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UBC Theses and Dissertations

Ecological physiology of conifer seedling and sapling suppression by, and release from, competing vegetation Bigley, Richard Ernest 1988

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ECOLOGICAL PHYSIOLOGY OF CONIFER SEEDLING AND SAPLING SUPPRESSION BY, AND RELEASE FROM, COMPETING VEGETATION By RICHARD ERNEST BIGLEY B . S c , Washington S t a t e U n i v e r s i t y , 1979 M . S c , U n i v e r s i t y o f B r i t i s h Columbia, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES ( F a c u l t y o f F o r e s t r y , Department o f F o r e s t S c i e n c e ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e s t a n d a r d UNIVERSITY OF BRITISH COLUMBIA October 1988 R i c h a r d E r n e s t B i g l e y , 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, 1 agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada Date Qc\7o&€£. </; /98fi DE-6 (2/88) ABSTRACT The o v e r a l l o b j e c t i v e o f t h i s t h e s i s was t o improve our u n d e r s t a n d i n g o f t h e l i g h t environment a s s o c i a t e d w i t h two o f t h e major deciduous c o m p e t i t o r s o f commercial c o n i f e r s e e d l i n g s i n low e l e v a t i o n c o a s t a l B r i t i s h Columbia, and t h e p h y s i o l o g i c a l response o f young c o n i f e r s t o s p e c i f i c e n v i r o nments and changes i n t h e environment. S t u d i e s were c o n d u c t e d t o i n v e s t i g a t e : 1) s e a s o n a l and h e r b i c i d e - i n d u c e d changes i n t h e l i g h t regimes beneath t h e c a n o p i e s o f two b r u s h s p e c i e s , 2) growth and p h y s i o l o g y o f s e e d l i n g s o f t h r e e c o n i f e r s p e c i e s i n s e v e r a l d i f f e r e n t d e c i d u o u s b r u s h environments t h r o u g h o u t t h e y e a r , and 3) changes i n t h e p h y s i o l o g y and growth o f s u p p r e s s e d c o n i f e r s a p l i n g s when d i f f e r e n t methods and s c h e d u l e s were used t o reduce s h a d i n g from an o v e r t o p p i n g r e d a l d e r canopy. S e a s o n a l changes i n t h e l i g h t q u a n t i t y and q u a l i t y were documented w i t h i n s a l m o n b e r r y (Rubus s p e c t a b i l i s P ursch) and below r e d a l d e r (Alnus r u b r a Bong.) c a n o p i e s . The p r e d i c t i o n o f l i g h t a t t e n u a t i o n w i t h i n s a l m onberry c a n o p i e s u s i n g t h e Beer-Lambert law was good f o r f o l i a t e d c a n o p i e s u s i n g l e a f a r e a i n d e x , and d e f o l i a t e d c a n o p i e s u s i n g stem a r e a i n d e x . As sa l m o n b e r r y l e a f a r e a i n c r e a s e d , t h e r a t i o o f r e d t o f a r - r e d l i g h t d e c l i n e d e x p o n e n t i a l l y . Growth o f grand f i r ( Abies q r a n d i s (Dougl.) F o r b e s ) , w e s t e r n hemlock (Tsuga h e t e r o p h y l l a (Raf.) Sarg.) and D o u g l a s - f i r (Pseudetsuga m e n z i e s i i ( M i r b e l ) Franco) i i i s e e d l i n g s d e c r e a s e d w i t h i n c r e a s e s i n t h e canopy d e n s i t y o f o v e r t o p p i n g d e c i d u o u s s p e c i e s . P h y s i o l o g i c a l d i f f e r e n c e s between c o n i f e r s p e c i e s and d i f f e r e n c e s between o v e r t o p p i n g canopy t r e a t m e n t s d e c l i n e d i n t h e autumn and w i n t e r . Based on t h e p h y s i o l o g i c a l measurements, s u p p r e s s i o n o f t h e shade i n t o l e r a n t D o u g l a s - f i r s e e d l i n g s was g r e a t l y reduced d u r i n g t h e p e r i o d t h a t o v e r t o p p i n g d e c i d u o u s c a n o p i e s were l e a f l e s s . A n i m a l damage reduces growth and p r o b a b l y i n c r e a s e s t h e d u r a t i o n s e e d l i n g s a r e under o v e r t o p p i n g c a n o p i e s . S u p p r e s s e d D o u g l a s - f i r s a p l i n g s r e l e a s e d from o v e r t o p p i n g by r e d a l d e r c a n o p i e s showed t h e g r e a t e s t growth response when t h e a l d e r c a n o p i e s were removed i n t h e s p r i n g ; complete removal o f t h e a l d e r canopy d u r i n g t h e summer had a p r e d i c t a b l y d e l e t e r i o u s e f f e c t on t h e s a p l i n g p h y s i o l o g y and growth. H e r b i c i d e i n j e c t i o n s r e s u l t e d i n a s l o w e r but p r e d i c t a b l e i n c r e a s e i n c o n i f e r growth. i v TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i i L I S T OF FIGURES x i L I S T OF APPENDICES x i i i ACKNOWLEDGEMENTS x i v CHAPTER 1. INTRODUCTION 1 A. RESEARCH OBJECTIVES 5 B. STUDY DESIGN 7 C. DESCRIPTION OF STUDY SITES 10 D. DESCRIPTION OF STUDY SPECIES .... 16 CHAPTER 2. SEASONAL AND HERBICIDE-INDUCED CHANGES IN THE LIGHT ENVIRONMENT WITHIN THE CANOPIES OF TWO DECIDUOUS SPECIES 19 INTRODUCTION 19 METHODS 23 A. Sample p l o t s 23 B. F i e l d t r e a t m e n t s 23 B. F i e l d measurements 23 RESULTS 28 A. D i s t r i b u t i o n o f l e a f and stem biomass, a r e a i n d e x , and l i g h t a t t e n u a t i o n w i t h i n s a l m o n b e r r y c a n o p i e s 28 B. Beer-Lambert e x t i n c t i o n c o e f f i c i e n t s 32 C. Annual changes i n l i g h t q u a n t i t y and q u a l i t y w i t h i n s a l m o n b e r r y c a n o p i e s 36 D. Annual and h e r b i c i d e - i n d u c e d changes i n l i g h t q u a n t i t y and q u a l i t y under r e d a l d e r c a n o p i e s 40 DISCUSSION 45 A. D i f f e r e n c e s i n canopy s t r u c t u r e and l i g h t a t t e n u a t i o n w i t h i n s a l m o n b e r r y t h i c k e t s o f d i f f e r e n t ages 45 B. S e a s o n a l changes i n l i g h t q u a n t i t y and q u a l i t y 50 C. H e r b i c i d e - i n d u c e d changes i n l i g h t q u a n t i t y and q u a l i t y 57 CONCLUSIONS 59 CHAPTER 3. PHYSIOLOGY AND GROWTH OF SEEDLINGS OF THREE CONIFER SPECIES UNDER DIFFERENT DENSITIES OF DECIDUOUS COMPETITORS 61 INTRODUCTION 61 METHODS 65 A. F i e l d t r e a t m e n t s 65 B. F i e l d measurements 67 RESULTS 72 A. S e e d l i n g p h y s i o l o g y 72 B. S e e d l i n g s u r v i v a l 80 C. S e e d l i n g growth 82 DISCUSSION 87 A. S e e d l i n g p h y s i o l o g y 87 B. S e e d l i n g s u r v i v a l and growth .... 8 9 CONCLUSIONS 94 CHAPTER 4. THE EFFECT OF TREATMENT AND TREATMENT TIMING ON THE RELEASE RESPONSE OF SUPPRESSED DOUGLAS-FIR SAPLINGS 95 INTRODUCTION 95 v i METHODS 101 A. F i e l d t r e a t m e n t s 101 B. F i e l d measurements 102 RESULTS 105 A. S a p l i n g p h y s i o l o g y 105 B. S a p l i n g morphology 129 DISCUSSION 136 A. E f f e c t o f t r e a t m e n t and t i m i n g on r e l e a s e response 136 B. S e l e c t i o n o f r e l e a s e t r e a t m e n t and t i m i n g '. . 144 C. The e c o l o g i c a l i m p l i c a t i o n s o f r e l e a s e t r e a t m e n t s 147 CONCLUSIONS 14 9 CHAPTER 5. APPLICATION OF FINDINGS AND CONCLUSIONS 150 LITERATURE CITED 155 APPENDICES 169 v i i LIST OF TABLES Tab l e 1. Mean monthly t e m p e r a t u r e and monthly p r e c i p i t a t i o n a t t h e A d m i n i s t r a t i o n B u i l d i n g s i n 1983 and 1984, and t h e 20 y e a r averages f o r t h e UBC R e s e a r c h F o r e s t . .12 T a b l e 2. Mean r e l a t i v e l i g h t (PPFD) i n t e n s i t y a t 50 cm, c u m u l a t i v e l e a f a r e a i n d e x (LAI) and stem a r e a i n d e x (SAI) above 50 cm, and Beer-Lambert e x t i n c t i o n c o e f f i c i e n t (K) t o 50 cm f o r d i f f e r e n t ages o f sal m o n b e r r y t h i c k e t s based on LAI o n l y (K F) and combined LAI and SAI ( K F + A ) i n t h e summer and SAI (K A) o n l y i n t h e w i n t e r (see F i g u r e s 2a t h r o u g h 2e f o r s p e c i f i c s t a n d data) 33 Table 3. H o r i z o n s p e c i f i c , v e r t i c a l d i s t r i b u t i o n o f Beer-Lambert e x t i n c t i o n c o e f f i c i e n t s (based on l e a f a r e a index) and s p e c i f i c l e a f a r e a s w i t h i n s a l m o n b e r r y c a n o p i e s o f d i f f e r e n t ages (see F i g u r e s 2a t h r o u g h 2e f o r s p e c i f i c s t a n d data) 35 T a b l e 4. V e r t i c a l measurements o f Z e t a ( r a t i o o f energy a t 660:730 nm) w i t h i n s a l m o n b e r r y c a n o p i e s o f d i f f e r e n t ages (see F i g u r e s 2a t h r o u g h 2e f o r s p e c i f i c s t a n d data) 39 T a b l e 5. P l a n t i n g s t o c k e s t a b l i s h e d w i t h i n salmonberry and r e d a l d e r s t a n d s 66 T a b l e 6. S p r i n g and summer means o f p h o t o s y n t h e t i c r a t e , Ps (mgC02*dm 2 * h r 1) , l e a f conductance, g-^ (em's ), vapor p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm - 2's ), l e a f water p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h i (mg'g - 1), o f D o u g l a s - f i r (DF), grand f i r (GF), and western hemlock (WH) s e e d l i n g s w i t h i n s a l m o n b e r r y stands o f d i f f e r e n t d e n s i t y 73 T a b l e 7. Autumn and w i n t e r means o f p h o t o s y n t h e t i c r a t e , Ps (mgC02' dm - 2 ' h r - 1 ) , l e a f conductance, g-^  (em's" ), v a p o r p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm *s ), l e a f water p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h i (mg'g--1-), o f D o u g l a s - f i r (DF) , grand f i r (GF), and we s t e r n hemlock (WH) s e e d l i n g s w i t h i n s a l m o n b e r r y stands o f d i f f e r e n t d e n s i t y 74 v i i i T a b l e 8. S p r i n g a n d summer means o f p h o t o s y n t h e t i c r a t e , Ps (mgC02*dm ^ ' h r ), l e a f conductance, g-j_ (em's ), vap o r p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol*m~^*s ), l e a f water p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h i ( m g ' g - 1 ) , o f D o u g l a s - f i r (DF), grand f i r (GF), and western hemlock (WH) s e e d l i n g s w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t y 75 Table 9. Autumn and w i n t e r means o f p h o t o s y n t h e t i c r a t e , Ps (mgCC>2 "dm-^ * h r - 1 ) , l e a f conductance, gj_ (em's" ) , vapor p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm s ), l e a f water p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h i (mg'g - ), o f D o u g l a s - f i r (DF), grand f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t y 76 Table 10. S u r v i v a l o f p l a n t e d s e e d l i n g s t h e f i r s t two y e a r s under d e c i d u o u s shade. P e r c e n t o f 40 s e e d l i n g s p e r s p e c i e s p e r t r e a t m e n t 81 Table 11. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA) o f 1984 f o l i a g e , r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), and r e l a t i v e h e i g h t growth r a t e (RHGR) f o r D o u g l a s - f i r (DF), grand f i r (GF), and we s t e r n hemlock (WH) s e e d l i n g s a f t e r t h r e e y e a r s o f growth w i t h i n s a l m o n b e r r y s t a n d s o f d i f f e r e n t d e n s i t i e s 83 Table 12. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA) o f 1984 f o l i a g e , r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), and r e l a t i v e h e i g h t growth r a t e (RHGR) f o r D o u g l a s - f i r (DF), gr a n d f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s a f t e r t h r e e y e a r s o f growth w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t i e s 84 Table 13. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance ( g ^ ) , l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) f o r c u r r e n t y e a r D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d a t Haney on May 24, 1983 f o l l o w e d t h r o u g h t i m e 106 Tab l e 14. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance ( g ^ ) , l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) f o r c u r r e n t y e a r D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d a t Haney on August 9 , 1983 f o l l o w e d t h r o u g h time 109 i x T a b l e 15. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance (g-^), l e a f water p o t e n t i a l (wp) , and c h l o r o p h y l l c o n t e n t ( c h l ) f o r c u r r e n t y e a r D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d a t Haney on June 9, 1984 f o l l o w e d t h r o u g h t i m e 113 Tab l e 16. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance (g-^) , l e a f water p o t e n t i a l (wp) , and c h l o r o p h y l l c o n t e n t ( c h l ) f o r c u r r e n t y e a r D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d a t Haney on August 7, 1984 f o l l o w e d t h r o u g h time 115 Tab l e 17. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance ( g ^ ) , and means o f l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) o f D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 as measured September 24, 1983 119 Table 18. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance ( g ^ ) , and means o f l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) o f D o u g l a s - f i r s a p l i n g s r e l e a s e d i n a t Haney 1984 as measured October 3, 1984 122 Table 19. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance ( g ^ ) , and means o f l e a f water p o t e n t i a l (wp) , and c h l o r o p h y l l c o n t e n t ( c h l ) o f 1983 and 1984 f o l i a g e from D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 as measured September 7, 1984 125 Tab l e 20. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance (g-^) , and means o f l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) o f 1983 and 1984 f o l i a g e from D o u g l a s - f i r s a p l i n g s m a n u a l l y r e l e a s e d i n 1983 a t P o w e l l R i v e r as measured on June 20, 1984 128 Tab l e 21. Mean v a l u e s o f c u r r e n t y e a r s p e c i f i c l e a f a r e a (SLA), f o r D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 and 1984 measured a t t h e end o f t h e gr o w i n g season o f r e l e a s e 132 T a b l e 22. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA), r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), r e l a t i v e h e i g h t growth r a t e (RHGR), and shoot t o r o o t r a t i o (S/R) f o r D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 and measured at t h e end o f t h e 1984 growing season 133 X T a b l e 23. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA) o f 1984 f o l i a g e , r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), and r e l a t i v e h e i g h t growth r a t e (RHGR) f o r D o u g l a s - f i r s a p l i n g s r e l e a s e d m a n u a l l y a t P o w e l l R i v e r i n 1983 and measured at t h e end o f t h e 1984 growing season 135 x i LIST OF FIGURES F i g u r e 1. L o c a t i o n o f s t u d y s i t e s on t h e U n i v e r s i t y o f B r i t i s h Columbia Research f o r e s t 11 F i g u r e 2a-e. V e r t i c a l d i s t r i b u t i o n o f l e a f and stem biomass, l e a f and stem a r e a i n d e x , and r e l a t i v e l i g h t (PPFD) i n t e n s i t y w i t h i n s a l m o n b e r r y t h i c k e t s i n t h e summer and t h e w i n t e r , (a) 1 - y e a r - o l d t h i c k e t ; (b) 2-y e a r - o l d t h i c k e t ; (c) 3 - y e a r - o l d t h i c k e t ; (d) 5-year-o l d t h i c k e t ; (e) 8 - y e a r - o l d t h i c k e t 29-31 F i g u r e 3. Mean monthly l i g h t (PPFD) i n t e n s i t y (at 50 cm) under a 5 - y e a r - o l d l i v e s a l m o n b e r r y t h i c k e t (LAI=10.7), and i n a c l e a r i n g . Mean monthly v a l u e s w i t h d i f f e r e n t l e t t e r s 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) 37 F i g u r e 4. S o l a r r a d i a t i o n q u a l i t y (at 50 cm) under a 5 - y e a r - o l d salmonberry t h i c k e t (LAI=10.7) 38 F i g u r e 5. Mean monthly l i g h t (PPFD) i n t e n s i t y (at 50 cm) under l i v e , h e r b i c i d e - d e f o l i a t e d r e d a l d e r s t a n d s (7 y e a r o l d , 8 m t a l l ) and i n a c l e a r i n g . Mean monthly v a l u e s w i t h d i f f e r e n t l e t t e r s a r e 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) 41 F i g u r e 6. Changes i n t h e r e l a t i v e l i g h t (PPFD) i n t e n s i t y b e n e a th a r e d a l d e r canopy (7 y e a r o l d , 8 m t a l l ) f o l l o w i n g a h e r b i c i d e a p p l i c a t i o n . P o i n t s s e p a r a t e d v e r t i c a l l y by more th a n t h e v e r t i c a l b a 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) 42 F i g u r e 7. S o l a r r a d i a t i o n q u a l i t y (at 50 cm) under a 7 - y e a r - o l d (8 m) r e d a l d e r canopy 44 F i g u r e 8a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance ( g ^ ) , and p h o t o s y n t h e s i s from t h e May 24, 1983 Haney r e l e a s e t r i a l s , (a) measured May 26, 1983 on 1983 f o l i a g e , (b) measured June 17, 1983 on 1983 f o l i a g e 107 F i g u r e 9a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance (g-]_) , and p h o t o s y n t h e s i s from t h e August 18, 1983 Haney r e l e a s e t r i a l s , (a) measured August 20, 1983 on 1983 f o l i a g e , (b) measured September 11, 1983 on 1983 f o l i a g e 110 x i i F i g u r e lOa-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c v a p or p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance ( g ^ ) , and p h o t o s y n t h e s i s from t h e June 9, 1984 Haney r e l e a s e t r i a l s , (a) measured June 11, 1984 on 1984 f o l i a g e , (b) measured J u l y 12, 1984 on 1984 f o l i a g e 114 F i g u r e l l a - b . D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c v a p o r p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance (gn), and p h o t o s y n t h e s i s from t h e August 7, 1984 Haney r e l e a s e t r i a l s , (a) measured August 9, 1984 on 1984 f o l i a g e . (b) measured September 7, 1984 on 1984 f o l i a g e . . . . 1 1 7 F i g u r e 12a-c. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c v a p o r p r e s s u r e d e f i c i t (D) , l e a f d i f f u s i v e conductance (g-^) , and p h o t o s y n t h e s i s from t h e 1983 Haney r e l e a s e t r i a l s , (a) measured September 24, 1983 on 1983 f o l i a g e , (b) measured September 7, 1984 on 1983 f o l i a g e . (c) measured September 8, 1984 on 1984 f o l i a g e . Box= May 24, 1983 t r e a t m e n t ; t r i a n g l e = August 18, 1983 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l 120 F i g u r e 13a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c v a p o r p r e s s u r e d e f i c i t (D) , l e a f d i f f u s i v e conductance (g-^) , and p h o t o s y n t h e s i s from t h e 1984 Haney r e l e a s e t r i a l s , (a) manual r e l e a s e , measured October 3, 1984 on 1984 f o l i a g e , (b) h e r b i c i d e r e l e a s e , measured October 3, 1984 on 1984 f o l i a g e . Box= June 9, 1984 t r e a t m e n t ; r i n g = J u l y 10, 1984 t r e a t m e n t ; t r i a n g l e = August 7, 1984 t r e a t m e n t ; diamond= September 5, 1984 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l 123 F i g u r e 14a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c v a p or p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance (g^ ), and p h o t o s y n t h e s i s from t h e 1983 P o w e l l R i v e r r e l e a s e t r i a l s , (a) measured June 20, 1984 on 1983 f o l i a g e , (b) measured June 20, 1984 on 1984 f o l i a g e . Box= June 7, 1983 t r e a t m e n t ; c i r c l e = J u l y 19, 1983 t r e a t m e n t ; t r i a n g l e = August 30, 1983 t r e a t m e n t ; diamond= December 27, 1984 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l . 130 x i i i LIST OF APPENDICES Appendix 1 Examples d a t a a n a y l s i s 169 Appendix 2 G l o s s a r y o f a b b r e v i a t i o n s u sed i n t h e t h e s i s 189 ACKNOWLEDGEMENTS I would l i k e t o e x p r e s s my s i n c e r e a p p r e c i a t i o n t o Dr. J.P. Kimmins who p r o v i d e d d i r e c t i o n and f i n a n c i a l a s s i s t a n c e a t a l l s t a g e s o f t h i s work. The o t h e r members o f my committee, D r s . A. B l a c k , P. J o l l i f f e , D. Lavender, and G. Weetman, I would l i k e t o thank f o r t h e i r a d v i c e and c r i t i c a l r e a d i n g o f t h i s t h e s i s . I am f u r t h e r i n d e b t e d t o t h e s t a f f o f t h e U n i v e r s i t y o f B r i t i s h Columbia R e s e a r c h F o r e s t , Dr. J . Bassman (now a t Washington S t a t e U n i v e r s i t y ) , and t h e many grad u a t e s t u d e n t s , u n d e r g r a d u a t e s t u d e n t s and s t u d e n t t e c h n i c i a n s t h a t have l e n t a hand and f r e e l y engaged i n t h e exchange o f i d e a s and equipment. F i n a n c i a l s u p p o r t f o r t h i s p r o j e c t has come from t h e Canadian F o r e s t r y S e r v i c e ENFOR and PRUF programs and t h e B.C. M i n i s t r y o f F o r e s t s . S p e c i a l t h a n k s t o t h e B.C. M i n i s t r y o f F o r e s t s R e s e a r c h s t a f f i n t h e Vancouver F o r e s t D i s t r i c t f o r a l l o w i n g s a m p l i n g on t h e i r r e s e a r c h i n s t a l l a t i o n near P o w e l l R i v e r . T h i s work would not have been p o s s i b l e w i t h o u t my w i f e J e a n n e t t e ' s p a t i e n c e , c o n v i c t i o n , and a s s i s t a n c e . 1 CHAPTER ONE INTRODUCTION Competing v e g e t a t i o n f r e q u e n t l y d e l a y s o r even p r e v e n t s t h e e s t a b l i s h m e n t o f crop t r e e s . A t t e m p t s t o i n c r e a s e t r e e growth by r e d u c i n g t h i s c o m p e t i t i o n have v a r i e d c o n s i d e r a b l y i n t h e i r s u c c e s s ( R u s s e l l 1961, D i e r a u f 1977, Stewart e t a l . 1984). Because t h e b i o l o g y o f c o n i f e r growth i n b r u s h environments i s p o o r l y u n d e r s t o o d , i t i s o f t e n d i f f i c u l t t o e x p l a i n t h i s v a r i a t i o n s a t i s f a c t o r i l y . K l e b ' s c o n c e p t , r e c e n t l y r e s t a t e d by Kramer (1987), p r o v i d e s an o u t l i n e by which t h e v a r i a t i o n i n c o n i f e r growth w i t h i n , and when r e l e a s e d from, competing v e g e t a t i o n might be u n d e r s t o o d . Kramer (1987) s t a t e s t h a t " h e r e d i t y and environment o p e r a t e c o o p e r a t i v e l y t h r o u g h t h e p h y s i o l o g i c a l and b i o c h e m i c a l p r o c e s s e s o f t h e t r e e t o det e r m i n e t h e q u a n t i t y and q u a l i t y o f growth...". One can c o n c l u d e from t h i s concept t h a t c u l t u r a l t r e a t m e n t s m o d i f y growth t h r o u g h changes i n p h y s i o l o g y . I n o r d e r , t o u n d e r s t a n d why and how cr o p t r e e s a r e a f f e c t e d by a p a r t i c u l a r f a c t o r or t r e a t m e n t , one must l e a r n how t h a t f a c t o r o r t r e a t m e n t a f f e c t s t h e i r p h y s i o l o g i c a l p r o c e s s e s . Trees a c c l i m a t e t o l o n g - t e r m changes i n t h e i r environment by means o f a v a r i e t y o f p h y s i o l o g i c a l and m o r p h o l o g i c a l changes t h a t a l l o w c o n t i n u e d f u n c t i o n i n t h a t new environment. A common e n v i r o n m e n t a l change t h a t can oc c u r i n t h e l i f e o f a t r e e i s m o d i f i c a t i o n i n l i g h t 2 c o n d i t i o n s as a r e s u l t o f a l t e r a t i o n i n t h e s u r r o u n d i n g v e g e t a t i o n . Deciduous v e g e t a t i o n i s t h e most common sour c e o f shade i n p l a n t a t i o n s o f young c o n i f e r s i n c o a s t a l P a c i f i c N orthwest, c r e a t i n g o v e r t o p p i n g canopy d e n s i t i e s t h a t v a r y g r e a t l y t h r o u g h o u t t h e y e a r . The m i c r o c l i m a t e below deciduous c a n o p i e s undergoes c o n s i d e r a b l e s e a s o n a l v a r i a t i o n ( H u t c h i s o n and Matt, 1977; Z a v i t k o v s k i , 1982). F o l i a t e d c a n o p i e s may i n t e r c e p t more t h a n 90% o f t h e i n c o m i n g p h o t o s y n t h e t i c a l l y - a c t i v e r a d i a t i o n i n comparison w i t h up t o 50% ' i n t e r c e p t i o n by l e a f l e s s c a n o p i e s (Monsi and S a e k i , 1953; R e i f s n y d e r and L u l l , 1965, Z a v i t k o v s k i , 1982). L i g h t q u a l i t y i s a l s o m o d i f i e d as t h e f o l i a g e s e l e c t i v e l y absorbs wavelengths c r i t i c a l f o r p h o t o s y n t h e s i s . K i r a e t a l . (1969) r e p o r t e d a good c o r r e l a t i o n s between l i g h t a t t e n u a t i o n and e i t h e r p h o t o s y n t h e s i s o r r e s p i r a t i o n w i t h i n hardwood c a n o p i e s . Very l i t t l e i s known about t h e shade c a s t by t h e common decidu o u s c o m p e t i t o r s i n west c o a s t f o r e s t s i n Canada and th e U n i t e d S t a t e s . Models f o r t h e d e s c r i p t i o n o f t h e l i g h t a t t e n u a t i o n i n de c i d u o u s c a n o p i e s e x i s t , b u t t h e y a re u n t e s t e d f o r t h e s p e c i e s competing w i t h P a c i f i c Northwest c o n i f e r s . A t r e e ' s a b i l i t y t o grow amongst c o m p e t i t o r s i s r e l a t e d t o i t s " t o l e r a n c e " , which i s d e f i n e d as t h e r e l a t i v e c a p a c i t y t o s u r v i v e and grow under c o n d i t i o n s o f low a v a i l a b l e l i g h t and h i g h r o o t c o m p e t i t i o n ( D a n i e l e t a l . 1979). The a b i l i t y t o w i t h s t a n d low l i g h t l e v e l s ( i . e . t o 3 be "shade t o l e r a n t " ) i s g e n e r a l l y c o n s i d e r e d t h e most i m p o r t a n t c h a r a c t e r i s t i c o f t o l e r a n c e ( S h i r l e y 1943, SAF, 1944). When c o n i f e r s grow w i t h i n d eciduous c a n o p i e s t h e r e l a t i v e s h a d i n g o f t h e canopy changes s e a s o n a l l y , and so may t h e r e l a t i v e p h y s i o l o g i c a l a c t i v i t y between s p e c i e s o f d i f f e r e n t shade t o l e r a n c e under t h o s e c a n o p i e s . In temperate r e g i o n s where w i n t e r s are m i l d , p h o t o s y n t h e s i s c o n t i n u e s y e a r round (Kramer and K o z l o w s k i , 1979). Helms (1965) found t h a t D o u g l a s - f i r i n t h e Western hemlock zone o f Washington s t a t e u s u a l l y have p o s i t i v e a s s i m i l a t i o n r a t e s t h r o u g h o u t t h e autumn and w i n t e r , t i m e s when deciduous c o m p e t i t o r s a r e l e a f l e s s . C a l c u l a t i o n s by Emmingham and Waring (1974) show t h a t D o u g l a s - f i r t r e e s i n t h a t same r e g i o n may accumulate more th a n 50 p e r c e n t o f t h e i r a n n u a l a s s i m i l a t e between October and May. D e s p i t e t h e p o t e n t i a l i m p o r t a n c e t h i s "non-growing season" p h o t o s y n t h e s i s may have f o r c o n i f e r growth, L i n d e r (1979, 1981) n o t e d i n h i s r e v i e w o f c o n i f e r p h o t o s y n t h e s i s s t u d i e s t h a t t h e r e have been v e r y few i n v e s t i g a t i o n s o f t h e f u l l a n n u a l c y c l e o f p h o t o s y n t h e s i s o f low e l e v a t i o n c o a s t a l f o r e s t c o n i f e r s . Autumn and w i n t e r p h o t o s y n t h e s i s may be a way i n which s h a d e - i n t o l e r a n t c o n i f e r s can s u r v i v e and grow under deciduous c o m p e t i t o r s . To l e s s e n t h e chances o f m o r t a l i t y and t o improve t h e growth o f young c o n i f e r p l a n t a t i o n s , a c o n s i d e r a b l e e f f o r t i s o f t e n put i n t o v e g e t a t i o n management t o reduce t h e d e n s i t y o f deciduous c o m p e t i t o r s . As mentioned p r e v i o u s l y , 4 t h e r e i s c o n s i d e r a b l e v a r i a t i o n i n t h e r e l e a s e response t h a t r e s u l t s from t h e s e e f f o r t s . One f a c t o r t h a t can e f f e c t b o t h t h e magnitude and t h e r a t e a t w h i c h response o c c u r s i s " r e l e a s e s h o c k " 1 . The o c c u r r e n c e and e x t e n t o f r e l e a s e shock i s r e l a t e d t o t h e a b i l i t y o f f o l i a g e t o a c c l i m a t e t o h i g h e r l i g h t e n v i r o n m e n t s . S i n c e t h e r a t e and e x t e n t t o w h i c h f o l i a g e can a c c l i m a t e t o changes i n l i g h t i s dependent on t h e m a t u r i t y o f f o l i a g e ( J u r i k e t a l . , 1979), and t o t h e magnitude o f l i g h t i n t e n s i t y change (Powles, 1984), i t i s l i k e l y t h a t t h e t i m i n g and method o f r e l e a s e w i l l a f f e c t t h e r e l e a s e r e s p o n s e . T h i s t h e s i s has t h r e e major s e c t i o n s , which d e s c r i b e t h e t h r e e s t u d i e s t h a t were u n d e r t a k e n . The f i r s t d e s c r i b e s t h e shade c a s t by two commonly o c c u r r i n g d e c i d u o u s c o m p e t i t o r s . The second examines t h e s e a s o n a l p a t t e r n s o f p h y s i o l o g y and growth o f t h r e e c o n i f e r s p e c i e s growing under d i f f e r e n t d e n s i t i e s o f t h e s e two deciduous c o m p e t i t o r s . The t h i r d e x p l o r e s e f f e c t s t h a t t h e t i m i n g and t h e method o f r e l e a s e have on t h e response o f s u p p r e s s e d D o u g l a s - f i r s a p l i n g s . 1 The term r e l e a s e shock i s c h a r a c t e r i z e d by t h e v i s u a l symptoms o f poor p l a n t a c c l i m a t i o n a f t e r exposure t o e n v i r o n m e n t s w i t h i n c r e a s e d l i g h t and m o i s t u r e d e f i c i t s (poor growth, c h l o r o s i s , c a s t i n g o f f o l i a g e e t c . ) . See Ronco (1975) f o r f u r t h e r d i s c u s s i o n and r e l a t e d terms. 5 RESEARCH OBJECTIVES The o v e r a l l o b j e c t i v e o f t h e r e s e a r c h r e p o r t e d i n t h i s t h e s i s was t o p r o v i d e an i m p r o v e d u n d e r s t a n d i n g o f t h e e n v i r o n m e n t c r e a t e d by d e c i d u o u s c o m p e t i t o r s , how i t changes t h r o u g h t i m e , and how c o n i f e r s r e s p o n d t o t h a t e n v i r o n m e n t and t o r e d u c t i o n s i n t h e i n f l u e n c e o f t h e d e c i d u o u s canopy. To s a t i s f y t h e s e o b j e c t i v e s t h e l i g h t e n v i r o n m e n t o f r e d a l d e r and s a l m o n b e r r y was m o n i t o r e d t h r o u g h o u t t h e y e a r and t h e a b i l i t y o f t h e B e e r - L a m b e r t Law t o p r e d i c t l i g h t a t t e n u a t i o n w i t h i n s a l m o n b e r r y c a n o p i e s was t e s t e d . E x p e r i m e n t s were c o n d u c t e d t o t e s t how c o n i f e r s e e d l i n g s were i n f l u e n c e d , p h y s i o l o g i c a l l y and m o r p h o l o g i c a l l y , by d i f f e r e n t d e n s i t i e s o f d e c i d u o u s c o m p e t i n g v e g e t a t i o n , and how s u p p r e s s e d s a p l i n g s a c c l i m a t e t o t h e r e m o v a l o f o v e r t o p p i n g d e c i d u o u s c o m p e t i t o r s . The f o l l o w i n g h y p o t h e s e s s e r v e d as t h e f o c u s o f t h i s r e s e a r c h . 1. The B e e r - L a m b e r t law w i l l a c c u r a t e l y d e s c r i b e l i g h t a t t e n u a t i o n w i t h i n s a l m o n b e r r y c a n o p i e s o f a v a r i e t y o f ages a t low e l e v a t i o n i n c o a s t a l B.C. 2. The shade f o l i a g e o f c o n i f e r s b e n e a t h d e c i d u o u s c a n o p i e s w i l l a c c l i m a t e t o t h e i n c r e a s e d l i g h t i n t h e autumn, and t h e r e f o r e p h o t o s y n t h e t i c d i f f e r e n c e s between s p e c i e s w i l l be l o w e r i n t h e autumn t h a n d u r i n g midsummer. 6 3. Growth d i f f e r e n c e s between s p e c i e s u n d e r d i f f e r e n t d e c i d u o u s c a n o p i e s w i l l be s m a l l e r i n t o l e r a n t s p e c i e s as compared w i t h l e s s t o l e r a n t s p e c i e s . 4. The method (manual o r h e r b i c i d e ) and t h e s e a s o n i n w h i c h s u p p r e s s e d D o u g l a s - f i r s a p l i n g s a r e r e l e a s e d f r o m o v e r t o p p i n g r e d a l d e r w i l l i n f l u e n c e t h e i r p h y s i o l o g i c a l s t a t u s d u r i n g and a f t e r a c c l i m a t i o n t o t h e i n c r e a s e d e x p o s u r e , and t h e i r s u b s e q u e n t g r o w t h . 7 STUDY DESIGN T h r e e e x p e r i m e n t s were c o n d u c t e d t o meet t h e r e s e a r c h o b j e c t i v e s : 1. C h a r a c t e r i z a t i o n o f t h e l i g h t e n v i r o n m e n t u n d e r s a l m o n b e r r y and r e d a l d e r c a n o p i e s ( C h a p t e r 2 ) . Changes i n t h e l i g h t e n v i r o n m e n t u n d e r s a l m o n b e r r y and r e d a l d e r c a n o p i e s were f o l l o w e d o v e r a 1 2 month p e r i o d . The v e r t i c a l d i s t r i b u t i o n o f above g r o u n d b i o m a s s , and t h e l i g h t a t t e n u a t i o n w i t h i n t h e c a n o p i e s was q u a n t i f i e d f o r s a l m o n b e r r y . The d a t a were o b t a i n e d by s a m p l i n g t h e same t h i c k e t i n c o n s e c u t i v e y e a r s and by s a m p l i n g two o t h e r s i t e s w h i c h v a r i e d i n age and a c t e d as a c h r o n o s e q u e n c e . 2. P h y s i o l o g y and g r o w t h o f u n d e r p l a n t e d s e e d l i n g s ( C h a p t e r 3 ) . C o n i f e r s e e d l i n g s p l a n t e d u n d e r d e c i d u o u s c a n o p i e s o f known c o m p o s i t i o n and d e n s i t y ( s h a d i n g ) were m a i n t a i n e d t h r o u g h a two y e a r e s t a b l i s h m e n t and a one y e a r measurement p e r i o d . Changes i n t h e i r p h y s i o l o g y o v e r a 12 month p e r i o d and t o t a l g r o w t h a t t h e end o f t h e t h i r d g r o w i n g s e a s o n from p l a n t i n g were me a s u r e d . S e e d l i n g s o f D o u g l a s - f i r , w e s t e r n h e mlock and g r a n d f i r were e s t a b l i s h e d u s i n g a c o m p l e t e l y r a n d o m i z e d d e s i g n on b o t h s a l m o n b e r r y and r e d a l d e r d o m i n a t e d s i t e s . A t e a c h s i t e , t h r e e r e p l i c a t e a r e a s e a c h 8 o f t h r e e canopy d e n s i t i e s were p r e p a r e d by manual c l i p p i n g t h e v e g e t a t i o n at ground l e v e l . The t h r e e canopy d e n s i t i e s were: (a) h i g h d e n s i t y a r e a s i n w h i c h t h e s e e d l i n g s r e c e i v e d o n l y 5-10% o f f u l l sun ( d etermined by l i g h t i n t e g r a t i o n over d a y l i g h t hours compared w i t h t h e same measurement i n a d j a c e n t open a r e a s ) . (b) medium d e n s i t y a r e a s ( c r e a t e d by t h i n n i n g ) i n which t h e s e e d l i n g s r e c e i v e d 25-35% o f f u l l s u n l i g h t . (c) low d e n s i t y a r e a s ( s m a l l gaps i n t h e stand) where t h e s e e d l i n g s r e c e i v e d about 90% o f f u l l s u n l i g h t . 