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Regeneration patterns on some old-growth and clearcut sites in the Mountain Hemlock zone of southern… Brett, Robert B. 1997

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R E G E N E R A T I O N P A T T E R N S ON S O M E OLD-GROWTH AND C L E A R C U T SITES IN T H E M O U N T A I N H E M L O C K Z O N E O F S O U T H E R N B R I T I S H C O L U M B I A  by  R O B E R T B. B R E T T B . A . University of W e s t e r n Ontario 1981  A T H E S I S S U B M I T T E D IN P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T S F O R T H E DEGREE OF MASTER OF SCIENCE  in  FACULTY OF GRADUATE  STUDIES  D e p a r t m e n t of Forestry (Forest S c i e n c e s )  W e a c c e p t this t h e s i s a s c o n f o r m i n g to the required s t a n d a r d  T H E UNIVERSITY O F BRITISH C O L U M B I A May  1997  © R o b e r t B r u c e Brett  In  presenting this  degree at the  thesis  in  University of  partial  fulfilment  of  of  department  this thesis for or  by  his  or  scholarly purposes may be her  representatives.  permission.  Department The University of British Columbia Vancouver, Canada  (2/88)  for  an advanced  Library shall make it  agree that permission for extensive  It  publication of this thesis for financial gain shall not  DE-6  requirements  British Columbia, I agree that the  freely available for reference and study. I further copying  the  is  granted  by the  understood  that  head of copying  my or  be allowed without my written  Abstract  P a t t e r n s of tree regeneration c h a n g e with elevation in old-growth forest s t a n d s o n British C o l u m b i a ' s s o u t h e r n c o a s t . At lower e l e v a t i o n s , w h e r e s n o w is infrequent, r e g e n e r a t i o n t e n d s to b e c e n t r e d in c a n o p y g a p s c a u s e d by the death of o n e or m o r e trees (the g a p m o d e l ) . A t higher e l e v a t i o n s , w h e r e s n o w usually r e m a i n s until early s u m m e r , regeneration is restricted to e l e v a t e d m i c r o s i t e s that e m e r g e earliest from the s n o w (the t r e e - i s l a n d m o d e l ) . Little is yet k n o w n about regeneration patterns in old-growth forest s t a n d s b e t w e e n t h e s e two s y s t e m s , t h o s e within the f o r e s t e d M o u n t a i n H e m l o c k ( M H ) b i o g e o c l i m a t i c s u b z o n e . O u r lack of k n o w l e d g e h a s b e c o m e m o r e of a c o n c e r n a s logging p r o g r e s s e s into higher e l e v a t i o n s of the s u b z o n e w h e r e there are e v e r - d e e p e r s n o w p a c k s . T o investigate t h e s e patterns, I e s t a b l i s h e d 12 s t u d y s i t e s in the T e t r a h e d r o n R a n g e near S e c h e l t , 5 0 k m northwest of V a n c o u v e r . S i x s i t e s w e r e in old-growth forest s t a n d s , a n d six w e r e in naturally-regenerated c l e a r c u t s that h a d b e e n l o g g e d 1.1-12 y e a r s prior to s a m p l i n g . S i x sites w e r e s t e e p ( - 5 0 % s l o p e ) a n d six w e r e flat (~ 2 5 % s l o p e ) . E l e v a t i o n s w e r e slightly higher for old-growth s i t e s ( 1 0 8 0 - 1 1 9 5 m) than c l e a r c u t s i t e s ( 1 0 6 0 - 1 1 0 0 m).  Old-Growth Sites: T r e e s w e r e very s l o w - g r o w i n g a n d took a n a v e r a g e of a l m o s t 5 0 0 y e a r s to enter the c a n o p y layer. R e g e n e r a t i o n w a s most s u c c e s s f u l o n m o u n d s a n d n e a r to a c a n o p y tree. It w a s unaffected by o v e r h e a d c a n o p y c o v e r (that is, the p r e s e n c e or a b s e n c e of a c a n o p y g a p ) , apparently b e c a u s e of the p r e v a l e n c e of l o w - a n g l e , diffuse light. In contrast to m o s t f o r e s t e d e c o s y s t e m s , a l m o s t all trees w e r e growing on the undisturbed forest floor rather than o n d e c a y i n g w o o d or mineral soil. O v e r a l l , regeneration patterns w e r e m o r e c o n s i s t e n t with the t r e e - i s l a n d m o d e l than the g a p m o d e l of regeneration s i n c e trees w e r e m o s t likely to s u r v i v e o n m o u n d s a n d c l o s e to a c a n o p y tree. Still, the p r e s e n c e of s o m e r e g e n e r a t i o n in g a p s , e s p e c i a l l y o n s t e e p s i t e s , s h o w e d that the study sites o c c u p i e d a transition b e t w e e n the g a p a n d t r e e - i s l a n d m o d e l s . T h e tree-island m o d e l w a s best e x p r e s s e d o n l a t e - s n o w m e l t s i t e s that w e r e m o s t similar to high-elevation s i t e s . It w a s a l s o m o r e a p p a r e n t in the r e g e n e r a t i o n  patterns of Chamaecyparis  nootkatensis  ( A l a s k a y e l l o w - c e d a r ) , a s p e c i e s n e a r the u p p e r limit  of its e l e v a t i o n a l r a n g e , than t h o s e of Tsuga mertensiana  (mountain h e m l o c k ) , a s p e c i e s in the  m i d d l e of its r a n g e . Clearcut  Sites: A l m o s t all trees >150 c m tall w e r e A. amabilis  ( P a c i f i c silver fir) w h i c h  h a d b e e n p r e s e n t in the p r e v i o u s old-growth s t a n d before cutting. A surprisingly high proportion of t r e e s (45%) e s t a b l i s h e d within a 3 - y e a r w i n d o w from 1 y e a r before logging through 1 y e a r after l o g g i n g , m o r e than half of w h i c h w e r e C. nootkatensis.  O n l y 2 0 % of r e g e n e r a t i o n  e s t a b l i s h e d m o r e than o n e y e a r after logging, a n d n o n e e s t a b l i s h e d >8 y e a r s after l o g g i n g . T h i s limited i n g r e s s likely resulted from the a b s e n c e d u e to clearcutting of n e a r b y s e e d - p r o d u c i n g t r e e s . T h e r e w a s m u c h m o r e friable forest floor a n d c o a r s e w o o d y d e b r i s (from logging s l a s h ) than in a d j a c e n t o l d - s t a n d s , but a l m o s t all regeneration w a s still f o u n d o n u n d i s t u r b e d forest floor. R e g e n e r a t i o n w a s l e s s c o m m o n o n m o u n d s in c l e a r c u t s than on m o u n d s in a d j a c e n t o l d growth s t a n d s , a p p a r e n t l y b e c a u s e m o u n d s w e r e disturbed during logging m o r e than other m i c r o s i t e s . T h e r e w a s no e v i d e n c e that Vaccinium  s p p . (blueberries a n d h u c k l e b e r r i e s )  i m p e d e d r e g e n e r a t i o n s i n c e 8 4 % of trees a n d s e e d l i n g s w e r e growing b e l o w or a m i d s t Vaccinium  a n d e s t a b l i s h m e n t a n d survival w a s higher w h e r e it w a s p r e s e n t .  T h e s t a n d s that d e v e l o p o n t h e s e c l e a r c u t s will remain for m a n y c e n t u r i e s d r a m a t i c a l l y different f r o m the old-growth forest s t a n d s they r e p l a c e d . W h e r e cutting is a p p r o p r i a t e , s u c h n e g a t i v e f e a t u r e s c o u l d b e a v o i d e d by leaving a n a d e q u a t e s e e d s o u r c e , retaining live a n d d e a d c a n o p y t r e e s , a n d protecting s u b - c a n o p y trees during cutting. S i t e s w o u l d then a l s o retain m a n y of the old-growth c h a r a c t e r i s t i c s required by wildlife a n d other, non-timber v a l u e s . R e s u l t s from old-growth sites highlight the site-specific nature of r e g e n e r a t i o n patterns a n d the a b r u p t n e s s of the transition to tree-island patterns. Y e t low-elevation cutting m e t h o d s , e s p e c i a l l y clearcutting, are still u s e d within this transition e v e n w h e r e r e g e n e r a t i o n r e q u i r e s the protection of a n o v e r h e a d c a n o p y . A n y p r e s e n c e of regeneration patterns m a t c h i n g the treei s l a n d m o d e l s h o u l d w a r n forest m a n a g e r s of potential regeneration p r o b l e m s . In s u c h a r e a s , the d e c i s i o n to cut s h o u l d not be automatic, e s p e c i a l l y given the s l o w growth a n d high n o n -  timber v a l u e s of t h e s e forests. W h e r e cutting d o e s o c c u r , it s h o u l d l e a v e a s m u c h of the s u b c a n o p y a n d c a n o p y layers a s p o s s i b l e . A s s n o w i n c r e a s e s further a n d there is a g r e a t e r p r e s e n c e of r e g e n e r a t i o n patterns matching the tree-island m o d e l , a n y cutting is inappropriate. T h e relationship b e t w e e n regeneration patterns a n d s n o w d e p t h s c o u l d p r o v i d e a n e c o l o g i c a l b a s i s for m a n a g i n g forests within the M H z o n e . S p e c i f i c a l l y , the p r e s e n c e of r e g e n e r a t i o n patterns that m a t c h the tree-island m o d e l (even if d i s c r e t e tree i s l a n d s a r e not present) is a reflection of s e v e r e growing conditions a n d potential r e g e n e r a t i o n p r o b l e m s . S i m p l e m e a s u r e s of the relative a b u n d a n c e of tree-island patterns c o u l d b e a d d e d during s t a n d a r d site d i a g n o s i s to d e t e r m i n e the severity of growing c o n d i t i o n s , e . g . , the proportion of u n d e r s t o r y a n d s u b - c a n o p y trees that are growing near a c a n o p y tree or o n m o u n d s . S u c h a c l a s s i f i c a t i o n w o u l d b e a p p l i c a b l e r e g a r d l e s s of m a n a g e m e n t objective.  V  Table of Contents Abstract  ii  T a b l e of C o n t e n t s  v  List of T a b l e s  vii  List of F i g u r e s  viii  Acknowledgements  ix  C h a p t e r 1. Introduction  1  1.1 T h e M o u n t a i n H e m l o c k (MH) Z o n e 1.2 R e g e n e r a t i o n P a t t e r n s in the M H Z o n e 1.3 O b j e c t i v e s a n d T h e s i s Outline C h a p t e r 2 . R e g e n e r a t i o n P a t t e r n s on O l d - G r o w t h S i t e s 2.1 Introduction 2.2 M e t h o d s Study A r e a Study Design Data Collected Data Analysis 2.3 Results Structure, C o m p o s i t i o n , a n d A g e T h e Microsite E n v i r o n m e n t Substrates Microtopography C a n o p y C o v e r a n d D i s t a n c e to the N e a r e s t C a n o p y T r e e S n o w - Microsite R e l a t i o n s h i p s Tree-Microsite Relationships Substrates Microtopography and Mound Partners C a n o p y C o v e r a n d D i s t a n c e to the N e a r e s t C a n o p y T r e e Interactions B e t w e e n Microsite F a c t o r s Growth Rates and Microsites Growth Form Anomalies 2.4 D i s c u s s i o n A r e m i c r o s i t e s , s n o w , a n d regeneration patterns related? D o regeneration patterns reflect the g a p or tree-island m o d e l ? 2.5 C o n c l u s i o n s C h a p t e r 3. Natural R e g e n e r a t i o n on C l e a r c u t S i t e s 3.1 Introduction 3.2 M e t h o d s Study A r e a Study Design Data Collected Data Analysis  1 3 5 6 6 7 7 9 12 18 20 20 24 24 25 25 27 33 33 34 36 42 45 45 46 46 49 51 53 53 53 53 54 55 56  vi  3.3 R e s u l t s Structure, C o m p o s i t i o n , a n d A g e Substrates Microtopography and Logging Slash Vaccinium Stocking Growth Form Anomalies 3.4 D i s c u s s i o n W a s natural regeneration s u c c e s s f u l ? Did m o s t natural regeneration e s t a b l i s h before or after l o g g i n g ? W h i c h s u b s t r a t e s f a v o u r e d natural r e g e n e r a t i o n ? W h i c h m i c r o t o p o g r a p h i c locations f a v o u r e d natural r e g e n e r a t i o n ? D i d competition with Vaccinium i m p e d e natural r e g e n e r a t i o n ? 3.5 C o n c l u s i o n s  59 59 65 67 68 70 72 74 74 75 77 78 79 80  C h a p t e r 4. S u m m a r y a n d C o n c l u s i o n s  84  Literature C i t e d  86  A p p e n d i x A . N o n - t r e e s p e c i e s by life form, o c c u r r e n c e , a n d percent c o v e r  94  A p p e n d i x B. C l a s s i f i c a t i o n of growth form a n o m a l i e s  95  A p p e n d i x C . R e g e n e r a t i o n status of clearcut study locations in 1 9 9 2  96  vii  List of Tables 2.1  O l d - g r o w t h study site d e s c r i p t i o n s  10  2.2  Definition of t e r m s u s e d in C h a p t e r 2  13  2.3  D e c a y classification for d e a d trees  14  2.4  S p e c i e s c o m p o s i t i o n by height c l a s s a n d site  21  2.5  P e r c e n t c o v e r of s u b s t r a t e s by site  25  2.6  C a n o p y c o v e r by site a n d by high a n d low s h a d e  26  2.7  S n o w d e p t h s by site a n d s l o p e type  28  2.8  R o o t i n g substrate of understory trees, s a p l i n g s , a n d s e e d l i n g s  34  2.9  L i v e m o u n d partners of live a n d d e a d c a n o p y trees  37  3.1  C l e a r c u t study site d e s c r i p t i o n s  54  3.2  Definition of t e r m s u s e d in C h a p t e r 3  58  3.3  P e r c e n t c o v e r of s u b s t r a t e s by site  65  3.4  G r o w t h form a n o m a l i e s by s p e c i e s  73  viii  List of Figures 1.1  Distribution of the M o u n t a i n H e m l o c k biogeoclimatic z o n e  2  1.2  E l e v a t i o n a l s e q u e n c e of biogeoclimatic z o n e s o n B . C . ' s s o u t h e r n c o a s t  2  2.1  L o c a t i o n of T e t r a h e d r o n P r o v i n c i a l P a r k a n d study a r e a  8  2.2  Site description a n d s a m p l i n g d e s i g n  11  2.3  C a n o p y c o v e r classification  13  2.4  Definition of high s h a d e a n d low s h a d e for understory t r e e s a n d q u a d r a t s  15  2.5  D e v e l o p m e n t a l s t a g e s of s e e d l i n g s  16  2.6  Height a n d d i a m e t e r distributions of trees by s p e c i e s  22  2.7  G r o w t h rate to a d i a m e t e r of 4 0 c m (at s t u m p or c o r e height)  23  2.8  Q u a d r a t s by c a n o p y c o v e r c l a s s a n d d i s t a n c e to nearest c a n o p y tree  27  2.9  S n o w d e p t h s c o m p a r e d to m i c r o t o p o g r a p h y  30  2 . 1 0 S n o w d e p t h s c o m p a r e d to c a n o p y c o v e r  31  2.11 S n o w d e p t h s c o m p a r e d to d i s t a n c e to the n e a r e s t c a n o p y tree  32  2 . 1 2 O b s e r v e d - t o - e x p e c t e d f r e q u e n c y of trees by m i c r o t o p o g r a p h y  35  2 . 1 3 F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of n o n - c a n o p y t r e e s by s l o p e  38  2 . 1 4 F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of s u b - c a n o p y t r e e s by c a n o p y c o v e r , d i s t a n c e to the nearest c a n o p y tree, a n d s l o p e  39  2 . 1 5 F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y by high a n d low s h a d e  41  2 . 1 6 S u m m a r y of d e a d trees by condition, s p e c i e s , a n d c a n o p y layer  43  2 . 1 7 F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of s u b - c a n o p y trees by m i c r o t o p o g r a p h y , c a n o p y c l a s s , a n d d i s t a n c e to the n e a r e s t c a n o p y tree  44  3.1  Jitter plot of heights of trees a n d s e e d l i n g s o n their y e a r of e s t a b l i s h m e n t  57  3.2  Height distributions of trees a n d s e e d l i n g s by s p e c i e s  59  3.3  Height distribution of trees a n d s e e d l i n g s by s p e c i e s a n d site  60  3.4  Height growth of A. amabilis  62  3.5  E s t i m a t e d a g e c l a s s distribution by s p e c i e s a n d height c l a s s  63  3.6  E s t i m a t e d a g e c l a s s distribution by height c l a s s a n d site  64  3.7  O b s e r v e d - t o - e x p e c t e d ratio o n a v a i l a b l e s u b s t r a t e s by s p e c i e s  66  3.8  T r e e s a n d s e e d l i n g s o n undisturbed forest floor by s p e c i e s a n d height  66  3.9  O b s e r v e d - t o - e x p e c t e d ratio of trees by m i c r o t o p o g r a p h y  67  on clearcut a n d old-growth sites  3.10 Height of t r e e s relative to Vaccinium  68  3.11  69  P r o j e c t e d f r e q u e n c y a n d s p e c i e s c o m p o s i t i o n of free-growing t r e e s  3.12 S t o c k i n g during the y e a r of s a m p l i n g a n d projected s t o c k i n g after 10 y e a r s  71  Acknowledgements M y greatest debt is to Dr. K a r e l K l i n k a w h o s e g e n u i n e interest a n d e n c o u r a g e m e n t first attracted m e to U B C F o r e s t S c i e n c e s a n d s u p p o r t e d m e throughout m y s t u d i e s . A n y o n e w h o h a s h a d the privilege of learning with Dr. K l i n k a k n o w s that a d a y in the field with him is better (and m o r e fun) than a y e a r in a n y c l a s s r o o m . I a l s o benefitted from the a s s i s t a n c e of m y e x c e l l e n t c o m m i t t e e . E v e r s i n c e Dr. K e n L e r t z m a n first invited m e to help him count s e e d l i n g s at C y p r e s s , he h a s b e e n a constant help o r g a n i z i n g m y thinking a n d writing. Dr. P e t e r M a r s h a l l is the b e s t statistician a n ecologist c o u l d a s k for, though he m a y not a p p r e c i a t e the a d v e r t i s e m e n t . B o b G r e e n a p p l i e d his characteristic t h o r o u g h n e s s to a subject he k n o w s thoroughly, the M H z o n e , a n d I v a l u e his c o m m e n t s a n d s u g g e s t i o n s highly. I a m grateful for financial support from the B . C . Ministry of F o r e s t s , a University G r a d u a t e F e l l o w s h i p from U B C , a n d s c h o l a r s h i p s from the family of D o n a l d S . M c P h e e . It w a s a n h o n o u r to work with Dr. J a r y D o b r y , m a s t e r d e n d r o c h r o n o l o g i s t . T h a n k s a l s o to three of m y excellent p r o f e s s o r s : Dr. L e e G a s s a n d Dr. Bill R e e s , both of w h o m contributed to a 1 8 0 - d e g r e e shift in my thinking, a n d Dr. L e s L a v k u l i c h , w h o taught m e the difference b e t w e e n soil a n d dirt. D o n M a c L a u r i n , R P F , h e l p e d fuel m y interest in forest m a n a g e m e n t a n d e n c o u r a g e d m y return to s c h o o l . I ran through a lot of field a s s i s t a n t s a n d e n j o y e d w o r k i n g with e a c h of t h e m : Lori D a n i e l s , M u r r a y D e e , Martin G o o s e n s , Terry H i g g i n s , D a w n M a n n i n g , J a n e M i l l e n , A n n e m e i k e S m i t s , P a l V a r g a , a n d C h r i s t o p h W i l d Burger. P a l V a r g a w a s e s p e c i a l l y helpful early o n , w h e n I only k n e w s a m p l i n g a s s o m e t h i n g d o n e at the buffet table. T h a n k s to C h r i s t i n e C h o u r m o u z i s a n d C h a s W e l l s for their wizardry in c o m p u t e r g r a p h i c s . A m o n g the p e o p l e w h o g e n e r o u s l y h e l p e d m e get m y b e a r i n g s in the T e t r a h e d r o n w e r e S i g L e h m a n of the S u n s h i n e C o a s t R e g i o n a l District, B r i a n S m a r t a n d the staff of the S e c h e l t F i e l d Office, a n d M i k e S c o t t of Interior. D a n B o u m a n , silviculturalist a n d friend of the T e t r a h e d r o n , a l l o w e d m e to u s e his beautiful h o m e . T h a n k s to the T e t r a h e d r o n S k i C l u b w h o s e b a c k c o u n t r y c a b i n s I visited with great p l e a s u r e . C o n g r a t s to all o n a great a c c o m p l i s h m e n t : T e t r a h e d r o n P r o v i n c i a l P a r k ! M y mother, Phyllis Brett, e n d u r e d m y trials of s t u d e n t h o o d for a longer time than m o s t yet s h e m a i n t a i n e d her s e n s e of h u m o u r through it all - t h a n k s M o m . A s for the rest of m y family, o k a y , I lost the bet. T h a n k s to t h o s e w h o kept m e s a n e , e s p e c i a l l y D a v e , K o e r n e r ' s , Lori, the K l i n k o i d s , A l e x , P a u l , M u r r a y , R i c k , a n d the P e a k C h a i r . A n d , m o s t important, t h a n k s to J a n e for her love, support, a n d e v e r - w i l l i n g n e s s to take off to the M H z o n e . B o b Brett M a y 5, 1 9 9 7  Chapter 1. Introduction  1.1  The Mountain Hemlock (MH) Zone T h e M o u n t a i n H e m l o c k ( M H ) z o n e , o n e of B . C . ' s 14 b i o g e o c l i m a t i c z o n e s , is l o c a t e d at  s u b a l p i n e e l e v a t i o n s from - 9 0 0 - 1 6 0 0 m in s o u t h e r n B . C . a n d 3 0 0 - 1 0 0 0 m in northern B . C . (Krajina 1 9 6 9 ; P o j a r e r a / . 1 9 9 1 ; Figure 1.1). It is divided into two s u b z o n e s : f o r e s t e d at lower e l e v a t i o n s , a n d p a r k l a n d at higher elevations ( B r o o k e e r a / . 1970). T h e c l o s e d - c a n o p y forests of the f o r e s t e d M H s u b z o n e , the f o c u s of this study, o c c u p y a n elevational b a n d b e t w e e n m o n t a n e f o r e s t s of the C o a s t a l W e s t e r n H e m l o c k ( C W H ) z o n e a n d tree i s l a n d s of the p a r k l a n d M H s u b z o n e (Orloci 1 9 6 5 ; B r o o k e e r a / . 1 9 7 0 ; Figure 1.2). F r e q u e n t s t o r m s a n d h e a v y precipitation ( - 1 7 0 0 - 5 0 0 0 m m annually) result f r o m the o r o g r a p h i c uplift of moist P a c i f i c air m a s s e s f o r c e d to rise by the c o a s t a l m o u n t a i n barrier ( B r o o k e e r a / . 1 9 7 0 ; Pojar e r a / . 1991). F r o m 2 0 - 7 0 % of precipitation falls a s s n o w w h i c h results in d e e p , h e a v y s n o w p a c k s (2-3+ m) a n d a s n o w - f r e e period of 3 - 5 m o n t h s ( B r o o k e et al. 1 9 7 0 ) . T h e transition from the C W H to M H z o n e , defined by the elevation at w h i c h 7". mertensiana  (Bong.) C a r r . (mountain h e m l o c k ) first o u t n u m b e r s Tsuga heterophylla  (Raf.)  S a r g . (western h e m l o c k ) , is often abrupt a n d c o i n c i d e s with greatly i n c r e a s e d s n o w ( P e t e r s o n 1 9 6 4 , 1 9 6 9 ; O r l o c i 1965). In addition to 7". mertensiana, amabilis  the other characteristic s p e c i e s of the M H z o n e a r e Abies  D o u g l . ex F o r b e s (Pacific silver fir) a n d Chamaecyparis  nootkatensis  (D. D o n ) S p a c h  ( A l a s k a y e l l o w - c e d a r ; B r o o k e e r a / . 1 9 7 0 ; Pojar e r a / . 1991). E a c h of t h e s e s p e c i e s is v e r y s h a d e - t o l e r a n t , long-lived, a n d m e e t s criteria for l a t e - s u c c e s s i o n a l or c l i m a x s p e c i e s (Minore 1 9 7 9 ; Krajina e r a / . 1 9 8 2 ; B u r n s a n d H o n k a l a 1990). T h e y a l s o grow well in full light a n d s h a r e c h a r a c t e r i s t i c s with w h a t w o u l d c o m m o n l y be c o n s i d e r e d p i o n e e r s p e c i e s (Herring a n d E t h e r i d g e 1 9 7 6 ; S e i d e l 1 9 8 5 ; A n t o s a n d Z o b e l 1 9 8 6 ; Arnott e r a / . 1 9 9 5 ) . T h e M H z o n e is u n u s u a l in that there is usually no c h a n g e in s p e c i e s c o m p o s i t i o n after d i s t u r b a n c e a s only t h e s e three s p e c i e s a r e c o m m o n in all s t a g e s of s t a n d d e v e l o p m e n t .  Figure 1.1 Distribution of the Mountain Hemlock biogeoclimatic zone.  Figure 1.2. Elevational sequence of biogeoclimatic zones on British Columbia's southern coast.  Approximate elevation above sea level  3  A l s o u n u s u a l , d u e to the c o o l , wet climate a n d d e e p s n o w p a c k s , is the i n f r e q u e n c y of major d i s t u r b a n c e s . S i n c e catastrophic d i s t u r b a n c e by fire, i n s e c t s , or d i s e a s e is rare (Brink  1959; B r o o k e e r a / . 1970; L e r t z m a n 1989), s t a n d i n g mortality a n d s m a l l - s c a l e w i n d t h r o w s are the d o m i n a n t f o r c e s of c a n o p y turnover ( L e r t z m a n  1992). T h o u g h fires d o o c c u r , a s s h o w n by  c h a r c o a l e v i d e n c e , their role in long-term s t a n d d y n a m i c s is minor (Brink 1959; 1970;  Krumlik 1979;  Brooke era/.  K. L e r t z m a n a n d L. B r u b a k e r , u n p u b l . data). E a c h of the three m a i n  s p e c i e s c o m m o n l y live to v e r y old a g e s with r e c o r d e d m a x i m u m s of 750 y e a r s for A.  1824 y e a r s for C. nootkatensis,  and  >1000 y e a r s for T. mertensiana  amabilis,  (Pojar a n d M a c K i n n o n  1994). T h e r e h a v e b e e n no additions or l o s s e s of tree s p e c i e s in the past 5,000 y e a r s ( H a n s e n 1947  in Brink 1959;  K. L e r t z m a n a n d L. B r u b a k e r , unpubl. data).  A b a s e l i n e study of u n l o g g e d e c o s y s t e m s in the M H z o n e w a s p u b l i s h e d by B r o o k e er al.  (1970) a s a compilation of two P h . D . t h e s e s ( P e t e r s o n 1964; B r o o k e 1966). It is the only  c o m p r e h e n s i v e work d e a l i n g with environment-vegetation relationships in the M H z o n e , t h o u g h its s t u d y a r e a w a s restricted to the s o u t h e r n c o a s t of B . C . ' s m a i n l a n d . O t h e r contributors to our u n d e r s t a n d i n g of the M H z o n e include Brink Klinka e r a / .  (1992+V+), a n d L e r t z m a n a n d his fellow r e s e a r c h e r s ( L e r t z m a n 1989, 1992, 1995;  Lertzman and Krebs  1.2  (1959, 1964), Krumlik (1979), P o j a r e r a / . (1991),  1991; L e r t z m a n etal. 1996).  Regeneration Patterns in the MH Zone T h e r e g e n e r a t i o n pattern of trees in a n y forested e c o s y s t e m is the product of m a n y  p r o c e s s e s that interact at a variety of s c a l e s . R e g e n e r a t i o n patterns are affected by s u c h c o a r s e - s c a l e factors a s regional climate, elevation, a s p e c t , a n d s l o p e , but a l s o by f i n e - s c a l e or m i c r o s i t e factors w h o s e influence is restricted to a n a r e a a s s m a l l a s 1-5 m (Oliver a n d L a r s o n 2  1990; S t a t h e r s e r a / . 1990). T h e m o s a i c of microsites h e l p s d e t e r m i n e the pattern of r e g e n e r a t i o n on a site ( G r u b b 1977;  H a r p e r 1977)  a n d a m o n g the microsite f a c t o r s k n o w n to  contribute to this pattern are substrate (Christy a n d M a c k  1984; H a r m o n a n d F r a n k l i n 1989);  4  m i c r o t o p o g r a p h y (Beatty 1 9 8 4 ; P e t e r s o n a n d C a m p b e l l 1993), a n d c a n o p y c o v e r , i.e., c l o s e d c a n o p y v s . c a n o p y g a p s (Piatt a n d S t r o n g 1989). S n o w , w h e r e a b u n d a n t , is k n o w n to c o m p o u n d the impact of m i c r o s i t e s o n r e g e n e r a t i o n patterns (Brink 1 9 5 9 , F o n d a a n d B l i s s 1 9 6 9 ; B r o o k e et al. 1 9 7 0 ; F r a n k l i n  era/.  1 9 7 1 ; L o w e r y 1972) a n d there are few forested e c o s y s t e m s in the world with m o r e s n o w than the M H z o n e ( B r o o k e et al. 1 9 7 0 ; Pojar era/.  1991). F i n e - s c a l e patterns of s n o w a c c u m u l a t i o n  a n d melt are affected by both m i c r o t o p o g r a p h y ( B r o o k e era/.  1 9 7 0 ; L o w e r y 1 9 7 2 ; Beatty 1984)  a n d c a n o p y cover (Golding and S w a n s o n 1978, 1986; Harestad and Bunnell 1 9 8 1 ; Berry and R o t h w e l l 1 9 9 2 ) . S n o w a c c u m u l a t e s least a n d melts earliest o n m o u n d s b e l o w c a n o p y trees b e c a u s e of the c o m b i n e d effects of c a n o p y interception, black b o d y radiation f r o m the tree bole, a n d s t e m drip ( B r o o k e era/.  1970). T h e growing s e a s o n n e a r c a n o p y t r e e s c a n b e >1  m o n t h longer than microsites only 5 m a w a y ( B r o o k e era/.  1970).  In m a n y forests w h e r e s n o w is rare, c a n o p y g a p s offer r e g e n e r a t i o n the greatest a c c e s s to light a n d other r e s o u r c e s a n d s o recruitment to the c a n o p y is highest in t h e m . W h e r e s n o w is a b u n d a n t , h o w e v e r , regeneration patterns are inverted a n d t r e e s c l u m p together o n e l e v a t e d i s l a n d s s i n c e only t h e s e microsites offer a l o n g - e n o u g h growing s e a s o n . G a p p r o c e s s e s are k n o w n to d o m i n a t e at elevations up to the C W H / M H transition ( L e r t z m a n a n d K r e b s 1 9 9 1 ; A r s e n a u l t 1 9 9 5 ; L e r t z m a n et al. 1996) while tree-island p r o c e s s e s define the p a r k l a n d M H s u b z o n e ( B r o o k e et al. 1 9 7 0 ; Franklin a n d D y r n e s s 1988). In the f o r e s t e d M H s u b z o n e , at e l e v a t i o n s b e t w e e n t h e s e two s y s t e m s , it is still u n k n o w n w h e t h e r t r e e s are m o r e likely to r e g e n e r a t e far from other trees or c l o s e to other trees. T h e r e g e n e r a t i o n of trees in the M H z o n e h a s b e c o m e a p r e s s i n g m a n a g e m e n t i s s u e s i n c e the introduction of logging in the 1 9 6 0 ' s . M u c h of the c o n c e r n h a s f o c u s s e d o n w h e t h e r l o w - e l e v a t i o n logging p r a c t i c e s are appropriate at t h e s e higher e l e v a t i o n s , e s p e c i a l l y s i n c e early r e g e n e r a t i o n p r o b l e m s w e r e linked to s l a s h b u r n i n g a n d the planting of s p e c i e s u n s u i t e d to a s n o w y climate (Franklin 1 9 6 4 ; R e u t e r 1 9 7 3 ; Utzig a n d Herring 1 9 7 4 ; K l i n k a a n d P e n d l  5  1 9 7 6 ) . F o r e s t e r s n o w a v o i d s l a s h b u r n i n g a n d planting a n d i n s t e a d rely a l m o s t e x c l u s i v e l y o n natural r e g e n e r a t i o n . In spite of better results, c o n c e r n s remain that natural r e g e n e r a t i o n is not entirely s u c c e s s f u l s i n c e it is often c l u m p e d a n d d o m i n a t e d by o n e s p e c i e s , A.  amabilis  ( K o p p e n a a l a n d Mitchell 1 9 9 2 ; K l i n k a e r a / . 1992). T h e r e are a l s o c o n c e r n s about the role of a d v a n c e r e g e n e r a t i o n (understory trees from the p r e v i o u s forest stand), a n d h o w natural r e g e n e r a t i o n is affected by s u c h microsite factors a s substrate, m i c r o t o p o g r a p h y , a n d c o m p e t i t i o n with Vaccinium  1.3  s p p . (blueberries a n d h u c k l e b e r r i e s ; K l i n k a et al. 1992).  Objectives and Thesis Outline M y objective is to a d v a n c e our u n d e r s t a n d i n g of regeneration patterns within the M H  z o n e by c o m p a r i n g a n d contrasting t h e s e patterns in old-growth s t a n d s a n d c l e a r c u t s . M y implicit a s s u m p t i o n is that learning h o w regeneration patterns in intact forests c h a n g e with e l e v a t i o n will help g u i d e forest m a n a g e m e n t o n sites throughout the M H z o n e , w h e t h e r they are to b e cut or not. T o facilitate c o m p a r i s o n s b e t w e e n old-growth s t a n d s a n d c l e a r c u t s , m y s a m p l i n g d e s i g n is a s similar a s p o s s i b l e for the two s y s t e m s . In C h a p t e r 2, I e x a m i n e the relationship b e t w e e n microsites a n d r e g e n e r a t i o n patterns in old-growth s t a n d s by a d d r e s s i n g two q u e s t i o n s : (1) A r e m i c r o s i t e s , s n o w , a n d r e g e n e r a t i o n patterns r e l a t e d ? ; a n d (2) D o regeneration patterns reflect the g a p or t r e e - i s l a n d m o d e l ? In C h a p t e r 3 , I a d d r e s s five q u e s t i o n s b a s e d o n c o n c e r n s r a i s e d by K l i n k a e r a / . (1992): (1) W a s natural r e g e n e r a t i o n s u c c e s s f u l ? ; (2) Did most natural regeneration e s t a b l i s h b e f o r e or after l o g g i n g ? ; (3) W h i c h s u b s t r a t e s f a v o u r e d natural r e g e n e r a t i o n ? ; (4) W h i c h m i c r o t o p o g r a p h i c l o c a t i o n s f a v o u r e d natural r e g e n e r a t i o n ? ; a n d (5) Did competition with Vaccinium natural r e g e n e r a t i o n ? C h a p t e r 4 s u m m a r i z e s my findings a n d c o n c l u s i o n s .  