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Aspects of needle morphology, biomass allocation and foliar nutrient composition in a young fertilized… Keane, Michael Gerard 1985

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ASPECTS OF NEEDLE MORPHOLOGY, BIOMASS ALLOCATION AND FOLIAR NUTRIENT COMPOSITION IN A YOUNG FERTILIZED STAND OF REPRESSED LODGEPOLE PINE by MICHAEL G. KEANE B.Ag.Sc.(For), University College Dublin, Ireland, 1978 M.Ag.Sc(For), U n i v e r s i t y College Dublin, Ireland, 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Faculty of Forestry, Department of Forest Sciences We accept this thesis as conforming to Jthe reauired standard THE UNIVERSITY OF BRITISH COLUMBIA May 1985 ®Michael G. Keane, 1985 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 of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. I t i s understood that copying or publication 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. requirements for an advanced degree at the University Department of The University of B r i t i s h Columbia 1956 Main Mall Van couve r, Canada V6T 1Y3 DE-6 C3/81) i i ABSTRACT The dramatic decline i n stand productivity associated with very high stand densities i n n a t u r a l l y regenerated p o s t - f i r e i n t e r i o r lodgepole pine (Pinus contorta var. l a t i f o l i a ) stands i s c a l l e d "repression". The reasons for i t are unknown. Biomass a l l o c a t i o n , needle morphology and f o l i a r n u t r i t i o n associated with repression were studied i n a 20-year-old stand oh plots at f i v e densities ranging from 3,500 to 109,000 sph and f e r t i l i z e d at 0, 100 and 200 kg N h a - 1 with ammonium n i t r a t e . At higher stand densities, s p e c i f i c leaf area increased while l e a f area index declined and l i g h t i n t e n s i t i e s increased below the canopy. As stand density increased from 5000 sph to 90,000 sph, the above-ground biomass decreased from 61 t ha-^- to 16 t ha~^, the proportion allocated to the stem increased from 58% to 78% and the leaf area/sapwood area decreased from 0.3 to 0.13 m^  cm-^. Mean earlywood percentage decreased from 62% to 8% i n codominants at 6,500 and 109,000 sph respec-t i v e l y . Although nitrogen deficiency was evident i n a l l stand densities, there were no s i g n i f i c a n t differences between vigorous and repressed stands for the various macro- (N, P, K, S) or micro-nutrients (Cu, Fe, 'active' Fe) examined. It i s hypothesized that the decreased proportion of earlywood i n repressed trees causes a reduction i n stem conductivity leading to the reported drop i n the leaf area/sapwood area r a t i o . The r e s u l t i n g decrease i n the photosynthetic/respiratory surface area r a t i o i n repressed stands may lead to t h e i r reduced p r o d u c t i v i t y . i i i TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i i i LIST OF TABLES v LIST OF FIGURES v i i LIST OF APPENDICES x ACKNOWLEDGEMENTS x i i CHAPTER 1. INTRODUCTION 1 CHAPTER 2. SITE DESCRIPTION 5 A. S i t e Location and Climate 5 B. S i t e C l a s s i f i c a t i o n 5 C. S o i l C h a r a c t e r i s t i c s 7 D. Stand C h a r a c t e r i s t i c s 8 CHAPTER 3. THE EXPERIMENT 10 CHAPTER 4. STUDY COMPONENT 1: NEEDLE MORPHOLOGY 13 A. I n t r o d u c t i o n 13 B. L i t e r a t u r e Review 14 C. Methods and M a t e r i a l s 19 D. Res u l t s and D i s c u s s i o n 26 1. S p e c i f i c l e a f area 26 2. Within stand l i g h t regime 33 E. Conclusions AO CHAPTER 5. STUDY COMPONENT 2: BIOMASS ALLOCATION 42 A. I n t r o d u c t i o n 42 B. L i t e r a t u r e Review 43 C. Methods and M a t e r i a l s 56 D. Results and D i s c u s s i o n 62 i v Page 1. General production 62 2. Component and t o t a l dry weight 74 3. Height growth . 88 4. Leaf area/sapwood area r e l a t i o n s h i p s 95 5. Stand density e f f e c t s on wood anatomy 102 E. Conclusions 112 CHAPTER 6. STUDY COMPONENT 3: FOLIAR NUTRIENT ANALYSIS 115 A. I n t r o d u c t i o n 115 B. L i t e r a t u r e Review 116 C. Methods and M a t e r i a l s 125 D. Results and D i s c u s s i o n 130 1. G r a p h i c a l a n a l y s i s of f i r s t year r e s u l t s ... 130 2. Three year a n a l y s i s f o r N, P and K 137 3. M i c r o n u t r i e n t a n a l y s i s 143 4. 1983 a n a l y s i s of N conc e n t r a t i o n as a f f e c t e d by needle age and crown p o s i t i o n 147 E. Conclusions 151 CHAPTER 7. THE CAUSAL MECHANISM FOR GROWTH STAGNATION IN L0DGEP0LE PINE 154 CHAPTER 8. GENERAL CONCLUSIONS 162 REFERENCES CITED 168 V LIST OF TABLES Table Page 1 Experimental Design 11 2 Equations f o r the e s t i m a t i o n of l e a f area i n p l o t s of varying density 2 5 3 Treatment means f o r s p e c i f i c l e a f area 27 4 Canopy l i g h t c h a r a c t e r i s t i c s measured with the chemical l i g h t meter 34 5 P l o t l e a f area c h a r a c t e r i s t i c s 36 6 L i g h t e x t i n c t i o n c o e f f i c i e n t s (k) 36 7 Tree and p l o t c h a r a c t e r i s t i c s measured at each sampling i n t e n s i t y 57 8 Number of harvested trees per p l o t at each sampling i n t e n s i t y 58 9 General p l o t c h a r a c t e r i s t i c s 63 10 Regression equations used i n dimension a n a l y s i s f o r the 2° sampling i n t e n s i t y 75 11 Regression equations used i n dimension a n a l y s i s f o r the 3° sampling i n t e n s i t y 75 12 Component r e g r e s s i o n equations f o r 2° sampling i n t e n s i t y 79 13 Component r e g r e s s i o n equations f o r 3° sampling i n t e n s i t y 80 14 Component dry weights by p l o t 81 15 Needle dry weight by age c l a s s 84 16 R e l a t i o n s h i p between lengths of successive leading shoots between trees from d i f f e r e n t stand d e n s i t i e s ... 92 17 Regression equations f o r p r e d i c t i o n of l e a f area from sapwood area and basal area 96 v i Table . Page 18 Wood anatomical c h a r a c t e r i s t i c s i n codominant trees from d i f f e r e n t stand densities 103 19 Earlywood and latewood percentages as affected by stand density 107 20 Chemical analysis carried out by year 127 21 Nitrogen:sulphur r a t i o s as affected by f e r t i l i z e r and stand density 146 v i i LIST OF FIGURES Figure Page 1 N a t u r a l d i s t r i b u t i o n of lodgepole pine 2 2 P l o t l o c a t i o n 6 3 Photographs of 5K (A), 50K (B) and 150K (C) stands .... 9 4 P l o t layout 12 5 C a l i b r a t i o n curve r e l a t i n g cumulative r a d i a t i o n (measured with the s o l a r monitor) to l i g h t absorbance (recorded by the spectrophotometer) 2A 6 Treatment i n t e r a c t i o n e f f e c t s on s p e c i f i c l e a f area ... 29 7 Dependence of w i t h i n stand l i g h t c o n d i t i o n s on the shading l e a f area 37 8 S p e c i f i c l e a f area i n d i f f e r e n t l i g h t regimes 39 9 Treatment e f f e c t s on mean height 64 10 E f f e c t of stand density on top height 66 11 E f f e c t of stand density on diameter 68 12 E f f e c t of stand density on basal area 69 13 E f f e c t of stand d e n s i t y on l i v e crown r a t i o 71 14 E f f e c t of stand density on m o r t a l i t y (%) 73 15 E f f e c t of stand density on t o t a l above-ground biomass . 77 16 Biomass a l l o c a t i o n between d i f f e r e n t stand d e n s i t i e s .. 82 17 T o t a l f o l i a r biomass as a f f e c t e d by stand density and ni t r o g e n f e r t i l i z a t i o n 85 18 Annual f o l i a r production as a percentage of the t o t a l f o l i a r biomass 87 19 The e f f e c t of stand density on the average needle r e t e n t i o n at d i f f e r e n t crown p o s i t i o n s 89 20 Height v s . age curves f o r mean trees i n each nominal d e n s i t y c l a s s 90 v i i i Figure Page 21 C o e f f i c i e n t s of determination ( r ^ ) between successive leading shoots over a 20-year period 93 22 The ef f e c t of stand density on leaf area index 98 23 The ef f e c t of stand density on the leaf arearsapwood area r a t i o 99 24 The r e l a t i o n s h i p between leaf area:sapwood area r a t i o and tree diameter 101 25 V a r i a t i o n i n mean ring densities over time between trees from vigorous and stagnant stands 105 26 V a r i a t i o n i n mean r i n g width over time between trees from vigorous and stagnant stands 106 27 Average density p r o f i l e s (1966-1983) for trees from a range of stand densities 108 28 Photographs of wood samples from vigorous and stagnant trees I l l 29 Schematic r e l a t i o n s h i p between concentration and absolute content of needles 128 30 Interpretation of d i r e c t i o n a l r e l a t i o n s h i p s between f o l i a r concentration and absolute content of an element following treatment 129 31 Density e f f e c t on needle weight and nitrogen composition 131 32 F e r t i l i z e r e f f e c t on needle weight and nitrogen composition 132 33 F e r t i l i z e r e f f e c t on needle weight and phosphorus composition 134 34 F e r t i l i z e r e f f e c t on needle weight and potassium composition 136 35 Density x f e r t i l i z e r x year i n t e r a c t i o n e f f e c t s on N concentration 138 36 F e r t i l i z e r e f f e c t on P concentration 141 i x Figure Page 37 Density x year i n t e r a c t i o n e f f e c t s on P concentration . 142 38 Density x year i n t e r a c t i o n e f f e c t s on K concentration . 144 39 F e r t i l i z e r e f f e c t on 'active' Fe 145 40 Density x f e r t i l i z e r x needle age i n t e r a c t i o n e f f e c t s on N concentration 148 41 Density x f e r t i l i z e r x crown p o s i t i o n i n t e r a c t i o n e f f e c t s on N concentration 149 42 A causal mechanism f o r growth stagnation i n lodgepole pine 159 43 I n t e r i o r lodgepole pine stand density diagram 161 X LIST OF APPENDICES Appendix Page A . l Site species l i s t 180 A. 2 S o i l p r o f i l e d e s c r i p t i o n 181 B. l Analysis of variance f o r s p e c i f i c leaf area 182 B.2 Analysis of variance for needle surface area 183 B. 3 Analysis of variance for needle dry weight 184 C l Analysis of variance for mean height 185 C. 2 Analysis of variance for mean diameter 186 C.3 Analysis of variance for basal area 186 C.4 Analysis of variance f o r l i v e crown r a t i o 187 C.5 Analysis of variance for mortality 187 C.6 Plots of residuals vs. i n d i v i d u a l independent variables 188 C.7 Plot biomass t o t a l s 195 C.8 Analysis of variance for t o t a l above-ground biomass .. 196 C.9 F u l l regression equations f o r t o t a l dry weight (2° sampling) 197 C.10 F u l l regression equations f o r t o t a l dry weight (3° sampling) 198 C . l l F u l l regression equations f o r component dry weight (2° sampling) 199 C.12 F u l l regression equations f o r component dry weight (3° sampling) 200 C.13 Analysis of variance for t o t a l f o l i a r biomass 201 C.14 Plot leaf area, sapwood area and leaf area index (LAI) 202 C.15 Analysis of variance f o r LAI 203 C.16 Analysis of variance for leaf area:sapwood area r a t i o 203 x i Appendix Page D.l Analysis of variance for density, f e r t i l i z e r and year e f f e c t s on N concentration 204 D.2 Analysis of variance for density, f e r t i l i z e r and year e f f e c t s on P concentration 205 D.3 Analysis of variance for density, f e r t i l i z e r and year e f f e c t s on K concentration 206 D.4 Analysis of variance for density, f e r t i l i z e r , needle age and crown p o s i t i o n e f f e c t s on f o l i a r N concentration 207 x i i ACKNOWLEDGEMENTS I wish to express my deepest appreciation to my supervisor, Dr. G.F. Weetman for his guidance and help which have contributed greatly to my work at UBC. I am also g r a t e f u l to the other members of my supervisory committee: Dr. T.A. Black, Dr. J.L. Crane, Dr. J.P. Kimmins, Dr. K. M i t c h e l l and Dr. J . Worrall for t h e i r help and constructive c r i t i c i s m of th i s t h e s i s . I would l i k e to thank Dr. J . Bassman who i n i t i a t e d the o v e r a l l project. The work contained i n t h i s thesis comprises only part of a larger study on the problem of repression i n lodgepole pine and his contribution to the development, design and sampling strategy are acknowledged. While conducting t h i s research, I was helped i n a vari e t y of ways by a number of other people and fr i e n d s . In p a r t i c u l a r , I would l i k e to thank Ms. C. Baker, Mr. P. Beaudry, Mr. R. Bigley, Mr. P. Comeau, Mr. K. Cr y s t a l , Mr. C. David and Mr. B. Wong. I would l i k e to acknowledge Mr. A. Vyse, Ministry of Forests (Williams Lake), for his support for the project; Dr. J . Demaerschalk and Dr. A. Kozak for t h e i r advice i n s t a t i s t i c a l analysis; Dr. J . Wilson for his support and help; Mr. L. Jozsa (Forintek) for carrying out the desitometry work, and Dr. B. van der Kamp f o r help with the photomicrographs. I would l i k e to thank the I r i s h Forest and W i l d l i f e Service and, i n p a r t i c u l a r , Dr. N. O'Carroll for granting me educational leave and the Natural Sciences and Engineering Research Council of Canada, the B.C. x i i i Science Council and the B.C. Mini s t r y of Forests f o r f i n a n c i a l support of the project. L a s t l y , I would l i k e to thank my parents f o r th e i r encouragement at a l l times during my education. To my wife, Lor, and c h i l d r e n , Grainne and Dave, for t h e i r love and for keeping this whole project i n perspective, I dedicate t h i s t h e s i s . 1 CHAPTER 1. INTRODUCTION As the l a s t of the old growth coastal forests of the P a c i f i c North West are l i q u i d a t e d , increasing attention i s being paid to a l t e r n a t i v e timber supplies, p a r t i c u l a r l y i n the i n t e r i o r of the region. In the l a s t two decades, lodgepole pine (Pinus contorta Dougl.) has contributed to t h i s change and has become an important timber species. It accounts f o r 20 and 40 percent of the annual harvests i n B r i t i s h Columbia and Alberta res p e c t i v e l y (Kennedy, 1985). The species i s also extremely important i n the U.S. and accounts for 16 percent of the annual lumber harvest i n the Rocky Mountain States (van Hooser and Keegan, 1985). The l i t e r a t u r e on the d i s t r i b u t i o n and botanical c h a r a c t e r i s t i c s of lodgepole pine has recently been reviewed ( C r i t c h f i e l d , 1980; Wheeler and C r i t c h f i e l d , 1985). It i s the most widely d i s t r i b u t e d conifer i n Western North America with a range spanning 33° of l a t i t u d e , 35° of longitude and over 3900 metres of elevation (Figure 1). More than any other western co n i f e r , i t forms pure or nearly pure stands (Eyre, 1980). Many of these stands have resulted from repeated f i r e s and there i s now strong evidence to suggest that the cone serotiny associated with many lodgepole pine stands i s la r g e l y an evolutionary response to these frequent destructive f i r e s (Perry and Lotan, 1979). This c h a r a c t e r i s t i c of serotiny, coupled with the species precocity (lodgepole pine i s reproductively active at a very early age), often leads to the development of immense seed reserves. A f i r e i n such a stand may release m i l l i o n s of seeds per hectare (Wheeler and C r i t c h f i e l d , 1985). Once germinated, the number of seedlings remains high and only very slowly succumbs to competition. Trees i n the r e s u l t i n g stand may have a mean diameter at breast height of only 4 to 5 cm a f t e r more than 50 years growth (Smithers, 1961). 2 Figure 1. Natural d i s t r i b u t i o n of lodgepole pine (from L i t t l e , 1971). Broken l i n e s mark approximate boundaries of c o a s t a l , Sierra-Cascade and Rocky Mountain-Intermountain races. 3 Extremely high stand densities are not unique to lodgepole pine. Western hemlock (Tsuga heterophylla (Raf.) Sarg.), amabilis f i r (Abies  amabilis (Dougl.) Forb.), red alder (Alnus rubra Bong.) and black cotton-wood (Populus trichocarpa Torr. and Grey) a l l regenerate dense stands. In lodgepole pine, however, the condition and subsequent reductions i n growth are most severe. The terms 'stagnant' or 'repressed' are often used to describe stands which show large reduction i n height growth when growing at extremely high d e n s i t i e s . M i t c h e l l and Goudie (1980) reported on reductions i n dominant height from 4 m to 1.2 m across a density range of 5,000 to 800,000 stems per hectare (sph) i n an 18-yearold stand of lodgepole pine. How does an i n t o l e r a n t , pioneer species l i k e lodgepole pine exist and grow at such high stand densities? P o s t - f i r e factors such as an i d e a l seedbed and large amounts of seed r e a d i l y explain why such high densities e s t a b l i s h i n i t i a l l y . The factors a f f e c t i n g subsequent reduc-tions In growth, e s p e c i a l l y i n height growth, are not understood. How-ever, the following hypotheses have been suggested by various authors. M i t c h e l l and Goudie (1980) hypothesized that excessive r e s p i r a t i o n and a shortage of moisture may cause the entire growth system to slow down while Worrall et^ aJL. (1985) rejected the hypothesis that the differences between vigorous and stagnant trees lay i n t h e i r a p i c a l meristem. Kimmins (1985, personal communication*-) suggests that i n t r a - s p e c i f i c competition could r e s u l t i n such intense competition for moisture and nutrients that the plants would a l l o c a t e such a high proportion of photo-synthate to production of f i n e roots and mycorrhizal fungi that i n s u f f i -cient f o l i a g e would be produced to induce competition for l i g h t at a l e v e l that would induce s e l f - t h i n n i n g . With the exception of the study of 1 Dr. J.P. Kimmins, Professor, Department of Forest Sciences, Faculty of Forestry, University of B.C. 4 Worrall et a l . (1985), however, none of these hypotheses have been rigorously tested and the causal mechanism for growth repression at high stand densities remains r e l a t i v e l y unexplored. The present study was i n i t i a t e d i n an attempt to understand better some of the growth processes involved i n repression of lodgepole pine. Despite the increasing importance of t h i s species i n many areas of Canada and the U.S., r e l a t i v e l y l i t t l e i s known about how i t adapts to growth at high stand d e n s i t i e s . It was f e l t that by monitoring changes i n biomass a l l o c a t i o n and stand h i s t o r y (using stem analysis techniques) a better insight into the phenomenon of repression might be gained. Changes i n f o l i a r morphology and nutrient r e l a t i o n s h i p s were also thought to be important. As mentioned e a r l i e r , however, i t i s often d i f f i c u l t to d i s t i n g u i s h between the causes and the e f f e c t s of growth variables at high stand d e n s i t i e s . The overall 1"objective of t h i s study, therefore, was to investigate  and describe above-ground biomass a l l o c a t i o n s t r a t e g i e s , needle  morphology and f o l i a r nutrient uptake and d i s t r i b u t i o n as influenced by  nitrogen f e r t i l i z a t i o n across an extreme range of densities i n a young  lodgepole pine stand. In order to examine these variables, s p e c i f i c hypotheses were set up and are dealt with i n turn i n the body of t h i s thesis i n the chapters dealing with the various study components. The C h i l c o t i n area, west of Williams Lake i n i n t e r i o r B r i t i s h Columbia, was chosen as the l o c a t i o n of the experiment because of the vast areas of repressed lodgepole pine i n the region. Excellent co-operation was also established with l o c a l M i n i s t r y of Forests personnel who helped with many of the l o g i s t i c problems i n setting-up and monitoring the experiment. 5 CHAPTER 2. SITE DESCRIPTION A. S i t e L o c a t i o n and Climate The s i t e of the experiments was located i n the Cariboo Forest Region i n I n t e r i o r B r i t i s h Columbia (52°07' N, 122°54' W). The area l i e s i n the C e n t r a l D o u g l a s - f i r Forest S e c t i o n of the Montane Forest Region (Rowe, 1972) and i n the ' C h i l c o t i n pine' subzone of the Sub-Boreal Spruce Zone (SBS (a)) (Annas and Coupe, 1979). The s i t e was close to 5 km on the Ross Lake Road and was approximately 90 km west of W i l l i a m s Lake (Figure 2) . A l l p l o t s were located w i t h i n 1 km of each other and at an e l e v a t i o n , of 1530 m. The area i n which the p l o t s are located i s c h a r a c t e r i z e d by an extremely c o l d dry c l i m a t e . T h i r t y year average values (1951-1980) f o r the c l o s e s t weather s t a t i o n ( A l e x i s Creek/Tautri Creek; 52°33' N, 123°11' W, e l e v a t i o n 1219 m) show a f r o s t - f r e e period of only 12 days ( J u l y 8-20) and only 709 growing degree days per annum. Mean annual p r e c i p i t a t i o n i s 464 mm, 270 mm of which comes as r a i n f a l l . H a l f (50.6%) of t h i s p r e c i p i t a t i o n f a l l s between May and September. The coldest month i s January with a mean d a i l y minimum of -21.2°C. The mean d a i l y maximum i n J u l y , the warmest month, i s 20°C while the mean d a i l y temperature f o r the year i s only 0.4°C (Environment Canada, 1982). B. S i t e C l a s s i f i c a t i o n A l l p l o t s consisted of pure even-aged (20 years i n 1981) lodgepole pine with some c o n t a i n i n g an o c c a s i o n a l white spruce (Picea glauca (Moench) Voss). The p r i n c i p a l shrubs i n the lowest density p l o t s (termed 6 Figure 2. Plot location. (Original'- from L i t t l e , 1971) 7 the 5K plots ) were Alnus v l r l d l s ssp. slnuata (Reg.) Rydb., S a l l x  bebblana Sarg. and Rosa a c l c u l a r i s L i n d l . while Calamagrostis rubescens Buckl., Llnnaea borealis L. and Vaccinium caespitosum Michx. made up the herb layer. Lichens included Cladonia, P e l t i g e r a and Stereocaulon species. The shrub layer i n the intermediate densities (20K and 50K) included Alnus v i r i d i s ssp. sinuata, Rosa a c i c u l a r i s and Spiraea b e t u l i f o l i a P a l l . The herb layer contained s i m i l a r species to the low density plots but with Linnaea b o r e a l i s being more common. The vegetation i n the high density plots (100K and 150K) was si m i l a r to the intermediate density but with less alder and Linnaea b o r e a l i s and more Shepherdia canadensis (L.) Nutt. Arctostaphylos uva-ursi (L.) Spreng. was also found i n these p l o t s . Both the low and high stocking plots had s l i g h t southerly aspects (slopes < 5%) while the plots of intermediate density had zero slope. The moisture and nutrient regimes of a l l density ranges were c l a s s i f i e d as mesic and mesotrophic respectively. A f u l l species l i s t i s given i n Appendix A . l . C. S o i l C h a r a c t e r i s t i c s A s o i l p r o f i l e d e s c r i p t i o n according to the Canadian system (Canada S o i l Survey Committee, 1978) i s given i n Appendix A.2. The s o i l was c l a s s i f i e d as a B r u n i s o l i c Gray L u v i s o l . The area was classed as well drained with a mor humus form and rooting depth to 40 cm. Rooting was r e s t r i c t e d by a Bt layer at that depth. Texture varied from a gravelly sandy loam i n the Ae^, Bm and Ae£ horizons to a gr a v e l l y clay loam i n the Bt horizon. The o v e r a l l coarse fragment content was 40 percent. 8 Generally, the LFH layer was shallow (2 cm) and the s o i l organic matter content was low. Because the s o i l climate of this subzone i s so cold and dry, short periods of drought may occur during the growing season (Annas and Coupe, 1979).. D. Stand C h a r a c t e r i s t i c s Plots were located within the Palmer Lake burn area. This area had been burned by w i l d f i r e i n 1959 and regenerated back to pure even-aged lodgepole pine. Because of an e a r l i e r unpublished study by M i t c h e l l and Goudie (1980) suggesting that repression began at a stand density of approximately 50,000 sph, plots were established at densities on either side of t h i s p i v o t a l f i g u r e . The f i v e nominal density classes established were 5000 sph (5K), 20,000 sph (20K), 50,000 sph (50K), 100,000 sph (100K) and 150,000 sph (150K). Actual densities varied somewhat from these nominal density classes because of the d i f f i c u l t y i n l o c a t i o n of suitable p l o t s , and subsequent mor t a l i t y . In 1981, the estimated stand age (at stump) was 20 years for a l l p l o t s . Tree heights ranged from 2 m to 6 m and diameter (at ground l e v e l ) varied from 2 cm to 10 cm (Figure 3). Figure 3. Photographs of 5K (A), 50K (B) and 150K (C) stands. 10 CHAPTER 3. THE EXPERIMENT An experiment was established i n May 1981 by Dr. J.H. Bassman to examine the ecophysiological basis of growth stagnation i n lodgepole pine. The o v e r a l l objectives were to investigate and describe the physiology of gas exchange, energy balance, water economy, and biomass a l l o c a t i o n with respect to this growth phenomenon. Experimental plots were established that represented nominal stocking density classes of 5,000, 20,000, 50,000, 100,000,^and 150,000 (5K through 150K respective-l y ) stems per ha. Plots were c i r c u l a r and varied i n size from 20 m2 f o r the 5K and 20K densities to 10 m2 f o r the 50K, 100K and 150K d e n s i t i e s . The number of trees i n each pl o t , therefore, was approxi-mately 10, 40, 50, 100 and 150 f o r each of the f i v e respective density c l a s s e s . Experimental design of the f e r t i l i z e r component consisted of a 3 x 3 f a c t o r i a l layout. Treatment levels included 0, 100 and 200 kg N ha -* ( f e r t i l i z e r ) and 5K, 50K and 150K (stand density). Plots were assigned to the various f e r t i l i z e r l e v e l s randomly within each density c l a s s . In t o t a l , s i x r e p l i c a t i o n s were established to enable a f a l l biomass harvest to be carried out on two r e p l i c a t i o n s i n each of three subsequent years, i . e . 1981 (block A), 1982 (block B) and 1983 (block C) (Table 1). Blocks A and B were also used by Drs. J . Bassman and J . Crane (Faculty of Forestry, University of B r i t i s h Columbia) for ecophysiology and biomass p a r t i t i o n i n g studies. Plot layout i s shown i n Figure 4. Information from block C on needle morphology and biomass a l l o c a t i o n i s used i n this t h e s i s . For the n u t r i t i o n a l component of the study, however, the problem of I n s u f f i c i e n t amounts of foliage for analysis was avoided by s e l e c t i o n of material from a l l three blocks. 11 TABLE 1. Experimental design. A l l blocks were established and f e r t i l i z e r treatments applied in May 1981. Plot codes 5K, 20K, 50K, 100K and 150K refer to the nominal density classes of 5000, 20,000, 50,000, 100,000 and 150,000 sph respectively. Each * represents one plot. 5K 20K 50K 100K 150K 0 kg N h a - 1 * * * * * * ** Block A 100 kg N h a - 1 ** ** ** (1981) 200 kg N h a - 1 ** ** ** 5K 20K 50K 100K 150K 0 kg N h a - 1 * * * * * * ** Block B 100 kg N h a - 1 ** ** ** (1982) 200 kg N h a - 1 ** ** ** 5K 20K 50K 100K 150K 0 kg N h a - 1 ** * ** * ** Block C 100 kg N h a - 1 ** ** ** (1983) 200 kg N h a - 1 ** ** ** 12 123c ALEXIS CREEK V^AROSSUKE HIGHWAY PLOT LOCATION ENLARGED 5K RISKE CREEK LEGEND • CONTROL o 100 kg N ha*1 5K, 50K * 200 kfl N ha"1 and150K • 20K o 100K Figure 4. Plot layout. 13 CHAPTER 4. STUDY COMPONENT 1: NEEDLE MORPHOLOGY A. Introduction Among the important factors influencing primary production of plant communities are l i g h t t r a n s m i s s i b i l i t y and s p e c i f i c leaf area (Tadaki, 1970). In general, needles f u l l y exposed to sunlight are heavier, contain less chorophyll and have smaller s p e c i f i c leaf areas than needles developed under shaded conditions (Lewandowska and J a r v i s , 1977). In lodgepole pine, leaf length, width and weight are reduced i n trees from repressed stands compared to trees from more vigorous stands (Worrall et a l . , 1985). It i s not known, however, how differences i n l i g h t climate i n these high-density stands ( i f such differences do e x i s t ) a f f e c t f o l i a r adapta-tions such as s p e c i f i c leaf area. Inadequate l i g h t was suggested by Zavitkovski and Dawson (1978) as being the p r i n c i p a l cause of mortality i n i r r i g a t e d and f e r t i l i z e d plantations of jack pine (Pinus banksiana Lamb.) grown at extremely high d e n s i t i e s . V a r i a t i o n i n s p e c i f i c leaf area within the canopy or between s i t e s also complicates the estimation of leaf area from data based on f o l i a r weight. S t r a t i f i c a t i o n of fo l i a g e by crown p o s i t i o n and age-class i s suggested as a way to Increase the accuracy of leaf area estimates (Sheltoh and Switzer, 1984). In attempting to understand how changes i n l i g h t climate might e f f e c t s p e c i f i c leaf area i n repressed stands, study component 1 reports on experiments which: (1) Test the eff e c t of f e r t i l i z e r , stand density, crown p o s i t i o n and needle age on s p e c i f i c leaf area. 14 (2) Measure the r e l a t i v e l i g h t i n t e n s i t i e s (I/Irj) beneath the canopy over a range of stand d e n s i t i e s . (3) Use the information from (2) and leaf area estimates to calculate l i g h t e x t i n c t i o n c o e f f i c i e n t s (k) and model the r e l a t i v e l i g h t i n t e n s i t i e s beneath the canopies. B. L i t e r a t u r e Review As plants grow they must be able to adapt both morphologically and p h y s i o l o g i c a l l y to a changing environment. For example, as the plant's l i g h t regime changes, a ph y s i o l o g i c a l response i n terms of changes i n l i g h t compensation often occurs (Bjorkman and Holmgren, 1963). This change i n within-stand l i g h t conditions seems to be of p a r t i c u l a r importance at the morphological l e v e l also. Adaptation of plants to l i g h t can involve a change i n a l l o c a t i o n of carbohydrates to crown, stem and root growth (Monsi and Murata, 1970). At the leaf l e v e l , t h i s change involves adjustments i n structure and pigment concentrations. Lewandowska and J a r v i s (1977) found that needles which had developed under shaded conditions ( i n the lower crown) showed an increase i n s p e c i f i c leaf area (needle surface area per needle dry weight, SLA) and pigment content over needles f u l l y exposed to sunlight ( i n the upper crown). Working with birch (Betula species) seedlings, Nygren and Kellomaki (1983) found that a r t i f i c i a l shading increased the SLA and the thickness of the leaf mesophyll while decreasing the maximum photosynthetic rate and the l i g h t i n t e n s i t y for photosynthetic saturation. The same authors showed that i n dense stands (up to 125,000 sph) i n p a r t i c u l a r , the SLA i n the lower crown was large compared with that i n the upper crown. 