3. P h y s i o l o g y and growth o f r e l e a s e d s a p l i n g s (Chapter 4 ) . The growth and p h y s i o l o g i c a l s t a t u s o f D o u g l a s - f i r s a p l i n g s a f t e r r e l e a s e from o v e r t o p p i n g by r e d a l d e r c a n o p i e s were examined u s i n g a s e r i e s o f s i t e s e s t a b l i s h e d o v e r t i m e . At each r e l e a s e t r e a t m e n t , p l o t s were e s t a b l i s h e d u s i n g a c o m p l e t e l y randomized d e s i g n c o n s i s t i n g o f an u n t r e a t e d c o n t r o l , a h e r b i c i d e r e l e a s e t r e a t m e n t , and a manual r e l e a s e t r e a t m e n t . A d e s c r i p t i o n o f p l o t e s t a b l i s h m e n t , e x p e r i m e n t a l t r e a t m e n t s , s p e c i f i c f i e l d and l a b o r a t o r y p r o c e d u r e s , and d a t a a n a l y s e s are found w i t h i n t h e methods s e c t i o n o f t h e a p p r o p r i a t e c h a p t e r (2, 3, 4 ) . These s t u d i e s r e q u i r e d t h e e s t a b l i s h m e n t o f r e p l i c a t e p l o t s i n t h r e e s e p a r a t e l o c a t i o n s . In each case a s u r v e y o f t h e p o t e n t i a l a r e a was c o n d u c t e d and l o c a t i o n s w i t h homogeneous v e g e t a t i v e 9 c o n d i t i o n s were s e l e c t e d t o reduce v a r i a b i l i t y between p l o t s a t a g i v e n s i t e . P l o t s w i t h i n s u i t a b l e a r e a s were mapped and randomly a s s i g n e d t o t h e d i f f e r e n t t r e a t m e n t s . For t h e s t u d i e s o f s a l m onberry growth and D o u g l a s - f i r r e l e a s e t h i s i n v o l v e d t h e p r e l o c a t i o n o f p l o t s f o r f u t u r e use. 10 DESCRIPTION OF STUDY SITES A. E n v i r o n m e n t a l s e t t i n g The major s t u d i e s were l o c a t e d i n t h e s o u t h e r n , lower e l e v a t i o n a r e a o f t h e U n i v e r s i t y o f B r i t i s h Columbia Research F o r e s t near Haney, B r i t i s h Columbia, a p p r o x i m a t e l y 50 km e a s t o f Vancouver ( F i g . 1 ) . The topography o f t h e study a r e a i s t y p i c a l o f t h e c o a s t a l f o o t h i l l s o f t h e mountains o f s o u t h w e s t e r n B. C : g e n t l e s l o p e s c o n s i s t i n g o f g l a c i o - m a r i n e m a t e r i a l s over a c i d igneous b e d r o c k . S o i l s on a l l p l o t s were h u m o - f e r r i c p o d z o l s (Canada S o i l Survey Committee, 1970) w i t h t e x t u r e s o f sandy loam t o loamy sand w i t h a low (<40%) c o a r s e fragment c o n t e n t . The c l i m a t e i s warm m a r i t i m e mesothermal w i t h t h e m a j o r i t y o f t h e average 220 cm o f p r e c i p i t a t i o n f a l l i n g i n t h e w i n t e r . Summers are warm and o f t e n have an extended d r y p e r i o d . Temperatures i n t h e w i n t e r a re g e n e r a l l y m i l d . T able 1 summarizes t h e tempe r a t u r e s and p r e c i p i t a t i o n d u r i n g t h e study p e r i o d as w e l l as t h e 20 y e a r averages (data from t h e weather s t a t i o n a t t h e Research F o r e s t a d m i n i s t r a t i o n o f f i c e . The s t u d y p l o t s were w i t h i n t h e d r y subzone o f t h e C o a s t a l Western Hemlock Zone ( K r a j i n a , 1965). A d e t a i l e d d e s c r i p t i o n o f t h e s o i l s and v e g e t a t i o n i n t h e a r e a o f t h e t h e s e p l o t s can be found i n K i i n k a (1976). P a r t o f t h e d a t a c o n t a i n e d i n Chapter 4 was c o l l e c t e d at a s i t e 16 km n o r t h w e s t o f P o w e l l R i v e r , B.C. near t h e head o f Okeover I n l e t (49.22°N 124.33°W). T h i s a r e a has F i g u r e 1. L o c a t i o n o f study s i t e s on t h e U n i v e r s i t y B r i t i s h Columbia Research f o r e s t . 12 Ta b l e 1. Mean monthly t e m p e r a t u r e and monthly p r e c i p i t a t i o n a t t h e A d m i n i s t r a t i o n B u i l d i n g s i n 1983 and 1984, and t h e 20 y e a r averages f o r t h e UBC Research F o r e s t . Temperature (°C) 1983 1984 20 y r Month Ave max Ave min Ave max Ave min Ave max Ave m: Jan 8.5 2.7 7.1 -1.9 3 .9 -1 .6 Feb 9.1 1.6 9.2 -2.1 6 . 6 0 .2 Mar 11.7 2.3 12.7 -0.2 8 .4 0 .8 Apr 14.7 2.5 13. 9 3.1 12 .4 3 .3 May 19.1 8.2 15.1 5.5 16 .8 6 . 6 Jun 18.7 10.3 18.1 9.3 19 .4 9 .4 J u l 20.9 9.7 24.2 11.2 22 .6 10 .9 Aug 23.4 10.5 22.5 11.0 21 . 9 10 . 9 Sep 18.9 7.9 19.1 8.1 19 .2 8 .8 Oct 14.0 3.2 11.9 4.5 13 .2 5 . 6 Nov 9.2 3.7 7.8 2.3 8 .0 1 .8 Dec 3.2 -5.1 3.3 -2.7 5 .3 0 .0 P r e c i p i t a t i o n (mm) 1983 1984 20 v r Jan 363.8 432.2 289 Feb 310.2 217.4 219 Mar 189.9 218.9 231 Apr 123. 6 186.1 154 May 86.4 211.3 111 Jun 153.3 133.4 92 J u l 247.0 21.3 68 Aug 44 .1 63.7 80 Sep 113.5 116.0 128 Oct 156.4 252.3 244 Nov 482.5 367.6 275 Dec 131.1 216.2 315 T o t a l 2401.8 2436.4 2206 13 g e n t l e topography and d u r i c h u m o - f e r r i c p o d z o l s s o i l d e r i v e d from g l a c i a l t i l l . The c l i m a t e i s d r y e r t h a n t h e Haney s i t e , r e c e i v i n g o n l y 120 cm o f p r e c i p i t a t i o n . Twenty y e a r average t e m p e r a t u r e s are 2 °C i n January and 17 °C i n J u l y . The a r e a f a l l s w i t h i n t h e wet subzone o f t h e C o a s t a l D o u g l a s - f i r Zone ( K r a j i n a , 1965). A. Sample l o c a t i o n s The d a t a f o r each o f t h e ex p e r i m e n t s r e p o r t e d i n C h a p t e r s 2, 3 and 4 were c o l l e c t e d d u r i n g 1982, 1983, and 1984. S i t e s used i n s t u d i e s r e p o r t e d i n Chapter 2 were from two s u b h y g r i c ( i m p e r f e c t l y d r a i n e d ) salmonberry t h i c k e t s ( F i g . 1 A, B) and from a mesic r e d a l d e r s t a n d ( F i g . 1 C ) . S i t e A had been c l e a r c u t and c a b l e y a r d e d i n t h e f a l l o f 1981. I t was c h a r a c t e r i z e d by a Tsuga h e t e r o p h y l l a / A c h l y s t r i p h y l l a - P o l v s t i c h u m munitum p l a n t a s s o c i a t i o n ( K i i n k a , 1976) and a moder humus form. The s i t e e l e v a t i o n was 200 m above sea l e v e l : t h e s l o p e was 10% t o t h e west. S i t e B, used i n s t u d i e s r e p o r t e d i n Cha p t e r s 2 and 3, c o n s i s t e d o f two s e p a r a t e s a l m o n b e r r y t h i c k e t s , one on t h e margin o f a c l e a r i n g and t h e second w i t h i n a 1 5 - y e a r - o l d D o u g l a s - f i r p l a n t a t i o n . B o t h t h i c k e t s were on l e v e l ground and o c c u p i e d over 500 irr - i n a r e a . The t h i c k e t b o r d e r i n g t h e c l e a r i n g was e i g h t y e a r s o l d and t h e o t h e r w i t h i n t h e p l a n t a t i o n was f i v e y e a r s o l d i n 1982. Both r e c e i v e d s u b s u r f a c e m o i s t u r e i n t h e summer and were c h a r a c t e r i z e d by th e Tsuga h e t e r o p h y l l a / P o l y s t i c h u m m u n i t u m - T i a r e l l a 14 t r i f o l i a t a p l a n t a s s o c i a t i o n ( K l i n k a , 1976) and had a m u l l humus form. S i t e C, used t o c o l l e c t d a t a f o r C h a p t e r s 2, 3 and 4, was an a l d e r s t a n d on a power l i n e r i g h t - o f - w a y near t h e b o r d e r o f t h e r e s e a r c h f o r e s t . The s l o p e was 5% t o t h e west. The a r e a was m o d e r a t e l y d r a i n e d and c h a r a c t e r i z e d by th e Tsuoa h e t e r o p h y l l a / A c h l v s t r i p h v l l a - P o l v s t i c h u m muniturn p l a n t a s s o c i a t i o n ( K l i n k a , 1976). T h i s a r e a was c l e a r e d and groomed w i t h t r a c t o r s i n 1973. The a d j a c e n t u n d i s t u r b e d f o r e s t a s s u r e d ample D o u g l a s - f i r r e g e n e r a t i o n w h i l e t h e h i g h degree o f s u r f a c e s o i l d i s t u r b a n c e g u a r a n t e e d prompt r e d a l d e r e s t a b l i s h m e n t . A l l D o u g l a s - f i r and r e d a l d e r used i n th e e x p e r i m e n t s were 7 t o 8 y e a r s o f age. D e n s i t i e s o f r e d a l d e r were a p p r o x i m a t e l y 1500 stems p e r h e c t a r e and formed a c l o s e d canopy 8 t o 9 meters t a l l . The h e i g h t s o f t h e D o u g l a s - f i r s a p l i n g s averaged 3 meters. The P o w e l l R i v e r s i t e was groomed w i t h a t r a c t o r a f t e r h a r v e s t i n 1978 and p l a n t e d w i t h D o u g l a s - f i r s e e d l i n g s i n 1979. Manual b r u s h i n g t r e a t m e n t s o f r e d a l d e r i n t h e p l a n t a t i o n i n t h e f a l l o f 1980 r e s u l t e d i n v e r y dense r e d a l d e r r e s p r o u t i n g , r a n g i n g from 4,300 t o 51,500 stems p e r h e c t a r e i n t h e study a r e a . By t h e s p r i n g o f 1983, t h e y e a r o f t h e t r e a t m e n t s r e p o r t e d i n t h i s t h e s i s , t h e r e d a l d e r c a n o p i e s were 3 meters t a l l and t h e D o u g l a s - f i r s e e d l i n g s were 1.5 meters i n h e i g h t . The s i t e b e l o n g s t o t h e Pseudotsuga m e n z i e s i i / G a u l t h e r i a s h a l l o n - B e r b e r i s n e r v o s a p l a n t a s s o c i a t i o n . The e l e v a t i o n was 100 m above sea l e v e l and t h e s l o p e was 10-15% t o t h e west. P e n d l and D'Anjou (1984) c o n t a i n s f u r t h e r d e t a i l s o f t h e P o w e l l R i v e r s i t e . 16 DESCRIPTION OF STUDY SPECIES The two de c i d u o u s s p e c i e s i n t h i s s t u d y were salmonberry (Rubus s p e c t a b i l i s Pursh) and r e d a l d e r (Alnus  r u b r a Bong.). Salmonberry i s a " s t r o n g l y r h i z o m a t o u s , t h i c k e t - f o r m i n g p e r e n n i a l s p e c i e s u s u a l l y 1-3 (5) m t a l l , t h e stem e r e c t t o a r c h i n g , u s u a l l y s t r o n g l y b r i s t l y b e l o w . . l e a v e s p i n n a t e l y 3 (5) f o l i a t e . . . " ( H i t c h c o c k e t a l . (1977). Salmonberry i s a common u n d e r s t o r y component o f l o w l a n d m o i s t f o r e s t s , but i t o c c u r s up t o an e l e v a t i o n o f about 1400 m i n t h e C o a s t a l Western Hemlock Zone o f t h e P a c i f i c N o r t h w e s t . Salmonberry can form e x t e n s i v e and dense shrub t h i c k e t s i n f o r e s t openings where i t can r e t a r d shade i n t o l e r a n t c o n i f e r r e g e n e r a t i o n by heavy s h a d i n g . Salmonberry a l s o grows i n a wide v a r i e t y o f mature f o r e s t s , u s u a l l y a s s o c i a t e d w i t h canopy openings, and i s c o n s i d e r e d t o be shade t o l e r a n t . Age o f t h e sal m o n b e r r y t h i c k e t s a t s i t e A was known from d i r e c t o b s e r v a t i o n a f t e r t h e c l e a r c u t t i n g ; p a r t s o f t h e same s i t e were sampled i n t h r e e c o n s e c u t i v e y e a r s . The ages o f t h e salmonberry t h i c k e t s a t s i t e B were d e t e r m i n e d from r e c o r d s o f d i s t u r b a n c e d a t e , t h e a g i n g o f n a t u r a l c o n i f e r s e e d l i n g s w i t h i n t h e salmonberry, and a g i n g o f t h e salmonberry r o o t s t o c k s , assuming t h a t r o o t s t o c k s do not de v e l o p f o r two y e a r s (Barbor, 1976). Red a l d e r commonly o c c u r s as a s e r a i s p e c i e s on p r o d u c t i v e s i t e s t h r o u g h o u t t h e P a c i f i c N o r t h w e s t . I t i s a r a p i d l y growing t r e e which can a t t a i n a maximum h e i g h t o f 17 25 m, and h e i g h t growth i n t h e f i r s t 10 y e a r s i s commonly about a meter a y e a r . Red a l d e r can produce dense shade and i t g e n e r a l l y s u p p r e s s e s t h e growth o f a l l but t h e most shade t o l e r a n t c o n i f e r s between t h e t i m e t h e a l d e r canopy c l o s e s and i t s canopy growth slows a t a s t a n d age o f 30 t o 40 y e a r s . Leaves o f r e d a l d e r a r e b r o a d l y e l l i p t i c and 5-15 cm l o n g . Red a l d e r o c c u r s on a wide range o f s i t e s i n t h e P a c i f i c Northwest up t o a p p r o x i m a t e l y 800 m i n e l e v a t i o n , and a c h i e v e s i t s b e s t growth on m o i s t s i t e s . The shade t o l e r a n c e o f a l d e r i s c o n s i d e r e d t o be low, and r e g e n e r a t i o n i s u s u a l l y r a p i d on exposed m i n e r a l s o i l w i t h i n t h e Western Hemlock Zone, except where f r o s t h e a v i n g o c c u r s and i t t e n d s t o be r e p l a c e d by b l a c k C o t t o n w o o d (Populus t r i c h o c a r p a T o r r . & G r a y ) . Three c o n i f e r s p e c i e s , w e s t e r n hemlock (Tsuaa  h e t e r o p h y l l a (Raf.) S a r g . , g r a n d - f i r (Abies a r a n d i s (Dougl.) L i n d l . , and D o u g l a s - f i r (Pseudotsuaa m e n z i e s i i (Mirb.) F r a n c o , were used i n t h i s s t u d y . These s p e c i e s r e p r e s e n t a range o f shade t o l e r a n c e , a l t h o u g h t h e i r shade t o l e r a n c e r a t i n g by d i f f e r e n t a u t h o r s v a r i e s somewhat (Minore, 197 9 ) , However, the r e l a t i v e o r d e r o f t o l e r a n c e i s always g i v e n as w e s t e r n hemlock ( v e r y - t o l e r a n t ) as t h e most shade t o l e r a n t f o l l o w e d by g r a n d - f i r ( t o l e r a n t ) and D o u g l a s - f i r ( i n t e r m e d i a t e t o l e r a n c e ) ( r a t i n g s a f t e r F o w e l l s , 1976). A l l t h r e e are commercial s p e c i e s t h a t commonly e n c o u n t e r e x t e n s i v e b r u s h c o m p e t i t i o n on c u t o v e r s e i t h e r when r e g e n e r a t i n g n a t u r a l l y o r when p l a n t e d . D o u g l a s - f i r i s t h e f o c u s o f t h e r e l e a s e s t u d i e s because i t s s u p p r e s s i o n by d e c i d u o u s c a n o p i e s i s p a r t i c u l a r l y s e v e r e and commonplace. 19 CHAPTER 2 SEASONAL AND HERBICIDE-INDUCED CHANGES IN THE LIGHT ENVIRONMENT WITHIN THE CANOPIES OF TWO DECIDUOUS SPECIES INTRODUCTION A common o b j e c t i v e o f v e g e t a t i o n management on m o i s t , f e r t i l e f o r e s t s i t e s i s t o reduce s h a d i n g by competing s p e c i e s so t h a t c r o p t r e e s can a c h i e v e h i g h growth r a t e s . Shading o f young c o n i f e r s on t h e s e p r o d u c t i v e s i t e s i n t h e P a c i f i c Northwest i s p r i m a r i l y by d e c i d u o u s s p e c i e s . L i t t l e i s known about t h e q u a l i t y , q u a n t i t y and dynamics o f t h e shade c a s t by deciduous c o m p e t i t o r s , d e s p i t e t h e c o n s i d e r a b l e e f f o r t t o l i m i t them t h r o u g h v e g e t a t i o n management. S t u d i e s o f t h e shade c a s t by b r o a d l e a f f o r e s t s and some a g r i c u l t u r a l c r o p s may p r o v i d e c l u e s about t h e l i g h t environment o f young c o n i f e r s w i t h i n t h e canopy o f deciduous p l a n t s . S t u d i e s o f deciduous f o r e s t c a n o p i e s have demonstrated t h a t f o l i a t e d and l e a f l e s s c a n o p i e s can i n t e r c e p t more t h a n 90% and 50% o f t h e i n c i d e n t p h o t o s y n t h e t i c a c t i v e r a d i a t i o n , r e s p e c t i v e l y (Monsi and S a e k i , 1953; G e i g e r , 1965; R e i f s n y d e r and L u l l , 1965; Horn, 1971; Z a v i t k o v s k i , 1974). However, few s t u d i e s g i v e i n s i g h t as t o how m o d i f i c a t i o n s i n l i g h t q u a l i t y may d i f f e r as p l a n t community s t r u c t u r e d e v e l o p s . The s e a s o n a l dynamics o f 20 l i g h t c o n d i t i o n s t h a t a r e a r e s u l t o f o v e r s t o r y f o l i a g e phenology are r e c e i v i n g i n c r e a s i n g r e s e a r c h a t t e n t i o n , i n p a r t because o f t h e c o n t r o l l i n g i n f l u e n c e t h a t o v e r s t o r y phenology has on u n d e r s t o r y p r o d u c t i v i t y (Blackman, 1962; McCree, 1984). The l i g h t environment w i t h i n d e c i d u o u s c a n o p i e s i s c o n s t a n t l y c h a n g i n g t h r o u g h annual canopy growth, s e a s o n a l f o l i a g e c y c l e s , and d i u r n a l p a t t e r n s o f shadow and s u n f l e e k s . L i g h t q u a l i t y i s a l s o m o d i f i e d as f o l i a g e s e l e c t i v e l y absorbs a g r e a t e r p r o p o r t i o n o f b l u e and r e d t h a n o f o t h e r w a v e l e n g t h s , and t h e l i g h t p a s s i n g t h r o u g h t h e canopy becomes i n c r e a s i n g l y e n r i c h e d w i t h g r e e n and n e a r -i n f r a r e d wavelengths (Federer and Tanner, 1966; Holmes and Smith, 1977; and F l o y d e t a l . , 1978). B o t h q u a n t i t a t i v e and q u a l i t a t i v e changes i n l i g h t a re i m p o r t a n t i n d e s c r i b i n g shade and i t s r o l e i n c a u s i n g p o s s i b l e morphogenetic responses o f p l a n t s g rowing w i t h i n d e c i d u o u s c a n o p i e s . E x p e r i m e n t a l e v i d e n c e summarized by Smith (1982) i l l u s t r a t e s t h e r o l e o f l i g h t q u a l i t y i n shade a c c l i m a t i o n t h r o u g h i t s e f f e c t on stem e x t e n s i o n , l e a f s t r u c t u r e and s i z e , and t h e p h y s i o l o g i c a l p r o c e s s e s . Monsi and S a e k i (1953) proposed t h a t t h e a t t e n u a t i o n o f l i g h t w i t h i n a canopy i s an e x p o n e n t i a l f u n c t i o n o f c u m u l a t i v e l e a f a r e a , i n accordance w i t h t h e Beer-Lambert e x t i n c t i o n law. M o n t e i t h (1965), K i r a e t a l . (1969), Newton and Blackman (1970), Kawahara and Tadaki (1978), L i n d r o t h and P e r t t u (1981), Wien (1982) and o t h e r s have found, t h a t 21 t h e Beer-Lambert law d e s c r i b e d t h e l i g h t a t t e n u a t i o n i n a number of d i f f e r e n t p l a n t communities. However, based on a r e v i e w o f l i g h t p e n e t r a t i o n i n t o p l a n t communities, Anderson (1964, 1966) warned t h a t t h e Beer-Lambert e x t i n c t i o n c o e f f i c i e n t may not be c o n s t a n t f o r a g i v e n canopy or s p e c i e s . She p o i n t e d out t h a t t h e assumptions made by t h e Beer-Lambert Law a r e u n l i k e l y t o be met i n n a t u r e , and demonstrated t h a t l e a f i n c l i n a t i o n , l i g h t p e n e t r a t i o n a n g l e , and d i f f u s e v s . beam r a d i a t i o n can have major i n f l u e n c e s on t h e e x t i n c t i o n c o e f f i c i e n t s o f c a n o p i e s . A r a k i (1985) suggested a s t r a t u m - s p e c i f i c approach f o r t h e c a l c u l a t i o n o f e x t i n c t i o n c o e f f i c i e n t s t o a v o i d t h e problems r e s u l t i n g from h e t e r o g e n e i t y i n canopy c h a r a c t e r i s t i c s . Yim e t a l . (1969) found t h a t stem s u r f a c e a r e a ( s u b s t i t u t e d f o r l e a f area) a c c u r a t e l y d e s c r i b e d t h e l i g h t a t t e n u a t i o n i n an a r t i f i c i a l l y d e f o l i a t e d shrub s t a n d . They found t h a t stems and t w i g s o f v a r i o u s shrub s p e c i e s i n t e r c e p t e d from 28 t o 69 p e r c e n t o f i n c i d e n t l i g h t . R o b e r t s and M i l l e r (1977) r e p o r t e d about 20% i n t e r c e p t i o n o f l i g h t i n b o t h t h e summer and w i n t e r f o r two shrub s p e c i e s . Newton and Blackman (1970) s t a t e d t h a t stem s u r f a c e a r e a must be i n c l u d e d f o r a v a l i d e s t i m a t i o n o f a canopy e x t i n c t i o n c o e f f i c i e n t . I t i s now r e c o g n i z e d t h a t stem i n t e r c e p t i o n o f l i g h t needs t o be c o n s i d e r e d , and t h a t "whole-shrub" e x t i n c t i o n c o e f f i c i e n t s (Roberts and M i l l e r , 22 1977), w h i c h i n c l u d e b o t h l e a f and stem a r e a , are v a l u a b l e f o r d e s c r i b i n g l i g h t w i t h i n many d i f f e r e n t p l a n t communities. H e r b i c i d e s are sometimes employed on p r o d u c t i v e f o r e s t l a n d t o reduce s h a d i n g by a v a r i e t y o f deciduous p l a n t s . The e f f e c t s o f h e r b i c i d e t r e a t m e n t s on b r u s h l i g h t e n v i r o nments have r a r e l y been examined (Rediske and S t a e b l e r , 1962; Re d i s k e e t a l . , 1963 and G o t t s c h a l k and Shure, 1979). S t u d i e s o f h e r b i c i d e - i n d u c e d changes i n l i g h t environment may h e l p us t o u n d e r s t a n d how p l a n t s w i t h i n d e f o l i a t e d c a n o p i e s respond t o t h e s e t r e a t m e n t s . T h i s c h a p t e r has t h r e e o b j e c t i v e s : 1) To c h a r a c t e r i z e t h e l i g h t environment below t h e c a n o p i e s o f two common de c i d u o u s c o m p e t i t o r s i n t h e P a c i f i c Northwest ( r e d a l d e r and s a l m o n b e r r y ) , and t o d e s c r i b e f o r salmonberry t h e w i t h i n - c a n o p y changes i n l i g h t q u a n t i t y and q u a l i t y t h a t t a k e p l a c e t h r o u g h a growing season, and from year t o y e a r as t h e canopy d e v e l o p s . 2) To t e s t t h e a p p r o p r i a t e n e s s o f th e Beer-Lambert e q u a t i o n f o r d e s c r i b i n g l i g h t a t t e n u a t i o n w i t h i n s a l m onberry t h i c k e t s . I t i s h y p o t h e s i z e d t h a t i n sa l m o n b e r r y c a n o p i e s , the Beer-Lambert law u s i n g l e a f a r e a i n d e x , can d e s c r i b e l i g h t a t t e n u a t i o n i n f o l i a t e d c a n o p i e s and i n d e f o l i a t e d c a n o p i e s u s i n g stem a r e a i n d e x . 3) t o d e s c r i b e t h e e f f e c t s o f a h e r b i c i d e t r e a t m e n t on l i g h t q u a n t i t y and q u a l i t y . 23 METHODS A. Sampling p l o t s Three r e p l i c a t e a r e a s c o n s i s t i n g o f homogeneous salm o n b e r r y t h i c k e t s were l o c a t e d a t s i t e A i n 1982 f o r s a m p l i n g i n 1982, 1983, and 1984 (see Ch a p t e r 1 f o r d e t a i l s o f t h e s i t e ) . A p l o t c e n t e r was e s t a b l i s h e d i n each r e p l i c a t e , and a sample t a k e n from each o f t h e t h r e e p l o t s i n each o f t h r e e y e a r s . Sampling l o c a t i o n s were l o c a t e d by measuring 2 m from t h e f i x e d p l o t c e n t e r , s u c c e s s i v e samples b e i n g l o c a t e d a l o n g d i f f e r e n t compass b e a r i n g s . In a d d i t i o n , s a l m o n b e r r y t h i c k e t s aged 5 and 8 y e a r s were sampled i n 1983 a t s i t e B. A l d e r d a t a were c o l l e c t e d from s i t e C. B. F i e l d t r e a t m e n t s  H e r b i c i d e t r e a t m e n t Stems o f r e d a l d e r were i n j e c t e d w i t h 2,4-D amine on May 24, 1983 i n o r d e r t o s t u d y t h e r a t e o f d e f o l a t i o n and i n c r e a s e s i n l i g h t beneath t h e c a n o p i e s . A p p r o x i m a t e l y 3 mL o f a 40% s o l u t i o n was used p e r c e n t i m e t e r o f stem d i a m e t e r . The h e r b i c i d e was a p p l i e d t o c u t s i n t h e b a r k and cambium t h a t were a n g l e d t o h o l d t h e h e r b i c i d e i n t h e c u t s u r f a c e . C. F i e l d measurements V e r t i c a l biomass and a r e a p r o f i l e s f o r salmonberry Salmonberry c a n o p i e s were d e s t r u c t i v e l y sampled i n J u l y u s i n g t h e s t r a t i f i e d c l i p t e c h n i q u e (50 cm i n t e r v a l s ) (Monsi 24 and S a e k i , 1953). A t a minimum of 2 m from t h e t h i c k e t margin, a i m sample p l o t was d e f i n e d on t h e ground by a square m e t a l p l o t frame. V e r t i c a l p o l e s were d r i v e n i n t o t h e ground a t each c o r n e r o f t h e p l o t frame t o d e f i n e t h e column o f v e g e t a t i o n t o be sampled. A l l l e a v e s and stems w i t h i n each 50 cm s t r a t u m (measured from t h e ground) were c l i p p e d and p l a c e d i n i n d i v i d u a l bags f o r t r a n s p o r t t o t h e l a b o r a t o r y . Three 1 m r e p l i c a t e p l o t s were sampled i n each o f t h e f i v e t h i c k e t ages (3 ages at s i t e A; 2 ages a t s i t e B) . In t h e l a b o r a t o r y , l e a v e s were s e p a r a t e d from stems. The s u r f a c e a r e a o f t h r e e 30 g subsamples o f l e a v e s from each s t r a t u m was d e t e r m i n e d w i t h a l e a f a r e a meter (LI-3000, Lambda Inst r u m e n t s ) b e f o r e d r y i n g . Stem a r e a was e s t i m a t e d by d i v i d i n g a l l t h e stems i n t o f o u r d i a m e t e r s i z e c l a s s e s (below 0.25, 0.25-0.49, 0.5-0.74, and 0.75 cm and l a r g e r ) , s u b sampling stems from each s i z e c l a s s , and d e t e r m i n i n g t h e p r o j e c t e d a r e a o f each subsample w i t h a l e a f a r e a meter. Leaves and stems were d r i e d a t 65°C t o a c o n s t a n t w e i g h t . The average s p e c i f i c stem a r e a per stem s i z e c l a s s was used t o c o n v e r t stem w e i g h t t o stem a r e a . I n t e g r a t i o n o f l i g h t w i t h i n and beneath c a n o p i e s The i n t e g r a t i o n o f l i g h t ( p h o t o s y n t h e t i c a l l y a c t i v e photon f l u x d e n s i t y , PPFD) w i t h i n t h e s a l m o n b e r r y c a n o p i e s and beneath t h e r e d a l d e r canopy was d e t e r m i n e d u s i n g t h e anthracene method (Dore, 1958; R e d i s k e e t a l . , 1963; Marquis 25 and Y e l e n o s k y , 1962; F i s h e r and M e r r i t t , 1973) . F i f t e e n b o r o s i l i c a t e v i a l s (7 mL) c o n t a i n i n g 6 mL o f a n t h r a c e n e s o l u t i o n (0.1 g an t h r a c e n e / 1 benzene) were used i n each canopy s t r a t a measured and i n a nearby unshaded a r e a . D i u r n a l i n t e g r a t i o n s o f l i g h t a t 50 cm were measured a t monthly i n t e r v a l s under t h e 5 - y e a r - o l d s a l m o n b e r r y t h i c k e t and t h e r e d a l d e r s t a n d i n 1983. L i g h t was i n t e g r a t e d a t 50 cm h e i g h t i n t e r v a l s w i t h i n salmonberry c a n o p i e s j u s t p r i o r t o d e s t r u c t i v e s a m p l i n g . V i a l s were suspended by a h o r i z o n t a l s t r i n g a t t a c h e d by e l a s t i c bands t o t h e v i a l cap. The exposed v i a l s were t r a n s p o r t e d i n a l i g h t - p r o o f c o n t a i n e r and a n a l y z e d w i t h i n two days o f exposure. Decreases i n anthracene c o n c e n t r a t i o n s r e s u l t i n g from exposure t o l i g h t were d e t e r m i n e d by changes i n UV a b s o r p t i o n u s i n g a UV s p e c t r o p h o t o m e t e r (Unicam SP8000) a t 350 nm w a v e l e n g t h . C a l i b r a t i o n o f a n t h r a c e n e c o n c e n t r a t i o n change t o c u m u l a t i v e p h o t o s y n t h e t i c a l l y a c t i v e photon f l u x d e n s i t y was made by c o r r e l a t i n g a n t h r a c e n e a b s o r p t i o n t o c u m u l a t i v e r e a d i n g s from quantum s e n s o r s (LI-190S, LI-COR) and an i n t e g r a t i n g s o l a r m o n i t o r (LI-1776, LI-COR). A r e g r e s s i o n e q u a t i o n 9 h a v i n g an r =0.97 (Appendix 1) was d e v e l o p e d t o c o n v e r t a n t h r a c e n e a b s o r p t i o n o f exposed v i a l s t o c u m u l a t i v e p h o t o s y n t h e t i c a l l y a c t i v e photon f l u x d e n s i t y (PPFD). 26 D e t e r m i n a t i o n o f l i g h t q u a l i t y w i t h i n c a n o p i e s The s p e c t r a l d i s t r i b u t i o n o f r a d i a n t energy i n t h e 300 t o 900 nm r e g i o n under s a l m o n b e r r y and r e d a l d e r c a n o p i e s was d e t e r m i n e d u s i n g a p o r t a b l e s p e c t r o r a d i o m e t e r (IL - 7 0 0 , I n t e r n a t i o n a l L i g h t ) . R a d i a n t energy measurements were t a k e n a t 20 nm wavelength i n t e r v a l s from 300 t o 900 nm under t h e 5 - y e a r - o l d salmonberry and t h e r e d a l d e r s t a n d under s l i g h t l y o v e r c a s t c o n d i t i o n s on September 19 and 20, 1983. The t r i p o d - m o u n t e d s e n s o r was h e l d a t 1 m above t h e ground. Measurements o f t h e photon f l u x a t 660 nm and 730 nm were a l s o d e t e r m i n e d a t 50 cm h e i g h t i n t e r v a l s w i t h i n one o f t h e sample p l o t s o f each o f t h e f i v e ages o f salmonberry t h i c k e t s b e f o r e t h e y were d e s t r u c t i v e l y sampled. C a l c u l a t i o n o f e x t i n c t i o n c o e f f i c i e n t s Beer-Lambert 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 f o r t h e summer and w i n t e r were c a l c u l a t e d from d a t a on l e a f a r e a i n d e x a l o n e , stem a r e a i n d e x a l o n e , and f o r t h e combined l e a f and stem a r e a i n d e x f o r t h e salmonberry t h i c k e t s o f v a r i o u s ages, and l i g h t v a l u e s d e t e r m i n e d i n b o t h t h e summer and w i n t e r . The e x t i n c t i o n c o e f f i c i e n t (K) d e s c r i b e s t h e amount o f a t t e n u a t i o n o f l i g h t w i t h i n a canopy i n r e l a t i o n t o a a r e a i n d e x . The g r e a t e r t h e K, t h e g r e a t e r t h e 27 attenuation for a given area index. The following equation was used to determine the extinction c o e f f i c i e n t (K). I 2 / I 0 =exp [-K(F or A)] where: I z = Photosynthetically active photon flux at height z with the canopy. I Q = Photosynthetically active photon flux above the canopy. K = Extinction c o e f f i c i e n t . F = Cumulative leaf area from the top of the canopy to z. A = Cumulative stem area from the top of the canopy to height z. Z = Height i n the canopy. Data analysis Data were subjected to a one-way analysis of variance. Significance between strata was determined at p< 0.05 with the Tukey multiple comparisons test (Stoline, 1981). Linear regression models were used to describe l i g h t attenuation i n r e l a t i o n to cumulative area indices. 28 RESULTS A. D i s t r i b u t i o n o f l e a f and stem biomass and a r e a i n d e x , and  t h e l i g h t a t t e n u a t i o n w i t h i n salmonberry c a n o p i e s The v e r t i c a l d i s t r i b u t i o n s o f l e a f and stem biomass and a r e a i n d i c e s , and t h e accompanying l i g h t a t t e n u a t i o n , w i t h i n s almonberry c a n o p i e s o f v a r i o u s ages are g i v e n i n F i g u r e 2. By t h e growing season f o l l o w i n g c l e a r c u t t i n g o f t h e o v e r s t o r y and removal o f c o m m e r c i a l l y v a l u a b l e p o r t i o n s o f the t r e e stems a t s i t e A, a salmonberry canopy had de v e l o p e d which was t a l l e r t h a n 50 cm ( F i g . 2a) and had a t o t a l l e a f a r e a i n d e x o f 0.8 nr-*m . By two and t h r e e y e a r s o f age, the same sa l m o n b e r r y t h i c k e t had l e a f a r e a i n d i c e s o f 3.0 9 _ 9 and 7.6 irr'm , r e s p e c t i v e l y ( F i g s . 2b and 2c). The canopy re a c h e d a h e i g h t o f 1 t o 1.5 m i n y e a r 2, and remained a t about t h e same h e i g h t i n year 3 as e l o n g a t i n g stems made a t r a n s i t i o n from t h e near v e r t i c a l growth o f t h e f i r s t y e a r t o an a r c h i n g form. I n t h e 5 - y e a r - o l d s t a n d t h e canopy h e i g h t was between 1.5 and 2 m ( F i g . 2d) w i t h a l e a f a r e a 9 _ 9 i n d e x o f 10.7 irr'm , w h i l e t h e 8 - y e a r - o l d salmonberry t h i c k e t had r e a c h e d a h e i g h t o f n e a r l y 3 m w i t h a c u m u l a t i v e l e a f a r e a i n d e x o f 13.0 m 2-m - 2 ( F i g . 2e). L e a f a r e a was always low a t t h e base o f t h e canopy and g e n e r a l l y i n c r e a s e d w i t h h e i g h t . _9 The r a t i o o f l e a f t o stem biomass (Kg'm ^) d e c r e a s e d from 0.8 t o 0.6 from year 1 t o year 2, as stem b r a n c h i n g and h e i g h t growth a c c e l e r a t e d . The r a t i o remained c o n s t a n t a t 2 9 200-1 £ o BIOMASS 1 yr old Legend E23 Stems EZ3 Leaves AREA & LIGHT INTENSITY 200 n Legend 0 100 200 300 400 Foliage or Stems (g/m2) 1.5 3 4.5 LAI or SAI (m2 • m z ) 0 25 50 75 100 Relative Light Intensity (%) F i g u r e 2a-e. V e r t i c a l d i s t r i b u t i o n o f l e a f and stem biomass, l e a f and stem a r e a i n d e x , and r e l a t i v e l i g h t (PPFD) i n t e n s i t y w i t h i n salmonberry t h i c k e t s i n t h e summer and t h e w i n t e r , (a) 1 - y e a r - o l d t h i c k e t ; (b) 2 - y e a r - o l d t h i c k e t ; (c) 3 - y e a r - o l d t h i c k e t ; (d) 5 - y e a r - o l d t h i c k e t ; (e) 8 - y e a r - o l d t h i c k e t . BIOMASS 3 yr old AREA & LIGHT INTENSITY 200-1 Legend U& Stems EZ3 Leaves Legend O Summer A W i n t e r 5 yr old Foliage or Stems (g/m2) LAI or SAI {m2 • nr2) 0 25 50 75 100 Relative Light Intensity {%) BIOMASS AREA & LIGHT INTENSITY 8 yr old Foliage (g/m2) LAI or SAI (m2 • rrr2) i i i i i i i i i i 0 0 . 5 1 1.5 2 0 2 5 5 0 7 5 1 0 0 Stems (kg/m2) Relative Light Intensity (%) to 32 about 0.6 i n s t a n d s o f ages 3 and 5. However, c o n t i n u e d growth o f stem d i a m e t e r , stem h e i g h t , an i n c r e a s e i n stem b r a n c h i n g , and a s l o w i n g o f l e a f biomass growth r a t e , r e s u l t e d i n a t o t a l l e a f t o stem weight r a t i o o f .15 i n t h e 8 - y e a r - o l d salmonberry t h i c k e t . In younger s a l m o n b e r r y t h i c k e t s , stem weight d e c l i n e d w i t h i n c r e a s i n g canopy h e i g h t , but i n t h e 8 - y e a r - o l d t h i c k e t stem biomass was g r e a t e s t between 1 and 2 m. The r a t i o o f l e a f a r e a t o stem a r e a remained c o n s i s t e n t at about 20 f o r t h e f i r s t 3 c o n s e c u t i v e y e a r s o f growth ( F i g s . 2a t h r o u g h 2 c ) . The 5 and 8 - y e a r - o l d t h i c k e t s had l e a f a r e a t o stem a r e a r a t i o s o f 31 and 7, r e s p e c t i v e l y . L i g h t i n t e n s i t y a t 50 cm e x p r e s s e d as p e r c e n t o f l i g h t i n t h e open d e c l i n e d as t h i c k e t s i n c r e a s e d i n age f o r b o t h summer f o l i a t e d and w i n t e r l e a f l e s s p e r i o d s ( F i g s . 