spp. impede  6  Chapter 2. Regeneration Patterns on Old-Growth Sites  2.1  Introduction P a t t e r n s of s n o w a c c u m u l a t i o n a n d melt magnify the impact of m i c r o s i t e s o n  r e g e n e r a t i o n in s u b a l p i n e forests (Brink 1 9 5 9 ; F o n d a a n d B l i s s 1 9 6 9 ; B r o o k e e r a / . 1 9 7 0 ; Franklin etal. 1 9 7 1 ; B a r b o u r etal. 1991). F i n e - s c a l e variations in m i c r o t o p o g r a p h y , light l e v e l s , a n d s u b s t r a t e c o m b i n e with s n o w to form a c o n t i n u u m of microsite c o n d i t i o n s that affect tree e s t a b l i s h m e n t , s u r v i v a l , a n d e v e n t u a l recruitment into s u b - c a n o p y a n d c a n o p y l a y e r s . T h e f o r e s t e d M H s u b z o n e , the f o c u s of this study, lies a b o v e the C o a s t a l W e s t e r n H e m l o c k ( C W H ) z o n e a n d b e l o w the p a r k l a n d M H s u b z o n e (Pojar etal. 1991). In the C W H z o n e , w h e r e s n o w is infrequent, r e g e n e r a t i o n is primarily through g a p d y n a m i c s (the g a p model) a n d is f o c u s s e d o n c a n o p y g a p s c a u s e d by the d e a t h of o n e or m a n y trees ( L e r t z m a n 1 9 9 2 ; A r s e n a u l t 1 9 9 5 ; L e r t z m a n et al. 1996). In contrast, regeneration in the v e r y s n o w y p a r k l a n d M H s u b z o n e follows the t r e e - i s l a n d m o d e l a n d is limited mostly to r a i s e d tree i s l a n d s w h e r e s n o w m e l t is earliest (Brink 1 9 5 9 ; B r o o k e etal. 1 9 7 0 ; Franklin a n d D y r n e s s 1988). T h e g a p a n d tree-island m o d e l s predict o p p o s i n g patterns. T h e g a p m o d e l predicts that m o s t r e g e n e r a t i o n will b e c e n t r e d in c a n o p y g a p s s i n c e light a n d other s c a r c e r e s o u r c e s are m o s t a v a i l a b l e far from other trees. T h e tree-island m o d e l predicts that r e g e n e r a t i o n will b e s u c c e s s f u l only n e a r other trees s i n c e the main limiting r e s o u r c e is length of g r o w i n g s e a s o n , not light. T h o u g h r e s e a r c h h a s e s t a b l i s h e d the p r e v a l e n c e of the g a p m o d e l at lower e l e v a t i o n s a n d the t r e e - i s l a n d m o d e l at higher e l e v a t i o n s , it h a s yet to a d d r e s s r e g e n e r a t i o n patterns at intermediate e l e v a t i o n s , i.e., within the f o r e s t e d M H s u b z o n e . T o i m p r o v e our u n d e r s t a n d i n g of regeneration patterns in the f o r e s t e d M H s u b z o n e , I will e x a m i n e two g e n e r a l q u e s t i o n s : (1) A r e m i c r o s i t e s , s n o w , a n d regeneration patterns r e l a t e d ? ; a n d (2) D o regeneration patterns reflect the g a p or t r e e - i s l a n d m o d e l ? I b e g i n by d e s c r i b i n g the structure a n d c o m p o s i t i o n of the study s t a n d s a s well a s the microsite  7  e n v i r o n m e n t . I then e x a m i n e patterns of s n o w a c c u m u l a t i o n a n d melt relating to t h e s e m i c r o s i t e s . Finally, I c o m p a r e the distribution of regeneration a n d m i c r o s i t e s .  2.2  Methods  Study Area T h e s t u d y a r e a is o n the s o u t h w e s t e r n e d g e of T e t r a h e d r o n P r o v i n c i a l P a r k , uphill of S e c h e l t a n d - 5 0 k m northwest of V a n c o u v e r (49° 3 5 ' N , 123° 3 8 ' W ; F i g u r e 2 . 1 ) . T h e a r e a lies within the W i n d w a r d M o i s t Maritime ( M H m m l ) variant of the f o r e s t e d M H s u b z o n e ( G r e e n a n d K l i n k a 1 9 9 4 ) . L o c a l t o p o g r a p h y is f o r m e d by rolling hills with rocky ridges, s t e e p m i d - s l o p e s , a n d flat v a l l e y b o t t o m s often p u n c t u a t e d by l a k e s . S n o w typically c o v e r s the g r o u n d from N o v e m b e r to M a y or J u n e a n d r e a c h e s a n a v e r a g e m a x i m u m depth of - 2 - 3 m in late April ( B . C . M i n . E n v . 1 9 8 5 ; 1 9 9 3 , 1 9 9 4 , 1995). S n o w p a c k s a r e very d e n s e , a v e r a g i n g - 4 0 % s n o w w a t e r e q u i v a l e n t ( S W E ) in J a n u a r y a n d F e b r u a r y a n d > 5 0 % S W E in late s p r i n g . S n o w d e p t h s v a r y abruptly d u e to slight variations in elevation, s l o p e , a s p e c t , a n d c a n o p y c o v e r a n d the length of the g r o w i n g s e a s o n c a n differ by more than 1 month within 5 m ( B r o o k e e r a / . 1970). W i t h i n c r e a s i n g elevation a n d s n o w d e p t h s , Tsuga mertensiana heterophylla,  Tsuga  a n d this c h a n g e in s p e c i e s d o m i n a n c e m a r k s the lower b o u n d a r y of the M H z o n e  ( B r o o k e e r a / . 1970). S i n c e 7". mertensiana heterophylla  replaces  is characteristic of c o l d , s n o w y c l i m a t e s while T.  is m o r e likely to be d a m a g e d by s n o w a n d frost ( M i n o r e 1 9 7 9 ; S c a g e l etal.  this transition is a l s o a proxy for greatly i n c r e a s e d s n o w d e p t h s . In addition to T. the two other major s p e c i e s in the study a r e a a r e Abies amabilis silver fir) a n d Chamaecyparis  nootkatensis  1 9 7 0 ; P o j a r etal. 1991). T. heterophylla at lower e l e v a t i o n s .  1989),  mertensiana,  D o u g l . ex F o r b e s ( P a c i f i c  (D. Don) S p a c h ( A l a s k a y e l l o w - c e d a r ; B r o o k e et al. is only c o m m o n o n s t e e p e r , s o u t h - a s p e c t s l o p e s a n d  8  Figure 2.1 Location of Tetrahedron Provincial Park and study area  9  E r i c a c e o u s s h r u b s , e s p e c i a l l y Vaccinium majority of understory v e g e t a t i o n . V . alaskaense ovalifolium  s p p . , m o s s e s , a n d s o m e h e r b s form the ( A l a s k a blueberry) is m o s t c o m m o n , while V.  ( o v a l - l e a v e d blueberry) a n d V. membranaceum  (black huckleberry) a r e m o r e  patchily distributed. O t h e r characteristic e r i c a c e o u s s h r u b s include Rhododendron (white-flowered r h o d o d e n d r o n ) , Menziesia pyroliflorus  ferruginea  (false a z a l e a ) , a n d  albiflorum  Cladothamnus  ( c o p p e r b u s h ) . M o s s e s c a n form a n a l m o s t c o n t i n u o u s carpet o n the forest floor  a n d include Rhytidiopsis  robusta  (pipecleaner m o s s ) , Dicranum  ( r e d - s t e m m e d f e a t h e r m o s s ) , a n d Rhizomnium m o s s layer include Rubus pedatus  schreberi  (fan m o s s ) . H e r b s g r o w i n g o n the  (five-leaved bramble) a n d , l e s s c o m m o n l y ,  uniflora ( q u e e n ' s cup) a n d Orthilia secunda fern) a n d h e r b s s u c h a s Tiarella  glabrescens  s p p . , Pleurozium  ( o n e - s i d e d wintergreen). Blechnum  Clintonia spicant  trifoliata (three-leaved f o a m flower) a n d Streptopus  (deer  spp.  (twistedstalk) are a b u n d a n t o n s e e p a g e sites a n d a l o n g s t r e a m e d g e s . S p e c i e s f o u n d in lates n o w m e l t a r e a s include Sphagnum empetriformis  girgensohnii  (white-toothed peat m o s s ) ,  (pink mountain-heather), a n d Luetkea  pectinata  Phyllodoce  (partridgefoot). A c o m p l e t e list  of s p e c i e s is i n c l u d e d a s A p p e n d i x A .  Study Design R e s e a r c h b e g a n in M a y , 1 9 9 3 . I e s t a b l i s h e d three study l o c a t i o n s in old-growth forest s t a n d s (Figure 2.1). E a c h study location c o n s i s t e d of o n e 'flat' site ( 1 7 - 2 5 % s l o p e ) a n d o n e s t e e p site ( 4 5 - 4 9 % s l o p e ) for a total of six sites (Figure 2 . 2 a ; T a b l e 2.1). T h e three flat s i t e s w e r e actually gently-sloping a n d I u s e the term only to c o n v e y that they w e r e flat relative to the three s t e e p s i t e s . T w o study locations, L e s s e r a n d S t e e l e , w e r e s o u t h - f a c i n g a n d o n e , E d w a r d s , w a s north-facing. E l e v a t i o n s a b o v e s e a level r a n g e d from 1 0 8 0 - 1 1 9 5 m. S i t e s e l e c t i o n criteria i n c l u d e d : (1) constant south or north a s p e c t ; (2) s t e e p site directly a b o v e or n e a r flat site; (3) limited e d a p h i c variation; a n d (4) p r e s e n c e of A. amabilis, a n d T.  mertensiana.  C.  nootkatensis,  10  T a b l e 2 . 1 . O l d - g r o w t h study site d e s c r i p t i o n s . Site c o d e s c o m b i n e the first initials of the study location a n d s l o p e type, e . g . , E F signifies E d w a r d s Flat. S o i l moisture r e g i m e s ( S M R ) a n d soil nutrient r e g i m e s ( S N R ) follow K l i n k a etal. (1989). S M R a b b r e v i a t i o n s : F = f r e s h ; M = moist; V M = v e r y moist. S N R a b b r e v i a t i o n s : P = poor; M = m e d i u m .  Study location  Slope type  Site Code  Elevation (m)  Slope  Edwards  Flat Steep  EF ES  1080 1140  17 45  Lesser  Flat Steep  LF LS  1195 1195  Steele  Flat Steep  SF SS  1135 1160  SMR  SNR  60 (NE) 64 (NE)  M/VM M  P P  22 46  222 (SW) 220 (SW)  M/VM F  P/M P  25 49  211 ( S W ) 213 (SW)  M F  P P  (%)  Aspect (deg. azim.)  I l o c a t e d two 5 0 m t r a n s e c t s o n e a c h site to a v o i d large d e v i a t i o n s in s l o p e a n d a s p e c t , with a horizontal transect a l o n g the contour a n d a vertical transect b i s e c t i n g at right a n g l e s (on the s l o p e line) to form a c r o s s (Figure 2.2b). I u s e d this c r o s s - s h a p e d d e s i g n b e c a u s e early tests s h o w e d that it c a p t u r e d m o r e microsite variability than a single 100 m t r a n s e c t . T r a n s e c t s w e r e m a r k e d by p l a c i n g a cloth m e a s u r i n g tape on the g r o u n d for the length of the t r a n s e c t a n d locating flags e v e r y 5 m. T h r e e t y p e s of s a m p l i n g a r e a s w e r e then e s t a b l i s h e d : quadrats,  stand structure  Microsite  plots, a n d age  Quadrats:  microsite  plots.  S i n c e I w a n t e d to quantify microsite g r a d i e n t s , I s a m p l e d  c o n t i g u o u s 1 m q u a d r a t s c e n t r e d o n e a c h site's two 5 0 m t r a n s e c t s (total s a m p l i n g a r e a = 2  0.01 h a p e r site). A folding 4 m levelling rod d e l i n e a t e d the q u a d r a t s with the cloth t a p e a s the midpoint. M i c r o s i t e s a m p l i n g i n c l u d e d all tree a n d non-tree v e g e t a t i o n . Stand Structure  Plots:  T o e x a m i n e the effect of m i c r o s i t e s o n taller t r e e s a n d to  d e t e r m i n e s t a n d structure, I n e e d e d a larger s a m p l i n g a r e a than the microsite plots a n d therefore u s e d 10 m by 5 0 m plots c e n t r e d on the midpoint of e a c h transect. S i n c e the middle 10 m of the two plots on e a c h site o v e r l a p p e d , the total a r e a s a m p l e d w a s 0.09 h a p e r site. O n l y t r e e s >1.3 m tall w e r e i n c l u d e d in s t a n d structure s a m p l i n g .  11  F i g u r e 2 . 2 . Site description a n d s a m p l i n g d e s i g n . (a) S l o p e t y p e s for the s i x plots. O n e flat a n d o n e s t e e p site w e r e e s t a b l i s h e d at e a c h of three s t u d y l o c a t i o n s ( E d w a r d s , L e s s e r , a n d S t e e l e ) . Site c o d e s c o m b i n e the first initials of the s t u d y location a n d of the s l o p e type (e.g., E F = E d w a r d s Flat). T h e t e r m s 'flat' a n d ' s t e e p ' a r e relative a n d flat s i t e s , t h o u g h m o r e gently s l o p i n g than s t e e p sites, h a d s l o p e s of up to 2 5 % . Range of slopes: for flat sites = 17-25%; for steep slopes = 45-49%.  y  Edwards Steep (ES)  s  -^o\varts^laUEF^  -^^Le^s^r^te^p^  '"'Lesser Flat (LF)  49 •  (b) T r a n s e c t d i m e n s i o n s a n d layout. O n e vertical a n d one horizontal transect w e r e l o c a t e d o n e a c h site with 5 0 c o n t i g u o u s 1 m x 1 m quadrats centred on them. S t a n d s t r u c t u r e plots w e r e next centred over the m i d d l e of t h e m i c r o s i t e quadrats. en  '"Steele Flat (SF)  39 36 35 34 33 32 ••  m  •  29 1 | 2 | 3 | 4 | S | 6 | 7 | 8 | 9 110| 11112113| 14| 15116117| 201211221218| 3 112 94 1 25 | 26 j 27 [ 281239 21130313311 34 1 35136 1 37 1 38 1 39 1 40141142143144 1 45146 1 47 1 48149 1 50 :-  : 19 17 16 15 14 13 12 11 10 9 8 7  horizontal transect  —  1m x 1m microsite quadrats  10m x 50m stand structure plots (includes microsite quadrats)  ~r  5 4  T~  2 1  |<  10 m  vertical transect >|  12  Age Plots:  A l l c o r e s w e r e taken from the E S ( E d w a r d s S t e e p ) site d u e to the  a c c e s s i b i l i t y of v i g o r o u s A. amabilis  a n d C. nootkatensis.  Stumps on an ecologically-equivalent  c l e a r c u t s t u d y location, B a t c h e l o r ( C h a p t e r 3), w e r e u s e d for Tsuga a n d additional C. nootkatensis  s a m p l e s . S a m p l e s for estimating a g e to breast-height w e r e a l s o t a k e n f r o m this  clearcut.  Data Collected Site Data:  E l e v a t i o n , s l o p e , a n d a s p e c t (in d e g r e e s azimuth) w e r e r e c o r d e d at e a c h  site. S n o w d e p t h s w e r e m e a s u r e d (±0.1 m) using a g r a d u a t e d pole at 0.5 m intervals a l o n g e a c h t r a n s e c t o n two study locations ( E d w a r d s a n d S t e e l e ) o n M a y 1 5 - 1 6 , 1 9 9 4 a n d all three s t u d y locations o n April 3 - 5 , 1 9 9 5 . A v e r a g e m a x i m u m s n o w d e p t h s w e r e e s t i m a t e d from the height (±0.1 m) of l i c h e n s o n the uphill s i d e of twenty r a n d o m l y c h o s e n trees o n e a c h site ( B r o o k e etal. 1 9 7 0 ; L o n g 1976). Microsite  (Quadrat)  Data:  I c l a s s i f i e d the c a n o p y c o v e r a b o v e e a c h quadrat a s follows:  c l o s e d c a n o p y (between two or m o r e c a n o p y trees with the c r o w n of a c a n o p y tree directly o v e r h e a d ) ; c a n o p y g a p (open s k y directly o v e r h e a d ) ; a n d e x p a n d e d g a p (between a c a n o p y g a p a n d the bole of a c a n o p y tree; R u n k l e 1 9 8 2 , 1 9 9 2 ; Figure 2.3). T h e relatively o p e n c a n o p y c o v e r of the s t u d y a r e a m a d e delineating c a n o p y g a p s difficult s o I s e t the m i n i m u m a r e a at 2 5 m . 1 c o n s i d e r e d a c a n o p y o p e n i n g to b e filled, i.e., n o longer a g a p , w h e n it i n c l u d e d a c a n o p y 2  tree (Table 2.2). T h i s criterion m e a n t that the height limit of trees within g a p s w a s - 1 5 m a n d w a s similar to other g a p s t u d i e s ( R u n k l e 1 9 8 1 ; Y a m a m o t o 1993). M a n y r e s e a r c h e r s limit their definition of g a p s to c a n o p y o p e n i n g s c a u s e d by the death of a b r a n c h or at least o n e tree ( R u n k l e 1992), but s i n c e m y g o a l w a s to d e s c r i b e the growing conditions for individual trees, I i n c l u d e d all g a p s that met m y other criteria.  13  F i g u r e 2 . 3 . C a n o p y c o v e r classification (Runkle 1982, 1992). Relative c a n o p y o p e n n e s s d e c r e a s e s from c a n o p y gap (eg), to e x p a n d e d g a p (eg), to c l o s e d c a n o p y (cc). O n l y c a n o p y g a p s are directly b e l o w o p e n sky. A n e x p a n d e d g a p is b e t w e e n a c a n o p y g a p a n d the b o l e s of trees at the e d g e of that g a p . R e m a i n i n g a r e a s are in c l o s e d c a n o p y . C a n o p y drip m i c r o s i t e s are directly below the e d g e of a c a n o p y tree's c r o w n .  expanded gap  canopy gap  (eg)  c a n o p y drip  expanded gap  (eg)  (eg)  c a n o p y drip  T a b l e 2 . 2 . Definition of t e r m s u s e d in C h a p t e r 2.  Term  Definition  Seedling  A n y s p e c i e s of tree <10 c m tall.  Sapling  A n y s p e c i e s of tree 1 0 - 1 2 9 c m tall.  Tree  A n y s p e c i e s of tree >1.3 m tall.  Understory  trees  S h o r t e r trees (most <6 m but all <8 m tall) w h o s e height growth rate w a s usually limited d u e to lack of light; lateral growth of t h e s e trees often e x c e e d e d height growth (umbrella growth form).  Sub-canopy  trees  T r e e s w h o s e heights w e r e intermediate b e t w e e n c a n o p y a n d understory trees ( - 6 - 1 7 m tall in the study a r e a ) .  Non-canopy  trees  T r e e s in s u b - c a n o p y a n d understory layers.  Canopy  trees  T h e tallest trees on a site w h o s e upper c r o w n s w e r e u n s h a d e d by other trees ( - 1 5 - 3 6 m tall in the study a r e a ) .  Mound  partners  All trees growing on the s a m e m o u n d .  14  F o r e a c h g a p , I r e c o r d e d its s i z e a n d the n u m b e r of g a p m a k e r s ( R u n k l e 1 9 8 1 , 1 9 9 2 ; L e r t z m a n 1989), d e f i n e d here a s d e a d c a n o p y trees >40 c m b a s e d i a m e t e r (the a p p r o x i m a t e lower limit of live c a n o p y trees). S i n c e g a p s i z e s w e r e e s t i m a t e d from g r o u n d l e v e l , they w e r e g r o u p e d into 5 0 m c l a s s e s , plus a 2 5 m c l a s s . T h e following d a t a w e r e r e c o r d e d for 2  2  g a p m a k e r s : s p e c i e s (if known); condition (standing d e a d , s n a p p e d >2 m a b o v e the g r o u n d , s t u m p <2 m tall, or u p r o o t e d ; L e r t z m a n a n d K r e b s 1 9 9 1 ; R u n k l e 1992), a n d d e c a y c l a s s (Table 2.3). T o e x p l o r e w h e t h e r n o n - c a n o p y trees w e r e d a m a g e d by s n o w s l o u g h i n g d o w n from c a n o p y t r e e s , q u a d r a t s directly b e l o w the outer projection of a c a n o p y tree's c r o w n w e r e c l a s s i f i e d a s c a n o p y drip (Figure 2.3).  T a b l e 2 . 3 . D e c a y classification for d e a d trees (following M a s e r etal. 1 9 7 9 , T r i s k a a n d C r o m a c k 1 9 7 9 , a n d S o l l i n s 1982).  Decay class  Structural integrity  Texture  M o s t l y intact Partly rotten M o s t l y rotten Totally rotten  Sound H e a r t w o o d s o u n d , s u p p o r t s o w n weight H e a r t w o o d rotten, d o e s not support o w n weight None  H a r d a n d dry H a r d , large p i e c e s Soft, b l o c k y p i e c e s Soft, p o w d e r y w h e n dry  I a d d e d two c a t e g o r i e s to m o r e fully d e s c r i b e the understory light e n v i r o n m e n t , low s h a d e a n d high s h a d e (Figure 2.4), but note that m y u s e of t h e s e t e r m s differs from that of O l i v e r a n d L a r s o n (1990). Q u a d r a t s or trees w e r e c o n s i d e r e d to b e in high s h a d e if a n o t h e r tree or a north-facing s l o p e b l o c k e d the s u n ' s rays a b o v e - 6 0 ° , the a p p r o x i m a t e elevation of the s u n at s u m m e r s o l s t i c e ( B r o o k e etal. 1970). Q u a d r a t s or t r e e s w e r e c o n s i d e r e d to b e in low s h a d e if the quadrat or tree's l e a d e r w e r e s h a d e d by a tree w h o s e b r a n c h e s w e r e <5 m a b o v e the g r o u n d . I c h o s e this 5 m limit b e c a u s e the d a r k e s t m i c r o s i t e s w e r e s h a d e d by n o n c a n o p y t r e e s a n d the lowest b r a n c h e s o n most c a n o p y trees w e r e >5 m a b o v e the g r o u n d .  15  F i g u r e 2.4. Definition of high s h a d e a n d low s h a d e for understory trees (<5 m tall) a n d q u a d r a t s . H i g h a n d low s h a d e w e r e d e t e r m i n e d in relation to the a p p r o x i m a t e elevation of the s u n at s u m m e r solstice ( - 6 0 ° a s s h o w n by d i a g o n a l arrows). A n understory tree or quadrat w a s c l a s s e d a s being in high s h a d e (HS) if there w a s a c a n o p y tree or northa s p e c t s l o p e b e t w e e n the s u n a n d the tree's leader or the quadrat s u r f a c e . A n understory tree or quadrat w a s c l a s s e d a s b e i n g in low s h a d e (LS) if the. b r a n c h e s of a n o t h e r tree w e r e b e t w e e n the s u n a n d the understory tree's l e a d e r or the quadrat s u r f a c e (<5 m a b o v e the ground). N o t e that t h e s e definitions are different than t h o s e u s e d by O l i v e r a n d L a r s o n (1990).  north  noHS, noHS, LS no LS  no HS, no HS, LS LS  HS, LS  HS, LS  south  I c a t e g o r i z e d e a c h quadrat by the following m i c r o t o p o g r a p h y c l a s s e s : d e p r e s s i o n m i c r o s i t e s , s l o p e m i c r o s i t e s (i.e., no m o u n d or d e p r e s s i o n ) , s m a l l m o u n d s (<25 c m off the average slope surface), medium mounds  (25-75 c m ) , a n d large m o u n d s (>75 c m ) . W h e r e  there w a s a m o u n d , I a l s o r e c o r d e d the position of the quadrat relative to it (top, downhill, uphill, or side) a n d its a s p e c t (flat, east, or w e s t ) . S u b s t r a t e s w e r e s a m p l e d by e x p o s i n g the top 10 c m of the forest floor with a g a r d e n trowel a n d estimating p e r c e n t c o v e r to the n e a r e s t 5%. At least 3 s a m p l e s w e r e e x p o s e d o n e a c h q u a d r a t with m o r e s a m p l e s w h e r e there w a s m o r e variability. I c l a s s i f i e d s u b s t r a t e s a s u n d i s t u r b e d forest floor, friable forest floor, d e c a y i n g w o o d , e x p o s e d d e c a y i n g w o o d , c o a r s e w o o d y d e b r i s , mineral s o i l , rock, or tree. Friable forest floor had a c r u m b l y texture while u n d i s t u r b e d forest floor w a s more difficult to penetrate with the trowel; t h e s e c l a s s e s c o r r e s p o n d to friable M o r m o d e r a n d c o m p a c t e d M o r h u m u s f o r m s , r e s p e c t i v e l y ( G r e e n et al.  16  1 9 9 3 ) . D e c a y i n g w o o d , which w a s bright orange, w a s s u b d i v i d e d into two c l a s s e s : e x p o s e d d e c a y i n g w o o d if on the ground s u r f a c e , a n d d e c a y i n g w o o d if b e l o w the s u r f a c e . C o a r s e w o o d y d e b r i s c o n s i s t e d of logs, b r a n c h e s , or s t u m p s that w e r e a b o v e the g r o u n d s u r f a c e . I r e c o r d e d the s p e c i e s , percent cover, a n d height (except for b r y o p h y t e s a n d lichens) of all non-tree vegetation. T r e e s e e d l i n g s were identified by s p e c i e s a n d c l a s s i f i e d into o n e of five d e v e l o p m e n t a l s t a g e s : new germinant, green c o t y l e d o n s , d e a d c o t y l e d o n s , no c o t y l e d o n s , a n d l a t e r a l l y - b r a n c h e d (Figure 2.5). D u e to difficulties in differentiating the two s p e c i e s of  Tsuga  s e e d l i n g s , I g r o u p e d them together.  F i g u r e 2 . 5 . D e v e l o p m e n t a l s t a g e s of s e e d l i n g s (after K o h y a m a 1983).  new germinant  green c o t l y e d o n s dead c o t y l e d o n s  no c o t y l e d o n s  laterally-branched  green cotyledons,  green cotyledons,  dead cotyledons,  no c o t y l e d o n s ,  no c o t y l e d o n s ,  no epicotyl  with e p i c o t y l  with e p i c o t y l  with epicotyl  1 or m o r e b r a n c h e s  I r e c o r d e d the following d a t a for all s a p l i n g s a n d t r e e s : s p e c i e s ; c a n o p y l a y e r (Table 2.2); height (using a steel tape m e a s u r e , a 4 m levelling rod, or a cloth tape, c l i n o m e t e r , a n d trigonometry); vigour (from 0 - 5, w h e r e 0 is d e a d a n d 5 is m o s t v i g o r o u s ; after L u t t m e r d i n g et al. 1 9 9 0 a n d C a r t e r a n d K l i n k a 1992); s i z e of m o u n d (if any) a n d position of tree relative to it (top, uphill, downhill, or e d g e ) ; a n d any growth a n o m a l i e s s u c h a s pistol butt ( s n o w crook) or u m b r e l l a growth forms ( A p p e n d i x B ) . I r e c o r d e d s u b s t r a t e s only for s a p l i n g s a n d t h o s e u n d e r s t o r y trees w h e r e the substrate w a s o b v i o u s . Height i n c r e m e n t s for the p r e v i o u s y e a r w e r e only r e c o r d e d for s a p l i n g s a n d trees w h o s e l e a d e r s w e r e visible a n d w h e r e the i n c r e m e n t a l growth w a s distinct. D i a m e t e r at breast height w a s r e c o r d e d for all t r e e s .  17  Stand Structure  Data:  T h e s a m e d a t a w e r e c o l l e c t e d o n s t a n d structure plots a s  m i c r o s i t e s q u a d r a t s e x c e p t that only trees (i.e., >1.3 m tall) w e r e i n c l u d e d , a n d d i s t a n c e to the n e a r e s t c a n o p y tree w a s r e c o r d e d while substrate w a s not. T o a d d r e s s the c o m p o s i t i o n a n d structure of individual m o u n d s , I c e n s u s e d all m o u n d s that s u p p o r t e d at least o n e tree a n d r e c o r d e d all t r e e s l o c a t e d o n the s a m e m o u n d (all of w h i c h I t e r m e d mound partners).  When  m o u n d s e x t e n d e d o u t s i d e plot b o u n d a r i e s , the s p e c i e s a n d c a n o p y layer of a n y additional m o u n d partners w e r e a l s o r e c o r d e d . Age Data:  O b t a i n i n g high quality c o r e s for tree ring a n a l y s i s in old f o r e s t s c a n b e  difficult d u e to large d i a m e t e r s ( B r o o k e etal. 1970), frequent heart rot ( B u r n s a n d H o n k a l a 1 9 9 0 ) , frost c r a c k s (K. L e r t z m a n a n d J . D o b r y , p e r s . c o m m . ) , a n d a s y m m e t r i c growth rings (Lorimer 1985), e s p e c i a l l y for Tsuga trees. I therefore u s e d a c o m b i n a t i o n of m e t h o d s for s a m p l i n g a g e s : c o r i n g for A. amabilis, s p e c i e s ) , a n d both m e t h o d s for C.  counting s t u m p rings for Tsuga (not identified to nootkatensis.  I s a m p l e d c a n o p y trees with a n increment c o r e following the m e t h o d s d e s c r i b e d by J o z s a (1988). T o a v o i d heartrot a n d m i s s i n g rings, only trees with g o o d vigour w e r e c h o s e n , t h o u g h this criterion likely b i a s e d the s a m p l e in favour of faster-growing, y o u n g e r t r e e s . T o a v o i d c o m p r e s s i o n w o o d , two c o r e s w e r e r e m o v e d at breast height from o p p o s i t e s i d e s of e a c h tree a n d at a n g l e s a p p r o x i m a t e l y p e r p e n d i c u l a r to the s l o p e . C o r e s w e r e m o u n t e d o n a w o o d e n f r a m e , s a n d e d to better differentiate rings, then c o u n t e d u s i n g a 4 0 x b i n o c u l a r m i c r o s c o p e . O n l y the c o r e that w a s c l o s e s t to the pith a n d p r o v i d e d the c l e a r e s t rings w a s u s e d in further d a t a a n a l y s i s . Tsuga a n d a n additional 5 C. nootkatensis  w e r e a g e d by counting s t u m p rings. I  d e c i d e d to include a s m a l l s a m p l e of C. nootkatensis  s t u m p s s i n c e r e a c h i n g the pith with a n  i n c r e m e n t c o r e r w a s i m p o s s i b l e for m a n y of the largest t r e e s . I cut a v - n o t c h o n the s t u m p from pith to outer e d g e with a large utility knife a n d a ruler. T h e rings then e x p o s e d o n the  18  s t u m p w e r e w e t t e d a n d / o r c h a l k e d to help differentiate rings, a n d c o u n t e d with a 10x h a n d lens. I e x c a v a t e d 2 0 d e a d understory trees to e s t a b l i s h a p p r o x i m a t e a g e s to s t u m p a n d c o r i n g heights. I cut d i s k s at the g r o u n d s u r f a c e a n d 1.3 m a b o v e the root collar, s a n d e d t h e m , a n d then c o u n t e d rings using a 4 0 x binocular m i c r o s c o p e . S e e d l i n g a g e s w e r e b a s e d o n a r a n d o m s a m p l e of at least 5 s e e d l i n g s (where possible) for e a c h d e v e l o p m e n t a l s t a g e a n d s p e c i e s . I cut the s e e d l i n g s with a r a z o r b l a d e at their root collar, b r u s h e d t h e m with c h a l k a n d / o r w a t e r to help differentiate rings, then c o u n t e d the rings u n d e r a 4 0 x b i n o c u l a r microscope.  Data Analysis M e a n s w e r e c o m p a r e d with t-tests a n d a n a l y s i s of v a r i a n c e u s i n g S i g m a S t a t ( K u o  etal.  1 9 8 7 ) . I first plotted d a t a to s c r e e n for e x t r e m e s k e w n e s s , bi-modality, a n d u n e q u a l v a r i a n c e , a n d t r a n s f o r m e d t h e m if n e c e s s a r y a n d appropriate. T h e d a t a w e r e then t e s t e d for normality (using the K o l m o g o r o y - S m i r n o v test) a n d e q u a l v a r i a n c e (using the L e v e n e m e d i a n test). W h e n they p a s s e d both tests at a = 0 . 0 5 , I u s e d the intended p a r a m e t r i c test. W h e n d a t a w e r e inappropriate for p a r a m e t r i c testing, e . g . , the m a n y z e r o v a l u e s for height i n c r e m e n t s a n d M a y s n o w d e p t h s , I u s e d the n o n - p a r a m e t r i c equivalent to the t-test ( M a n n - W h i t n e y test) or a n a l y s i s of v a r i a n c e ( K r u s k a l - W a l l i s test) or, in e x t r e m e c a s e s , s i m p l y d e s c r i b e d the d a t a without testing. Multiple c o m p a r i s o n s after p a r a m e t r i c a n d n o n - p a r a m e t r i c a n a l y s i s of v a r i a n c e w e r e p e r f o r m e d using the S t u d e n t - N e u m a n - K e u l s ( S N K ) test only w h e n there w e r e significant d i f f e r e n c e s b e t w e e n s a m p l e s (Zar 1984). W h e n s a m p l e s i z e s w e r e u n e q u a l in n o n - p a r a m e t r i c multiple c o m p a r i s o n s , I a p p l i e d D u n n ' s test. I u s e d c h i - s q u a r e (x ) a n a l y s i s to test the o b s e r v e d - t o - e x p e c t e d f r e q u e n c i e s of t r e e s , 2  s a p l i n g s , a n d s e e d l i n g s in relation to microsite factors. E x p e c t e d f r e q u e n c i e s w e r e b a s e d o n the null h y p o t h e s i s that regeneration w a s randomly distributed a n d its o c c u r r e n c e o n a particular microsite w a s proportional to the availability of that microsite. F o r e x a m p l e , if  19  d e c a y i n g w o o d c o v e r e d 2 0 % of the g r o u n d s u r f a c e , w e w o u l d e x p e c t it to support 2 0 % of r e g e n e r a t i o n . C o n t i n g e n c y t a b l e s w e r e u s e d to c o m p a r e o b s e r v e d f r e q u e n c i e s o n different m i c r o s i t e s to e a c h other. T h e Y a t e s continuity correction w a s a p p l i e d to all 2 x 2 c h i - s q u a r e a n d c o n t i n g e n c y table tests to better m a t c h the x  2  distribution (Zar 1984). T o further prevent  b i a s , I c o m b i n e d c l a s s e s s o that no e x p e c t e d c o u n t s w e r e l e s s than 1.0 a n d no m o r e than 2 0 % of e x p e c t e d c o u n t s w e r e l e s s than 5 (Zar 1984). T o prevent o v e r - e m p h a s i z i n g the importance of rare m i c r o s i t e s , I s h o w both a c t u a l f r e q u e n c i e s a n d the ratio of o b s e r v e d - t o - e x p e c t e d f r e q u e n c i e s u s e d in c h i - s q u a r e a n a l y s i s ( F i g u r e s 2 . 