15 The same phenomenon has been documented f o r conifers (Tadaki, 1970; Gholz et a l . , 1976; Benecke, 1979; Del Rio and Berg, 1979; Kellomakl and Oker-Blom, 1981; Shelton and Swltzer, 1984). Benecke (1979) found that SLA Increased from 129 cm^g-! to 169 cm 2g~l between sun and shade needles i n young, thinned Monterey pine (Pinus radiata D. Don). There was an even greater increase (127-183 cm 2g - 1) i n a s i m i l a r unthinned stand. To determine the e f f e c t of thinning i n t e n s i t y on SLA of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Del Rio and Berg (1979) examined seedlings established beneath three i n t e n s i t i e s of overstory thinning. They found that s p e c i f i c leaf area was negatively related to the logorithm of d a i l y sunlight received at the crown. As well as the expected changes i n SLA with changes i n whorl p o s i -t i o n , Kellomakl and Oker-Blom (1981) showed that, for 20 year-old Scots pine (Pinus s y l v e s t r i s L . ) , the SLA values were three to four times greater i n suppressed trees than i n dominants. They suggested that t h i s phenomenon was a growth strategy allowing substantial penetration of l i g h t i n the upper canopy with increased l i g h t capture by the lower crown and suppressed trees. Within any one crown p o s i t i o n s p e c i f i c leaf area also varies with leaf age (Gholz et a l . , 1976; Benecke, 1979; Shelton and Switzer, 1984). Gholz et^ a l . (1976) found that SLA varied from approximately 200 cm 2g~l f o r current needles to 150 cm 2g -l for needles three years and older i n mature Douglas-fir from a va r i e t y of locations i n Oregon. A s i m i l a r s i g n i f i c a n t decrease i n needle area/unit weight with increasing needle age i n both upper and lower crown positions was shown by Benecke (1979) i n New Zealand. 16 Despite t h i s well-documented evidence showing how SLA decreases as needles age, few authors suggest reasons why t h i s change i n needle morphology occurs. I f SLA r e l a t i o n s h i p s were e n t i r e l y dependent on the l i g h t environment, then one would expect that current needles, being exposed to higher l i g h t i n t e n s i t i e s would have lower SLA values than older needles. This i s not the case, however. The apparent reason f o r t h i s phenomenon i s that, as needles age, t h e i r dry weight increases (due to laying down of c e l l w a l l material, etc.) while t h e i r surface area remains the same. Therefore, over time, needle SLA w i l l decrease ( J o l l i f f e , personal communication 2). The l i t e r a t u r e evidence for the e f f e c t s of s i t e q u a l i t y and stand n u t r i t i o n on SLA agrees that the e f f e c t s are usually small but disagrees as to th e i r d i r e c t i o n . Shelton and Switzer (1984) found that SLA d i f f e r -ences i n l o b l o l l y pine (Pinus taeda L.) due to s i t e differences were only four percent. In 9-year-old Monterey pine, nitrogen f e r t i l i z e r (400 kg N ha~l as ammonium sulphate) caused a decrease i n SLA (Benecke, 1979) while the same l e v e l of nitrogen (as calcium ammonium n i t r a t e ) resulted i n an increase i n SLA i n Scots pine (Kellomakl et a l . , 1982). The l a t t e r work also showed that higher le v e l s of N caused SLA to again drop and that the effect of the f e r t i l i z e r on SLA was dependent on the crown p o s i t i o n . Mellor and Tregunna (1972), however, found that d i f f e r e n t sources of nitrogen had no e f f e c t on the r e l a t i o n s h i p between leaf area and dry weight In seedlings of western hemlock (Tsuga heterophylla (Raf.) Sarg.), Douglas-fir and lodgepole pine. 2Dr. P. J o l l i f f e , Department of Plant Science, Faculty of A g r i c u l t u r e , U n i v e r s i t y of B r i t i s h Columbia. 17 The only evide nee from the l i t e r a t u r e for v a r i a b i l i t y i n SLA i n lodgepole pine comes from a c l o n a l t r i a l i n Scotland (Cannell et a l . , 1983). A l l seven clones examined showed expected trends i n SLA with changes i n needle age and crown p o s i t i o n . No reports have been found i n the l i t e r a t u r e r e l a t i n g extremely high density to SLA i n lodgepole pine. Some work has been done, however, on a close associate, jack pine, a species with which lodgepole pine frequently hybridizes (Strong and Za v i t k o v i s k i , 1978). In a 6-year-old plantation, they found that mean s p e c i f i c leaf area ( f o r a mid-crown position) varied from 142 to 84 cm2g~ over a density range of 27,000 to 190,000 sph, re s p e c t i v e l y . Because of the ef f e c t of a l l these parameters (needle age, crown po s i t i o n , stand density, etc.) on s p e c i f i c leaf area, the SLA must be determined i f one wants to estimate leaf area from data based on f o l i a r weight. Omission of the v a r i a b i l i t y i n SLA may lead to biased estimates of t o t a l leaf areas of trees. Similar implications exist f o r converting photosynthetic or t r a n s p i r a t i o n a l measurements to a per hectare basis. Hence, s t r a t i f i c a t i o n of the canopy into h o r i z o n t a l l y d i f f e r e n t layers and needle age classes i s recommended as a way to increase the accuracy of leaf area estimates (Shelton and Switzer, 1984). In attempting to describe how leaf area e f f e c t s l i g h t attenuation within the crown and i n turn e f f e c t s the SLA, many authors have used an equation s i m i l a r to the Beer-Lambert-Bouguer law (Monsi and Saeki, 1953, cit e d i n Satoo and Madgwick, 1982; Tadaki, 1970). This law shows that transmission of p a r a l l e l monochromatic rad i a t i o n into a stand follows an exponential decay with leaf area index accumulated from the top of the canopy (F), thus: 18 I / I 0 " e ~ k * ( 1 ) where: I = average short-wave (or solar) irradiance at l e v e l z. IQ = short-wave (or solar) irradiance received above the canopy. k = e x t i n c t i o n c o e f f i c i e n t . Knowing the r e l a t i v e short-wave (or solar) irradiance below the crown canopy ( I / IQ) and the accumulated leaf area, the ext i n c t i o n c o e f f i c i e n t (k) can be calculated for various forest canopies. C o e f f i c i e n t s for canopies have been l i s t e d by J a r v i s e_t a l . ( 1 9 7 6 ) and l i e between 0 . 2 8 - 0 . 5 7 . Of the parameters contained i n equation ( 1 ) , F can be measured or calculated (from needle dry weight and SLA) and LQ i s r e l a t i v e l y e a s i l y measured above the canopy. The measurement of solar r a d i a t i o n beneath a plant canopy (I) can, however, present problems because of the great s p a t i a l and temporal v a r i a t i o n In the l i g h t environment (Gay et^ a l . , 1 9 7 1 ; Salminen et a l . , 1 9 8 3 ) . There are two main sources of this v a r i a -t i o n . F i r s t l y , transmitted r a d i a t i o n i s affected by the earth's diurnal and seasonal r o t a t i o n . Secondly, because of stand structure and the ro t a t i o n of the earth and the movement of the canopy elements, a d d i t i o n a l v a r i a b i l i t y i s created at the f l o o r of the plant community. Of the many methods of measuring photosynthetic r a d i a t i o n now i n use, and capable of simultaneously sampling many points beneath a plant canopy, one of the cheapest and most useful i s the technique f o r measuring r a d i a t i o n v i a the photo-conversion of anthracene i n benzene solution to dianthracene (Marquis and Yelenosky, 1 9 6 2 ; Fisher and M e r r i t t , 1 9 7 3 ) . This method was f i r s t described i n the lat e f i f t i e s 19 (Dore, 1958) and i s based on the fact that anthracene i n benzene w i l l polymerize Into Insoluble dianthracene upon exposure to sunlight. It of f e r s the following advantages: • I t i s comparatively Inexpensive. • I t measures the cumulative l i g h t during a period of time. • It i s capable of measuring many locations simultaneously. I t s main disadvantages are that: • Instantaneous values of l i g h t i n t e n s i t y are unavailable. • The absorption region for the anthracene i n benzene i s i n the u l t r a v i o l e t (0.35-0.36 um) part of the spectrum and thus does not correspond with chlorophyll absorption. In order to use t h i s method, i t i s necessary that u l t r a v i o l e t l i g h t be a constant f r a c t i o n of the photosynthetic irradiance. This i s true only when measurements are not carried out at or near sunrise or sunset and when the plant canopy does not s p e c t r a l l y a l t e r the sunlight as i t passes through. Pine canopies are generally regarded to act as neutral f i l t e r s i n t h i s regard (Reifsnyder and L u l l , 1965). C. Methods and Materials S p e c i f i c Leaf Area Measurement Only the plots from the lowest (5K), intermediate (50K) and highest (150K) density ranges were chosen. These, i n f a c t o r i a l combination with the three f e r t i l i z e r l e v e l s ( c o n t r o l , 100 kg N h a - 1 and 200 kg N h a - 1 ) gave a t o t a l of 9 p l o t s . Within each p l o t , needles from three crown positions (upper, mid and lower crown) and four needle age classes (current, current + 1, current + 2 and current + 3 and older) were chosen. Whorl numbers 3, 6 and 9 (counted from the top downwards) were 20 taken to represent upper, mid and lower crown positions r e s p e c t i v e l y . As the upper crown p o s i t i o n thus had only three age classes of needles (the mid and lower each being divided into four) the crown po s i t i o n x needle age class combination within each plot contained eleven samples. Each sample contained needle f a s c i c l e s pooled from 3-5 trees per p l o t . From t h i s pooled sample 30 needles were chosen randomly on which the i n d i v i d u a l SLA measurements were to be carried out. The t o t a l number of needles used i n the determination of SLA was therefore 2970 (30 x 9 x 11). C o l l e c t i o n of needles was carried out i n the f a l l of 1983. As needles were c o l l e c t e d i n the f i e l d they were placed i n p l a s t i c bags containing moistened pieces of tissue paper and sealed. This was to prevent dehydration and possible changes i n surface area before process-ing. Samples were then placed i n a cooler i n the f i e l d and r e f r i g e r a t e d i n the laboratory p r i o r to their being measured. Only one needle from each f a s c i c l e was taken for measurement. In lodgepole pine, f a s c i c l e s are usually made up of two needles together forming a c y l i n d e r . Each needle has one f l a t diametrical surface and one curved outer surface. The surface area of each needle therefore consists of half the surface area of a c y l i n d e r (less the top and bottom) plus the length x width of the f l a t surface. Needle surface areas were calculated according to the equation: S.A. = + d l (2) = 1.5708 d l + d l (3) - 2.5708 d l . (4) where S.A., d and 1 represent surface area (cm^), needle diameter (cm) and needle length (cm) r e s p e c t i v e l y . To allow for needle taper t h i s 2 1 surface area was then reduced by 6 per cent (Pearson, 1982). Needle length was measured to the nearest mm while needle width was measured to the nearest 0.1 mm using a measuring magnifier. A f t e r measurement, i n d i v i d u a l needles were placed i n marked glass v i a l s and dried at 80°C for 24 hours. Individual needle dry weights were determined to the nearest mg. S p e c i f i c leaf area was then calculated for each needle by d i v i d i n g i t s surface area (cm 2) by i t s dry weight (g). Light Measurements Methods for using the chemical l i g h t meter generally followed those outlined i n the l i t e r a t u r e (Marquis and Yelenosky, 1962; Fi s h e r and M e r r i t t , 1973). The concentration of the stock solution used was 0.1 g of anthracene/1 of benzene. Because i t i s l i g h t s e n s i t i v e once i t i s mixed, the stock so l u t i o n was kept i n a dark glass b o t t l e inside a l i g h t -proof box u n t i l required. The s o l u t i o n i s not affected by exposure to ordinary room l i g h t for short periods of time. The v i a l s used were 7 ml b o r o s i l i c a t e glass s c i n t i l l a t i o n v i a l s with f o i l l i n e d screw caps. These performed well and there were no problems with breakages^ corrosion, leakage or evaporation of the s o l u t i o n . One day before going into the f i e l d , s u f f i c i e n t v i a l s to carry out the e n t i r e experiment (220) were f i l l e d with the stock s o l u t i o n . The v i a l s were stored and transported i n light-proof boxes (embedded i n foam to prevent breakage). The experiment was carried out over two days, J u l y 28th and 29th, 1984. Because the l a s t of the o r i g i n a l plots had been harvested the previous f a l l (1983), new plots had to be located. Five c i r c u l a r plots were established with densities of 5,500 (5.5K), 24,000 (24K), 38,000 22 (38K), 83,000 (83K) and 113,000 stems per hectare (113K). Plot area was 20 m2 f o r the 5.5K plot and 10 m2 f o r a l l others. Diameters (at ground l e v e l ) were measured for a l l trees In each plot to the nearest mm. The proper number of sampling points ( v i a l s ) to provide s t a t i s t i c a l r e l i a b i l i t y has been calculated for a dense pine forest (Fisher and M e r r i t t , 1973). They suggest 8-12 v i a l s f o r a 22-year old red pine (Pinus resinosa A i t . ) stand. Eighteen v i a l s per plot were used i n the present study - three above the canopy and f i f t e e n below. The below-canopy v i a l s were hung from s t r i n g and suspended approximately 40 cm above the ground l e v e l . The strings were arranged i n two east-west transects i n the northern portion of each pl o t . The above-canopy v i a l s were suspended at 40-50 cm above the crowns using lightweight aluminium poles for support. On each of the two days of the experiment, the v i a l s were exposed from 10.00 hrs to 16.00 hrs approximately. It took t h i r t y minutes to set out the v i a l s required f or each days measurements. To ensure that each v i a l was exposed for the same length of time, the v i a l s were col l e c t e d i n the afternoon i n the same order as they had been set out that morning. On July 29th, another set of measurements was taken to determine a c a l i b r a t i o n curve between the chemical l i g h t meter (measuring u l t r a -v i o l e t l i g h t ) and a photosynthetic quantum sensor (LI-COR Solar Monitor LI-1776) (measuring photosynthetic photon f l u x density, PPFD). This c a l i b r a t i o n curve was determined at the experimental s i t e rather than at UBC to account for changes i n the q u a l i t y of solar r a d i a t i o n , p a r t i c u l a r -l y the i n t e n s i f i c a t i o n of the UV r a d i a t i o n components, occurring at high elevations (Caldwell, 1980). The set up for the v i a l s was si m i l a r to 23 that described already. The sensor of the Monitor was placed i n the centre of the v i a l s . T h i r t y - s i x v i a l s were used and three v i a l s were removed every t h i r t y minutes f o r the duration of the experiment (6 hours). The solar monitor measured integrated r a d i a t i o n measurements (mol m - 2) at t h i r t y minute i n t e r v a l s for the same period. After exposure each v i a l was again placed i n the lightproof boxes for return to the laboratory. Upon exposure to l i g h t , the anthracene (C14H10) In benzene polymerizes into insoluble dianthracene (Cj.4^0)2 • The samples were then analysed to determine the amount of unconverted anthracene remaining i n s o l u t i o n . This analysis was made with a spectrophotometer (UNICAM SP8000). A l l samples were thus analysed within f i v e days of returning to the laboratory. Figure 5 shows the r e l a t i o n s h i p between the cumulative PPFD (measured with the Solar Monitor) and the absorbance readings from the spectrophotometer. V i a l s with higher absorbance values indicate higher concentrations of anthracene remaining i n solution and thus less exposure to sunlight. For pr e d i c t i v e purposes, a regression equation was developed with 1/(absorbance) as the independent v a r i a b l e (Figure 5), thus: Cumulative PPFD - -1.1364 + 2.0762 ( a b s o ^ b a n c e ) (5) (mol m - 2) The equation was highly s i g n i f i c a n t (p <0.001) and had r 2 and standard error values of 0.91 and 2.76 respectively. This equation was used for c a l c u l a t i o n of a l l subsequent r a d i a t i o n measurements from the chemical l i g h t meter for both the above (IQ) and below (I) canopy positions. 24 Figure 5. C a l i b r a t i o n curve r e l a t i n g cumulative r a d i a t i o n (measured with the Solar Monitor) to l i g h t absorbance (recorded by the spectrophotometer). 25 C a l c u l a t i o n of the Light E x t i n c t i o n C o e f f i c i e n t s With the I and IQ values (calculated from the regression) and the lea f area index f o r each pl o t , the e x t i n c t i o n c o e f f i c i e n t (k) was calcu-lated from equation (1). Regression equations were used to ca l c u l a t e leaf area (m 2) from sapwood area (cm 2). Basal area (over-bark) was f i r s t l y calculated from diameter for each tree. A regression equation (based on 88 trees) was then used to estimate sapwood area from basal area (over-bark). The equation was: Sapwood Area = -0.43102 + 0.93644 Basal Area (6) 2 2 cm cm* This was highly s i g n i f i c a n t (P <0.001) with r 2 and standard error values of 0.9996 and 0.446 res p e c t i v e l y . From the calculated sapwood area, l e a f area was estimated f o r each tree from the equations i n Table 2, the p a r t i c u l a r equation used depending on stand density. More detail e d information on the derivation of these equations i s given i n the biomass a l l o c a t i o n component of the present study. Leaf areas per tree were then summed for each plot and leaf area indices calculated depending on plot s i z e . TABLE 2. Equations for the estimation of leaf area i n plots of varying density (P <0.0001 i n a l l cases) Component Predictor Plot „ Standard (Y) (X) ID a b r error n Leaf area* Sapwood area 5.5K 0.21268 0.29117 0.86 2.968 18 24K, 38K -0.46905 0.26006 0.93 0.531 35 83K, 113K -0.17745 0.22065 0.87 0.176 35 •Model: Y(m2) = a + bX (cm2). 26 S t a t i s t i c a l Analysis The s p e c i f i c leaf area data were subjected to a multi-way analysis of variance. This was done using the UBC Genlin programme (Greig and B j e r r i n g , 1980). This programme i s based on analysis of variance for unequal subclass numbers using the least squares method (Steel and T o r r i e , 1960) and i s suitable f or an unbalanced analysis of variance. Main factors were f e r t i l i z e r l e v e l , density, crown position and needle age c l a s s . The analysis of variance for the f u l l data set i s given i n Appendix B . l . Because the o r i g i n a l data did not conform to homogeneity of variance assumptions i t was l o g a r i t h m i c a l l y transformed. The ANOVA tables for both 'raw' and transformed data are shown i n Appendix B . l . Because the transformation had l i t t l e e f f e c t on the s i g n i f i c a n c e of the variabl e s , the following discussion w i l l deal only with the o r i g i n a l untransformed data. A s i m i l a r analysis was carried out f o r both compo-nents of SLA i . e . needle surface area and needle dry weight. Results show si m i l a r s i g n i f i c a n t variables to the s p e c i f i c leaf area analysis and are not discussed i n the t h e s i s . The analysis of variance tables for both these variables are presented i n Appendices B.2 and B.3. D. Results and Discussion 1. S p e c i f i c Leaf Area Treatment means for s p e c i f i c leaf area are given i n Table 3. V a r i a -b i l i t y over the range of treatments was high; minimum and maximum values were 72 cm 2g~l and 176 cm 2g~l res p e c t i v e l y with an o v e r a l l mean of 108 cm^g-!. General values from the l i t e r a t u r e f o r lodgepole pine include 83 cm 2g - 1 (Cannell et a l . , 1983), 74 cm 2g - 1 (Pearson, 1982) and 196 cm 2g - 1 27 TABLE 3. Treatment means for s p e c i f i c leaf area. In each case, the mean i s calculated from n = 30. Crown positions 1, 2 and 3 r e f e r to whorls 3, 6 and 9, r e s p e c t i v e l y . Stand F e r t i l i z e r Crown Needle age cla s s density l e v e l p o s i t i o n s p h kg N ha" 1 1983 1982 1981 1980+ 5000 0 1 115.6 93.5 96.4 2 134.2 108.3 87.6 94.8 3 152.4 102.6 101.9 91.3 100 1 111.2 95.6 85.7 2 143.6 108.5 90.9 83.1 3 141.0 120.1 97.1 95.6 200 1 100.8 82.4 79.0 2 103.7 83.5 85.6 80.2 3 113.5 91.0 82.8 86.5 50000 0 1 119.7 107.4 107.4 2 123.1 103.5 99.5 97.3 3 167.7 119.7 112.7 92.8 100 1 105.7 72.0 89.3 2 113.7 100.2 98.0 101.1 3 146.3 116.0 114.5 97.8 200 1 114.9 98.3 99.3 2 121.8 101.8 91.5 91.9 3 142.5 118.8 110.3 99.8 150000 0 1 144.1 93.7 95.4 2 174.3 100.5 95.7 85.8 3 176.3 113.8 99.1 92.9 100 1 148.1 101.2 98.7 2 173.0 93.1 102.3 98.0 3 162.6 90.1 82.2 95.1 200 1 150.0 92.3 95.6 2 144.6 99.1 98.9 99.0 3 159.2 108.3 110.4 100.5 28 (Mellor and Tregunna, 1972). These l i t e r a t u r e values come from an 8-year-old c l o n a l t r i a l , estimated values for a 15 cm tree from allometric equations and 18-week-old f e r t i l i z e d seedlings, r e s p e c t i v e l y . S p e c i f i c leaf areas i n the present study are therefore within the values reported for the species i n the l i t e r a t u r e . Because of the nature of these l i t e r a t u r e values, however, d i r e c t comparisons may not be useful . A more meaningful comparison could be made with the present study and that of Strong and Zavitkovski (1978). These workers measured s p e c i f i c leaf area of jack pine at densities of up to 190,000 sph. Over the e n t i r e range of densities and at three d i f f e r e n t crown positions they found a range i n SLA values of between 84 and 189 cm2g~^, SLA being affected by stand density, crown p o s i t i o n and needle age c l a s s . From the analysis of variance table (Appendix B.l) the s i g n i f i c a n t variables (at the 0.05 l e v e l ) included crown p o s i t i o n (C), needle age cla s s (A) and the i n t e r a c t i o n s , density (D) * A, C * A, D * f e r t i l i z e r l e v e l (F) and D * F * A * C. Because the D * F * A * C i n t e r a c t i o n was s i g n i f i c a n t , a l l four factors influenced the s p e c i f i c leaf area, and i n t e r p r e t a t i o n of the data was made d i f f i c u l t . Any one treatment e f f e c t could not be examined i n i s o l a t i o n as a l l other treatments were a f f e c t i n g the SLA at the same time. For the same reasons i t was very d i f f i c u l t to. i l l u s t r a t e g r a p h i c a l l y the e f f e c t s of the f u l l treatment combinations on any one graph. In an attempt to demonstrate the combined effect of a l l treatments, Figure 6 shows the e n t i r e data set brought together i n 9 sub-figures. The following discussion w i l l be confined to trends and v i s u a l i n t e r p r e t a t i o n of the sub-figures because of the highly s i g n i f i c a n t D * F * A * C i n t e r a c t i o n . As already stated, i t must not be forgotten that 29 Figure 6. Treatment Interaction e f f e c t s on s p e c i f i c leaf area (SLA cm2 g - 1 ) . Treatment l e v e l s are: F l (0 kg N h a - 1 ) , F2 (100 kg N h a - 1 ) , F3 (200 kg N h a - 1 ) , Dl (5K), D2 (50K) and D3 (150K). Needle age classes are C (current years f o l i a g e ) , 1 (one-year-old), 2 (two-year-old), 3+ (three-year-old and older) while whorl position are for upper (A), mid (o) and lower (•) crown po s i t i o n s . Needle Age Class 31 a l l of the four factors are a f f e c t i n g the s p e c i f i c leaf area simultaneously. In general, the o v e r a l l e f f e c t of f e r t i l i z e r treatment was small and density dependent. In a l l three densities i t s ef f e c t was to reduce the mean SLA. The o v e r a l l mean values for f e r t i l i z e r show that the 200 kg N h a - 1 reduced the SLA by only 7% over the control (112 to 104 cm 2g~l). As already indicated, most workers agree that f e r t i l i z e r e f f ects on SLA are small but disagree as to whether f e r t i l i z e r increases or decreases the SLA. Kellomaki et a l . (1982) found that 200 kg N h a - 1 increased SLA of Scots pine by 4%. This increase, however, depended on crown p o s i t i o n and i n the middle crown the f e r t i l i z e r reduced SLA by 4%. Monterey pine examined by Benecke (1979) showed an o v e r a l l reduction of 13% i n SLA a f t e r a p p l i c a t i o n of 400 kg N h a - 1 . The e f f e c t s of stand density on SLA are best i l l u s t r a t e d by the con t r o l sub-figures i n Figure 6. Increasing stand density increased the o v e r a l l mean SLA from 101 cm 2g - 1 to 114 cm 2g - 1 for the 5K and 15OK densities r e s p e c t i v e l y . The e f f e c t , however, was highly dependent on both needle age class and crown p o s i t i o n . Nygren and Kellomaki (1983) concluded that s p e c i f i c leaf area was considerably modified by stand density i n young birch stands of up to 125,000 sph. They found that s p e c i f i c leaf area i n the lower canopy increased by over 100% at the highest density l e v e l . In t h e i r plots, however, LAI was s t i l l increasing even at densities i n excess of 120,000 sph. LAI was estimated for each of the present plots and w i l l be discussed i n the following section dealing with l i g h t e x t i n c t i o n measurements. For high density jack pine, Strong and Zavitkovski (1978) found that highest SLA values occurred i n current year's needles i n the lower crown of t h e i r high density plots 32 (190,000 sph). Their o v e r a l l s p e c i f i c leaf area figures, however, indicated that increasing density tended to decrease rather than increase SLA. They did not calculate the LAI of these stands. The modest increases i n SLA with increasing stand density would seem, therefore, not to be correlated with density per se but rather with some other stand fa c t o r , probably LAI or leaf biomass. The e f f e c t of crown p o s i t i o n on SLA shows a general increase from upper to lower crown posi t i o n s . For current years needles t h i s i s the case i n s i x of the nine plots and Is true for a l l of the control p l o t s . The lower crown po s i t i o n appears to have a greater effect on the SLA than e i t h e r the middle or upper crown. This i s e s p e c i a l l y evident i n the 50K p l o t s . Needles from shoots elongated i n 1981 (C+2) show much less v a r i a -b i l i t y i n SLA than 1983 (C) needles i r r e s p e c t i v e of t h e i r crown p o s i t i o n . Crown p o s i t i o n would, therefore, seem to have i t ' s strongest influence of SLA i n younger f o l i a g e . Like the e f f e c t of density already discussed, the effect of crown po s i t i o n on SLA would appear to be more a function of the canopy s t r u c -ture than of simply crown p o s i t i o n . Most published work on e f f e c t s of crown p o s i t i o n on SLA do not include LAI or crown biomass ca l c u l a t i o n s and are thus d i f f i c u l t to compare to the present r e s u l t s . There i s good agreement, however, between the general trend of increasing SLA with depth i n the canopy i n the present study and many reports i n the l i t e r a -ture (Kinerson, 1975; Benecke, 1979; Kellomakl and Oker-Blom, 1981; Shelton and Switzer, 1984). Despite the obvious d i f f i c u l t i e s i n i n t e r p r e t a t i o n caused by the D * F * A * C i n t e r a c t i o n , the e f f e c t of needle age on s p e c i f i c leaf area i s evident i n a l l the sub-figures. In a l l d e n s i t i e s , f e r t i l i z e r l e v e l s 3 3 and crown positions, there i s an obvious decline i n SLA between current years needles (1983) and those three-years-old and older (1980 and o l d e r ) . The e f f e c t of needle age seems stronger than any of the other e f f e c t s . The decrease i n SLA i s most evident between current and one-year-old needles. The change between one-year-old and older needles i s less obvious and in t e r a c t s strongly with the other treatments. The ef f e c t of needle age i s strongest i n the 150K p l o t s . These high density plots show a 38% decrease i n SLA between current and one-year-old needles while the 5K and 50K plots show 21% and 19% decreases r e s p e c t i v e l y . These e f f e c t s of needle age class on surface area-weight r e l a t i o n -ships are consistent with those of other coniferous species. Tucker and Emmingham (1977) found the highest SLA i n western hemlock for current needles (235 cm 2g - 1) and the lowest for 3-year-old needles (127 cm 2g - 1). Gholz e_t a l . (1976) found a s i m i l a r decline i n SLA with needle age for a number of conifers In western Oregon. The r e s u l t s presented here also question the assumption of Kellomaki and Oker-Blom (1981) that SLA of d i f f e r e n t needle age classes were the same as that f or current needles i n t h e i r work with Scots pine. 2. Within Stand Light Regime The cumulative photosynthetic photon fluxes calculated from the c a l i b r a t i o n curve are shown i n Table 4. Mean cumulative PPFD (above the canopy) of a l l pl o t s on July 28th was 32.44 mol m~2 for the 6-hour exposure period. This i s equivalent to a f l u x density of 1502 umol m~ 2s - 1. The second day of the experiment, July 29th showed a s l i g h t l y higher cumulative PPFD (33.6 mol m~2) and f l u x density (1556 umol m~ 2s - 1) over the same exposure period. The weather on both days was s i m i l a r -sunny with some high cloud i n the afternoon. 3 4 TABLE 4 . Canopy l i g h t c h a r a c t e r i s t i c s measured with the chemical l i g h t meter. A l l PPFD data were measured over a 6 hour period on each day ( 1 0 . 0 0 - 1 6 . 0 0 h r s ) . I Q and I r e f e r to above and below canopy positions and are the means of 3 and 1 5 measurements res p e c t i v e l y . Date Stand density Canopy (x 1 0 sph) pos i t i o n PPFD mol m Cumulative Transmittance -2 d/I 0) J u l y 2 8 , 1 9 8 3 5.5 io I 3 6 . 6 1 5 . 2 5 0 . 1 4 2 4 io I 3 1 . 8 2 4 . 5 8 0 . 1 4 3 8 io I 3 2 . 9 0 5 . 3 9 0 . 1 6 8 3 io I 2 8 . 5 2 9 . 1 4 0 . 3 2 1 1 3 io I 3 2 . 3 5 7 . 2 7 0 . 2 2 J u l y 2 9 , 1 9 8 3 5.5 io I 3 8 . 0 4 6 . 3 3 0 . 1 7 2 4 io I 3 1 . 8 2 4 . 5 1 0 . 1 4 3 8 io I 3 5 . 2 9 5 . 8 5 0 . 1 7 8 3 io I 2 9 . 4 0 1 0 . 2 7 0 . 3 5 .113 io I 3 3 . 4 7 8 . 2 2 0 . 2 5 Over the two-day study period, i t was the 24K density which allowed le a s t l i g h t penetration (approx. 14%) and the 83K density which allowed most (approx. 33%). This i s not what one would have expected on the basis of density alone. If density were the only c r i t e r i o n f o r l i g h t attenuation then one would expect that at higher densities less l i g h t would penetrate through the canopy to ground l e v e l . This assumes, how-ever, increasing leaf area with increasing density. The plots used i n the l i g h t e x t i n c t i o n measurements showed a marked height reduction i n the 83 and 113K p l o t s . The f o l i a g e biomass or LAI of the plots should deter-mine l i g h t attenuation rather than density alone. As suggested by the l i g h t e x t i n c t i o n data, the highest LAI (7.25) was found i n the 24K plot (Table 5). S i m i l a r l y , l i g h t attenuation was least i n the 83K plot which carried an LAI of 2.76. The k values calcu-lated f o r the Beer-Lambert-Bouguer equation are shown i n Table 6. One-way analysis of variance showed no s i g n i f i c a n t difference between the mean k values from each of the two days of the experiment. The data presented i n Table 6 suggest that k values increased i n repressed stands Indicating that the stand architecture i n these stands resulted i n lower l i g h t penetration for a given LAI compared to more vigorous stands (Figure 7). The models i n Figure 7 suggest that the main differences i n extinc-t i o n c o e f f i c i e n t s l i e between the 5.5 and 24K stands and the 38, 83 and 113K stands. The rate of l i g h t e x t i n c t i o n was most marked with a cumula-t i v e leaf area index of less than 3 m2m~2. With increasing leaf area, the rate was slower and l e v e l l e d off when the cumulative leaf area exceeded 9 m2m-2. At higher leaf areas than t h i s , the r a d i a t i o n values below the canopy were about 7% of that above depending on stand density. 