2a t h r o u g h 2 e ) . In a l l c a n o p i e s , l i g h t i n t e n s i t y d e c l i n e d w i t h depth i n t h e canopy. Minimum d i u r n a l i n t e g r a t e d l i g h t i n t e n s i t i e s o f about 9% f u l l sun were found under t h e 5 and 8 y e a r - o l d salmonberry t h i c k e t s . However, i n s t a n t a n e o u s measurements under t h e s e c a n o p i e s , a v o i d i n g s u n f l e c k s , t y p i c a l l y gave v a l u e s o f 0.5 t o 3% o f t h e unshaded mid-day l i g h t v a l u e s . B. Beer-Lambert e x t i n c t i o n c o e f f i c i e n t s The e x t i n c t i o n c o e f f i c i e n t based on c u m u l a t i v e l e a f a r e a i n d e x (K F) f o r salmonberry c a n o p i e s above 50 cm d e c l i n e d as l e a f a r e a i n d e x and stem a r e a i n d e x i n c r e a s e d i n T a b l e 2. Mean r e l a t i v e l i g h t (PPFD) i n t e n s i t y at 50 cm, c u m u l a t i v e l e a f a r e a i n d e x (LAI) and stem a r e a i n d e x (SAI) above 50 cm, and Beer-Lambert e x t i n c t i o n c o e f f i c i e n t s (K) t o 50 cm f o r d i f f e r e n t ages o f salmonberry t h i c k e t s based on LAI o n l y (K F) and combined LAI and SAI ( K F + A ) i n t h e summer and SAI (K A) o n l y i n t h e w i n t e r (see F i g u r e s 2a t h r o u g h 2e f o r s p e c i f i c s t a n d d a t a ) . — s u m m e r — St a n d age % l i g h t 9 LAI KF+A at 50 cm (m 2 •m~Z) 1 7 8 a 1 . 6e 1 . 91a 1.83a 2 12b 2 .0d . 91b .87b 3 10c 7 • 4c .27d .2 6e 5 3d 10 .4b .4 6c .46c 8 2d 13 . 0a .42c .38d --wi n t e r — S t a n d age % at l i g h t 50 cm (m* SAI •m z ) K A 1 9 8 a 1 .02d t— - i o i o r . i. O a 2 8 6b . 08c 12 .42b 3 77c .2 9b 3 .73c 5 64d .24b 4 .69c 8 42e 1 .41a .88d Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). 34 t h e f i r s t 3 y e a r s o f growth (Table 2) . The c u m u l a t i v e K F ' s of t h e 5 and 8 - y e a r - o l d t h i c k e t s were b o t h g r e a t e r t h a n t h a t of t h e 3 - y e a r - o l d t h i c k e t , but 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 each o t h e r . The a d d i t i o n o f stem a r e a i n d e x (A) t o t h e c a l c u l a t i o n K F + A d e c r e a s e d t h e e x t i n c t i o n c o e f f i c i e n t f o r 1 t o 3 y e a r o l d t h i c k e t s by about 3-4% compared t o v a l u e s o b t a i n e d u s i n g l e a f a r e a i n d e x a l o n e (Table 2). The i n c l u s i o n o f stem a r e a t o t h e c a l c u l a t i o n o f e x t i n c t i o n c o e f f i c i e n t s made no d i f f e r e n c e i n t h e 5 - y e a r - o l d salmonberry t h i c k e t , and r e s u l t e d i n a 10% r e d u c t i o n i n the 8 - y e a r - o l d t h i c k e t . However, e x t i n c t i o n c o e f f i c i e n t s based on stem a r e a i n d e x and w i n t e r l i g h t l e v e l s (K A) show t h a t t h e p r e s e n c e o f even s m a l l stem area s can have a s i g n i f i c a n t e f f e c t on l i g h t r e a c h i n g 50 cm on c l e a r w i n t e r days. L i g h t l e v e l s (summer f o r K F and K F + A , w i n t e r f o r K A) d e c l i n e d l o g a r i t h m i c a l l y w i t h i n c r e a s i n g a r e a i n d i c e s . R e g r e s s i o n s o f l o g r e l a t i v e l i g h t i n t e n s i t y on a r e a i n d i c e s had r 2 v a l u e s o f 0.79, 0.79, and 0.83 f o r K F, K F + A , and K A r e s p e c t i v e l y (Appendix 1). Changes i n K F between d i f f e r e n t canopy s t r a t a a r e g i v e n i n T a ble 3. In c a n o p i e s younger t h a n 8 y e a r s , t h e h i g h e s t K F v a l u e was always a t t h e t o p o f t h e canopy. I n t h e 8-y e a r - o l d t h i c k e t t h e v a l u e s o f K F i n c r e a s e d w i t h d e p t h t h r o u g h t h e canopy. A v a r i e t y o f l e a f a n g l e s c o u l d be found t h r o u g h o u t t h e c a n o p i e s , but t h e i n c l i n a t i o n o f l e a v e s i n th e upper most s t r a t a o f l e a v e s were g e n e r a l l y i n t h e range o f 45 t o 8 5 ° . The a n g l e d e c l i n e d downward t h r o u g h t h e 35 Table 3. Horizon-specific, v e r t i c a l d i s t r i b u t i o n of Beer-Lambert extinction c o e f f i c i e n t s (based on leaf area index) and s p e c i f i c leaf areas within salmonberry canopies of d i f f e r e n t ages (see Figures 2a through 2e for s p e c i f i c stand data). Beer-Lambert extinction c o e f f i c i e n t s (KF) canopy horizon — s t a n d age ( y e a r s ) — (cm) 8 22e 30d 77c 43b 38a 1 2 3 5 250-300 200-250 150-200 100-150 50-100 1.91 1.61a1 .7 9b .54a .23b 1.30a 1 .23c 13 .41b 56 S p e c i f i c leaf area (cm a - 1 ) 50 cm canopy horizon base (cm) 1 — s t a n d 2 age ( y e a r s ) — 3 5 8 250-300 200-250 150-200 100-150 50-100 0- 50 162b1 172a 153c 164b 180a 149b 150b 227a 156e 158e 163d 173d 168c 206c 188b 228b 196a 256a 1 Mean values within a column followed with ^different l e t t e r s 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). 36 canopy t o n e a r l y z e r o at t h e base o f t h e canopy. S p e c i f i c l e a f a r e a i n c r e a s e d w i t h depth i n a l l o f t h e c a n o p i e s (Table 3 ) . C. A n n u a l changes i n l i g h t q u a n t i t y and q u a l i t y w i t h i n  s a l m o n b e r r y c a n o p i e s . S e a s o n a l averages o f l i g h t (PPFD) i n t e g r a t e d under a s a l m o n b e r r y canopy and i n an unshaded a r e a are shown i n F i g u r e 3 . The h i g h e s t l i g h t under t h e salmonberry was d u r i n g March and t h e l o w e s t was i n June and J u l y . F l o w e r i n g and l e a f e x p a n s i o n began i n March and r e s u l t e d i n r e d u c t i o n s i n t o t a l l i g h t p e n e t r a t i o n . D e c l i n e s i n r e l a t i v e l i g h t i n t e n s i t y c o n t i n u e d as f o l i a g e d e v e l o p e d t h r o u g h t h e s p r i n g r e a c h i n g about 9% f u l l sun i n May. L i g h t l e v e l s i n c r e a s e d as l e a v e s senesced i n t h e autumn, but dead l e a v e s were commonly e n t r a p p e d by and draped o v e r b r a n c h e s , and t h e s e may have had a c o n t i n u e d i n f l u e n c e on l i g h t a t t e n u a t i o n t h r o u g h o u t t h e w i n t e r . The s p e c t r a l energy d i s t r i b u t i o n o f l i g h t under a 5 - y e a r - o l d salmonberry t h i c k e t i s shown i n F i g u r e 4 . W i t h i n th e p h o t o s y n t h e t i c a l l y a c t i v e spectrum, a l a r g e r amount o f th e b l u e and r e d l i g h t was absorbed by t h e canopy, c r e a t i n g an environment e n r i c h e d i n g r e e n . The r a t i o o f r e d (660) t o f a r - r e d (730) l i g h t (or z e t a ) , w i t h i n s a l m o n b e r r y c a n o p i e s o f d i f f e r e n t ages i s g i v e n i n T a b l e 4 . The z e t a v a l u e s c o n s i s t e n t l y d e c l i n e d w i t h d epth t h r o u g h a l l t h e c a n o p i e s . F i g u r e 3. Mean m o n t h l y l i g h t (PPFD) i n t e n s i t y ( at 50 cm) u n d e r a 5 - y e a r - o l d l i v e s a l m o n b e r r y t h i c k e t (LAI=10.7), and i n a c l e a r i n g . Mean m o n t h l y v a l u e s w i t h d i f f e r e n t l e t t e r s a r e 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). 100000 10000-E c E 1000T 100-10-- ^ ^ ^ \ Legend A No canopy • Live canopy 300 400 500 600 700 Wavelength (nm) 800 900 F i g u r e 4. S o l a r r a d i a t i o n q u a l i t y (at 50 cm) under a 5 - y e a r - o l d salmonber t h i c k e t (LAI = 10.7) . Table 4. V e r t i c a l measurements of Zeta (ratio of energy at 660 and at 730 nm) within salmonberry canopies of d i f f e r e n t ages (see Figures 2a through 2e for s p e c i f i c stand data). canopy horizon — s t a n d age ( y e a r s ) — (cm) 2 3 5 8 above canopy 1.06 1.07 1.06 1.07 250 .50 200 .36 150 .20 100 .58 .14 100 .65 .54 .26 .14 50 .41 .32 .14 .13 40 As canopy l e a f a r e a i n c r e a s e d , t h e z e t a v a l u e s d e c l i n e d ? e x p o n e n t i a l l y (r =0.88, Appendix 1 ) . D. Annual and h e r b i c i d e - i n d u c e d changes i n l i g h t q u a n t i t y  and g u a l i t y under r e d a l d e r c a n o p i e s . The annual c y c l e o f r a d i a t i o n p e n e t r a t i o n below l i v e and h e r b i c i d e - k i l l e d r e d a l d e r c a n o p i e s i s shown i n F i g u r e 5. The h e r b i c i d e - k i l l e d canopy p r o v i d e d r e l a t i v e l y c o n s t a n t r e d u c t i o n i n l i g h t t h r o u g h o u t t h e y e a r . The l i v e canopy p r o v i d e d t h e same l e v e l o f shade as h e r b i c i d e - k i l l e d t r e e s from November t h r o u g h March, but t h e d i f f e r e n c e i n l i g h t below t h e l i v e and dead c a n o p i e s i n c r e a s e d w i t h t h e onset o f f l o w e r i n g and l e a f e x p a n s i o n i n A p r i l . The c u m u l a t i v e l i g h t was s i m i l a r under t h e l i v e canopy f o r t h e days measured i n March, A p r i l , and May, a l t h o u g h i n c i d e n t r a d i a t i o n above t h e s t a n d i n c r e a s e d o ver t h i s p e r i o d . Through t h e summer (June, J u l y and A u g u s t ) , l i g h t l e v e l s below t h e canopy remained c l o s e t o t h e annu a l minimum. By November, l e a f a b s c i s s i o n had a l l o w e d l i g h t l e v e l s under t h e l i v e canopy t o e q u a l t h o s e o f t h e dead canopy. The time c o u r s e o f r e d a l d e r d e f o l i a t i o n a f t e r i n j e c t i o n w i t h 2,4-D amine on May 24, 1983 i s shown i n F i g u r e 6. No s i g n i f i c a n t change i n l i g h t p e n e t r a t i o n o c c u r r e d f o r t h r e e weeks a f t e r t r e a t m e n t ; however, l e a f c u r l i n g and some browning was n o t e d i n some cases a f t e r one week. The canopy t y p i c a l l y d e f o l i a t e d s l o w l y o ver t h e two months f o l l o w i n g t h e h e r b i c i d e t r e a t m e n t , r e g a r d l e s s o f t h e Treatment E222 Live canopy \Z3 Dead canopy CLJ No canopy DEC JAN FEB MAR APR MAY JUN - JUL AUG SEP OCT NOV F i g u r e 5. Mean monthly l i g h t (PPFD) i n t e n s i t y (at 50 cm) under l i v e , h e r b i c i d e - d e f o l i a t e d r e d a l d e r stands (7 y e a r o l d , 8 m t a l l ) and i n a c l e a r i n g . Mean monthly v a l u e s w i t h d i f f e r e n t l e t t e r s a r e 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) . 42 100 -i 8 0 ' co 6 0 -C CD O 40 CD CL 20 0 0 4 6 8 Time (weeks) 10 5 2 F i g u r e 6. Changes i n t h e r e l a t i v e l i g h t (PPFD) i n t e n s i t y b e neath a r e d a l d e r canopy (7 y e a r o l d , 8 m t a l l ) f o l l o w i n g a h e r b i c i d e a p p l i c a t i o n . P o i n t s s e p a r a t e d v e r t i c a l l y by more t h a n t h e v e r t i c a l b a 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). 43 season o f t r e a t m e n t . E xcept i n t h e case o f a poor h e r b i c i d e a p p l i c a t i o n , t h e r e d a l d e r canopy was l e a f l e s s a y e a r a f t e r t r e a t m e n t . Breakage o f branches and s u b s e q u e n t l y o f stems r e s u l t e d i n t h e e l i m i n a t i o n of. t h e o v e r t o p p i n g dead woody canopy over t h e f o l l o w i n g 3 6 months. F i g u r e 7 shows t h e s p e c t r a l energy d i s t r i b u t i o n o f l i g h t under f o l i a t e d and d e f o l i a t e d r e d a l d e r . The h e r b i c i d e - d e f o l i a t e d canopy d i d not a l t e r t h e s p e c t r a l q u a l i t y o f energy t h a t p e n e t r a t e d below t h e canopy, but a c t e d as a n e u t r a l d e n s i t y f i l t e r and reduced t h e t o t a l amount o f energy e q u a l l y a c r o s s t h e spectrum. In c o n t r a s t , t h e f o l i a t e d canopy s t r o n g l y d e p l e t e d energy i n t h e wave-l e n g t h s below 740 nm, e s p e c i a l l y around 680 nm. The z e t a v a l u e s under t h e l i v e r e d a l d e r were 0.13 compared w i t h 1.19 under t h e dead canopy, and 1.13 w i t h o u t a canopy. 100000^ 10000-E c E 1000-100-10-CT. ^3 Legend A No canopy X Dead canopy • Live canopy 300 400 500 600 700 Wavelength (nm) T 800 900 F i g u r e 7. S o l a r r a d i a t i o n q u a l i t y (at 50 cm) under a 7 - y e a r - o l d (8 m) r e d a l d e r canopy. ' 45 DISCUSSION A. D i f f e r e n c e s i n canopy s t r u c t u r e and l i g h t a t t e n u a t i o n  w i t h i n s a l m o n b e r r y t h i c k e t s o f d i f f e r e n t ages As t h e salmonberry c a n o p i e s d e v e l o p e d , major changes o c c u r r e d i n t h e v e r t i c a l d i s t r i b u t i o n and q u a l i t y o f t h e a s s o c i a t e d shade. These m o d i f i c a t i o n s o f t h e l i g h t m i c r o e n v i r o n m e n t c o n t i n u e d t o i n c r e a s e as t h e t o t a l l e a f a r e a i n d e x o f t h e canopy i n c r e a s e d . The r a t e o f l i g h t a t t e n u a t i o n w i t h depth i n t h e s a l m o n b e r r y c a n o p i e s v a r i e d w i t h t h i c k e t age because o f d i f f e r e n c e s i n l e a f d i s t r i b u t i o n , s p e c i f i c l e a f a r e a , l e a f o r i e n t a t i o n and canopy s t r u c t u r e . Canopy s t r u c t u r e Salmonberry c a n o p i e s d e v e l o p e d c o n s i d e r a b l e l e a f a r e a s v e r y r a p i d l y . There was a g e n e r a l l y p a r a l l e l development o f l e a v e s and stems w i t h i n t h i c k e t s as would be p r e d i c t e d by t h e p i p e model h y p o t h e s i s ( S h i n o z a k i e t a l . , 1964a,b). L e a f biomass i n c r e a s e d d i s p r o p o r t i o n a t e l y more t h a n stem biomass o n l y i n t h e second y e a r . The o l d e s t canopy (year 8) showed a v e r t i c a l d i s t r i b u t i o n i n which l e a f a r e a i n d e x was c o n c e n t r a t e d a t t h e t o p and d e c l i n e d w i t h each s u c c e s s i v e 50 cm h o r i z o n . The Beer-Lambert e x t i n c t i o n c o e f f i c i e n t s suggest t h a t , p a r t i c u l a r l y i n t h e 8 - y e a r - o l d canopy, l e a f o r i e n t a t i o n was t h e dominant f a c t o r i n d e t e r m i n i n g l i g h t a t t e n u a t i o n . 46 Blackman (1962) h y p o t h e s i z e d t h a t t h e most e f f i c i e n t arrangement o f l e a v e s f o r d r y - m a t t e r p r o d u c t i o n would have s t e e p l y i n c l i n e d l e a v e s at t h e t o p o f t h e canopy, and p r o g r e s s i v e l y l e s s i n c l i n e d or h o r i z o n t a l l e a v e s at t h e base. The 8 - y e a r - o l d salmonberry canopy had t h e p a t t e r n o f e x t i n c t i o n c o e f f i c i e n t s t h a t Blackman would have p r e d i c t e d f o r a h i g h l y p r o d u c t i v e canopy arrangement. Canopy e x t i n c t i o n c o e f f i c i e n t s In g e n e r a l , t h e e x t i n c t i o n c o e f f i c i e n t o f t h e upper canopy s t r a t a d e c l i n e d as t h i c k e t l e a f a r e a i n c r e a s e d (Table 3 ) . The e x c e p t i o n was t h e 5 - y e a r - o l d t h i c k e t w hich had a g r e a t e r K F t h a n t h e 3 - y e a r - o l d canopy. I t i s p o s s i b l e t h a t t h e r e was g r e a t e r m o i s t u r e a v a i l a b i l i t y a t t h e s i t e on which t h e 5 - y e a r - o l d t h i c k e t was growing, and t h a t t h i s may have r e s u l t e d i n a d i f f e r e n t p a t t e r n o f s a l m o n b e r r y growth on t h a t s i t e . The a d d i t i o n o f stem a r e a t o t h e c a l c u l a t i o n o f e x t i n c t i o n c o e f f i c i e n t s reduced t h e v a l u e s f o r t h e 50-100 cm s t r a t u m o f t h e 8 - y e a r - o l d t h i c k e t i n h a l f , but had l i t t l e i n f l u e n c e on t h e e x t i n c t i o n c o e f f i c i e n t s i n o t h e r c a n o p i e s o r t h e upper h o r i z o n s o f t h e 8 - y e a r - o l d t h i c k e t . Newton and Blackman (1970) found t h a t t h e r e d u c t i o n i n e x t i n c t i o n c o e f f i c i e n t w i t h th e a d d i t i o n o f stem a r e a v a r i e d c o n s i d e r a b l y , depending on t h e p l a n t s p e c i e s . The c a l c u l a t i o n o f K A i l l u s t r a t e s how f a c t o r s not d i r e c t l y d i s c e r n i b l e from biomass c l i p p i n g can s t r o n g l y 47 i n f l u e n c e l i g h t a t t e n u a t i o n . In t h e w i n t e r , t h e p a t h l e n g t h of beam r a d i a t i o n t h r o u g h t h e canopy g r e a t l y extends t h e shadow c a s t by any o v e r t o p p i n g canopy. In sa l m o n b e r r y , dead l e a v e s o f t e n remain w i t h i n t h e canopy and c r e a t e a l i g h t - o b s t r u c t i n g a r e a t h a t i s v e r y d i f f i c u l t t o q u a n t i f y . No attempt was made t o q u a n t i f y dead l e a v e s w i t h i n t h e c a n o p i e s i n t h e s t u d y p l o t s a t t h e t i m e o f t h e w i n t e r l i g h t measurements. I t was n o t e d t h a t s h a d i n g from t h e dead l e a v e s was g r e a t e s t i n t h e autumn and e a r l y w i n t e r , and t h a t t h i s s o u r c e o f s h a d i n g can be s i g n i f i c a n t w i t h i n an e x t e n s i v e a r e a o f dense salmonberry t h i c k e t s . C a u t i o n s h o u l d a l s o be used i n i n t e r p r e t i n g t h e K A v a l u e s , because l i g h t measurements used f o r t h e i r c a l c u l a t i o n were t a k e n on days w i t h few c l o u d s . I f K A v a l u e s had been c a l c u l a t e d w i t h l i g h t measurements from days dominated by d i f f u s e r a t h e r t h a n d i r e c t beam r a d i a t i o n , t h e r e s u l t a n t e x t i n c t i o n c o e f f i c i e n t s would l i k e l y have been g r e a t l y reduced. F o l i a g e c h a r a c t e r i s t i c s A reduced e x t i n c t i o n c o e f f i c i e n t p r o v i d e s a g r e a t e r c a p a b i l i t y t o s u p p o r t l a r g e r l e a f a r e a s i n lo w e r canopy s t r a t a . S p e c i f i c l e a f a r e a s from t h e 3- and 8 - y e a r - o l d t h i c k e t s s u p p o r t t h i s i d e a . Where upper s t r a t a e x t i n c t i o n c o e f f i c i e n t s were r e l a t i v e l y low, t h e r e was no s i g n i f i c a n t i n c r e a s e i n s p e c i f i c l e a f a r e a i n t h e s t r a t a d i r e c t l y below (Table 3 ) . 48 Salmonberry l e a v e s showed g r e a t p l a s t i c i t y i n s p e c i f i c l e a f a r e a i n response t o t h e d i f f e r e n t l i g h t e n v i r onments w i t h i n t h e c a n o p i e s . Kawahara and T a d a k i (1978) and A r a k i (1980) r e p o r t e d i n c r e a s e d s p e c i f i c l e a f a r e a w i t h d e p t h i n a number o f b r o a d l e a f c a n o p i e s . The degree o f l e a f response s h o u l d , however, depend on t h e shade t o l e r a n c e o f t h e p l a n t s p e c i e s . The s e l f s h a d i n g t h a t produced t h e o b s e r v e d p a t t e r n o f s p e c i f i c l e a f a r e a s w i t h i n t h e salmonberry c a n o p i e s a f f e c t s t h e growth o f t h e s a l m o n b e r r y as w e l l as t h e environment f o r c o n i f e r s w i t h i n t h e canopy. Swartz e t a l . (1984) and Wright and W a i s t e r (1984) s t u d i e d l i g h t i n t e r c e p t i o n i n commercial Rubus s p e c i e s t h a t have s i m i l a r a r c h i t e c t u r e t o s a l m o n b e r r y . B o t h papers s u g g e s t e d t h a t s e l f s h a d i n g reduces p r o d u c t i v i t y i n r a p i d l y growing Rubus t h i c k e t s . Because o f t h e c o m p l e x i t y o f l e a f a n g l e s and f o l d i n g o f l e a v e s w i t h i n t h e s a l m o n b e r r y c a n o p i e s , no r e l i a b l e q u a n t i t a t i v e d a t a are a v a i l a b l e on l e a f a n g l e s . I t was o b s e r v e d t h a t b o t h t h e a n g l e o f t h e l e a f m i d - r i b and t h e a n g l e o f t h e l e a f b l a d e from t h e m i d - r i b changed t h r o u g h o u t t h e growing season. L e a f a n g l e s appeared t o be s t e e p e s t s h o r t l y a f t e r l e a f e x p a n s i o n was complete, but f l u c t u a t e d i n t h e l a t e summer and autumn, p o s s i b l y i n response t o t u r g o r l o s s as s o i l m o i s t u r e d e c l i n e d . The p o s s i b i l i t y o f h e l i o t r o p i s m i n f o l i a g e i s r a r e l y mentioned i n d i s c u s s i o n s i n t h e l i t e r a t u r e on v a r i a t i o n i n canopy l e a f i n c l i n a t i o n . 49 Monsi and S a e k i (1953) s u g g e s t e d t h a t t h e Beer-Lambert e x t i n c t i o n c o e f f i c i e n t based on l e a f a r e a i n d e x i s c l o s e l y c o r r e l a t e d w i t h t h e i n c l i n a t i o n o f l e a v e s i n t h e canopy. Data from t h i s s tudy s u p p o r t t h e i r p r o p o s a l t h a t t h e e x t i n c t i o n c o e f f i c i e n t o f a canopy can be app r o x i m a t e d by t h e c o s i n e o f t h e average l e a f a n g l e . T h i s r e l a t i o n s h i p may be v a l u a b l e f o r f i e l d comparisons o f upper canopy s t r a t a i n whi c h l e a v e s a re g e n e r a l l y u n i f o r m l y d i s t r i b u t e d and a r e o f a p p r o x i m a t e l y t h e same s p e c i f i c l e a f a r e a . Canopy dynamics The d i s t r i b u t i o n o f shade i n c a n o p i e s o f s i m i l a r h e i g h t can v a r y g r e a t l y and change w i t h t i m e . C o n s e q u e n t l y , d e s c r i p t i o n s o f t h e r e l a t i v e canopy p o s i t i o n o f c o n i f e r s e e d l i n g s w i t h i n d eciduous c a n o p i e s may v a r y i n t h e i r i m p l i c a t i o n s f o r t h e s e e d l i n g ' s l i g h t environment. Changes i n t h e c a n o p i e s o f competing s p e c i e s s u r r o u n d i n g c r o p c o n i f e r s may be an u n d e r l y i n g and p e r s i s t e n t problem w i t h c o n i f e r s e e d l i n g - s h r u b c o m p e t i t i o n i n d i c e s . Any c h a r a c t e r i z a t i o n o f t h e m i c r o c l i m a t e beneath deciduous c a n o p i e s s u f f e r s from t h e t r a n s i t o r y n a t u r e o f c o n d i t i o n s w i t h i n t h e canopy, such as pigment c o n t e n t (Sanger, 1971) and f o l i a g e c h a r a c t e r i s t i c s ( T a d a k i , 1966; Kawahara and T a d a k i , 1978). V a r i a t i o n i n h e i g h t growth i n c r e m e n t , maximum t h i c k e t h e i g h t , and l e a f a r e a i n d e x a r e p r o b a b l y c l o s e l y r e l a t e d t o th e m o i s t u r e regime o f t h e s p e c i f i c s i t e . Data from 50 Henstrom and Logan (1986) show t h a t s a l m o n b e r r y canopy h e i g h t growth i s c l e a r l y r e l a t e d t o ecosystem m o i s t u r e . The g r e a t e s t h e i g h t and l e a f a r e a i n d e x o f salmonberry o c c u r r e d on t h e m o i s t ( s u b h y g r i c t o h y g r i c ) s i t e s . A l e a f a r e a i n d e x of 13 i s p r o b a b l y about t h e maximum f o r s a l m o n b e r r y . One meter i s t h e t y p i c a l maximum sa l m o n b e r r y canopy h e i g h t on d r i e r ( s u b x e r i c ) s i t e s . Canopy h e i g h t appeared t o l e v e l o f f e v e n t u a l l y a t a l l s i t e s because a d d i t i o n a l stem growth c o n t i n u e d t h e l e n g t h o f a r c h i n g canes r a t h e r t h a n e l e v a t i n g t h e g r o w i n g t i p f u r t h e r above t h e ground. B. S e a s o n a l changes i n l i g h t q u a n t i t y and q u a l i t y I n t e r a c t i o n s o f s o l a r a n g l e , weather c o n d i t i o n s , a i r q u a l i t y , and canopy phenology and s t r u c t u r e combine t o produce a c o n s t a n t l y changing and c y c l i c l i g h t environment beneath d e c i d u o u s c a n o p i e s . The e x t e n t t o which p l a n t phenology c o n t r o l s l i g h t p e n e t r a t i o n was c l e a r i n b o t h t h e r e d a l d e r and salmonberry c a n o p i e s . Salmonberry r e g u l a r l y f o l i a t e s e a r l i e r t h a n r e d a l d e r on c o a s t a l s i t e s i n Washington and B r i t i s h Columbia. The p r e c o c i o u s development o f s a l m o n b e r r y may i n c r e a s e s u c c e s s f u l f l o w e r i n g and a l l o w a r a p i d s t a r t t o l e a f e x p a n s i o n when salmonberry o c c u r s , as i t does commonly, i n t h e u n d e r s t o r y o f deciduous t r e e s l i k e r e d a l d e r o r b i g l e a f maple. P l a n t age, t h e s p e c i f i c s i t e , and weather c o n d i t i o n s a l l may i n f l u e n c e t h e t i m i n g o f f o l i a g e development and can d e l a y o r advance t h e development o f c a n o p i e s by a c o u p l e 51 weeks a t t h e b e g i n n i n g o f each new gr o w i n g season. Annual v a r i a t i o n i n t h e t i m e o f l i t t e r f a l l i n r e d a l d e r was r e p o r t e d by Z a v i t k o v s k i and Newton (1971). L i g h t q u a n t i t y The l o w e s t l i g h t i n t e n s i t y under b o t h t h e salmonberry and r e d a l d e r c a n o p i e s was d u r i n g t h e p e r i o d o f g r e a t e s t i n c i d e n t r a d i a t i o n (summer s o l s t i c e ) . T h i s c o i n c i d e n c e o f minimum l i g h t p e n e t r a t i o n under de c i d u o u s c a n o p i e s at maximum i n c i d e n t r a d i a t i o n has been r e p o r t e d by o t h e r s ( H u t c h i s o n and M a t t , 1977; Z a v i t k o v s k i , 1982) . Z a v i t k o v s k i (1982) s u s p e c t s t h a t t h i s r e l a t i o n s h i p g e n e r a l l y a p p l i e s t o a l l d e c i d u o u s c a n o p i e s . I t i s r e a s o n a b l e t o h y p o t h e s i z e t h a t p l a n t phenology i s t i m e d t o a l l o w peak l e a f a r e a development, o r f o l i a g e c h a r a c t e r i s t i c s t h a t maximize l e a f i n t e r c e p t i o n o f l i g h t , a t a t i m e when t h e environment can supp o r t t h e g r e a t e s t amount o f f o l i a g e . The l o s s o f l e a v e s i n t h e autumn i n b o t h t h e salmonberry and r e d a l d e r c a n o p i e s was o f f s e t by t h e d e c l i n e i n s o l a r a n g l e , w i t h t h e r e s u l t t h a t t h e t o t a l amount o f l i g h t r e a c h i n g t h e ground beneath l i v e d e c i d u o u s c a n o p i e s was s i m i l a r i n t h e summer and e a r l y w i n t e r ( F i g s 3 and 5 ) . S l i g h t i n c r e a s e s i n l i g h t p e n e t r a t i o n i n August and September c o u l d have r e s u l t e d from e a r l y l e a f f a l l o r i n s e c t d e f o l i a t i o n . D u r i n g t h a t p e r i o d , l i t t e r f a l l i n c r e a s e d and many o f t h e l e a v e s c o n t a i n e d h o l e s , s u g g e s t i n g t h a t t h e y had 52 been f e d on by t h e a l d e r f l e a b e e t l e ( A l t i c a ambiens LeConte) or o t h e r i n s e c t s . By November, l e a f a b s c i s s i o n had a l l o w e d l i g h t l e v e l s under the l i v e r e d a l d e r canopy t o e q u a l t h o s e o f t h e dead canopy. W i n t e r d e f o l i a t i o n was u s u a l l y not complete i n r e d a l d e r a t t h e s t u d y l o c a t i o n ; o f t e n t h e uppermost l e a v e s o f t h e canopy remained green and a t t a c h e d t o t h e stem t i p s u n t i l t h e f o l l o w i n g s p r i n g . However, t h e s e few l e a v e s produced l i t t l e shade i n comparison t o t h e r e d a l d e r stems. S e a s o n a l c y c l e s i n l i g h t p e n e t r a t i o n were a l s o e v i d e n t i n l e a f l e s s c a n o p i e s t h r o u g h t h e e f f e c t o f t h e changing s o l a r a n g l e . As s o l a r e l e v a t i o n d e c l i n e s , t h e o p t i c a l p a t h l e n g t h t h r o u g h t h e s t a n d i n c r e a s e s and e x c l u d e s a g r e a t e r p r o p o r t i o n o f beam r a d i a t i o n . At w i n t e r s o l s t i c e , the l i g h t r e a c h i n g t h e f l o o r o f most deciduous s t a n d s i s dominated by d i f f u s e r a d i a t i o n (Anderson, 1964). The r e s u l t i n g s e a s o n a l c y c l e o f l i g h t under deciduous c a n o p i e s p r e s c r i b e s l i m i t s not o n l y on t o t a l r a d i a t i o n , but t h e e x t e n t o f l i g h t q u a l i t y m o d i f i c a t i o n s . D i f f u s e l i g h t i s l e s s l i k e l y t o have an a l t e r e d s p e c t r a l energy d i s t r i b u t i o n (Holmes and McCartney, 1976; Holmes and Smith, 1977). Averages shown i n F i g u r e s 3 and 5 a r e not a r e p r e s e n t a t i v e c h a r a c t e r i z a t i o n o f t h e a n n u a l l i g h t environment w i t h i n t h o s e c a n o p i e s because measurements were o n l y t a k e n on s e l e c t e d r a i n l e s s days. However, th e average incoming l i g h t d u r i n g t h e days i n w h i c h measurements were 53 t a k e n were s i m i l a r t o t h o s e measured at n e a r l y t h e same l a t i t u d e (45° 33') i n W i s c o n s i n by Z a v i t k o v s k i (1982). Both s t a n d d e n s i t y and canopy h e i g h t can have a s t r o n g e f f e c t on l i g h t p e n e t r a t i o n . Few d a t a are a v a i l a b l e on l i g h t l e v e l s under r e d a l d e r stands o f d i f f e r e n t d e n s i t i e s ( B i g l e y and Graham, i n p r e p a r a t i o n ) . Z a v i t k o v s k i e t a l . (1976), w o r k i n g w i t h h y b r i d p o p l a r , s u g g e s t e d t h a t d e n s i t y i s l e s s i m p o r t a n t i n d e t e r m i n i n g l i g h t t r a n s m i s s i o n i n hardwood stands t h a n i n c o n i f e r stands because o f t h e e x t e n s i v e growth o f l a t e r a l branches i n hardwoods. There i s c o n s i d e r a b l e i n t e r e s t i n t h e P a c i f i c Northwest i n t h e use of low d e n s i t y p l a n t i n g s o f r e d a l d e r f o r s o i l augmentation ( A t k i n s o n et a l . , 1979). S t u d i e s o f s e a s o n a l l i g h t t r e n d s w i t h i n low d e n s i t y r e d a l d e r stands would h e l p p r o v i d e d e n s i t y g u i d e l i n e s f o r mixed r e d a l d e r - c o n i f e r p l a n t a t i o n s . Stand h e i g h t d i r e c t l y i n f l u e n c e s t h e o p t i c a l p a t h l e n g t h year around, a l t h o u g h s t u d i e s by B a l d o c c h i e t a l . (1984) show t h a t t h e i m p o r t a n c e o f s o l a r a n g l e d i m i n i s h e s as t h e a n g l e d e c l i n e s because of i n c r e a s e s i n t h e p r o p o r t i o n of d i f f u s e r a d i a t i o n a t t i m e s of t h e y e a r when t h e a n g l e i s s m a l l . They r e p o r t e d t h a t f o r a l e a f l e s s o a k - h i c k o r y s t a n d , d i f f u s e r a d i a t i o n c o m p r i s e s between 35 and 62 p e r c e n t of the t o t a l r a d i a t i o n and i s s u f f i c i e n t t o c o u n t e r t h e e f f e c t o f s o l a r e l e v a t i o n on beam r a d i a t i o n . 