1 3 , 2 . 1 4 , a n d 2.17). F o r e x a m p l e , a rare microsite c o u l d support twice a s m a n y t r e e s a s e x p e c t e d yet affect regeneration patterns only slightly. B e f o r e correlations w e r e p e r f o r m e d in S Y S Y A T for W i n d o w s (Wilkinson e r a / . 1 9 9 2 ) , d a t a w e r e t e s t e d a n d t r a n s f o r m e d a s d e s c r i b e d a b o v e . T h e overall error rate of multiple correlations w a s controlled by a B o n f e r o n n i correction ( G l a n t z 1992). S p e a r m a n rank correlations w e r e u s e d w h e n proxy v a l u e s w e r e a s s i g n e d to m i c r o t o p o g r a p h y a n d c a n o p y c o v e r c l a s s e s ( F i g u r e s 2.9 a n d 2.10); t h e s e are ordinal v a l u e s b a s e d o n predictions of s n o w depth relative to other microsites a n d s o are inappropriate for P e a r s o n correlations ( G l a n t z 1 9 9 2 ) . T o allow c o m p a r i s o n s with F i g u r e s 2.9 a n d 2 . 1 0 , I reported S p e a r m a n rank correlations in F i g u r e 2.11 (a c o m p a r i s o n b e t w e e n actual d i s t a n c e to the n e a r e s t c a n o p y tree a n d s n o w depth) w h e r e P e a r s o n correlations w o u l d otherwise be preferable. M y a n a l y s i s of height growth rates w a s restricted to A. amabilis  s i n c e it w a s the only  s p e c i e s with a determinate growth form that a l l o w e d a n a c c u r a t e m e a s u r e m e n t of the p r e v i o u s y e a r ' s height increment, e s p e c i a l l y for s u p p r e s s e d t r e e s . All tests w e r e c o n d u c t e d with a = 0 . 0 5 . T h e type of transformation, w h e n u s e d , is • s p e c i f i e d with test results a n d all d a t a are p r e s e n t e d in their original units. All m e a n s a r e p r e s e n t e d with s t a n d a r d deviations, e . g . , 8 3 ± 4 6 y e a r s .  20  2.3  Results  Structure, Composition, and Age M o s t c a n o p y t r e e s w e r e either T. mertensiana  or C. nootkatensis,  while A.  amabilis  d o m i n a t e d all shorter height c l a s s e s e x c e p t s e e d l i n g s (Table 2.4 a n d Figure 2 . 6 a ) . T h e height distribution of A. amabilis nootkatensis  followed a s t e e p i n v e r s e - J , or negative e x p o n e n t i a l , c u r v e . C.  a n d T. mertensiana  h a d flatter, slightly b i m o d a l distributions resulting from f e w e r  individuals in shorter, a n d m o r e in taller, height c l a s s e s . T. heterophylla  canopy trees were  p r e s e n t o n only three sites ( L S , S F , a n d S S ) a n d virtually a b s e n t a m o n g s u b - c a n o p y t r e e s . D i a m e t e r distributions s h o w e d similar patterns to height distributions e x c e p t that C. nootkatensis  h a d a longer tail than other s p e c i e s a n d T. mertensiana  s h o w e d m o r e of a n  i n v e r s e - J s h a p e d c u r v e (Figure 2.6b). C a n o p y trees of e a c h s p e c i e s w e r e taller a n d h a d larger d i a m e t e r s o n s t e e p than flat sites ( M a n n - W h i t n e y test; T > 6 2 2 7 ; p < 0.029). C a n o p y t r e e s w e r e v e r y old a n d s l o w - g r o w i n g a s it took t h e m a n a v e r a g e of - 4 8 8 y e a r s to r e a c h the c a n o p y layer. T h i s m i n i m u m estimate i n c l u d e s 8 3 ± 4 6 y e a r s to g r o w to b r e a s t height (1.3 m) a n d a further 4 0 5 ± 1 1 2 y e a r s to grow to a d i a m e t e r of 4 0 c m (the lower limit of m o s t c a n o p y trees). E s t i m a t e d a g e s r a n g e d from 370-901 y e a r s for A. amabilis 1 4 0 4 y e a r s for C. nootkatensis  (n = 22), 3 9 5 -  (n = 22), a n d 3 1 9 - 8 9 7 for Tsuga (n = 12). S o m e t r e e s g r e w  faster than others, but the overall trend w a s constant, s l o w growth (Figure 2.7). T h i s trend c o n t r a s t e d with that e x p e c t e d with the g a p m o d e l , w h e r e understory a n d s u b - c a n o p y t r e e s r e s p o n d to the formation of a n e w g a p by growing m u c h faster a n d maintaining that faster growth rate a s they grow into the c a n o p y layer. Of the three s p e c i e s , only Tsuga t e n d e d to g r o w faster with i n c r e a s e d s i z e , e s p e c i a l l y at d i a m e t e r s >10 c m .  21  T a b l e 2.4.  S p e c i e s c o m p o s i t i o n (frequency per hectare) by height c l a s s a n d site.  Tsuga  s e e d l i n g s w e r e not identified to s p e c i e s .  Height C l a s s  Site  Species  EF  ES  LF  SF  LS  SS  Mean  (%)  C a n o p y trees A. C. T. T.  amabilis  67  33  111  78  33  33  59  (20.6)  nootkatensis mertensiana heterophylla  133 111 0  67 78 0  111 133 0  122 111 33  44 133 44  78 122 44  93 115 20  (32.3) (40.0) (7.1)  Total  311  178  356  344  256  278  287 (100.0)  89 22  156  67  144 11  (47.1)  0  33 0  89 26  (13.7)  33  78 44  0 222  69 6  (36.3) (2.9)  167  0 278  67 11 111  67  0 144  133 11 211  189 (100.0)  200 456 422  511 378 322  1078 433  1000 78  444 0  944 0  696 224  (58.3) (18.8)  233 11  78  0  356 11  67  11  (20.6) (2.3)  1089  1211  1878  1322  56 1078  246 28  Total  78 589  1194 (100.0)  S u b - c a n o p y trees A. amabilis nootkatensis  44  C. T.  mertensiana  T.  heterophylla Total  67 11  Understory trees A. amabilis C. nootkatensis T. T.  mertensiana heterophylla  Saplings A.  44  amabilis  4000  4600  2400  5700  15400  8100  6700  (79.0)  C. T.  nootkatensis mertensiana  600 1600  900 200  400 100  700 0  1700 2200  200  750  (8.8)  100  700  (8.3)  T.  heterophylla  300 6000  0  0  1700  0  333  (3.9)  Total  0 6200  2900  6400  21000  8400  Seedlings A. amabilis  25400  35300  38700  119200  116300  38900  62300  (33.4)  29400  45000  117400  101200  71100  74000  73017  (39.1)  51317  (27.5)  C.  nootkatensis Tsuga Total  78600  32700  71700  30600  48700  45600  133400  113000  227800  251000  236100  158500  8483 (100.0)  186633 (100.0)  22  F i g u r e 2.6. Height (a) a n d d i a m e t e r (b) distributions of t r e e s >1.3 m tall by s p e c i e s . T h e s h o r t e s t height c l a s s i n c l u d e s t r e e s from 1.3-3.9 m tall. T h e y - a x i s s c a l e d o e s not s h o w full f r e q u e n c i e s for A. amabilis in the s m a l l e s t height a n d d i a m e t e r c l a s s e s ; a c t u a l f r e q u e n c i e s a r e i n c l u d e d at the top of the histogram bar. D i a m e t e r s w e r e m e a s u r e d at b r e a s t height.  250  A. amabilis  C. nootkatensis  T. mertensiana  T. heterophylla  upper limit of height class (m)  upper limit of height class (m)  (a) Height distribution by s p e c i e s .  (b) Diameter (at breast height) distribution by s p e c i e s .  23  F i g u r e 2.7. G r o w t h rate to a d i a m e t e r of 4 0 c m (at s t u m p or c o r e height). S i n c e the d i a m e t e r at breast-height of most c a n o p y trees w a s >40 c m , t h e s e c h a r t s reflect growth rates for u n d e r s t o r y a n d s u b - c a n o p y trees ( e a c h line r e p r e s e n t s o n e tree). A g e s d o not include the n u m b e r of y e a r s it took trees to r e a c h breast height. N o t e that flatter s l o p e s indicate faster growth rates.  /  24  T h e r e w e r e m a n y s e e d l i n g s of e a c h s p e c i e s , but A. amabilis  w a s m o s t likely to s u r v i v e  to the l a t e r a l l y - b r a n c h e d s t a g e : there w e r e 16 laterally-branched A. amabilis e v e r y 2 C. nootkatensis  a n d o n e Tsuga. C. nootkatensis  s e e d l i n g s for  w a s most c o m m o n a m o n g n e w  g e r m i n a n t s a n d s e e d l i n g s with g r e e n c o t y l e d o n s . Tsuga w a s most c o m m o n a m o n g s e e d l i n g s with no c o t y l e d o n s , though this result m a y the difficulty in differentiating s t a g e s for Tsuga. amabilis  A.  w e r e s t r a n g e l y rare a m o n g n e w g e r m i n a n t s a s only 9 w e r e f o u n d o n all q u a d r a t s  (= 1 5 0 / h a ) . S e e d l i n g a g e s for e a c h s p e c i e s i n c r e a s e d with their s t a g e of d e v e l o p m e n t (two-way a n a l y s i s of v a r i a n c e o n natural log-transformed d a t a ; F > 1 7 . 1 ; p < 0 . 0 0 0 1 ) , a n d A.  amabilis  w e r e o l d e s t at e a c h s t a g e . L a t e r a l l y - b r a n c h e d s e e d l i n g s a v e r a g e d 6.4 ± 1 . 6 c m in height a n d 12.4 ± 7 . 4 y e a r s of a g e , a n d the oldest w a s a 2 7 y e a r - o l d A. amabilis. growth of s e e d l i n g s a n d s a p l i n g s , particularly A. amabilis, s t e m t h r o u g h soil c r e e p . F o r e x a m p l e , o n e A. amabilis  T h e a n n u a l height  w a s offset by burying of the lower  s a p l i n g that w a s 6 0 c m tall h a d >60  growth rings buried b e l o w the g r o u n d s u r f a c e .  The Microsite Environment Substrates U n d i s t u r b e d forest floor c o v e r e d 8 0 % of the g r o u n d s u r f a c e a n d d e c a y i n g w o o d or c o a r s e w o o d y d e b r i s c o v e r e d most of the rest (Table 2.5). M o s t c o a r s e w o o d y d e b r i s c o n s i s t e d of the s t e m s of fallen trees. M i n e r a l soil w a s rare e x c e p t w h e r e run-off f r o m a n e w logging r o a d d r a i n e d onto the E F site. T h o u g h not quantified, m o s t u n d i s t u r b e d forest floor w a s v e r y c o m p a c t e d a n d c o n s i s t e d of a g r e a s y , very a c i d i c h u m u s with a b u n d a n t f u n g a l h y p h a e ( H e m i m o r a n d H u m i m o r h u m u s f o r m s , G r e e n etal. 1993). M o s s c o v e r e d 4 2 % of the g r o u n d .  25  T a b l e 2 . 5 . P e r c e n t c o v e r of s u b s t r a t e s by site. A b b r e v i a t i o n s : uff = u n d i s t u r b e d forest floor; fff = friable forest floor; d w = d e c a y i n g w o o d ; e d w = e x p o s e d d e c a y i n g w o o d ; c w d = c o a r s e w o o d y d e b r i s ; m s = mineral soil. substrate Site  uff  fff  EF ES LF LS SF SS Mean  76.7 88.9 75.5 80.5 83.2 75.3 80.0  0.2 0.0 0.2 0.0 0.4 0.1 0.2  dw 5.6 0.3 9.2 9.5 9.2 8.8 7.1  edw 1.9 3.1 0.3 0.0 0.2 0.0 0.9  cwd  ms  9.6 3.1 11.0 4.6 3.9 10.8 7.1  2.4 0.0 0.7 0.0 0.2 0.0 0.6  rock 0.5 2.2 0.4 1.6 0.0 0.0 0.8  tree 3.1 2.6 2.8 4.0 3.1 5.2 3.4  Total 100.0 100.0 100.0. 100.0 100.0 100.0 100.0  Microtopography M o u n d s c o v e r e d 2 8 % of the g r o u n d with a l m o s t the s a m e proportion o n flat a n d s t e e p s i t e s . T h e y w e r e a l m o s t equally divided a m o n g s m a l l , m e d i u m , a n d large s i z e s . S l o p e m i c r o s i t e s w e r e the m o s t c o m m o n a n d c o v e r e d 7 1 % of s t e e p a n d 4 7 % of flat s i t e s . M o s t of the difference b e t w e e n site t y p e s w a s d u e to the p r e s e n c e of m o r e d e p r e s s i o n m i c r o s i t e s o n flat (23%) c o m p a r e d to s t e e p (3%) sites.  Canopy  Cover and Distance  to the Nearest  Canopy  Tree  O n a v e r a g e , 3 5 % of q u a d r a t s w e r e in c a n o p y g a p , 3 8 % w e r e in e x p a n d e d g a p , a n d 2 7 % w e r e in c l o s e d c a n o p y (Table 2.6). But t h e s e a v e r a g e s m a s k the great variation in the " g a p p i n e s s " of individual s i t e s s i n c e the proportion of q u a d r a t s in c l o s e d c a n o p y r a n g e d from 1 1 % o n the E F site to 4 4 % o n the S S site. C o n s i s t e n t with their defining c h a r a c t e r i s t i c , all c l o s e d c a n o p y q u a d r a t s w e r e in high s h a d e but there w a s a l s o high s h a d e on 4 1 % of e x p a n d e d g a p a n d 3 4 % of c a n o p y g a p q u a d r a t s . T h e r e w a s low s h a d e o n 3 4 % of q u a d r a t s , with the lowest proportion on c l o s e d c a n o p y q u a d r a t s . Q u a d r a t s in c l o s e d c a n o p y w e r e m o s t likely to b e heavily s h a d e d (both high a n d low s h a d e ) . Q u a d r a t s in c a n o p y g a p s w e r e m o s t likely to b e u n s h a d e d (no high or low s h a d e ) , though the majority (53%) h a d s o m e sort of  26  s h a d i n g . T h e m a i n c o n c l u s i o n to d r a w from t h e s e results is that c a n o p y c o v e r a l o n e d o e s not fully d e s c r i b e the light environment of understory trees. G a p s i z e s a v e r a g e d 99 ± 1 0 6 m in a distribution that w a s s k e w e d to lower v a l u e s . 2  A l t h o u g h the m e d i a n g a p s i z e w a s 5 0 m on both flat a n d s t e e p s i t e s , m e a n s w e r e higher o n 2  the flat site of e a c h study location ( E F > L F > S F > E S > L S > S S ; s k e w e d distributions a n d low s a m p l e s i z e s p r e v e n t e d testing), d u e to the few, but v e r y large g a p s o n t h e s e s i t e s . E a c h flat site, but no s t e e p site, h a d o n e g a p with a n a r e a >400 m . T h e proportion of g a p s that h a d 2  no g a p m a k e r followed the s a m e ranking a s m e a n g a p s i z e a n d r a n g e d f r o m 1 0 0 % o n the north-facing E F site to 5 0 % on the south-facing S S site.  T a b l e 2.6. C a n o p y c o v e r (a) by site; a n d (b) by high s h a d e a n d low s h a d e (in percent). S e e F i g u r e 2 . 3 for definitions of c a n o p y c o v e r c l a s s e s a n d Figure 2.4 for definitions of high a n d low s h a d e . A b b r e v i a t i o n s : c c = c l o s e d c a n o p y ; e g - e x p a n d e d g a p ; eg = c a n o p y gap. C a n o p y cover class Site EF ES LF LS SF SS Flat Steep Total (a) B y site  cc  eg  11.0 26.0 24.0 23.0 34.0 44.0 23.0 31.0 27.0  45.0 36.0 34.0 44.0 40.0 29.0 39.7 36.3 38.0  High/low  eg  Total  shade  44.0 38.0 42.0 33.0 26.0 27.0 37.3 32.7 35.0  100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0  HS no H S LS no L S HS, LS H S , no L S no H S , L S no H S , no L S Total  C a n o p y cover c l a s s cc 26.5 0.3 7.8 19.2 7.7 18.8 0.2 0.2 27.0  eg  eg  Total  15.5 22.3 13.5 24.5 4.0 11.5 9.5 12.8 38.0  12.0 23.0 13.0 22.0 5.0 7.0 8.0 15.0 35.0  54.0 45.7 34.3 65.7 16.7 37.3 17.7 28.0 100.0  (b) By high s h a d e (HS) and low s h a d e (LS).  G a p terminology implies a relationship b e t w e e n c a n o p y c o v e r a n d d i s t a n c e to the n e a r e s t c a n o p y tree s o that c l o s e d c a n o p y microsites s h o u l d be c l o s e s t to, a n d c a n o p y g a p m i c r o s i t e s farthest f r o m , the n e a r e s t c a n o p y tree. A s e x p e c t e d , m o s t q u a d r a t s in c l o s e d c a n o p y w e r e <2 m from a c a n o p y tree; most in e x p a n d e d g a p w e r e 2-3.9 m f r o m a c a n o p y tree; a n d m o s t in c a n o p y g a p w e r e >4 m from a c a n o p y tree (Figure 2.8). T h e m a i n o v e r l a p in this c l a s s i f i c a t i o n w a s c a u s e d by the high proportion of q u a d r a t s in e x p a n d e d g a p that w e r e <2  27  m f r o m a c a n o p y tree. C a n o p y drip w a s present o n 2 4 % of q u a d r a t s a n d m o s t (68%) c a n o p y drip q u a d r a t s w e r e 3-4.9 m from the n e a r e s t c a n o p y tree.  F i g u r e 2 . 8 . Q u a d r a t s by c a n o p y c o v e r c l a s s a n d d i s t a n c e to the n e a r e s t c a n o p y tree (in percent).  40  -I  closed canopy quadrats (°/  30  •  —•—  20 expanded gap 10  n U  canopy gap  • <1  i  —•  ~~ •  "~"  1.0-1.9  2.0-2.9  3.0-3.9  4.0-4.9  '1  5+  distance to the nearest canopy tree (m)  Snow - Microsite Relationships April s n o w a v e r a g e d 1.7 ± 0 . 5 m in depth, with a m a x i m u m of 3 . 3 m , a n d it d e c r e a s e d in m e a n d e p t h b y s t u d y location a s follows: L e s s e r > E d w a r d s > S t e e l e (Table 2.7). T h e r e w a s c o m p l e t e s n o w c o v e r in April a n d a l m o s t identical d e p t h s o n flat a n d s t e e p sites of e a c h s t u d y location. Major differences only b e c a m e a p p a r e n t a s s n o w m e l t e d . B y m i d - M a y , s t e e p a n d s o u t h - f a c i n g sites h a d melted m o r e than flat a n d north-facing sites a n d the proportion of b a r e g r o u n d r a n g e d from 8 7 % o n the S S site to 1 6 % o n the E F site. T h e s e site r a n k i n g s w e r e similar to t h o s e for c a n o p y c o v e r , m e a n g a p s i z e , a n d proportion of c a n o p y g a p s with n o g a p m a k e r (previous section). T h e a v e r a g e m a x i m u m s n o w d e p t h , e s t i m a t e d from lichen height, w a s 2 . 9 ± 0 . 3 m, - 7 0 % higher than m e a n April s n o w d e p t h s .  28  T a b l e 2 . 7 . S n o w d e p t h s (in metres) by site a n d s l o p e type. M a y s n o w d e p t h s w e r e not m e a s u r e d o n the L F a n d L S study sites. Lichen height (m) Site EF ES LF LS SF SS Flat Steep Total  M e a n (s.d.) 2.9 3.2 3.2 3.0 2.3 2.8 2.8 3.0 2.9  (0.2) (0.4) (0.3) (0.3) (0.2) (0.3) (0.2). (0.3) (0.3)  Range 2.5-3.2 2.7-3.8 2.6-3.6 2.5-3.6 1.9-2.6 2.4-3.2 1.9-3.6 2.4-3.8 1.9-3.8  April 3-5, 1995 M e a n (s.d.) 1.6 1.8 2.1 1.9 1.4 1.4 1.7 1.7 1.7  (0.4) (0.4) (0.5) (0.4) (0.4) (0.3) (0.5) (0.4) (0.5)  May 15-16, 1994  Range  M e a n (s.d.)  0.5-2.7 0.6-2.4 0.5-3.3 0.4-3.0 0.1-2.3 0.2-2.2 0.1-3.3 0.2-3.0 0.1-3.3  0.4 (0.4) 0.2 (0.2)  Range  0.0-1.5 0.0-0.7 Not sampled Not sampled 0.1 (0.2) 0.0-0.7 0.0 (0.1) 0.0-0.6 0.3 (0.3) 0.0-1.5 0.1 (0.2) 0.0-0.7 0.2 (0.3) 0.0-1.5  Bare (%) 16.0 41.6  56.4 87.1 36.4 64.4 50.4  T h r e e factors w e r e e x p e c t e d to affect s n o w d e p t h s : m i c r o t o p o g r a p h y , c a n o p y c o v e r , a n d d i s t a n c e to the n e a r e s t c a n o p y tree. A s e x p e c t e d , April a n d M a y s n o w p a c k s w e r e g e n e r a l l y d e e p e r o n n o n - m o u n d m i c r o s i t e s , in c a n o p y g a p s , a n d farther from c a n o p y t r e e s ( a n a l y s i s of v a r i a n c e a n d K r u s k a l - W a l l i s tests; p < 0.0001 for all tests). T o further e x a m i n e the c o r r e s p o n d e n c e b e t w e e n s n o w d e p t h s a n d t h e s e microsite factors o n individual s a m p l i n g points, I plotted s n o w d e p t h s a l o n g e a c h transect (Figures 2.9 to 2.11). E a c h of t h e s e three figures c o n s i s t s of a pair of charts for e a c h of eight t r a n s e c t s from the E d w a r d s a n d S t e e l e study locations (the L e s s e r study location is not i n c l u d e d b e c a u s e M a y s n o w d e p t h s w e r e not recorded). T h e upper chart in e a c h pair plots April (solid line) a n d M a y ( d a s h e d line) s n o w d e p t h s . T h e lower chart plots proxy v a l u e s for m i c r o t o p o g r a p h y c l a s s (Figure 2.9), proxy v a l u e s for c a n o p y c o v e r (Figure 2.10), a n d actual v a l u e s for d i s t a n c e to the n e a r e s t c a n o p y tree (Figure 2.11). T h e proxy v a l u e s in t h e s e first two figures reflect e x p e c t e d s n o w d e p t h s s o that 1 = s h a l l o w e s t a n d 3 = d e e p e s t . P r o x y v a l u e s for m i c r o t o p o g r a p h i c c l a s s e s in F i g u r e 2.9 a r e : m o u n d s = 1, s l o p e microsites = 2 , a n d d e p r e s s i o n m i c r o s i t e s = 3. P r o x y v a l u e s for c a n o p y c o v e r c l a s s e s in Figure 2.10 a r e : c l o s e d c a n o p y = 1; e x p a n d e d g a p = 2; a n d c a n o p y g a p = 3 . P a t t e r n s of the lower line c a n b e c o m p a r e d to April a n d M a y s n o w d e p t h s to d e t e r m i n e the c o r r e s p o n d e n c e b e t w e e n e x p e c t e d a n d a c t u a l s n o w d e p t h s .  29  S p e a r m a n correlation v a l u e s (r ) b e t w e e n microsite factors a n d April s n o w d e p t h s a r e i n c l u d e d s  with e a c h transect. S n o w d e p t h s s h o w e d strikingly similar trends in M a y 1 9 9 4 a n d April 1 9 9 5 in spite of b e i n g m e a s u r e d in different y e a r s . T h e c o r r e s p o n d e n c e w a s c l e a r e s t o n the site with the d e e p e s t s n o w in M a y , E F ( P e a r s o n correlations for the two t r a n s e c t s : r = 0.94 a n d 0.84; F i g u r e s 2.9 to 2.11), but microsites with the least s n o w in April melted first on all t r a n s e c t s . T h e three microsite factors w e r e , h o w e v e r , imperfectly related to s n o w d e p t h s o n individual s a m p l i n g points. T h e poorest predictor of April s n o w d e p t h s o n individual s a m p l i n g points w a s m i c r o t o p o g r a p h y (Figure 2.9) while d i s t a n c e to the n e a r e s t c a n o p y tree w a s best (Figure 2.11), e s p e c i a l l y in the near perfect relationship b e t w e e n m i c r o s i t e s c l o s e to a c a n o p y tree a n d early s n o w m e l t . T h e relationship b e t w e e n the three factors a n d s n o w d e p t h s w a s positive o n all e x c e p t o n e transect, S F V , w h e r e there w a s a w e a k l y negative relationship b e t w e e n " g a p p i n e s s " a n d s n o w d e p t h s ( r = - 0 . 4 4 , p < 0.002). s  O n e of the p o s s i b l e r e a s o n s for the relatively low c o r r e s p o n d e n c e b e t w e e n microsite f a c t o r s a n d s n o w d e p t h s on individual s a m p l i n g points (Figures 2.9 to 2.11) w a s that t h e s e figures did not t a k e into a c c o u n t the c o m b i n e d effect of m o r e than o n e microsite factor. T h e proportion of m i c r o s i t e s that w e r e bare of s n o w in M a y illustrates this c o m b i n e d effect. U s i n g the three microsite factors individually, the following proportion of m i c r o s i t e s h a d m e l t e d out by M a y : 6 3 % of m o u n d s c o m p a r e d to 2 3 % of d e p r e s s i o n m i c r o s i t e s ; 6 5 % in c l o s e d c a n o p y c o m p a r e d to 4 1 % in c a n o p y g a p ; a n d 6 7 % that w e r e <2 m from the n e a r e s t c a n o p y tree c o m p a r e d to 3 8 % that w e r e >4 m from the n e a r e s t c a n o p y tree. C o m b i n i n g t h e s e f a c t o r s i n c r e a s e d d i f f e r e n c e s in melting patterns, e . g . , 8 3 % of m o u n d s in c l o s e d c a n o p y a n d <2 m f r o m the n e a r e s t c a n o p y tree w e r e bare c o m p a r e d to 8 % of d e p r e s s i o n m i c r o s i t e s in c a n o p y g a p that w e r e >4 m from the n e a r e s t c a n o p y tree.  30  F i g u r e s 2.9. S n o w d e p t h s c o m p a r e d to m i c r o t o p o g r a p h y . E a c h transect c o n s i s t s of two charts. T h e u p p e r chart plots April (upper, solid line) a n d M a y (lower, d a s h e d line) s n o w d e p t h s a l o n g the transect. T h e lower chart a p p l i e s proxy v a l u e s by microtopography: m o u n d s (mound) = 1; s l o p e microsites (slope) = 2 ; a n d d e p r e s s i o n microsites (dep.) = 3. Note that e a c h site h a s two t r a n s e c t s , o n e horizontal (e.g., E F H ) a n d o n e vertical (e.g., E F V ) . S p e a r m a n rank correlation v a l u e s ( r ) for April s n o w depths a n d m i c r o t o p o g r a p h y proxy v a l u e s a r e i n c l u d e d at the lower right of e a c h transect pair. A n asterisk indicates p < 0 . 0 5 using a B o n f e r o n n i c o r r e c t i o n . s  dep.=3 slope=2 mound=1 30  a) E F H  10  50  0  r ( A p r i l ) = 0.21  10  b) E F V  s  r ( A p r i l ) = 0.21 s  dep.=3 slope=2 mound=1 30  40  50  0  10  c) E S H  r ( A p r i l ) = 0.24  d) E S V  r (April) = 0.29  e) S F H  r (April) = 0.28  f)SFV  r ( A p r i l ) = 0.02  g) S S H  r ( A p r i l ) = 0.48*  h) S S V  r ( A p r i l ) = 0.06  s  s  dep.=3 slope=2 mound=1  s  s  300 200  dep.=3 slope=2 mound=1  s  transect d i s t a n c e (m)  s  t r a n s e c t d i s t a n c e (m)  31  F i g u r e s 2 . 1 0 . S n o w d e p t h s c o m p a r e d to c a n o p y c o v e r . E a c h transect c o n s i s t s of two charts. T h e u p p e r chart plots April (upper, solid line) a n d M a y (lower, d a s h e d line) s n o w d e p t h s a l o n g the transect. T h e lower chart a p p l i e s proxy v a l u e s by c a n o p y c o v e r : c l o s e d c a n o p y (cc) = 1; e x p a n d e d g a p (eg) = 2 ; a n d c a n o p y g a p (eg) = 3. Note that e a c h site h a s two transects, o n e horizontal (e.g., E F H ) a n d o n e vertical (e.g., E F V ) . S p e a r m a n rank correlation v a l u e s (r ) for April s n o w d e p t h s a n d c a n o p y c o v e r proxy v a l u e s are i n c l u d e d at the lower right of e a c h transect pair. A n asterisk indicates p < 0.05 using a B o n f e r o n n i correction. s  300  1 £ •8  200  1  1  1  1  -  100 1  ,  L^i—  a) E F H  r ( A p r i l ) = 0.57*  b) E F V  r ( A p r i l ) = 0.23  e) S F H  r (April) = -0.07  f) S F V  r (April) = -0.44*  g) S S H  r ( A p r i l ) = 0.36  h)SSV  r ( A p r i l ) = 0.14  s  s  s  transect d i s t a n c e (m)  s  s  s  t r a n s e c t d i s t a n c e (m)  32  F i g u r e s 2.11. S n o w d e p t h s c o m p a r e d to d i s t a n c e to the nearest c a n o p y tree. E a c h transect c o n s i s t s of two charts. T h e upper chart plots April (upper, solid line) a n d M a y (lower, d a s h e d line) s n o w d e p t h s a l o n g the transect. T h e lower chart applies actual d i s t a n c e s to the n e a r e s t c a n o p y tree (in m). Note that e a c h site h a s two transects, o n e horizontal (e.g., E F H ) a n d o n e vertical (e.g., E F V ) . S p e a r m a n rank correlation v a l u e s (r ) for April s n o w d e p t h s a n d d i s t a n c e tb the nearest c a n o p y tree are included at the lower right of e a c h t r a n s e c t pair. A n asterisk indicates p < 0.05 using a Bonferonni correction. s  300  0  10  20  a) E F H  30  40  50  r (April) = 0.71*  0  10  20  b) E F V  s  30  40  50  r (April) = 0.35* s  300  0  10  20  30  40  50  0  10  20  30  40  c) E S H  r (April) = 0.32*  d) E S V  r (April) = 0.56*  e)SFH  r (April) = 0.35*  f) S F V  r (April) = -0.23  s  s  300  300  i  g)SSH  s  ,  1  1  1  r (April) = 0.43* s  t r a n s e c t d i s t a n c e (m)  1  |  s  1  h) S S V  1  '  '  r ( A p r i l ) = 0.29 s  transect d i s t a n c e (m)  50  33  It is a l s o difficult to u s e a s i m p l e correlation to d e t e r m i n e the strength of the relationship b e t w e e n microsite factors a n d s n o w d e p t h s s i n c e s m a l l shifts b e t w e e n v a r i a b l e s r e d u c e the r  s  v a l u e . F o r e x a m p l e , p e a k s a n d troughs in s n o w d e p t h s a n d d i s t a n c e to the n e a r e s t c a n o p y tree s h o w n for the E F V a n d E S H t r a n s e c t s w e r e likely related m o r e strongly than s h o w n statistically ( r = 0.35 s  offset (Figure  a n d 0.32,  respectively) b e c a u s e they w e r e slightly, but inconsistently,  2.11). T h e r e w a s no c o n s i s t e n t e a s t - w e s t or uphill-downhill shift a s w o u l d b e  e x p e c t e d if factors s u c h a s a s p e c t or the direction of prevailing w i n d s d e t e r m i n e d s n o w patterns at this s c a l e . G a p s i z e w a s related to s n o w d e p t h s only o n the north-facing study location, E d w a r d s , w h e r e the m e d i a n April depth in g a p s >50 m (the m e d i a n size) w a s 1.8 m c o m p a r e d to 1.4  m  2  in s m a l l e r g a p s , a n d m e d i a n M a y d e p t h s w e r e 0.2 m a n d 0.0 m, respectively (lack of replication p r e v e n t e d testing). M e d i a n d e p t h s o n the s o u t h - f a c i n g study location, S t e e l e , w e r e the s a m e r e g a r d l e s s of g a p s i z e in both April (1.4 m) a n d M a y (0.0 m). T h e s e t r e n d s w e r e similar o n both flat a n d s t e e p s i t e s within e a c h study location. S n o w o n c a n o p y drip q u a d r a t s w a s not a p p r e c i a b l y d e e p e r in either April or M a y ( M a n n - W h i t n e y test; T  < 49519; p > 0.11).  Tree-Microsite Relationships Substrates U n d i s t u r b e d forest floor s u p p o r t e d m o r e s e e d l i n g s , s a p l i n g s , a n d understory t r e e s than expected  (x > 12.0; p < 0.001; T a b l e 2.8). S u r v i v a l w a s apparently higher o n u n d i s t u r b e d 2  forest floor than other s u b s t r a t e s a s it a c c o u n t e d for 80% of g r o u n d c o v e r , but s u p p o r t e d  82%  of s e e d l i n g s , 92% of s a p l i n g s , a n d 99% of understory t r e e s . M o s t other r e g e n e r a t i o n w a s c e n t r e d o n d e c a y i n g w o o d w h i c h s u p p o r t e d 9% of s e e d l i n g s but only 6% of s a p l i n g s a n d 1% of u n d e r s t o r y t r e e s . D e c a y i n g w o o d s u p p o r t e d 20% of T. mertensiana  s a p l i n g s but no T.  34  mertensiana  understory t r e e s . C o a r s e w o o d y debris s u p p o r t e d 7 % of all s e e d l i n g s , mostly n e w  g e r m i n a n t s , but no regeneration >30 c m tall. T h e r e w a s little or no relationship b e t w e e n m o s s c o v e r a n d s e e d l i n g s or s a p l i n g s . T h e highest correlation v a l u e of nine tests w a s that for m o s s c o v e r a n d A. amabilis  s e e d l i n g s , yet  e v e n this relationship w a s w e a k ( r = 0.37; p < 0 . 0 0 0 1 ; B o n f e r o n n i correction a p p l i e d ) . s  T a b l e 2 . 8 . R o o t i n g substrate of understory t r e e s , s a p l i n g s , a n d s e e d l i n g s (in p e r c e n t ) . Tsuga s e e d l i n g s w e r e not identified to s p e c i e s . T h e s a m p l e s i z e of understory t r e e s w a s limited by the difficulty in identifying s u b s t r a t e s for taller t r e e s . S e e T a b l e 2 . 5 for a k e y to a b b r e v i a t i o n s . Height class fff  Substrate dw edw  Species  n  uff  Understory trees A. amabilis C. nootkatensis T. mertensiana T. heterophylla Total  42 12 17 3 74  97.6 100.0 100.0 100.0 98.6  0.0 0.0 0.0 0.0 0.0  2.4 0.0 0.0 0.0 1.4  0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0  100.0 100.0 100.0 100.0 100.0  A. amabilis nootkatensis mertensiana heterophylla Total  402 45 40 20 507  95.3 82.2 70.0 85.0 91.7  0.0 2.2 10.0 0.0 1.0  3.7 8.9 20.0 10.0 5.7  0.2 6.7 0.0 0.0 0.8  0.5 0.0 0.0 0.0 0.4  0.2 0.0 0.0 5.0 0.4  100.0 100.0 100.0 100.0 100.0  A. amabilis nootkatensis Tsuga Total  3738 4381 3079 11198  88.0 81.8 74.0 81.7  0.0 0.3 0.3 0.2  8.1 8.6 12.2 9.4  0.7 1.2  3.1 7.7 11.4 7.2  0.0 0.4 0.7 0.4  100.0 100.0 100.0 100.0  cwd  ms  Total  Saplings C. T. T.  