36 TABLE 5. Plot leaf area c h a r a c t e r i s t i c s Mean diameter Plot size Plot leaf area LAI Pl o t ID + SD (cm) (m2) (m2) (m2m~2^ 5.5K 7.25+2.44 20 137.6 6.9 24K 4.16+1.26 10 72.5 7.3 38K 3.07 + 0.9 10 52.4 5.2 83K 1.84 + 0.58 10 27.6 2.8 113K 1.90 + 0.53 10 40.6 4.1 TABLE 6. Light e x t i n c t i o n c o e f f i c i e n t s (k) Plot ID Date 5.5K 24K 38K 83K 113K J u l y 28th 0.282 0.267 0.345 0.412 0.368 July 29th 0.261 0.270 0.343 0.381 0.346 37 'A 0.0 0.2 0.4 0.6 0.8 1.0 Figure 7. Dependence of within stand l i g h t conditions on the shading leaf area. Data points represent measurements taken on two days, J u l y 28th and July 29th 1984. The models are estimated from the Beer-Lambert-Bouguer equation using the k values calculated f or the i n d i v i d u a l stand d e n s i t i e s . LAI Is given on a t o t a l leaf area basis for stand densities of 5.5K (A), 24K (o), 38K (•), 83K (•) and 113K (•). 38 In an attempt to examine the r e l a t i o n s h i p between needle morphology and l i g h t regime, the s p e c i f i c leaf area of current year f o l i a g e i n the lower crown p o s i t i o n was plotted against r e l a t i v e l i g h t i n t e n s i t y for a number of p l o t s . The r e l a t i v e l i g h t i n t e n s i t y measurements were calcu-lated using the models i l l u s t r a t e d i n Figure 7. The LAI values were calculated as before from the 1983 biomass plots (the same plots i n which the SLA measurements were taken). S p e c i f i c leaf area did not c o r r e l a t e w e l l with p r e v a i l i n g l i g h t conditions (Figure 8). The reason for t h i s lack of c o r r e l a t i o n may be found In a discussion of the stand structure. The r e l a t i v e l i g h t i n t e n s i t i e s calculated f o r Figure 8 may be true for the below-canopy conditions but do not adequately describe the l i g h t environment i n which these needles developed. F i r s t l y , i n the more widely-spaced stands (5K density), trees often carried l i v e branches below the ninth whorl (the crown p o s i t i o n from which SLA samples were taken for the 'lower crown'). In these stands e s p e c i a l l y , the l i g h t climate below the canopy d i f f e r e d greatly from that experienced at the ninth whorl. The problem was further accentuated by the vigour and more acute branch angle evident i n the lower density stands. Because of this 'upsweep' of branches, the current years f o l i a g e of the s i x t h and ninth whorls was often at a much higher p o s i t i o n i n the crown i n the 5K stands, r e l a t i v e to the 50K and 150K stands. Because of the improved l i g h t environment i n t h i s crown p o s i t i o n , current year's needles i n the low density stands did not develop as high a s p e c i f i c leaf area as would have been predicted. 39 180 - i 1 6 0 -O 1 4 0 -< _J IS) 1 2 0 -100 H— 0.0 0.2 0 . 4 "A 0.6 Figure 8 . S p e c i f i c leaf area i n d i f f e r e n t l i g h t regimes. I/IQ values are predicted from the equations described In Figure 7 while SLA values are for current year's f o l i a g e from the lower crown po s i t i o n s . 40 E. Conclusions From the ANOVA table and graphical i l l u s t r a t i o n s presented here i t can be concluded that f e r t i l i z e r , density, crown po s i t i o n and needle age clas s a l l had an ef f e c t on s p e c i f i c leaf area i n these young lodgepole pine stands. The SLA was most affected by needle age, probably as a resu l t of a change i n l i g n i n a l l o c a t i o n as needles aged. The effects of the other variables also show strong trends but may be more i n d i c a t i v e of changes i n leaf biomass brought about by these treatments than of dir e c t e f f e c t s of the variables themselves on SLA. The range of values reported here (72-176 cm 2g - 1) f o r SLA compare quite w e l l with those from the l i t e r a t u r e (83-196 cm 2g - 1) f o r the same species. Results from a high-density jack pine stand show a s i m i l a r range (84-189 cm^g L ) . The general e f f e c t s of the treatments also show si m i l a r trends to those reported i n the l i t e r a t u r e . F e r t i l i z e r e f f e c t s are s t i l l disputed among workers, r e s u l t s often being confounded by changes i n the l i g h t i n t erception of the canopy brought about by the treatment. The implications of these r e s u l t s f o r growth studies are important. The s t r a t i f i c a t i o n of a stand's f o l i a g e by needle age and crown po s i t i o n i s e s s e n t i a l f o r accurate pr e d i c t i o n of leaf area from dry weight. Omission of t h i s v a r i a t i o n could lead to serious bias i n estimates of leaf area. The SLA also varied with f e r t i l i z e r treatment and stand density and the v a r i a t i o n may be important i n c e r t a i n s i t u a t i o n s . The increase i n SLA i n the more suppressed stands In the present study may be an adaptation to Improve the s u r v i v a l of these trees at such high d e n s i t i e s , as suggested by Grime (1978). 41 Measurements of the below-canopy l i g h t climate indicate that l i g h t l e v e l s were higher (34% of above-canopy l e v e l s ) under the dense stand than under the less dense stand (14% of above-canopy l e v e l s ) even though l i g h t e x t i n c t i o n c o e f f i c i e n t s (Jc) increased i n repressed stands. LAI was reduced at higher stand d e n s i t i e s , however, and the proportion of l i g h t transmitted was described using the Beer-Lambert-Bouguer equation. Below-canopy l i g h t l e v e l s did not show the expected r e l a t i o n s h i p with s p e c i f i c leaf area and, i n f a c t , suggested that at higher l i g h t l e v e l s , s p e c i f i c leaf area increased. A change i n branch angle due to increased vigour i n trees from the lower stand densities i s suggested as a possible explanation for t h i s apparent c o n t r a d i c t i o n . 42 CHAPTER 5. STUDY COMPONENT 2: BIOMASS ALLOCATION A. Introduction The quantity of dry matter produced by forests has long been of i n t e r e s t to f o r e s t e r s , ecologists and plant p h y s i o l o g i s t s . More recently, the manner i n which t h i s dry matter i s allocated to f o l i a g e , branches, stems and roots has been evaluated (Kira and Shidei, 1967; Persson, 1980; Keyes and G r i e r , 1981; Pearson et a l . , 1984). Trees growing at high stand densities generally a l l o c a t e a greater proportion of t h e i r t o t a l above-ground biomass to stem production than do more open-grown trees ( B a s k e r v i l l e , 1973; Zavitkovski and Dawson, 1978; M i t c h e l l and Goudie, 1980). The l a t t e r authors have suggested that the subsequently increased respiratory surface area i n repressed lodgepole pine may be contributng to the reduced height found i n these stands. Less work has been done, however, on possible causes for t h i s s h i f t i n biomass a l l o c a t i o n to stemwood at high stand d e n s i t i e s . Changes i n wood anatomy and, i n p a r t i c u l a r , the capacity of the sapwood to store and conduct water have been suggested as possible explanations by Albrektson (1984) and Pearson et a l . (1984). In neither of these studies, however, were there any measurements on wood anatomy. In t h i s study component, ; some of these variables are investigated as i t i s f e l t that they may be important i n repression of lodgepole pine. More s p e c i f i c a l l y , t h i s chapter reports on experiments which: 1. Test the e f f e c t s of stand density and f e r t i l i z e r a p p l i c a t i o n on some general biomass c h a r a c t e r i s t i c s . 2. Examine the effect of stand density on resource a l l o c a t i o n between f o l i a g e , branches and stemwood. 43 3. Test the hypothesis that leader growth i n any year i s dependent on leader growth i n the previous year and that t h i s r e l a t i o n s h i p i s affected by stand density. 4. Test the hypotheses that leaf area/sapwood area ratios are dependent on stand density and tree s i z e . 5. Examine the e f f e c t s of stand density on wood anatomy. B. L i t e r a t u r e Review Measuring Biomass Production Accurate estimation of biomass production, and i n p a r t i c u l a r i t s dynamics, i s e s s e n t i a l i f one i s to measure fo r e s t productivity. Net primary pro d u c t i v i t y (NPP), the t o t a l amount of organic matter annually produced by a f o r e s t , i s often the only complete measure of forest dry matter production (Assman, 1970). This can be expressed i n terms of gaseous exchange as: NPP = GTP - Ra (7) where GTP i s gross primary production or t o t a l photosynthetic a s s i m i l a -t i o n for a year and Ra i s t o t a l metabolic r e s p i r a t i o n by green plants for the same year. The difference between these two terms i s the sensible (weighable) dry matter production. Both terms on the right-hand side of equation (7) are extremely d i f f i c u l t to measure, e s p e c i a l l y i n forest trees. Another method used to measure net primary productivity examines the sum of i t s components. Thus; NPP = AB + D + G (8) 44 where &B i s biomass increment over a year (above and below ground), D i s det r i t u s production (including m o r tality, l i t t e r f a l l , herb and f i n e root turnover) and G i s grazing (by above- and below-ground organisms) (Grier, 1979). These components and t h e i r r e l a t i v e proportions vary with s i t e , species, age, and time of year. Biomass increment i s greatest i n young stands and may become zero to negative i n overmature stands (Grier and Logan, 1977) while leaf biomass s t a b i l i z e s a f t e r canopy closure. Inversely, d e t r i t u s production i s r e l a t i v e l y small i n young stands but i s the major component of net production i n older stands (Fujimori et a l . , 1976). The woody component In detritus also increases as the stand ages. The f i n a l term i n the above equation, G, i s grazing. The magnitude of t h i s term i s extremely variable but i t may prove important i n c e r t a i n s i t u a t i o n s , e s p e c i a l l y on f e r t i l i z e d stands ( S u l l i v a n and S u l l i v a n , 1982). Mammal grazing can also be important i n the herb and shrub l a y e r s . As indicated above, each of the various components making up net primary productivity has an above-ground and a below-ground portion. The below-ground component has remained the lesser-explored of the two, p r i n c i p a l l y because of the d i f f i c u l t y i n studying t h i s area. Recent work has indicated that a substantial proportion of t o t a l ecosystem producti-v i t y occurs below-ground, pr i m a r i l y as f i n e roots (Agren et a l . , 1980; Grier et_ &!•, 1981; Keyes and G r i e r , 1981; Santantonio et_ a l . , 1977). However, much work s t i l l remains to be done i n t h i s f i e l d , p a r t i c u l a r l y i n r e l a t i o n to v a r i a b i l i t y i n f i n e root biomass due to s o i l nutrient and moisture regimes and ra t i o s of above-ground to below-ground p r o d u c t i v i t i e s . 45 For e i t h e r above-ground or below-ground components, a d i r e c t measurement or weighing of forest biomass on a large scale Is u n r e a l i s t i c . Estimates are therefore made on a sample of the population. Two main methods have been used as bases for these estimates. They are the Mean Tree method and Logarithmic Regression method. Although the former method may prove reasonable i t does have disadvantages. It does not i l l u s t r a t e the changing patterns of f o l i a g e d i s t r i b u t i o n among trees of d i f f e r e n t classes and thus f a i l s to predict the photosynthetic c a p a b i l i -t i e s of trees of varying s i z e (Madgwick, 1973). It i s also biased towards low estimates. The l a t t e r method estimates tree biomass on the basis of c o r r e l a t i o n between the amount of stem, branch, root, f o l i a g e , etc. of a tree and i t s stem diameter (Kira and Shidei, 1967). This method i s now preferred over the Mean Tree method. Maximum Size-density Relationships Work on forest y i e l d i n Europe i n the middle of t h i s century led to the two main theories r e l a t i n g f o r e s t production to stand density - the Moller theory and the Assman theory. The l a t t e r theory states that growth per unit area increases with increased stocking u n t i l optimal production i s reached at some definable density. Beyond that point production decreases (Assman, 1970). Moller (1946) developed the hypothesis that production increases with increased stocking u n t i l f u l l s i t e occupancy i s achieved. Beyond th i s point increased density does not affect the amount of growth but only i t s d i s t r i b u t i o n i . e . growth on a small number of large trees at low densities and on a large number of small trees at higher d e n s i t i e s . He further postulated that only at extremely high densities does production 46 decline (Moller, 1946). The reason for the drop i n production at these high densities i s due to increased surface area of boles and branches which might indicate that r e s p i r a t i o n could become l i m i t i n g . B a s k e r v i l l e (1965) examined dry-matter production i n immature balsam f i r (Abies balsamea (L.) M i l l . ) over a density range of approximately 1,700 - 12,400 sph. His conclusions did not agree with either those of Assman or Moller. Over the range examined, fo l i a g e biomass increased with increasing density. He also concluded that the "most e f f i c i e n t production of dry matter i s by the largest number of small crowns". Yoda and others (1963), i n examinations of competition-induced mortality i n various vegetable and cereal crops, developed the density e f f e c t law and the -3/2 power law of s e l f - t h i n n i n g . The density effect law i s concerned with the r e l a t i o n between stands of d i f f e r e n t density which started growing simultaneously and have continued to grow under s i m i l a r habitat conditions. The -3/2 power law describes a maximum s i z e -density r e l a t i o n s h i p applicable to stands of any age or s i t e . Yoda and co-workers observed that for low i n i t i a l planting densities there was no mortality, but as i n i t i a l densities increased the density of surviving plants at a f i x e d time after sowing approached a fixed maximum. F e r t i -l i z e r a p p l i c a t i o n increased growth rates but did not change maximum density for a given average plant weight. To quantify mean plant weight-density r e l a t i o n s h i p s Yoda et^ a l . (1963) also established plots i n several weed species. They found that i n s p i t e of differences i n age, stage of growth and environmental conditions, a single l i n e represented the plant size-density r e l a t i o n s h i p throughout the stands for each species. In a l l of the species examined the slope of the l i n e was -1.5 when the logarithms of mean plant weight 47 were plotted against logarithms of density. The r e l a t i o n s h i p was found to hold true for tree species also e.g. Abies sachalinensis (Masters.) and Betula spp. In natural stands of Pinus d e n s i f l o r a (Sieb. and Zucc.) at densities up to 50,000 sph the -3/2 power law applied to stem volume as well as weight. In B r i t a i n , Harper (1977) tested the -3/2 power law and found that i t f i t t e d quite well to volume/density data from Forestry Management Tables (Bradley et a l . , 1966). The slopes for the various species tested (both coniferous and deciduous) varied between -1.72 and -1.82. Another method of expressing above-ground biomass has been suggested by Kira and Shidei (1967). This parameter i s termed dry matter density and i s the biomass of a e r i a l shoots (expressed i n kg m - 2) divided by the height of dominant trees (m). In most forests t h i s dry matter density i s independent of stand height and tends to be about 1 to 1.5 kg m - 3. However, i n c e r t a i n shrub communities and dense stands of c o n i f e r saplings (e.g Abies sa c h a l i n e n s i s ) , dry matter densities of 10 to 15 kg m - 3 were reported. As part of the Canadian Forest Service's ENF0R programme, Peterson et a l . (1982) have used t h i s measure of biomass to assess the s u i t a b i l i t y f o r biomass harvest of various young tree and shrub stands i n Alberta, . Saskatchewan and Manitoba. Among the species examined was lodgepole pine. The pine (1.66 kg m~3 at age 8) c a r r i e d a higher dry matter density than aspen (Populus tremuloides Michx.) (0.72 kg m - 3), alder (Alnus rugosa (Du Roi) Spreng.) (0.82 kg m~ 3), white birch (Betula papyrifera Marsh.) (0.38 kg m~3) or jack pine (0.59 kg m~3) of s i m i l a r age. Of a l l the species examined only willow ( S a l i x spp.) carried a higher dry matter density (2.16 kg m - 3) at 8 years old. Over stands of varying d e n s i t i e s , lodgepole pine showed a general trend of increasing 48 dry matter density with age (maximum of 2.30 kg m - J at age 25 years). As mentioned e a r l i e r , K i r a and Shidei (1967) also referred to the increasing s i g n i f i c a n c e of resp i r a t o r y losses as stand density increased. They found that f o l i a g e r e s p i r a t i o n (per tree) increased r a p i d l y with tree s i z e but tended to approach a c e r t a i n asymptotic value i n very large trees. Respiration of woody organs however continued to increase at larger diameters. From the slopes of the diameter at breast height (dbh) - wood r e s p i r a t i o n curve, the authors then concluded that for small trees r e s p i r a t i o n of woody organs was proportional to t h e i r weight and that for larger trees i t i s proportional to t h e i r surface area. The range of dbh's examined i n the study was 5 to 100 cm. The importance of r e s p i r a t i o n losses i n dense stands of small trees was demonstrated when average measured r e s p i r a t i o n rate/tree weight was plotted against dbh. The range i n r e s p i r a t i o n rate was 65-8 mg CO2 k g - 1 fresh wt h r - 1 r e s p e c t i v e l y for the dbh range of 5-100 cm. This increased r e s p i r a t i o n i n stands of high density has already been suggested as one of the c r i t i c a l factors i n stagnation of lodgepole pine ( M i t c h e l l and Goudie, 1980). They found that, over a wide range of densities (5,000-800,000 trees/ha), bole surface area of the stands increased as the number of trees increased whereas fo l i a g e mass culminated and declined. This negative feedback loop, caused by the entire system slowing down due to r e s p i r a t i o n claiming a disproportionately large amount of the photosynthate seems to agree with the 'sink e f f e c t ' suggested by Sweet and Wareing (1966). This negative feedback on growth i s greatest when plants are closest together and suggests that a low metabolic sink demand 49 acts as an i n t e r n a l regulator of translocation from the leaves. This, i n turn, controls the rate of CO2 uptake. One method of increasing sink strength i s through f e r t i l i z a t i o n , thus leading to better u t i l i z a t i o n of the carbohydrate reserves, given that sink strength i s l i m i t i n g growth (Ericsson, 1979). Few published reports have been found i n the l i t e r a t u r e r e l a t i n g extremely high density to height and diameter growth, mortality and bio-mass production i n lodgepole pine. However some work has been done on a close associate, jack pine, a species with which lodgepole pine frequent-l y hybridizes. Zavitkovski and Dawson (1978), i n attempting to i d e n t i f y a combination of spacing and r o t a t i o n regimes to maximize biomass produc-t i o n , established plantations of jack pine at d i f f e r e n t d e n s i t i e s . The spacings used were equivalent to approximately 27,000, 108,000 and 191,000 sph and are within the range of the present study. At age seven the e f f e c t of spacing on mean height growth differences was s i g n i f i c a n t with mean height increasing as i n i t i a l spacing was increased. A s i m i l a r i n s i g n i f i c a n t trend was found for dominant height. The reduction i n height at the closer spacings i n the l a t t e r work was ascribed to c r i t i c a l s o i l moisture shortages. However, i n the work described by Zavitkovski and Dawson the plantations were grown under intensive care including f e r t i l i z a t i o n and i r r i g a t i o n . A severe competition for l i g h t was suggested as the primary cause of t h i s marked height reduction. On a sunny day, l i g h t under a l l three densities was less than 1% of f u l l sunlight, below the photosynthetic compensation point for the species. The effect of i n i t i a l spacing on mortality was also very s i g n i f i -cant. At age seven the percentage s u r v i v a l was 49, 68 and 94 for the 50 191,000, 108,000 and 27,000 sph established r e s p e c t i v e l y . The authors do not say so but i t would seem that the i r r i g a t i o n and f e r t i l i z e r a p p l i c a -t i o n would bring forward the age at which competition would begin and thus increase mortality. Data on above-ground biomass showed that at age 7 the highest biomass l e v e l s (t h a - 1 ) were i n the intermediate spacing. However, changes i n biomass accumulation were s t i l l occurring and the authors postulated that i n a few years the widest spacing would have the highest t o t a l biomass. This i s of i n t e r e s t i n comparison with the work of M i t c h e l l and Goudie (1980). They found that i n an 18-year-old stand of lodgepole pine the highest biomass l e v e l s occurred at a density intermediate between the extremes of the wide range under study. Perhaps i n the jack pine study t h i s whole process has been accelerated by the f e r t i l i z a t i o n / i r r i g a t i o n treatment. Dry weights for the jack pine (approximately 50 t h a - 1 for a l l spacings at 7 years) were higher than those reported for the lodgepole pine (40 t h a - 1 at 50,000 sph at 18 years). In the jack pine stands, needle biomass increased r a p i d l y during the f i r s t 4 to 6 years i n a l l densities and then l e v e l l e d o f f between 10 and 13 t h a - 1 . A f t e r 6 years the needle dry weight had already begun to decline i n the clo s e s t spacing. The authors hypothesized that no further increases would take place i n leaf biomass even at the widest spacing as already there was such a small percent of f u l l sunlight penetrating to ground l e v e l . I r r i g a t i o n and f e r t i l i z a t i o n increased leaf biomass s u b s t a n t i a l l y over stands treated i n the usual way. Recently, Worrall et a l . (1985) used a r e c i p r o c a l grafting technique between vigorous and repressed trees to i d e n t i f y a possible cause of the condition of growth repression i n lodgepole pine. The authors tested the 51 hypothesis that growth repression was not caused by environmental factors per se, but by the i n d i r e c t e f f e c t of the environment on a p i c a l growth through hormonal a c t i v i t y . Growth was found to be controlled e n t i r e l y by the type of rootstock however, and the hypothesis was r e j e c t e d . A s i m i l a r type of experiment had previously been carried out i n B r i t a i n using sugar beet and spinach beet (both v a r i e t i e s of Beta  v u l g a r i s ) but with a d i f f e r e n t i n t e r p r e t a t i o n of the r e s u l t s (Thome and Evans, 1964). Sugar beet has a larger storage root and greater a s s i m i l a -t i o n rate than spinach beet. The experimenters again used r e c i p r o c a l grafts ( i n a l l four possible combinations) to determine whether the larger root was a r e s u l t or a cause of the greater a s s i m i l a t i o n rate i n the sugar beet. Results showed that grafts with sugar beet roots had a greater net a s s i m i l a t i o n rate than grafts with spinach beet roots, i r r e s -pective of the type of scion used. As i n the lodgepole pine experiment, therefore, the growth was governed e n t i r e l y by the type of rootstock. The authors interpreted the r e s u l t s to suggest that sugar beet roots increased the net a s s i m i l a t i o n rate of scions grafted on to them by providing a more e f f i c i e n t 'sink' for assimilates than spinach beet roots. Could the same phenomenon be a cause i n the repression of lodgepole pine? L i t t l e work has been done on the e f f e c t s of high stand density on the amount of root biomass, and the data that are available for lodgepole pine seems to be c o n f l i c t i n g . M i t c h e l l and Goudie (1980) found that root biomass followed the same pattern as above-ground biomass - increasing up to a stand density of 50,000 and thereafter dropping at higher stand d e n s i t i e s . In t h e i r study, however, much of the f i n e root biomass may have been l o s t because of the 'hydraulic excavation' method used to determine the below-ground biomass component. Over the density range examined, the proportion of biomass allocated to roots increased from 9% (at 5,000 sph) to 15% (at 800,000 sph). In older stands (>75 years) i n 52 Wyoming, the percentage allocated to roots was greater (21-33%) but showed a s i m i l a r increase with stand density (Pearson et a l . , 1984). A root-pruning experiment i n a thinned stagnant stand, currently being c a r r i e d out by Worrall e_t a l . (1985) may help to answer some of the questions on what i s happening i n the root systems of these stands. Biomass of Lodgepole Pine Biomass estimates for lodgepole pine have been investigated by many workers In North America (Johnstone, 1971; Hanson, 1975; Gary, 1976; Singh, 1982; Pearson et a l . , 1984), Europe (Cannell, 1974) and New Zealand (Nordmeyer, 1980). Most of these studies, however, have concen-trated on older stands (70 years and o l d e r ) . Besides the work of M i t c h e l l and Goudie (1980) already referred to, only Hanson (1975) and Peterson e_t a l . (1982) have examined biomass a l l o c a t i o n i n younger stands i n North America. Although some of these workers have included a range of densities i t i s d i f f i c u l t to know i f the stands were stagnated because of the d i f f e r -ences i n age and lack of height information. Gary (1976) did f i n d a decrease i n mean height from 10.8 m to 7.5 m over a density range of 2000 to 25,000 stems per ha i n an 80-year-old stand i n Wyoming. Pearson et a l . (1984) s i m i l a r l y noted a drop i n height i n the denser stands of t h e i r study. They suggested that 'stand density i s an important factor c o n t r o l l i n g the biomass dimensions of lodgepole pine f o r e s t s . ' An important finding of t h e i r work was a s h i f t i n biomass a l l o c a t i o n from aboveground to belowground with increasing density. Their study i s one of the few i n lodgepole pine to include f i n e root 53 biomass i n t h e i r estimates. A useful review of biomass estimators from other lodgepole pine studies i s also given. In younger lodgepole pine stands (7-9 yrs) i n Western Canada, Peterson et al_. (1982) found that dominant height dropped from 3.81 m at 41,000 sph to 1.43 m at 338,000 sph. Their regression equations with the highest r 2 values had mean age and number of stems per hectare as the independent v a r i a b l e s . Diameter and height proved to be of low r e l i a -b i l i t y as estimators of biomass. In e f f o r t s to improve tree growth, many studies have been carried out on spacing of lodgepole pine (Alexander, 1965; Dahms, 1971; Cole, 1975; Johnstone, 1981a,b, 1982). The most dramatic e f f e c t of spacing i s usually on diameter growth. Height growth response i s more e r r a t i c , however, and depends on various stand and s i t e f a c t o r s . Even a f t e r 10 years, Johnstone (1982) found that spacing effects on height growth were "inconclusive and undramatic." The same author also emphasized the importance of stand age i n determining responses to thinning. As stand age increases the opportunity of gaining post-treatment response declin e s . Leaf Area/Sapwood Area Relationships Leaf area i s d i f f i c u l t to measure d i r e c t l y i n c o n i f e r s . However, allometric methods have been developed r e l a t i n g the amount of f o l i a g e to more e a s i l y measured parameters of growth such as diameter. Much of the o r i g i n a l work done i n t h i s f i e l d was carried out from analysis of various vascular plants (Shinozaki et a l . , 1964a, 1964b). A close c o r r e l a t i o n between the d i s t r i b u t i o n of" leaf biomass and non-photosynthetic organs at respective horizons above the ground was shown. This led to a new 54 i n t e r p r e t a t i o n of plant form, i n which the stems and branches consisted of a number of unit pipes each supporting a unit amount of photosynthetic organs. They thus proposed a new method for estimating leaf biomass from the cross-sectional area of the trunk at the height just below the lowest l i v i n g branch. They concluded that as you move down the stem, away from the crown, an increasing proportion of the vascular system was non-conducting. They did not, however, quantify t h i s r e l a t i o n s h i p . This concept has since been used to estimate the canopy leaf area from knowledge of the sapwood area at breast height (Grier and Waring, 1974; Whitehead, 1978; Waring et a l . , 1982). The l a t t e r authors examined ten conifer species, including lodgepole pine, i n western Oregon and tested the a p p l i c a b i l i t y of the pipe model theory i n predicting canopy leaf area. They found excellent c o r r e l a t i o n s between sapwood cross-s e c t i o n a l areas (measured at breast height) and t o t a l leaf areas. They also compared c o e f f i c i e n t s of leaf area:sapwood area for each species sampled at breast height and at the base of the crown. These c o e f f i -cients were not s i g n i f i c a n t l y d i f f e r e n t . The l a t t e r could be expected since a l l of t h e i r sample trees were small, with many having l i v e crowns down to near breast height. At any given sapwood area, lodgepole pine c a r r i e d the lowest t o t a l leaf area of a l l species examined. S i m i l a r l y , comparisons between lodgepole pine and other conifers i n r e l a t i o n to projected leaf area:sapwood area r a t i o s (m2cm - 2) show almost a f i v e f o l d range. Mean values from three studies (Kaufmann and Troendle, 1981; Whitehead, 1981; Waring et a l . , 1982) show lodgepole pine to have a r a t i o of 0.17 compared to 0.25 for ponderosa pine, 0.32 for Engelmann spruce, 0.54 f o r Douglas-fir, and 0.75 for subalpine f i r . In general, the larger c o e f f i c i e n t s are associated with taxa that grow i n mild 55 climates or that represent shade tolerant species. Species adapted to d r i e r environments show progressively smaller c o e f f i c i e n t s . This i s i n agreement with Running et a l . (1975) who stressed the importance of a low l e a f area to sapwood area r a t i o i n trees growing i n drought prone areas. Waring et al_. (1981) have developed t h i s further and shown a strong negative r e l a t i o n s h i p between growth e f f i c i e n c y (stemwood production per unit of leaf area, E) and leaf area index i n Douglas-fir. Growth e f f i c i e n c y declined from almost 250 g m~2y~l to 60 g m~2y-l with Increasing levels of leaf area index. The reasons suggested for t h i s drop i n E have been that photosynthetic e f f i c i e n c y i s reduced and stemwood production has a lower p r i o r i t y than the growth of many other tissues (Waring, 1983). Pearson (1982) recently substantiated some of the findings of the above authors for lodgepole pine. Nevertheless, he stated that the leaf area/sapwood area r e l a t i o n s h i p was strongly dependent on stand density and that the above figures for leaf area/sapwood area r a t i o s were s i m i l a r to his estimates only i n stands of intermediate density. For dense stands (> 5000 sph), he found the r a t i o to be approximately 0.08 m - 2cm - 2. In the denser stands he also found sapwood area to be marginally i n f e r i o r to basal area as a predictor of f o l i a g e biomass. In Douglas-fir, the leaf area/sapwood area r e l a t i o n s h i p has been found to be affected by f e r t i -l i z e r treatment as well as by thinning (Brix and M i t c h e l l , 1983). Caution must therefore be used i n extrapolating such r e l a t i o n s h i p s between s i t e s . 