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Water relations, survival and growth of conifer seedlings planted on a high elevation south-facing clearcut Livingston, Nigel Jonathan 1986

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WATER RELATIONS, SURVIVAL AND GROWTH OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT  By  NIGEL JONATHAN  LIVINGSTON  B . S c , U n i v e r s i t y o f N o t t i n g h a m , 1977 M . S c . , U n i v e r s i t y o f G u e l p h , 1980  A THESIS SUBMITTED  I N PARTIAL  FULFILLMENT  REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  in  THE FACULTY Department  We a c c e p t  this  OF GRADUATE of Soil  thesis  to the required  THE UNIVERSITY  STUDIES  Science  as c o n f o r m i n g standardy  OF B R I T I S H  COLUMBIA  A p r i l 1986  ® Nigel  Jonathan  Livingston  OF THE  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  Iti s  understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l n o t be allowed without my  permission.  Department o f The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  1Q \  //£, /  19U  Columbia  written  -  ii  ABSTRACT  Equal Franco), silver  numbers o f D o u g l a s - f i r  western  fir  planted,  British  (Abies  in  elevation  hemlock  Columbia.  and g r o w t h .  located  A number o f  survival  the  high  Island, determine  increase  survival  seedlings  rates,  regardless of  to  t r e a t m e n t , were untreated  survived.  the  and  seedlings  lowered t h e i r  a growing  season  in  of  Douglas-fir  osmotic  exhibited  seedlings,  Survival  s u r v i v e and g r o w b e c a u s e t h e y were h i g h l y  potentials  seedlings seedlings  drought potential  rates  of  these  seedlings  by  response to d e c l i n i n g  and c o n s e q u e n t l y w e r e a b l e t o m a i n t a i n t u r g o r .  over soil  The  were n e v e r l e s s t h a n 50% o f  those  irrigated.  Western hemlock, seedlings  spring  i r r i g a t i o n , and i r r i g a t i o n  r a n g e d f r o m 81% t o 95%.  MPa i n t h e c o u r s e o f  were  inclining  A p p r o x i m a t e l y 72% and 82% o f  Unirrigated  transpiration that  shade c a r d s ,  received treatment  water  included  Pacific  on a s o u t h - f a c i n g  t r e a t m e n t s were a p p l i e d t o  1981 and 1982 r e s p e c t i v e l y ,  were a b l e t o  1.1  styroplugs  and  combined.  by D o u g l a s - f i r .  tolerant.  Sarg.),  seedlings,,were  s e e d l i n g m i c r o c l i m a t e would  provision of  The h i g h e s t  that  of  Forbes)  (Raf.)  (Mirb.)  on Mount A r r o w s m i t h , V a n c o u v e r  These t r e a t m e n t s  shade c a r d s  in  (Doug.)  1981 and 1 9 8 2 , as 1-0  whether m o d i f i c a t i o n  planted  (Tsuga h e t e r o p h y l l a  amabilis  clearcut  southwest,  (Pseudotsuga m e n z i e s i i  lacked  and t o  stress  an e v e n g r e a t e r e x t e n t ,  a v o i d a n c e and t o l e r a n c e  C o n s e q u e n t l y t h e r e was v e r y p o o r  survival  of  Pacific  silver  mechanisms.  both s p e c i e s .  Survival  fir  rates  were s i g n i f i c a n t l y  never exceeded  64% i n e i t h e r  The e x t e n t by c h a n g e s shoots shoots, lowest  and t y p e o f  and t h e s m a l l e s t but shoot  generally  conductance  to  root  (g )  in a l l  Shaded s e e d l i n g s  roots,  than untreated  variable,  that  for  of  correlated with estimates  seedling estimates of  average  related  hourly  had  seedlings  largest  larger which  seedling  and a v e r a g e  had  the  seasonal  g  irradiance,  root  zone  s  as an  c o u l d be  in  growing  season t o t a l  soil g . s  independent  explained.  d r y m a t t e r a c c u m u l a t i o n were  seedling  growing  in  stomatal  the v a r i a b i l i t y  f r o m s u n r i s e was i n c l u d e d  of  affected  developed the  average s o l a r  o v e r 70% o f  o v e r 85% o f t h e v a r i a b i l i t y  Measurements  but  ratios.  a n a l y s i s model  hours  was m a r k e d l y  systems.  t e m p e r a t u r e , vapour p r e s s u r e d e f i c i t  When t h e number o f  species  seedlings  d r y mass  accounted  and i r r i g a t i o n  Irrigated  t o measurements of  s  water p o t e n t i a l ,  with  growth  root  less  by s h a d e c a r d s  species.  in microclimate.  A boundary-line  air  increased  better  season t r a n s p i r a t i o n seedling  g . s  than  -  iv  -  TABLE OF CONTENTS  Page ABSTRACT  ii  TABLE OF CONTENTS  iv  L I S T OF TABLES  vii  LIST  xii  OF FIGURES  NOTATION  xviii  ACKNOWLEDGEMENTS  xxi  INTRODUCTION CHAPTER 1  1  WATER STRESS AND SURVIVAL OF THREE S P E C I E S OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT I. II.  Introduction  5  Methods  6  A. B. C.  Site Description Experimental Design Measurements  6 7 9  1. 2. 3.  9 9  4. 5. III.  Results A. B. C. D.  IV. V.  4  Growing Season Weather O b s e r v a t i o n s R o o t Zone S o i l W a t e r P o t e n t i a l T o t a l T w i g X y l e m W a t e r P o t e n t i a l and Osmotic P o t e n t i a l Seedling Transpiration Seedling Survival  11 13 17  and D i s c u s s i o n  17  Growing Season Weather O b s e r v a t i o n s T o t a l Twig Xylem P o t e n t i a l , Needle O s m o t i c P o t e n t i a l and T u r g o r P o t e n t i a l S e e d l i n g T r a n s p i r a t i o n Rates Seedling Survival  17  1.  Seedlings  Planted  i n 1981  39  2.  Seedlings  Planted  in  44  1982  18 33 39  Conclusions  48  References  49  -  V  -  Page CHAPTER  2  STOMATAL CHARACTERISTICS AND TRANSPIRATION OF THREE S P E C I E S OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT I. II.  Introduction  55  Methods  57  A. III.  B. C. D. E. F. G.  V.  CHAPTER  3  Site  and E x p e r i m e n t a l  Design  57  B. M e a s u r e m e n t s and D a t a A n a l y s i s R e s u l t s and D i s c u s s i o n A.  IV.  54  57 59  Response o f g t o Changes i n S o l a r Irradiance Response o f g t o Changes i n A i r Temperature Response o f g t o Changes i n Vapour Pressure D e f i c i t Response o f g t o Changes i n T u r g o r P o t e n t i a l and S o i l W a t e r P o t e n t i a l R e l a t i o n s h i p o f g t o t h e Time s i n c e Sunrise V a r i a t i o n s of g with Respect to S e e d l i n g Age and Time o f P l a n t i n g C a l c u l a t i n g g$ and E f r o m B o u n d a r y - L i n e Relationships s  II.  61  s  67  s  70  s  76  s  80 81  Conclusions  86  References  90  THE GROWTH AND WATER USE OF THREE S P E C I E S OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT I.  61  s  Introduction  98 99  Methods  101  A.  Micrometeorological  B.  Growth Measurements  102  1.  Seedling  102  2.  Leaf  C.  Measurements  101  Height  A r e a and S h o o t and R o o t  Calculations  Dry M a s s . . .  102 103  1.  Stomatal  Conductance  2.  Transpiration  103 105  -  vi  -  Page III.  Results  105  A. B.  105 106  Growing Season Weather O b s e r v a t i o n s Growth 1. 2. 3.  C.  IV. V. VI.  H e i g h t and L e a f A r e a o f P l a n t e d i n 1981 H e i g h t and L e a f A r e a o f P l a n t e d i n 1982 S h o o t and R o o t D r y Mass R o o t D r y Mass R a t i o  Seedlings 108 Seedlings 108 and S h o o t  to  Estimates of Total Seedling Stomatal C o n d u c t a n c e , S e a s o n a l T r a n s p i r a t i o n and W a t e r Use E f f i c i e n c y  APPENDIX  APPENDIX  123  Discussion  125  Conclusions  134  References  135  CONCLUSIONS  APPENDIX  Ill  137  I - D e r i v a t i o n of Water-Release Curves f o r the D e t e r m i n a t i o n of C o n i f e r S e e d l i n g Osmotic Potential II  III  142  - An I n s t r u m e n t f o r M e a s u r i n g t h e A v e r a g e S t o m a t a l Conductance of C o n i f e r Seedlings ( L i v i n g s t o n et a l _ . , 1984, C a n . J . F o r . R e s . 14: 512-517)  148  - Soil  155  Water R e t e n t i o n  Curves  - vi i  L I S T OF  T a b l e 1.1  -  TABLES  D a i l y minimum m e a s u r e d v a l u e s o f t o t a l t w i g x y l e m w a t e r p o t e n t i a l ( ^ T t x ) (MPa) and average root zone s o i l water p o t e n t i a l (^ ) (MPa) f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r b e t w e e n May and A u g u s t 1981. S e e d l i n g s w e r e p l a n t e d i n 1982. Standard d e v i a t i o n s are given in brackets , s  T a b l e 1.2  Measured v a l u e s of a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l (i|/ s ) (MPa) and d a i l y minimum t o t a l t w i g xylem p o t e n t i a l (^Ttx) ( a ) f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r b e t w e e n May and S e p t e m b e r 1983. S e e d l i n g s were p l a n t e d i n 1982. Standard d e v i a t i o n s are given i n brackets M p  Table  1.3  M e a s u r e d v a l u e s o f minimum o s m o t i c p o t e n t i a l i ^ ) (MPa) b e t w e e n May and S e p t e m b e r 1982 f o r shaded ( u s i n g s h a d e c a r d s ) and n o n - s h a d e d D o u g l a s - f i r , w e s t e r n h e m l o c k , and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n 1981. Standard d e v i a t i o n s are given i n brackets  T a b l e 1.4  M e a s u r e d v a l u e s o f minimum o s m o t i c p o t e n t i a l { % ) (MPa) f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s b e t w e e n May and S e p t e m b e r 1983. S e e d l i n g s were p l a n t e d i n 1982. Standard d e v i a t i o n s are given in b r a c k e t s  T a b l e 1.5  M e a s u r e d v a l u e s o f d a i l y minimum o s m o t i c p o t e n t i a l (^ir) (MPa) b e t w e e n May and S e p t e m b e r 1982 for u n t r e a t e d p l a n t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r seedlings planted in the previous y e a r ( P ) and p l a n t e d i n t h e c u r r e n t y e a r ( C ) . Standard d e v i a t i o n s are given i n b r a c k e t s ,  T a b l e 1.6  V a l u e s o f l i n e a r r e g r e s s i o n c o e f f i c i e n t s and r for the r e l a t i o n s h i p : E = a + (i|>s - ^ T t x ) / t" i r r i g a t e d (1) and n o n - i r r i g a t e d ( N I ) D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s . The u n i t s o f a and b a r e y g cm s and MPa/(pg c m s ) . respectively 2  0  - 2  T a b l e 1.7  o r  _ 1  D a i l y t r a n s p i r a t i o n g d a y ) of shaded ( u s i n g shade c a r d s ) and u n s h a d e d D o u g l a s - f i r s e e d l i n g s on J u n e 10, J u n e 12 and J u n e 13, 1982. The t o t a l p r o j e c t e d n e e d l e a r e a (cm ) i s g i v e n i n b r a c k e t s . The a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l was -0.10 MPa on J u n e 12 , - 1  -  vi i i  Page T a b l e 1.8  Table  Table  Table  1.9  2.1  2.2  P e r c e n t s u r v i v a l i n A p r i l 1 9 8 2 , 1983 and 1984 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r s e e d l i n g s p l a n t e d i n A p i r l 1 9 8 1 . Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t , w h i c h was a p p l i e d t o e a c h s p e c i e s i n e a c h y e a r . .  45  P e r c e n t s u r v i v a l i n A p r i l 1 9 8 3 and 1984 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r s e e d l i n g s p l a n t e d i n A p r i l 1 9 8 2 . Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t , w h i c h was a p p l i e d t o e a c h s p e c i e s i n e a c h y e a r . .  46  The maximum s t o m a t a l c o n d u c t a n c e m e a s u r e d ( g and t h e number o f t i m e s t h i s v a l u e was o b t a i n e d f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r seedlings  60  s m a x  ) (n)  Values of the c o e f f i c i e n t a in the equation; 9s/9smax - e~ d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g where g i s a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) » gsmax maximum g (cm s ) and R i s t h e h o u r l y a v e r a g e g l o b a l s o l a r i r r a d i a n c e (W m ) =  1  s  s  _ 1  1 S  _ 1  s  s  63  - 2  T a b l e 2.3  V a l u e s o f t h e c o e f f i c i e n t b and T in the equation; g / g = 1-b (T ~ ^max) d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g where g i s t h e a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s 9smax maximum gs ( s * ) , T i s the hourly a v e r a g e a i r t e m p e r a t u r e (°C) and T x i s t h e a i r t e m p e r a t u r e at which g = g m a x  s  s  m  a  x  s  1 S  c m  - 1  )  1  m a  s  Table  2.4  s  m  a  66  x  Values of the c o e f f i c i e n t , D and n , i n t h e equation; g /g max = l / U ( D / D . ) ) derived by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g where g is a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) » 9smax maximum g (cm s ) » D "is t h e h o u r l y a v e r a g e v a p o u r p r e s s u r e d e f i c i t ( k P a ) and D o . 5 i s t h e vapour p r e s s u r e d e f i c i t at which g i s h a l f 0 > 5  +  s  S  n  0  5  s  - 1  1 S  - 1  s  s  9smax  69  -  ix  -  Page Table 2.5  Values  of  the c o e f f i c i e n t s ,  k, m and n i n  the  e q u a t i o n s gs/9smax (0 2. ^s 1. " 0 * 1 and 9 s / 9 s m a x • m * - n ( * < - 0 . 1 MPa) d e r i v e d by boundary-line a n a l y s i s for D o u g l a s - f i r , western h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g where g i s the average s e e d l i n g stomatal conductance (cm s ) gsmax maximum g§ (cm s " ) and y i s t h e a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l ( M P a ) . . .  75  V a l u e s o f t h e c o e f f i c i e n t , q , r and s i n t h e e q u a t i o n ; gs/9max = P + q t + r t d e r i v e d by boundary-line a n a l y s i s for D o u g l a s - f i r , western h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s w h e r e g$ i s the average s e e d l i n g stomatal conductance (cm s ) f 9smax maximum g (cm s ~ M and t i s t h e number o f h o u r s f r o m s u n r i s e  79  The p e r c e n t a g e o f t h e v a r i a n c e o f t h e a v e r a g e stomatal conductance of D o u g l a s - f i r (DF), Western h e m l o c k (WH) and P a c i f i c s i l v e r f i r ( P S F ) s e e d l i n g s , m e a s u r e d on 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 , e x p l a i n e d by t h e b o u n d a r y - l i n e a n a l y s i s model u s i n g the individual v a r i a b l e s , R (global solar i r r a d i a n c e ) , T ( a i r temperature) D (vapour pressure d e f i c i t ) \|> ( a v e r a g e r o o t z o n e w a t e r p o t e n t i a l ) and t ( t h e number o f h o u r s f r o m s u n r i s e ) , and t h e variables in combination  82  Values of c o e f f i c i e n t s in the l i n e a r r e g r e s s i o n equation; g - | = V g + w f o r i r r i g a t e d and n o n - i r r i g a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 , w h e r e Sscalc i s e e d l i n g stomatal conductance using the b o u n d a r y - l i n e a n a l y s i s model and g i s measured stomatal conductance. A l s o shown a r e t h e number o f data points ( n ) , the c o e f f i c i e n t of determination ( r ) and t h e s t a n d a r d e r r o r o f e s t i m a t e ( S E E )  89  =  s  e  s  s  _ 1  1 S  1  s  T a b l e 2.6  2  _ 1  1 S  s  Table  2.7  s  s  T a b l e 2.8  s c a  e  s  s  s  T a b l e 3.1  T a b l e 3.2  M o r p h o l o g y o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r s e e d l i n g s at the time of planting. Standard d e v i a t i o n s are given in brackets  107  S e e d l i n g h e i g h t (mm) i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r seedling planted in A p r i l 1981. Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t w h i c h was a p p l i e d t o e a c h s p e c i e s i n each y e a r  109  -  X  -  Page Table 3.3  T a b l e 3.4  T a b l e 3.5  Table  Table  Table  Table  3.6  3.7  3.8  3.9  L e a f a r e a ( c m ) i n O c t o b e r 1 9 8 2 , 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r seedlings planted in A p r i l 1981. Standard d e v i a t i o n s were g i v e n i n b r a c k e t s  110  S e e d l i n g h e i g h t (mm) i n O c t o b e r o f D o u g l a s - f i r , w e s t e r n hemlock s i l v e r f i r seedlings planted in f o l l o w e d by t h e same l e t t e r a r e d i f f e r e n t (t=0.05) according to M u l t i p l e Range T e s t was a p p l i e d each year  112  2  1 9 8 2 , 1982 and 1983 and P a c i f i c A p r i l 1982. Numbers not s i g n i f i c a n t l y D u n c a n ' s New to each s p e c i e s i n  L e a f a r e a ( c m ) i n O c t o b e r 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . Maximum s t a n d a r d d e v i a t i o n s are given in b r a c k e t s  113  M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f D o u g l a s - f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1982. Standard d e v i a t i o n s are given in b r a c k e t s  120  M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s are given in b r a c k e t s  121  M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f P a c i f i c s j l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1982. Standard d e v i a t i o n s are given in brackets  122  2  Dry m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n (EJOT) d WUF. d u r i n g t h e g r o w i n g s e a s o n i n 1 9 8 1 , 1982 and 1983 o f D o u g l a s - f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s of Y are bracketed. The r o o t mean s q u a r e e r r o r s f o r E J O T w e r e t y p i c a l l y 26%. T h e s e e r r o r s were d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n ( 2 ) and a s s u m i n g a 20% e r r o r f o r A , a 20% e r r o r i n D and b y using the standard e r r o r of estimate f o r c a l c u l a t e d v e r s u s measured g reported in Chapter 2  127  Dry m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n (EJOT) E d u r i n g t h e g r o w i n g s e a s o n i n 1982 and 1983 o f w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s of Y are bracketed. The r o o t mean s q u a r e e r r o r s f o r EjOT t y p i c a l l y 28%. T h e s e e r r o r s were d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n ( 2 ) and a s s u m i n g a 20% e r r o r f o r A , a 10% e r r o r i n D and b y using the standard e r r o r of estimate for c a l c u l a t e d v e r s u s measured g reported in Chapter 2  128  a n  s  Table  3.10  w  e  a  n  r  e  d  W I J  s  - xi  -  Page T a b l e 3.11  Dry m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n ( E J O T ) and WUE d u r i n g t h e g r o w i n g s e a s o n i n 1983 o f P a c i f i c s i l v e r - f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1982. Standard d e v i a t i o n s of Y are bracketed. The r o o t mean s q u a r e e r r o r s f o r E j O T w e r e t y p i c a l l y 30%. T h e s e e r r o r s were d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n ( 2 ) and a s s u m i n g a 20% e r r o r i n A , a 10% e r r o r i n D, and by u s i n g t h e standard e r r o r of estimate f o r c a l c u l a t e d versus measured g reported in Chapter 2 s  Table A I . l  The d i f f e r e n c e b e t w e e n t h e o s m o t i c p o t e n t i a l a t f u l l t u r g o r (^Q) d osmotic p o t e n t i a l at zero t u r g o r (Vir) o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r shoots. A l s o shown a r e t h e corresponding values of a p o p l a s t i c water content (B). V a l u e s were o b t a i n e d f r o m w a t e r - r e l e a s e c u r v e s . E a c h number i s t h e a v e r a g e o f 10 m e a s u r e m e n t s  129  a n  147  -  xi i  L I S T OF  -  FIGURES  Page Figure  1.1  Measurements o f o s m o t i c p o t e n t i a l at f u l l t u r g o r o b t a i n e d from w a t e r - r e l e a s e c u r v e s ( i | % ) v e r s u s t h o s e o b t a i n e d f r o m p r e v i o u s l y f r o z e n sap (\|%) f o r D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r f i r ( P S F ) 0  Figure  Figure  Figure  Figure  1.2  1.3  1.4  1.5  14  C o u r s e s o f a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l p r e c i p i t a t i o n ( P ) and maximum v a p o u r p r e s s u r e d e f i c i t (D) d u r i n g t h e 1981 g r o w i n g s e a s o n  (^ ),  C o u r s e s o f a v e r a g e r o o t zone s o i l water p o t e n t i a l p r e c i p i t a t i o n ( P ) and maximum v a p o u r p r e s s u r e d e f i c i t (D) d u r i n g t h e 1982 g r o w i n g s e a s o n  (<|> ),  C o u r s e s o f a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l p r e c i p i t a t i o n ( P ) and maximum v a p o u r p r e s s u r e d e f i c i t (D) d u r i n g t h e 1983 g r o w i n g s e a s o n  (^ ),  s  19 s  20 s  21  R e l a t i o n s h i p b e t w e e n predawn t o t a l t w i g x y l e m w a t e r p o t e n t i a l (^Ttx) l a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l (i|> ) f o r n o n - i r r i g a t e d D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r - f i r ( P S F ) . M e a s u r e m e n t s were made i n 1 9 8 1 , 1982 and 1 9 8 3 . A l s o shown i s t h e 1:1 l i n e . Linear regression a n a l y s i s i n d i c a t e s predawn \pjtx (MPa) = 0 . 8 6 3 ^ (MPa) - 0 . 3 5 7 ( r = 0 . 8 9 ) ( d a s h e d l i n e )  22  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 g r o w i n g s e a s o n , f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) D o u g l a s - f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . V a l u e s o f minimum t u r g o r p o t e n t i a l were o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r p o t e n t i a l . . . .  25  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 g r o w i n g s e a s o n , f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n May 1 9 8 2 . V a l u e s o f minimum t u r g o r p o t e n t i a l were o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r potential  26  a n f  s  2  Figure  Figure  1.6  1.7  -  xi i i  -  Page Figure  Figure  Figure  Figure  Figure  1.8  1.9  1.10  1.11  1.12  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 growing s e a s o n , f o r i r r i g a t e d (IRR) and n o n - i r r i g a t e d (NON-IRR) P a c i f i c s i l v e r - f i r s e e d l i n g s p l a n t e d i n May 1982. V a l u e s o f minimum t u r g o r p o t e n t i a l w e r e o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r potential The r e l a t i o n s h i p b e t w e e n d a i l y t r a n s p i r a t i o n ( E ) and a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l f o r n o n - i r r i g a t e d D o u g l a s - f i r (DF), western h e m l o c k (WH) and P a c i f i c s i l v e r - f i r ( P S F ) seedlings. M e a s u r e m e n t s were made i n 1982 on s e e d l i n g s p l a n t e d i n May o f t h a t y e a r . Each point represents the average E f o r three seedlings. The c u r v e s were f i t t e d by e y e  27  ,  34  The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f d a i l y t r a n s p i r a t i o n per u n i t p r o j e c t e d l e a f area of n o n - i r r i g a t e d s e e d l i n g s to that of i r r i g a t e d s e e d l i n g s ( E ^ T / E J ) and a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l (i|>s) f o r D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r - f i r ( P S F ) M e a s u r e m e n t s w e r e made i n 1982 on s e e d l i n g s p l a n t e d i n May o f t h a t y e a r  35  The d a i l y c o u r s e o f t r a n s p i r a t i o n ( E ) p e r u n i t p r o j e c t e d l e a f a r e a f o r i r r i g a t e d ( I R R ) and n o n i r r i g a t e d (NON-IRR) D o u g l a s - f i r s e e d l i n g s , and v a p o u r p r e s s u r e d e f i c i t (D) f o r J u l y 24 and J u l y 27, 1982. The v a l u e s o f i|>s on J u l y 24 and J u l y 27 w e r e - 0 . 5 MPa and - 0 . 7 MPa, r e s p e c t i v e l y ,  38  C o u r s e s o f s t o m a t a l c o n d u c t a n c e (gs)» transpiration r a t e ( E ) and t o t a l t w i g x y l e m p o t e n t i a l ( t T t x ) f° s h a d e d ( c l o s e d c i r c l e s ) and u n s h a d e d ( o p e n c i r c l e s ) D o u g l a s - f i r s e e d l i n g s on J u n e 13, 1982  41  C o u r s e s o f t e m p e r a t u r e o f s h a d e d ( d a s h e d l i n e ) and unshaded ( d o t t e d l i n e ) n e e d l e s o f a D o u g l a s - f i r s e e d l i n g , and a i r t e m p e r a t u r e ( s o l i d l i n e ) a t 20 cm h e i g h t n e a r t h e u n s h a d e d s e e d l i n g on J u n e 13, 1982..  42  Courses of vapour pressure d e f i c i t ( s o l i d l i n e ) , v a p o u r p r e s s u r e d i f f e r e n c e b e t w e e n an u n s h a d e d D o u g l a s - f i r n e e d l e and t h e a i r ( b r o k e n l i n e ) and t h e vapour p r e s s u r e d i f f e r e n c e between a shaded D o u g l a s - f i r n e e d l e and t h e a i r ( d o t t e d l i n e ) on J u n e 13, 1982  43  r  Figure  Figure  1.13  1.14  - xiv  Page Figure  2.1  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (gsmax) global solar-irradiance ( R ) f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d ( o ) Douglas-fir seedlings. Each p o i n t i s t h e a v e r a g e of three measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s t h e upper l i m i t o f the o b s e r v a t i o n s , b. Comparison o f the b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between 9s/9smax ^ ^s f ° D o u g l a s - f i r ( s o l i d l i n e ) , w e s t e r n h e m l o c k ( d o t t e d l i n e ) and P a c i f i c s i l v e r - f i r (broken l i n e ) . (PPFD i n ymol m s" i s a p p r o x i m a t e l y 2.04 t i m e s R i n Wnr )  62  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (gsmax) t e m p e r a t u r e (T) f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r seedlings. Each p o i n t i s t h e a v e r a g e o f t h r e e m e a s u r e m e n t s . , A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s the upper l i m i t o f t h e o b s e r v a t i o n s . b. Comparison o f t h e b o u n d a r y - l i n e s f o r the r e l a t i o n s h i p between gs/9smax d T for D o u g l a s - f i r ( s o l i d l i n e ) , w e s t e r n hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r - f i r ( b r o k e n l i n e )  65  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g s ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (gsmax) ' vapour p r e s s u r e d e f i c i t (D) f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d ( o ) Douglas-fir seedlings. Each p o i n t i s t h e a v e r a g e of three measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s t h e upper l i m i t o f the o b s e r v a t i o n s , b. Comparison o f the b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between 9s/9smax 0 for Douglas-fir (solid l i n e ) , w e s t e r n h e m l o c k ( d o t t e d l i n e ) and P a c i f i c s i l v e r - f i r (broken l i n e )  68  The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (gsmax) d the turgor potential f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r seedlings. The s e e d l i n g s were p l a n t e d i n 1982 and t h e m e a s u r e m e n t s were made on 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2  71  s  a n c l  s  an<  r  - 2  1  2  s  Figure  2.2  s  a  n  d  a  i  r  a n  Figure  2.3  a n f  a n c l  Figure  2.4  s  a n  -  XV  -  Page Figure  2.5  The r e l a t i o n s h i p b e t w e e n t h e s t o m a t a l c o n d u c t a n c e o f a D o u g l a s - f i r s e e d l i n g and t h e h o u r l y a v e r a g e v a p o u r p r e s s u r e d e f i c i t (D) ( o ) , and t u r g o r p o t e n t i a l (\|> ) (•) m e a s u r e d on J u l y 2 7 , 1 9 8 2 . The " o n e s " mark t h e t i m e ( 0 6 : 0 0 PST) when t h e f i r s t m e a s u r e m e n t s were m a d e . M e a s u r e m e n t s were r e p e a t e d e v e r y h o u r u n t i l 2 1 . 0 0 PST  72  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g $ ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (gsmax) a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l (i|> ) f o r non-irrigated Douglas-fir seedlings. Each p o i n t i s t h e a v e r a g e of three measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s the upper l i m i t of the o b s e r v a t i o n s , b. Comparison o f the b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between 9 s / 9 s m a x and i|) f o r D o u g l a s - f i r ( s o l i d l i n e ) , w e s t e r n h e m l o c k ( d o t t e d l i n e ) and P a c i f i c s i l v e r - f i r (broken l i n e )  74  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e ( g s m a x ) and t h e t i m e s i n c e s u n r i s e ( t ) f o r i r r i g a t e d (•) and n o n - i r r i g a t e d ( o ) Douglas-fir seedlings. Each p o i n t i s t h e a v e r a g e o f t h r e e measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s the upper l i m i t o f the o b s e r v a t i o n s , b. Comparison of the boundaryl i n e s f o r t h e r e l a t i o n s h i p between gs/gsmax t f o r D o u g l a s - f i r ( s o l i d l i n e ) , w e s t e r n hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r - f i r ( b r o k e n l i n e ) . . .  78  The d a i l y c o u r s e s o f m e a s u r e d ( o p e n s y m b o l s ) and c a l c u l a t e d ( c l o s e d symbols) stomatal conductance (gs) " i r r i g a t e d ( s o l i d l i n e s ) and n o n - i r r i g a t e d ( d o t t e d l i n e s ) D o u g l a s - f i r s e e d l i n g s on J u l y 2 8 , 1982. S t o m a t a l c o n d u c t a n c e was c a l c u l a t e d w i t h (•) and w i t h o u t t i m e s i n c e s u n r i s e (A) as a variable. The a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l was - 0 . 7 3 MPa  84  The d a i l y c o u r s e s o f m e a s u r e d ( o p e n s y m b o l s ) and c a l c u l a t e d ( c l o s e d symbols) stomatal conductance ( g s ) f o r i r r i g a t e d ( s o l i d l i n e s ) and n o n - i r r i g a t e d ( d o t t e d l i n e s ) D o u g l a s - f i r s e e d l i n g s on A u g u s t 2 1 , 1982. S t o m a t a l c o n d u c t a n c e was c a l c u l a t e d w i t h (•) and w i t h o u t t i m e s i n c e s u n r i s e (A) as a v a r i a b l e . The a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l was - 1 . 1 MPa  85  p  Figure  2.6  a n d  s  S  Figure  2.7  s  a n d  Figure  2.8  T  Figure  2.9  o r  - xvi -  Page F i g u r e 2.10  Comparison of c a l c u l a t e d stomatal conductance (9scalc) measured s t o m a t a l c o n d u c t a n c e ( g ) f o r i r r i g a t e d ( o ) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) a n d P a c i f i c s i l v e r f i r ( P S F ) s e e d l i n g s , p l a n t e d i n 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 . The r e g r e s s i o n l i n e s shown ( b r o k e n l i n e s ) a r e f o r a l l t h e p o i n t s . The s l o p e s and i n t e r c e p t s o f t h e s e l i n e s a r e g i v e n i n Table 2.8 W  l  t  n  s  F i g u r e 2.11  Comparison o f c a l c u l a t e d d a i l y t r a n s p i r a t i o n rate ( E i ) u s i n g values of g obtained from e q u a t i o n ( 4 ) w i t h R , D, T , i> and t a s v a r i a b l e s , w i t h d a i l y t r a n s p i r a t i o n r a t e (E) t h a t was c a l c u l a t e d u s i n g m e a s u r e d v a l u e s o f stomatal conductance. B o t h E and E i c a l c u l a t e d a s t h e sum o f t h e h o u r l y p r o d u c t s o f g and ( D / R T ' ) f o r i r r i g a t e d ( c l o s e d s y m b o l s ) and n o n - i r r i g a t e d ( o p e n s y m b o l s ) D o u g l a s - f i r ( o ) , w e s t e r n hemlock ( o ) and P a c i f i c s i l v e r f i r ( o ) s e e d l i n g s , p l a n t e d i n 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 . A l s o shown i s t h e 1:1 l i n e . Linear regression analysis indicates E i (g c m " d a y ) = 0 . 