Seedlings C.  Microtopography  and Mound  1.4 1.1  Partners  T r e e s w e r e disproportionately c o m m o n o n m o u n d s , e s p e c i a l l y m e d i u m - s i z e d m o u n d s , a n d this pattern b e c a m e m o r e p r o n o u n c e d a m o n g taller trees (Figure 2.12). Of five height c l a s s e s , only s e e d l i n g s w e r e not o v e r - r e p r e s e n t e d o n m o u n d s (56.70 < x  2  < 486.43; p <  35  0 . 0 0 1 ) . M o u n d s o c c u p i e d only 2 8 % of the g r o u n d s u r f a c e but s u p p o r t e d 4 1 % of understory, 6 1 % of s u b - c a n o p y , a n d 9 7 % of c a n o p y t r e e s . F o r e a c h s u b - c a n o p y tree, there w e r e 2 0 8 8 s e e d l i n g s o n n o n - m o u n d microsites c o m p a r e d to only 3 2 8 s e e d l i n g s o n m o u n d s . B o t h of t h e s e results provide e v i d e n c e that trees w e r e m o s t likely to survive o n m o u n d s . C. nootkatensis m o s t likely a n d T. mertensiana  was  w a s least likely to b e l o c a t e d o n m o u n d s . T h e proportion of  s u b - c a n o p y trees o n m o u n d s w a s highest on the late-snowmelt sites, E F (87%) a n d E S (77%) a n d lowest o n the two e a r l y - s n o w m e l t sites, S F (60%) a n d S S (53%).  F i g u r e 2 . 1 2 . O b s e r v e d - t o - e x p e c t e d f r e q u e n c y of trees by m i c r o t o p o g r a p h y . T h e x - a x i s c r o s s e s the y - a x i s at a n o b s e r v e d - t o - e x p e c t e d ratio of 1.0, i.e., w h e r e the f r e q u e n c y of t r e e s w a s e q u a l to what w a s e x p e c t e d .  5 T  N o n - c a n o p y t r e e s on m o u n d s w e r e m o r e c o m m o n o n the downhill than uphill s i d e , e s p e c i a l l y a m o n g s u b - c a n o p y trees a n d o n s t e e p sites. O n s t e e p s i t e s , 4 3 % of t r e e s w e r e downhill c o m p a r e d to 8 % uphill; on flat sites, 2 5 % of trees w e r e downhill c o m p a r e d to 1 3 % uphill. T h e a p p a r e n t survival of trees w a s greater on the downhill s i d e of m o u n d s a s there w a s a higher proportion of s u b - c a n o p y than understory trees l o c a t e d o n t h e s e m i c r o s i t e s o n both s l o p e t y p e s . N o n - c a n o p y trees w e r e m o r e likely to b e o n the top of m o u n d s o n flat (21%) than  36  s t e e p (11%) s i t e s . T h e r e w a s no relationship b e t w e e n m o u n d a s p e c t (i.e., e a s t - c o m p a r e d to w e s t - f a c i n g ) a n d tree location. A total of 2 4 0 m o u n d s that s u p p o r t e d at least o n e tree w e r e c e n s u s e d . T h e m e a n n u m b e r of m o u n d partners (trees on the s a m e m o u n d ) by m o u n d s i z e w a s : 1.4 ± 0 . 6 (small), 2.8 ± 2 . 2 ( m e d i u m ) , a n d 4 . 3 ± 2 . 6 (large). At least o n e live c a n o p y tree o c c u p i e d 128 of s a m p l e d m o u n d s but only four m o u n d s s u p p o r t e d >3 c a n o p y t r e e s . M o r e than o n e c a n o p y tree of the s a m e s p e c i e s on a m o u n d w a s u n c o m m o n e x c e p t for C. nootkatensis.  T h e r e w a s no  e v i d e n c e of l a r g e - s c a l e mortality o n m o u n d s a s 1 5 % of m o u n d s i n c l u d e d o n e d e a d c a n o p y tree, but n o n e h a d m o r e . T h e r e w a s at least o n e live tree ( r e g a r d l e s s of c a n o p y layer) o n 9 2 % of m o u n d s a n d at least o n e d e a d tree o n 2 3 % of m o u n d s . M o u n d s o c c u p i e d by live C. nootkatensis  c a n o p y trees s u p p o r t e d m o r e m o u n d partners  (4.8 ± 3 . 3 ; n = 46) than t h o s e o c c u p i e d by A. amabilis ± 2 . 0 ; n = 12), or T. mertensiana  (3.4 ± 2 . 9 ; n = 29), T. heterophylla  (2.6 ± 2 . 3 ; n = 6 0 ; T a b l e 2.9). C. nootkatensis  (3.1  w a s a l s o the  m o s t c o m m o n c a n o p y tree s h a r i n g a m o u n d with o n e or m o r e other c a n o p y tree, while A. amabilis  w a s the s u b - c a n o p y a n d understory s p e c i e s m o s t c o m m o n o n c a n o p y tree m o u n d s .  T. mertensiana  w a s most likely a n d C. nootkatensis  w a s least likely to b e the only c a n o p y tree  o n a m o u n d . S u b - c a n o p y trees w e r e present o n 2 4 % of all c e n s u s e d m o u n d s a n d 2 5 % of m o u n d s with at least o n e live or d e a d c a n o p y tree. T h e s e results m a y indicate that m o u n d s a r e a m o r e important a d v a n t a g e to regeneration than the p r e s e n c e of a c a n o p y tree, e s p e c i a l l y for T.  mertensiana.  Canopy  Cover and Distance  to the Nearest  Canopy  Tree  R e g e n e r a t i o n patterns w e r e affected by proximity to the n e a r e s t c a n o p y but not o v e r h e a d c a n o p y c o v e r , e s p e c i a l l y a m o n g s u b - c a n o p y trees a n d o n flat s i t e s ( F i g u r e 2.13). W i t h i n c r e a s i n g height, regeneration w a s increasingly likely to b e o n m i c r o s i t e s that w e r e <2 m from the n e a r e s t c a n o p y tree than farther a w a y . T h e r e w e r e f e w e r s e e d l i n g s a n d s a p l i n g s than  37  e x p e c t e d o n t h e s e c l o s e r microsites (x > 2 5 . 8 2 ; p < 0.01), but 1 4 % m o r e u n d e r s t o r y t r e e s a n d 2  5 6 % m o r e s u b - c a n o p y trees than e x p e c t e d (x > 7.86; p < 0.025). C a n o p y c o v e r , in contrast, 2  w a s statistically unrelated to the location of understory or s u b - c a n o p y trees (x < 4 . 6 0 ; p > 2  0.10). Still, there w e r e m a n y s u b - c a n o p y trees in c a n o p y g a p s (Figure 2 . 1 3 a ) , e s p e c i a l l y T. mertensiana  o n s t e e p , s o u t h - f a c i n g sites, w h i c h indicated that regeneration w a s not restricted  only to tree i s l a n d s .  T a b l e 2 . 9 . Live m o u n d partners of live a n d d e a d c a n o p y t r e e s . O n l y m o u n d s that c o n t a i n e d at least o n e tree are listed (= 5 3 % of all m o u n d s s a m p l e d ) . C o l u m n s list the n u m b e r of live a n d d e a d c a n o p y trees o c c u p y i n g a m o u n d . R o w s list the n u m b e r of live m o u n d partners o c c u p y i n g the s a m e m o u n d . A b b r e v i a t i o n s : Aa = Abies amabilis; Cn Chamaecyparis nootkatensis; Tm = Tsuga mertensiana; Th = Tsuga heterophylla; unk. = u n k n o w n . C a n o p y layer M o u n d partner  S p e c i e s of live c a n o p y tree Aa  Cn  Tm  Th  Total  S p e c i e s of d e a d c a n o p y tree Aa  Cn Tsuqa  unk. Total  Live c a n o p y trees None Aa Cn Tm Th  20 1 6 2 0  27 7 7 8 2  50 2 8 2 2  8 0 2 2 1  105 10 23 14 5  1 0 0 0 0  5 1 1 1 0  5 0 3 0 0  11 4 3 0 3  22 5 7 1 3  Live s u b - c a n o p y trees None Aa Cn Tm Th  21 5 1 2 0  22 15 3 7 0  49 6 2 4 0  10 1 0 1 1  102 27 6 14 1  1 0 0 0 0  6 2 0 0 0  7 0 0 1 0  16 2 2 0 0  30 4 2 1 0  Live understory trees None Aa Cn Tm Th  15 10 3 8 2  12 30 6 14 1  30 26 4 3 0  6 4 0 3 1  63 70 13 28 4  0 1 0 0 0  3 5 3 1 1  5 3 0 0 0  12 6 1 4 3  20 15 4 5 4  Total no. of m o u n d s  29  46  60  12  147  1  8  8  20  37  38  F i g u r e 2 . 1 3 . F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of n o n - c a n o p y t r e e s by s l o p e type. Left-hand figures (a, c) present results by c a n o p y c o v e r a n d right-hand figures (b, d) p r e s e n t results by d i s t a n c e to the nearest c a n o p y tree. U p p e r figures (a, b) p r e s e n t actual f r e q u e n c i e s per hectare a n d lower figures (c, d) present ratios of o b s e r v e d f r e q u e n c i e s to t h o s e e x p e c t e d by the availability of e a c h c a n o p y c o v e r or d i s t a n c e c l a s s . S y m b o l s : understory trees = circles; s u b - c a n o p y trees = s q u a r e s ; flat sites = o p e n s y m b o l s ; s t e e p sites = solid s y m b o l s . Note that there are two s c a l e s o n the y - a x i s s c a l e in F i g u r e s (a) a n d (b). T h e y are p r e s e n t e d this w a y to highlight t r e n d s a m o n g s u b - c a n o p y trees a n d to allow c o m p a r i s o n s of s l o p e s b e t w e e n s u b - c a n o p y a n d understory trees: a similar s l o p e m e a n s that the proportional (not absolute) c h a n g e in f r e q u e n c y is similar.  canopy cover class  distance to the nearest canopy tree  (a) Frequency by canopy cover  (b) Frequency by distance to the nearest canopy tree  (c) Observed-to-expected ratio by canopy cover  (d) Observed-to-expected ratio by distance to the nearest c a n o p y tree  39  Figure 2.14. Frequency and observed-to-expected frequency of sub-canopy trees by canopy cover, distance to the nearest canopy tree, and slope. Upper figures (a) present actual frequencies per hectare and lower figures (b) present ratios of observed frequencies to those expected by the availability of each combination of canopy cover and distance class. • flat sites; • steep sites.  60 expanded gap  canopy g a p .  40  20  <2m  2-3.9m  4+m  <2m  2-3.9m  4+m  <2m  2-3.9m  4+m  distance to the nearest canopy tree  (a) Frequency per hectare  < 2 m  2-3.9 m  4+ m  <2 m  2-3.9 m  4+m  <2 m  2-3.9 m  4+m  distance to the nearest canopy tree  Most sub-canopy trees in closed canopy and expanded gap were <2 m from a canopy tree while most in canopy gap were >4 m from a canopy tree (Figure 2.14). On their own, these results are not surprising since most closed canopy microsites were close to a canopy tree and most canopy gap microsites were far from a canopy tree (Figure 2.8). What was not anticipated, however, was that microsites <2 m from a canopy tree supported more subcanopy trees than expected, regardless of canopy cover (x = 13.88; p < 0.001). This trend 2  was strongest on flat sites, where observed-to-expected ratios declined consistently with  40  increasing distance from a canopy tree. The only exception was in canopy gaps on steep sites where both actual frequencies and observed-to-expected ratios were higher >4 m from a canopy tree than 2-3.9 m from a canopy tree; most of these trees (82%) were T.  mertensiana.  These results provide evidence that tree-island processes predominate on flat sites while both gap and tree-island processes are present on steep sites. In stands where both processes are active, regeneration might be expected to be most successful on microsites close to a canopy tree and also in canopy gap, and least successful on microsites far from a canopy tree but also in closed canopy. Though this expectation was supported by the data (Figure 2.14), the rarity of these microsites (7 of each, out of a total of 600 quadrats) limited their possible impact on regeneration. Apparent survival, expressed as the ratio of sub-canopy to understory trees, was greatest for all species on closed canopy microsites on both flat and steep sites. T. mertensiana  was the species most likely, and C. nootkatensis  canopy layer in canopy gaps. T. mertensiana  least likely, to survive to the sub-  and C. nootkatensis  understory trees were the  only species present in the large, late-snowmelt canopy gaps that were especially common on flat sites. Survival on these microsites was apparently poor as they included few sub-canopy trees of any species. High and low shade affected regeneration patterns differently by species and height class (Figure 2.15). Seedlings of all species were over-represented on microsites that were in high shade but not low shade (HS, no LS); these were also the microsites most likely to be close to a canopy tree (Table 2.6) and thus receive the greatest seed rain. Two patterns emerged among saplings and understory trees (<5 m tall), one for A. amabilis and one for C. nootkatensis  and T. mertensiana.  The two patterns were most clearly displayed by the different  effect of high and low shade on understory trees. High shade had no effect on the location of A. amabilis mertensiana  (x = 0.00; p > 0.95) but was associated with fewer C. nootkatensis 2  and T.  than expected (x > 17.51; p < 0.001). In contrast, low shade had no effect on the 2  41  latter two s p e c i e s (x < 1.37; 2  expected  p > 0.10)  but w a s a s s o c i a t e d with f e w e r A. amabilis  (x = 4.15; p < 0.05). T h e a b u n d a n c e of C: nootkatensis 2  than  a n d T. mertensiana  in  u n s h a d e d m i c r o s i t e s (i.e., no H S a n d no L S ) w a s c o n s i s t e n t with their ability to s u r v i v e to the u n d e r s t o r y l a y e r j n l a t e - s n o w m e l t g a p s . U n d e r s t o r y trees of t h e s e two s p e c i e s t h u s m a t c h e d the r e g e n e r a t i o n patterns predicted by the g a p m o d e l better than did A.  amabilis.  F i g u r e 2.15. F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of s e e d l i n g s , s a p l i n g s , a n d u n d e r s t o r y trees <5 m tall by high s h a d e ( H S ) a n d low s h a d e ( L S ) . U p p e r f i g u r e s (a) p r e s e n t a c t u a l f r e q u e n c i e s per h e c t a r e a n d lower figures (b) p r e s e n t ratios of o b s e r v e d f r e q u e n c i e s to t h o s e e x p e c t e d by the availability of e a c h c o m b i n a t i o n of high s h a d e a n d low s h a d e . O A. amabilis; • C. nootkatensis; • T. mertensiana.  HS, LS noHS, HS, noHS, LS noLS noLS  HS, LS  noHS, HS, noHS, LS noLS noLS  HS, noHS, HS, noHS, LS LS noLS noLS  (a) F r e q u e n c y by high a n d low s h a d e  (b) Ratio of observed-to-expected frequencies by high a n d low s h a d e  42  Microsites under canopy drip supported more saplings than expected (x = 15.60; p < 2  0.005), but lower apparent survival removed this advantage among understory and subcanopy layers (x < 5.97; 0.05 < p < 0.10). Thirty-six percent of saplings, but only 22% of 2  understory and sub-canopy trees and 24% of quadrats, were located below canopy drip. A total of 40 gapmakers (dead trees or stumps >40 cm diameter) were present on the study plots, of which all but one uprooted tree were in various stages of decay consistent with a standing death (Figure 2.16a). Eighty-five percent of stumps were evidently long dead since they were either mostly or totally rotten (Figure 2.16b). Most gapmakers could not be identified to species due to decay, though these were likely to be A. amabilis or Tsuga since C. nootkatensis  was more easily identified (Figure 2.16c). The species mix of dead and live trees  was similar except that there were no dead sub-canopy or understory C.  Interactions  Between  Microsite  nootkatensis.  Factors  How did microtopography combine with canopy cover and distance to the nearest canopy tree to affect the location of sub-canopy trees? Microtopography was the over-riding factor as the highest frequencies and the only observed-to-expected ratios >1.0 were on mounds, regardless of canopy cover or distance class (Figure 2.17). The microsites with the most sub-canopy trees were those on mounds and most related to canopy trees, i.e., in closed canopy or <2 m from a canopy tree. C. nootkatensis  was especially likely to be restricted to  these microsites. The notable exception to these trends was on steep sites where there were many sub-canopy trees, mostly T. mertensiana, m from a canopy tree.  on non-mound microsites in canopy gap or >2  43  F i g u r e 2 . 1 6 . S u m m a r y of the 4 0 d e a d trees present o n the study plots: (a) d e a d c a n o p y t r e e s by condition; (b) c a n o p y tree s t u m p s by d e c a y c l a s s ; a n d (c) d e a d t r e e s by s p e c i e s a n d c a n o p y layer. S e e T a b l e 2.3 for definitions of d e c a y c l a s s e s .  30  30  20  10  standing  broken  stump  mostly intact  uprooted  (a) D e a d c a n o p y t r e e s by condition  mostly rotten  totally rotten  (b) C a n o p y tree s t u m p s by d e c a y c l a s s  Aa  canopy trees  partly rotten  sub-canopy trees  (c) D e a d t r e e s by s p e c i e s a n d c a n o p y layer  •  Cn  Tsuga  M  understory trees  unknown  44  F i g u r e 2 . 1 7 . F r e q u e n c y a n d o b s e r v e d - t o - e x p e c t e d f r e q u e n c y of s u b - c a n o p y t r e e s by m i c r o t o p o g r a p h y , c a n o p y c o v e r , a n d d i s t a n c e to the n e a r e s t c a n o p y tree. L e f t - h a n d figures ( a , c) p r e s e n t results by c a n o p y c o v e r a n d right-hand figures (b, d) p r e s e n t results by d i s t a n c e to the nearest c a n o p y tree. U p p e r figures ( a , b) p r e s e n t actual f r e q u e n c i e s p e r hectare a n d lower figures (c, d) p r e s e n t ratios of o b s e r v e d f r e q u e n c i e s to t h o s e e x p e c t e d by the availability of e a c h c a n o p y c o v e r or d i s t a n c e c l a s s . A b b r e v i a t i o n s : c c = c l o s e d c a n o p y ; e g = e x p a n d e d g a p ; eg = c a n o p y g a p . • flat s i t e s ; • steep sites.  80  80  60  60  40  40  20  20  -tmound, mound, mound, cc  eg  eg  no  no  no  mound, mound, cc  eg  mound,  <2m  2-3.9m  4+m  <2m  no 2-3.9m  no mound, 4+m  (b) Frequency by distance to the nearest canopy tree  A  3 -•  2  no  no  o  2 •  £  1  /  no  \  mound mound mound cc £  no  mound, mound,  eg  (a) Frequency by canopy cover  V.  -t-  mound, mound, mound,  eg -+-  1 mound, mound, cc  eg  eg -+-  mound, eg  (c) Ratio of observed-to-expected frequencies by canopy cover  mound, mound, <2m  2-3.9m  no no no mound mound mound \ <2m 2-3.9m 4+m  mound, 4+m  (d) Ratio of observed-to-expected frequencies by distance to the nearest canopy tree  45  Growth Rates and  Microsites  M o s t n o n - c a n o p y A. amabilis  trees grew slowly: m e d i a n height i n c r e m e n t s w e r e 1  c m / y r for understory trees a n d 10 c m / y r for s u b - c a n o p y trees. M e d i a n relative growth rates, e x p r e s s e d a s the a n n u a l height growth per c m of height, w e r e higher for s u b - c a n o p y t r e e s (0.010 c m / c m / y r , or 1% per yr) than understory trees (0.006 c m / c m / y r , or 0 . 6 % p e r yr; M a n n W h i t n e y test; T = 1 0 1 1 4 ; p < 0.002). Relative growth rates w e r e 2 0 % higher for u n d e r s t o r y t r e e s a n d 4 5 % higher for s u b - c a n o p y trees o n flat sites c o m p a r e d to s t e e p s i t e s (t-test for s u b c a n o p y t r e e s ; t = - 2 . 5 7 ; p =0.015; M a n n - W h i t n e y test for understory t r e e s ; T = 3 1 6 1 4 ; p = 0 . 0 2 1 ) , a n u n e x p e c t e d result given that growing s e a s o n s w e r e shorter o n flat s i t e s . T h e only statistically significant relationship b e t w e e n microsite factors a n d relative growth rates w a s that understory trees grew 2 9 % faster o n m o u n d s ( M a n n - W h i t n e y test; T = 3 9 3 9 8 ; p = 0.006). T h o u g h low s a m p l e s i z e s p r e v e n t e d further statistical testing, contrasting t r e n d s for understory a n d s u b - c a n o p y trees w e r e evident. A m o n g understory t r e e s , relative growth rates w e r e highest in c a n o p y g a p a n d >2 m from a c a n o p y tree. S u b - c a n o p y t r e e s , h o w e v e r , g r e w a s fast in c l o s e d c a n o p y a s c a n o p y g a p (and 1 0 % faster than in e x p a n d e d g a p ) , a n d > 1 4 % faster o n microsites <2 m from a c a n o p y tree than t h o s e farther a w a y . R e l a t i v e growth rates w e r e a l s o r e c o r d e d by high a n d low s h a d e c o n d i t i o n s for A.  amabilis  u n d e r s t o r y t r e e s <5 m tall. L o w s h a d e w a s a s s o c i a t e d with 4 3 % s l o w e r growth ( M a n n - W h i t n e y test; T = 1 4 5 2 3 ; p < 0 . 0 0 0 1 ) , while high s h a d e h a d no effect ( M a n n - W h i t n e y test; T = 2 8 0 4 5 ; p = 0.553).  Growth Form  Anomalies  M o s t understory trees h a d m o r e than o n e growth form a n o m a l y , though f e w w e r e e x t r e m e . T h e majority w e r e s t e m a n o m a l i e s , e s p e c i a l l y pistol butts, s t e m s w e e p s , a n d d o g legs (definitions of t h e s e t e r m s are i n c l u d e d a s A p p e n d i x B ) . U m b r e l l a growth f o r m s w e r e m u c h m o r e c o m m o n a m o n g A. amabilis  (80%) than other s p e c i e s (13%). Part of this  46  difference w a s likely b e c a u s e the determinate growth form of A. amabilis s h a p e m o r e o b v i o u s . Tsuga a n d C. nootkatensis  m a d e the u m b r e l l a  w e r e m o r e likely to be bent in s t e m s w e e p or  prostrate growth f o r m s , e s p e c i a l l y in late-snowmelt g a p s . M o r e e x t r e m e a n o m a l i e s , like b r o k e n t o p s , d o g l e g s , pistol butts, a n d s t e m s w e e p s , w e r e e s p e c i a l l y c o m m o n o n l a t e - s n o w m e l t a n d rock wall m i c r o s i t e s a n d s o w e r e likely c a u s e d by the weight or m o v e m e n t of s n o w . A l m o s t all u n d e r s t o r y tree s t e m s h a d m a n y c a l l u s e s that indicated n u m e r o u s b r e a k s of the terminal l e a d e r , likely a l s o d u e to s n o w . T h e f r e q u e n c y a n d severity of t h e s e c a l l u s e s w a s not quantified. T h e r e w a s no e v i d e n c e to s h o w that c a n o p y c o v e r , p r e s e n c e of c a n o p y drip, or m i c r o t o p o g r a p h y w e r e related to growth form a n o m a l i e s . Tsuga, e s p e c i a l l y in the s u b - c a n o p y layer, w a s most likely to h a v e a pistol b u t t - s h a p e d lower s t e m . Pistol-butted s t e m s apparently straightened with height growth a s they w e r e least c o m m o n a n d s e v e r e in the c a n o p y layer. C a n o p y trees h a d s e v e r e pistol butt (i.e., >50 c m horizontal d i s t a n c e ) in <10% of c a s e s . S u b - c a n o p y T. mertensiana  a n d C. nootkatensis  had  the highest i n c i d e n c e of s e v e r e pistol butt with >30% of trees affected. L e s s than 1% of all t r e e s h a d pistol butts with a horizontal d i s t a n c e of >100 c m . S l o p e did not affect the i n c i d e n c e or severity of pistol butt.  2.4  Discussion  Are microsites, snow, and regeneration patterns related? T h o u g h m e a n s n o w d e p t h s w e r e related to microsite factors, s n o w on individual s a m p l i n g points (every 0.5 m) w a s surprisingly variable. G i v e n this variability, t r e e - b a s e d rather than q u a d r a t - b a s e d m e a s u r e m e n t s w o u l d h a v e b e e n preferable. N e v e r t h e l e s s , the s t r o n g c o r r e s p o n d e n c e b e t w e e n microsite factors a n d s n o w , a n d b e t w e e n microsite f a c t o r s a n d r e g e n e r a t i o n , s h o w s the impact of s n o w on regeneration patterns. C o n s i s t e n t with the treeisland m o d e l of r e g e n e r a t i o n , survival w a s highest o n m o u n d s a n d m i c r o s i t e s c l o s e to a c a n o p y tree, both of w h i c h w e r e in turn related to longer growing s e a s o n s .  47  W h i l e site a n d microsite factors affected patterns of s n o w a c c u m u l a t i o n ( m e a s u r e d in April), their impact w a s most a p p a r e n t in h o w they affected s n o w m e l t ( m e a s u r e d in m i d - M a y ) . T h e o p e n n e s s of the c a n o p y o n s o m e sites (especially E F ) w a s a s s o c i a t e d with, a n d a p p a r e n t l y c a u s e d by, d e e p a n d late-melting s n o w that affected r e g e n e r a t i o n patterns. T h e s e g a p s w e r e up to o n e tree height in diameter, w h i c h is the s i z e that retains s n o w l o n g e s t ( G o l d i n g a n d S w a n s o n 1 9 7 8 ; B e r r y a n d Rothwell 1992). T h e m o s t o b v i o u s effect of s n o w in l a t e - s n o w m e l t g a p s w a s the rarity of c a n o p y tree s t u m p s or live s u b - c a n o p y t r e e s . S u c h g a p s h a v e not s u p p o r t e d c a n o p y trees for m a n y c e n t u r i e s nor a r e they likely to in the n e a r future. L a t e s n o w m e l t in g a p s therefore contributes to the greater o p e n n e s s of t h e s e s t a n d s c o m p a r e d to t h o s e in lower-elevation, g a p - d r i v e n s y s t e m s (reviewed in L e r t z m a n 1 9 8 9 ) . O v e r h e a d c a n o p y c o v e r d i d not prove to be a useful predictor of r e g e n e r a t i o n patterns in t h e s e s t a n d s . T h e distinction b e t w e e n microsites that a r e in g a p s a n d t h o s e that a r e not b e c o m e s l e s s c l e a r with i n c r e a s i n g elevation a s overall c a n o p y o p e n n e s s ( g a p p i n e s s ) i n c r e a s e s . T h o u g h I k n o w of n o quantification for this a s s e r t i o n , light levels b e l o w the c a n o p y a r e a l m o s t certainly higher a n d more h o m o g e n e o u s in t h e s e s t a n d s than in old-growth s t a n d s at lower e l e v a t i o n s . T r e e s a r e not a s tall, their b r a n c h e s a r e shorter, there is a limited s u b c a n o p y layer, a n d g a p s remain uninhabited for longer. T h e result, c o m b i n e d with the low a n g l e of g r o w i n g s e a s o n sunlight at t h e s e latitudes ( B r o o k e etal. 1 9 7 0 ; C a n h a m etal. 1 9 9 0 ; v a n Pelt 1 9 9 5 ) , is a n i n c r e a s e d i m p o r t a n c e of diffuse light a n d s u n f l e c k s with a predictably l e s s e r i n f l u e n c e of g a p p r o c e s s e s . A t s o m e point in the elevational transition from g a p to t r e e - i s l a n d p r o c e s s e s , the relationship b e t w e e n c a n o p y c o v e r a n d regeneration m u s t therefore d e c r e a s e s o m u c h a s to b e unimportant. D u e to the o v e r w h e l m i n g c o v e r a n d i m p o r t a n c e of u n d i s t u r b e d forest floor, a n d in c o n t r a s t to other s y s t e m s s h a r i n g o n e or all of the s a m e g e n e r a , r e g e n e r a t i o n patterns w e r e not strongly affected by substrate heterogeneity. In other s y s t e m s , r e g e n e r a t i o n is disproportionately c o m m o n o n 'disturbed' s u b s t r a t e s , t h o s e that a r e p r o d u c t s of d i s t u r b a n c e s  48  too recent to allow the formation of a thick h u m u s layer, e . g . , d e c a y i n g w o o d , c o a r s e w o o d y d e b r i s , a n d mineral soil (Minore 1 9 7 2 ; C h r i s t y a n d M a c k 1 9 8 4 ; A n t o s a n d Z o b e l 1 9 8 6 , H a r m o n a n d Franklin 1 9 8 9 ; L e r t z m a n 1 9 9 2 ; D a n i e l s 1994). Disturbed s u b s t r a t e s a r e important in m o r e continental s u b a l p i n e forests of w e s t e r n North A m e r i c a a s w e l l , e s p e c i a l l y for the r e g e n e r a t i o n of Picea (e.g., K n a p p a n d S m i t h 1 9 8 2 ; H a r v e y etal. 1 9 8 7 ; V a r g a 1997). W h y w e r e d i s t u r b e d s u b s t r a t e s s o unimportant h e r e ? T h e c o m m o n explanation for the a b u n d a n c e of regeneration o n c o a r s e w o o d y d e b r i s in other s y s t e m s is that its elevation off the forest floor r e d u c e s competition ( H a r m o n a n d Franklin 1 9 8 9 ; L e r t z m a n 1989) or prevents burying by litter (Thornburgh 1 9 6 9 ; C h r i s t y a n d M a c k 1 9 8 4 ) . E l e v a t e d microsites w e r e a s s o c i a t e d with s u c c e s s f u l regeneration h e r e , a s d e m o n s t r a t e d by the a b u n d a n c e of trees o n m o u n d s (mostly f o r m e d o v e r b o u l d e r s ) . B u t a l m o s t all s u c h m o u n d s w e r e c o v e r e d by h u m u s to a depth of at least 10 c m w h i c h s h o w e d that m a n y y e a r s h a d p a s s e d s i n c e the last d i s t u r b a n c e . T h e s e factors a r g u e a g a i n s t a n important role for anything but the most d e c a y e d w o o d , i.e., that w h i c h is b e i n g i n c o r p o r a t e d into the forest floor. T h e y a l s o s u g g e s t that w h e r e s t u m p r e m a i n s a r e f o u n d b e n e a t h a c a n o p y tree, a s p r e v i o u s l y reported in the M H z o n e ( P e t e r s o n 1964; L e r t z m a n 1989), the e s t a b l i s h m e n t of the c a n o p y tree w a s likely p o s s i b l e only after h u m u s h a d f o r m e d o v e r the stump. T w o p o s s i b l e r e a s o n s for the l e s s e r i m p o r t a n c e of w o o d y s u b s t r a t e s f o u n d here a r e : (1) native M H s p e c i e s m a y b e l e s s a d a p t e d to t h e s e s u b s t r a t e s than the P a c i f i c N o r t h w e s t s p e c i e s usually cited a s c o l o n i z i n g t h e m , T. heterophylla  a n d Picea s p p . ; a n d (2) r e g e n e r a t i o n m a y b e  rooted i n s e c u r e l y in w o o d y s u b s t r a t e s , e s p e c i a l l y c o a r s e w o o d y d e b r i s , a n d therefore m o r e s u s c e p t i b l e to uprooting through s n o w c r e e p . A third r e a s o n m a y b e that m a n y s t u d i e s , e s p e c i a l l y t h o s e b a s e d o n e x p e r i m e n t a l d a t a , rely o n results from only the first f e w y e a r s after germination (e.g., C h r i s t y a n d M a c k 1 9 8 4 ; H a r m o n a n d Franklin 1 9 8 9 ; H a r v e y etal. 1 9 8 7 ; N a k a m u r a 1992). A s H a r m o n a n d Franklin (1989) c a u t i o n , a f o c u s o n e s t a b l i s h m e n t rather  49  than survival m a y o v e r - e s t i m a t e the i m p o r t a n c e of s o m e s u b s t r a t e s e s p e c i a l l y if, a s in the c a s e of c o a r s e w o o d y d e b r i s , future mortality m a y b e higher than o n the forest floor. In contrast to w o o d y s u b s t r a t e s , the lack of regeneration o n mineral soil likely resulted f r o m the rarity of s o i l - e x p o s i n g windthrows a n d its resulting unavailability a s a s u b s t r a t e . T. mertensiana,  A. amabilis,  a n d C. nootkatensis  are k n o w n to r e g e n e r a t e s u c c e s s f u l l y o n  m i n e r a l soil ( B u r n s a n d H o n k a l a 1990), a n d this w a s s h o w n by the a b u n d a n t r e g e n e r a t i o n of t h e s e s p e c i e s o n the o n e windthrow microsite within the study plots. T h e neutral or w e a k l y positive relationship b e t w e e n m o s s c o v e r a n d r e g e n e r a t i o n patterns c o n t r a s t s with two other s t u d i e s . H a r m o n a n d Franklin (1989) e x p l a i n the p o o r r e g e n e r a t i o n o n m o s s in their study a s d u e to competition b e t w e e n trees a n d the m o s s , but primarily w h e n m o s s m a t s a r e m u c h thicker (>10 c m ) than s e e n a m o n g the m o s s s p e c i e s d e s c r i b e d h e r e . T h o u g h N a k a m u r a (1992) f o u n d lower mortality for 2 y e a r - o l d s e e d l i n g s o n m o s s than o n other s e e d b e d s , he did not c o m p a r e mortality rates o n m o s s to t h o s e o n u n d i s t u r b e d forest floor nor did he track later s u r v i v a l . S n o w c r e e p c a n exert e x t r e m e downhill p r e s s u r e s in high s n o w a r e a s ( H u z i o k a et al. 1 9 6 7 ; M a c k a y a n d M a t h e w s 1 9 6 7 ; B r o o k e e r a / . 