 0 . 1023 a . 9 9 1 8 0 . 1545 5 .3182 0 . 1746 4 .7071 0 . 1 129 7 . 2 8 0 3 0 . 2000 3 .5184 0. 1896 3 .8173 0 . 1342 5 . 3 9 5 2 0 . 2894 2 . 1630 0 . .2154 2 .9058 0 . 1739 3 . 5 9 9 5 0 . 4749 1 . 1119 0. .2591 2 .0378 0 . 2497 2 . 1 145 0 . .9112 0 . 4720 0 . 3367 1 . 2775 0 . 408 1 1 . 0 5 3 8 2 . 1864 0 . 1519 0 . 4904 0 .6773 0 . 8019 0 . 4142 7. . 7560 0 .0302 0 . 8734 0 .2682 2 . 1658 0 . 1082 72 . 0973 0 .0019 2. 5583 0 .0533 12 . 7444 0 . 0 1 0 7 0 . OOOO 0 . 0 0 0 0 0 . OOOO 0 .0000 0. OOOO 0 OOOO SEEDL ING #13 SEEDLING #14 SEEDLING #15 RES UPTK RES UPTK RES UPTK 0 . 2327 9 . 0000 0 . 2354 8 .9001 0 . 2460 8 . 5165 0 . 2219 9 . 0000 0 . 2253 8 .8633 0 . 2346 8 .5121 0 . 21 10 9 . 0000 0 . 2154 8 .8143 0 . 2233 8 . 5035 0 . 2001 9. . 0000 0 . 2058 8 . 7497 0 . 2122 8 .4876 0 . 1892 8 .9996 0 . 1965 8. .6652 0 . 20 13 8. . 4593 0 . 1784 8 . 9974 0 . 1876 8 . 5559 0. 1908 8. .4 109 0 . 1677 8 . 9859 0 . 1791 8 . 4157 0 . 1809 8. . 3318 0 . 1576 8 . 9416 0 . 17 11 8. 2379 0 . 17 17 8. 207 3 0 . 1488 8 . 8 100 0 . 1636 8 . 0 1 5 0 0 . 1635 8. . 0198 0 . 1427 8 . 5008 0 . 1568 7. 7386 0 . 1566 7 7492 0 . 14 10 7 . 9133 0 . 1507 7 . 4003 0 . 15 13 7. 3751 0 . 1455 6. 9918 0 . 1455 6. 9918 0. 1479 6. 8808 0 . 1592 5 . 7755 0 . 1414 6 . 5059 0 . M 7 0 6. 2568 0 . 1867 4 . 4024 0 . 1384 5. 937 1 0. 1492 5. 5062 0 . 2366 3 . 0588 0 . 1370 5 . 2835 0. I557 4 . 6 4 7 8 0 . 3279 1 . 9091 0 . 1376 4 . 5482 0 . 1683 3. 7183 0 . 5043 1 . 0469 0 . 14 1 1 3. 7413 0 . 1905 2 . 77 1 1 0 . 887 1 0 . 4848 0 . 1492 2. 8828 0 . 2298 1 . 8 7 1 8 1 . 8962 0 . 1752 0 . 1656 2. 0059 0 . 3047 1 . 0 9 0 0 5. 7141 0 . 0 4 1 0 0 . 2015 1 . 1626 0 . 4782 0 . 4 8 9 9 4 0 . 2503 0 . 0034 0 . 3134 0 . 4351 1. 1400 • 0 . 1196 0 . OOOO 0 . OOOO 0 . OOOO 0 . OOOO 0. OOOO 0 . OOOO CORE USAGE OBJECT CODE= 2288 BYTES.ARRAY AREA ' 3348 B Y T E S , T O T A L AREA A V A I L A B L E ' 102400 BYTES D IAGNOST ICS NUMBER OF ERRORS ' O. NUMBER OF WARNINGS' O. NUMBER OF EXTENS IONS ' 2 COMPILE T I M E ' 0 . 0 6 8 SEC . EXECUT ION T I M E ' 0 . 1 0 6 S E C . WATFIV - JUL 1973 V1L4 1 5 : 3 7 : 3 6 THURSDAY /STOP E x e c u t i o n t e r m i n a t e d 1 5 : 3 7 : 3 7 T = 0 . 1 9 RC '1 $ 0 . 1 9 SS IGNOFF - 100 -APPENDIX IV Observed Uptake Rates i n Ponderosa Pine Compared to Average Uptake Curves - 101 -1 = z 1 1 1 1 r -3.0 -2.0 -1.0 0 Soil Water Potential (MPa) Figure IV A OBSERVED UPTAKE IN PONDEROSA PINE PER UNIT ROOT AREA vs SOIL WATER POTENTIAL (Uptake Curve for Regression Model I is Shown) - 102 -Mac-Figure IV B OBSERVED UPTAKE IN PONDEROSA PINE vs SOIL WATER POTENTIAL . (Uptake Curve for Regression Model II is Shown) - 103 -APPENDIX V Uptake and Needle