UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A simulation of predation by non-game birds on the mountain pine beetle (Dendroctonus ponderosae Hopkins) Korol, Jerome John 1985

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1986_A6_7 K67_4.pdf [ 6.06MB ]
Metadata
JSON: 831-1.0096698.json
JSON-LD: 831-1.0096698-ld.json
RDF/XML (Pretty): 831-1.0096698-rdf.xml
RDF/JSON: 831-1.0096698-rdf.json
Turtle: 831-1.0096698-turtle.txt
N-Triples: 831-1.0096698-rdf-ntriples.txt
Original Record: 831-1.0096698-source.json
Full Text
831-1.0096698-fulltext.txt
Citation
831-1.0096698.ris

Full Text

SIMULATION OF PREDATION BY NON-GAME BIRDS ON THE MOUNTAIN PINE BEETLE (DENDROCTONUS PONDEROSAE HOPKINS) by JEROME JOHN KOROL A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF FORESTRY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d UNIVERSITY OF BRITISH COLUMBIA OCTOBER 14, 1985 © JEROME JOHN KOROL, 1985 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the r e q u i r e m e n t s f o r an advanced degree a t the UNIVERSITY OF BRITISH COLUMBIA, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . DEPARTMENT OF FORESTRY UNIVERSITY OF BRITISH COLUMBIA 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: OCTOBER 14, 1985 ABSTRACT A v a i l a b l e i n f o r m a t i o n on b i r d - l o d g e p o l e p i n e , b i r d -mountain p i n e b e e t l e , and mountain p i n e b e e t l e - l o d g e p o l e p i n e i n t e r a c t i o n s was r e v i e w e d . A computer model was c o n s t r u c t e d f o r the purpose of s i m u l a t i n g v a r i a t i o n s i n th e s e i n t e r a c t i o n s . Three l o d g e p o l e p i n e s t a n d s t r u c t u r e s and t h r e e s e t s of b i r d r e sponses t o changes i n b e e t l e d e n s i t y were s i m u l a t e d . I t was de t e r m i n e d t h a t b i r d s may be a b l e t o s u p p r e s s b e e t l e p o p u l a t i o n growth and reduce maximum b e e t l e d e n s i t y under ' t y p i c a l ' s t a n d c o n d i t i o n s , but c o u l d o n l y p r e v e n t an e p i d e m i c when u n r e a l i s t i c a l l y h i g h b i r d d e n s i t i e s were assumed. I n c r e a s i n g b a s e - l i n e b i r d d e n s i t i e s t o l e v e l s which were r e a l i s t i c a l l y o b t a i n a b l e had e f f e c t s s i m i l a r t o tho s e o b t a i n e d when p r e d a t o r e f f i c i e n c y was i n c r e a s e d . No amount of a v i a n p r e d a t i o n c o u l d p r e v e n t a massive e p i d e m i c from o c c u r r i n g when s t a n d c o n d i t i o n s were such t h a t b e e t l e p r o d u c t i v i t y was o p t i m i z e d . A mountain p i n e b e e t l e e p i d e m i c , as w e l l as b i r d f u n c t i o n a l and n u m e r i c a l r e s p o n s e s , d i d not o c c u r when a s t a n d s t r u c t u r e r e p r e s e n t i n g a p r e v e n t i v e t h i n n i n g was s i m u l a t e d . P r e v e n t i v e s i l v i c u l t u r a l methods such as t h i n n i n g or r e d u c t i o n of r o t a t i o n age, combined w i t h p r a c t i c e s such as r e t e n t i o n of w i l d l i f e t r e e s on c l e a r c u t s i t e s i n o r d e r t o i n c r e a s e non-game b i r d d e n s i t i e s , c o u l d h e l p p r e v e n t endemic b e e t l e p o p u l a t i o n s from r e a c h i n g e p i demic l e v e l s . i i R E S U M E L e r a p p o r t r e v o i t l e s d o n n e e s e x i s t a n t e s s u r 1 ' i n t e r a c t i o n q u i e x i s t e r e s p e c t i v e m e n t e n t r e l e s o i s e a u x e t l e p i n l o d g e p o l e (Pinus contort a ) , e n t r e l e s o i s e a u x e t l e s c o t y l e d u p i n d e m o n t a g n e (Dendroctonus ponderosae) e t e n t r e c e d e r n i e r e t l e p i n l o d g e p o l e . O n e e l a b o r e u n m o d e l e i n f o r m a t i q u e d e s t i n e a s i m u l e r d i f f e r e n t e s v a r i a t i o n s d a n s c e i n t e r a c t i o n s . O n a s i m u l e t r o i s d i f f e r e n t s p e u p l e m e n t s d e s p i n s l o d g e p o l e e t t r o i s e n s e m b l e s d i f f e r e n t s d e r e a c t i o n s d e s o i s e a u x e n r e s p o n s e a u x v a r i a t i o n s d e d e n s i t e d e p e u p l e m e n t d e s s c o t y l e s . O n e e t a b l i q u e l e s o i s e a u x e t a i e n t c a p a b l e s d ' a r r e t e r l e d e v e l o p p e m e n t d e s s c o t y l e s e t d ' e n r e d u i r e l a d e n s i t e m a x i m u m d a n s c e r t a i n e s c o n d i t i o n s p r e c i s e s d e d e n s i t e f o r e s t i e r e , m a i s q u e i l s n e p o u v a i e n t c e p e n d a n t e n e m p e c h e r l e d e v e l o p p e m e n t e p i d e m i q u e q u e s i c e s o i s e a u x e t a i e n t e n n o m b r e a n o r m a l e m e n t e l e v e . L ' a c c r o i s s e m e n t d e l a d e n s i t e d e s o i s e a u x a d e s n i v e a u x a c c e p t a b l e s e s t c e n s e a v o i r l e meme e f f e t q u e c e l u i q u i e s t o b t e n u p a r u n e e f f i c a c i t e a c c r u e d e s p r e d a t e u r s . Meme t r e s e l e v e e , l a p r e d a t i o n p a r l e s o i s e a u x n ' e s t p a s c a p a b l e d ' e m p e c h e r l e d e v e l o p p e m e n t e p i d e m i q u e d e s s c o t y l e s l o r s q u e l a d e n s i t e d u p e u p l e m e n t f o r e s t i e r e s t t e l l e q u e l a m u l t i p l i c a t i o n d e c e s i n s e c t e s s ' e n t r o u v e f a v o r i s e e a u m a x i m u m , o n a c o n s t a t e q u e n i l a m u t i p l i c a t i o n e f f r e n e e d e s s c o t y l e s d u p i n d e m o n t a g n e n i l e s r e a c t i o n s f o n c t i o n n e l l e s e t n u m e r i q u e s d e s o i s e a u x n e s e p r o d u i s a i e n t l o r s q u e l ' o n s i m u l a i t u n e d e n s i t e f o r e s t i e r e o b t e n u e a p r e s e c l a i r c i s s a g e . L e s m e t h o d e s s y l v i c o l e s p r e v e n t i v e s t e l l e s q u e l ' e c l a i r c i s s a g e o u l ' a b a i s s e m e n t d e l ' a g e d e r o t a t i o n , c o m b i n e e s a d e s p r a t i q u e s t e l l e s q u e l e m a i n t i e n d ' a r b r e s p r e f e r e s p a r l e d a n s l e s p a r t i e s c o u p e e s a b l a n c , e n v u e d ' a u g m e n t e r l a d e n s i t e d e p o p u l a t i o n d e s o i s e a u x a u t r e s q u e l e g i b i e r , t o u t e s c e s m e t h o d e s p o u r r a i e n t c o n t r i b u e r a e m p e c h e r l e s p o p u l a t i o n s e n d e m i q u e d e s c o t y l e s d ' a t t e i n d r e d e s n i v e a u x e p i d e m i q u e s . ACKNOWLEDGEMENTS T h i s r e p o r t i s a s y n t h e s i s of i n f o r m a t i o n drawn from a number of b i o l o g i c a l d i s c i p l i n e s . Many p r o f e s s i o n a l s who r e p r e s e n t t h e s e d i s c i p l i n e s a s s i s t e d g r e a t l y throughout the s t u d y , and I w i s h t o e x p r e s s my g r a t i t u d e t o them. Stephen Wetmore, Canadian W i l d l i f e S e r v i c e ; Dr. F r e d B u n n e l l , Dr. D a v i d T a i t , Dr. John McLean, and Dr. Lee Gass, U n i v e r s i t y of B r i t i s h C o lumbia; and Dr. C a r l W a l t e r s , I n s t i t u t e of A n i m a l Resource E c o l o g y a l l shared t h e i r e x p e r i e n c e and e x p e r t i s e d u r i n g numerous d i s c u s s i o n s , and a l s o r e v i e w e d and e d i t e d d r a f t s of the r e p o r t . T e r r y Shore, C o l i n Wood, Dr. John H a r r i s , Dr. Henry Moeck, Dr. Imre Otv o s , Dr. Les S a f r a n y i k , Dr. Roy Shepherd, and Dr. S t e w a rt Whitney, a l l of the P a c i f i c F o r e s t r y C e n t r e , d i s c u s s e d the p r o j e c t w i t h me on s e v e r a l o c c a s i o n s , p r o v i d e d b o t h p u b l i s h e d and u n p u b l i s h e d d a t a , and a l s o t h o u g h t f u l l y r e v i e w e d e a r l y m a n u s c r i p t s . Wayne Campbell and John Cooper, P r o v i n c i a l Museum of B r i t i s h C olumbia; Dr. John -Borden, Simon F r a s e r U n i v e r s i t y ; Dr. Edward G a r t o n , U n i v e r s i t y of Idaho; Dr. T o r o l f T o r g e r s e n , P a c i f i c Northwest F o r e s t and Range E x p e r i m e n t a l S t a t i o n ; and Dr. Gene Amman, I n t e r m o u n t a i n F o r e s t and Range E x p e r i m e n t a l S t a t i o n k i n d l y p r o v i d e d b o t h p u b l i s h e d and u n p u b l i s h e d d a t a . I thank my w i f e Ronni f o r s h a r i n g w i t h me her knowledge of s i l v i c u l t u r a l methods c u r r e n t l y i n use by f o r e s t companies i n s o u t h - c e n t r a l B r i t i s h C o lumbia, and f o r a s s i s t i n g me w i t h t y p i n g and g r a p h i c s . F i n a l l y , I am g r a t e f u l t o Stephen Wetmore and the Canadian W i l d l i f e S e r v i c e f o r p r o v i d i n g f u n d i n g f o r t h i s s t u d y . T a b l e of C o n t e n t s ABSTRACT i i ACKNOWLEDGEMENTS i i i LIST OF FIGURES v i i LIST OF TABLES x i i i 'l . INTRODUCTION 1 1 .1 O b j e c t i v e s 3 1 .2 Scope 5 2. APPLICABLE THEORY 8 2.1 I n s e c t E p i d e m i o l o g y 8 2.2 P r e d a t o r Responses To Changes i n Prey D e n s i t y ..17 2.2.1 The f u n c t i o n a l r e sponse 17 2.2.2 The n u m e r i c a l r e s p o n s e 21 3. GENERAL CONSIDERATIONS FOR MODEL DEVELOPMENT 27 3. 1 The I n s e c t 27 3.1.1 L i f e c y c l e 27 3.1.2 F a c t o r s i n f l u e n c i n g e p i d e m i c s 30 3.1.3 Pa s t h i s t o r y and c u r r e n t t r e n d s 34 3.2 The Host Tree S p e c i e s 35 3.2.1 Lodgepole p i n e c h a r a c t e r i s t i c s 35 3.2.2 Tree and s t a n d s u s c e p t i b i l i t y 37 3.2.3 Mountain , p i n e b e e t l e e f f e c t s on t r e e s and s t a n d s 42 3.2.4 S i l v i c u l t u r a l a pproaches t o r e d u c i n g s u s c e p t i b i l i t y 43 3.3 The A v i a n P r e d a t o r s 48 i v 3.3.1 P r e d a t o r i m p a c t s 48 3.3.2 H a b i t a t r e q u i r e m e n t s 55 3.3.3 A v i a n r e s p o n s e s t o t i m b e r h a r v e s t i n g 58 STRUCTURE OF THE SIMULATION MODEL 60 4.1 Lodgepole P i n e Stand S t r u c t u r e 60 4.2 Mountain P i n e B e e t l e P o p u l a t i o n D i s t r i b u t i o n ...62 4.3 Lodgepole P i n e M o r t a l i t y 64 4.4 Mountain P i n e B e e t l e P r o d u c t i v i t y 66 4.5 Mountain P i n e B e e t l e M o r t a l i t y 67 SIMULATION RESULTS AND DISCUSSION 77 5.1 S i m u l a t e d S c e n a r i o s 77 5.2 The C o n t r o l Stand 79 5.2.1 S c e n a r i o 1: Normal p r e d a t o r r e s p o n s e s ....79 5.2.2 S c e n a r i o 2: E f f i c i e n t p r e d a t o r s 93 5.2.3 S c e n a r i o 3: Twice normal p r e d a t o r d e n s i t y 94 5.3 The Senescent Stand 99 5.3.1 S c e n a r i o 4: Normal p r e d a t o r r e s p o n s e s ....99 5.3.2 S c e n a r i o 5: E f f i c i e n t p r e d a t o r s 111 5.3.3 S c e n a r i o 6: Twice normal p r e d a t o r d e n s i t y 112 5.4 The Thinned Stand 114 5.4.1 S c e n a r i o s 7 and 8: Normal and e f f i c i e n t p r e d a t o r s 115 5.4.2 S c e n a r i o 9: Twice normal p r e d a t o r d e n s i t y 120 5.5 S e n s i t i v i t y A n a l y s i s And Model L i m i t a t i o n s ....125 6. CONCLUSIONS 128 6.1 Res e a r c h Needs 129 REFERENCES CITED , 133 APPENDIX 1 COMMON AND SCIENTIFIC NAMES 148 APPENDIX 2 KEY REFERENCES USED IN MODEL CONSTRUCTION 151 APPENDIX 3 BASIC MOUNTAIN PINE BEETLE SIMULATION MODEL 155 APPENDIX 4 GLOSSARY OF SIMULATION MODEL VARIABLES 163 APPENDIX 5 INITIAL VALUES OF SELECTED MODEL PARAMETERS 172 v i LIST OF FIGURES F i g u r e 1: Area i n f e s t e d by t h e mountain p i n e b e e t l e i n B r i t i s h C o l u m b i a , 1973-1984 2 F i g u r e 2: L o c a t i o n s of mountain p i n e b e e t l e i n f e s t a t i o n s i n B r i t i s h Columbia 1984 6 F i g u r e 3: I n f l u e n c e of ' t o l e r a n t ' c o n t r o l f a c t o r s 9 F i g u r e 4: I n f l u e n c e of ' i n t o l e r a n t ' c o n t r o l f a c t o r s 11 F i g u r e 5: A p o p u l a t i o n r eplacement c u r v e w i t h t h r e e e q u i l i b r i a 13 F i g u r e 6: A s e r i e s of p o p u l a t i o n replacement c u r v e s i l l u s t r a t i n g e f f e c t of d i f f e r e n t h a b i t a t s on number of e q u i l i b r i a 14 F i g u r e 7: An e q u i l i b r i u m m a n i f o l d i l l u s t r a t i n g p o p u l a t i o n r e s p o n s e s t o h a b i t a t d e g r a d a t i o n . . . . 15 F i g u r e 8: Four t y p e s of p r e d a t o r f u n c t i o n a l r e s p o n s e s t o changes i n pr e y d e n s i t y 18 v i i F i g u r e 9: P r o p o r t i o n of p r e y p o p u l a t i o n t a k e n per u n i t time by p r e d a t o r s e x h i b i t i n g the f u n c t i o n a l r e s p o n s e s i l l u s t r a t e d i n F i g . 8 20 F i g u r e 10: Three t y p e s of p r e d a t o r n u m e r i c a l responses t o changes i n prey d e n s i t y 22 F i g u r e 11: T o t a l p r e d a t o r r e s p o n s e s t o changes i n prey d e n s i t y 26 F i g u r e 12: Mountain p i n e b e e t l e l i f e c y c l e 28 F i g u r e 13: Change i n f r e q u e n c y of r e s i s t a n t l o d g e p o l e p i n e f o r d i f f e r e n t aged t r e e s 41 F i g u r e 14: M o r t a l i t y i n a l o d g e p o l e p i n e s t a n d a t t a c k e d by the mountain p i n e b e e t l e i n r e l a t i o n t o t r e e DBH 44 F i g u r e 15: M o r t a l i t y i n two l o d g e p o l e p i n e s t a n d s a t t a c k e d by the mountain p i n e b e e t l e i n r e l a t i o n t o t r e e DBH 45 F i g u r e 16: B a s i c f l o w d i a g r a m of the s i m u l a t i o n model 61 v i i i F i g u r e 17: S i m p l i f i e d f l o w diagram of sequence used t o d e t e r m i n e consumption of l a r v a e by w i n t e r woodpeckers 69 F i g u r e 18: S i m p l i f i e d f l o w diagram of sequence used t o d e t e r m i n e b e e t l e consumption by summer b i r d s 74 F i g u r e 19: Diagram of 3 X 3 f a c t o r i a l d e s i g n used i n the s i m u l a t i o n s 78 F i g u r e 20: Y e a r l y mountain p i n e b e e t l e autumn d e n s i t y i n the c o n t r o l s t a n d 80 F i g u r e 21: Y e a r l y t o t a l s t a n d d e n s i t y f o r the c o n t r o l s t a n d 82 F i g u r e 22: I n i t i a l and f i n a l s t a n d s t r u c t u r e s f o r the c o n t r o l s t a n d 83 F i g u r e 23: T o t a l t r e e m o r t a l i t y f o r each d i a m e t e r c l a s s i n the c o n t r o l s t a n d 84 F i g u r e 24: Y e a r l y w i n t e r b i r d d e n s i t y i n the c o n t r o l s t a n d 85 F i g u r e 25: W i n t e r b i r d d e n s i t y i n the c o n t r o l s t a n d r e l a t i v e t o l a r v a l d e n s i t y 86 i x F i g u r e 26: P e r c e n t of w i n t e r l a r v a l p o p u l a t i o n consumed by woodpeckers i n the c o n t r o l s t a n d 87 F i g u r e 27: T o t a l summer b i r d d e n s i t y i n t h e c o n t r o l s t a n d 88 F i g u r e 28: T o t a l summer b i r d d e n s i t y i n the c o n t r o l stand r e l a t i v e t o a d u l t d e n s i t y 89 F i g u r e 29: P e r c e n t of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the c o n t r o l s t a n d 91 F i g u r e 30: Y e a r l y mountain p i n e b e e t l e autumn d e n s i t y i n the senescent s t a n d 100 F i g u r e 31: Y e a r l y t o t a l s t a n d d e n s i t y f o r t h e senescent stand 102 F i g u r e 32: I n i t i a l and f i n a l s t a n d s t r u c t u r e s f o r the senescent s t a n d 103 F i g u r e 33: T o t a l t r e e m o r t a l i t y f o r each d i a m e t e r c l a s s i n the sene s c e n t s t a n d 104 F i g u r e 34: Y e a r l y w i n t e r b i r d d e n s i t y i n t h e senescent stand 105 x F i g u r e 35: W i n t e r b i r d d e n s i t y i n the senescent s t a n d r e l a t i v e t o l a r v a l d e n s i t y 106 F i g u r e 36: P e r c e n t of w i n t e r l a r v a l p o p u l a t i o n consumed by woodpeckers i n the senescent s t a n d 1 07 F i g u r e 37: T o t a l summer b i r d d e n s i t y i n the senescent s t a n d 108 F i g u r e 38: T o t a l summer b i r d d e n s i t y i n the senescent s t a n d r e l a t i v e t o a d u l t d e n s i t y . . . . 109 F i g u r e 39: P e r c e n t of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the senescent s t a n d 110 F i g u r e 40: Y e a r l y mountain p i n e b e e t l e autumn d e n s i t y i n the t h i n n e d s t a n d 116 F i g u r e 41: Y e a r l y t o t a l s t a n d d e n s i t y f o r the t h i n n e d s t a n d 117 F i g u r e 42: I n i t i a l and f i n a l s t a n d s t r u c t u r e s f o r the t h i n n e d s t a n d 118 x i F i g u r e 43: T o t a l t r e e m o r t a l i t y f o r each d i a m e t e r c l a s s i n the t h i n n e d s t a n d 119 F i g u r e 44: P e r c e n t of w i n t e r l a r v a l p o p u l a t i o n consumed by woodpeckers i n t h e t h i n n e d s t a n d 121 F i g u r e 45: P e r c e n t of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the t h i n n e d s t a n d 1 22 x i i LIST OF TABLES Table 1: Avian p r e d a t o r s of the mountain pine b e e t l e 4 9 x i i i 1. INTRODUCTION I r r u p t i v e i n s e c t s i n f e s t e d more than 680,000 h e c t a r e s of c o m m e r c i a l l y v a l u a b l e f o r e s t l a n d i n B r i t i s h Columbia i n 1984. T h i s r e p r e s e n t s an i n c r e a s e of over 500% s i n c e 1979 ( F i d d i c k and Van S i c k l e 1980, Wood et al. 1 985). A p p r o x i m a t e l y 482,300 h e c t a r e s , or r o u g h l y 71% of the t o t a l a r e a , were i n f e s t e d by t h e mountain p i n e b e e t l e . 1 The mountain p i n e b e e t l e i s c o n s i d e r e d the most s e r i o u s enemy of l o d g e p o l e p i n e t r e e s i n w e s t e r n Canada ( S a f r a n y i k et al. 1974, S a f r a n y i k 1984 p e r s o n a l c o m m u n i c a t i o n ) , and the most s i g n i f i c a n t i n s e c t problem i n B r i t i s h C o l u m b i a . S i n c e 1972 i t has k i l l e d more than 172 m i l l i o n l o d g e p o l e p i n e t r e e s . In 1984 a l o n e the b e e t l e k i l l e d a p p r o x i m a t e l y 41 m i l l i o n t r e e s (Wood et al. l 9 8 5 ) ( F i g u r e 1 ) . A number of s i l v i c u l t u r a l , c h e m i c a l , and b i o l o g i c a l methods have been s u g g e s t e d f o r the c o n t r o l or p r e v e n t i o n of e p i d e m i c s by i r r u p t i v e i n s e c t s ( S a f r a n y i k et al. 1974, Amman et al. 1977, Hodgkinson et al. 1979, S a f r a n y i k el al. 1981, Manning et al. 1982, Takekawa et al. 1982, Moeck and S a f r a n y i k 1984). B i o l o g i c a l methods i n c l u d e the use of pheromones, v i r u s e s , b a c t e r i a , p a r a s i t o i d s , and i n v e r t e b r a t e and v e r t e b r a t e p r e d a t o r s (Hodgkinson et al. 1979, Takekawa et al. 1982, Moeck and S a f r a n y i k 1984). 'Common names a r e used i n t h e t e x t . A l l s c i e n t i f i c names appear i n APPENDIX 1. 1 2 F i g u r e 1: Area i n f e s t e d by the mountain p i n e b e e t l e i n B r i t i s h Columbia, 1970-1984 (Compiled from F o r e s t I n s e c t and D i s e a s e Survey f i l e r e p o r t s ) . 3 B i r d s have l o n g been c o n s i d e r e d major v e r t e b r a t e p r e d a t o r s of f o r e s t i n s e c t s . Boesenberg (in Otvos 1979) n o t e d t h a t b i r d s were p r o t e c t e d as e a r l y as 1335 by d i s c e r n i n g S w i s s a u t h o r i t i e s who r e c o g n i z e d t h e i r v a l u e . Recent i n v e s t i g a t i o n s by T o r g e r s e n and Campbell (1982), Campbell et al . (1983), and Takekawa and G a r t o n ( 1984), s u p p o r t e d by numerous e a r l i e r s t u d i e s , have q u a n t i t a t i v e l y d e m o n s t r a t e d the consumptive a b i l i t i e s of i n s e c t i v o r o u s b i r d s . D e t e r m i n i n g the a b i l i t y of b i r d s t o c o n t r o l f o r e s t i n s e c t p o p u l a t i o n s (i.e. p r e v e n t e p i d e m i c s ) , however, r e q u i r e s more than a knowledge of the number of i n s e c t l a r v a e t h a t a b i r d can consume. I t a l s o r e q u i r e s an u n d e r s t a n d i n g of i n s e c t l i f e c y c l e s and o u t b r e a k dynamics, the b i r d s ' r e s p o n s e s t o changes i n i n s e c t abundance and d i s t r i b u t i o n , and the manner i n which both b i r d s and t h e i r i n s e c t p r e y a r e a f f e c t e d by t i m b e r management p r a c t i c e s . 1.1 OBJECTIVES T h i s s t u d y can be c o n s i d e r e d on two l e v e l s . F i r s t , i t i s a g e n e r a l e x a m i n a t i o n of m u l t i p l e r e s o u r c e management. In t h i s s e n s e , i t examines the management of l o d g e p o l e p i n e s t a n d s t o m a i n t a i n t i m b e r p r o d u c t i o n w h i l e s i m u l t a n e o u s l y r e d u c i n g s t a n d s u s c e p t i b i l i t y t o i n s e c t a t t a c k , and e n h a n c i n g l o c a l p o p u l a t i o n s of i n s e c t i v o r o u s , non-game 4 b i r d s . Second, i t i s a d e t a i l e d s t u d y of the impacts of a c l a s s of v e r t e b r a t e p r e d a t o r s on i n v e r t e b r a t e p r e y over a range of p r e d a t o r - p r e y d e n s i t i e s and h a b i t a t c o n d i t i o n s . The mountain p i n e b e e t l e was chosen as the s u b j e c t of t h i s i n v e s t i g a t i o n f o r t h e f o l l o w i n g r e a s o n s : 1. I t i s one of t h e most d e s t r u c t i v e c o n i f e r o u s f o r e s t i n s e c t s , not o n l y i n B r i t i s h C o l u m b i a , but i n the w e s t e r n U n i t e d S t a t e s as w e l l . 2 . Due t o i t s d e s t r u c t i v e a b i l i t i e s t h e r e has been a c o n s i d e r a b l e amount of r e s e a r c h c o nducted on t h i s spec i e s . 3. There a r e two d i s t i n c t p e r i o d s of a v i a n p r e d a t i o n (which may be r e f e r r e d t o as the w i n t e r and summer p e r i o d s ) d u r i n g the b e e t l e ' s l i f e c y c l e . They e f f e c t two d i f f e r e n t mountain p i n e b e e t l e l i f e s t a g e s ; the o v e r w i n t e r i n g l a r v a and the a t t a c k i n g a d u l t . 4. The b i r d s r e s p o n s i b l e f o r p r e d a t i o n d u r i n g t h e s e p e r i o d s r e p r e s e n t , f o r t h e most p a r t , two d i f f e r e n t a v i a n O r d e r s ; t h e P i c i f o r m e s (woodpeckers) and the P a s s e r i f o r m e s ( p e r c h i n g b i r d s ) . 