1 9 7 0 ; L o w e r y 1972), but its i m p a c t o n r e g e n e r a t i o n patterns here c a n only b e inferred. T h e strong t e n d e n c y of n o n - c a n o p y t r e e s to b e downhill of m o u n d s , e s p e c i a l l y o n s t e e p sites, s u g g e s t s that s n o w c r e e p r e d u c e d s u r v i v a l o n the uphill s i d e (Williams 1 9 6 6 ; B r o o k e etal. 1 9 7 0 ; L e a p h a r t etal. 1 9 7 2 ; L o w e r y 1 9 7 2 ; M e g a h a n a n d S t e e l e 1 9 8 7 , 1988). That the proportion of individuals downhill of m o u n d s w a s g r e a t e r a m o n g s u b - c a n o p y than understory trees s u p p o r t s this e x p l a n a t i o n .  Do regeneration patterns reflect the gap or tree-island model? R e g e n e r a t i o n patterns c o n s i s t e n t with t h o s e predicted by the t r e e - i s l a n d m o d e l a n d , to a l e s s e r d e g r e e , t h o s e predicted by the g a p m o d e l , s h o w that the study s t a n d s o c c u p y a transition b e t w e e n high- a n d low-elevation e c o s y s t e m s . A s e x p e c t e d in s u c h a transition, r e g e n e r a t i o n patterns w e r e not c o n s i s t e n t a m o n g s p e c i e s or sites a n d w e r e a p p a r e n t l y related  50  to the impact of s n o w . F o r e x a m p l e , regeneration o n late-snowmelt s i t e s w a s more.likely to m a t c h the t r e e - i s l a n d m o d e l than regeneration on e a r l y - s n o w m e l t s i t e s . W h i l e I u s e d n o n c a n o p y t r e e s to r e a c h this c o n c l u s i o n , it is a l s o reflected in the c o m p o s i t i o n of c a n o p y t r e e s . T h e s p e c i e s b e s t a d a p t e d to h e a v y s n o w , C. nootkatensis 1 9 7 0 ) , o u t n u m b e r e d A. amabilis  a n d T. mertensiana  ( B r o o k e et al.  in e a c h c a n o p y layer o n only o n e site, E F , the site with the  latest s n o w m e l t . A n d the s p e c i e s best a d a p t e d to lower e l e v a t i o n s , 7". heterophylla,  reached  the c a n o p y layer o n only three sites: both s o u t h - f a c i n g s t e e p s i t e s ( S S a n d L S ) a n d the flat site with the earliest s n o w m e l t ( S F ) . S p e c i e s c o u l d a l s o b e differentiated by their regeneration patterns. C.  nootkatensis  r e g e n e r a t i o n m a t c h e d the tree-island m o d e l most c l o s e l y a s it w a s m o s t c o m m o n o n m o u n d s a n d n e a r to a c a n o p y tree. T. mertensiana  s h o w e d m o r e of a m i x e d pattern s i n c e it w a s a b l e to  r e g e n e r a t e both c l o s e to a c a n o p y tree a n d , e s p e c i a l l y on s t e e p , s o u t h - f a c i n g s i t e s , in c a n o p y g a p s . Its u s e of m o u n d s w a s a l s o l e s s than the other s p e c i e s . T h e difference b e t w e e n t h e s e s p e c i e s m a y b e related to their e c o l o g i c a l n i c h e s . That is, the r e g e n e r a t i o n of a s p e c i e s n e a r the u p p e r limit of its elevational range ( s u c h a s C. nootkatensis) s n o w than a s p e c i e s in the middle of its range s u c h a s T.  m a y b e m o r e restricted by  mertensiana.  W h e r e r e g e n e r a t i o n follows the g a p m o d e l , the d e a t h of o n e or m o r e c a n o p y t r e e s s h o u l d l e a d to the faster growth of n o n - c a n o p y trees in the n e w g a p . H o w e v e r , m o s t g a p s w e r e not c a u s e d by the recent d e a t h of a c a n o p y tree (as s h o w n by the a b s e n c e or a d v a n c e d d e c a y of g a p m a k e r s ) . N o r w a s there a n y e v i d e n c e that trees e n t e r e d the c a n o p y layer by s u d d e n l y growing faster (releasing) a s w o u l d be e x p e c t e d under the g a p m o d e l : m o s t c a n o p y t r e e s h a d a history of growing slowly a n d steadily. T h e only p o s s i b l e e x c e p t i o n w a s T. mertensiana  w h i c h t e n d e d to grow faster o n c e it r e a c h e d a breast-height d i a m e t e r of - 1 0 c m .  T h i s result w a s b a s e d o n 12 s a m p l e s that w e r e not in c l o s e proximity to e a c h other, a n d w o u l d likely h a v e b e e n subject to different o v e r h e a d c a n o p y conditions. T h e similarity of the d i a m e t e r at w h i c h they b e g a n to grow faster s u g g e s t s that the c a u s e w a s growth a b o v e the s n o w p a c k  51  rather than the formation of n e w g a p s (though there m a y b e a relationship b e t w e e n the two). O t h e r r e s e a r c h e r s h a v e a l s o h y p o t h e s i z e d that trees larger than about 10 c m at b r e a s t height a v o i d b e i n g t r a p p e d under s n o w during the winter a n d s o c a n t a k e a d v a n t a g e of a longer g r o w i n g s e a s o n (Brink 1 9 5 9 ; B r o o k e e r a / . 1 9 7 0 ; L e r t z m a n 1989). T h o u g h the growth patterns of understory A. amabilis  w e r e similar to t h o s e p r e d i c t e d by  the g a p m o d e l (faster growth in c a n o p y g a p s a n d far from c a n o p y trees), the contrasting trends for s u b - c a n o p y trees m o r e c l o s e l y m a t c h e d the tree-island m o d e l . S m a l l s a m p l e s i z e s a m o n g s u b - c a n o p y t r e e s a n d the a b s e n c e of growth rate d a t a for T. mertensiana  a n d C.  nootkatensis  allow only tentative c o n c l u s i o n s to be m a d e , but t h e s e are trends supporting other results a l r e a d y p r e s e n t e d , i.e., that the location a n d growth rates of understory trees are not n e c e s s a r i l y g o o d indicators of the future d e v e l o p m e n t of a s t a n d . T h e implicit a s s u m p t i o n throughout this study h a s b e e n that the p r e s e n t growth e n v i r o n m e n t is representative of past conditions. F r o m o n e p e r s p e c t i v e , this a s s u m p t i o n m a y b e r e a s o n a b l e . T h e p r e v a l e n c e of v e r y old trees, single s n a g s , a n d a thick h u m u s layer (also reported by B r o o k e etal. 1 9 7 0 a n d L e r t z m a n 1989) s u g g e s t that the study s t a n d s h a v e b e e n at a similar s t a g e of d e v e l o p m e n t (true old-growth, sensu Oliver a n d L a r s o n 1990) for m a n y c e n t u r i e s . H o w e v e r , the c y c l e from germination to s e n e s c e n c e is long e n o u g h to s p a n major climatic fluctuations that undoubtedly alter the proportion of precipitation falling a s s n o w . R e g e n e r a t i o n patterns, s o strongly affected by s n o w , w o u l d therefore by c h a n g e d a n d the e l e v a t i o n a l b a n d that c o n t a i n s the transition from g a p to t r e e - i s l a n d p r o c e s s e s w o u l d a c c o r d i n g l y m o v e higher or lower. T h e forested M H s u b z o n e , the e x p r e s s i o n of this transition, is therefore not fixed at a certain elevation.  2.5  Conclusions R e g e n e r a t i o n patterns in the study s t a n d s represent a transition from the g a p m o d e l to  the t r e e - i s l a n d m o d e l a n d are related to s n o w , particularly patterns of s n o w m e l t . T h e tree-  52  i s l a n d m o d e l is e x p r e s s e d most clearly o n late-snowmelt sites a n d by C. nootkatensis, s p e c i e s n e a r the upper limit of its r a n g e . T. mertensiana,  a  a s p e c i e s in the middle of its r a n g e , is  c a p a b l e of regenerating near c a n o p y trees a n d , e s p e c i a l l y o n e a r l y - s n o w m e l t s i t e s , in c a n o p y gaps. R e g e n e r a t i o n patterns a r e important b e y o n d their theoretical interest. T h i s s t u d y s h o w s that i n c r e a s e d s n o w restricts regeneration to microsites protected by a n o v e r h e a d c a n o p y , e v e n w h e r e d i s c r e t e tree i s l a n d s a r e not present. R e g e n e r a t i o n patterns a r e therefore e c o l o g i c a l indicators of site severity a n d s h o u l d b e c o n s i d e r e d w h e n m a n a g e m e n t d e c i s i o n s a r e m a d e . F o r e x a m p l e , they c o u l d be u s e d to help delineate the three m a n a g e m e n t c l a s s e s p r o p o s e d by K l i n k a etal. (1992) for s t a n d s in the f o r e s t e d M H s u b z o n e : (1) s t a n d s w h e r e r e g e n e r a t i o n after cutting is likely to be problem-free, though s l o w ; (2) s t a n d s that a r e m a r g i n a l for timber production d u e to potential regeneration p r o b l e m s a n d the i m p o r t a n c e of other, n o n timber v a l u e s ; a n d (3) s t a n d s unsuitable for cutting. I believe that t h e s e c l a s s e s c o i n c i d e (at least roughly) with s t a n d s w h e r e regeneration patterns m a t c h : (1) the g a p m o d e l ; (2) a transition b e t w e e n g a p a n d tree-island m o d e l s ; a n d (3) the t r e e - i s l a n d m o d e l . R e g e n e r a t i o n patterns c o u l d b e i n c l u d e d in site r e c o n n a i s s a n c e to quantify the p r e s e n c e of patterns m a t c h i n g the tree-island m o d e l , a n d therefore to estimate site severity. S p e c i f i c a l l y , s u c h a r e c o n n a i s s a n c e s h o u l d quantify the proportion of s u b - c a n o p y t r e e s o n m o u n d s a n d c l o s e to c a n o p y trees c o m p a r e d to t h o s e in c a n o p y g a p s . T h e s e indicators c o u l d then b e b o l s t e r e d by s t a n d a r d m e a s u r e s of site classification ( G r e e n a n d K l i n k a 1 9 9 4 ) including: height of the c a n o p y layer, s p e c i e s c o m p o s i t i o n (especially the proportion of T. heterophylla  c o m p a r e d to T. mertensiana),  percent c a n o p y c l o s u r e , indicator plant a n a l y s i s  ( K l i n k a etal. 1989), a n d date of s n o w m e l t . S u c h a classification w o u l d b e valid w h e t h e r the m a n a g e m e n t f o c u s w a s timber, water, wildlife, recreation, or w i l d e r n e s s .  53  Chapter 3. Natural Regeneration on Clearcut Sites  3.1  Introduction T h e b e s t m e t h o d for regenerating l o g g e d sites in the M H z o n e r e m a i n s u n c l e a r after  a p p r o x i m a t e l y 3 0 y e a r s of logging history. E v e r s i n c e early regeneration failures w e r e linked to s l a s h b u r n i n g a n d the planting of unsuitable, low-elevation s p e c i e s ( R e u t e r 1 9 7 3 ; U t z i g a n d H e r r i n g 1 9 7 4 ; K l i n k a a n d P e n d l 1976), most sites h a v e b e e n left to r e g e n e r a t e naturally. T h o u g h this c h a n g e h a s i m p r o v e d results, K l i n k a et al. (1992) identified a n u m b e r of silvicultural c o n c e r n s within the z o n e , m a n y of w h i c h c e n t r e d on the role of natural r e g e n e r a t i o n . B a s e d o n t h e s e c o n c e r n s , I undertook a s u r v e y of naturally-regenerating s i t e s to a n s w e r the following q u e s t i o n s : 1.  W a s natural regeneration s u c c e s s f u l ?  2.  D i d m o s t natural regeneration establish before or after l o g g i n g ?  3.  W h i c h s u b s t r a t e s f a v o u r e d natural r e g e n e r a t i o n ?  4.  W h i c h m i c r o t o p o g r a p h i c locations f a v o u r e d natural r e g e n e r a t i o n ?  5.  D i d competition with Vaccinium  i m p e d e natural r e g e n e r a t i o n ?  T h i s c h a p t e r c o m p l e m e n t s the study of regeneration patterns in old-growth s t a n d s in C h a p t e r 2 a n d , w h e r e appropriate, I c o m p a r e results from clearcut a n d old-growth s i t e s .  3.2  Methods  Study Area T h e s t u d y a r e a a n d its old-growth s t a n d s are d e s c r i b e d in S e c t i o n 2 . 2 . S i m i l a r s t a n d s at e l e v a t i o n s <1100 m w e r e clearcut b e t w e e n 1 9 7 5 a n d 1 9 8 5 then left to r e g e n e r a t e naturally without s l a s h b u r n i n g or planting. Vaccinium  alaskaense  ( A l a s k a blueberry) d o m i n a t e s the n o n -  tree v e g e t a t i o n o n t h e s e c l e a r c u t s . O t h e r s h r u b s that are locally a b u n d a n t include V. ovalifolium  ( o v a l - l e a v e d blueberry), V. membranaceum  (black huckleberry),  Rhododendron  54  albiflorum  (white-flowered r h o d o d e n d r o n ) , a n d Menziesia  ferruginea  (false a z a l e a ) . V e r y little  light r e a c h e s the g r o u n d under t h e s e s h r u b s s o little e l s e g r o w s other than a minor c o v e r of Cornus  canadensis  Rhytidiopsis Dicranum  (bunchberry), Rubus pedatus  robusta  (five-leaved b r a m b l e ) , a n d m o s s e s s u c h a s  ( p i p e c l e a n e r m o s s ) , Polytrichum  s p p . Epilobium  angustifolium  Drier s i t e s m a y support Linnaea  juniperinum  (juniper h a i r c a p m o s s ) , a n d  (fireweed) is c o m m o n o n m i c r o s i t e s without  borealis  (twinflower) a n d Hieracium  h a w k w e e d ) , while wetter s i t e s support Lysichitum viride (Indian hellebore), Coptis asplenifolia  americanum  albiflorum  Vaccinium.  (white-flowered  (skunk c a b b a g e ) ,  Veratrum  (fern-leaved goldthread), a n d Sphagnum  spp.  (peat m o s s e s ) . A c o m p l e t e list of s p e c i e s is i n c l u d e d a s A p p e n d i x A .  Study Design I e s t a b l i s h e d three study locations in c l e a r c u t s that h a d b e e n l o g g e d 1 1 - 1 2 y e a r s prior to s a m p l i n g (Figure 2.1). E a c h study location c o n s i s t e d of o n e 'flat' site ( 2 2 - 2 4 % s l o p e ) a n d o n e s t e e p site ( 4 9 - 5 3 % s l o p e ) for a total of six sites (Figure 2 . 2 a ; T a b l e 3.1). E l e v a t i o n s a b o v e s e a level r a n g e d from 1 0 6 0 - 1 1 0 0 m. I l o c a t e d t r a n s e c t s a n d 1 m microsite q u a d r a t s a s fully 2  d e s c r i b e d in S e c t i o n 2.2 a n d s h o w n in Figure 2 . 2 b .  T a b l e 3 . 1 . C l e a r c u t study site d e s c r i p t i o n s . Site c o d e s c o m b i n e the first initial of the s t u d y location a n d the s l o p e type, e . g . , B F signifies B a t c h e l o r Flat. S o i l moisture r e g i m e s ( S M R ) a n d soil nutrient r e g i m e s ( S N R ) follow K l i n k a etal. (1989). S M R a b b r e v i a t i o n s : F = f r e s h ; M = moist; V M = v e r y moist. S N R a b b r e v i a t i o n s : P = poor; M = m e d i u m .  Study location  Slope type  Site code  Elevation  Slope  (m)  (%)  Batchelor  Flat Steep  BF BS  1070 1090  24 50  Mayne  Flat Steep  MF MS  1080 1100  22 49  Tannis  Flat Steep  TF TS  1060 1090  23 53  Y e a r of logging  SMR  SNR  1981 1981  M/VM M  P P  198 (S) 190 (S)  1981 1981  M/VM F  P/M P  191 (S) 192 (S)  1982 1982  M F  P P  Aspect (deg. azim.) 24 (NE) 24 (NE)  55  S t u d y locations w e r e s e l e c t e d to meet the following criteria: (1) c o n s t a n t s o u t h or north a s p e c t ; (2) s t e e p site directly a b o v e or near flat site; (3) limited e d a p h i c variation; (4) similar d a t e of logging with e n o u g h d e l a y to d i s p l a y regeneration; (5) not b u r n e d or p l a n t e d ; (6) n o s k i d r o a d s or other s e v e r e logging d i s t u r b a n c e ; (7) a b u n d a n t Vaccinium; r e p r e s e n t a t i o n of T. heterophylla.  a n d (8) limited  T o allow c o m p a r i s o n s , I attempted to m a t c h the a s p e c t s a n d  s l o p e s of s t u d y locations in c l e a r c u t s with t h o s e of the old-growth s t a n d s d e s c r i b e d in C h a p t e r 2 ( T a b l e 2.1). H o w e v e r , p r o g r e s s i v e logging left old-growth s t a n d s only at e l e v a t i o n s higher than c l e a r c u t s for all e x c e p t the north-aspect pairing of the B a t c h e l o r a n d E d w a r d s s t u d y l o c a t i o n s . I a l s o i n t e n d e d to test the effect of forest e d g e s on natural r e g e n e r a t i o n , but the f e w forest e d g e s left in the study a r e a did not m e e t m y s e l e c t i o n criteria. T h e B a t c h e l o r a n d M a y n e study locations w e r e at lower e l e v a t i o n s of the W i n d w a r d M o i s t M a r i t i m e ( M H m m l ) biogeoclimatic variant of the M H z o n e ( G r e e n a n d K l i n k a 1994). M a p s p r e p a r e d by the B . C . Ministry of F o r e s t s (1992) s h o w the T a n n i s study location b e l o w the M H b o u n d a r y , within the M o n t a n e V e r y W e t Maritime ( C W H v m 2 ) variant of the C W H z o n e . H o w e v e r , t h e s e m a p s w e r e p r e p a r e d at a s c a l e that w a s too c o a r s e to distinguish the v a r i a b l e transition b e t w e e n z o n e s in the study a r e a (Brett 1996). A c l o s e r i n s p e c t i o n of the T a n n i s study location s h o w e d a slightly greater p r e s e n c e of T. mertensiana  than T. heterophylla,  especially  o n flatter portions, w h i c h met the definition of the M H rather than the C W H z o n e .  Data Collected Site a n d microsite s a m p l i n g m e t h o d s w e r e the s a m e a s d e s c r i b e d for old-growth s i t e s ( S e c t i o n 2.2), e x c e p t that c a n o p y c o v e r classification w a s u n n e c e s s a r y a n d a g e s w e r e s a m p l e d differently. T o relate tree a g e s a n d heights, I r a n d o m l y s a m p l e d two trees of e a c h s p e c i e s a n d f r o m e a c h 10 c m height c l a s s (10-149 cm) from microsite q u a d r a t s at e a c h s t u d y l o c a t i o n . S i n c e t r e e s >150 c m tall w e r e a l m o s t a l w a y s m u c h older than the a g e of the c l e a r c u t (as s h o w n by visible height r e l e a s e a n d c o n f i r m e d by limited destructive s a m p l i n g ) , further  56  destructive s a m p l i n g w a s restricted to trees <150 c m tall. F i v e s e e d l i n g s , of e a c h d e v e l o p m e n t a l s t a g e (Figure 2.5) a n d s p e c i e s , a n d from e a c h study location, w e r e a l s o r a n d o m l y s a m p l e d . W h e n tree or s e e d l i n g s a m p l e s w e r e u n a v a i l a b l e within microsite q u a d r a t b o u n d a r i e s , I s a m p l e d adjacent individuals (if present). All s a m p l e s w e r e e x c a v a t e d or cut to include their root collar. S a m p l e s w e r e s a n d e d or re-cut with a r a z o r b l a d e , c h a l k e d a n d / o r w e t t e d to better differentiate rings, then rings w e r e c o u n t e d using a 4 0 x b i n o c u l a r m i c r o s c o p e . D u e to i n c o m p l e t e or m i s s i n g rings, reported a g e s s h o u l d be c o n s i d e r e d m i n i m a . W h e n s a m p l e s s h o w e d a d r a m a t i c i n c r e a s e in the rate of d i a m e t e r growth (diameter r e l e a s e ) , I e s t i m a t e d the n u m b e r of y e a r s s i n c e r e l e a s e by counting the n u m b e r of rings o u t w a r d from the point at w h i c h ring widths noticeably i n c r e a s e d . A d d i t i o n a l d a t a w e r e r e c o r d e d in the field for trees that s h o w e d e v i d e n c e of a d r a m a t i c i n c r e a s e in the rate of height growth (height r e l e a s e ) . Height r e l e a s e w a s clearly d i s p l a y e d in the growth w h o r l s of A. amabilis nootkatensis  a n d Tsuga.  a n d s o m e w h a t l e s s clearly in the a n n u a l i n c r e m e n t s of C.  I m e a s u r e d r e l e a s e height to the n e a r e s t 0.1 m a n d r e c o r d e d the  n u m b e r of y e a r s s i n c e height r e l e a s e . W h e r e p o s s i b l e , t h e s e d a t a i n c l u d e d two t r e e s from e a c h 10 c m height c l a s s >150 c m tall.  Data Analysis A n a l y t i c a l m e t h o d s are d e s c r i b e d fully in C h a p t e r 2. T h e following only e x p l a i n s d e v i a t i o n s from that d e s c r i p t i o n . Ages:  M y m a i n g o a l in s a m p l i n g a g e s w a s to d e t e r m i n e the proportion of t r e e s that  w e r e a l r e a d y e s t a b l i s h e d at the time of logging (residuals, or a d v a n c e regeneration), a n d t h o s e that e s t a b l i s h e d after logging (ingress). A g e s w e r e s a m p l e d o v e r a r a n g e of h e i g h t s to d e r i v e a r e g r e s s i o n line a n d predict the a g e distribution of u n s a m p l e d trees but, s i n c e a g e s w e r e poorly related to heights (Figure 3.1), trees w e r e instead g r o u p e d into a g e c l a s s e s . In addition to a g e c l a s s e s that I t e r m e d r e s i d u a l s a n d i n g r e s s , I identified a third a g e c l a s s (germinants) b e c a u s e there w a s a distinct group of trees that g e r m i n a t e d b e t w e e n 1 y e a r before a n d 1 y e a r after  57  logging (Figure 3 . 1 ; T a b l e 3.2). T h e a g e distribution w a s then e s t i m a t e d within e a c h study location by multiplying the proportion of r e s i d u a l s , g e r m i n a n t s , a n d i n g r e s s s a m p l e d in e a c h 10 c m height c l a s s by the f r e q u e n c y of all trees in that height c l a s s . Substrate:  T o f o c u s on s u b s t r a t e s inhabited by t r e e s , " u n a v a i l a b l e " s u b s t r a t e s including  logging s l a s h , rock, a n d s t u m p s w e r e r e m o v e d from c h i - s q u a r e a n d c o n t i n g e n c y table a n a l y s e s (only 1 tree, 11 c m tall, w a s growing o n a n y of t h e s e s u r f a c e s ) . A s a result, x  2  values  for the r e m a i n i n g "available" s u b s t r a t e s are m o r e c o n s e r v a t i v e ( b e c a u s e e x p e c t e d v a l u e s a r e higher) but are a l s o more likely to differentiate b e t w e e n t h e s e s u b s t r a t e s .  Figure 3 . 1 . Jitter plot of heights of s a m p l e d trees a n d s e e d l i n g s on the y e a r of their e s t a b l i s h m e n t (n = 210). D a t a points are offset from e a c h other (jittered) s o that ail c a n b e s e e n . T h e y e a r of e s t a b l i s h m e n t is reported relative to the y e a r of l o g g i n g s o that negative v a l u e s indicate trees a n d s e e d l i n g s that e s t a b l i s h e d b e f o r e l o g g i n g , positive v a l u e s indicate e s t a b l i s h m e n t after logging, a n d z e r o v a l u e s indicate e s t a b l i s h m e n t during the y e a r of logging. N o trees w e r e f o u n d that e s t a b l i s h e d > 8 y e a r s after l o g g i n g . T h e -5 c l a s s includes all trees that e s t a b l i s h e d 5 or m o r e y e a r s b e f o r e l o g g i n g .  500 400  I  —  I  I  I  I  l  I  I  i  i  i  i  i  «  300  ingress  germinants  residuals  E o  I  o  P  o  n  ffi 200 - ?>  0  „ o  */.  * o  100  %  0  <#  •  « o«  *<> o  0 a 0  0 -2  +1  +2  +4  +5  +6  establishment year (relative to logging)  +7 +8  58  T a b l e 3.2. Definition of t e r m s u s e d in C h a p t e r 3. N o t e that the definition for t r e e s in C h a p t e r 3 i n c l u d e s what w e r e c a l l e d s a p l i n g s in C h a p t e r 2.  Term  Definition  Seedling  A n y tree s p e c i e s <10 c m tall.  Tree  A n y tree s p e c i e s > 10 c m tall.  Ingress  T r e e s a n d s e e d l i n g s e s t a b l i s h e d >2 y e a r s after l o g g i n g .  Germinant  T r e e s a n d s e e d l i n g s e s t a b l i s h e d within ±1 y e a r of l o g g i n g .  Residual  T r e e s a n d s e e d l i n g s e s t a b l i s h e d >2 y e a r s before logging ( a d v a n c e regeneration).  Vaccinium:  A tree is c o n s i d e r e d free-growing in B . C . if it m e e t s m i n i m u m height  r e q u i r e m e n t s or, w h e n growing a m i d s t other vegetation (e.g. Vaccinium)  is 1.25 t i m e s the  height of that v e g e t a t i o n ( B . C . Ministry of F o r e s t s 1995). T o project the n u m b e r of y e a r s it w o u l d t a k e t r e e s growing b e l o w Vaccinium  to b e c o m e f r e e - g r o w i n g , I u s e d m e a n A.  amabilis  growth rates within e a c h 10 c m height c l a s s (the height growth of the other s p e c i e s w a s too difficult to d i s c e r n , e s p e c i a l l y w h e n they w e r e s u p p r e s s e d ) . I projected future growth by a d d i n g the i n c r e m e n t that c o r r e s p o n d e d to a tree's height c l a s s to that tree's height, r e p e a t i n g until it r e a c h e d the next c l a s s , then a d d i n g the appropriate i n c r e m e n t from this next c l a s s . I r e p e a t e d this p r o c e s s until the tree w a s 125 c m tall (using the a s s u m p t i o n that Vaccinium  seldom grew  taller than 1 0 0 c m ) . Stocking:  S t o c k i n g is a m e a s u r e of the distribution of f r e e - g r o w i n g trees ( s e e a b o v e )  that are a l s o w e l l - s p a c e d . T h e B . C . Ministry of F o r e s t s (1995) a p p l i e s a m i n i m u m inter-tree s p a c i n g of 2 m, a n d only o n e free-growing tree within that s p a c i n g contributes to s t o c k i n g . T o d e t e r m i n e s t o c k i n g , I c o m b i n e d two microsite q u a d r a t s to c r e a t e o n e 2 m cell then c a l c u l a t e d 2  the p r e s e n c e or a b s e n c e of at least o n e free-growing tree within that cell. T o project future s t o c k i n g , I u s e d growth projections a s d e s c r i b e d in the p a r a g r a p h a b o v e , but with o n e modification. F o r trees growing without s u r r o u n d i n g v e g e t a t i o n , but b e l o w m i n i m u m height r e q u i r e m e n t s , I projected the n u m b e r of y e a r s to e x c e e d that m i n i m u m height.  59  3.3  Results  Structure, Composition, and Age A. amabilis  w a s the most c o m m o n s p e c i e s overall a n d for t r e e s >150 c m tall (Figure  3.2). C. nootkatensis was  w a s a s a b u n d a n t a s A. amabilis  in shorter height c l a s s e s while  Tsuga  least c o m m o n throughout the height r a n g e . T h e tallest r e c o r d e d tree w a s 4 . 3 5 m in  height. S i n c e only o n e Pinus monticola was  D o u g l . e x D . D o n (western white pine) w a s r e c o r d e d it  e x c l u d e d from further a n a l y s i s . W h e n there is a constant i n g r e s s of s e e d l i n g s , a s o n the old-growth s i t e s of C h a p t e r 2 ,  height distributions follow a n i n v e r s e - J s h a p e with f r e q u e n c i e s d e c r e a s i n g e x p o n e n t i a l l y from shorter to taller height c l a s s e s . T h e relative scarcity of s e e d l i n g s o n clearcut s i t e s , h o w e v e r , s h o w e d that i n g r e s s w a s not constant, e s p e c i a l l y for A. amabilis.  T h e r e w e r e only 1 2 3 3  s e e d l i n g s / h a o n clearcut sites ( c o m p a r e d to 1 8 7 , 0 0 0 / h a o n old-growth sites), a n d n o n e e s t a b l i s h e d in the 4 y e a r s before s a m p l i n g . M o s t s e e d l i n g s (64%) w e r e restricted to o n e site, B F , a n d 5 0 % of all s e e d l i n g s w e r e C. nootkatensis  ( F i g u r e s 3.2 a n d 3.3). Within e a c h s t u d y  location, flat s i t e s h a d m o r e s e e d l i n g s than s t e e p sites.  F i g u r e 3 . 2 . Height distribution of trees a n d s e e d l i n g s b y s p e c i e s .  1000  C. nootkatensis  A. amabilis  to JZ CD CL  B-  1000 CO  750  T. mertensiana  500  CT CD  CD  750  o  500  c  CD  1000  T. heterophylla  CD  CT 2 5 0  250  CD fiffififyrrr^  0 C  M  ^  f  C  O  C  O  O  O  f/y/ywjS^ U  T  l  O  i  i  C  O  1  0  0  1  0 > 0 > 0 C M ^ C  0 > 0 ) 0 D C O O 1-  upper limit of height class (cm)  > C J > 0 C M ^ C T-  } 0 > O C O T-  T-  + O  O CM  upper limit of height class (cm)  60  Figure 3.3. Height distribution of trees and seedlings by species and site. Key to species abbreviations: Aa = Abies amabilis; Cn = Chamaecyparis nootkatensis; Tm = Tsuga mertensiana;  Th = Tsuga  heterophylla.  6000  6000  Batchelor Flat (BF)  Tannis Flat (TF)  4000  4000  4000  2000  2000  2000  6000  6000  Tannis Steep (TS)  _  6000  Batchelor Steep (BS)  6000  Mayne Steep (MS)  Mayne Flat (MF)  4000  4000  4000  2000  2000  2000  upper limit of height class (cm)  61  S i n c e s i t e s h a d a similar n u m b e r of trees >150 c m tall, the large d i f f e r e n c e s in their height distributions w e r e c a u s e d mainly by different f r e q u e n c i e s of shorter t r e e s a n d s e e d l i n g s (Figure 3.3). T h r e e sites ( B F , B S , a n d T F ) h a d m a n y m o r e s e e d l i n g s a n d t r e e s <150 c m tall than the r e m a i n i n g three sites ( T S , M F , a n d M S ) . T h e B F site s u p p o r t e d the m o s t r e g e n e r a t i o n <150 c m tall (31,300 s t e m s / h a ) , followed by the B S a n d T S sites (10,800 a n d 9 , 8 0 0 s t e m s / h a , r e s p e c t i v e l y ) . D e n s i t i e s o n the three l e s s - p o p u l a t e d sites w e r e 2 5 0 0 - 4 6 0 0 s t e m s / h a . T h e m a g n i t u d e of t h e s e differences w a s not a p p a r e n t w h e n s e l e c t i n g s i t e s s i n c e m o s t shorter t r e e s were hidden under A. amabilis  Vaccinium. w a s present throughout the height range on all s i t e s but w a s m o s t  a b u n d a n t o n the two north-facing sites, B F a n d B S . C. nootkatensis flat than s t e e p site of e a c h study location. T. mertensiana heterophylla  w a s m o r e c o m m o n o n the  w a s m u c h m o r e a b u n d a n t than T.  o n north-facing sites a n d slightly m o r e a b u n d a n t o n three of four s o u t h - f a c i n g  s i t e s (all e x c e p t the T S site). T h e T S site h a d few T. heterophylla  (500/ha) a n d no T.  mertensiana. A. amabilis  trees grew faster on clearcut than old-growth s i t e s ( M a n n - W h i t n e y test of  relative growth rates; T = 1 4 9 9 5 5 ; p < 0.0001) a n d height growth o n clearcut s i t e s w a s positively related to height ( P e a r s o n correlation o n natural l o g - t r a n s f o r m e d d a t a ; r = 0 . 8 3 ; p < 0 . 0 0 0 1 ; F i g u r e 3.4). T h e m e a n height of r e s i d u a l s at r e l e a s e w a s 4 7 . 7 ± 3 4 . 2 c m (n = 62) a n d r a n g e d f r o m 42.1 ± 2 1 . 5 c m for C. nootkatensis  to 6 0 . 0 ± 3 6 . 1 c m for T. heterophylla.  Maximum  height at r e l e a s e w a s 170 c m . T h e r e w a s a d e l a y of 2.9 ± 1 . 6 y e a r s before d i a m e t e r r e l e a s e a n d height r e l e a s e o c c u r r e d a l m o s t 2 y e a r s later, 4.8 ± 1 . 3 y e a r s after l o g g i n g . M e a n height growth rate of t r e e s before a n d after r e l e a s e w a s 3.2 c m / y r a n d 18.6 c m / y r , r e s p e c t i v e l y , a n d their m e a n a g e w a s 4 8 . 5 ± 1 4 . 