Water Po t e n t i a l Data for Ponderosa Pine - 104 -UPTAKE DATA Seedling U Seedling U Number fs(MPa) (mg s"1 m-2) Number ¥ s(MPa) (mg s -1 rn"2) 1 -0.38 3.933 6 -0.06 11.96 -0.43 3.865 -0.30 11.13 -0.48 2.906 -0.43 12.03 -0.49 5.782 -0.67 11.78 -0.52 1.653 -0.81 10.52 -0.68 1.482 -1.57 4.766 -0.96 2.471 -1.93 2.244 -2.06 1.455 -2.10 2.167 2 -0.80 6.254 7 -0.64 9.557 -0.90 3.809 -0.71 8.836 -0.91 7.659 -0.76 9.137 -0.96 9.676 -0.81 8.949 -2.81 2.526 -0.94 9.095 -3.23 2.355 -1.12 -1.85 7.392 2.493 3 -0.40 8.623 -2.04 2.371 -0.43 8.210 -3.06 0.07567 -0.48 -0.50 7.591 7.522 8 -0.46 4.460 -1.94 2.026 -0.52 -0.67 4.013 1.726 4 -0.82 10.43 -0.88 1.364 -0.94 10.13 -1.12 1.508 -0.99 9.513 -1.84 1.455 -1.05 9.732 -2.26 1.248 -1.38 4.849 -1.89 1.143 -1.91 1.178 -2.39 0.5685 -2.08 -2.21 0.8754 1.037 9 -0.40 9.393 -3.09 0.5946 -0.51 -0.61 9.940 8.437 5 -0.31 4.015 -0.66 7.889 -0.34 4.172 -0.79 5.694 -0.42 3.992 -1.70 2.701 -0.41 -0.44 4.009 3.818 10 -0.77 8.838 -0.57 1.716 -1.02 7.462 -1.67 1.685 -1.04 9.820 -2.11 1.584 -1.03 11.78 -3.13 0.1641 -1.46 -2.13 -2.99 3.936 1.274 1.175 - 105 -UPTAKE DATA Seedling U Number ^s(MPa) (mg s _1 m~2) 11 -0.01 9.008 -0.94 5.968 -1.16 7.860 -1.04 9.211 -1.28 3.333 -1.28 1.847 -1.53 3.067 -1.69 3.536 -2.00 1.514 12 -0.01 11.78 -0.26 10.22 -0.38 13.98 -0.72 13.58 -2.39 3.137 13 -0.75 8.739 -0.98 7.626 -1.14 7.950 -1.08 7.745 -1.35 3.838 -1.73 1.483 -2.37 1.328 -2.45 0.1826 -3.04 0.09314 14 -0.38 9.638 -0.46 8.799 -0.49 8.053 -0.86 7.491 -1.24 3.143 -1.87 2.375 -2.98 1.083 106 -NEEDLE WATER POTENTIAL DATA *S(MPa) YN(MPa) *S(MPa) l'N(MPa) *S(MPa) ^ ( M P a ) -0.54 -2.57 -0.08 -1.34 -2.32 -.1.70 -0.19 -2.26 -1.91 -2.17 -2.08 -2.13 -0.75 -2.59 -0.77 -2.36 -2.78 -2.21 -1.16 -2.26 -0.01 -2.12 -1.69 -2.64 -1.12 -2.50 -0.61 -2.06 -2.43 -2.21 -0.40 -2.23 -1.36 -2.16 -1.86 -2.55 -0.46 -2.32 -1.24 -2.09 -1.71 -2.00 -0.47 -2.40 -0.57 -2.68 -1.96 -2.14 -0.01 -2.14 -0.61 -2.50 -1.41 -1.97 -0.26 -2.45 -1.14 -2.41 -2.25 -2.01 -0.50 -2.65 -0.95 -2.26 -1.67 -2.31 -0.63 -2.89 -1.03 -1.85 -2.42 -2.00 -0.01 -2.02 -4.22 -1.92 -3.24 -2.51 -0.21 -1.99 -4.67 -2.78 -2.91 -1.94 -0.04 -1.63 -2.09 -2.21 -3.71 -2.22 -0.15 -1.73 -3.47 -2.35 - 107 -APPENDIX VI Data for Douglas-Fir Experiment - 108 -CONTROL TREATMENT Resistance Seedlino ¥ s ¥ N Number (MPa) (MPa) Seedling Root Area Needle Area (TPa s Kg-1) (TPa s m2 Kg" 1) (TPa s m2 Kg" 1) 1 -0.24 -2.29 10.4699 0.1669 0.09104 -0.48 -2.82 12.6350 0.2014 0.02291 -0.74 -2.10 11.0749 0.1766 0.09630 -1.14 -2.14 16.1996 0.2583 0.1409 -2.06 -2.98 15.0548 0.2400 0.1309 -2.55 -3.12 16.8739 0.2690 0.1467 2 -0.78 -2.95 13.2317 0.3178 0.1331 -0.49 -2.86 14.9338 0.3587 0.1503 -0.58 -3.20 18.4507 