9 8 E (g c m " d a y - ) + 0 . 0 0 2 (r = 0.96) (dashed l i n e ) c a  c  s  s  s  c  s  a  c  w  e  r  e  V  c  2  1  2  a  Figure  Figure  Figure  3.1  3.2  3.3  3.4  c  1  2  Figure  87  88  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 a n d 1983 o f u n t r e a t e d ( o ) , shaded ( • ) , i r r i g a t e d ( o ) and i r r i g a t e d and s h a d e d ( • ) D o u g l a s - f i r s e e d l i n g s p l a n t e d i n May 1982  114  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 a n d 1983 o f u n t r e a t e d ( o ) , s h a d e d ( • ) , i r r i g a t e d ( • ) and i r r i g a t e d and s h a d e d ( • ) w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n May 1982  115  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 a n d 1983 o f u n t r e a t e d ( o ) , s h a d e d ( • ) , i r r i g a t e d ( a ) and i r r i g a t e d and s h a d e d ( • ) P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1982  116  Seasonal c o u r s e o f s e e d l i n g p r o j e c t e d l e a f area (A) i n 1982 and 1983 o f u n t r e a t e d ( o ) , shaded ( • ) , i r r i g a t e d ( • ) and i r r i g a t e d and s h a d e d ( • ) D o u g l a s f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . The B r o k e n l i n e shows t h e e s t i m a t e d s e a s o n a l c o u r s e o f l e a f a r e a t h a t was u s e d i n t h e c a l c u l a t i o n o f t h e g r o w i n g s e a s o n t r a n s p i r a t i o n o f i r r i g a t e d and shaded seedlings  117  -  xvii  -  Page Figure  Figure  Figure  3.5  3.6  3.7  S e a s o n a l c o u r s e o f p r o j e c t e d l e a f a r e a (A) i n J982 and 1983 o f u n t r e a t e d ( o ) and i r r i g a t e d (•) w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n May 1982  118  S e a s o n a l c o u r s e o f p r o j e c t e d l e a f a r e a (A) i n 1982 and 1983 o f u n t r e a t e d ( o ) and i r r i g a t e d (•) P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1982  119  The r e l a t i o n s h i p b e t w e e n g r o w i n g s e a s o n s e e d l i n g d r y m a t t e r a c c u m u l a t i o n ( Y ) and t h e a v e r a g e g r o w i n g season s e e d l i n g canopy conductance ( g ) f o r D o u g l a s - f i r s e e d l i n g s i n 1 9 8 1 , 1982 and 1 9 8 3 . The s l o p e o f t h e l i n e f o r c e d t h r o u g h z e r o i s 0 . 2 3 1 g / ( c m s " ) and t h e e q u a t i o n o f t h e l i n e f i t t e d t h r o u g h t h e d a t a p o i n t s by l i n e a r r e g r e s s i o n i s Y ( g ) = 0 . 1 5 4 g£ ( c m S " ) + 1.31 ( r = 0.68) c  3  1  3  Figure  3.8  1  2  The r e l a t i o n s h i p b e t w e e n g r o w i n g s e a s o n s e e d l i n g d r y m a t t e r a c c u m u l a t i o n (Y) and g r o w i n g s e a s o n s e e d l i n g t r a n s p i r a t i o n (EJOT) f o r D o u g l a s - f i r s e e d l i n g s i n 1 9 8 1 , 1982 and 1 9 8 3 . The c l o s e d c i r c l e s i n d i c a t e shaded t r e a t m e n t s . The s l o p e o f the l i n e f o r c e d through zero i s 0.0022 g / g . The e q u a t i o n o f t h e l i n e f i t t e d t h r o u g h a l l t h e d a t a p o i n t s by l i n e a r r e g r e s s i o n i s Y ( g ) = 0 . 0 0 2 7 ET0T ( 9 ) - ° . 8 3 ( r = 0 . 7 8 ) , and t h e e q u a t i o n o f t h e l i n e , a l s o f i t t e d by l i n e a r r e g r e s s i o n , t h r o u g h t h e p o i n t s e x c l u d i n g shade t r e a t m e n t s i s Y(g) = 0.0036 E QT (g) - 2 . 0 ( r = 0.88)  124  2  2  T  Figure  Figure  AI.l  AI.2  126  The r e l a t i o n s h i p b e t w e e n s e e d l i n g s h o o t mass and s h o o t t o t a l x y l e m p o t e n t i a l ( s h o o t T|») f o r a Douglas-fir seedling. The mass o f t h e s h o o t when s h o o t t i s z e r o (Mg) was d e t e r m i n e d f r o m t h e l e a s t squares of r e g r e s s i o n of the l i n e a r p o r t i o n of the line  145  The r e l a t i o n s h i p b e t w e e n s e e d l i n g s h o o t r e l a t i v e w a t e r c o n t e n t ( s h o o t RwC) and t h e i n v e r s e o f s h o o t t o t a l xylem p o t e n t i a l ((shoot ^ ) ) . The a p o p l a s t i c water content (B), osmotic p o t e n t i a l a t f u l l t u r g o r (<|%o) a n d ^ o s m o t i c p o t e n t i a l a t zero turgor ( K ) are i n d i c a t e d '  146  S o i l w a t e r r e t e n t i o n c u r v e s f o r 0 - 5 cm 5 - 1 0 ( o ) and 1 5 - 2 5 cm (•) d e p t h s  157  - 1  Figure  AIII.l  (•),  -  xviii  -  NOTATION  A  seedling  g  S e e d l i n g c a n o p y c o n d u c t a n c e d e f i n e d as t h e p r o d u c t o f s e e d l i n g p r o j e c t e d l e a f a r e a and t h e a v e r a g e s e e d l i n g c o n d u c t a n c e (cm s )  g"  a r e a on a p r o j e c t e d  average growing  c  B  tissue  C  leaf  C0  2  water f r a c t i o n  concentration  vapour p r e s s u r e d e f i c i t  D DQ  5  E  (cm  seedling  season s e e d l i n g canopy c o n d u c t a n c e  apoplastic  internal  i  area basis  (L L '  - 1  )  the stomatal  (cm  s  3  _ 1  )  (dimensionless) 1  o r cm  3  m ) - 3  (kPa)  v a p o u r p r e s s u r e d e f i c i t , d e t e r m i n e d by b o u n d a r y - l i n e a n a l y s i s , a t w h i c h s e e d l i n g s t o m a t a l c o n d u c t a n c e i s h a l f i t s maximum v a l u e (kPa) seedling transpiration day- )  rate  per u n i t  projected  leaf  area  (g c m  1  Ej  t r a n s p i r a t i o n rate per u n i t s e e d l i n g s (g cm~ d a y ) 2  E  N I  projected  leaf  area of  irrigated  - 1  t r a n s p i r a t i o n r a t e per u n i t p r o j e c t e d l e a f area of n o n - i r r i g a t e d , u n s h a d e d s e e d l i n g s (g c m day ) - 2  - 1  ^TOT  t o t a l amount o f w a t e r t r a n s p i r e d by a s e e d l i n g d u r i n g a season (g)  M  s h o o t mass a t a g i v e n s h o o t w a t e r p o t e n t i a l  M  D  shoot  d r y mass  M  Q  shoot  d r y mass a t rate  growing  (g)  (g) full  (mm d a y  turgor  P  rainfall  R  global solar irradiance s u r f a c e ) (W m )  - 1  (g)  ) (i.e.,  solar irradiance  on a  horizontal  - 2  R  y  the  gas c o n s t a n t  for  water vapour  (0.462 m  3  kPa k g -  1  K  _ 1  )  - 2  -  T  air  T'  absolute  T  a i r t e m p e r a t u r e d e t e r m i n e d by b o u n d a r y l i n e a n a l y s i s a t s e e d l i n g s t o m a t a l c o n d u c t a n c e i s a t i t s maximum (°C)  m a x  T  temperature  xix  (°C)  a i r temperature  (K)  temperature of  unshaded n e e d l e  1"nsh  temperature of  shaded n e e d l e  d  needle diameter  (m)  e,  vapour pressure  of the a i r  e  v a p o u r p r e s s u r e o f t h e s t o m a t a l c a v i t i e s assumed t o be s a t u r a t e d vapour pressure at needle temperature (kPa)  n  n  a  e  which  (°C) (°C)  (kPa) the  vapour p r e s s u r e of t h e s t o m a t a l c a v i t i e s o f shaded s e e d l i n g s assumed t o be t h e s a t u r a t e d v a p o u r p r e s s u r e a t n e e d l e t e m p e r a t u r e (kPa)  n  e*(T)  saturation  vapour p r e s s u r e  g^  boundary  g  average s e e d l i n g stomatal conductance ( i . e . , the t r a n s p i r a t i o n r a t e per u n i t needle p r o j e c t e d area per u n i t d i f f e r e n c e i n v a p o u r p r e s s u r e b e t w e e n s t o m a t a l and a i r c a v i t i e s ) (cm s )  l a y e r conductance  at temperature T on one s i d e  of  (kPa)  needle  (cm  s  - 1  )  _ 1  g. , smax  maximum s t o m a t a l  r  c o e f f i c i e n t of d e t e r m i n a t i o n (dimensionless)  m  2  u  t  time  since  u  wind speed  conductance  sunrise (m  s  _ 1  (cm  s  - 1  )  in a linear  regression  (h)  )  t u r g o r p o t e n t i a l c a l c u l a t e d by s u b t r a c t i n g n e e d l e p o t e n t i a l f r o m t o t a l x y l e m p o t e n t i a l (MPa) ip  s  analysis  osmotic  average s o i l w a t e r p o t e n t i a l measured o v e r t h e v e r t i c a l e x t e n t of t h e s e e d l i n g r o o t zone a p p r o x i m a t e l y 0.5 m from t h e s e e d l i n g ( c a l c u l a t e d as t h e a r i t h m e t i c a v e r a g e o f t h e s o i l w a t e r p o t e n t i a l a t t h e 5 0 , 1 0 0 , 200 and 300 mm d e p t h s ) (MPa)  -  total *Ttx  t  o  t  a  l  needle  xylem p o t e n t i a l  twig xylem p o t e n t i a l  -  XX  (MPa)  (MPa)  i|>  needle  osmotic  potential  (MPa)  i|>  needle  osmotic  potential  at  full  turgor  (MPa)  V  needle  osmotic p o t e n t i a l  at  zero turgor  (MPa)  - xxi -  ACKNOWLEDGEMENTS  It  i s impossible to adequately  t o my w i f e ,  Eleanor,  of  for the duration  patience  her encouragement without It  which  thank Dr.  supervisor,  the design  friend.  for his guidance,  and D r . L . F . E b e l l  Additional  whom I t h a n k .  Council Council.  by S e c t i o n 88 f u n d s were p r o v i d e d  and a g r a n t  D r . M.D. N o v a k ,  advice  and a s s i s t a n c e  t o Doug Beames who n o t  in v i r t u a l l y every b u t was a l s o  aspect  a good chamber  d u r i n g my r e s e a r c h , and a l s o and i n t e r e s t  i n my w o r k . of Soil  miss our lunch-time  to MacMillan-Bloedel this  I  Science  and s t i m u l a t i n g a t m o s p h e r e c r e a t e d b y  I shall  f o r me t o c o n d u c t  funds  and e m o t i o n a l ,  and f r i e n d s h i p .  e n j o y e d my s t a y i n t h e D e p a r t m e n t  G . D u n s w o r t h who i n i t i a t e d  supported  her f o r  f o r machining the porometer  f o r h i s support  I am v e r y g r a t e f u l opportunity  indebted  o f the porometer  because of t h e f r i e n d l y  my c o l l e a g u e s  Mr.  assiduity  and e x p e r i e n c e  for his collaboration  D.L. S p i t t l e h o u s e  least  help  Mr. J . Baranowski  I have g r e a t l y not  I thank  both f i n a n c i a l  for their  I am g r e a t l y  and c o n s t r u c t i o n  I thank  reservoir  a l s o t o r e c o r d my t h a n k s t o D r . T . A . B l a c k , my  invaluable  and Bob S t a t h e r s Dr.  at U.B.C.  t h e o t h e r members o f my s u p e r v i s o r y c o m m i t t e e :  provided  o f my g r a t i t u d e  n o t have c o m p l e t e d my t h e s i s .  d u r i n g my P h . D . p r o g r a m .  of  o f my s t u d i e s  and f o r h e r s u p p o r t ,  I could  T.M. B a l l a r d ,  only  the extent  who m a i n t a i n e d a s e e m i n g l y i n e x a u s t i b l e  i s a pleasure  academic  express  discussions.  L t d . , who p r o v i d e d t h e  r e s e a r c h , and i n p a r t i c u l a r  the research  project  from t h e B . C . M i n i s t r y by c o n t r a c t s  from t h e N a t u r a l  to  w h i c h was m a i n l y of  Forests.  from t h e B . C . S c i e n c e  S c i e n c e and E n g i n e e r i n g  Research  -  1 -  INTRODUCTION  It  is  Pacific  Northwest,  and t h a t yields the  now g e n e r a l l y  only  once c o n s i d e r e d  intensive  and t h e  of  Forest  obligation  for  acts Act  of  conifer  s u c h as t h e  holders  to  which  is  1975).  exposed  south-facing  Seedling  by B . C .  slopes.  on Mount  selected  because  it  seedling The  that  s t u d y began at  western  hemlock  out  B.C.  a  As p a r t  of  Island.  the  The  failures,  in  treatments  the  in  site.  April  1981 when n e a r l y  cause  on study,  water  on a site  none o f  was  which  study Stathers  These c o n s i s t e d  and P a c i f i c  silver  of  fir  a randomized c o m p l e t e - b l o c k s u c h as t h e  p r o v i s i o n of  equal  3,000  (1983)  a major cause  seedlings  number o f  seedlings. design to  of  shade c a r d s or  were  Douglas-fir,  The s e e d l i n g s test  by  planting  planted  were l i k e l y  1972,  lands.  to a three year  the  with  legal  important  years after  seedlings  planting  temperatures  in  cutover  S e c t i o n 88 f u n d s , o f  conifer  had a h i s t o r y o f  Oregon  particularly difficult  problem led  Forests  that  has been l i m i t e d  five  This  limitless  mortality.  planted  laid  in  the  A r r o w s m i t h , Vancouver  high surface  Act,  s i n g l e most  first  the  somewhat a s s u a g e d  reforest  Island,  is  from  ensure  t o be t h e  be s a t i s f a c t o r i l y e x p l a i n e d .  concluded  far  in  1 9 7 8 , w h i c h makes i t  successfully  and g r o w t h o f  located  has been  in  establishment  M i n i s t r y of  survival  in  is will  Practices  on V a n c o u v e r  considered  clearcut  could  Forest  tenure  seedling mortality  relations,  concern  Columbia  success  supply of timber  operations  British  (Arnott  supported  Public  the  inexhaustible,  in  Reforestation stress  that  reforestation  c a n be s u s t a i n e d .  passing  water  recognized  whether  inclining  the  were  -  seedlings species,  to the southwest s u c h as P a c i f i c  would  silver  increase fir,  sites.  In May 1982 a p p r o x i m a t e l y  planted  u s i n g t h e same s p e c i e s ,  previous year. cards),  low s o i l study  of  1,000  rationale that  high s o i l  form the b a s i s  has been w r i t t e n  in  In C h a p t e r 1, turgor  even i n  it  additional  shade  the  irrigation  shade  system)  Irrigation separate  on s e e d l i n g  survival.  of the three chapters  The  results  comprising t h i s  was  the  s u r f a c e t e m p e r a t u r e , h i g h e v a p o r a t i v e demand  paper  of  and  this  thesis,  which  format.  the seasonal potential  and d i u r n a l  and o s m o t i c and s o i l  course  potential  species  a r e p r e s e n t e d , as a r e t h e e f f e c t s  water of  of  discussed  in  twig  and t h e  potential  xylem relationship  for  s h a d i n g and  i r r i g a t i o n on b o t h s e e d l i n g w a t e r u s e and s e e d l i n g is  t y p e as i n  m i g h t be p o s s i b l e t o  such  were  ( p r o v i d e d by  by a t r i c k l e  seedling transpiration  survival  tolerate  seedlings  p r o v e n a n c e and s t o c k  between  seedling  those  n o r m a l l y cannot  and no s h a d e and no i r r i g a t i o n .  water p o t e n t i a l  potential,  which  ( w a t e r was p r o v i d e d  s h a d e and i r r i g a t i o n ,  effects  survival  F o u r t r e a t m e n t s were t e s t e d :  irrigation  used w i t h the  2 -  the  trickle  survival.  r e l a t i o n to drought  three  Finally  tolerance  mechanisms. In C h a p t e r 2 , t h e s t o m a t a l to environmental these  responses  and p h y s i o l o g i c a l  of each of  variables  are d e s c r i b e d .  r e s p o n s e s o v e r two y e a r s and d i f f e r e n c e s  and two y e a r o l d  seedlings  Finally,  a boundary-line  measured  stomatal  conductance,  o f t h e same s p e c i e s  a n a l y s i s model  responses,  generated  is  by t h i s  of  developed. model  the three  in  responses  are a l s o  stomatal Values  Changes between  in one  discussed.  behaviour, of  species,  based  on  stomatal  a r e combined w i t h measured  hourly  -  averages of seedling  vapour  water  pressure d e f i c i t ,  root  of  t r e a t m e n t s on t h e m o n t h l y and  The s e a s o n a l  conductance  period.  1,  of  shoot  height  estimate  are c a l c u l a t e d  use e f f i c i e n c y  I describes  II  of the  using  daily  is  published  used  seasonal  is  developed  over the then  in  same  estimated. pressure-volume  potential.  paper t h a t d e s c r i b e s  porometer  of  stomatal  used t o g e n e r a t e osmotic  and  species  t h e model  production  seedling  seedling  area,  seasonal  each s p e c i e s  the technique  is a previously  and t e s t i n g  of  and l e a f  each o f the  u s e and a v e r a g e  the d e t e r m i n a t i o n of  Appendix design  water  seedlings  The w a t e r  for  area to  i r r i g a t i o n , s h a d e and a c o m b i n a t i o n  and a r e r e l a t e d t o d r y m a t t e r  Appendix curves  and l e a f  shoot dry m a t t e r accumulation of  reported.  Chapter  -  use.  In C h a p t e r 3 , t h e e f f e c t s these  3  in t h i s  the  study.  REFERENCES  Arnott, J.T. trees in  1975. F i e l d p e r f o r m a n c e o f c o n t a i n e r - g r o w n and Coastal B r i t i s h Columbia. C a n . J . F o r . R e s . 5:  bareroot 186-195.  Stathers, R.J. 1 9 8 3 . A s t u d y o f s o i l t e m p e r a t u r e and s e e d l i n g s u r v i v a l in a forest clearcut. M.Sc. T h e s i s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, B.C., Canada.  -  4  -  CHAPTER 1  WATER STRESS AND SURVIVAL OF THREE S P E C I E S OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT  - 5 -  WATER STRESS AND SURVIVAL OF THREE S P E C I E S OF CONIFER PLANTED ON A HIGH ELEVATION SOUTH-FACING  I. Water  stress  major f a c t o r s Northwest  resulting  m a i n t a i n adequate evaporative  cell  Watts  (Hsaio  Jones  seedling  Stress arises  Even low l e v e l s  of  (1983) has d e f i n e d  two g r o u p s :  (i)  minimize the occurrence of mechanisms increase.  increases  H s a i o j i t ^]_.  cell  potential  tial  the c e l l  One e x t r e m e l y  solute  the  Pacific  inability  to  atmospheric  Prolonged  stress  can  (Walton 1980;  can a d v e r s e l y  is  of  plants  contribute  affect  stress  cell  Full  while  less  in  observed  i n many wood p l a n t s and S h u l a 1 9 8 4 )  at the  partial  than t h a t  .  survive  a v o i d a n c e mechanisms and  (ii)  activity  (Tyree  that  stress  as p l a n t  tolerance  water-  mechanism  i s m a i n t a i n e d by means  of  ( B e r n s t e i n 1 9 6 1 ; Osmond 1 9 6 3 ;  same r a t e  Osmotic  cell  as t h e t o t a l  t u r g o r maintenance  i n ¥j.  drought  tolerance  t u r g o r m a i n t e n a n c e o c c u r s when t h e  decreases {yj)  turgor  to  to drought  important stress  concentration  decrease  Ritchie  high  that maintain physiological  1976).  osmotic of  i n the  a plant's  damaging water d e f i c i t s ,  a d j u s t m e n t whereby in  of  stress  the a b i l i t y  c a n be s e p a r a t e d i n t o  osmotic  through  t o be one o f  e t jil_. 1 9 7 6 ) .  that  is  regeneration  d e v e l o p m e n t and m o r p h o l o g y  Mechanisms  deficits  considered  water p o t e n t i a l .  as d r o u g h t t o l e r a n c e .  tolerance  is  turgor in conditions  on p l a n t  et a]_. 1 9 8 1 ) .  growth  from drought  demand o r l o w s o i l  have m a j o r e f f e c t s  CLEARCUT  INTRODUCTION  limiting conifer  (Arnott 1975).  SEEDLINGS  poten-  o c c u r s when  a d j u s t m e n t has  et al_. 1 9 7 8 ; P a r k e r £ t _aU  the  been 1982;  - 6  Treatments duration  and l e v e l  effective  in  of  soil  Drip  seedling microclimate  water s t r e s s .  increasing  e t al_. 1 9 8 0 ) . raising  that modify  -  seedling  water potential  Shade c a r d s ,  survival  i r r i g a t i o n of  can a f f e c t for  on s i t e s  seedlings  example,  i n Oregon  was e f f e c t i v e  and d e c r e a s i n g  soil  both  the  were  (Hobbs  in  both  temperature  (Stathers  1983). The diurnal  objective courses  potential,  of  osmotic  of  this  seedling twig potential,  t r a n s p i r a t i o n and s o i l species  of  conifers  The e f f e c t s relations survival  of  water  Site  the  potential,  survival  be d i s c u s s e d i n  (49°  seasonal  high  be r e p o r t e d .  relation  seedling of  three  elevation  on b o t h  clear-cut.  seedling  Finally  to drought  and  turgor  and t h e s u r v i v a l  irrigation  will  between  water-  seedling  tolerance  mechanisms.  METHODS  of  124°  fragments  till.  The  l o c a t e d a t an e l e v a t i o n  36'W).  This  (0.15 -  The  soil,  is  variable 0.65  an O r t h i c depth  communication)  of  1150 m on a  Island,  characterized surface  Humo-Ferric  ( 0 . 4 - 1.2  m) and  British by  soil  temper-  Podzol,  and i s  is  volumetric  g r e a t e r t h a n 2 mm) o v e r c o m p a c t  s i t e was h a r v e s t e d i n 1974  personal  area  summer- d r o u g h t and v e r y h i g h  sandy loam of  coarse  is  on M t . A r r o w s m i t h , V a n c o u v e r  (Stathers 1983).  a gravelly  Ltd.,  site  slope  1 3 ' N,  extended periods atures  the  Description  south-facing  Columbia  relationship  s h a d i n g and t r i c k l e  The e x p e r i m e n t a l 30°  to describe  xylem water p o t e n t i a l ,  II. A.  is  p l a n t e d on a s o u t h - f a c i n g  and s e e d l i n g will  chapter  ( J . Driburg, MacMillan c o v e r e d by a c a n o p y o f  glacial Bloedel  fireweed  - 7 -  (Epilobium angustifolium L.). salal of  (Gaultheria  Lupine  shallop Pursh.).  a predominantly D o u g l a s - f i r  overstory  and w e s t e r n h e m l o c k  (Lupinus  latifolius  The a d j a c e n t  natural  (Pseudotsuga m e n z i e s i i (Tsuga h e t e r o p h y l l a  Agardb.) forest  (Mirb.)  (Raf.  and  consists  Franco)  Sarg.)  understory.  B.  Experimental During the  Design  first  p l a n t e d on t h e s i t e ,  two w e e k s o f A p r i l 1.5  e l e v a t i o n provenances silver  fir  plugs.  The  planting. of  (Abies  the  m apart.  seedlings  were k e p t  organic  in cold  in mineral  l a y e r which  seedlings  1-0  storage soil  were  numbers o f  w e s t e r n hemlock  (Dougl.) Forbes)  They were p l a n t e d  surface  T h e r e were equal  of D o u g l a s - f i r ,  amabilis  1981, 2,880  and  high-  Pacific  container-grown for  which  styro-  f o u r months p r i o r required  ranged between 0.00  the  to  removal  and 0 . 0 5 m i n  thickness. The to t e s t  s e e d l i n g s were three  laid  treatments  for  out  i n a randomized complete-block  each of  species-treatment  c o m b i n a t i o n s were  these  subsequently  not  b l o c k s were  included  in  t o as t h e s e l f - s h a d i n g  inclined  to the southwest  d u r i n g the middle of  (hereafter  referred  t o as t h e  root  the day.  nine (eight  survival).  I n one  (hereafter-  s e e d l i n g s were  planted  c o l l a r w o u l d be s h a d e d by In t h e o t h e r  shade c a r d t r e a t m e n t )  of  s a m p l i n g and w e r e  g r o w t h and  the  The  i n 32 b l o c k s  the treatments.  treatment)  so t h a t  species.  destructive  a n a l y s i s of  two o f  referred  foliage  replicated  used f o r  i n any s t a t i s t i c a l  S h a d e was p r o v i d e d  the three  design  shade  the  treatment  s h a d e was  provided  by a 0 . 2 m h i g h x 0 . 3 m w i d e w a x e d c a r d b o a r d s h a d e c a r d ( m a n u f a c t u r e d  by  - 8  International a b o u t 0.05  F o r e s t S u p p l i e s , E u g e n e , O r e g o n , U . S . A . ) w h i c h was  m to the  a b o u t 10 - 20° back provided at  small  southwest of over the  solar  the  During the were p l a n t e d .  first  zenith  angles.  and w i t h o u t  two w e e k s o f  blocks  (the  sampling).  The  May 1982,  treatments:  placed  in  the  shade  same t h r e e  as i n  temperature  in order to  (Stathers  survival  the and  effect  the  El  received hours. the s o i l  irrigation  water  soil  There  type were  same s i z e  irrigation,  (control).  separate  stock  the e f f e c t s supply,  and shade  Irrigation of  and  conductance  water p o t e n t i a l  was  soil  evaporative  and ( i i ) on  s y s t e m ( c o m p o n e n t s m a n u f a c t u r e d by  seedlings.  individual  approximately  U.S.A.)  W a t e r was  to a gasoline-powered  e m i t t e r s to  previous year),  and s t o m a t a l  sustained high  Cajon, C a l i f o r n i a ,  irrigated  firetruck  of  (i)  the  for  to  seedling  development.  A trickle Systems,  the p r e v i o u s y e a r .  1983), s o i l  demand on s e e d l i n g w a t e r s t r e s s determine  the  create  were used  provenance,  of  (control)  seedlings  t h e s e were used t o  species,  be  cards.  a n o t h e r 1,080  and no s h a d e and no i r r i g a t i o n  c h o s e n as a t r e a t m e n t surface  of  placed  sloped  shade would  shade  ( p r o v i d e d by s h a d e c a r d s  same p o s i t i o n  and i r r i g a t i o n  s h a d e c a r d was  r e m a i n i n g 360 s e e d l i n g s  and p l a n t i n g t e c h n i q u e w e r e u s e d as i n four  The  In t h e t h i r d t r e a t m e n t  S e v e n h u n d r e d and t w e n t y  additional  destructive  stem.  s e e d l i n g to ensure that  s e e d l i n g s were p l a n t e d v e r t i c a l l y  eight  -  was i n s t a l l e d t o  siphoned  pump t h a t d e l i v e r e d w a t e r During  irrigation  nine l i t r e s  of water per hour  W a t e r was a p p l i e d when t e n s i o m e t e r s water  potential  ( Y ) was l e s s S  supply water  f r o m a 3,500-L  seedlings.  each for  on t h e s i t e  t h a n -0.04  MPa.  Drip-Eze to  capacity  through  drip  seedling three to  four-  indicated  that  - 9 -  C.  Measurements  1.  Growing Season Weather  Observations  I n 1 9 8 1 , 1982 and 1983 s t a n d a r d f o r e s t m i c r o c l i m a t e w e r e made f r o m May u n t i l with  a horizontally  Lincoln,  positioned  Nebraska, U.S.A.)  standard pyranometer  each s e a s o n .  rain  (Model  gauge  which at  polystyrene  sensor  N.Y.,  U.S.A.)  Corporation, of  the  field the  201,  UUT-51J1,  U.S.A.),  season.  had a s t a l l i n g  014A M e t - O n e ,  u s i n g a Model CR-21  Soil  Water  water p o t e n t i a l s  tensiometers  sulphonated  Research Fenwal  C o r p . , New  D a t a was  data logger tape  York,  Electronics  respectively.  s t o r e d on a u d i o c a s s e t t e for  and a i r -  The  calibration  checked  in  the  significantly  recorded  as one hourScientific,  later-  processing.  Potential greater  t h a n - 0 . 1 MPa w e r e m e a s u r e d  i n s t a l l e d on two p l o t s .  The t e n s i o m e t e r s ,  a  U.S.A.)  (Campbell and  during  m height with  Sunneyvale, C a l i f o r n i a , 1  bucket  California,  humidity  d i d not change  speed o f 0.5 m s " .  beginning  a tipping  s e n s o r w h i c h was f r e q u e n t l y  t r a n s f e r r e d to a microcomputer  Root Zone S o i l  at the  W i n d s p e e d was m e a s u r e d a t t h e 0 . 4  (Model  or t o t a l s  a  Inc.,  laboratory  Berkeley,  Relative  Phys-Chemical  (Model  Framingham, M a s s . ,  Logan, Utah, U . S . A . ) ,  2.  1 mm.  a  Holland)  Inc.,  measured  Li-200S, Li-cor  was m e a s u r e d w i t h  u s i n g an Assmann p s y c h r o m e t e r ,  averages  (Model  t h e 1 m h e i g h t was m e a s u r e d w i t h  and t h e r m i s t o r  cup anemometer which  Rainfall  (Model  i r r a d i a n c e was  w h i c h was c a l i b r a t e d w i t h  RG2501, S i e r r a M i s c o ,  r e l a t i v e humidity  growing  solar  pyranometer  had a r e s o l u t i o n of  temperature  Global  ( K i p p and Z o n e n , D e l f t ,  and end o f  U.S.A.)  October.  measurements  similar  using to  - 10  those  d e s c r i b e d by Van B a v e l  (Soil  Moisture  an a i r - e n t r y  Equipment C o r p . ,  v a l u e of 0.1  12 mm d i a m e t e r s t e e l About 1 cm  3  MPa.  Soil  ( 1 9 6 8 ) , had p o r o u s  Access  into  o f m o i s t s a n d was p o u r e d Pairs  of  the  into  to the d e s i r e d hole  before  water p o t e n t i a l s  a Model  less  HR-33T  metric  and dew p o i n t m o d e s .  apart,  were  installed in  tensiometers.  (Wescor  Pairs  of  Inc.,  Logan, Utah,  (Wescor  thermocouple  t h e same p l o t s  Inc.)  depth. a  were  psychro-  psychrometers,  a n d a t t h e same d e p t h s  the  plots.  Two a c c e s s  holes  the s i d e  of  the hole  was l i g h t l y  packed around the  been p u s h e d t o t h e e n d o f  Measurements t h e end o f  was c a l c u l a t e d  of f  s  the  thermocouple  the access  p s y c h r o m e t e r w i r e was t h e n b u r i e d the thermocouple  nearest  hole.  seedling.  i n the l a r g e  were t a k e n e v e r y  September i n each y e a r . as t h e a r i t h m e t i c  the  average of  days from  average all  at  each  rod  it  about soil  had  refilled  installed.  two t o s i x The  about  thermocouple  h o l e w h i c h was  p s y c h r o m e t e r s h a d been  the  Stone-free  psychrometer a f t e r Most of  300 mm  as  A 150-mrn by 300-mrn h o l e was e x c a v a t e d t o b e d r o c k  100 mm i n t o  thermocouple  U.S.A.)  on  t h e a b o v e d e p t h s w e r e made by d r i v i n g a 9-mm d i a m e t e r s t e e l  until  a  t h a n - 0 . 1 MPa w e r e m e a s u r e d u s i n g M o d e l  500 mm f r o m a s e e d l i n g on e a c h o f  all  with  a t t h e 5 0 , 1 0 0 , 1 5 0 , 2 0 0 , 300 a n d 500 mm d e p t h s .  dew p o i n t m i c r o v o l t m e t e r  s  U.S.A.)  t e n s i o m e t e r s 300 mm a p a r t  with  ¥  soil  an a c c e s s  psychrometers  after  cups  h o l e s w e r e made by d r i v i n g  PCT-55 t h e r m o c o u p l e  of  ceramic  Santa Barbara, C a l i f o r n i a ,  rod v e r t i c a l l y  t e n s i o m e t e r was i n s e r t e d . installed  et  -  mid-May  r o o t zone v a l u e  the tensiometer  p s y c h r o m e t e r measurements t o a depth of  300 mm.  or  of  - 11 -  3.  Total  Twig Xylem Water P o t e n t i a l  and Osmotic  Total  twig  (Tjtx)  pressure tional  chamber  Twigs  seedlings with  which  surgical  i s very small  scissors,  2 - 4  species  measured w i t h  s  U.S.A.).  for seedlings  The  containing  minutes  of e x c i s i o n .  Hourly  on s e l e c t e d  bags  gravita-  removed  from  (Dow C h e m i c a l  damp t i s s u e ,  and t r a n s w  e  r  e  No more t h a n 2 t w i g s  measurements o f Y j t x  days d u r i n g  a  ( K a u f m a n n 1 9 7 7 ) , was  chamber where measurements o f y y t x  r e m o v e d f r o m any s e e d l i n g . three  a  sealed in Ziploc  I n d . , U.S.A.)  ported to the pressure  all  w  r a n g i n g f r o m 30 t o 60 mm i n l e n g t h w e r e  Indianapolis,  obtained within  potential  (PMS I n c . , C o r v a l l i s , O r e g o n ,  component,  neglected.  Corp.,  xylem water  Potential  w  e  the three years  r  e  '  m a c  of  were  e  o  n  field  observations. Measurements  of ^  p s y c h r o m e t e r chambers voltmeter.  were  (Wescor  of ^  Inc.) with  an HR-33T  dew p o i n t  sap e x t r a c t e d w i t h m o d i f i e d 6 . 3 mm d i a m e t e r d i s c s  discs  were  vice-grips  of f i l t e r  that  paper.  vials,  whose  vials  were t h e n p l a c e d  and a c e t o n e  sap d u r i n g s t o r a g e . because,  flask  t o p r e v e n t any c h e m i c a l  ensured  samples.  The  i n p a r a f i l m and p l a c e d  o p e n i n g s were c o v e r e d w i t h i n a thermos  and t h e i r  s q u a s h e d them b e t w e e n two  The use o f v i c e - g r i p s  i m m e d i a t e l y wrapped  tight  A t predawn,  removed from a s e l e c t e d s e e d l i n g  t h e same p r e s s u r e w o u l d be e x e r t e d on d i f f e r e n t  saturated  micro-  1 9 8 3 , a n d May a n d O c t o b e r 1 9 8 3 ,  w e r e made e v e r y t h r e e t o f o u r w e e k s .  