6 y e a r s . O n l y 2 0 % of all trees a n d s e e d l i n g s e s t a b l i s h e d m o r e than o n e y e a r after logging (Figure 3.5a). Of t h o s e that e s t a b l i s h e d earlier, 3 5 % w e r e r e s i d u a l s a n d 4 5 % w e r e g e r m i n a n t s . T h e r e w a s no i n g r e s s of A. amabilis  >5 y e a r s after logging a n d no i n g r e s s of a n y s p e c i e s >8  62  y e a r s after logging. T h e majority (76%) of residuals w e r e A. amabilis of all g e r m i n a n t s a n d i n g r e s s w e r e C. nootkatensis.  T. mertensiana  while a p p r o x i m a t e l y half w a s almost evenly  distributed a m o n g a g e c l a s s e s but s h o w e d relatively strong i n g r e s s . T. heterophylla  h a d the  f e w e s t residuals. T h e n u m b e r of residuals w a s similar a c r o s s height c l a s s e s but their proportion of regeneration i n c r e a s e d with height (Figure 3.5b). A l m o s t all trees >150 c m tall w e r e r e s i d u a l s . A l m o s t all (94%) ingress and 6 4 % of g e r m i n a n t s w e r e <50 c m tall. Destructive s a m p l i n g of trees revealed that m o r e w e r e r e s i d u a l s than w a s originally r e c o r d e d during non-destructive s a m p l i n g . E x c a v a t i o n s r e v e a l e d very thick root b a s e s , s p r o u t i n g , and/or re-orienting of c r u s h e d b r a n c h e s a n d s t e m s . F o r e x a m p l e , what a p p e a r e d to b e s e v e r a l s e p a r a t e , 2 m tall a n d s e x u a l l y mature C. nootkatensis  turned out to b e b r a n c h e s of  a s i n g l e tree c r u s h e d during l o g g i n g .  F i g u r e 3.4. Height growth of A. amabilis on clearcut s i t e s (n=295) a n d old-growth s i t e s (n=434). N o s e e d l i n g s (height <10 cm) are i n c l u d e d . 50  40 E  30 ©  c  © f t  ©  20 © ©  ©•  10  ©©  « 9  ©  ©  ©© « • © ooo© © o© ©  * © « ©  «  100  200  300  400  500  100  200  height (cm)  height (cm)  C l e a r c u t sites  300  Old-growth sites  500  63  F i g u r e 3.5. E s t i m a t e d a g e c l a s s distribution: (a) by s p e c i e s , a n d (b) by height c l a s s .  4000 A. amabilis  CD C. nootkatensis  residual  H  T. mertensiana  germinant  H  T. heterophylla  ingress  (a) E s t i m a t e d a g e c l a s s distribution b y s p e c i e s  4000 residual  germinant 3 ingress  3000 >> 2000 p 1000  <50  Ml  50-99  100-149  150+  height class (cm)  (b) E s t i m a t e d a g e c l a s s distribution b y height c l a s s  D i f f e r e n c e s in the a b u n d a n c e of g e r m i n a n t s a n d i n g r e s s c a u s e d m o s t of the variation in height distributions a m o n g sites s i n c e the f r e q u e n c y of r e s i d u a l s , e s p e c i a l l y t h o s e >150 c m tall, w a s similar (Figure 3.6). T h r e e sites ( B F , B S , a n d T F ) h a d m a n y m o r e i n g r e s s a n d g e r m i n a n t s than the r e m a i n i n g three s i t e s ( T S , M F , a n d M S ) , a n d there w e r e m o r e i n g r e s s a n d g e r m i n a n t s o n the flat site of e a c h study location pairing. T h e M S site w a s e s p e c i a l l y u n d e r p o p u l a t e d b y g e r m i n a n t s a n d i n g r e s s a s A. amabilis r e s i d u a l s m a d e up 9 0 % of r e g e n e r a t i o n . Within e a c h s t u d y location, the flat site h a d m o r e g e r m i n a n t s a n d i n g r e s s than the s t e e p site.  64  F i g u r e 3 . 6 . E s t i m a t e d a g e c l a s s distribution by height c l a s s a n d site. N o t e that the s c a l e for the B a t c h e l o r Flat ( B F ) site is slightly different than for other s i t e s .  Tannis Flat (TF) 12000  12000  8000  8000  4000  4000  <50  5s  Tannis Steep (TS)  50-99  100-149  150+  <50  100-149  height class (cm)  Mayne Flat (MF)  Mayne Steep (MS)  12000  12000  8000  8000  4000  4000  <50  50-99  height class (cm)  50-99  100-149  height class (cm)  150+  <50  50-99  100-149  height class (cm)  150+  150+  65  Substrates Relative to adjacent old-growth stands (Chapter 2), there was less undisturbed forest floor and much more friable forest floor (Table 3.3). Logging slash more than tripled the proportion of coarse woody debris on clearcut sites compared to old-growth sites. Undisturbed forest floor on clearcut sites covered 55% of the ground surface on flat sites compared to 27% on steep sites. Steep sites had more friable forest floor (especially on the TS site), logging slash, and exposed rock than flat sites. Friable forest floor consisted of a Mormoder humus form (Green etal. 1993) that indicated greater biological activity than the Mor humus form of undisturbed forest floor (Green and Bernardy 1991). There was virtually no mineral soil. Unavailable substrates (logging slash, rock, and stumps) covered 32% of the ground surface compared to 11% on old-growth sites. Moss cover was lower on clearcut (5%) than old-growth (42%) sites. Table 3.3. Percent cover of substrates by site. Key: uff = undisturbed forest floor; fff = friable forest floor; dw = decaying wood; edw = exposed decaying wood; ms = mineral soil. Slash includes both naturally-occurring coarse woody debris (= CWD in Table 2.5) and logging slash. The stump class also includes standing trees on old-growth sites. Available substrates  Unavailable substrates  Site  uff  fff  dw  edw  ms  slash  rock  stump Total  BF BS MF MS TF TS  59.4 41.5 57.1 38.3 49.4 27.4  8.2 11.5 9.4 12.3 11.6 30.2  7.5 8.7 8.6 7.5 4.6 5.3  0.7 2.5 0.9 3.8 1.6 1.3  0.0 0.0 0.2 0.0 0.0 0.0  20.8 28.4 22.3 31.4 25.8 21.5  0.9 0.2 0.0 4.7 0.4 8.9  2.6 7.2 1.6 2.2 6.7 5.7  100.0 100.0 100.0 100.0 100.0 100.1  clearcut total old-growth total  45.5 80.0  13.8 0.2  7.0 7.1  1.8 0.9  0.0 0.6  25.0 7.1  2.5 0.8  4.3 3.4  100.0 100.0  Undisturbed forest floor supported more trees and seedlings of each species than expected (4.84 < x < 71.81; 0.0001 < p < 0.05; Figure 3.7), and even more than on old-growth 2  sites (28% compared to 4% more than expected on clearcut and old-growth sites, respectively). Friable forest floor and exposed decaying wood supported the least regeneration  66  relative to their a b u n d a n c e . Tsuga w e r e the only trees a n d s e e d l i n g s m o r e c o m m o n than e x p e c t e d o n a s u b s t r a t e other than undisturbed forest floor ( d e c a y i n g w o o d ) , but they w e r e still >4 t i m e s m o r e c o m m o n o n undisturbed forest floor. S i n c e taller trees w e r e m o r e likely to b e o n u n d i s t u r b e d forest floor than w e r e shorter trees a n d s e e d l i n g s , survival w a s likely g r e a t e r o n that s u b s t r a t e for all s p e c i e s e x c e p t T. heterophylla  (Figure 3.8). U n d i s t u r b e d forest floor  s u p p o r t e d >90% of regeneration r e g a r d l e s s of a g e c l a s s .  F i g u r e 3.7. O b s e r v e d - t o - e x p e c t e d ratio o n available s u b s t r a t e s by s p e c i e s . T h e f r e q u e n c y of t r e e s a n d s e e d l i n g s o n a substrate (observed) is c o m p a r e d to the p e r c e n t c o v e r of that s u b s t r a t e (expected). K e y to s p e c i e s a b b r e v i a t i o n s : Aa = Abies amabilis; Cn = Chamaecyparis nootkatensis; Tm = Tsuga mertensiana; Th = Tsuga heterophylla.  I  undisturbed forest floor  d  friable forest floor  ED decaying wood  2.00  2 T3 B o  1.73 1.34  1.38  1.29 1.14  CD  Q. <> j  exposed decaying wood  1.00  E3  E2  Es3 0.29 I  0.28 0.00  1r  0.51  0.4: 0.12  Iii  1.14  0.41  0.28 0.14  0.10  0.26  F i g u r e 3.8. T r e e s a n d s e e d l i n g s o n undisturbed forest floor by s p e c i e s a n d height c l a s s (in percent). Note that the y - a x i s d o e s not e x t e n d to z e r o . 100 T  <50  50-99 height class (cm)  100+  67  Microtopography and Logging Slash T r e e s w e r e not o v e r - r e p r e s e n t e d on m o u n d s in c l e a r c u t s a s they w e r e in old-growth s t a n d s (Figure 3.9). O n flat sites, trees w e r e o v e r - r e p r e s e n t e d o n d e p r e s s i o n m i c r o s i t e s a n d u n d e r - r e p r e s e n t e d o n s l o p e microsites (x > 2 1 . 4 3 ; p < 0.001), but unrelated to m o u n d s (x 2  2  0 . 0 1 4 ; p > 0.90). M o s t trees on d e p r e s s i o n microsites w e r e C. nootkatensis mertensiana.  =  a n d T.  O n s t e e p sites, trees w e r e o v e r - r e p r e s e n t e d o n s l o p e m i c r o s i t e s a n d u n d e r -  r e p r e s e n t e d o n m o u n d s (x  2  > 5.22; p < 0.025), but unrelated to d e p r e s s i o n m i c r o s i t e s (x  2  =  3 . 2 6 ; 0 . 0 5 < p < 0.10). O n l y 1 2 % of i n g r e s s w e r e located on m o u n d s c o m p a r e d to 2 2 % of r e s i d u a l s a n d g e r m i n a n t s . It is u n c l e a r w h y i n g r e s s w e r e u n a b l e to take a d v a n t a g e of t h e s e l e s s - p o p u l a t e d m i c r o s i t e s o n either flat or s t e e p sites, but it m a y h a v e b e e n related to the lower proportion of u n d i s t u r b e d forest floor o n m o u n d (36%) than n o n - m o u n d (49%) m i c r o s i t e s . A s o n old-growth sites, more trees growing o n m o u n d s w e r e l o c a t e d downhill of the m o u n d o n s t e e p s i t e s (53%) than flat sites ( 3 1 % ; x = 4 . 2 8 ; p = 0.039); f e w w e r e l o c a t e d uphill 2  of m o u n d s o n either s t e e p (6%) or flat (10%) sites. F e w e r trees than e x p e c t e d w e r e l o c a t e d b e s i d e logging s l a s h (fallen logs) on flat sites (x = 3 1 . 5 9 ; p < 0.001), but o n s t e e p s i t e s there 2  w a s n o relationship (x = 1.85; p > 0.10). A m o n g trees that w e r e growing b e s i d e l o g g i n g s l a s h , 2  m o r e w e r e l o c a t e d downhill than uphill: 4 5 % c o m p a r e d to 2 5 % on flat s i t e s , a n d 6 3 % c o m p a r e d to 2 0 % o n s t e e p sites, respectively.  F i g u r e 3.9. O b s e r v e d - t o - e x p e c t e d ratio of trees by m i c r o t o p o g r a p h i c c l a s s o n (a) c l e a r c u t s i t e s , a n d (b) old-growth sites. C l e a r c u t d a t a include trees >10 c m tall, but old-growth d a t a include only understory trees >130 c m tall. O flat sites; • s t e e p sites.  mound  slope  depression  mound  slope  depression  68  Vaccinium  Though at least some Vaccinium was found on 88% of clearcut and 90% of old-growth quadrats, it was taller and had greater cover on clearcut sites (0.70 m and 53%, respectively) than old-growth sites (0.51 m and 28%, respectively). Though not quantified, Vaccinium  on  clearcuts was also denser (had a higher leaf area index) than on old-growth sites, so microsites below Vaccinium  were far darker. The percent cover of Vaccinium  was higher on  flat (59%) than steep (46%) sites, but heights were similar between slope types.  Vaccinium  cover was positively, though weakly, related to the cover of undisturbed forest floor (Pearson correlation on arcsine square root-transformed data; r = 0.54; p < 0.0001). Of all trees, 84% were on microsites with Vaccinium surrounding Vaccinium  and 52% were shorter than the  (Figure 3.10). A. amabilis was more common than expected on  microsites with Vaccinium  while other species, particularly T. heterophylla,  were less common  than expected, (x > 5.10; p < 0.025). Germinants were under-represented on 2  Vaccinium  microsites (x = 5.50; p < 0.025), though most (78%) were still associated with it. 2  Vaccinium  was unrelated to the location of either ingress (90%) or residuals (92%, x < 0.73; p > 0.75). 2  Figure 3.10. Height of trees relative to  A. amabilis  Did Vaccinium above Vaccinium  Vaccinium.  C nootkatensis  T. mertensiana  T. heterophylla  slow height growth or reduce vigour? A. amabilis grew fastest amidst but  (14.8 ±11.2 cm/year), less quickly without Vaccinium  slowest below Vaccinium  (7.9 ±8.3 cm/year), and  (2.0 ±2.3 cm/year). This range of growth rates, however, was  69  related to a tree's a b s o l u t e height (F = 1 8 3 . 6 ; p < 0.0001) rather than its height relative to Vaccinium  ( F = 0 . 7 3 4 ; p = 0.533), e.g., shorter trees g r e w m o r e slowly r e g a r d l e s s of  Vaccinium  ( A N O V A of natural log-transformed height increment c o v a r i e d with natural l o g - t r a n s f o r m e d height). Vaccinium Vaccinium  w a s similarly unrelated to tree vigour a s trees growing o n m i c r o s i t e s with  w e r e e q u a l l y v i g o r o u s a s t h o s e growing without. T h e r e w e r e n o d e a d t r e e s or trees  likely to d i e within o n e y e a r (vigour <2), r e g a r d l e s s of Vaccinium  cover.  D u r i n g the y e a r of s a m p l i n g , 3 5 8 3 t r e e s / h a ( 3 4 % of all trees) w e r e f r e e - g r o w i n g a c c o r d i n g to B . C . Ministry of F o r e s t s (1995) guidelines, i.e., either growing without or >1.25 of Vaccinium  Vaccinium  height (Figure 3.11). W i t h c o n t i n u e d growth, a n additional 2 4 1 7 a n d  2 2 0 0 t r e e s / h a will b e a d d e d after 10 a n d 2 0 y e a r s , respectively. A l l trees a n d s e e d l i n g s currently g r o w i n g o n the study sites will b e >1.25 the height of Vaccinium  within 4 5 y e a r s .  Without additional i n g r e s s , the s p e c i e s mix of free-growing trees will r e m a i n similar o v e r the next 4 5 y e a r s . A. amabilis  a n d C. nootkatensis  r e s p e c t i v e l y , while T. mertensiana  will i n c r e a s e from 4 3 to 4 7 % a n d 3 3 to 3 5 % ,  a n d T. heterophylla  will d e c r e a s e from 15 to 1 2 % a n d 9 to  6%, respectively. F i g u r e 3 . 1 1 . P r o j e c t e d f r e q u e n c y a n d s p e c i e s c o m p o s i t i o n of trees >1.25 t i m e s the height of Vaccinium, the height c o n s i d e r e d b y the B . C . Ministry of F o r e s t s (1995) to b e f r e e g r o w i n g . Height growth rates a r e b a s e d o n the a n n u a l height i n c r e m e n t of A. amabilis within e a c h 1 0 c m height c l a s s , w h i c h w e r e a d d e d iteratively to e a c h tree's height. T h e y e a r of s a m p l i n g is y e a r 0.  I  A. amabilis  O C nootkatensis  d  T. mertensiana  H  T. heterophylla  9000  I§ CD CD  J=  6000  3000  .-•••lllll 0  5  10  15  20  25  years after sampling  30  35  40  45  70  Stocking T h e B . C . Ministry of F o r e s t s (1995) a s s e s s e s post-logging r e g e n e r a t i o n in the M H z o n e in t w o s t a g e s : (1) a s t o c k i n g s u r v e y d e t e r m i n e s w h e t h e r there is a n a d e q u a t e distribution of w e l l - s p a c e d t r e e s that are e c o l o g i c a l l y appropriate for the site; a n d (2) a f r e e - g r o w i n g s u r v e y 8 y e a r s later d e t e r m i n e s w h e t h e r a m i n i m u m n u m b e r of w e l l - s p a c e d t r e e s a r e >1.25 the height of n o n - c r o p v e g e t a t i o n o r taller than a m i n i m u m height.  1  B y 1 9 9 2 , 10-11 y e a r s after l o g g i n g  a n d o n e y e a r before s a m p l i n g , all sites h a d satisfied the m i n i m u m s t o c k i n g s t a n d a r d ( M S S ) of 5 0 0 s t e m s / h a , though n o n e w a s a b o v e the target s t o c k i n g s t a n d a r d ( T S S ) of 9 0 0 s t e m s / h a ( B . C . Ministry of F o r e s t s 1 9 9 2 ; A p p e n d i x C ) . S i n c e regeneration c a n b e p a t c h y e v e n o n s i t e s that e x c e e d the M S S (Klinka et al. 1992), I u s e d a f i n e r - s c a l e m e t h o d for a s s e s s i n g its distribution in the y e a r of s a m p l i n g , then e s t i m a t e d growth rates to c r e a t e a projected distribution 1 0 y e a r s later. T h e s t o c k i n g p e r c e n t a g e s p r e s e n t e d h e r e a r e therefore not directly c o m p a r a b l e to Ministry of F o r e s t c a l c u l a t i o n s but rather indicate the relative p a t c h i n e s s of r e g e n e r a t i o n o n the s i x s i t e s . T h e l e g a c y of taller r e s i d u a l s (>150 cm) o n the s i x sites limited d i f f e r e n c e s in s t o c k i n g at the time of s a m p l i n g a s s t o c k i n g r a n g e d from 1 8 % ( M S ) to 3 8 % ( B F ; F i g u r e 3.12). D i f f e r e n c e s b e t w e e n s i t e s , h o w e v e r , will i n c r e a s e after 10 y e a r s of c o n t i n u e d growth d u e to d i f f e r e n c e s in the a b u n d a n c e of shorter trees. A v e r a g e s t o c k i n g o n the three s i t e s with m o r e short t r e e s ( B F , B S , a n d T F ) will i n c r e a s e from 3 5 % to 6 3 % c o m p a r e d to a n i n c r e a s e from 2 4 % to only 3 3 % o n the three sites with fewer short trees ( M F , M S , a n d T S ) .  1  Stocking guidelines for the M H m m l variant (B.C. Ministry of Forests 1995) are:  •  Minimum heights by species: 0.60 m for A. amabilis ; 1.0 m for C. nootkatensis and 7. mertensiana; and (CWHvm2 variant only) 1.75 m for T. heterophylla.  •  Minimum height relative to neighboring vegetation (free-growing height): 1.25 times the height of neighboring vegetation within a 1 m radius.  •  Well-spaced guidelines: 2 m spacing (3.14 m diameter) between free-growing trees.  71  F i g u r e 3 . 1 2 . S t o c k i n g during the y e a r of s a m p l i n g a n d projected s t o c k i n g after 10 y e a r s . B l a c k b a r s indicate the p r e s e n c e of at least o n e free-growing tree m e e t i n g m i n i m u m height g u i d e l i n e s ( B . C . Ministry of F o r e s t s 1995). S i t e s include o n e horizontal t r a n s e c t (charts o n left) a n d o n e vertical transect (charts o n right). Within e a c h transect, s t o c k i n g 0 y e a r s (upper) a n d 10 y e a r s (lower) after s a m p l i n g are p r e s e n t e d . P e r c e n t s t o c k i n g after 0 a n d 10 y e a r s is listed at the lower right of e a c h site. P r o j e c t e d s t o c k i n g is b a s e d o n A.  amabilis growth rates.  III II  0 yrs  I II llll  10yrs  III I III II mill i mumii site stocking after 0 and 10 years:  Batchelor Flat (BF)  0 yrs  10 yrs  I  I II  I II  I  Hill Mill III III  O)  10 yrs  _c Q. E a  I II I II llll I i mini ii IIII i  i  site stocking after 0 and 10 years:  d) i_  ((B 0 <TJ  0 yrs  I  i_  10 yrs  I  HI M l  O  II  10 yrs  II II  III II II 1IU II II  10 yrs  I  1 I  II I Mill  Mayne Steep (MS)  horizontal transect distance (2m quadrats)  36%, 56%  1  II I 26%, 34%  I I I I III site stocking after 0 and 10 years:  Mayne Flat (MF)  Oyrs  I I II  site stocking after 0 and 10 years:  Tannis Steep (TS)  0 yrs  30%,, 64%  I Mil I I IIII urn i I I  Tannis Flat (TF)  (0  II II II  site stocking after 0 and 10 years:  Batchelor Steep (BS)  0 yrs  I  38%, 68%  I  28%, 36%  H I II  site stocking after 0 and 10 years:  18%, 28%  vertical transect distance (2m quadrats)  72  T h i s growth of shorter trees to free-growing height in the 10 y e a r s after s a m p l i n g will r e d u c e the n u m b e r of t r e e l e s s p a t c h e s , but mostly o n the three m o r e - p o p u l a t e d s i t e s (Figure 3.12). F r e q u e n t p a t c h e s of >10 m will remain on the l e s s - p o p u l a t e d s i t e s , while n o p a t c h >8 m is likely to r e m a i n o n the m o r e - p o p u l a t e d sites. S o m e of the p a t c h e s o b v i o u s l y resulted from d i s t u r b a n c e by logging a s s h o w n by large a c c u m u l a t i o n s of s l a s h a n d friable forest floor. S t u m p s of c a n o p y trees (>40 c m b a s e diameter) a n d s u b - c a n o p y trees (20-39.9 c m b a s e d i a m e t e r ) w e r e f o u n d o n s o m e t r e e l e s s p a t c h e s w h i c h s h o w e d that t h e s e m i c r o s i t e s s u p p o r t e d t r e e s in the f o r m e r old-growth s t a n d . T h e addition of s p a c i n g a n d m i n i m u m height r e q u i r e m e n t s to f r e e - g r o w i n g r e q u i r e m e n t s (previous section) f a v o u r e d A. amabilis s a m p l i n g , A. amabilis  o v e r other s p e c i e s . At the time of  c o m p r i s e d 5 8 % of s t o c k i n g c o m p a r e d to 4 3 % of f r e e - g r o w i n g t r e e s .  S t o c k i n g contributed by other s p e c i e s included C. nootkatensis a n d T. heterophylla  (1%). After 10 y e a r s , the proportion of A. amabilis  5 0 % of s t o c k i n g a n d C. nootkatensis a n d T. heterophylla  (27%), T. mertensiana  (14%),  will d e c r e a s e slightly to  will i n c r e a s e to 3 4 % . P r o p o r t i o n s of T. mertensiana  (13%)  (3%) will r e m a i n a p p r o x i m a t e l y the s a m e .  S e e d l i n g s w e r e unequally distributed a m o n g the 6 0 0 q u a d r a t s a s 11 c l u m p s of >2 individuals c o n t a i n e d 5 3 of 7 4 s e e d l i n g s . S i n c e no relationship b e t w e e n s e e d l i n g location a n d m i c r o s i t e f a c t o r s c o u l d b e identified, the likely c a u s e of c l u m p i n g w a s the distribution of s e e d s . S u c h infrequent a n d c l u m p e d i n g r e s s m e a n s that current t r e e l e s s p a t c h e s a r e unlikely to b e filled by s e e d i n g from o u t s i d e the sites.  Growth Form Anomalies T r e e s >1.3 m tall on clearcut sites w e r e m o r e likely to b e chlorotic or c r u s h e d by logging s l a s h a n d l e s s likely to d i s p l a y u m b r e l l a or s t e m s w e e p growth f o r m s than u n d e r s t o r y t r e e s o n old-growth s i t e s (Table 3.4). T h e i n c i d e n c e of c h l o r o s i s , h o w e v e r , w a s still low. Of 2 0 chlorotic t r e e s , 18 w e r e A. amabilis  a n d 14 of t h e s e w e r e l o c a t e d o n the flat, s o u t h - a s p e c t  s i t e s , T F a n d M F . T h e a n n u a l height growth of chlorotic trees s l o w e d to 5 4 % that of other trees  73  after a p p r o x i m a t e l y 6-7 y e a r s of strong r e l e a s e , but still g r e w a l m o s t 5 % per y e a r ( m e a n relative height growth rate = 0.05 ± 0 . 0 3 c m / c m / y r ) . C h l o r o s i s w a s unrelated to Vaccinium s u b s t r a t e . T r e e s growing a m i d s t but shorter than Vaccinium growth form a n o m a l i e s than trees taller than Vaccinium  or  w e r e slightly l e s s likely to h a v e  or o n m i c r o s i t e s without  Vaccinium.  Pistol-butted trees w e r e slightly m o r e c o m m o n o n clearcut than old-growth s i t e s but w e r e l e s s s e v e r e : only 4 % of pistol butts h a d a horizontal d i s t a n c e >50 c m .  T a b l e 3.4. G r o w t h form a n o m a l i e s by s p e c i e s ( e x p r e s s e d a s a ratio of trees with a n o m a l i e s to t h o s e without). Old-growth d a t a include only understory trees >130 c m tall. T o m a k e c o m p a r i s o n s e a s i e r , clearcut d a t a are a l s o limited to trees >130 c m tall. G r o w t h form a n o m a l i e s are d e f i n e d in A p p e n d i x B.  G r o w t h form anomaly  Abies amabilis  C.  S p e c i e s o n clearcut s i t e s  total for  nootka- T. mert- T. heterotensis ensiana phylla  old-growth total  sites  0.14 0.00 0.14 0.14 0.14 0.00 0.71 0.00 0.00 0.14 0.00  0.05 0.21 0.16 0.03 0.13 0.08 0.79 0.00 0.00 0.11 0.01  0.06 0.03 0.01 0.08 0.16 0.06 0.62 0.01 0.00 0.34 0.52  96 1.57  645 1.90  B r o k e n top Chlorotic Crushed D a m a g e d leader D o g leg Multiple l e a d e r s P i s t o l butt Prostrate S h r u b (bush) Stem sweep Umbrella  0.05 0.31 0.14 0.03 0.12 0.02 0.83 0.00 0.00 0.07 0.00  0.05 0.11 0.16 0.00 0.11 0.37 0.63 0.00 0.00 0.32 0.05  0.00 0.00 0.25 0.00 0.17 0.00 0.92 0.00 0.00 0.00 0.00  S a m p l e s i z e (n)  58 1.57  19 1.79  12  7  1.33  1.43  O v e r a l l ratio  74  3.4  Discussion  Was natural regeneration successful? T h e determination of regeneration s u c c e s s d e p e n d s on the criteria u s e d . A c c o r d i n g to Ministry of F o r e s t s criteria, the study sites are s u c c e s s f u l l y r e g e n e r a t e d : there a r e not only e n o u g h t r e e s to p r o d u c e a future c r o p , there are s o m a n y that future thinning will b e n e e d e d ( B . C . Ministry of F o r e s t s 1 9 9 2 ; A p p e n d i x C ) . T h e r e w e r e a n u m b e r of c o n c e r n s identified in this study, h o w e v e r , e s p e c i a l l y regarding the s p e c i e s mix a n d structure of the future s t a n d , a s well a s the distribution of regeneration. N a t u r a l regeneration w a s u n s u c c e s s f u l from the standpoint of maintaining the s a m e proportion of s p e c i e s that w a s in the p r e v i o u s old-growth s t a n d . C l e a r c u t t i n g in the M H z o n e u s u a l l y results in a s p e c i e s shift to A. amabilis  d u e to its a b u n d a n c e a s a d v a n c e r e g e n e r a t i o n  in old-growth s t a n d s (Klinka etal. 1 9 9 2 ; K o p p e n a a l a n d Mitchell 1 9 9 2 ; Arnott etal. 1 9 9 5 ; C h a p t e r 2). T h e strong c o m p o n e n t of C. nootkatensis  w a s l e s s e x p e c t e d a n d w a s d u e to  s t r o n g e s t a b l i s h m e n t in the y e a r s just before a n d after logging. T h e r e w a s likely a large b a n k of g e r m i n a n t s in the p r e v i o u s old-growth s t a n d ( C h a p t e r 2), a n d this m a y h a v e b e e n b o l s t e r e d by a h e a v y s e e d y e a r that c o i n c i d e d with the y e a r of logging. W h e t h e r the strong p r e s e n c e of C. nootkatensis  will remain throughout s t a n d d e v e l o p m e n t is u n c l e a r s i n c e there is s o m e doubt  a b o u t its ability to survive into upper c a n o p y layers under low light conditions ( K l i n k a et al. 1 9 9 2 ) . T h e minor p r e s e n c e of T. mertensiana  contrasts with its d o m i n a n c e a m o n g c a n o p y  t r e e s in a d j a c e n t old-growth s t a n d s ( C h a p t e r 2) a n d w a s likely d u e to a lack of s e e d s . D o e s the d u m p i n e s s of trees a n d the m a n y t r e e l e s s p a t c h e s , e s p e c i a l l y o n the three l e s s - p o p u l a t e d s i t e s , constitute u n s u c c e s s f u l r e g e n e r a t i o n ? It is unrealistic (and p r o b a b l y u n d e s i r a b l e ) to e x p e c t full site o c c u p a n c y s i n c e t r e e l e s s p a t c h e s (gaps) a r e c o m m o n in the M H z o n e ( L e r t z m a n etal. 1 9 9 6 ; C h a p t e r 2), e s p e c i a l l y on flat sites. H o w e v e r , 2 of the 3 s i t e s that h a d m a n y t r e e l e s s p a t c h e s w e r e s t e e p a n d m a n y of t h o s e p a t c h e s c o n t a i n e d s t u m p s w h i c h s h o w e d that they h a d b e e n o c c u p i e d in the p r e v i o u s s t a n d .  75  R e g e n e r a t i o n w a s m o s t s u c c e s s f u l o n flat a n d north-facing s i t e s likely a s a result of lower mortality from heat a n d moisture s t r e s s c o m p a r e d to s o u t h - f a c i n g s i t e s , e s p e c i a l l y t h o s e that a r e s t e e p ( R e u t e r 1 9 7 3 ; S e i d e l a n d C o o l e y 1 9 7 4 ; Ballard etal. 1 9 7 7 ; E m m i n g h a m a n d H a l v e r s o n 1 9 8 1 ) . E v e n within the relatively c o o l a n d w e t M H z o n e , the r e m o v a l of t h e forest c a n o p y c a n result in lethal conditions, particularly w h e n it a l s o c a u s e s faster s n o w m e l t ( R e u t e r 1 9 7 4 ; p e r s . o b s . ) . B e s i d e s b e i n g relatively drier a n d w a r m e r than flat sites, s t e e p s i t e s h a d m o r e d i s t u r b e d (friable) forest floor a n d w e r e m o r e likely to b e c o v e r e d b y logging s l a s h a n d e x p o s e d rock. T h e c o m b i n a t i o n of higher t e m p e r a t u r e s a n d unsuitable, e a s i l y dried-out s u b s t r a t e s a p p a r e n t l y r e d u c e d survival a n d / o r e s t a b l i s h m e n t o n t h e s e s i t e s . M o i s t u r e s t r e s s m a y h a v e affected s p e c i e s c o m p o s i t i o n a s w e l l . A. amabilis mertensiana  w e r e l e s s c o m m o n o n s o u t h - f a c i n g sites than w e r e C. nootkatensis  heterophylla.  A. amabilis  a n d 7".  a n d T.  is k n o w n to h a v e high moisture r e q u i r e m e n t s (Herring a n d E t h e r i d g e  1 9 7 6 ; K o t a r 1 9 7 7 , 1 9 7 8 ; Krajina e r a / . 1982) a n d partial sunlight n e a r s t a n d e d g e s i m p r o v e s s u r v i v a l a n d growth for both A. amabilis 1995) a n d T. mertensiana  (Herring a n d E t h e r i d g e 1 9 7 6 ; W a g n e r 1 9 8 0 ; v a n P e l t  ( B u r n s a n d H o n k a l a 1990).  T h e r e is a c o n c e r n that s n o w c a n s e r i o u s l y d a m a g e r e g e n e r a t i o n in t h e M H z o n e , e s p e c i a l l y C. nootkatensis  a n d T. mertensiana  ( S c a g e l etal. 1 9 8 9 ; K l i n k a etal. 1 9 9 2 ; Arnott et  al. 1 9 9 5 ) . I b e l i e v e there a r e three r e a s o n s w h y s u c h d a m a g e w a s not evident h e r e : (1) n a t u r a l l y - r e g e n e r a t e d trees a r e l e s s s u s c e p t i b l e to d a m a g e than planted trees (Arnott et al. 1 9 9 5 ) ; (2) m o s t r e g e n e r a t i o n w a s short e n o u g h to b e protected u n d e r t h e winter s n o w p a c k a n d not y e t subject to i n c r e a s e d d a m a g e with growth a b o v e t h e s n o w p a c k (Arnott etal. 1 9 9 5 ; R. G r e e n , p e r s . c o m m . ) ; a n d (3) the location of the study sites at the lowest e l e v a t i o n s of t h e M H z o n e m e a n t s n o w l o a d s w e r e not great e n o u g h to c a u s e s e r i o u s d a m a g e .  