54 L i g h t q u a l i t y The s p e c t r a l d i s t r i b u t i o n s o f l i g h t measured under b o t h t h e salmonberry and r e d a l d e r f o l i a t e d c a n o p i e s were s i m i l a r t o t h o s e measured under a v a r i e t y o f o t h e r d e c i d u o u s c a n o p i e s (Federer and Tanner, 1966; Freyman, 1968; F l o y d e t a l . , 1978; Bjorkman and Ludlow, 1972) and t o l i g h t t r a n s m i s s i o n t h r o u g h i n d i v i d u a l l e a v e s o f b r o a d - l e a v e d t r e e s p e c i e s (Loomis, 1965; Horn, 1971). These measurements were t a k e n i n l a t e summer and p r o b a b l y r e p r e s e n t the maximum e x t e n t o f s e l e c t i v e a b s o r p t i o n o f l i g h t w i t h i n t h e c a n o p i e s . Because the s p e c t r a l d i s t r i b u t i o n of l i g h t p e n e t r a t i n g t h e canopy i s s e n s i t i v e t o t h e pigment c o n t e n t w i t h i n t h e f o l i a g e , the time c o u r s e o f l i g h t a t t e n u a t i o n changes i n a l e a f i n g canopy i s p r o b a b l y l o n g e r f o r l i g h t q u a l i t y t h a n f o r q u a n t i t y . Sanger (1971) i l l u s t r a t e d how t h e pigment c o n t e n t o f l e a v e s may not r e a c h a maximum u n t i l a f t e r l e a f a r e a growth has c o n c l u d e d . I t i s p o s s i b l e t h a t t h e r e s u l t i n g e x t e n d e d p e r i o d o f h i g h e r z e t a v a l u e s i s i m p o r t a n t i n t h e morphogenic response o f p l a n t s d e v e l o p i n g f o l i a g e b e n eath d e c i d u o u s c a n o p i e s . T a s k e r and Smith (1977) found t h a t z e t a changes commonly t a k e p l a c e i n d e p e n d e n t l y o f changes i n i n t e n s i t y o f l i g h t i n s e v e r a l b r o a d - l e a v e d f o r e s t s . F l o y d e t a l . (1978) found t h a t t h e r a t i o o f s p e c t r a l energy o f l i g h t a t 450 and a t 625 nm t o l i g h t at 550 nm (green) i n c r e a s e d as f o l i a g e d e v e l o p e d i n t h e s p r i n g under a mixed oak and y e l l o w p o p l a r canopy. Autumn l e a f senescence o f t e n i n v o l v e s t h e d i f f e r e n t i a l 55 l o s s o f pigments. F e d e r e r and Tanner (1966) found t h a t o n l y t h e y e l l o w r e g i o n o f t h e spectrum was a l t e r e d under s e n e s c i n g sugar maple. Thus, as l e a f pigments change i n t h e s p r i n g and a g a i n i n t h e autumn, so does l i g h t q u a l i t y , perhaps w i t h o u t a measurable e f f e c t on t o t a l l i g h t q u a n t i t y w i t h i n t h e canopy. When r e d a l d e r and salmonberry l e a v e s s e n e s c e , most f a l l as green l i t t e r . However, b o t h v i n e maple and b i g l e a f maple o c c u r w i d e l y i n young c o n i f e r p l a n t a t i o n s i n t h e P a c i f i c Northwest and have a senescence p e r i o d where a c c e s s o r y pigments dominate t h e f o l i a g e and s e l e c t i v e l y f i l t e r l i g h t t o t h e u n d e r s t o r y f o r a c o n s i d e r a b l e p e r i o d . Holmes and McCartney (197 6) found a good e x p o n e n t i a l r e l a t i o n s h i p between z e t a and l e a f a r e a i n d e x . Z e t a became f a i r l y s t a b l e w i t h i n t h e lower canopy h o r i z o n s d u r i n g p e r i o d s when r a d i a t i o n i n t h e p h o t o s y n t h e t i c a l l y a c t i v e r e g i o n c o n t i n u e d t o d e c l i n e . Holmes and McCartney (1976) s u g g e s t e d t h a t i n canopy s t r a t a i n which senesence o f l e a v e s had begun, c h l o r o p h y l l c o n t e n t would be reduced and m o d i f i c a t i o n o f t h e s p e c t r a l q u a l i t y o f p e n e t r a t i n g l i g h t w ould d e c l i n e . In salmonberry, and l i k e l y i n most c a n o p i e s w i t h l a r g e l i g h t g r a d i e n t s , t h e r e e x i s t s h a d e - a c c l i m a t e d l e a v e s a t t h e base of t h e canopy w h i c h have h i g h e r s p e c i f i c l e a f a r e a s , lower pigment c o n t e n t s and t h u s a d i m i n i s h e d a b i l i t y t o modify t r a n s m i t t e d l i g h t . Low e x t i n c t i o n c o e f f i c i e n t s i n t h e upper canopy s t r a t a may a i d i n t h e maintenance o f h i g h z e t a v a l u e s and a f a v o r a b l e l i g h t 56 environment t o s u p p o r t s u n - a c c l i m a t e d l e a v e s l ower i n t h e canopy. S u n f l e e k s Sun f l e c k s l i k e l y p l a y an i m p o r t a n t r o l e i n t h e p h y s i o l o g y o f c o n i f e r s e e d l i n g s w i t h i n c a n o p i e s o f deciduous p l a n t s t h r o u g h t h e i r e f f e c t s on b o t h l i g h t q u a l i t y and q u a n t i t y . L i g h t l e v e l s i n deep shade under e i t h e r s a l m o nberry o r r e d a l d e r c a n o p i e s were commonly found t o be between 0.5 and 3% o f f u l l sun. Z a v i t k o v s k i (1982) r e p o r t e d t h a t under a h y b r i d p o p l a r s t a n d , t h e average i n t e n s i t y can be as low as 0.18% o f t h e open sun. The u n d e r s t o r y beneath de c i d u o u s shrubs i s not s u b j e c t e d t o s uch low l i g h t c o n t i n u o u s l y , however. I n t e g r a t e d v a l u e s o f l i g h t over th e d a y l i g h t hours under f o l i a t e d r e d a l d e r and salmonberry c a n o p i e s o f t e n approached 10% o f f u l l sun. The average s u n f l e c k l i g h t i n t e n s i t y under r e d a l d e r was 42% o f f u l l sun; o t h e r s have r e p o r t e d average s u n f l e c k l i g h t i n t e n s i t i e s o f 31% f o r p o p l a r p l a n t a t i o n s ( Z a v i t k o v s k i , 1982), 46% i n a mixed hardwood f o r e s t ( A l l a r d , 1947), and 20% i n a Queensland r a i n f o r e s t (Bjorkman and Ludlow, 1972). Z a v i t k o v s k i (1982) found t h a t s u n f l e c k s c o n t r i b u t e d 66 t o 89% o f t h e t o t a l p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n under p o p l a r s t a n d s . The comparison o f i n t e g r a t e d l i g h t measurements and measurements o f shade a v o i d i n g sun f l e c k s under b o t h r e d a l d e r and s a l m onberry a l s o s u p p o r t th e statement t h a t t h e m a j o r i t y o f l i g h t i n c i d e n t a t 50 cm i s 57 p r o v i d e d by sun f l e c k s . U t i l i z a t i o n o f s u n f l e c k s by o v e r t o p p e d c o n i f e r s e e d l i n g s may be h i g h as demonstrated by s t u d i e s o f i n t e r m i t t e n t l i g h t on p h o t o s y n t h e s i s (McCree and Loomis, 1969; S i e r z b i c k i , 1980). Sun f l e c k s a l s o p r o v i d e l i g h t o f a more b a l a n c e d s p e c t r a l q u a l i t y t o t h e l o w e r canopy. Holmes and Smith (1977) found t h a t s u n f l e c k s w i t h i n a wheat canopy had d e c r e a s e d z e t a v a l u e s , but s u n f l e c k s a r e g e n e r a l l y t hought t o have o n l y minute or no s h i f t s i n s p e c t r a l q u a l i t y (Horn, 1971; Bjorkman and Ludlow, 1972; Smith and G e l l e r , 1980; and G r o s s , 1982). The r a p i d movement o f s u n f l e c k s (due t o d i s t u r b a n c e o f t h e canopy by wind) may average any s p e c t r a l v a r i a t i o n i n s u n f l e c k s r e s u l t i n g from d i f f r a c t i o n t h r o u g h t h e canopy. C. H e r b i c i d e - i n d u c e d changes i n l i g h t q u a n t i t y and q u a l i t y I n i t i a l m o d i f i c a t i o n s i n t h e canopy o f r e d a l d e r due t o h e r b i c i d e t r e a t m e n t s were s i m i l a r t o t h o s e t h a t o c c u r d u r i n g autumn senescence. F o l l o w i n g d e f o l i a t i o n , however, t h e r e was a second phase i n w h i c h canopy d i s i n t e g r a t i o n l e d t o t h e e l i m i n a t i o n o f a l l canopy s h a d i n g . The d e f o l i a t i o n o f r e d a l d e r s t a r t e d p r e d i c t a b l y w i t h i n t h e f i r s t month a f t e r t h e h e r b i c i d e a p p l i c a t i o n , a l t h o u g h t h e d e f o l i a t i o n r a t e v a r i e d . The l i g h t regime f o l l o w i n g t r e a t m e n t depended on t h e t i m i n g of t h e t r e a t m e n t . Treatments e a r l y i n t h e g r o w i n g season e x p e r i e n c e d h i g h e r l i g h t a t t h e base o f t h e canopy because of t h e h i g h e r s o l a r a n g l e a t t h e t i m e o f d e f o l i a t i o n . 58 The second phase o f response (the downing o f woody m a t e r i a l ) may v a r y c o n s i d e r a b l y i n d u r a t i o n . Method o f k i l l i n g , age and form o f t h e p l a n t , r o o t i n g s u b s t r a t e , t y p e o f wood decay agents a c t i n g on t h e wood, and exposure t o t h e weather a l l may i n f l u e n c e t h e r a t e a t which branches and b o l e s a r e removed from t h e canopy. Stem g i r d l i n g may prove t o be a p l a u s i b l e means o f canopy removal w i t h m i c r o c l i m a t e m o d i f i c a t i o n s s i m i l a r t o t h o s e which h e r b i c i d e s i n d u c e . However, my o b s e r v a t i o n s suggest t h a t t h e t i m e c o u r s e o f d e f o l i a t i o n and canopy break-up w i l l l i k e l y be l e n g t h e n e d by stem g i r d l i n g , because o f slow d e p l e t i o n o f s t e m - s t o r e d m o i s t u r e and c a r b o h y d r a t e s , and t h e p o s s i b i l i t y o f i n c o m p l e t e s e v e r i n g o f t h e c o n d u c t i n g t i s s u e . H e r b i c i d e - k i l l i n g o f salmonberry t h i c k e t s a l s o has a p e r i o d a f t e r d e f o l i a t i o n where t h e stems decay and f a l l from t h e canopy. O b s e r v a t i o n s o f h e r b i c i d e - t r e a t e d s a l m o n b e r r y t h i c k e t s suggest t h a t stems may remain i n p l a c e f o r s e v e r a l y e a r s f o l l o w i n g d e f o l i a t i o n . N o n - f o l i a r components o f t h e canopy have not been found t o modify t h e s p e c t r a l d i s t r i b u t i o n o f l i g h t p e n e t r a t i n g c a n o p i e s . These d e f o l i a t e d c a n o p i e s s h o u l d have l i t t l e i n f l u e n c e on t h e l i g h t environment o t h e r t h a n p r o v i d i n g l i m i t e d n e u t r a l d e n s i t y s h a d i n g . 59 CONCLUSIONS 1. L i g h t b e n e a t h r e d a l d e r and s a l m o n b e r r y c a n o p i e s v a r i e s t h r o u g h o u t t h e y e a r i n b o t h i n t e n s i t y and s p e c t r a l c o m p o s i t i o n , and t h i s v a r i a t i o n i s s t r o n g l y c o n t r o l l e d by p l a n t p h e n o l o g y . 2. M o d i f i c a t i o n s i n t h e l i g h t e n v i r o n m e n t w i t h i n s a l m o n b e r r y c a n o p i e s a r e a c c e n t u a t e d as t h e canopy grows f r o m y e a r t o y e a r . 3. I n s a l m o n b e r r y , t h e B e e r - L a m b e r t law d e s c r i b e s l i g h t a t t e n u a t i o n w e l l w h i l e t h e c a n o p y i s f o l i a t e d and d e f o l i a t e d , u s i n g l e a f a r e a i n d e x a n d stem a r e a i n d e x , r e s p e c t i v e l y . 4 . The B e e r - L a m b e r t law, a p p l i e d t o t h e canopy as a whole, p o o r l y d e s c r i b e s t h e s u c c e s s i o n o f e n v i r o n m e n t s a c o n i f e r s e e d l i n g w o u l d e n c o u n t e r w h i l e g r o w i n g up t h r o u g h a s a l m o n b e r r y canopy. 5. L e a f c h a r a c t e r i s t i c s o t h e r t h a n s u r f a c e a r e a , s u c h as l e a f t h i c k n e s s and t h e a n g l e o f l e a f o r i e n t a t i o n , a r e b e l i e v e d t o be i m p o r t a n t i n d e s c r i b i n g l i g h t a t t e n u a t i o n i n s a l m o n b e r r y t h i c k e t s . 6. Changes i n t h e l i g h t e n v i r o n m e n t u n d e r r e d a l d e r c a u s e d by h e r b i c i d e t r e a t m e n t s o c c u r r a p i d l y i n t h e f i r s t few months b u t may have a t i m e c o u r s e up t o s e v e r a l y e a r s l o n g . 7. Sun f l e c k s make an i m p o r t a n t c o n t r i b u t i o n t o t h e t o t a l l i g h t ene rgy r e c e i v e d by s e e d l i n g s b e n e a t h a canopy , and t h e y may h e l p t o b a l a n c e l i g h t q u a l i t y w i t h i n t h e d e c i d u o u s c a n o p i e s s t u d i e d . 8 . H e r b i c i d e s p r o v i d e a v a l u a b l e , b u t s e l d o m l y u s e d t o o l f o r t h e s t u d y o f canopy a r c h i t e c t u r e by p r o v i d i n g c h a n g i n g l e v e l s o f d e f o l i a t i o n . 61 CHAPTER 3 PHYSIOLOGY AND GROWTH OF SEEDLINGS OF THREE CONIFER SPECIES UNDER DIFFERENT DENSITIES OF DECIDUOUS COMPETITORS INTRODUCTION The e s t a b l i s h m e n t o f c o n i f e r s e e d l i n g s on p r o d u c t i v e s i t e s i n t h e P a c i f i c Northwest o f t e n i n c l u d e s a p e r i o d o f s h a d i n g by d e c i d u o u s shrubs or t r e e s . C o m p e t i t i o n from t h o s e d e c i d u o u s s p e c i e s i s a major cause o f reduced e a r l y growth and i n c r e a s e d e a r l y m o r t a l i t y o f c o n i f e r s e e d l i n g s . However, complete removal o f t h e o v e r t o p p i n g c o m p e t i t o r s may not be p o s s i b l e , p r a c t i c a l , or d e s i r a b l e (e.g. i n r i p a r i a n z o n e s ) . Some de c i d u o u s canopy encroachment i s u s u a l l y i n e v i t a b l e d e s p i t e v a r i o u s s t r a t e g i e s t o a v o i d such c o m p e t i t i o n (e.g. s i t e p r e p a r a t i o n and prompt p l a n t i n g o f l a r g e p l a n t i n g s t o c k ) . The concept o f shade t o l e r a n c e p r o v i d e s t h e b a s i s f o r an u n d e r s t a n d i n g o f c o n i f e r growth i n d i f f e r e n t l i g h t e n v i r o n m e n t s . By d e f i n i t i o n , s h a d e - t o l e r a n t c o n i f e r s s h o u l d have g r e a t e r s u r v i v a l and growth under t h e c a n o p i e s o f o t h e r p l a n t s t h a n l e s s s h a d e - t o l e r a n t p l a n t s have. Much o f t h e e a r l y work i n t h i s f i e l d was conducted under u n v a r y i n g l i g h t c o n d i t i o n s t h a t do not r e f l e c t n a t u r a l c o n d i t i o n s (e.g. Krueger, 1967; Logan, 1969; Magnussen and P e s c h l , 1981). C o n t i n u a l shade and n e u t r a l d e n s i t y f i l t e r i n g a r e more 62 i n d i c a t i v e o f i n t a c t c o n i f e r o u s c a n o p i e s t h a n o f t h e l i g h t e n vironments c r e a t e d by d e c i d u o u s shrubs or t r e e s . Dunlap and Helms (1983) r e v i e w e d the e f f e c t s o f shade on t h e growth o f p l a n t e d s t o c k , and c o n c l u d e d t h a t t h e growth r e l a t i o n s h i p s between t r e e s o f d i f f e r e n t r e l a t i v e t o l e r a n c e i n f i e l d s i t u a t i o n s a r e p o o r l y u n d e r s t o o d . Ruth (1957) found t h e t e n y e a r s u r v i v a l o f b o t h t h e r e l a t i v e l y shade i n t o l e r a n t D o u g l a s - f i r and s h a d e - t o l e r a n t w e s t e r n hemlock t o be o n l y 17% under deep c o n i f e r o u s shade. Newton and White (1983) found t h a t w e s t e r n hemlock s e e d l i n g s p l a n t e d under salmonberry c a n o p i e s performed p o o r l y i n b o t h s u r v i v a l and growth. However, shade t o l e r a n c e remains t h e s i n g l e b e s t g u i d e t o p r e d i c t i n g t h e l i k e l i h o o d o f s u p p r e s s i o n i n shade. P e r r y e t a l . (1985) s u g g e s t e d t h a t g r a nd f i r might be a good c a n d i d a t e f o r p l a n t i n g i n p r e e x i s t i n g c a n o p i e s because i t i s shade t o l e r a n t and appeared not t o be s e r i o u s l y damaged by a n i m a l s . Shade t o l e r a n t s p e c i e s have g r e a t e r p h o t o s y n t h e t i c e f f i c i e n t l y a t low l i g h t i n t e n s i t y and g e n e r a l l y have h i g h e r growth r a t e s i n shade as compared t o shade i n t o l e r a n t s p e c i e s (Armitage and V i n e s , 1982). However, t h e l i g h t under deciduous c a n o p i e s i s s u b j e c t t o wide s e a s o n a l changes, and p h y s i o l o g i c a l d i f f e r e n c e s between p l a n t s shaded by deciduous c a n o p i e s and t h o s e not shaded may change s e a s o n a l l y . H a l a s (1971) found t h a t t h e w i n t e r p h o t o s y n t h e t i c a c t i v i t y o f shaded p l a n t s d e c l i n e d l e s s t h a n p l a n t s grown under h i g h l i g h t . He c o n c l u d e d t h a t t h e shaded 63 p l a n t s had a more f a v o r a b l e g rowing c o n d i t i o n w i t h r e d u c e d i n c i d e n c e o f f r o s t , s m a l l e r a i r t e m p e r a t u r e f l u c t u a t i o n s and r e d u c e d a i r vapor p r e s s u r e d e f i c i t s . F r y and P h i l l i p s (1977) found c o n s i d e r a b l e p h o t o s y n t h e t i c a c t i v i t y i n g r and f i r and w e s t e r n hemlock t h r o u g h o u t t h e y e a r i n s o u t h e r n E n g l a n d . Helms (1963) r e p o r t e d t h a t D o u g l a s - f i r i n Washington s t a t e was c a p a b l e o f h i g h p h o t o s y n t h e t i c r a t e s i n t h e w i n t e r when a p p r o p r i a t e c l i m a t i c c o n d i t i o n s o c c u r r e d . The o b j e c t i v e o f t h e s t u d i e s p r e s e n t e d i n t h i s c h a p t e r i s t o compare the growth and s e a s o n a l p a t t e r n s o f c e r t a i n p h y s i o l o g i c a l parameters between c o n i f e r s e e d l i n g s o f d i f f e r e n t shade t o l e r a n c e under de c i d u o u s c a n o p i e s o f d i f f e r e n t d e n s i t y ( r e l a t i v e s h a d i n g ) . S i n c e i t i s known t h a t p h o t o s y n t h e s i s i s c a r r i e d out year around i n t h e c o a s t a l P a c i f i c Northwest, i t i s l i k e l y t h a t i n c r e a s e s i n l i g h t i n t e n s i t y a f t e r autumn l e a f drop c o u l d be u t i l i z e d by c o n i f e r s o v e r t o p p e d by d e c i d u o u s c a n o p i e s . I t i s h y p o t h e s i z e d t h a t shade t o l e r a n t t r e e s e e d l i n g s w i l l have g r e a t e r p h o t o s y n t h e t i c r a t e s t h a n shade i n t o l e r a n t t r e e s e e d l i n g s d u r i n g t h e p e r i o d s t h a t d e c i d u o u s c o m p e t i t o r s are f o l i a t e d , but t h a t the d i f f e r e n c e between s e e d l i n g s o f d i f f e r e n t t o l e r a n c e w i l l d i m i n i s h d u r i n g t h e p e r i o d s t h a t c o m p e t i t o r s are l e a f l e s s . I f t h e concept of shade t o l e r a n c e p r o v i d e s a good model f o r s e e d l i n g growth under d e c i d u o u s c a n o p i e s i n t h e P a c i f i c N o r t h w e s t , t h e n s e e d l i n g growth under i n c r e a s i n g canopy d e n s i t y s h o u l d d e c l i n e t o t h e g r e a t e s t e x t e n t i n s e e d l i n g s o f t h e l o w e s t shade t o l e r a n c e . I t i s h y p o t h e s i z e d t h a t growth r a t e s o f s e e d l i n g s under d e c i d u o u s c a n o p i e s o f s a l m o n b e r r y and r e d a l d e r w i l l d e c r e a s e i n o r d e r o f d e c r e a s i n g shade t o l e r a n c e as canopy d e n s i t y i n c r e a s e s . 65 METHODS F i e l d t r e a t m e n t s P l o t e s t a b l i s h m e n t P l o t s were e s t a b l i s h e d i n t h e s p r i n g o f 1982 a t l o c a t i o n s B and C, t h e s i t e s dominated by s a l monberry and by 7 - y e a r - o l d r e d a l d e r , r e s p e c t i v e l y . At b o t h s i t e s , p l o t s w i t h h i g h , medium, and low canopy d e n s i t y were e s t a b l i s h e d by manual c l i p p i n g / c u t t i n g . The h i g h d e n s i t y p l o t s had u n d i s t u r b e d c a n o p i e s and growing-season average l i g h t l e v e l s o f 2-10% o f f u l l sun. A canopy o f medium d e n s i t y was a t t a i n e d by removal of whole p l a n t s u n t i l an average o f 25 t o 40 p e r c e n t f u l l sun r e ached s e e d l i n g l e v e l (50 cm). The low d e n s i t y p l o t s had a l l p l a n t biomass above 10 t o 20 cm from th e s o i l s u r f a c e removed and r e c e i v e d about 90% f u l l sun a t s e e d l i n g l e v e l . These canopy d e n s i t i e s were m a i n t a i n e d t h r o u g h o u t t h e two y e a r measurement p e r i o d . F i f t e e n s e e d l i n g s o f each s p e c i e s (western hemlock, grand f i r and D o u g l a s - f i r ) were p l a n t e d w i t h i n each of t h r e e r e p l i c a t e 40 m' r e c t a n g u l a r p l o t s o f each d e n s i t y . P l a n t i n g was c o n ducted i n e a r l y March of 1982 w i t h t h e s e e d l i n g s t o c k t y p e i n d i c a t e d i n T a b l e 5. Screen e x c l o s u r e s were p l a c e d around t e n s e e d l i n g s o f each s p e c i e s w i t h i n each t r e a t m e n t t o r e s t r i c t a n i m a l damage and a s s u r e a s u f f i c i e n t number o f s e e d l i n g s w i t h o u t damaged f o l i a g e f o r t h e p h y s i o l o g i c a l measurements. 66 T a b l e 5. P l a n t i n g s t o c k e s t a b l i s h e d w i t h i n s a l m o n b e r r y and r e d a l d e r s t a n d s . Seed s o u r c e S p e c i e s S e e d l o t " Douglas 2891 - f i r Grand f i r 2899 Western hemlock 3906 e l e v a t i o n (m) Stock t y p e N u r s e r y 175 111 340 2 + 0 BR 2 + 1 BR 1+1 PBR Green Timbers C h i l l i w a c k S u r r e y B r i t i s h Columbia M i n i s t r y o f F o r e s t s , F o r e s t S e r v i c e i d e n t i f i c a t i o n . 67 F i e l d Measurements Schedule o f measurements A l l measurements o f t r e e p h y s i o l o g y were r e p e a t e d a t f o u r d i f f e r e n t t i m e s o f t h e y e a r . Two measurements were c o n d u c t e d when t h e o v e r t o p p i n g c a n o p i e s were f o l i a t e d (June and August, 1984), and two when t h e c a n o p i e s were d e f o l i a t e d (November, 1983 and F e b r u a r y , 1984) . P h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n and vapor p r e s s u r e  d e f i c i t s A l l measurements o f l i g h t r e p o r t e d i n t h i s Chapter and i n C h a p t e r 4 a r e i n micromoles o f p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n (PPFD). L i g h t l e v e l s t a k e n d u r i n g t h e p h o t o s y n t h e t i c d e t e r m i n a t i o n s were measured by p l a c i n g a quantum s e n s o r (LI-COR LI-190S) a l o n g s i d e t h e sample chamber o f t h e i n s t r u m e n t used t o measure p h o t o s y n t h e t i c r a t e s ( d e s c r i b e d below) and r e c o r d i n g a s i n g l e i n s t a n t a n e o u s v a l u e . To c h a r a c t e r i z e t h e s h a d i n g o f s p e c i f i c t r e a t m e n t s , i n c o m i n g r a d i a t i o n was i n t e g r a t e d u s i n g t h e c h e m i c a l (anthracene) p r o c e d u r e d e s c r i b e d i n Ch a p t e r 2. Vapor p r e s s u r e d e f i c i t s were c a l c u l a t e d from measurements t a k e n w i t h a thermocouple psychrometer a t t h e t i m e o f t h e p h o t o s y n t h e t i c measurements. P h o t o s y n t h e s i s P h o t o s y n t h e t i c r a t e s were measured u s i n g t h e 1^C02 method d e s c r i b e d by Shimshi (1969) and N e i l s o n (1977). 68 M o d i f i c a t i o n s t o t h e . o r i g i n a l gas exposure a p p a r a t u s d e s c r i b e d by P r i c e e t a l . (1986) were used. A l l p h o t o s y n t h e t i c measurements f o r a s p e c i f i c t r e a t m e n t were r e p l i c a t e d f i v e t i m e s u s i n g n e e d l e p a i r s t h a t were e x c i s e d from f i v e measurement t r e e s (one d e t e r m i n a t i o n p e r t r e e ) i m m e d i a t e l y b e f o r e measurement. To p r e p a r e f o r a measurement, s e v e r a l n e e d l e s were c a r e f u l l y removed from t h e m i d d l e s e c t i o n (to reduce v a r i a t i o n i n n e e d l e s i z e and m a t u r i t y ) o f a t w i g , and d i v i d e d i n t o s e t s f o r conductance measurements, p h o t o s y n t h e t i c measurements, and t h e measurement o f l e a f w i d t h . To d e t e r m i n e p h o t o s y n t h e t i c r a t e s , p a i r s o f n e e d l e s were s e a l e d i n a 300 mmJ chamber, and exposed t o a i r c o n t a i n i n g 323 ppm 1 2 C 0 2 - 1 4 C 0 2 (6.19 u C i - 1 1 4 C 0 2 ) , 20.8% 0 2, and 78% N 2 (and .95% A) f o r 20 s e c . Gas f l o w r a t e s o f 1.40 m l ' s - ^ t h r o u g h t h e chamber were c a l i b r a t e d a t t h e b e g i n n i n g of each measurement s e r i e s a t a s i t e . I mmediately a f t e r t h e exposure p e r i o d , t h e n e e d l e s were removed from t h e chamber and a 7 mm segment from t h e exposed s e c t i o n o f each n e e d l e was c u t w i t h a paper punch and s e a l e d i n a 20 mL g l a s s s c i n t i l l a t i o n v i a l c o n t a i n i n g 2 mL t i s s u e s o l u b i l i z e r (NCS, Amersham C o r p . ) . W i t h i n two weeks o f c o l l e c t i o n , samples were p r e p a r e d f o r l i q u i d s c i n t i l l a t i o n c o u n t i n g . In o r d e r t o s o l u b i l i z e t h e l e a f t i s s u e and reduce c o l o r q u e n c h i n g , t i s s u e d i g e s t i o n (12-48 h a t 50 °C), f o l l o w e d by b l e a c h i n g w i t h 0.5-1 mL 6% hydrogen p e r o x i d e f o r a 24 h p e r i o d a t 50 °C were r e q u i r e d . 69 Some samples r e q u i r e d an a d d i t i o n a l 0.5 mL o f hydrogen p e r o x i d e and warming (6-12 h a t 50 °C) t o c o n t r o l e x c e s s i v e q u enching. Once b l e a c h i n g was complete, an 18 mL a l i q u o t o f s c i n t i l l a t i o n c o c k t a i l ( t o l u e n e , 100 p a r t s ; e t h y l e n e g l y c o l monoethyl e t h e r , 40 p a r t s ; POPOP-PPO ( S p e c t a f l u o r , Amersham C o r p . ) , 6 p a r t s ) was added t o each v i a l . R a d i o a s s y was t h e n c o n ducted u s i n g a l i q u i d s c i n t i l l a t i o n s p e c t r o m e t e r . C o u n t i n g e f f i c i e n c i e s averaged 82%. C a l c u l a t i o n o f CO2 uptake by f o l i a g e f o l l o w e d T i e s z e n e t a l . (1974) . L e a f d i f f u s i v e conductance A d i f f u s i v e r e s i s t a n c e porometer (LI-COR 700) on medium c y c l e was used t o measure l e a f d i f f u s i v e c o n d u c t a n c e . The conductance v a l u e s p r e s e n t e d are t h e average o f t h r e e d e t e r m i n a t i o n s u s i n g d e t a c h e d n e e d l e s . I n o r d e r t o a s s u r e a c o n t i n u o u s l e a f s u r f a c e a r e a over t h e a p e r t u r e t o t h e measurement chamber, t h r e e t o f i v e c o n i f e r n e e d l e s were p l a c e d s i d e - b y - s i d e on c e l l o p h a n e t a p e , t h e n t h e n e e d l e s backed by t h e t a p e were p l a c e d so t h a t t h e n e e d l e s l a i d p e r p e n d i c u l a r t o t h e measurement opening. These measurements were c o n c u r r e n t w i t h t h e p h o t o s y n t h e t i c d e t e r m i n a t i o n s . L e a f water p o t e n t i a l s L e a f water p o t e n t i a l s were t a k e n b e f o r e 0900 t o 1000 h r on f o l i a g e from s e e d l i n g s u s i n g t h e p s y c h c r o m e t r i c method (Wescor Dew p o i n t m i c r o v o l t m e t e r model HR-33 and sample 70 chamber C-51). Because l e a f water p o t e n t i a l measurements were t i m e consuming, a l l measurements were t a k e n t h e day b e f o r e p h o t o s y n t h e t i c and l e a f conductance measurements. A s i n g l e l e a f water p o t e n t i a l measurement was made from t h r e e o f t h e f i v e measurement t r e e s used i n f o r t h e p h o t o s y n t h e t i c measurements. C h l o r o p h y l l c o n t e n t i n f o l i a g e C h l o r o p h y l l c o n t e n t o f c u r r e n t y e a r f o l i a g e o f each t r e e s p e c i e s i n each t r e a t m e n t was d e t e r m i n e d . A t w i g from each o f t h r e e sample s e e d l i n g s i n each p l o t was t a k e n from t h e t o p t h i r d o f t h e crown and s t o r e d a t 5 °C u n t i l e x t r a c t i o n ( s t o r a g e u s u a l l y 3-5 d a y s ) . F o l i a g e samples from t h r e e sample s e e d l i n g s p e r p l o t were e x t r a c t e d , and t h e d a t a were averaged f o r each p l o t . C h l o r o p h y l l was e x t r a c t e d i n acetone and p e t r o l e u m e t h e r u s i n g t h e method d e s c r i b e d by Smith and B e n i t e z (1955). Pigment a b s o r b e n c i e s were d e t e r m i n e d u s i n g a s p e c t r o p h o t o m e t e r . C h l o r o p h y l l (a+b) c o n t e n t was e x p r e s s e d on a f r e s h weight b a s i s . Growth a n a l y s i s Growth a n a l y s i s was c o n d u c t e d on s e e d l i n g s w i t h i n p l o t s w h i c h were d e s t r u c t i v e l y sampled i n October o f 1984. F o l i a g e from s i x s e e d l i n g s from each p l o t was p a r t i t i o n e d by a n n u a l age c l a s s . Stems and washed r o o t s were d r i e d a t 65°C f o r 120 hours and f o l i a g e f o r 48 hours b e f o r e d e t e r m i n i n g d r y w e i g h t . The r e l a t i v e component growth r a t e s were 71 c a l c u l a t e d f o l l o w i n g L e d i g (1974). L e a f a r e a d e t e r m i n a t i o n s were made on subsamples o f each f o l i a g e age c l a s s u s i n g a LI-3000 (Lambda Instruments) l e a f a r e a meter b e f o r e d r y i n g . Data a n a l y s i s Data were s u b j e c t e d t o a one-way a n a l y s i s o f v a r i a n c e . S i g n i f i c a n c e between t r e a t m e n t s / s p e c i e s was d e t e r m i n e d a t p< 0.05 w i t h t h e Tukey m u l t i p l e comparisons t e s t ( S t o l i n e , 1981). 72 RESULTS S e e d l i n g p h y s i o l o g y P h o t o s y n t h e s i s D i f f e r e n c e s i n t h e p h o t o s y n t h e t i c r a t e between s p e c i e s w i t h i n a g i v e n canopy d e n s i t y , and between d i f f e r e n t canopy d e n s i t y t r e a t m e n t s d i m i n i s h e d d u r i n g t h e p e r i o d t h a t t h e deci d u o u s c a n o p i e s were l e a f l e s s , i n comparison t o t h e midsummer p e r i o d . Grand f i r g rowing w i t h a low d e n s i t y o v e r t o p p i n g canopy c o n s i s t e n t l y had t h e g r e a t e s t p h o t o s y n t h e t i c r a t e (Tables 6, 7, 8 and 9 ) , e x c e p t f o r one s e t o f measurements i n t h e w i n t e r (Table 9 ) . The l o w e s t p h o t o s y n t h e t i c r a t e s i n t h e s p r i n g and summer were t h o s e o f D o u g l a s - f i r under t h e h i g h d e n s i t y c a n o p i e s (Tables 6 and 8 ) . A t t h e autumn and w i n t e r measurements t h e D o u g l a s - f i r r a t e s were c l o s e r t o t h o s e o f t h e o t h e r s p e c i e s , and a t t h e sal m o n b e r r y s i t e , t h e D o u g l a s - f i r autumn and w i n t e r r a t e s e q u a l e d t h o s e o f t h e grand f i r (Tables 7 and 9 ) . The performance o f a s p e c i f i c s p e c i e s between t h e d i f f e r e n t t r e a t m e n t s v a r i e d w i t h s p e c i e s and season. D u r i n g t h e s p r i n g measurement a t t h e s a l m o n b e r r y s i t e , a l l s p e c i e s were s i g n i f i c a n t l y d i f f e r e n t between t r e a t m e n t s w i t h t h e low canopy d e n s i t y t r e a t m e n t h a v i n g t h e g r e a t e s t , and t h e h i g h canopy d e n s i t y t r e a t m e n t t h e l o w e s t p h o t o s y n t h e t i c r a t e s . At t h e summer measurement t h e medium and h i g h canopy d e n s i t y t r e a t m e n t s d i d not d i f f e r s i g n i f i c a n t l y (Table 6 ) . The o n l y s i g n i f i c a n t d i f f e r e n c e i n t h e autumn and w i n t e r d a t a was t h e 73 T a b l e 6. S p r i n g and summer means of p h o t o s y n t h e t i c r a t e , Ps (mgCC>2'dm 'hr I) , l e a f conductance, g-^  (em's" ), vapor p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm 2 ' s •"•) , l e a f w a ter p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h l (mg'g a ) , o f D o u g l a s - f i r (DF), grand f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s w i t h i n salmonberry s t a n d s o f d i f f e r e n t d e n s i t y . s p r i n g (June 14, 1984; C l e a r 22 t o 9.5°C) Treatment/ Ps g x D PPFD wp C h l s p e c i e s Low 1.2 1100 DF 5.6c 1 .16bc -0.2c 2.65b GF 8.6a .18a -0.2c 2.71b WH 6.7b .18ab -0.3bc 1.66c Medium 0.4 400 DF 3.4e .12de -0.5ab 3.27a GF 5.8c .16ab -0.5abc 3.44a WH 4.7d .14cd -0.3c 2.51b Hig h 0.4 2 65 DF i . 7 f .07f -0.6a 3.38a GF 3.6d .10e -0.4abc 3.34a WH 3.7d .07f -0.5abc 2.62b summer (August 23, 1984; Broken c l o u d 19.5 t o 11°C) Low 1.1 1500 DF 5.6b .0 9ab -l.Oabc 2.56b GF 7.9a .10a -0.8abc 2.43bc WH 5.1b .06abc -0.8abc 2.03d Medium 0.6 380 DF 1.5de .05abc -1.2a 3.15a GF 3.4c .08ab -0.9abc 3.24a WH 3.2c .10a -0.6c 2.07cd Hig h 0.8 120 DF 0.6e .02c -1.1a 3.03a GF 2.5cd .04bc -l.Oab 3.13a WH 2.8c .05abc -0.7bc 2.07cd Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a re 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). 74 T a b l e 7. Autumn and w i n t e r means o f p h o t o s y n t h e t i c r a t e , Ps (mgC02*dm 2 ' h r - 1 ) , l e a f conductance, g^ _ (era's" ) , v a p o r p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm - 2's ), l e a f w a ter p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h l (m g ' g - 1 ) , o f D o u g l a s - f i r (DF), grand f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s w i t h i n salmonberry s t a n d s o f d i f f e r e n t d e n s i t y . Treatment/ s p e c i e s Low DF GF WH Medium autumn (November 28, 1983; Cloudy 7.5 t o 0.5°C) Ps 5.0a 1 4.3a 5. Oa 91 09a 08ab 07ab D 0.4 PPFD 962 wp C h l -0.2cd 2.50b -0.2cd 2.54b -0.4abc 2.07c 0.3 884 DF GF WH H i g h DF GF WH Low DF GF WH Medium DF GF WH Hi g h DF GF WH 5.0a 3.7b 4.2ab 5. 3a 4.3ab 4. l a b 09a 05bc 03d . 08ab . 06bc . 04cd 0.3' 787 -0.2d 3.04a -0.3bcd 3.13a -0.5a 2.10c -0.3bcd 3.12a -0.4ab 3.14a -0.3bcd 1.94c -winte r ( February 17, 1984; C l e a r 9 t o -7°C) 0.5 831 3. 6ab 4 .2a 3.1bcd 3.4abc 3.8ab 2.6d 3.5abc 3.2bcd 2.8cd 03ab 04a 03ab . 03ab . 03ab ,04ab 03ab 02b 02b 0.6 716 0.5 720 -0.8ab 2.30bc -0.6d 2.48b -0.9a 2.03c -0.7bcd 2.56b -0.6cd 3.17a -0.8ab 2.06c -0.6d 2.95a -0.5d 3.02a -0.8abc 2.23bc Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). T a b l e 8. S p r i n g and summer means o f p h o t o s y n t h e t i c r a t e , Ps (mgC0 2'dm - 2'hr - 1) , l e a f conductance, g-^  ( e m ' s ) , vapor p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm s ), l e a f w a t e r p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h l (mg'g ), o f D o u g l a s - f i r (DF), g r a n d f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t y . s p r i n g (June 16, 1984 C l e a r 17 t o 8°C) Treatment/ s p e c i e s Ps 9 l D PPFD wp C h l Low 0.9 1316 DF GF WH S ^ b c 1 6. 8a 6. 3ab . 12ab • 15a .15a -0 .2c -0.3bc -0.4ab 2.7 9cd 2.62cd 2.04e Medium 0.3 672 DF GF WH 4.4d 5.8abc 5.2dc .0 9bc .14a .14a -0.2c -0.3bc -0 .5a 3.19a 2.93bc 2.62d H i g h 0.3 182 DF GF WH 1.3f 2.8e 2. 5e .03d .07c . 05cd -0.3bc -0 .2c -0.4ab 3.12ab 3.23a 2.88bc summer Low (August 24, 1984; Cloudy 1.6 22 t o 1462 1 0 ° C ) — DF GF WH 4.7ab 5.4a 4. l b c .0 9ab .12a .07bc -0.7a -0.5abc -0.7a 2. 62b 2.54b 1. 65d Medium 0.4 359 DF GF WH 2.7de 3. 2d 3.4bcd . 05cd .07bc . 07bc -0.6abc -0.4bc -0.5abc 3.07a 3.16a 2.06c H i g h 0.5 146 DF GF WH 1.3f 2.0ef 1.3f .02d .0 6c .04cd -0.6ab -0.4c -0.5abc 3.14a 3.24a 1.94cd ^ Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). 76 Ta b l e 9. Autumn and w i n t e r means o f p h o t o s y n t h e t i c r a t e , Ps (mgCC^'dm Z'hr ), l e a f conductance, g± (em's - ), vapor p r e s s u r e d e f i c i t , D (KPa), p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n d u r i n g Ps measurements, PPFD (uMol'm *s ), l e a f water p o t e n t i a l , wp (MPa), and c h l o r o p h y l l c o n t e n t , C h l ( m g ' g - 1 ) , o f D o u g l a s - f i r (DF), grand f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t y . autumn Treatment/ s p e c i e s (November Ps 29, 1983; 9 l C l oudy D 5.5 PPFD t o -1° wp C) — C h l Low 0.2 734 DF GF WH 4 .2a 1 4.8a 4.4a . 08ab .05bcd .0 6abc -0.2a -0.1a -0.3a 2. 60b 2.57b 2.08c Medium 0.1 769 DF GF WH 4.4a 4.6a 4.1a .09a . 04cd . 05bcd -0.3a -0.2a -0.2a 3 .00a 3.12a 2.12c High 0.1 642 DF GF WH 4.3a 4.5a 4.1a . 0 6abc .05bcd .03d -0 .2a -0.2a -0.3a 3.05a 3.17a 1.99c w i n t e r Low (February 29, 1984; O v e r c a s t 0.8 734 10 t o 0 .5°C) — DF GF WH 4. l a 3.4b 3.1b . 03a . 02a . 03a -0. 6a -0. 8a -0.7a 2. 66b 2.50bc 2.07d Medium 0.7 676 DF GF WH 3. 6ab 3.2ab 3. 3ab . 03a .02a .03a -0.7a -0. 6a -0. 6a 2.55bc 3.19a 2.07d High 0.7 572 DF GF WH 2.8b 3.4ab 3.1b .04a . 03a . 03a -0.5a -0.7a -0. 6a 3.12a 3.04a 2.2 9cd 1 Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). w i n t e r v a l u e f o r grand f i r under h i g h d e n s i t y w h i c h was low e r t h a n t h e v a l u e s f o r t h e low d e n s i t y t r e a t m e n t on t h a t s a m p l i n g d a t e (Table 7 ) . A s i m i l a r s e a s o n a l p a t t e r n was r e p e a t e d a t t h e r e d a l d e r s i t e . I n t h e s p r i n g and summer a g i v e n s p e c i e s g e n e r a l l y had reduced p h o t o s y n t h e s i s w i t h i n c r e a s i n g o v e r t o p p i n g canopy d e n s i t y (Table 8). I n t h e autumn and w i n t e r t h e o n l y s i g n i f i c a n t d i f f e r e n c e between t r e a t m e n t s was a lower p h o t o s y n t h e t i c r a t e i n D o u g l a s - f i r under h i g h d e n s i t y canopy t r e a t m e n t as compared w i t h t h e o t h e r t r e a t m e n t s (Table 9). Comparison between s p e c i e s w i t h i n t r e a t m e n t s shows t h e g r e a t e s t d i f f e r e n c e s i n t h e s p r i n g (Table 8) and t h e l e a s t i n t h e autumn (Table 9). In t h e s p r i n g and summer a t t h e salmonberry s i t e , D o u g l a s - f i r e q u a l e d t h e p h o t o s y n t h e t i c r a t e o f hemlock o n l y under t h e l o w e s t canopy d e n s i t y i n t h e summer. Hemlock p h o t o s y n t h e t i c r a t e s matched grand f i r t h r o u g h o u t t h e y e a r under h i g h d e n s i t y , i n t h e summer a t medium d e n s i t y t r e a t m e n t s , and f o r a l l t r e a t m e n t s i n t h e autumn. D o u g l a s - f i r was e q u a l t o grand f i r under a l l t r e a t m e n t s i n t h e autumn and a t t h e medium d e n s i t y t r e a t m e n t i n t h e w i n t e r . In t h e s p r i n g and summer D o u g l a s - f i r p e r f o r m e d b e t t e r i n r e l a t i o n t o hemlock a t t h e r e d a l d e r s i t e t h a n a t t h e salmonberry s i t e (Table 6 vs 8). Hemlock had g r e a t e r p h o t o s y n t h e t i c r a t e s t h a n D o u g l a s - f i r o n l y a t t h e low d e n s i t y t r e a t m e n t i n t h e s p r i n g . I n t h e s p r i n g and summer 78 D o u g l a s - f i r e q u a l e d g r a n d f i r o n l y a t t h e medium canopy d e n s i t y . D o u g l a s - f i r was e q u a l t o grand f i r a t a l l t r e a t m e n t s i n t h e autumn, but was g r e a t e r a t t h e low d e n s i t y t r e a t m e n t i n t h e w i n t e r . Hemlock p h o t o s y n t h e t i c r a t e s were below t h o s e o f D o u g l a s - f i r w i t h i n t h e low d e n s i t y i n t h e summer and w i n t e r . L e a f conductance There were fewer d i f f e r e n c e s between s p e c i e s i n l e a f conductance t h a n i n p h o t o s y n t h e s i s . S p r i n g and summer l e a f conductances d e c l i n e d w i t h i n c r e a s i n g o v e r t o p p i n g canopy d e n s i t y (Table 6 and 8 ) . Few s i g n i f i c a n t d i f f e r e n c e s o c c u r r e d i n t h e w i n t e r (Tables 7 and 9 ) . As r e f l e c t e d i n t h e p h o t o s y n t h e s i s measurements, grand f i r g e n e r a l l y had t h e g r e a t e s t conductance. A t t h e salmonberry and r e d a l d e r s i t e s , D o u g l a s - f i r s u r p a s s e d t h e conductance o f g r a n d f i r o n l y under t h e medium d e n s i t y canopy i n t h e autumn (Table 8 and 9 ) . In t h e p e r i o d between t h e autumn and w i n t e r measurements, t h e medium d e n s i t y t r e a t m e n t v a l u e s became more s i m i l a r t o t h o s e o f t h e low d e n s i t y t h a n t h e h i g h d e n s i t y t r e a t m e n t . D o u g l a s - f i r showed no s i g n i f i c a n t d i f f e r e n c e between t r e a t m e n t s i n t h e autumn and w i n t e r w h i l e w e s t e r n hemlock c o n t i n u e d t o show d i f f e r e n c e s between low and h i g h d e n s i t y t r e a t m e n t s . 