b e t w e e n 10 - 15 n e e d l e s w e r e  ice  u s i n g Model C - 5 2 t h e r m o c o u p l e  B e t w e e n May 1 9 8 2 a n d M a r c h  measurements  that  obtained  in  air-  p a r a f i l m and c a p p e d .  The  containing a solution  of dry  transformation occurring  Sap was e x t r a c t e d f r o m t h e n e e d l e s  d u r i n g t h e f r e e z i n g and t h a w i n g of p l a n t  before  tissue,  cell  i n the  freezing membranes  - 12  are  r u p t u r e d and a p o p l a s t i c  water  -  dilutes  sap f r o m t h e  symplast  ( M a r k h a r t e t al_. 1 9 8 1 ; C a m p b e l l  e t a]_. 1 9 7 9 ; T y r e e  lected  a n a l y s e d w i t h i n 48 h o u r s .  i n t h e f i e l d were  thawed w i t h i n  five  mized p o s s i b l e the osmotic 1983).  minutes of  their  removal  enzymatic h y d r o l y s i s  potential  Each  always  of  t h e sap  of  t h a w e d d i s c was p l a c e d  in  f o r a minimum o f before  the  calculated This  sample ^  thermocouple  the temperature. using three  The  et  This  by s u b t r a c t i n g y  n  from  The  to  dew  point  had b e e n a d j u s t e d  potential  each  (?p)  was  determinations  of l  release  as d e s c r i b e d by S c h o l a n d e r e t al_. ( 1 9 6 5 ) and Brown  Tanner because  curves (1983).  turgor  (Appendix  n  at 1).  each s p e c i e s . of  a x i s were  (i.e.  obtained  Y^)  using  waterand  The two m e a s u r e m e n t s a r e e x p e c t e d t o show g o o d a g r e e m e n t  data from w a t e r - r e l e a s e  between ^  halves  full  sample  with  %  at  for  Tytx*  m e t h o d was v a l i d a t e d by c o m p a r i n g m e a s u r e m e n t s o f w n  box  dissipate  using the  turgor  of  a styrofoam  T h r e e r e p l i c a t e m e a s u r e m e n t s w e r e made f o r  s e p a r a t e C-52 c h a m b e r s .  mini-  Tanner  solutions  in  gradients  coefficient  were  psychrometer  u s i n g KC1 s a l t  thermal  col-  lowers  1 9 7 9 ; Brown and  was o b t a i n e d  cooling  Samples  and s u g a r s w h i c h  s a m p l e c h a m b e r was k e p t  15 m i n u t e s t o a l l o w  measurement.  mode a f t e r  The  Samples  vials.  a thermocouple  s a m p l e c h a m b e r w h i c h h a d been c a l i b r a t e d known o s m o t i c p o t e n t i a l .  from the  starch  (Turner  1976).  full  turgor  and z e r o  Water-release Before  curves  a p o l y s t y r e n e cup w h i c h  was f i l l e d w i t h w a t e r  turgor  c u r v e s were  e x c i s i o n of  glued together  indicated did  that  not exceed 0.3  generated f o r  the seedlings had b e e n c u t  around the base of  differences  ten  MPa  seedlings  a t predawn t h e along i t s  of  two  longitudinal  the s e e d l i n g stem.  The  cup  and t h e i m m e r s e d s t e m e x c i s e d a b o u t 5 cm f r o m  the  -  base.  The  hours were  s h o o t was l e f t  before  sap  ally  slightly  shows  higher  have been t h e  dilution using  4.  1.1  of  the  the  is  temperature,  sap w i t h  e  stomatal layer  a  for  the  At  determination  of  a minimum o f this  y  time  using  v  12  needles  the  of  30 c o m p a r i s o n s  agreement,  v  v  obtained of  the  frozen  from the  damage t o  apoplastic  of  cell  water  of  the  s a p was  release  methods. gener-  curves.  membranes and  during the  two  This  subsequent  extraction  process  Transpiration  the e  n  rate  is  of  gas c o n s t a n t is  the  shaded s e e d l i n g s  - e a ) / ^ -  n  the  the  of  the  was e s t i m a t e d  using  + gb^HRvT')  for water  saturated  vapour pressure  conductance  1  of  (1)  vapour, T'  s a t u r a t e d vapour  (assumed t o equal  ture),  for  results  result  transpiration  v  dark  c u r v e was g e n e r a t e d .  than  E = (e  where R  the  vice-grips.  Seedling The  ties  the  t h e r e was e x c e l l e n t  might  in  method.  Figure While  shoot  -  rehydrate  a water-release  removed from the  frozen  to  13  pressure  is of  the  vapour pressure the  seedling,  air,  and  g  s  is  the  at  the  absolute stomatal needle  average  air cavi-  temperahypo-  is  the  average  boundary  of  the  needles  on  conductance. The  behind  boundary  shade  l a y e r conductance  c a r d s was e s t i m a t e d  ^  (cm s  _ 1  )  seedlings  using  = (l/1.84)(u/d ) /2 1  n  (2)  - 14 -  Release Curve l|> (MPa) no  F i g u r e 1.1  Measurements o f osmotic p o t e n t i a l at f u l l t u r g o r obtained from w a t e r - r e l e a s e curves (^Q) versus those obtained from p r e v i o u s l y f r o z e n sap for Douglas-fir (DF), western hemlock (WH) and P a c i f i c s i l v e r f i r ( P S F ) .  - 15  where  d  n  is  the  needle  d i a m e t e r i n m and u i s  ( S p i t t l e h o u s e and B l a c k given the iage  relatively  1982).  This  low d e n s i t y  ( L a n d s b e r g e t a]_. 1 9 7 1 ) .  from Grant  ( 1 9 8 3 ) who s u g g e s t s  microscale  turbulence  porous  Stathers et windspeeds those  is  at  that  for the  seedling height  are  never l e s s  Consequently  flow  'sees'  than  In winds  results s  _ 1  )  highly  length.  indicated  ( e . g . 0 . 1 5 m) a r e a minimum o f  anemometer i n d i c a t e d 10% o f  those  at  that  that  50% o f  .  t o 3 . 9 cm s  _ 1  The  s  open.  u at  the  (at 0.4 m h e i g h t )  l  0.001 m i n  s m a l l e s t of  t h a n maximum m e a s u r e d g  a  wind  i n the  s h a d e c a r d was a s s u m e d t o be 5% o f  r a n g i n g f r o m 0 . 5 - 1.0 m s ~  greater  typically  t h e same h e i g h t  would  almost s i x times  fol-  d e t e r m i n e d by  site,  a shaded needle  from 2.3  seedling  (< 1.5 m  needle  l  1,  t h e s h o o t as a  roughness  t h e c o r r e s p o n d i n g minimum g^, f o r range  of  s u p p o r t e d by  r e l a t e d to  surface  factor the  s~  in m  F u r t h e r m o r e , measurements of wind speed b e h i n d  u behind the  0.4 m h e i g h t .  of  low windspeeds  scale  of  is  the Mount A r r o w s m i t h  shade c a r d u s i n g a hot w i r e speeds  assumption  using values  a t 0.4 m h e i g h t .  assumes a s h e l t e r  This  such t h a t  al_. (1985) f o r  the windspeed  and open s t r u c t u r e  twig cylinder with a length  Aerodynamic theory,  -  these  for  diameter,  values  is  Douglas-fir  seedlings. The t r a n s p i r a t i o n simplified  v e r s i o n of  - e )  the  a  « D,  negligible  rate of  u n s h a d e d s e e d l i n g s was e s t i m a t e d u s i n g  (1) w h i c h  vapour p r e s s u r e  compared w i t h  1 9 7 8 ; R i h a and C a m p b e l l  gs" . 1  a s s u m e s gb i s deficit This  of  large  the a i r ,  c a n be w r i t t e n  enough t h a t and t h a t as  g  _ D  (Tan e t  (e 1  n  is  al.  1985)  E = D g /(R T') s  v  (3)  a  - 16  Equation  ( 3 ) was u s e d b e c a u s e  to  least  be a t  neglecting  10 t i m e s  boundary  underestimate  Values  only 4 - 8 % with  the  l a y e r conductance results  difference  of D at less  (1978) suggested  compensates  that the  f r o m u s i n g D as an e s t i m a t e o f  the  needle  stomatal  s c r e e n h e i g h t were used s i n c e  humidity  estimated  somewhat f o r  between  than those  relative  u n s h a d e d s e e d l i n g s was  T a n e t a]_.  s  of E t h a t  vapour pressure air.  g .  gb o f  -  that  cavities these  had been m e a s u r e d a t  and t e m p e r a t u r e  sensors  and  the  values  seedling  were height  i n the CS-102  poro-  meter. Measurements meter  of  g  w e r e made w i t h  s  (Micromet Systems I n c . ,  foliage  is  enclosed  Vancouver,  by a s t a i n l e s s  minute  during this  Hourly  measurements of  measurement g  s  a CS-102 t r a n s i e n t  steel  Canada).  All  chamber f o r  b e t w e e n J u n e 10 a n d S e p t e m b e r 9 ,  three  sunny  all  t h r e e weeks of  day. the  Total g  s  1 9 8 2 , 10 o f w h i c h w e r e  (Model  using  regression equations  of  needles  needle  projected  Li-3000, Li-Cor  dried  leaf  measurements e i t h e r  meter  Inc.,  that  t o 65°C f o r  Lincoln,  relate  one day  thermocouple.  needle with side with  the thermocouple  a drop of  junction  cyanoacrylate  II).  on 16 d a y s sunny a l l  day,  these  days  within area or  by  area to the  e t al_. 1 9 8 4 ) . ( 0 . 0 7 5 mm)  copper-  to the n e e d l e ' s  Another  fine wire  mass  Seedling  t h i s w i r e was wound a r o u n d  attached  glue.  (Appendix  Nebraska, U.S.A.),  (Livingston  one  using a leaf  projected needle  A b o u t 4 0 mm o f  than  Four of  directly  poro-  seedling's  a r e a was d e t e r m i n e d  t e m p e r a t u r e was m e a s u r e d w i t h a f i n e w i r e  constantan  less  species  and on 5 d a y s b e t w e e n J u n e 6 and A u g u s t 1 4 , 1 9 8 3 . were  the  ( L i v i n g s t o n e t al_. 1 9 8 4 )  w e r e made on a l l  type  a  under-  thermocouple  made f r o m t h i s w i r e was p l a c e d a p p r o x i m a t e l y 50 mm b e h i n d a s h a d e  card  - 17  a n d 200 mm a b o v e t h e sandwiching surfaces  5.  the  s h i e l d was p r o v i d e d  b e t w e e n two p l a s t i c  spoons,  the  aluminized mylar tape.  by  outside  Both  thermo-  r e f e r e n c e d to a t h e r m i s t o r thermometer l o c a t e d 0.5 m soil  surface.  Seedling Survival  1981,  1982 and 1983  was a s s e s s e d m o n t h l y  (seedling height,  measured c o n c u r r e n t l y ) . system a chlorosis 50% o f  ' 3 ' was or  their  A visual  necrosis, needle  a  area a f f e c t e d ,  a  t h a n 100% b u t more t h a n 50% o f  III.  a r e a was  from the time the  rain  deficits  that  signs  this  of no more  ' 1 ' was a s s i g n e d t o s e e d l i n g s their  needle  area a f f e c t e d .  n e c r o t i c were c o n s i d e r e d  s e a s o n was c h a r a c t e r i z e d by c o o l  than with  Seed-  t o be  air  relative humidities  resulted  t h e end o f  - 1 . 7 MPa on A u g u s t 2 5 , r e f l e c t i n g  mid-July.  temperatures  a t t i m e s exceeded 4 . 5 kPa until  and w e t An  dead.  (Figure August  the coarse  in  weather  extended  10 a n d A u g u s t 26 d u r i n g w h i c h  Extremely high  decreased from mid-July  In  seedlings with  s e e d l i n g s were p l a n t e d u n t i l  fell.  25 - 37°C) and l o w  no v i s i b l e  was  Observations  d r y p e r i o d o c c u r r e d between J u l y 10 mm o f  i n Chapter 3,  in  RESULTS AND DISCUSSION  Growing Season Weather The 1 9 8 1 g r o w i n g  October  r a n k i n g s y s t e m was u s e d .  ' 2 ' was a s s i g n e d t o  needle  f r o m May u n t i l  discussed  assigned to seedlings with  l i n g s whose e n t i r e  A.  A radiative  of w h i c h were c o a t e d w i t h  Seedling survival  less  surface.  the thermocouple  c o u p l e s were beneath  soil  -  less  than  (maxima r a n g e d  from  vapour  1.2).  Root  reaching  nature of  pressure z o n e <y  s  a minimum o f  the s o i l .  A  -  vegetation  removal  which  soil  water  that,  at  the  accounts  for  The hot  y  s  0.3 m depth,  growing  (Figure  rainfall  cast  days were  fall  occurred  probe,  s u c h as  in  indicated  fireweed,  depletion.  summer d r o u g h t was  A u g u s t w h i c h was  the  broken  sufficient  to  spring  by a s h o r t  and a  period  significantly  frequent.  the weather  driest  of  the  The  of  longest  of weather the  period without  records  southeast  during the e a r l y  three years  part  1983 was e x c e p t i o n a l l y  t h e 44 d a y s b e t w e e n J u l y  15 km t o  years,  Total  summer o f  wet  f r o m May t h r o u g h S e p t e m b e r was 399 mm.  basis  approximately  B.  a neutron  vegetation,  water  4 m x 4 m plots,  i n 1982 was c h a r a c t e r i z e d by a w e t  The  during  On t h e  that  i n 1983 i n  of  raise  1.3).  Total  for  conducted  competing  soil  season  early  By c o n t r a s t  1.4).  the  summer.  in  -  c o n t e n t was m e a s u r e d w i t h  much o f  and dry  rainfall  experiment  18  the  (i.e  the  part  1 9 8 2 ) was  of  the  and  appreciable  Alberni  site)  cool.  Cloudy  14 a n d A u g u s t  from P o r t  of  and  for  s i m i l a r to the  rain-  (Fig.  (located  the  growing  28  over-  previous  season  of  10-year  ten the  average  year.  Twig Xylem P o t e n t i a l ,  Needle Osmotic  Potential  and  Turgor  Potentials Predawn lower  than Y  values are  of  All rrtx  s  when f  predawn  similar  Kelliher  values  et  to  species  b e t w e e n May  yjtx  f°  the  r  > - 0 . 5 MPa  s  fT/tx  those  al_.  of  w  e  r  e  found  three  (Figure  generally  species 1.5).  closer  by o t h e r w o r k e r s  to  were  significantly  For  Y  <p s .  These  (Cleary  s  < -0.5  MPa  results  1971; H a l l g r e n  1978;  1984). exhibited a progressive and A u g u s t o f  1981.  decrease  This  in  daily  corresponded to  minimum a  similar  - 19 -  1981 MAY  F i g u r e 1.2  JUN  JUL  AUG  SEP  Courses of average root zone s o i l water p o t e n t i a l (i|< s ), p r e c i p i t a t i o n (P) and maximum vapour p r e s s u r e d e f i c i t (D) d u r i n g the 1981 growing s e a s o n .  - 20 -  1982 MAY  F i g u r e 1.3  JUN  JUL  AUG  SEP  Courses o f average root zone s o i l water p o t e n t i a l ( * ) , p r e c i p i t a t i o n ( P ) and maximum vapour p r e s s u r e d e f i c i t (D) d u r i n g the 1982 growing s e a s o n . s  Figure  1.4  C o u r s e s o f a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l (i|>s)» p r e c i p i t a t i o n ( P ) and maximum v a p o u r p r e s s u r e d e f i c i t (D) d u r i n g t h e 1983 g r o w i n g s e a s o n .  - 22 -  Figure  1.5  R e l a t i o n s h i p b e t w e e n predawn t o t a l t w i g x y l e m w a t e r p o t e n t i a l (^Ttx) a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l (ii» ) f o r n o n - i r r i g a t e d D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r f i r ( P S F ) . M e a s u r e m e n t s were made i n 1981, 1982 and 1983. A l s o shown i s t h e 1:1 l i n e . Linear regression analysis indicates a  n  d  s  predawn (dashed  n t x fMPa) = 0.863 ) line).  s  (MPa)  -  0.357 ( r = 0.89) 2  - 23  decline  i n average  minimum ^ j t hemlock  1.6,  1.7  (Table  between J u l y of  "TTT o f  in v  especially  in  treatments  the  were  occurring occurred likely Y,, The  at  values  the w i n t e r , foliar is  solute  decrease  are c o n s i s t e n t with  cold  seedlings  1.3).  and w e s t e r n these  (Figures  ^  values  1982  of  y  and  for  a  short  the  irri-  s  season.  species  1.6  - 1.8).  season.  progres-  of  with  irrig-  non-irrigated  until  Observed values  because  March 1 9 8 3 .  summer and  throughout  d o c u m e n t e d phenomenon o f  ( L e v i t t 1980).  plant  Values  species of  different  to those  of  the  seedlings  ^  for  that  i n S e p t e m b e r was  dehydration  i n many woody  significantly  adjustment  heavy r a i n  the  July  minimum v a l u e s  The o s m o t i c  increase  of  Douglas-fir  In the  r a t h e r than c e l l  the w e l l  (Ritchie  in  a a  Values  lower than those  p e r i o d of  occurring  hemlock  exhibited  o c c u r r e d b e t w e e n J u n e and  d i d not  hardiness  were not  for  daily western  I n 1982 b o t h  species  m e a s u r e d a t t h e end o f  sugar concentrations  Douglas-fir  by  summer e x c e p t  stem e l o n g a t i o n )  the f i e l d  shaded s e e d l i n g s  values  in  in  accumulation  of  (Table  all  the f i e l d  and t r e a t m e n t s  associated with  in  observed in  b e i n g most p r o n o u n c e d  p a r t of  a reduction  species  in  summer  b e t w e e n May and t h e f i r s t  in all low  treatments  latter  t h e end of  due t o  followed  high  n o t made i n 1 9 8 1 .  differences  greatest  (coinciding with  persisted all  t r e a t m e n t s were a l w a y s  the  the  1.2)  decrease  T h i s was a l s o  In 1983 r e l a t i v e l y  d u r i n g the  v  non-irrigated  ated treatments,  The  and A u g u s t .  g a t e d and n o n - i r r i g a t e d decrease  1.1).  in Douglas-fir,  silver fir.  and 1 . 8 ) .  Measurements  sive  (Table  was m o s t p r o n o u n c e d  x  minimum YJ^X  period  z o n e v$  and t h e n P a c i f i c  (Figures daily  root  -  ^ in  high that  in unshaded  irrigated  are s i m i l a r to other  published  and S h u l a 1 9 8 4 ; K a n d i k o e t al_. 1 9 8 0 ) .  - 24  Table 1.1.  -  D a i l y minimum m e a s u r e d v a l u e s o f t o t a l t w i g x y l e m w a t e r p o t e n t i a l (vjtx) (MPa) and a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l ( ¥ 5 ) (MPa) f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s b e t w e e n May and August 1981. S e e d l i n g s were p l a n t e d i n A p r i l 1 9 8 1 . S t a n d a r d d e v i a t i o n s o f vjtx given in brackets. a  *s May  30  Douglas-fir  r  e  Western hemlock  Pacific  -0.09  -1.8  (0.1)  -1.3  (0.1)  —  silver —  June  15  -0.15  -1.9  (0.2)  -1.4  (0.1)  -1.1  (0.1)  July  27  -0.32  -1.9  (0.1)  -1.6  (0.1)  -1.2  (0.2)  -1.70  -3.2  (0.2)  -1.9  (0.2)  -1.6  (0.2)  August  25  - 25  MAY  JUN  -  JUL  AUG  SEP  -0.4 Figure  1.6  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 g r o w i n g s e a s o n , f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) D o u g l a s - f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . V a l u e s o f minimum t u r g o r p o t e n t i a l were o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r potential  - 26  MAY  JUN  -  JUL  AUG  SEP  co  2  <  i X -3  CD  a.  -1  i 5  to o -3  Figure  1.7  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 g r o w i n g s e a s o n , f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n May 1 9 8 2 . V a l u e s o f minimum t u r g o r p o t e n t i a l were o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r potential.  - 27  MAY  JUN  -  JUL  AUG  SEP  -1  -  9>x  2  -3 0  1 o  Figure  1.8  -2  • PR o NON-IRR  C o u r s e s o f minimum t w i g x y l e m w a t e r p o t e n t i a l , o s m o t i c p o t e n t i a l and minimum t u r g o r p o t e n t i a l , d u r i n g t h e 1982 g r o w i n g s e a s o n , f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1982. V a l u e s o f minimum t u r g o r p o t e n t i a l w e r e o b t a i n e d by s u b t r a c t i n g o s m o t i c p o t e n t i a l f r o m minimum t w i g x y l e m w a t e r potential.  - 28  Table 1.2.  -  Measured v a l u e s of a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l ( Y ) ( M P a ) and d a i l y minimum t o t a l t w i g x y l e m p o t e n t i a l (4'Ttx)( ) u n t r e a t e d D o u g l a s - f i r , w e s t e r n hemlock a n d P a c i f i c s i l v e r f i r s e e d l i n g s b e t w e e n May and S e p t e m b e r 1983. S e e d l i n g s were p l a n t e d i n A p r i l 1 9 8 1 . Standard d e v i a t i o n s of yytx given in brackets. s  M P a  f  o  r  a  *s May  20  r  e  Douglas-fir  Western hemlock  Pacific  silver  -0.06  -1.6  (0.2)  -1.2  (0.1)  -0.9  (0.1)  June  13  -0.05  -1.7  (0.1)  -1.4  (0.2)  -1.1  (0.2)  July  27  -0.18  -2.2  (0.3)  -1.6  (0.1)  -1.1  (0.1)  August 1  -0.91  -2.4  (0.2)  -1.6  (0.2)  -1.0  (0.1)  September 8  -0.05  -1.8  (0.1)  -1.3  (0.1)  -0.9  (0.2)  - 29  Table 1.3.  -  M e a s u r e d v a l u e s o f minimum o s m o t i c p o t e n t i a l (4^) (MPa) b e t w e e n May a n d S e p t e m b e r 1982 f o r s h a d e d ( u s i n g s h a d e c a r d s ) and n o n - s h a d e d D o u g l a s - f i r , w e s t e r n h e m l o c k , a n d P a c i f i c s i l v e r f i r seedlings planted in 1981. Standard d e v i a t i o n s are given in b r a c k e t s .  Douglas-fir May 4  Western hemlock  Pacific  silver  fir  shade no s h a d e  -1.8 -1.9  (0.2) (0.2)  -1.0 -1.2  (0.2) (0.2)  -0.8 -0.9  (0.2) (0.1)  June  16  shade no s h a d e  -1.8 -2.1  (0.1) (0.3)  -1.0 -1.2  (0.1) (0.2)  -0.9 -0.9  (0.1) (0.2)  July  27  shade no s h a d e  -2.4 -2.6  (0.1) (0.3)  -1.8 -1.7  (0.1) (0.2)  -1.3 -1.2  (0.1) (0.2)  shade no s h a d e  -2.9 -2.9  (0.2) (0.2)  -1.7 -1.9  (0.2) (0.2)  -1.5 -1.3  (0.2) (0.1)  shade no s h a d e  -3.0 -2.9  (0.3) (0.2)  -1.8 -2.0  (0.2) (0.1)  -1.4  August  26  September  9  _  _  (0.2)  - 30 -  I n 1983 s m a l l e r changes species  (Table  exceptionally osmotic gated  The f a c t  that less  w e t summer, a n d t h a t  treatments  suggests  but r a t h e r a response  seedlings osmotic  planted  adjustment occurred  adjustment  to environmental no d i f f e r e n c e  i n 1981 a n d 1 9 8 2 .  in the greater-  i s not a seasonal  stress. in daily  It is likely  irri-  that  T a b l e 1 . 5 shows minimum y  of  n  considerable  a d j u s t m e n t o c c u r r e d i n t h e v e r y d r y summer o f 1 9 8 1 c o r r e s p o n d i n g  to the progressive  decline  I n 1982 o s m o t i c  in y  the P a c i f i c seedlings  s  a n d minimum d a i l y  (Table 1 . 1 ) . seedlings  d u r i n g t h e summer ( F i g 1 . 6 ) .  s i l v e r - f i r and, to a lesser- e x t e n t ,  were  ¥rtx  adjustment enabled the D o u g l a s - f i r  consistently maintain turgor  unable to maintain turgor  In c o n t r a s t ,  the western  throughout  to  hemlock  t h e same  period  1.7 and 1 . 8 ) . There are three p o s s i b l e  explanations  Yp c o m p u t e d f o r a l l t h e s p e c i e s : s a p by a p o p l a s t i c overestimate  water  of v  n  and, therefore,  a  n  1982 d i d n o t r e v e a l  values  ( i ) t h e r e was some d i l u t i o n  an u n d e r e s t i m a t e  xylem water  o f ¥p,  of  of the  l e d t o an (ii)  p o t e n t i a l ; however,  w h i c h w e r e made e v e r y two h o u r s  d  values  y  u  sap s a m p l e s w e r e t a k e n a t p r e d a w n r a t h e r  a t t h e t i m e o f minimum t o t a l ments o f ¥ j t x  f o r the negative  during the e x t r a c t i o n process which  was o v e r e s t i m a t e d b e c a u s e  July  were o b s e r v e d i n a l l t h e  i n t h e p r e v i o u s y e a r much  that osmotic  i n 1982 t h e r e was v i r t u a l l y  (Fig.  potential  a d j u s t m e n t was o b s e r v e d i n t h e n o n - i r r i g a t e d t h a n i n t h e  response that  1.4).  i n osmotic  significant  diurnal  changes  measure-  on two d a y s in y \ %  than  in  and ( i i i )  o f Yp w e r e u n d e r e s t i m a t e d b e c a u s e t h e y w e r e c o m p u t e d by s u b -  tracting  needle  osmotic  rather- than needle  potential  from t o t a l  osmotic p o t e n t i a l  twig  from t o t a l  xylem water  needle  potential  xylem water  - 31  Table 1.4.  M e a s u r e d v a l u e s o f minimum o s m o t i c p o t e n t i a l ( v ) (MPa) f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s b e t w e e n May and S e p t e m b e r 1 9 8 3 . S e e d l i n g s w e r e p l a n t e d i n May 1 9 8 1 . S t a n d a r d d e v i a t i o n s given in brackets. v  Douglas-fir May  20  -  Western  hemlock  Pacific  silver  -2.1  (0.2)  -1.3  (0.1)  -0.9  (0.1)  June  13  -2.0  (0.2)  -1.5  (0.2)  -1.0  (0.2)  July  27  -2.3  (0.1)  -1.4  (0.1)  -1.0  (0.1)  -2.7  (0.3)  -1.7  (0.2)  -0.9  (0.1)  -2.7  (0.2)  -1.3  (0.1)  -1.1  (0.2)  August  21  September 8  are  fir  - 32  Table 1.5.  -  M e a s u r e d v a l u e s o f d a i l y minimum o s m o t i c p o t e n t i a l (<?„) (MPa) b e t w e e n May and S e p t e m b e r 1982 f o r u n t r e a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k , and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n t h e p r e v i o u s y e a r ( P ) and p l a n t e d i n the c u r r e n t year (C). Standard d e v i a t i o n s are given i n brackets.  Dougl a s - f i r  W e s t e r n hemlock  Pacific  silver  May 4  P C  -1.9 -1.8  (0.2) (0.2)  -1.2 -1.4  (0.1) (0.2)  -0.9 -0.7  (0.1) (0.2)  J u n e 16  P C  -2.1 -2.0  (0.2) (0.3)  -1.2  (0.2)  -0.9 -1.2  (0.1) (0.1)  July  P C  -2.6 -2.5  (0.3) (0.2)  -1.7 -1.8  (0.1) (0.1)  -1.2 -1.0  (0.2) (0.1)  A u g u s t 26  P C  -2.9 -2.9  (0.1) (0.2)  -1.9 -1.6  (0.2) (0.2)  -1.3 -1.1  (0.2) (0.1)  September 9  P C  -2.9 -2.7  (0.1) (0.2)  -2.0 -2.2  (0.1) (0.3)  -1.4  (0.1)  27  -  -  -  - 33  potential study  of  (?jnx).  the p i t h  filling  of  yjtx  of  the  w  e  C.  "d  al  e  seedlings, l  s  (1971),  e  s  than  s  of Yjtx*  found t h a t  ^rnx*  They  t w i g a c t e d as a w a t e r  chamber  pressure  *  n  trees  hypothesized  sink  so  c o n t r a s t K e l l i h e r e t JJ1_. 1984 found  no s i g n i f i c a n t  chamber  that an  working  difference  between  Yrnx-  The maximum d a i l y  Rates  transpiration  (E) o f w e s t e r n hemlock  rates  and P a c i f i c  lings.  Daily  transpiration  d i d not  decrease with  i r r i g a t e d western Figure irrigated function  1.10  <F . s  decreasing  r a t i o of  (ENJ.) t o t h a t s  silver-fir, tolerance  to maintain  silver fir  daily  of  the  seedlings  t r a n s p i r a t i o n of  irrigated  - 1 . 2 MPa t h e  of  daily  seedlings  transpiration  s e e d l i n g s was o v e r 50% o f  respectively,  and i n d i c a t e s  by D o u g l a s - f i r  to the a b i l i t y relatively  high  of  the  values  were  that  of  the  greater  seedlings.  (Fig.  g  s  as ¥  as  of  decreased.  a  non-  and of  seed-  Pacific stress  The m a i n t e n a n c e  s  1.9).  non-  non-irrigated Douglas-fir of  seedlings  irrigated  degree  seed-  non-  (Ej)  c o m p a r e s w i t h 40% a n d 25% f o r w e s t e r n h e m l o c k  exhibited  corresponded  of  seedlings  area  those of D o u g l a s - f i r  <ps as much as t h o s e  shows t h e  At v  of  leaf  non-irrigated Douglas-fir  and P a c i f i c  irrigated Douglas-fir This  of  hemlock  seedlings of  rates  on a p r o j e c t e d  silver fir  a p p r o x i m a t e l y 60% a n d 43%, r e s p e c t i v e l y ,  lings.  i n a growth  sap d u r i n g p r e s s u r i z a t i o n w o u l d l e a d t o  Seedling Transpiration  basis  y  w a  a Douglas-fir  w i t h young D o u g l a s - f i r a  r  pith with  underestimation  *Ttx  and H i n k l e y  two-year-old Douglas-fir  measurements of that  Ritchie  -  of  turgor  seedlings  - 34 -  Figure  1.9  The r e l a t i o n s h i p between d a i l y t r a n s p i r a t i o n (E) and average root zone s o i l water p o t e n t i a l (ij/ s ) f o r n o n - i r r i g a t e d D o u g l a s - f i r ( D F ) , western hemlock (WH) and P a c i f i c s i l v e r f i r (PSF) s e e d l i n g s . Measurements were made i n 1982 on s e e d l i n g s planted i n May o f t h a t y e a r . Each p o i n t r e p r e s e n t s the average E f o r t h r e e s e e d l i n g s . The c u r v e s were f i t t e d by e y e .  - 35 -  « •  i  —i  i  —1  >  — i —  •  •  1 10  T"  •  •  - 05  DF  1982  • •  •  • •  _  0-5 Ew/E i  WH  *  *  _i  *  *  "—  i  •  Figure  1.10  *  05 PSF  *  -12  *  1  -1-0  -08  i  -0-6  Vs (MPa)  i -04  <  -02  The r e l a t i o n s h i p between the r a t i o o f d a i l y t r a n s p i r a t i o n per u n i t p r o j e c t e d l e a f area o f n o n - I r r i g a t e d s e e d l i n g s to t h a t o f I r r i g a t e d s e e d l i n g s ( E N I / E J ) and average root zone s o i l water p o t e n t i a l ( * ) f o r D o u g l a s - f i r ( D F ) , western hemlock (WH) and P a c i f i c s i l v e r f i r ( P S F ) . Measurements were made i n 1982 on s e e d l i n g s p l a n t e d in May of that y e a r . s  - 36  All  three  potential non-zero results  species  drop  in  the  intercept in Fig.  e t al_. ( 1 9 8 4 ) .  showed a l i n e a r soil-plant  (Table  1.5  three,  greater  the  However,  value of  than t h a t  for  Transpiration on d a y s w i t h stomatal tance  high  closure  scatter  of  in F i g .  seedlings  pronounced  on t h e  the  deficits  at  greater  is  This  seedlings  on J u l y  similar  transpiration  to those  of  daily  rates  factor  27,  conduc-  in Chapter  for  of  2).  irrigated  some o f 1.11  in  the which  high D  1982).  The e f f e c t  24 t o J u l y  27 was more  t h a n on t h e  (July on  non-irrigated  seed-  l i m i t e d by l o w ¥ .  This  s  of  non-irrigated 27  (0.83)  to  despite  day.  seedlings  unshaded s e e d l i n g s  complete  non-irrigated  transpiration  latter of  s  reduced  stomatal  in F i g .  24 ( 0 . 6 8 ) t h a n on J u l y  on t h e  y  22 - 28%  almost  rates  accounts  i r r i g a t e d and  very high D ( J u l y  ratio  Kelliher  as  greatly  length  illustrated  i n c r e a s e d D from J u l y  b e i n g 0 . 2 5 MPa l o w e r Daily  of  the context of  of  seedlings  the  b i n c r e a s e d by a  because  resulted irrigated  view of  in  that,  s e e d l i n g s were  r a t e s were a l r e a d y  a lower  a  s e e d l i n g s was o n l y  l i n g s whose t r a n s p i r a t i o n in  rate with  a r e c o m p a r e d on a day w i t h m o d e r a t e l y  irrigated  water  seedlings.  decreased.  of  the  r e p o r t e d by  findings  value of  species,  rates  1 9 8 2 ) and a day w i t h  t r a n s p i r a t i o n of  to t h e i r  the c o n i f e r  The e f f e c t  transpiration  Douglas-fir  to that  between the t r a n s p i r a t i o n  seedlings  1.10.  result  discussed in the  between  not unexpected  the untreated  vapour pressure is  is  the  irrigated of  days d i f f e r e n c e s  the hourly  24,  - 1 . 1 MPa,  the  (This  and n o n - i r r i g a t e d  This  a similar  b for  relationship  s y s t e m and t r a n s p i r a t i o n  in contrast  rates  characteristics  On s u c h  1.6).  and i s  decreased from -0.01 to of  -  b e h i n d shade c a r d s  on t h e t h r e e  days  were  i n June  1982  - 37  Table 1.6.  -  V a l u e s of l i n e a r r e g r e s s i o n c o e f f i c i e n t s and r f o r the relationship: E = a + (Y - ¥ Ttx)/ f° i r r i g a t e d (I) a n d n o n - i r r i g a t e d ( N I ) D o u g l a s - f i r , w e s t e r n h e m l o c k and Pacific silver f i r seedlings. The u n i t s o f a and b a r e pg c m s" and M P a / ( y g c m s ) , respectively. 2  b  r  s  - 2  1  - 2  Treatment  Species  - 1  a  b  r  2  Douglas-fir  I NI  -1.72 -1.45  0.36 0.44  0.88 0.79  Western  hemlock  I NI  -0.83 -0.29  0.43 0.55  0.86 0.81  Pacific  silver  I NI  -0.65 -0.19  0.47 0.59  0.92 0.83  fir  - 38  -  Time (PST)  Figure  1.11  The d a i l y c o u r s e o f t r a n s p i r a t i o n ( E ) p e r u n i t p r o j e c t e d l e a f a r e a f o r i r r i g a t e d ( I R R ) and n o n - i r r i g a t e d (NON-IRR) D o u g l a s - f i r s e e d l i n g s , and v a p o u r p r e s s u r e d e f i c i t (D) f o r J u l y 24 and J u l y 2 7 , 1 9 8 2 . The v a l u e s o f * on J u l y 24 and J u l y 27 w e r e - 0 . 5 MPa and - 0 . 7 M P a , r e s p e c t i v e l y . s  - 39  when m e a s u r e m e n t s w e r e t a k e n seedlings  had h i g h e r  ponded w i t h were  the  lower  result  of  (Fig.  1.13)  cards  (Fig. 1.14).  of  the  is  s  (Fig.  relatively  1.12);  n  - e ) a  rapidly  high  than t h a t  of  The  of  seedlings  reflects year. the  These  corres-  differences  temperatures  - e )  behind the  found  the t r a n s p i r a t i o n  a  to t h e i r  shade  in  rates.  