Did most natural regeneration establish before or after logging? W h i l e the i m p o r t a n c e of r e s i d u a l s in regenerating s i t e s h a s b e e n p r e v i o u s l y reported (e.g., H e r r i n g a n d E t h e r i d g e 1 9 7 6 ; V o g t etal. 1 9 8 9 ; G r e e n a n d B e r n a r d y 1 9 9 1 ; K l i n k a etal.  76  1 9 9 2 ) , the role of g e r m i n a n t s h a s not, likely b e c a u s e s u c h s t u d i e s limited their f o c u s to two a g e c l a s s e s : p r e - a n d p o s t - l o g g i n g . In this study, g e r m i n a n t s e s t a b l i s h i n g within a 3 - y e a r w i n d o w from o n e y e a r before logging to o n e y e a r after logging a c c o u n t e d for a l m o s t half of all r e g e n e r a t i o n . S e p a r a t i n g this a g e c l a s s from post-logging regeneration highlighted the lack of i n g r e s s that might h a v e r e m a i n e d h i d d e n o t h e r w i s e . S o m e might a r g u e that they a r e the result of p o s t - l o g g i n g growing conditions, but I believe that there is a l s o a n a s p e c t of l e g a c y in that m o s t w e r e from the s e e d l i n g or germinant b a n k (sensu  K o h y a m a 1983) of the p r e v i o u s o l d -  growth s t a n d a n d m o s t g e r m i n a t e d o n its undisturbed forest floor, e v e n if their s u b s e q u e n t growth w a s in a clearcut. T h e relative u n i m p o r t a n c e of i n g r e s s w a s surprising, e s p e c i a l l y the lack of i n g r e s s m o r e than a f e w y e a r s after logging. S i n c e i n g r e s s c a n b e a n important s o u r c e of r e g e n e r a t i o n ( M i n o r e a n d D u b r a s i c h 1 9 8 1 ; Arnott etal. 1995), its scarcity h e r e i n d i c a t e s that the availability of s e e d s w a s i n a d e q u a t e or that there w e r e p r o b l e m s with germination a n d s u r v i v a l . T h e rapid d e c r e a s e in e s t a b l i s h m e n t after logging s u g g e s t s that off-site s e e d s w e r e n e v e r important contributors to regeneration a n d that the d e c r e a s e c o i n c i d e d with the depletion of the s e e d b a n k ( K l i n k a a n d P e n d l 1976) Ingress w a s clearly not limited only by the lack of growing s p a c e (sensu  Oliver and  L a r s o n 1990) s i n c e there w e r e n u m e r o u s p a t c h e s w h e r e no t r e e s a n d virtually n o other v e g e t a t i o n w e r e g r o w i n g , e s p e c i a l l y o n s t u m p m o u n d s . Instead, the m a i n limitation to i n g r e s s w a s a l m o s t certainly the a b s e n c e of nearby, s e e d - p r o d u c i n g t r e e s . T h e c l o s e s t r e m a i n i n g c a n o p y t r e e s to a n y study location w e r e in a narrow fringe, 1-2 trees d e e p , at a l a k e e d g e - 1 0 0 - 2 0 0 m from the B a t c h e l o r study location. T h e c a n o p y trees c l o s e s t to the M a y n e a n d T a n n i s s t u d y l o c a t i o n s w e r e - 2 0 0 - 1 4 0 0 m distant. S i n c e s e e d d e n s i t i e s of the native s p e c i e s d e c r e a s e rapidly a w a y from a s t a n d e d g e (Franklin a n d S m i t h 1 9 7 4 ; C a r k i n etal. 1 9 7 8 ; B u r n s a n d H o n k a l a 1990), there w o u l d b e f e w s e e d s a v a i l a b l e o n the study locations. Further i n g r e s s will therefore b e d e l a y e d until regenerating trees r e a c h s e x u a l maturity. T h e relative l a c k of T.  77  mertensiana  c o m p a r e d to adjacent old-growth s t a n d s w a s likely a l s o c a u s e d by the  unavailability of s e e d s s i n c e it c a n v i g o r o u s l y c o l o n i z e l o g g e d a r e a s w h e n there is a d e q u a t e s e e d (Franklin a n d S m i t h 1974; S e i d e l a n d C o o l e y 1974).  Which substrates favoured natural regeneration? A s d i s c u s s e d in C h a p t e r 2, s u c c e s s f u l regeneration in other s y s t e m s is c o m m o n l y related to d i s t u r b e d s u b s t r a t e s , e s p e c i a l l y mineral soil, d e c a y i n g w o o d , a n d c o a r s e w o o d y d e b r i s (e.g., V o g t 1 9 8 9 ; S p i t t l e h o u s e a n d S t a t h e r s 1 9 9 0 ; C o a t e s etal. 1991). In contrast, m o s t r e g e n e r a t i o n in both clearcut a n d old-growth sites of this study, a n d c l e a r c u t s i t e s of at least o n e other s t u d y in the M H z o n e ( G r e e n a n d B e r n a r d y 1991), w a s o n u n d i s t u r b e d forest floor. T h e relationship b e t w e e n undisturbed microsites a n d r e s i d u a l s c a n b e partially e x p l a i n e d by higher s u r v i v a l rates during logging, but the o v e r w h e l m i n g majority of g e r m i n a n t s a n d i n g r e s s w e r e a l s o o n u n d i s t u r b e d forest floor. P o o r r e g e n e r a t i o n o n friable forest floor h a s b e e n noted in other s t u d i e s a n d e x p l a i n e d a s the result of the adaptation of native s p e c i e s , particularly A. amabilis,  to r e g e n e r a t i o n o n  thick, matted M o r h u m u s f o r m s ( G r e e n a n d B e r n a r d y 1 9 9 1 ; K l i n k a etal. 1 9 9 2 ; C h a p t e r 2). T h e transition to a friable M o r m o d e r or M o d e r h u m u s form m a y a l s o h a v e i n c r e a s e d the porosity of the forest floor a n d , together with the lack of s h a d i n g o n t h e s e m i c r o s i t e s , resulted in g r e a t e r m o i s t u r e s t r e s s . N o t r e e s w e r e growing on the m a n y fallen logs left after logging a n d t r e e l e s s p a t c h e s w e r e e s p e c i a l l y evident w h e r e logging s l a s h h a d b e e n piled n e a r l a n d i n g s . T h e bark w a s still intact o n m a n y of t h e s e fallen trees a n d , b a s e d o n o b s e r v a t i o n s from a d j a c e n t o l d growth s t a n d s ( C h a p t e r 2), it m a y be centuries before they h a v e d e c a y e d e n o u g h to b e a p p r o p r i a t e s e e d b e d s for r e g e n e r a t i o n . In a g r e e m e n t with w a r n i n g s a g a i n s t e x t r e m e soil d i s t u r b a n c e ( G r e e n a n d B e r n a r d y 1 9 9 1 ; K l i n k a etal. 1 9 9 2 ; B a n n e r etal. 1993), t r e e l e s s p a t c h e s o n a d j a c e n t s i t e s w e r e often a s s o c i a t e d with the e x p o s e d mineral soil o n s k i d d e r trails.  78 Which microtopographic locations favoured natural regeneration? T h e neutral or negative a s s o c i a t i o n b e t w e e n m o u n d s a n d natural r e g e n e r a t i o n c o n t r a s t e d with that s e e n in old-growth s t a n d s ( C h a p t e r 2) a n d w a s likely c a u s e d by l o g g i n g . L o g g i n g m a y h a v e c h a n g e d the relationship b e t w e e n regeneration patterns a n d m o u n d s in at least three w a y s . First, direct a n d indirect mortality from logging w o u l d be highest o n m o u n d s s i n c e they s u p p o r t e d a l m o s t all c a n o p y trees in the p r e v i o u s old-growth s t a n d . S e c o n d , forest floor d i s t u r b a n c e w a s greatest on m o u n d s a n d this d i s t u r b a n c e a p p a r e n t l y r e d u c e d the ability of s e e d s to g e r m i n a t e . Third, trees establishing o n m o u n d s after logging might not h a v e h a d the s a m e microclimatic a d v a n t a g e a s trees on m o u n d s in old-growth s t a n d s . S n o w m e l t e d s e v e r a l w e e k s earlier o n clearcut than old-growth sites (unpubl. data) s o the a d v a n t a g e of the longer g r o w i n g s e a s o n on m o u n d s w o u l d be l e s s a n d , without the s h a d i n g of c a n o p y t r e e s , the m o i s t u r e s t r e s s w o u l d b e greater. T h i s is not to s a y , h o w e v e r , that m i c r o t o p o g r a p h y will not affect r e g e n e r a t i o n patterns in the future. In old-growth s t a n d s , m o u n d s w e r e a s s o c i a t e d m o r e with g r e a t e r s u r v i v a l than e s t a b l i s h m e n t s o , a s the c a n o p y c l o s e s o n t h e s e c l e a r c u t s , they m a y yet affect s t a n d d e v e l o p m e n t . If s n o w w a s l e s s of a factor on clearcut than old-growth sites, w h y w a s there a similar p r o p e n s i t y for t r e e s o n m o u n d s to be on the downhill s i d e , not to mention a t e n d e n c y for trees to b e o n the downhill s i d e of logging s l a s h ? A n o b v i o u s e x p l a n a t i o n for t h e s e patterns is that they w e r e s i m p l y artifacts from the p r e v i o u s old-growth s t a n d , but this w o u l d not e x p l a i n w h y t r e e s downhill of logging s l a s h s u r v i v e d better. S n o w c r e e p m a y h a v e b e e n a factor, but it is a l s o p o s s i b l e that b e c a u s e uphill microsites h a d l e s s s n o w , there w a s m o r e d a m a g e f r o m frost a n d i c e . Similarly, uphill microsites w o u l d b e subject to greater moisture s t r e s s during the g r o w i n g s e a s o n a n d this m a y a l s o h a v e r e d u c e d s u r v i v a l . Finally, soil c r e e p limited the height growth a n d likely the survival of s e e d l i n g s o n old-growth sites ( C h a p t e r 2), s o it c a n n o t b e ruled out a s a factor o n clearcut sites, e s p e c i a l l y s i n c e the forest floor d i s t u r b a n c e a n d s l a s h c a u s e d by logging i n c r e a s e d the material prone to m o v i n g downhill.  79  Did competition with Vaccinium impede natural regeneration? C o m p e t i t i o n c a n b e d e f i n e d a s : "...the negative effects w h i c h o n e o r g a n i s m h a s u p o n a n o t h e r by c o n s u m i n g , or controlling a c c e s s to, a r e s o u r c e that is limited in availability" ( K e d d y 1 9 8 9 , p.2). S h r u b s a n d h e r b s c a n c o m p e t e in this s e n s e with trees for s u c h r e s o u r c e s a s light, water, a n d nutrients (e.g., O l i v e r a n d L a r s o n 1 9 9 0 ; Burton 1 9 9 3 ; G r e e n a n d K l i n k a 1994). T h e n e g a t i v e i m p a c t s of e r i c a c e o u s s h r u b s o n tree survival a n d growth a r e w e l l - d o c u m e n t e d (e.g., R a d o s e v i c h 1 9 8 4 ; M e s s i e r a n d K i m m i n s 1 9 9 0 ; d e M o n t i g n y 1 9 9 2 ; G . W e e t m a n in K o p p e n a a l a n d Mitchell 1 9 9 2 ; Mallik 1995). L e s s reported is a positive relationship, or facilitation ( C o n n e l l a n d S l a t y e r 1 9 7 7 ; B e r k o w i t z etal. 1995), b e t w e e n trees a n d s h r u b s s u c h a s Vaccinium  Vaccinium.  c a n protect trees from s u n - s c a l d (Kotar 1 9 7 8 ; M i n o r e 1986) a s well a s frost d a m a g e  a n d s n o w p r e s s ( S c a g e l etal. 1989). Natural regeneration is a l s o m o r e s u c c e s s f u l o n t h o s e c l e a r c u t s i t e s w h e r e Vaccinium  w a s present in the p r e v i o u s old-growth s t a n d ( G r e e n a n d  B e r n a r d y 1991). H o w then did Vaccinium  affect natural regeneration in this s t u d y ?  M y results s h o w n o e v i d e n c e that Vaccinium  impeded regeneration since most  r e g e n e r a t i o n , r e g a r d l e s s of a g e c l a s s , w a s a s s o c i a t e d with it. O n e s u r p r i s e w a s that o v e r half of all r e g e n e r a t i o n w a s b e l o w the Vaccinium  c a n o p y a n d therefore only n o t i c e a b l e u n d e r c l o s e  e x a m i n a t i o n . A s predicted by K l i n k a etal. (1992), this b a n k of o t h e r w i s e invisible r e g e n e r a t i o n s h o u l d c o n t i n u e to a d d to site s t o c k i n g a s it eventually o v e r t o p s the Vaccinium. a s s o c i a t i o n of r e s i d u a l s , Vaccinium,  The  a n d undisturbed forest floor is further e v i d e n c e that lack of  l o g g i n g d i s t u r b a n c e i n c r e a s e d the survival of a d v a n c e regeneration from the p r e v i o u s o l d growth s t a n d . In addition, microsites with Vaccinium  microsites s u p p o r t e d the majority of  i n g r e s s w h i c h s h o w e d that they p r o v i d e d m o r e f a v o u r a b l e conditions for tree e s t a b l i s h m e n t t h a n m i c r o s i t e s without  Vaccinium.  C h l o r o s i s a n d growth c h e c k h a v e b e e n reported o n M H s i t e s with a b u n d a n t  Vaccinium  a n d a n u n d i s t u r b e d , c o m p a c t e d , a n d thick forest floor ( G . W e e t m a n in K o p p e n a a l a n d Mitchell 1 9 9 2 ; K l i n k a etal. 1992). H o w e v e r , not only w e r e c h l o r o s i s a n d growth c h e c k u n c o m m o n o n the s t u d y s i t e s , they w e r e a l s o unrelated to substrate or Vaccinium  c o v e r , a n d limited a l m o s t  80  e x c l u s i v e l y to A. amabilis nootkatensis  o n flat, s o u t h - a s p e c t sites, notably the T F site. S i n c e healthy C.  o u t n u m b e r e d chlorotic A. amabilis  o n this site, c h l o r o s i s w a s likely c a u s e d by site  rather than microsite factors. F o r e x a m p l e , A. amabilis nootkatensis  m a y b e l e s s w e l l - a d a p t e d than C.  to the e x t r e m e s in soil moisture a n d temperature o n a flat, w a r m - a s p e c t site that  is n o longer s h a d e d by a forest c a n o p y .  3.5 Conclusions M a n y of the regeneration p r o b l e m s identified here w e r e predictable c o n s e q u e n c e s of e x t e n s i v e clearcutting at lower elevations of the M H z o n e . T h e shift to A. amabilis,  the lack of  i n g r e s s a n d structural diversity, a n d the c l u m p e d regeneration pattern h a v e all b e e n reported b e f o r e . Y e t d e s p i t e calls for alternatives s p a n n i n g m o r e than 3 0 y e a r s (Franklin 1 9 6 4 ; B r o o k e etal. 1 9 7 0 ; R e u t e r 1 9 7 3 ; Utzig a n d Herring 1974, V o g t etal. 1 9 8 9 ; B a n n e r etal.  1993),  traditional clearcutting r e m a i n s the d o m i n a n t cutting m e t h o d in the M H z o n e . C o s t e f f e c t i v e n e s s is u n d o u b t e d l y a n important r e a s o n for the o v e r w h e l m i n g u s e of clearcutting, but it is a l s o b a s e d o n the p r e m i s e that m a x i m u m growth rates will b e a c h i e v e d with the total r e m o v a l of the c a n o p y layer. In the M H z o n e , h o w e v e r , tree e s t a b l i s h m e n t , s u r v i v a l , a n d growth form a r e likely m o r e important c o n s i d e r a t i o n s than growth rates ( S c a g e l etal.  1989;.  K l i n k a etal. 1 9 9 2 ; C h a p t e r 2 ) . C l e a r c u t t i n g d o e s not take a d v a n t a g e of the m a n y n o n - c a n o p y t r e e s a l r e a d y e s t a b l i s h e d in a n old-growth s t a n d that, if p r e s e r v e d , c o u l d jump-start r e g e n e r a t i o n a n d retain a better s p e c i e s mix a n d m o r e structural diversity. N o r is it intended to l e a v e a s o u r c e of s e e d s to e n s u r e a c o n t i n u o u s i n g r e s s of regeneration. A s a n e x a m p l e of a different a p p r o a c h to r e g e n e r a t i n g s i t e s in the M H z o n e , a partial cut near the study s i t e s (on the C h a p m a n P l a t e a u ) left a variety of s n a g s , live but low vigour c a n o p y t r e e s , a n d m u c h of the s u b - c a n o p y layer. A s a result, there is m u c h higher structural diversity, m o r e a b u n d a n t C. nootkatensis mertensiana,  a n d T.  a n d greater i n g r e s s than o n a n y of the study s i t e s . In spite of the h i g h g r a d i n g of  81  c a n o p y t r e e s a n d e x c e s s i v e d i s t u r b a n c e c a u s e d by s k i d trails, r e g e n e r a t i o n is v i g o r o u s a n d the site retains m a n y c h a r a c t e r i s t i c s of the p r e v i o u s old-growth s t a n d k n o w n to b e required by wildlife ( H o p w o o d 1991). R e t a i n i n g taller a d v a n c e regeneration w o u l d a l s o r e d u c e rotation a g e s a n d i n c r e a s e y i e l d s . F o r e x a m p l e , o n e study of a d v a n c e r e g e n e r a t i o n in Q u e b e c f o u n d that a n i n c r e a s e of 3 m in the height of a d v a n c e regeneration is equivalent to a n i n c r e a s e of 3 m in site index (Pothier e r a / . 1995). In old-growth s t a n d s adjacent to t h e s e c l e a r c u t s , there w a s a pool of >300 T. mertensiana  a n d C. nootkatensis  understory a n d s u b - c a n o p y trees p e r h a that w e r e >2 m tall  a n d h a d g o o d vigour (i.e., vigour >3; C h a p t e r 2), yet n o s u c h trees s u r v i v e d logging o n t h e s e c l e a r c u t s . P r e s e r v i n g taller trees w o u l d h a v e b e e n e s p e c i a l l y a d v a n t a g e o u s o n the three l e s s p o p u l a t e d s i t e s w h e r e i n g r e s s w a s s o poor. It is e s p e c i a l l y striking to note that 7 % of t r e e l e s s p a t c h e s c o n t a i n e d the s t u m p s of s u b - c a n o p y trees (i.e., 2 0 - 4 0 c m b a s e diameter) f r o m the p r e v i o u s old-growth s t a n d w h i c h n e e d not h a v e b e e n cut. P r e s e r v i n g a d v a n c e regeneration is k n o w n to improve s u c c e s s after cutting in the M H z o n e (e.g., Franklin 1 9 6 4 ; K l i n k a a n d P e n d l 1 9 7 6 ; E m m i n g h a m a n d H a l v e r s o n 1 9 8 1 ; B u r n s a n d H o n k a l a 1 9 9 0 ; G r e e n a n d B e r n a r d y 1 9 9 1 ; K l i n k a etal. 1 9 9 2 ; B a n n e r etal. 1 9 9 3 ) but the p r e s e r v a t i o n of taller trees is actively restricted by current policy. N o t only h a v e s a f e t y c o n c e r n s led to a 3 m " k n o c k d o w n " rule, w h e r e all trees >3 m tall must b e cut, but current s t o c k i n g s t a n d a r d s only a c c e p t a d v a n c e regeneration shorter than 1.0 m ( C . nootkatensis T. mertensiana)  or 1.5 m (A. amabilis;  and  B . C . Ministry of F o r e s t s 1995). T h i s p r e f e r e n c e for short  a d v a n c e r e g e n e r a t i o n apparently s t e m s from Herring a n d E t h e r i d g e ' s (1976) s t u d y that e v a l u a t e d A. amabilis  a d v a n c e regeneration o n 11 c l e a r c u t s s i t e s l o c a t e d in the C W H z o n e .  T h e a u t h o r s r e c o m m e n d e d a g a i n s t p r e s e r v i n g a d v a n c e regeneration >2 m tall d u e to a n i n c r e a s e d risk of d a m a g e during close-utilization logging, i.e., w h e r e all s t e m s o v e r a m i n i m u m s i z e m u s t b e r e m o v e d from the site.  82  T h e r e a r e s e v e r a l r e a s o n s to revisit the lack of a c c e p t a n c e for taller a d v a n c e r e g e n e r a t i o n in the M H z o n e . Close-utilization clearcutting is inappropriate o n m a n y s i t e s in the M H z o n e for the r e a s o n s given a b o v e (and in C h a p t e r 2), a n d a l s o b e c a u s e c l o s e utilization i n c r e a s e s the i n c i d e n c e of d a m a g e from logging (Herring a n d E t h e r i d g e 1976). T h o u g h Herring a n d E t h e r i d g e s h o w that d a m a g e is m o r e frequently incurred by taller A. amabilis, they f o u n d a l m o s t no i n c i d e n c e of d e c a y resulting from d a m a g e a n d , in fact, n o t e d that d a m a g e w a s a l m o s t u n n o t i c e a b l e in m a n y trees after 2 0 - 3 0 y e a r s . Part of the b i a s a g a i n s t taller r e g e n e r a t i o n m a y b e b a s e d on a fear that it is not a b l e to s u r v i v e the abrupt c h a n g e in growing c o n d i t i o n s after logging. But the s u c c e s s of taller regeneration o n the partial cut d e s c r i b e d a b o v e s h o w s that taller trees c a n thrive, at least w h e r e s o m e c a n o p y c o v e r is left intact. A n d finally, the interdictions a g a i n s t taller a d v a n c e regeneration w e r e i m p l e m e n t e d at a time w h e n c o n c e r n s for s p e c i e s a n d structural diversity w e r e not a s important a s they are t o d a y ( H o p w o o d 1991). K l i n k a etal. (1992) linked c h l o r o s i s a n d growth c h e c k to the tying-up of nutrients in thick a n d c o m p a c t e d M o r h u m u s f o r m s , e s p e c i a l l y w h e r e d e c a y i n g w o o d is a major c o m p o n e n t . T h e y therefore s u g g e s t e d that s o m e d i s t u r b a n c e of the forest floor w o u l d i m p r o v e nutrient availability. H o w e v e r , growth c h e c k is not a major p r o b l e m h e r e a n d a n y a d v a n t a g e s of greater nutrient availability w o u l d likely be o u t w e i g h e d by the l o s s of r e s i d u a l s with greater d i s t u r b a n c e during logging. B o t h C h a p t e r 2 a n d C h a p t e r 3 s h o w e d the great variability of r e g e n e r a t i o n patterns a m o n g a d j a c e n t s i t e s . T h i s variability s t r e s s e s the n e e d for all a s p e c t s of m a n a g e m e n t to b e s i t e - s p e c i f i c , including B . C . Ministry of F o r e s t s s u r v e y s . F o r e x a m p l e , s u r v e y s o n t h e s e s i t e s w o u l d h a v e p r o v i d e d a better a s s e s s m e n t of regeneration if sites w e r e properly stratified by e d a p h i c c o n d i t i o n s . Instead, the s u r v e y a r e a s r a n g e d in s i z e from 2 9 - 8 2 h a a n d s p a n n e d a large e d a p h i c r a n g e . T h e s u r v e y that c o n t a i n e d the two T a n n i s s i t e s , for e x a m p l e , i n c l u d e d s o u t h a n d north a s p e c t s , flat a n d s t e e p s l o p e s , a n d ridge tops a n d b o g s . A s a result, it c o u l d  83  not differentiate the r e a s o n a b l y g o o d regeneration o n the T F site from the p o o r r e g e n e r a t i o n o n the T S site. C h a p t e r 2 a l s o s h o w e d that there is n o abrupt e c o l o g i c a l b o u n d a r y b e t w e e n the two Tsuga s p e c i e s a s implied by the current s t o c k i n g s t a n d a r d s w h i c h allow only o n e s p e c i e s of Tsuga o n s i t e s in the study a r e a : T. heterophylla  o n C W H v m 2 s i t e s (except o n o n e v e r y moist  site s e r i e s at higher elevations) a n d T. mertensiana 1995). T h e a c c e p t a n c e of T. mertensiana  o n M H m m l sites ( B . C . Ministry of F o r e s t s  just b e l o w the C W H / M H b o u n d a r y might r e d u c e  growth rates, but w o u l d a l s o r e d u c e the risk of d a m a g e from frost a n d s n o w . All s t u d i e s of post-logging regeneration in the M H z o n e , including this o n e , h a v e b e e n at its lowest limits. R e g e n e r a t i o n s u c c e s s a n d growth rates will only d e c r e a s e a s higher e l e v a t i o n s i t e s a r e l o g g e d (Klinka etal. 1 9 9 2 ; B a n n e r etal. 1 9 9 3 ; K l i n k a 1 9 9 6 ; B. S p l e c h t n a u n p u b l . data). C h a p t e r 2 s h o w e d that the forested M H s u b z o n e o c c u p i e s a transition b e t w e e n g a p a n d t r e e - i s l a n d s y s t e m s a n d it is likely that regeneration b e c o m e s u n f e a s i b l e s o m e w h e r e within this transition (Klinka etal. 1992).  84  Chapter 4. Summary and Conclusions  C h a p t e r 2 d e s c r i b e s regeneration patterns within old-growth s t a n d s that a r e transitional b e t w e e n l o w e r - e l e v a t i o n , g a p - d r i v e n forests a n d tree i s l a n d s at higher e l e v a t i o n s . C o n s i s t e n t with p r e d i c t i o n s of the tree-island m o d e l , regeneration in t h e s e s t a n d s is most s u c c e s s f u l c l o s e to a c a n o p y tree a n d on m o u n d s rather than in c a n o p y g a p s . Late-melting s n o w i n c r e a s e s the p r e v a l e n c e of r e g e n e r a t i o n patterns m a t c h i n g the tree-island m o d e l . T h o u g h r e g e n e r a t i o n w a s p r e s e n t in c a n o p y g a p s , the formation of g a p s d o e s not drive r e g e n e r a t i o n patterns a s at lower e l e v a t i o n s w h e r e s n o w is infrequent. W h i l e C h a p t e r 2 d e m o n s t r a t e s that microsites a n d s n o w are related to r e g e n e r a t i o n patterns in old-growth s t a n d s , C h a p t e r 3 s h o w s that the pattern of natural r e g e n e r a t i o n after clearcutting is mostly a n artifact of r e s i d u a l s a n d g e r m i n a n t s from the p r e v i o u s old-growth s t a n d . M o s t natural regeneration is thus related to microsites undisturbed by l o g g i n g , i.e., t h o s e with a n intact forest floor a n d a b u n d a n t  Vaccinium c o v e r . It a r g u e s that c l a s s i f y i n g the  a g e of natural r e g e n e r a t i o n a s either pre- or post-logging m a s k s the fact that p o s t - l o g g i n g i n g r e s s from s e e d s originating off-site w a s negligible. T h o u g h w e t e n d to picture biogeoclimatic units a s discrete lines o n a m a p , the reality is m u c h different. Within the study a r e a , for e x a m p l e , tree-island e c o s y s t e m s that are similar to t h o s e in the p a r k l a n d M H s u b z o n e in both vegetation a n d p h y s i o g n o m y inhabit flat s i t e s a s low a s 1 0 0 0 m, while forest s t a n d s d o m i n a t e d by  T. heterophylla c a n b e o n s t e e p s i t e s at  e l e v a t i o n s a s high a s 1 1 5 0 m (Brett 1996). T h o u g h s u c h variability d o e s not affect forest p l a n n i n g o n a b r o a d s c a l e , it m u s t be a d d r e s s e d w h e n d e a l i n g at the s t a n d l e v e l , particularly within a transitional a r e a s u c h a s the forested M H s u b z o n e . O u r current policy v i e w s the forested M H s u b z o n e a s a n e x t e n s i o n of l o w e r - e l e v a t i o n f o r e s t s , albeit with different s p e c i e s . A s s u c h , m u c h of the s u b z o n e h a s b e e n c l e a r c u t or is s c h e d u l e d for clearcutting in the n e a r future. But the high non-timber v a l u e s in t h e s e f o r e s t s , a s well a s their s l o w growth, a r g u e s a g a i n s t their automatic inclusion a s s o u r c e s of timber. If  85  the d e c i s i o n to cut is m a d e , m e t h o d s s h o u l d be heavily modified. S i n c e r e g e n e r a t i o n requires the protection from s n o w provided by a n o v e r h e a d c a n o p y , a n y cutting at lower e l e v a t i o n s of the M H z o n e s h o u l d retain a s m u c h of the c a n o p y a n d s u b - c a n o p y l a y e r s a s p o s s i b l e . At higher e l e v a t i o n s a n d o n late-snowmelt sites, a n y cutting is inappropriate. C h a p t e r 2 c o n c l u d e s with a s u g g e s t i o n to u s e regeneration patterns a s a n e c o l o g i c a l b a s i s for the m a n a g e m e n t c l a s s e s first d e s c r i b e d by K l i n k a etal. (1992). A s the cutting of M H s t a n d s p r o g r e s s e s up to elevations w h e r e tree-island p r o c e s s e s d o m i n a t e , it is time to revisit the w i s d o m of cutting t h e s e forests, e s p e c i a l l y by clearcutting.  86  Literature Cited A n t o s , J . A . a n d D . B . Z o b e l . 1 9 8 6 . Habitat relationships of Chamaecyparis nootkatensis in s o u t h e r n W a s h i n g t o n , O r e g o n , a n d C a l i f o r n i a . C a n . J . Bot. 64(9): 1 8 9 8 - 1 9 0 9 . Arnott, J . T . , R . K . S c a g e l , R . C . E v a n s , a n d F.T. P e n d l . 1 9 9 5 . High elevation r e g e n e r a t i o n strategies for s u b a l p i n e a n d m o n t a n e forests of c o a s t a l British C o l u m b i a . C a n . F o r . S e r v . a n d B . C . M i n . For., Victoria, B . C . F R D A R e p . N o . 2 2 9 . 3 0 p p . A r s e n a u l t , A . 1 9 9 5 . Pattern a n d p r o c e s s in old-growth t e m p e r a t e rainforests of s o u t h e r n British C o l u m b i a . P h . D . t h e s i s , Univ. Brit. C o l u m b i a . 186 pp. B . C . Ministry of F o r e s t s . 1 9 9 2 . R e g e n e r a t i o n s u r v e y s for c u t b l o c k s 150 a n d 5 7 . S e c h e l t Field Office, S e c h e l t , B . C . B . C . Ministry of F o r e s t s . 1 9 9 5 . E s t a b l i s h m e n t to free growing g u i d e b o o k , V a n c o u v e r F o r e s t R e g i o n . B . C . M i n . For. a n d B . C . E n v . , Victoria, B . C . 130 p p . B . C . Ministry of the E n v i r o n m e n t . 1 9 8 5 . S u m m a r y of s n o w s u r v e y m e a s u r e m e n t s in British C o l u m b i a 1935-1985. B . C . Min. Env., Water M a n a g e . Branch, Victoria, B . C . B . C . Ministry of the E n v i r o n m e n t . 1 9 9 3 , 1 9 9 4 , a n d 1 9 9 5 . S n o w s u r v e y bulletin. M o n t h l y reports for M a r c h (inc. J a n . a n d F e b . ) , April, M a y , a n d J u n e . W a t e r M a n a g e . B r a n c h , B . C . M i n . E n v . , L a n d s , a n d P a r k s (before 1994) a n d B . C . M i n . E n v . (1994-95), V i c t o r i a , B C . Ballard, T . M . , T.A. Black, and K . G . McNaughton. 1977. S u m m e r energy balance and t e m p e r a t u r e s in a forest clearcut in s o u t h e a s t e r n British C o l u m b i a . In Brit. C o l u m b i a S o i l S c i . W o r k s h o p Report, M e e t i n g N o . 6, B . C . M i n . A g r i c , V i c t o r i a , B . C . p p . 7 4 - 8 6 . B a n n e r , B., W . M a c K e n z i e , S . H a e u s s l e r , S . T h o m s o n , J . Pojar, a n d R. T r o w b r i d g e . 1 9 9 3 . A field guide to site identification a n d interpretation for the P r i n c e R u p e r t F o r e s t R e g i o n . B . C . Min. For. R e s . Prog., Land M a n a g e . Handbook No. 26. B a r b o u r , M . G . , N . H . B e r g , T . G . F . Kittel, a n d M . E . K u n z . 1 9 9 1 . S n o w p a c k a n d the distribution of a major v e g e t a t i o n e c o t o n e in the S i e r r a N e v a d a of C a l i f o r n i a . J . B i o g e o g . 18: 1 4 1 149. Beatty, S . W . 1 9 8 4 . Influence of m i c r o t o p o g r a p h y a n d c a n o p y s p e c i e s o n spatial patterns of forest understory plants. E c o l o g y 65(5): 1 4 0 6 - 1 4 1 9 . B e r k o w i t z , A . R . , C D . C a n h a m , a n d V . R . Kelly. 1 9 9 5 . C o m p e t i t i o n v s . facilitation of tree s e e d l i n g growth a n d survival in early s u c c e s s i o n a l c o m m u n i t i e s . E c o l o g y 76(4): 1 1 5 6 1168. B e r r y , G . L . a n d R . L . R o t h w e l l . 1 9 9 2 . S n o w ablation in s m a l l forest o p e n i n g s in s o u t h w e s t A l b e r t a . C a n . J . For. R e s . 2 2 : 1 3 2 6 - 1 3 3 1 .  87  Brett, R . B . 1 9 9 6 . Delineation of M H forested a n d p a r k l a n d s u b z o n e s in the C h a p m a n A s s e s s m e n t Unit. C o n t r a c t report for the V a n . For. R e g i o n , B . C . M i n . F o r . , N a n a i m o , B.C. 11pp. Brink, V . C . 1 9 5 9 . A directional c h a n g e in the s u b a l p i n e forest-heath e c o t o n e in G a r i b a l d i P a r k , British C o l u m b i a . E c o l o g y 4 0 : 1 0 - 1 6 . Brink, V . C . 1 9 6 4 . Plant e s t a b l i s h m e n t in the high snowfall alpine a n d s u b a l p i n e r e g i o n s of British C o l u m b i a . E c o l o g y 45(3): 4 3 1 - 4 3 8 . B r o o k e , R . C . 1 9 6 6 . V e g e t a t i o n - e n v i r o n m e n t relationships of s u b a l p i n e M o u n t a i n H e m l o c k z o n e e c o s y s t e m s . P h . D . t h e s i s , University of British C o l u m b i a , V a n c o u v e r , B . C . 2 2 5 pp, A p p . 110 p p . B r o o k e , R . C , E . B . P e t e r s o n , a n d V . J . Krajina. 1 9 7 0 . T h e s u b a l p i n e M o u n t a i n H e m l o c k z o n e . Ecol. Western N. Amer. 2: 148-349. B u r n s , R . M . a n d B . H . H o n k a l a . 1 9 9 0 . S i l v i c s of North A m e r i c a . V o l . 1 C o n i f e r s . U S D A F o r . S e r v . A g r i . H a n d b o o k 4 4 5 , W a s h i n g t o n , D . C . 6 7 5 pp. B u r t o n , P . J . 1 9 9 3 . S o m e limitations inherent to static i n d i c e s of plant c o m p e t i t i o n . C a n . J . F o r . Res. 23: 2141-2152. C a n h a m , C D . , J . S . D e n s l o w , W . J . Piatt, J . R . R u n k l e , T . A . S p i e s a n d P . S . W h i t e . 1 9 9 0 . Light r e g i m e s b e n e a t h c l o s e d c a n o p i e s a n d tree-fall g a p s in t e m p e r a t e a n d tropical f o r e s t s . C a n . J . For. R e s . 20: 620-631. C a r k i n , R . E . , J . F . F r a n k l i n , J . B o o t h , a n d C E . S m i t h . 1 9 7 8 . S e e d i n g habits of u p p e r - s l o p e tree s p e c i e s . IV. S e e d flight of noble fir a n d P a c i f i c silver fir. U S D A F o r . S e r v . R e s . N o t e P N W - 3 1 2 , P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 10 pp. C a r t e r , R . E . a n d K. K l i n k a . 