5. The p r e d a t o r s from t h e s e d i f f e r e n t O r d e r s a l s o g e n e r a l l y use two d i f f e r e n t methods of f o r a g i n g ; e x c a v a t i o n and b a r k - g l e a n i n g . W i t h t h i s i n s e c t and i t s a v i a n p r e d a t o r s i n mind, the o b j e c t i v e s of t h e s t u d y were: 5 1 . To e s t a b l i s h b r o ad, g e n e r a l c o n c e p t u a l models d e s c r i b i n g t h e i n t e r a c t i o n s of t h e i n s e c t , i t s a v i a n p r e d a t o r s , and f o r e s t s t a n d s t r u c t u r e t h r o u g h a n a l y s i s of the l i t e r a t u r e and c o n s u l t a t i o n w i t h e x p e r t s . 2 . To document i m p o r t a n t problem a r e a s i n B r i t i s h Columbia were b i r d s may be i m p o r t a n t c o n t r o l l i n g a g e n t s . 3 . To examine some case h i s t o r i e s from B r i t i s h Columbia t o t e s t the v a l i d i t y of the c o n c e p t u a l models, and t o d e v e l o p hypotheses f o r f u t u r e t e s t i n g . 4. To d e v e l o p c o n d i t i o n a l s t a t e m e n t s t h a t p r e d i c t or d e s c r i b e the r e s p o n s e s of the b i r d - i n s e c t system t o f o r e s t management p r a c t i c e s used i n B r i t i s h Columbia. 5 . To i d e n t i f y s u b j e c t a r e a s t h a t r e q u i r e f u r t h e r r e s e a r c h because d a t a a re i n c o m p l e t e or - l a c k i n g . 1 . 2 SCOPE The purpose of t h i s s t u d y , i n p a r t , was t o examine the p o s s i b l e impacts of r e l e v a n t t i m b e r management p r a c t i c e s used i n B r i t i s h Columbia on b i r d / i n s e c t dynamics. T h i s was a c c o m p l i s h e d t h r o u g h the c o n s t r u c t i o n and use of a computer s i m u l a t i o n model. The model was d e s i g n e d t o r e p r e s e n t c o n d i t i o n s t h a t commonly o c c u r i n B r i t i s h Columbia where the mountain p i n e b e e t l e i s found ( F i g u r e 2 ) . U n f o r t u n a t e l y , the amount of i n f o r m a t i o n s p e c i f i c t o the p r o v i n c e o f t e n was e x t r e m e l y l i m i t e d . T h e r e f o r e , much of t h e d a t a used i n the 6 F i g u r e 2: L o c a t i o n of mountain p i n e b e e t l e i n f e s t a t i o n s i n B r i t i s h C o l u m b i a , 1970-1984 ( c o m p i l e d from F o r e s t I n s e c t and D i s e a s e Survey f i l e r e p o r t s ) . 7 construct ion of the s imulat ion model came from research conducted in the western United States . These values were a l t e r e d occas ional ly in an attempt to represent p r o v i n c i a l condi t ions i f s u f f i c i e n t background material was a v a i l a b l e to support the a l t e r a t i o n . 2. APPLICABLE THEORY 2.1 INSECT EPIDEMIOLOGY The f o r e s t ecosystem i s home f o r a wide v a r i e t y of i n s e c t s p e c i e s , most e x i s t i n g a t low p o p u l a t i o n d e n s i t i e s t h a t a r e r e l a t i v e l y s t a b l e . However, p o p u l a t i o n s of some s p e c i e s a r e c a p a b l e of d r a m a t i c i n c r e a s e s i n a s h o r t p e r i o d of t i m e . These i n c r e a s e s a r e r e f e r r e d t o as o u t b r e a k s , i r r u p t i o n s , or e p i d e m i c s . Widespread damage or d e s t r u c t i o n of v a l u a b l e t i m b e r may o c c u r , depending on the i n s e c t ( s ) i n v o l v e d . S p e c i e s t h a t p o s s e s s t h i s p o t e n t i a l a r e termed ' i r r u p t i v e ' i n s e c t s by e n t o m o l o g i s t s , and 'pes t ' i n s e c t s by the f o r e s t i n d u s t r y . I r r u p t i v e i n s e c t s p e c i e s a r e o f t e n p r e s e n t i n the f o r e s t s a t low, or endemic, l e v e l s . B i o t i c f a c t o r s (e.g. p r e d a t i o n ) and a b i o t i c f a c t o r s (e.g. t e m p e r a t u r e ) combine t o h o l d them a t th e s e l e v e l s by im p o s i n g a d e n s i t y - d e p e n d e n t n e g a t i v e feedback such t h a t p o p u l a t i o n replacement approaches z e r o as d e n s i t y c o n t i n u e s t o i n c r e a s e . Berryman (1978) used the term ' t o l e r a n t ' t o d e s c r i b e f a c t o r s t h a t can c o n t r o l a p o p u l a t i o n i n t h i s manner. The e f f e c t s of d e n s i t y - d e p e n d e n t f a c t o r s on an i n s e c t p o p u l a t i o n a r e shown i n F i g u r e 3. The h o r i z o n t a l l i n e r e p r e s e n t s a replacement v a l u e of 1.0 (one o f f s p r i n g 8 9 F i g u r e 3: I n f l u e n c e of ' t o l e r a n t ' c o n t r o l f a c t o r s (Berryman 1978). 10 produced per parent). The point where the two l i n e s intersect i s the single, t h e o r e t i c a l l y stable equilibrium of the population (S), corresponding to the insect density N. Populations having densities greater than N w i l l have replacement values less than 1.0, and w i l l decrease to S. Conversely, populations with densities less than N w i l l have replacement values greater than 1.0, and w i l l increase to S. This figure, and figures 4 through 7 do not include the th e o r e t i c a l "Allee" e f f e c t at very low population d e n s i t i e s . Some c o n t r o l l i n g factors do not function at a l l population densities, and have been termed 'intolerant' by Berryman (1978). Bird predation, for instance, eventually loses i t s effectiveness as insect densities continue to increase. Predation, i n i t i a l l y producing a negative feedback, becomes an inverse density-dependent process producing a posit i v e feedback on the insect population (Morris 1963, Berryman 1982). As a re s u l t , the rate of replacement begins to increase (Figure 4). When the population replacement curve again intersects the l i n e representing a replacement value of 1.0, a second equilibrium point, U, corresponding to insect density T, i s established. This second equilibrium point, unlike S, has been shown to be unstable (Morris 1963, Takahashi 1964, Holl i n g 1973, Berryman 1981). Insect populations with densities less than T w i l l have replacement values less than F i g u r e 4: I n f l u e n c e of ' i n t o l e r a n t ' c o n t r o l f a c t o r s (Berryman 1978). 12 1.0, and w i l l d e c r e a s e t o S ( d e n s i t y N ) . P o p u l a t i o n s w i t h d e n s i t i e s e x c e e d i n g T w i l l c o n t i n u e t o i n c r e a s e . The d e n s i t y T i s thought t o s e p a r a t e the domain of endemic from epidemic b e h a v i o r (Berryman 1982) I n s e c t p o p u l a t i o n growth does not c o n t i n u e i n f i n i t e l y . C o m p e t i t i o n f o r l i m i t e d r e s o u r c e s e v e n t u a l l y r e t u r n s p o p u l a t i o n replacement t o 1.0 ( M o r r i s 1963, Takahashi 1964 Berryman 1981), as i l l u s t r a t e d i n F i g u r e 5. P o p u l a t i o n s t h a t exceed the o u t b r e a k t h r e s h o l d d e n s i t y T w i l l i n c r e a s e t o the s t a b l e p o i n t S 2 ( d e n s i t y N 2 ) . F i g u r e 6 i l l u s t r a t e s t he dynamics of an i n s e c t outbreak i f a c o n s t a n t environment i s assumed. However, i f the same p o p u l a t i o n was s u b j e c t t o a d i f f e r e n t s e t of e n v i r o n m e n t a l f a c t o r s , a s i m i l a r replacement c u r v e w i t h d i f f e r e n t e q u i l i b r i u m p o i n t s would r e s u l t . D i f f e r e n c e s i n h a b i t a t q u a l i t y c o u l d have t h e e f f e c t of i n c r e a s i n g or d e c r e a s i n g the p o p u l a t i o n replacement c u r v e r e l a t i v e t o the l i n e where replacement e q u a l s 1.0. For example, a p o p u l a t i o n would s t a b i l i z e a t a g r e a t e r d e n s i t y i n a more f a v o r a b l e environment than i n a l e s s f a v o r a b l e one ( F i g u r e 6, l i n e s A and D, r e s p e c t i v e l y ) . I n c l u d i n g the e f f e c t s of h a b i t a t v a r i a b i l i t y on replacement and p o p u l a t i o n d e n s i t y e n a b l e s e x a m i n a t i o n of ou t b r e a k dynamics i n t h r e e d i m e n s i o n s . F i g u r e 7 i s an example of an e q u i l i b r i u m m a n i f o l d ( H o l l i n g et al. 1977). 13 F i g u r e 5: A p o p u l a t i o n replacement curve with three e q u i l i b r i a (Berryman 1978). 14 POPULATION DENSITY F i g u r e 6: A s e r i e s of p o p u l a t i o n replacement c u r v e s i l l u s t r a t i n g t he e f f e c t s of d i f f e r e n t h a b i t a t s on number of e q u i l i b r i a ( C l a r k et al. 1977). 15 F i g u r e 7 : A n e q u i l i b r i u m m a n i f o l d i l l u s t r a t i n g p o p u l a t i o n r e s p o n s e s t o h a b i t a t d e g r a d a t i o n ( B e r r y m a n 1 9 7 8 ) . 16 The e q u i l i b r i u m p o i n t s S,, S 2, and U of F i g u r e 6 a r e now p a r t of a continuum of e q u i l i b r i u m v a l u e s from A t o D on the p l a n e where replacement e q u a l s 1.0. P o i n t s a l o n g the l i n e s A-B and C-D a r e s t a b l e , w h i l e p o i n t s on t h e l i n e B-C are u n s t a b l e . A p o p u l a t i o n a t the l o w e r , s t a b l e e q u i l i b r i u m S, can now f o l l o w two p a t h s i n t o the epidemic domain. F i r s t , i t may respond t o an improvement i n h a b i t a t q u a l i t y and move from t o B. At t h i s p o i n t the p o p u l a t i o n c r o s s e s the epidemic t h r e s h o l d and moves t o S 3 where i t s t a b i l i z e s . The second p a t h i n v o l v e s a l a r g e i n c r e a s e i n d e n s i t y , perhaps through i n s e c t i m m i g r a t i o n . The p o p u l a t i o n would move from S! d i r e c t l y t o U, and would then move t o and s t a b i l i z e a t p o i n t S 2 • D u r i n g the c o u r s e of an epidemic many i n s e c t s , through t h e i r own f e e d i n g a c t i v i t y , reduce the s u i t a b i l i t y of t h e i r h a b i t a t . S h o u l d t h i s o c cur the t r a j e c t o r y of the p o p u l a t i o n growth would be d i v e r t e d t o S a or S 5 depending on the e x t e n t of h a b i t a t d e g r a d a t i o n . A c o n t i n u a t i o n of h a b i t a t d e g r a d a t i o n a t t h i s time would move the p o p u l a t i o n toward C. At t h i s p o i n t p o p u l a t i o n replacement would f a l l below 1.0, and the epidemic would b e g i n t o c o l l a p s e . 17 2.2 PREDATOR RESPONSES TO CHANGES IN PREY DENSITY Solomon (1949) d i v i d e d a p r e d a t o r ' s r e s p o n s e s t o the changes i n i t s p r e y ' s d e n s i t y i n t o two major components. The term f u n c t i o n a l response was used t o d e s c r i b e a change i n the number of pr e y c a p t u r e d per p r e d a t o r . T h i s may a l s o be viewed as a change i n the p r o p o r t i o n of the p r e d a t o r ' s d i e t r e p r e s e n t e d by a p a r t i c u l a r prey s p e c i e s . A change i n the d e n s i t y of p r e d a t o r s i n response t o a change i n pr e y d e n s i t y was termed a n u m e r i c a l r e s p o n s e . 2.2.1 THE FUNCTIONAL RESPONSE Three b a s i c forms of the f u n c t i o n a l r e s ponse were proposed by H o l l i n g (1959). A Type I response was a d i r e c t l i n e a r response i n which the p r e d a t o r ' s s e a r c h r a t e was c o n s t a n t , and the number of pr e y t a k e n i n c r e a s e d i n d i r e c t p r o p o r t i o n t o t h e pr e y d e n s i t y ( F i g u r e 8, graph A ) . At some prey d e n s i t y the p r e d a t o r became s a t i a t e d , or the t i m e spent s e a r c h i n g f o r and h a n d l i n g the p r e y had been reduced t o a minimum. The number of pr e y t a k e n then became c o n s t a n t . A Type I response was found t o be t y p i c a l of f i l t e r - f e e d i n g i n v e r t e b r a t e s . In a Type I I , or h y p e r b o l i c , f u n c t i o n a l r e s p o n s e ( F i g u r e 8, graph B) the number of prey t a k e n d i m i n i s h e d p r o g r e s s i v e l y . T h i s produced an i n v e r s e d e n s i t y - d e p e n d e n t m o r t a l i t y over the range of pr e y d e n s i t i e s . T h i s t y p e of P R E Y D E N S I T Y F i g u r e 8: Four types of predator f u n c t i o n a l responses to changes i n prey d e n s i t y ( H o l l i n g 1959). 19 T h i s type of response was common i n p r e d a t o r y i n s e c t s . F i g u r e 8 ( g r a p h C) i l l u s t r a t e s a Type I I I (or sigmoid) f u n c t i o n a l r e s p o n s e . The number of prey t a k e n i n i t i a l l y i n c r e a s e d as p r e y d e n s i t y i n c r e a s e d , then d e c r e a s e d i n much the same manner as the Type I I r e s p o n s e , because of s a t i a t i o n and/or h a n d l i n g time e f f e c t s . The r e s u l t a n t prey m o r t a l i t y was d e n s i t y - d e p e n d e n t a t f i r s t , then became i n v e r s e l y d e n s i t y - d e p e n d e n t as p r e y d e n s i t y c o n t i n u e d t o i n c r e a s e . S t u d i e s by B e t t s (1955), B a l d w i n (1960), and Mook (1963) documented the Type I I I response i n some i n s e c t i v o r o u s b i r d s . H o l l i n g (1959) o r i g i n a l l y proposed two forms of the Type I I I response ( F i g u r e 8, graphs C and D). In form C, the response of t h e p r e d a t o r s was immediate. The second form (D) i n c l u d e d a t i m e - l a g e f f e c t . T h i s m o d i f i c a t i o n has s i n c e been used t o accomodate e f f e c t s such as prey s w i t c h i n g (Murdoch 1969), changes i n p r e d a t o r f e e d i n g b e h a v i o r (Kendeigh 1947, M o r r i s et al. 1958, McCambridge and K n i g h t 1972), e l e c t i v i t y ( I v l e v 1961), s e a r c h image f o r m a t i o n ( D e R u i t e r 1952, T i n b e r g e n 1960), c r i t i c a l p rey d e n s i t y (Kendeigh 1947, T i n b e r g e n 1960, Beaver 1967), and minimum prey s i z e ( Kendeigh 1947, T i n b e r g e n 1960, K o p l i n and B a l d w i n 1970). The p r o p o r t i o n of the prey p o p u l a t i o n t a k e n by p r e d a t o r s r e p r e s e n t i n g each of H o l l i n g ' s o r i g i n a l response t y p e s i s shown i n F i g u r e 9. The Type I and Type I I responses 20 0 PREY DENSITY F i g u r e 9: P r o p o r t i o n of prey t a k e n per u n i t time by p r e d a t o r s e x h i b i t i n g the f u n c t i o n a l r e s p o n s e s i l l u s t r a t e d i n F i g u r e 8 ( H o l l i n g 1965). 21 (A and B) a l l o w a c o n s t a n t o r i n c r e a s i n g p r o p o r t i o n of the prey t o s u r v i v e as prey d e n s i t y i n c r e a s e s . T h i s c r e a t e s a p o s i t i v e feedback on the p o p u l a t i o n . T h e r e f o r e t h e s e response Types cannot have a r e g u l a t i n g e f f e c t on the pr e y p o p u l a t i o n (Berryman 1981). However, i n t h e Type I I I response t h e p r e d a t o r i n i t i a l l y t a k e s an i n c r e a s i n g p r o p o r t i o n of the p r e y p o p u l a t i o n . T h i s c r e a t e s a d e n s i t y - d e p e n d e n t n e g a t i v e feedback on the pr e y when i t s d e n s i t y i s low. The i n i t i a l d e n s i t y - d e p e n d e n t m o r t a l i t y i s c r i t i c a l t o the concept of b i o l o g i c a l c o n t r o l i n t h a t Type I I I p r e d a t o r s , i f they r e a c t q u i c k l y t o prey p o p u l a t i o n i n c r e a s e s , may be a b l e t o p r e v e n t i n s e c t d e n s i t i e s from moving beyond the t h r e s h o l d d e n s i t y shown i n F i g u r e 4. 2.2.2 THE NUMERICAL RESPONSE The n u m e r i c a l response of a p r e d a t o r can take t h r e e b a s i c forms ( F i g u r e 10). Curves A , B and C r e p r e s e n t a d i r e c t n u m e r i c a l r e s p o n s e , no re s p o n s e , and an i n v e r s e r e s p o n s e , r e s p e c t i v e l y . A l l t h r e e response t y p e s have been r e p o r t e d f o r a v i a n p r e d a t o r s of i r r u p t i v e i n s e c t s (Kendeigh 1947). The d i r e c t response can oc c u r i n t h r e e ways: t h r o u g h a g g r e g a t i o n of the p r e d a t o r , t h r o u g h an i n c r e a s e i n p r e d a t o r s u r v i v a l , o r through an i n c r e a s e i n p r e d a t o r r e p r o d u c t i o n . I n c r e a s e t h r o u g h a g g r e g a t i o n i s the most commonly r e p o r t e d 22 F i g u r e 10: Three types of predator numerical responses to changes i n prey d e n s i t y ( E l s e t h and Baumgardner 1981). 23 form of d i r e c t response. I t can occur t e m p o r a r i l y , or on a d a i l y or seasonal b a s i s . B l a c k f o r d (1955), f o r example, found t h a t s e v e r a l s p e c i e s of woodpeckers ent e r e d a burned area each day to feed on the b e e t l e l a r v a e i n the dead t r e e s , and r e t u r n e d to t h e i r r o o s t s i n the nearby unburned woods i n the evening. During an outbreak of the e a s t e r n spruce budworm Kendeigh (1947) noted temporary i n c r e a s e s i n the numbers of savannah and white-crowned sparrows, and s e v e r a l s p e c i e s of w a r b l e r s . These b i r d s were present f o r a few days only, and appeared to have taken advantage of the a v a i l a b l e food source as they passed through the area d u r i n g m i g r a t i o n . During the same study Kendeigh d e s c r i b e d the breeding b i r d p o p u l a t i o n of the area as being composed of a nucleus of permanent r e s i d e n t s , and a l a r g e r number of b i r d s that remained only f o r the summer. He suggested that the i n i t i a l i n f l u x of m i g r a t o r y b i r d s c o n s i s t e d predominantly of those that had- nested i n the area the p r e v i o u s s p r i n g . The l a t e r - a r r i v i n g migrants may have i n c l u d e d a l a r g e p r o p o r t i o n of b i r d s t h a t were r a i s e d i n the area the p r e v i o u s s p r i n g . Those l a t e - a r r i v i n g b i r d s that found s i t e s s t i l l a v a i l a b l e e s t a b l i s h e d t e r r i t o r i e s of t h e i r own. The three b i r d s p e c i e s that e x h i b i t e d the g r e a t e s t numerical response were seasonal s p e c i e s . 24 As n o t e d by Kendeigh ( 1 9 4 7 ) , the s e a s o n a l b i r d p o p u l a t i o n was composed m o s t l y of b i r d s t h a t had n e s t e d i n the a r e a t h e p r e v i o u s s p r i n g , p l u s some b i r d s t h a t were r a i s e d i n t h e a r e a t h a t s p r i n g . The f o l l o w i n g y e a r a l a r g e r number of b i r d s r e t u r n e d t o the a r e a . In t h i s manner the b r e e d i n g season p o p u l a t i o n i n c r e a s e d d u r i n g the e p i d e m i c . The upper l i m i t on t o t a l b i r d d e n s i t y may have been f i x e d by f a c t o r s s uch as a l i m i t e d number of nest s i t e s or maximum co m p r e s s i o n of t e r r i t o r i e s . Otvos (1965) proposed an a l t e r n a t i v e p r o c e s s t h r o u g h which b i r d d e n s i t y c o u l d i n c r e a s e d u r i n g the c o u r s e of a bark b e e t l e i n f e s t a t i o n . As t h e i n f e s t a t i o n p r o g r e s s e d , an i n c r e a s i n g number of t r e e s were k i l l e d by the i n s e c t s . T h i s r e s u l t e d i n an i n c r e a s e i n t h e number of p o t e n t i a l n e s t s i t e s a v a i l a b l e t o the woodpeckers. N u m e r i c a l responses may a l s o occur due t o i n c r e a s e s i n b i r d r e p r o d u c t i o n . Lack (1955) found t h a t the c l u t c h s i z e of B r i t i s h t i t m i c e i n c r e a s e d i n y e a r s when c a t e r p i l l a r s were more abundant. MacArthur (1958) d e s c r i b e d the p o p u l a t i o n e c o l o g y of f i v e s p e c i e s of w a r b l e r s i n e a s t e r n Canada. He found t h a t t h e c l u t c h s i z e of the b a y - b r e a s t e d w a r b l e r was s i g n i f i c a n t l y l a r g e r d u r i n g s p r u c e budworm ou t b r e a k y e a r s , but he d i d not have s u f f i c i e n t d a t a t o make s i m i l a r c o m p a r i s o n s f o r the o t h e r s p e c i e s . 25 P r e d a t o r f u n c t i o n a l and n u m e r i c a l responses can occur s i m u l t a n e o u s l y . In F i g u r e 11 the f u n c t i o n a l responses a r e p l o t t e d as the p r o p o r t i o n of the p r e y p o p u l a t i o n t a k e n per p r e d a t o r . The n u m e r i c a l responses a r e p l o t t e d as p r e d a t o r d e n s i t y . The combined impact ( t o t a l e f f e c t ) on the prey p o p u l a t i o n i s c a l c u l a t e d by m u l t i p l y i n g the c o r r e s p o n d i n g v a l u e s of the f u n c t i o n a l and n u m e r i c a l r e s p o n s e s . The t o t a l e f f e c t of the Type I and Type I I responses produces a d e n s i t y - d e p e n d e n t m o r t a l i t y o n l y i f the d i r e c t n u m e r i c a l response o c c u r s s i m u l t a n e o u s l y . The Type I I I r e s p o n s e , however, i s c a p a b l e of p r o d u c i n g d e n s i t y - d e p e n d e n t m o r t a l i t y even i f an i n v e r s e n u m e r i c a l response o c c u r s . T h e r e f o r e , i t appears t h a t the Type I I I p r e d a t o r s ( v e r t e b r a t e s ) a re the o n l y ones c a p a b l e of e x e r t i n g c o n t r o l over t h e p o p u l a t i o n s of t h e i r p r e y through both f u n c t i o n a l and n u m e r i c a l r e s p o n s e s . 26 NUMERICAL FUNCTIONAL TOTAL RESPONSE RESPONSE RESPONSE PREY DENSITY F i g u r e 11: T o t a l p r e d a t o r r e s p o n s e s t o changes i n pr e y d e n s i t y ( E l s e t h and Baumgardner 1981). 3. GENERAL CONSIDERATIONS FOR MODEL DEVELOPMENT 3.1 THE INSECT 3.1.1 L I F E CYCLE The mountain p i n e b e e t l e u s u a l l y has a 1-year l i f e c y c l e ( F i g u r e 12). A d u l t s emerge between l a t e J u l y and mid-August ( R e i d 1962a), and f l y t o u n i n f e s t e d t r e e s where the females bore t h r o u g h the o u t e r bark and b e g i n c o n s t r u c t i o n of an egg g a l l e r y i n the t r e e phloem. At t h i s time the a t t a c k i n g b e e t l e s a l s o i n n o c u l a t e the host t r e e w i t h one or more s p e c i e s of b l u e s t a i n f u n g i . The f u n g i a r e im p o r t a n t i n s l o w i n g down the t r e e ' s r e s i n r e s p o n s e s , e n a b l i n g the females t o b u i l d egg g a l l e r i e s . D u r i n g g a l l e r y c o n s t r u c t i o n the females combine two c h e m i c a l s , t rans-verbenol and e x o - b r e v i c o m i n , from t h e i r b o d i e s w i t h h o s t - t r e e monoterpenes such as alpha-pinene, beta-phellandrene, and myrcene t o c r e a t e a pheromone t h a t a t t r a c t s more b e e t l e s t o the t r e e ( V i t e and Pitman 1968, C o l e et al. 1981, and Borden et al. 1983). Once mated, the females l a y 40 t o 80 eggs each (Peterman 1974, S a f r a n y i k et al. 1974), though more than 200 eggs per female has been r e c o r d e d i n B r i t i s h Columbia ( R e i d 1962b). Depending on c l i m a t e , weather, and date of i n i t i a l emergence an a d u l t female may re-emerge, a t t a c k a new t r e e , mate, and l a y more 27 28 K E Y L i f e C y c l e S t a g e s a : A d u l t b: F l i g h t a n d a t t a c k c : E g g d : L a r v a e : L a r v a l d o r m a n c y £ : P u p a S u s c e p t i b i l i t y To A v i a n P r e d a t i o n i : W o o d p e c k e r s o n l y 2: A l l p r e d a t o r s o e c i e s 3: L o w s u s c e p t i b i l i c y t o a l l s p e c i e s F i g u r e 1 2 : Mountain p i n e b e e t l e l i f e c y c l e . 