79 Leaf water potential Few s i g n i f i c a n t differences occurred i n leaf water p o t e n t i a l between species growing at d i f f e r e n t canopy density treatments (Tables 6, 7, 8, and 9). When a difference occurred at the salmonberry s i t e i t was generally under the medium or high density treatment. Comparing species within treatments, hemlock showed a d i f f e r e n t pattern between the red alder and salmonberry s i t e s i n the spring (Tables 6 and 8). At the red alder s i t e hemlock had consistently greater water stress than either Douglas-fir and/or grand f i r . At the salmonberry s i t e western hemlock was lower only under the medium density treatment. In the summer, western hemlock water stress remained r e l a t i v e l y low under the canopies. In the autumn and winter there was no s i g n i f i c a n t difference between species within a treatment at the red alder s i t e . Douglas-fir had lower l e a f water potentials than western hemlock at the medium density salmonberry s i t e in the autumn. Grand f i r was below hemlock at a l l treatments i n the winter (Tables 7 and 9). Chlorophyll content The relationship between chlorophyll content and species within a treatment was very consistent and may have only changed under the medium density treatment i n the winter, when the grand f i r chlorophyll content was above that of Douglas-fir. Grand f i r chlorophyll content was 80 c o n s i s t e n t l y g r e a t e r t h a n w e s t e r n hemlock c h l o r o p h y l l c o n t e n t . Between t r e a t m e n t s , s e e d l i n g s under t h e low d e n s i t y canopy t r e a t m e n t g e n e r a l l y had lower c h l o r o p h y l l c o n t e n t t h a n t h e h i g h d e n s i t y canopy t r e a t m e n t (Tables 6, 7, 8 and 9 ) . Hemlock showed no s i g n i f i c a n t d i f f e r e n c e s between t r e a t m e n t s i n t h e autumn and w i n t e r a t b o t h t h e r e d a l d e r and s a l m o n b e r r y s i t e s and t h e s a l m o n b e r r y i n t h e summer. Between t h e autumn and w i n t e r t h e c h l o r o p h y l l c o n t e n t o f D o u g l a s - f i r a t t h e medium d e n s i t y t r e a t m e n t came t o resemble t h e low, t h e n t h e h i g h canopy d e n s i t y t r e a t m e n t and b o t h t h e r e d a l d e r and salmonberry s i t e s ( Tables 7 and 9 ) . S e e d l i n g s u r v i v a l Grand f i r s e e d l i n g s c o n s i s t e n t l y had g r e a t e r s u r v i v a l t h a n D o u g l a s - f i r o r w e s t e r n hemlock s e e d l i n g s a f t e r two g r o w i n g seasons under a l l d e n s i t i e s o f b o t h t h e salmonberry and a l d e r c a n o p i e s (Table 10). Western hemlock had i n t e r m e d i a t e s u r v i v a l and D o u g l a s - f i r t h e l o w e s t on a l l p l o t s on b o t h t h e salmonberry and a l d e r s i t e s , except t h e low d e n s i t y a l d e r p l o t . The low d e n s i t y p l o t s g e n e r a l l y had t h e g r e a t e s t s u r v i v a l . S u r v i v a l under t h e medium and h i g h d e n s i t y c a n o p i e s were s i m i l a r i n most c a s e s . The w i d e s t v a r i a t i o n s 81 T a b l e 10. S u r v i v a l o f p l a n t e d s e e d l i n g s a f t e r t h e second g r o w i n g season under deciduous shade. P e r c e n t o f 40 s e e d l i n g s p e r s p e c i e s p e r shrub d e n s i t y t r e a t m e n t . Treatment/ Salmonberry Red A l s p e c i e s Low DF 72 82 GF 88 92 WH 82 72 Medium DF 53 42 GF 75 82 WH 60 68 H i g h DF 32 52 GF 78 82 WH 64 72 82 were e x h i b i t e d by D o u g l a s - f i r w h i c h had much lower s u r v i v a l under t h e h i g h d e n s i t y t h a n t h e medium d e n s i t y s almonberry, but p o o r e r s u r v i v a l under t h e medium d e n s i t y a l d e r t h a n t h e h i g h d e n s i t y a l d e r . S e e d l i n g growth S p e c i f i c l e a f a r e a The s p e c i f i c l e a f a r e a o f t r e e s e e d l i n g s under b o t h t h e r e d a l d e r and salmonberry c a n o p i e s v a r i e d among t r e a t m e n t s and s p e c i e s (Tables 11 and 12). In g e n e r a l , s p e c i f i c l e a f a r e a i n c r e a s e d w i t h g r e a t e r o v e r t o p p i n g canopy d e n s i t y . W i t h no o v e r t o p p i n g canopy (low d e n s i t y t r e a t m e n t ) w e s t e r n hemlock s e e d l i n g s had a s i g n i f i c a n t l y h i g h e r s p e c i f i c l e a f a r e a t h a n D o u g l a s - f i r and grand f i r a t b o t h t h e salmonberry and r e d a l d e r s i t e s . I n t h e medium d e n s i t y t r e a t m e n t s p e c i f i c l e a f a r e a a t t h e salmonberry s i t e was d i f f e r e n t f o r a l l t h e s p e c i e s . The o n l y s p e c i e s not t o have a s i g n i f i c a n t change i n s p e c i f i c l e a f a r e a between t r e a t m e n t s a t a g i v e n s i t e was g r a n d f i r under medium and h i g h d e n s i t y r e d a l d e r . L e a f growth r a t e The l e a f growth r a t e d e c r e a s e d i n g r a n d f i r and D o u g l a s - f i r a t b o t h s i t e s w i t h i n c r e a s i n g o v e r t o p p i n g canopy d e n s i t y . At t h e salmonberry s i t e t h e r e were no s i g n i f i c a n t 83 T a b l e 11. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA) o f 1984 f o l i a g e , r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), and r e l a t i v e h e i g h t growth r a t e (RHGR) f o r D o u g l a s - f i r (DF), grand f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s a f t e r t h r e e y e a r s o f growth w i t h i n s a lmonberry s t a n d s o f d i f f e r e n t d e n s i t i e s . T r e a t - SLA RLGR RDGR RHGR ment/ (cm^'g i) (g-yr i ' g l) (mm* y r 'mm ) (cm'yr "cm s p e c i e s Low DF 8 3 ^ 1.2ab 0.7bc 0.85a GF 80f 1.7a 1.4a 0.90a WH 109e 0.9bc 0 . 9ab 0.82a Medium DF 162c 0.4cd 0.3c 0.4 6ab GF 136d 0.8bcd 0.9ab 0.64ab WH 177b 1.2ab 0. 8bc 0.76a High DF 180b 0.3d 0.3c 0.22b GF 154c 0.3d 0. 6bc 0.58ab WH 214a 0.6bcd 0.7bc 0.72a Mean v a l u e s f o l l o w e d by d i f f e r e n t l e t t e r s w i t h i n a column 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). 84 Ta b l e 12. Mean v a l u e s o f s p e c i f i c l e a f a r e a (SLA) o f 1984 f o l i a g e , r e l a t i v e l e a f growth r a t e (RLGR), r e l a t i v e d i a m e t e r growth r a t e (RDGR), and r e l a t i v e h e i g h t growth r a t e (RHGR) f o r D o u g l a s - f i r (DF), g r a n d f i r (GF), and w e s t e r n hemlock (WH) s e e d l i n g s a f t e r t h r e e y e a r s o f growth w i t h i n r e d a l d e r s t a n d s o f d i f f e r e n t d e n s i t i e s . T r e a t -ment/ s p e c i e s SLA RLGR RDG (cm 2'g ^) (g'yr 1 ' g (mm'yr -1 ^ 5 _! mm )(cm'yr 'cm ) Low DF GF WH 73 f J 82f HOe 1.4ab 1.6a 1.Oabc 0. 9abc 1.3a 1. l a b 0.62abc 0.87a 0.65abc Medium DF GF WH 132d 141cd 170b 0.7c 1.5ab l.Obc 0.4cd 0.8abcd 1.2ab 0.37bc 0.71ab 0.70ab H i g h DF GF WH 165b 158bc 198a 0.5c 0.7c 0. 6c 0.3d 0.6bcd 0.8abed 0 .30c 0.54abc 0.66abc Mean v a l u e s f o l l o w e d by d i f f e r e n t l e t t e r s w i t h i n a column a r e 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). 85 d i f f e r e n c e s between D o u g l a s - f i r and grand f i r a t any d e n s i t i e s . A n i m a l c l i p p i n g o f grand f i r f o l i a g e was n o t i c e a b l y g r e a t e r than on t h e o t h e r s e e d l i n g s . The w e s t e r n hemlock s e e d l i n g s at t h e r e d a l d e r s i t e had s i g n i f i c a n t l y g r e a t e r f o l i a g e growth r a t e s t h a n D o u g l a s - f i r when t h e r e was an o v e r t o p p i n g canopy. R e l a t i v e d i a m e t e r growth r a t e There was no s i g n i f i c a n t change i n t h e r e l a t i v e d i a m e t e r growth r a t e i n D o u g l a s - f i r o r w e s t e r n hemlock between salmonberry t r e a t m e n t d e n s i t i e s . Grand f i r c o n s i s t e n t l y grew f a s t e r t h a n D o u g l a s - f i r a t a l l s a l m o n b e r r y t r e a t m e n t d e n s i t i e s . Western hemlock growth was i n t e r m e d i a t e a t b o t h t h e low and medium d e n s i t i e s o f s a l m o n b e r r y . There was no s i g n i f i c a n t d i f f e r e n c e between s p e c i e s a t t h e h i g h d e n s i t y s a l m o n b e r r y p l o t s . At t h e r e d a l d e r s i t e t h e medium d e n s i t y was i n t e r m e d i a t e i n growth f o r D o u g l a s - f i r and grand f i r , but w e s t e r n hemlock d i d not d i f f e r between t r e a t m e n t s . There was no s i g n i f i c a n t d i f f e r e n c e between s p e c i e s r e l a t i v e d i a m e t e r growth r a t e f o r t h e low and h i g h d e n s i t y r e d a l d e r t r e a t m e n t s . At t h e medium d e n s i t y r e d a l d e r t r e a t m e n t grand f i r was i n t e r m e d i a t e i n r e l a t i v e d i a m e t e r growth r a t e . R e l a t i v e h e i g h t growth r a t e On b o t h t h e salmonberry and r e d a l d e r p l o t s w e s t e r n hemlock and g r a n d f i r d i d not d i f f e r s i g n i f i c a n t l y i n r e l a t i v e h e i g h t growth r a t e between t r e a t m e n t s . D o u g l a s - f h e i g h t growth d e c l i n e d w i t h i n c r e a s i n g o v e r t o p p i n g canopy d e n s i t y . 87 DISCUSSION As h y p o t h e s i z e d , D o u g l a s - f i r s e e d l i n g s were a b l e t o u t i l i z e s e a s o n a l i n c r e a s e s i n l i g h t t h a t o c c u r r e d i n t h e autumn and w i n t e r t o narrow t h e p h y s i o l o g i c a l d i f f e r e n c e s between i t and s e e d l i n g s w i t h g r e a t e r shade t o l e r a n c e . However, a c h i e v e d growth, as an i n t e g r a t o r o f p h y s i o l o g i c a l s u c c e s s and e n v i r o n m e n t a l h a z a r d s , s u g g e s t s t h a t growth o f D o u g l a s - f i r d e c l i n e s s h a r p l y as shade from deciduous c o m p e t i t o r s i n c r e a s e s . With adequate p r o t e c t i o n from a n i m a l damage, p l a n t e d grand f i r may be an e x c e l l e n t c h o i c e f o r e s t a b l i s h m e n t i n u n a v o i d a b l y shrubby a r e a s . S e e d l i n g p h y s i o l o g y L i m i t a t i o n s o f t h e methodology r e s t r i c t e d measurements t o days when t h e c o n i f e r f o l i a g e was d r y . In t h e C o a s t a l w e s t e r n hemlock zone t h i s i s not t h e t y p i c a l s i t u a t i o n i n th e autumn and w i n t e r months. Helms (1963) i n d i c a t e d t h a t t h e s e d r y and r e l a t i v e l y warm days were t h e p e r i o d s o f maximum p h o t o s y n t h e t i c a c t i v i t y i n t h o s e seasons. T h e r e f o r e , t h e p h o t o s y n t h e t i c r a t e s t h a t a re r e p o r t e d here f o r t h e s p r i n g , autumn and w i n t e r might be c o n s i d e r e d among the maximums f o r t h o s e p e r i o d s . I n t h e summer, Helms r e p o r t e d t h a t r a i n y days may improve t h e m o i s t u r e r e l a t i o n s o f t h e t r e e and a l l o w g r e a t e r p h o t o s y n t h e t i c r a t e s ; i f so the v a l u e s r e p o r t e d here a re more s e a s o n a l l y t y p i c a l , but perhaps among t h e lower o f t h e p o s s i b l e v a l u e s . In i n t e r p r e t i n g s e a s o n a l d i f f e r e n c e s between s p e c i e s t h e r e 88 c o u l d be c o n f o u n d i n g between s p e c i e s and t r e a t m e n t s , and d i f f e r e n t r a t e s i n which t h e p h o t o s y n t h e t i c r a t e i n c r e a s e s w i t h l e a f m a t u r i t y . No attempt was made t o s e p a r a t e s e a s o n a l d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e and p h o t o s y n t h e t i c c a p a c i t y o f t h e l e a v e s as a f u n c t i o n o f l e a f age. T h i s p o s s i b l e s o u r c e o f c o n f o u n d i n g would be t h e g r e a t e s t i n t h e s p r i n g when t h e r a t e o f i n c r e a s e o f new l e a f p h o t o s y n t h e t i c c a p a c i t y i s t h e s t e e p e s t (Fry and P h i l l i p s , 1977; S e s t a k , 1985). S i n c e no measurements o f r e s p i r a t i o n were made, i t i s d i f f i c u l t t o determine t h e net c o n t r i b u t i o n t h a t changes i n g r o s s p h o t o s y n t h e t i c r a t e s made t o changes i n net C O 2 u p t a k e . R e s u l t s from t h i s experiment s u p p o r t t h e statement t h a t shade t o l e r a n t s p e c i e s o f t e n have g r e a t e r p h o t o s y n t h e t i c r a t e s i n shaded environments t h a n under h i g h l i g h t (Leverenz and J a r v i s , 1980; Hodges and S c o t t , 1968) . However, under a decid u o u s canopy t h e magnitude and t h e f r e q u e n c y o f d i f f e r e n c e s may v a r y s e a s o n a l l y . I n t h e w i n t e r , D o u g l a s - f i r under t h e medium and h i g h d e n s i t y canopy t r e a t m e n t showed th e a b i l i t y t o have p h o t o s y n t h e t i c r a t e s g r e a t e r t h a n o r e q u a l t o t h e low d e n s i t y t r e a t m e n t and g r a n d f i r under t h e same t r e a t m e n t . Helms (1963) a l s o found s u p p r e s s e d D o u g l a s - f i r t o be c a p a b l e o f h i g h a s s i m i l a t i o n r a t e s i n t h e autumn and w i n t e r . D u r i n g p e r i o d s when adequate l i g h t p e n e t r a t e d t o t h e s u p p r e s s e d t r e e s t h e i r p h o t o s y n t h e t i c r a t e s were g r e a t e r t h a n dominant t r e e s . 89 The fewer number o f d i f f e r e n c e s i n l e a f conductance, c h l o r o p h y l l c o n t e n t , an l e a f water p o t e n t i a l i n t h e autumn t h a n a t t h e o t h e r s a m p l i n g t i m e s may have r e s u l t e d from t h e onset o f c o l d h a r d e n i n g (Fry and P h i l l i p s , 1977). The g r e a t e r l e a f water p o t e n t i a l s a t t h e s a l m o n b e r r y s i t e may have r e s u l t e d from d r y i n g o f t h e low b u l k d e n s i t y o r g a n i c m a t e r i a l t h a t t y p i c a l l y accumulates under s a l m o n b e r r y s t a n d s . Drew and F e r r e l l (1979) r e p o r t e d t h a t D o u g l a s - f i r w ater p o t e n t i a l s a r e lower i n t h e w i n t e r r e g a r d l e s s o f l e a f w a ter p o t e n t i a l s and t h a t p l a n t s grown under low l i g h t had low e r water p o t e n t i a l s t h a n p l a n t s under f u l l sun. The l a r g e r o o t systems on t h e low canopy d e n s i t y t r e a t m e n t s e e d l i n g s may have compensated f o r t h e h i g h e r m o i s t u r e demands i n t h o s e p l o t s , r e s u l t i n g i n t h e l a c k o f water p o t e n t i a l d i f f e r e n c e s between t r e a t m e n t s . Drew and F e r r e l l (1979) r e p o r t e d t h a t s t o m a t a l c l o s u r e i s more s e n s i t i v e t o vapor p r e s s u r e d e f i c i t s i n t h e autumn r e g a r d l e s s o f p l a n t w ater p o t e n t i a l . T h i s would e x p l a i n why l e a f conductance i s down i n t h e w i n t e r w h i l e water p o t e n t i a l s t a y e d about t h e same. S e e d l i n g s u r v i v a l and growth No s i n g l e agent appeared r e s p o n s i b l e f o r t h e m o r t a l i t y o f t h e p l a n t e d s e e d l i n g s . S e v e r a l f a c t o r s such as t h e l a t e p l a n t i n g f o r t h a t e l e v a t i o n , t h e l o n g e r d u r a t i o n o f s t o r a g e o f s e e d l i n g s b e f o r e p l a n t i n g , d i f f i c u l t i e s i n p l a n t i n g w i t h i n e x i s t i n g c a n o p i e s and r o o t networks, and e v e r p r e s e n t 90 a n i m a l damage may have i n f l u e n c e d s u r v i v a l o f s e e d l i n g s . Most m o r t a l i t y o c c u r r e d w i t h i n t h e f i r s t y e a r , s u g g e s t i n g t h a t i n i t i a l e s t a b l i s h m e n t r a t h e r t h a n f o l i a g e damage from a n i m a l s was t h e dominant cause. Between-species t r e n d s i n s e e d l i n g s u r v i v a l a r e d i f f i c u l t t o i n t e r p r e t . G r e a t e r s u r v i v a l i s r e l a t e d t o i n c r e a s i n g s t o c k s i z e . A l t h o u g h l a r g e s t o c k was d i f f i c u l t t o p l a n t , t h e l a r g e g r and f i r s e e d l i n g s (2+1 BR) e s t a b l i s h e d r e a d i l y . The we s t e r n hemlock s e e d l i n g s had a tendency t o d r y and c a s t n e e d l e s , sometimes w i t h i n a few weeks o f p l a n t i n g , d e s p i t e m o i s t s o i l s . D o u g l a s - f i r s t o c k was t h e s m a l l e s t , but t h e e a s i e s t t o p l a n t . Newton (1978) , Newton and White (1983) and S t e i n (1984) found t h a t l a r g e r s e e d l i n g s have g r e a t e r s u r v i v a l and a b i l i t y t o outgrow shrub c a n o p i e s . Newton and White (1983) r e p o r t e d poor s u r v i v a l o f w e s t e r n hemlock o u t p l a n t e d w i t h i n e x i s t i n g and e s t a b l i s h i n g s a l m o n b e r r y c a n o p i e s . These r e s u l t s suggest t h a t D o u g l a s - f i r w i l l o n l y t o l e r a t e low l e v e l s o f o v e r t o p p i n g l i v e c a n o p i e s b e f o r e s u r v i v a l and growth are reduced from t h a t o f t h e unshaded c o n d i t i o n . However, Ruth (1956) r e p o r t e d t h a t t h i r d y e a r s u r v i v a l o f D o u g l a s - f i r and w e s t e r n hemlock s e e d l i n g s remained i n t h e 90 p e r c e n t i l e u n t i l s e e d l i n g s were c o m p l e t e l y o v e r t o p p e d by de c i d u o u s c a n o p i e s . In t h e e x p e r i m e n t s r e p o r t e d h e r e , above-ground c o m p e t i t i o n was c o n t r o l l e d w h i l e below ground c o m p e t i t i o n from r e s p r o u t s was l e f t unchecked. Below-ground c o m p e t i t i o n i s i m p o r t a n t , but 91 t h e e l i m i n a t i o n o f below-ground c o m p e t i t i o n i s not f e a s i b l e i n o p e r a t i o n a l f o r e s t r y o t h e r t h a n t h e s h o r t p e r i o d s a f t e r a l a r g e a p p l i c a t i o n o f h e r b i c i d e s o r m e c h a n i c a l s c a r i f i c a t i o n . . By means o f canopy m a n i p u l a t i o n and t r e n c h i n g around r o o t s o f w e s t e r n hemlock, C h r i s t y (1986) d e m o n s t r a t e d t h a t t h e r e d u c t i o n o f below ground c o m p e t i t i o n had a l e s s e r e f f e c t t h a n i n c r e a s i n g l i g h t i n t h e s i t u a t i o n b e i n g s t u d i e d , but t h a t t h e r e was a s t r o n g s y n e r g i s t i c e f f e c t between r e d u c t i o n o f above and below ground c o m p e t i t i o n . O v e r a l l growth o f s e e d l i n g s g e n e r a l l y d e c r e a s e d w i t h i n c r e a s i n g canopy d e n s i t y . D o u g l a s - f i r , t h e l e a s t shade t o l e r a n t o f t h e c o n i f e r s s t u d i e d , had t h e most pronounced growth r e d u c t i o n w i t h i n c r e a s i n g shade. Both shaded w e s t e r n hemlock and grand f i r showed t h e a b i l i t y t o m a i n t a i n e x c e l l e n t growth r e l a t i v e t o unshaded s e e d l i n g s . The l o n g t e rm p r o s p e c t s o f w e s t e r n hemlock and grand f i r emergence from t h e salmonberry canopy appear good. R e s u l t s from t h e s p e c i f i c l e a f a r e a measurements suggest t h a t t h e l i g h t l e v e l s were l o w e r under t h e s a l m o n b e r r y c a n o p i e s f o r a g i v e n t r e a t m e n t d e n s i t y t h a n under t h e r e d a l d e r . D o u g l a s - f i r and w e s t e r n hemlock t e n d e d t o have l a r g e r s p e c i f i c l e a f a r e a s under salmonberry t h a n f o r s i m i l a r t r e a t m e n t s on t h e Red a l d e r s i t e . Grand f i r s p e c i f i c l e a f a r e a s were about t h e same a t b o t h s i t e s . The res p o n s e o f s p e c i f i c l e a f a r e a was v e r y s e n s i t i v e t o t r e a t m e n t c o n f i r m i n g t h e f i n d i n g s o f D e l R i o and Berg (197 9) 92 f o r D o u g l a s - f i r , Tucker and Emmingham (1977) f o r hemlock and Tucker (1983) f o r grand f i r , t h a t s p e c i f i c l e a f a r e a i s a good i n d i c a t o r o f l i g h t environment. Removal o f buds and f o l i a g e by a n i m a l s was a major i d e n t i f i a b l e cause o f growth r e d u c t i o n and v a r i a t i o n i n a l l t h r e e c o n i f e r s p e c i e s i n a l l p l o t s . Grand f i r was t h e most s u s c e p t i b l e f o l l o w e d by D o u g l a s - f i r and w e s t e r n hemlock (which was r a r e l y damaged). G r a z i n g may have a c t e d t o e q u a l i z e growth between s p e c i e s . Ruth (1956) found a n i m a l b r o w s i n g o f s e e d l i n g s t o i n c r e a s e w i t h t h e amount o f o v e r t o p p i n g canopy. Browsing a f f e c t e d h e i g h t growth t o t h e g r e a t e s t e x t e n t f o r D o u g l a s - f i r , a l t h o u g h s e v e r a l grand f i r had m i s s i n g o r damaged l e a d e r s . D i a m e t e r growth i s l i k e l y t h e b e s t i n d i c a t o r o f s e e d l i n g e s t a b l i s h m e n t and growth because o f no d i r e c t a n i m a l damage and t h e a l l o m e t r i c r e l a t i o n s h i p between d i a m e t e r growth and r o o t development. However, r e d u c t i o n s i n h e i g h t growth a r e i m p o r t a n t because th e y a c t t o p r o l o n g t h e s u p p r e s s i o n by t h e o v e r t o p p i n g canopy. The main e f f e c t o f a n i m a l damage appeared t o be on l e a f growth r a t e s . Some o f t h e new growth on a p p r o x i m a t e l y 75% o f D o u g l a s - f i r and grand f i r and 30% o f hemlock was c l i p p e d l e a v i n g some p a r t i a l n e e d l e s . P a r t i a l n e e d l e s had t h e same s p e c i f i c l e a f a r e a as i n t a c t n e e d l e s ; b u t , p a r t i a l removal o f l e a v e s c o u l d p o s s i b l y a c t t o l o w e r s p e c i f i c l e a f areas i f t h e s i n k f o r a v a i l a b l e c a r b o h y d r a t e s i s r e d u c e d . 93 Based on the type of i n j u r i e s , and the time i n which they occurred (March through June), and sightings i n the area, I believe grouse were doing the majority of damage to a l l the seedlings. Fowle (1943) (cited i n Lawrence et a l . , 1961) observed heavy and repeated d e f o l i a t i o n i n j u r i e s from grouse in Douglas-fir plantations on Vancouver Island. Grouse c l i p p i n g of foliage was found i n the f i r s t 5 years in 51% of plantations widely scattered in coastal Washington and Oregon (Black et a l . 1979). On two high-site Douglas-fir plantations in southwestern Washington, Black et al.(1979) reported that buds removed by grouse was the f i r s t i n a succession of animal damage agents consisting of grouse, hare, and deer, with in some cases over 80% of trees damaged by grouse by the second growing season. 94 CONCLUSIONS 1. D i f f e r e n c e s i n t h e p h y s i o l o g y between s p e c i e s w i t h i n t h e d i f f e r e n t t r e a t m e n t s had a s e a s o n a l c y c l e . These d i f f e r e n c e s were g r e a t e s t i n t h e s p r i n g and summer and l e a s t i n t h e autumn and w i n t e r , s u g g e s t i n g s u p p r e s s i o n by deciduous c a n o p i e s v a r i e s g r e a t l y from season t o season. 2. S u p p r e s s i o n o f D o u g l a s - f i r s e e d l i n g s by deciduous c a n o p i e s i s g r e a t l y reduced d u r i n g t h e p e r i o d t h a t d e c i d u o u s c a n o p i e s a re l e a f l e s s . 3. P h y s i o l o g i c a l d i f f e r e n c e s between t r e e s o f d i f f e r e n t t o l e r a n c e can be reduced i n t h e autumn and w i n t e r . 4. S p e c i f i c l e a f a r e a and l e a f growth r a t e s o f a l l s p e c i e s responded s e n s i t i v e l y t o t r e a t m e n t s and a r e l i k e l y an e x c e l l e n t i n d e x o f t h e degree o f s h a d i n g . 5. The growth o f shade t o l e r a n t s p e c i e s d e c l i n e d l e s s w i t h i n c r e a s i n g d eciduous s h a d i n g t h a n t h a t o f shade i n t o l e r a n t s p e c i e s . 6. A n i m a l damage p r o b a b l y reduces growth and i n c r e a s e s t h e d u r a t i o n s e e d l i n g s a re under a canopy. 95 CHAPTER 4 THE EFFECT OF TREATMENT AND TREATMENT TIMING ON THE RELEASE RESPONSE OF SUPPRESSED DOUGLAS-FIR SAPLINGS INTRODUCTION The o b j e c t i v e o f c o n i f e r r e l e a s e i s t o i n c r e a s e o r m a i n t a i n t h e r a t e o f c r o p t r e e growth by removal o f competing v e g e t a t i o n . C o n i f e r r e l e a s e i s most o f t e n r e q u i r e d when competing v e g e t a t i o n o v e r t o p s crop t r e e s , but t h e s u c c e s s i n i n c r e a s i n g c o n i f e r growth by removing o v e r t o p p i n g v e g e t a t i o n has been v a r i a b l e ( D i e r a u f , 1977; MacLean and Morgan, 1983; St e w a r t e t a l . , 1984). C o n i f e r r e s p o n s e t o r e l e a s e from o v e r t o p p i n g c o m p e t i t o r s depends on a c c l i m a t i o n from a shaded environment t o an unshaded o r p a r t l y shaded environment, a p r o c e s s which i n v o l v e s a v a r i e t y o f p h y s i o l o g i c a l and m o r p h o l o g i c a l changes. U n l e s s t h e s e changes o c c u r , t h e r e l e a s e d c o n i f e r i s u n l i k e l y t o b e n e f i t from t h e r e l e a s e . The f o l i a g e morphology a t t h e t i m e o f c o n i f e r r e l e a s e t r e a t m e n t s a f f e c t s t h e a b i l i t y o f s u p p r e s s e d c o n i f e r s t o u t i l i z e t h e i n c r e a s e d l i g h t . R a p i d l y o c c u r r i n g p h y s i o l o g i c a l changes, such as changes i n pigment c o n t e n t , may a l l o w p l a n t s t o e x p l o i t temporary i n c r e a s e s i n l i g h t . I f l i g h t c o n d i t i o n s remain i n c r e a s e d t h r o u g h o u t t h e development o f new f o l i a g e (as i n t h e case o f r e l e a s e t r e a t m e n t s ) , changes i n s t r u c t u r e and t h e r e f o r e i n f u n c t i o n 96 a l l o w t h e p l a n t t o i n c r e a s i n g l y a c c l i m a t e t o t h e new e n v i r o n m e n t a l c o n d i t i o n s ( L a r c h e r , 1980). W a l l a c e and Dunn (1980) and Tucker and Emmingham (1977) r e c o g n i z e d t h a t i n i t i a l a c c l i m a t i o n o f r e l e a s e d f o r e s t t r e e s r e q u i r e s i n i t i a l changes i n p h y s i o l o g y (e.g. l e a f d i f f u s i v e c o n d u c t a n c e ) , but c o n t i n u e d p o s i t i v e r e s p o n s e t o r e l e a s e t r e a t m e n t s u l t i m a t e l y depends on a d j u s t m e n t s i n l e a f anatomy. P l a n t s undergo a wide number o f changes i n response t o h i g h e r l i g h t levels-.. (Boardman, 1977; P a t t e r s o n , 1980) . A c c l i m a t i o n o f t h e shade f o l i a g e o f shade i n t o l e r a n t s p e c i e s t o i n c r e a s e d l i g h t i n t e n s i t y g e n e r a l l y r e s u l t s i n h i g h e r p h o t o s y n t h e t i c l i g h t s a t u r a t i o n (Boardman, 1977; Kramer and K o z l o w s k i ; 1979; L a r c h e r , 1980), and h i g h e r dark r e s p i r a t i o n (Loach, 1967; Gauhl, 1976) and p h o t o r e s p i r a t i o n ( Z e l a w s k i , 1967). L e a f s t o m a t a l f r e q u e n c y and conductance a l s o i n c r e a s e (Holmgren, 1968; C r o o k s t o n e t a l . , 1975). The c h l o r o p h y l l c o n t e n t o f shade f o l i a g e (on an a r e a b a s i s ) i s g e n e r a l l y h i g h e r t h a n t h a t o f sun f o l i a g e (Lewandowska e t a l . , 1976), and c o n i f e r s grown i n low l i g h t environments have h i g h e r s p e c i f i c l e a f areas (Del R i o and Berg, 1979; Tucker and Emmingham, 1977; Munch, 1975). Aussenac (1973) r e v i e w e d s t r u c t u r a l d i f f e r e n c e s i n c o n i f e r f o l i a g e grown under d i f f e r i n g l i g h t e n v i r o n m e n t s . Boardman (1977), Clough e t a l . (1979), Bunce et a l . (1977), Nobel (1976), and P i e t e r s (1974) c o n c l u d e d t h a t t h e m a j o r i t y o f t h e 97 d i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e between sun and shade p l a n t s c o u l d be a t t r i b u t e d t o i r r e v e r s i b l e changes i n i n t e r n a l l e a f a r e a . Drew and F e r r e l l (1977) and K e l l e r and Tregunna (1976) found t h a t shade-grown p l a n t s o f D o u g l a s - f i r and w e s t e r n hemlock, r e s p e c t i v e l y , had a reduced a b i l i t y t o a v o i d d e s i c c a t i o n . I n g e n e r a l , p l a n t s from shaded environments had a l e s s x e r o p h y t i c anatomy and p o o r e r r o o t development as compared t o p l a n t s from unshaded e n v i r o n m e n t s ( K e l l e r , 197 3; B r i x , 1967; P h i l l i p s , 1967). The r a t e and t h e e x t e n t t o which f o l i a g e o f a g i v e n s p e c i e s can a c c l i m a t e t o changes i n t h e l i g h t environment depend p r i m a r i l y on t h e s t a g e o f l e a f development (Gauhl, 1976; S e s t a k , 1977; Bunce e t a l . , 1977; P e a r c e and Lee, 1969; P r i o u l e t a l . , 1980; J u r i k e t a l . , 1979), on p l a n t p r e c o n d i t i o n i n g ( P r i o u l e t a l . , 1980; Seemann e t a l . , 1986; S t r a n d and O q u i s t ; 1985), and on t h e magnitude o f l i g h t i n t e n s i t y change (Powles, 1984). K e l l e r and Tregunna (1976) o b s e r v e d c h l o r o s i s and b l e a c h i n g o f f o l i a g e w i t h i n hours o f removing a r e d a l d e r canopy from w e s t e r n hemlock. A c c l i m a t i o n o f c h l o r o p h y l l i n p l a n t s t r a n s f e r r e d from low t o h i g h l i g h t can be complete i n 2 days (Lonneburg e t a l . , 1985) and t h e e n t i r e p h o t o s y n t h e t i c a p p a r a t u s can a c c l i m a t e w i t h i n a week (Hatch e t a l . , 1969). C r o o k s t o n e t a l . (1975) and Gauhl (1976) found t h a t i n c r e a s e s i n l i g h t r e s u l t e d i n g r e a t e r dark r e s p i r a t i o n w i t h i n a day i n some c a s e s . These s t u d i e s 9 8 emphasize t h e c o m p l e x i t y o f changes t h a t t a k e p l a c e as p h y s i o l o g i c a l p r o c e s s e s r espond t o b o t h endogenous and exogenous i n f l u e n c e s . Bunce e t a l . (1977) f o l l o w e d t h e time c o u r s e o f p h o t o s y n t h e t i c l i g h t a c c l i m a t i o n i n soybean. They found t h a t when t r a n s f e r r i n g low l i g h t - a c c l i m a t e d p l a n t s from low t o h i g h l i g h t , changes i n p h o t o s y n t h e t i c r a t e , l e a f d i f f u s i v e conductance, l e a f w ater p o t e n t i a l , l e a f anatomy, p h o t o s y n t h e t i c u n i t s i z e , and g l y c o l a t e o x i d a s e a c t i v i t y were complete w i t h i n one day, whereas c h l o r o p h y l l c o n t e n t , number o f p h o t o s y n t h e t i c u n i t s , s p e c i f i c l e a f a r e a and malat e dehydrogenase a c t i v i t y showed s l o w e r change. P h o t o i n h i b i t i o n i s a major l i m i t a t i o n t o t h e a b i l i t y o f shade grown p l a n t s t o a c c l i m a t e t o h i g h e r l i g h t e n v i r onments (Powles, 1984). P h o t o i n h i b i t i o n r e s u l t s i n sharp d e c l i n e s i n t h e p h o t o s y n t h e t i c c a p a c i t y o f f o l i a g e , w hich i n s e v e r e c a s e s i s i r r e v e r s i b l e . F o l i a g e t h a t d e v e l o p e d i n shade o r w h i c h has been i n shade f o r an extended p e r i o d , i s p a r t i c u l a r l y prone t o p h o t o i n h i b i t i o n when s u d d e n l y exposed t o h i g h l i g h t , e s p e c i a l l y as water s t r e s s i n c r e a s e s ( L i c h t e n t h a l e r e t a l . , 1983; Gauhl, 1976; Ogren and O q u i s t , 1985; Bjorkman and Powles, 1983). However, Sharp and Boyer (1986) found t h a t i n h i b i t i o n o f e l e c t r o n t r a n s p o r t f u n c t i o n o c c u r r e d a t low water p o t e n t i a l s r e g a r d l e s s o f t h e l i g h t e x p o s u r e . Mid-day r e d u c t i o n s i n p h o t o s y n t h e s i s have been a t t r i b u t e d t o a wide v a r i e t y o f e n v i r o n m e n t a l and p h y s i o l o g i c a l v a r i a b l e s i n c l u d i n g p h o t o i n h i b i t i o n (Helms, 99 1963). The diurnal course of photosynthesis should give clues as to the a b i l i t y of conifers to acclimate to conditions after release. Ronco (1975) brought attention to the importance of measures to avoid s o l a r i z a t i o n (of which photoinhibition may be a major part) of newly planted seedlings. The symptoms of photooxidation which t y p i c a l l y accompany a l l but minor photoinhibition (Powles, 1984; Kok et a l . , 1965) are often exhibited by recently released suppressed conifers (e.g. Gorden, 1973; Ferguson and Adams, 1980; Siedel, 1980; Conard and Radosevich, 1982). In short, -a suppressed conifer's a b i l i t y to acclimate to the conditions created by a release treatment i s an important determinant of the release response. The objective of t h i s chapter i s to investigate the r e l a t i o n s h i p between conifer response to d i f f e r e n t release methods (manual and herbicide treatments) and to the timing of these treatments. Two hypotheses are examined: 1, that the way i n which conifers are released (quickly with manual treatments or slowly with herbicide treatments) w i l l influence the rate in which they acclimate and u t i l i z e the new l i g h t environment, and 2, that because of greater phenotypic p l a s t i c i t y early in the year, and because water stress i s expected to be higher l a t e r i n the growing season, the capacity for suppressed conifer saplings to acclimate to release conditions w i l l decrease throughout the growing season. 