1 9 9 2 . Variation in s h a d e t o l e r a n c e of Douglas-fir, w e s t e r n h e m l o c k , a n d w e s t e r n r e d c e d a r in c o a s t a l British C o l u m b i a . For. E c o l . M a n a g e . 5 5 : 8 7 - 1 0 5 . C h r i s t y , E . J . a n d R . N . M a c k . 1 9 8 4 . Variation in d e m o g r a p h y of juvenile Tsuga a c r o s s the s u b s t r a t u m m o s a i c . J o u r n a l of E c o l o g y 7 2 : 7 5 - 9 1 .  heterophylla  Coates, K.D., W . H . Emmingham, and S . R . Radosevich. 1991. Conifer-seedling s u c c e s s and m i c r o c l i m a t e at different levels of herb a n d s h r u b c o v e r in a Rhododendron Vaccinium - Menziesia c o m m u n i t y of south central British C o l u m b i a . C a n . J . F o r . R e s . 21: 858-866. C o n n e l l , J . H . a n d R . O . Slatyer. 1 9 7 7 . M e c h a n i s m s of s u c c e s s i o n in natural c o m m u n i t i e s a n d their role in c o m m u n i t y stability a n d o r g a n i z a t i o n . A m e r . Natur. 1 1 1 : 1 1 1 9 - 1 1 4 4 . D a n i e l s , L . D . 1 9 9 4 . Structure a n d regeneration of old growth Thuja plicata s t a n d s n e a r V a n c o u v e r , British C o l u m b i a . M . S c . t h e s i s , Univ. Brit. C o l u m b i a . 9 8 pp.  88  d e M o n t i g n y , L . E . 1 9 9 2 . A n investigation into the factors contributing to the g r o w t h - c h e c k of conifer regeneration o n northern V a n c o u v e r Island. P h . D . t h e s i s . Univ. British C o l u m b i a , V a n c o u v e r , B . C . 191 pp. E m m i n g h a m , W . H . a n d N . M . H a l v e r s o n . 1 9 8 1 . C o m m u n i t y t y p e s , productivity, a n d reforestation: m a n a g e m e n t implications for the P a c i f i c S i l v e r Fir Z o n e of the C a s c a d e M o u n t a i n s . In C D . Oliver a n d R . M . K e n a d y (eds.). P r o c e e d i n g s of the biology a n d m a n a g e m e n t of true fir in the P a c i f i c Northwest s y m p o s i u m . Contribution 4 5 , University of W a s h i n g t o n C o l l e g e of F o r e s t R e s o u r c e s , Seattle, W A . pp. 2 9 1 - 3 0 3 . F o n d a , R . W . a n d L . C B l i s s . 1 9 6 9 . F o r e s t vegetation of the M o n t a n e a n d S u b a l p i n e Z o n e s , Olympic Mountains, Washington. Ecol. Monog. 39: 271-301. F r a n k l i n , J . F . 1 9 6 4 . E c o l o g y a n d silviculture of the true fir-hemlock forests of the P a c i f i c Northwest. Proc. S o c . A m . Foresters 1964: 28-32. F r a n k l i n , J . F . , W . H . Moir, G . W . D o u g l a s , a n d C . W i b e r g . 1 9 7 1 . Invasion of s u b a l p i n e m e a d o w s by t r e e s in the C a s c a d e R a n g e , W a s h i n g t o n a n d O r e g o n . Arctic a n d A l p i n e R e s . 3(3), pp. 215-224. F r a n k l i n , J . F . a n d C E . S m i t h . 1 9 7 4 . S e e d i n g habits of u p p e r - s l o p e tree s p e c i e s . II. D i s p e r s a l of a m o u n t a i n h e m l o c k s e e d c r o p o n a clearcut. U S D A F o r . S e r v . R e s . N o t e P N W - 2 1 4 , P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 9 pp.. F r a n k l i n , J . F . a n d C T . D y r n e s s . 1 9 8 8 . Natural vegetation of O r e g o n a n d W a s h i n g t o n . O r e g o n S t a t e Univ. P r e s s , C o r v a l l i s , O R . 4 5 2 pp. G l a n t z , S . A . 1 9 9 2 . P r i m e r of Biostatistics. Third Edition. M c G r a w - H i l l , N e w Y o r k , N Y . 4 4 0 p p . G o l d i n g , D.L. a n d R . H . S w a n s o n . 1 9 7 8 . S n o w a c c u m u l a t i o n a n d melt in s m a l l forest o p e n i n g s in A l b e r t a . C a n . J . For. R e s . 8(4): 3 8 0 - 3 8 8 . G o l d i n g , D.L. a n d R . H . S w a n s o n . 1986. S n o w distribution patterns in c l e a r i n g s a n d the a d j a c e n t forest. W a t e r R e s o u r c e s R e s e a r c h , 22(13): 1 9 3 1 - 1 9 4 0 . G r e e n , R . N . a n d P . B e r n a r d y . 1 9 9 1 . Natural regeneration failure at high e l e v a t i o n s in the C h i p m u n k C r e e k d r a i n a g e , C h i l l i w a c k F o r e s t District. R e s . M e m o 5 9 , B . C . M i n . F o r . V i c t o r i a , B . C . 3 pp. G r e e n , R . N . , R . L . T r o w b r i d g e , a n d K. K l i n k a . 1 9 9 3 . T o w a r d s a t a x o n o m i c c l a s s i f i c a t i o n of h u m u s f o r m s . F o r . S c i . M o n o g . 2 9 (supplement to For. S c i . 39). G r e e n , R . N . a n d K. K l i n k a . 1 9 9 4 . A field guide to site identification a n d interpretation for the V a n c o u v e r F o r e s t R e g i o n . B . C . M i n . For., Victoria, B . C . 2 8 5 p p . G r u b b , P . J . 1 9 7 7 . T h e m a i n t e n a n c e of s p e c i e s - r i c h n e s s in plant c o m m u n i t i e s : T h e i m p o r t a n c e of the regeneration n i c h e . Biol. R e v . 5 2 : 1 0 7 - 1 4 5 . H a r e s t a d , A . S . a n d F . L . B u n n e l l . 1 9 8 1 . Prediction of s n o w - w a t e r e q u i v a l e n t s in c o n i f e r o u s f o r e s t s . C a n . J . For. R e s . 1 1 : 8 5 4 - 8 5 7 .  89  H a r m o n , M . E . a n d J . F . Franklin. 1989. T r e e s e e d l i n g s on logs in Picea-Tsuga O r e g o n a n d W a s h i n g t o n . E c o l o g y 70(1): 4 8 - 5 9 .  forests of  H a r p e r , J . L . 1 9 7 7 . P o p u l a t i o n biology of plants. A c a d e m i c P r e s s , L o n d o n . 8 9 2 p p . H a r v e y , A . E . , M . F . J u r g e n s e n , M . J . L a r s e n , a n d R.T. G r a h a m . 1 9 8 7 . R e l a t i o n s h i p s a m o n g soil microsite, e c t o m y c o r r h i z a e , a n d natural conifer regeneration of old-growth f o r e s t s in w e s t e r n M o n t a n a . C a n . J . For. R e s . 17: 5 8 - 6 2 . H e r r i n g , L . J . a n d D . E . E t h e r i d g e . 1976. A d v a n c e a m a b i l i s fir regeneration in the V a n c o u v e r F o r e s t District. B . C . For. S e r v . a n d C a n . For. S e r v . Joint R e p . 5. P a c i f i c F o r e s t R e s e a r c h C e n t r e , Victoria, B . C . 2 3 pp. H o p w o o d , D. 1 9 9 1 . P r i n c i p l e s a n d practices of N e w Forestry: a guide for British C o l u m b i a n s . L a n d M a n a g e . R e p . N o . 7 1 , B . C . M i n . For., Victoria, B . C . 9 5 p p . H u z i o k a , T., H. S h i m u z u , E . A k i t a y a , a n d H. Narita. 1 9 6 7 . O b s e r v a t i o n of c r e e p rate of s n o w o n m o u n t a i n s l o p e s , T e s h i o District, H o k k a i d o . In H. d u r a (ed.) P h y s i c s of s n o w a n d ice. P r o c . Int. C o n f . L o w T e m p . S c i . , V . 1 . , Pt. 2 . Inst. L o w T e m p . S c i . , H o k k a i d o Univ., S a p p o r o , J a p a n , pp. 1 1 7 7 - 1 1 8 3 . J o s z a , L. 1 9 8 8 . Increment c o r e s a m p l i n g for high quality c o r e s . S p e c i a l P u b . N o . S P - 3 0 . Forintek C a n a d a C o r p . , V a n c o u v e r , B . C . 26 pp. K e d d y , P . A . 1 9 8 9 . C o m p e t i t i o n . C h a p m a n a n d Hall, L o n d o n . 2 0 2 pp. K l i n k a , K. a n d F. P e n d l . 1 9 7 6 . P r o b l e m a n a l y s i s of regeneration in high elevation in the V a n c o u v e r F o r e s t R e g i o n . B . C . For. S e r v . R e s . Div. L a n d M a n a g e . S e r i e s R e p . N o . 2, V i c t o r i a , B . C . 90 pp. K l i n k a , K., V . J . Krajina, A . C e s k a , a n d A . M . S c a g e l . 1 9 8 9 . Indicator plants of c o a s t a l British C o l u m b i a . University of British C o l u m b i a P r e s s , V a n c o u v e r , B . C . 2 8 8 pp. K l i n k a , K., R . E . C a r t e r , G . F . W e e t m a n , a n d M . Jull. 1 9 9 2 . Silvicultural a n a l y s i s of the s u b a l p i n e M o u n t a i n H e m l o c k z o n e . B . C . M i n . For., B u r n a b y , B . C . 4 6 pp. K n a p p , A . K . a n d W . K . S m i t h . 1 9 8 2 . F a c t o r s influencing understory s e e d l i n g e s t a b l i s h m e n t of E n g e l m a n n s p r u c e [Picea engelmannii) a n d s u b a l p i n e fir (Abies lasiocarpa) in s o u t h e a s t W y o m i n g . C a n . J . Bot. 6 0 : 2 7 5 3 - 2 7 6 1 . K o h y a m a , T. 1 9 8 3 . S e e d l i n g s t a g e of two s u b a l p i n e Abies s p e c i e s in distinction f r o m s a p l i n g s t a g e : a m a t t e r - e c o n o m i c a n a l y s i s . Bot M a g . (Tokyo) 9 6 : 4 9 - 6 5 . K o p p e n a a l , R . S . a n d A . K . Mitchell. 1 9 9 2 . R e g e n e r a t i o n of m o n t a n e forests in the C o a s t a l W e s t e r n H e m l o c k z o n e of British C o l u m b i a : a literature review. F o r . C a n . a n d B . C . M i n . For., Victoria, B . C . F R D A R e p . N o . 192. 2 2 pp. K o t a r , J . 1 9 7 7 . Altitudinal distribution of A b i e s amabilis a s a function of moisture s t r e s s . In R . D . A n d r e w s III (ed.). P r o c . S y m p . on Terrestrial a n d A q u a t i c E c o l o g i c a l S t u d i e s of the Northwest. Dept. Biol., E a s t e r n W a s h . State C o l l e g e , C h e n e y , W a s h . pp. 9 - 2 1 .  90  K o t a r , J . 1 9 7 8 . R e l a t i o n s h i p of early s e e d l i n g d e v e l o p m e n t to altitudinal distribution of amabilis. Bull. T o r r e y Bot. C l u b 105(4): 2 8 9 - 2 9 5 .  Abies  K r a j i n a , V . J . 1 9 6 9 . E c o l o g y of forest trees in British C o l u m b i a . E c o l . W e s t e r n N . A m e r . 2: 1146. K r a j i n a , V . J . , K. K l i n k a , a n d J . W o r r a l l . 1 9 8 2 . Distribution a n d e c o l o g i c a l c h a r a c t e r i s t i c s of t r e e s a n d s h r u b s of British C o l u m b i a . Faculty of Forestry, Univ. Brit. C o l u m b i a , V a n c o u v e r , B . C . 131 pp. Krumlik, G . J . 1 9 7 9 . C o m p a r a t i v e a n a l y s i s of nutrient cycling in the s u b a l p i n e M o u n t a i n H e m l o c k Z o n e . P h . D . t h e s i s , Univ. Brit. C o l u m b i a , V a n c o u v e r . 196 p p . K u o , J . , E . F o x , S . A . G l a n t z , a n d S . M c D o n a l d . 1 9 8 7 . S i g m a S t a t for W i n d o w s J a n d e l Scientific, S a n Rafael, C A . L e a p h a r t , C D . , R . D . H u n g e r f o r d , a n d H . E . J o h n s o n . 1 9 7 2 . S t e m deformities in y o u n g t r e e s c a u s e d by s n o w p a c k a n d its m o v e m e n t . U S D A F o r . S e r v . R e s . N o t e I N T - 1 5 8 . Intermountain F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , O g d e n , U T . 10 pp. L e r t z m a n , K . P . 1 9 8 9 . G a p - p h a s e d y n a m i c s in a s u b a l p i n e old-growth forest. P h . D . t h e s i s , Univ. British C o l u m b i a , V a n c o u v e r , B . C . 167 pp. L e r t z m a n , K . P . 1 9 9 2 . P a t t e r n s of g a p - p h a s e r e p l a c e m e n t in a s u b a l p i n e , old-growth forest. E c o l o g y 73(2): 6 5 7 - 6 6 9 . L e r t z m a n , K . P . 1 9 9 5 . F o r e s t d y n a m i c s , differential mortality a n d v a r i a b l e recruitment J . V e g . S c i . 6: 1 9 1 - 2 0 4 .  patterns.  L e r t z m a n , K . P . a n d C . J . K r e b s . 1 9 9 1 . G a p - p h a s e structure of a s u b a l p i n e old-growth forest. C a n . J . For. R e s . 2 1 : 1730-1741. L e r t z m a n , K . P . , G . D . S u t h e r l a n d , A . Inselberg, a n d S . S a u n d e r s . 1 9 9 6 . C a n o p y g a p s a n d the l a n d s c a p e m o s a i c in a c o a s t a l t e m p e r a t e rainforest. E c o l o g y 77(4): 1 2 5 4 - 1 2 7 0 . L o n g , J . N . 1 9 7 6 . F o r e s t vegetation d y n a m i c s within the Abies amabilis Z o n e of a w e s t e r n C a s c a d e s w a t e r s h e d . P h . D. t h e s i s , University of W a s h i n g t o n , S e a t t l e . 174 pp. L o r i m e r , C . G . 1 9 8 5 . M e t h o d o l o g i c a l c o n s i d e r a t i o n s in the a n a l y s i s of forest d i s t u r b a n c e history. C a n . J . F o r . R e s . 15: 2 0 0 - 2 1 3 . L o w e r y , R . F . 1 9 7 2 . E c o l o g y of s u b a l p i n e z o n e tree c l u m p s in the North C a s c a d e M o u n t a i n s of W a s h i n g t o n . P h . D . dissertation. Univ. W a s h i n g t o n . 138 pp. L u t t m e r d i n g , H.A., D.A. D e m a r c h i , E . C L e a , D . V . M e i d i n g e r , a n d T. V o i d . 1 9 9 0 . D e s c r i b i n g e c o s y s t e m s in the field. 2 n d E d . M O E M a n u a l 1 1 , B . C . Ministry of the E n v i r o n m e n t , V i c t o r i a , B . C . 2 1 3 pp. M a c k a y , J . R . a n d W . H . M a t h e w s . 1967. O b s e r v a t i o n s on p r e s s u r e s e x e r t e d by c r e e p i n g s n o w , M o u n t S e y m o u r , British C o l u m b i a , C a n a d a . In H. d u r a (ed.) P h y s i c s of s n o w a n d ice.  91  P r o c . Int. C o n f . L o w T e m p . S c i . , V . 1 . , Pt. 2. Inst. L o w T e m p . S c i . , H o k k a i d o Univ., S a p p o r o , J a p a n , pp. 1 1 8 5 - 1 1 9 7 . Mallik, A . U . 1 9 9 5 . C o n v e r s i o n of t e m p e r a t e forests into h e a t h s : role of e c o s y s t e m d i s t u r b a n c e a n d e r i c a c e o u s plants. E n v . M a n a g e . 19(5): 6 7 5 - 6 8 4 . M a s e r , C , R . G . A n d e r s o n , K. C r o m a c k Jr., J . T . W i l l i a m s , a n d R . E . Martin. 1 9 7 9 . D e a d a n d d o w n w o o d y material. In J . W . T h o m a s (ed.). Wildlife habitats in m a n a g e d f o r e s t s - t h e B l u e M o u n t a i n s of O r e g o n a n d W a s h i n g t o n . U S D A For. S e r v . A g r i c . H a n d b o o k 5 5 3 , P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t Station, P o r t l a n d , O R . p p . 7 8 - 9 5 . M e g a h a n , W . F . a n d R. S t e e l e . 1 9 8 7 . A n a p p r o a c h for predicting s n o w d a m a g e to p o n d e r o s a pine plantations. F o r . S c i . 33(2): 4 8 5 - 5 0 3 . M e g a h a n , W . F . a n d R. S t e e l e . 1988. A field guide for predicting s n o w d a m a g e to p o n d e r o s a pine plantations. U S D A For. S e r v . R e s . Note. I N T - 3 8 5 . Intermountain R e s e a r c h S t a t i o n , O g d e n , U T . 9 pp. M e s s i e r , C . a n d J . P . K i m m i n s . 1 9 9 0 . F a c t o r s limiting c o n i f e r o u s s e e d l i n g growth in recently clearcut sites d o m i n a t e d by Gaultheria shallon in the C W H v m s u b z o n e . F R D A R e p . 1 4 9 , B . C . M i n . For., Victoria, B . C . 30 pp. M i n o r e , D. 1 9 7 2 . G e r m i n a t i o n a n d early growth of c o a s t a l tree s p e c i e s o n o r g a n i c s e e d b e d s . U S D A For. S e r v . R e s . P a p . P N W - 1 3 5 , P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 18 pp. M i n o r e , F. 1 9 7 9 . C o m p a r a t i v e a u t e c o l o g i c a l characteristics of northwestern tree s p e c i e s : a literature review. U S D A For. S e r v . , G e n . T e c h . R e p . P N W - 8 7 . P a c i f i c N o r t h w e s t F o r e s t a n d R a n g e E x p e r i m e n t Station, P o r t l a n d , O R . 7 2 pp. M i n o r e , D. 1 9 8 6 . G e r m i n a t i o n , survival a n d early growth of conifer s e e d l i n g s in two habitat t y p e s . U S D A For. S e r v . R e s . P a p . P N W - 3 4 8 , P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 2 5 pp. M i n o r e , D. a n d M . E . D u b r a s i c h . 1 9 8 1 . R e g e n e r a t i o n after clearcutting in s u b a l p i n e s t a n d s n e a r W i n d i g o P a s s , O r e g o n . J . Forestry 7 9 ( 9 ) : 6 1 9 - 6 2 1 . N a k a m u r a , T. 1 9 9 2 . Effect of b r y o p h y t e s o n survival of conifer s e e d l i n g s in s u b a l p i n e f o r e s t s of central J a p a n . E c o l . R e s . 7: 1 5 5 - 1 6 2 . O l i v e r , C D . a n d B . C . L a r s o n . 1 9 9 0 . F o r e s t s t a n d d y n a m i c s . M c G r a w - H i l l , Inc., N e w Y o r k . 4 6 7 PPO r l o c i , L. 1 9 6 5 . T h e C o a s t a l W e s t e r n H e m l o c k Z o n e o n the s o u t h w e s t e r n British C o l u m b i a m a i n l a n d . / n V . J . Krajina (ed.). E c o l o g y of W e s t e r n North A m e r i c a , V o l . 1. U n i v . Brit. C o l . Dept. Bot., V a n c o u v e r , pp. 18-34. P e t e r s o n , C . J . a n d J . E . C a m p b e l l . 1 9 9 3 . Microsite differences a n d t e m p o r a l c h a n g e in plant c o m m u n i t i e s of treefall pits a n d m o u n d s in a n old-growth forest. Bull. T o r r e y Bot. C l u b 120(4): 4 5 1 - 4 6 0 .  92  P e t e r s o n , E . B . 1 9 6 4 . Plant a s s o c i a t i o n s in the s u b a l p i n e M o u n t a i n H e m l o c k z o n e of s o u t h e r n British C o l u m b i a . P h . D . T h e s i s . D e p a r t m e n t s of B i o l o g y a n d B o t a n y , U n i v . of British C o l u m b i a , V a n c o u v e r , B . C . 171 pp. P e t e r s o n , E . B . 1 9 6 9 . R a d i o s o n d e d a t a for characterization of a mountain e n v i r o n m e n t in British C o l u m b i a . E c o l o g y 50(2): 2 0 0 - 2 0 5 . Piatt, W . J . a n d D . R . S t r o n g (eds.). 1 9 8 9 . S p e c i a l feature - treefall g a p s a n d forest d y n a m i c s . E c o l o g y 70(3): 5 3 5 - 5 7 6 . Pojar, J . , K. K l i n k a , a n d D.A. D e m a r c h i . 1 9 9 1 . M o u n t a i n H e m l o c k z o n e . In D. M e i d i n g e r a n d J . P o j a r (eds.). S p e c . R e p . S e r i e s 6, B . C . M i n . For., V i c t o r i a , B . C . , pp. 1 1 3 - 1 2 4 . Pojar, J . a n d A . M a c K i n n o n . 1994. P l a n t s of c o a s t a l British C o l u m b i a including W a s h i n g t o n , O r e g o n , a n d A l a s k a . L o n e P i n e P u b l i s h i n g , V a n c o u v e r , B . C . 5 2 8 pp. Pothier, D., R. D o u c e t , a n d J . Bolly. 1 9 9 5 . T h e effect of a d v a n c e regeneration height o n future yield of b l a c k s p r u c e s t a n d s . C a n . J . For. R e s . 25(4): 5 3 6 - 5 4 4 . R a d o s e v i c h , S . R . 1 9 8 4 . Interference b e t w e e n greenleaf m a n z a n i t a (Arctostaphylos patula) a n d p o n d e r o s a pine (Pinus ponderosa). In M . L . D u r y e a a n d G . N G r o w n (eds.). S e e d l i n g p h y s i o l o g y a n d reforestation s u c c e s s . Nijhoff/Junk P u b l i s h e r s , Dordrecht, T h e Netherlands, pp. 259-270. R e u t e r , F. 1 9 7 3 . High elevation reforestation p r o b l e m s in the V a n c o u v e r F o r e s t District: a p r o b l e m a n a l y s i s . B . C . For. S e r v . , Victoria, B . C . 4 6 pp. R u n k l e , J . R . 1 9 8 1 . G a p regeneration in s o m e old-growth forests of the e a s t e r n U n i t e d S t a t e s . E c o l o g y 62(4): 1 0 4 1 - 1 0 5 1 . R u n k l e , J . R . 1 9 8 2 . P a t t e r n s of d i s t u r b a n c e in s o m e old-growth m e s i c forests of e a s t e r n North A m e r i c a . E c o l o g y 63(5): 1 5 3 3 - 1 5 4 6 . R u n k l e , J . R . 1 9 9 2 . G u i d e l i n e s a n d s a m p l e protocol for s a m p l i n g forest g a p s . G e n . T e c h . R e p . P N W - G T R - 2 8 3 . U S D A For. S e r v . P a c i f i c Northwest R e s e a r c h S t a t i o n , P o r t l a n d , O r e g o n . 4 4 pp. S c a g e l , R., R. G r e e n , H. v o n H a h n , a n d R. E v a n s . 1 9 8 9 . Exploratory high-elevation r e g e n e r a t i o n trials in the V a n c o u v e r F o r e s t R e g i o n : 1 0 - y e a r s p e c i e s p e r f o r m a n c e of p l a n t e d stock. F R D A R e p . 0 9 8 , B . C . M i n . For., Victoria, B . C . S e i d e l , K . W . 1 9 8 5 . G r o w t h r e s p o n s e of s u p p r e s s e d true fir a n d mountain h e m l o c k after r e l e a s e . U S D A For. S e r v . R e s . N o t e P N W - 3 4 4 . P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 2 2 pp. S e i d e l , K . W . a n d R. C o o l e y . 1 9 7 4 . Natural reproduction of g r a n d fir a n d m o u n t a i n h e m l o c k after s h e l t e r w o o d cutting in central O r e g o n . U S D A F o r . S e r v . R e s . N o t e P N W - 2 2 9 . P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 10 pp.  93  S o l l i n s , P. 1 9 8 2 . Input a n d d e c a y of c o a r s e w o o d y debris in c o n i f e r o u s s t a n d s in w e s t e r n O r e g o n a n d W a s h i n g t o n . C a n . J . For. R e s . 12(1): 1 8 - 2 8 . S p i t t l e h o u s e , D.L. a n d R . J . S t a t h e r s . 1 9 9 0 . S e e d l i n g microclimate. B . C . M i n . For., L a n d M a n a g e . R e p . N o . 6 5 , Victoria, B . C . 2 8 pp. S t a t h e r s , R . J . , R. T r o w b r i d g e , D.L. S p i t t l e h o u s e , A . M a c a d a m , a n d J . P . K i m m i n s . 1 9 9 0 . E c o l o g i c a l principles: b a s i c c o n c e p t s . In R e g e n e r a t i n g British C o l u m b i a f o r e s t s . D . P . L a v e n d e r , R. P a r i s h , C M . J o h n s o n , G . M o n t g o m e r y , A . V y s e , R . A . Willis, a n d D. W i n s t o n (eds.). Univ. British C o l u m b i a P r e s s , V a n c o u v e r , B . C . pp. 4 5 - 5 4 . T h o r n b u r g h , D.A. 1 9 6 9 . D y n a m i c s of the true-fir h e m l o c k forests of the w e s t s l o p e of the W a s h i n g t o n C a s c a d e R a n g e . P h . D . t h e s i s . University of W a s h i n g t o n , S e a t t l e . 2 1 0 pp. T r i s k a , F . J . a n d K. C r o m a c k J r . 1979. T h e role of w o o d debris in forests a n d s t r e a m s . In F o r e s t s : fresh p e r s p e c t i v e s from e c o s y s t e m a n a l y s i s . R . H . W a r i n g (ed.). P r o c . 40th B i o l o g y C o l l o q u i u m , A p r . 1979, C o r v a l l i s . O r e g o n State University P r e s s , C o r v a l l i s , O R . pp. 171-190. U t z i g , G . a n d L. Herring. 1974. F a c t o r s significant to high elevation forest m a n a g e m e n t : a report e m p h a s i z i n g soil stability a n d s t a n d regeneration. B . C . F o r . S e r v . R e s . Div., V i c t o r i a , B . C . 5 2 pp. V a n Pelt, R. 1 9 9 5 . U n d e r s t o r y tree r e s p o n s e to c a n o p y g a p s in old-growth D o u g l a s - f i r forests of the P a c i f i c Northwest. P h . D . dissertation. Univ. W a s h i n g t o n . 2 3 2 p p . V a r g a , P. 1 9 9 7 . Structure a n d regeneration pattern of old-growth s t a n d s in the M o i s t C o l d E n g e l m a n n S p r u c e - S u b a l p i n e Fir S u b z o n e of central British C o l u m b i a . M . S c . t h e s i s . University of British C o l u m b i a , V a n c o u v e r , B . C . 111 pp. V o g t , K., E . M o o r e , S . G o w e r , D. Vogt, D. S p r u g e l , a n d D. G r i e r . 1 9 8 9 . Productivity of u p p e r s l o p e s forests in the Pacific Northwest. In D.A. Perry, R. M e u r i s s e , R. Miller, J . B o y l e , J . M e a n s , C . R . P e r r y , a n d R . F . P o w e r s (eds.). Maintaining the long-term productivity of P a c i f i c Northwest e c o s y s t e m s . T i m b e r P r e s s , P o r t l a n d , O r e g o n , pp. 1 3 7 - 1 6 3 . W a g n e r , R. 1 9 8 0 . Natural regeneration at the e d g e of a n Abies amabilis Z o n e c l e a r c u t o n the w e s t s l o p e of the central W a s h i n g t o n C a s c a d e s . M . S c . t h e s i s , Univ. W a s h i n g t o n , S e a t t l e , W a s h i n g t o n . 7 2 pp. W i l k i n s o n , L , M . Hill, S . M i c e l i , G . B i r k e n b e u e l , a n d E . V a n g . 1 9 9 2 . S Y S T A T for W i n d o w s . E v a n s t o n II: S Y S T A T Inc. W i l l i a m s , C . B . 1 9 6 6 . S n o w d a m a g e to coniferous s e e d l i n g s a n d s a p l i n g s . U S D A F o r . S e r v . R e s . Note P N W - 4 0 . P a c i f i c Northwest F o r e s t a n d R a n g e E x p e r i m e n t S t a t i o n , P o r t l a n d , O R . 10 p p . Y a m a m o t o , S . - l . 1 9 9 3 . G a p characteristics a n d g a p regeneration in a s u b a l p i n e c o n i f e r o u s forest o n Mt O n t a k e , central H o n s h u , J a p a n . E c o l . R e s . 8: 2 7 7 - 2 8 5 . Z a r , J . H . 1 9 8 4 . Biostatistical a n a l y s i s . P r e n t i c e - H a l l . E n g l e w o o d Cliffs, N J , U S A . 7 1 8 p p .  94  A p p e n d i x A . N o n - t r e e s p e c i e s by life-form (Klinka etal. 1989), o c c u r r e n c e , a n d p e r c e n t c o v e r . N o m e n c l a t u r e follows K l i n k a etal. (1989) a n d P o j a r a n d M a c K i n n o n (1994).  Life form  Deciduous shrubs  Evergreen shrubs  Ferns and fern allies  Herbs (forbs)  Lichens Liverworts  Mosses  Saprophytes  Clearcut sites Cover (%)  Species  Common name  Cladothamnus pyroliflorus Menziesia ferruginea Rhododendron albiflorum Rubus spectabilis Salix scouleriana Sambucus racemosa Sorbus sitchensis Vaccinium spp. Chimaphila menziesii Gaultheria humifusa Gaultheria ovatifolia Linnaea borealis Phyllodoce empetriformis Athyrium filix-femina Blechnum spicant Dryopteris expansa Gymnocarpium dryopteris Lycopodium clavatum Polystichum munitum Anaphalis margaritacea Arnica cordifolia Caltha biflora Clintonia uniflora Coptis asplenifolia Cornus canadensis Dicentra formosa Epilobium angustifolium Goodyera oblongifolia Hieracium albiflorum Listera caurina Listera cordata Luetkea pectinata Lysichitum americanum Mycelis muralis Orthilia secunda Parnassia fimbriata Pedicularis bracteosa Rubus pedatus Streptopus amplexifolius Streptopus roseus Streptopus streptopoides Tiarella trifoliata Tiarella unifoliata Veratrum viride Cladina spp. Barbilophozia floerkei Bazzania tricentra Calypogeia trichomanis Pellia neesiana Dicranum spp. Mnium spinulosum Pleurozium schreberi Polytrichum juniperinum Pseudotaxiphyllum elegans Rhizomnium glabrescens Rhytidiadelphus loreus Rhytidiopsis robusta Sphagnum fuscum/rubellum Sphagnum girgensohnii Corallorhiza mertensiana  Copperbush False azalea White-flowered rhododendron  Total number of species (% cover)  Salmonberry Scouler's willow Red elderberry Sitka mountain ash Huckleberry (blueberry) Menzies' pipsissewa Alpine wintergreen  Quadrats 0 67 23 2 3 6 1 53 0 4  Western tea-berry Twinflower Pink mountain-heather Lady fern Deer fern Spiny wood fern Oak fern Running club moss Sword fern Pearly everlasting  33 23 1 12 6 4  Heart-leaved arnica Two-flowered marsh marigold  0 11  Queen's cup Fern-leaved goldthread Bunchberry Bleeding heart Fireweed Rattlesnake-plantain White-flowered hawkweed Northwestern twayblade Heart-leaved twayblade Partridgefoot Skunk cabbage Wall-lettuce One-sided wintergreen Fringed grass-of-Parnassus Bracted lousewort Five-leaved bramble Clasping twistedstalk Rosy twistedstalk Small twistedstalk Three-leaved foam flower One-leaved foam flower Indian false hellebore Shrub lichens Snow-mat liverwort Three-toothed whip liverwort n/a Ring pellia Dusky fork moss, broom moss Menzies' red-mouthed mnium Red-stemmed  feathermoss  Juniper haircap moss Small flat moss Fan moss Lanky moss Pipecleaner moss Red peat mosses White-toothed peat moss Western coralroot  13 3 1 18  38 6 257  0.00 1.70 0.67 0.03 0.37 0.18 0.01 52.68 0.00 0.02 0.42 0.46 0.00 0.12 0.47  Old-growth sites Quadrats 55 69 39 0 0 0 1 54 6 6 15 0 14 0  Cover (%) 1.57 1.31 0.49 0.00 0.00 0.00 0.06 27.57 0.01 0.13 0.18 0.00 0.03  0.15 0.00 0.03 0.01  26 0 4 5 0  0.00 0.96 0.00 0.04 0.01 0.00  0.01 0.00 0.67  0 18 0  0.00 0.25 0.00  0.28 0.18 3.12 0.05 3.08 0.00 0.05  3 7  0.03 0.00 0.00 0.00  0 57 7  0.01 0.01 0.15 0.00 0.00 0.03 0.00 0.02 0.02 0.01 0.40 0.00 0.13 0.03  8  0.11  358 5 3 1  5.52  424  2.34  0.02 0.01 0.00  19 61 36  0.05 0.27 0.10  2 0 13  0.00 0.00 0.17  8 43 65  0.01 0.09 0.57  36 3  0.11  28 1  0.06 0.03  56 14  1.11 0.17 0.04  3 347 1 12 0 2 0 6 6 1 0 0  0.00 0.00 0.00 0.14  0 0  0.01 0.00 0.00  0 174  0.00 1.43  0 33  0.00 0.34  55 0 1  0.24 0.00 0.00  72  0.45  242  2.16 0.27  6 9 0  0.15 0.00  46 (75.83)  45 0 1 7 0 1 11 4 17  6 318 13  6.18 0.12  53  0.87  3 16 15  0.06 0.31 1.10  188 477  3.30  0  27.28 0.00  66 4  2.78 0.02  47 (80.35)  95  A p p e n d i x B. C l a s s i f i c a t i o n of growth form a n o m a l i e s . C l a s s e s follow L e a p h a r t etal. S c a g e l etal. (1989), a n d p e r s o n a l o b s e r v a t i o n s .  Growth Form Anomaly  Definition  Broken  A b s e n c e of leader a n d e v i d e n c e of b r e a k a g e .  top ( B T )  (1972),  Chlorotic  (CL)  Y e l l o w i s h discolouration of foliage.  Crushed  (CR)  Part of s t e m or w h o l e tree p i n n e d under c o a r s e w o o d y d e b r i s , c o m m o n l y logging s l a s h in c l e a r c u t s .  Damaged  leader  (DL)  L e a d e r m i s s i n g or d e f o r m e d .  Dog leg ( D G )  Horizontal growth a b o v e the tree b a s e of >5 c m . H o r i z o n t a l d i s t a n c e a n d height to resumption of vertical growth w e r e m e a s u r e d to d e s c r i b e the severity of deformity. Direction of d o g leg w a s a l s o noted (i.e., uphill, downhill, east, west).  Multiple  M o r e than o n e leader a n d n o c l e a r a p i c a l d o m i n a n c e by a n y . Multiple l e a d e r s w e r e generally f o u n d originating from the top half of s t e m s . N o distinction w a s m a d e for b a s a l forking a s d e s c r i b e d in S c a g e l etal. (1989).  leaders ( M L )  Pistol butt ( P B )  Horizontal growth from the tree b a s e of >5 c m . H o r i z o n t a l a n d vertical d i s t a n c e s a n d direction of deformity w e r e a s noted for "dog leg" above.  Prostrate  A n g l e of s t e m from b a s e to tip <45 d e g r e e s .  (PR)  Shrub ( S H )  N o c l e a r a p i c a l d o m i n a n c e s h o w n by m a n y l e a d e r s originating from n e a r the tree b a s e .  Spire ( S P )  D i e b a c k of tree top characteristic e s p e c i a l l y of c a n o p y C. nootkatensis.  S f e m sweep ( S W )  C u r v e d growth form r e s e m b l i n g the s h a p e of a h o c k e y stick w h e r e the a n g l e of s t e m from b a s e to tip >45 d e g r e e s .  Umbrella  Horizontal growth greater than vertical growth resulting in a n u m b r e l l a or p a l m tree a p p e a r a n c e .  (UM)  96  A p p e n d i x C . R e g e n e r a t i o n status of clearcut study locations in 1 9 9 2 ( B . C . Ministry of F o r e s t s ) , o n e y e a r before s a m p l i n g .  S t u d y location  Survey area Total s t e m s / h a M i n i m u m s t o c k i n g s t a n d a r d (stems/ha) T a r g e t s t o c k i n g s t a n d a r d (stems/ha) W e l l - s p a c e d t r e e s (stem/ha) F r e e - g r o w i n g t r e e s (stems/ha) Successfully stocked? Free-growing? Well-spaced stems: A. amabilis C. nootkatensis T. mertensiana T. heterophylla  Batchelor  Mayne  Tannis  39 ha 12567 500 900 883 700 yes yes 67% 10% 17% 6%  29 ha 6400 500 900 900 320 yes no 58% 12% 27% 3%  82 ha 3560 500 900 860 680 yes yes 56% 18% 0% 26%  R e c o m m e n d e d future action by study location ( B . C . Ministry of F o r e s t s 1992): Batchelor:  1 9 9 7 p r e - s t a n d tending s u r v e y for p o s s i b l e 1 9 9 8 i n c r e m e n t a l juvenile s p a c i n g .  Mayne:  1 9 9 7 free-growing s u r v e y in 1 9 9 7 ; predicted to be free of b r u s h in 4 - 5 y e a r s .  Tannis:  1 9 9 7 p r e - s t a n d tending s u r v e y for p o s s i b l e 1 9 9 8 i n c r e m e n t a l juvenile s p a c i n g .  

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