29 more eggs. T h i s phenomenon i s c o n s i d e r e d r a r e n o r t h of Montana (Amman and C o l e 1983) though i t was ob s e r v e d near Invermere, B. C. by R e i d (1962a). Eggs h a t c h a f t e r about two weeks ( R e i d and Gates 1970). The l a r v a e f e e d on the t r e e phloem (or i n n e r b a r k ) , and move at a p p r o x i m a t e l y r i g h t a n g l e s t o the v e r t i c a l egg g a l l e r y (Amman and C o l e 1983). The mountain p i n e b e e t l e d e v e l o p s t h r o u g h f o u r l a r v a l i n s t a r s b e f o r e p u p a t i o n . Depending on date of h a t c h the brood may d e v e l o p from egg t o t e n e r a l (immature) a d u l t b e f o r e becoming dormant f o r the w i n t e r ( R e i d 1962a). A l l eggs and most of the s m a l l l a r v a e t h a t e n t e r the w i n t e r a r e k i l l e d by c o l d t e m p e r a t u r e s (Amman 1973). A d u l t s t h a t emerged and a t t a c k e d l a t e i n the summer may s u r v i v e t h r o u g h the w i n t e r i f t e m p e r a t u r e s a r e m i l d , o t h e r w i s e few a d u l t s emerge f o r a second summer (Amman and C o l e 1983). In A p r i l o r May the s u r v i v i n g l a r v a e resume f e e d i n g , e x c a v a t e a c e l l i n the bark or sapwood, and pupate. The pupae mature i n one t o two weeks. F o l l o w i n g a p e r i o d of r e l a t i v e l y h i g h t e m p e r a t u r e s and abundant s u n s h i n e the b e e t l e s emerge. A l l b e e t l e s from a common chamber emerge t h r o u g h one h o l e i n the bark ( R e i d 1963). Most b e e t l e s emerge i n a p e r i o d of about one week ( R e i d 1962a, S t a l l c u p 1963, Rasmussen 1974), though the emergence p e r i o d may l a s t o ver f o u r weeks. 30 3.1.2 FACTORS INFLUENCING EPIDEMICS The e x a c t n a t u r e of the p r o c e s s e s t h a t s h i f t mountain p i n e b e e t l e p o p u l a t i o n s from endemic t o ep i d e m i c l e v e l s a r e o n l y p a r t i a l l y u n d e r s t o o d . D u r i n g e p i d e m i c s even the l a r g e s t , most v i g o r o u s l y growing t r e e s may be overcome by mass a t t a c k ( S a f r a n y i k et al. 1974, S a f r a n y i k 1984 p e r s o n a l c o m m u n i c a t i o n ) . B e e t l e p r o d u c t i o n i n t h e s e t r e e s i s h i g h , r e s u l t i n g i n p o p u l a t i o n growth. At endemic l e v e l s , however, t h e r e i s u s u a l l y an i n s u f f i c i e n t number of b e e t l e s p r e s e n t t o i n f e s t t h e l a r g e t r e e s . C o n s e q u e n t l y , the p o p u l a t i o n remains a t a c o n s t a n t l e v e l or d e c l i n e s . Two g e n e r a l t h e o r i e s t o e x p l a i n the t r a n s i t i o n from endemic t o epidemic b e h a v i o r have e v o l v e d . One i n v o l v e s p r i o r i n f e s t a t i o n by secondary bark b e e t l e s , p a r t i c u l a r l y e n g r a v e r b e e t l e s . A s m a l l number of mountain p i n e b e e t l e s may s u r v i v e i n and emerge from t r e e s i n i t i a l l y i n f e s t e d by the engraver b e e t l e s . When s e v e r a l of t h e s e i n f e s t e d t r e e s a r e s i t u a t e d c l o s e t o g e t h e r the combined number of emerging mountain p i n e b e e t l e s may be s u f f i c i e n t t o s u c c e s s f u l l y a t t a c k a l a r g e , u n i n f e s t e d t r e e nearby (Amman 1978, R a f f a and Berryman 1980, Amman and S a f r a n y i k 1985). In the second t h e o r y , the p i n e b e e t l e s a t t a c k l a r g e t r e e s which a r e under s t r e s s , and can t h e r e f o r e be s u c c e s s f u l l y i n f e s t e d by a s m a l l e r number of b e e t l e s . Some of the p o s s i b l e s o u r c e s of t r e e s t r e s s i n c l u d e d i s e a s e s such 31 as r o o t r o t s ( S t a r k and Cobb, J r . 1969, R a f f a and Berryman 1980, Gara el al. 1985), r u s t s , and dwarf m i s t l e t o e ( S c h m i t z 1985 p e r s o n a l c o m m u n i c a t i o n ) , smog ( S t a r k and Cobb, J r . 1969), i n s e c t d e f o l i a t i o n (Amman and S a f r a n y i k 1985), drought ( S a f r a n y i k et al. 1974, Amman 1978, Berryman and S t a r k 1985), s e a s o n a l and on t o n g e n a l d e c l i n e s i n t r e e v i g o u r ( S a f r a n y i k et al. 1974, Amman 1978), and l i g h t n i n g s t r i k e s ( R a f f a and Berryman 1980, Berryman and S t a r k 1985, Schmitz 1985 p e r s o n a l c o m m u n i c a t i o n ) . F u r t h e r m o r e , f a c t o r s such as t r e e d i s e a s e s and l i g h t n i n g s t r i k e s o f t e n a f f e c t s m a l l , i s o l a t e d groups of t r e e s (Schmitz and T a y l o r 1969, Schmitz 1985 p e r s o n a l c o m m u n i c a t i o n ) . T h i s i s o l a t i o n would a s s i s t i n the l o c a l c o n c e n t r a t i o n of t h e mountain p i n e b e e t l e p o p u l a t i o n . Once the b e e t l e p o p u l a t i o n b e g i n s t o expand, the sp r e a d of the epi d e m i c may be s i g n i f i c a n t l y i n f l u e n c e d by s i t e weather, e l e v a t i o n , l a t i t u d e , and the e x t e n t of the a v a i l a b l e f o o d s o u r c e . The r a t e of mountain p i n e b e e t l e development v a r i e s w i t h t emperature ( R e i d and Gates 1970, S a f r a n y i k et al. 1974). C o o l summer te m p e r a t u r e s may ex t e n d the l i f e c y c l e t o two y e a r s ( R e i d 1962a). T h i s l o n g e r l i f e c y c l e exposes the immature s t a g e s t o m o r t a l i t y f a c t o r s f o r l o n g e r p e r i o d s of time ( S a f r a n y i k et al. 1974). C o o l summers may a l s o cause a d u l t emergence and f l i g h t t o oc c u r l a t e r than n o r m a l . Eggs l a i d by the s e l a t e - e m e r g i n g a d u l t s may not 32 h a t c h b e f o r e the onset of w i n t e r . The p r o b a b i l i t y of t h e s e eggs s u r v i v i n g t h r o u g h t h e w i n t e r i s e x t r e m e l y low i n w e s t e r n Canada except a l o n g B r i t i s h Columbia's s o u t h e r n c o a s t ( S a f r a n y i k et al. 1974). Exposure t o summer t e m p e r a t u r e s of about 38 °C f o r l o n g p e r i o d s of time w i l l k i l l a l l s t a g e s , however the c r i t i c a l t e m perature f o r s h o r t time p e r i o d s i s 43.3 °C ( S a f r a n y i k et al. 1974). Optimum weather c o n d i t i o n s f o r mountain p i n e b e e t l e p o p u l a t i o n growth a r e a m o d e r a t e l y warm autumn, m i l d w i n t e r , moderate weather i n the s p r i n g and e a r l y summer, and h o t , d r y weather i n J u l y and August ( R e i d 1963). When d e t e r m i n i n g b e e t l e development and/or s u r v i v a l i t i s i m p o r t a n t t o c o n s i d e r the e l e v a t i o n and l a t i t u d e of the s i t e . These two f a c t o r s can have a major i n f l u e n c e on t e m p e r a t u r e as i n d i c a t e d by Hopkins' B i o c l i m a t i c Law (Hopkins 1920). R e i d (1962a) found t h a t broods of the mountain p i n e b e e t l e r a i s e d a t Invermere, B.C. ( e l e v a t i o n 835 m) d e v e l o p e d from egg t o t e n e r a l a d u l t between J u l y and September, w h i l e broods r a i s e d i n the B a n f f a r e a ( e l e v a t i o n 1366 m) where t e m p e r a t u r e s averaged s i x t o e i g h t degrees lower r e a c h e d o n l y the f o u r t h i n s t a r s t a g e i n the same time p e r i o d . Amman (1973) s t u d i e d mountain p i n e b e e t l e p o p u l a t i o n s a t f o u r e l e v a t i o n s (1923, 2130, 2450, and 2573-2750 m ) and d e t e r m i n e d t h a t eggs c o n s t i t u t e d 12% of the w i n t e r 33 p o p u l a t i o n a t 1923 m, and 90% a t 2573-2750 m, which a l s o i n d i c a t e d slower development a t h i g h e r e l e v a t i o n s . In a d d i t i o n , Amman (1973) found t h a t s u r v i v a l r a t e s changed w i t h e l e v a t i o n . P a r e n t a d u l t w i n t e r s u r v i v a l , f o r i n s t a n c e , was 67% a t the lowes t e l e v a t i o n compared t o 12% a t the h i g h e s t e l e v a t i o n . As a r e s u l t of lower t o t a l b e e t l e s u r v i v a l fewer t r e e s were k i l l e d a t the h i g h e r e l e v a t i o n s . S i t e l a t i t u d e can a l s o i n f l u e n c e the mountain p i n e b e e t l e l i f e c y c l e . R e i d (1962a) found t h a t no b e e t l e s p r i n g f l i g h t s o c c u r r e d i n the Invermere study area though he s t a t e d t h a t they were "common" i n the more s o u t h e r n r e g i o n s . Amman et al. (1973) found t h a t t r e e m o r t a l i t y from b e e t l e a t t a c k a t 2830 m at 40° N was e q u a l t o m o r t a l i t y a t 2615 m at 43° N (Amman et al. 1973). In B r i t i s h Columbia S a f r a n y i k et al. (1974) c o n s i d e r e d t h e i r c l i m a t e - b a s e d mountain p i n e b e e t l e h a z a r d map t o be v a l i d from 770 m a t the n o r t h e r n l i m i t of the b e e t l e s ' d i s t r i b u t i o n t o 1230 m i n southern B.C. The b e e t l e s ' food s o u r c e i s the phloem of the t r e e . The amount of phloem i s c o n s i d e r e d t o be the p r i m a r y f a c t o r i n d e t e r m i n i n g brood s u r v i v a l and p r o d u c t i o n (Amman 1969, Amman 1972a, Amman 1972b, Berryman 1976). I n g e n e r a l , the number of eggs l a i d , t he s i z e of l a t e i n s t a r l a r v a e , and the r a t i o of emerging b e e t l e s t o p a r e n t a t t a c k i n g b e e t l e s a r e a l l g r e a t e r i n t r e e s w i t h t h i c k phloem (Amman and Pace 1976, 34 Amman et al. 1977, Amman and C o l e 1983). Because phloem t h i c k n e s s i s p o s i t i v e l y c o r r e l a t e d t o t r e e d i a m e t e r (Amman 1969), and i s a l s o r e l a t e d t o good t r e e v i g o u r ( C o l e 1973) l a r g e , v i g o r o u s t r e e s produce more b e e t l e s than do s m a l l and/or n o n - v i g o r o u s t r e e s . A l a r g e number of t r e e s i n a s t a n d , however, does not n e c e s s a r i l y produce an i n c r e a s e d s u p p l y of phloem. Trees i n dense st a n d s g e n e r a l l y have t h i n n e r phloem than t h o s e grown i n more open s t a n d s (Amman et al. 1977). There e x i s t s a t r a d e - o f f , t h e n , between the amount of phloem a v a i l a b l e per t r e e and the t o t a l amount a v a i l a b l e i n the s t a n d . For l o d g e p o l e p i n e s t a n d s i n g e n e r a l , the mountain p i n e b e e t l e i s food (phloem) l i m i t e d where d e v e l o p m e n t a l t e m p e r a t u r e s a r e optimum, and l i m i t e d by c l i m a t e a t h i g h e l e v a t i o n s or a t the n o r t h e r n l a t i t u d i n a l l i m i t s of the i t s o c c u r r e n c e (Amman 1969, Amman and C o l e 1983). 3.1.3 PAST HISTORY AND CURRENT TRENDS In B r i t i s h Columbia mountain p i n e b e e t l e a c t i v i t y was f i r s t r e c o r d e d i n 1910 (Manning et al. 1982). The a r e a s where damage h i s t o r i c a l l y has been the g r e a t e s t a re the C h i l c o t i n P l a t e a u , and the s o u t h - c e n t r a l and s o u t h - e a s t e r n i n t e r i o r . In r e c e n t t i m e s i n f e s t a t i o n s have i n c r e a s e d s i g n i f i c a n t l y , e s p e c i a l l y i n the C h i l c o t i n P l a t e a u of the C a r i b o o F o r e s t D i s t r i c t . 35 A p p r o x i m a t e l y 2/3 of the i n f e s t a t i o n s mapped i n 1984 were twenty h e c t a r e s or l e s s i n a r e a ; and on about 2/3 of the mapped a r e a l e s s than 30% of the s u s c e p t i b l e h o s t t r e e s were a t t a c k e d . F u r t h e r m o r e , t h e r a t i o of o v e r w i n t e r i n g progeny t o parent b e e t l e s ranged from 0.6 t o 25.0 i n the Kamloops, C a r i b o o and N e l s o n Regions (Wood and Van S i c k l e 1984b). A f a c t o r of 4.1 or g r e a t e r i n d i c a t e s a r i s i n g p o p u l a t i o n . O v e r a l l , t h e r e i s a g r e a t p o t e n t i a l f o r expanding and i n t e n s i f i e d a t t a c k s i n the t h r e e Regions l i s t e d above. 3.2 THE HOST TREE SPECIES 3.2.1 LODGEPOLE PINE CHARACTERISTICS The mountain p i n e b e e t l e has been o b s e r v e d t o i n f e s t t en n a t i v e p i n e s p e c i e s (Wood 1963) and f i v e e x o t i c p i n e s p e c i e s ( F u r n i s s and Schenk 1969). I n B r i t i s h Columbia the pri m a r y h o s t t r e e i s l o d g e p o l e p i n e ( R e i d 1962a, Amman and Co l e 1983, S a f r a n y i k 1984 p e r s o n a l c o m m u n i c a t i o n ) . E c o l o g i c a l l y , t h i s s p e c i e s i s m o d e r a t e l y drought r e s i s t a n t , shade i n t o l e r a n t , an a g g r e s s i v e p i o n e e r s p e c i e s ( K r a j i n a et al. 1982, Angove and B a n c r o f t 1983), and s u s c e p t i b l e t o f i r e . T r e e s may produce seed by the age of f i v e y e a r s . The cones mature i n one y e a r , and a r e o f t e n , though not a l w a y s , s e r o t i n o u s , i n c r e a s i n g t h e a b i l i t y of the s p e c i e s t o invade 36 and r e g e n e r a t e a s i t e a f t e r a f i r e (Arno 1980) Lodgepole p i n e can be c l a s s i f i e d as a s e r a i , p e r s i s t e n t s e r a i , or c l i m a x s p e c i e s depending on s i t e l o c a t i o n ( V o l l a n d 1985). I t i s s e r a i where c o n d i t i o n s a l l o w t h e e s t a b l i s h m e n t and growth of s h a d e - t o l e r a n t s p e c i e s . On s i t e s where d i s t u r b a n c e s o c c u r p e r i o d i c a l l y or where the environment i s o n l y m a r g i n a l l y s u i t e d f o r the e s t a b l i s h m e n t of competing s p e c i e s , l o d g e p o l e p i n e i s c o n s i d e r e d a p e r s i s t e n t s e r a i s p e c i e s ( V o l l a n d 1985). I t may be c l a s s i f i e d as a c l i m a x s p e c i e s when c y c l i c w i l d f i r e s have removed the seed source of s h a d e - t o l e r a n t competing s p e c i e s , or edaphic c o n d i t i o n s are such t h a t no o t h e r s p e c i e s can become e s t a b l i s h e d on the s i t e ( P f i s t e r et al. 1977, V o l l a n d 1985). W i l d f i r e s a r e c o n s i d e r e d t o be the f a c t o r most r e s p o n s i b l e f o r the e s t a b l i s h m e n t and s t r u c t u r e of e x t e n s i v e , even-aged l o d g e p o l e p i n e s t a n d s common i n western Canada and the western U n i t e d S t a t e s (Brown 1973). In B r i t i s h Columbia c l e a r c u t t i n g i s t h e most commonly used method f o r h a r v e s t i n g l o d g e p o l e p i n e (Anonymous 1981, Schmidt and A l e x a n d e r 1985). The s l a s h t h a t remains a f t e r h a r v e s t i n g i s u s u a l l y wind-rowed and burned. T h i s t r e a t m e n t exposes m i n e r a l s o i l and s i m u l t a n e o u s l y opens any s e r o t i n o u s cones on the s i t e . S i t e r e g e n e r a t i o n g e n e r a l l y r e l i e s on n a t u r a l r e s e e d i n g , though some a r e a s a r e seeded or p l a n t e d . 37 3.2.2 TREE AND STAND SUSCEPTIBILITY When the mountain p i n e b e e t l e i s p r e s e n t a t epidemic l e v e l s i n d i v i d u a l t r e e s u s c e p t i b i l i t y t o a t t a c k depends i n i t i a l l y on t r e e d i a m e t e r a t b r e a s t h e i g h t (DBH), and u l t i m a t e l y on t r e e v i g o u r . In o t h e r words, a t r e e may be a t t a c k e d because of i t s s i z e b u t , once a t t a c k e d , i t s s u r v i v a l depends on i t s a b i l i t y t o r e s i s t the a t t a c k . D u r i n g an i n f e s t a t i o n , a t t a c k i n g mountain p i n e b e e t l e s appear t o e x h i b i t a ' p r e f e r e n c e ' f o r the l a r g e r d i a m e t e r t r e e s i n a s t a n d (Hopping and B e a l l 1948, C o l e and Amman 1969, S a f r a n y i k et al. 1974). Research by Shepherd (1966) has shown t h a t a t t a c k i n g b e e t l e s a r e a t t r a c t e d t o l a r g e , dark o b j e c t s s i l h o u e t t e d a g a i n s t a l i g h t e r background, i n d i c a t i n g t h a t a t t a c k may be based a t l e a s t p a r t l y on v i s u a l c u e s . However, C o l e et al. (1981) s u g g e s t e d t h a t the b e e t l e s may a l s o respond t o o l f a c t o r y s t i m u l i i n the form of t e r p e n e s t h a t o c c u r i n g r e a t e r q u a n t i t i e s i n l a r g e r t r e e s . B u r n e l l (1977), i n h i s t h e o r y on mountain p i n e b e e t l e a g g r e g a t i o n , assumed t h a t t h e r e was a s m a l l number of p i o n e e r or f i r s t a t t a c k i n g b e e t l e s , and t h a t each s u s c e p t i b l e t r e e had a t h r e s h o l d number of p i o n e e r b e e t l e s r e q u i r e d t o i n d u c e mass a t t a c k ( a g g r e g a t i o n of a l a r g e number of b e e t l e s ) of the t r e e . The i n i t i a l r e s p onse of a t r e e t o p i o n e e r b e e t l e a t t a c k i s an e x t e n s i v e f l o w of r e s i n from d u c t s s e v e r e d by the b o r i n g a c t i v i t y of the b e e t l e s . I f 38 t h e a t t a c k e d t r e e i s r e s i s t a n t and v i g o r o u s l y growing i t s response may be r a p i d and m assive enough t o overwhelm the p i o n e e r b e e t l e s , and p r e v e n t t h e i r e s t a b l i s h m e n t . A n o n - r e s i s t a n t t r e e of low v i g o u r w i l l produce o n l y a l i m i t e d r e s i n r e s ponse, and the p i o n e e r b e e t l e s w i l l have s u f f i c i e n t time t o r e l e a s e the a g g r e g a t i n g pheromone t h a t i n i t i a t e s mass a t t a c k . Once mass a t t a c k has begun the t r e e has l i t t l e chance of s u r v i v a l . S a f r a n y i k et al. (1974) examined a t t a c k e d t r e e s i n two b e e t l e - i n f e s t e d s t a n d s and found t h a t the c u m u l a t i v e a n n u a l growth of some t r e e s d e c l i n e d much more w i t h time than o t h e r s . The s l o w - g r o w i n g , ' n o n - r e s i s t a n t ' t r e e s were found t o s u f f e r g r e a t e r m o r t a l i t y than f a s t e r g r o w i n g , ' r e s i s t a n t ' t r e e s . U s i n g a d i f f e r e n t a pproach, Waring et al. (1980) d e f i n e d t r e e v i g o u r as the c u r r e n t growth ( i n grams of stemwood produced) per square meter of crown l e a f s u r f a c e . M i t c h e l l et al. (1983) examined t r e e s i n t h r e e i n f e s t e d s t a n d s and, u s i n g Waring's d e f i n i t i o n , compared t r e e v i g o u r t o b e e t l e - c a u s e d t r e e m o r t a l i t y . They found t h a t m o r t a l i t y i n c r e a s e d n o t i c e a b l y when t r e e s produced l e s s than 80 grams of stemwood per square meter of f o l i a g e . I n d i v i d u a l t r e e s w i t h v i g o u r r a t i n g s of 100 grams or more of stemwood produced were r a r e l y a t t a c k e d or k i l l e d . 39 Stand s u s c e p t i b i l i t y t o mountain p i n e b e e t l e e p i d e m i c s i s g r e a t l y i n f l u e n c e d by s t a n d age, diameter d i s t r i b u t i o n , s t a n d d e n s i t y , and o v e r a l l s t a n d r e s i s t a n c e and v i g o u r as d e f i n e d above. Four o t h e r v a r i a b l e s (weather, e l e v a t i o n , l a t i t u d e , and food s u p p l y ) were d i s c u s s e d i n s e c t i o n 3.1.2. Outbreaks of mountain p i n e b e e t l e r a r e l y d e v e l o p i n stan d s w i t h an average age of l e s s than 60 y e a r s . The phloem on the young t r e e s i s too t h i n f o r h i g h b e e t l e p r o d u c t i v i t y , and m o r t a l i t y f a c t o r s such as f r e e z i n g and d e s i c c a t i o n a r e g r e a t e r i n s m a l l e r t r e e s ( S a f r a n y i k et al. 1974, Amman et al. 1977, Amman and Col e 1983). Assuming t h a t the s m a l l e r t r e e s a r e the younger t r e e s , stands w i t h an average age of 60 t o 80 y e a r s a re c o n s i d e r e d i n t e r m e d i a t e r i s k s , and st a n d s g r e a t e r than 80 or 90 y e a r s o l d p r e s e n t the g r e a t e s t p o t e n t i a l f o r i n f e s t a t i o n ( S a f r a n y i k et al . 1974, Amman et al. 1977). In g e n e r a l , l a r g e t r e e s produce more b e e t l e s than do s m a l l t r e e s because of t h e i r g r e a t e r average phloem t h i c k n e s s . The r a t i o of emerging t o a t t a c k i n g b e e t l e s i s u s u a l l y l e s s than one i n t r e e s s m a l l e r than 25 cm a t DBH, but may be as g r e a t as s i x or e i g h t i n t r e e s g r e a t e r than 40 cm DBH ( S a f r a n y i k et al . 1974, Amman et al. 1977). T h e r e f o r e , stands w i t h a h i g h p r o p o r t i o n of l a r g e d i a m e t e r t r e e s a r e more s u s c e p t i b l e t o i n f e s t a t i o n . 