56 In Scotland, Whitehead et a l . (1984) found that introduction of stemwood permeability improved the o v e r a l l r e l a t i o n s h i p between sapwood area and leaf area f o r Sitka spruce (Plcea s i t c h e n s i s (Bong.) Carr.) and lodgepole pine. Using a p h y s i o l o g i c a l analysis based on Darcy's law, they also suggested that the r a t i o of fol i a g e area to sapwood area for a tree was proportional to sapwood permeability and to the water po t e n t i a l gradient i n the stem and inversely proportional to the product of the mean vapour pressure d e f i c i t of the a i r at the s i t e and a 'mean weighted average shoot conductance. 1 C. Methods and Materials Plot l o c a t i o n , vegetation, s o i l s , e t c . have already been described i n e a r l i e r chapters. The method used i n the estimation of biomass com-bined double sampling with regression (Cochran, 1963) with a dry-to-fresh weight r a t i o technique (Brix, 1983). The biomass harvest was carr i e d out i n the plots i n the f a l l of 1983 and for each plot Involved three i n t e n s i t i e s of sampling. Table 7 shows the c h a r a c t e r i s t i c s measured at each i n t e n s i t y . Harvested trees i n the most detailed inten-s i t y of sampling (1°) were chosen to represent a range of diameter clas s e s . The number of trees sampled at each i n t e n s i t y varied with plot density (Table 8). Totals of 88 and 198 trees were sampled i n the 1° and 2° i n t e n s i t y r e s p e c t i v e l y . A f t e r the trees i n the 1° and 2° sampling were f e l l e d , whole trees were returned to the f i e l d - s t a t i o n (less than one hour's drive from the plots) f o r measurement. For both i n t e n s i t i e s of sampling, the fresh weight of a l l branches was obtained for each whorl. In the 1° sampled TABLE 7. Tree and plot c h a r a c t e r i s t i c s measured at each sampling i n t e n s i t y . Intensity C h a r a c t e r i s t i c 1° 2° Diameter (base) * * Diameter ( L . C . ) a * * Height ( t o t a l ) * * Height ( L . C . ) b * * Number of l i v e whorls * * Number of l i v e ' f a l s e ' whorls * * Number of dead whorls c * * Annual height increment ('83, '82, '81) * * Whorl fresh weight * * Number of branches/whorl * * Number of needle age classes/branch * Foliage branch biomass by age class * Stem fresh weight * * Dead branch weight * Diameter measured at the base of the l i v e crown. Height measured from the ground up to base of the l i v e crown. Any whorl containing no l i v e f o l i a g e . 58 TABLE 8. Number of harvested trees per plot at each sampling intensity. Nominal Plot s i z e Number of harvested trees Total number of density m2 1° 2° 3 ° a trees/plot 5K 20 3 — 7 10 2 OK 20 5 3 32 40 5 OK 10 5 5 40 50 10 OK 10 5 15 80 100 150K 10 5 25 120 150 a Approximate numbers only, varied with actual plot density. 5 9 trees, the r a t i o of dry-to-fresh weight was determined, by needle age c l a s s , for f o l i a g e and branchwood for one representative branch per whorl. This r a t i o was then used f o r conversion from f r e s h to dry weights for these biomass components for the remaining branches. A f t e r fresh weighing, e n t i r e stems were sectioned and dried and the r a t i o of dry-to-fresh weight determined. Fresh and dry weights were also measured f o r dead branches ( i . e . carrying no l i v e f o l i a g e ) on a l l trees from the 1° sampling i n t e n s i t y . No dry weight measurements were taken on samples from the 2° i n t e n s i t y . On completion of the 1° and 2° harvests, the remaining l i v e trees i n each plot were f e l l e d and measured for d i a -meter and height. The number of dead trees were then counted. After drying, sapwood area (at ground l e v e l ) was measured. No heartwood could be v i s i b l y distinguished i n the samples and staining with 0.1 N f e r r i c n i t r a t e (USDA, 1962) confirmed that the samples contained only sapwood. Stem analysis of height increment since establishment was ca r r i e d out for each tree i n the 1° sampling i n t e n s i t y ( t o t a l of 88 t r e e s ) . Leaf area was estimated from f o l i a g e biomass and previously c a l c u -lated s p e c i f i c leaf area data. The f o l i a g e biomass (g) was f i r s t l y p a r t i t i o n e d into needle age class (current, 1-year-old, 2-year-old, 3-year-old and older) and crown p o s i t i o n (upper, middle and lower). These figures were then m u l t i p l i e d by the appropriate s p e c i f i c leaf area values (cm2g~l) t o give weighted leaf area per tree. Using either sapwood area or basal area as single predictors, leaf area was then estimated from simple l i n e a r regression models. For the above-ground biomass estimations, the type of independent variable chosen depended on whether the equations were to be used on the 60 2° or 3° sampling i n t e n s i t i e s . For those to be used on the 2° data, the independent variables tested included diameter (D^,), diameter at the base of the l i v e crown ( D c ) , height (H), crown length (CL), D^2H and ( D c ) 2 H . Independent variables for use with the 3° data were more l i m i t e d and were D b, H and D b 2H. For both data sets, the s e l e c t i o n of the independent variables for the regression models used the backward, stepwise regression method (Draper and Smith, 1966). The MIDAS programme (Fox and Guire, 1976) was used for t h i s variable s e l e c t i o n procedure. Separate regression equations were calculated f or low (5K), mid (20K, 50K) and high (100K, 150K) stand d e n s i t i e s . Both c o r r e l a t i o n c o e f f i c i e n t ( r 2 ) and standard error (SE) were considered together i n i n t e r p r e t i n g predictor p r e c i s i o n . Where predicted values calculated from the component equations did not sum to the predicted values calculated from the t o t a l equations the same model f o r the component and t o t a l weights was used - even i f some of the terms were not s i g n i f i c a n t . This avoided the problem of 'non-a d d i t i v i t y ' caused by the non-significant terms being dropped from the various models (Kozak, 1970). Non-additivity could have been a problem i n the present study as many of the components were to be discussed i n terms of percentages rather than dry weights. In analysing the e f f e c t s of density and f e r t i l i z e r (and their i n t e r -actions) on various dependent variabl e s , treatment effects were p a r t i -tioned and trend analysis was applied ( L i t t l e , 1981). This technique, often referred to as 'orthogonal comparisons', p a r t i t i o n s the treatment sum of squares Into l i n e a r and quadratic components for each factor and for the i n t e r a c t i o n of fa c t o r s . Regression analysis (again using the 61 backward, stepwise method) was then used f o r the s e l e c t i o n of s i g n i f i c a n t variables i n the equation. To examine the e f f e c t s of stand density on wood anatomy, trees were selected from the c o n t r o l ( u n f e r t i l i z e d ) plots i n each nominal density c l a s s . One tree per class was chosen from the middle diameter class range i . e . representing a tree of intermediate-codominant height status. Oven-dry discs were selected from ground l e v e l i n each tree and r a d i a l cross-sections (Including the pith) were removed for the subsequent scanning. Various wood anatomical c h a r a c t e r i s t i c s were then measured aft e r the sections had been extracted i n alcohol/benzene overnight. A computerized scanning densitometer system was used f o r the measurements, data-acquisition and processing. The basic technique used i n X-ray densitometry projects a beam of X-radiation through the wood section onto a sheet of X-ray f i l m . This i s then developed and scanned on a densitometer that converts the f i l m density of the wood image to plotted or d i g i t a l form. For each year scanned, the programme used measured and printed distance from the p i t h , r i n g width, earlywood width, latewood width, ring density, earlywood density, latewood density, minimum ring density and maximum rin g density. Percent latewood values were based on s p e c i f i c density l e v e l s (greater than 0.54 g cm3) and not on the c l a s s i c a l Mork d e f i n i t i o n (Mork, 1928). A l l densitometer measurements were ca r r i e d out at the Western Forest Products Laboratory i n Vancouver and a more detailed d e s c r i p t i o n of methods used are given i n Parker et a l . (1980). 62 D. Results and Discussion 1. General Production As indicated e a r l i e r , actual plot density varied within nominal density classes and ranged from 3500-8000 sph for the 5K c l a s s , 41,000-54,000 sph for the 50K class and 82,000-109,000 sph for the 150K class (Table 9). In the following presentation of r e s u l t s and discussion therefore, these nominal density classes (5K - 150K) should be taken only as i n d i c a t i v e of low, intermediate and high stand d e n s i t i e s . Where possible, data w i l l be presented on an i n d i v i d u a l plot basis, using actual plot d e n s i t i e s . Height Increasing stand density reduced mean tree height over the range of densities Included i n the study (3,500-109,000 sph) (Table 9 and Figure 9). Equation 9 shows the s i g n i f i c a n t (at the 0.05 l e v e l ) variables remaining i n the regression equation a f t e r backward stepwise a n a l y s i s . Mean Height (m) = 5.071 - 0.341 x 10~ 4(D) + 0.125 x 1 0 - 1 ( F ) - 0.454 x 1 0 ~ 4 ( F 2 ) - 0.156 x 10~ 6(D x F) + 0.601 x 1 0 ~ 1 A ( D 2 x F 2 ) (9) In equation 9, D refers to stand density (sph) and F to f e r t i l i z e r l e v e l (kg N h a - 1 ) . The upper and lower l i m i t s used f o r each variable i n the regression equation were 3,500-109,000 sph for stand density and 0-200 kg N h a - 1 for f e r t i l i z e r l e v e l . The analysis of variance table f o r equation 9 i s shown i n Appendix C . l . The regression was s i g n i f i c a n t at the 0.0001 l e v e l with r 2 = 0.98 and SE = 0.245. Extrapolation beyond these l i m i t s may not be v a l i d and, for example, at stand densities of less than 3500 sph i t i s expected that mean height w i l l not continue to 63 TABLE 9. General plot c h a r a c t e r i s t i c s . Plot ID a Number stems/ha Mean height (m) Mean diameter (cm) Plot basal 2 -1 area m ha 5K 111 112 211 212 311 312 8,000 6,500 6,500 6,000 3,500 5,500 4.97 4.77 5.65 5.61 5.71 5.00 8.37 8.66 8.79 9.42 10.69 8.77 48.41 41.09 41.82 45.36 32.22 37.55 2 OK 5 OK 20K 121 122 221 222 321 322 20,500 48,000 54,000 43,000 42,000 41,000 43,000 4.34 3.42 3.16 3.75 3.98 3.94 3.24 4.51 3.23 3.28 3.50 3.75 3.75 3.17 36.30 43.92 50.60 46.72 51.11 49.20 37.43 100K 150K 10 OK 131 132 231 232 331 332 81,000 109,000 99,000 83,000 82,000 84,000 100,000 2.05 1.59 1.75 2.27 1.94 1.74 1.77 1.96 1.66 1.78 2.14 2.05 1.93 1.81 26.34 25.52 26.37 32.36 30.34 25.76 27.36 a Code e.g. I l l refers to: l e v e l of f e r t i l i z e r applied ( 1 = CTRL, 2 = 100 kg N h a - 1 , 3 = 200 kg N h a - 1 ) nominal density c l a s s (1 = 5K, 2 = 50K, 3 = 150K r e p l i c a t i o n (1 = Rep. 1 , 2 = Rep. 2). 64 Figure 9. Treatment e f f e c t s on mean height. Curves are f i t t e d using equation 9. 65 increase but w i l l ' f l a t t e n out'. Figure 9 demonstrates that the decrease i n mean tree height with increasing stand density i s quite l i n e a r over the e n t i r e range of density classes examined. M i t c h e l l and Goudie (1980) found that height remained unaltered by density up to approximately 50,000 sph. At stand densities greater than t h i s , however, height was reduced. Their work, however, looked, not at mean height, but at top height, defined as the mean height of the 100 trees of greatest diameter per hectare. With increasing stand density i t would be expected that the greater number of intermediate and suppressed trees would ' p u l l down' the mean height compared to the top height. Figure 10 i l l u s t r a t e s the e f f e c t of stand density on top height for the present study. The curve i s approaching that found by M i t c h e l l and Goudie and shows that, although top height i s decreasing over the entire range of densities examined, i t drops quite sharply at densities greater than 50,000 sph. The decrease i n top height over the 5,000-50,000 sph range (not found by M i t c h e l l and Goudie) may be explained by the d i f f e r -ence i n stand age between the two studies. Perhaps at age 18, repression of top height had not yet begun i n the 50K density range. At age 23 (the present study), however, a stand density of 50,000 sph was s u f f i c i e n t to cause some reduction i n top height. This suggests that stands may grow into a repressed state. The difference between the two studies i s also probably affected by the measure of stand density - M i t c h e l l and Goudie used the density established while the present study used the standing density. Further comparisons between the two studies may be complicated by difference i n s i t e . The above comments, however, do i l l u s t r a t e that any 66 120 Stand Density (sph 10 ) Figure 10. E f f e c t of stand density on top height. Top height defined as the mean height of the two largest diameter trees per p l o t . F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N ha" 1 (O) and 200 kg N h a - 1 (A). 67 d e f i n i t i o n of repression i n terms of height growth must be q u a l i f i e d by stand age and method of expression of height growth (mean top height). Diameter Analysis of variance for stand density and f e r t i l i z e r l e v e l on mean diameter indicated that neither f e r t i l i z e r (three years a f t e r a p p l i c a -t i o n ) or i t s i n t e r a c t i o n s had any e f f e c t , the s i g n i f i c a n t variables being D and . When the model was plotted, however, i t did not f i t the measured data, p a r t i c u l a r l y at the higher stand d e n s i t i e s . A d i f f e r e n t model was therefore generated, incorporating a D^ v a r i a b l e , to improve the o v e r a l l f i t (Equation 10). Diameter (cm) = 10.743 - 0.308 x 10~ 3(D) + 0.387 x 1 0 - 8 ( D 2 ) - 0.168 x 1 0" 1 3(D 3) (10) This l a t t e r model was s i g n i f i c a n t at the 0.0001 l e v e l with r 2 = 0.98 and SE = 0.512. The analysis of variance for the regression equation i s given i n Appendix C.2. Figure 11 demonstrates the density e f f e c t on mean diameter. Basal Area Basal area (m2 h a - 1 ) , unlike height and diameter, does not show as dramatic a decrease with increasing stand density (Figure 12). Basal area increased up to a stand density of approximately 50,000 sph and only then declined. The increase i n the number of stems per hectare between 5,000-50,000 obviously compensates s u f f i c i e n t l y to maintain basal area despite the large drop i n diameter between these two density classes. Figure 11. E f f e c t of stand density on mean diameter (measured at ground l e v e l ) . F e r t i l i z e r l e v e l s are: 0 kg N ha" 1 (•), 100 kg N ha" 1 (o) and 200 kg N ha" 1 (A). The curve i s calculated from equation 10. 6 9 Figure 12. E f f e c t of stand density on basal area (measured at ground l e v e l ) . F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N h a - 1 (o) and 200 kg N ha" 1 (A), the curve i s calculated from equation 11. 70 In the extremely high stand densities (80,000-100,000 sph) however, t h i s compensation i s not s u f f i c i e n t and basal area declines. Like diameter, basal area i s not affected by f e r t i l i z e r or i t s i n t e r a c t i o n with density. Equation 11 shows the s i g n i f i c a n t terms as the constant term and D 2. Basal Area (m 2ha - 1) = 43.957 - 0.172 x 10~ 8(D 2) (11) This equation i s s i g n i f i c a n t at the 0.001 l e v e l with r 2 = 0.54 and SE = 6.302. The analysis of variance for t h i s equation i s shown i n Appendix C.3. Live Crown Ratio Figure 13 shows the e f f e c t of stand density on l i v e crown r a t i o (defined as the r a t i o of crown length to tree height). At low stand d e n s i t i e s , trees are carrying l i v e crown on aproximately 80 percent of t h e i r t o t a l height. This r a t i o i s reduced to 40 percent at extremely high stand d e n s i t i e s . The ANOVA table (see Appendix C.4) and equation 12 suggest that l i v e crown r a t i o was not effected by f e r t i l i z e r a p p l i c a t i o n and that the r e l a t i o n s h i p was described by a D 2 r e l a t i o n s h i p : Live crown r a t i o = 0.80 - 0.693 x 10~ 5(D) + 0.329 x 1 0 _ 1 ° ( D 2 ) (12) The regression equation had an r 2 = 0.92, SE = 0.41 and was s i g n i f i c a n t at the 0.0001 l e v e l . Gary (1976) measured the same r a t i o for 80 year-old lodgepole pine and found that the r a t i o decreased from 0.58 i n a thinned stand to 0.35 i n an adjacent 'dog h a i r ' stand growing at about 25,000 sph. Figure 13. E f f e c t of stand density on l i v e crown r a t i o (defined as the r a t i o of live-crown depth to t o t a l tree height). F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N h a - 1 (o) and 200 kg N h a - 1 (A). Curve i s f i t t e d from equation 12. 72 M o r t a l i t y The type of mortality found i n the plots was of two types. Most plot s of a l l densities contained dead trees with p a r t i a l crowns"of dead f o l i a g e . Other p l o t s , e s p e c i a l l y i n the higher d e n s i t i e s (100K and 150K) contained many trees which had had t h e i r e n t i r e upper stem (including crowns) removed. From the s i z e of the dead trees, i t was estimated that they had mostly died i n the f i v e to ten years before the harvest (1983). This l a t t e r damage was probably caused by mammals, e s p e c i a l l y snowshoe hares (Lepus americanus Erxleben) over the winter when snow depth e f f e c -t i v e l y raised the 'ground l e v e l ' and enabled these mammals to browse at heights not normally possible during the summer. For the present discussion, mortality i s defined as the number of trees k i l l e d by e i t h e r method, divided by the t o t a l number of trees ( l i v e + dead) i n the plot and expressed as a percentage. Figure 14 shows the . e f f e c t of stand density on mortality. The ANOVA table (Appendix C.5) and equation 13 show that t h i s mortality r e l a t i o n s h i p i s described by a 2 D r e l a t i o n s h i p and that f e r t i l i z e r a p p l i c a t i o n had no e f f e c t on mortality. M o r t a l i t y (%) = 7.67 + 0.362 x 10~ 8(D 2) (13) The regression equation has an r 2 = 0.84, SE = 6.38 and i s s i g n i f i c a n t at the .0001 l e v e l . M o r t a l i t y ranged from approximately 10% i n the lowest density stands to 50% i n the highest density. L i t t l e data are available i n the l i t e r a -ture for comparison. In a 7 year-old jack pine plantation, Zavitkovski and Dawson (1978) reported s u r v i v a l s of 94%, 68% and 49% i n stands i n i t i a l l y established at 27,000, 107,000 and 190,000 sph, r e s p e c t i v e l y . Despite the difference i n age between t h e i r stands and those of the 73 Stand Density (sph 103) Figure 14. E f f e c t of stand density on mortality. Mortality i s defined as the number of l i v e trees per plot divided by the t o t a l number ( l i v e plus dead) and expressed on a percent basis. F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N h a - 1 (o) and 200 kg N ha" 1 (A). The curve i s f i t t e d from equation 13. 74 present study mean height i n the jack pine range from 3-3.5 m as the plantations were frequently watered and f e r t i l i z e d . True mortality (related to the number of trees i n i t i a l l y established) i s d i f f i c u l t to estimate i n the present lodgepole pine stands, e s p e c i a l l y i n the higher d e n s i t i e s . Equation 13 suggests that D 2 alone i s contributing to mortality and that f e r t i l i z e r i s not increasing the mortality %, even i n the highest density p l o t s . Perhaps mortality, three years a f t e r f e r t i l i z a t i o n , has not yet begun to be affected by the f e r t i l i z a t i o n . 2. Component and T o t a l Dry Weight  Tot a l Dry Weight The regression equations used i n dimensional analysis for the 2° and 3° sampling are shown i n Tables 10 and 11 re s p e c t i v e l y . Equations f o r use i n the 2° sampling i n t e n s i t y show higher r 2 and lower standard error values than those for s i m i l a r density ranges i n the 3° sampling i n t e n s i t y because of the extra independent variables (D c and CL) ava i l a b l e i n the former sampling scheme. The regression equations i n Tables 10 and 11 include only the s i g n i -f i c a n t independent variables a f t e r the elimination process (backward, stepwise). A l l equations were s i g n i f i c a n t at the .0001 l e v e l with r 2 values ranging from .94 to .99. Plots of residuals vs. the i n d i v i d u a l independent variables for a l l densities combined are shown i n Appendix C.6. The problem of heterogeneity was reduced by developing separate sets of equations f o r the low, intermediate and high stand d e n s i t i e s . Using these two sets of equations and the 'weighed' biomass from the 1° sampling scheme, plot t o t a l s were calculated and are shown i n Appendix 75 TABLE 10. Regression equations used in dimensional analysis for the 2° sampling i n t e n s i t y . A l l equations are s i g n i f i c a n t at the .0001 l e v e l . Stand a J, c 2 density Component Equation r S.F.. 5K Total above-ground - 1564.7 + 739.5(D.) - 1487.0(D ) + 40.7(D 2H) .98 548.7 D C D 20K, 50K Total above-ground - -320.7 + 311.1(D ) + 13.0(D 2H) .99 127.6 C D 100K, 150K Total above-ground - -13.0 + 84.2(H) -133.2(CL) + 46.1(D 2H) .98 30.7 c TABLE 11. Regression equations used in dimensional analysis for the 3° sampling Intensity. A l l equations are s i g n i f i c a n t at the .0001 l e v e l . a b c 2 Stand density Component Equation r S.E. 5K Total above-ground - 754.3 + 16.9(D 2H) .94 90 5.3 D 20K, 50K Total above-ground - -533.4 + 317.6(D.) + 11.3(D 2H) .98 138.5 D D 100K, 150K Total above-ground - 26.9 + 23.4(D 2H) .96 37.8 D 8 Stand density " Nominal stand density. b Total above-ground dry weight (g) - branches + stems + f o l i a g e . c Abbreviations are Dj, - diameter, cm (ground l e v e l ) ; D c diameter at the base of the l i v e crown, cm; H • height, m; CL • l i v e crown length, m. 76 > C.7. Total above-ground biomass i s shown per plot and per ha (taking into account the va r i a t i o n s i n plot s i z e ) . Total above-ground biomass (t h a - 1 ) i s also shown i n Figure 15. It was not affected by f e r t i l i z e r or i t s i n t e r a c t i o n with density (Equation 14). Total above-ground biomass (t h a - 1 ) = 54.382 - 0.389 x 10~ 8(D 2) (14) Equation 14 i s s i g n i f i c a n t at the .0001 l e v e l with r 2 = 0.79 and SE = 8.01 and i t s analysis of variance table i s shown i n Appendix C.8. Above-ground biomass ranged from 15.74 t h a - 1 at 109,000 sph to 61.38 t h a - 1 at 8,000 sph. Few data are available f o r comparison i n the l i t e r a t u r e on lodgepole pine. The above figures are within the 13.8 - 141.7 t h a - 1 range found by Peterson e_t^  a_l» (1982) i n the p r a i r i e provinces of Canada. Their work examined 7-25 year old stands of lodgepole pine at stand densities ranging from 35,800 sph to 338,200 sph. Estimates from the present study are well below the 144-200 t ha-*-reported for fast-growing 13-17 year old lodgepole pine i n New Zealand (Nordmeyer, 1980). Stocking i n the l a t t e r study ranged from 4,430 -7,500 sph and i s therefore within the range of the low density plots (5K) of the present work. At a stand density of 73,000 sph, Zavitkovski and Dawson (1978) reported jack pine to be carrying a t o t a l tree biomass of 57 t ha~l at age 7. Their plantations, however, were i r r i g a t e d and f e r t i l i z e d . At higher stand densities (approximately 94,000 sph) however, t o t a l above-ground biomass dropped to 47 t h a - 1 . 77 Figure 15. E f f e c t of stand density on t o t a l above-ground biomass. Biomass i s estimated from the regression equations i n Tables 10 and 11. F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N h a - 1 (o) and 200 kg N h a - 1 (£). Curve i s calculated from equation 14. 78 Component Dry Weight Regression equations to predict component dry weights (stem, branch and f o l i a g e ) are given i n Tables 12 and 13 for the 2° and 3° sampling i n t e n s i t i e s r e s p e c t i v e l y . These equations include only the s i g n i f i c a n t variables a f t e r the non-significant variables have been eliminated using the elimination process (backward, stepwise). A l l equations for use with the 2° sampling i n t e n s i t y show higher r 2 and lower SE values than those for use with the 3°. Inclusion of the extra independent v a r i a b l e s , d i a -meter at the base of the l i v e crown (D c) and length of the l i v e crown (CL), improved the regression equations i n the 2° sampling. Each of the nine equations i n Table 12 include one or both of these variables either 2 alone or i n combination with another variables (e.g. D c H). Because no trees were sampled i n the 5K density cl a s s i n the 2° phase of the biomass harvest, the f i r s t three equations i n Table 12 were not used i n the estimations of component dry weights. They are included here, how-ever, for completeness and f o r comparison purposes. Table 14 shows the component and t o t a l dry weights for each plot as calculated from the ' f u l l ' regression equations (including non-significant terms). These equations are given i n Appendices C.9. to C.12. A d d i t i -v i t y of components was obtained and any small differences are due to rounding e r r o r s . Comparison of the t o t a l plot dry weights between Table 14 and those calculated from the regression equations using only s i g n i f i -cant v a r i a b l e s (Appendix C.7) shows that the differences between the plot t o t a l s can be quite large when calculated using the two methods. Biomass d i s t r i b u t i o n among tree components ( i n percent) for the d i f f e r e n t stand densities i s shown i n Figure 16. With increasing stand density there i s a ' s h i f t ' i n biomass a l l o c a t i o n from f o l i a g e and TABLE 12. Component regression equations for 2° sampling Intensity. A l l equations are s i g n i f i c a n t at the .0001 l e v e l . S t a n d a b 2 density Component Equation 0 r S.E. 5K Stem - -1921.7 + 1622.3(D) - 185.1(D 2) + 20.74(D 2H) .99 256.5 b b + 11.38(D c 2H) - 1069.2(CL) Branches - 890.35 - 272.10(H) + 8.19(D c 2H) .94 191.9 Foliage - -239.1 + 21.86(D 2) - 3.18(D 2H) + 6.90(D 2H) .94 214.2 D D C 20K, 50K Stem - 0549.5 + 141.99(D ) + 323.5(H) + 4.53(D 2H) C D + 8.10(D 2H) - 298.18(CL) .99 80.2 c Branches - 126.99 - 185.72(1),) + 49.97(D 2 ) - 3.66(D 2H) D D b + 75.1(CL) .94 35.4 Foliage - -65.56 + 21.99(D 2 ) - 2.32(D 2H) + 3.12(D 2H) .96 40.0 b D C 100K, 150K Stem « -75.57 + 168.5(D V) - 79.10<D.2) + 24.79(D V 2H) b b b + 40.5(D 2 ) .99 16.1 c Branches - 9.94 - 27.49(D ) + 20.87(D 2 ) .91 6.1 c c Foliage - 56.09 - 33.92(H) - 20.93(D 2 ) + 10.92(D 2H) D D + 19.78(D c 2) .92 14.5 a Stand density » Nominal stand density. b A l l component weights in g. c Abbreviations are D b • diameter (ground l e v e l ) , cm. D c « diameter (base of l i v e crown), cm. H - height, m. CL » length of l i v e crown, m. TABLE 13. Component regression equations for 3° sampling Intensity. A l l equations are s i g n i f i c a n t at the .0001 l e v e l . S t a n d a b c 2 density Component Equation r S.E. 5K Stem - -3468.4 + 1116.5(D V) - U7.72(D 2 ) .97 437.2 D D + 18.441 (D 2H) D Branches - -1682.5 + 356.52(D. ) .90 239.5 o Foliage - -1578.2 + 386.65(D U) .89 278.6 D 20K, 50K Stem - -372.97 + 190.84(H) + 10.2(D 2H) .98 101.1 D Branches - 56.24 - 77.61(D V) + 31.25(D 2 ) - 1.84(D 2H) .91 41.2 D D D Foliage - -57.31 + 19.06(D b 2) .96 43.2 100K, 150K Stem - -142.29 + 188.33(D.) - 55.81(D 2 ) + 20.7(D 2H) . .98 18.8 b b b Branches - -10.18 + 6.35(D 2 ) .90 6.4 D Foliage - -8.26 + 5.60(D 2H) .89 15.8 b a Stand density - Nominal stand density. A l l component weights In g. c Abbreviations are D b « diameter (ground l e v e l ) , cm. H » height, m. 81 TABLE 14. Component dry weights by plot. Density Stand density Foliage Branches Stem Total Class P l o t ID 3 sph t ha 1 t ha 1 t ha 1 t ha 1 5K 111 8,000 211 6,500 311 3,500 112 6,500 212 6,000 312 5,500 20K 20K 20,500 50K 121 43,000 221 43,000 321 41,000 122 54,000 222 42,000 322 43,000 100K 100K 81,000 150K 131 109,000 231 83,000 331 84,000 132 99,000 232 82,000 332 100,000 12.94 10.63 34.51 58.09 11.33 9.35 37.78 58.47 8.72 7.26 24.46 40.43 11.78 9.55 27.64 48.96 11.10 9.49 35.39 55.99 9.34 7.88 26.03 43.25 7.51 4.45 31.23 43.20 7.84 4.28 34.71 46.82 8.90 4.73 40.11 53.74 9.67 4.97 43.10 57.74 9.13 4.79 37.35 51.27 10.10 5.48 44.23 59.80 6.59 6.59 28.29 38.31 3.10 1.25 14.85 19.19 2.21 0.92 11.65 14.78 4.79 1.84 19.64 26.26 2.59 1.09 12.39 16.07 2.86 1.12 13.54 17.52 4.15 1.64 16.07 21.86 2.95 1.19 14.11 18.25 a Plot code as previously defined e.g. Table 8. 