0.4431 0.1856 -0.57 -2.61 14.3662 0.3450 0.1446 -0.70 -2.70 28.6164 0.6873 0.2879 -1.01 -3.14 26.5553 0.6378 0.2672 3 -0.09 -2.24 9.0256 0.2305 0.1184 -0.80 -2.86 11.1231 0.2840 0.1459 -0.91 -2.96 11.6876 0.2985 0.1533 -1.37 -3.11 25.6259 0.6544 0.3362 -2.07 -3.12 31.4937 0.8042 0.4131 -2.35 -3.17 29.7857 0.7606 0.3907 4 -0.09 -2.68 11.6382 0.3347 0.1505 -0.29 -2.33 12.0496 0.3465 0.1558 -0.88 -2.94 14.0903 0.4502 0.1822 -0.93 -3.11 16.0530 0.4615 0.2075 -2.43 -3.10 19.5237 0.5614 0.2524 -2.26 -3.28 25.8364 0.7430 0.3340 5 -0.07 -2.81 14.3832 0.4153 0.1552 -0.30 -3.04 19.9128 0.5750 0.2149 -0.43 -2.87 16.6553 0.4809 0.1797 -0.83 -2.69 17.1113 0.4941 0.1847 -2.62 -3.11 17.6386 0.5093 0.1904 -2.78 -3.35 17.4365 0.5035 0.1882 - 109 -PLANTED TREATMENT Resistance Seedling V s * N Number (MPa) (MPa) Seedling Root Area Needle Area (TPa s Kg-1) (TPa s m2 Kg-1) (TPa s m2 Kg" 1) 1 -0.186 -2.89 102.2113 2.832 0.8966 -0.48 -2.76 98.4592 2.728 0.8637 -0.48 -3.37 104.0403 2.883 0.9126 -0.48 -3.25 98.7232 2.735 0.8265 -0.51 -2.52 103.3425 2.863 0.8652 -0.82 -2.22 131.7647 3.651 1.103 2 -0.079 -2.42 110.6123 2.343 1.867 -0.54 -2.60 83.4302 1.762 1.408 -0.51 -2.68 39.0600 0.8250 0.6593 -0.38 -2.94 67.8978 1.434 1.146 -0.47 -2.68 118.7463 2.508 2.004 -0.58 -2.34 117.5355 2.482 1.984 3 -0.30 -2.37 77.9804 1.963 0.9326 -0.72 -2.68 67.8905 1.709 0.8120 -0.95 -2.34 57.9167 1.458 0.6927 -0.91 -2.53 56.9658 1.434 0.6813 -1.01 -2.06 62.3697 1.570 0.7459 -0.99 -2.22 56.0722 1.411 0.6706 4 -0.094 -2.67 54.0960 1.911 0.5232 -0.49 -2.61 49.0629 1.734 0.4745 -0.48 -2.22 47.4807 1.678 0.4592 -0.59 -2.46 43.9750 1.554 0.4253 -0.66 -2.59 46.9984 1.661 0.4546 -0.66 -3.00 51.2270 1.810 0.4955 5 -0.58 -2.27 41.0296 1.476 0.5608 -0.23 -2.23 48.4919 1.745 0.6628 -0.25 -2.59 41.9358 1.509 0.5732 -0.30 -2.14 37.2600 1.341 0.5093 -0.37 -2.27 40.3943 1.453 0.5521 -0.37 -2.22 56.0076 2.015 0.7656 - 110 -PLANTED AND VIBRATED TREATMENT Resistance Sf*f*H 1 i nn ¥N V> t» V_y l _ i J L 1 |U Number (MPa) (MPa) Seedling Root Area Needle Area (TPa s Kg" 1) (TPa s m2 Kg"1) (TPa s m2 Kg"1) 1 -0.185 -2.66 4.9239 0.1400 0.06730 -0.43 -2.17 14.0940 0.4007 0.1926 -1.36 -2.72 12.2400 0.3480 0.1673 -2.00 -2.86 12.2857 0.3493 0.1679 -2.85 -3.11 14.9614 0.4254 0.2045 -2.93 -3.22 17.0779 0.4856 0.2334 2 -0.30 -3.12 7.1064 0.1769 0.08505 -0.25 -2.86 11.6547 0.2934 0.1413 -0.31 -2.66 14.1000 0.3554 0.1709 -0.39 -2.70 11.6962 0.2948 0.1418 -0.48 -2.93 13.2935 0.3351 0.1611 -0.99 -2.72 14.8286 0.3738 0.1797 3 -0.079 -2.95 6.9542 0.1516 0.07294 -0.41 -2.97 15.3600 0.3349 0.1611 -0.51 -3.20 16.4136 0.3579 0.1722 -0.64 -2.60 10.9490 0.2387 0.1148 -1.56 -2.55 14.8500 0.3238 0.1558 -2.36 -2.47 15.9141 0.3470 0.1669 4 -0.20 -2.37 6.6150 0.2076 0.06229 -0.62 -2.59 10.6380 0.3339 0.1002 -0.67 -2.44 09.9562 0.3125 0.09375 -0.75 -2.60 13.6227 0.4276 0.1283 -1.36 -2.45 12.7985 0.4018 0.1205 -1.84 -2.70 12.7323 0.3997 0.1199 5 -0.11 -2.76 5.5038 0.2396 0.1069 -0.55 -3.13 10.7169 0.4665 0.2083 -0.49 -2.93 12.5486 0.5462 0.2438 -0.58 -3.06 12.5550 0.5465 0.2439 -0.51 -2.12 18.1125 0.7884 0.3519 -2.35 -2.14 19.8427 0.8637 0.3855 - 111 -MEANS AND STANDARD DEVIATIONS (S.D.) Control Planted Planted and Vibrated T s (MPa) Mean -1.095 -0.516 -0.936 S.D. 0.859 0.249 0.837 R(TPa s Kg"1) (per seedling) Mean 17.318 70.433 12.478 S.D. 6.1290 28.652 3.6360 R(TPa s m2 Kg"1) (per root area) Mean 0.43365 1.9493 0.37554 S.D. 0.18210 0.62642 0.15889 R(TPa s m2 Kg"1) (per needle area) Mean 0.19175 0.85104 0.16406 S.D. 0.088282 0.43669 0.074710 - 112 -APPENDIX VII S t a t i s t i c a l Summaries f o r Resistance i n Douglas-Fir Seedlings - 113 -COVARIANCE ANALYSIS PER SEEDLING ANOVA Source D.F. SS MS F P r o b a b i l i t y Treatment 2 9.554574 4.777287 73.7506 0.0000 Within Treatment 12 7.77315 x 10-1 6.47762 x IO" 2 4.9085 0.0000 Error 74 9.765572 x 10-1 1.319672 x IO" 2 Total 89 11.371552 Covariate Regression C o e f f i c i e n t Standard Error F Value P r o b a b i l i t y PSI -0.10577 0.01887 31.4127 0.0000 - 114 -COVARIANCE ANALYSIS PER UNIT ROOT AREA ANOVA Source D.F. SS MS F P r o b a b i l i t y Treatment 2 9.265220 4.632609 28.6792 0.0000 Within Treatment 12 1.938382 1.615318 x 10-1 12.2485 0.0000 Error 74 9.759058 x 10-1 1.318792 x IO" 2 Total 89 12.225852 Covariate Regression C o e f f i c i e n t Standard Error F Value P r o b a b i l i t y PSI -0.10581 0.01886 31.4835 0.0000 - 115 -COVARIANCE ANALYSIS PER NEEDLE AREA ANOVA Source D.F. SS MS F P r o b a b i l i t y Treatment 2 11.731708 5.865853 50.7649 0.0000 Within Treatment 12 1.386592 1.155493 x 10" 1 8.7554 0.0000 Error 74 9.76618 x 10" 1 1.31975 x IO" 2 Total 89 14.176537 Covariate PSI Regression C o e f f i c i e n t -0.10589 Standard Error 0.01887 F Value 31.4793 Pr o b a b i l i t y 0.0000 - 116 -APPENDIX VIII Stomata! Resistance Measurements and Estimated Maximum Transpiration Rates - 117 -STOMATAL RESISTANCE Species Stomatal Resistance (s/cm) d Ponderosa Pine 2.91 Douglas-Fir 2.28 Douglas-Fir 2.78 Douglas-Fir 2.64 Douglas-Fir 2.87 dMeasured i n the growth chamber with a ven t i l a t e d d i f f u s i o n porometer; s o i l water content was s l i g h t l y below f i e l d capacity for a l l seedlings. An estimate of the maximum t r a n s p i r a t i o n rate for seedlings in the growth chamber can be made using the r e l a t i o n s h i p : p l " p a T = — r