40 Stand d e n s i t y i n f l u e n c e s average t r e e phloem t h i c k n e s s . G e n e r a l l y , low d e n s i t y s t a n d s have a g r e a t e r p r o p o r t i o n of l a r g e d i a m e t e r t r e e s w i t h t h i c k phloem, and so a r e more s u s c e p t i b l e t o o u t b r e a k s . H i g h - d e n s i t y ' d o g h a i r ' stands of l o d g e p o l e p i n e r a r e l y undergo i n f e s t a t i o n . Both S a f r a n y i k et al . (1974) and M i t c h e l l et al . (1983) r e l a t e d s t a n d s u s c e p t i b i l i t y t o the p r o p o r t i o n of the s t a n d made up of ' r e s i s t a n t ' or ' v i g o r o u s ' t r e e s as d e f i n e d p r e v i o u s l y . S a f r a n y i k et al. (1974) found t h a t the number of r e s i s t a n t t r e e s i n a s t a n d v a r i e d both s e a s o n a l l y and over the ' l i f e ' of the s t a n d . S e a s o n a l l y , the number of r e s i s t a n t t r e e s i n c r e a s e d u n t i l J u l y , then d e c r e a s e d . Over the s t a n d l i f e t he p r o p o r t i o n of r e s i s t a n t t r e e s i n c r e a s e d u n t i l an age of 40 t o 60 y e a r s , then r a p i d l y d e c r e a s e d ( F i g u r e 13). The maximum l e v e l of s t a n d r e s i s t a n c e was found t o be p o s i t i v e l y c o r r e l a t e d w i t h the maximum c u r r e n t a n n u a l increment and the c u l m i n a t i o n of b a s a l a r e a growth, assuming a f u l l y s t o c k e d s t a n d . M i t c h e l l et al. (1983) r e l a t e d i n d i v i d u a l t r e e v i g o u r as d e f i n e d by Waring et al. (1980) t o l e a f a r e a index and b a s a l a r e a , then compared the r e s u l t s t o the b e e t l e - c a u s e d m o r t a l i t y on s e v e r a l s t a n d s . Those s t a n d s w i t h l e a f a r e a i n d i c e s of a p p r o x i m a t e l y 1.0, and b a s a l a r e a s of r o u g h l y 15.0 square meters per h e c t a r e had the lowe s t m o r t a l i t i e s However, Waring et al. (1980) p o i n t e d out t h a t the r e s u l t s 41 100 0 I i i i i 1-20 21-40 41-60 61-80 81-110 111-140 A G E O F T R E E S F i g u r e 13: Change i n f r e q u e n c y of r e s i s t a n t l o d g e p o l e p i n e t r e e s f o r d i f f e r e n t aged s t a n d s ( S a f r a n y i k et at. 1974). 42 were p r e l i m i n a r y , r e q u i r e d f u r t h e r r e s e a r c h , and s h o u l d not be used as a guide f o r s t a n d management. 3.2.3 MOUNTAIN PINE BEETLE EFFECTS ON TREES AND STANDS A t t a c k of a t r e e by the mountain p i n e b e e t l e produces one of t h r e e r e s u l t s : s u c c e s s f u l r e s i n response by the t r e e , a ' s t r i p ' ( p a r t i a l ) a t t a c k , o r de a t h of the t r e e . I f the t r e e ' s r e s i n response ( s e c t i o n 3.2.2) i s s u c c e s s f u l the b e e t l e i s ' p i t c h e d out' of the t r e e . R e s i d u a l p i t c h tubes on the b o l e of the t r e e may be the o n l y i n d i c a t i o n t h a t the t r e e was once a t t a c k e d . In some c a s e s , the b e e t l e i s o n l y p a r t i a l l y s u c c e s s f u l i n i t s a t t a c k . T h i s r e s u l t s i n a ' s t r i p ' a t t a c k i n which o n l y a v e r t i c a l s e c t i o n on p a r t of the t r e e i s i n f e s t e d . A l t h o u g h s t r i p a t t a c k s may o c c u r i n 15% o f the a t t a c k e d t r e e s i n a st a n d (Wood and Woensdregt 1981) t h e dynamics of t h i s type of a t t a c k a r e c u r r e n t l y not w e l l u n d e r s t o o d . I t i s known t h a t t r e e s may s u r v i v e a s t r i p a t t a c k , however t h e i r r e s i s t a n c e t o f u r t h e r a t t a c k may be l e s s e n e d (Rasmussen 1974, B u r n e l l et al. In P r e s s ) . B e e t l e c o l o n i z a t i o n w i l l be s u c c e s s f u l i f the t r e e ' s r e s i n response i s i n s u f f i c i e n t t o c o n t a i n t h e f u n g i and b e e t l e s . F o l l o w i n g g e r m i n a t i o n the f u n g a l s p o r e s p e n e t r a t e l i v e phloem and xylem c e l l s . The f u n g i i n t e r f e r e w i t h water c o n d u c t i o n and the t r e e ' s d e f e n s i v e r e s i n r e s p o n s e . A l s o , 43 w e l l - d e v e l o p e d b l u e - s t a i n f u n g i cause the t r e e t o dry r a p i d l y i n the w i n t e r a f t e r a t t a c k , but remain more moist the f o l l o w i n g summer, r e d u c i n g b e e t l e m o r t a l i t y due t o d e s i c c a t i o n (Amman et al. 1977). The growing f u n g i move r a p i d l y i n a v e r t i c a l d i r e c t i o n , but s l o w l y i n a h o r i z o n t a l d i r e c t i o n . The b e e t l e l a r v a e , however, fee d more or l e s s h o r i z o n t a l l y , t h u s s p r e a d i n g the f u n g i . In t h i s manner the combined a c t i o n of the b e e t l e - f u n g i a s s o c i a t i o n e s s e n t i a l l y g i r d l e s t h e t r e e . As an i n f e s t a t i o n p r o g r e s s e s the mountain p i n e b e e t l e s g e n e r a l l y a t t a c k the l a r g e s t r e m a i n i n g l i v e t r e e s . However, o v e r a l l p o p u l a t i o n p r o d u c t i v i t y d e c l i n e s as the b e e t l e s a re f o r c e d t o a t t a c k s m a l l e r t r e e s , and the outb r e a k e v e n t u a l l y c o l l a p s e s . The o v e r a l l e f f e c t of a mountain p i n e b e e t l e i n f e s t a t i o n i s a p r o p o r t i o n a t e l y g r e a t e r m o r t a l i t y i n the l a r g e r DBH c l a s s e s ( F i g u r e s 14 and 15), and a r e d u c t i o n i n average s t a n d d i a m e t e r . 3.2.4 SILVICULTURAL APPROACHES TO REDUCING SUSCEPTIBILITY I t has been suggested t h a t the s u s c e p t i b i l i t y of a s t a n d t o a t t a c k by mountain p i n e b e e t l e can be reduced t h r o u g h s i l v i c u l t u r a l methods. Stands s h o u l d f i r s t be ranked a c c o r d i n g t o s u s c e p t i b i l i t y , and tho s e w i t h the g r e a t e s t p r o b a b i l i t y of outb r e a k g i v e n t r e a t m e n t p r i o r i t y . 44 1 0 0 - i 2 0 3 0 4 0 5 0 6 0 DBH (cm) Figure 14: Mortality in a lodgepole pine stand attacked by the mountain beetle in r e l a t i o n to tree DBH (Hopping and Beall 1948). 45 100-I S >-80-60-O U J or 40-20-• o o o 10 20 30 DBH (cm) 40 F i g u r e 15: M o r t a l i t y i n two l o d g e p o l e p i n e s t a n d s a t t a c k e d by the mountain b e e t l e i n r e l a t i o n t o t r e e DBH ( C o l e and Amman 1969). 46 In a r e a s where l o d g e p o l e p i n e stands a r e c h r o n i c a l l y s u s c e p t i b l e t o b e e t l e o u t b r e a k s the replacement of p i n e s by a non-host s p e c i e s may be the b e s t o p t i o n . In some a r e a s , l o d g e p o l e p i n e i s not the c l i m a x s p e c i e s but p e r s i s t s i n the s t a n d because of i t s c o m p e t i t i v e a b i l i t i e s and/or a l i m i t e d c l i m a x s p e c i e s seed source ( P f i s t e r et al . 1977, V o l l a n d 1985). In these a r e a s c o n v e r s i o n t o the c l i m a x s p e c i e s s h o u l d be encouraged. C l e a r c u t t i n g , however, o f t e n r e s u l t s i n s i t e c o n d i t i o n s t h a t p r e c l u d e the e s t a b l i s h m e n t of s h a d e - t o l e r a n t replacement s p e c i e s . T h e r e f o r e , an e x t e n s i v e p l a n t i n g campaign would p r o b a b l y be n e c e s s a r y . T h i n n i n g from above i s a second a l t e r n a t i v e . In t h i s method the most s u s c e p t i b l e t r e e s would be removed, and the r e s i d u a l p i n e stems would a c t as nurse t r e e s p r o v i d i n g shade and s h e l t e r t o a i d the e s t a b l i s h m e n t of the new, c l i m a x s p e c i e s . There a r e two p o s s i b l e drawbacks. F i r s t , p l a n t i n g may be n e c e s s a r y and second, the r e s i d u a l stems may be s u b j e c t t o stem c o l l a p s e or windthrow. An a l t e r n a t i v e t o t o t a l replacement of l o d g e p o l e p i n e i s the c r e a t i o n of m i x e d - s p e c i e s stands ( S a f r a n y i k et al. 1974, Amman et al . 1977). T h i s o p t i o n has s e v e r a l advantages. F i r s t , the i n s e c t s u s c e p t i b i l i t y of mixed s p e c i e s s t a n d s i s lower than t h a t of pure s t a n d s . Even i f the mixed s p e c i e s s t a n d s were a t t a c k e d , the l o s s i n terms of r e s i d u a l s t o c k i n g would be l e s s than t h a t of a pure s t a n d 47 (Amman et al. 1977). A mosaic of age c l a s s e s would a l s o h e l p p r e v e n t the s i m u l t a n e o u s development of o u t b r e a k s over l a r g e a r e a s ( S a f r a n y i k et al. 1974). One p o s s i b l e drawback would be the complex management n e c e s s a r y f o r the maintenance and h a r v e s t i n g of such s t a n d s . In some s t a n d s , c o n v e r s i o n t o or i n t r o d u c t i o n of a second s p e c i e s may not be p o s s i b l e . In t h i s c a s e , the two best a v a i l a b l e o p t i o n s a r e t h i n n i n g ( e i t h e r p r e - c o m m e r c i a l or c o m m e r c i a l ) , or a r e d u c t i o n of the r o t a t i o n age. The mountain p i n e b e e t l e appears t o show a p r e f e r e n c e f o r l a r g e r d i a m e t e r t r e e s ( C o l e and Amman 1969, S a f r a n y i k et . al. 1975) and s u r v i v e s and rep r o d u c e s b e t t e r i n t h e i r t h i c k e r phloem. T h e r e f o r e , removal of thes e l a r g e r t r e e s would reduce the p o t e n t i a l f o r i n f e s t a t i o n . S a f r a n y i k et al. (1974) and Amman et al. (1977) agreed t h a t t he removal of t r e e s g r e a t e r than 20 cm a t DBH would reduce s t a n d s u s c e p t i b i l i t y . The p o t e n t i a l f o r a mountain p i n e b e e t l e o u t b r e a k i n c r e a s e s w i t h s t a n d age, p a r t i c u l a r l y a f t e r age 80 y e a r s . S a f r a n y i k et al. (1974) i n d i c a t e d t h a t t r e e and st a n d r e s i s t a n c e i s g r e a t e s t between the ages of 40 and 60 y e a r s . T h e r e f o r e , a r e d u c t i o n i n r o t a t i o n age c o u l d a l s o reduce the s u s c e p t i b i l i t y of a s t a n d t o mountain p i n e b e e t l e a t t a c k . One f i n a l o p t i o n a v a i l a b l e i s t o do n o t h i n g t o p r e v e n t or c o n t r o l i n f e s t a t i o n s , and a l l o w them t o run t h e i r n a t u r a l c o u r s e (Amman 1976). The many openings c r e a t e d by the dea t h 48 of the l o d g e p o l e p i n e t r e e s would a l l o w n a t u r a l s u c c e s s i o n t o t a k e p l a c e . D o u g l a s - f i r would become dominant a t lower e l e v a t i o n s , and Engelmann s p r u c e and s u b a l p i n e f i r a t h i g h e r e l e v a t i o n s ( P f i s t e r et al. 1977). S t a n d i n g w i l d l i f e t r e e s (or snags) would p r o v i d e p e r c h e s f o r some r a p t o r s , and nest s i t e s f o r c a v i t y - n e s t i n g b i r d s (Amman et al. 1977, L e s t e r 1980). F a l l e n l o g s would p r o v i d e nest s i t e s f o r g r o u n d - n e s t i n g b i r d s , and bedding and cover f o r v a r i o u s l a r g e and s m a l l mammals (Thomas 1979). However, d o i n g n o t h i n g does have i t s n e g a t i v e e f f e c t s . An outbreak i n one s t a n d may s p r e a d t o a n o t h e r s t a n d where the d o - n o t h i n g o p t i o n i s not a c c e p t a b l e . The o p t i o n a l s o r e s u l t s i n a l a r g e amount of unused t i m b e r . F i n a l l y , t h e dead t r e e s add t o the b u i l d - u p of the s t a n d ' s f i r e f u e l l o a d (Brown 1973). 3.3 THE AVIAN PREDATORS 3.3.1 PREDATOR IMPACTS To da t e n i n e t e e n s p e c i e s of b i r d s have been i d e n t i f i e d as p r e d a t o r s of the mountain p i n e b e e t l e (Table 1 ) . D u r i n g the w i n t e r , when the l a r v a e a r e beneath the b a r k , o n l y b i r d s of the woodpecker f a m i l y can f e e d e f f e c t i v e l y on them. Woodpeckers have numerous s p e c i a l a d a p t a t i o n s t h a t enable them t o f i n d and remove wood-boring i n s e c t s . They have s h a r p , c h i s e l - l i k e b i l l s t h a t a l l o w e x c a v a t i o n t h r o u g h l i v e 49 T a b l e 1: A v i a n P r e d a t o r s Of The Mountain P i n e B e e t l e BIRD SPECIES SOURCE Common nighthawk 1 P i l e a t e d woodpecker 5 H a i r y woodpecker 1,4,5,6,7 Downy woodpecker 4,5,6,7 B l a c k - b a c k e d woodpecker 6 Thre e - t o e d woodpecker 1,6 Western wood pewee 4 O l i v e - s i d e d f l y c a t c h e r 4,7 Empidonax s s p . 4 C l a r k ' s n u t c r a c k e r 4 Mountain c h i c k a d e e e 4 W h i t e - b r e a s t e d n u t h a t c h 4 Red-brea s t e d n u t h a t c h 1 Pygmy n u t h a t c h 4 Brown c r e e p e r 4 American r o b i n 4 Townsend's s o l i t a i r e 4 Mountain b l u e b i r d 2,3 Yellow-rumped w a r b l e r 4 1: Rust 1929 2: Blackman 1931 3: B e a l 1939 4: S t a l l c u p 1963 5: Amman 1973 6: L e s t e r 1980 7: Otvos and S t a r k 1985 50 or dead wood, and t h e i r s t r o n g neck muscles and t h i c k s k u l l a bsorb the shock of the blows. The e x t r e m e l y l o n g , b a r b - t i p p e d tongue can be extended f a r beyond the b i l l i n ord e r t o l o c a t e and withdraw i n s e c t s from deep w i t h i n the t r e e . The sha r p - c l a w e d f e e t , u s u a l l y w i t h two t o e s f o r w a r d and two t o e s back, a r e d e s i g n e d f o r c l i n g i n g t o ba r k . The f e e t and s t i f f , t a p e r e d t a i l f e a t h e r s s t a b i l i z e the b i r d , and c o n t r i b u t e t o the e f f i c i e n c y of the p e c k i n g a c t i o n . (Bent 1939, Jackman 1975). Amman (1973) r e p o r t e d the p r e d a t i o n of o v e r w i n t e r i n g mountain p i n e b e e t l e a d u l t s by the h a i r y and downy woodpeckers. M o r t a l i t y due t o the woodpeckers v a r i e d depending on e l e v a t i o n . Woodpeckers consumed an e s t i m a t e d 54% of the p a r e n t a d u l t s a t h i g h e l e v a t i o n s (2573-2750 m), 37% a t 2450 m, and 21% a t 2130 m. Woodpecker-caused m o r t a l i t y was not measured a t 1923 m, but was assumed t o be s m a l l . Amman suggested t h a t woodpecker p r e d a t i o n was g r e a t e s t a t h i g h e l e v a t i o n s because the l a r v a e were l a r g e r and more numerous. F u r t h e r m o r e , p r e f e r e n c e f o r the p a r e n t a d u l t s over the l a r v a e may have been due t o t h e s m a l l e r s i z e of t he l a r v a e . S t u d i e s on woodpecker p r e d a t i o n of the Engelmann spruce b e e t l e ( K o p l i n and B a l d w i n 1970) and ev e n i n g grosbeak p r e d a t i o n of the e a s t e r n s p r u c e budworm ( B l a i s and Pa r k s 1964) appear t o s u p p o r t Amman's o b s e r v a t i o n s c o n c e r n i n g the i n f l u e n c e of p r e y s i z e . 51 In Montana, L e s t e r (1980) s t u d i e d woodpecker p r e d a t i o n i n 8 stands w i t h d i f f e r e n t mountain p i n e b e e t l e p o p u l a t i o n d e n s i t i e s . The most common woodpecker s p e c i e s d u r i n g t h e w i n t e r were the t h r e e - t o e d , h a i r y , and b l a c k - b a c k e d woodpeckers. Though no stomach samples were t a k e n , L e s t e r made some e s t i m a t e s of brood m o r t a l i t y due t o woodpeckers based on bark d i s t u r b a n c e . Woodpecker f e e d i n g d i s t u r b e d a p p r o x i m a t e l y 10% of the bark on b e e t l e - a t t a c k e d l o d g e p o l e p i n e s . Most of the bark removal was i n patc h e s of l e s s than or e q u a l t o 6.45 cm 2 i n a r e a . Bark b e e t l e l a r v a e i n phloem a d j a c e n t t o a r e a s d i s t u r b e d by woodpeckers may d i e from d e s i c c a t i o n and i n c r e a s e d exposure t o c o l d t e m p e r a t u r e s (Otvos 1979). L e s t e r (1980) e s t i m a t e d t h a t the zone of such i n d i r e c t i n f l u e n c e was 1.3 cm wide around the ar e a of bark removal. Based on e s t i m a t e d d i r e c t consumption by woodpeckers, and , the i n d i r e c t e f f e c t of the zone of i n f l u e n c e of d i s t u r b e d bark, she e s t i m a t e d t h a t woodpeckers were r e s p o n s i b l e f o r about 30% of the t o t a l b e e t l e brood m o r t a l i t y . C o l e (1981) examined r i s k s and causes of m o r t a l i t y i n p r e - e p i d e m i c , e p i d e m i c , and p o s t - e p i d e m i c p o p u l a t i o n s of t h e mountain p i n e b e e t l e i n 23-cm, 30-cm, and 38-cm t r e e d i a m e t e r c l a s s e s . The p r o b a b i l i t y of l a r v a l m o r t a l i t y from woodpeckers was lowest i n 38-cm t r e e s r e g a r d l e s s of i n f e s t a t i o n s t a g e , d e c r e a s e d w i t h i n f e s t a t i o n s tage i n t h e 52 30-cm t r e e d i a m e t e r c l a s s , and i n c r e a s e d w i t h i n f e s t a t i o n s t a g e i n the 23-cm s t a g e . C o l e s u g g e s t e d t h a t snow d e p t h , bark t h i c k n e s s , and b e e t l e d e n s i t i e s may have been i m p o r t a n t f a c t o r s i n t r e e s e l e c t i o n by woodpeckers. There have been no s t u d i e s conducted i n B r i t i s h C olumbia s p e c i f i c a l l y aimed a t d e t e r m i n i n g t h e impact of w i n t e r f e e d i n g by woodpeckers on mountain p i n e b e e t l e p o p u l a t i o n s . However, o b s e r v a t i o n s made by Moeck, Otvos, and Whitney (1984 p e r s o n a l c o m m u n i c a t i o n ) , and u n p u b l i s h e d d a t a made a v a i l a b l e by S a f r a n y i k (1984 p e r s o n a l communication) a r e r e l e v a n t t o t h i s t o p i c . Dr.'s Moeck and Whitney, i n t h e i r r e s e a r c h on the mountain p i n e b e e t l e , r e q u i r e d i n f o r m a t i o n about o v e r w i n t e r i n g m o r t a l i t y . In e a r l y s t u d i e s t hey made e s t i m a t e s or c o u n t s of b e e t l e brood s i z e i n the autumn, o n l y t o r e t u r n i n the s p r i n g t o f i n d the bark c h i p p e d o f f by woodpeckers and the brood d e s t r o y e d . From t h e i r d e s c r i p t i o n s and d e s c r i p t i o n s o f f e r e d by a s s i s t a n t s , i t appeared t h a t h a i r y and t h r e e - t o e d woodpeckers were a c t i v e i n the a r e a . On some t r e e s t h e bark had been removed down t o about s n o w l i n e , w h i l e on o t h e r s the b i r d s had e v i d e n t l y worked the same t r e e as the snow m e l t e d and removed the bark down t o ground l e v e l . The o b s e r v a t i o n s of Dr.'s Moeck, O t v o s , and Whitney c o n c e r n i n g the s i z e of t r e e s t h a t t h e woodpeckers f e d on appear t o agree w i t h the o b s e r v a t i o n s made by L e s t e r (1980). She found t h a t the 53 woodpeckers chose t r e e s w i t h an average DBH of 24.9 cm (±5.1 cm). D u r i n g some e a r l i e r i n v e s t i g a t i o n s Dr. S a f r a n y i k a l s o found i t n e c e s s a r y t o 'cage' t r e e s w i t h w i r e i n or d e r t o p r e v e n t woodpeckers from d e s t r o y i n g the b r o o d . The s p r i n g brood d e n s i t i e s i n bark a r e a s p r o t e c t e d from woodpeckers averaged 40, 30.2, 20.2, and 27 l a r v a e per 80 square i n c h sample u n i t a t 4 t r e e h e i g h t s . D e n s i t i e s of c o r r e s p o n d i n g u n p r o t e c t e d a r e a s a v e r a g e d 25, 16.4, 9.2 and 8 l a r v a e per sample u n i t . Though t h e s e v a l u e s cannot be r e l a t e d t o mountain p i n e b e e t l e p o p u l a t i o n d e n s i t i e s t h e y can be used as an i n d i c a t i o n of t h e impact t h a t moderate bark d i s t u r b a n c e by woodpeckers can have on brood s u r v i v a l . D u r i n g the b e e t l e s ' s h o r t f l i g h t and a t t a c k p e r i o d i n the summer, they a r e s u s c e p t i b l e t o p r e d a t i o n by a l a r g e r number and v a r i e t y of b i r d s p e c i e s than d u r i n g the w i n t e r . S t u d i e s c o n ducted by Rust (1929 and 1930) and S t a l l c u p (1963) examined the b i r d s t h a t f e e d on the b e e t l e s a t t h i s t i m e . In h i s f i r s t s t u d y , Rust (1929) found t h a t the common nighthawk was the most i m p o r t a n t p r e d a t o r . Ten nighthawk stomachs c o n t a i n e d two t o 289 (avg. 76) a d u l t p i n e b e e t l e s r e p r e s e n t i n g , i n the l a t t e r c a s e , 20% of t h e t o t a l volume of food consumed. The t h r e e - t o e d and h a i r y woodpeckers were next i n i m p o r t a n c e , a v e r a g i n g about 2.7 and 1.5 b e e t l e s per stomach, r e s p e c t i v e l y . 54 One year l a t e r Rust (1930) found t h a t the importance of the s p e c i e s i n terms of b e e t l e s consumed was r e v e r s e d . The t h r e e - t o e d and h a i r y woodpeckers averaged 74.7 and f o u r t e e n b e e t l e s per stomach, r e s p e c t i v e l y . The f o u r t e e n nighthawks averaged o n l y f i v e b e e t l e s per stomach. Rust suggested t h a t the change may have o c c u r r e d because the h e a v i e s t c o n c e n t r a t i o n of the mountain p i n e b e e t l e moved s i x t o ten m i l e s west of the a r e a i n v e s t i g a t e d the p r e v i o u s y e a r . The woodpeckers moved w i t h the i n f e s t a t i o n , w h i l e the nighthawks s t a y e d near t h e i r e s t a b l i s h e d b r e e d i n g grounds. S t a l l c u p (1963) examined not o n l y the number of b e e t l e s taken per b i r d , but a l s o the d e n s i t i e s of the b i r d and mountain p i n e b e e t l e p o p u l a t i o n s . Based on stomach c o n t e n t s , b i r d and b e e t l e d e n s i t i e s artd w e i g h t s , and the assumption t h a t the b i r d s consumed d a i l y a q u a n t i t y of food e q u a l t o about 25% of t h e i r body w e i g h t , S t a l l c u p c a l c u l a t e d t h a t the b i r d s c o u l d have consumed a maximum of 2358 a d u l t b e e t l e s per a c r e . T h i s f i g u r e r e p r e s e n t e d 11.6% of the e s t i m a t e d mountain p i n e b e e t l e p o p u l a t i o n . In terms of the p r o p o r t i o n of the b i r d stomach c o n t e n t s r e p r e s e n t e d by b e e t l e f r a g m e n t s , the most i m p o r t a n t b i r d s p e c i e s were the r e d - b r e a s t e d n u t h a t c h , western wood pewee, brown c r e e p e r , pygmy n u t h a t c h and Empidonax f l y c a t c h e r s . 55 3.3.2 HABITAT REQUIREMENTS Based on the a v a i l a b l e i n f o r m a t i o n , the most i m p o r t a n t a v i a n p r e d a t o r s of the mountain p i n e b e e t l e d u r i n g i t s f l i g h t p e r i o d a r e the mountain b l u e b i r d , common nighthawk, h a i r y and t h r e e - t o e d woodpeckers, pygmy and r e d - b r e a s t e d n u t h a t c h e s , brown c r e e p e r , and w e s t e r n wood pewee. The f i r s t two s p e c i e s f e e d by f l y c a t c h i n g ( c a p t u r i n g i n s e c t s on the w i n g ) . These b i r d s a r e r e s p o n s i b l e f o r c a t c h i n g the b e e t l e s as they seek new t r e e s t o a t t a c k . Both b i r d s e x h i b i t a p r e f e r e n c e f o r open h a b i t a t s ( Godfrey 1979, Thomas 1979), so t h e i r e f f e c t i v e n e s s i n dense l o d g e p o l e p i n e s t a n d s would be l i m i t e d . Though they share the same f e e d i n g method the n e s t i n g r e q u i r e m e n t s of the two s p e c i e s a r e q u i t e d i f f e r e n t . The mountain b l u e b i r d i s a secondary c a v i t y n e s t e r (Thomas 1979). I t r e q u i r e s a c a v i t y i n a t r e e f o r n e s t i n g but cannot e x c a v a t e i t s own, so i t must depend on n a t u r a l c a v i t i e s or t h o s e e x c a v a t e d by o t h e r b i r d s . The common nighthawk does not r e q u i r e t r e e s f o r n e s t i n g . In f a c t , i t b u i l d s no n e s t but s i m p l y l a y s i t s eggs on the ground, p r e f e r a b l y on sand, g r a v e l , or r o c k . I n f o r m a t i o n from th e V e r t e b r a t e Zoology D i v i s i o n of the B r i t i s h Columbia P r o v i n c i a l Museum i n d i c a t e d t h a t b o t h of t h e s e s p e c i e s o c c u r i n t h e i n t e r i o r of B r i t i s h C o l u m b i a , and may be r a i s i n g young a t the time of b e e t l e f l i g h t . 