82 5 0 K 1 0 0 K FOLIAGE STEM Legend Figure 16. Biomass a l l o c a t i o n between d i f f e r e n t stand d e n s i t i e s . * 83 branches to stem. Between low density (5K) and high density (150K) plo t s , f o l i a g e decreased from 23.1% to 15.7%, branches from 18.8% to 6.3% while a l l o c a t i o n to the stem increased from 58.1% to 78.0%. This a l l o c a -t i o n shows the same general trend as that demonstrated by M i t c h e l l and Goudie (1980) f o r somewhat sim i l a r stands. In the present study, how-ever, the s h i f t to stem a l l o c a t i o n seems to be greater. In the jack pine study already discussed, the general trend i n biomass d i s t r i b u t i o n i s again s i m i l a r (Zavitkovski and Dawson, 1978). Biomass d i s t r i b u t i o n (%) between foliage:branches:stem was 24:26:48 at a stand density of 27,000 sph and 21:19:59 at a stand density of 94,000 sph. Annual Production of Foliage T o t a l f o l i a r biomass by age-class i s shown In Table 15. Annual production i s shown for each year since f e r t i l i z e r was applied (May 1981). A l l f o l i a g e produced p r i o r to f e r t i l i z a t i o n (1980 and older) i s ' also included i n the "C+3+" c l a s s . Using the regression technique already outlined, the s i g n i f i c a n t independent variables remaining i n the equation to predict t o t a l f o l i a r biomass are shown i n equation 15. To t a l F o l i a r Biomass (g) = 14,888 - 0.270(D) + 0.158 x 10~ 4(D 2) - 0.155(F) 2 + 0.858 x 10~ 5(DF 2) -10 2 2 - 0.738 x 10 (D F ) (15) This equation i s s i g n i f i c a n t at the 0.0001 l e v e l with r 2 = 0.83 and SE = 1863.7 and i t s analysis of variance i s given i n Appendix C.13. The ef f e c t s of density and f e r t i l i z e r (and th e i r i n t e r a c t i o n s ) are shown i n Figure 17. Using the data from Table 15, the e f f e c t of f e r t i l i z e r and density can more e a s i l y be understood by examination of the annual f o l i a r 84 TABLE 15. Needle dry weight (kg h a - 1 ) by age c l a s s . F e r t i l i z e r was applied i n May 1981 • Density Plot No. trees Current (C) C+l C+2 C+3+ Class ID per ha 1983 1982 1981 1980+ 5K 111 8,000 2,157.0 2,700.7 2,067.7 5,850.6 211 6,500 2,272.0 2,947.9 2,127.7 5,745.6 311 3,500 1,266.9 1,319.5 1,087.6 3,600.3 112 6,500 2,002.7 2,854.9 2,214.8 8,060.8 212 6,000 1,954.6 2,656.6 2,060.2 4,129.6 312 5,500 1,712.0 2,246.4 1,559.6 4,938.1 2 OK 2 OK 20,500 1,377.5 1,645.3 1,089.8 3,875.3 50K 121 43,000 1,197.2 1,425.9 918.2 2,535.9 221 43,000 934.3 1,236.9 855.6 2,284.0 321 41,000 2,400.0 2,447.6 1,792.1 5,028.1 122 54,000 1,442.8 1,771.9 1,415.3 4,075.2 222 42,000 879.8 1,411.5 901.5 2,070.2 322 43,000 1,497.0 1,907.3 1,412.9 4,305.3 100K 100K 81,000 619.1 857.8 532.2 1,251.8 150K 131 109,000 765.1 1,046.6 911.5 1,486.9 231 83,000 776.6 1,208.7 750.8 1,085.5 331 84,000 1,006.3 1,053.5 415.5 861.6 132 99,000 807.4 977.0 642.0 1,608.1 232 82,000 541.0 847.5 476.6 730.4 332 100,000 1,117.8 1,170.5 468.3 942.6 Figure 17. Total f o l i a r biomass as affected by stand density and nitrogen f e r t i l i z a t i o n . Curves are f i t t e d from equation 15. 86 production expressed as a percentage of the t o t a l (Figure 18). For less confusion, the nominal density classes are used but one must remember that actual stand density i s varying somewhat between the f e r t i l i z e r l e v e l s within a density c l a s s . The d i s t r i b u t i o n pattern was affected by both f e r t i l i z a t i o n and stand density. In the control p l o t s , with increasing stand density a smaller proportion of f o l i a g e was found in the C+3+ (1980+) age class (49.8% i n the 5K, 37.5% i n the 150K). This pattern was accentuated by f e r t i l i z a t i o n , e s p e c i a l l y at the highest stand density where only 25.6% of the t o t a l f o l i a g e was i n this age class when f e r t i l i z e d at 200 kg N h a - 1 . This phenomenon i s possibly as a r e s u l t of changes i n needle retention brought about by both increased stand density and f e r t i l i z e r a p p l i c a t i o n . This w i l l be discussed i n more d e t a i l i n the next section. Figure 18 also shows that, i n a l l treatments (except one), the proportion of f o l i a g e produced i n 1982 i s greater than e i t h e r 1981 or 1983. This suggests that environmental e f f e c t s i n either 1982 or i n 1981 (because lodgepole pine i s determinate) were more conducive to needle growth i n 1982. R a i n f a l l records for July/August from nearby A l e x i s Creek/Tautri Creek show that r a i n f a l l i n 1982 was greater than 200 mm. Figures for 1981 and 1983 are 115 mm and 125 mm respectively. Needle Retention As indicated above, needle retention does seem to be affected by ei t h e r f e r t i l i z e r treatment and stand density. Needle retention i s , however, d i f f i c u l t to measure as i t i s also determined by the whorl p o s i t i o n . A branch whorl i s made up of the f i r s t - o r d e r branch axes which a r i s e from l a t e r a l buds on the main axis i n a c e r t a i n year. In the F1 F 2 F 3 Figure 18. Annual f o l i a r production as a percentage of the t o t a l f o l i a r biomass. F e r t i l i z e r levels are: 0 kg N h a - 1 ( F l ) , 100 kg N h a - 1 (F2) and 200 kg N h a - 1 (F3) while stand density l e v e l s were 5K ( D l ) , 50K (D2) and 150K (D3). 88 following discussion whorls are numbered from the top of the tree downwards, 1, 2, 3...n. It i s also important to note that the following r e l a t e s only to the presence of f o l i a g e at a p a r t i c u l a r whorl p o s i t i o n and not to i t s amount. Figure 19 shows the ef f e c t of stand density (control plots only) on the average number of needle age classes retained at each whorl p o s i t i o n . No difference e x i s t s between the various stand densities i n the upper f i v e whorls. Beginning at whorl 6, however, trees i n the highest stand density range (150,000 sph) begin to lose needles. The maximum needle retention for t h i s stand density occurs at whorl 7 where the average number of needle age classes retained i s 6.4. For the intermediate density c l a s s (50,000 sph), the deviation from f u l l needle retention begins at whorl 7. The maximum needle retention (7.3 years) occurs at the eight whorl p o s i t i o n i n t h i s density c l a s s . For the vigorous, low stand density c l a s s (5,000 sph), maximum needle re t e n t i o n (8.5 years) occurs at whorl p o s i t i o n 11. Therefore, with increasing stand density, the whorl p o s i t i o n at which maximum needle retention occurs i s found at higher positions i n the crown. S i m i l a r l y , the number of year's f o l i a g e retained at maximum retention increases with decreasing stand density. 3. Height Growth Stem analysis showed that the pattern of height growth has changed between the various stand densities since the time of seedling e s t a b l i s h -ment (Figure 20). For the f i r s t two.years of measurable height growth (1962 and 1963) i t i s the trees of the high density (150,000 sph) stand that show marginally best height growth. From 1964-1973, trees from the 89 Figure 19. The e f f e c t of stand density on the average needle retention at d i f f e r e n t crown positions. 90 Figure 20. Height vs. age curves for mean trees in each nominal density c l a s s . Height was established from stem analysis on trees from the 1° sampling i n t e n s i t y . i 91 intermediate density (50,000 sph) stands show best height growth. At the time of biomass harvest (1983), i t was the vigorous, low density stand (5,000 sph) that had been growing fastest since 1974. Height of the 5K trees did not exceed that of the 150K trees u n t i l 1968 i . e . approximately 7 years a f t e r establishment. Table 16 and Figure 21 show the c o e f f i c i e n t s of determination be-tween leading shoot length i n any year and length of the leading shoot i n the previous year, between 1963 and 1983. In the vigorous trees, t h i s r e l a t i o n s h i p i s not s i g n i f i c a n t i n 11 out of the 20 years examined. The intermediate and high density stands, however, show s i g n i f i c a n t r e l a t i o n -ships for 17 and 15 years r e s p e c t i v l e y . Where the r e l a t i o n s h i p i s s i g n i f i c a n t , only three of the regressions i n the vigorous stands are s i g n i f i c a n t at the 1% l e v e l whereas a l l regressions attained t h i s s i g n i f i c a n c e l e v e l i n the repressed stands. A l l of the non-significant regressions i n the repressed stands occurred p r i o r to 1969, the period when height growth i n these stands was greatest. Inversely, vigorous stands i n the same period show twice as many s i g n i f i c a n t to non-significant regressions - at a time when they were growing slowly. In general, therefore, the r e l a t i o n s h i p between lengths of successive leading shoots i s greatest when the length of these shoots i s small. In the period 1970-83, 17% and 48% on average of the v a r i a t i o n i n height increment i n any year was associated with height increment of the previous year i n the vigorous and suppressed stands re s p e c t i v e l y . When the c o e f f i c i e n t s of determination ( r 2 ) are compared between d i f f e r e n t stand densities over time (Figure 21), other, possibly environ-mental, factors are suggested as being important i n th i s o v e r a l l process 92 TABLE 16. Relationship between lengths of successive leading shoots between trees from d i f f e r e n t stand d e n s i t i e s . For each regression equation n = 18 f o r the 5,000 sph and n = 30 f o r 50,000 and 150,000 sph. C o e f f i c i e n t of determination ( r ^ ) Year 5000 sph 50,000 sph 150,000 sph 83 vs. 82 0.33 (*) 0.64 (**) 0.55 (**) 82 vs. 81 0.18 (NS) 0.25 (*.*) 0.41 (**) 81 vs. 80 0.06 (NS) 0.38 (**) 0.39 (**) 80 vs. 79 0.27 (*) 0.43 (**) 0.64 (**) 79 vs. 78 0.28 (*) 0.58 (**) 0.69 (**) 78 vs. 77 0.04 (NS) 0.37 (**) 0.68 (**) 77 vs. 76 0.13 (NS) 0.39 (**) 0.45 (**) 76 vs. 75 0.07 (NS) 0.41 (**) 0.51 (**) 75 vs. 74 0.05 (NS) 0.38 (**) 0.40 (**) 74 vs. 73 0.02 (NS) 0.24 (**) 0.37 (**) 73 vs. 72 0.44 (**) 0.28 (**) 0.54 (**) 72 vs. 71 0.16 (NS) 0.10 (NS) 0.23 (**) 71 vs. 70 0.17 (NS) 0.17 (*) 0.34 (**) 70 vs. 69 0.40 (**) 0.49 (**) 0.39 (**) 69 vs. 68 0.46 (**) 0.32 (**) 0.09 (NS) 68 vs. 67 0.33 (*) 0.24 (**) 0.03 (NS) 67 vs. 66 0.21 (NS) 0.43 (**) 0.30 (**) 66 vs. 65 0.38 (*) 0.61 (**) 0.14 (NS) 65 vs. 64 0.61 (*) 0.01 (NS) 0.02 (NS) 64 vs. 63 0.59 (NS) 0.05 (NS) 0.21 (NS) a * - s i g n i f i c a n t at the 0.05 (5%) l e v e l . ** - s i g n i f i c a n t at the 0.01 (1%) l e v e l . NS - not s i g n i f i c a n t at the 0.05 (5%) l e v e l . 93 1964 1968 1972 1976 YEAR 1980 1984 Figure 21. C o e f f i c i e n t s of determination ( r 2 ) between successive leading shoots over a 20-year period. For each year, the r 2 value plotted i s from the regression of height increment i n that year on height increment of the previous year. 94 of determination of height growth. Figure 21 shows, not only the r e l a -t i v e magnitudes of the r 2 between the various d e n s i t i e s , but also that increases or decreases i n the r 2 values occur approximately i n the same year between stand d e n s i t i e s . This alignment of the peaks and troughs i s strongest from 1970 to the year of harvest i n 1983. This i n t e r p l a y between i n t e r n a l (autogenetic) and external (environ-mental) factors a f f e c t i n g height growth has probably resulted In the va r i a t i o n s i n height growth between the stand densities since e s t a b l i s h -ment (Figure 20). Trees i n repressed stands show more autogenetic control than trees i n vigorous stands. F l o w e r - E l l i s et a l . (1976) have suggested that the amount of control on growth w i l l also be influenced by the number of needle age classes present - previously good growth, normally implying an increase i n needle biomass i n the t o t a l population, may 'dampen' or reduce the Impact of a single poor year. External environmental factors therefore a f f e c t the rate of photo-synthesis, which consequently a f f e c t growth. It has also been suggested that the reverse s i t u a t i o n can also be important and that growth rate i t s e l f can influence the photosynthetic rate by a f f e c t i n g the rate of removal of assimilates from the production areas. Sweet and Wareing (1966) found that the rate of photosynthesis i n Monterey pine seedlings was i n some part subject to control by the growth of the plants. How-ever, the mechanism was not f u l l y determined and they suggested that e i t h e r the reduction i n sink strength or a hormonal i n t e r p r e t a t i o n might be possible. They also suggested that both these factors may be i n t e r -acting and together influencing growth. The patterns of growth shown i n Figure 21 for the repressed vs. vigorous stands indicate that perhaps a s i m i l a r mechanism of control may 95 be contributing to the reduction i n height growth i n overstocked lodge-pole pine. The control of growth, therefore, may be as much from within the plant as from external f a c t o r s . 4. Leaf Area/Sapwood Area Relationships As indicated already i n the Methods se c t i o n , leaf area (LA) was predicted from sapwood area (SA). I n i t i a l l y , both sapwood area and basal area (BA) were tested as independent v a r i a b l e s . Because a l l the trees i n these stands were e n t i r e l y sapwood, both SA (underbark) and BA (overbark) gave very s i m i l a r regression equations (Table 17). In a l l densities, BA c o n s i s t e n t l y gave higher r 2 values and smaller standard errors than SA. Pearson ejt a l . (1984) found that SA was a more precise predictor of f o l i a g e biomass than was BA i n most of t h e i r lodgepole pine stands. In t h e i r most dense c l a s s (>9,000 sph) however, the Improvement i n standard error through use of SA instead of BA was matched by a lowering of the r 2 value. Their work was carried out i n older (>75 years) stands where the differences between sapwood area and basal area were probably quite large. T o t a l leaf area index (LAI) ranged from 2.33 - 13.43 with consi-derable differences between densities (Appendix C.14). Mean LAI for the low density (5K) pl o t s was 11.25 compared to 3.27 f o r the high density (150K) p l o t s . Pearson et a l . (1984) reported that LAI dropped only s l i g h t l y (7.3 - 7.1) between low (2,217 sph) and high (14,640 sph) density stands and used t h e i r r e s u l t s to support the hypothesis that LAI i s more dependent on s i t e water balance than on forest structure (Grier and Running, 1977). Basal area increased (42 - 50 m2 h a - 1 ) , however, 96 TABLE 17. Regression equations for prediction of leaf area from sapwood area and basal area. A l l equations are s i g n i f i c a n t at the .0001 l e v e l . Stand a b 2 density Component Equation r S.E. 5K LA 0.213 + 0.291 (SA) 0.86 2.968 -0.262 + 0.278 (BA) 0.88 2.834 20K, 50K LA -0.469+0.260 (SA) 0.93 0.531 -0.545 + 0.240 (BA) 0.94 0.524 100K, 150K LA -0.177 + 0.221 (SA) 0.87 0.176 -0.216 + 0.198 (BA) 0.89 0.168 a Leaf area (LA) i n m2. k Sapwood area (SA) and basal area (BA) i n cm2. 97 between t h e i r low and high density stands, i n contrast to the reduction i n basal area with increasing stand density already reported i n the current work (Figure 12). Mean LAI i n the low density p l o t s (11.25) was greater than the 4.5 - 9.9 reported by Pearson et a l . (1984) f o r much older stands (75 - 200 years). LAI was not affected by f e r t i l i z e r a p p l i c a t i o n (Figure 22) and i s described by equation 16. The regression LAI = 11.855 - 0.8996 x 10~ 4(D) (16) i s s i g n i f i c a n t at the 0.0001 l e v e l with r 2 = .84 and SE = 1.476. Its analysis of variance i s given i n Appendix C.15. The r a t i o of leaf area to sapwood area (LA/SA) also d i f f e r e d among the stands (Appendix C.5). LA/SA r a t i o dropped from a mean of 0.3 m2cm~2 i n the 5K plots to 0.15 m 2cm - 2 i n the 150K p l o t s . Kaufmann and Troendle (1981) found a LA/SA r a t i o of 0.49 m 2cm - 2 f o r a moderately dense lodgepole pine stand i n Colorado, s i m i l a r to the 0.52 m2cm~2 reported by Pearson e_t a l / (1984) for t h e i r stand of moderate density. The l a t t e r workers, however, found that t h i s r a t i o depended on stand density and ranged from 0.57 m 2cm - 2 i n a low-density o l d growth stand to 0.20 m 2cm - 2 i n a high density stand. This r a t i o was not affected by f e r t i l i z e r i n the present study and the s i g n i f i c a n t independent variables included only the D and D 2 terms (Equation 17 and Figure 23). Leaf area:sapwood area r a t i o = 0.305 - 0.251 x 10~ 5(D) + 0.814 x 1 0 - 1 1 ( D 2 ) (m 2cm - 2) (17) The equation was s i g n i f i c a n t at the .0001 l e v e l with r 2 = 0.97 and SE = 0.0112 and i t s analysis of variance i s shown i n Appendix C.16. 15 o-| 1 1 1 1 1 1 1 1 — 0 30 60 90 120 Stand Density (sph 10 ) Figure 22. The e f f e c t of stand density on leaf area index (LAI). LAI i s expressed on a t o t a l leaf area basis. F e r t i l i z e r l e v e l s are: 0 kg N h a - 1 (•), 100 kg N h a - 1 (o) and 200 kg N h a - 1 (A). The l i n e i s f i t t e d from equation 16. 99 Figure 23. The ef f e c t of stand density on leaf area:sapwood area r a t i o . F e r t i l i z e r l e v e l s are: 0 kg N ha" 1 (•), 100 kg N h a - 1 (o) and 200 kg N h a - 1 (A). The curve i s f i t t e d from equation 17. 100 A l l of the above discussion on LA/SA r a t i o s has dealt with mean values for plots of various stand d e n s i t i e s . Within any stand of a pa r t i c u l a r density, however, a va r i e t y of tree sizes w i l l be found - from dominant to suppressed trees. I t might be expected, therefore, that LA/SA r a t i o would be related to i n d i v i d u a l tree diameter and through t h i s , i n d i r e c t l y to stand density. This r e l a t i o n s h i p between LA/SA r a t i o and tree diameter for i n d i v i d u a l trees i s shown i n Figure 24. The v a r i a -b i l i t y of values for the r a t i o s of Individual trees i s now much greater than already reported f o r the plots and ranges from 0.05 m2cm~2 for small diameter trees (1.5 cm) to 0.3 - 0.35 m 2cm - 2 f o r larger diameter trees (9 cm and l a r g e r ) . Why do repressed stands or suppressed trees i n more vigorous stands put p r o p o r t i o n a l l y more biomass into sapwood area than into leaf area? The p h y s i o l o g i c a l balance between the capacity of sapwood to conduct and store water and the t r a n s p i r a t i o n a l demand of the fo l i a g e i s obviously being affected by stem diameter (and i n d i r e c t l y stand density) i n the present study, with less leaf area per unit sapwood area i n trees from the more dense stands. Pearson et a l . (1984) suggested that t h i s observation could be partly explained by differences i n the sapwood volume:sapwood area r a t i o between trees of d i f f e r e n t growth form and that differences i n the leaf area:sapwood volume r a t i o between trees from open and dense stands probably were much smaller than the LA/SA r a t i o . Sapwood volume was not measured i n the present study. Because the trees had no heartwood, however, stem dry weight might be used as an estimate of sapwood volume. This does not account for bark or for differences i n s p e c i f i c gravity of wood between d i f f e r e n t stand d e n s i t i e s . 101 0.4 0.3-E o < CO 0.2 0.1 0.0 A A" A A A A A 0 • o • • A A A A A • • • • • A o* • o A \* o a o • W • • Diameter (cm) 12 Figure 24. The r e l a t i o n s h i p between leaf area:sapwood area r a t i o and tree diameter. Nominal density classes included are 5K (A), 50K (•) and 150K (o). 1 0 2 Calculations from Table 14 give mean f o l i a g e dry weight:stem dry weight r a t i o s of 0.35 g g - 1 f o r the 5K plots and 0.22 g g - 1 f o r the 150K p l o t s . This r a t i o i s somewhat less variable between open and dense stands than the LA/SA r a t i o (as suggested by Pearson et^ al_., 1984) but c l e a r l y does not f u l l y explain the differences found i n the l a t t e r r a t i o between stands of d i f f e r e n t density. Like the LA/SA r a t i o , the f o l i a g e dry weight:stem dry weight r a t i o showed greater v a r i a b i l i t y between i n d i v i -dual trees e.g. from 0.4 g g - 1 f o r a dominant tree i n the 5K density c l a s s to 0.09 g g ~ l f o r a suppressed tree i n the 150K density c l a s s . Another consideration to help explain the reasons behind the drop i n LA/SA r a t i o with increasing stand density i s the change brought about i n wood morphology as a r e s u l t of trees growing at d i f f e r e n t stand densities (Albrektson, 1984; Pearson et a l . , 1984). Whitehead and J a r v i s (1981) showed that, i n general, water conduction i s favoured by long, t h i n walled, wide tracheids and negatively related to wood density. Albrektson (1984) suggests that "the p h y s i o l o g i c a l balance between the demand for water from the crown and the a b i l i t y of the stem to conduct i t , may not be adequately described by just the quantitative variable of sapwood basal area. The a b i l i t y of the sapwood to conduct water must also be described." It would seem, therefore, that the type of sapwood ( s p e c i f i c gravity, r e l a t i v e proportions of earlywood and latewood, etc.) and not simply the amount present, i s important. 5. Stand Density E f f e c t s on Wood Anatomy Intra-ring density p r o f i l e s produced by the densitometer over the twenty (approximately) scanned years show marked contrasts between trees from d i f f e r e n t stand densities (Table 18). Mean annual ring width was 103 TABLE 18. Wood anatomical c h a r a c t e r i s t i c s i n codominant trees from d i f f e r e n t stand d e n s i t i e s . A l l values are means of approximately 20 years (standard deviations given i n parenthesis). Stand density Ring width Earlywood width Latewood width Ring density sph mm mm mm g cm-3 6,500 2.37 (.68) 1.46 (.77) 0.91 (.38) 0.52 (.06) 20,500 0.91 (.23) 0.52 (.24) 0.40 (.13) 0.54 (.07) 48,000 0.66 (.25) 0.23 (.16) 0.43 (.15) 0.61 (.04) 109,000 0.37 (.11) 0.03 (.05) 0.35 (.10) 0.70 (.07) 104 reduced from 2.37 mm to 0.37 mm over the stand density range 6,500 -109,000 sph. Over the same range, oven dry wood density increased from 0.52 - 0.70 g cm--*. These wood density figures are, i n general, higher than those reported by Singh (1984) for lodgepole pine i n A l b e r t a . His data ranged from 0.38 to 0.54 g cm-3 with a mean of 0.44 g cm~3. Examination of the annual density p r o f i l e s of a vigorous and stag-nant tree (Figure 25) suggest that for the f i r s t 3-4 years a f t e r estab-lishment there was l i t t l e difference i n ring density between the trees. Af t e r that period, and p a r t i c u l a r l y from 1970 onwards, the tree from the repressed stand shows c o n s i s t e n t l y greater wood density than the tree from the vigorous stand. Over the same time period, the same trees also show quite d i s t i n c t patterns of growth i n terms of r i n g width (Figure 26). Both the vigorous and repressed trees show quite s i m i l a r ring widths for the f i r s t two to three years a f t e r establishment. After the mid 1960s, however, the vigorous tree shows a dramatic increase i n average ring width for the next 5-6 years. Between 1971 and the time of harvest (1983) the r a d i a l growth of the vigorous tree fluctuates about a ring width of approximate-l y 2.5 mm y r - 1 . The tree from the repressed stand, however, shows l i t t l e f l u c t u a t i o n ( i n absolute terms) and, apart from 1965 and 1966, i s c o n s i s t e n t l y below 0.5 mm y r - 1 . This would seem to suggest, as already discussed for height growth, that, except for the f i r s t few years a f t e r establishment, the trees i n the repressed stands have always shown reduced growth. This, i n turn, probably indicates that seedling density immediately a f t e r establishment was much higher than the present stand density of 109,000 sph. 105 1 O z 0.2-0-1 1 p - — 1 . . 1 1 1 , . 1 . . . 1 1 , 1 — 1964 1 9 6 8 1972 1976 1 9 8 0 1 9 8 4 YEAR Figure 25. V a r i a t i o n i n mean ring densities over time between trees from vigorous (6.5K) and stagnant (109K) stands. 106 4 o H — » — i — i — i — i — i — * — i i i i — i — i — ' ' i * — 1 1 1964 1968 1972 1976 1980 1984 YEAR Figure 26. V a r i a t i o n i n mean ring width over time between trees from vigorous (6.5K) and stagnant (109K) stands. 107 Of greater importance to the water movement e f f i c i e n c y within vigorous and repressed trees, however, are the r e l a t i v e proportions of earlywood and latewood found i n trees growing i n both types of stand (Figure 27 and Table 19). Although the l o c a t i o n of the earlywood-latewood boundary may change according to the various d e f i n i t i o n s used (see Worrall, 1970), the s p e c i f i c density d e f i n i t i o n i s used throughout the following discussion (see Parker et a l . , 1980). TABLE 19. Earlywood and latewood percentages as affected by stand density Stand density sph Earlywood % Latewood % 6,500 61.6 38.4 20,500 56.5 43.5 48,000 34.8 65.2 109,000 7.9 92.1 In attempting to explain the differences i n cambial growth between vigorous and suppressed trees i t must be understood how th i s growth i s influenced by a p i c a l growth and crown structure (Larson, 1969). In red pine, any factor that i n h i b i t e d or suppressed needle growth was r e f l e c t e d by a commensurate decrease i n tracheid growth (Larson, 1964). The hormonal theory of wood formation emphasizes the importance of hormones produced i n the crown i n earlywood-latewood r e l a t i o n s . It i s now generally accepted that large-diameter earlywood tracheids are formed 103 T r 1 2 Ring width (mm) 0 Figure 27. Average density p r o f i l e s (1966-1983) f o r trees from a range of stand d e n s i t i e s . 109 during the period of shoot elongation and high auxin synthesis, while narrow diameter latewood c e l l s are formed a f t e r shoot elongation has stopped and auxin synthesis i s reduced. Because both needle and leader growth are reduced i n suppressed trees i t might therefore be expected that the amount of auxin synthesis could also be reduced, leading to less earlywood compared to trees growing vigorously. Table 19 shows that t h i s , i n f a c t , may be happening i n the lodgepole pine stands, with vigorous and repressed trees having 61.6% and 7.9% earlywood r e s p e c t i v e l y . The o v e r a l l effect of high stand density, therefore, i s to shorten the period f o r photosynthesis, auxin synthesis and general crown a c t i v i t y compared to stands at lower densi-t i e s and thus reduce the period for the production of large diameter tracheids. This i s i n d i r e c t contrast to the e f f e c t s of a thinning treatment on red and jack pines reported by Zahner and O l i v e r (1962). Bassett (1966) measured the amount and duration of r a d i a l growth i n a thinned stand of 30-year-old l o b l o l l y pine i n the southern United States. He found that dominants and codominants grew longer and f a s t e r i n l i g h t l y stocked stands than i n heavily stocked stands. On average, dominant trees grew during 80% of the growing season compared to suppressed trees which increased i n diameter only during 28% of the growing period. This i s further evidence to suggest, therefore, that repressed trees of lodgepole pine may have a shorter seasonal growth period than more vigorous trees, and that t h i s r e s u l t s i n reductions i n the amount of earlywood found i n trees growing at high stand d e n s i t i e s . The height to the bottom of the l i v e crown i s also important i n determining the date of i n i t i a t i o n of r a d i a l growth at the base of the tree. In general, more suppressed trees, carrying t h e i r smaller crowns 110 higher on the main stem, i n i t i a t e growth at the stem base l a t e r than vigorous, dominant trees of the same height (Kozlowski and Peterson, 1962; Larson, 1969). This e f f e c t may be lessened somewhat i n the present lodgepole pine stands because of the marked reduction In the height of i n d i v i d u a l trees growing i n the high density stands. The hormone theory i s concerned almost e x c l u s i v e l y with the regula-t i o n of tracheid diameter. Latewood formation, however, depends not only on a reduction i n tracheid diameter but also on tracheid w a l l thickness. The l a t t e r seems to be determined by factors other than hormonal, mainly by the amount of sucrose, or photosynthate, reaching each tracheid and to the period of time tracheids remain a l i v e i n a s s i m i l a t i o n (Larson, 1960). Although Table 19 shows that the proportion of latewood increases from 38% to 92% with an increase i n stand density from 6,500 sph to 109,000 sph, i t must not be forgotten that any factor a f f e c t i n g only earlywood width, also automatically a f f e c t s latewood % (see Discussion i n Worrall, 1970). Therefore, Figure 27 and Table 19 might suggest that the main ef f e c t of increasing stand density on wood anatomy i n these lodge-pole pine stands was to reduce the earlywood width d r a s t i c a l l y . E f f e c t s on the amount of latewood were fewer and more complex (being i n d i r e c t l y affected by earlywood width). Microscopic examination of wood samples from both vigorous and stagnant trees subsequent to the above densitometry work suggests, however, that the proportions of latewood shown in Table 19 may have been exaggerated by the method of measurement (Figure 28) as suggested by 3 Worrall (personal communication ). The percent latewood seems to have Dr. J . Worrall, Faculty of Forestry, Un i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C. V(25X) S(25X) Figure 28. Photographs of wood samples from vigorous (v) and stagnants (s) trees. 112 been overestimated i n both vigorous and stagnant trees - the o v e r a l l trend of a decreasing proportion of earlywood i n stagnant trees i s therefore s t i l l evident. Measurements from photographs of wood samples suggest that the earlywood % Is 85-90% for trees from vigorous stands and 60-65% for trees from stagnant stands while mean lumen diameter i n the former i s greater than that i n the l a t t e r . The o v e r a l l effect of increasing stand density, therefore, may be to reduce the hydraulic conductivity i n the stem. This i s achieved through reductions i n the proportion of earlywood and i n mean lumen diameter of that earlywood i n trees from stagnant stands. E. Conclusions Data from a complete harvest of a l l pl o t s showed that, over the stand density range examined (3,500-109,000 sph), mean height, top height, mean diameter, plot basal area and t o t a l above-ground biomass generally decreased with increasing stand density. Top height showed less of a reduction than mean height i n the 5,000-50,000 sph range, while the l a t t e r ranged from 5-6 m at 5,000 sph to under 2 m at 100,000 sph. Basal area (measured at ground l e v e l ) peaked i n the stands of i n t e r -mediate density, while t o t a l above-ground biomass varied l i t t l e between low and intermediate stand densities (40-60 t h a - 1 ) but decreased to 15-25 t h a - 1 at the high d e n s i t i e s . Tree mortality ranged from zero percent i n the low, to f i f t y percent i n the high stand d e n s i t i e s , suggesting that i n i t i a l stocking was much higher than the present number of l i v e trees would i n d i c a t e . 