lower  shaded s e e d l i n g s ,  of  t h e e a r l y m o r n i n g when  had h i g h e r After  unshaded  (e  n  of  - e ) a  1 1 : 0 0 h PST  decreased  g  s  and, as  more  causing transpiration  than the  of  transpiration  had s i m i l a r v a l u e s  unshaded s e e d l i n g s  rates  l a y e r conductance  B e f o r e 1 1 : 0 0 h PST  typically  transpiration s  unshaded  rates  of  latter.  Seedling Survival In a l l  of  n  be m o s t p r o n o u n c e d  t h e f o r m e r t o d e c r e a s e more r a p i d l y  D.  (e  unshaded s e e d l i n g s  g  1.12).  lower boundary  (Smith 1980).  however,  increased,  lower  days  i n the morning which  daytime needle  also contributed  will  higher  lower  three  s e e d l i n g s w e r e d e c r e a s e d as a r e s u l t  and s h a d e d s e e d l i n g s  consequently, (e  spruce  On a l l  (Fig.  (1979) a l s o  temperatures.  The e f f e c t  seedlings  slightly  Kaufmann  shaded s e e d l i n g s  rates  minimum T j t x  and, consequently,  needle  rates. g  the  shaded Engelmann  lowered  (Table 1.7).  transpiration  daily  -  species planted  and t r e a t m e n t s  t h e r e were h i g h e r  i n 1981 t h a n o f  t h e much s e v e r e r c o n d i t i o n s  S i m i l a r l y the  low m o r t a l i t y  r e l a t i v e l y mild conditions  of  those planted  rates  i n 1982.  t h a t were p r e v a l e n t  d u r i n g t h e summer o f that  year.  of  in 1983  mortality This  the  earlier  reflects  - 40  Table 1.7.  -  D a i l y t r a n s p i r a t i o n (g d a y ) o f s h a d e d ( u s i n g s h a d e c a r d s ) a n d u n s h a d e d D o u g l a s - f i r s e e d l i n g s on J u n e 1 0 , J u n e 12 a n d June 13, 1982. The t o t a l p r o j e c t e d n e e d l e a r e a ( c m ) i s given in brackets. The a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l was - 0 . 1 0 MPa on J u n e 1 2 . 1  2  Shade  No  shade  J u n e 10  6.5 (124.3)  6.4 (134.5)  J u n e 12  9.2 (141.0)  7.6 (128.8)  J u n e 13  8.1 (124.3)  7.8 (134.5)  - 41  6  9  12  -  15  Time (PST)  Figure  1.12  Courses of stomatal conductance ( g ) , t r a n s p i r a t i o n rate ( E ) and t o t a l t w i g x y l e m p o t e n t i a l ( i J r t x ) f ° shaded ( c l o s e d c i r c l e s ) and u n s h a d e d ( o p e n c i r c l e s ) D o u g l a s - f i r s e e d l i n g s on J u n e 1 3 , 1 9 8 2 . s  r  - 42  -  35  10  Figure  1  0  1.13  1  "  4  8  "  1  12  16  Time (PST)  1  1  20 24  C o u r s e s o f t e m p e r a t u r e o f s h a d e d ( d a s h e d l i n e ) and u n s h a d e d ( d o t t e d l i n e ) n e e d l e s o f a D o u g l a s - f i r s e e d l i n g , and a i r t e m p e r a t u r e ( s o l i d l i n e ) a t 2f) cm h e i g h t n e a r t h e u n s h a d e d s e e d l i n g on J u n e 1 3 , 1 9 8 2 .  - 43  Figure  1.14  -  Courses of vapour p r e s s u r e d e f i c i t ( s o l i d l i n e ) , vapour p r e s s u r e d i f f e r e n c e b e t w e e n an u n s h a d e d D o u g l a s - f i r n e e d l e and t h e a i r ( b r o k e n l i n e ) and t h e v a p o u r p r e s s u r e d i f f e r e n c e b e t w e e n a s h a d e d D o u g l a s - f i r n e e d l e and t h e a i r ( d o t t e d l i n e ) on J u n e 1 3 , 1 9 8 2 .  - 44  1.  Seedlings planted in The s u r v i v a l  1.8  for  each of  figures  of  the  are given  "3"  following  April.  t h e end o f  This,  region  (7%) and P a c i f i c  species.  The high  seedlings  survival  increased  with  (as  s e e d l i n g s which  and t h e  Most of conditions  (4%).  significantly  increased  rates  the  in  had  of  all  of  far  in Douglas-fir  the species  in  little  greater  of  survival  hemlock  from  survival  only D o u g l a s - f i r  dead  in  elimin-  all  because Inclining  seedlings,  had r e s p o n d e d difference  of  the  the  and by  geotropically  between  inclined  control.  the s e e d l i n g m o r t a l i t y occurred  were most s e v e r e .  was  that  Severe n e c r o s i s  in  observed.  the  a  conditions.  the untreated s e e d l i n g s .  survival  were  that winters  Shade c a r d s , w h i l s t  f i r s t year  and c h l o r o s i s  o b s e r v e d i n m i d - A u g u s t 1 9 8 1 , and by S e p t e m b e r o f mortality  fact  the u n t r e a t e d western  f r o m t h e n on t h e r e was no o b s e r v a b l e  seedlings  the  as a l i v e ) ,  t h e r e was s i g n i f i c a n t l y  was n o t as p r o n o u n c e d  the second y e a r s e e d l i n g s so t h a t  the  Table  Survival  October  r e l a t i v e l y mild suggests  (72%) t h a n i n  silver-fir  effect  together  are  three years  seedling mortality,  already  o v e r 90% o f  c o u l d be a t t r i b u t e d t o w i n t e r  untreated Douglas-fir  ating  r a t h e r than the previous  ( a n d h e n c e had been c l a s s i f i e d  the s e e d l i n g m o r t a l i t y  in  summarized i n  and t r e a t m e n t c o m b i n a t i o n s .  (1983)) because  t h e Mount A r r o w s m i t h  At  i n 1981 i s  s e v e r e damage d u r i n g t h e summer and w h i c h h a d been d e s i g n a t e d  i n O c t o b e r 1981  by t h e  planted  species  for April  r e p o r t e d by S t a t h e r s suffered  1981  seedlings nine  -  that year  when  were  first  significant  - 45  Table 1.8.  P e r c e n t s u r v i v a l i n A p r i l 1 9 8 2 , 1983 a n d 1984 o f D o u g l a s - f i r , w e s t e r n hemlock and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1 9 8 1 . Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t , w h i c h was a p p l i e d to each s p e c i e s i n each y e a r .  April Treatment  -  Douglas-fir  1982  Western hemlock  Pacific  silver  Control  88  (a)  25 ( a )  11  (a)  Self  91 ( a )  25 ( a )  13  (a)  98 ( a )  63 ( b )  38  (b)  shade  Shade c a r d s  April Treatment  Douglas-fir  1983  Western hemlock  Pacific  silver  Control  74  (a)  14 ( a )  8  (a)  Self  86  (b)  19 ( a )  9  (a)  97  (b)  48 ( b )  34  (b)  shade  Shade c a r d s  April Treatment  Douglas-fir  Control  72 ( a )  Self  81  shade  Shade c a r d s  (a)  95 ( b )  fir  fir  1984  Western hemlock  Pacific  silver  7 (a)  4  (a)  13 ( a )  7  (a)  31  (b)  42  (b)  fir  - 46  Table 1.9.  -  P e r c e n t s u r v i v a l i n A p r i l 1983 and 1984 o f D o u g l a s - f i r , w e s t e r n hemlock and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1982. Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t , w h i c h was a p p l i e d t o e a c h s p e c i e s i n each y e a r .  April Treatment  Douglas-fir  1983  Western hemlock  Pacific  silver  Control  88  (a)  40  (a)  30  (a)  Shade c a r d s  93 ( a )  71  (b)  57  (b)  Irrigation  91  60  (b)  59  (b)  I r r i g a t i o n and shade c a r d s  90 ( a )  74 ( b )  60  (b)  (a)  April Treatment  Douglas-fir  fir  1984  Western hemlock  Pacific  silver  Control  82  (a)  34  (a)  19  (a)  Shade c a r d s  89  (a)  63  (b)  45  (b)  Irrigation  87  (a)  57 ( b )  43  (b)  I r r i g a t i o n and shade c a r d s  83  (a)  64  53  (b)  (b)  fir  - 47  2.  Seedlings planted in As i n  the case of  greater  survival  hemlock  and P a c i f i c  observation  1981 p l a n t e d s e e d l i n g s  silver-fir  only  turgor throughout  the season  periods  of  also  explain  in  did  throughout  silver-fir  in  irrigated  Pacific ly,  silver  in  rates  shade c a r d s  fir  t  h  a  n  there  fir  were  seedlings would  rates  of  the  in Chapter 3 ) ,  unshaded s e e d l i n g s  in  survival  western in  these  seedlings.  both western  to m a i n t a i n onwards  hemlock  turgor  t u r g o r was  shaded w e s t e r n hemlock 1984 w e r e 63% and 45%,  rates  reducing mortality  shaded s e e d l i n g s  although  not able  in April  Until  mortality  higher  seedlings.  than the c o n t r o l  area of  of  from m i d - J u l y  to s u r v i v a l  needle  Yjtx  the  maintain  seedlings.This  irrigation  non-irrigated,  on s e e d l i n g t u r g o r .  (discussed  to  silver  western  to  In c o n t r a s t ,  that of non-irrigated  despite  although  effect  lings  rates  s e e d l i n g s were  seedlings  higher in  corresponds  the P a c i f i c  seedlings  non-irrigated for  and w e r e s i m i l a r  significantly of  season,  than  Survival  - 1.8).  w e s t e r n hemlock  twice  show t h a t  silver-fir the  This  s e e d l i n g s were a b l e  in  not prevent high  and 1.8  and P a c i f i c  the untreated  i n t h e 1981 and 1982 s u r v i v a l  t r e a t m e n t s was a p p r o x i m a t e l y 1.7  in  significantly  in 1981.  and P a c i f i c  Figures  t h e r e was  than  1.9).  1.6  loss  the  the d i f f e r e n c e s  Irrigation hemlock  (Figs.  turgor  to a l e s s e r extent,  planted  (Table  the D o u g l a s - f i r  and,  seedlings  1982  in untreated Douglas-fir  that  considerable  -  for  the  respective-  i r r i g a t e d treatments  treatments. could  and  The  be d u e ,  in  limited part,  to  success their  t h e end o f J u n e 1 9 8 2 , when t h e  began t o  exceed t h a t of  shaded s e e d l i n g s  ( F i g . 1.12)  while  total  non-shaded  had h i g h e r  minimum  having s i m i l a r  but  ^  seed-  - 48 -  (Table  1.3).  Consequently,  shaded s e e d l i n g s  t u r g o r than unshaded s e e d l i n g s o c c u r r e d between p l a n t i n g significant with  interaction  Pacific  silver-fir  Stathers cause  between  difference  in survival  soil  other  In a d d i t i o n ,  to the d i r e c t  temperatures  was l i k e l y  occurred  shaded,  and, hence,  the  survival.  only  Furthermore  tempera-  significant  and c o n t r o l  o f shade c a r d s  thermal  i n 1981  surface  he a r g u e d t h a t  effect  f r o m 60 - 70°C t o 30 - 35°C,  of D o u g l a s - f i r  except  t h e major-  stress.  This  soil  treat-  on r e d u c -  o f s h a d e c a r d s on s e e d l i n g t u r g o r  argument  nor d i d  it  surface  had l i m i t e d s u c c e s s  in  i t d i d n o t e x p l a i n why t h e  s e e d l i n g s was so much g r e a t e r  than t h a t  of the  species.  IV. Douglas-fir high  treatments  (and i r r i g a t i o n ) , w h i l e d e c r e a s i n g  increasing seedling survival  stress  between n o n - i r r i g a t e d  not consider- the e f f e c t  temperatures  shade and i r r i g a t i o n  and t h a t h i g h e r m o r t a l i t y  in 1981.  e x p l a i n why s h a d i n g  that  i n 1984 ( T a b l e 1 . 9 ) .  m e n t s c o u l d be a t t r i b u t e d ing surface  of  T h e r e was n o t a  t h e magnitude and d u r a t i o n o f h i g h  greater  did  and t h e b e g i n n i n g o f J u l y .  of s e e d l i n g m o r t a l i t y  t u r e s were  levels  during the period of water s t r e s s  (1983) argued t h a t thermal  t h a n i n 1982 b e c a u s e  maintained higher  elevation  tolerance.  south-facing  osmotic  throughout  seedlings  planted site,  i n t h e s p r i n g as 1-0 s t y r o p l u g s  exhibited a high  T h e m e c h a n i s m a p p e a r e d t o be s t r e s s  considerable turgor  seedlings,  CONCLUSIONS  not only  degree o f  tolerance  the growing  season.  Consequently  survived severe drought  b u t were  drought  resulting  adjustment which enabled the s e e d l i n g s  at a  to  from  maintain  the D o u g l a s - f i r able t o maintain  - 49  daily  transpiration  rates  t h a t were never l e s s  a c h i e v e d under optimum s o i l were,  however,  silver of  fir  deficits  the lack  of  consequently  both  stress  avoidance  increased the s u r v i v a l planted  effect  of D o u g l a s - f i r  regardless both  of  survival the  shade c a r d s  treatment.  and P a c i f i c  results  indicate  climate  does  seedlings seedling  its  on  planted  significant  survival  irrigation in  of  both  a seedling's  shade c a r d s  in  Inclining  seedlings  and  These  The h i g h e r s u r v i v a l o f of  high  western  level.  and d u r i n g t h e m o r n i n g t h e r e b y  micro-  shaded reducing  increasing  had o n l y  a small  survival.  V. Arnott, J.T. trees Bernstein, I.  increase  survival.  rates  and  seedlings  had no  shade c a r d s ,  c o u l d be e x p l a i n e d by t h e e f f e c t transpiration  because  s e e d l i n g s w h i c h was g e n e r a l l y  t h a t even d r a m a t i c m o d i f i c a t i o n  not ensure  Pacific  drought  s i l v e r - f i r b u t n o t t o an a c c e p t a b l e  t h e d a i l y minimum v a l u e o f Y j t x ' effect  to cope w i t h  1982; i r r i g a t i o n  did  stomatal  extent,  of D o u g l a s - f i r  The u s e o f  and i r r i g a t i o n  hemlock  reduced  by  mortality.  i n 1981, but not those on t h e  rates  moisture conditions  and t o l e r a n c e m e c h a n i s m s  extremely high  in  those  Transpiration  and t o an e v e n g r e a t e r  exhibited a failure  suffered  Shade c a r d s  soil  that considerably  Western hemlock,  seedlings,  t h a n 50% o f  moisture conditions.  markedly l i m i t e d under a l l  high vapour pressure conductance.  -  1975.  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H.T.  1980.  efficiency Physiol.  fluxes  in  15:701-707.  changes  of  Douglas-fir  tissue-water seedlings.  148:339-345.  resistance  in three conifers  under f i e l d  conditions.  D.L.  Processes  and T . A .  Black.  In:  Areas.  1983.  Proc. June  A study of  in a forest  to water  use  Plant  T.A.  temperature in For.  Tan, C . S . , T.A.  A growing  season  Black, forest  Met. Black,  water-  trees  C a n . H y d r o l . Symp. 8 2 ,  14-15, 1982, F r e d e r i c t o n , soil  clearcut.  B r i t i s h Columbia, Vancouver, R.J.,  1982.  used to p a r t i t i o n w a t e r use between  Infor.  R.J.  Ecology  Science  Hemmingsen.  aerodynamic  pp. 195-214.  of  and E . A .  of  story.  survival  Bradstreet  vascular plants.  Importance  model  model  systems of  Hammel, E . D .  balance  Agri.  63:1259-1267.  Res.  Seasonal  species  65:132-135.  Spittlehouse,  Stathers,  For.  1982.  t h r e e woody  Estimating water  1984.  and r o o t  Sap p r e s s u r e i n  W.K.  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A .  seasonal  and o n t o g e n e t i c  of  Populus,  Acer,  Talbot.  1978.  changes  in  the  T s u g a and P i c e a .  Can.  56:635-647.  Van B a v e l , C . H . M . , properties  of  G.B.  W a l t o n , D.C.  Soil 1980.  Reviews  Watts, S., J.L. and s h o o t  Stirk,  a clay  by r o o t s .  profiles.  Annual  in  Negative turgor pressure  Can. J .  tissue-water  uptake  crops  1978.  5:597-608.  The c h a r a c t e r i s t i c s  J.  Tonnet.  on t h e w a t e r p o t e n t i a l  fallacy? Tyree,  -  and K . J .  loam s o i l  I.  Brust.  and t h e  Interpretation  S c i . S o c . Am. P r o c . Biochemistry of  Plant  Rodriguez, growth of  Botany 47:595-602.  S.E.  plants  field  Evans,  Hydraulic  measurements o f  of water content  and  water-  pressure  32:310-317.  and p h y s i o l o g y  Physiology.  1968.  of  abscisic  acid.  31:453-489.  and W . J .  treated with  Davies.  abscisic  1981.  acid.  Root  Annal  of  -  54  -  CHAPTER  2  STOMATAL CHARACTERISTICS AND TRANSPIRATION OF THREE S P E C I E S OF CONIFER SEEDLINGS PLANTED ON A HIGH ELEVATION SOUTH-FACING CLEARCUT  - 55  STOMATAL CHARACTERISTICS  -  AND TRANSPIRATION  OF THREE S P E C I E S OF  SEEDLINGS PLANTED ON A SOUTH-FACING HIGH ELEVATION  I.  tree breeders  realistic  criteria  and o p e r a t i o n a l In t h i s stomata i n ments of  the  selection  of  treatments  that will  optimize  r e g a r d much i n t e r e s t  the  the  seedling water  relations  and s i l v i c u l t u r a l i s t s c a n e s t a b l i s h  for  r e g u l a t i o n of  stomatal  CLEARCUT  INTRODUCTION  A thorough u n d e r s t a n d i n g of before  species,  is the  has been f o c u s e d on t h e  role  of  seedlings  to environmental (Livingston  Kaufmann 1 9 8 1 ) ,  intensive  studies  various  environmental  adequate knowledge  of  ately  at present there  these  variables  control  (Lassoie  construction  of  that  mined r e l a t i o n s variables.  ( G r o s s n i k l e and B l a k e  variables stomatal is  upon s t o m a t a l action  aperture et j i K  to explain  a m e c h a n i s t i c model (1976) c a l l s stomatal  Measureconditions  e t al_. 1 9 8 4 ; such  the e f f e c t s depends  level. of  1984).  of  Although  stomatal  a "phenomenological  it  precludes is  and v a r i o u s  of  action  or the  possible  model".  using experimentally  conductance  of  the e f f e c t s  this  action,  of  Unfortun-  r a t h e r t h a n t h e i r mode o f  conductance  between s t o m a t a l  of  conductance  at the c e l l u l a r  1981).  type  of  1 9 8 5 ; Hobbs  c o n s i d e r a b l y more k n o w l e d g e  1982; J a r v i s  predicts  field  a s a t i s f a c t o r y model  on s t o m a t a l  t o produce what J a r v i s a model  few  h a v e been r e p o r t e d development of  stock  regeneration.  instrumentation  The  most  provenance,  h a v e been l i m i t e d by i n a d e q u a t e  responses  required  t r a n s p i r a t i o n and p h o t o s y n t h e s i s .  responses  and t o d a t e  CONIFER  That deter-  enviromental  is  - 56  A commonly u s e d a p p r o a c h boundary-line points  in  of  g  points  against  s  on t h i s  ance  f o r a given value of  this  line  represent  boundary-line the  ently.  s u c h as t h a t Jarvis  curves idual  and T a n n e r This  chapter  conifer  (ii)  regular  below which  1976).  are  In  multipli-  interactions  and a i r  and c o n t i n u o u s .  independdo  temperature  For  obtained from c o n t r o l l e d  the assumption t h a t  occur (Ng a n d  boundary-line this  such measured responses  in  reason  environment  response functions  same as t h o s e t h a t o c c u r  (i)  describes  variables  the  (global  ( D ) , and n e e d l e  indiv-  studies  measured i n  the f i e l d .  h a v e been  seedlings  of  stomatal  the  However,  reported  solar  water  responses  irradiance  potential  turgor potential  one and two y e a r o l d  to  (Kanemasu  environmental  (R ), s  air  ( ? ) , vapour s  ( Y ) ) of three  g r o w i n g on a s o u t h - f a c i n g ,  e x a m i n e s how t h e s e r e s p o n s e s  responses  for  to the v a r i a b l e s that  deficit  factors  is  conduct-  points  variables,  are required to generate  average r o o t zone s o i l  sure d e f i c i t of  It  1967).  and p h y s i o l o g i c a l (T),  responds  pressure  points  are often  between  variable.  (Webb 1 9 7 2 ; J a r v i s  the l i m i t i n g  conductance  upper-most  t h e maximum p o s s i b l e  l i m i t e d by o t h e r  assumed t h a t  be b o t h  are the  the  is  1981).  number o f  1983) w i t h  differences  represent  t h e r e h a v e been some r e p o r t s  that w i l l  laboratory  ature  is  drawn t h r o u g h  the independent v a r i a b l e w h i l s t  between v a p o u r  functions  (Jones  it  1980; Leverenz  A large  line  type modeling  independent  also determined  and t h a t s t o m a t a l However  a single  conductances  curves are  s i m p l e s t case  cative  in phenomenological  a n a l y s i s , whereby a c u r v e i s  a plot  assumed t h a t  -  p  temperpres-  species  high e l e v a t i o n  clearcut,  c h a n g e o v e r two y e a r s a n d c o m p a r e s seedlings  of  t h e same  species,  the  (iii)  - 57  describes  and t e s t s  a boundary-line  w h i c h was d e v e l o p e d  for  S i t e and E x p e r i m e n t a l The s i t e  C h a p t e r 1. of  1150 m on a 30°  Douglas-fir  (Dougl.)  1-0  Sarg.)  container  randomized complete-block lings high  per b l o c k .  stock  (control). that ¥  B.  s  design.  b l o c k s were l a i d  self  silver  Standard hourly  numbers  fir  sandy  of hemlock  (Abies  amabilis  out i n 90  a seed-  s h a d e p r o v i d e d by 0 . 2 m  same t h r e e  I n May 1982 species,  ( w a t e r was p r o v i d e d by a  site  eight  Four-  trickle  and no s h a d e and no on t h e  the  proven-  as i n t h e p r e v i o u s y e a r .  irrigation  indicated  MPa.  Analysis  average m i c r o m e t e o r o l o g i c a l  the 1 m h e i g h t ,  elevation  a gravelly  Franco), western  and a c o n t r o l .  shade and i r r i g a t i o n ,  than -0.04  a t an  in  s h a d e p r o v i d e d by p l a n t i n g  out u s i n g the  irrigation  Measurements and Data  T and D a t  1981 e q u a l  W a t e r was a p p l i e d when t e n s i o m e t e r s  was l e s s  is  detail  T h e r e w e r e 32 b l o c k s w i t h  t y p e and p l a n t i n g t e c h n i q u e  system),  behaviour  transpiration.  grown s t y r o p l u g s w e r e l a i d  shade c a r d s ,  t r e a t m e n t s were t e s t e d : irrigation  soil  and P a c i f i c  i n c l i n e d to the southwest,  additional ance,  (Mirb.)  in  located  There were t h r e e t r e a t m e n t s :  by 0 . 3 m w i d e  seedlings  is  The  In A p r i l  (Pseudotsuga menziesii  Forbes)  site  slope.  till.  (Raf.  seedling  design are described  south-facing  (Tsuga h e t e r o p h y l l a  stomatal  METHODS  the experimental  loam o v e r compact g l a c i a l  daily  of  Design  and e x p e r i m e n t a l  Briefly,  a n a l y s i s model  the e s t i m a t i o n of  II. A.  -  windspeed  measurements of  (u) a t t h e 0 . 4  m height  and  R , s  - 58  precipitation, thermocouple Stomatal  and m e a s u r e m e n t s o f  psychrometers  measurements of  13 d a y s , 9,  nine  6 and August 14,  (Appendix  seedling g  days,  1983.  s  average  projected needle  determined w i t h i n using a leaf U.S.A.),  in Chapter  g , s  tensiometers 1.  described  type  porometer  in Chapter  w e r e made on t h e t h r e e day,  and  1.  species  on  b e t w e e n J u n e 10 a n d S e p t e m b e r day,  seedlings  in  the  between June planted  irrigated  in  and  A p p r o x i m a t e l y 400 h o u r l y  values  e a c h c a l c u l a t e d by a v e r a g i n g 2 t o 3 m e a s u r e species  area  area meter  also  no s h a d e .  (A),  i n 1982, w h i l e  required  t h r e e weeks o f (Model  the  g  s  needles  160 w e r e made i n 1 9 8 3 .  i n t h e measurement o f measurements e i t h e r  Li-3000, Li-Cor  o r by u s i n g r e g r e s s i o n e q u a t i o n s  a r e a t o t h e mass o f et  with  M e a s u r e m e n t s w e r e made on s e e d l i n g s  m e n t s , w e r e made on e a c h The  s  f o u r o f w h i c h were sunny a l l  treatments with  seedling  II)  sunny a l l  1981 a n d 1982 b u t w e r e c o n f i n e d t o  of  zone v  are d e s c r i b e d  of which were  1 9 8 2 a n d on f i v e  non-irrigated  root  c o n d u c t a n c e was m e a s u r e d u s i n g a t r a n s i e n t  ( L i v i n g s t o n ^ t a]_. 1 9 8 4 ) Hourly  -  that  d r i e d t o 65°C f o r  Inc.,  one day  s  was  directly  Lincoln,  relate  g ,  Nebraska,  projected  needle  (Livingston  a]_. 1 9 8 4 ) . H o u r l y measurements  similarly  sized,  Oregon, U . S . A . ) . ling.  of  w e r e a l s o made on d i f f e r e n t ,  vjt  x  seedlings with  a pressure  No more t h a n two t w i g s w e r e  Approximately  e v e r y 3 t o 4 weeks  1982 a n d 1983 m e a s u r e m e n t s o f  ^  by s u b t r a c t i n g  ^tx  were o b t a i n e d w i t h  from  (PMS I n c . ,  r e m o v e d f r o m any  during the  p s y c h r o m e t e r chambers u s i n g t h e t e c h n i q u e calculated  chamber  described  but Corvallis, seed-  growing seasons  in  thermocouple in Chapter  1 and  - 59  Boundary-line between since  g  a n a l y s i s was p e r f o r m e d t o d e t e r m i n e t h e  and R ,  s  D, Y  T,  s  sunrise  (t).  All  but m u l t i p l i c a t i v e l y . function  of R ,  T,  s  gsmax i s  tions  that describe  s  and a v e r a g e  the  previous  that  gb i s  large  that  the boundary  the stomatal  sum o f  chapter,  (gs  The maximum v a l u e s  ively before  and P a c i f i c  (Table 2 . 1 ) . solar  reported  S  rate  o  f  for  n  - e  - 1  the  a  a  products  is well  (gb  are the  func-  between  of  - 1  )  is  leaf  area  basis  average values As d i s c u s s e d  assumption f o r  of in  needles  a p p r o x i m a t e d by D and negligible  compared  to  ).  RESULTS AND DISCUSSION  of  silver  5 9  was  s  relation  on a p r o j e c t e d  g  measured f o r  s  fir  were 0 . 4 4 ,  Douglas-fir, 0.31  and 0 . 2 4  These v a l u e s were o b s e r v e d i n  °«  g  variable.  the 1 m h e i g h t .  noon and o n l y when D < 1.0  g max  that  g , h and j  makes t h e r e a s o n a b l e  resistance  resistance  independently  (1)  curves  the hourly  enough t h a t e layer  initially  and f,  each  V  III.  hemlock  of  D/(R T' ) at  this  to act  p  transpiration  value of  hours  h(D) j ( y )  the b o u n d a r y - l i n e  was c a l c u l a t e d as t h e g  9(T)  average value  seedling  number o f  relationship  i.e.  t h e maximum c o n d u c t a n c e  and t h e h o u r l y Daily  , and t h e  P  I t was h y p o t h e s i z e d  D and ¥ p ,  where  s  and Y  s  v a r i a b l e s were c o n s i d e r e d  9 s = 9smax f<M  g  -  s _ 1  1 n  kPa.  Douglas-fir  western cm s " ,  irrigated  Murphy  1  seedlings  and F e r r e l l  saplings, while  respect-  (1982)  Hallgren  -  60  -  Table  2.1  The maximum s t o m a t a l c o n d u c t a n c e m e a s u r e d ( g ) and t h e number o f t i m e s t h i s v a l u e was o b t a i n e d (n) f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and Pacific silver f i r seedlings. s r T i a x  Species  g  s  m  a  x  (cm  s- ) 1  Douglas-fir  0.44  6  Western  hemlock  0.31  2  Paci f i c  s i 1ver  0.24  3  fir  - 61  (1978) w o r k i n g w i t h s  - 1  .  Running  Douglas-fir  seedlings  ( 1 9 7 6 ) r e p o r t e d a gsmax ° f  w e s t e r n hemlock w h i l e  Teskey  in Pacific  seedlings.  A.  silver fir  Response  of  g  F i g u r e 2.1a Douglas-fir besides  R  curves  for  s  -  is  s  the  plotted  limit the  g .  three  relationship  against R  s  species  Solar  °»  f  1  for  1 - 3 m tall  o f 0 . 3 5 cm  s  o b t a i n e d when g s / g s m a x  analysis  (Figure 2.1b)  cm  4 3  s"  1  Irradiance  and i n d i c a t e s  Boundary-line  s  0*23 cm s "  in Global  o  S  e t al_. ( 1 9 8 4 ) o b s e r v e d g  t o Changes  shows  measured g max  that  other  produced  which  f°  r  variables  response  c a n be d e s c r i b e d  by  -aR 9s/9smax = 1 - e  where a i s  a constant.  species  are  between  gs/gsmax  s"  1  given  Values  in Table 2.2. a  n  d  of  (2)  s  the constant Response  photosynthetic  photon  c a n be g e n e r a t e d by m u l t i p l y i n g R  curves flux  in W n r  s  in  (2) for  for the  density 2  the  by 2 . 0 4  three  relation in  ymol  nr  (Meek e t  2  al.  1984). In g e n e r a l light  than those  2.1b). that  The  found  Douglas-fir of western  response in  other  of  1978).  B.  g  of  The o b v i o u s  s  g  s  hemlock to l i g h t  studies  H i n c k l e y e t al_.  Response  s t o m a t a o p e n e d more r a p i d l y w i t h  and vapour p r e s s u r e  deficits  for  on c o n i f e r s  t o changes  difficulty  and P a c i f i c  in  in A i r  these  silver fir  increasing (Figure  s p e c i e s was t y p i c a l  of  ( L e v e r e n z 1 9 7 4 ; Tan e t al_. 1 9 7 7 ;  Temperature  s e p a r a t i n g the e f f e c t s  of  temperature  on gs has l e d t o c o n t r a d i c t o r y  results  - 52 -  F i g u r e 2.1  a . The r e l a t i o n s h i p between the r a t i o of the stomatal conductance ( g ) to the maximum stomatal conductance (Ssnax) g l o b a l sol a r - i r r a d i a n c e ( R ) f o r i r r i g a t e H (•) and n o n - i r r i g a t e d (o) D o u g l a s - f i r s e e d l i n g s . Each p o i n t i s the average of t h r e e measurements. A l s o shown i s the b o u n d a r y - l i n e which i n d i c a t e s the upper l i m i t of the o b s e r v a t i o n s , b. Comparison of the b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between gs/gsmax s for Douglas-fir ( s o l i d l i n e ) , western hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r f i r (broken l i n e ) . (PPFD i n ymol n r s is a p p r o x i m a t e l y 2.04 t i m e s R i n W m ) . s  a n f 1  s  a n n l  R  2  -2  s  - 1  -  63  Table  -  2.2  -aR Values of the c o e f f i c i e n t a in the equation; g / g = 1 - e d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g w h e r e g i s the average s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) gsmax i s maximum g (cm s ) » and R i s t h e h o u r l y a v e r a g e g l o b a l s o l a r i r r a d i a n c e (W m ). s  s  s n i a x  s  - 1  _ 1  s  s  Year of Planting  Year of Measurement  Douglas-fir  Western hemlock  Pacific silver fir  1981  1982  0.018  0.013  0.010  1981  1983  0.019  0.012  1982  1982  0.018  0.012  0.011  - 64 -  (Jones  1983).  related  However e v i d e n c e  action  contention The  hemlock  t h a t T i s an i n d e p e n d e n t  relationship  and P a c i f i c  relationships  o f t h e enzymes i n v o l v e d  is  s  in  ( R o g e r s e t j i l _ . 1 9 7 9 ; O u t l a w e t ail_. 1 9 7 9 ) s u p p o r t s t h e  between  shown i n F i g u r e 2 . 2 a .  with  variable.  gs/9smax  Maximum g  s  a  n  d  f°  T  occurred  a pronounced  decline  (Figure 2.2b).  r  Douglas-fir  a t a b o u t 18°C.  s i l v e r - f i r boundary-line  a n d 17.0°C, r e s p e c t i v e l y  in g  analysis s  All  is In western  revealed  above and below  similar17.5°C  the boundary-line  analysis  c a n be d e s c r i b e d by  9 s / 9 s m a x * 1 - b(T - T  where  t h e optimum t e m p e r a t u r e f o r g  to the temperature c h a r a c t e r i s t i c s  stomatal  curves  that  b i s a constant  maximum g  s  occurs.  and T  Values  m  a  x  )  (3)  2  i s the a i r temperature at which  m a x  of the constants  i n (3) are given  in  Table 2.3. A similar Leverenz Scots  (1974), J a r v i s  pine  (Pinus  b e l o w 20°C.  D.  t o t e m p e r a t u r e h a s been r e p o r t e d by  ( 1 9 7 5 ) a n d by Ng ( 1 9 7 8 ) who f o u n d t h a t  g  s  in  s y l v e s t r i s L . ) , a t c o n s t a n t D, d e c r e a s e d a b o v e a n d e t a]_. ( 1 9 8 0 ) f o u n d t h a t  o v e r a 13°C t o 29°C r a n g e on g Kaufmann  (1976) and Running  a t u r e was n o t a s i g n i f i c a n t under f i e l d  s  In c o n t r a s t W a r r i t  had no e f f e c t constant  response of g  conditions  variable  s  of apple  trees  (1976) c o n c l u d e d  controlling  p r o v i d e d D was t a k e n i n t o  g  s  in  temperature at  that  conifers  account.  