56 The woodpeckers, n u t h a t c h e s , and brown c r e e p e r do most of t h e i r summer f e e d i n g by g l e a n i n g i n s e c t s from the bark of t r e e t r u n k s and l i m b s . These b i r d s would fe e d on the b e e t l e s as they emerged from t r e e s and as th e y l a n d e d on new t r e e s . The female mountain p i n e b e e t l e s do not s i m p l y bore i n t o a t r e e as soon they l a n d . They examine the bark, a v o i d smooth a r e a s , and u s u a l l y bore i n t o the t r e e i n bark c r e v i c e s or under s c a l e s (Rasmussen 1974). The e x a m i n a t i o n s u s u a l l y l a s t l e s s than 30 minutes each but t h i s would g i v e the b a r k - g l e a n i n g b i r d s time t o l o c a t e the b e e t l e s b e f o r e they bored i n t o t he t r e e . Censuses conducted i n Montana by L e s t e r (1980) i n d i c a t e d t h a t the t h r e e - t o e d and h a i r y woodpeckers were the most common -woodpeckers d u r i n g the b r e e d i n g -season i n mountain p i n e b e e t l e - i n f e s t e d l o d g e p o l e p i n e s t a n d s . She found a t o t a l of e i g h t h a i r y and e l e v e n t h r e e - t o e d woodpecker n e s t s . Seven of the e i g h t h a i r y woodpecker n e s t s were found i n aspen or b i r c h . Nine of the e l e v e n t h r e e - t o e d woodpecker n e s t s were i n l o d g e p o l e p i n e , seven of which had been k i l l e d by the mountain p i n e b e e t l e . One of the c o n c l u s i o n s made by L e s t e r (1980) was t h a t t h e t h r e e - t o e d woodpecker, because of i t s a b i l i t y t o use l o d g e p o l e p i n e as a nest t r e e , would have the g r e a t e r a b i l i t y t o f o l l o w the i n f e s t a t i o n as i t spread t o new a r e a s . The h a i r y woodpecker n e s t s more o f t e n i n softwoods (Thomas 1979, L e s t e r 1980), 57 and may not show as g r e a t a response t o the b e e t l e o u t b r e a k . Both n u t h a t c h e s have the a b i l i t y t o e x c a v a t e t h e i r own nest c a v i t i e s (Thomas 1979). Of the two s p e c i e s l i s t e d the r e d - b r e a s t e d n u t h a t c h i s more common i n l o d g e p o l e p i n e communities ( A u s t i n and P e r r y 1979, Thomas 1979). I n f o r m a t i o n from the P r o v i n c i a l Museum i n d i c a t e d t h a t both s p e c i e s a r e r e s i d e n t i n the i n t e r i o r , and may be r a i s i n g young d u r i n g the b e e t l e f l i g h t p e r i o d . The brown c r e e p e r i s c o n s i d e r e d a secondary c a v i t y n e s t e r (Thomas 1979). T h i s s p e c i e s u s u a l l y shows a p r e f e r e n c e f o r o l d e r , u n d i s t u r b e d s t a n d s ( A u s t i n and P e r r y 1979, V e r n e r 1980). P r o v i n c i a l Museum d a t a shows t h i s s p e c i e s t o be a r e s i d e n t of the i n t e r i o r , but t h e r e i s l i t t l e a d d i t i o n a l i n f o r m a t i o n c o n c e r n i n g p e r i o d s of n e s t i n g or f l e d g i n g . P r o v i n c i a l i n f o r m a t i o n c o n c e r n i n g t h e we s t e r n wood pewee i s a l s o l i m i t e d . I t can be found i n a wide v a r i e t y of c o n i f e r h a b i t a t s but p r e f e r s t o nes t i n o l d e r s t a n d s (Thomas 1979). I n f o r m a t i o n from the P r o v i n c i a l Museum i n d i c a t e s t h a t i t w i l l n e s t i n mixed l o d g e p o l e p i n e / a s p e n s t a n d s i n the i n t e r i o r . Nest r e c o r d s i n d i c a t e b r e e d i n g as e a r l y as June 22 and as l a t e as August 6. The h a i r y and t h r e e - t o e d woodpeckers a r e the most i m p o r t a n t p r e d a t o r s of the mountain p i n e b e e t l e d u r i n g the w i n t e r (Amman 1973, L e s t e r 1980), though t h e b l a c k - b a c k e d 58 woodpecker may a l s o be i m p o r t a n t ( L e s t e r 1980). D u r i n g the w i n t e r , n e s t t r e e r e q u i r e m e n t s no l o n g e r l i m i t b i r d d e n s i t i e s . F u r t h e r m o r e , t e r r i t o r i e s a r e not defended d u r i n g the w i n t e r , so f e e d i n g by m i x e d - s p e c i e s f l o c k s of up t o s i x b i r d s may be observed ( B a l d w i n 1960). P r o v i n c i a l Museum r e c o r d s i n d i c a t e t h a t the t h r e e woodpecker s p e c i e s l i s t e d can be found i n the i n t e r i o r throughout the w i n t e r , though d e t a i l e d h a b i t a t i n f o r m a t i o n i s s c a r c e . 3.3.3 AVIAN RESPONSES TO TIMBER HARVESTING As noted i n s e c t i o n 3.2.1. the most common method of h a r v e s t i n g l o d g e p o l e p i n e i n the i n t e r i o r i s c l e a r c u t t i n g . T h i s method, th r o u g h i t s r a p i d removal of the o v e r s t o r y and s i m u l t a n e o u s c r e a t i o n of a l a r g e open s i t e , can have d r a s t i c e f f e c t s on b i r d p o p u l a t i o n s . E i g h t b i r d s p e c i e s were l i s t e d as i m p o r t a n t p r e d a t o r s of the mountain p i n e b e e t l e . Two of t h e s e , the mountain b l u e b i r d and common nighthawk, would p r o b a b l y b e n e f i t from a c l e a r c u t . Both r e q u i r e l a r g e , open a r e a s f o r f e e d i n g . The common nighthawk, which n e s t s on the ground i n open h a b i t a t s , would p r o b a b l y b e n e f i t most. The mountain b l u e b i r d r e q u i r e s a t r e e c a v i t y i n which t o n e s t . I f nest s i t e s were a v a i l a b l e a d j a c e n t t o the c l e a r c u t i t would b e n e f i t from the open f e e d i n g a r e a . In the stu d y by A u s t i n and P e r r y (1979) the mountain b l u e b i r d was absent from the mature and s t a g n a t e d l o d g e p o l e p i n e s t a n d s , but d i d 59 o c c u r i n t h e r e c e n t l y c l e a r c u t a r e a . Three s p e c i e s , the r e d - b r e a s t e d and pygmy n u t h a t c h e s and t h e brown c r e e p e r , would be a d v e r s e l y a f f e c t e d by a c l e a r c u t . A u s t i n and P e r r y (1979), Schwab (1979), S c o u l l a r (1980) and P e t e r s o n (1982) agreed t h a t the r e d - b r e a s t e d n u t h a t c h i s a s s o c i a t e d w i t h mature f o r e s t s t a n d s . I t was a l s o the o n l y s p e c i e s of the t h r e e l i s t e d found t o n e s t i n s e n e s c e n t l o d g e p o l e p i n e s t a n d s ( A u s t i n and P e r r y 1979). S z a r o and B a l d a (1979) and S c o t t (1979) i n d i c a t e d t h a t the pygmy n u t h a t c h would d e c r e a s e on l o g g e d s t a n d s . The brown c r e e p e r was a s s o c i a t e d w i t h mature, but not s e n e s c e n t or h a r v e s t e d , s t a n d s ( A u s t i n and P e r r y 1979, V e r n e r 1980). Woodpecker response t o c l e a r c u t t i n g appeared t o depend on whether or not w i l d l i f e t r e e s were l e f t on the s i t e . S t u d i e s i n ponderosa p i n e communities i n A r i z o n a by S c o t t and Oldemeyer (1983) and i n mixed pine-hardwood f o r e s t i n Texas by D i c k s o n et al. ( 1983) i n d i c a t e d t h a t by l e a v i n g some w i l d l i f e t r e e s on c l e a r c u t a r e a s the n e g a t i v e impact of the c u t on woodpeckers (and c a v i t y n e s t e r s i n g e n e r a l ) c o u l d be l e s s e n e d . O n l y one s t u d y , t h a t of S z a r o and B a l d a (1979) examined the impact of l o g g i n g on the w e s t e r n wood pewee. T h i s s p e c i e s was absent from uncut and c l e a r c u t s t a n d s , r e a c h i n g i t s g r e a t e s t d e n s i t y on p a r t i a l l y c u t s t a n d s . E v i d e n t l y , a moderate d e c r e a s e i n s t a n d d e n s i t y p r o v e d most b e n e f i c i a l . 4. STRUCTURE OF THE SIMULATION MODEL The b a s i c s t r u c t u r e of the mountain p i n e b e e t l e - b i r d s i m u l a t i o n model has been o u t l i n e d i n a s i m p l i f i e d f l o w diagram ( F i g u r e 16). In the f i g u r e the numerals a s s o c i a t e d w i t h some of the v a r i a b l e s i d e n t i f y t he s o u r c e s (Appendix 2) used t o dete r m i n e the v a l u e or v a l u e s of t h a t v a r i a b l e . 4.1 LODGEPOLE PINE STAND STRUCTURE F o l l o w i n g the examples of K l e i n et. al. 1978, C o l e and McGregor 1983, and o t h e r s the s t a n d s t r u c t u r e and d e n s i t y was d e t e r m i n e d by the number of t r e e s i n each of s i x diam e t e r c l a s s e s ; 12.7-17.5, 17.6-22.6, 22.7-27.7, 27.8-32.8, 32.9-37.8, and 37.9-42.9 cm a t b r e a s t h e i g h t . For conv e n i e n c e t h e s e a r e r e f e r r e d t o as the 15, 20, 25, 30, 35, and 40-cm DBH c l a s s e s . Trees w i t h a DBH of 12.6 cm or l e s s were not i n c l u d e d i n the model because they a r e r a r e l y a t t a c k e d (Hopping and B e a l l 1948, Amman and C o l e 1969, S a f r a n y i k 1984 p e r s o n a l c o m m u n i c a t i o n ) . Trees l a r g e r than 43 cm DBH were not i n c l u d e d because s p e c i f i c i n f o r m a t i o n on i n s e c t a t t a c k d e n s i t y , i n s e c t s u r v i v a l , t r e e m o r t a l i t y , e t c . was e x t r e m e l y l i m i t e d or n o n - e x i s t a n t . The s t a n d a r e a (ha) i s s e t p r i o r t o s i m u l a t i o n . A revi e w of F o r e s t I n s e c t And D i s e a s e Survey f i l e r e p o r t s f o r the p r o v i n c e of B r i t i s h C olumbia, and f o r the C a r i b o o , Kamloops, and Ne l s o n F o r e s t Regions i n d i c a t e d t h a t 60 WOODPECKER WINTER OEMS ITT NUMBER OP MPB LARVAE CONSUMED BT ONE WOODPECKER IN ONE DAT DURATION Or * PERIOD Of PREDATION MPB POPULATION PHLOEM THICKNESS DISTRIBUTION OP WOODPECKER WINTER PEEDING BIRDS' SUMMER DENSITIES NUMBER Or MPB ADULTS CONSUMED BT ONE BIRD IN ONE DAT DURATION Or PERIOD Or PREDATION TREE 'ATTRACTIVENESS' ATTACKED TREE SURFACE AREA EGG MORTAL!TT AUTUMN MORTALITT INITIAL WINTER MORTALITT SPRING MORTALITT EARLT SUMMER MORTAL! TI DISPERSAL OUT OP THE INrESTED STAND SEX RATIO PROPORTION Or 10 EEMALES MATED EGGS PER rEMALE II MORTALITT DUE TO WOODPECKERS MORTALITY DUE TO 13 COLD TEMPERATURE MORTALITT DUE TO 13 DESICCATION MORTALITY DUE TO 9IRDS MORTALITT DUE TO 14 ALL OTHER CAUSES STAND DENSITY AND STRUCTURE DISTRIBUTION Or ATTACKING MPB POPULATION MPB PER TREE EGGS PER TREE INITIAL NUMBER OP LARVAE PER TREE LARVAE PER TREE AT BEGINNING OP WINTER WINTER LARVAE (WOODPECKER WINTER POOD SOURCE) LARVAE PER TREE AT END OP WINTER NEW HPB POPULATION LARVAE PER TREE AT END OP SPRING ADULTS EMERGING PER TREE MPB ATTACK OEMSITT TREES KILLED PER DBH CLASS Figure 16: Basic flow diagram of the s i m u l a t i o n model. 62 i n f e s t a t i o n s range from a few t o g r e a t e r than 400 h e c t a r e s i n a r e a , Most, however, a r e l e s s than 50 h e c t a r e s . The s t a n d a r e a used f o r a l l s i m u l a t i o n s was 20 h e c t a r e s , a f t e r Manning et al. (1982). The s t a n d age was m o d e l l e d as a p p r o x i m a t e l y 100 y e a r s ; an age when almost a l l l o d g e p o l e p i n e s t a n d s a r e s u s c e p t i b l e t o mountain p i n e b e e t l e a t t a c k . To a v o i d the complex and confounding a f f e c t s of topography the s t a n d was assumed t o be l e v e l . 4.2 MOUNTAIN PINE BEETLE POPULATION DISTRIBUTION The s i z e of the i n i t i a l b e e t l e p o p u l a t i o n i s s e t b e f o r e the s i m u l a t i o n b e g i n s . For a l l s i m u l a t i o n s an i n i t i a l d e n s i t y of 750 b e e t l e s per h e c t a r e was used ( K l e i n et al. 1978, B u r n e l l et al. In P r e s s ) . Once s t a n d c h a r a c t e r i s t i c s and i n i t i a l b e e t l e d e n s i t y are e s t a b l i s h e d , the b e e t l e p o p u l a t i o n i s d i s t r i b u t e d among the host t r e e s . D i s t r i b u t i o n i s based on the p r o p o r t i o n of the t r e e s i n the s t a n d r e p r e s e n t e d by each diameter c l a s s ( P ; ) , and the ' a t t r a c t i v e n e s s ' v a l u e ( A ; ) f o r the i t h diameter c l a s s . The A; v a l u e s were d e t e r m i n e d by c a l c u l a t i n g (DBH 6);, then r e - s c a l i n g the f i g u r e s such t h a t the v a l u e f o r the l a r g e s t c l a s s was e q u a l t o 0.95. ' R e l a t i v e a t t r a c t i v e n e s s ' v a l u e s (RA;) were then c a l c u l a t e d by 63 RA; = A;/A; maximum. (1 ) The ' t o t a l a t t r a c t i v e n e s s ' (TA;) of each diameter c l a s s was then e q u a l t o The p r o p o r t i o n of the mountain p i n e b e e t l e p o p u l a t i o n a s s i g n e d t o the i t h d i a m e t e r c l a s s (PB,) was c a l c u l a t e d by and the a c t u a l number of b e e t l e s a s s i g n e d t o each c l a s s (NB;) was e q u a l t o where ALLBET was the t o t a l mountain p i n e b e e t l e p o p u l a t i o n i n the s t a n d . In t h i s manner the b e e t l e s were c o n c e n t r a t e d i n the l a r g e diameter t r e e s a t the b e g i n n i n g of the i n f e s t a t i o n , and p r o g r e s s i v e l y s h i f t e d t o the s m a l l e r t r e e s as the l a r g e r ones were k i l l e d . TA; = RA;P; (2) PB; = TA;/£ TAj (3) NB; = PB;(ALLBET) (4) 64 4.3 LODGEPOLE PINE MORTALITY Tree m o r t a l i t y depended on the b e e t l e a t t a c k d e n s i t y and t h e s u r f a c e a r e a of the a t t a c k e d p o r t i o n of the t r e e . Mean a t t a c k d e n s i t y was i n i t i a l l y s e t a t a r e l a t i v e l y low v a l u e of 58 a t t a c k s per m2 because, t h e o r e t i c a l l y , the b e e t l e s , when at endemic l e v e l s , a t t a c k t r e e s of lower than a v e r a g e v i g o u r ( s e c t i o n 3.1.2), and fewer b e e t l e s a r e n e c e s s a r y t o k i l l t he t r e e . A t t a c k d e n s i t y then i n c r e a s e d , and became a s y m p t o t i c a t 75 a t t a c k s per m2 by the t h i r d year of the i n f e s t a t i o n . T h i s number i s an a p p r o x i m a t i o n of the o p t i m a l a t t a c k d e n s i t y f o r the mountain p i n e b e e t l e (Berryman el al. 1985). O v e r a l l p o p u l a t i o n p r o d u c t i v i t y d e c r e a s e s a t both lower or h i g h e r a t t a c k d e n s i t i e s due t o a low number of eggs produced, and the e f f e c t s of w i t h i n - and between-brood c o m p e t i t i o n , r e s p e c t i v e l y ( R e i d 1963). The a t t a c k d e n s i t y i n c r e a s e d from z e r o t o t e n p e r c e n t , depending on t h e s i z e of the a t t a c k i n g b e e t l e p o p u l a t i o n ( K l e i n et al . 1977). Mountain p i n e b e e t l e s u s u a l l y c o n c e n t r a t e t h e i r a t t a c k s i n t he lower 2.4 t o 4.6 metres of a t r e e (Rasmussen 1974, L e s t e r 1980), though t h i s f i g u r e v a r i e s w i t h t r e e d i a m e t e r and the st a g e of t h e i n f e s t a t i o n (Shepherd 1965, S a f r a n y i k 1968, K l e i n et al. 1978, S a f r a n y i k 1984 p e r s o n a l c o m m u n i c a t i o n ) . In t h e model the a t t a c k e d s u r f a c e a r e a of a t r e e (ASRF) i s c a l c u l a t e d by ASRF = -3.78 + (0.3221 DIAM;) (5) where t r e e d i a m e t e r a t b r e a s t h e i g h t i s measured i n c e n t i m e t e r s , and s u r f a c e a r e a i n square metres. T h i s e q u a t i o n was d e r i v e d from measurements r e c o r d e d by L e s t e r (1980). As the i n f e s t a t i o n p r o g r e s s e s the a t t a c k e d s u r f a c e a r e a i s i n c r e a s e d by a p p r o x i m a t e l y ten p e r c e n t due t o the i n c r e a s e d h e i g h t of a t t a c k . Due t o the l a c k of d a t a no attempt was made t o s t r a t i f y the a t t a c k d e n s i t i e s by diameter c l a s s . The number of a t t a c k s r e q u i r e d t o k i l l a t r e e was c a l c u l a t e d by m u l t i p l y i n g the a t t a c k e d s u r f a c e area by the a t t a c k d e n s i t y . The t o t a l number of t r e e s k i l l e d per diameter c l a s s , TREKIL;, was then equal t o TREKIL; - TOTTAT j/TATT; (6) where TOTTAT; was the t o t a l number of a t t a c k i n g b e e t l e s i n the d iameter c l a s s , and TATT; was the number of a t t a c k s per t r e e . P a r t i a l or ' s t r i p ' a t t a c k dynamics ( s e c t i o n 3.2.3) are c u r r e n t l y not w e l l u nderstood or documented and were not i n c l u d e d i n the model. The number of dead t r e e s i n each DBH c l a s s was removed from the p o o l of l i v e t r e e s per DBH c l a s s a t the end of each y e a r l y i t e r a t i o n of the model, thus s e t t i n g s t a n d c o n d i t i o n s f o r the next y e a r . 66 4.4 MOUNTAIN PINE BEETLE PRODUCTIVITY The number of eggs l a i d i n each t r e e was dependent on th e number of females p r e s e n t and the number of eggs produced per female. The p r o p o r t i o n of the b e e t l e p o p u l a t i o n t h a t was female (PROFEM) v a r i e s c o n s i d e r a b l y w i t h t r e e d i a m e t e r and the stage of i n f e s t a t i o n (Amman and C o l e 1983), and was c a l c u l a t e d by PROFEM; = 0.6919 - (0.0035 DIAM;) (7) from B u r n e l l et . al. (In P r e s s ) . The number of eggs l a i d per female can v a r y g r e a t l y , from one or two t o more than 200 i n one i n s t a n c e ( R e i d 1962b). V a l u e s u s u a l l y range between 40 and 80 eggs per female (Peterman 1974, S a f r a n y i k et al. 1974). Female f e c u n d i t y was found t o be r e l a t e d t o the t h i c k n e s s of t h e h o s t t r e e phloem (Amman and C o l e 1983) which, i n t u r n , was r e l a t e d t o t r e e diameter (Amman 1969, Amman 1972a, 1972b). I n the model, females i n t r e e s w i t h t h i n phloem ( a p p r o x i m a t e l y 1.0 mm) produced 40 eggs, w h i l e those i n t r e e s w i t h t h i c k phloem (4.6 mm) produced a maximum of 80 eggs. Data on the p r o p o r t i o n of the female p o p u l a t i o n t h a t i s mated a r e c u r r e n t l y u n a v a i l a b l e . In the model i t was assumed t h a t 95 % of the females were s u c c e s s f u l l y mated. Egg h a t c h 67 v a r i e s between 82% and 98 %, depending on t h e di a m e t e r of the a t t a c k e d t r e e and the st a g e of the i n f e s t a t i o n ( R e i d 1962b, Amman and C o l e 1983). 