1 0 0 These hypotheses were t e s t e d i n a s e r i e s of manual and h e r b i c i d e r e l e a s e treatments conducted at d i f f e r e n t times of the year. D i f f e r e n c e s i n p h y s i o l o g i c a l a c c l i m a t i o n response (photosynthetic r a t e , l e a f d i f f u s i v e conductance, l e a f water p o t e n t i a l , and c h l o r o p h y l l content) and morphological response (growth of f o l i a g e , stem diameter, and height) w i l l be used t o show the e f f e c t s of d i f f e r e n t treatments on D o u g l a s - f i r r e l e a s e response. 101 METHODS A. F i e l d t r e a t m e n t s R e l e a s e t r e a t m e n t s a t two l o c a t i o n s were used t o examine t h e h y p o t h e s e s . At Haney, r e l e a s e t r e a t m e n t s were conducted f o r two c o n s e c u t i v e y e a r s and were u t i l i z e d f o r i n t e n s i v e measurements. Treatments c o n d u c t e d a t t h e P o w e l l R i v e r s i t e were used t o s u p p l y a d d i t i o n a l i n f o r m a t i o n on t h e second y e a r response o f s a p l i n g s . Haney ? E i g h t e e n 630 m s u b p l o t s were i d e n t i f i e d w i t h i n a r e a s o f t h e s i t e C r e d a l d e r s t a n d t h a t were homogeneous and had at l e a s t 200 c o n i f e r s a p l i n g s p e r ha. The f o l l o w i n g t h r e e t r e a t m e n t p l o t s were e s t a b l i s h e d on each o f s i x t r e a t m e n t d a t e s (May 24 and August 18 i n 1983, and June 9, J u l y 10, August 7, and September 5 i n 1984): 1) an u n t r e a t e d c o n t r o l p l o t , 2) a manual t r e a t m e n t , and 3) an h e r b i c i d e t r e a t m e n t . The r e d a l d e r canopy was removed i n t h e manual t r e a t m e n t by f e l l i n g at about 30 cm h e i g h t w i t h c h a i n saws. M a n u a l l y f e l l e d a l d e r stems were removed from t h e r e s e a r c h p l o t s t o a l l o w g r e a t e r a c c e s s d u r i n g p h y s i o l o g i c a l measurements. In t h e h e r b i c i d e t r e a t m e n t , t h e r e d a l d e r canopy was k i l l e d w i t h an i n j e c t i o n o f 2,4-D amine 9 a t about 1.5 m i n h e i g h t . A 230 m measurement p l o t was e s t a b l i s h e d a t t h e c e n t e r o f each t r e a t m e n t p l o t . A l l c o n i f e r s a p l i n g s w i t h i n t h e measurement p l o t were tagged (an 102 average o f 17 p e r p l o t ) , and f i v e o f t h e s e were chosen at random t o be sampled. P o w e l l R i v e r The study a r e a c o n s i s t e d o f two c o n t i g u o u s b l o c k s each h a v i n g f i v e 0.11 ha p l o t s ( f o u r t r e a t m e n t s and a c o n t r o l ) (see P e n d l and D'Anjou, 1984). An a d d i t i o n a l s e t o f 0.11 ha t r e a t m e n t p l o t s (the December r e l e a s e t r e a t m e n t ) was e s t a b l i s h e d on t h e same s i t e 150 m t o t h e n o r t h o f t h e two c o n t i g u o u s b l o c k s . The t r e a t m e n t s c o n s i s t e d o f t h e f e l l i n g o f t h e a l d e r a t f o u r t i m e s i n 1983: 1) June 7 and 8, 2) J u l y 19 t h r o u g h 21, 3) August 30 t h r o u g h September 1, and 4) December 27, p l u s an u n t r e a t e d c o n t r o l . The a l d e r stems were s m a l l enough t h a t t h e y were l e f t where t h e y f e l l . Only 9 c o n i f e r s i n t h e c e n t e r 230 m measurement p l o t o f each t r e a t m e n t p l o t were i n c l u d e d i n t h e random s e l e c t i o n o f f i v e sample t r e e s . B. F i e l d Measurements Schedule o f measurements The f o l l o w i n g measurements o f t r e e p h y s i o l o g y and environment were made s e v e r a l t i m e s f o l l o w i n g t r e a t m e n t s . T y p i c a l l y two t o f o u r s e t s o f measurements were t a k e n t h e f i r s t week a f t e r t h e t r e a t m e n t s . One or two o f t h e s e were d i u r n a l s e t s o f measurements, t h e r e m a i n i n g were measurements t a k e n i n t h e morning o n l y between 0800 and 103 1130. Additional morning only or diurnal measurements were t y p i c a l l y taken after one month and again at the end of the growing season (September-October). Photosynthetically-active radiation Measurement of s p e c i f i c l i g h t conditions at the time of the photosynthetic determinations was with a quantum sensor as described i n the methods section of Chapter 3. To characterize the shading of s p e c i f i c treatments, incoming ra d i a t i o n was integrated using a chemical (anthracene) procedure described i n Chapter 2. Leaf d i f f u s i v e conductance and vapor pressure d e f i c i t s Leaf d i f f u s i v e conductance (three replicates from three saplings per plot) and vapor pressure d e f i c i t s were determined as described i n the methods section of Chapter 3. Photosynthesis Photosynthetic rates (five r e p l i c a t e s per sample plot one from each of f i v e measurement saplings) were measured using methods described i n Chapter 3. Chlorophyll content in foliage Following release treatments at the Haney s i t e , and i n the autumn at both s i t e s , the chlorophyll content of foliage was determined on both treatment and control trees using the methods described i n Chapter 3. Several twigs were taken 104 from the top third, of -the crown of each of three sample trees i n each measurement plot and combined with a composite sample. One chlorophyll determination was made from each composite sample. Growth analysis Growth analysis (methods c i t e d i n Chapter 3) was conducted on six conifer saplings within each measurement plot that was sampled in October of 1984. Coarse root biomass was determined for six saplings from each of the Haney 1983 and Powell River release treatments i n the f a l l of 1984. Roots were removed by loosening the s o i l surrounding the stump and l i f t i n g the root system out. Coarse roots rarely broke during excavation and recovery was good. Leaf water potentials Leaf water potentials (three r e p l i c a t e s , one each from three of the f i v e sample measurement saplings per plot) were determined using methods c i t e d in Chapter 3. Data analysis Data were subjected to an one-way analysis of variance. Significance between treatments was determined at p< 0.05 with the Tukey multiple comparisons t e s t (Stoline, 1981). 105 RESULTS A. Sapling physiology I n i t i a l changes in sapling physiology af t e r release  treatments a. 1983 Haney experiments One day a f t e r the May 24, 1983 removal of the red alder canopy in the manual release treatment, photosynthetic rate and leaf water po t e n t i a l were s i g n i f i c a n t l y higher than the control values, and chlorophyll content had declined 20% from the content of control foliage (Table 13). There was no s i g n i f i c a n t change i n leaf d i f f u s i v e conductance. Measurements on day two after the treatments showed lea f d i f f u s i v e conductance of the manual treatment had risen s i g n i f i c a n t l y r e l a t i v e to the control, while l e a f water poten t i a l had further declined from control values. Average photosynthetic rate for the manual treatment remained s i g n i f i c a n t l y greater than the herbicide and the control treatments. However, Figure 8a shows differences i n average photosynthetic rate to be a result of high morning values. In the afternoon, gas exchange was the same for a l l the treatments. One month afte r the release treatments, the herbicide treatment showed s i g n i f i c a n t l y higher photosynthetic rate and leaf d i f f u s i v e conductance than the control; however the herbicide treatment averages were s t i l l s i g n i f i c a n t l y below 106 Table 13. Mean values of photosynthesis, l e a f d i f f u s i v e conductance , leaf water pote n t i a l , and chlorophyll content for current year Douglas - f i r foliage from saplings released at Haney on May 24 , 1983 followed through time. photosynthesis leaf d i f f u s i v e conductance Days afte r (mgCO, •dm z • hr !) (cm* s - 1 ) treatment M H C M H C 1, 3.2a 2 1.2b 1.1b .08a .06a . 06a 2 3 3.1a 1.1b 1.0b .12a .06b . 05b 4 3.0a 1.5b 1.6b .16a .08b . 07b 7^ 5. 6a 1.4b 1.5b .15a .10b . 0 6b 24 J 5.2a 3.7b . 8c .17a .13b . 06c leaf water chlorophyll p o t e n t i a l content Days afte r (MPa) (mg'g - 1 ) treatment M H C M H C 1 -1.6b -.7a -. 8a 2.67b 3.44a 3.32a 2 -2 .2b -.8a -.7a 2.63b 3.28a 3.48a 4 -1. 9b -. 6a -.6a 2.61b 3.18a 3.40a 7 -1.2b -.7a -.7a 2.54b 3.32a 3.46a 24 -1.0a -. 6a -.7a 2.33b 2.53b 3.06a Manual treatment (M), herbicide treatment (H), untreated control (C). p Mean values within a row followed with d i f f e r e n t l e t t e r s 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). Mean from diurnal measurements. T I 1 T 1 0 J 1 1 1 T p B 10 12 14 16 e 10 12 14 IB Time (hr) Time (hr) Release type manual release herbicide release control F i g u r e 8a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e conductance ( g ^ ) , and p h o t o s y n t h e s i s from the May 24, 1983 Haney r e l e a s e t r i a l s , (a) measured May 26, 1983 on 1983 f o l i a g e , (b) measured June 17, 1983 on 1983 f o l i a g e . 108 t h o s e o f t h e manual t r e a t m e n t (Table 13). C h l o r o p h y l l c o n t e n t o f t h e r e l e a s e t r e a t m e n t s were b o t h below t h e c o n t r o l , but t h e manual t r e a t m e n t l e a f water p o t e n t i a l was no l o n g e r d i f f e r e n t from t h e h e r b i c i d e r e l e a s e and c o n t r o l v a l u e s . F i g u r e 8b shows t h a t 22 days a f t e r t h e r e l e a s e t r e a t m e n t , t h e manual t r e a t m e n t p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance no l o n g e r d e c l i n e d s h a r p l y i n t h e a f t e r n o o n , d e s p i t e a r i s i n g v a p o r p r e s s u r e d e f i c i t on t h e day o f measurement. In a d d i t i o n , as d e f o l i a t i o n o f t h e canopy c o n t i n u e d i n t h e h e r b i c i d e t r e a t m e n t , p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance r a t e s r o s e so t h a t b o t h t r e a t m e n t s showed c o n s i s t e n t l y h i g h e r p h o t o s y n t h e t i c r a t e s t h a n t h e c o n t r o l v a l u e s . R e l e a s e t r e a t m e n t s i d e n t i c a l t o t h o s e e s t a b l i s h e d i n May 1983 were r e p l i c a t e d on a p l o t on August 7, 1983 . T h i s r e s u l t e d i n t h e same i n i t i a l p a t t e r n o f p h y s i o l o g i c a l d i f f e r e n c e s between t r e a t m e n t s (Table 14). I n c r e a s e s i n average p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e c o nductance, and d e c l i n e s i n l e a f water p o t e n t i a l and c h l o r o p h y l l c o n t e n t , were measured i n t h e manual r e l e a s e t r e a t m e n t . The d i u r n a l p a t t e r n o f p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e c onductance two days a f t e r t h e manual t r e a t m e n t ( F i g . 9a) showed h i g h p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e c onductance v a l u e s i n t h e morning, which d e c l i n e d i n t h e a f t e r n o o n as d i d t h e May r e l e a s e upon t r e a t m e n t . T a b l e 14. Mean v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e c onductance, l e a f water p o t e n t i a l , and c h l o r o p h y l l c o n t e n t f o r c u r r e n t y e a r D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d at Haney on August 9, 1983 f o l l o w e d t h r o u g h t i m e . p h o t o s y n t h e s i s l e a f d i f f u s i v e conductance Days a f t e r (mgCOo'dm 2 'hr 1) _1 (em's ) t r e a t m e n t M x H C M H C 1. 3 . 6 a 2 1.2b 1.1b .17a .09b . 08b 2 3 2 .9a . 6b .6b .10a .04b . 04b 4 3 . 3a 1.5b 1.6b .16a .10b . 0 9b 7^ 2 . Oa 1.1b 1.2b .12a .09b . 08b 2 .4b 2.7a .7c . 11a .14a . 05b l e a f water c h l o r o p h y l l p o t e n t i a l c o n t e n t Days a f t e r (MPa) (mg-g x) t r e a t m e n t M H C M H C 1 -2 .8b -1.3a -1.3a 2. 61b 3.23a 3.12a 2 -2 . 6b -1.2a -1.4a 1.30b 2.89a 2.83a 4 -2 .4a -1.2a -1.1a 1.21b 2.82a 2.89a 7 -1 .8b -1.3a -1.3a 1.28b 2.82a 2.89a 22 -2 .2b -1.5a - 1 . 6a 1.06b 2.46a 2.86a Manual t r e a t m e n t (M), h e r b i c i d e t r e a t m e n t (H), u n t r e a t e d c o n t r o l (C). 2 Mean v a l u e s w i t h i n a row f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). Mean from d i u r n a l measurements. 0 J 1 1 1 1 1 0 i ( 1 ( l r~ B 10 12 14 16 6 8 10 12 14 10 Time (hr) Time (hr) Release type manual release herbicide release control F i g u r e 9a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), atmos p h e r i c vapor p r e s s u r e d e f i c i t (D) , l e a f d i f f u s i v e c onductance (g-^) , and p h o t o s y n t h e s i s from t h e August 18, 1983 Haney r e l e a s e t r i a l s , (a) measured August 20, 1983 on 1983 f o l i a g e , (b) measured September 11, 1983 on 1983 f o l i a g e . I l l Three weeks a f t e r t h e August r e l e a s e ( F i g . 9b) t h e manual t r e a t m e n t p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance v a l u e s c o n t i n u e d t h e p a t t e r n o f d e c l i n i n g from e a r l y morning v a l u e s t o v a l u e s s i m i l a r t o t h o s e o f t h e u n t r e a t e d c o n t r o l by m i d - a f t e r n o o n . The average p h o t o s y n t h e t i c r a t e o f t h e h e r b i c i d e t r e a t m e n t was s i g n i f i c a n t l y h i g h e r t h a n t h e manual t r e a t m e n t , and appeared t o be s t r o n g l y c o n t r o l l e d by l i g h t l e v e l s . L e a f water p o t e n t i a l and c h l o r o p h y l l c o n t e n t o f t h e manual t r e a t m e n t remained s i g n i f i c a n t l y lower than t h e o t h e r t r e a t m e n t s a f t e r t h r e e weeks. C h l o r o p h y l l c o n t e n t o f t h e manual t r e a t m e n t was o n l y 37% o f t h e c o n t r o l v a l u e s . D e s p i t e s i g n i f i c a n t changes i n t h e p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance i n t h e h e r b i c i d e t r e a t m e n t a f t e r t h r e e weeks, t h e r e were no changes i n l e a f water p o t e n t i a l and c h l o r o p h y l l c o n t e n t r e l a t i v e t o t h e c o n t r o l . b. 1984 Haney e x p e r i m e n t s A r e p e a t o f t h e 1983 manual and h e r b i c i d e r e l e a s e t r e a t m e n t s was c o n d u c t e d i n t h e same s t a n d i n 1984 t o e x p l o r e i n more d e t a i l t h e e f f e c t s o f t i m i n g on i n i t i a l r e l e a s e r e s p o n s e . The e a r l i e s t 1984 r e l e a s e p e r i o d was June 9, and t h e immediate changes i n t h e p h y s i o l o g y between t r e a t m e n t s were s i m i l a r t o t h o s e measured i n e a r l y 1983. Two days a f t e r t h e t r e a t m e n t s , average p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance o f t h e manual t r e a t m e n t were s i g n i f i c a n t l y g r e a t e r t h a n t h o s e o f t h e h e r b i c i d e t r e a t m e n t 112 o r t h e c o n t r o l (Table 15), and t h e d i u r n a l p a t t e r n ( F i g . 10a) showed r a p i d d e c l i n e s from i n i t i a l l y h i g h p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance e a r l y i n t h e day. S i g n i f i c a n t r e d u c t i o n s i n l e a f w ater p o t e n t i a l and c h l o r o p h y l l c o n t e n t a l s o accompanied t h e manual t r e a t m e n t . D i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance between t h e manual t r e a t m e n t and t h e h e r b i c i d e and c o n t r o l t r e a t m e n t s c o n t i n u e d t o i n c r e a s e o v er t h e f o l l o w i n g weeks. The d i f f e r e n c e i n l e a f w a t e r p o t e n t i a l measured between t h e manual and c o n t r o l t r e a t m e n t s t h e second day a f t e r r e l e a s e had d i m i n i s h e d a f t e r two weeks. A month a f t e r t h e t r e a t m e n t s , average p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance o f a l l t r e a t m e n t s were s i g n i f i c a n t l y d i f f e r e n t from each o t h e r (Table 1 5 ) . D i f f e r e n c e s i n l e a f w ater p o t e n t i a l between t h e t r e a t m e n t s and t h e c o n t r o l were not s i g n i f i c a n t . The d i u r n a l p a t t e r n o f p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e c onductance o f t h e manual t r e a t m e n t a month a f t e r t r e a t m e n t no l o n g e r showed t h e sharp mid-day d e c l i n e s e x h i b i t e d two days a f t e r t r e a t m e n t ( F i g . 9a and 10b). Both t h e p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance o f t h e h e r b i c i d e t r e a t m e n t t r e e s had i n c r e a s e d above c o n t r o l l e v e l s by day 30. The August 9, 1984 r e l e a s e t r e a t m e n t showed i n i t i a l changes i n p h o t o s y n t h e t i c r a t e a f t e r two days t h a t were s i m i l a r t o t h o s e measured i n t h e August 1983 r e l e a s e p e r i o d . The average p h o t o s y n t h e t i c r a t e was i n c r e a s e d (Table 16), and t h e d i u r n a l p a t t e r n showed a h i g h p h o t o s y n t h e t i c r a t e 113 Table 15. Mean values of photosynthesis, leaf d i f f u s i v e conductance, leaf water po t e n t i a l , and chlorophyll content for current year Douglas-fir foliage from saplings released at Haney on June 9, 1984 followed through time. Days afte r treatment photosynthesis (mgC02'dm-2"hr"1) M1 H C leaf d i f f u s i v e conductance (cm* s - 1 ) M H 2 2.9a 2 .8b 1 .Ob .07a .08a . 09a 4 3.5a 1.2b 1 .lb .16a .09b . 09b 15 5.4a 1.6b 1 .3b .18a .10b . 09b 30 4.9a 2.3b ,7c .18a .14b . 0 6c leaf water chlorophyll potential content Days a f t e r (MPa) (mg-g x) treatment M H C M H C 1 -1.2b -.6a -. 5a 2.62b 3.18a 3.01a 4 -1.3b -.2a -,3a 2.2 6b 3.16a 3.12a 15 -. 8a -,4a -. 5a 2.57b 2.92ab i 3.18a 30 -. 5a -.3a -.2a 2.12b 2.74a 3.21a Manual treatment (M), herbicide treatment (H), untreated control (C). 2 Mean values within a row followed with d i f f e r e n t l e t t e r s 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). 0-J 1 1 i 1 1 1 0 J 1 i 1 8 10 12 14 16 18 8 10 12 Time (hr) Time (hr) Release type manual release herbicid_e_release control F i g u r e lOa-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e c o n ductance ( g 1 ) , and p h o t o s y n t h e s i s from t h e June 9, 1984 Haney r e l e a s e t r i a l s , (a) measured June 11, 1984 on 1984 f o l i a g e , (b) measured J u l y 12, 1984 on 1984 f o l i a g e . 115 Table 16. Mean values of p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance, l e a f water p o t e n t i a l , and c h l o r o p h y l l content f o r c u r r e n t year D o u g l a s - f i r f o l i a g e from s a p l i n g s r e l e a s e d at Haney on August 7, 1984 f o l l o w e d through time. p h o t o s y n t h e s i s l e a f d i f f u s i v e Days a f t e r (mgC0 2'dm - 2'hr - 1) treatment M 1 H C 2 3 2.0a 2 1.0b .8b 4 4.2a 1.1b 1.0b 15 3.4a 2.6b 1.2c 30 3 1.9a 2.2a .9b conductance (cm- s x) M H C .06a .04a .04a . 14a .04b .05b .11a .12a .06b .08b .16a .08b l e a f water p o t e n t i a l c h l o r o p h y l l content Days a f t e r (MPa) (mg'g l) treatment M H C M H C 2 -2.6b -.7a -.7a 2 . 44b 2.88a 2 . 80a 4 -2.6b -.6a -.6a 1 .55b 2.77a 2 .84a 15 -2.6b -.7a -. 6a 1 .71b 2 .58a 2 .59a 30 -2.6b -1.3a -.8a .84c 2.14b 2 .71a Manual treatment (M), h e r b i c i d e treatment (H), u n t r e a t e d c o n t r o l (C). ? Mean v a l u e s w i t h i n a row f o l l o w e d w i t h d i f f e r e n t l e t t e r s 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). Mean from d i u r n a l measurements. 116 e a r l y i n t h e day, f o l l o w e d by a s t e e p d e c l i n e ( F i g . 11a). No s i g n i f i c a n t i n c r e a s e i n l e a f d i f f u s i v e conductance accompanied t h e i n c r e a s e i n manual t r e a t m e n t p h o t o s y n t h e t i c r a t e a t t h e second day measurement. A month a f t e r t h e August 1984 r e l e a s e t r e a t m e n t , average p h o t o s y n t h e t i c r a t e s o f t h e manual and h e r b i c i d e t r e a t m e n t s were n e a r l y t h e same (Table 16), d e s p i t e t h e h i g h e r l i g h t l e v e l s w i t h i n t h e manual t r e a t m e n t ( F i g . l i b ) . L e a f d i f f u s i v e conductance o f f o l i a g e i n t h e manual t r e a t m e n t was s i g n i f i c a n t l y lower t h a n t h a t o f f o l i a g e i n the h e r b i c i d e t r e a t m e n t (Table 16). L e a f w a t e r p o t e n t i a l and c h l o r o p h y l l c o n t e n t o f t h e manual t r e a t m e n t remained s i g n i f i c a n t l y l o w e r t h a n b o t h t h e h e r b i c i d e and c o n t r o l . U n l i k e t h e o t h e r r e l e a s e p e r i o d s , t h e August 1984 h e r b i c i d e t r e a t m e n t showed s i g n i f i c a n t l y h i g h e r p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance over t h e c o n t r o l a f t e r two weeks. These i n c r e a s e s were not accompanied by changes i n l e a f water p o t e n t i a l o r c h l o r o p h y l l c o n t e n t u n t i l c h l o r o p h y l l c o n t e n t had d e c r e a s e d when measured 30 days a f t e r t r e a t m e n t (Table 1 6 ) . I n t e g r a t e d l i g h t l e v e l s were not measured over t h e p e r i o d a f t e r t h e August 1984 h e r b i c i d e r e l e a s e t r e a t m e n t , so comparison w i t h d e f o l i a t i o n r a t e s i n o t h e r p e r i o d s cannot be made. However, canopy d e f o l i a t i o n was o b s e r v e d t o be p a r t i c u l a r l y r a p i d on t h e August 1984 p l o t . The d i u r n a l T 1 r 1 1 1 1 0 J 1 1 - i 1 r 8 10 11 12 13 14 16 8 10 12 14 16 Time (hr) Time (hr) Release type manual release herbicide release control F i g u r e l l a - b . D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D) , l e a f d i f f u s i v e c o n ductance (g-^) , and p h o t o s y n t h e s i s from t h e August 7, 1984 Haney r e l e a s e t r i a l s , (a) measured August 9, 1984 on 1984 f o l i a g e , (b) measured September 7, 1984 on 1984 f o l i a g e . 118 p a t t e r n o f p h o t o s y n t h e t i c r a t e f o r t h e h e r b i c i d e t r e a t m e n t a month a f t e r t r e a t m e n t shows t h a t r e l a t i v e l y s m a l l changes i n t h e l i g h t c o n d i t i o n s compared t o t h e manual t r e a t m e n t r e s u l t e d i n a g r e a t l y i n c r e a s e d p h o t o s y n t h e t i c r a t e ( F i g . l i b ) . End o f f i r s t g r o w i n g season d i f f e r e n c e s i n t h e p h y s i o l o g y o f  s a p l i n g s a t t r i b u t e d t o d i f f e r e n t r e l e a s e t r e a t m e n t s . a. 1983 Hanev e x p e r i m e n t s T a b l e 17 p r o v i d e s a comparison o f t h e p h y s i o l o g y o f t h e s a p l i n g s i n t h e f o u r 1983 t r e a t m e n t / d a t e r e l e a s e c o m b i n a t i o n s as measured i n September o f 1983. Average v a l u e s o f t h e p h y s i o l o g i c a l c h a r a c t e r i s t i c s d i d not d i f f e r s i g n i f i c a n t l y between e i t h e r o f t h e May t r e a t m e n t s . The manual t r e a t m e n t from August c o n s i s t e n t l y d i f f e r e d from t h e h e r b i c i d e t r e a t m e n t and t h e c o n t r o l . P h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance o f t h e manual t r e a t m e n t c o n t i n u e d t o drop over t h e two weeks between t h e one-month p o s t - t r e a t m e n t measurements (Table 14) and t h e end o f September measurements (Table 1 7 ) . The d i u r n a l p a t t e r n o f p h o t o s y n t h e t i c r a t e ( F i g . 12a) shows t h e May manual r e l e a s e t r e a t m e n t and t h e August h e r b i c i d e t r e a t m e n t had g r e a t e r a f t e r n o o n d e p r e s s i o n o f b o t h p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance as compared w i t h t h e May h e r b i c i d e r e l e a s e . 119 T a b l e 17. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s (Ps) , l e a f d i f f u s i v e conductance (g-^) , and means o f l e a f water p o t e n t i a l (wp), and c h l o r o p h y l l c o n t e n t ( c h l ) o f D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 as measured September 24, 1983. P s _ 2 - i 9 i - i Treatment (mgC02'dm ^'hr x) (em's ) M1May 24 4.6a 2 .22a M Aug. 18 .3d .05c H May 24 4.4a .23a H Aug. 18 3.2b .19ab C o n t r o l 1.3c .14b wp c h l (MPa) (mg'g 1) -. 6a 2.36c 2.0b .98d -. 6a 2.41c -.7a 2.77b -. 6a 3.28a Manual r e l e a s e t r e a t m e n t (M), h e r b i c i d e r e l e a s e t r e a t m e n t (H) . Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). Time (hr) Time (hi) Time (hr) Release type manual release herbicide release control F i g u r e 12a-c. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e c onductance ( g ^ ) , and p h o t o s y n t h e s i s from t h e 1983 Haney r e l e a s e t r i a l s , (a) measured September 24, 1983 on 1983 f o l i a g e , (b) measured September 7, 1984 on 1983 f o l i a g e , (c) measured September 8, 1984 on 1984 f o l i a g e . Box= May 24, 1983 t r e a t m e n t ; t r i a n g l e = August 18, 1983 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l . 121 b. 1984 Haney ex p e r i m e n t s Treatment d i f f e r e n c e s a t t h e end o f t h e growing season f o r t h e 1984 t r e a t m e n t s a r e shown i n Table 18. Mean v a l u e s o f p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance were not s i g n i f i c a n t l y d i f f e r e n t f o r t h e manual t r e a t m e n t s e s t a b l i s h e d i n June and J u l y , and d i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance f o r t h e s e t r e a t m e n t s ( F i g . 13b) are v e r y s i m i l a r . Manual r e l e a s e t r e a t m e n t s e s t a b l i s h e d i n August and September had s i m i l a r p h o t o s y n t h e t i c r a t e , l e a f d i f f u s i v e conductance, and c h l o r o p h y l l c o n t e n t . R e d u c t i o n s i n l e a f water p o t e n t i a l were g r e a t e s t i n t h e August manual t r e a t m e n t f o l i a g e as compared t o a l l o t h e r t r e a t m e n t s . The p h o t o s y n t h e t i c r a t e s o f t h e h e r b i c i d e t r e a t m e n t s were s i m i l a r t o t h o s e o f t h e manual t r e a t m e n t s e s t a b l i s h e d i n August and September (Table 18). However, the l e a f d i f f u s i v e conductances o f t h e h e r b i c i d e t r e a t m e n t s were s i m i l a r t o t h o s e o f t h e June and J u l y manual t r e a t m e n t s (Table 1 8 ) . The d i u r n a l p a t t e r n o f t h e v a r i o u s 1984 h e r b i c i d e r e l e a s e p e r i o d s shows a c o n s i s t e n t n e s t i n g o f e n v i r o n m e n t a l c o n d i t i o n s and p h y s i o l o g i c a l r e s p o n s e ( F i g 13b). The l o n g e r t h e t i m e s i n c e t r e a t m e n t , th e g r e a t e r t h e l i g h t l e v e l w i t h i n t h e p l o t , and t h e h i g h e r t h e p h o t o s y n t h e t i c r a t e . C h l o r o p h y l l c o n t e n t g e n e r a l l y d e c r e a s e d w i t h i n c r e a s e d t i m e s i n c e h e r b i c i d e t r e a t m e n t (Table 1 8 ) . 122 Table 18. Mean values of photosynthesis (Ps), leaf d i f f u s i v e conductance (g-^ ) , and means of l e a f water pot e n t i a l (wp), and chlorophyll content (chl) of Douglas-fir saplings released at Haney in 1984 as measured October 3, 1984. Ps g^ wp c n l _ 1 Treatment (mgC0 2'dm - 2-hr - 1) (em's - 1) (MPa) (mg'g-1) MiJune 9 4.4a .20a -.4a 2.0 9d M J u l . 10 4.9a . 17ab 2.29cd M Aug. 7 2.3c . 05c -1.6b 1.19e M Sept. 5 2.8bc . 08c . 94e H June 9 2.8bc .19a -. 3a 2.34cd H J u l . 10 3.3b . 15b 2.54bc H Aug. 7 2.1c . 18a -. 3a 2.70b H Sept. 5 1.6c .13b 2.77b Control l . l d .07c -.4a 3.30a Manual treatment (M), herbicide treatment (H), untreated control (C). p Mean values within a column followed with d i f f e r e n t l e t t e r s 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). 3 Oct. 1984 10 12 14 Time (hr) „ 2000 T 1600 D-n- -o 1000-^ 600 a. O. 2 •XL E •a o i tn J= c E > "D O n ° 8 3 Oct. 1984 -T 1 1 1 " • : - : - : : - - B —-'8 ;8:,, -j5r--- ---A B 10 12 14 Time (hr) Release type manual release herbicide release F i g u r e 13a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D), l e a f d i f f u s i v e c onductance ( g ^ ) , and p h o t o s y n t h e s i s from the 1984 Haney r e l e a s e t r i a l s , (a) manual r e l e a s e , measured October 3, 1984 on 1984 f o l i a g e , (b) h e r b i c i d e r e l e a s e , measured October 3, 1984 on 1984 f o l i a g e . Box= June 9, 1984 t r e a t m e n t ; r i n g = J u l y 10, 1984 t r e a t m e n t ; t r i a n g l e = August 7, 1984 t r e a t m e n t ; diamond^ September 5, 1984 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l . 124 Comparison o f t h e p h y s i o l o g y o f s u c c e s s i v e age c l a s s e s o f f o l i a g e a f t e r r e l e a s e a. 1983 Hanev e x p e r i m e n t s Mean d i u r n a l v a l u e s o f p h o t o s y n t h e t i c r a t e , l e a f d i f f u s i v e conductance, and means o f morning d e t e r m i n a t i o n s o f l e a f water p o t e n t i a l and c h l o r o p h y l l c o n t e n t t a k e n a t t h e end o f t h e second growing season f o r t h e 1983 r e l e a s e t r e a t m e n t s a r e p r e s e n t e d i n Table 19. In 1983, t h e p h o t o s y n t h e t i c r a t e o f t h e August manual t r e a t m e n t was s i g n i f i c a n t l y l o w e r t h a n t h e o t h e r r e l e a s e t r e a t m e n t s and t h e c o n t r o l (Table 17). In 1984, t h e d i f f e r e n c e remained between t h e August manual t r e a t m e n t and t h e o t h e r t r e a t m e n t s ; however, t h e p h o t o s y n t h e t i c r a t e o f t h e 1983 f o l i a g e i n 1984 was s i g n i f i c a n t l y h i g h e r t h a n comparable c o n t r o l v a l u e s . D i f f e r e n c e s i n p h o t o s y n t h e t i c r a t e between t h e two May t r e a t m e n t s and t h e August h e r b i c i d e t r e a t m e n t t h a t were seen i n 1983 had d i m i n i s h e d when t h e 1983 f o l i a g e was remeasured i n 1984 (Table 1 9 ) . P h o t o s y n t h e t i c r a t e f o r t h e 1984 f o l i a g e d i d not d i f f e r s i g n i f i c a n t l y between t h e t r e a t m e n t s (Table 1 9 ) . Only t r e e s on t h e August manual t r e a t m e n t produced 1984 f o l i a g e t h a t had s i g n i f i c a n t l y g r e a t e r average p h o t o s y n t h e t i c r a t e t h a n t h a t o f t h e 1983-produced f o l i a g e i n 1984. F i g u r e s 12b and 12c compare t h e September 1984 d i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c r a t e measured i n t h e two age c l a s s e s o f f o l i a g e on t h e 1983 r e l e a s e t r e a t m e n t s . F i g u r e 12b shows t h a t f o l i a g e on t h e 1983 August manual t r e a t m e n t c o n t i n u e d 125 T a b l e 19. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e conductance, and means o f l e a f water p o t e n t i a l , and c h l o r o p h y l l c o n t e n t o f 1983 and 1984 f o l i a g e from D o u g l a s - f i r s a p l i n g s r e l e a s e d a t Haney i n 1983 as measured September 7, 1984. p h o t o s y n t h e s i s l e a f d i f f u s i v e conductance (mgC0 2'dm - 2'hr - 1) (em's - 1) Treatment 8 3 2 84 6%3 83 84 4% M XMay 5. 5a 6. Oa 9 .21a .22a 5 H May 5.2a 5. 3a 2 .21a .21a 0 M Aug. 2.1b 5. 5a 162* .16a .20a 25 H Aug. 4. 9a 4 .7a -4 .20a .19a -5 C o n t r o l 1.4c 1.4b . l i b . l i b l e a f water c h l o r o p h y l l p o t e n t i a l c o n t e n t (MPa)• (mg'g x) 8 3 84 &% 8 3 84 ft% M May -. 3a -.5b 67* 2.35b 2.12c -10 H May -. 5ab -.4ab -20 2.4 6b 1.92c -22 M Aug. -.8c -.5b -38* 1.12c 1. 61d 44* H Aug. -.4ab -. 3a 25 2.50b 2.45b -2 C o n t r o l -. 6bc -.7c 17 2.78a 3.34a 20 Manual r e l e a s e t r e a t m e n t (M), h e r b i c i d e r e l e a s e t r e a t m e n t (H) . ? Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). 9 J P e r c e n t d i f f e r e n c e between 1983 and 1984 f o l i a g e v a l u e s . * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e (p<0.05) between f o l i a g e age c l a s s e s . 126 t o d e c l i n e s h a r p l y i n p h o t o s y n t h e t i c r a t e t h r o u g h o u t t h e day, r e a c h i n g v a l u e s a t o r below t h o s e o f t h e c o n t r o l . The 1984 p h o t o s y n t h e s i s p a t t e r n s o f 1983 f o l i a g e from t h e o t h e r r e l e a s e t r e a t m e n t s are s i m i l a r t o each o t h e r ( F i g . 12b). D i u r n a l p h o t o s y n t h e t i c p a t t e r n s o f t h e 1984 f o l i a g e o f t h e 1983 r e l e a s e t r e a t m e n t s a p l i n g s ( F i g . 