temper-  - 65 -  F i g u r e 2.2  The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g $ ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (g ) and a i r t e m p e r a t u r e ( T ) f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d (o) D o u g l a s - f i r s e e d l i n g s . Each p o i n t i s t h e average o f t h r e e m e a s u r e m e n t s . A l s o shown i s t h e b o u n d a r y - l i n e w h i c h i n d i c a t e s t h e upper l i m i t o f t h e observations, b. Comparison o f t h e b o u n d a r y - l i n e s for t h e r e l a t i o n s h i p b e t w e e n gs/gsmax d T for Douglas-fir ( s o l i d l i n e ) , w e s t e r n hemlock H o t t e d l i n e ) and P a c i f i c s i l v e r f i r (broken l i n e ) . s m a x  a r ,  -  66 -  Table  2.3  V a l u e s o f t h e c o e f f i c i e n t b and T i n t h e e q u a t i o n ; gs/gsmax = 1 - b (T - T ) d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g w h e r e g i s t h e a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) g max i s maximum g (cm s ) » T i s t h e h o u r l y a v e r a g e a i r t e m p e r a t u r e (°C) and T i s the a i r t e m p e r a t u r e a t w h i c h g = gsmax • m a x  m a x  s  S  s  - 1  m a x  s  Year of Planting  Year o f Measurement  Douglas-fir D  T  m a x  Western hemlock b T  m a x  1981  1982  0.0053  18.0  0.0054  18.0  1981  1983  0.0061  18.0  0.0053  17.5  1982  1982  0.0058  18.0  0.0066  17.5  Pacific silver fir b T  m a x  0.0102  17.0  0.0097  17.5  - 67  C.  Responses Although  known,  it  is  D directly results  accepted that  1980; J a r v i s  i n c a s e s when g  by a c h a n g e  in Chapter  pendent  of  Well of  s  is  in water  defined  relations  of  2.3a  stomate  boundary-line  and b c a n a l l  maximum. This  a constant All  0  species  effect  w e s t e r n hemlock in  and D .  5  +  is  the three  A s i m i l a r type of  the  other  studies  declines  the l e a f  epidermis  the l e a f  Tyree  For  as  r e p o n s e must be  a  caused  (Farquhar 1983)  (Sheriff  inde-  1984).  c u r v e s were o b t a i n e d boundary  v a l u e o f D when g in  g  in P a c i f i c  s  analysis by  on c o n i f e r s  of  g  s  is  s  to  half  the  as D e x c e e d e d 1  silver fir  are presented  response  from  (4)  The c o r r e s p o n d i n g  species  curvilinear  1984).  be d e s c r i b e d  showed a m a r k e d d e c l i n e  and D o u g l a s - f i r .  that  W o e s ) " )  was m o s t p r o n o u n c e d  (4) f o r  been o b s e r v e d i n  1  The  increased  and Kay 1 9 7 7 ;  (Maier-Maercker of  not  potential  of  the whole  the bulk  "C  to D i s  transpiration  potential  gs/gmax v e r s u s D ( F i g u r e 2 . 3 a ) .  n is  (Sheriff  stomatal  either  and c o n t i n u o u s  shown i n F i g u r e  constants  of  a d j a c e n t to each  the water  l e a f water  1981; S h e r i f f  1) and t h e w a t e r  relations  responds  s  so r e d u c e d t h a t  the  Deficit  stomata respond to  rates  and M o r r i s o n  V^smax "  kPa.  the  g  reduced bulk  (Tan e t al_. 1 9 7 7 ) ,  1978) o r t h e c e l l s  where  in Vapour P r e s s u r e  t h e e x a c t m e c h a n i s m by w h i c h  increases  curves  t o Changes  r a t h e r than to the  reported  plots  s  from i n c r e a s e d t r a n s p i r a t i o n  example,  whole  g  generally  and Y a n o u l i s  (as  of  -  values  followed of  in Table  the 2.4.  i n c r e a s i n g D has  ( L e v e r e n z 1 9 7 4 ; Tan e t  al.  by  - 68 -  Figure  2.3  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (9smax) v a p o u r p r e s s u r e d e f i c i t (D) f o r i r r i g a t e d (•) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r s e e d l i n g s . Fach p o i n t i s the average o f t h r e e measurements. A l s o shown i s t h e b o u n d a r y - 1 i n p which i n d i c a t e s t h e upper l i m i t o f t h e observations, b. Comparison o f t h e b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between gs/gsmax Douglas-fir ( s o l i d l i n e ) , w e s t e r n hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r f i r (broken l i n e ) . s  a n c 1  a  n  d  n  f  o  r  -  69  Table  -  2.4  V a l u e s o f t h e c o e f f i c i e n t , D . 5 and n , i n t h e e q u a t i o n ; g s / g s m a x = 1 ( 1 + ( D / D . 5 ) ) d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g where g i s the a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) , gsmax maximum g (cm s ) , D i s t h e h o u r l y a v e r a g e v a p o u r p r e s s u r e d e f i c i t ( k P a ) and D o . 5 "is t h e v a p o u r p r e s s u r e d e f i c i t a t w h i c h g i s h a l f gsmax* 0  n  0  s  1 S  s  s  Year of Planting  Year of Measurement  Douglas-fir Do.5  Western hemlock  Pacific silver fir  n  Do.5  n  Do.5  1.80  1981  1982  2.42  4.71  2.23  5.50  1981  1983  2.39  4.74  2.10  5.51  -  1982  1982  2.31  4.85  2.16  5.64  1.91  - 70  1 9 7 7 ; Ng 1 9 7 8 ; W a t t s  and N e i l s o n 1 9 7 8 ; J o h n s o n  Kelliher  1985; G r o s s n i c k l e and B l a k e  1984)  r e v i e w i n g o t h e r work  in  used to r e l a t e  D.  Response  g  to  s  of  g  s  -  1986).  suggests  and F e r r e l l  However,  that  a linear  1983;  Running  (1980 and  function  can  be  D.  t o Changes  in Turgor  Potential  and S o i l  Water  Potential The  scatter plot  for Douglas-fir the  other  and b o u n d a r y - l i n e  (Figure 2.4)  two s p e c i e s ,  shows  which  increasing  which  bulk  an e s t i m a t e o f  pressure of g  s  and n o t  guard c e l l s vice  versa.  increased evaporation point  the  hysteresis  other  the  rate  ¥p d e c r e a s e s  in Figure  t h r e s h o l d fp  between  g  s  increased  limiting  and F e r r e l l  factors  are  indicates  it  the  is of  Vp,  on  result  affected  by  that  at  some  g . s  of  Figure  turgor  the  likely  effect  for  limiting,  that  cells,  is  and * p . after  plotted  the  2.5  strong  shows  that  r e a c h i n g a minimum a t m i d -  increase  in  g  s  and t h a t  some  s  indication  studies  is  those  g .  or y j t x below which  in other  of  versus  r a t h e r than the  feedback 2.4  gs/gsmax  as a r e s u l t  as s t o m a t a o p e n ,  potential  T h e r e was no c l e a r  This  pressure  t h e r e was n o t a c o r r e s p o n d i n g  f a c t o r was  reported  turgor  Since  relation  turgor  typical  and a s s o c i a t e d e p i d e r m a l  scatter  in the  even though morning,  >pp.  l o w e r e d ^p has a n e g a t i v e  Some o f  is  t h a t when no o t h e r  9s/9smax d e c r e a s e s w i t h is  curve for  i n any o f  stomata r a p i d l y  on gymnosperms  1979; Teskey e t a l .  the s p e c i e s , close  of  a  as has  critical been  ( W a r i n g a n d R u n n i n g 1 9 7 8 ; Drew  1984; G r o s s n i c k l e and B l a k e  1985).  - 71  Figure  2.4  -  The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l conductance (Qsmax) and t h e t u r g o r p o t e n t i a l f o r i r r i g a t e d (•) and n o n - i r r i g a t e d (o) D o u g l a s - f i r s e e d l i n g s . The s e e d l i n g s were p l a n t e d i n 1982 and t h e m e a s u r e m e n t s were made on 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 . s  - 72 -  % 0.4  0  0.5  i  1  1 1  D  Figure  2.5  (MPa) 1.5 1  2  1  (kPa)  The r e l a t i o n s h i p b e t w e e n t h e s t o m a t a l c o n d u c t a n c e o f a D o u g l a s - f i r s e e d l i n g and t h e h o u r l y a v e r a g e v a p o u r p r e s s u r e d e f i c i t (D) ( o ) , and t u r g o r p o t e n t i a l [ % ) (•) m e a s u r e d o n J u l y 2 7 , 1 9 8 2 . The " o n e s " mark t h e t i m e ( 0 6 : 0 0 PST) when t h e f i r s t m e a s u r e m e n t s were m a d e . Measurements were r e p e a t e d e v e r y hour u n t i l 2 1 . 0 0 PST.  - 73 -  The  scatter  significant  plot  influence  in part controlled consequently factors Curves  shown i n F i g u r e of v  (predawn)  l° »  1 S  9s  w  almost completely  f o r the three  species  9s/9smax = e  k  Y  1 S  yjtx'  suggest W  n  limited all  override  d e r i v e d from b o u n d a r y - l i n e  plots  T h i s would  s  by a b a s e  base y j t x  which  on g .  s  2.6a i l l u s t r a t e s  e  *s  n  there  that  g  w  a  (0 > *  s  n  d  responses.  o f 9s/9smax versus  v  s  ( F i g u r e 2 . 6 b ) a r e d e s c r i b e d by t h e  s  is  s  l° »  1 S  is a  day by h y d r a u l i c  the other  analysis  that  following  > - 0 . 1 MPa)  (5)  and  9 s / 9 s m a x = nvp  s  - n  < - 0 . 1 MPa)  w h e r e k, m a n d n a r e c o n s t a n t s .  The v a l u e s  i n Table 2 . 5 .  curves  when no o t h e r g , s  with  s  This  silver  factors  decreasing  - 1 . 5 MPa, g 9smax-  The b o u n d a r y - l i n e  are l i m i t i n g ,  ¥ 5 , occurs  of D o u g l a s - f i r  seedling transpiration  low Y  s  rate  species,  of decrease  is approximately  that in  A t <r o f s  50% o f  hemlock  and P a c i f i c  correspond to the reduction  i n r e s p o n s e t o r e d u c e d 4> b e t w e e n s  i n t h e amount o f o s m o t i c 1) w h i c h ,  to maintain r e l a t i v e l y  than w e s t e r n hemlock  are given  in  t h a t w e r e o b s e r v e d i n 1982 ( C h a p t e r 1 ) .  (discussed i n Chapter  seedlings  in a l l  between 0 a n d - 0 . 1 MPa.  These f i g u r e s  the differences  species  Douglas-fir  indicate,  the l a r g e s t  seedlings  rates  correspond to differences by e a c h  of these constants  c o m p a r e s t o 30% a n d 18% f o r w e s t e r n  f i r , respectively.  Furthermore,  (6)  or P a c i f i c  adjustment  f o r example,  higher  silver f i r  levels  species exhibited  enabled  of turgor  seedlings.  at  - 74 -  Figure  2.6  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (9smax) a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l (^ ) for non-irrigated Douglas-fir seedlings. Each p o i n t i s the average o f t h r e e measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s t h e upper l i m i t o f t h e observations, b. Comparison o f t h e b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between g / g s m a x ^s f o r D o u g l a s - f i r ( s o l i d l i n e ) , w e s t e r n hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r f i r (broken l i n e ) . s  a  n  d  s  a n f l  s  Table  2.5  V a l u e s o f t h e c o e f f i c i e n t , k, m and p i n t h e e q u a t i o n s g s / g s n a x ( 0 2. ^s i i ) ' g /g = m <)J + n ( ^ < - 0 . 1 MPa) d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r s e e d l i n g where g i s t h e a v e r a g e s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm 9smax i t h e maximum g (cm s " ) and ip i s t h e a v e r a g e r o o t z o n e s o i l w a t e r p o t e n t i a l ( M P a ) . =  s  s r n a x  s  e  M P a  a n c  s  s  s )» _ 1  s  s  Year of Planting  s  Year of Measurement  Douglas-fir  Western  hemlock  Pacific  silver-fir  k  m  n  k  m  n  k  m  n  1981  1982  1.74  0.21  0.86  1.76  0.37  0.88  3.01  0.26  0.77  1981  1983  1.51  0.24  0.88  1.73  0.32  0.87  3.01  -  -  1982  1982  1.63  0.26  0.88  1.86  0.38  0.87  3.34  0.39  0.75  <J1  - 76  A similar been r e p o r t e d  response in other  E.  Running close  1 S  between  On a l l  i n c l u d i n g those  closure. afternoon  2.5).  Light  lings,  being located  direct  solar  Other Murphy  researchers  report  spruce  spruce  s h o o t s was h i g h e s t  sitchensis  day.  in  2,  3 and 4 )  the e a r l y In  recovery  day,  when  were  this  increase  in  g  time because  slope,  g  s  stoma-  in  the  (Figure  s  the  were s t i l l  seed-  exposed  to  angles.  saplings  courses  in  five  seedlings,  Kaufmann  Leverenz et  the average  g  of  s  decline g . s  g ; s  habitat  and M i l n e j^t j*l_.  Carr).  i n average  l e v e l s were  measured  in  types,  (1976) (1985)  in in  al_.  (1982)  of S i t k a  spruce  m o r n i n g and t h e n p r o g r e s s i v e l y  some c a s e s  even though l i g h t  closed.  that  al.  S  t h e r e was p r o n o u n c e d  similar diurnal  (Bong.)  m o r n i n g when t h e maximum a v e r a g e almost  sun  (1982) i n D o u g l a s - f i r  when t h e r e was a s l i g h t day,  facing  have r e p o r t e d  all  conductances  not l i m i t i n g a t t h i s  even a t low  for Y  that  i n D and i n c r e a s e  (Picea engelmannii P a r r y ) ,  (Picea  the  stomatal  (1982) i n D o u g l a s - f i r  (their Figures  throughout  the h i g h e s t  et  Sunrise  t h a t were o v e r c a s t  on a s o u t h w e s t  irradiance  has  x  zero.  and t h e T i m e s i n c e  a marked d e c r e a s e  l e v e l s were  D u r y e a and L a v e n d e r  Sitka  to  t h e r e was n o t a c o r r e s p o n d i n g  and F e r r e l l  Englemann  (1984) i m p l i e s  the morning a f t e r which  Despite  late  s  t o predawn ¥rt.  ( R u n n i n g 1976 a n d 1 9 8 0 ; K e l l i h e r  Relationship days,  g  as t h a t  s  than - 1 . 5 MPa, gs/9smax  during the middle of  the  to n  s  However,  measurements were t a k e n ,  tal  g  studies  1985; K e l l i h e r 1 9 8 5 ) . lower  of  -  declined  was i n t e r r u p t e d a t T o w a r d s t h e end  s i m i l a r to those  in  the  was m e a s u r e d , t h e s t o m a t a  noon  of  early were  - 77  Figure of  hours  2.7  shows  the s c a t t e r  from s u n r i s e  derived for  (t)  plot  of  second o r d e r  The factors  limiting,  recovery diurnal at  g  will  s  i n the l a t t e r pattern of  g  the guard c e l l s  guard c e l l  ion  curves  is  s  Hiron  fully  (1969),Wright  of  the day.  1974),  is  near  zero.  It  is  The  with  possible  acid  (ABA)  length of  close might well  ABA i s  of  that  no  this  concentration in  regulating  time t h a t  the  d e p e n d on how sites.  leaf  Wright  and have  1 9 8 1 ) and t h e  The e x a c t m e c h a n i s m by w h i c h ABA p r o d u c t i o n and R a s c h k e  t r i g g e r e d when Yp o f  in  chloroplasts  (Hartung et  n o t known; however, P i e r c e is  no other-  e n d o g e n o u s ABA i n c r e a s e m a r k e d l y  synthesized in  cytoplasm  2.6.  mid-morning with  known t o p l a y a k e y r o l e  (Hsiao 1976).  the l e a f  t h a t ABA p r o d u c t i o n  after  that,  ( 1 9 7 7 ) , S i v a k u m a r a n e t a]_. ( 1 9 8 0 ) and o t h e r s  ( W a l t o n e t aj_. 1 9 7 6 ) . triggered  indicate  m e t a b o l i s e d o r moves t o o t h e r  water-stressed plants.  be  (7)  r e l a t e d to a b s c i s i c  demonstrated t h a t concentrations  (Milborrow  c u r v e s can a l l  q and r a r e g i v e n i n T a b l e  decline  stomata remain c l o s e d or p a r t i a l l y q u i c k l y ABA i s  curves  2  ( F i g u r e 2.7b)  s i n c e ABA i s  transport  p,  rapidly  part  number  polynomial  the constants  boundary-line  the  and t h e b o u n d a r y - l i n e  The b o u n d a r y - l i n e  9s/9smax = P + q t + r t  where the v a l u e s of  gs/Ssmax v e r s u s  for Douglas-fir  the three s p e c i e s .  d e s c r i b e d by t h e  -  the bulk  (1980) leaf  roots is  speculate falls  to  - 78 -  1.0  •  *• O ^^•'•^ • • • «w ••• O O O O O^S. • • • o o . • V\. O O O ox. • c m O O O \\ O O O o o o OOO O • \• O O O O O o \ o o O O O O O O 0O * .O O O O oo • \ 0 o o o \ • o o • o o o o O O O o O 0 o o o o o o o o o O O oo oo 0 Oo 0 o o 0 o O OO o o o o o o O OOOo O o Oo oo • • • • • e  0.5  0  0  o 0 o  x CD  0  CO  1.0  ,rj)  o o o o  o o o o o  o  •  t  • o o o  OOO  0.0  E  (a)  • • •  o o o • • o o o  o\ o • • o o o  \ \ X o o o o o  \  \  \ \ o  \ o \  \  o \ O > O OO O.OO O — , .  •  CO  0.5  0.0 3  6  9  12  15  Time from sunrise (h)  Figure  2.7  a . The r e l a t i o n s h i p b e t w e e n t h e r a t i o o f t h e s t o m a t a l c o n d u c t a n c e ( g ) t o t h e maximum s t o m a t a l c o n d u c t a n c e (g ) and t h e t i m e s i n c e s u n r i s e ( t ) f o r i r r i g a t e d ( • ) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r s e e d l i n g s . Fach p o i n t i s the average o f t h r e e measurements. A l s o shown i s t h e b o u n d a r y - l i n e which i n d i c a t e s t h e upper l i m i t o f t h e observations, h . Comparison o f t h e b o u n d a r y - l i n e s f o r t h e r e l a t i o n s h i p between g / g s m a x t for Douglas-fir ( s o l i d l i n e ) , w e s t e r n hemlock ( d o t t e d l i n e ) and P a c i f i c s i l v e r f i r (broken l i n e ) . s  s n a x  a n r t  s  Table  2.6  V a l u e s o f t h e c o e f f i c i e n t , q , r and s i n t h e e q u a t i o n ; g / g s m a x = p + q t + r t d e r i v e d by b o u n d a r y - l i n e a n a l y s i s f o r D o u g l a s - f i r , w e s t e r n hemlock and P a c i f i c s i l v e r f i r s e e d l i n g s w h e r e g i s the average s e e d l i n g s t o m a t a l c o n d u c t a n c e (cm s ) » Qsmax t h e maximum g (cm s " ) and t i s t h e number o f h o u r s from s u n r i s e . 2  s  s  - 1  1 S  1  s  Year of Planting  Year of Measurement  Douglas-fir P  q  Western r  P  q  hemlock r  Pacific  silver  fir  P  q  r  1981  1982  0.66  0.09  -0.008  0.44  0.14  -0.007  0.71  0.08  -0.006  1981  1983  0.70  0.08  -0.007  0.46  0.12  -0.007  -  -  -  1982  1982  0.67  0.08  -0.005  0.45  0.13  -0.007  0.71  0.08  -0.006  - 80  E.  Variation  of  The v a l u e s  g  of  with  s  respect  in  t h a t y e a r or  of  seedlings  different  in 1981.  of  a seedling's  new n e e d l e s  differences changes  in  the  the t o t a l stomatal  the o v e r a l l season.  of  the  found t h a t white  to  b a n k s i a n a Lamb.)  (1976)  area,  behaviour seedling  s  spruce  so t h a t ,  between  response  These f i n d i n g s  of  needles;  increases  glauca  et  Grossnickle  - 3.6  the July  in  significant  needles,  marked  i n D,  at a l l  pine of  S i t k a spruce  for  over  (1985)  stomata i n  new n e e d l e s .  emerged  was  and B l a k e  levels  of  found t h a t ,  new  a t low v a l u e s  jack  during  those  foliage  Voss.)  In c o n t r a s t ,  newly  the  compare  at higher values of  i n D than stomata i n  observed t h a t stomata i n  3.4  al_. ( 1 9 8 2 )  increases  stomata i n o l d needles,  increases  porometer of  s  2.6).  by t h e e n d o f  new and o l d  (Moench)  however,  i n D.  the  are not c o n s i s t e n t w i t h  foliage.  to  -  h a d t h e r e been  one y e a r - o l d S i t k a s p r u c e  (Picea  2.2  w o u l d h a v e been o b s e r v e d  example, Leverenz  sensitivity  than stomata i n o l d e r more s e n s i t i v e  needle  significantly  to d i r e c t l y  However,  planted  characteristics  the average g  was n o t p o s s i b l e  two y e a r - o l d  showed l e s s  to  in  a b o u t 30% ( F i g u r e s  g  sensitive  was e n c l o s e d  constituted  same c o n d i t i o n s ,  needles  foliage  (Tables  typically  For  that  m e a s u r e d i n 1982  needles.  researchers.  twice  conductance  time. analysis  seedlings  1983 w e r e n o t  and, t h e r e f o r e , it  for  new and o l d  in  the growing  no d i f f e r e n t  of  C h a p t e r 3) o f  other  study  seedling obtained, responses  by b o u n d a r y - l i n e  S i m i l a r l y stomatal  from c h a r a c t e r i s t i c s  chamber used i n t h i s  stomatal  obtained  ( p l a n t e d i n 1981) measured i n  Since a l l  entire  t o s e e d l i n g age and p l a n t i n g  the c o e f f i c i e n t s  o f m e a s u r e m e n t s made i n 1982 w e r e  -  of  D, t h e y  D, were  (Pinus D, w e r e Watts  et  needles  more al. were  - 81  more s e n s i t i v e t o D t h a n s t o m a t a i n differences nearly  year-old  g  s  needles,  late July. in  red pine  was h i g h e r  Calculating g  boundary-line  in  Waggoner (Pinus  and T u r n e r  newly emerged n e e d l e s  s  and E f r o m B o u n d a r y - L i n e  conductance  calculated  analysis  data,  and n o n - i r r i g a t e d  of  seedlings  conductances  9s  with  these  (1971) found  resinosa A i t . ) ,  where  for  than i n  one  the the  same  Relationships  from the  collected  relationships  only  one  were  obtained calculated  = 9smax ( s > f  9(T)  R  independent  variable  derived  i n 1982 on s e e d l i n g s  t h a t y e a r , were compared w i t h measured v a l u e s  Stomatal  but t h a t  needles.  Stomatal  in  in  response  v a l u e o f D,  older  r e s p o n s e w e r e n o t o b s e r v e d when s h o o t e x p a n s i o n was  complete  opposite  F.  in  -  of  g  of  s  i n 1982 a n d 1983  from  planted  irrigated  (Table  2.7).  using  h(D) j ( y ) s  k(t)  (8)  or combinations  of  independent  variables. No s i n g l e the R  s  for  variation  environmental in  g  s  for  by c o m b i n i n g a l l  the the  could account  the s p e c i e s .  and P a c i f i c  variation variables  for  more t h a n 30% o f two  t,  variables,  the v a r i a t i o n  silver fir,  in Douglas-fir except  for  The u s e o f  60%, 58% and 61% o f  w e s t e r n hemlock  No more t h a n 70% o f for  i n any o f  and D, c o u l d a c c o u n t Douglas-fir,  variable  g  s  could  in  g  s  respectively. be  accounted  c o m p a r e d t o 67% and 64%  Table  2.7  The p e r c e n t a g e o f t h e v a r i a n c e o f t h e a v e r a g e s t o m a t a l c o n d u c t a n c e o f D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r f i r ( P S F ) s e e d l i n g s , measured on 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 , e x p l a i n e d by t h e b o u n d a r y - l i n e a n a l y s i s model u s i n g t h e i n d i v i d u a l v a r i a b l e s , R ( g l o b a l s o l a r i r r a d i a n c e ) , T ( a i r t e m p e r a t u r e ) D ( v a p o u r p r e s s u r e d e f i c i t ) i|> ( a v e r a g e r o o t zone w a t e r p o t e n t i a l ) and t ( t h e number o f h o u r s f r o m s u n r i s e ) , and t h e v a r i a b l e s i n c o m b i n a t i o n . s  s  % Variance Explained  % Variance  Explained  Variable  DF  WH  PSF  Combination of V a r i a b l e s  DF  WH  PSF  Rs  27  30  24  R ,D  60  58  61  T  15  18  17  Rs.n.^s  67  63  65  D  19  21  16  Rs,n,*s,T  70  67  69  5  8  9  R ,D,T,t  78  72  77  41  37  39  89  87  85  •s t  S  s  - 83  f o r w e s t e r n hemlock  and P a c i f i c  alone  less  accounted  species,  it  difference (Figures  did account, in  2.8  of  s  between  changes  in  could  account  photosynthetic  were l o w ,  d i d the  explained  variation.  only  deficit, did  not  However,  increase  independent so t h a t  2.8  t h e amount o f  that  do n o t  greatly  g  of  it  s  all for  l o w D.  part  the  of  apple  flux  is  a n d 87% and 85% i n w e s t e r n h e m l o c k  by  s  defi-  the  temperature  variables  d i d not  at  e t aj_. ( 1 9 8 0 )  leaves  density  could  be  and vapour  pressure  s u c h as T and  Y[t%  variability. the i n c l u s i o n  variable  values  of of  and P a c i f i c since  t as  s  an  calculated This  on some d a y s  (Fig.  i n the  2.8)  Jones  s  is it  morning.  t o 89% i n  silver fir,  g  effect  i n c r e a s e d t h e amount  conductance  not unique,  conductance  increase  the very low measured g  i n the stomatal  g  in  t h e summer when Y $  of  However,  t as an i n d e p e n d e n t  is  in  exceed the measured v a l u e s .  inclusion  result  stomatal  and v a p o u r p r e s s u r e  the afternoon  The  This  of  explained  to explain  2.7).  s  other  not p o s s i b l e  (Table  in  y  seedlings  Similarly Warrit  was  explained v a r i a b i l i t y  density  photon  limits  m o s t p r o n o u n c e d on d a y s w i t h  of  s  variables,  the v a r i a t i o n  inclusion  in  show t h a t  variable  they  g  Whilst  e t ^1_. ( 1 9 8 1 ) who,  significantly  effect.  inclusion  and 2.9  flux  the  the v a r i a t i o n  the  70% o f  of F f t x  by p h o t o s y n t h e t i c  and t h a t  Figures  for  i n the l a t t e r  inclusion  t h a t most of for  and n o n - i r r i g a t e d  t o measurements of  photon  any t i m e h a v e a s i g n i f i c a n t  accounted  in  the o t h e r  h a v e been r e p o r t e d by J a r v i s  They f o u n d t h a t  found  the v a r i a t i o n  when c o m b i n e d w i t h irrigated  respectively.  2.9).  results  pine,  silver fir,  t h a n 10% o f  t h e same t y p e o f model  Scots  cit.  g  and  Similar fitting  for  -  of  Douglas-fir respectively  (1983),  in  - 84 -  0.5  6  9  12  Time  Figure  2.8  15  18  21  (PST)  The d a i l y c o u r s e s o f m e a s u r e d ( o p e n s y m b o l s ) and c a l c u l a t e d ( c l o s e d symbols) stomatal conductance ( g ) for i r r i g a t e d ( s o l i d l i n e s ) and n o n - i r r i g a t e d ( d o t t e d l i n e s ) D o u g l a s - f i r s e e d l i n g s on J u l y 2 8 , 1 9 8 2 . S t o m a t a l c o n d u c t a n c e was c a l c u l a t e d w i t h (•) and w i t h o u t t i m e s i n c e s u n r i s e ( A ) as a variable. The a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l was - 0 . 7 3 MPa. s  - 85  -  0.5  Time  Figure  2.9  (PST)  The d a i l y c o u r s e s o f m e a s u r e d ( o p e n s y m b o l s ) and c a l c u l a t e d ( c l o s e d symbols) stomatal conductance ( g ) f o r i r r i g a t e d ( s o l i d l i n e s ) and n o n - i r r i g a t e d ( d o t t e d l i n e s ) D o u g l a s - f i r s e e d l i n g s on A u g u s t 2 1 , 1 9 8 2 . S t o m a t a l c o n d u c t a n c e was c a l c u l a t e d w i t h (•) and w i t h o u t t i m e s i n c e s u n r i s e (A) as a variable. The a v e r a g e r o o t zone s o i l w a t e r p o t e n t i a l was - 1 . 1 MPa. s  - 86  reviewing multiple response,  r e g r e s s i o n models  found t h a t  an i n d e p e n d e n t  frequently  it  D, T , <F  of  calculated  g  seedlings  were  irrigated  seedlings  not  The  combined d a t a , ficantly  The  slopes  v e r s u s measured g  (Table 2 . 8 ) .  s  significantly  to  i r r i g a t e d and  and i n t e r c e p t s for  each  different  and i n t e r c e p t s species,  so t h a t  include  time  as  non-irrigated  equation  with  regressions non-irrigated i r r i g a t e d and n o n -  t o b e l o n g t o t h e same of  regression  which T t e s t s  f r o m one and z e r o ,  of  i r r i g a t e d and  c o u l d be c o n s i d e r e d  slopes  for  differ  of  s  c a l c u l a t e d using the boundary-line  s  and t .  s  stomatal  variable.  seedlings with s  used to determine  had been n e c e s s a r y  F i g u r e 2.10 compares measured g  R ,  -  population  equations  r e v e a l e d d i d not  respectively,  are presented  for  the  signiin  Table  2.8 F i g u r e 2.11 modeled d a i l y  shows  the e x c e l l e n t  transpiration  rates  agreement between measured  for  the t h r e e  r a t e s w e r e b e t t e r e s t i m a t e d on a d a i l y basis,  because  in  and u n d e r e s t i m a t e d  general in  g  s  was s l i g h t l y  the afternoon  IV. Boundary-line successfully  accounted  w e s t e r n hemlock basis in  g  s  for  and P a c i f i c  was s l i g h t l y  the a f t e r n o o n .  hours  analysis  basis,  of the  species.  r a t h e r t h a n an  2.8  and  hourly  the  morning  2.9).  CONCLUSIONS field  g  s  stomatal  silver fir  data produced behaviour seedlings.  of  functions  that  Douglas-fir,  However,  o v e r e s t i m a t e d i n t h e m o r n i n g and  Best  Transpiration  overestimated in  (Figures  and  on an  hourly  underestimated  r e s u l t s w e r e a c h i e v e d by i n c l u d i n g t h e number  f r o m s u n r i s e as an i n d e p e n d e n t  variable.  of  - 87  Figure  2.10  -  Comparison of c a l c u l a t e d stomatal conductance ( g s c a l c ) w i t h measured s t o m a t a l c o n d u c t a n c e ( g ) f o r i r r i g a t e d (o) and n o n - i r r i g a t e d ( o ) D o u g l a s - f i r ( D F ) , w e s t e r n h e m l o c k (WH) and P a c i f i c s i l v e r - f i r ( P S F ) s e e d l i n g s , p l a n t e d i n 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 . The r e g r e s s i o n l i n e s shown ( b r o k e n l i n e s ) a r e f o r a l l t h e points. The s l o p e s and i n t e r c e p t s o f t h e s e l i n e s a r e g i v e n in Table 2.8. s  - 88 -  Figure  2.11  Comparison of c a l c u l a t e d d i a l y t r a n s p i r a t i o n r a t e ( E - | ) u s i n g v a l u e s of g o b t a i n e d from e q u a t i o n (8) w i t h R , D, T , ¥ and t as v a r i a b l e s , w i t h d a i l y t r a n s p i r a t i o n r a t e ( E ) t h a t was c a l c u l a t e d u s i n g m e a s u r e d v a l u e s o f stomatal conductance. B o t h E and E i were c a l c u l a t e d a s t h e sum o f t h e h o u r l y p r o d u c t o f g and ( D / R T ' ) f o r i r r i g a t e d ( c l o s e d s y m b o l s ) and n o n - i r r i g a t e d ( o p e n s y m b o l s ) D o u g l a s - f i r ( o ) , w e s t e r n h e m l o c k ( • ) and P a c i f i c s i l v e r f i r (O) s e e d l i n g s , p l a n t e d i n 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 . A l s o shown i s t h e 1:1 l i n e . Linearregression analysis indicates E i (g c m d a y " ) = 0.98 E (g c m - d a y " ) + 0 . 0 0 2 ( r = 0 . 9 8 ) ( d a s h e d l i n e ) . c a  s  s  s  c  a  c  s  V  - 2  c  2  1  2  a  c  1  C  - 89  Table  -  2.8  Values of c o e f f i c i e n t s in the l i n e a r regression equation; gscalc Vg + w f o r i r r i g a t e d and n o n - i r r i g a t e d D o u g l a s - f i r , w e s t e r n h e m l o c k ana P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 , f o r 13 d a y s b e t w e e n J u n e and S e p t e m b e r 1 9 8 2 , w h e r e g s c a l c i s s e e d l i n g s t o m a t a l c o n d u c t a n c e u s i n g t h e b o u n d a r y - l i n e a n a l y s i s model and g i s measured stomatal conductance. A l s o shown a r e t h e number o f d a t a p o i n t s ( n ) , t h e c o e f f i c i e n t o f d e t e r m i n a t i o n ( r ) and t h e s t a n d a r d e r r o r o f e s t i m a t e (SEE). =  s  2  Species  v  w  n  r  Irrigated Non-Irrigated Combined Data  1.06 1.02 1.05  -0.016 -0.006 -0.012  203 203 406  0.87 0.90 0.89  0.07 0.06 0.07  Western hemlock Irrigated Non-Irrigated Combined Data  1.10 0.96 1.08  0.015 -0.003 0.008  197 204 401  0.86 0.89 0.87  0.05 0.06 0.05  Pacific silver fir Irrigated Non-Irrigated Combined Data  1.09 1.06 1.07  0.020 -0.006 0.004  150 120 370  0.84 0.89 0.86  0.04 0.03 0.03  2  SEE  Douglas-fi r  - 90  T h e r e was no e v i d e n c e turgor  potential  caused  a corresponding  cause  transpiration The mental  variables  Daily were  t h e r e was c r i t i c a l  stomata c l o s e d  decrease  in  g .  to decrease  although  Increasing  s  as a r e s u l t  in  responses  of  all  response  between  of  g  species  g  threshold  a decrease s  the  appeared  in  ?  to  s  rates  to changes  planted  in  n o r were  e s t i m a t e d by summing t h e p r o d u c t average  there  i n 1981 and 1 9 8 2 .  on a p r o j e c t e d l e a f  and t h e m e a s u r e d h o u r l y  environ-  of  the  area  basis  calculated  values  of  function  in  D/(R T' ). 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Silviculturists sites  by p l a n t i n g  highest  growth  physiological  rates.  will water  not  only  as w a t e r d e f i c i t s  that  avoid stress  regeneration  s u r v i v e drought that  increase  only  root  on  b u t have  can  (Jones  by c l o s i n g t h e i r  during a period of drought,  be a b l e t o d e v e l o p an e x t e n s i v e  dry  the  maintain 1983) w i l l  grow  stomata.  stress tolerant  s y s t e m and t h e r e b y  seedlngs increase  uptake.  change t h i s (Kozlowski  ratio,  root  ratio  1982; Lopushinsky  a high  shoot  and r o o t s  of  appropriate  to  planting r a t i o of  surface,  at  root  ratio will  either  stock  effects  and B e e b e 1 9 7 6 ) .  