4.5 MOUNTAIN PINE BEETLE MORTALITY R e s e a r c h e r s have examined a wide v a r i e t y of f a c t o r s t h a t cause mountain p i n e b e e t l e m o r t a l i t y ( R e i d 1962b, Amman 1973, C o l e 1974, and Amman and C o l e 1983). U n f o r t u n a t e l y , a l l f a c t o r s e x h i b i t c o n s i d e r a b l e v a r i a t i o n depending on e l e v a t i o n , l a t i t u d e , t r e e d i a m e t e r , and the stage of the i n f e s t a t i o n . T h i s model d i d not attempt t o s i m u l a t e each i n d i v i d u a l f a c t o r . I n s t e a d , w i t h a few e x c e p t i o n s d e s c r i b e d below, a g e n e r a l m o r t a l i t y r a t e was a p p l i e d t o the b e e t l e p o p u l a t i o n i n each t r e e a t t h e beg i n n i n g ' of autumn, w i n t e r , s p r i n g , and summer. These b a s i c m o r t a l i t y r a t e s were m o d i f i e d by t r e e d i a m e t e r and p o p u l a t i o n d e n s i t y t o account f o r such e f f e c t s as c r o w d i n g and the lower i n s u l a t i v e p r o p e r t y of t h i n n e r b a r k . D u r i n g the w i n t e r , t h r e e i n d i v i d u a l m o r t a l i t y f a c t o r s were s i m u l a t e d i n a d d i t i o n t o the g e n e r a l w i n t e r m o r t a l i t y . These i n c l u d e d m o r t a l i t y due t o c o l d t e m p e r a t u r e s , d e s i c c a t i o n , and woodpecker p r e d a t i o n . The f i r s t two f a c t o r s were s e l e c t e d because they a r e the major s o u r c e s of m o r t a l i t y d u r i n g the w i n t e r . They were s i m u l a t e d i n a s i m i l a r manner t o the g e n e r a l m o r t a l i t y r a t e s , v a r y i n g i n 68 r e l a t i o n t o t r e e d i a m e t e r and p o p u l a t i o n d e n s i t y . Woodpecker p r e d a t i o n , a major f o c u s of the model, was c a l c u l a t e d i n a more complex manner, as i l l u s t r a t e d i n the f l o w diagram ( F i g u r e 17). The t h r e e major f a c t o r s t h a t d e t e r m i n e m o r t a l i t y due t o woodpeckers d u r i n g t h e w i n t e r a r e the number of b i r d s p r e s e n t , the l e n g t h of the p e r i o d of p r e d a t i o n , and the number of l a r v a e one b i r d consumes i n a day. Woodpecker w i n t e r p o p u l a t i o n d e n s i t i e s (WPSTD) v a r i e d w i t h the number of l a r v a e a v a i l a b l e i n the w i n t e r . The b i r d s e x h i b i t e d a d i r e c t n u m e r i c a l r e sponse as d e s c r i b e d i n s e c t i o n 2.2.2. The d u r a t i o n of the p e r i o d of p r e d a t i o n (WINTER) was f i x e d a t 123 days t o a p p r o x i m a t e the p e r i o d of g r e a t e s t p r e d a t i o n betweem December 1 and March 31. Four major s t e p s were r e q u i r e d t o c a l c u l a t e the number of l a r v a e each b i r d consumed i n a day. F i r s t , the d a i l y energy r e q u i r e m e n t i n k i l o c a l o r i e s per gram of bodyweight (WKGD), i s c a l c u l a t e d by WKGD = 0.64 - (0.008 x TEMP) (8) where TEMP i s the average w i n t e r t e m p e r a t u r e i n degrees c e n t i g r a d e . T h i s e q u a t i o n was d e r i v e d from measurements r e c o r d e d by K o p l i n ( 1 9 67). The second s t e p i s AVERAGE WINTER TEMPERATURE KILOCALORIES PER 1 8 GRAM BODY WEIGHT REQUIRED PER WOODPECKER PER DAT WOODPECKER WEIGHT 19 KILOCALORIES REQUIRED PER WOODPECKER PER DAT PROPORTION OF 2 0 WOODPECKER'S DIET REPRESENTED BT MOUNTAIN PINE BEETLE LARVAE CALORIC VALUE OF ONE MOUNTAIN PINE BEETLE LARVAE 21 PROPORTION OF DAILT ENERGETIC REQUIREMENT FILLED BT MOUNTAIN PINE BEETLE LARVAE NUMBER OF MOUNTAIN PINE BEETLE LARVAE CONSUMED BY ONE WOODPECKER IN ONE DAT F i g u r e 17: S i m p l i f i e d flow digram of sequence used to determine l a r v a e consumption by winter woodpeckers. WPKD = WKGD x WPWT (9) where WPWT i s the woodpecker's w e i g h t i n grams, and WPKD i s the number of k i l o c a l o r i e s r e q u i r e d per day per b i r d t o m a i n t a i n body w e i g h t . I n the t h i r d s t e p , WPKD i s m u l t i p l i e d by the p r o p o r t i o n of the b i r d ' s d i e t made up of mountain p i n e b e e t l e l a r v a e (DIET) t o de t e r m i n e the p r o p o r t i o n of the woodpecker's d a i l y c a l o r i c r e q u i r e m e n t f i l l e d by b e e t l e l a r v a e . Changes i n DIET f o l l o w a s i g m o i d f u n c t i o n a l response as d e s c r i b e d i n s e c t i o n 2.2 .1. To d e r i v e t he number of l a r v a e consumed by one woodpecker i n one day (CATAWP), the number of k i l o c a l o r i e s i n the woodpecker's d i e t o b t a i n e d from l a r v a e i s d i v i d e d by the c a l o r i c v a l u e of one l a r v a t o dete r m i n e the number of l a r v a e consumed by one woodpecker i n one day (CATAWP). The e q u a t i o n CATAWP = CATWPD x WINTER X WPSTD (10) where CATWPD i s the number of l a r v a e consumed by a l l woodpeckers i n the s t a n d i n one day, d e t e r m i n e d t h e number of l a r v a e consumed by a l l woodpeckers i n the s t a n d d u r i n g t h e w i n t e r (CATAWP). Once the number of l a r v a e consumed by woodpeckers has been c a l c u l a t e d i t i s n e c e s s a r y t o det e r m i n e the so u r c e of 71 the l a r v a e ; t h a t i s , the number of l a r v a e removed from each t r e e , and the number of t r e e s per DBH c l a s s from w h i c h t h e l a r v a e were removed. U n f o r t u n a t e l y , t h e r e i s a s u r p r i s i n g d e a r t h of i n f o r m a t i o n i n t h i s a r e a , c o n s i d e r i n g the v i s i b i l i t y and r e c u r r e n c e of bark removal by woodpeckers. Bark removal by woodpeckers may be r e l a t e d t o bark b e e t l e d e n s i t y ( H u t c h i n s o n 1951, Beaver 1967, McCambridge and K n i g h t 1972, L e s t e r 1980). When i n s e c t d e n s i t i e s a r e g r e a t s m a l l groups of woodpeckers have been known t o work on o n l y a few t r e e s u n t i l most of the bark has been removed (Massey and Wygant 1954). E s t i m a t e s of the p e r c e n t a g e o f the bark b e e t l e brood d e s t r o y e d by woodpecker f e e d i n g a c t i v i t y ranged from 13% ( K o p l i n and B a l d w i n 1970) t o 98% (Massey and Wygant 1954, K n i g h t 1958). T h e r e f o r e , i t i s assumed t h a t , t h r o u g h bark removal and subsequent f e e d i n g , woodpeckers remove 20% t o 80% of the p i n e b e e t l e brood i n a t r e e , depending on i n i t i a l w i n t e r l a r v a l d e n s i t y . Ten p e r c e n t of the b r ood i s assumed t o be p r o t e c t e d from woodpeckers by snow, s u f f e r i n g m o r t a l i t y from d e s i c c a t i o n o n l y . The b a l a n c e of the brood undergoes m o r t a l i t y from b o t h d e s i c c a t i o n and c o l d t e m p e r a t u r e s . To c a l c u l a t e the number of woodpeckered 2 t r e e s i t was f i r s t n e c e s s a r y t o d e t e r m i n e the number of l a r v a e removed 2"Woodpeckered" i s a term used by some a u t h o r s t o i n d i c a t e a t r e e from which bark has been removed t h r o u g h a woodpecker's f e e d i n g a c t i v i t y . 72 from each d i a m e t e r c l a s s each w i n t e r . For s i m p l i c i t y , i t was assumed t h a t the d i s t r i b u t i o n of woodpecker w i n t e r f e e d i n g (DSTWPF) was p r o p o r t i o n a l t o the d i s t r i b u t i o n of l a r v a e a v a i l a b l e a t the s t a r t of the w i n t e r . DSTWPF was determined by DSTWPF| = WSLRVH;/WSLRVT (11) where WSLRVH; i s the number of l a r v a e a v a i l a b l e per h e c t a r e d u r i n g the w i n t e r i n the i t h DBH c l a s s , and WSLRVT i s the t o t a l number of l a r v a e a v a i l a b l e per h e c t a r e . M u l t i p l y i n g DSTWPF; by the t o t a l number of l a r v a e consumed each w i n t e r (CATWWH), y i e l d e d the number of l a r v a e consumed per h e c t a r e per DBH c l a s s d u r i n g the w i n t e r (CCWPH). D i v i d i n g t h i s f i g u r e by the number of l a r v a e removed from each t r e e d etermined the number of woodpeckered t r e e s per h e c t a r e i n each DBH c l a s s (WPTRHA). L a s t l y , the e q u a t i o n UWPTHA; = TREKHA;-WPTRHA; (12) where TREKHA; i s the number of t r e e s k i l l e d t h a t year i n the i t h DBH c l a s s , d e t e r m i n e d the number of non-woodpeckered t r e e s per h e c t a r e per DBH c l a s s . Larvae i n the woodpeckered t r e e s were s u b j e c t e d t o g r e a t e r m o r t a l i t y from d e s i c c a t i o n and c o l d t e m p e r a t u r e s due t o bark removal than those i n 73 non-woodpeckered t r e e s (Otvos 1979). The b e e t l e s t h a t s u r v i v e d s p r i n g and. e a r l y summer m o r t a l i t y r e p r e s e n t the emerging a d u l t b e e t l e p o p u l a t i o n . F o l l o w i n g emergence, they d i e from ' f l i g h t - p e r i o d ' m o r t a l i t y f a c t o r s , d i s p e r s e out of the s t a n d , o r s u r v i v e and remain i n the s t a n d t o a t t a c k new t r e e s . The impact and e x t e n t of m o r t a l i t y d u r i n g t h e f l i g h t and a t t a c k p e r i o d i s l a r g e l y unknown. T h i s m o r t a l i t y may r e s u l t from a v a r i e t y of f a c t o r s i n c l u d i n g f i s h , shrews, a n t s , b a t s , b i r d s , v e h i c l e w i n d s h i e l d s , f o r e s t f i r e s , e t c . In the model t h e r e a r e two forms of f l i g h t p e r i o d m o r t a l i t y : b i r d s , and o t h e r c a u s e s . M o r t a l i t y from o t h e r causes was assumed t o be a c o n s t a n t at ten p e r c e n t . M o r t a l i t y due t o summer b i r d s was c a l c u l a t e d i n a s i m i l a r manner ( F i g u r e 18) t o woodpecker-caused m o r t a l i t y i n t he w i n t e r . S p e c i f i c e n e r g e t i c i n f o r m a t i o n c o n c e r n i n g the r e d - b r e a s t e d n u t h a t c h and the brown c r e e p e r (two of the t h r e e summer b i r d s p e c i e s modelled) was not a v a i l a b l e . T h e r e f o r e , a g e n e r a l m e t a b o l i c e q u a t i o n (Kendeigh 1970) was used t o d e t e r m i n e the d a i l y e n e r g e t i c requirement ( i n k i l o c a l o r i e s ) per b i r d (CALB;) through the e q u a t i o n CALB j = 1 .5720 (BIRDW °' 6 2 1° ) (13) where BIRDW i s the b i r d ' s weight i n grams. A s i m i l a r e q u a t i o n BIRD WEIGHT 22 KILOCALORIES REQUIRED PER BIRD PER DAT 23 PROPORTION OF 2 4 DIET REPRESENTED BY MOUNTAIN PINE BEETLE ADULTS PROPORTION OF DAILY ENERGETIC REQUIREMENT FILLED BY MOUNTAIN PINE BEETLE ADULTS CALORIC VALUE OF 2 5 ONE MOUNTAIN PINE BEETLE ADULT NUMBER OF MOUNTAIN PINE BEETLE ADULTS CONSUMED BY ONE BIRD IN ONE DAT B Figure 18: S i m p l i f i e d flow digram of sequence used to determine b e e t l e consumption by summer b i r d s . —i it* 75 CALB 2 = 0.5404 (BIRDW " ) (14) was used t o c a l c u l a t e d a i l y e n e r g e t i c r e q u i r e m e n t s f o r the n o n - P a s s e r i n e woodpecker (Kendeigh 1970). CALB, and CALB 2 were m u l t i p l i e d by a c o r r e c t i o n f a c t o r of 1.5 t o c o n v e r t s t a n d a r d m e t a b o l i c r e q u i r e m e n t s t o an a p p r o x i m a t i o n of e x i s t e n c e l e v e l r e q u i r e m e n t s . T h i s c o r r e c t i o n was u n n e c e s s a r y f o r w i n t e r woodpeckers because i t had a l r e a d y been i n c l u d e d i n the c a l c u l a t i o n s by K o p l i n (1967). As i n t h e w i n t e r c a l c u l a t i o n s , the p r o p o r t i o n of the d i e t r e p r e s e n t e d by mountain p i n e b e e t l e s was used t o d e t e r m i n e the p r o p o r t i o n of the d a i l y e n e r g e t i c r e q u i r e m e n t f i l l e d by a d u l t p i n e b e e t l e s . T h i s f i g u r e , d i v i d e d by the c a l o r i c v a l u e of one a d u l t b e e t l e , y i e l d e d the number of b e e t l e s consumed per b i r d per day. As i n w i n t e r c a l c u l a t i o n s t h i s f i g u r e was m u l t i p l i e d by the number of b i r d s i n the s t a n d and the d u r a t i o n of p e r i o d of p r e d a t i o n t o d e t e r m i n e the t o t a l number of a d u l t b e e t l e s consumed by summer b i r d s . B e e t l e s not k i l l e d i n f l i g h t were s u b j e c t e d t o d i s p e r s a l out of the s t a n d . A g a i n , no a c t u a l f i g u r e s a r e a v a i l a b l e , though Canadian and U.S. r e s e a r c h on t h i s s u b j e c t c o n t i n u e s ( S a f r a n y i k 1985 p e r s o n a l c o m m u n i c a t i o n ) . In the model, d i s p e r s i o n i s dependent on the average DBH of the s t a n d . B r i e f l y , d i s p e r s i o n from the s t a n d i s a t i t s l o w e s t 76 l e v e l (1%) when many, large host trees are e a s i l y a v a i l a b l e . As the infestation progresses and large, preferred trees become scarce, dispersion increases, becoming asymptotic at 40%. Beetles remaining in the stand after dispersal form the mountain pine beetle population for the next i t e r a t i o n of the model. A l i s t i n g of the basic mountain pine beetle simulation model and a glossary of the variables used in the model are found in Appendices 3 and 4. 5. SIMULATION RESULTS AND DISCUSSION 5.1 SIMULATED SCENARIOS Nine s c e n a r i o s , w i t h d i f f e r e n t c o m b i n a t i o n s of s t a n d s t r u c t u r e and b i r d r e s p o n s e s , were s i m u l a t e d ( F i g u r e 19). The t h r e e s t a n d s t r u c t u r e s were c o n t r o l ('normal'), s e n e s c e n t , and t h i n n e d . The c o n t r o l s t a n d had a di a m e t e r d i s t r i b u t i o n c o n s i d e r e d t y p i c a l f o r s t a n d s commonly a t t a c k e d by the mountain p i n e b e e t l e ( C o l e et al. 1976), and r e p r e s e n t e d an a p p r o x i m a t i o n of an 'average' l o d g e p o l e p i n e s t a n d . The senescent s t a n d had a more t i g h t l y even-aged, s i n g l e - s t o r i e d s t r u c t u r e , w i t h most of the t r e e s c o n c e n t r a t e d i n the l a r g e r DBH c l a s s e s . D e n s i t y was s l i g h t l y l e s s than t h a t of the c o n t r o l stand." In the t h i n n e d s t a n d t r e e d e n s i t i e s i n the 15 and 20 cm-DBH c l a s s e s were the same as t h o s e i n the c o n t r o l s t a n d . D e n s i t i e s i n the 25, 30, 35, and 40-cm c l a s s e s , however, were reduced by 95% based on the s u g g e s t i o n s of S a f r a n y i k et al. ( 1974), and Amman et al . (1977) f o r r e d u c i n g s t a n d s u s c e p t i b i l i t y t o b e e t l e a t t a c k ( s e c t i o n 3.2.4). Three c o m b i n a t i o n s of b i r d f u n c t i o n a l and n u m e r i c a l r e s p o n s e s were a l s o s i m u l a t e d . As a c o n t r o l , t h e maximum b i r d d e n s i t i e s and the maximum p r o p o r t i o n of mountain p i n e b e e t l e l a r v a e o r a d u l t s i n the b i r d s ' d i e t s were a p p r o x i m a t i o n s of 'normal' c o n d i t i o n s f o r each s t a n d 77 78 STAND STRUCTURE C o n t r o l Senescent T h i n n e d Normal 1 4 7 E f f i c i e n t 2 5 8 2 X C o n t r o l D e n s i t y 3 6 9 F i g u r e 19: Diagram of 3 X 3 f a c t o r i a l d e s i g n used i n the s i m u l a t i o n s . 79 s t r u c t u r e , as were the i n s e c t d e n s i t i e s a t which the maximum re s p o n s e s o c c u r r e d . The second c o m b i n a t i o n of r e s p o n s e s s i m u l a t e d more e f f i c i e n t a v i a n p r e d a t o r s whose f u n c t i o n a l and n u m e r i c a l responses a t t a i n e d t h e i r maximum v a l u e s a t a p p r o x i m a t e l y h a l f the b e e t l e d e n s i t y r e q u i r e d by t h e normal p r e d a t o r s . In the t h i r d s e t of c o m b i n a t i o n s t h e f u n c t i o n a l r esponse was assumed t o be normal, but the b i r d d e n s i t i e s were dou b l e t h o s e t h a t o c c u r r d i n the c o n t r o l s t a n d . The l a s t two c o m b i n a t i o n s of res p o n s e s were s i m u l a t e d i n o r d e r t o compare changes due t o i n c r e a s e d p r e d a t o r e f f i c i e n c y t o t h o s e caused by i n c r e a s e d d e n s i t y a l o n e . I n i t i a l v a l u e s of some key v a r i a b l e s a r e found i n Appendix 5. 5.2 THE CONTROL STAND 5.2.1 SCENARIO 1; NORMAL PREDATOR RESPONSES The mountain p i n e b e e t l e p o p u l a t i o n a c h i e v e d i t s g r e a t e s t d e n s i t y i n the c o n t r o l s t a n d i n t h i s s c e n a r i o ( F i g u r e 2 0). Maximum l a t e summer d e n s i t y (65,777 a d u l t b e e t l e s per h e c t a r e ) o c c u r r e d i n year n i n e of a s i x t e e n year i n f e s t a t i o n . The extended d u r a t i o n of the outbr e a k was due, u l t i m a t e l y , t o the d e n s i t y and s t r u c t u r e of the s t a n d . I n i t i a l p o p u l a t i o n growth was slow because of poor fo o d q u a l i t y ( t h i n phloem) r e s u l t i n g from a h i g h s t a n d d e n s i t y (Amman et el. 1977), and a g r e a t e r number of t r e e s i n the 80 F i g u r e 20: Y e a r l y mountain pine b e e t l e autumn d e n s i t y i n the c o n t r o l stand. 81 smaller diameter classes (Cole and Amman 1980). Because expansion was slow, the beetle population did not rapidly deplete i t s food supply, enabling the population to persist in the stand for a long period of time. By the end of the in f e s t a t i o n approximately 325 trees per hectare, or roughly 17% of the o r i g i n a l stand, had been k i l l e d by the beetles (Figures 21 and 22). Tree mortality increased with diameter, ranging from 3% in the 15-cm D B H c l a s s to 65% in the 40-cm class (Figure 23). This pattern commonly occurs during mountain pine beetle outbreaks (see Figures 13 and 14). Winter woodpecker densities attained a maximum of 25 birds per 100 hectares in year f i v e of the i n f e s t a t i o n , corresponding to a winter l a r v a l density of 93,011 larvae per hectare (Figures 24 and 25). At t h i s time, the woodpeckers f i r s t achieved t h e i r peak consumption of 21,108 larvae per hectare per winter. However, the maximum percentage l a r v a l consumption, 26% of the winter l a r v a l population, occurred in the previous year, corresponding to a population of 59,711 larvae per hectare (Figure 26). Total summer b i r d density for the three species simulated reached a peak of 50 individuals per 100 hectares in year seven of the outbreak, corresponding to a beetle density of 38,464 beetles per hectare (Figures 27 and 28). The maximum consumption of 329 adult beetles during the 82 F i g u r e 21: Y e a r l y t o t a l s t a n d d e n s i t y f o r t h e c o n t r o l s t a n d . 83 DIAMETER CLASS (cm) F i g u r e 22: I n i t i a l and f i n a l s t a n d s t r u c t u r e s f o r t h e c o n t r o l s t a n d . 84 F i g u r e 23: T o t a l t r e e m o r t a l i t y f o r each diameter c l a s s i n the c o n t r o l stand. 85 F i g u r e 24: Y e a r l y winter b i r d d e n s i t y i n the c o n t r o l stand. 86 F i g u r e 25: W i n t e r b i r d d e n s i t y r e l a t i v e t o l a r v a l d e n s i t y . i n the c o n t r o l s t a n d F i g u r e 26: Percent of winter l a v a l p o p u l a t i o n by woodpeckers i n the c o n t r o l stand. consumed 88 F i g u r e 27: T o t a l summer b i r d d e n s i t y i n the c o n t r o l stand. 89 F i g u r e 28: T o t a l summer b i r d d e n s i t y i n the c o n t r o l stand r e l a t i v e to a d u l t d e n s i t y . 90 21-day f l i g h t p e r i o d o c c u r r e d a t the same t i m e . U n l i k e w i n t e r a v i a n p r e d a t i o n , the summer maximum p e r c e n t a g e c o n s u m p t i o n , 0.9% of the emerging a d u l t b e e t l e p o p u l a t i o n ( F i g u r e 2 9 ) , o c c u r r e d i n the same year as t h e maximum numeric consumption. T h i s was due t o a c o m b i n a t i o n of the s l o w e r growth of the emergent b e e t l e p o p u l a t i o n and slowe r b i r d r e s p o n s e s . For s e v e r a l r e a s o n s t h e p e r c e n t a g e of t h e prey p o p u l a t i o n consumed by summer b i r d s was o n l y about 3% of the w i n t e r p r e y consumption. F i r s t , b i r d e n e r g e t i c r e q u i r e m e n t s a r e much lower i n t h e summer ( K o p l i n 1967, Kendeigh 1970). Second, the b e e t l e s a r e found on the e x t e r i o r of the t r e e so the b i r d s do not have t o expend energy t o remove the b e e t l e s from beneath the b a r k . T h i r d , t h e a d u l t b e e t l e s a r e l a r g e r t h e n the l a r v a e , and have a h i g h e r c a l o r i c v a l u e ( K o p l i n 1967, Otvos 1969), so fewer i n s e c t s a r e needed t o s a t i s f y b i r d c a l o r i c r e q u i r e m e n t s . F i n a l l y , t h e r e i s a g r e a t e r abundance of a l t e r n a t e p r e y a v a i l a b l e d u r i n g the summer. The p e r c e n t of b e e t l e s i n the b i r d s ' summer d i e t s i s s m a l l e r than d u r i n g the w i n t e r , so fewer b e e t l e s a re consumed. Consumption of the summer a d u l t b e e t l e p o p u l a t i o n was a l s o 7% t o 10% of t h a t e s t i m a t e d by S t a l l c u p (1963). There were s e v e r a l r e a s o n s f o r t h e d i f f e r e n c e s i n e s t i m a t e s . F i r s t , S t a l l c u p made h i s c a l c u l a t i o n s based on a b i r d 91 F i g u r e 29: Percent of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the c o n t r o l stand. 92 p o p u l a t i o n d e n s i t y of a p p r o x i m a t e l y 1.2 b i r d s per h e c t a r e , whereas the model c a l c u l a t e d a maximum of 0.5 b i r d s per h e c t a r e . Second, S t a l l c u p c a l c u l a t e d consumption by assuming t h a t each b i r d a t e d a i l y q u a n t i t i e s of food e q u i v a l e n t t o 25% of t h e i r body w e i g h t . The method f o r d e t e r m i n a t i o n of d a i l y consumption used i n t h e model was d e s c r i b e d i n s e c t i o n 4.5. The c a l c u l a t i o n s made by S t a l l c u p a l s o assumed a l o n g e r f l i g h t p e r i o d . Through t h e s e methods, S t a l l c u p c a l c u l a t e d t h e t o t a l m o r t a l i t y due t o a v i a n p r e d a t i o n d u r i n g the f l i g h t p e r i o d t o be 2730 b e e t l e s . The model c a l c u l a t e d t h i s t o t a l t o be 329 b e e t l e s . These v a l u e s were d i v i d e d by b e e t l e p o p u l a t i o n d e n s i t y t o d e t e r m i n e the p r o p o r t i o n consumed. In S t a l l c u p ' s s t u d y , the e s t i m a t e d emerging b e e t l e p o p u l a t i o n d e n s i t y was 1306 b e e t l e s per h e c t a r e , whereas th e model c a l c u l a t e d a d e n s i t y of 39,464 b e e t l e s per h e c t a r e . The c o m b i n a t i o n of g r e a t e r t o t a l consumption and lower b e e t l e d e n s i t y e x p l a i n s the d i f f e r e n c e i n t h e e s t i m a t e s . D e s p i t e the more d e t a i l e d method f o r c a l c u l a t i n g the consumption of the p r e y , the v a l u e s d e t e r m i n e d by the model f o r the p e r c e n t a g e of the b e e t l e p o p u l a t i o n consumed may be an u n d e r e s t i m a t e s s i m p l y because t h e l a c k of b a s i c d a t a on b i r d d e n s i t i e s l i m i t e d the model t o t h e s i m u l a t i o n of o n l y t h r e e summer b i r d s p e c i e s , t h e h a i r y woodpecker, brown c r e e p e r , and r e d - b r e a s t e d n u t h a t c h . The t o t a l b i r d d e n s i t y may a c t u a l l y be f o u r t o t e n t i m e s g r e a t e r ( S t a l l c u p 1963, 93 T a y l o r 1969, Roppe 1974, Hein 1980), so t o t a l consumption would be i n c r e a s e d , as would th e impact of summer p r e d a t i o n . An i m p o r t a n t consequence of the summer b i r d s ' slow f u n c t i o n a l and n u m e r i c a l r esponses i s e v i d e n t i n F i g u r e 29. The e a r l y e x p a n s i o n of the mountain p i n e b e e t l e p o p u l a t i o n beyond the endemic l e v e l , though slow, was s t i l l s u f f i c i e n t l y r a p i d t o exceed th e b i r d s ' a b i l i t y t o respond. As a r e s u l t , t h e p ercentage of the emerging b e e t l e p o p u l a t i o n consumed by b i r d s i n i t i a l l y d e c r e a s e d . Though t o t a l consumption by summer b i r d s removes o n l y a s m a l l p e r c e n t of t h e b e e t l e p o p u l a t i o n , phenomenon such as the i n i t i a l d e c r e a s e i n p ercentage consumption may a s s i s t the b e e t l e s i n c r o s s i n g the outbreak t h r e s h o l d t h e o r i z e d by Berryman (1978, 1981) and o t h e r s . 