l + r a where T i s the tr a n s p i r a t i o n rate i n mg cm - 2, Pj_ i s the water vapour density i n the l e a f (mg cm - 3), P a i s the water vapour density i n the a i r (mg cm - 3), r^ i s lea f resistance (s cm - 1), and r a i s boundary layer resistance (s cm""1). Assuming that leaf and a i r temperatures are equal (at 20°C) and boundary layer resistance i s low (approximately 0.5 s cm_1) in the well v e n t i l a t e d growth chamber, then for ponderosa pine: 6.058 x IO" 3 mg cm - 3 T = = 1.7 x 10" 3 mg s~ 1 cm"2 3.5 s cm - 1 and for Douglas-fir (using the average of the four measurements of stomatal r e s i s t a n c e ) : 6.058 x 10~ 3 mg cm"3 T = = 1.9 x 1 0 - 3 mg s~ 1 cm - 2 3.14 s cm - 1 - 118 -The average maximum observed t r a n s p i r a t i o n rate for ponderosa pine was about 1.6 x 10 _3 m g s-1 c m - 2 . The maximum predicted t r a n s p i r a t i o n rates for uptake Models I and II are 5 x 1 0 - 3 mg s"1 cm - 2 and 2 x 1 0 - 3 mg s -1 cm - 2 r e s p e c t i v e l y . Maximum observed rates for Douglas-fir seedlings (at s o i l water pot e n t i a l s greater than -0.1 MPa) are about 1.8 x 10 - 3, 1.7 x 1 0 - 3 and 1.8 x 1 0 - 3 mg cm - 2 for control treatment seedlings 3, 4 and 5 re s p e c t i v e l y . APPENDIX IX Seedling and Water Pathway Dimensions I - 120 -PONDEROSA PINE INDIVIDUAL SEEDLING DIMENSIONS Seedling Number Root Area (cm2) Needle Area (cm2) Needle Area: Root Area Ratio 0D Root: Shoot Ratio 1 146 36 0.25 2.35 2 164 53 0.33 1.95 3 145 61 0.42 1.60 4 84 40 0.48 2.11 5 125 35 0.28 2.31 6 97 48 0.49 1.14 7 121 42 0.35 2.01 8 132 36 0.27 2.37 9 73 36 0.50 1.17 10 102 50 0.50 2.21 11 89 31 0.35 1.79 12 128 65 0.51 1.16 13 94 46 0.49 2.13 14 120 48 0.40 1.57 - 121 -DOUGLAS-FIR INDIVIDUAL SEEDLING DIMENSIONS Treatment Seedling Number Root Area (cm 2) Needle Area (cm 2) Needle Area: Root Area Ratio 0D Root: Shoot Ratio Control 1 159 87 0.54 0.40 2 240 101 0.42 0.71 3 255 131 0.51 --4 288 129 0.45 --5 289 108 0.37 0.69 Planted 1 277 84 0.30 0.81 2 211 107 0.51 0.39 3 252 120 0.48 --4 353 97 0.27 --5 360 98 0.27 0.66 Planted and 1 284 137 0.48 Vibrated 2 252 121 0.48 0.28 3 218 105 0.48 --314 94 0.30 1.02 5 435 194 0.45 0.40 - 122 -AVERAGE WATERFLOW PATHWAY DIMENSIONS Treatment S o i l Volume (cm3) Total Root Length (cm) (cm) 7b (cm) Ponderosa Pine 360 1210 0.19 0.0132 Douglas-Fir Control 370 2198 0.14 0.0141 Douglas-Fir Planted 370 2608 0.12 0.0144 Douglas-Fir Planted and Vibrated 370 2411 0.14 0.0158 aZ i s the calculated average distance that water must move through the s o i l to a root surface &r i s the calculated weighted average root radius - 123 -APPENDIX X S o i l P h y s i c a l