ratio  transpiring  and  For example a  be more s u s c e p t i b l e  (Drew and F e r e l l  leaf  to  1979).  surface area to water  by n u r s e r y p r a c t i c e s  microclimate, for  on s u r v i v a l  ability  The  shoots  most  absorbing  and L o n g 1 9 7 3 ) , o r by m o d i f y i n g shade  growth  desiccation  s u c h as w r e n c h i n g o r  e x a m p l e , by p r o v i d i n g  to  seedling  c a n be m a n i p u l a t e d t o p r o v i d e t h e  ( D u r y e a and L a v e n d e r 1 9 8 2 ; E i s seedling's  p l a n t i n g , and t h e s e e d l i n g ' s  c a n have s i g n i f i c a n t  than a s e e d l i n g with a lower  root  that  Stress-tolerant seedlings  activity  The s h o o t t o  with  INTRODUCTION  o b t a i n t h e most s u c c e s s f u l  seedlings  more t h a n s e e d l i n g s Furthermore,  will  CLEARCUT  (Drew  pruning a 1983).  -  A number o f transpiration However,  leaf  is  ( G i l e s et  Tanner  related to  stomatal  constant. species;  1981).  the  Wong e t however,  both d i u r n a l l y  al_. 1 9 8 4 ; W a l l i s  to g . internal  other workers  photon  flux  (PPFD)  growth with t r a n s p i r a t i o n  well  being  correlated  being decreased  to  shoot of  by l o w s o i l of t h i s  species  elevation  of  clearcut  matter production transpiration  2.  conifer and  is  et  of  and s h o o t seedlings  a  is  a number  Leverenz  (D) i s  low  photosynthetic  be due t o  of  (i)  and  and h i g h  D.  these treatments  on t h e  growth d u r i n g t h e  growing  boundary-line  growing  relationship  season high  season  growing  conductance  of  monthly  g r o w i n g on a s o u t h - f a c i n g  of t o t a l  is  photosynthesis  (1) t o d e s c r i b e t h e e f f e c t s  season stomatal  of  varies  low t o moderate D ) , which  related to values  conductance  for  conifers  (2) t o d e t e r m i n e whether t o t a l  better  (C-j)  al_. 1 9 8 6 ;  both t r a n s p i r a t i o n  is  into  The s t r o n g c o r r e l a t i o n  appears to  chapter  root  leaf  C-j i n  better  the  t o be t r u e  (Price  water p o t e n t i a l s  or average growing  using the stomatal Chapter  s  s h a d e and a c o m b i n a t i o n  g r o w t h , and t o t a l  three  by g .  to D (for  (ii)  is  the  be l i m i t e d by l o w  in trees  and  of  flux  2  to  1976).  likely  vapour p r e s s u r e d e f i c i t  and n o t  proportional PPFD,  The o b j e c t i v e irrigation,  could  correlated  is  argument  have shown t h a t  d a y s , when t h e  density  transpiration  to t h i s  and d u r i n g a d r y i n g p e r i o d  high, photosynthesis  growth  concentration  2  well  because the net C 0  s  C0  is  e t al_. 1983; B o y e r  al_. ( 1 9 7 9 ) have shown t h i s  On o v e r c a s t  s  (g )  Central  s  growth  (1983) argue t h a t  conductance  proportional  -  have shown t h a t  and S i n c l a i r  assumption that  and g  studies  100  dry  season  calculated  described  in  -  II.  The e x p e r i m e n t a l 1.  Briefly,  menziesii Sarg.)  in April  (Mirb.)  design.  silver  fir  styroplugs  shadecards,  self  the southwest, using the  same t h r e e  by s h a d e c a r d s ) ,  irrigation  in the  system),  irrigation.  (Tsuga h e t e r o p h y l l a (Dougl.)  the  soil  water  I n 1982 e i g h t  solar  irrigation  precipitation  (ip s )  were  Logan,  Utah, U.S.A.)  There  were  stock  inclined  t y p e and  shade  trickle  no  on t h e s i t e  than -0.04  laid  planting  by a  and no s h a d e and  was l e s s  to  b l o c k s were  ( w a t e r was p r o v i d e d  ( R ) , wind speed s  (T)  hourly  indicated  MPa.  average measurements  at the experimental  of  (u) at t h e 0.4 m h e i g h t ,  and r e l a t i v e  recorded with a data logger  1 9 8 1 , 1982 and 1 9 8 3 .  block  Measurements  and a i r t e m p e r a t u r e  height  1-0  F o u r t r e a t m e n t s were t e s t e d :  in Chapter 1 continuous  irradiance  per b l o c k .  additional  provenance,  s h a d e and i r r i g a t i o n ,  Micrometeorological  Forbes)  (Raf.  by 0 . 2 m h i g h by 0 . 3 m w i d e  previous year.  potential  Chapter  i n a randomized complete  W a t e r was a p p l i e d when t e n s i o m e t e r s  As d e s c r i b e d  in  out  in  (Pseudotsuga  by p l a n t i n g t h e s e e d l i n g s  species,  (provided  global  were l a i d  and a c o n t r o l .  as  A.  hemlock  (Abies amabilis  shade p r o v i d e d  in detail  numbers o f D o u g l a s - f i r  shade p r o v i d e d  technique  that  are d e s c r i b e d  T h e r e w e r e 32 b l o c k s w i t h 90 s e e d l i n g s  three treatments:  out  and d e s i g n  1981 e q u a l  -  METHODS  Franco), western  and P a c i f i c  container-grown  site  101  h u m i d i t y at t h e 1 m  (CR21, Campbell  Scientific  s i t e d u r i n g the growing  Inc.,  season  -  Soil  water p o t e n t i a l s  tensiometers Soil  water  installed  potentials  thermocouple  throughout  at the less  installed of  season  at the  i n each y e a r .  p s y c h r o m e t e r measurements t o a depth of  1.  soil  stick  Seedling  as t h e a r i t h m e t i c  defined of  all  living  s e e d l i n g s , many o f  the  end o f  the  analysis  2.  average of  as t h e d i s t a n c e  all  six  days  root  zone  the  value  tensiometer  300 mm.  the  study  of  that  (as  height  reported  in  the  leader  to  a metre  i n 1 9 8 1 , 1 9 8 2 , and 1 9 8 3 . some g r o w t h , d i e d  C h a p t e r 1) and were n o t  Data a n a l y s i s  in October  of  was m e a s u r e d w i t h  which e x h i b i t e d  data.  were a l i v e  from the t i p  seedlings  e a c h m o n t h , f r o m May t o O c t o b e r ,  seedlings  The a v e r a g e  the  Height  surface,  number o f  as  Measurements  The h e i g h t , the  same d e p t h s  s  or  Growth  using  i|> were t a k e n e v e r y two t o  \|> was c a l c u l a t e d  B.  using  5 0 , 1 0 0 , 1 5 0 , 2 0 0 , 300 and 500 mm d e p t h .  of  s  MPa were m e a s u r e d  t h a n - 0 . 1 MPa were m e a s u r e d  Measurements  the growing  -  g r e a t e r than -0.1  psychrometers  tensiometers.  102  A  large  before  included  was p e r f o r m e d on o n l y  in  those  1983.  L e a f A r e a and S h o o t and R o o t D r y Mass  The t o t a l  projected  needle  directly,  u s i n g an a r e a m e t e r  Nebraska,  U.S.A.),  projected  needle  o r by u s i n g  area of  (Model  seedlings  Li-3000, Li-Cor  regression  a r e a t o t h e mass o f  was d e t e r m i n e d  equations  needles  dried  Inc., that  either  Lincoln, related  t o 65°C f o r  one  day.  -  Only a l i m i t e d measurement because While  of  it  because the  seedlings  poor  survival  of  that  as p o s s i b l e  the  be c o n t i n u e d  were  small it  that  (described  growing  season of  seedlings  were h a r v e s t e d  surviving  seedlings.  a drying leaf  C.  oven a t  area of  w o u l d make any  as l a r g e  ground  so t h a t  during for  a number the  a growing  stomatal  of  study season  conductance  seedlings  were h a r v e s t e d  in  g  unshaded  s  were made on  seedlings  of  irrigated  all  the  species,  Between 3 and 4 s e e d l i n g s  of  In a d d i t i o n ,  at the b e g i n n i n g  the 3 years  of  the  in those treatments  48 h o u r s .  study,  and  a  were s a m p l e d e v e r y t i m e a l e a f  These s e e d l i n g s  65°C f o r  that  treatments.  The m a j o r i t y o f  and s p e c i e s  each of  particular  and  for  seedlings.  was m a d e .  t h e measurement  sample s i z e  in the  area  were h a r v e s t e d  and n o n - i r r i g a t e d  determination  of  leaf  chapters)  unshaded,  treatment  for  preceeding  i n t e n s i v e measurements of  particular  in  Accordingly  1982 when  on s h a d e d D o u g l a s - f i r  nature  had been s e l e c t e d  in the  area d e t e r m i n a t i o n .  selected  was f e l t  be l e f t  beyond 1 9 8 3 .  seedlings  measurements  should  -  seedlings  analysis d i f f i c u l t ,  only those  leaf  seedlings  of the d e s t r u c t i v e  was r e c o g n i s e d  statistical  could  number o f  103  area  and end o f  the  b e t w e e n 3 and 10  where t h e r e were  were washed o f  soil  enough  and p l a c e d  Before drying the t o t a l  in  projected  e a c h s e e d l i n g was m e a s u r e d .  Calculations 1.  Stomatal  Hourly sunrise  values  and s u n s e t  Conductance of  average  seedling  were e s t i m a t e d  for  stomatal  conductance  e v e r y day o f  between  the growing  season  in  -  1981,  104  -  1982 and 1 9 8 3 u s i n g t h e b o u n d a r y - l i n e  a n a l y s i s model  described  in  C h a p t e r 2 where  9  =  g  S  smax  f  (  R  s  g ( T )  )  J<*s>  h ( D )  k ( t )  and 9smax i s t h e maximum s t o m a t a l  conductance,  hours  and k a r e t h e  from s u n r i s e  the boundary-line average of not  13 d a y s  It  product  conductance  of the t o t a l  average d a i l y  used i n t h e  planted  enables  sized  other days. course  of  This  season value of averaging growing  functions  seedling  values of  season.  g  c  were  f r o m m e a s u r e m e n t s made on of that  year.  b a s i s , was c a l c u l a t e d area  conductance  and  those  c  by i n t e r p o l a t i n g  height  was  s  as  (A) o f t h e s e e d l i n g (g ).  This  s  to  be  the and  conductance  of  area  not  b e t w e e n m e a s u r e m e n t s made on  was b a s e d on t h e o b s e r v e d  and l e a f  the  calculation  F o r d a y s when m e a s u r e m e n t s o f A were  interpolation  seedling  hourly  ( g ) , w h i c h c a n be c o n s i d e r e d  needle  stomatal  seedlings.  m a d e , A was e s t i m a t e d  and t h e  describe  s  a c o m p a r i s o n o f t h e g r o w t h and s t o m a t a l  differently  s  that  i|> were n o t made,  in A p r i l  on a s e e d l i n g  projected  seedling  functions  of  d u r i n g t h e d a y i|> d i d  had been d e t e r m i n e d  1982 on s e e d l i n g s  stomatal  t h e number  b e t w e e n m e a s u r e m e n t s made on p r e c e d i n g  The c o n s t a n t s  in Chapter 2 t h a t  is  between g  was assumed t h a t  S e e d l i n g canopy conductance the  relation  F o r d a y s when m e a s u r e m e n t s o f  days.  in  h, j  f o r the  by i n t e r p o l a t i n g  succeeding reported  curves  g,  each v a r i a b l e .  change.  estimated  and f ,  t  ( 1 )  (discussed  canopy c o n d u c t a n c e  w h i c h were computed  (g£)  seasonal  below).  A growing  was e s t i m a t e d  f o r e v e r y day o f  the  by  -  Hourly sunrise  values  of  and s u n s e t ,  1981,  unshaded  1982  t r a n s p i r a t i o n , on a s e e d l i n g  were e s t i m a t e d  and 1983.  seedlings  Hourly  v  is  t e m p e r a t u r e and t h e  for  assumptions  t h a t D approximates the vapour cavities  and t h a t  negligible  the  needle  compared t o  Chapter 2 c a l c u l a t i o n s seedlings  using  transpiration transpired  rates  summing t h e  hourly  water  in  Growing Season Weather The w e a t h e r  in  detail  layer  in  shaded  T'  is  and  the absolute  E for  in  (gs )« - 1  rates  of  (gb~M  t h e shaded  small  The t o t a l  it  in Douglas-fir  in  amount o f  that  the water  ( E J Q T ) was c a l c u l a t e d  e v e r y day o f t h a t  1)  stomatal  was f o u n d  errors  air  is  Although  assumptions,  season  Chapter  between t h e  resistance  acceptably  seedlings.  of  of  (2)  vapour,  growing  by  season.  RESULTS  Observations  o b s e r v a t i o n s made i n 1981,  i n C h a p t e r 1.  rates  season  T')  resistance  a growing  estimates  between  the growing  a r e made ( a s d i s c u s s e d  III.  A.  v  making t h e s e  these  by a s e e d l i n g  /(R  boundary  (2) r e s u l t e d of  s  transpiration  were made w i t h o u t  calculations  e v e r y day o f  pressure difference  stomatal of  basis,  from  A D g  t h e gas c o n s t a n t  for  transpiration  were c o m p u t e d  E =  where R  -  Transpi r a t i o n  2.  in  105  Briefly,  the  1981  1982  and 1983  growing  season  are was  described  - 106 -  characterized  by c o o l  planted  mid-July.  until  and A u g u s t air  4.5  kPa.  less  than  occurred  10 mm o f r a i n  were  b e t w e e n J u l y 10  fell.  Extremely  high  (maxima r a n g e d f r o m 25°C t o 37°C) and l o w a b s o l u t e  resulted Root  from t h e time t h e s e e d l i n g s  An e x t e n d e d d r y p e r i o d  26 d u r i n g w h i c h  temperatures  humidities  and wet w e a t h e r  zone  i n vapour p r e s s u r e d e f i c i t s s  decreased  from m i d - J u l y  that until  at times  exceeded  t h e end o f  August  r e a c h i n g a minimum o f - 1 . 7 MPa on A u g u s t 2 5 . The g r o w i n g hot  season  and d r y summer.  rainfall  i n 1982 was c h a r a c t e r i z e d  The summer d r o u g h t was b r o k e n by a s h o r t  i n early August.  d e c r e a s e d t o - 0 . 7 5 MPa. until  by a wet s p r i n g a n d a  Before t h i s Root  rainfall,  z o n e \|> d e c r e a s e d s  root  s  from e a r l y  August  t h e b e g i n n i n g o f S e p t e m b e r r e a c h i n g a minimum o f - 1 . 2 M P a . t h e summer o f 1983 was e x c e p t i o n a l l y wet and c o o l .  rainfall  f r o m May t o t h e end o f S e p t e m b e r was 399 mm.  z o n e i|> o f - 0 . 5 MPa was r e a c h e d s  of  z o n e i|> had  contrast  B.  period  By  Total  A minimum  root  i n mid-August.  Growth The m o r p h o l o g i c a l  planted large  characteristics  i n 1981 and 1982 a r e s u m m a r i z e d i n T a b l e 3 . 1 .  overall  differences  although the roots  between s e e d l i n g s  o f t h e 1982 D o u g l a s - f i r  s m a l l e r than those of seedlings  planted  C o n v e r s e l y w e s t e r n hemlock and P a c i f i c 1982 had s l i g h t l y 1981.  of the seedlings  larger  root  o f t h e same  before  were  There were not species,  s e e d l i n g s were  in the previous  they  slightly  year.  s i l v e r f i r seedlings  planted  systems than those o f s e e d l i n g s  in  planted  in  -  107  Table  -  3.1  Morphology of D o u g l a s - f i r , western s e e d l i n g s at the time of p l a n t i n g . brackets.  h e m l o c k and P a c i f i c s i l v e r f i r Standard d e v i a t i o n s are given  Species  Height (mm)  Year  Shoot t o Root R a t i o  Dry  in  Weight (g)  D o u g l a s -• f i r  1981 1982  144 152  (9) (12)  2.4 2.6  (0.2) (0.2)  3.7 3.4  (0.4) (0.2)  Western  1981 1982  116 109  (13) (6)  3.1 2.8  (0.2) (0.2)  1.1 1.3  (0.2) (0.2)  1981 1982  91 82  (7) (8)  2.8 2.6  (0.1) (0.2)  1.2 1.4  (0.2) (0.3)  hemlock  Paci f i c s i l v e r  fir  -  1.  Height  and L e a f  A summary o f 1981 i s  presented  shade c a r d s growth.  increase  in  Douglas-fir  height  height  In a l l  shaded  seedlings.  in  hemlock  1981  in  planted  provision  promoting  height  effect  height.  (300%) f o l l o w e d  on  by  in  of  relative  shaded  (260% and 150% r e s p e c t i v e l y ) .  were a p p r o x i m a t e l y  treatments  place  the  e x h i b i t e d the l a r g e s t  seedlings  seedlings  took  species  had no s i g n i f i c a n t  seedlings  In a l l  the  treatment  over the 3 years  growth t h a t  growing  fir  and w e s t e r n  species  unshaded  seedlings  silver  Planted  h e i g h t m e a s u r e m e n t s made on s e e d l i n g s  in Table 3 . 2 .  Inclining  -  Seedlings  was t h e most e f f e c t i v e  Shaded P a c i f i c  In a l l  the  Area of  108  and s p e c i e s  over 3 years  18% t a l l e r  than  o v e r 70% o f  was a c c o m p l i s h e d  the  in the  first  season.  Table 3.3 harvested October  at  shows t h e t o t a l  t h e end o f e a c h g r o w i n g  1983.  By t h e  shaded D o u g l a s - f i r exceeded  projected  those  of  respectively.  end o f t h e  western unshaded  more p r o n o u n c e d  over the  height,  most o f  the  season  followed  growing  and P a c i f i c  seedlings  These d i f f e r e n c e s  in  in  leaf  by a p r o n o u n c e d  leaf  seedlings 1981  and  season the  leaf  areas  silver  seedlings  fir  of  by a p p r o x i m a t e l y 20%, 25% and 28%  n e x t two y e a r s .  increase  area of  season between A p r i l  first  hemlock  leaf  a r e a between t r e a t m e n t s As was t h e c a s e w i t h  area occurred  decline  i n growth  in the rates  in  became  seedling  first  growing  subsequent  years.  2.  Height  Shaded, i n 1 9 8 1 , were  and L e a f A r e a o f  non-irrigated significantly  Seedlings Planted  seedlings taller  planted  in  in  1982  1982, l i k e  (with the exception  of  those western  planted  -  109  Table  -  3.2  S e e d l i n g h e i g h t (mm) i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g p l a n t e d i n A p r i l 1 9 8 1 . Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t w h i c h was a p p l i e d t o each s p e c i e s i n each y e a r .  Treatment October  hem!ock  Pacific silver fir  283 ( a ) 288 ( a ) 331 ( b )  150 ( a ) 141 ( a ) 164 ( b )  116 ( a ) 122 ( a ) 140 ( b )  310 ( a ) 360 ( b )  173 ( a ) 192 ( a )  141 ( a ) 162 ( b )  348 ( a ) 410 ( b )  201 ( a ) 237 ( b )  161 ( a ) 187 ( b )  1982  Control Shade C a r d s  October  Western  1981  Control S e l f Shade Shade C a r d s  October  Douglas-fi r  1983  Control Shade C a r d s  -  110  Table  -  3.3  L e a f a r e a ( c m ) i n O c t o b e r 1 9 8 2 , 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1 9 8 1 . Standard d e v i a t i o n s are given in b r a c k e t s . 2  Treatment October  hemlock  Pacific  silver  120 144  (26) (30)  50 62  (8) (14)  54 69  (12) (14)  133 172  (18) (24)  68 88  (16) (12)  63  (16)  158 217  (18) (21)  83 121  (14) (19)  91 128  1982  Control Shade C a r d s  October  Western  1981  Control Shade C a r d s  October  Douglas-fir  -  —  1983  Control Shade C a r d s  (14) (22)  fir  - Ill -  hemlock), (Tables the  and had l a r g e r  3.4  and 3 . 5 ) .  same h e i g h t  area.  In a l l  as u n s h a d e d ,  the species by t h o s e  By t h e  October  end o f  and P a c i f i c  areas  In g e n e r a l  was e x h i b i t e d  hemlock  leaf  than  the biggest  fir  untreated  seedlings increase  that  1983 t h e l e a f  silver  areas  of  seedlings  respectively.  The c o r r e s p o n d i n g  of  but  in  were b o t h  seedlings  exceeded those  that  were  shaded, n o n - i r r i g a t e d  irrigated  seedlings  seedlings  seedlings  were  had a s m a l l e r  height  irrigated  Douglas-fir,  that  untreated  received  and l e a f and  leaf area  shaded.  western  this  treatment  by a p p r o x i m a t e l y 70%, 65% and 50%  differences  in  height  were 40%, 30% and  in  1982 and 1983 f o r  50% r e s p e c t i v e l y . The species  seasonal  are presented  seedlings  planted  the beginning Differences in  the  height  Figures  occurred  end o f  Seedling of  to  3.3.  in the  first  As was t h e c a s e  height  June of  leaf  seedling  However d i f f e r e n c e s growing  3.1  height  increase  the  between t r e a t m e n t s d i d  to that  subsequent  not  first  become more  area development  height  (Figures  two m o n t h s a f t e r  between t r e a t m e n t s  growing  seedlings  root  pronounced  followed  a in  seedlings  became more  that  were  pronounced  seasons.  and t o t a l  planted  between  season.  3.4 t o 3 . 6 ) the  the 3  with  occurred  S h o o t and R o o t D r y Mass and S h o o t t o R o o t D r y Mass  Shoot,  3.8.  seedling  May and t h e  pattern  planted.  of  in  of  1 9 8 1 , most o f t h e  year.  most g r o w t h  3.  of  in  in  following  similar  in  courses  in  d r y m a s s e s , and s h o o t  to  1981 and 1982 a r e p r e s e n t e d  Generally seedlings  that  were b o t h  irrigated  Ratio  r o o t d r y mass  ratios  in Tables  to  3.6  and s h a d e d had  the  -  112  Table  -  3.4  S e e d l i n g h e i g h t (mm) i n O c t o b e r 1 9 8 2 , 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1 9 8 2 . Numbers f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t ( t = 0 . 0 5 ) a c c o r d i n g t o D u n c a n ' s New M u l t i p l e Range T e s t was a p p l i e d t o each s p e c i e s i n each y e a r .  Treatment October  Western  hemlock  Pacific  silver  1982  Control Shade C a r d s Irrigation I r r i g a t i o n and Shade C a r d s  October  Douglas-fi r  296 ( a ) 345 ( b ) 337 ( b ) 368 ( b )  168 178 181 212  (a) (a) (a) (b)  127 ( a ) 153 ( b ) 159 (b) 182 ( c )  333 ( a ) 391 ( b ) 421 ( c ) 461 ( c )  204 ( a ) 210 ( a ) 241 ( a ) 265 (b)  157 ( a ) 191 ( b ) 214 ( b ) 239 ( c )  1983  Control Shade C a r d s Irrigation I r r i g a t i o n and Shade C a r d s  fir  -  113  Table  -  3.5  L e a f a r e a ( c m ) i n O c t o b e r 1982 and 1983 o f D o u g l a s - f i r , w e s t e r n and P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . Standard d e v i a t i o n s are given in b r a c k e t s . 2  Treatment October  Western  135 155 161 171  (18) (24) (24)  57  (21)  70 78  141 170 190 234  (22) (27) (24) (30)  68 80 94 112  hemlock  Pacific  silver  1982  Control Shade C a r d s Irrigation I r r i g a t i o n and Shade C a r d s  October  Douglas-fi r  hemlock  -  (ID  63  (14) (12)  83  (6)  78  (ID  -  -  -  -  (12)  (16)  1983  Control Shade C a r d s Irrigation I r r i g a t i o n and Shade C a r d s  (17) (12)  106 118  (10)  -  (13) (15)  fir  Figure  3.1  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 and 1 9 8 3 o f u n t r e a t e d ( o ) , s h a d e d ( t ) , i r r i g a t e d (Q) and i r r i g a t e d and s h a d e d (•) D o u g l a s - f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 .  -  Figure  3.2  115  -  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 and 1983 o f u n t r e a t e d ( o ) , s h a d e d ( • ) , i r r i g a t e d (•) and i r r i g a t e d and s h a d e d (•) w e s t e r n h e m l o c k s e e d l i n g s p l a n t e d i n May 1 9 8 2 .  -  Figure 3.3  116  -  S e a s o n a l c o u r s e o f s e e d l i n g h e i g h t i n 1982 and 1983 o f u n t r e a t e d ( o ) , s h a d e d ( • ) , i r r i g a t e d (•) and i r r i g a t e d and s h a d e d (•) P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n May 1982.  -  117  -  240  E o  200  -  160  -  120  80  MAY  JUN  JUL 1982  Figure  3.4  AUG  SEP  MAY  JUN  JUL  AUG  SEP  1983  S e a s o n a l c o u r s e o f s e e d l i n g p r o j e c t e d l e a f a r e a ( A ) i n 1982 and 1983 o f u n t r e a t e d ( o ) , s h a d e d ( t ) , i r r i g a t e d ( o ) and i r r i g a t e d and s h a d e d (•) D o u g l a s - f i r s e e d l i n g s p l a n t e d i n May 1 9 8 2 . The B r o k e n l i n e shows t h e e s t i m a t e d s e a s o n a l c o u r s e o f l e a f a r e a t h a t was u s e d i n t h e c a l c u l a t i o n o f t h e g r o w i n g s e a s o n t r a n s p i r a t i o n o f i r r i g a t e d and s h a d e d seedlings.  -  118  -  110  30  I  1  MAY  .  1  JUN  JUL AUG 1982  Figure  3.5  »-  SEP  1  1  1  MAY  1  JUN  1  1  JUL AUG  SEP  1983  S e a s o n a l c o u r s e o f p r o j e c t e d l e a f a r e a (A) o f u n t r e a t e d ( o ) and i r r i g a t e d (•) w e s t e r n s e e d l i n g s p l a n t e d i n May 1 9 8 2 .  i n 1982 and hemlock  1983  -  30  MAY  JUN  JUL AUG  1982  Figure  3.6  119  SEP  -  MAY  JUN  JUL AUG  SEP  1983  S e a s o n a l c o u r s e o f p r o j e c t e d l e a f a r e a (A) o f u n t r e a t e d ( o ) and i r r i g a t e d (•) P a c i f i c s e e d l i n g s p l a n t e d i n May 1 9 8 2 .  i n 1982 and 1 9 8 3 silver fir  Table M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f Standard d e v i a t i o n s are given i n b r a c k e t s .  Year Planted Control II  II  Irrigation  Shade  Card  I r r i g a t i o n and Shade C a r d  Year Measured  3.6  Douglas-fir  seedlings  Shoot D r y Mass ( g )  planted  Root D r y Mass ( g )  in  April  1981 and May  T o t a l Dry Mass ( g )  (0.5) (0.9)  (0.3) (0.4) (0.6) (0.4) (0.5)  5.4 9.1 13.7 6.1 9.8  (0.7)  (l.D  1.3 2.8 4.2 1.5 2.6  5.8 9.5  (1.0) (1.3)  1.6 2.4  (0.2) (0.4)  7.4 11.9  1982 1983  8.2 12.6  (1.5) (2.8)  2.5 4.2  (0.5) (0.7)  1983  10.2  (1.6)  2.4  (0.4)  1981 1981 1981 1982 1982  1981 1982 1983 1982 1983  4.1 6.3 9.5 4.6 7.2  1982 1982  1982 1983  1981 1981 1982  (0.6) (0.9)  1982.  Shoot t o D r y Mass  Root Ratio  3.2 2.2 2.2 3.0 2.7  (0.3) (0.3) (0.2) (0.3) (0.2)  (l.D  (1.5)  3.6 4.1  (0.2) (0.2)  10.7 16.8  (1.8) (3.1)  3.4 3.0  (0.2) (0.1)  12.6  (1.9)  4.3  (0.2)  (1.2) (1.4) (0.8) (1.3)  Table  3.7  M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f w e s t e r n h e m l o c k s e e d l i n g s 1982. Standard d e v i a t i o n s are given i n b r a c k e t s .  Year Planted Control II  Irrigation .Shade  Card  I r r i g a t i o n and Shade C a r d  Year Measured  Shoot Dry Mass ( g )  planted  Root Dry Mass ( g )  in April  1981 and  T o t a l Dry Mass ( g )  May  Shoot t o D r y Mass  Root Ratio  1981 1982  1982 1983  1.4 1.8  (0.3) (0.3)  0.7 0.8  (0.1) (0.2)  2.1 2.6  (0.4) (0.4)  2.2 2.1  (0.4) (0.2)  1982  1983  2.3  (0.4)  0.9  (0.2)  3.2  (0.6)  2.6  (0.1)  1982  1983  2.1  (0.5)  0.9  (0.3)  3.0  (0.7)  2.4  (0.2)  1982  1983  2.6  (0.4)  0.9  (0.2)  3.5  (0.5)  2.8  (0.1)  Table M o r p h o l o g y i n O c t o b e r 1 9 8 1 , 1982 and 1983 o f P a c i f i c 1982. Standard d e v i a t i o n s are given i n b r a c k e t s .  Year Planted  Year Measured  3.8  silver fir  Shoot Dry Mass ( g )  seedlings  Root D r y Mass ( g )  planted  in April  T o t a l Dry Mass ( g )  1981 and May  Shoot t o D r y Mass  Root Ratio  1981 1982  1983 1983  2.2 1.6  (0.4) (0.3)  0.7 0.6  (0.2) (0.2)  2.9 2.2  (0.6) (0.4)  3.1 2.5  (0.4) (0.8)  Irrigation  1982  1983  2.3  (0.5)  0.6  (0.3)  2.9  (0.8)  4.0  (l.D  I r r i g a t i o n and Shade C a r d  1982  1983  2.4  (0.3)  0.7  (0.2)  3.1  (0.5)  3.3  (0.4)  Control II  -  largest  shoot  seedlings.  and t o t a l  The t o t a l  w e s t e r n hemlock  123  d r y masses f o l l o w e d  d r y masses o f  and P a c i f i c  silver  Untreated  d r y masses but c o n v e r s e l y than  had t h e l o w e s t  seedlings. in  increased  shoot to  occurring  in  seedlings  had h i g h e r  in  shoot  All  total  root d r y masses  of  seedlings all  the  seedlings, this  the other  increase  In g e n e r a l , u n s h a d e d  r o o t d r y mass r a t i o s t h a n  ratio  treatments  with the l a r g e s t  seedlings.  Seedling Stomatal Conductance,  and W a t e r U s e  Cgc)  for  irrigated  shaded  dry weight  of  Douglas-fir  from t h a t o f  end o f  the growing be a c c o u n t e d  Values  seedlings seedlings, season. for  Seasonal  Efficiency  between t h e t o t a l  in Figure 3.7.  season  could  seasons.  and  seedlings.  relationship  conductance  total  to  shoot  untreated  hemlock  growing  by 20%, 60% and  r o o t d r y mass r a t i o s  1982 and 1983 and e s t i m a t e s o f  presented  had t h e l o w e s t  d r y mass r a t i o s  shaded i r r i g a t e d  Transpiration  (Y)  root  Estimates of Total  The  shoot t o  Douglas-fir,  seedlings  Consequently  irrigated  a f t e r one  had s i m i l a r o r e v e n g r e a t e r  s u c c e s s i v e growing  non-irrigated  C.  seedlings  With the exception of western  decreased  irrigated  seedlings  untreated  any o f t h e o t h e r t r e a t m e n t s .  typically  by u n s h a d e d  unshaded fir  season t y p i c a l l y exceeded t h o s e of 90% r e s p e c t i v e l y .  -  season dry matter  average growing  seedlings of  planted  Y were o b t a i n e d  in  season  canopy  1981 and 1982  by s u b t r a c t i n g  harvested at the beginning in the  accumulation  of  the  same t r e a t m e n t , h a r v e s t e d  A p p r o x i m a t e l y 65% o f t h e v a r i a t i o n  by " g . c  A higher  fraction  of the  is the  growing at in Y  variation  the  -  Figure  3.7  The r e l a t i o n s h i p a c c u m u l a t i o n (Y)  124  -  between growing season s e e d l i n g d r y m a t t e r and t h e a v e r a g e g r o w i n g s e a s o n t o t a l  s e e d l i n g s t o m a t a l c o n d u c t a n c e Cgc) for Douglas-fir s e e d l i n g s i n 1 9 8 1 , 1982 and 1 9 8 3 . The s l o p e o f t h e l i n e f o r c e d through zero i s 0.231 g/(cm s ) and t h e e q u a t i o n o f t h e l i n e f i t t e d t h r o u g h t h e d a t a p o i n t s by l i n e a r r e g r e s s i o n i s Y ( g ) = 0 . 1 5 4 " g ( c m s ) + 1.31 (r = 0.68). 3  3  c  z  - 1  -  in  Y was a c c o u n t e d  for  seedling  transpiration  obtained  (r  analysis  since the  production  = 0.88)  of  unshaded  seedlings  of  per  water  through water the  unit  zero  (with  The  of  1 g of dry  treatments  for  Douglas-fir,  hemlock  of  water  results  seedling's  species  of  WUE r a n g e d  seedlings,  than t h a t  regression  of  same amount line  0.0022 which  seedlings.  forced is  The  ( 4 5 0 g) e x p e n d e d d u r i n g  seedlings  the  inverse  the  receiving  in Tables  fir  seedlings  different  3.9 t o 3 . 1 1 .  from 0.0017 t o 0.0029  silver  study  (Table  had l o w e r  In  3.9).  WUE w h i c h  DISCUSSION  indicate  that  modification  by p r o v i d i n g  seedling  considerable  growth.  western bias  It  is  of  a  shade o r w a t e r ,  t h e s e t r e a t m e n t s , can have a p r o n o u n c e d  i n the case of  that  the  dry matter  lower  is  was  0.0015.  this  and t y p e o f  particularly  included)  are given  m i c r o c l i m a t e , whether  combination the extent  of  from  fit  matter.  IV.  The  the  of the D o u g l a s - f i r  and P a c i f i c  from 0.0011 t o  the t o t a l  season  regression  used a p p r o x i m a t e l y t h e  u s e d , and WUE o f  the three  values  that  linear  growing  were e x c l u d e d  slope of  seedlings  (WUE)  The g r o w t h , w a t e r  ranged  area.  shaded  The b e s t  was s i g n i f i c a n t l y  even t h o u g h t h e y leaf  estimated total  seedlings  indicated  seedlings  -  Y to  3.8).  shaded  g i v e s t h e amount o f  production  Western  (Figure  when  use e f f i c i e n c y  slope  by r e l a t i n g  results  these  125  effect  important  h e m l o c k and P a c i f i c  was i n t r o d u c e d  into  to  a  on  both  recognise,  silver  the  or  fir  results  of  -  Figure  3.8  126  -  The r e l a t i o n s h i p b e t w e e n g r o w i n g s e a s o n s e e d l i n g d r y m a t t e r a c c u m u l a t i o n ( Y ) and g r o w i n g s e a s o n s e e d l i n g t r a n s p i r a t i o n (EJOT) D o u g l a s - f i r s e e d l i n g s i n 1 9 8 1 , 1982 a n d 1 9 8 3 . The c l o s e d c i r c l e s i n d i c a t e s h a d e d t r e a t m e n t s . The s l o p e of t h e l i n e f o r c e d through zero i s 0.0022 g / g . The e q u a t i o n o f t h e l i n e f i t t e d t h r o u g h a l l t h e d a t a p o i n t s by l i n e a r r e g r e s s i o n i s Y(g) • 0.0027 E J O T (9) -0*83 (r = 0 . 7 8 ) , and t h e e q u a t i o n o f t h e l i n e , a l s o f i t t e d by l i n e a r r e g r e s s i o n , t h r o u g h t h e p o i n t s e x c l u d i n g shade t r e a t m e n t s i s Y(g) = 0 . 0 0 3 6 EjQT (9) - 2 . 