5.2.2 SCENARIO 2: EFFICIENT PREDATORS An i n c r e a s e i n the e f f i c i e n c y of the a v i a n p r e d a t o r s had two major impacts on the mountain p i n e b e e t l e p o p u l a t i o n ( F i g u r e 2 0 ) . F i r s t , p o p u l a t i o n growth was reduced, d e l a y i n g the peak p o p u l a t i o n d e n s i t y by one y e a r . Second, the peak d e n s i t y was 5% l e s s than t h a t of the c o n t r o l s t a n d . As a r e s u l t of lower b e e t l e d e n s i t y , the t o t a l s t a n d and i n d i v i d u a l DBH c l a s s t r e e m o r t a l i t i e s were a l s o reduced ( F i g u r e s 21, 22, and 2 3 ) . The t o t a l s t a n d m o r t a l i t y d e c r e a s e d from 17% t o 16%, w h i l e m o r t a l i t y per each DBH 94 c l a s s ranged from 0.1% of t h e t r e e s i n t h e 15-cm c l a s s t o 1.5% of t h e t r e e i n t h e 40-cm c l a s s . G r e a t e r p r e d a t o r e f f i c i e n c y r e s u l t e d i n more r a p i d achievement of peak w i n t e r woodpecker p o p u l a t i o n d e n s i t y ( F i g u r e s 24 and 2 5 ) , and an i n c r e a s e i n t h e w i n t e r consumption t o 37% of t h e l a r v a l p o p u l a t i o n ( F i g u r e 2 6 ) . A d d i t i o n a l l y , peak w i n t e r consumption o c c u r r e d a y e a r e a r l i e r t h a n w i t h 'normal' p r e d a t o r r e s p o n s e s , and a t a lower l a r v a l p o p u l a t i o n d e n s i t y of 45,813 l a r v a e per h e c t a r e . Changes i n b i r d d e n s i t y and p r e d a t i o n d u r i n g the b e e t l e s ' f l i g h t p e r i o d e x h i b i t e d a p a t t e r n s i m i l a r t o t h a t of the w i n t e r b i r d s ( F i g u r e s 27-29). In t h i s s i m u l a t i o n a maximum consumption of 1% of the emerging a d u l t b e e t l e p o p u l a t i o n was a c h i e v e d a t a b e e t l e d e n s i t y of 23,508 b e e t l e s per h e c t a r e , compared t o 38,464 when p r e d a t o r r e s p o n s e s were l e s s e f f i c i e n t . I t was a l s o e v i d e n t from F i g u r e 29 t h a t the i n c r e a s e d p r e d a t o r e f f i c i e n c y d i d not p r e v e n t the b e e t l e p o p u l a t i o n from growing a t a r a t e beyond the summer b i r d s ' a b i l i t y t o respond. 5.2.3 SCENARIO 3: TWICE NORMAL PREDATOR DENSITY In t h i s s c e n a r i o , the mountain p i n e b e e t l e p o p u l a t i o n never reached an e p i demic l e v e l ( F i g u r e 2 0 ) . I n s t e a d , i t i n c r e a s e d t o 5,799 b e e t l e s per h e c t a r e , or r o u g h l y 7.7 times 95 g r e a t e r than an endemic p o p u l a t i o n d e n s i t y , by y e a r seven, t h e r e a f t e r d e c l i n i n g g r a d u a l l y . Even a t year s i x t e e n the p o p u l a t i o n was s t i l l a t a d e n s i t y of 5,576 b e e t l e s per h e c t a r e (7.4 t i m e s g r e a t e r than an endemic p o p u l a t i o n d e n s i t y ) . Due t o the low b e e t l e d e n s i t y , the t o t a l s t a n d and i n d i v i d u a l DBH c l a s s t r e e m o r t a l i t i e s were v e r y low and, a f t e r t h e i n i t i a l i n s e c t p o p u l a t i o n i n c r e a s e , remained f a i r l y c o n s t a n t ( F i g u r e s 21 and 2 2 ) . T o t a l s t a n d t r e e m o r t a l i t y a f t e r s i x t e e n y e a r s was o n l y 4%. F i n a l m o r t a l i t y per DBH c l a s s ( F i g u r e 23) ranged from 0.6% of the t r e e s i n the 15-cm c l a s s t o 20% of the t r e e s i n the 40 c m - c l a s s . The reduced m o r t a l i t y r a t e of t r e e s i n t h e l a r g e r DBH c l a s s e s was p a r t i c u l a r l y i m p o r t a n t i n t h a t the presence of t h e s e l a r g e r t r e e s e n a b l e d the b e e t l e p o p u l a t i o n t o m a i n t a i n i t s e l f i n the f a c e of heavy a v i a n p r e d a t i o n . W i n t e r woodpecker d e n s i t y reached a maximum of 37.5 b i r d s per h e c t a r e a t year f o u r of the i n f e s t a t i o n when l a r v a e were p r e s e n t a t a d e n s i t y of 48,976 l a r v a e per h e c t a r e ( F i g u r e s 24 and 2 5 ) . W i n t e r consumption by woodpeckers peaked a t 57% of the l a r v a l p o p u l a t i o n i n y e a r f i v e ( F i g u r e 2 6 ) , t h r e e y e a r s p r i o r t o the peak l a r v a l d e n s i t y . Consumption remained a t a p p r o x i m a t e l y t h i s l e v e l d u r i n g the remainder of t h e i n f e s t a t i o n , i n response t o n e a r l y c o n s t a n t p r e d a t o r and prey p o p u l a t i o n d e n s i t i e s . 96 The summer b i r d d e n s i t i e s and consumption f o l l o w e d much the same p a t t e r n as t h a t e x h i b i t e d d u r i n g the winter ( F i g u r e s 27, 28, and 29). However, peak consumption of 1% occ u r r e d i n year three of the i n f e s t a t i o n . From that p o i n t on, consumption remained approximately c o n s t a n t . As t o t a l b i r d p r e d a t i o n reached i t s maximum l e v e l i n year f i v e , while the pine b e e t l e p o p u l a t i o n c o n t i n u e d to i n c r e a s e u n t i l year seven, d e c l i n i n g t h e r e a f t e r , i t i s reasonable to assume that other m o r t a l i t y f a c t o r s i n combination with avian p r e d a t i o n were r e s p o n s i b l e f o r keeping the i n s e c t p o p u l a t i o n i n check. The r e a l v alue of the i n i t i a l l y h i g h b i r d d e n s i t i e s may have been i n s u f f i c i e n t l y slowing b e e t l e p o p u l a t i o n growth to permit the combination'of a l l f a c t o r s to gain c o n t r o l over the i n s e c t p o p u l a t i o n , and re v e r s e i t s growth. When c o n s i d e r i n g the impacts of avian p r e d a t i o n i n t h i s s c e n a r i o one should r e c a l l t h a t only b i r d d e n s i t i e s were doubled. The p r o p o r t i o n of the l a r v a e or b e e t l e s i n the b i r d s ' d i e t s was the same as i n the f i r s t ( c o n t r o l ) s c e n a r i o . A l s o , b i r d d e n s i t i e s were doubled at a l l b e e t l e p o p u l a t i o n d e n s i t i e s , endemic as w e l l as epidemic. Yet even with the d o u b l i n g of pr e d a t o r d e n s i t i e s i t was the ' e f f i c i e n t ' p r e d a t o r s t h a t e x h i b i t e d a f a s t e r t o t a l response to changes i n i n s e c t d e n s i t y . In summary, the mountain pine b e e t l e p o p u l a t i o n reached i t s g r e a t e s t peak d e n s i t y i n S c e n a r i o 1 when the b i r d s 97 e x h i b i t e d normal f u n c t i o n a l and n u m e r i c a l r e s p o n s e s . A p p r o x i m a t e l y 17% of the t r e e s i n the s t a n d were k i l l e d by the b e e t l e s . Consumption of t h e l a r v a e d u r i n g t h e w i n t e r a c c o u n t e d f o r 26% of t h e p o p u l a t i o n , which compares f a v o r a b l y w i t h L e s t e r ' s (1980) e s t i m a t e of 30%. Summer b i r d s consumed an e s t i m a t e d 0.9% of the emerging b e e t l e p o p u l a t i o n . T h i s v a l u e i s much lo w e r than t h a t of S t a l l c u p (1963) due t o the d i f f e r e n c e s i n b e e t l e and b i r d d e n s i t i e s , and the methods used t o c a l c u l a t e consumption. The v a l u e c a l c u l a t e d by the model may be an u n d e r e s t i m a t e due t o the low number of b i r d s p e c i e s s i m u l a t e d . I n c r e a s e s i n p r e d a t o r e f f i c i e n c y ( S c e n a r i o 2) r e s u l t e d i n g r e a t e r w i n t e r and summer consumption, and e a r l i e r achievement of maximum consumption. T h i s , i n t u r n , h e l p e d d e l a y the growth of the b e e t l e p o p u l a t i o n and reduce peak b e e t l e d e n s i t y . However, t r e e m o r t a l i t y was o n l y s l i g h t l y r e d u c e d , and remained a t about 16%. D o u b l i n g t h e p r e d a t o r d e n s i t i e s ( S c e n a r i o 3 ) , p r e v e n t e d an ou t b r e a k of major p r o p o r t i o n s , l e a d i n g i n s t e a d t o a l o n g - t e r m l o w - l e v e l i n f e s t a t i o n . The r e s u l t i n g t o t a l t r e e m o r t a l i t y and i n d i v i d u a l DBH c l a s s m o r t a l i t i e s were g r e a t l y reduced. H i g h woodpecker w i n t e r d e n s i t i e s , combined w i t h r e l a t i v e l y low l a r v a l d e n s i t i e s , r e s u l t e d i n a peak consumption of 57% of th e l a r v a l p o p u l a t i o n . Peak summer p r e d a t i o n was a l s o i n c r e a s e d , and a t t a i n e d a maximum v a l u e of 1% of the 98 emerging b e e t l e p o p u l a t i o n . In none of t h r e e s c e n a r i o s , however, d i d the b e e t l e p o p u l a t i o n f a i l t o i n c r e a s e beyond i t s endemic l e v e l . The f i r s t t h r e e s c e n a r i o s i l l u s t r a t e t h e d i f f e r e n c e s i n i m p a c t s between i n c r e a s e d p r e d a t o r e f f i c i e n c y and i n c r e a s e d b i r d d e n s i t i e s , p a r t i c u l a r l y when i n s e c t s are a t endemic l e v e l s . The more e f f i c i e n t p r e d a t o r s h e l p e d d e l a y the i n f e s t a t i o n and reduce peak d e n s i t y , but o n l y when b i r d d e n s i t i e s were g r e a t e r a t a l l i n s e c t d e n s i t i e s was a major i n f e s t a t i o n p r e v e n t e d . However, the b i r d d e n s i t i e s s i m u l a t e d i n S c e n a r i o 3 a r e p r o b a b l y h i g h e r than th o s e which can be r e a l i s t i c a l l y m a i n t a i n e d ( T a y l o r 1969, Roppe 1974, A u s t i n and P e r r y 1979). R e s e a r c h e r s have i n d i c a t e d t h a t the d e n s i t i e s of some i m p o r t a n t mountain p i n e b e e t l e consuming b i r d s p e c i e s may a c t u a l l y be i n c r e a s e d by 25% t h r o u g h c a r e f u l management p r a c t i c e s ( A u s t i n and P e r r y 1979, D i c k s o n et al . 1983, S c o t t and Oldenmyer 1983, Marcot 1983). T h e r e f o r e , a s c e n a r i o i n which maximum summer b i r d d e n s i t i e s were 1.25 t i m e s g r e a t e r than 'normal' was s i m u l a t e d . The r e s u l t s of t h i s s c e n a r i o were v e r y s i m i l a r t o t h o s e of the e f f i c i e n t p r e d a t o r s c e n a r i o (#2). Through v a r i a t i o n s i n s i m u l a t i o n parameters i t was found t h a t i n c r e a s e s i n b i r d d e n s i t i e s of between 150% and 175% were r e q u i r e d b e f o r e any major imp a c t s on b e e t l e p o p u l a t i o n d e n s i t y were e v i d e n t . However, r e d u c i n g b i r d d e n s i t i e s t o 10% of 'normal' r e s u l t e d 99 i n b e e t l e p o p u l a t i o n growth t o a maximum of 84,911 b e e t l e s per h e c t a r e , a p p r o x i m a t e l y 29% g r e a t e r than t h e peak d e n s i t y i n t he f i r s t s c e n a r i o . As a r e s u l t more than 90 a d d i t i o n a l t r e e s per h e c t a r e were k i l l e d ; an i n c r e a s e i n t o t a l s t and t r e e m o r t a l i t y of more than 19%. Consumption of the w i n t e r l a r v a l p o p u l a t i o n by woodpeckers reached o n l y 3%, w h i l e a d u l t b e e t l e consumption i n t h e summer never i n c r e a s e d beyond 0.1%. The importance of b e e t l e p r e d a t i o n by f o r e s t b i r d s was q u i t e e v i d e n t i n t h i s s i m u l a t i o n . Another s i g n i f i c a n t d i f f e r e n c e between S c e n a r i o s 2 and 3 i s t h a t , a l t h o u g h i t i s d i f f i c u l t , i f not i m p o s s i b l e , t o manage s t a n d s t o a c c e l e r a t e t h e b i r d f u n c t i o n a l r e s p o n s e s , management p r a c t i c e s can i n c r e a s e b a s e l i n e b i r d d e n s i t i e s . S t u d i e s l i k e t h o s e of D i c k s o n et at. (1983), Marcot (1983), and S c o t t and Oldenmyer (1983) i n d i c a t e d t h a t even the d r a s t i c e f f e c t s of c l e a r c u t t i n g on p o p u l a t i o n d e n s i t i e s of some b i r d s p e c i e s can be reduced t h r o u g h c a r e f u l p l a n n i n g and e x e c u t i o n . 5.3 THE SENESCENT STAND 5.3.1 SCENARIO 4: NORMAL PREDATOR RESPONSES The mountain p i n e b e e t l e p o p u l a t i o n a c h i e v e d a peak autumn d e n s i t y of 438,420 b e e t l e s per h e c t a r e a t year seven of a t h i r t e e n year i n f e s t a t i o n ( F i g u r e 3 0 ) . T h i s was the 100 F i g u r e 30: Y e a r l y mountain pi n e b e e t l e autumn d e n s i t y i n the senescent stand. 101 g r e a t e s t b e e t l e p o p u l a t i o n d e n s i t y a c h i e v e d i n any of the n i n e s c e n a r i o s . The r a p i d e x p a n s i o n t o a v e r y h i g h d e n s i t y was due m o s t l y t o the l a r g e number of t r e e s i n t h e 30, 35, and 40-cm DBH c l a s s e s where b e e t l e p r o d u c t i v i t y i s g r e a t e s t . T o t a l s t a n d and i n d i v i d u a l DBH c l a s s t r e e m o r t a l i t i e s were a l s o g r e a t e s t i n t h i s s c e n a r i o ; a p p r o x i m a t e l y double t h o s e found i n S c e n a r i o 1. J u s t over 1198 t r e e s per h e c t a r e (64% of the o r i g i n a l s t a n d ) , were k i l l e d by t h e b e e t l e ( F i g u r e 3 1 ) . F i n a l m o r t a l i t y i n t h e 15-cm DBH c l a s s r e a c h e d 5%, w h i l e 100% of the t r e e s i n t h e l a r g e s t c l a s s ( F i g u r e s 32 and 33) were k i l l e d by y e a r n i n e . W i n t e r woodpeckers f i r s t r eached t h e i r maximum d e n s i t y of 25 b i r d s per h e c t a r e i n y e a r f o u r , c o r r e s p o n d i n g t o a d e n s i t y of 197,882 l a r v a e per h e c t a r e ( F i g u r e s 34 and 3 5 ) . The w i n t e r consumption by woodpeckers peaked a t 24% of the w i n t e r l a r v a l p o p u l a t i o n ( F i g u r e 36) i n year t h r e e , f i v e y e a r s p r i o r t o the maximum l a r v a l d e n s i t y . The peak consumption was s l i g h t l y l e s s than t h a t r e c o r d e d i n S c e n a r i o 1, and a l s o o c c u r r e d a year e a r l i e r . T h i s was p r o b a b l y due t o the more r a p i d b e e t l e p o p u l a t i o n growth. A s i m i l a r p a t t e r n was e v i d e n t f o r summer b i r d d e n s i t i e s and a d u l t b e e t l e consumption ( F i g u r e s 37, 38, and 3 9 ) . The maximum consumption, 0.7% of the emerging a d u l t p o p u l a t i o n , was o n l y 0.3% l e s s than i t was i n S c e n a r i o 1, and as w i t h w i n t e r consumption, the peak o c c u r r e d e a r l i e r . 1 0 2 F i g u r e 31: Y e a r l y t o t a l stand d e n s i t y f o r the senescent stand. 103 F i g u r e 32: I n i t i a l and f i n a l s t a n d s t r u c t u r e s f o r the s e n e s c e n t s t a n d . 104 - i 1 1 1 1 1 15 20 25 30 35 40 DBH CLASS (cm) F i g u r e 33: T o t a l t r e e m o r a t i l t y f o r each diameter c l a s s i n the senescent stand. 105 60 1 1 1 1 1 1 i i I 0 2 4 6 8 10 12 14 16 YEAR OF INFESTATION F i g u r e 34: Y e a r l y w i n t e r b i r d d e n s i t y i n t h e s e n e s c e n t s t a n d . 106 - — — • • ]—•—1 j i i i i i i ii\ i i i r i i T T 0 5 0 1 0 0 1 0 0 0 1 0 0 0 0 LARVAE (Thousands ha 1) F i g u r e 35: W i n t e r b i r d d e n s i t y i n t h e s e n e s c e n t s t a n d r e l a t i v e t o l a r v a l d e n s i t y . 107 60 50 H O W 40 XV) z 8 30 g Q. o Q_ 20 H 10 A Normal 0 Eff icient • 2 X Normal Density / •. \ \ \ \ \ 10 100 ,1000 LARVAE (Thousands ha"1) 10000 F i g u r e 36: Percent of winter l a r v a l p o p u l a t i o n consumed by woodpeckers i n the senescent stand. 108 120 F i g u r e 37: T o t a l summer b i r d d e n s i t y i n the senescent stand. 1 0 9 120 F i g u r e 38: T o t a l summer b i r d d e n s i t y i n the senescent-s t a n d r e l a t i v e t o a d u l t d e n s i t y . 1 1 0 F i g u r e 3 9 : Percent of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the senescent s t a n d . 111 5.3.2 SCENARIO 5: EFFICIENT PREDATORS As i n S c e n a r i o 2, an i n c r e a s e i n p r e d a t o r e f f i c i e n c y i n c r e a s e d w i n t e r and summer p r e d a t i o n , d e p r e s s e d b e e t l e p o p u l a t i o n growth, and a i d e d i n r e d u c i n g the peak b e e t l e p o p u l a t i o n d e n s i t y ( F i g u r e 3 0 ) . However, the achievement of th e peak d e n s i t y was not d e l a y e d as i t was i n S c e n a r i o 2. Due t o t h e l a r g e food s u p p l y , b e e t l e p o p u l a t i o n growth i n t h i s s t a n d was too r a p i d f o r the b i r d s t o sup p r e s s f o r l o n g , d e s p i t e the e a r l i e r f u n c t i o n a l and n u m e r i c a l r esponses of the b i r d s . A l t h o u g h maximum mountain ' p i n e b e e t l e d e n s i t y was reduced 16% from t h a t of the p r e v i o u s s c e n a r i o , the t o t a l t r e e m o r t a l i t y f o r S c e n a r i o 5 ( F i g u r e 31) was a p p r o x i m a t e l y e q u a l t o the t o t a l t r e e m o r t a l i t y of s c e n a r i o 4. T h i s was most l i k e l y due t o the b e e t l e p o p u l a t i o n i n S c e n a r i o 5 r e m a i n i n g a t g r e a t e r d e n s i t i e s i n y e a r s t e n t o t h i r t e e n of the i n f e s t a t i o n . D u r i n g those f i n a l f o u r y e a r s the b e e t l e s k i l l e d a p p r o x i m a t e l y 100 more t r e e s per h e c t a r e , r e s u l t i n g i n t he n e a r - e q u a l t o t a l m o r t a l i t i e s . Compared t o S c e n a r i o 4, the i n d i v i d u a l DBH c l a s s m o r t a l i t i e s i n S c e n a r i o 5 ( F i g u r e s 32 and 33) were reduced i n a l l but the 40-cm c l a s s where, once a g a i n , a l l t r e e s were k i l l e d by year n i n e . The maximum w i n t e r b i r d d e n s i t y of 25 b i r d s per h e c t a r e o c c u r r e d a t a d e n s i t y of 32,835 l a r v a e per h e c t a r e i n year 2 ( F i g u r e s 34 and 35). W i n t e r consumption by woodpeckers, 34% 1 12 of t h e l a r v a l p o p u l a t i o n , was s l i g h t l y l e s s than t h a t r e c o r d e d i n S c e n a r i o 2, and a l s o o c c u r r e d two y e a r s e a r l i e r ( F i g u r e 3 6 ) . Both the r e d u c t i o n i n and e a r l i e r o c c u r r e n c e of peak w i n t e r consumption was due, f o r the most p a r t , t o the r a p i d e x p a n s i o n of the b e e t l e p o p u l a t i o n . Summer b i r d d e n s i t i e s and p r e d a t i o n f o l l o w e d a s i m i l a r p a t t e r n ( F i g u r e s 37 and 3B), w i t h a maximum consumption of 1% of t h e emerging p o p u l a t i o n c o r r e s p o n d i n g t o a b e e t l e d e n s i t y of r o u g h l y 7,226 b e e t l e per h e c t a r e ( F i g u r e 3 9 ) . 5.3.3 SCENARIO 6; TWICE NORMAL PREDATOR DENSITY The r e s u l t s of S c e n a r i o 6 were v e r y d i f f e r e n t than t h o s e of S c e n a r i o 3. The e x t e n s i v e f o o d s o u r c e i n the se n e s c e n t s t a n d , r e p r e s e n t e d by the t r e e s i n t h e l a r g e DBH c l a s s e s , p e r m i t t e d the b e e t l e p o p u l a t i o n t o expand r a p i d l y . Though growth was d e p r e s s e d and the peak d e n s i t y was d e l a y e d by a y e a r , the d o u b l i n g of p r e d a t o r d e n s i t i e s c o u l d not p r e v e n t t h e epidemic from o c c u r r i n g ( F i g u r e 3 0 ) . S u r p r i s i n g l y , the maximum autumn d e n s i t y i n t h i s s c e n a r i o (375,065 b e e t l e s per h e c t a r e ) was a c t u a l l y 2% g r e a t e r than t h a t of S c e n a r i o 5. As a r e s u l t 111 more t r e e s per h e c t a r e were k i l l e d ( F i g u r e 3 1 ) , i n c r e a s i n g t o t a l s t a n d m o r t a l i t y t o 70%. Tree m o r t a l i t y i n the i n d i v i d u a l DBH c l a s s e s ranged from 7% of t h e t r e e s i n the 15-cm c l a s s t o 98% of the t r e e s i n t he 35-cm c l a s s ( F i g u r e s 32 and 3 3 ) . Once a g a i n , a l l 113 t r e e s i n the 40-cm c l a s s were k i l l e d , though t h i s d i d not occur u n t i l year ten of the i n f e s t a t i o n . Woodpeckers f i r s t reached t h e i r maximum d e n s i t y of 50 i n d i v i d u a l s per hectare i n year three when l a r v a e were present at a d e n s i t y of 76,136 l a r v a e per hectare ( F i g u r e s 34 and 35). The peak winter consumption by woodpeckers accounted f o r 58% of the l a r v a l p o p u l a t i o n i n year three of the i n f e s t a t i o n . T h i s value was s l i g h t l y lower than that of S c e n a r i o 3, however, i t o c c u r r e d two years e a r l i e r . Again, the summer b i r d d e n s i t i e s and p r e d a t i o n e x h i b i t e d a t y p i c a l p a t t e r n ( F i g u r e s 37, 38, and 39). The b i r d s consumed a maximum of 2% of the emerging b e e t l e p o p u l a t i o n . T h i s value i s the g r e a t e s t consumption by summer b i r d s i n any of the nine s c e n a r i o s . In summary, the great number of t r e e s i n the l a r g e DBH c l a s s e s p r o v i d e d the b e e t l e s with an abundant food source. As a r e s u l t , the b e e t l e p o p u l a t i o n r a p i d l y a t t a i n e d a h i g h d e n s i t y . T o t a l stand m o r t a l i t y i n Scenario 4 was more than three times g r e a t e r than i n the c o n t r o l s c e n a r i o (#1). Peak winter and summer p r e d a t i o n by b i r d s was reduced, and a l s o o c c u r r e d e a r l i e r i n response to the r a p i d b e e t l e growth. I n c r e a s i n g the e f f i c i e n c y of the b i r d s had l i t t l e impact on the b e e t l e p o p u l a t i o n . Peak d e n s i t y was s l i g h t l y reduced but i t was not d e l a y e d as i n Scenario 2. T o t a l stand m o r t a l i t y was p r a c t i c a l l y unchanged from Sc e n a r i o 4. 1 14 D o u b l i n g the b i r d d e n s i t i e s ( S c e n a r i o 6) d i d not p r e v e n t t h e o u t b r e a k , as i n S c e n a r i o 3. B e e t l e p o p u l a t i o n growth was s i m p l y too r a p i d f o r the b i r d s t o have such an e f f e c t . The t o t a l s t a n d m o r t a l i t y of 70% was the h i g h e s t r e c o r d e d f o r any of the n i n e s c e n a r i o s . T h i s was due t o the b e e t l e p o p u l a t i o n r e m a i n i n g a t a h i g h d e n s i t y f o r a l o n g e r p e r i o d of t i m e , and k i l l i n g more t r e e s i n the s m a l l e r d i a m e t e r c l a s s e s . W i n t e r p r e d a t i o n by b i r d s a c c o u n t e d f o r 53% of t h e l a r v a l p o p u l a t i o n , w h i l e the summer consumption ( 2 % of t h e emerging b e e t l e p o p u l a t i o n ) was the h i g h e s t r e c o r d e d i n any of the n i n e s c e n a r i o s . T h i s second set of s c e n a r i o s i l l u s t r a t e s t he a b i l i t y of the mountain p i n e b e e t l e t o ta k e advantage of a l a r g e food s o u r c e , as i s c u r r e n t l y e v i d e n t i n t h e C h i l c o t i n P l a t e a u a r e a i n B.C. In c a s e s such as t h i s , b i r d s may reduce the peak b e e t l e p o p u l a t i o n d e n s i t y s l i g h t l y , but i t i s v e r y u n l i k e l y t h a t any n a t u r a l or enhanced b i r d p o p u l a t i o n would be a b l e t o p r e v e n t the o u t b r e a k . 