113 Estimates from regression equations f o r component and t o t a l above-ground biomass i n d i c a t e that the proportion allocated to f o l i a g e , branches and stem i s density dependent. Between low (5K) and high (150K) stand d e n s i t i e s , the proportion allocated to f o l i a g e and branches was reduced while a l l o c a t i o n to the stem increased from 58% to 78% r e s p e c t i v e l y . Height vs. age curves (from stem analysis estimates) i n d i c a t e that for the f i r s t two years a f t e r establishment, the trees from the high stand densities were the t a l l e s t . From the t h i r d to the twelfth year af t e r establishment, trees from the intermediate density are the t a l l e s t . Analysis of t h i s growth suggests that height growth of trees i n repressed stands i s more c l o s e l y c o r r e l a t e d with height growth of the previous year than i t i s i n more vigorous stands. The mechanism of t h i s 'internal c o n t r o l ' i s not understood but may be related to sink strength or hormonal c o n t r o l . Leaf area index (LAI ( t o t a l ) ) ranged from 8-13 m2 m - 2 i n the low density plots to 2-4 m2 m - 2 i n the high density p l o t s . The drop i n LAI was l i n e a r over the range of densities examined. The leaf area: sapwood area r a t i o was not found to be species s p e c i f i c but varied with stand density. Trees from the low density plots c a r r i e d , on average, 0.3 m2 of f o l i a g e per cm2 of sapwood while trees from repressed stands c a r r i e d only 0.14 m2 of f o l i a g e per cm2 of sapwood. Examination of sapwood from trees from both vigorous and repressed stands showed a marked reduction i n the earlywood percent i n trees from repressed stands. This decrease i n the proportion of earlywood probably causes a reduction 114 i n water movement e f f i c i e n c y i n trees from repressed stands, r e s u l t i n g i n t h e i r having to decrease t h e i r leaf area:sapwood area r a t i o . The r e s u l t i n g s h i f t from productive tissue ( l e a f area) to consumptive tissue (cambial surface area) may be causing these stands to devote t h e i r energy to r e s p i r a t i o n at the expense of height growth, as suggested by M i t c h e l l and Goudie (1980). 115 CHAPTER 6. STUDY COMPONENT 3: FOLIAR NUTRIENT ANALYSIS A. Introduction As indicated e a r l i e r , moisture d e f i c i t s have been suggested as being one of the factors causing or prolonging growth repression i n dense stands of lodgepole pine. Besides moisture d e f i c i t s the other major com-ponent i n s i t e q u a l i t y i s s o i l and plant nutrient status. It i s also a fa c t o r over which the forest manager has more control than moisture a v a i l a b i l i t y . The two factors are Interdependent, however, and moisture d e f i c i t s can reduce growth no matter how inherently f e r t i l e a s i t e may be. Moreover, f o l i a r analysis has shown repressed stands i n the v i c i n i t y of the present study s i t e to be d e f i c i e n t i n c e r t a i n nutrients, p a r t i c u -l a r l y nitrogen, over a density range of 6,000 - 170,000 sph (B a l l a r d , 1981). Of the many methods available to predict f e r t i l i z e r response i n forest stands, f o l i a r analysis seems to be the most promising (Morrison, 1974). It can be a rapid, inexpensive and yet r e l i a b l e a l t e r n a t i v e to f i e l d t r i a l s which are often c o s t l y to e s t a b l i s h and maintain. The establishment of c r i t i c a l l e v e l s of nutrients f or a p a r t i c u l a r stand, however, often involves extrapolation from a reference stand from which the c r i t i c a l l e v e l s were experimentally derived, usually a f t e r some form of adjustment or c a l i b r a t i o n (Weetman and Fournier, 1982). No such c r i t i c a l l e v e l s e x i s t f o r suppressed lodgepole pine stands and i t i s not known how c l o s e l y the normal c r i t i c a l l e v e l s for the species might apply to stands growing at extreme d e n s i t i e s . The approach taken i n i n t e r p r e t i n g the r e s u l t s from the f o l i a r nutrient analysis i n the present study involves a combination of: 116 1) a graphical i n t e r p r e t a t i o n following a system described by Timmer and Stone (1978) and 2) a more t r a d i t i o n a l approach of treatment e f f e c t s on various nutrient concentrations. More s p e c i f i c a l l y , t h i s study component reports on experiments which: 1. Use a graphical technique to examine the e f f e c t s of nitrogen l e v e l and stand density on needle weight and N, P and K concentrations and contents i n f o l i a g e produced i n the year of f e r t i l i z a t i o n . 2. Test the hypothesis that N, P and K concentrations change over a three-year period since time of f e r t i l i z a t i o n and that t h i s Is affected by stand density and f e r t i l i z e r l e v e l . 3. Test the hypothesis that l e v e l s of some elements (S, Cu, Fe and 'active' Fe) are affected by f e r t i l i z e r l e v e l and stand density two growing seasons af t e r f e r t i l i z a t i o n . 4. Test the hypothesis that N concentration i s dependent on f o l i a r age, crown position, f e r t i l i z e r l e v e l and stand density three growing seasons a f t e r f e r t i l i z a t i o n . B. L i t e r a t u r e Review  F o l i a r Analysis F o l i a r analysis i s a valuable tool i n i d e n t i f y i n g nutrient d e f i c i e n -cies i n forest trees. It i s most e f f e c t i v e i n areas where acute d e f i c i e n c i e s occur e.g. i n parts of the southeastern United States, Queensland and parts of New Zealand (van den Driessche, 1979). In general, d e f i c i e n c i e s are not as acute i n the P a c i f i c North West. Many of these s i t e s respond well to f e r t i l i z e r a p p l i c a t i o n . Tissue analysis 117 however, does not cons i s t e n t l y predict whether a growth response w i l l occur and secondly i t does not quantify t h i s response. F o l i a r nutrient l e v e l s are also known to change as the plant grows. M i l l e r eit al_. (1981) concluded that f o r diagnostic purposes c r i t i c a l f o l i a r nitrogen l e v e l s must be q u a l i f i e d by the age and developmental stage of the tree. They also found that r e l a t i o n s h i p s between f o l i a r nitrogen levels and growth of Scots pine could be improved by including factors such as r a i n f a l l and temperature. Light may also be an important l i m i t i n g factor as shown by response to f e r t i l i z a t i o n i n thinned vs. unthinned stands of Douglas-fir (Brix and E b e l l , 1969). Recently, the expression of mineral composition as a percentage of dry weight of tissue has come under c r i t i c i s m (Gholz 1978; Smith et a l . , 1981). The l a t t e r workers found that by expressing mineral composition i n terms of content per unit of leaf area they eliminated much of the v a r i a b i l i t y caused by changes i n carbohydrate reserves that confounded r e s u l t s when mineral composition was expressed i n terms of percentage of dry weight. It also followed the standardized methodology used i n expressing gas exchange from canopies (Campbell, 1977). Smith and coworkers compared contrasting s i t e s i n the Coast Range and Cascade Mountains i n western Oregon and found that major errors i n i n t e r p r e t a t i o n were l i k e l y i f f o l i a r analysis was expressed as a percentage of dry weight. This was p a r t i c u l a r l y true i n the Cascades because foliage weight changed abruptly before and aft e r the growing season. Another possible disadvantage of using concentration as a measure of nutrient status following f e r t i l i z a t i o n has been described as the "Steenbjerg e f f e c t " (Steenbjerg, 1954). This i s caused by an increase i n fo l i a g e dry weight (brought about by f e r t i l i z e r a p p l ication) causing an 118 actual decrease i n concentration. Thus, the concentration of nutrients i s 'diluted' i n the plant t i s s u e . By expressing f o l i a r nutrient data on a content basis (e.g. mg/100 needles) one might avoid misinterpretation due to the d i l u t i o n e f f e c t . It i s uncertain whether using content per unit of leaf area would reduce t h i s d i l u t i o n effect because of the v a r i a b i l i t y i n s p e c i f i c leaf area already discussed i n this t h e s i s . Another approach, somewhat between the t r a d i t i o n a l approach and that of Smith and h i s co-workers, uses an integrated approach involving com-parisons of both n u t r i t i o n a l and dimensional parameters of f o l i a g e . This approach has been used s u c c e s s f u l l y i n characterizing responses i n a number of f e r t i l i z e r t r i a l s (Brix and E b e l l , 1969; Weetman and Algar, 1974; Morrow and Timmer, 1981). These l a t t e r studies have examined nutrient content (mg/100 f a s c i c l e s ) as well as the t r a d i t i o n a l nutrient concentration (% dry weight) i n expressing changes i n f o l i a r nutrient levels In response to f e r t i l i z a t i o n . More s p e c i f i c d e t a i l s on t h i s method w i l l be given i n the Materials and Methods section. Expressing f o l i a r nutrient l e v e l s as nutrient content (so c a l l e d extensive units) also has cer t a i n disadvantages. There i s a shortage of comparative data at present (perhaps less of a problem over time) and r e s u l t s are constrained by lack of universal a p p l i c a b i l i t y for reasons outlined e a r l i e r . In an attempt to overcome some of these problems various authors have suggested using multiple regression analysis as an approach to the study of growth-nutrient r e l a t i o n s h i p s under conditions of def i c i e n c y of more than one nutrient (see Prusinkiewicz, 1982). Assuming that: ( i ) nutrient status of the tree has a major e f f e c t on the size of i t s a s s i m i l a t i n g organs; 119 (11) f o l i a g e mass (leaf area) i s one of the most important factors determining the current wood increment. A multiple regression equation can be used, of the type: Y = b0 + E V i <*•ml* 2> n> (18) i=i where: Y • oven-dry weight of 100 pairs of needles; = nutrients; bj = p a r t i a l regression c o e f f i c i e n t s ; n = number of independent variables ( n u t r i e n t s ) . This can be regarded as a model of the e f f e c t of the current nutrient status of the stand on the needle mass and thus i n turn on the nutrient dependent growth p o t e n t i a l of the stand (Prusinkiewicz, 1982). It i s thus possible to reach an objective assessment of the nutrient status of a stand and to plan a suitable f e r t i l i z e r regime based on t h i s assessment. The use of f o l i a r a n a l y s i s , however, i s not free from l i m i t a t i o n s . C r i t i c a l l e v e l s , defined as associated with 90 percent of maximum y i e l d , are often determined under co n t r o l l e d greenhouse experiments on seedlings and t h e i r a p p l i c a b i l i t y to field-grown or older crops may be question-able. The same authors found that optimum nitrogen levels also vary depending on the growth parameter i n question. C r i t i c a l l e v e l s f o r macro-nutrients i n lodgepole pine come mainly from Swan (1972), Everard (1973) and Binns et^ a l . , 1980. Recently, c r i t i c a l l e v e l s f o r some micronutrients i n lodgepole pine have been established from greenhouse and f i e l d experiments (Majid, 1984). He found that the deficiency ranges were from 7-16 ppm f o r boron, 120 1.8-3.0 ppm for copper, 32-45 ppm for "active" iron and 44-53 ppm for t o t a l i r o n . It has also been suggested that nutrient deficiency may i n h i b i t growth primarily by i n h i b i t i n g , hormone synthesis. Wareing (1974) noted that tissue analysis of d i f f e r e n t tree species grown under varying nutrient regimes showed that nutrient content of a more demanding species (sycamore) did not" d i f f e r greatly from that of a less demanding one ( b i r c h ) . External a p p l i c a t i o n of quite small amounts of cytokinin to nitrogen-deficient plants resulted i n an immediate stimulation of growth. He suggested that the poor growth shown by Sitka spruce (Picea s i t c h e n s i s (Bong.) Carr.) on some poor sandy s o i l s i n B r i t a i n (about 1 metre over a period of 20 years) may be p a r t l y caused by the i n h i b i t i o n of hormone synthesis by some nutrient deficiency. Mechanism of Response to Nitrogen F e r t i l i z a t i o n Most forest f e r t i l i z a t i o n studies have been concerned with response i n terms of increased stem growth and the optimum levels of f e r t i l i z e r to use. R e l a t i v e l y few have examined the mechanism of response by monitor-ing changes i n the p h y s i o l o g i c a l processes which determine tree growth. In the 1960s some work was i n i t i a t e d i n stands of Douglas-fir to examine such mechanisms. Helms (1964) did not f i n d any effect of nitrogen f e r t i -l i z a t i o n on the rate of photosynthesis per unit leaf area and concluded that volume increments must be the r e s u l t of increases i n the amount of f o l i a g e . Brix and E b e l l (1969) confirmed this when they found increases i n needle length and width and i n the number of needles per shoot as a r e s u l t of nitrogen f e r t i l i z a t i o n . Again, they found no differences i n photosynthetic rates per unit leaf area between treated and c o n t r o l 121 trees. Unlike Helms however, Brix and E b e l l (1969) concluded that the increased f o l i a g e did not give a f u l l explanation for greater growth a f t e r f e r t i l i z a t i o n . In the same stand i n which he had done his previous work, Brix again examined the effects of f e r t i l i z a t i o n on photosynthesis i n a new experi-ment (Brix, 1971). This time he did f i n d increases i n the rates of net photosynthesis per unit leaf area i n the treated trees. In the year of f e r t i l i z a t i o n , the rate was increased only for current shoots. However, increased photosynthesis occurred i n both current ( i n June) and 1-year-old shoots ( i n June and July) the following year. The response to f e r t i -l i z e r treatment was also l i g h t dependent - only at l i g h t i n t e n s i t i e s of approximately 400 umol m - 2 s - 1 or greater did photosynthetic rates (per unit leaf area) increase. It seems therefore that, other stand factors being equal, increased growth i s due to a combination of a higher photosynthetic capacity and to increases In leaf area. This l a t t e r improvement i s usually through dimensional increases i n needles already present, Increases i n numbers and s i z e of future needles and improved needle retention. Decreases i n l i t t e r f a l l and increased needle retention a f t e r f e r t i l i z a t i o n have been reported by Gessel and Turner (1976). The importance of t h i s type of increase i n leaf area to photosynthetic rates has not been reported i n the l i t e r a t u r e . Some evidence of the importance of needle retention i n pines follow-ing nitrogen f e r t i l i z a t i o n has been found i n Corsican pine (Pinus nigra var. maritima ( A i t . ) M e l v . ) ( M i l l e r and M i l l e r , 1976). In t h i s study, i t was demonstrated that the greater part of the increase i n needle area i n the f i r s t year was due to improved needle retention. As indicated above l i g h t i n t e n s i t i e s would also be an important factor i n the contribution 122 of increased needle retention to growth rates. More recent work by B r i x (1981) did not fin d an improvement i n needle retention r e s u l t i n g from f e r t i l i z a t i o n i n Douglas-fir. In fact needle retention of 5- and 6-year-old needles was decreased by f e r t i l i z a t i o n . This may, however, also be also related to s e v e r i t y of the i n i t i a l nutrient d e f i c i e n c y . Using c l a s s i c a l growth analysis methods employed extensively i n a g r i c u l t u r e , B r i x (1983) demonstrated further the break-down of t h i s response. He calculated net a s s i m i l a t i o n rate (E) (dry weight increases per unit of f o l i a g e and of time) i n r e l a t i o n to nitrogen f e r t i l i z a t i o n and thinning. Annual values of E_ were increased during the f i r s t 3-4 years, but not thereafter. The increased E_ accounted for 37% of the t o t a l stemwood dry matter response to f e r t i l i z a t i o n ; the remainder was due to an increase i n f o l i a r mass. In the same study, the author also found that both treatments contributed a greater percentage of a l l o c a t i o n to branches and f o l i a g e and less to stemwood. F e r t i l i z a t i o n , unlike thinning, did not e f f e c t tree taper as the response was s i m i l a r throughout the crown. The importance of the increased f o l i a r mass i s stressed - e s p e c i a l l y i n the long term. Thus, the long term response to f e r t i l i z a t i o n i s highly dependent on the i n i t i a l f o l i a g e biomass l e v e l before treatment - related i n turn to l i g h t u t i l i z a t i o n and other s i t e factors l i m i t i n g growth. F e r t i l i z e r - D e n s i t y Relationships The importance of growing stock l e v e l s to f e r t i l i z e r response must be considered i n forest management planning. An increase i n leaf area w i l l only benefit growth i f the amount of leaves or t h e i r d i s t r i b u t i o n i s i n s u f f i c i e n t for optimum u t i l i z a t i o n of available l i g h t (Brix, 1971). As 123 mentioned e a r l i e r , response to f e r t i l i z a t i o n can be reduced by low l i g h t l e v e l s . Therefore, climate and i n t e r n a l stand conditions a f f e c t i n g the l i g h t regime of the i n d i v i d u a l needles, such as stand density, crown depth and shape, needle d i s t r i b u t i o n and retention within the crown, are important for a growth response to nitrogen f e r t i l i z a t i o n . At low stocking l e v e l s there i s abundant room f o r crown and root expansion. Even as stand density increases, however, growth response of stands w i l l r i s e to an optimum stocking l e v e l (Strand and De B e l l , 1979). As stocking increases beyond t h i s optimum, growth responses become less and less because crown and root expansion becomes r e s t r i c t e d . As such l i m i t a t i o n s (e.g l i g h t and/or moisture) increase i n severity, the poten-t i a l f o r response to N f e r t i l i z e r approaches zero. Nitrogen f e r t i l i z e r a p p l i c a t i o n increases rates of growth and i n so doing accelerates the usual process of an increase i n stand growth compared to that i n an u n f e r t i l i z e d stand. This effect i s e s p e c i a l l y pronounced i n young stands and those of low stocking. Response may be low or even negative i n overstocked stands, the l a t t e r r e s u l t i n g from mortality accounting for more than the stand i s putting on i n increment (Strand and De B e l l , 1979). It has been suggested that mortality caused by nitrogen f e r t i l i z a t i o n be used as a s u b s t i t u t i o n f o r other precommerT c i a l thinning treatments. M i l l e r (1976) however, concluded that mortality caused by f e r t i l i z i n g stands of Douglas-fir and western hemlock was less b e n e f i c i a l than growing stock reductions by mechanical thinning. I t was also f e l t that increased competition would result i n an increased mortality rate for understory trees only i n stands where the understory trees had marginal vigour to begin with. Perhaps at extremely high 124 d e n s i t i e s , even dominants may not have the growing space required to develop the increased crowns necessary to demonstrate maximum response to additions of nitrogen. Very l i t t l e information i s available on f e r t i l i z e r e f f e c t s on growth of lodgepole pine at high d e n s i t i e s . Even though densities examined i n a recent nursery study were greater than those of the present work, the seedlings were only two years old and mortality, due to i n t e n s i t y of com-p e t i t i o n , had not yet begun (van den Driessche, 1982). In an unpublished report, Brkich (1981) reported heavy mortality i n a dense (ca. 250,000 sph) 18-year-old lodgepole pine stand which had been treated with 200 -800 kg N/ha by eit h e r a s t r i p or broadcast method. However, his r e s u l t s were seriously confounded by density reductions caused by snowshoe hares e s p e c i a l l y at the higher f e r t i l i z e r l e v e l s . F e r t i l i z e r Response i n Lodgepole Pine In comparison to many other species, very l i t t l e work has been published on f e r t i l i z a t i o n of lodgepole pine stands i n North America. Linteau (1962) reported on an ap p l i c a t i o n of magnesium oxide and potas-sium chloride both alone and i n combination to a 4-year-old lodgepole pine plantation i n Quebec. After the second growing season, the double treatment produced s i g n i f i c a n t increases i n growth over other treatments. B e l l a (1968) reported on an experiment using three levels each of nitrogen (as urea), super phosphate and ammonium phosphate sulphate. Neither the P or the S treatment showed s i g n i f i c a n t f o l i a r response; how-ever, there was a volume response over a seven-year period. 125 In Oregon, large s i g n i f i c a n t increases i n annual volume, basal area and bole area were reported a f t e r a p p l i c a t i o n of N, P, and S to a pole-size lodgepole pine stand (Cochran, 1975). Volume responses were high (+100%) over a four year period a f t e r a p p l i c a t i o n . This increase i n volume was without any s i g n i f i c a n t increase i n height growth. More recently, response to N, P, and K treatments were monitored i n 17 thinned lodgepole pine stands i n the i n t e r i o r of B r i t i s h Columbia (Weetman and Fournier, 1982). The experimental method used was a combination of "mini" plots and graphical analysis of s h i f t s i n nutrient concentration, nutrient content and unit f a s c i c l e weight. Generally, d e f i c i e n c i e s of P, K, Ca or Mg were not diagnosed e i t h e r with or without N additions. Response to N additions was highly variable and the authors suggest that the number of plots used i n the t r i a l s was not s u f f i c i e n t to cover the range of v a r i a b i l i t y i n s o i l type and climate found i n the B.C. I n t e r i o r . C. Methods and Materials  F e r t i l i z e r A p p l i c a t i o n The f e r t i l i z e r used was ammonium n i t r a t e (33% N) applied at the rates of 0, 100 and 200 kg N h a - 1 . F e r t i l i z e r was applied by hand i n la t e May of 1981 before bud f l u s h . There were no further applications. Ammonium n i t r a t e was chosen to avoid possible nitrogen losses associated with v o l a t i l i z a t i o n with spring urea applications i n a dry climate. Foliage Sampling Within each p l o t , samples were taken from 5 to 10 trees depending on tree s i z e and a v a i l a b i l i t y of f o l i a g e . Current year's foliage from the upper t h i r d of the tree crown was sampled i n each year. In the 1983 126 harvest, more detailed samples were taken. Foliage from upper, mid and lower crown positions was sampled and age classes sampled included current ('83), one-year-old ('82), two-year-old ('81) and three-year and older ('80+). Samples were oven-dried at 70°C f o r 20-24 hours within one day of t h e i r being c o l l e c t e d i n the f i e l d . A f t e r drying, each sample was kept i n a brown paper bag u n t i l transportation to the laboratory. Before chemical a n a l y s i s , a l l samples were ground to a f i n e powder using a household coffee grinder and the ground samples kept i n sealed p l a s t i c bags. Chemical Analysis of Foliage Samples The samples were analysed f o r t o t a l N, P and K for each of the three sampling periods. In addition, micronutrient analysis was carried out i n year 2 (1982) (Table 20). Analyses of the 1981 and 1982 samples were performed by Norwest S o i l Research Inc. (Vancouver). Total N was deter-mined using the Kjeldahl digestion with a sulphuric acid/potassium sulphate/copper sulphate digestion mixture with determination by d i s t i l -l a t i o n and a boric acid i n d i c a t o r . Fe, Cu, K, Ca and Mg were measured by atomic absorption spectroscopy and P and sulphate-S by a Technicon Auto-analyzer. Active Fe was also determined because of the concept that only a f r a c t i o n of the t o t a l i r o n i s metabolically active (Oserkowsky, 1933). The method used for active i r o n determination follows Oserkowsky's procedure as modified s l i g h t l y by B a l l a r d (1981). The general c r i t i c a l l e vels used i n the discussion also come from B a l l a r d (1981) - based mainly on values from the l i t e r a t u r e . 127 TABLE 20. Chemical analysis carried out by year Year Elements analysed 1981 N P K 1982 N P K S Cu Fe AFe 1983 N P K S t a t i s t i c a l Analysis Micronutrient data from year two and N, P and K from a l l three years of the experiment were subjected to analysis of variance and means were separated by Duncan's New M u l t i p l e Range Test. The detailed analysis of N concentration from year three of the experiment was carried out using the UBC Genlin programme (Greig and B j e r r i n g , 1980). This programme i s based on analysis of variance for unequal subclass numbers using the least squares method and i s suitable for an unbalanced analysis of variance. F o l i a r Diagnosis System Diagnostic i n t e r p r e t a t i o n of f i r s t year r e s u l t s follows a system described by Weetman and Algar (1974) and Timmer and Stone (1978). To f a c i l i t a t e i n t e r p r e t a t i o n , changes i n needle weight, concentration and content are displayed i n a single graph for each element. F o l i a r responses are depicted by arrows j o i n i n g the control with s p e c i f i c t r e a t -ments (Figures 29 and 30). The graphs are constructed by p l o t t i n g element concentration against element content, while the diagonal l i n e s represent increments of unit needle weight. Truncated graphs (Figure 30) 128 £ UNIT N E E D L E WEIGHT, mg /needle J3*L o 6 O o UJ UJ - J £ U J 0 / / // ' 7 / / / 7 / / // / Fig 30 E L E M E N T CONTENT, j j g / needle Figure 29. Schematic r e l a t i o n s h i p between concentration and absolute content of needles (from Timmer, 1979). 129 i < bJ O z O 9 I- * lJ £ -J "3$ UNIT NEEDLE WEIGHT, mg/needle /FV UNTREATED / / «5TATIW/ ' y STATUS /./ / / / / ////// ELEMENT CONTENT, j ig / needle R E S P O N S E I N C H A N C E I N D I R E C T I O N O F S H I F T N E E D L E N U T R I E N T N U T R I E N T P O S S I B L E W E I G H T C O N C . C O N T E N T S T A T U S D I A G N O S I S A + - + D I L U T I O N N O N — L I M I T I N G • + 0 + U N C H A N G E D N O N — L I M I T I N G C + + + D E F I C I E N C Y L I M I T I N G D O + L U X U R Y C O N S U M P T I O N N O N - T O X I C E — ++ + E X C E S S T O X I C f — - - E X C E S S A N T A G O N I S T I C Figure 30. Interpretation of d i r e c t i o n a l relationships between f o l i a r concentration and absolute content of an element following treatment (from Timmer, 1979). 130 show portions of the complete graph (Figure 29). Interpretation of such graphs depends on the d i r e c t i o n of the s h i f t (Figure 30). More detailed discussion of these d i r e c t i o n a l s h i f t s i s given i n Timmer and Stone (1978). D. Results and Discussion 1. Graphical Analysis of F i r s t Year Results  Nitrogen The e f f e c t of stand density on needle weight and nitrogen composi-t i o n (both concentration and content) can be i l l u s t r a t e d by examination of date f r om the u n f e r t i l i z e d p l o t s (Figure 31). The 5000 sph plots are taken here as the c o n t r o l . At 50,000 sph, both unit needle weight and N content decreased r e l a t i v e to the control (5,000 sph). N concentration (%) was r e l a t i v e l y unchanged, increasing only s l i g h t l y . Increasing stand density even further to 150,000 sph showed trends s i m i l a r i n d i r e c t i o n to but greater i n magnitude than the 50,000 sph density. Unit needle weight was approximately 50% that of the control with N content reduced also. N concentration (%) showed a s l i g h t decrease compared to the c o n t r o l . The e f f e c t s of N a d d i t i o n were, i n general, to reverse these density e f f e c t s (Figure 32). In each stand density, f e r t i l i z e r a p p l i c a t i o n caused a 'C' s h i f t , implying that N was i n i t i a l l y l i m i t i n g growth. Looking at the d i f f e r e n t stand densities i n d i v i d u a l l y , other more s p e c i -f i c e f f e c t s can be observed. In the 5,000 sph p l o t s , N a p p l i c a t i o n had greatest e f f e c t on N concentration and content with a lesser effect on u n i t needle weight. Increased N l e v e l from 100 to 200 kg N h a - 1 likewise 131 Figure 31. Density e f f e c t on needle weight and nitrogen composition. The lowest density c l a s s (5K) i s taken here as the control ( ). 132 Figure 32. F e r t i l i z e r e f f e c t on needle weight and nitrogen composition. D i r e c t i o n a l s h i f t s show response to either 100 kg N h a - 1 (F2) or 200 kg N ha"* (F3) r e l a t i v e to the c o n t r o l (•) for each nominal density c l a s s . 133 caused greater increases i n N concentration and content than i n needle weight. In the intermediate stand density (50,000 sph), the general e f f e c t of f e r t i l i z e r a p p l i c a t i o n showed very s i m i l a r trends to those for the 5,000 sph stand. The difference i n response between the 100 and 200 kg N h a - 1 f e r t i l i z e r l e v e l s , however, was quite small f o r a l l three variables measured. Results were most dramatic i n the high density stands (150,000 sph) with increases i n N concentration, content and needle weight. N concentration was increased by over 100% by the 200 kg N h a - 1 treatment. The o v e r a l l trends i n t h i s density were quite s i m i l a r to those i n the low density stand with l i t t l e a d d i t i o n a l increase i n needle weight brought about by the heavier a p p l i c a t i o n of N. In a l l stand densities f e r t i l i z e r therefore caused 'C s h i f t s suggesting that t h i s element was l i m i t i n g growth over the e n t i r e range of d e n s i t i e s . Phosphorus The e f f e c t of increasing stand density on needle weight and f o l i a r P composition can be seen by examination of the c o n t r o l p l o t s (Figure 33). Increasing stand density from control (5,000 sph) to 50,000 sph resulted i n a drop i n both unit needle weight and P content. P concentration (%) remained unchanged. At 150,000 sph, the increase i n stand density caused a reduction i n a l l three v a r i a b l e s . As demonstrated above f o r N, the e f f e c t of f e r t i l i z a t i o n was again to cause a r e v e r s a l of these density e f f e c t s (Figure 33). Both the 5K and 150K plots show a 'C s h i f t (an increase i n a l l three variables) suggesting that the added nutrient (N) has had a synergistic effect on 134 Figure 33. F e r t i l i z e r e f f e c t on needle weight and phosphorus composition. D i r e c t i o n a l s h i f t s show response to eit h e r 100 kg N ha" 1 (F2) or 200 kg N ha~* (F3) r e l a t i v e to the c o n t r o l (•) for each nominal density c l a s s . 