0 ( r = 0.88). f  o  r  2  2  Table  3.9  D r y m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n ( E T Q J ) and WUE d u r i n g t h e g r o w i n g s e a s o n i n 1 9 8 1 , 1982 and 1983 o f D o u g l a s - f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s of Y are bracketed. The r o o t mean s q u a r e e r r o r s f o r ETQJ were t y p i c a l l y 26%. T h e s e e r r o r s were d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n (2) and a s s u m i n g a 20% e r r o r f o r A, a 10% e r r o r i n D and by u s i n g t h e s t a n d a r d e r r o r o f e s t i m a t e f o r c a l c u l a t e d v e r s u s measured g r e p o r t e d i n C h a p t e r 2 . s  Year Planted  Year Measured  Y (g)  E  T0T  (g)  WUE (g  g- ) 1  1981 1981 1981 1982 1982  1981 1982 1983 1982 1983  1.9 3.6 5.2 2.6 3.4  (0.4) (0.7) (1.2) (0.7) (0.8)  1100 1500 1800 1300 1600  0.0017 0.0024 0.0029 0.0020 0.0021  Irrigation n  1982 1982  1982 1983  3.6 4.2  (0.9) (1.0)  1700 1800  0.0021 0.0023  Shade  1981 1981  1982 1983  3.5 5.1  (1.0) (1.2)  1800 2100  0.0019 0.0024  1982  1983  4.0  (0.8)  2000  0.0020  Control II II II II  Card  I r r i g a t i o n and Shade C a r d  Table  3.10  Dry m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n (EJOT) "E d u r i n g t h e g r o w i n g s e a s o n i n 1982 and 1 9 8 3 o f w e s t e r n hemlock s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s of Y are bracketed. The r o o t mean s q u a r e e r r o r s f o r EjOT were t y p i c a l l y 28%. T h e s e e r r o r s were d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n ( 2 ) and a s s u m i n g a 20% e r r o r f o r A, a 10% e r r o r i n D and by u s i n g t h e s t a n d a r d e r r o r o f e s t i m a t e f o r c a l c u l a t e d v e r s u s measured g reported in Chapter 2. a  n  d  Wu  s  Year Planted  Year Measured  Y (g)  E  T  0  T  (g)  WUE (g g"  )  Control  1981 1982  1982 1983  0.6 0.6  (0.3) (0.2)  500 400  0.0012 0.0015  Irrigation  1982  1983  0.9  (0.3)  700  0.0013  Shade  1981  1983  0.7  (0.3)  800  o.oong  1982  1983  1.1  (0.3)  800  0.0014  Card  I r r i g a t i o n and Shade C a r d  Table  3.11  D r y m a t t e r a c c u m u l a t i o n ( Y ) , s e e d l i n g t r a n s p i r a t i o n ( E T Q J ) and WUE d u r i n g t h e g r o w i n g s e a s o n i n 1983 o f P a c i f i c s i l v e r f i r s e e d l i n g s p l a n t e d i n A p r i l 1981 and May 1 9 8 2 . Standard d e v i a t i o n s of Y are b r a c k e t e d . The r o o t mean s q u a r e e r r o r s f o r ETQJ were t y p i c a l l y 30%. T h e s e e r r o r s w e r e d e t e r m i n e d by d i f f e r e n t i a t i n g e q u a t i o n ( 2 ) and a s s u m i n g a 20% e r r o r i n A , a 10% e r r o r i n D, and by u s i n g t h e s t a n d a r d e r r o r o f e s t i m a t e f o r c a l c u l a t e d v e r s u s measured g reported in Chapter 2. s  Year Planted  Year Measured  Y (g)  E  T  0  T  (g)  WUE (g g  _ 1  )  Control  1981 1982  1983 1983  0.7 0.6  (0.3) (0.3)  600 500  0.0012 0.0012  Irrigation  1982  1983  0.8  (0.2)  700  0.0010  I r r i g a t i o n and Shade C a r d  1982  1983  0.9  (0.3)  800  0.0011  -  because the  only the  study  growth  relatively  (see Tables  winter  during the  few s e e d l i n g s  and 1.9  study,  and P a c i f i c  buds c o n t a i n  first  and K o z l o w s k i  water  were n u r s e r y stress  The  1-0  raised  history,  would  beginning  of  seedlings,  rates  achieve  severe.  The  t h e end  included  in  enough  a r e not  this  stomatal  of  the  achieved  is  that  but  species  l i k e l y due,  in  limited part,  have a  Such the  conditions  silver  species  fir  in the  seedlings,  exposing  very  displays,  what  behaviour.  The  in  order  s t r e s s e d when w a t e r did  did  exhibited  non-responsive  prevent d e s i c c a t i o n  and h e n c e the  this  were i r r i g a t e d  good g r o w t h w i t h o u t  not  were s e v e r e enough t o c a u s e  Conversely Douglas-fir  severe desiccation In b o t h  to  Pacific  (Chapter 1 ) ,  became h i g h l y that  this  leaf  site.  u s e d more w a t e r t h a n j u s t i f i e d  seedlings  in  good g r o w t h b e t w e e n  untreated  indicate  (Kramer  styroplugs, did number o f  that  expand  used  the environmental  tolerant  and c o n s e q u e n t l y  e v a p o r a t i v e demand.  seasons  that  so  will  season  species,  at the experimental  as o p t i m i s t i c  control  growing  these  grown  June i f  stress  species,  Even t h o s e  tolerant,  of  species  leaves that  have had a l a r g e  fact  o f m o r t a l i t y would  of  the  following  g r o w t h e v e n when c o n d i t i o n s  growth  limited.  the  all  as c o n t a i n e r  and w o u l d  (1983) d e s c r i b e s  seedlings  of  survived until  are determinate  have been e x p e c t e d t o e x h i b i t  which  significant  fir  seedlings  May and t h e end o f  become t o o  Jones  that  C h a p t e r 1) were  primordia of  t h r e e months o f  1979).  seedlings  high  in  silver  p r i m o r d i a when t h e y were p l a n t e d  not  -  analysis.  Douglas-fir their  1.8  130  not face  to was  display of  which  high are  stress  themselves to the  risk  mortality. shoot  growth  to the drought  in  subsequent  conditions,  growing that  occurred  -  in July  and A u g u s t  new l e a f  that  The f a c t  the next y e a r s  growth through  its  and e x p a n d e d  significantly  effected  not  effect  had l e s s  that  severe weather  growth,  causes  particularly Increased shoot  adaptations  which  current  primordia western  growing  the growth  hemlock  in the  in the  also  in the  rate of  applies  shoot  to the other in their  i n t h e i r development  and  growth, to e x p l o i t  a larger soil  v o l u m e , and  transpirational  area,  ( H s i a o and A c e v e d o  are both  1974).  t o be r e l a t e d t o a b s c i s i c  Such  Acid  roots  years  (ABA)  year  is  of  morphology, or  shoots.  decreased  and H i r o n  concentrations,  (CK) c o n c e n t r a t i o n s  (Vaadia 1976),  species,  morphological  al_., 1980), to c y t o k i n i n  in water-stressed tissue  in  important  Sivakumaran et  1971).  year  growth  first  (Wright  and I m b e r ,  not  following  in water-stressed plants  (Tal  are  first  increase  decrease  an  conditions.  to the  are thought  is  primordia  carbohydrates  to drought  but  development.  of  limit  suggests  growth  s e a s o n and a r e  to water-stress  changes  in the a l l o c a t i o n  root  between  seasons  and s h o o t  exhibited  reduction  seedlings  significant  growth, to  changes  f o r the  area  of  conditions.  growing seasons, which  the exposure of  leaf  surprising that  which  subsequent  fir,  i n t h e same g r o w i n g  p l a n t i n g was g r e a t e r t h a n t h a t  One e x p l a n a t i o n  on l e a f  silver  after  leaf  only effects  by t h e p r e v i o u s y e a r s  somewhat  in  s u c c e s s i v e growth  The m a j o r i t y o f  both produced  is  in  and P a c i f i c  indeterminate species.  it  differences  s u c h as i r r i g a t i o n  Unlike Douglas-fir  Therefore  that  became more p r o n o u n c e d  a treatment  -  i n b o t h 1981 and 1 9 8 2 , l i m i t i n g t h e d e v e l o p m e n t  primordia.  treatments  131  1969; which  o r t o ABA t o CK  ratios  It  is  significant  that  132  -  in a l l  the  species,  the  largest  amount o f  the  largest  and most p r o l o n g e d  untreated Douglas-fir long).  It  few r o o t s  is  root  -  the  and had t h e h i g h e s t  water d e f i c i t s  irrigated shoot  to  of  seedlings, root  The e f f e c t s to  Ferrell  root  explanation  light  is  levels  of  long-term effects  shade c a r d s  d r y mass r a t i o s  f o r the greater  on s e e d l i n g  The  which developed  i r r i g a t i o n was no  must be  that  these seedlings  Douglas-fir conductances  reported  longer  presented  had t h e i r  growth  reduction  in  shaded  2.8  indicate that  thereby  leaf  areas  shaded  but s i m i l a r  o f t h e same s p e c i e s , water per u n i t  l i m i t e d by a r e d u c t i o n  in  leaf  and  This  result,  season dry matter p r o d u c t i o n  a r e a , must  photosynthesis.  together with the fact  was b e t t e r  season t r a n s p i r a t i o n than to estimates  stomatal  therefore  that  levels growing  related to estimates of of  growing  have  This  p h o t o s y n t h e s i s was l i k e l y due t o t h e l o w e r l i g h t  shade c a r d s .  low  area.  s e e d l i n g s , w h i c h had l a r g e r  w o u l d h a v e u s e d s i m i l a r amounts o f  on  by Drew and  were a b l e t o c o m p e n s a t e f o r t h e  in Figure  t o unshaded s e e d l i n g s  benefits  One  by t h e  by a l l o c a t i n g more d r y m a t t e r t o t h e s h o o t s  results  be  considered.  seedlings.  growth e x h i b i t e d  surface  very  g r o w t h , and i n p a r t i c u l a r  are s i m i l a r to those  shoot  increasing the photosynthetic  behind  if  the  were o v e r 1 m  d r y mass r a t i o s , w o u l d  ( 1 9 7 7 ) and Drew ( 1 9 8 3 ) f o r D o u g l a s - f i r  seedlings  that  to  some o f  T h i s d e m o n s t r a t e s t h a t when a s s e s s i n g t h e o v e r a l l  a particular treatment,  shoot  roots  showing  were exposed  (after 3 years  had d e v e l o p e d  v e r y u n l i k e l y t o s u r v i v e a summer d r o u g h t available.  seedlings  development were t h o s e t h a t  seedlings  l i k e l y that  the  season t o t a l  growing stomatal  -  conductance  would  (1986)  Douglas-fir,  that  conductance  on C-j i s  photosynthesis limited  support  -  the c o n t e n t i o n , which e x h i b i t s  a carbon d i o x i d e  rates  by s t o m a t a l  133  and t h e r e f o r e conductance  presented  little  dependence  insensitive  growth  unless  rates,  D is  by P r i c e  et  of  species,  stomatal  and  are g e n e r a l l y  h i g h and l i g h t  al.  that not  is  saturating. The  small  differences  and n o n - i r r i g a t e d seedling  Douglas-fir  conductance  water  as d e s c r i b e d  were  use f o r  the  seedling  on s e e d l i n g  however,  d a y as ^  loblolly that  values  Price  Douglas-fir  trees.  used, could  s  in  its  be due t o t h e is  limited,  effect  The f a c t  on that  in the estimates  be u s e f u l  only  the e f f e c t s  of  in  fact  that  under  all  differences seedlings  of  growing  shows t h a t  not  irrigated  stomatal  and n o n - i r r i g a t e d  and s p e c i e s  predicting  between  in  dry  in  all  season  the  predicting  particular  treatments  growth.  The e s t i m a t e s seasonal  irrigated  same t r e a t m e n t s  g r o w t h , but  might  Chapter 2.  similar to differences  t r a n s p i r a t i o n model  to  in  production  growth,  by h i g h D t h r o u g h  a c c u m u l a t i o n between  species  seedlings  t r a n s p i r a t i o n , and t h e r e f o r e  moisture conditions,  matter  in dry matter  et  trees  declined  of for  seasonal C  agricultural  3  a}_. ( 1 9 8 6 ) but  report  show t h a t  and d i f f e r e d  Seiler  and J o h n s o n  pine  (Pinus taeda  were g i v e n m o i s t u r e  WUE f o r  stress  crops  between report  seedlings  species  reviewed  much h i g h e r  WUE c h a n g e d  (1985) L.)  the three  daily  higher which  conditioning  and  daily  similar  by J o n e s values  substantially  irrigated  are  of  to  (1983); WUE  f r o m day  for to  non-irrigated values of  increased  treatments.  in  WUE  seedings  for  -  V.  Shade, distinct  irrigation  effect  south-facing treatment, after  received  or a combination  high e l e v a t i o n  This decline  of  conifer  clearcut.  showed a p r o n o u n c e d  shade,  -  CONCLUSIONS  on t h e g r o w t h o f  planting.  134  seedings  All  decline  in  was l e s s  these treatments planted  seedlings seasonal  pronounced  shoot  mass  had t h e  lowest  the  that  In t h o s e  seedlings  in  root  shoot t o  root  dry  ratios. Douglas-fir  so t h a t matter  seedlings  e x h i b i t e d a high degree  e v e n i n t h e d r i e s t y e a r t h e r e was o n l y accumulation  Western  hemlock  drought  tolerant,  between  and P a c i f i c  irrigated silver  surviving  seedlings  avoidance  b e c a u s e much o f  planting,  was i n t h e  and n o n - i r r i g a t e d  fir  summing t h e  growing product  boundary-line  D/(R T'). V  Less  tolerance  a 20% d i f f e r e n c e  seedlings,  this  not  and many s u b s e q u e n t l y d i e d .  behaviour  c o u l d not  be d e s c r i b e d  the growth, e s p e c i a l l y  in  dry  seedlings.  despite  being  as  thereby Even  in  drought  in the f i r s t year  after  shoots.  Growing season s e e d l i n g dry matter production estimates of  of drought  e x p e n d e d v a l u a b l e w a t e r t o a c h i e v e g r o w t h and  exposed themselves to d e s i c c a t i o n  the  of  g r o w t h one y e a r  in seedlings  i r r i g a t i o n , o r s h a d e and i r r i g a t i o n .  consequently these seedlings  on a  regardless  w h e r e t r e a t m e n t was w i t h h e l d , t h e r e was a m a r k e d i n c r e a s e growth,  had a  was w e l l  related  s e a s o n s e e d l i n g t r a n s p i r a t i o n t h a t were d e r i v e d of  values  of  a n a l y s i s model  success  seedling described  was a c h i e v e d  in  leaf  area,  g , s  in Chapter 2,  obtained and  r e l a t i n g dry matter  to by  from  hourly production  -  to  estimates of  This  is  (1986) in  growing  consistent which  photosynthesis  season t o t a l  with the  indicate is  135  that,  results  -  seedling of  Leverenz  with decreasing  g r e a t e r than t h a t  VI.  stomatal  in  conductance.  ( 1 9 8 1 ) and P r i c e  light  stomatal  l e v e l s , the  et  al.  reduction  conductance.  REFERENCES  B o y e r , J . D . 1 9 7 6 . W a t e r d e f i c i t s and p h o t o s y n t h e s i s . In w a t e r d e f i c i t s and p l a n t g r o w t h . V o l . 4 , E d i t e d by T . T . K o z l o w s k i . Academic P r e s s , New Y o r k , p p . 1 5 3 - 1 9 0 . Drew,  A.P. 1983. O p t i m i z i n g g r o w t h and d e v e l o p m e n t s e e d l i n g s by a l t e r i n g l i g h t i n t e n s i t y . Can. J . 425-428.  o f 2-0 D o u g l a s - f i r For. Res. 13:  D r e w , A . P . , and W.K. F e r r e l l . 1979. Seasonal changes i n the water b a l a n c e o f D o u g l a s - f i r ( P s e u d o t s u g a m e n z i e s i i ) s e e d l i n g s grown under d i f f e r e n t l i g h t i n t e n s i t i e s . C a n . J . B o t . 57: 6 6 6 - 6 7 4 . D u r y e a , M . L . , and D . P . L a v e n d e r . 1 9 8 2 . W a t e r r e l a t i o n s , g r o w t h , and s u r v i v a l of root-wrenched D o u g l a s - f i r s e e d l i n g s . Can. J . F o r . Res. 12: 545-555. Eis,  S . , and J . R . L o n g . 1 9 7 3 . Root p r u n i n g i n t h e n u r s e r y . S e r v . Tree P l a n t . Notes, 24(1): 20-22.  G i l e s , D.G., growing balance  U.S.  For.  T . A . B l a c k , and D . L . S p i t t l e h o u s e . 1985. Determination of s e a s o n s o i l w a t e r d e f i c i t s on a f o r e s t e d s l o p e u s i n g w a t e r analysis. Can. J . F o r . Res. 15: 107-114.  H s i a o , T . C . , and E. A c e v e d o . 1974. P l a n t responses to water d e f i c i t s , w a t e r use e f f i c i e n c y and d r o u g h t r e s i s t a n c e . A g r i c . M e t e o r o l . 14: 59-84. J o n e s , H . G . 1 9 8 3 . P l a n t s and m i c r o c l i m a t e : a q u a n t i t a t i v e a p p r o a c h environmental plant physiology. Cambridge U n i v e r s i t y P r e s s , C a m b r i d g e , U.K. Kozlowski, T.T. deficits. Kramer, P . J . , Academic  1982. W a t e r s u p p l y and t r e e g r o w t h . F o r e s t r y A b s t r a c t s , 43: 5 7 - 9 5 .  and T . T . K o z l o w s k i . P r e s s , New Y o r k .  1979.  Physiology  Part  of  1.  woody  to  Water  plants.  -  136  -  L e v e r e n z , J.W. 1981. P h o t o s y n t h e s i s and t r a n s p i r a t i o n i n l a r g e forest-grown Douglas-fir: diurnal v a r i a t i o n . Can. J . B o t . 59: 349-356. L o p u s h i n s k y , W., to survival seedlings.  and T . B e e b e . 1976. R e l a t i o n s h i p of shoot-root ratio and g r o w t h o f o u t p l a n t e d D o u g l a s - f i r and P o n d e r o s a p i n e U . S . D e p . A g r i c . F o r . S e r v . R e s . N o t e PNW-274.  P r i c e , D . T . , T . A . B l a c k , and F . M . K e l l i h e r . 1986. E f f e c t s of s a l a l u n d e r s t o r y r e m o v a l on p h o t o s y n t h e t i c r a t e and s t o m a t a l c o n d u c t a n c e of young D o u g l a s - f i r t r e e s . Can. J . For. Res. In p r e s s . S e i l e r , J . R . and J . D . J o h n s o n . 1985. P h o t o s y n t h e s i s and t r a n s p i r a t i o n o f L o b l o l l y p i n e s e e d l i n g s as i n f l u e n c e d by m o i s t u r e - s t r e s s conditioning. F o r e s t S c i . 3: 7 4 2 - 7 4 9 . S i v a k u m a r a n , S . , R. H o r g a n , J . H e a l d , and M.A. H a l l . 1980. Effect w a t e r s t r e s s on m e t a b o l i s m o f a b s c i s i c a c i d i n P o p u l u s r o b u s t a s c h n i e d and E u p h o r b i a l a t h y r u s L. P l a n t , C e l l and E n v i r o n m e n t , 163-173. Tal,  of x 3:  M . , and D. I m b e r . 1 9 7 1 . A b n o r m a l s t o m a t a l b e h a v i o u r and h o r m o n a l i n b a l a n c e i n f l a c c a , a w i l t y mutant of t o m a t o . III. Hormonal e f f e c t s on t h e w a t e r s t a t u s i n t h e p l a n t . Plant P h y s i o l . 47: 849-950.  T a n n e r , C . B . , and T . R . S i n c l a i r . 1983. E f f i c i e n t w a t e r use i n c r o p p r o d u c t i o n : research or r e - s e a r c h ? _In_ L i m i t a t i o n s t o e f f i c i e n t w a t e r use i n crop p r o d u c t i o n . E d i t e d by H.M. T a y l o r , W.R. J o r d a n and T . R . S i n c l a i r . Madison, Wis. The A m e r i c a n S o c i e t y o f Agronomy. V a a d i a , Y. 1976. P l a n t hormones and w a t e r R . S o c . L o n d o n , S e r . B. 273: 5 1 3 - 5 2 2 .  stress.  Phil.  Trans.  Wong, S . C . , I . R . C o w a n , and G . D . F a r q u h a r . 1979. Stomatal conductance correlates with photosynthetic capacity. Nature (London), 282: 424-426. W r i g h t , S . T . C , and R . W . P . H e r o n . 1969. (+) - a b s c i s i c g r o w t h i n h i b i t o r i n d e t a c h e d wheat l e a v e s f o l l o w i n g wilting. N a t u r e , 224: 719-720.  a c i d , the a period of  W a l l i s , C . H . , T . A . B l a c k , 0 . H e r t z m a n , and V . J . W a l t o n . 1983. A p p l i c a t i o n o f a w a t e r b a l a n c e model t o e s t i m a t i n g hay g r o w t h t h e Peace R i v e r r e g i o n . Atmosphere-ocean, 21: 326-343.  in  -  137  -  CONCLUSIONS  Douglas-fir  seedlings,  were s u c c e s s f u l l y clearcut.  established  The s e e d l i n g s  w h i c h e n a b l e d them t o demand and l o w s o i l to maintain daily those  achieved  tolerance  planted  in the  spring  on a s o u t h - f a c i n g  exhibited  as 1-0  high  a high degree of  elevation drought  s u r v i v e and g r o w i n c o n d i t i o n s  water p o t e n t i a l s .  transpiration  Douglas-fir  rates that  under optimum s o i l  of  tolerance  high  atmospheric  seedlings  were n e v e r l e s s  moisture conditions.  was a c h i e v e d b e c a u s e s e e d l i n g s  stryroplugs,  were  t h a n 50% o f  Drought  were a b l e t o l o w e r  their  osmotic  p o t e n t i a l , w h i c h a p p e a r e d t o be due t o a c c u m u l a t i o n o f  in  cells,  leaf  and t h e r e b y m a i n t a i n t u r g o r t h r o u g h o u t  season.  T h i s mechanism i s  The f a c t  that  little  when s e e d l i n g s  were i r r i g a t e d  seedlings, were not drought  hemlock,  provision  of  treatments,  of  planted  as 1-0  established. stress  3 years,  increased  survival  extent,  styroplugs  avoidance  the s e e d l i n g s '  significantly  (Jones  1983).  i n a wet summer and  the osmotic  Both s p e c i e s  solutes  growing  a d j u s t m e n t was  r a t h e r than being a seasonal Pacific  silver  a t t h e same  were u n a b l e t o  and t o l e r a n c e  of  survival  of the seedlings  in both  receiving  t r e a t m e n t s n e v e r e x c e e d e d 65% and was l o w e r t h a n t h a t  fir  site, survive  mechanisms.  water or a combination  seedling  a  response.  m i c r o c l i m a t e , whether through  shade o r t h e a p p l i c a t i o n  after  that  and t o an e v e r g r e a t e r  because they lacked  Major m o d i f i c a t i o n  However,  stress  w h i c h were a l s o  successfully  suggests  the  stress tolerance  osmotic adjustment occurred  response to environmental Western  an e x a m p l e o f  able  of  these  species.  these  achieved  the  by  -  Douglas-fir  seedlings that  and P a c i f i c  silver  fir  138  had r e c e i v e d  -  no t r e a t m e n t .  seedlings, despite  expended v a l u a b l e water  in  achieving  Western  not b e i n g drought  shoot  growth  t h e r e b y exposed themselves t o d e s s i c a t i o n .  after  hemlock  tolerant,  planting,  C o n s e q u e n t l y many  and  seedlings  died. T h e r e was e v i d e n c e seedings  that  temperature, morning vapour air.  shade c a r d s , reduced  as a r e s u l t  Because  seedling of  unshaded  (i)  this  difference  seedlings,  a decrease  The e x t e n t by c h a n g e s  unshaded  and t y p e o f  in  second  growing  conditions  shoot  that  phenomenon was l e a s t largest  shoots  likely  increased  behind  shade c a r d s .  growth All  stomatal  cavities rate  )  - 1  in  and  of  had h i g h e r t u r g o r  the  in  there  shaded  the  the  resulted  and ( i i )  potential  all  species  an was  no  and  potentials  This  first  irrigated  smallest  root  growth t o compensate  Untreated  in  was l i k e l y  in t h e i r in  was m a r k e d l y  regardless  and an i n c r e a s e  seasons.  and had t h e  in  seedlings,  growth  occurred  s y s t e m s and c o n s e q u e n t l y  g s  seedlings.  pronounced  shoot  surface  t e m p e r a t u r e and h e n c e  in t r a n s p i r a t i o n  seedlings  Douglas-fir  (i.e.,  twig xylem p o t e n t i a l  shaded  showed a d e c l i n e  drought  needle  on  soil  rates  needle  between t h e o s m o t i c  in microclimate.  and t h i r d  in  between  reduction  the  s i m i l a r l y sized  from r e d u c i n g  transpiration  i n t h e minimum t o t a l  significant  the  apart  pressure difference  increase  than  from e x p e r i m e n t s conducted  root in  growth  which  systems.  Shaded  shoot to  in  growth.  seedlings  for  treatment,  response to  year of  the lower  seedlings developed  had t h e l o w e s t  of the  affected  their the This  developed  light  the l a r g e s t  r o o t d r y mass  seedlings levels root ratios.  -  The soil,  stomatal  conductances  were m a r k e d l y r e d u c e d  response, other  and a l s o t h e  environmental  seedlings (Jarvis act  1976) o f  the  field  whether  variability  by i n c l u d i n g variable.  critical  in  summing t h e  s  the  or  hours  inclusion  could  hourly  leaf  area.  conductance.  PPFD i s  usually  low)  (ii)  rates D is  for  variable only  70% o f  rates  stomata  the  s  obtained  from  estimated  V  with  growing  growing  season  season  average growing  The b e t t e r  as f o l l o w s .  a r e l o w when ( i ) h i g h enough  D is  so t h a t  and  seedling  seedling  season  correlation  by  the  hourly average D/(R T')  Estimates of  a  closed.  were s u c c e s s f u l l y  average g ,  all  achieved  T h e r e was no e v i d e n c e o f  below which  in  o v e r 85% o f  independent  and g r o w t h can be e x p l a i n e d  and p h o t o s y n t h e s i s  that,  as an  potential  transpiration of  functions  variables  from s u n r i s e  be e x p l a i n e d .  turgor  all  o n l y be  this  between  analysis  could  of  differ  response  Boundary-line  in  air  not  success  were b e t t e r c o r r e l a t e d  stomatal  p o t e n t i a l , did  n o n - i r r i g a t e d , accounted of  This  irradiance,  in  dry  t o changes  with the assumption that  a n a l y s i s m o d e l , measured  projected  transpiration rates  data,  s  accumulation than e s t i m a t e s of  seedling  water  solar  n o r were t h e r e d i f f e r e n c e s  number o f  product  transpiration  conductance  such as g l o b a l  This level  s  seedling  boundary-line  matter  g .  threshold  Daily  seedling  in  g  g  i n wet o r  pressure d e f i c i t s .  stomatal  zone s o i l  whether  but m u l t i p i i c a t i v e l y , produced  Without  variability  root  irrigated  the  seedlings,  i n two s u c c e s s i v e y e a r s .  independently  species,  -  by h i g h v a p o u r  variables,  seasons  planted  all  response of  t e m p e r a t u r e and a v e r a g e o v e r two g r o w i n g  of  139  dry  total  between  seedling  Transpiration low  there  (on s u c h is  days  stomatal  -  closure  and  (iii)  the s o i l  a r e h i g h when PPFD i s  140  -  water p o t e n t i a l  high, soil  is  low.  water p o t e n t i a l  is  h i g h enough t o c a u s e s t o m a t a l  closure.  The p o o r e r  conductance  suprising  in  (1981)  and g r o w t h  and P r i c e  photosynthesis, and n o t  possible replant  eta]_.  not  in  and h e n c e g r o w t h , a t l o w P P F D ,  is  on s i t e s t h a t  successful  and t h a t  seedlings  seedlings'  microclimate, provided the correct seedlings,  efficiencies  (0.0022 g g - )  agricultural  crops.  1  non-irrigated  is  that  Provided Douglas-fir  fact  was o n l y 20% l e s s  - 1 . 2 MPa.  After 3 years non-irrigated  0 . 1 5 m.  would  soil  is  at  the  planted.  reduced  can  C  use  quickly  by l o w s o i l  water  dry matter accumulation  than t h a t  s e a s o n when s o i l  water  seedlings  season such s e e d l i n g s  water content  a  3  of  potentials  had d e v e l o p e d  reached roots  a radius  would o n l y d e p l e t e  by a maximum o f 4% e v e n a s s u m i n g t h a t  u s e a s much w a t e r as i r r i g a t e d  seedlings.  in  irrigated  v o l u m e a p p r o x i m a t e l y 1 m d e e p and w i t h  During a growing  volumetric  seedlings  that  even i n a g r o w i n g  a soil  species  of  is to  s e a s o n and had w a t e r  n o t be g r e a t l y  shown by t h e  seedlings  exploited  l i m i t e d by PPFD  were s i m i l a r t o t h o s e o f  seedlings,  that  Leverenz  e v e n when i r r i g a t e d , o n l y t r a n s p i r e d  growth w i l l  This  often  even w i t h o u t m a j o r m o d i f i c a t i o n  2.5 L o f water d u r i n g a growing  potentials.  between  conifers  c a n be e s t a b l i s h e d ,  high l e v e l s ,  roots,  correlation  seedling establishment  acceptably  establish  not  had p r e v i o u s l y been c o n s i d e r e d d i f f i c u l t  due t o d r o u g h t ,  maximum o f  h i g h and D i s  conductance.  s t u d y has shown t h a t  Douglas-fir  rates  v i e w o f t h e work o f  ( 1 9 8 6 ) who showed t h a t  by s t o m a t a l  This  is  However b o t h  of  the they  -  141  -  REFERENCES  J a r v i s , P.G. 1976. The i n t e r p r e t a t i o n and t h e v a r i a t i o n s i n l e a f w a t e r - p o t e n t i a l and s t o m a t a l c o n d u c t a n c e f o u n d i n c a n o p i e s i n t h e field. P h i l . T r a n s . R. S o c , L o n d o n , S e r B. 2 7 3 : 5 9 3 - 6 1 0 . J o n e s , H.G. Press.  1983. P l a n t s and M i c r o c l i m a t e . Cambridge, U.K.  L e v e r e n z , J.W. 1981. Photosynthesis forest-grown Douglas-fir t r e e s .  Cambridge  and t r a n s p i r a t i o n Can. J . For. Res.  University  in large 14: 4 8 1 - 4 8 7 .  P r i c e , D . T . , T . A . B l a c k and F . M . K e l l i h e r . 1986. E f f e c t s of s a l a l u n d e r s t o r y r e m o v a l on p h o t o s y n t h e t i c r a t e and s t o m a t a l c o n d u c t a n c e of young D o u g l a s - f i r t r e e s . C a n . J . F o r . R e s . 16 ( i n p r e s s ) .  -  142  -  APPENDIX  I  DERIVATION OF WATER-RELEASE CURVES FOR THE DETERMINATION CONIFER  SEEDLING OSMOTIC  POTENTIAL  OF  -  143  -  APPENDIX  I  DERIVATION OF WATER-RELEASE CONIFER  SEEDLING OSMOTIC  Measurements o f the osmotic zero turgor seedlings  (^)  of  for  rehydrated Corp.,  ten  section  was t h e n c u t  outside  the  seal.  of  each  and s e a l e d  Indianapolis,  Ind.)  and w e i g h e d .  The bagged  shoot  end o f t h e  pressurized  at a r a t e o f  the endpoint, shoot  was c o n t i n u e d the  beyond t h e After  last  endpoint  approximately  reweighed. -4.5  were o b t a i n e d  to  Values  (%o)  were  Curves  weighing  shoot  sealed  in  from a  The c h a m b e r  and t h e n  s  slowly  (i{i)  -3.5  At The  obtained  point. - 0.3  Other  MPa  sap w i t h a t i s s u e .  p r e s s u r e was r e l e a s e d were o b t a i n e d  surface.  released.  one d a t a  and a b s o r b i n g t h e e m e r g i n g  was  .  _ 1  xylem p o t e n t i a l  s h o o t mass p r o v i d e d  extend  a pressure  s a p a p p e a r e d on t h e c u t  M P a , and - 3 . 0 t o  were  a small  stem t o  by p r e s s u r i z i n g t h e c h a m b e r 0.2  -4.5  generated  bag (Dow C h e m i c a l  Following  shoot  and  silver-fir  was c u t  a p p r o x i m a t e l y 6 kPa  s h o o t mass and  -5.0 MPa, -4.0 t o  ziploc  was t h e n  The  15 m i n u t e s t h e of  A shoot  allow the  p r e s s u r e was r e c o r d e d  was removed and w e i g h e d .  points  turgor  curves that  stem e x p o s e d .  until  f r o m t h i s m e a s u r e m e n t and t h e data  full  h e m l o c k and P a c i f i c  in a small  chamber w i t h t h e c u t  Pressurization  at  species.  f r o m t h e bag t o  with a i r  POTENTIAL  by S c h o l a n d e r e t ail_. ( 1 9 6 5 ) .  seedlings  seedling  western  from w a t e r - r e l e a s e  u s i n g t h e method d e s c r i b e d generated  potential  Douglas-fir,  were o b t a i n e d  CURVES FOR THE DETERMINATION OF  and t h e  until for  shoot  shoot <J> was  Douglas-fir,  -  western  h e m l o c k and P a c i f i c  pressure  was r e c o r d e d , t h e  48 h o u r s t o  obtain  Figure  AI.l  Douglas-fir squares as t h e  shoot  a typical  seedling.  The  regression line s h o o t mass a t  content  silver-fir  full  respectively.  plot  of  (RWC) was t h e n c a l c u a t e d  portion of  (M ).  The  0  s h o o t mass a t a g i v e n i|4 and  To o b t a i n (Figure (B)  is  shoot  so  AI.2).  (Tyree  given  1976)  100°C  for  shoot  s h o o t mass f o r  <> | = 0) o f  Figure  AI.l  relative  the  least  was  taken  a  water  - M )  (AI.l)  rf  shoot Tp.  RWC was p l o t t e d  i|% i n  so t h a t  against  the a p o p l a s t i c the  sympl a s t  ij>  1/shoot water  at  fraction  a given  that  Below the t u r g o r relationship  loss  B and a s l o p e o f  loss  MPa.  point,  shoot  l/(<Wro ( 1 - B ) ) .  