12c) are s i m i l a r t o each o t h e r except f o r drops i n b o t h p h o t o s y n t h e t i c r a t e and l e a f d i f f u s i v e conductance o f f o l i a g e from t h e August manual t r e a t m e n t l a t e i n t h e day. Shading from t h e s t a n d i n g d e f o l i a t e d canopy i n t h e h e r b i c i d e t r e a t m e n t appeared t o have l i t t l e e f f e c t i n a l l o w i n g 1983 and 1984 f o l i a g e t o a c h i e v e t h e same p h o t o s y n t h e t i c r a t e as t h e manual r e l e a s e t r e a t m e n t (Table 19). L e a f d i f f u s i v e conductance averages (Table 19) showed no s i g n i f i c a n t d i f f e r e n c e s between r e l e a s e t r e a t m e n t s f o r b o t h 1983 and 1984-produced f o l i a g e . F u r t h e r , t h e r e were no s i g n i f i c a n t d i f f e r e n c e s between age c l a s s e s o f f o l i a g e f o r t h e s p e c i f i c t r e a t m e n t s . F o r a l l b u t t h e August manual t r e a t m e n t t h i s r e l a t i o n s h i p between l e a f d i f f u s i v e conductance and t r e a t m e n t resembled measurements on 1983 f o l i a g e a t t h e end o f t h e 1983 growing season (Table 17) . I n 1983, l e a f d i f f u s i v e conductance f o r t h e August manual t r e a t m e n t was v e r y low as compared t o a l l o t h e r t r e a t m e n t s (Table 17). D i f f e r e n c e s i n l e a f d i f f u s i v e c onductance o f 1983 f o l i a g e between t h e August manual t r e a t m e n t and t h e o t h e r t r e a t m e n t s d i m i n i s h e d over t h e 1984 g r o w i n g season. L e a f water p o t e n t i a l remained s i g n i f i c a n t l y 127 h i g h e r as compared t o t h e o t h e r t r e a t m e n t s (Table 19). The manual t r e a t m e n t s had s i g n i f i c a n t l e a f water p o t e n t i a l d i f f e r e n c e s between 1984 f o l i a g e and f o l i a g e from th e 1983 r e l e a s e t r e a t m e n t s (Table 1 9 ) . The p a t t e r n o f c h l o r o p h y l l c o n t e n t d i f f e r e n c e s between t r e a t m e n t s were s i m i l a r comparing t h e 1983 and 1984 f o l i a g e , e x c e p t t h e August h e r b i c i d e t r e a t m e n t d i d not d e c l i n e i n 1984 as much as t h e May t r e a t m e n t s . The August manual t r e a t m e n t showed a s i g n i f i c a n t i n c r e a s e i n c h l o r o p h y l l c o n t e n t between age c l a s s . b. 1983 P o w e l l R i v e r e x p e r i m e n t s Manual r e l e a s e t r i a l s e s t a b l i s h e d a t P o w e l l R i v e r i n 1983 p r o v i d e d a r e p l i c a t i o n o f t h e s t u d y o f y e a r - t o - y e a r changes i n t h e f o l i a g e o f t h e Haney 1983 r e l e a s e t r i a l s , but w i t h a w i d e r range of r e l e a s e p e r i o d s . As was seen i n t h e 1983 f o l i a g e from Haney manual r e l e a s e t r e a t m e n t s (Table 1 9 ) , t h e p h o t o s y n t h e t i c r a t e and t h e l e a f d i f f u s i v e c onductance o f f o l i a g e o f t r e e s i n t h e P o w e l l R i v e r p l o t s (Table 20) e s t a b l i s h e d l a t e i n t h e g r o w i n g season (August) were c o n s i d e r a b l y lower than t h o s e r e l e a s e d e a r l i e r i n t h e y e a r (June and J u l y ) . (The manual r e l e a s e conducted i n December had a p h o t o s y n t h e t i c r a t e i n t e r m e d i a t e between t h e c o n t r o l and August r e l e a s e t r e e v a l u e s . ) In c o n t r a s t t o t h e 1984 f o l i a g e p h o t o s y n t h e t i c r a t e from t h e Haney 1983 r e l e a s e t r e a t m e n t s , t h e p h o t o s y n t h e t i c r a t e o f t h e 1984 P o w e l l R i v e r 128 T a b l e 20. Mean d i u r n a l v a l u e s o f p h o t o s y n t h e s i s , l e a f d i f f u s i v e c onductance, and means o f l e a f w a t e r p o t e n t i a l , and c h l o r o p h y l l c o n t e n t o f 1983 and 1984 f o l i a g e from D o u g l a s - f i r s a p l i n g s r e l e a s e d m a n u a l l y i n 1983 a t P o w e l l R i v e r as measured on June 20, 1984. p h o t o s y n t h e s i s l e a f d i f f u s i v e c onductance (mgC0 2'dm - 2'hr 1) (em's 1 ) Treatment 8 3 1 84 A% 2 83 84 a% June 7 3.7a 4.6a 24* . 17a .13a -24* J u l y 19 4.0a 4.6a 15 .19a .14a -26* Aug. 30 .4d 2.6b 550* .0 9b .15a 21* Dec. 30 2.2b 3.7a 68* .0 9b .08b -11 C o n t r o l 1.0c .8c -20 .0 6b .05b -17 c h l o r o p h y l l c o n t e n t (mg'g x) 83 84 a% June 7 2.32b 1.81b -22* J u l y 19 2 .18b 1.82b -17* Aug. 30 .68d 1.33c 96* Dec. 30 1.76c 1.83b -4 C o n t r o l 3.16a 3.40a 8 Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). 2 P e r c e n t d i f f e r e n c e between 1983 and 1984. * i n d i c a t e s s i g n i f i c a n t d i f f e r e n c e (p<0.05) between f o l i a g e age c l a s s e s . 129 f o l i a g e remained s i g n i f i c a n t l y d i f f e r e n t between t h e August and o t h e r t r e a t m e n t p e r i o d s . The d i u r n a l p a t t e r n o f p h o t o s y n t h e s i s i n t h e 1983 f o l i a g e from t h e P o w e l l R i v e r r e l e a s e t r e a t m e n t s ( F i g . 14a) showed r a p i d drops i n r a t e s from morning measurements f o r t h e August and December t r e a t m e n t s . T h i s p a t t e r n i s s i m i l a r t o what was o b s e r v e d i n t h e f i r s t days a f t e r manual r e l e a s e t r e a t m e n t s a t Haney i n 1983 ( F i g . 9) and 1984 ( F i g . 11). The d i u r n a l p a t t e r n o f p h o t o s y n t h e t i c r a t e f o r t h e 1984 f o l i a g e from t h e P o w e l l R i v e r r e l e a s e t r e a t m e n t s ( F i g . 14b) shows h i g h e r morning v a l u e s f o r a l l t r e a t m e n t s as compared t o t h e 1983 f o l i a g e . L e a f d i f f u s i v e conductance o f t h e 1983 and t h e 1984 f o l i a g e from t h e P o w e l l R i v e r t r e a t m e n t s were s i m i l a r between t r e a t m e n t s , except f o r t h e August r e l e a s e (Table 2 0 ) . The June and J u l y f o l i a g e had showed s i g n i f i c a n t d e c l i n e s i n l e a f d i f f u s i v e conductance between t h e 1983 and 1984 age c l a s s e s . Changes i n c h l o r o p h y l l c o n t e n t between 1983 and 1984 f o l i a g e v a r i e d g r e a t l y . The f o l i a g e from t h e June and J u l y r e l e a s e p e r i o d s b o t h had s i g n i f i c a n t d e c r e a s e s i n c h l o r o p h y l l c o n t e n t i n 1984; t h e August t r e a t m e n t f o l i a g e i n c r e a s e d i n c h l o r o p h y l l c o n t e n t . B. S a p l i n g morphology Changes i n f o l i a g e s p e c i f i c l e a f a r e a t h e g r o w i n g season o f  r e l e a s e Few s i g n i f i c a n t r e d u c t i o n s i n s p e c i f i c l e a f a r e a o c c u r r e d t h e same y e a r as t h e t r e a t m e n t . Only f o l i a g e from Release type manual release control Time (hr) Time (hr) F i g u r e 14a-b. D i u r n a l p a t t e r n s o f p h o t o s y n t h e t i c photon f l u x d e n s i t y (PPFD), a t m o s p h e r i c vapor p r e s s u r e d e f i c i t (D) , l e a f d i f f u s i v e conductance (g-jj , and p h o t o s y n t h e s i s from the 1983 P o w e l l R i v e r r e l e a s e t r i a l s , (a) measured June 20, 1984 on 1983 f o l i a g e , (b) measured June 20, 1984 on 1984 f o l i a g e . Box= June 7, 1983 t r e a t m e n t ; c i r c l e = J u l y 19, 1983 t r e a t m e n t ; t r i a n g l e ^ August 30, 1983 t r e a t m e n t ; diamond= December 27, 1984 t r e a t m e n t ; s o l i d dot= u n t r e a t e d c o n t r o l . t h e 1983 May manual and t h e 1984 June manual t r e a t m e n t s d e c l i n e d i n s p e c i f i c l e a f a r e a by t h e end o f t h e f i r s t g r o w i n g season a f t e r r e l e a s e (Table 2 1 ) . Changes i n growth two g r o w i n g seasons a f t e r r e l e a s e a. 1983 Haney e x p e r i m e n t s T a b l e 22 shows t h a t s i g n i f i c a n t d e c r e a s e s i n s p e c i f i c l e a f a r e a o c c u r r e d i n f o l i a g e o f t h e August manual and h e r b i c i d e t r e a t m e n t s between 1983 and 1984. The p a t t e r n s s i g n i f i c a n t d i f f e r e n c e s between 1984 measurements were i d e n t i c a l between s p e c i f i c l e a f a r e a , r e l a t i v e l e a f a r e a growth r a t e , and shoot t o r o o t r a t i o . Where t h e manual t r e a t m e n t s were d i f f e r e n t from t h e h e r b i c i d e t r e a t m e n t s , b o t h were d i f f e r e n t from t h e c o n t r o l . I n each c h a r a c t e r i s t i c , t h e h e r b i c i d e t r e a t m e n t gave i n t e r m e d i a t e v a l u e s . R e l a t i v e d i a m e t e r growth r a t e was g r e a t e s t i n t r e e s from t h e May manual r e l e a s e t r e a t m e n t (Table 2 2 ) . There were no d i f f e r e n c e s between t h e r e l a t i v e d i a m e t e r growth r a t e s o f t h e o t h e r r e l e a s e t r e a t m e n t s , which were a l l s i g n i f i c a n t l y g r e a t e r t h a n t h e c o n t r o l . H e i g h t growth was o n l y s i g n i f i c a n t l y g r e a t e r t h a n t h e c o n t r o l f o r t h e May manual r e l e a s e t r e a t m e n t . b. 1983 P o w e l l R i v e r e x p e r i m e n t The P o w e l l R i v e r r e l e a s e t r e a t m e n t s a l l had s i g n i f i c a n t l y lower 1984 f o l i a g e s p e c i f i c l e a f a r e a t h a n 132 Table 21. Mean values of current year s p e c i f i c leaf area (SLA), for Douglas-fir saplings released at Haney i n 1983 and 1984 measured at the end of the growing season of release. Treatment ( c n r - g x ) — 1983 — — 1984 — MXMay 89b 2 M June 110b M Aug. 188a M July 168a H May 173a M Aug. 175a H Aug. 184a M Sept. 184a Control 170a H June 162a H July 178a H Aug. 182a H Sept. 169a Control 176a 1 Manual treatment (M), herbicide treatment (H), control (C) . ? Mean values within a column followed with d i f f e l e t t e r s 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) 133 Table 22. Mean values of s p e c i f i c l e a f area (SLA), r e l a t i v e l e a f growth rate (RLGR), r e l a t i v e diameter growth rate (RDGR), r e l a t i v e height growth rate (RHGR), and shoot to root r a t i o (S/R) for Douglas-fir saplings released at Haney in 1983 and measured at the end of the 1984 growing season. SLA ^ G R _ i Treatment (cm2*g • ) (<?'yr 9" ) (mirryr 'mm ) a% M1May 72c 2 -19 3 1.66a .89a M Aug. 79c -58* 1.72a .62b H May 111b -36* 1.12b .52b H Aug. 123b -33* 1.21b .41b Control 183a 8 .45c .31c RHGR S/R (cirryr 1 • cm 1) (g'g ) M May .52a 3.1c M Aug. .34b 3.5c H May .42ab 4.1b H Aug. .45ab 4.3b Control .25b 5.6a Manual treatment (M), herbicide treatment (H), untreated control (C). p Mean values within a column followed with d i f f e r e n t l e t t e r s 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). 3 Percent difference between 1983 (Table 22) and 1984. * indicates s i g n i f i c a n t difference (p<0.05) between foliage age classes. 134 c o n t r o l a t t h e end o f t h e 1984 growing season (Table 2 3 ) . R e l a t i v e l e a f growth r a t e and r e l a t i v e d i a m e t e r growth r a t e b o t h showed t h e g r e a t e s t i n c r e a s e s i n t h e June r e l e a s e , f o l l o w e d by t h e J u l y t r e a t m e n t . N e i t h e r r e l a t i v e l e a f a r e a growth r a t e nor r e l a t i v e d i a m e t e r growth r a t e f o r t h e August r e l e a s e were g r e a t e r t h a n t h e c o n t r o l . There were no s i g n i f i c a n t d i f f e r e n c e s between t h e r e l a t i v e h e i g h t growth r a t e s o f any o f t h e r e l e a s e t r e a t m e n t s and t h e c o n t r o l . 135 Table 23. Mean values of s p e c i f i c leaf area (SLA) of 1984 foliage, r e l a t i v e leaf growth rate (RLGR), r e l a t i v e diameter growth rate (RDGR), and r e l a t i v e height growth rate (RHGR) for Douglas-fir saplings released manually at Powell River i n 1983 and measured at the end of the 1984 growing season. Release § L A _ i RLGR RDGR date (cm2*g ) (g'yr ^'g ^ ) (mm'yr 1,mm 1) June 7 87c 1 1.48a .55a July 19 90bc .80b .38b Aug. 30 112b .32c .18c Control 150a .30c .25c RHGR (cm'yr "cm ) June 7 .39a July 19 .51a Aug. 30 .4 6a Control .30a Mean v a l u e s w i t h i n a column f o l l o w e d w i t h d i f f e r e n t l e t t e r s a r e 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). 136 DISCUSSION A. E f f e c t o f t r e a t m e n t and t i m i n g on r e l e a s e response The s u p p r e s s e d D o u g l a s - f i r i n t h e s e r i e s o f e x p e r i m e n t s p r e s e n t e d here showed an a b i l i t y t o r a p i d l y u t i l i z e i n c r e a s e s i n l i g h t made a v a i l a b l e by r e l e a s e . However, t h e t i m i n g o f t h e r e l e a s e t r e a t m e n t i n r e l a t i o n t o season had d i s t i n c t consequences f o r t h e c o n t i n u e d maintenance o f e l e v a t e d p h o t o s y n t h e t i c r a t e s and achievement o f i n c r e a s e d growth. The a c c l i m a t i o n o f s u p p r e s s e d t r e e s t o r e l e a s e c o n d i t i o n s v a r i e d a c c o r d i n g t o t h e r a t e , e x t e n t and t i m i n g o f s p e c i f i c changes. Treatment and t i m i n g b o t h had an e f f e c t on t h e r e l a t i o n s h i p between t h e p h y s i o l o g i c a l and m o r p h o l o g i c a l c h a r a c t e r i s t i c s measured. Rate and e x t e n t o f a c c l i m a t i o n a f t e r r e l e a s e R e s u l t s from th e manual r e l e a s e t r e a t m e n t s showed, as o t h e r s have ( K e l l e r and Tregunna, 197 6; Lonneburg e t a l . , 1985; Hatch e t a l . , 1969), t h a t t h e i n i t i a l changes i n t h e p h y s i o l o g y o f p l a n t s s w i t c h e d from a low t o a h i g h l i g h t e nvironment can be r a p i d . Changes i n l e a f d i f f u s i v e c o nductance l a g g e d a day o r two b e h i n d changes i n p h o t o s y n t h e t i c r a t e , d e s p i t e changes i n l e a f water p o t e n t i a l and c h l o r o p h y l l c o n t e n t i n manual r e l e a s e t r e a t m e n t s (Tables 13, 15, 16). Sampling was t o o i n f r e q u e n t t o d e t e c t t h e f u l l sequence o f response i n t h e h e r b i c i d e t r e a t m e n t s , but when i n c r e a s e s i n p h o t o s y n t h e t i c r a t e were measured ( u s u a l l y a f t e r about one month), l e a f d i f f u s i v e conductance had i n c r e a s e d , but not l e a f water p o t e n t i a l . Powles (1984) summarized e v i d e n c e which s u g g e s t s t h a t t h e r a t e and e x t e n t o f l i g h t a c c l i m a t i o n i s g r e a t e r i n t h e absence o f m o i s t u r e s t r e s s . The r e l a t i v e l y lower m o i s t u r e s t r e s s o f t h e h e r b i c i d e t r e a t m e n t s compared t o t h e manual t r e a t m e n t s may have been i m p o r t a n t i n a l l o w i n g f o l i a g e on h e r b i c i d e r e l e a s e d s a p l i n g s t o a c c l i m a t e t o a g r e a t e r e x t e n t t o t h e r e l e a s e c o n d i t i o n s (Table 19). D i f f e r e n c e s i n t h e st a g e o f l e a f development may have been i m p o r t a n t i n l i m i t i n g t h e re s p o n s e o f f o l i a g e i n r e l e a s e t r e a t m e n t s conducted i n t h e l a t t e r p a r t o f t h e growing season (Tables 17, 18, and 2 0 ) . The a b i l i t y o f l e a v e s t o a c c l i m a t e t o a d i f f e r e n t l i g h t regime v a r y w i t h t h e degree o f d i f f e r e n t i a t i o n o f t h e i n d i v i d u a l l e a v e s o r p a r t o f l e a f . P e a r c e and Lee (1969), and J u r i k e t a l . (1979) found t h a t t h e g r e a t e s t p o t e n t i a l f o r l i g h t a c c l i m a t i o n was when l e a v e s were e x p a n d i n g . P r i o u l e t a l . (1980) found t h a t t h e magnitude o f t h e m o d i f i c a t i o n s p o s s i b l e when l e a v e s a re exposed t o a d i f f e r e n t l i g h t i n t e n s i t y v a r i e d w i t h t h e stage o f development, and t h e s p e c i f i c p h y s i o l o g i c a l o r s t r u c t u r a l p arameter c o n s i d e r e d . Changes i n t h e environment as a r e s u l t o f t h e manual r e l e a s e t r e a t m e n t s were extreme compared t o changes i n most p u b l i s h e d r e p o r t s s t u d y i n g a c c l i m a t i o n o f shade f o l i a g e t o i n c r e a s e d l i g h t i n t e n s i t y . However, t h e r a t e s a t which p h y s i o l o g i c a l changes o c c u r r e d i n r e l e a s e d s a p l i n g s were 138 si m i l a r to those observed i n studies i n more controlled environments with a variety of plants (Keller and Tregunna, 1976; Lonneburg et a l . , 1985; Hatch et a l . , 1969). Response of sapling photosynthesis, water re l a t i o n s and  chlorophyll content to release When any i n i t i a l release response was detectable, photosynthetic rates were higher than the c o n t r o l . Saplings released with the manual treatment early i n the growing season maintained and actually continued to increase the elevated photosynthetic rate measured following release. This trend represented an increasing acclimation of saplings to t h e i r new environment. In contrast, those saplings released manually l a t e r in the growing season tended to have constant or d e c l i n i n g photosynthetic rates over time. This i n a b i l i t y to increase or maintain photosynthesis suggests that the e f f e c t s of photoinhibition were more dominant than acclimation. Differences i n the response of manual treatments r e f l e c t e d s i g n i f i c a n t reductions i n the a b i l i t y of the suppressed saplings to acclimate to rapid and major changes i n the unshaded condition in the second half of the growing season. Conifer responses to the herbicide treatment were less dependent on treatment timing than were the manual treatments. Response was closely correlated to increases in the l i g h t environment as the red alder canopy defoliated. However, without comparative photosynthetic measurements 139 between saplings from the treatments under con t r o l l e d conditions, differences i n capacity at a given time cannot be determined. A lowering of the s u s c e p t i b i l i t y of the released trees to mid-day photosynthetic rate reductions through time allowed average photosynthetic rates to increase i n the early season manual release treatments and the herbicide treatments. Data given i n Figure 12a and Tables 17 and 18 show that reductions i n l e a f water potentials and increased l e a f d i f f u s i v e conductance accompanied reduced tendency towards photosynthetic rate declines. This suggests that water stress was central to the diurnal fluctuations i n the observed photosynthetic rate. In general, the r e s u l t s from a l l release treatments show that leaf d i f f u s i v e conductance i n released Douglas-fir declines with increasing atmospheric moisture demand, and that these reductions i n d i f f u s i v e conductance coincide with a lowering of photosynthetic rate. However, K e l l e r and Tregunna (197 6) found that when suppressed western hemlock seedlings were rapidly exposed to an unshaded environment, l e a f conductance did not decline, to the severe detriment of l e a f water p o t e n t i a l . K e l l e r and Tregunna (197 6) suggested that shade foliage of released hemlock maintains r e l a t i v e l y high leaf conductance to maintain a favorable i n t e r n a l C O 2 concentration to support the higher possible photosynthetic rates r e s u l t i n g from the increase i n l i g h t . Bunce (1981) found that the s e n s i t i v i t y of leaf conductance to change in 140 v a p o r p r e s s u r e d e f i c i t was n e g a t i v e l y c o r r e l a t e d w i t h t h e l e n g t h o f t h e r o o t system p e r u n i t o f p l a n t a r e a . I t i s r e a s o n a b l e t o h y p o t h e s i z e t h a t t h e e n l a r g e d r o o t systems on s a p l i n g s from th e e a r l y r e l e a s e t r e a t m e n t s reduced s u s c e p t i b i l i t y t o water s t r e s s and t h u s mid-day p h o t o s y n t h e t i c d e c l i n e s i n t h o s e t r e a t m e n t s . S a p l i n g s r e l e a s e d i n August o f 1983 a t b o t h Haney and P o w e l l R i v e r showed poor r e c o v e r y o ver t i m e from t h e e f f e c t s o f p h o t o i n h i b i t i o n (Tables 19 and 2 0 ) , and t h e low p h o t o s y n t h e t i c r a t e i s a l s o r e f l e c t e d i n t h e poor performance o f t h e f o l l o w i n g y e a r s ' f o l i a g e p h o t o s y n t h e t i c r a t e (Table 20) and r o o t growth (Table 2 2 ) . T h i s s u g g e s t s t h a t r e c o v e r y from t h e e f f e c t s o f p h o t o i n h i b i t i o n i s not a s s u r e d w i t h t h e development o f new f o l i a g e w i t h i n t h e new e n v i r o n m e n t . When p h o t o i n h i b i t i o n was l e s s s e v e r e (Table 13, manual t r e a t m e n t ) , t h e p h o t o s y n t h e t i c performance o f c u r r e n t - y e a r f o l i a g e s l o w l y i n c r e a s e d o ver t i m e . F o l i a g e d e v e l o p i n g t h e y e a r f o l l o w i n g t h e r e l e a s e t r e a t m e n t had a r e l a t i v e l y h i g h p h o t o s y n t h e t i c r a t e , which by t h a t t i m e , t h e p r e v i o u s - y e a r - f o l i a g e c o u l d n e a r l y match. S a p l i n g s i n t r e a t m e n t s t h a t m a i n t a i n e d a p a t t e r n o f h i g h l e a f water p o t e n t i a l and d e c l i n e s i n p h o t o s y n t h e t i c r a t e had c h l o r o p h y l l c o n c e n t r a t i o n s s i g n i f i c a n t l y below t h o s e o f s a p l i n g s i n o t h e r t r e a t m e n t s , perhaps because o f e x t e n s i v e p h o t o o x i d a t i o n f o l l o w i n g p h o t o i n h i b i t i o n . The c h l o r o p h y l l c o n t e n t o f f o l i a g e g e n e r a l l y d e c l i n e s as e x p o s ure t o g r e a t e r l i g h t i n t e n s i t i e s i n c r e a s e s (Boardman 141 1977) . Water s t r e s s g e n e r a l l y i s t h o u g h t t o encourage b o t h p h o t o i n h i b i t i o n and p h o t o o x i d a t i o n (Gauhl, 197 6; Osmond, 1983; Powles and Bjorkman, 1983) . Low l e a f water p o t e n t i a l s reduce r a t e s o f pigment f o r m a t i o n (Hemming, 1965; A l b e r t e e t a l . , 1975, 1976). F u r t h e r , s t o m a t a l c o n t r o l can be g r e a t l y r e d u c e d w i t h t h e d e s t r u c t i v e l o s s o f c h l o r o p h y l l (Davies and K o z l o w s k i 1974) , p o s s i b l y p r o v i d i n g a p o s i t i v e feed-back t o low w a t e r p o t e n t i a l s and c o n t i n u e d c h l o r o p h y l l l o s s . F o l i a g e and stem growth response t o r e l e a s e S a p l i n g s r e l e a s e d a f t e r June were u n a b l e t o change f o l i a g e s p e c i f i c l e a f a r e a s i g n i f i c a n t l y u n t i l t h e f o l l o w i n g g r o wing s e a s o n . A l s o , i f f o l i a g e i s damaged (as i n d i c a t e d by p h o t o s y n t h e t i c r a t e and l e a f w a t e r p o t e n t i a l ) , as i n t h e P o w e l l R i v e r August r e l e a s e , i t may i n f l u e n c e t h e f u t u r e a b i l i t y o f t h e t r e e t o produce f o l i a g e t h a t can f u l l y u t i l i z e t h e environment by i n c r e a s e d p h o t o s y n t h e t i c r a t e (Table 2 0 ) , and t h i s w i l l be r e f l e c t e d i n l ower growth (Table 2 3 ) . The a b i l i t y o f f o l i a g e from s a p l i n g s i n t h e e a r l y g r o wing season manual t r e a t m e n t t o d e c r e a s e i n s p e c i f i c l e a f a r e a i s an i n d i c a t i o n t h a t b e f o r e J u l y , c o n t i n u e d l e a f development may a l l o w s t r u c t u r a l change i n response t o e n v i r o n m e n t a l change. J u r i k e t a l . (197 9) showed t h a t l e a f anatomy and p h o t o s y n t h e s i s can be m o d i f i e d d u r i n g e x p a n s i o n o f t h e l e a f t o more a c c u r a t e l y r e f l e c t t h e p r e v a i l i n g l i g h t c o n d i t i o n s . However, P a t t e r s o n (1980) c a u t i o n s t h a t some 142 apparent changes i n s p e c i f i c l e a f a r e a w i t h i n c r e a s e d l i g h t may r e s u l t from weight added by i n c r e a s e d s t a r c h and not i n c r e a s e d l e a f volume. I n c r e a s e s i n we i g h t c o u l d a l s o r e s u l t from a d d i t i o n s o f c u t i c l e d e p o s i t i o n encouraged by h i g h e v a p o r a t i v e c o n d i t i o n s as o b s e r v e d by K e l l e r (1973). Data from t h e 1983 r e l e a s e e x p e r i m e n t s (Table 22) i n d i c a t e g r e a t l y i n c r e a s e d r o o t growth on r e l e a s e d s a p l i n g s . Major s h i f t s i n t h e p h o t o s y n t h e t i c p a r t i t i o n i n g ( S i l v i u s , 1979) and biomass a l l o c a t i o n ( B r i x , 1967; Webb, 1977) o f p l a n t s accompany t h e t r a n s i t i o n t o i n c r e a s e d l i g h t i n t e n s i t i e s . Shaded D o u g l a s - f i r produce and m a i n t a i n f o l i a g e a t t h e expense o f r o o t s (Drew and F e r r e l l , 1977; Webb, 1977). Because l i g h t s u p p r e s s e d p l a n t s have a l a r g e s h o o t - t o - r o o t r a t i o , i t has been s u g g e s t e d t h a t a poor growth response by r e l e a s e d t r e e s may be due t o m o i s t u r e s t r e s s ( H e r r i n g and E t h e r i d g e , 1976; K o t o r , 1972). S t u d i e s from c o n t r o l l e d environments s u p p o r t t h i s h y p o t h e s i s (Magnussen, 1981; Magnussen and P e s c h l , 1981). B e f o r e r e l e a s e , r o o t systems were c o n c e n t r a t e d near t h e s u r f a c e o f the m i n e r a l s o i l and s a p l i n g s c o u l d be e a s i l y l o d g e d . Root growth f o l l o w i n g r e l e a s e would a l l o w s a p l i n g s t o r e s i s t l o d g i n g , w h i c h would be i m p o r t a n t t o t h e c o n t i n u e d s u r v i v a l o f b o t h t h e m a n u a l l y - r e l e a s e d t r e e s i n r e s i s t i n g i n c r e a s e d exposure t o wind and p r e c i p i t a t i o n , and a l s o t o t h e h e r b i c i d e - r e l e a s e d s a p l i n g s i n a v o i d i n g damage when t h e o v e r s t o r y b e g i n s t o break-up and l o d g e . 143 L a r g e r r o o t i n g s u r f a c e s are p r o b a b l y i m p o r t a n t i n i n c r e a s i n g t h e s u p p l y o f m o i s t u r e t o s u p p o r t t h e g r e a t e r l e a f d i f f u s i v e conductance (thus p h o t o s y n t h e t i c r a t e s ) and growth r a t e s o b s e r v e d i n t h e p o s i t i v e response t o c o n i f e r r e l e a s e . An i n c r e a s e i n r o o t growth i s perhaps a p r e r e q u i s i t e t o i n c r e a s e s i n l e a f a r e a growth r a t e and d i a m e t e r growth (Table 2 2 ) . Where t r e a t m e n t s r e s u l t e d i n low p h o t o s y n t h e t i c r a t e and l e a f water p o t e n t i a l , i t was o b s e r v e d t h a t t h e o l d e r f o l i a g e age c l a s s e s would b e g i n t o senesce (e.g. August 1983, September 1984 a t Haney and P o w e l l R i v e r August 1983). L e a f a b s c i s s i o n a f t e r c o n i f e r r e l e a s e has been r e p o r t e d by o t h e r s ( B e l l o n and K o w a l s k i , 1968; Gordon, 1973; Tucker and Emmingham, 1977). Tucker and Emmingham (1977) s u g g e s t e d t h a t r e d u c t i o n s i n l e a f a r e a may be an i m p o r t a n t r e sponse t o h e l p a d j u s t t h e c o n i f e r shoot t o r o o t r a t i o t o i n c r e a s e d e v a p o r a t i v e demand. The p h y s i o l o g i c a l c o n d i t i o n a f t e r r e l e a s e had an impact on t h e f u t u r e growth o f s a p l i n g s . Those t r e a t m e n t s w i t h t r e e s t h a t showed poor p h o t o s y n t h e t i c a c t i v i t y and low l e a f water p o t e n t i a l s (Tables 17 and 20) a l s o showed a poor a b i l i t y t o i n c r e a s e i n d i a m e t e r and l e a f a r e a two seasons a f t e r r e l e a s e (Tables 22 and 2 3 ) . Hoyer and B e l z (1984) a l s o s u g g e s t e d a d e l a y i n t h e r e l e a s e response o f s u p p r e s s e d D o u g l a s - f i r r e l e a s e d m a n u a l l y from r e d a l d e r t h r o u g h o u t t h e growing season. P r o d u c t i o n o f new l e a f a r e a i s p a r t i c u l a r l y i m p o r t a n t i f a c c l i m a t i o n o f shade f o l i a g e i s l i m i t e d a f t e r r e l e a s e . 144 B u i l d i n g o f s u n - a c c l i m a t e d f o l i a g e a r e a on t r e e s r e l e a s e d l a t e i n t h e growing season i s not o n l y handicapped by poor c u r r e n t - y e a r f o l i a g e p h o t o s y n t h e t i c a c t i v i t y , but a l s o by d e t e r m i n a t e buds which r e f l e c t e i t h e r t h e shaded c o n d i t i o n ( i f s e t b e f o r e t h e r e l e a s e t r e a t m e n t ) , where l e a f a r e a growth r a t e s a r e low, o r t h e p h y s i o l o g i c a l s t r e s s o f r e l e a s e ( i f buds d e v e l o p e d a t t h e t i m e o f r e l e a s e ) . The g e n e r a l l y more c o n s i s t e n t p h y s i o l o g i c a l s t a t u s o f s a p l i n g s f o l l o w i n g r e l e a s e i n t h e h e r b i c i d e r e l e a s e t r e a t m e n t s i s r e f l e c t e d i n t h e more c o n s i s t e n t and i n t e r m e d i a t e growth i n c r e a s e s f o l l o w i n g r e l e a s e . S t e i n (1985) found t h a t s u p p r e s s e d D o u g l a s - f i r r e l e a s e d w i t h h e r b i c i d e s show i n t e r m e d i a t e growth t h r e e y e a r s a f t e r r e l e a s e as compared w i t h manual r e l e a s e and c o n t r o l t r e e s . B. S e l e c t i o n o f r e l e a s e t r e a t m e n t and t i m i n g . The r e l a t i v e response o f s a p l i n g s t o manual and h e r b i c i d e r e l e a s e t r e a t m e n t s was h i g h l y dependent on t h e season o f t h e t r e a t m e n t . B o t h p h y s i o l o g i c a l and growth d a t a s t r o n g l y s u p p o r t th e c o n c l u s i o n t h a t s a p l i n g s r e l e a s e d e a r l y i n t h e growing season responded more f a v o r a b l y t o manual r e l e a s e t h a n t h o s e r e l e a s e d m a n u a l l y l a t e r i n t h e g r o w i n g season or t h a n t h o s e r e l e a s e d by h e r b i c i d e s . However, a t some p o i n t midway t h r o u g h t h e g rowing season, r e l e a s e r e s p o n s e d i m i n i s h e d t o t h e p o i n t a t which i n i t i a l growth was m a r g i n a l and d e l a y e d , and s u r v i v a l o f t h e r e l e a s e d t r e e s may have been t h r e a t e n e d . The h e r b i c i d e - r e l e a s e t r e a t m e n t , 145 a l t h o u g h r e s u l t i n g i n s l o w e r response because of t h e d e l a y i n t r e a t m e n t e f f e c t on environment, gave more p r e d i c t a b l e r e l e a s e r e s p o n s e s . The s e l e c t i o n o f a r e l e a s e t r e a t m e n t s h o u l d c o n s i d e r t h e t r e a t m e n t t i m i n g and a l s o t h e degree and t h e d u r a t i o n o f c r o p t r e e s u p p r e s s i o n . As t h e s e e x p e r i m e n t s showed, the l o n g e r t h e s a p l i n g s d e v e l o p e d under t h e canopy t h r o u g h t h e g r owing season, t h e more c r i t i c a l t h e r e l e a s e method. D o u g l a s - f i r t h a t had not been s u p p r e s s e d f o r as l o n g (eg. l e s s t h a n 5 t o 6 y e ars) may not have had such a s e v e re r e l e a s e r e s p o n s e , because t h e magnitude o f a c c l i m a t i o n would not have been as g r e a t ; t h e l e v e l o f s u p p r e s s i o n (degree o f shading) c o u l d d e t e r m i n e t h e amount o f a c c l i m a t i o n r e q u i r e d . More i n f o r m a t i o n on t h e i n f l u e n c e o f degree and d u r a t i o n o f s h a d i n g on t h e a c c l i m a t i o n p r o c e s s c o u l d p r o v i d e f o r i n c r e a s e d p r e d i c t i v e a b i l i t y and c o n f i d e n c e i n a n t i c i p a t i n g r esponse t o t h e t i m i n g o f t r e a t m e n t s . C h a p t e r s 2 and 3 p r o v i d e some o f t h i s i n f o r m a t i o n . The e x a m i n a t i o n o f l e a f a r e a o f s u c c e s s i v e l e a f age c l a s s e s , t h e s h o o t - t o - r o o t r a t i o , o r t h e r a t i o o f stem d i a m e t e r t o stem h e i g h t c o u l d g i v e e v i d e n c e as t o t h e h i s t o r y o f s a p l i n g s ' s u p p r e s s i o n . The s a p l i n g s t h a t were r e l e a s e d a t Haney were c o n s i d e r e d s e v e r e l y s u p p r e s s e d and had been f o r a c o n s i d e r a b l e t i m e . T h e i r r e l e a s e r e s ponse may r e p r e s e n t an extreme example o f r e l e a s e r e s p o n s e . However, t h e P o w e l l R i v e r t r i a l s i l l u s t r a t e how s i m i l a r r e s p o n s e s can o c c u r i n 146 s a p l i n g s w i t h a s h o r t e r h i s t o r y and l e s s e r degree o f s u p p r e s s i o n . The phenology o f t h e c o m p e t i t o r and i t s s u s c e p t i b i l i t y t o t h e c o n t r o l t r e a t m e n t i s t y p i c a l l y t h e g r e a t e s t c o n s i d e r a t i o n i n t h e s e l e c t i o n o f manual t r e a t m e n t t i m i n g . Hoyer and B e l z (1984) r e p o r t e d on a t r e a t m e n t window w i t h t h e aim o f m i n i m i z i n g r e d a l d e r r e s p r o u t i n g a f t e r manual c u t t i n g , and t h u s m a x i m i z i n g t h e p e r i o d t h a t young c o n i f e r s would be f r e e from l i g h t c o m p e t i t i o n . Based on a s e r i e s o f r e d a l d e r c u t t i n g t r i a l s , t h e s e a u t h o r s s u g g e s t e d t h a t t h e optimum p e r i o d f o r r e d a l d e r c u t t i n g was between e a r l y J u l y and t h e end o f August. Treatments on e i t h e r s i d e o f t h i s p e r i o d f a i l e d t o p r o v i d e as good a c o n t r o l o f a l d e r s p r o u t i n g . When h e r b i c i d e s are a p p l i e d , s u s c e p t i b i l i t y o f t h e c o n i f e r c r o p i s o f immediate i m p o r t a n c e , because o f t h e h a z a r d o f damaging newly expanding f o l i a g e . Thus, h e r b i c i d e t r e a t m e n t t i m i n g i s u s u a l l y much more c o g n i z a n t o f c r o p phenology. S u c c e s s f u l c o n i f e r r e l e a s e o b v i o u s l y r e q u i r e s c o n s i d e r a t i o n o f t h e b i o l o g y o f b o t h t h e c r o p and c o m p e t i t o r . Cost and e f f e c t i v e n e s s o f r e l e a s e t r e a t m e n t a r e a l s o o f i m p o r t a n c e , but r e l i a b l e d a t a are s c a r c e . I n a r a r e s t u d y t h a t compares the c o s t o f r e l e a s e t r e a t m e n t s , M i l l e r (1984) found t h a t t h e c o s t o f c h a i n saw b r u s h i n g was l e s s t h a n e i t h e r b a s a l s p r a y i n g o r stem i n j e c t i o n w i t h h e r b i c i d e s i n an A p p a l a c h i a n hardwood f o r e s t . Manual t r e a t m e n t s a l s o have t h e advantage o f ease i n i d e n t i f y i n g any u n t r e a t e d a r e a s . 