135 the P composition. In the intermediate density (50K), however, the e f f e c t i s a 'B' s h i f t (weight and content increase without a change i n concentration) r e s u l t i n g from nutrient transport into the f o l i a g e just being s u f f i c i e n t to keep pace with needle expansion. Potassium The e f f e c t s of stand density on K composition are quite s i m i l a r to those already described for N (Figure 34). Increasing stand density causes appreciable reductions i n needle weight and K content with a lesser e f f e c t on K concentration. The e f f e c t s of N ap p l i c a t i o n on K composition are quite d i f f e r e n t from the e f f e c t s on N or P composition. The amount of N applied (100 or 200 kg N h a - 1 ) i s also important, with an obvious Interaction e f f e c t between the l e v e l of N and stand density (Figure 34). The a p p l i c a t i o n of 100 kg N ha i n the 5K and 150K stands and of 200 kg N h a - 1 i n the 50K stand caused 'C s h i f t s , again i l l u s t r a t i n g a s y n e r g i s t i c effect of those levels of applied N on the K composition. An 'A' s h i f t , however, resulted when the 200 kg N h a - 1 treatment was applied to the 5K and 150K stands or the 100 kg N h a - 1 to the 50K stand. This 'A' s h i f t (decreasing concentration with increasing leaf weight and content) i s probably caused by a d i l u t i o n i n the K concentration brought about by the a d d i t i o n a l growth. Although the e f f e c t of f e r t i l i z a t i o n on K concentration may seem quite large from Figure 34, the o v e r a l l effect i s not s i g n i f i c a n t (see l a t e r sections i n t h i s chapter). The unit dimensions on the y axis were used here for c l a r i t y i n i n t e r p r e t a t i o n of the graphical diagnosis but 136 Figure 34. F e r t i l i z e r e f f e c t on needle weight and potassium composition. D i r e c t i o n a l s h i f t s show response to either 100 kg N ha" 1 (F2) or 200 kg N h a - 1 (F3) r e l a t i v e to the c o n t r o l (•) for each nominal density c l a s s . 137 may be misleading when discussing the r e l a t i v e magnitude of change i n K percent. 2. Three Year Analysis f o r N, P and K  Nitrogen F e r t i l i z e r , year and t h e i r i n t e r a c t i o n s with stand density a l l had s i g n i f i c a n t e ffects on N concentration (%) (see ANOVA table i n Appendix D . l ) . Because the second-order i n t e r a c t i o n , D x F x Y, i s s i g n i f i c a n t , the e f f e c t s of any of the main treatments, D, F or Y could only be interpreted i n the context of t h i s o v e r a l l i n t e r a c t i o n . The o v e r a l l treatment e f f e c t s are therefore shown together i n the three sub-plots of Figure 35. From Figure 35, i t can be seen that a l l three stand densities show the same general trend of a decrease i n N percent since the year of f e r t i l i z a t i o n . By the f a l l of 1983, three growing seasons a f t e r the stands had been f e r t i l i z e d , a l l f e r t i l i z e d plots (except one) were at or below the control l e v e l s . The only exception was the 200 kg N h a - 1 treatment i n the 50,000 sph stand which was s i g n i f i c a n t l y greater than the c o n t r o l . In the low (5,000 sph) and intermediate (50,000 sph) stand d e n s i t i e s , the c o n t r o l plots showed a s i g n i f i c a n t decrease over the three year period. A s i m i l a r i n s i g n i f i c a n t trend was observed for the high density (150,000 sph) stand. It i s not known whether the general decrease with N concentration over time i s related to increasing stand age or i s simply a r e s u l t of weather conditions over the three years. The fact that f o l i a g e was sampled from d i f f e r e n t plots i n each year may also be contributing to the v a r i a b i l i t y . 138 1.7-. 5 K 1.8-i » » B 0 198' 198 J 1983 YEAR Figure 35. Density x f e r t i l i z e r x year i n t e r a c t i o n e f f e c t s on N .concentration. Arrows indicate time of f e r t i l i z e r a p p l i c a t i o n (May 1981). N con-centration was not measured p r i o r to f e r t i l i z a t i o n - 1980 values shown are therefore approximate only. Foliage was sampled from d i f f e r e n t plots i n each of the years since f e r t i l i z a t i o n . Values outside the range delineated by the v e r t i c a l bars are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). 139 In the low density stand, both l e v e l s of f e r t i l i z e r had s i g n i f i c a n t , p o s i t i v e e f f e c t s on N concentration i n the f a l l of 1981 (one growing season a f t e r treatment). N concentration was increased from 1.1% (con-t r o l ) to 1.4% and 1.7% by the 100 kg N h a - 1 and 200 kg N h a - 1 treatments re s p e c t i v e l y . After two growing seasons, only the higher l e v e l of f e r t i -l i z e r had a s i g n i f i c a n t e f f e c t . By 1983, there were no s i g n i f i c a n t differences between treatments. The intermediate stand density showed similar-trends to the low stand density, already discussed, with generally lower N concentrations throughout. By 1983, however, the 200 kg N h a - 1 treatment was s t i l l showing a s i g n i f i c a n t l y greater N% l e v e l than the c o n t r o l . As already discussed i n the section dealing with the graphical diagnosis, the most dramatic e f f e c t s of applied N were i n the high density stand. In 1981, the 200 kg N h a - 1 treatment caused an increase i n N% from 1.0% (control) to 2.1%. Although reduced s i g n i f i c a n t l y i n amount by the following year, the e f f e c t was s t i l l s i g n i f i c a n t . A l l treatments were below the 0.9% l e v e l by 1983 and threre was no s i g n i f i c a n t difference between f e r t i l i z e d and control p l o t s . Taking l e v e l s of l e s s than 1.2% to represent moderate to severe deficiency i n N for lodgepole pine ( B a l l a r d , 1979), the data i n Figure 3.5 would suggest that a l l control plots (over the e n t i r e range of densities) were d e f i c i e n t i n nitrogen. S i m i l a r l y , a l l plots (control and f e r t i -l i z e d ) i n 1983 are N d e f i c i e n t . In contrast, only some of the 1981 p l o t s (200 kg N h a - 1 f o r low and intermediate d e n s i t i e s , 100 and 200 kg N h a - 1 for the high density) show concentrations greater than 1.5%, representing adequate or very s l i g h t l y d e f i c i e n t l e v e l s ( B a l l a r d , 1979). In a l l three 140 years examined, not only were a l l d e n s i t i e s (control p l o t s ) d e f i c i e n t i n N, there was also no s i g n i f i c a n t difference i n N concentration between the various stand d e n s i t i e s . Phosphorus The s i g n i f i c a n t variables i n the analysis of variance for treatment e f f e c t s on %P are f e r t i l i z e r , year and the Interaction, density x year (ANOVA table i n Appendix D.2). The general e f f e c t of f e r t i l i z e r a p p l i c a -t i o n over the e n t i r e 3-year sampling period was s i m i l a r to that already discussed f o r 1981 i n the previous section dealing with graphical diagno-s i s . The a p p l i c a t i o n of N f e r t i l i z e r seems to have had a s y n e r g i s t i c e f f e c t on P concentration (Figure 36). Using the values of 0.12% and 0.15% to represent d e f i c i e n t and adequate levels of P r e s p e c t i v e l y (B a l l a r d , 1979), the l e v e l s of P shown i n Figure 36 a l l represent severe to moderate d e f i c i e n c i e s of P. The density x year Interaction again shows s i m i l a r trends to some of the graphical r e s u l t s already discussed, i n that the low and high density stands seem to behave a l i k e and opposite to the intermediate density (Figure 37). The o v e r a l l e f f e c t of year i s to show a decrease i n P per-cent over the three year period. In the intermediate density, t h i s decrease i s mostly i n the t h i r d year whereas i n the low and high density stands the decrease occurred i n 1982 and then increased i n the following year. As already demonstrated f o r Figure 36, a l l P concentration figures are well below those suggested to be adequate f o r the species. Potassium Nitrogen f e r t i l i z a t i o n had no s i g n i f i c a n t e f fect on K concentration, the s i g n i f i c a n t variables i n the analysis of variance being density, year 141 Figure 36. F e r t i l i z e r e f f e c t on P concentration. Data not followed by the same l e t t e r are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). 142 0.10 1981 1982 1983 YEAR Figure 37. Density x year i n t e r a c t i o n e f f e c t s on P concentration. Data not followed by the same l e t t e r are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). Stand densities are 5K (A), 50K (•) and 150K (o). 143 and t h e i r i n t e r a c t i o n (D x Y) (ANOVA table i n Appendix D.3). K concen-t r a t i o n was effected strongly by year (Figure 38) and the s i g n i f i c a n t difference between d i f f e r e n t stand densities was only seen i n 1983 where the low density stand has a higher K concentration than either the intermediate or high stand density. Differences between years may have been affected by sampling of f o l i a g e from d i f f e r e n t plots i n each year. The range of K values (0.4-0.7%) indicates that concentrations of t h i s element represent moderate deficiency to adequate l e v e l s depending on year and stand density. 3. Micronutrient Analysis As indicated i n the Methods section, analysis for micronutrients was c a r r i e d out i n the second year of the experiment (1982). The elements examined included sulphur (S), copper (Cu), i r o n (Fe) and a c t i v e - i r o n (AFe). The analyses of variance i n d i c a t e , however, that for S, Cu and Fe, density, f e r t i l i z e r or t h e i r i n t e r a c t i o n (D x F) had no effect on nutrient composition (ppm) of these elements. The only s i g n i f i c a n t e f f e c t of a treatment on any of the micronutrients was a positive e f f e c t of f e r t i l i z e r l e v e l on AFe (Figure 39). The range of nutrient compositions i n the plots was 608-784 ppm (S), 1.1-3.5 ppm (Cu), 240-348 ppm (Fe) and 35-114 ppm (AFe). C r i t i c a l values fo r sulphur are not r e a d i l y a v a i l a b l e for lodgepole pine. Nitrogen: sulphur r a t i o s have been used, however, and i t has been suggested that an N/S r a t i o greater than 14.6 may indicate an S deficiency (K e l l y and Lambert, 1972; Turner et a l . , 1977). Table 21 shows the calculated N/S r a t i o s f o r the present p l o t s , and suggests that f e r t i l i z e r a p p l i c a t i o n , 0.8 o c o o 0.7-? 0.6-^ 0.5-0.4-0.3 1981 1982 YEAR 1983 Figure 38. Density x year i n t e r a c t i o n e f f e c t s on K concentration. Data not followed by the same l e t t e r are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). Stand densities are 5K (A), 50K (•) and 150K (o). Figure 39. F e r t i l i z e r e f f e c t on 'active' Fe. Data not followed by the same l e t t e r are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). 146 TABLE 21. Nitrogen:sulphur r a t i o s as affected by f e r t i l i z e r and stand density. Values greater than the c r i t i c a l l e v e l (14.6) may ind i c a t e S defic i e n c y . Stand density (sph) 5,000 50,000 150,000 0 13.9 13.5 13.6 Nitrogen f e r t i l i z e r 100 14.3 15.9 17.3 Level (kg N ha *) 200 20.8 18.9 20.5 e s p e c i a l l y i n the higher density pl o t s may have induced a sulphur defici e n c y . Copper l e v e l s (mostly below 2.5 ppm) are a l l quite low and below the c r i t i c a l 4.1 ppm suggested recently for lodgepole pine growing under f i e l d conditions (Majid, 1984). Values f o r AFe, however, are above the 25-33 ppm c r i t i c a l region for the species suggested by the same author. In a greenhouse study with lodgepole pine, Majid (1984) found that increases i n f o l i a r nitrogen were associated with decreases in f o l i a r copper and t o t a l and active forms of i r o n . In the present study, the opposite was observed and the highest l e v e l of applied N (200 kg ha -*) resulted i n increases of 41%, 11% and 155% over the controls for Cu, Fe and AFe r e s p e c t i v e l y . 147 4. 1983 Analysis of N Concentration as Affected by Needle Age and  Crown P o s i t i o n Of the main treatments applied, F, C and A each had a s i g n i f i c a n t e f f e c t on N concentration. The i n t e r a c t i o n s F x A, D x F ( f i r s t order) and D x F x A , D x F x C (second order) were also s i g n i f i c a n t (Appendix D.4). Because of the s i g n i f i c a n c e of the second order i n t e r a c t i o n s , none of the treatment e f f e c t s could be examined i n i s o l a t i o n from the others. To help i n i n t e r p r e t a t i o n of the r e s u l t s , the second order i n t e r a c t i o n s , D x F x A and D x F x C, are shown i n the subplots of Figures 40 and 41, r e s p e c t i v e l y . In the low density stand (5,000 sph, Figure 40), the o v e r a l l e f f e c t of the f e r t i l i z e r treatment was quite small i n a l l needle age c l a s s e s . The 100 kg N h a - 1 treatment did not r e s u l t i n a s i g n i f i c a n t l y greater N concentration than the control In any age class and i n the current (1983) years f o l i a g e was, i n f a c t , below the control l e v e l . The higher l e v e l of applied N (200 kg N h a - 1 ) did r e s u l t i n a s i g n i f i c a n t l y greater N concentration i n the f o l i a g e produced i n the growing season a f t e r f e r t i l i z a t i o n (1981) but not i n any of the other age classes. Using the c r i t i c a l levels already discussed (Ballard, 1979), f o l i a g e from a l l needle age classes i n these low stand density plots was severely d e f i c i e n t i n nitrogen, i r r e s p e c t i v e of f e r t i l i z e r treatment. In the intermediate stand density, the treatment e f f e c t s were quite d i f f e r e n t (50,000 sph, Figure 40). As i n the low stand density, the 100 kg N h a - 1 treatment had no s i g n i f i c a n t e f f e c t compared to the control i n any of the age classes examined. The 200 kg N h a - 1 , however, resulted i n s i g n i f i c a n t l y greater N concentration i n foliage produced i n a l l three growing seasons since the treatments were applied. 148 5 K 1.4 -1.? -C + 3 + 0 2 0 1 C Needle Age Class Figure 40. Density x f e r t i l i z e r x needle age i n t e r a c t i o n effects on N concentration. Needle age classes include C (1983), C+l (1982), C+2 (1981) and C+3+ (1980 and older) while f e r t i l i z e r l e v e l s used were 0 kg N ha" 1 (•), 100 kg N h a - 1 (o) and 200 kg N ha"l (A). Values outside the range delineated by the v e r t i c a l bars are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). 149 i.e-< 5 K J 0 ( 1 - i * • -Crown Position Figure 41. Density x f e r t i l i z e r x crown position i n t e r a c t i o n effects on K concentration. Crown positions are: 1 (whorl 3), 2 (whorl 6 ) and 3 (whorl 9) while f e r t i l i z e r l e v e l s used were 0 kg N ha" 1 (•), 100 kg N ha" 1 (o) and 200 kg N ha" 1 (A). Values outside the range delineated by the v e r t i c a l bars are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). 150 The general shape of the response i n the high density stand i s s i m i l a r to that f o r the intermediate density (150,000 sph, Figure 40). Again the main ef f e c t Is i n fol i a g e produced the growing season a f t e r f e r t i l i z a t i o n (1981), with both l e v e l s of applied N r e s u l t i n g In s i g n i f i -cant increases i n N percent over the c o n t r o l . At th i s stand density, the 200 kg N h a - 1 has also had a s i g n i f i c a n t p o s i t i v e e f f e c t on %N i n fol i a g e produced p r i o r to f e r t i l i z a t i o n . Only the 1981 foliage from the more heavily f e r t i l i z e d plots i n the intermediate and high stand densi-t i e s show f o l i a r N concentrations approaching the l e v e l (1.5%) considered adequate f or the species ( B a l l a r d , 1979). The i n t e r a c t i o n D x F x C i s shown i n Figure 41. In the low stand density p l o t s , only the f e r t i l i z e d plots show a s i g n i f i c a n t decrease i n N percent from upper to lower crown positions. N concentration i n the con-t r o l plots i s not affected by crown p o s i t i o n . Only at the upper crown p o s i t i o n do the f e r t i l i z e d plots show s i g n i f i c a n t greater N concentration than the controls. In the intermediate stand density, only the 200 kg N ha-*- has any s i g n i f i c a n t e f f e c t on %N over the co n t r o l . As i n the low stand density, crown po s i t i o n has no effect on N concentration i n the control p l o t s . In the f e r t i l i z e d p l o t s , the general trend i s for a decrease i n N concentration from upper to lower crown p o s i t i o n , again s i m i l a r to the low density p l o t s . In the high density stands, t h i s trend i s absent with no s i g n i f i -cant change i n N percent with crown p o s i t i o n . This i s the case for a l l f e r t i l i z e r treatments. 151 E. Discussion Because of the lack of work i n the f i e l d of lodgepole pine n u t r i -t i o n , p a r t i c u l a r l y In stagnant stands, few data are available f or comparison with the r e s u l t s presented here. Dickey (1981) found a reduction of 35 percent i n needle weight over a density range of 6,000-170,000 sph while Worrall et a l . (1985) found a reduction of 52 percent between vigorous and stagnant trees for the same variable. The r e s u l t s presented by the l a t t e r workers are quite s i m i l a r to the 55 percent reduction found i n needle weight between vigorous and stagnant trees i n the present study. The e f f e c t of increasing stand density on N concentration i n lodge-pole pine seems to be inconsistent and dependent on s i t e . Worrall et^ a l . (1985) reported that N concentration was not s i g n i f i c a n t l y d i f f e r e n t between vigorous and stagnant trees while Dickey (1981) reported that for a s i t e close to that used by Worrall and coworkers, N concentration declined with increasing stand density. At a s i t e situated within 5 km of the present study s i t e , Dickey (1981) found no s i g n i f i c a n t r e l a t i o n -ship between N concentration and stand density (s i m i l a r to that shown i n Figure 31). P and K concentrations were not found to be affected by stand density i n e i t h e r of the above two studies. The general C s h i f t s reported here f o r N a f t e r f e r t i l i z a t i o n correspond to those found by Weetman and Fournier (1982) i n thinned and unthinned (approximately 20,000 sph) lodgepole pine stands i n Spillimacheen, B.C. For P concentrations, the same workers reported on an A s h i f t a f t e r f e r t i l i z a t i o n i n t h e i r unthinned stand, i n d i c a t i n g that phosphorus supply was d i l u t e d by add i t i o n a l growth. Figure 33 shows that 152 t h i s did not occur i n the present study with C s h i f t s i n the low and high stand densities i n d i c a t i n g that the added N had a synergistic e f f e c t on P composition. Results are quite s i m i l a r between the two studies for changes i n K percent with N f e r t i l i z a t i o n having no s i g n i f i c a n t e f f e c t . The drop i n f o l i a r N l e v e l s shown i n Figure 35 agrees with the general trends reported for f e r t i l i z a t i o n response In northern c o n i -ferous forests (Armson et a l . , 1975; M i l l e r et^ al«» 1981). By 1983, three growing seasons a f t e r f e r t i l i z a t i o n , f o l i a r N concentrations were 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 controls i n either the vigorous or repressed stands. The f o l i a r micronutrient l e v e l s reported here are within the range presented by B a l l a r d (1981) for stagnant stands located close to the present study s i t e . Table 21 shows that N f e r t i l i z a t i o n has induced sulphur d e f i c i e n c i e s , p a r t i c u l a r l y at the higher stand densities - as predicted by Ballard (1981). Copper l e v e l s , generally le s s than 2.5 ppm, are below the c r i t i c a l l e v e l for the species and suggest possible moderate deficiency. F o l i a r copper l e v e l s reported by Ballard (1981) were 2.0 ppm over the e n t i r e density range examined (6,000 - 170,000 sph). Both t o t a l i r o n and active i r o n values reported here seem adequate for a l l stand d e n s i t i e s . Although the c r i t i c a l l e v e l s of Bal l a r d (1979) have been used here for comparison, i t i s not known how relevent these general lodgepole pine values are for stagnant stands. Perhaps trees growing at such high densities do not require the N l e v e l s thought to be adequate for the species growing at more 'normal' stand d e n s i t i e s . For example, trees from stagnant stands do not show the usual deficiency symptoms associated 153 with low N a v a i l a b i l i t y . This may support the hypothesis of Ingestad (1982) that deficiency symptoms disappear when the i n t e r n a l nitrogen concentration i s stable, independent of l e v e l . One would expect, therefore, that i f t h i s were true then a stand which i s currently undergoing suppression (and therefore showing changes In r e l a t i v e growth rate) might display deficiency symptoms. In the present study, the s i m i l a r i t y i n behavior of the 5K and 150K stands ( p a r t i c u l a r l y i n f i r s t - y e a r response to f e r t i l i z a t i o n ) may be because of t h e i r stable r e l a t i v e growth rates. The 50K stands (perhaps currently succumbing to repression) behaved d i f f e r e n t l y - whether t h i s i s due to the nitrogen f l u x density model suggested by Ingestad (1982) i s not known but may warrant further i n v e s t i g a t i o n . 154 CHAPTER 7. THE CAUSAL MECHANISM FOR GROWTH STAGNATION IN LODGEPOLE PINE Over a wide range of stand d e n s i t i e s , height growth i n many tree species i s independent of stocking, being mainly affected by s i t e q u a l i t y . This i s not the case for lodgepole pine growing at extremely high stand d e n s i t i e s . In the present study of a f i r e originated 20-year-old stand, top height declined from 5.5 m at 5,000 sph to less than 2.5 m at 100,000 sph. An explanation f o r this reduction i n height growth i s not r e a d i l y available from the l i t e r a t u r e . Only M i t c h e l l and Goudle (1980) and Worrall £t al_. (1985) have attempted to i d e n t i f y possible causes for growth repression In lodgepole pine, or suggested any e a s i l y testable hypotheses regarding i t . Other workers have suggested possible explanations for these reduc-tions i n height growth for other tree species. Zavitkovski and Dawson (1978) suggested that low l i g h t l e v e l s i n dense stands of jack pine may have been the main factor l i m i t i n g height growth. Their work was c a r r i e d out i n plantations which were f e r t i l i z e d and i r r i g a t e d . This suggests that nutrient and water supply to the roots were not growth l i m i t i n g . In t h i s study, the f i r s t component suggests that l i g h t l e v e l s are,, i n f a c t , greater beneath the canopy of repressed stands than under more vigorous stands. Because of differences i n canopy architecture between trees from vigorous and repressed stands, however, f o l i a g e may develop at a lower l i g h t i n t e n s i t y i n repressed stands. Mean s p e c i f i c leaf area, for example, was found to Increase with stand density, suggesting an adaption to lower l i g h t l e v e l s by f o l i a g e as i t develops i n higher stand d e n s i t i e s . 155 Reductions i n e i t h e r moisture or nutrient a v a i l a b i l i t y , or both, have also been suggested as possible causal factors of repression i n lodgepole pine ( M i t c h e l l and Goudie, 1980). Water r e l a t i o n s of repressed trees remain unexplored but the findings of Zavitkovski and Dawson (1978) suggest that height growth i n jack pine may be reduced even i n the presence of apparently adequate supplies of moisture to the roots. The same may be said for nutrients as the plantations were f e r t i l i z e d annually (although the authors do not say what type of f e r t i l i z e r was used). F o l i a r analysis work i n stands of lodgepole pine generally show no differences i n concentrations of macro or micronutrients between vigorous or repressed trees, although s i t e differences may affect t h i s r e l a t i o n s h i p ( B a l l a r d , 1981; Dickey, 1981 and Worrall et_ a l . , 1985). The f o l i a r analysis component (3) of the present study, confirms these general trends although sulphur d e f i c i e n c i e s were apparently induced by nitrogen f e r t i l i z a t i o n , e s p e c i a l l y at higher stand d e n s i t i e s . The most recent contribution to our understanding of repression -and the only published work s p e c i f i c to lodgepole pine comes from Worrall et a l . (1985). They rejected the hypothesis that the differences between vigorous and repressed trees lay i n t h e i r a p i c a l meristems and showed that, three growing seasons a f t e r r e c i p r o c a l g r a f t i n g , growth was governed e n t i r e l y by the type of rootstock. Evidence from stem analysis data, presented i n study component 2, suggests that, despite the r e s u l t s presented by Worrall e_t a l . , epigenetic factors may be contributing to the reduction i n height growth i n stagnant stands. The mechanism of t h i s i n t e r n a l regulation of growth i s not understood but i t may be related to hormone lev e l s or metabolic sink strength. 156 The amount of photosynthate used i n r e s p i r a t i o n may also be an important factor i n reduced growth of stands growing at high stand d e n s i t i e s . A forest stand composed of many small trees consumes a greater amount by r e s p i r a t i o n than a stand of the same species composed of fewer large trees (Kira and Shidei, 1967). This i s mainly due to the fact that r e s p i r a t i o n i n woody tissues i s more c l o s e l y related to surface area than to weight (Kinerson, 1975). Rates of r e s p i r a t i o n were not measured i n the present study. Between low and high stand d e n s i t i e s , however, a s h i f t i n biomass a l l o c a t i o n from fo l i a g e and branches to stem was found, s i m i l a r to that reported by B a s k e r v i l l e (1965) f o r balsam f i r . In repressed stands of lodgepole pine, therefore, the proportion of productive to consumptive tissue i s reduced i n comparison to more vigorous stands. The reasons behind t h i s s h i f t to stem production i n stands growing at high density have not been explored i n the l i t e r a t u r e . In f a c t , the pipe model theory has been used by many workers i n estimating f o l i a g e area or weight on the assumption that the r a t i o of foliage to sapwood area i s species s p e c i f i c and unaffected by stand structure or treatment (Whitehead, 1978; Kaufmann and Troendle, 1981). More recently, however, Pearson et a l . (1984) have shown that the leaf area:sapwood area r a t i o i s density dependent In lodgepole pine and suggested (but did not measure) that the v a r i a t i o n was due to the differences i n the sapwood's a b i l i t y to conduct and store water. In stagnant stands or suppressed trees i n more vigorous stands, the leaf area:sapwood area r a t i o was found to decrease by up to 80% with decreasing stem diameter i n the present study (study component 2). 157 Needle s i z e and shoot length are reduced i n stagnant trees. I f the period when the trees are ' i n candle' i s also l e s s , then i t might be expected that the time a v a i l a b l e for earlywood production might"be reduced, according to the hormonal theory of wood formation (Larson, 1969). Measurements on wood samples, from both vigorous and stagnant trees, showed that earlywood percent decreased from 62 to 8% across a density range from 6,500 to 109,000 sph. Although the method used i n assessing t h i s percentage may have exaggerated the amount of latewood, subsequent microscopic examination showed that the o v e r a l l trends Indicated were correct and that trees growing i n stagnant stands contained proportionally less earlywood than trees growing i n more open stands. This would suggest that conductivity i s reduced i n stems of stagnant trees (Edwards and J a r v i s , 1982) and supports the hypothesis of Whitehead et a l . (1984) that the r e l a t i o n s h i p between fo l i a g e area and sapwood area depends, not only on the amount of sapwood, but also on i t s permeability. The reduction i n conductivity also suggests that the amount of water (and nutrients) reaching the crown w i l l be reduced i n stagnant trees. This may explain why dense plantations of jack pine showed low height growth even with frequent f e r t i l i z a t i o n and i r r i g a t i o n . Stagnant trees may respond to this reduced conductivity by either l i m i t i n g t h e i r f o l i a g e production or by a l l o c a t i n g r e l a t i v e l y more photosynthate to xylem i n the stem to compensate for the reduction i n conductivity. In the stands under study, the reductions i n leaf area are greater than the reductions i n sapwood area between vigorous and stagnant stands, suggesting that control of the former may be more important. 158 The r e l a t i o n s h i p between f o l i a g e area and sapwood area might also be expected to be dependent on the rate at which the water i s transpired at the f o l i a g e (Whitehead et a l . , 1984). No measurements of t r a n s p i r a t i o n were conducted i n the present study, however, some work has been done on comparison of t r a n s p i r a t i o n rates between trees from 'average' stands (2,200 sph) and dense stands (14,600 sph) of older lodgepole pine i n Wyoming (Knight et a l . , 1981). They observed that the two forest stands, although of contrasting structure, had the same tra n s p i r a t i o n rates (per unit of leaf area). Whatever the reasons behind t h i s s h i f t i n leaf area:sapwood area r a t i o as stand density increases, i t does occur and presumably leads to an increasing r a t i o of consumptive to productive tissue i n stagnant stands. One would expect perhaps, that, as the trees grow the s i t u a t i o n would not improve because the reduction i n available moisture and nutrients (caused by the decrease i n conductivity) would lead to less f o l i a g e production which, i n turn, would reduce the amount of earlywood production (Figure 42). Root biomass was not measured i n the present study although i t has been suggested that the root/shoot metabolic r a t i o i n stagnant trees may be too high (Worrall et_ a l . , 1985). Pearson et a l . (1984) found that f or older (>70 years) stands of lodgepole pine, the root:shoot biomass r a t i o s ranged from 0.27 to 0.50, with the highest values i n the dense stands. Evidence from some workers would suggest that one might expect this s h i f t to f i n e root biomass to occur i n stagnant stands ( M i t c h e l l and Goudie, 1980; Pearson et a l . , 1984). A l t e r n a t i v e l y , because leaf area i s reduced so much i n repressed stands, one might expect that less moisture would be 159 Forest F i r e Extremely High Density Regenera-t i o n Established 5yrs1 Very I E a r l y I Canopy I Closure! Declines i n Available Nutrients/Mois-ture. Reductions in Light Levels in Lower Canopy iDeclines i n Mois-I Iture and Nutrient 1 Supply to Foliage Reduced Needle and Shoot Growth Negative Feedback Reduces Stemwood Conductivity of Water and Nutrients Leads to Reduced • Earlywood Production Stand Height and Growth Below Site Potential Limits Production of Foliage Bio-mass LA/SA Ratio Declines Unknown Inte nal (Epigene t i c ) Factors ^••fl^^Bw Reduced ^ ^ f c Strength Reduc IDecreased Productive ITissue (foliage) 1 Increased Consumptivi •Tissue (cambium) tions i n Increased Annual Height A l l o c a t i o n to Growth Pime Root Biomass Figure 42. Suggested causal mechanisms for high density induced repression of s i t e growth potential i n lodgepole pine. 160 required, although t h i s r e l a t i o n s h i p i s also affected by the rate of water loss per unit of leaf area. I t has also been shown that the peak i n f i n e and mycorrhizal root biomass i s reached around the time of canopy closure (Vogt et a l . , 1983). If the high density stands of the present study were i n i t i a l l y estab-lished at densities of 250,000 or greater (not unreasonable, given the high m o r t a l i t y ) , then canopy closure probably occurred before the trees were 5-7 years old (growing at 20 cm spacing). If the amount of root biomass peaked around t h i s time and above-ground biomass continued to grow, however, there may not be as large a root:shoot r a t i o i n the present stands as expected. This area of a l l o c a t i o n to f i n e root biomass obviously warrants further Investigation. The consequences of high density induced repression i n lodgepole pine are of i n t e r e s t to forest managers. These effects have been specu-lated on by Smith (1985, personal communication^) i n r e l a t i o n to the -3/2 power law (Figure 43). A zone of repression i s suggested between r e l a -t i v e density l i n e s 84 and 100. This zone must be avoided i n designing management regimes i n order to avoid height growth reductions leading to losses i n merchantable size material within projected rotation periods. It i s suggested that any thinning treatment, i f I t i s to be e f f e c t i v e , ; must be carried out p r i o r to stagnation occurring. Figure 42 would suggest that t h i s treatment would have to be accomplished at canopy closure or at least before stands reached maximum LAI to avoid entering the negative feedback loop induced by the reduced hydraulic conductivity. Dr. N.J. Smith, Department of Forest Science, Faculty of Forestry, U n i v e r s i t y of B.C. 125 400 1000 4000 10000 Stand Density (sph) Figure 43. I n t e r i o r lodgepole pine stand density diagram (from Flewelling and Drew, 1985). Suggested area of repression added by N.J. Smith (UBC, 1985). Diagonal l i n e s show r e l a t i v e density curves (defined as number of trees per hectare/ maximum number of trees per hectare x 100%). 