an e s t i m a t e o f  Table A I . l Turgor  = (RWC - B ) / ( « ^ = ^  1 / s h o o t i|> and s h o o t  between  RWC = 1 g i v e s  0.3  to  final  by  1/^  to  Q  An a s s u m p t i o n i s made t h a t  constant RWC i s  shoot  the  as d  the  ij> v e r s u s  shoot  RWC = (M - M ) / ( M where M i s  and t h e n d r i e d  ( s h o o t mass a t  the l i n e a r  turgor  After  (M^).  intercept  for  -  was w e i g h e d  s h o o t d r y mass  shows  144  ^  0  The  in the  shows t h e d i f f e r e n c e s  point  for  all  the  species.  i r ( j  (1 - B ) )  which  (AI.3)  results  in  a linear  RWC w i t h an RWC i n t e r c e p t intercept  of  this  line  equal  at  sympl a s t .  between  i | % 0 and ^  This difference  at  all  never  the exceeded  - 145 -  Shoot Mass (9)  lire A I . l  The r e l a t i o n s h i p b e t w e e n s e e d l i n g s h o o t mass and s h o o t t o t a l xylem p o t e n t i a l (shoot for a Douglas-fir seedling. The mass o f t h e s h o o t when s h o o t i|> i s z e r o ( M ) was d e t e r m i n e d f r o m t h e l e a s t s q u a r e s r e g r e s s i o n o f the l i n e a r portion of the l i n e . 0  - 146  -  Shoot RWC  -10  Figure  AI.2  The r e l a t i o n s h i p b e t w e e n s e e d l i n g s h o o t r e l a t i v e w a t e r c o n t e n t ( s h o o t RWC) and t h e i n v e r s e o f s h o o t t o t a l x y l e m p o t e n t i a l ( ( s h o o t 'J>)" )« The a p o p l a s t i c w a t e r c o n t e n t ( B ) , o s m o t i c p o t e n t i a l a t f u l l t u r g o r (^0) and o s m o t i c p o t e n t i a l a t z e r o t u r g o r (i)4) are i n d i c a t e d . 1  -  147  Table  -  AI.l  The d i f f e r e n c e b e t w e e n t h e o s m o t i c p o t e n t i a l a t f u l l t u r g o r (%o) and o s m o t i c p o t e n t i a l a t z e r o t u r g o r (Vir) o f D o u g l a s - f i r , w e s t e r n h e m l o c k and P a c i f i c s i l v e r - f i r s h o o t s . A l s o shown a r e t h e c o r r e s p o n d values of a p o p l a s t i c water content ( B ) . V a l u e s were o b t a i n e d from water-release curves. E a c h number i s t h e a v e r a g e o f 10 m e a s u r e m e n t s .  •  Species  -  (MPa)  B  D o u g l a s -• f i r  0.28  0.28  Western  0.23  0.29  0.21  0.23  hemlock  Paci f i c s i l v e r - f i r  - 148 -  APPENDIX  II  AN INSTRUMENT FOR MEASURING THE AVERAGE STOMATAL OF CONIFER S E E D L I N G S .  CONDUCTANCE  ( L i v i n g s t o n et a l . , 1984, Can. J . 14:  512-517)  For.  Sci.  -  149 -  An instrument for measuring the average stomatal conductance of conifer seedlings N . J . LIVINGSTON, T . A . BLACK, AND D. BEAMES  Deportment of Soil Science. University of British Columbia. Vancouver. B.C.. Canada V6T 2A2 AND B. G. DltNSWORTH  Woodlands Services. MacMillan  Bloedel Co. Ltd.. Nanaimo. B.C.. Canada V9R 5H9  Received August 26. 1983' Accepted March IS. 1984 LIVINGSTON. N. J . , T. A. BLACK. D. BEAMES. and B G. DUNSWORTH. 1984. An instrument for measuring the average  stomata! conductance of conifer seedlings Can. J. For. Res. 14: 512—517. A ventilated, transient-type porometer was designed to oondestructively measure the average stomatal conductance of conifer seedlings. The porometer consists of a low-power microprocessor unit and a stainless steel chamber which encloses the seedling. Conductance is calculated from the measured rate of increase in chamber relative humidity above the ambient level. Consequently, chamber air does not have to be dried prior to measurement. Direct readout of stomatal conductance is provided by means of a liquid crystal display and a serial (RS232) port. Porometer calibration over a range of humidities showed that the effective chamber volume was consistently 259 larger than the actual chamber volume. Stomatal conductance measurements made on Douglas-fir (Pseudotsuga menziesii (Mirb. I Franco) seedlings using the porometer agreed well with average values obtained with a ventilated diffusion porometer using four needle samples. The porometer proved to be very convenient to use in a forest clearcut environment, with the measurement procedure taking about I min. Measurements can be made on a seedling over the growing season because the use of the instrument causes no injury to stem, branches, and needles. LIVINGSTON. N. J . T. A. BLACK. D. BEAMES et B. G. DUNSWORTH. 1984. An instrument for measuring the average stomatal  conductance of conifer seedlings. Can J. For. Res. 14: 512-517. Un porometre ventite du type a transit a iii mis au point pour mesurer de facon non-destructive la conductance stomatique moyenne. Le porometre compone un microprocesseur de faible puissance et unc chambre en acier inoxydable qui enferme le semis. La conductance est calculee a partir de ia mesure du taux d augmentation d'humiditc relative au-dessus du niveau ambiant Consequemment lair de la chambre n'a pas a itre deshumidifie' avant la prise de donnees. La lecture directe de la conductance stomatique est rendue possible par un affichage a crista! liquide et par une interface a port serie (RS 232). La calibrage du porometre sur une gam me d'humidiles a montrt que le volume efficace euil de facon consistante 259 plus grande comparativement au volume des chambres utilisees actuellement. Des mesures de la conductance stomatique effectuees sur de* semis de sapinde Douglas {Pseudotsuga menziesii (Mirb.) Franco) avec le porometre son; en accord avec les valeurs moyennes obtenues avec un porometre de diffusion ventile' utilisant des echantillons a 4 aiguilles. Le porometre s'est avert efficace dans le contexle forestier dune coupe d'eclaircie. la prise de mesure ne neeessitant approximativement que I min. Des mesures peuvenl etre prises sur un semis pendant la saison de croissancc car ('utilisation de I'instrument ne cause aucune blessure a la tige. aux rameaux et aux aiguilles [Traduit par Ic journal)  Introduction  The most promising approach to quantitative measurements of stomatal conductance is provided by water vapour diffusion porometers. These can be categorized into two classes, those that take measurements under steady state conditions (e.g., Beardsell et al. 1972) and those thai measure rales of change of relative humidity (e.g.. Kanemasu et al. 1969). While a number of systems have been devised to meet specialized needs (e.g.. Bingham and Coyne 1977; Kohsiek 1981: Kaufmann 1981), porometer methods published to date are often inadequate for use in certain applications. For example, our studies of water stress in conifer seedlings required a rugged and portable instrument that would nondestructively measure the average stomatal conductance of seedlings of various species growing in high elevation clearcuts and allow measurements to be made on the same seedling over the growing season. This paper describes the design, calibration, and tests of an instrument that satisfies these requirements. The instrument is microprocessor based and gives a direct readout of stomatal conductance and transpiration rate obtained from transient 'Revised manuscript received February 6. 1984.  measurements of relative humidity in a chamber placed over a seedling. Porometer design The flux of water vapour from a seedling (F. milligrams per second) in a well-stirred porometer chamber is given by [I]  F = <Ap,/Ar)V  where Ap, is the change in water vapour density, p. (milligrams per cubic centimetre) over the time period A i (seconds), and V is the volume of the chamber (cubic centimetres). The average stomatal conductance of the seedling (#.. centimetres per second) is given by [2] *. = F/(A(p.»(D - » P>  where A is the projected area of the evaporating leaf or needle surface (square centimetres). p,*(7") is the saturation water vapour density (milligrams per cubic centimetre) at air temperature (T). It is assumed that the air in the stomatal cavities is saturated and that the boundary layer resistance is negligibly small so that the needle is at the same temperature as the air in the chamber. In this transient system, values of g. can be  -  150 -  LIVINGSTON ET  AL.  UIMU mnzir ',  S U I T fSTTOH PLATE  FIG. 2. Circuit used to generate frequencies from the Vaisala relative humidity- and thermistor sensors.  F)G. 1. Diagram of the stainless steel porometer chamber showing the removable top plate with fan and sensors, and the split bottom plate. The parts arc as follows: (I) hinge for bottom plate: (2) tightening clamp for bottom plate; (3) hinge for clamping rod; (4) aluminum clamping rod; (5) soft rubber gasket: (6) foam rubber gasket; (7) hole for seedling stem; (8) teflon gasket; (9) DC fan; (10) electrical connector; (II) humidity and temperature sensing unit: (12) clamping rod slot; (13) wing nut. obtained over a wide range of ambient vapour densities, but measurements must be completed before the decrease in water vapour density deficit is large enough to affect the stomatal conductance. Because the conductance is measured at ambient vapour density, the chamber air does not require drying before each measurement. The porometer system has two subunits: (/) a porometer chamber containing a humidity sensor, a temperature sensor, and a DC-powered fan, and ( « ) a low power microprocessor unit and liquid crystal display housed in a snail carrying case. The case also contains the system's power supplies, four 6 V 2.6 A h solid-gel rechargeable batteries (Elpower Corp., Santa Ana, C A , U . S . A . ) . A 1.5-m electrical cable with connectors at both ends links the porometer chamber to the microprocessor unit. Porometer d u m b e r The chamber, designed to accommodate conifer seedlings up to 30 cm in height, consists of three pans: a thin-walled stainless steel cylinder, a removable top plate, and a split bottom plate, both of which are machined from stainless steel (316) (Fig. 1). This material was chosen to minimize tarnishing and water adsorption by the chamber walls (Dixon and Grace 1982). Because the cylinder is open at both ends, chamber vapour density equilibrates quickly to that of the surrounding air before each measurement. The bottom plate is hinged  and has a 1 5-cm diameter hole at its centre. This enables it to be opened and clamped around the base of a seedling. A pliable rubber gasket lining the hole and the inner edges of the plate ensures an air-tight seal around the stem of the seedling. The inside surfaces of the top and bottom plates each have a teflon gasket seated in a milled groove that runs on the inside of a lip at the edge of each plate. An effective seal is thereby established when the cylinder is placed between the plates. Separate relative humidity and temperature sensing units, described in a later section, are mounted on a circuit board measuring 2.4 cm wide by 4.4 cm long, which is attached to the underside of the top plate. The circuit board is protected by a stainless steel cover with the sensing elements exposed to the chamber. A 6-V DC fan (R. Marx-Luder, 1721 Gemmrigheim/Neckar, Germany) is mounted on the top plate. Power for the fan (300 mA) is provided by two of the 6 V •olid-gel batteries connected in parallel, that are housed with the microprocessor unit. We have found that this fan could be replaced with two 30 mA 12 V DC Micronel fans. Electronics Humidity  and temperature  tensing  The relative humidity sensing element is a thin film capacitor with an organic polymer dielectric (Humicap mode) 6064. Vaisala Company, Finland). The capacitance of the sensor depends on water adsorption in the organic polymer layer. The capacitance ranges from approximately 44 pF at 0% relative humidity (RH) to 57 pF at 100% R H . Because of the sensor's small capacitance, the length of its leads are minimized to reduce stray capacitance. An integrated circuit function generator (XR-2206, Exar Integrated Systems Inc.. Sunnyvale, C A , U . S . A . ) chosen for its excellent frequency •ability (20 ppm °C~') is used to produce a square wave signal, the frequency (f ) of which is inversely proportional to the product of die sensor capacitance and a fixed value resistor (Fig. 2). Two of the 6-V batteries are connected in series, and the output is regulated down to 10 V for the XR-2206 circuitry. The output of the generator is linearly related to RH (±0.1 % RH) between IS and 8 5 % , which is the normal operating range of the porometer and which corresponds to a frequency range of 7 5 - 6 5 kHz. The humidity tensor was calibrated by means of a constant temperature water bath and a dewpoint hygrometer. Saturated air was passed through the water bath and then the dewpoint hygrometer to measure the dewpoint temperature. It was men passed over the humidity sensor and the resulting relative humidity reading recorded. m  Air temperature (D is tensed with a precision thermistor (FenwaU U U A 35JI). An additional XR-2206 is employed to  -  CAN.  M SOCt*  J. FOR  OP 1S02  T WOJOH FAN  mc«op«oc£ssc*  —{ *S-ZSZ-c""]  VOLTAGE •EtUUTWS  1  cnton  MM  I  KCHAWEABU MTTHIES  FIG. 3. Schematic of the seedling porometer electronics. generate a square wave signal, the frequency </T) of which is inversely proportional to the product of the thermistor resistance and a fixed capacitor. The output frequency of the oscillator ranges between 20 and 200 kHz, which corresponds to a temperature range of 0 - 5 O ° C . Microprocessor  unit  151 -  R E S . V O L . 14. 1984  sampled, displayed, and then updated every 2 s. When stomatal conductance or vapour flux is monitored, the first reading is not displayed until 8 s have elapsed because of the curve smoothing routine described earlier. The fan is automatically shut off after 40 s to conserve battery power. Teats and calibration  Chamber ventilation  It is important that air in the seedling chamber is well mixed to ensure that the humidity sensor measures the true average chamber humidity and that a high boundary layer conductance results in needle temperature being maintained close to air temperature. To determine the extent of mixing throughout the chamber, air speeds were measured systematically using a hotwire anemometer. No stagnation spots were found when a Douglas-fir (Pseudotsugo memiesii (Mir.) Franco) seedling with a projected needle area of approximately 370 crrr was placed in the chamber. Typically, air speeds ranged from 80 to 180 cm s~' which correspond to boundary layer conductances ranging from 7 to 9 cm s~', respectively (Landsberg and Thorn 1971). The lowest air speed of 35 cm s"' was measured in a small region near the bottom of the chamber. This corresponds to a boundary layer conductance of 5 cm $"'.  The square wave outputs from the humidity and temperature sensors in the porometer chamber are carried via the connector cable to the microprocessor unit (Fig. 3) and are sampled every Fine wire (0.075 mm) copper-con stantan thermocouples 2 s. A timer which measures the length of one period of a were used to measure differences between needle and air square wave is used to determine the signal frequency to an temperatures in laboratory and greenhouse experiments conaccuracy equivalent to ± 0 . 0 3 % R H and ± 0 . 0 7 ° C from 0 to ducted on Douglas-fir seedlings. At low stomatal conductances 70°C. The microprocessor C P U (RCA 1802) is programmed to (0.05 cm s" 1 ) needle temperature was approximately 0.08°C compute the values of relative humidity and temperature from lower than air temperature, while at intermediate conductances the respective frequencies. The calibrations of the sensor units (0.20 cm s~') needle temperature was approximately 0.15°C are entered and stored in the microprocessor by means of a lower than air temperature. These measurements confirmed 16-key keyboard. calculations, based on energy balance and exchange theory Four quadratic equations which are monotonic and continapplied to a leaf (Campbell 1977), in which net longwave uous, arc used to compute saturated vapour density over the radiation exchange between seedling and the chamber was range 0 - S O ° C Values of saturated vapour density are accurate approximated using the Christiansen equation (Jacob 1957). to within 0.1 % of the Smithsonian Meteorological Table values Calculations using our lowest estimate of boundary layer (List 1951) over this range. The water vapour flux is calculated conductance showed that even at extremely high stomatal using [ I ] after applying the least squares method of smoothing conductance (0.7 cm s~') needle temperature would only be over four points so that four measurements are taken before the 0.9°C lower than air temperature. However, when chamber first value is computed, g, is then calculated using [2] with the temperature exceeds air temperature by S°C. at this stomatal average values of the four p, and T measurements. After this, conductance, needle temperature would only be 0.5°C lower the computation is updated every 2 s and relayed to the liquid than air temperature. crystal display. Water vapour adsorption Three C M O S erasable programmable read-only memory There are numerous surfaces within the porometer chamber (EPROM) chips (27CI6), which provide a total of 6 K bytes that can adsorb water vapour (Gandar and Tanner 1976). These of storage space, hold the various computational routines. include the chamber walls and fan blades. Unless the adsorpApproximately 0.25 K bytes of C M O S random access memtion or de sorption of this water vapour is very small compared ory (RAM) is used to store the constants used in the comwith the increase in water vapour density in the chamber, putations. The values of these constants, which include the resulting from seedling transpiration, significant errors can chamber volume and leaf area, are entered directly from the arise when measuring transpiration rate and stomatal conduckeyboard. A continuous memory is provided by a 3.6-V tance. A calibration procedure is therefore necessary to quannickel-cadmium battery backup system which enables contify and correct for water vapour sorption effects. For this stants to be stored for periods of many months. This battery purpose, an artificial seedling consisting of an aluminum stem system is trickle charged by the solid-gel batteries. The same and four stainless steel leaves was constructed. Saturated filter 12-V power supply used for the XR-2206 circuitry is regulated paper of known surface area was attached to the leaves to down to 5 V to power the microprocessor system which draws provide an evaporating surface. The base of the seedling rested approximately 10 mA. on the pan of a balance with a resolution of I mg beneath the After the porometer chamber is placed over a conifer seedporometer chamber, so that the seedling stem entered the chamling one of seven variables (f , fx, R H . T, p., F, and g,) can ber through the hole in the base plate exposing the leaves to the be monitored on the display by pressing the appropriate funcinside of the chamber. Evaporation rate was determined by tion key on the keyboard. This immediately activates the fan in measuring the loss of water every 5 s. Vapour fluxes ranged the porometer chamber. After a 2-s delay, to ensure that comfrom 0 to 1.4 mg s"' which were similar in magnitude to vapour plete mixing of the air has taken place, the selected quantity is lH  -  152 -  LIVINGSTON ET AL.  TIME It) FIG. 5. A typical time course of average seedling stomatal conductance during the period of measurement. 0-2  0-4  0-6  0-8  tO  A c t u a l flux (mg f )  FIG 4. Apparent water vapour flux (App) measured by the seedling porometer versus actual flux (Act) measured by weight loss of an artificial seedling. See text for the results of comparison using saturated filter paper discs. fluxes measured in the field, the maximum of which seldom exceeded 0.7 mg s"'. Following the method of Kaufmann (1981), the gravimetrically determined vapour flux was regressed against that calculated from measured changes of relative humidity in the chamber (Fig. 4). The slope of the regression line is 0.8, which indicates that 25% of the water vapour added to the chamber is adsorbed by internal surfaces. The calibration factor, 1.25, is entered into the microprocessor memory and can be changed at any time using the keyboard. This implies that the effective volume of the porometer chamber is 25% greater than the actual chamber volume (Turner and Parlange 1970). The test was repeated using 1 cm 3 saturated filter paper discs and a 0.01 mg resolution balance. The slope and the intercept of the regression line were 0.83 and 0.00, respectively (r 2 = 0.96), for fluxes ranging from 0 to 0.15 mg s " ' , while the smallest detectable flux was 0.01 mg s"'. Because the vapour fluxes were measured over a wide range of relative humidities and over time periods ranging from 5 to 30 s, it appears that the adsorption of water vapour is proportional to the rate of change of absolute humidity in the chamber. This is in contrast with Kaufmann (1981) who found that in a teflon-lined chamber there was an inexplicably sharp onset of adsorption at high fluxes of water vapour. Leaf area  determinations  The total needle area of a seedling must be known to obtain an absolute measurement of stomatal conductance (see [2]). Accordingly, a method was devised that enables a quick and nondestructive estimate of projected needle area. Eighty one seedlings were sampled, consisting of equal numbers of Douglas-fir. western hemlock (Tsuga heterophylla (Raf.) Sarg.). and Pacific silver fir (Abies amabilis (Doug.) Forbes) seedlings. The height (/V), crown length, root collar diameter (X>), and number of branches (£) were measured on each and their projected area measured with an area meter (model Li-3000, Licor Inc.. Lincoln, N E , U . S . A . ) . The resulting  TABLE 1. The mean ratio of stomatal conductance measurements made on 22 Douglas-fir seedlings after 20 s to those made 10. 30. 40. 60. and 120 s after the porometer was placed around each seedling Time interval (s)  Ratio Standard deviation  10  20  30  40  60  120  1.1  10  1.0  1.1  14  16  0.2  0  0.1  0.2  0.3  0.4  equations which best estimated projected needle area in square centimetres are as follows: Douglas-fir, A = 18.3 D B + 30.58 <r' = 0.92); western hemlock, A = 10.4 DB + 2.50 (r = 0.82); Pacific silver fir, A = 18.0 D H + 6.70 (r 3 = 0.86) where D and W are in centimetres. These equations were only used when individual seedlings could not be destructively sampled to determine their projected needle area. 2  Time course of measurements  on conifer  seedlings  Experiments were carried out to determine (i) the time required to obtain steady stomatal conductance readings and (ii) the effect of depriving the seeding of light during the measurement period. Measurements were made outdoors over a 2-min period on 22 1 -and 2-year-old Douglas-fir seedlings on the University of British Columbia campus and on planted seedlings at a high elevation research site in the Cameron Valley, Vancouver Island. Figure 5 shows a typical time course of stomatal conductance obtained using the porometer on an individual seedling. The results snow that a steady reading of stomatal conductance can be obtained within 20 s of the chamber being placed around the seedling and that slow response to light deprivation is apparent after about 40 s. This is further illustrated in Table I which shows the ratio of stomatal conductance measurements made after 20 s to those made after •elected time intervals for the 22 seedlings. The time taken to reach a steady reading of stomatal conductance was independent of the water vapour flux or the stomatal conductance being measured. The maximum increase in the relative humidity in the chamber over the first 20 s was 5 % .  Field measurements  The porometer was used on a regular basis from June to September 1982. Measurements of stomatal conductance and  -  CAN. I. FOR.  153 -  VOL. 14.  IW4  3-0  2  2-0  o to >  Q|  SEEDLING  .  1  1  I  I  I  L I  POROMETER 0 . ( c m f )  FIG 6 Comparison of the average needle conductance of Douglasfir seedlings measured using a ventilated diffusion porometer that uses four-needle samples with the average needle conductance measured using the seedling porometer. Linear regression analysis indicates needle porometer g. « 0.81 seedling porometer g, + 0.005 (r s = 0.97). transpiration rate were made on Douglas-fir, western hemlock, and Pacific silver fir seedlings that were growing on a high elevation, south-facing clearcut slope in the Cameron Valley. It took about 1 min to make a complete measurement. This included the time required to position the baseplate (approximately 20 s), make the measurement (20 s), and remove the entire porometer. The porometer proved to be convenient to use in a forest clearcut environment. After the 4 months of field 1 use, the calibration of the sensors had not changed significantly. The calibrations of the humidity and temperature sensors were checked against an Assmann psychrometer at the beginning of each day. Care was taken to ensure the porometer chamber was kept in the shade when it was not in use. Radiative heating of the stainless steel walls of the porometer chamber sometimes resulted in the air temperature in the sunlit chamber being raised as much as 3°C above that of the external air. This effect can be reduced by painting the outside surfaces white or covering them with aluminized mylar. Measurements of stomatal conductance made on Douglas-fir seedlings were compared with those made with a ventilated diffusion porometer described by Tan and Black (1978). The Utter measurement used samples of four needles which were removed from the same seedlings. Figure 6 shows the results of this comparison for August 24, 1982. Seven seedlings were used in the study and measurements were made at hourly intervals throughout the day. At the end of the experiment the needle area of each seedling was determined using a leaf area meter. In general, conductance measurements made on individual needles were 19% lower than those made on whole seedlings. This difference might have resulted because of the approximately 3 min it took to remove the needles from the seedlings, transport them in a sealed plastic bag to the needle  TIME  (h)  FIG 7. Comparison of the daytime course of average stomatal conductance of irrigated Douglas-fir. western hemlock, and Pacific silver fir seedlings growing in a nigh elevation forest clearcut in the Cameron Valley. Also shown is the course of the water vapour pressure deficit (VPD). DF, Douglas-fir. WH. western hemlock; PSF. Pacific silver fir. porometer, and make the measurement. During this time some stomatal closure might have occurred. Evaporation from the bark of the snoots and stem had virtually no effect on the whole seedling conductance measurements. Tests in a greenhouse showed that this evaporative flux accounted for less than 0.5% of the total water loss from a Douglas-fir seedling with an average stomatal conductance of 0.28 cm s ' 1 . Figure 7 shows the diurnal courses of stomatal conductance of irrigated Douglas-fir, western hemlock, and Pacific silver fir seedlings growing in the high elevation clearcut, measured using the seedling porometer throughout August 7, 1982, which was a clear day. Leaf area was calculated using the regression equations given previously. A l l species showed a marked reduction in stomatal conductance during the afternoon when vapour pressure deficit was high. Summary A transient-type porometer was developed that nondestructively measures the stomatal conductance of conifer seedlings. The instrument was used successfully in a high elevation forest clearcut over a summer to determine the stomatal characteristics of Douglas-fir, western hemlock, and Pacific silver fir seedlings. There was good agreement between measurements made with the porometer on Intact seedlings and those made on •elected needles by a ventilated diffusion porometer.  Acknowledgnnents We thank Mr. J. Baranowski for valuable assistance in the design and machining of the porometer chamber, and Mr. F. KelUher for making the ventilated porometer measurements of  -  154 -  L I V I N G S T O N ET A X  needle conductance in the field. This research was supported by a British Columbia Ministry of Forests contract, and grants from the British Columbia Science Council and the Natural Sciences and Engineering Research Council of Canada. BEARDSELL. M. F . P. C. JARVIS. and B. DAVIDSON. 1972. A null  balance diffusion porometer suitable for use with leaves of many shapes. J. Appl. Ecol. 9: 677 -690.  BINGHAM. C. E.. and P. I. COYNE. 1977. A portable, temperature-  controlled steady-state porometer for field measurements of transpiration and photosynthesis. Photosynthetic^. II: 148-160. CAMPBELL. C. C. 1977. An introduction loenvironmental biophysics. Springer-Verlag. New York. DIXON. W.. and J. GRACE. 1982. Water uptake by some chamber materials. Plant Cell Environ. 5: 323-327. GANDAR. P. W . and C. B. TANNER. 1976 Water vapour sorption by the walls and sensors of stomatal diffusion porometers. Agron. J. 68: 245 - 249. JACOB. M. 1957. Heat transfer. Vol II. John Wiley. Nev. York.  KANEMASI'. E. T . . G. W. THI'RTELL. and C. B. TANNER  1969  Design, calibration and field use of a stomatal diffusion porometer Plant Physiol. 44: 881-885. KAUFMANN. M. R 1981. Automatic determination of conductance. transpiration and environmental conditions in forest trees. For Sci 27: 817-827. KOHS1EK. W 1981. A rapid-circulation evaporation chamber for measuring bulk stomatal resistance. J. Appl. Meteorol. 20: 42-5?. LANDSBERG. J. J., and A. S. T/HOM 1971. Aerodynamic properties of  a plant of complex structure. Q. J. R. Meteorol Soc. 97:565 - 570 LIST. R. J. 1951. Smithsonian meteorological tables Vol. 114 Smithsonian Institution Press. Washington. DC. TAN. C. S.. and T. A. BLACK. 1978 Evaluation of a ventilated diffusion porometer for the measurement of stomatal diffusion resistance of Douglas-fir needles Arch Meteorol Geophv* Bioklimatol Ser B. 26: 257-273 TURNER. N. C . and J Y. PARLANCE. 1970. Analysis of operation  and calibration of ventilated diffusion porometer. Plant Phvsiol 46: 175-177.  - 155 -  APPENDIX  III  SOIL WATER RETENTION CURVES  -  156  -  APPENDIX  III  S O I L WATER RETENTION CURVES  The p u r p o s e o f t h i s water  retention curves  volumetric 5-10  (soil  water content  (9)  i s to  site.  (m  3  H 0 M  - 3  2  content  plates.  laboratory-determined  ))  (i|>s)  (MPa)  at three depths  sandy loam a t t h e  The r e t e n t i o n c u r v e s  using Soil  mount  Moisture  h a v e been c o r r e c t e d  Vs  ( 0 - 5 cm,  The m e a s u r e m e n t s were made on  ( 5 . 3 6 cm d i a m e t e r x 3 . 9 3 cm l o n g )  pressure  give the  water matrix p o t e n t i a l  c m , and 1 5 - 2 5 cm) f o r t h e g r a v e l l y  Arrowsmith experimental cores  appendix  undisturbed Inc.  for  (64% a t 0 - 5 cm, 68% a t 5 - 1 0 cm and 67% a t 1 5 - 2 5 c m ) .  stone  -  Figure  AIII.l  157 -  S o i l w a t e r r e t e n t i o n c u r v e s f o r 0 - 5 cm ( • ) , 5 - 1 0 (o) and 1 5 - 2 5 cm ('•) d e p t h s  

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