P r o p e r t i e s - 124 -SOIL PHYSICAL PROPERTIES Treatment % Sand* % S i L t a % C l a y d Average Bulk Density (Kg m - 3) K sb(cm d" 1) Control 79 17 4 995 0.96 Planted 79 17 4 1020 1.00 Planted and Vibrated 79 17 4 984 0.95 aBased on 2 mm and smaller f r a c t i o n , hydrometer method DSaturated hydraulic conductivity, constant head permeameter method — I 1 -1.0 -0.1 -0.01 Soil Water Potential (MPa) Figure X A SOIL WATER RETENTION CURVE FOR DOUGLAS FIR (ALL TREATMENTS) (Determined by Pressure Plate Extraction Method) - 126 -APPENDIX XI Estimates of S o i l Resistance - 127 -DOUGLAS-FIR CONTROL SEEDLINGS MMPa) 6(m3 m - 3 ) a Kb (Kg m-1 Pa" 1 s" 1) R c (TPa s Kg" 1) Rs/RT d -0.53 .06 6.25 x 10" 1 1 2.9 x 10-* ---0.81 .03 4.25 x 10" 1 2 4.3 x 10-3 ---1.5 .015 3.27 x 10" 13 5.5 x 10-2 .006 aVoiumetric water content estimated from water retention curve bUnsaturated hydraulic conductivity estimated by the method shown by dackson (1972); converted from cm day - 1 to pressure units by: 1 cm day" 1 = 1.18 x 10~ 8 Kg n r 1 Pa" 1 s _ 1 C a l c u l a t e d s o i l resistance a f t e r Gardner (1960) dRatio of calculated s o i l resistance to minimum observed t o t a l resistance (shown at = -1.5 MPa only) - 128 -DOUGLAS-FIR PLANTED SEEDLINGS Ys(MPa) e(m 3 n r 3 ) d Kb (Kg n r 1 Pa" 1 s" 1) R c (TPa s Kg-1) Rs/RT d -0.53 .06 6.73 x 10-1 1 3.5 x 1 0-4 -0.81 .03 4.48 x 10" 1 2 5.2 x 10" 3 ---1.5 .015 3.47 x 10" 1 3 6.8 x IO" 2 .002 aVolumetric water content estimated from water retention curve bUnsaturated hydraulic conductivity estimated by the method shown by Jackson (1972); converted from cm day"1 to pressure units by: 1 cm day" 1 = 1.18 x 10" 8 Kg n r 1 Pa" 1 s" 1 C a l c u l a t e d s o i l resistance a f t e r Gardner (1960) ^Ratio of calculated s o i l resistance to minimum observed t o t a l resistance (shown at ^ s = -1.5 MPa only) - 129 -DOUGLAS-FIR PLANTED AND VIBRATED SEEDLINGS Vs(MPa) 6 (m 3 n T 3 ) a Kb (Kg n r 1 Pa" 1 s" 1) R C (TPa s Kg"-") Rs/RT d -0.53 .06 5.00 x 1 0 " 1 1 3.5 x 1 0-4 — -0.81 .03 3.36 x 1 0 " 1 2 5.3 x 10" 3 — -1.5 .015 2.55 x 1 0 " 1 3 6.9 x 10- 2 .014 a V o l u m e t r i c water content estimated from water r e t e n t i o n curve bUnsaturated h y d r a u l i c c o n d u c t i v i t y estimated by the method shown by Oackson (1972); converted from cm d a y 1 to pressure u n i t s by: 1 cm d a y 1 = 1.18 x 10" 8 Kg n r 1 Pa" 1 s" 1 C a l c u l a t e d s o i l r e s i s t a n c e a f t e r Gardner (1960) dRatio of c a l c u l a t e d s o i l r e s i s t a n c e to minimum observed t o t a l r e s i s t a n c e (shown at ^ s = -1.5 MPa only) 

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