162 CHAPTER 8. GENERAL CONCLUSIONS Pl o t 8 were established In twenty-year-old lodgepole pine growing at f i v e d i f f e r e n t stand densities ranging from 3,500 sph to 109,000 sph. Nitrogen f e r t i l i z e r was applied to the low, mid and high density cl a s s e s . F e r t i l i z e r was applied as ammonium n i t r a t e (33% N) at the rates of 0 kg N h a - 1 ( c o n t r o l ) , 100 kg N h a - 1 or 200 kg N h a - 1 . F o l i a r nutrient compositions were examined i n the f a l l of each of three subsequent years a f t e r f e r t i l i z a t i o n and a destructive harvest was carried out i n the t h i r d year to determine the pattern of biomass a l l o c a t i o n between stands of d i f f e r e n t density. From the r e s u l t s presented i n e a r l i e r chapters, the following conclusions may be drawn. • In attempting to examine the e f f e c t s of f e r t i l i z e r (F), stand density (D), crown p o s i t i o n (C) and needle age (A) on s p e c i f i c leaf area (SLA, fresh needle surface area/dry weight), i n t e r p r e -t a t i o n of re s u l t s was made d i f f i c u l t by a s i g n i f i c a n t D * F * A * C i n t e r a c t i o n . Treatments, however, could be ranked according to t h e i r magnitude of ef f e c t on SLA. In general, SLA decreased with increasing age of f o l i a g e , increased with increasing depth i n the canopy and with increasing stand density and decreased s l i g h t l y with increasing f e r t i l i z e r a p p l i c a t i o n . • The below-canopy l i g h t climate measured with a chemical (anthracene i n benzene) l i g h t meter indicated that l i g h t l e v e l s were higher (34% of above-canopy l e v e l s ) under the dense stands compared to the less dense stands (14% of above-canopy l e v e l s ) . This i s opposite to what one might expect on the basis of stand density alone. This apparent anomaly could be explained, how-ever, a f t e r examination of leaf area index (LAI) values 163 calculated for the various stand d e n s i t i e s . Because LAI was reduced at high stand d e n s i t i e s , the r e l a t i v e l i g h t measurements were described using the Beer-Lambert equation even though e x t i n c t i o n c o e f f i c i e n t s increased with increasing stand density. The measured l i g h t environment, however, beneath the various stand densities did not explain the changes, already outlined, i n SLA. The main reason suggested for t h i s i s that, at the lower stand d e n s i t i e s , branches are larger and generally sweep upwards more than those at higher stand d e n s i t i e s . The f o l i a g e of trees growing i n the low density stands probably develops i n a better l i g h t environment, therefore, than f o l i a g e from a s i m i l a r crown p o s i t i o n i n a high density stand. • Data from a complete harvest of a l l plots showed that mean tree height was inversely proportional to stand density, ranging from 5-6 m at 5,000 sph to less than 2 m at 100,000 sph. Top height, although showing the same o v e r a l l decrease with increasing stand density was less density-dependent, e s p e c i a l l y In the 5,000 -50,000 sph range. The decrease i n top height over the e n t i r e range of stand densities d i f f e r s from the trend reported for younger stands by M i t c h e l l and Goudie (1980) and suggests that stands may not show any signs of repression (e.g. reduced height growth) u n t i l l a t e r i n the r o t a t i o n . Stands, therefore, may grow into a state of repression. • Analysis of variance for basal area indicate that i t was not affected by f e r t i l i z e r treatment. The largest basal area, 50 m2 h a - 1 (measured at ground l e v e l ) was found i n stands of intermediate stand density ( i . e . approximately 50,000). • M o r t a l i t y ranged from 0%-50% and was d i r e c t l y proportional to (stand d e n s i t y ) 2 . High density plots obviously were established 164 at much greater densities than the present number of l i v e trees would i n d i c a t e . True mortality, based on the number of trees dying since the stands were established, i s d i f f i c u l t to estimate, e s p e c i a l l y i n the higher stand d e n s i t i e s . • From a random s e l e c t i o n of trees by diameter c l a s s , multiple l i n e a r regressions, accounting f o r low, intermediate and high stand densities, were generated for estimates of t o t a l above-ground biomass and various biomass components. Independent variables included diameter (D), height (H), diameter at the base of the l i v e crown (D c) and length of the l i v e crown (CL). Estimates from these equations gave t o t a l above-ground biomass ranging from 61 t h a - 1 at 8,000 sph to 16 t h a - 1 at 109,000 sph. • Ensuring a d d i t i v i t y , s i m i l a r regression equations were generated f o r each component of above-ground biomass ( f o l i a g e , branches and stems). With increasing stand density the proportion of t o t a l biomass allocated to the stem Increased (58% to 78% between low (5K) and high (150K) stand densities r e s p e c t i v e l y ) . Further analysis on needle retention showed that below the s i x t h whorl, trees growing i n low density stands showed greater needle reten-t i o n than trees growing at higher stand d e n s i t i e s . • Stem analysis of height growth between low and high density stands suggested that height growth of trees i n repressed stands i s more c l o s e l y c o r r e l a t e d with height growth of the previous year than i t i s i n more vigorous stands. This, i n turn, possibly indicates a greater degree of i n t e r n a l growth control by lodge-pole pine growing at high d e n s i t i e s . The mechanism of this c o n t r o l i s not f u l l y understood but i t may be hormonal or re l a t e d to sink strength (Sweet and Wareing, 1966). The large degree of control of height growth from within the plant may also be 165 rel a t e d to "environmental preconditioning", a concept suggested by Rowe (1964). Both basal area and sapwood area gave s i m i l a r regression equations when used as independent variables to predict leaf area. Leaf area index ranged from 13.43 m.2m~2 at 8,000 sph to 2.33 m2m~2 at 109,000 sph and was not affected by f e r t i l i z e r a p p l i c a t i o n . The r a t i o of leaf area to sapwood area decreased from a mean of 0.3 m2 cm - 2 i n the 5K plots to 0.14 m2 cm - 2 i n the 150K p l o t s . This r e s u l t s agrees with recent work by B r i x and M i t c h e l l (1983) and Pearson et^ a l . (1984) who found that the leaf area/sapwood area r a t i o i s not species s p e c i f i c and may vary depending on stand conditions. On an Individual tree basis, t h i s leaf area/sapwood area r a t i o was found to be dependent on tree diameter - smaller diameter trees having proportionally more sapwood area than larger diameter trees. X-ray densitometry revealed differences i n oven-dry wood density between trees from d i f f e r e n t stand d e n s i t i e s . Mean earlywood percentage decreased from 62% to 8% i n codominants from stand densities of 6,500 sph to 109,000 sph re s p e c t i v e l y . It i s suggested that t h i s reduction i n earlywood % causes a drop i n hydraulic conductivity i n tree stems from repressed stands and leads to the changes, already discussed, i n leaf area/sapwood area r a t i o s i n these trees. The increase i n biomass a l l o c a t i o n to the stemwood i n repressed trees probably leads to th e i r having an ever- increasing respiratory/photosynthetic area r a t i o as discussed by M i t c h e l l and Goudie (1980). Graphical diagnosis of f i r s t year f o l i a r analysis data suggests that nitrogen a p p l i c a t i o n generally reversed the e f f e c t s of high stand density on N content, N concentration and needle weight. 166 The e f f e c t s of N a p p l i c a t i o n on the f o l i a r P status were quite s i m i l a r but more density dependent. E f f e c t s on f o l i a r K composi-t i o n depended both on stand density and l e v e l of f e r t i l i z e r applied but were generally not s i g n i f i c a n t . • Annual f o l i a r analyses for the three years a f t e r f e r t i l i z a t i o n 8how that a l l stand densities have the same general trend of a decrease i n N percent over time. By the end of t h i s period most f e r t i l i z e d plots were at or below the control l e v e l s . At any time since f e r t i l i z a t i o n , few of the f e r t i l i z e d plots showed N concentrations greater than the 1.5% thought to be adequate f o r lodgepole pine. S i m i l a r l y , a l l c o n t r o l plots were severely d e f i c i e n t i n nitrogen and there was no s i g n i f i c a n t difference i n N percent between the various stand d e n s i t i e s . • Micronutrient analysis i n the second year of the experiment indicated that, of the micronutrients analysed (S, Cu, Fe, 'AFe'), the only s i g n i f i c a n t e f fect was a p o s i t i v e e f f e c t of f e r t i l i z e r l e v e l on 'AFe'. Nitrogen f e r t i l i z e r a p p l i c a t i o n caused an increase i n the nitrogen:sulphur r a t i o , e s p e c i a l l y i n the higher density p l o t s , possibly inducing a sulphur deficiency. • Analysis of f o l i a g e by crown p o s i t i o n and needle age class showed that s i g n i f i c a n t differences i n N concentration between d i f f e r e n t age classes of needles only existed i n the intermediate and high stand d e n s i t i e s . Decreases i n N concentration at lower crown positions were only evident i n the low and intermediate stand d e n s i t i e s . The magnitude of t h i s decrease with depth depended on the l e v e l of f e r t i l i z e r applied. From study component 1 of the present work, i t can therefore be concluded that l i g h t does not appear to be a growth-limiting factor i n repressed stands of lodgepole pine. For reasons outlined e a r l i e r , 167 however, i t appears that f o l i a g e develops at lower l i g h t i n t e n s i t i e s i n repressed stands and that l i g h t may have been l i m i t i n g growth at some stage i n the development of repressed stands. The high correlations between height growth i n successive years i n trees from repressed stands suggests a greater degree of i n t e r n a l growth co n t r o l i n these stands. It i s not known whether t h i s phenomenon i s a causal factor of repression or simply prolongs the growth retardation once i t has begun. The mechanism of this growth control Is not under-stood and future research into the differences between hormonal levels i s vigorous and repressed stands may improve over understanding of the problem. From study component 2, dealing with biomass a l l o c a t i o n and wood anatomy, i t can be concluded that, because of the reduction i n earlywood percent i n trees from repressed stands, conductivity may be reduced i n stems of repressed trees. This, i n turn, may lead to declines i n moisture and nutrient supplies to the fol i a g e causing the measured reduc-tions i n needle and shoot growth. This negative feedback cycle i s completed when the subsequently reduced auxin l e v e l s again lead to reduced earlywood production. Both leaf area and leaf area:sapwood area are subsequently reduced i n trees from repressed stands, leading to decreased productive and increased consumptive t i s s u e . The o v e r a l l objective i n the present research was to gain a better • understanding of some of the growth processes involved i n repression of lodgepole pine when growing at high stand d e n s i t i e s . 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APPENDIX A.1 Sit e Species L i s t Vascular plants: Alnus v i r i d i s ssp sinuata  Arctostaphylos uva-ursi  Arnica c o r d i f o l i a  Aster conspicuus  Calamagrostls rubescens  Carex concinnoides  Cornus canadensis  Epilobium a r g u s t i f o l l u m  Fragarla v i r g i n i a r i a  Hieracuim spp. Juniperus communis  Linnaea bo r e a l i s  O r t h i l l a secunda  Picea glauca  Pinus contorta  Pyrola spp. Rosa a c i c u l a r i s  S a l i x bebbiana  Shepherdia canadensis  Spiraea b e t u l i f o l i a  Vaccinium caespitosum  Vaccinium membraceum  Viburnum edule Moss and Lichens: Cladonia spp. P e l t i g e r a spp. Polytrichum spp. Stereocaulon spp. sitka alder kinnikinnick heart-leaved arnica showy aster pinegrass northwestern sedge bunchberry fireweed wild strawberry hawkweed common juniper twinflower one-sided wintergreen white spruce lodgepole pine wintergreen p r i c k l y rose Bebb's willow s o o p o l a l l i e birch-leaved spiraea dwarf blueberry black blueberry high-bush cranberry 181 APPENDIX A.2 S o i l P r o f i l e Description Horizon Depth (cm) Comments L 2-05 Mostly pine needles F 0.5-0 Black and f e l t y , no mycelia seen Ael 0-0.5 Bm 0.5-20 gravelly, sandy loam; 40% coarse fragments (mostly gravels); dry; medium-coarse roots present Ae2 20-40 gravelly, sandy loam; 40% coarse fragments (some cobbles and stones); dry; M-C roots present Bt 40+ gravelly, c l a y loam; 40% coarse fragments, fine roots present; moist C l a s s i f i c a t i o n : B r u n i s o l i c Gray L u v i s o l . APPENDIX B.l Analysis of variance of s p e c i f i c leaf area with varying levels of f e r t i l i z e r (F), density (D), crown po s i t i o n (C) and needle age . cla s s (A) for both o r i g i n a l and log a r i t h m i c a l l y transformed data. Transformed data O r i g i n a l data Source of v a r i a t i o n Degrees of freedom Sum of squares Probability Test term Sum of squares P r o b a b i l i t y F 2 0.126 0.543 D * F 31533 0.350 D 2 0.326 0.270 D * F 86426 0.112 C 2 0.399 0.013* D * F * C 118710 0.001** A 4 3.521 0.000** D * F * A 101120 0.000** D * A 8 0.301 0.017* D * F * A 152870 0.000** F * A 8 0.058 0.711 D * F * A 24997 0.115 D * C 4 0.160 0.272 D * F * C 33101 0.118 F * C 4 0.048 0.757 D * F C 10256 0.557 C * A 4 0.045 0.454 D * F * A * C 30188 0.005** C * A * D 8 0.037 0.905 D * F * A * C 7159 0.708 C * A * F 8 0.031 0.943 D * F * A c 12968 0.348 D * F 4 0.353 0.001** D * F * A * c 45680 0.001** D * F * A 16 0.174 0.553 D * F * A * c 24147 0.370 D * F * C 8 0.204 0.088 D * F * A * c 21254 0.000** D * F * A * C 16 0.187 0.000** Residual 21254 0.000** Residual 2871 2.165 734040 Total 2969 7.925 2303100 ** = s i g n i f i c a n t at P <0.01, * = s i g n i f i c a n t at P <0.05. 183 APPENDIX B.2 Analysis of variance for needle surface area. Treatments are f e r t i l i z e r (F), stand density (D), crown p o s i t i o n (C) and needle age class (A). Source of Degrees of Sum of F- r a t i o P r o b a b i l i t y v a r i a t i o n freedom squares F 2 48.31 1.03 0.441 D 2 187.75 3.99 0.111 C 2 103.92 41.60 0.000** A 4 165.67 35.07 0.000** D * A 8 17.95 1.90 0.131 F * A 8 13.94 1.47 0.242 D * C 4 30.46 6.10 0.015* F * C 4 4.17 0.84 0.539 C * A 4 19.32 4.02 0.019* C * A * D 8 6.18 0.64 0.731 C * A * F 8 3.43 0.36 0.928 D * F 4 94.11 19.60 0.000** D * F * A 16 18.90 0.98 0.513 D * F * C 8 9.99 1.04 0.447 D * F * A *C 16 19.21 21.43 0.000** Residual 2871 160.84 Total 2960 874.93 * = s i g n i f i c a n t at P <0.05. ** = s i g n i f i c a n t at P <0.01. 184 APPENDIX B.3 Analysis of variance for needle dry weight. Treatments are f e r t i l i z e r (F), stand density (D), crown p o s i t i o n (C) and needle age class (A). Source of Degrees of Sum of F- r a t i o P r o b a b i l i t y v a r i a t i o n freedom squares F 2 9671.5 0.97 0.454 D 2 30176.0 3.02 0.159 C 2 15595.0 22.40 0.001** A 4 41265.0 49.32 0.000** D * A 8 4069.0 2.43 0.062 F * A 8 2133.4 1.27 0.322 D * C 4 5189.8 3.73 0.054 F * C 4 583.56 0.42 0.751 C * A 4 1897.3 2.24 0.111 C * A * D 8 733.37 0.43 0.885 C * A * F 8 582.61 0.34 0.935 D * F 4 19999.0 23.57 0.000** D * F * A 16 3347.0 0.99 0.511 D * F * C 8 2785.0 1.64 0.190 D * F * A *C 16 3393.4 21.47 0.000** Residual 2871 28366.0 Total 2969 165300.0 ** = s i g n i f i c a n t at P <0.01. 185 APPENDIX C l Analysis of variance for height. Variable C o e f f i c i e n t Standard error t-stat S i g n i f i c a n c e Constant 5.071 0.141 36.037 .0000** D -0.341 X l O " 4 0.214 X l O " 5 15.966 .0000** F 0.125 X 10" 1 0.312 X l O " 2 4.005 .0013** F 2 -0.454 X l O " 4 0.135 X l O " 4 3.372 .0046** D x F -0.156 X 10" 6 0.414 X l O " 7 . 3.768 .0021** 2 2 D x F 0.601 X l O " 1 4 0.192 X l O " 1 4 3.136 .0073** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . 186 APPENDIX C.2 Analysis of variance for mean diameter. Variable C o e f f i c i e n t Standard error t - s t a t a Significance Constant 10.743 0.319 33.714 .0000** D -0.308 X l O " 3 0.326 X 10" 4 9.455 .0000** D 2 -0.387 X 10~ 8 0.754 X l O " 9 5.129 .0001** D 3 -0.168 X 10" 1 3 0.466 X 10" 1 4 3.602 .0024** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX C.3 Analysis of variance f o r basal area. a b Variable C o e f f i c i e n t Standard error t-stat Significance Constant 43.957 1.937 22.696 .0000** D 2 -0.172 x 10~ 8 0.370 x 10~ 9 4.642 .0002** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . 187 APPENDIX C.4 Analysis of variance for l i v e crown r a t i o . 3. Variable C o e f f i c i e n t Standard error t-stat S i g n i f i c a n c e Constant 0.798 0.204 x 1 0 - 1 39.09 .0000** D 2 -0.693 x 10" 5 0.101 x 10" 5 6.89 .0000** D 2 0.329 x 1 0 ~ 1 0 0.938 x 1 0 ~ U 3.51 .0027** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX C.5 Analysis of variance f o r mortality. Variable C o e f f i c i e n t Standard error t-stat S i g n i f i c a n c e Constant 7.67 1.961 3.912 .001 ** D 2 -0.362 x 10~ 8 0.374 x 10~ 9 9.67 .0000** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . 188 O 'in -0.4-0.0 4.0 8.0 Tree Dry Wt (kg) 12.0 APPENDIX C 6 Plots of r e s i d u a l s vs. i n d i v i d u a l independent variables. Figure A l . Residuals vs. tree dry weight. 1 8 9 D '{/) <D Cr: 1.6 1.2-0.8-0.4 0.0 -0.4 -0.8 • • • _ • • • • • • • • • • • • • • _• • • • • • • 0.0 2.0 4.0 Height (m) 6.0 APPENDIX C.6 Plots of r e s i d u a l s vs. i n d i v i d u a l independent variables. Figure A2. Residuals vs. height. 190 V) O •3 '(/) -0.4 0 . 0 3.0 6.0 9.0 Diameter (cm) 12.0 APPENDIX C . 6 Plots of re s i d u a l s vs. i n d i v i d u a l independent v a r i a b l e s . Figure A3. Residuals vs. diameter. 1.6 1.2-0.8 0.4-0.0 -0.4-• •• • 1 •••• ••• ••••• • • • n r - IV. -0.8-1 ' ' r 0.0 3.0 6.0 9.0 Diameter (Base of live crown,cm) APPENDIX C.6 Plots of re s i d u a l s vs. i n d i v i d u a l independent variables. Figure A4. Residuals vs. diameter at the base of the l i v e crown. 192 JLO D 3 -0.4-2.0 4.0 Live Crown Depth(m) APPENDIX C.6 Plots of r e s i d u a l s vs. i n d i v i d u a l independent variables. Figure A 5 . Residuals vs. depth of l i v e crown. 193 O ZJ 'to 0.0 200.0 400.0 D2 H 600.0 800.0 APPENDIX C.6 Plots of r e s i d u a l s vs. i n d i v i d u a l independent variables. Figure A6. Residuals vs. diameter squared x height. 1.6 1.2-0.8 V) D 3 "</) or 0.4-0.0 -0.4 -0.8 100 200 DC2H 300 400 APPENDIX C.6 P l o t s of r e s i d u a l s v s . i n d i v i d u a l independent v a r i a b l e s . F i g ure A7. Residuals v s . diameter at base of the l i v e crown squared x height. 195 APPENDIX C.7 Plot biomass t o t a l s - T o t a l plot dry weight i s the sum of biomass weighed i n the 1° and estimated from the 2° and 3° sampling i n t e n s i t i e s . Nominal Plot area Total biomass density 2 Stand density Total plot _^ cl a s s Plot ID a m sph dry wt (kg) t ha 5K 111 20 8,000 122.76 61.38 211 20 6,500 118.67 59.34 311 20 3,500 85.41 42.71 112 20 6,500 99.55 49.78 212 20 6,000 119.09 59.55 312 20 5,500 96.18 48.09 20K 20K 10 20,500 86.07 43.04 50K 121 10 48,000 46.80 46.80 221 10 43,000 53,32 53.32 321 10 41,000 57.58 57.58 122 10 54,000 53.18 53.18 222 10 42,000 59.25 59.25 322 10 43,000 39.03 39.03 100K 100K 10 81,000 19.09 19.09 150K 131 10 109,000 15.74 15.74 231 10 83,000 26.34 26.34 331 10 84,000 16.08 16.08 132 10 99,000 17.61 17.61 232 10 82,000 21.93 21.93 332 10 100,000 18.19 18.19 Plot code as previously defined e.g. Table 8. APPENDIX C.8 Analysis of variance for t o t a l above-ground biomass. Variable C o e f f i c i e n t Standard error t-stat Significance Constant 54.382 2.463 22.076 .0000** D 2 -0.389 x l 0 ~ 8 0.470 x 10~ 9 8.273 .0000** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX C.9 F u l l regression equations used for t o t a l dry weights for the 2° sampling i n t e n s i t y . A l l equations are s i g n i f i c a n t at the .0001 l e v e l . Stand density Component Equation SE 5K Total aboveground = -2730 + 1596.3(D b) + 149.8(D C) + 93.6(H) .99 + 6.87(Dfc2) - U . l ( D b 2 H ) - 271.5 ( D c 2 ) + 70.5 (D C 2H) - 1281.7(d) 539.0 20K, 50K Total aboveground = -521.1 - 182.7(D b) + 310.2(D C) + 268.7(H) + 92.6(D b 2) - 6.79(D b 2H) - 86.8(D C 2) + 26.1(D C 2H) - 223.1(CL) .99 127.6 100K, 150K Total aboveground = -33.2 + 297.7(D b) - 252.5(D c) + 10.98(H) -240.6(D b 2) + 85.2(D b 2H) + 383.1(D C 2) - 103.5(D C 2H) .98 30.0 - 88.8(d) a Stand density = nominal stand density. D T o t a l aboveground dry weight (g) = branches + stems + f o l i a g e . c Abbreviations are D b =.diameter (ground l e v e l ) , cm; D c = diameter at the base of the l i v e crown, cm; H = height, m; CL = l i v e crown length, m. APPENDIX C.10 F u l l regression equations used for t o t a l dry weights for the 3° sampling i n t e n s i t y . A l l equations are s i g n i f i c a n t at the .0001 l e v e l . a b c 2 Stand Component Equation r SE density 5K Total aboveground = -7611.2 + 2616.0(D b) - 461.4(H) .96 823.9 -169.6(D b 2) + 20.4(D b 2H) 20K, 50K Total aboveground = -585.6 + 90.68(D b) + 149.3(H) .98 138.5 +38.13(D b 2) + 7.32(D b 2H) 100K, 150K Total aboveground = -147.4 + 249.3(D b) - 40.7(H) .97 36.0 -78.8(D b 2) + 33.98(D b 2H) a Stand density = nominal stand density. D T o t a l aboveground dry weight (g) = branches + stems + f o l i a g e . c Abbreviations are Ihj = diameter (ground l e v e l ) , cm; D c = diameter at the base of the l i v e crown, cm; H = height, m; CL = l i v e crown length, m. M VO 00 199 APPENDIX C . l l F u l l regression equations used for component dry weights In the 2° sampling Intensity. A i l equations are s i g n i f i c a n t at the .0001 l e v e l . Stand density Component Equation SE 5K Stem - -2373.5 + 1234.6(D b) + 365.7(D c) + 315.6(H) - 156.8(D^) .99 279.7 18.8(D b 2H) - 19.7(D c 2) + l l . l ( D c 2 H ) - 1251.5(CL) Branches - 501.6 + 81.1(D. ) - 200.8(D ) - 177.2(H) + 54.0(D 2 ) .95 221.8 b e b -8.95(D b 2H) - 67.9(D c 2) + 20.2(D c 2H) + 53.3(CL) Foliage - -858.2 + 280.7(D.) - 15.2(D ) - 44.7(H) + 109.6(D 2 ) .95 237.0 D C b -21.0(D 2H) - 183.9(D 2 ) + 39.2(D 2H) - 83.4(a) D C C 20K, 50K Stem - 106.3 - 129.4(D V) - 103.8(D ) + 13.8(H) + _52.8(D,/) .99 81.6 b e b -6.3(D 2H) + 3.4(D 2 ) + 3.8(D 2H) + 77.9(CL) D C C Branches - 106.3 - 129.4(D.) - 103.8(D ) + 13.8(H) + 52.8(D 2 ) .94 36.0 b e b -6.3(D 2H) + 3.4(D 2 ) + 3.8(D 2H) + 77.9(CL) D C C Foliage - -57.2 - 37.2(DJ - 8.1(D ) + 3.3(H) + 37.6(D 2 ) .97 43.0 D C D -4.5(D 2H) - 13.3(D 2 ) + 5.4(D 2H) + 34.1(d) b c c 100K, 150K Stem - -82.2 + 187.2(D t) - 118.2(D ) + 45.2(H) - 118.3(D 2 ) b e b 38.7(D 2H) + 167.0(D 2 ) - 38.2(D 2H) - 67.5(CL) D C C Branches - 17.7 - 2.7(D L) - 32.0(D ) - 1.53(H) - 11.9(D 2 ) D C D +6.83(D,2H) + A4.4(D 2 ) - 12.6(D 2H) + 3.8(d) D C C Foliage - 31.3 + 113.2(D V) - 102.3(D ) - 32.7(H) - 110.5(D.2) D C D 39.7(D 2H) + 171.7(D 2 ) - 52.7(D 2H) - 25.2(CL) D C C .99 .92 .93 15.6 6.3 14.4 200 APPENDIX C.12 F u l l regression equations used for component dry weight i n the 3° sampling Intensity. A l l equations are s i g n i f i c a n t at the .0001 l e v e l . Stand Component Equation r^ SE density 5K Stem - -32.31.1 + 1334.6(D.) - 229.7(H) - 141.2(D 2) .97 449.4 b b +2-.6(D 2H) D Branches • -1593.6 + 510.7(D.) - 152.7(H) - 11.1(D 2 ) .91 258.3 b b -0.601(D. 2H) D Foliage - -2786.5 + 770.7(D.) - - 79.0(H) - 17.3(D 2 ) .90 286.9 b b -0.803(D 2H) D 20K, 50K Stem - -578.1 + 282.1(D.) + 87.9(H) - 37.9(D 2 ) .98 98.4 p b -12.2(D 2B) D Branches - 79.9 - 170.4(D V) + 43.3(H) + 48.9(D 2 ) .92 41.1 b D -3.60(D 2H) D Foliage - -87.5 - 20.95(D.) + 18.04(H) + 27.17(D U 2) .96 44.5 b b -1.31(D b 2H) 100K, 150K Stem - -142.0 + 181.5(Db> + 3.95(H) - 53.3(Db2) .98 19.1 +20.2(D 2H) D Branches - 3.68 - 12.85(D,) + 0.75(H) + 7.40(D 2 ) .90 6.5 b b -K).64(D 2H) b Foliage - -9.006 + 80.74(Dfc) - 45.4(H) - 32.9(D f c 2) .90 15.7 +13.2(D 2H) D 201 APPENDIX C.13 Analysis of variance for t o t a l f o l i a r biomass. Variable C o e f f i c i e n t a b Standard error t-stat Significance Constant D DF 2 2 D F 14,888.0 -0.270 0.158 x 10 -0.155 0.858 x 10 -0.738 x 10 -5 -5 -10 1,292.3 0.613 x 10 -1 0.551 x 10 -6 0.531 x 10 -1 0.266 x 10 -5 0.247 x 10 -10 11.521 4.403 2.875 2.923 3.226 2.988 .0000** .0006** .0122* .0111* .0061** .0098** a Absolute value. b * s i g n i f i c a n t at the 0.05 (5%) l e v e l . ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . 202 APPENDIX C.14 Plot leaf area, sapwood area and leaf area index (LAI). Stand T.I ^  -i £ Plot sap- T A / ^ A Leaf Area a . . Plot leaf . K LA/SA _ , Density Plot density wood area Index LAI 2 2 —2 2 —2 Class ID sph area (m ) (cm) (m cm ) (mm ) 5K 111 8,000 268.62 899.79 0.299 13.43 211 6,500 230.74 777.56 0.297 11.54 311 3,500 175.93 600.37 0.293 8.80 112 6,500 231.72 763.87 0.303 11.59 212 6,000 239.02 844.30 0.283 11.95 312 5,500 203.69 698.59 0.292 10.18 2 OK 2 OK 20,500 149.53 662.16 0.226 7.48 5 OK 121 43,000 78.48 390.63 0.201 7.85 221 43,000 89.39 418.99 0.213 8.94 321 41,000 97.50 443.10 0.220 9.75 122 54,000 91.89 450.58 0.204 9.19 222 42,000 101.06 460.52 0.219 10.11 322 43,000 66.62 331.96 0.201 6.66 100K 10 OK 81,000 31.75 211.77 0.150 3.18 150K 131 109,000 23.26 192.00 0.121 2.33 231 83,000 44.85 267.27 0.168 4.49 331 84,000 30.51 205.01 0.149 3.05 132 99,000 27.48 204.22 0.135 2.75 232 82,000 40.24 248.78 0.162 4.02 332 100,000 29.69 213.09 0.139 2.97 a Plot s i z e i s 20 mz for the 5K and 20K p l o t s . A l l other plots are 10 ml. 203 APPENDIX C.15 Analysis of variance for LAI. Variable C o e f f i c i e n t Standard error t-stat Significance Constant 11.855 0.556 21.313 .0000** D -0.8996 x 10 _ A 0.928 x 10~ 5 9.699 .0000** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX C.16 Analysis of variance f o r leaf area:sapwood area r a t i o . Variable C o e f f i c i e n t Standard error t-stat Significance -2 Constant 0.305 0.553 X 10 55.219 .0000** D -0.251 x 10~ 5 0.272 X 10" 6 9.699 .0000** D 2 0.814 x l O ' 1 1 0.254 X 10" 1 1 3.204 .0052** a Absolute value. b ** s i g n i f i c a n t at the 0.01 (1%) l e v e l . 204 APPENDIX D.l Analysis of variance for density (D), f e r t i l i z e r (F) and year (Y) e f f e c t s on N concentration. Source Degrees of freedom Sum of squares F-value P r o b a b i l i t y 3 D F D x F Y D x Y F x Y D x F x Y Error 2 2 4 2 4 4 8 26 4.02 x 10 1.17 8.52 x 10 2.73 1.65 x 10 4.87 x 10 2.60 x 10 1.96 x 10 -2 -2 -1 -1 -1 -1 2.67 77.79 2.83 181.56 5.48 16.20 4.32 0.0865 (NS) 0.0000 (**) 0.0446 (*) 0.0000 (**) 0.0025 (**) 0.0000 (**) 0.0021 (**) a N.S. = * = ** = not s i g n i f i c a n t at the 5% l e v e l , s i g n i f i c a n t at the 0.05 (5%) l e v e l , s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX D.2 Analysis of variance for density (D), f e r t i l i z e r (F) and year (Y) e f f e c t s on P concentration. Degrees of Sum of Source freedom squares F-value P r o b a b i l i t y 3 D 2 1.23 x 1 0 - 5 0.08 0.9138 (NS) F 2 1.09 x 1 0 - 3 7.29 0.0032 (**) D x F 4 1.50 x 1 0 - 4 0.50 0.7369 (NS) Y 2 1.69 x 1 0 - 3 ' 11.27 0.0003 (**) D x Y 4 1.04 x 1 0 - 3 3.48 0.0210 (*) F x Y 4 5.48 x 1 0 _ 4 1.83 0.1524 (NS) D x F x Y 8 5.10 x 1 0 - 4 0.85 0.5683 (NS) -3 E r r o r 26 1.96 x 10 a N.S. * ** = not s i g n i f i c a n t at the 5% l e v e l . = s i g n i f i c a n t at the 0.05 (5%) l e v e l . = s i g n i f i c a n t at the 0.01 (1%) l e v e l . 206 APPENDIX D.3 Analysis of variance for density (D), f e r t i l i z e r (F) and year (Y) e f f e c t s on K concentration. Degrees of Sum of Source freedom squares F-value P r o b a b i l i t y 3 D 2 8.73 x 1 0 - 3 3.36 0.0492 (*) F 2 5.51 x 1 0 - 3 2.12 0.1380 (NS) D x F 4 9.64 x 1 0 _ 3 1.86 0.1474 (NS) Y 2 5.83 x 1 0 _ 1 224.48 0.0000 (**) D x Y 4 1.71 x 1 0 - 2 3.30 0.0257 (*) F x Y 4 1.28 x 1 0 - 3 0.25 0.8421 (NS) D x F x Y 8 1.58 x 1 0 _ 2 1.53 0.1964 (NS) -2 E r r o r 26 3.37 x 10 3 N.S. ** = not s i g n i f i c a n t at the 5% l e v e l . = s i g n i f i c a n t at the 0.05 (5%) l e v e l . = s i g n i f i c a n t at the 0.01 (1%) l e v e l . APPENDIX D.4 Analysis of variance for density (D), f e r t i l i z e r ( F ) , needle age (A) and crown p o s i t i o n (C) e f f e c t s on f o l i a r N concentration Degrees of Sum of Source freedom squares F-ratio P r o b a b i l i t y 3 F 2 2.870 7.86 0.04112 (*) D 2 0.142 0.39 0.70032 (NS) C 2 0.304 6.11 0.02446 (*) A 3 1.060 10.31 0.00122 (**) D x A 6 0.123 0.60 0.72608 (NS) F x A 6 0.880 4.28 0.01547 (*) D x C 4 0.326 3.27 0.072 00 (NS) F x C 4 0.105 1.05 0.43765 (NS) C x A 5 0.017 0.39 0.85279 (NS) C x A x D 10 0.071 0.83 0.60641 (NS) C x A x F 10 0.088 1.03 0.45626 (NS) D x F 4 0.730 21.21 0.00000 (**) D x F x A 12 0.411 3.98 0.00319 (**) D x F x C 8 0.199 2.89 0.02573 (*) D x F x A x C 20 0.172 0.38 0.99251 (NS) Error 99 2.264 N.S. = not s i g n i f i c a n t at the 5% l e v e l . * = s i g n i f i c a n t at the 0.05 (5%) l e v e l . ** = s i g n i f i c a n t at the 0.01 (1%) l e v e l . 

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