147 However, manual c u t t i n g o f a l d e r u s u a l l y r e s u l t s i n s p r o u t i n g which can q u i c k l y r e e s t a b l i s h c o m p e t i t i o n f o r l i g h t ( H a r r i n g t o n 1984, Hoyer and B e l z (1984) . I n manual t r e a t m e n t s o f r e d a l d e r , r e t u r n t r e a t m e n t s may be r e q u i r e d , e s p e c i a l l y i f c o n i f e r r e l e a s e response i s d e l a y e d . A d d i t i o n a l t r e a t m e n t s may a l s o be r e q u i r e d w i t h h e r b i c i d e i n j e c t i o n s s i n c e i n d i v i d u a l t r e e s may be m i s s e d o r t h e a p p l i c a t i o n may be i n s u f f i c i e n t t o p r o v i d e t h e d e s i r e d l e v e l o f c o n t r o l . C. The e c o l o g i c a l i m p l i c a t i o n s o f r e l e a s e t r e a t m e n t s The e c o l o g i c a l i m p l i c a t i o n s o f t h e t y p e and t i m i n g o f r e l e a s e t r e a t m e n t s r e l a t e t o t h e r a t e a t which e n v i r o n m e n t a l p r o c e s s e s are changed and t h e c a p a b i l i t y o f t h e c r o p t r e e s t o expand t h e i r c a n o p i e s and r o o t s t o occupy t h e new space and c a p t u r e u n u t i l i z e d r e s o u r c e s . The removal o f a r e d a l d e r canopy not o n l y i n c r e a s e s l i g h t , but may i n c r e a s e s o i l m o i s t u r e t h r o u g h reduced canopy e v a p o t r a n s p i r a t i o n and p r o b a b l y r e s u l t s i n i n c r e a s e s i n a v a i l a b l e s o i l n u t r i e n t s . B i g l e y and Kimmins (1983) showed t h a t t h e removal o f a r e d a l d e r canopy w i t h h e r b i c i d e s r e s u l t e d i n h i g h e r s o i l m i n e r a l i z a t i o n r a t e s and i n c r e a s e d c o n c e n t r a t i o n s o f a v a i l a b l e n u t r i e n t s w i t h i n t h e s o i l . I f c o n i f e r r e l e a s e r e s p onse i s d e l a y e d , t h e p u l s e o f i n c r e a s e d n u t r i e n t a v a i l a b i l i t y which may o n l y l a s t one or two g r owing seasons may be l o s t from t h e s i t e , and w i l l perhaps be u t i l i z e d by p o t e n t i a l c o m p e t i t o r s r a t h e r t h a n by t h e r e l e a s e d t r e e s . 148 The l o n g e r t h e d e l a y , t h e g r e a t e r t h e chance t h a t s p r o u t i n g a l d e r o r o t h e r s p e c i e s w i l l e s t a b l i s h a dominant canopy and c o n t i n u e t h e growth s u p p r e s s i o n o f t h e D o u g l a s - f i r . The r a t e o f canopy removal may a l s o i n f l u e n c e t h e e c o l o g i c a l s u c c e s s i o n o f non-crop s p e c i e s . Shade t o l e r a n t g r a s s e s were o b s e r v e d t o i n c r e a s e under h e r b i c i d e t r e a t e d r e d a l d e r c a n o p i e s a t Haney, whereas Rubus u r s i n u s and Rubus  p a r v i f l o r u s r e a d i l y e s t a b l i s h e d i n openings c r e a t e d by t h e manual t r e a t m e n t s . C o n t r o l o f non-crop s p e c i e s c o m p o s i t i o n may be an i m p o r t a n t c o n s i d e r a t i o n where c o n i f e r r e l e a s e i s c o n s i d e r e d i n areas where w i l d l i f e needs s h o u l d be w e i g h t e d h e a v i l y , o r where p o t e n t i a l c o m p e t i t o r s a re o f c o n c e r n . CONCLUSIONS 1. S u p p r e s s e d D o u g l a s - f i r r a p i d l y b e g an a c c l i m a t i o n t o c o n d i t i o n s c r e a t e d by r e l e a s e t r e a t m e n t s . 2. The t i m i n g o f t h e r e l e a s e t r e a t m e n t s i n r e l a t i o n t o t h e g r o w i n g s e a s o n d e t e r m i n e d f u t u r e p h y s i o l o g i c a l c o n d i t i o n and g r o w t h r a t e . 3. M a n u a l r e l e a s e t r e a t m e n t s a f t e r June s t r o n g l y showed t h e e f f e c t s o f p h o t o i n h i b i t i o n . 4. H e r b i c i d e t r e a t m e n t r e s p o n s e was l e s s d e p e n d e n t on t r e a t m e n t t i m i n g t h a n manual r e l e a s e . 5. L a r g e i n c r e a s e s i n r o o t g r o w t h were i n d i c a t i v e o f s a p l i n g s t h a t h a d t h e g r e a t e s t p o s i t i v e r e s p o n s e t o r e l e a s e . 6 . H e i g h t g r o w t h was a p o o r i n d i c a t o r o f i n i t i a l r e l e a s e r e s p o n s e . 150 CHAPTER 5 APPLICATION OF FINDINGS AND CONCLUSIONS F o r e s t v e g e t a t i o n management has emerged as a r e s e a r c h p r i o r i t y and as a r e c o g n i z e d s u b d i s c i p l i n e o f f o r e s t r y . W i t h t h i s a t t e n t i o n has come a p r o f u s i o n o f new i n f o r m a t i o n on t h e r e l a t i o n s h i p between young c o n i f e r s and a s s o c i a t e d non-crop v e g e t a t i o n . I n o r d e r t o be o f p o t e n t i a l b e n e f i t t o managers, t h i s i n f o r m a t i o n s h o u l d s t r e n g t h e n t h e e c o l o g i c a l b a s i s o f t h e v e g e t a t i o n management p r o c e s s . S o l v i n g t h e problems f a c i n g l a n d managers due t o c o m p e t i t i o n from non-cr o p v e g e t a t i o n i n young p l a n t a t i o n s i n v o l v e s t h r e e phases: 1) t h e r e c o g n i t i o n o f a weed problem, 2) p r e d i c t i o n o f f u t u r e c o m p e t i t i v e outcomes and 3) s e l e c t i o n and a p p l i c a t i o n o f t r e a t m e n t s . The f o l l o w i n g d i s c u s s e s t h e s e t h r e e phases and r e l a t e s them t o i n f o r m a t i o n p r e s e n t e d i n t h e p r e v i o u s t h r e e c h a p t e r s . 1. R e c o g n i t i o n o f t h e e x i s t e n c e o f a problem. The r e c o g n i t i o n o f what l e v e l o f c a n o p y / r o o t encroachment c o n s t i t u t e s s u f f i c i e n t c o m p e t i t i o n t o war r a n t c o n t r o l , remains p r i m a r i l y s u b j e c t i v e . Competing v e g e t a t i o n i n f o r e s t p l a n t a t i o n s changes c o n s i d e r a b l y t h r o u g h t i m e and th e t r a n s f e r o f i n f o r m a t i o n from p l a c e t o p l a c e i s r i s k y . Many p u b l i s h e d r e p o r t s i n f o r e s t v e g e t a t i o n management s t i l l g i v e poor d e s c r i p t i o n s o f t h e c o m p e t i t i v e environment s t u d i e d . A major o b s t a c l e t o t h e r e c o g n i t i o n o f s i g n i f i c a n t 151 c o m p e t i t i v e s i t u a t i o n s i s our i n a b i l i t y t o d e s c r i b e t h e i n f l u e n c e o f competing v e g e t a t i o n on c r o p t r e e s . Because o f t h e immense v a r i a t i o n i n s p e c i e s and s i t e c o m b i n a t i o n s t h a t o c c u r , r e c o g n i t i o n o f p o t e n t i a l problems are dependent on t h e e x t e n t o f e x p e r i e n c e t h e i n d i v i d u a l a s s e s s i n g t h e p l a n t a t i o n . An u n d e r s t a n d i n g o f t h e canopy growth and l i g h t environment r e l a t i o n s h i p s d e s c r i b e d i n t h e t h e s i s may h e l p p e r s o n s t o b e t t e r a s s e s s t h e c o m p e t i t i v e n a t u r e o f d e c i d u o u s c a n o p i e s . In d e s c r i b i n g t h e c o m p e t i t i o n environment, i t has been shown t h a t l i g h t q u a l i t y and q u a n t i t y can v a r y t o some e x t e n t i n d e p e n d e n t l y and t h a t shade c h a r a c t e r i s t i c s , i n c l u d i n g t h e s e a s o n a l c y c l e , may be s p e c i e s s p e c i f i c . M i x t u r e s o f s p e c i e s would p r e s e n t c o n s i d e r a b l e c o m p l e x i t y f o r d e s c r i p t i v e p u r p o s e s . I t i s c l e a r from r e s u l t s p r e s e n t e d i n t h i s t h e s i s t h a t t h e Beer-Lambert law a p p l i e d t o t h e canopy as a whole i s a p oor d e s c r i p t i o n o f t h e s u c c e s s i o n o f environments a c o n i f e r s e e d l i n g would e n c o u n t e r w h i l e growing t h r o u g h a salmonberry canopy. A s i n g l e s a l m o n b e r r y canopy has h o r i z o n s o f v e r y d i f f e r e n t c o m p o s i t i o n and a d e s c r i p t i o n o f them s h o u l d be a b l e t o r e f l e c t t h e h e t e r o g e n e i t y i n s p e c i f i c l e a f a r e a , l e a f a n g l e , and d i s t r i b u t i o n t h a t o c c u r s w i t h i n t h e canopy. The r e s u l t s g i v e n here show t h a t a s p e c i f i c h e i g h t i n t h e canopy w i l l have a s u c c e s s i o n o f d i f f e r e n t e n v i r onments o v e r t i m e . S i n c e t h e l i g h t environment at a g i v e n p o s i t i o n w i t h i n a deciduous canopy changes t h r o u g h t i m e , s u r v e y 152 methods which e s t i m a t e coverage and canopy encroachment s h o u l d c o n s i d e r t h e v e r t i c a l d i s t r i b u t i o n o f t h e c a n o p i e s t h e y a r e d e s c r i b i n g . Changes i n l i g h t q u a l i t y w i t h canopy development and t h e subsequent e f f e c t on c o n i f e r growth a r e r a r e l y c o n s i d e r e d i n t h e assessment o f deciduous shrub c o m p e t i t i o n . T h i s work has shown t h a t e a r l y growth o f sa l m o n b e r r y c a n o p i e s q u i c k l y e s t a b l i s h shade t h a t has l i g h t q u a l i t y a l t e r e d from t h e unshaded c o n d i t i o n . These r e d u c t i o n s i n l i g h t q u a l i t y may not be c o n s i d e r e d i m p o r t a n t on t h e i r own, but f u t u r e work s h o u l d a l s o examine t h e e f f e c t s o f t h e s e s h i f t s i n l i g h t q u a l i t y on c o n i f e r growth. 2. P r e d i c t i o n o f f u t u r e c o m p e t i t i v e i n t e r a c t i o n s . I n o r d e r t o make d e c i s i o n s c o n c e r n i n g t h e c o n t r o l o f competing v e g e t a t i o n , one must p r e d i c t t h e r e l a t i v e impact o f c o m p e t i t i o n on f u t u r e c u m u l a t i v e growth. An u n d e r s t a n d i n g o f s p e c i e s shade t o l e r a n c e i s v e r y i m p o r t a n t t o a n t i c i p a t i n g c o m p e t i t i v e s i t u a t i o n s . S e l e c t i o n o f c o n i f e r s p e c i e s i s one o f t h e managers' most p o w e r f u l t o o l s i n e s t a b l i s h i n g p l a n t a t i o n s i n a r e a s o f h i g h b r u s h h a z a r d . Use o f grand f i r i n t h e c o a s t a l D o u g l a s - f i r and Western hemlock zones l o o k s v e r y p r o m i s i n g i f a n i m a l damage can be kept i n check. Western hemlock i s a l s o a good a l t e r n a t i v e t o D o u g l a s - f i r , p a r t i c u l a r l y where advance r e g e n e r a t i o n can be u t i l i z e d . C a u t i o n s h o u l d be used when t h e p o t e n t i a l growth i n low l i g h t o f a s p e c i e s i s d e t e r m i n e d from r e p o r t s u s i n g n e u t r a l d e n s i t y shade and/or c o n t i n u o u s shade. The 153 a s s i m i l a t i o n o c c u r r i n g d u r i n g t h e season when deciduous c a n o p i e s a r e l e a f l e s s may a l l o w o v e r t o p p e d s e e d l i n g s t o grow at f a s t e r r a t e s t h a n would be e x p e c t e d from measurements o f t h e l i g h t environment i n summer. Because s h a d i n g i s o f prime i m p o r t a n c e on p r o d u c t i v e s i t e s , t h e p r e d i c t i v e f o c u s i s on t h e r e l a t i v e h e i g h t growth o f b o t h t h e c r o p and c o m p e t i t o r . There i s some e v i d e n c e i n t h e l i t e r a t u r e t h a t p a t t e r n s o f canopy h e i g h t development may d i f f e r by s i t e . In t h e absence o f t e s t e d i n d i c e s o r models, t h e f o r e s t e r must depend on r e c o g n i t i o n and p r e v i o u s knowledge o f s p e c i e s c o m b i n a t i o n s and s p e c i f i c s i t e s . E c o l o g i c a l s i t e t y p i n g s h o u l d h e l p i n s i m p l i f y i n g i n f o r m a t i o n t r a n s f e r and p r o j e c t i n g i n t o t h e f u t u r e f o r a number o f s i l v i c u l t u r a l p r a c t i c e s (e.g. B i g l e y and Henderson, i n p r e s s ) . U n d e r s t a n d i n g d i f f e r e n c e s i n v e g e t a t i o n development can be u s e f u l i n a n t i c i p a t i n g and a s s i g n i n g t r e a t m e n t p r i o r i t i e s . 3. S e l e c t i o n and a p p l i c a t i o n o f t r e a t m e n t s . Much p r o g r e s s has been made i n r e c e n t y e a r s i n t h e a r e a o f t r e a t m e n t t e c h n o l o g y i n v e g e t a t i o n management. New h e r b i c i d e f o r m u l a t i o n s , d e l i v e r y equipment, and t e s t i n g e x p e r i e n c e a l l o w g r e a t e r s p e c i f i c i t y i n r e d u c i n g problem v e g e t a t i o n . C o n t i n u e d development o f b o t h hand and power t o o l s f o r m e c h a n i c a l k i l l i n g o f u n d e s i r e d v e g e t a t i o n i s a l s o v e r y i m p o r t a n t f o r m a i n t a i n i n g s e l e c t i v i t y and f l e x i b i l i t y o f t r e a t m e n t s . 154 R e s u l t s g i v e n h e r e demonstrate one s i d e o f a c o n f l i c t i n t r e a t m e n t t i m i n g s t r a t e g y f o r r e d a l d e r r e l e a s e . My r e s u l t s i n d i c a t e t h a t t h e chances o f poor r e l e a s e response i n c r e a s e o v er t h e growing season. August and September are th e b e s t months t o m a n u a l l y c u t r e d a l d e r t o m i n i m i z e r e s p r o u t i n g ( H a r r i n g t o n , 1984 and Hoyer and B e l z , 1984), but from a p h y s i o l o g i c a l p o i n t o f view, t h i s i s a l s o t h e worst t i m e t o r e l e a s e o v e r t o p p e d D o u g l a s - f i r . I f done p r o p e r l y , manual r e l e a s e s h o u l d be t h e method o f c h o i c e i n most c a s e s . Growth response i s r a p i d and p l a n n i n g , worker t r a i n i n g and s u p e r v i s i o n may be l o w e r . The consequences o f b o t h poor a l d e r s p r o u t i n g c o n t r o l and r e l e a s e t i m i n g have been i l l u s t r a t e d e x p e r i m e n t a l l y a t t h e P o w e l l R i v e r s i t e . A l s o as c o n i f e r a c c l i m a t i o n t o shade i n c r e a s e s (shade f o l i a g e i s more numerous and extreme) one can c o n c l u d e from t h e l i t e r a t u r e t h a t t h e t i m i n g and mode o f r e l e a s e l i k e l y becomes more c r i t i c a l . When o v e r t o p p e d c o n i f e r s a re not y e t showing t h e s i g n s o f s u p p r e s s i o n , g r e a t e r f l e x i b i l i t y i n r e l e a s e method and t i m i n g a re l i k e l y . 155 LITERATURE CITED A l b e r t e , R. S., E.L. F i s c u s and A.W. Waylor. 1975. The e f f e c t s o f water s t r e s s on t h e development o f t h e p h o t o s y n t h e t i c a p p a r a t u s i n green l e a v e s . P l a n t P h y s i o l . 55:317-321. A l b e r t e , R.S., P.R. M c Clure and J.P. Thornber. 1976. P h o t o s y n t h e s i s i n t r e e s , o r g a n i z a t i o n o f c h l o r o p h y l l and p h o t o s y n t h e t i c u n i t s i z e i n i s o l a t e d gymnosperm c h l o r o p l a s t s . P l a n t P h y s i o l . 58:341-344. A l l a r d , H.A. 1947. L i g h t i n t e n s i t y s t u d i e s i n Canaan V a l l e y , WV. C astenea 12:63-74. Anderson, M.C. 1964. S t u d i e s o f t h e woodland l i g h t c l i m a t e ( I I ) S e a s o n a l v a r i a t i o n i n l i g h t c l i m a t e . J . E c o l . 52:643-663. Anderson, M.C. 1966. Stand s t r u c t u r e and l i g h t p e n e t r a t i o n ( I I ) A t h e o r e t i c a l a n a l y s i s . J . A p p l E c o l . 3:41-54. A r a k i , M. 1980. 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Dry m a t t e r p r o d u c t i o n , l e a f a r e a development, and l i g h t i n t e r c e p t i o n o f cowpea l i n e s w i t h b r o a d and narrow l e a f l e t shape. Crop S c i . 22:733-737. W r i g h t , C.J., P.D. W a i s t e r . 1984. L i g h t i n t e r c e p t i o n and f r u i t i n g cane a r c h i t e c t u r e i n t h e r e d r a s p b e r r y grown under annual and b i e n n i a l management. J . H o r t . S c i . 59:395-402. Yim, Y - J , H. Ogawa, and T. K i r a . 1969. L i g h t i n t e r c e p t i o n by stems i n p l a n t communities. Jap. J . E c o l . 19:233-238. Z a v i t k o v s k i , J . 1974. S o l a r r a d i a t i o n measurements i n t h e E n t e r p r i s e R a d i a t i o n F o r e s t , pp 33-45. I n : Rudolph, T.D. ( e d . ) , E n t e r p r i s e R a d i a t i o n F o r e s t . U.S. Atom. Energy Comm. P u b l . TID-26113. Z a v i t k o v s k i , J . 1982. C h a r a c t e r i z a t i o n o f l i g h t c l i m a t e under c a n o p i e s of i n t e n s i v e l y c u l t u r e d h y b r i d p o p l a r p l a n t a t i o n s . A g r i c . Meteor. 25:245-255. Z a v i t k o v s k i , J . and M. Newton. 1971. L i t t e r f a l l and l i t t e r a c c u m u l a t i o n i n r e d a l d e r s t a n d s i n w a s t e r n Oregon. P l a n t and s o i l 35:257-268. Z a v i t k o v s k i , J . , J.G. I s e b r a n d s and D.H. Dawson. 1976. P r o d u c t i v i t y and u t i l i z a t i o n p o t e n t i a l o f s h o r t -r o t a t i o n Populus i n t h e Lake S t a t e s . pp. 392-401. I n : T h i e l g e s , B.A. and S.B. Land ( e d s . ) , P r o c . Symp. E a s t e r n Cottonwood and R e l a t e d S p e c i e s . L o u i s i a n a S t a t e U n i v . 169 APPENDIX 1 Examples o f d a t a a n a l y s i s ( A d d i t i o n a l t a b l e s not p r e s e n t e d i n t h i s appendix are a v a i l a b l e from t h e a u t h o r ) Regressions i n Chapter Anthracene absorbence vs. cumulative light Regression Analysis - Beciprocal model; i/Y = a+bX Dependent variable: 8:ANTHCAL.ABS Independent variable: B:ANTHCAL.MOLIS Standard T Prob. Parameter Estimate Error Wal ue Level Intercept 0.135352 0.0138269 9.73898 2.42029E-14 Slope 0.0345317 7.57676E-4 45.5758 0 Analysis of Variance Source Sum of Squares Df Mean Square F-Ratio Prob. Level Model 10.0754 1 10.0754 "077.1517 00000 Error .310436 64 .004851 Total (Corr.) 10.385797 65 Correlation C oefficient = 0.984941 E-squared = 97.01 percent Stnd. Error of Est. = 0.069646 10 20 30 40 Cumulative l ight (Moles) Leaf area index vs Summer light Regression Analysis - Linear model: Y = a«-bX Dependent variables BsftPP!>2. logsura Independent variable: 3: APP!>2. LAI Standard 7 ?rcb. Parameter Tstiraate Zrrsr Uaiuc Levei Intercept 1.85S62 0.0697905 2S.5437 0 Siope -0.103912 3.33042S-2 -11.7=7= 4.529711-14 Analysis of Variance Source S'JfT: O f Squares Df Mean Square 7-Patio Prob. Level Jtodei 3.04S3S V 9.04il-: L3S.4769S 00000 Errtr 2.417120 37 .05::2: Tctai (Ccrr Ccrrelat ion Coefficient = -0.39333? 8-squared = 78.91 percent Stna. Error of Est. = 0.255553 3 s 3 12 15 2 2 Leaf area index (mm ) Leaf and stem area index vs. Summer light Regression Analysis - Linear model: Y - a+bX Sependent variable: E:APPD2.logsum Independent variable: B:AP?D2.lasa Parameter Estimate Standard Error "T Value Prcb. .Level Intercept Slope 1.94353 -0.09=0757 0.063611? 3.1542E-3 26.3697 -11.7324 0 4.37423E-14 Analysis oi Variance Source Mode: Zrrcr Sum G: Squares Df 3.05114 i .412251 27 Mean Square 3.05114 .C65199 •-Ratio Prcb. 133.92401 Lsve« 00000 Total (Corr t l .462495 38 Ccrrelatlcn Coefficient = -0. S£S57? fi-souared = 78.56 «src=r.t :tnd. Error c- Est. = 0.25524 r-T,. 1.6 * i.2 1 •t-> -§> 0.3 -s_ QJ i — E -" 0.4 ° -I J I J . . . . . . . . . . I I I j I J L 12 16 2 2 Leaf and stem area index (mm ) Stem area index vs. Winter light Regression Analysis - Linear model: Y = a+bX Dependent variable: E:AP?D2.Icgwin Independent variable: SSAPPU2.SAI Standard -T Prob. Parameter Estimate Error Value Level Intercept 1.96071 3.071O1Z-3 216.152 0 Slope -0.212425 0.0157662 -13.5352 6.65134E-16 Analysis cf '.'ar i anoe Source Sum of Squares Df Mean Square F-?.atio Prob. Level rtcdel .2=3=4 1 .35264 183.20204 .00000 Error .073441 37 .00123: Total (Corr.l .437076 33 Correlatton Coe fficient = -0. 912125 F.-squared = 83. 20 percent Stnd. Error of Est. = 0.0445521 2 — 0 0.4 0.8 1.2 l.S Stem area index (m 'm ) Cumulative leaf area index vs. Red to Far-red r a t i o Regression Analysis - Exponential model: Y = exp(arbX) Dependent variable: 2;7fi33.:eta Independent variable: B:7S23.iai. Standard T . Prob. Parameter Estimate Srrcr Value Level Intercept -0.172523 0.100913 -1.70953 0.107952 Stops -0.134514 0.0120259 -10.3266 3.263371-3 Analysis cf Variance Source Sum at' Squares l( Mean Square •-Patio Proc. Level Mode I 3.44353 1 3.44363 105.53959 .00000 Grrcr 1.133390 15 .079226 Total (Corr ) 9.637016 16 Corre! at i on Coefficient = -0.986315 E-squared = 67.67 percent Stria. Error of Est. = 0.261471 3 6 9 12 Cumulative leaf area index (m 2 ,m 2) 15 ANOVA on l i g h t v a l u e s i n Table 177 Summer light values Qne-Uay Analysis cf Variance Data? B:L1CHTDA7. surnl i t Level codes: B:LICHTDAT.sum Labels: Sance test' Confidence le»el: 95 Analysis of variance Source o: variation Sum cf Squares d.f. Mean square F-ratio Sig. level Between groups 178514.98 4 44623.744 999.959 .0000 Within groups 1133.02 220 5.150 Total <corrected) 17964S.00 224 Table of means for 3:LIQHTDAT. sumlit by BsLISHTDAT.su.ro Stnd. Error Stnd. Error 95 Percent Level Count Avera-j'e (internal) < pooled s) intervals for mean si 45 76.577773 .4544326 .3332997 75.334632 77.320923 s2 45 12.155556 .3595103 .3332557 11.412410 12.393701 s3 45 10.23S3S9 .4002305 .3382997 9.545743 11.032035 s4 45 2.622222 .2091030 .3332997 1.S7S07? 3.365363 s5 45 2.355556 .1302231 .3332997 1.612410 3.093701 Total 225 20.300000 .1512322 .1512922 20.467555 21.132345 Multiple range analysis for B:LICHTDAT.suml i t by E:LIGH72AT. sum Method: 95 Percent Level Count Average Homogeneous Groups s5 45 2.355556 * s4 45 2.622222 * s3 45 10.283339 * sa 45 12.155556 * s i 45 76.577773 * 178 Winter Tign't"va 1 lies One-Way Analysis of Marsance Data; E:LI£H7I>A7. win! i t Level codes: BsLlSHTPAT.win Labels: Kangc- test: Confidence l e v e l : 55 Analysis of variance Source of variation ; SUIT. of Squares ci. f. Hean square F-ratio Sig. level Between groups 52015.218 4 20503.325 574.713 .0000 Within groups 4627.8=7 220 21.036 TetaL 'I corrected) S6643.182 224 5 mi55irig value( s) have beer, excluded. Table of means for B: L!GHTDAT. mini i t by B:LIGHTDAT.win Stnd. Error- Stnd. Error 95 Percent Level Count Average ( i nter-na!) (pooled E) i ntervai s for mean wi 45 96.933333 .4124330 .6337114 95.431419 93.435243 ui2 45 96.666647 .7373648 .6337114 35.164752 33.163531 w3 45 76.422222 .5099900 .6337114 74.520303 77.924137 w4 45 64.244444 .6147641 .6337114 62.742530 65.746359 W3 45 4i.7?77?S .9523333 . 6-337114 40.275863 43.279692 Total 225 73.203339 .3057650 .3057650 72.537212 73.330565 Multiple range analysis for E:L!GK7DAT.winiit by E:LiGHTDAT. win Method: 95 Percent Level Count Average Homogeneous Croups w5 45 41.777773 * w4 45 64.244444 * a3 45 76.422222 * w2 45 So.666667 * 45 36.933333 * 179 ANOVA on p h o t o s y n t h e t i c and l e a f conductance v a l u e s i n T a b l e 5. 180 Summer leaf conductance values One-Way Analysis of Variance Data: 8:G3.gsbsu Level codes: B:GS.treat Labels: Range test: Confidence level: 95 Analysis of variance Source of variation Sum of Squares d. f. Mean square F-rati o Sig. level Between groups 0194667 3 .0024333 12.396 . 0000 Ui thin groups • 0035333 13 .0001963 Total ( corrected) • 0230000 26 1 missing valuet s) have been excl uded. T able of means for B:GS.gsbsu by B:G3. treat Stnd. Error Stnd. Error 95 Percen Level Count Average (i nternal) < pooled s) intervals for mean HD 3 .0166667 .0033333 .0080390 -.0089650 .0422983 HG 3 .0400000 .0057735 .0080890 .0143684 .0656316 HH 3 .0466667 .0033333 .0080890 .0210350 .0722983 LD 3 .0366667 .0033333 .0080890 .0610350 .1122983 LG 3 .0966667 .0088192 .0080890 .0710350 .1222933 LH 3 .0566667 .0088192 .0080890 .0310350 .0822983 MD 3 .0466667 .0033333 .0080890 .0210350 .0722983 MG 3 .0833333 .0145297 .0080890 .0577017 .1089650 MH 3 .0966667 .0120185 .0080890 .0710350 .1222983 Total r>t c i .0633333 .0026963 .0026963 .0547895 .0713772 Multiple range analysis for E:GS.gsbsu by B: GS.treat Method! : 95 Percent Level Count Average Homogeneous Groups HD 3 .0166667 * HC 3 .0400000 *# HH 3 .0466667 *** MD 3 .0466667 *** LH 3 .0566667 *** MG 3 .0333333 ** LD 3 .0866667 ** LG ? .0966667 k MH 3 .0966667 * Spring leaf conductance .values . . . • ,, Une-wau Analysis ot Variance Data: BiGS.gsbsp Level codes: B:GS.treat Labels: Range test: Confidence level: 95 Analysis of variance Source of variation Sum of Squares d. f. Mean square F-ratio Sig. level Between groups 0440000 3 .0055000 92.312 . 0000 Within groups • 0010667 18 .0000593 Total ( corrected) .0450667 26 1 missi ng value< s) h ave been excl uded. Table of means for B:GS.g sbsp by B:GS. treat Stnd. Error Stnd. Error 95 Percent Level Count Average (i nternal) ipooled s) i ntervals for mean HD 3 .0666667 .0033333 .0044444 .0525336 .0807498 HS 3 .1033333 .0033333 .0044444 .0892502 .1174164 HH 3 .0733333 .0066667 .0044444 .0592502 .0874164 LD 3 .1533333 .0033333 .0044444 .1392502 .1674164 LG 3 .1833333 .0033333 .0044444 .1692502 .1974164 LH 3 .1800000 .0057735 .0044444 .1659169 .1940831 MD 3 .1233333 .0033333 .0044444 .1092502 .1374164 MG 3 .1566667 .0033333 .0044444 .1425836 .1707498 MH 3 .1400000 .0057735 .0044444 .1259169 .1540831 Total 2? .1311111 .0014815 .0014815 .1264167 .1353055 Multiple range analysis for B:GS.gsbsp by B:GS.treat Method: 95 Percent Level Count Average Homogeneous Groups HD 3 .0666667 * HH 3 .0733333 tr HG 3 .1033333 * MD 3 .1233333 MH 3 .1400000 *# LD 3 .1533333 ** MG 3 .1566667 LH 3 .1300000 ** LG 3 .1333333 * Summer photosynthetic values One -Way Analysis of Variance Data*. B:PS.psbsu Level codes: B:PS.treat Labels Range test: Confidence level : 95 Analysis of variance Source of variation Sum of Squares d.f. Mean square F-ratio Sig. level Between groups 199.43373 3 24.304222 114.393 . 0000 Within groups 7.77200 36 .215839 Total (corrected) 206.20578 44 1 missing value< s) have been excl uded. Table of means for B:PS.psbsu by B:PS.treat Stnd. Error Stnd. Error 95 Percent Level Count Average (i nternal) (pooled s) i ntervals for mean HD 5 .6000000 .0707107 .2077926 -.0176058 1.2176058 HG 5 2.5000000 .0707107 .2077926 1.3823942 3.1176053 HH 5 2.8200000 .1327567 .2077926 2.2023942 3.4376058 LD 5 5.5600000 .0673233 .2077926 4.9423942 6.1776058 LG 5 7.8800000 .3813135 .2077926 7.2623942 8.4976058 LH 5 5.0600000 .2336664 .2077926 4.4423942 5.6776058 MD 5 1.5000000 .0836660 .2077926 .3823942 2.1176053 MG 5 3.4000000 .2213594 .2077926 2.7823942 4.0176058 MH 5 3.2400000 .2908608 .2077926 2.6223942 3.3576053 Total 45 3.6177778 .0692642 .0692642 3.4119092 3.8236464 Multiple range analysis for B:PS.psbsu by B:PS.treat Method: 95 Percent Level Count Average Homogeneous Groups HD 5 .6000000 MD 5 1.5000000 HG 5 2.50OOO0O HH 5 2.3200000 MH C 3:2400000 MG 5 3.4000000 •LH 5 5.0600000 LD 5 5.5600000 LG 5 7.9300000 Spring photosynthetic values Qne-Uay Analysis cf Variance Data: B:pS.psbsp Level codes: E:PS . treat Labels: Range test: Confidence level : Q 5 Analysis of variance Source of variation Sum of Squares d.f. Mean square F-ratio Sig. ievel Between groups 172.14178 3 21.517722 658.706 . 0000 Within groups 1.17600 36 .032667 Total \ corrected) 173.31778 44 1 missing value(s ) have been excluded. Table of means for B:P3.p sbsp by B:PS.treat Stnd. Error Stnd. Error 95 Percent Level Count Average (internal) '. pool ed s) i ntervals for mean HD 5 1.6800000 .0969536 .0808290 1.4397582 1.9202418 HG 5 3.6200000 .0374166 .0808290 3.3797582 3.8602418 HH 5 3.7000000 .0774597 .0808290 3.4597582 3.9402418 LD 5 5.6200000 .0734847 .0808290 5.3797582 5.8602418 LG 5 8.6400000 .0812404 .0808290 8.3997582 3.8802418 LH 5 6.7400000 .0678233 .0808290 6.4997582 6.9802418 MD 5 3.4200000 .0860233 .0808290 3.1797582 3.6602418 MG 5 5.8200000 .0489898 .0808290 5.5797582 6.0602418 MH 5 4.6600000 .1249000 .0808290 4.4197582 4.9002418 Total 45 4.8777778 .0269430 .0269430 4.7976972 4.9578584 Multiple range analysis for B:PS.psbsp by B:P3.treat Method: 95 Percent Level Count Average Homogeneous Croups HD 5 1.6300000 * MD C J 3.4200000 HG c •J 3.6200000 HH c J 3.70OOOO0 * MH c J 4.6600000 -LD 5 5.6200000 * MG 5 5.8200000 * LH c 6.740000Q LG 5 3.6400000 ANOVA on growth data i n Table 185 Specific leaf area One-Uay Analysis o: Variance . • • . Data: i :GJ0UTHC3.ESLfi Level : odes: B : G ?. 0 U' labels: Banff i ?• s * : Cc>n(: ier.c t J f ve. 1 ; 95 Analysis cf variance Source 01 variation Sum of Squares d.f. ^ean square F-ratio S i g . level Between oroups 152214.25 8 19026.731 388.121 . 0000 •Ji tMr. groups 3525.56 72 4 5.022 Totai (corrected) 155743.30 SO Table o: means far ?: GECuiTHCS. 3SLA by 3:C?.CUT«C3. treat Stnd. Error Stnd. Error 95 Percent Level Count Average (internal) (pooled s) i ntervals for mean HD 9 180.44444 2.2980131 2.3336477 173.72900 187.15989 HG 9 153.S3889 1.9539450 :.3338477 147.17345 160.60433 HH 9 214.11111 3.1066436 2.3336477 207.39567 220.32655 LD 9 83.00000 1.6583124 2.3338477 76.23456 89.71544 LG 9 79.77778 1.9348972 2.3338477 73.06234 86.49322 LH 9 108.77778 2.4876237 2.3338477 102.06234 115.45322 MD 9 162.66667. 3.0092450 2.333B477 155.95122 169.23211 MG 9 136.11111 1.2585577 2.333S477 129.39567 142.62=55 MH 9 176.77778 2.5861693 2.3333477 170.06234 133.45322 Total 81 143.55062 .7779492 .7779492 141.71214 146. ',;i10 Multiple range analysis.for 8:GR0WTHC3.ESLA by B: GR0UTHC3.tr Method: : 55 Percent Level Count Average Homogeneous Croups LG 9 79.77773 LD 9 93.00000 * LH 9 108.7777S MG 9 136.11111 HG 9 152.3°SS9 * MD 9 162.66667 * MH Q 176.77778 * MD C 180.44444 rirl 214.11111 Leaf growth rate One-Way Analysis cf Variance Data: •:GSDuTHCS.BLAG Levei codes: :-: GK0UTHC3. treat Late 1s: Range Cor. f i dence i eve:: Analysis c: variance Source oi variation Surr. of Squares i . f. Mean square F-rat;o 3 i g . leve! Between groups 15.797778 S 1. 9747c«iii 20.534 . VJJ'J Uithin groups 6.324444 72 .0947940 Total ; corrected) SO Table of means for E:CRQUTHC3.BLAG by B:GR0UTHC3.treat Stnd. Error Stnd. Error 95 Percent Level Count Average (internal) (pooled s) intervals for mean HD Q 3111111 .0512197 .1026233 .0155215 5064005 HG 9 3000000 .0897527 .1026233 .0047103 ,5952897 HH 9 6444444 .0851651 .1026233 .3491548 ,9397341 LD ? 1. 2111111 . 1111111 .1026233 .9153215 4. • ,5064005 LG 9 1. 6555556 .1226004 .1026233 1.3602659 1, ,9508452 LH 5 9444444 .1055556 .1026233 .6491548 1, .2397341 MD 9 3666667 .0687184 .1026233 .0713770 .6619563 MG Q 7666667 .0957427 .1026233 .4713770 i , .0619563 MH 9 i . • 1666667 .1563472 .1026233 .8713770 .4619563 Total 81 8185185 .0342078 .0342078 .7200SS6 .9169484 Multiple range analysis for B:GRGUTHC3.BLAG by B:GP.0UTHC3. tr Method: 95 Percent Level Count Average Homogeneous Groups HG 9 .3000000 * HD 9 ,3111111 MD 9 .3666667 ** HH c .6444444 * * * MG Ct .7566667 *** LH 9 .9444444 <r* MH 9 .1666667 ** LD Q 1 .2111111 ** 9 1 .6555555 Relative diameter growth rate One-iiiay Analysis cf '-.'ariar.ee i-ata: E: GRCUTHC3. EDG Level codes: 3: GP.P/J7HC2. treat Label s: range t est: n f i den:e leve; Analysis ::' variance Source of variation Sum of Squares d. f. Mean square F-ratio rig. level Between groups 3. 1.0218327 12.569 Uithir. groups c 6733323 72 .0737953 Total (corrected) 13 848395 90 Table of means for 3:GE0UTHC3. BDG by B:GJ.01i.'THC3. treat Stnd. Error Stnd. Error 95 Percent Leve 1 Count Average (internal) <pooled s) intervals for mean HD • 5 .2777778 .0595757 .0935689 .0085414 • .5470142 HG 5 .577777b .0741204 .0935689 .3065414 .6470142 HH 9 .6888889 .0633431 .0935689 .4196525 .9581253 LD 9 .7111111 .1033393 .0935689 .4418747 .9803475 LG 9 1.3666667 .1290994 .0935689 1.0974303 1.5359030 LH 9 .8777778 .1139905 .0935689 .6085414 1.1470142 MD 9 .2666667 .0577350 .0935689 -.0025697 .5359030 MG 9 .9111111 .0975156 .0935689 .6418747 1.1803475 MH 9 .8000000 .1116034 .0935519 .5307636 1.0692364 Total SI .7197521 .0311896 .0311896 .6300076 .9094935 Multipi e range analysis for B:GJ;QL I7HC3.BDG by E: GR0UTHC3.tr Method: 95 Percent Leve i Count Average Homogeneous Groups MD 9 .2666667 * HD 9 • 2777778 * HG 9 .577777S » + HH 9 .6388S39 ** LD 5 .7111111 ** MH 9 .3000000 L P .3777773 ** MG 9 .9111111 ** LG 1.3666667 * 188 Relative height growth rate One-Way Analysis of Variance Data: S:CR0UTHC3.BHC Level cries: : :GK0L'7'-"3. treat Labe i s : Far.ge t est: Cc nfiaence level : ?5 An&i S j i s ci va r: ar.re Source of variation Sum of Squares a.f. Mean square F-rat: o : i 9. i eve; Setueer groups j . 3419556 8 .4177444 6. 205 . 0000 Within groups 4. S472C00 72 .0673222 "otal ( corrected) . 1891555 60 Table of means for E:GR0ulTHC3. BHG by B:CRDUTHC3. treat Stnd. Error Stnd. Error 35 Percent Level Court Average (internal) (pooled s) intervals lor mean HD 5 .2233333 .0771182 .0S6/.:54 -.0255295 .4721562 HG S .5888889 .0632773 .0364S34 .3400260 .6377517 HH 9 .7211111 .0518734 .0864S34 .4722483 .5699740 LD 9 .8555556 .1269855 .0864884 .6066527 1.1044134 LG 9 .9011111 .1022449 .0864864 .6522463 1.1499740 LH 9 .8233333 .0879867 .0864884 .5744705 1.0721962 MD 9 . 4622222 .0672429 .0864584 .2123594 .7110651 MG 9 .6433333 .0591138 .0864384 .3944705 .3921962 MH 9 .757777S .1110528 .09646 34 .5039149 1.0066406 Total SI .6640741 .028S295 .0288295 .5811198 .7470234 Multiple range anal usis for B:GR0UTHC3.BHG by B: GRGUTHC3. tr Method: S5 Percent Level Count Average homogeneous Croups HD 9 .2233333 * MD J ** HG 9 .5886539 ** MG s .6433332 *•* liH .721111' * MH 9 .75777-3 t LH 9 .i23w-ij •*• LD 9 .3555556 *• 9 .9011111 189 APPENDIX 2 G l o s s a r y o f a b b r e v i a t i o n s used i n t h e t h e s i s 190 A b b r e v i a t i o n s : Tree s p e c i e s DF D o u g l a s - f i r (Pseudotsuga m e n z i e s i i (Mirb.) Franco) GF Grand f i r ( A b i e s q r a n d i s (Dougl.) L i n d l . ) WH Western hemlock (Tsuga h e t e r o p h y l l a (Raf.) Sarg.) P h y s i o l o g i c a l measurements C h l C h l o r o p h y l l c o n t e n t , (mg'g x) D A t m o s p h e r i c vapor p r e s s u r e d e f i c i t , (KPa) g^ L e a f d i f f u s i v e conductance, (em's ) — 7 — 1 PPFD P h o t o s y n t h e t i c photon f l u x d e n s i t y , (uMol'm s •"•) (a Mole (Mol) i s Avogadros' number o f photons i n t h e p a s t c a l l e d an E i n s t e i n ) Ps P h o t o s y n t h e t i c r a t e , (mgC0 2'dm - 2'hr - 1) wp Le a f water p o t e n t i a l , (MPa) Growth measurements LAI 7 7 L e a f a r e a i n d e x (m^'m ) RDGR R e l a t i v e d i a m e t e r growth r a t e (mm'yr -RHGR R e l a t i v e h e i g h t growth r a t e (cm'yr -- 1"' cm - 1) RLAGR R e l a t i v e l e a f a r e a growth r a t e ( g ' y r -SAI p p Stem a r e a i n d e x (m m^) SLA p —1 S p e c i f i c l e a f a r e a (cm *g ) S/R Shoot t o r o o t r a t i o ( g ' g - 1 ) 

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