5.4 THE THINNED STAND The r o l e of a v i a n p r e d a t o r s i n the f o l l o w i n g s c e n a r i o s was g r e a t l y reduced f o r t h r e e r e a s o n s . F i r s t , the major r e d u c t i o n i n the number of t r e e s i n the f o u r l a r g e s t DBH c l a s s e s g r e a t l y reduced t o t a l b e e t l e p o p u l a t i o n p r o d u c t i v i t y . Second, a l l of the b i r d s p e c i e s used i n the 115 s i m u l a t i o n s a r e n e g a t i v e l y a f f e c t e d by major t h i n n i n g o p e r a t i o n s . T h e r e f o r e , t h e i r i n i t i a l and peak d e n s i t i e s (Appendix 5) were much r e d u c e d . F i n a l l y , t h e mountain p i n e b e e t l e p o p u l a t i o n never i n c r e a s e d beyond the o r i g i n a l endemic d e n s i t y , so b i r d d e n s i t i e s and the p e r c e n t a g e of l a r v a e or b e e t l e s i n t h e i r d i e t s d i d not i n c r e a s e beyond the o r i g i n a l l e v e l s . In o t h e r words, the n u m e r i c a l and f u n c t i o n a l r e sponses d i d not o c c u r . Due t o the absence of t h e s e r e s p o n s e s , the normal and e f f i c i e n t p r e d a t o r s c e n a r i o s a r e the same, and a r e d i s c u s s e d as one. 5.4.1 SCENARIOS 7 AND 8: NORMAL AND EFFICIENT PREDATORS In t h e s e two s c e n a r i o s the mountain p i n e b e e t l e p o p u l a t i o n i m m e d i a t e l y d e c l i n e d from i t s endemic l e v e l . By y e a r t e n t h e r e were o n l y 54 b e e t l e s per h e c t a r e ( F i g u r e 4 0 ) , a d e c r e a s e of 93%. In t h e f i r s t year of the s c e n a r i o s , o n l y 743 b e e t l e s s u r v i v e d t o emerge i n the summer, and the • f l i g h t - p e r i o d m o r t a l i t y had not y e t been a p p l i e d . The t o t a l s t a n d t r e e m o r t a l i t y was o n l y 1.0% a t the end of ten y e a r s ( F i g u r e 4 1 ) . Though l a r g e d i a m e t e r t r e e s r e p r e s e n t e d o n l y a minor p r o p o r t i o n of the s t a n d ( F i g u r e 4 2 ) , the b e e t l e s were s t i l l a t t r a c t e d t o them. I n d i v i d u a l DBH c l a s s m o r t a l i t y ranged from 15% of t h e t r e e s i n the 40-cm c l a s s t o o n l y 1% i n t h e 15-cm c l a s s ( F i g u r e 4 3 ) . 1 16 F i g u r e 40: Y e a r l y mountain b e e t l e autumn d e n s i t y i n the t h i n n e d stand. 1 17 F i g u r e 41: Y e a r l y t o t a l s t a n d d e n s i t y f o r the the t h i n n e d stand. 118 DIAMETER CLASS F i g u r e 42: I n i t i a l and f i n a l stand s t r u c t u r e s f o r the the thinned stand. 1 1 9 120 Changes i n t h e p e r c e n t a g e of the b e e t l e p o p u l a t i o n consumed by w i n t e r and summer a v i a n p r e d a t o r s were due m a i n l y t o t h e changes i n the d e n s i t y of the b e e t l e p o p u l a t i o n i t s e l f . F o r the most p a r t , t h e a c t u a l number of l a r v a e or a d u l t b e e t l e s consumed by t h e b i r d s remained c o n s t a n t . However, the p r o p o r t i o n consumed i n c r e a s e d s i m p l y because the i n s e c t p o p u l a t i o n d e c r e a s e d . When the l a r v a l o r a d u l t b e e t l e d e n s i t i e s became t o o low, the p r o p o r t i o n of the i n s e c t s i n t h e b i r d s ' d i e t s dropped t o z e r o , and t h e c o r r e s p o n d i n g p r o p o r t i o n of the i n s e c t p o p u l a t i o n consumed f e l l t o z e r o as w e l l . The maximum consumption of the w i n t e r l a r v a l p o p u l a t i o n was 0.3% ( F i g u r e 4 4 ) , w h i l e maximum summer consumption was 0.1% of t h e . emerging a d u l t p o p u l a t i o n ( F i g u r e 4 5 ) . 5.4.2 SCENARIO 9: TWICE NORMAL PREDATOR DENSITY The mountain p i n e b e e t l e p o p u l a t i o n d e c r e a s e d more r a p i d l y i n t h i s s c e n a r i o than i n the p r e v i o u s two s c e n a r i o s ( F i g u r e 4 0 ) . By the end of the t e n year s i m u l a t i o n , t h e r e were o n l y 53 b e e t l e s per h e c t a r e , 2% l e s s than i n S c e n a r i o s 7 and 8. T h i s p o p u l a t i o n r e d u c t i o n d i d not have a major impact on t o t a l s t a n d t r e e m o r t a l i t y . A f t e r t en y e a r s i t was v i r t u a l l y e q u a l t o t h a t of the p r e v i o u s two s c e n a r i o s , h a v i n g been reduced by o n l y 0.004% ( F i g u r e 4 1 ) . The 121 F i g u r e 44: Percent of winter l a r v a l p o p u l a t i o n consumed by woodpeckers i n the thinned stand. 1 2 2 F i g u r e 45: Percent of emerging a d u l t p o p u l a t i o n consumed by summer b i r d s i n the thinned stand. 123 c o r r e s p o n d i n g i n d i v i d u a l DBH c l a s s m o r t a l i t i e s ( F i g u r e 42) were reduced t o an even l e s s e r degree. Consumption of the l a r v a l p o p u l a t i o n by woodpeckers was about double t h a t of S c e n a r i o s 7 and 8. P r a c t i c a l l y a l l changes i n t h e p r o p o r t i o n of t h e p o p u l a t i o n consumed were due t o changes i n the l a r v a l p o p u l a t i o n d e n s i t y . Maximum w i n t e r consumption by b i r d s r e p r e s e n t e d 0.6% of the l a r v a l p o p u l a t i o n ( F i g u r e 4 4 ) . Summer a v i a n p r e d a t i o n e x h i b i t e d a n e a r l y i d e n t i c a l p a t t e r n ( F i g u r e 4 5 ) . P r e d a t i o n i n t h i s s c e n a r i o , however, was 2.3 t i m e s t h a t of S c e n a r i o s 7 and 8, due t o t h e c u m u l a t i v e e f f e c t of s i m u l a t i n g t h r e e s p e c i e s i n s t e a d of one. T o t a l summer consumption was a maximum of 0.2% of the emerging a d u l t b e e t l e p o p u l a t i o n . To summarize, i n S c e n a r i o s 7 t h r o u g h 9 the s m a l l s u p p l y of good q u a l i t y food had a f a r more s i g n i f i c a n t impact on b e e t l e dynamics than d i d a v i a n p r e d a t i o n . In a l l t h r e e s c e n a r i o s t h e b e e t l e p o p u l a t i o n i m m e d i a t e l y d e c l i n e d from i t s o r i g i n a l endemic l e v e l . T o t a l s t a n d and i n d i v i d u a l DBH-class t r e e m o r t a l i t i e s were a l l e x p e c t e d l y low. The maximum t o t a l s t a n d m o r t a l i t y was 1.0%. Maximum i n d i v i d u a l DBH c l a s s m o r t a l i t y was 15% of the t r e e s i n the 40-cm c l a s s of S c e n a r i o s 7 and 8. As a r e s u l t of t h e immediate d e c l i n e i n b e e t l e p o p u l a t i o n d e n s i t y , a v i a n f u n c t i o n a l and n u m e r i c a l r e s p o n s e s 124 d i d not o c c u r . Changes i n t h e p r o p o r t i o n of t h e i n s e c t p o p u l a t i o n consumed by b i r d s were due m o s t l y t o t h e d e c r e a s e s i n i n s e c t p o p u l a t i o n d e n s i t y . At e x t r e m e l y low b e e t l e d e n s i t i e s the consumption dropped t o z e r o when t h e p r o p o r t i o n of l a r v a e or b e e t l e s i n t h e b i r d s ' d i e t s became z e r o . Changes i n p r e d a t o r e f f i c i e n c y had no e f f e c t on consumption because the f u n c t i o n a l and n u m e r i c a l r e s p o n s e s d i d not o c c u r . D o u b l i n g the b i r d d e n s i t i e s e s s e n t i a l l y d o u b l e d the p r o p o r t i o n of the b e e t l e p o p u l a t i o n consumed as a r e s u l t of t h e dynamics d e s c r i b e d above. Maximum w i n t e r consumption was 0.6% of the l a r v a l p o p u l a t i o n , w h i l e maximum summer consumption was 0.2% of t h e emerging a d u l t b e e t l e p o p u l a t i o n . The t h i r d s e t of s c e n a r i o s i n d i c a t e d t h a t p r e v e n t i v e management can have a major impact on b e e t l e dynamics. The b e e t l e p o p u l a t i o n d e c l i n e d due t o an in a d e q u a t e food s o u r c e . B i r d d e n s i t i e s were reduced, and f u n c t i o n a l and n u m e r i c a l r e s p o n s e s d i d not o c c u r . However, the p r o p o r t i o n of the i n s e c t p o p u l a t i o n consumed by b i r d s s t i l l i n c r e a s e d . The p a t t e r n of t o t a l consumption was the same as t h a t d e s c r i b e d by H o l l i n g (1959), but as the r e s u l t of a t o t a l l y d i f f e r e n t p r o c e s s . These f i n a l t h r e e s c e n a r i o s i l l u s t r a t e d a management p r a c t i c e which reduces s t a n d s u s c e p t i b i l i t y t o the mountain p i n e b e e t l e , w h i l e s i m u l t a n e o u s l y i n c r e a s i n g t h e a v i a n impact on t h e i n s e c t . 125 5.5 SENSITIVITY ANALYSIS AND MODEL LIMITATIONS Each y e a r l y i t e r a t i o n of the mountain p i n e b e e t l e s i m u l a t i o n model r e q u i r e d the c a l c u l a t i o n of more than 70 parameters f o r each of s i x t r e e DBH c l a s s e s . The v a l u e s f o r many of t h e s e p a r a m e t e r s were d e r i v e d from p u b l i c a t i o n s t h a t r e p r e s e n t e d summaries of many o t h e r s t u d i e s . In o t h e r c a s e s , th e s i m u l a t i o n v a l u e s were the b e s t e s t i m a t e s of f a c t o r s t h a t have proven e x t r e m e l y d i f f i c u l t t o a c c u r a t e l y measure i n the f i e l d . A r b i t r a r i l y chosen v a l u e s based on r e l a t e d s t u d i e s were used i n a few c a s e s when no o t h e r i n f o r m a t i o n was a v a i l a b l e . Because of t h e s e drawbacks and gaps i n d a t a , i t p roved i m p o s s i b l e t o p l a c e m e a n i n g f u l c o n f i d e n c e i n t e r v a l s on the model r e s u l t s . In an attempt t o examine model a c c u r a c y and s e n s i t i v i t y seven v a r i a b l e s were a l t e r e d by +20%, and t h e impact on s i m u l a t i o n r e s u l t s r e c o r d e d . The magnitude of the impact was a s s e s s e d by m o n i t o r i n g the amount of change i n two o u t p u t v a r i a b l e s ; mountain p i n e b e e t l e autumn d e n s i t y , and t o t a l t r e e m o r t a l i t y i n an i n t e r m e d i a t e (25 cm) DBH c l a s s . A l t e r a t i o n of t h r e e v a r i a b l e s , the p r o p o r t i o n of the a d u l t b e e t l e . p o p u l a t i o n d i s p e r s i n g out of the s t a n d , and the c a l o r i c v a l u e of one a d u l t b e e t l e and one l a r v a , changed the b e e t l e autumn d e n s i t y l e s s than 10%. T h i s a l t e r a t i o n i n b e e t l e d e n s i t y r e s u l t e d i n an i n c r e a s e / d e c r e a s e i n t r e e m o r t a l i t y of s l i g h t l y l e s s than 1%. The p r o p o r t i o n of 126 b e e t l e s l e a v i n g t h e s t a n d was one of the v a r i a b l e s about which p r a c t i c a l l y no i n f o r m a t i o n i s a v a i l a b l e , though f i e l d i n v e s t i g a t i o n s a r e i n p r o g r e s s . The c a l o r i c v a l u e s of d i f f e r e n t b e e t l e l i f e s t a g e s were not d i f f i c u l t t o d e t e r m i n e , and c u r r e n t l y do not p r e s e n t a problem. Two a d d i t i o n a l v a r i a b l e s , t h e p r o p o r t i o n of t h e a d u l t b e e t l e p o p u l a t i o n k i l l e d d u r i n g t h e f l i g h t / a t t a c k p e r i o d by causes o t h e r than a v i a n p r e d a t o r s , and t o t a l b e e t l e a t t a c k d e n s i t y , a l t e r e d b e e t l e d e n s i t y by 9% t o 11% and 14% t o 17%, r e s p e c t i v e l y . T h i s r e s u l t e d i n changes i n t r e e m o r t a l i t y s l i g h t l y more than 1%. L i k e the p r o p o r t i o n of t h e b e e t l e p o p u l a t i o n d i s p e r s i n g from the s t a n d , t h e p r o p o r t i o n k i l l e d d u r i n g t h e f l i g h t p e r i o d by causes o t h e r t h a n b i r d s i s not w e l l known because i t i s so d i f f i c u l t t o measure. A t t a c k d e n s i t y i s s i m p l y beyond g e n e r a l i z a t i o n because a p a r t i c u l a r d e n s i t y w i l l have a d i f f e r e n t e f f e c t on each i n d i v i d u a l t r e e , depending on the t r e e ' s h i s t o r y and c u r r e n t s t a t e of v i g o u r . The f i n a l t h r e e v a r i a b l e s , phloem t h i c k n e s s , number of eggs l a i d per femal e , and p r o p o r t i o n of females i n t h e a t t a c k i n g p o p u l a t i o n , had the g r e a t e s t i m pact, a l t e r i n g b e e t l e p o p u l a t i o n d e n s i t y by a maximum of 144%, 90%, and 57%, r e s p e c t i v e l y . These l a r g e i n c r e a s e s , however, o n l y i n c r e a s e d t r e e m o r t a l i t y by, a t most, 18%. These l a s t t h r e e v a r i a b l e s , p a r t i c u l a r l y phloem t h i c k n e s s and the number of 127 eggs l a i d per female, were c l o s e l y l i n k e d . T r e e s w i t h t h i c k e r phloem produced females c a p a b l e of l a y i n g more eggs. The p r o p o r t i o n of females may be r e l a t e d t o the o t h e r s i n t h a t i t v a r i e s over the d u r a t i o n of the o u t b r e a k , depending on t r e e DBH. The cause or ca u s e s of t h i s v a r i a t i o n a r e not w e l l u n d e r s t o o d a t t h i s t i m e . The computer model d e v e l o p e d f o r t h i s s t u d y f u n c t i o n s a c c u r a t e l y under the c o n d i t i o n s s e t f o r t h i n t h i s r e p o r t . However, c a u t i o n s h o u l d be used when i n t e r p r e t i n g t h e model r e s u l t s . The model, as a h i g h l y s i m p l i f i e d r e p r e s e n t a t i o n of the r e a l b i r d i n s e c t f o r e s t system cannot s i m u l a t e a l l key r e l a t i o n s h i p s . For i n s t a n c e , the assumption was made t h a t the s i m u l a t e d s t a n d was s t a t i c . A l t h o u g h i n f e s t a t i o n s of up t o s i x t e e n y e a r s were s i m u l a t e d the t r e e s i n the s t a n d s d i d not age. N a t u r a l m o r t a l i t y of t r e e s d i d not o c c u r , and new, young t r e e s d i d not 'grow i n t o ' the s m a l l e s t DBH c l a s s . A second, perhaps more i m p o r t a n t , c h a r a c t e r i s t i c of the model i s t h a t i t s i m u l a t e s t e m p o r a l but not s p a t i a l r e l a t i o n s h i p s . The mountain p i n e b e e t l e i n f e s t a t i o n s d e v e l o p i n and s p r e a d t h r o u g h a 20 h e c t a r e s t a n d i n time o n l y . T h e r e f o r e , e f f e c t s such as the outward s p r e a d i n g of an i n f e s t a t i o n from an i n i t i a l l y l o c a l i z e d p o p u l a t i o n cannot be s i m u l a t e d . I t i s hoped t h a t c o n t i n u e d i n v e s t i g a t i o n s of b i r d i n s e c t i n t e r a c t i o n s w i l l make i n c l u s i o n of t h e s e s p a t i a l i n t e r - r e l a t i o n s h i p s p o s s i b l e . 6. CONCLUSIONS The v a l u e of non-game b i r d p r e d a t i o n of the mountain p i n e b e e t l e was e v i d e n t i n the l a r g e numbers of i n s e c t s t h a t t h e b i r d s consumed, and i n the p r o p o r t i o n of the p o p u l a t i o n d e s t r o y e d d i r e c t l y t h r o u g h consumption and i n d i r e c t l y t h r o u g h the e f f e c t s of bark removal. D u r i n g the w i n t e r , one b i r d a l o n e c o u l d consume more than 86,000 l a r v a e , a c c o u n t i n g f o r up t o 10% of the l o c a l l a r v a l p o p u l a t i o n . The t o t a l impact on the i n s e c t p o p u l a t i o n depended on the speed w i t h which the b i r d community responded t o changes i n i n s e c t d e n s i t y , and on the endemic and maximum b i r d d e n s i t i e s . When f u n c t i o n a l and n u m e r i c a l r e s p o n s e s o c c u r r e d r a p i d l y the i n i t i a l e x p a n s i o n of the b e e t l e p o p u l a t i o n was s u p p r e s s e d , and peak b e e t l e p o p u l a t i o n d e n s i t y was reduced. I n i t i a l b i r d d e n s i t i e s and maximum d e n s i t y a c h i e v e d d u r i n g n u m e r i c a l response appeared t o be more im p o r t a n t than speed of response i n the s u p p r e s s i o n of b e e t l e p o p u l a t i o n growth. I t was o n l y when b i r d d e n s i t i e s were i n i t i a l l y h i g h t h a t t h e r e was an immediate i n c r e a s e i n the p r o p o r t i o n of the b e e t l e p o p u l a t i o n consumed. The r e s u l t s of t h i s model gave no i n d i c a t i o n t h a t b i r d p r e d a t i o n a l o n e was s u f f i c i e n t t o p r e v e n t a major p i n e b e e t l e o u t b r e a k i n a s u s c e p t i b l e s t a n d , even when i n i t i a l b i r d d e n s i t i e s were h i g h or the b i r d s ' responses r a p i d . In 128 129 s t a n d s where the d i a m e t e r d i s t r i b u t i o n was such t h a t b e e t l e p r o d u c t i v i t y was o p t i m i z e d even u n r e a l i s t i c a l l y h i g h b i r d d e n s i t i e s c o u l d not p r e v e n t the outbreak from o c c u r r i n g . Major e p i d e m i c s d i d not occur i n s t a n d s where p r e v e n t i v e s i l v i c u l t u r a l methods were used. In t h e s e s t a n d s t h e b e e t l e p o p u l a t i o n s never i n c r e a s e d beyond the endemic l e v e l , so a v i a n f u n c t i o n a l and n u m e r i c a l r e s p o n s e s d i d not o c c u r . The p r o p o r t i o n of the b e e t l e p o p u l a t i o n consumed by b i r d s i n c r e a s e d , however, because the number of i n s e c t s consumed remained c o n s t a n t w h i l e i n s e c t p o p u l a t i o n d e n s i t y d e c l i n e d . A c o m b i n a t i o n of p r e v e n t i v e t h i n n i n g and i n t e l l i g e n t non-game b i r d h a b i t a t management d e s i g n e d t o i n c r e a s e b i r d d e n s i t i e s would have the g r e a t e s t impact on l o c a l b e e t l e p o p u l a t i o n s . The t h i n n i n g would e f f e c t i v e l y remove the b e e t l e s ' f o o d s u p p l y , w h i l e p r o p e r b i r d h a b i t a t management would reduce the more d r a s t i c impacts of the c u t . The b i r d s would be p r e s e n t t o f e e d on b e e t l e s moving i n t o the t h i n n e d s t a n d and, more i m p o r t a n t l y , would p r o b a b l y f e e d on b e e t l e s moving i n t o t h e a d j a c e n t u n t h i n n e d stands as w e l l . 6.1 RESEARCH NEEDS D u r i n g t h e c o n s t r u c t i o n of the s i m u l a t i o n model i t became a p p a r e n t t h a t most of the gaps i n the c u r r e n t knowledge of b i r d - m o u n t a i n p i n e b e e t l e i n t e r a c t i o n s c o n c e r n 130 the b i r d s , not the i n s e c t s . C o n s i d e r i n g the amount and d i s t r i b u t i o n of l o d g e p o l e p i n e i n B r i t i s h C o lumbia, and the e x t e n t of mountain p i n e b e e t l e i n f e s t a t i o n s , the l a c k of b a s i c d a t a c o n c e r n i n g b i r d s i n p r o v i n c i a l l o d g e p o l e p i n e s t a n d s i s d i s m a y i n g . Most of t h e b i r d d e n s i t y f i g u r e s used i n the s i m u l a t i o n model had t o be d e r i v e d from d a t a c o l l e c t e d i n A r i z o n a , C o l o r a d o , and Wyoming. Though not a B i o g e o c l i m a t i c U n i t i n B.C., e x t e n s i v e , pure s t a n d s of l o d g e p o l e p i n e c e r t a i n l y r e p r e s e n t a d i s t i n c t f o r e s t type w i t h t h e i r own p a r t i c u l a r a v i f a u n a . There i s an need f o r the c o l l e c t i o n of b a s i c d a t a on w i n t e r , b r e e d i n g , and p o s t - b r e e d i n g b i r d d e n s i t i e s i n p r o v i n c i a l l o d g e p o l e p i n e s t a n d s . S t r a t i f i c a t i o n by s u c c e s s i o n a l s t a g e or age c l a s s , as i n the r e s e a r c h conducted by L o f r o t h and Wetmore (1985), i s s t r o n g l y recommended. S t r a t i f i c a t i o n by s t a n d d e n s i t y and/or e l e v a t i o n a r e o t h e r p o s s i b i l i t i e s . More d e t a i l e d i n v e s t i g a t i o n s of b i r d - m o u n t a i n p i n e b e e t l e dynamics s h o u l d f o c u s on b i r d r e s p o n s e s , both f u n c t i o n a l and n u m e r i c a l , t o i n s e c t d e n s i t y changes, and b i r d r e s p o n s e s t o l o d g e p o l e p i n e management p r a c t i c e s . The r e s e a r c h conducted by L e s t e r (1980) p r o v i d e s a b a s i c example f o r the i n v e s t i g a t i o n of a v i a n n u m e r i c a l responses t o a mountain p i n e b e e t l e i n f e s t a t i o n . I d e a l l y , b oth summer and w i n t e r b i r d censuses s h o u l d be conducted i n s t a n d s of comparable age and d e n s i t y where the mountain p i n e b e e t l e i s 131 e x i s t i n g a t endemic, e p i d e m i c , and p o s t - e p i d e m i c l e v e l s . A d d i t i o n a l l y , i t s h o u l d be p o s s i b l e t o s e l e c t a s t a n d where the b e e t l e i s a t an endemic l e v e l , and a l s o i n the p a t h of the i n f e s t a t i o n f r o n t , so as t o conduct s e q u e n t i a l censuses as the i n f e s t a t i o n moves t h r o u g h the s t a n d . Such m o n i t o r i n g of b i r d d e n s i t i e s i n s t a n d s of d i f f e r e n t i n s e c t d e n s i t i e s or s e q u e n t i a l l y i n one s t a n d as d e n s i t i e s change, or b o t h , s h o u l d a i d i n d e t e r m i n i n g the type of n u m e r i c a l response t h a t the b i r d s e x h i b i t . S i m i l a r l y , i t s h o u l d be p o s s i b l e t o d i s t i n g u i s h the type of f u n c t i o n a l response t h a t the b i r d s e x h i b i t by r e c o r d i n g changes i n d i e t s a t d i f f e r e n t l e v e l s of i n s e c t d e n s i t y . T h i s i n f o r m a t i o n would be more d i f f i c u l t t o c o l l e c t because d e s t r u c t i v e s a m p l i n g would almost c e r t a i n l y be n e c e s s a r y , though the use of e m e t i c s (ie. Zach and F a l l s 1976) may o f f e r an a l t e r n a t i v e . I n f o r m a t i o n r e l a t i n g b i r d d e n s i t i e s t o p r o v i n c i a l l o d g e p o l e p i n e management p r a c t i c e s would be v e r y v a l u a b l e , p r o v i d e d t h a t d a t a were c o l l e c t e d b o t h b e f o r e and a f t e r the p r a c t i c e i n q u e s t i o n was a p p l i e d . As w i t h the b a s i c b i r d d e n s i t i e s , the b i r d r e s p o n s e s t o the t h i n n i n g s i m u l a t e d w i t h t h i s model were based on d a t a from the western U n i t e d S t a t e s . D e c i s i o n s on the management of non-game b i r d s i n B r i t i s h Columbia would u n d o u b t e d l y be more a c c u r a t e i f p r o v i n c i a l d a t a were a v a i l a b l e . 132 L a s t l y , more d e t a i l e d i n f o r m a t i o n c o n c e r n i n g woodpecker w i n t e r f e e d i n g methods and s t r a t e g i e s i s needed. The b i r d s have a w e l l developed a b i l i t y t o a c c u r a t e l y l o c a t e i n s e c t s beneath t r e e bark, p o s s i b l y t h r o u g h a u d i t o r y cues (Bent 1939, Otvos 1970). I t a l s o appears t h a t t h e y can a s s e s s s t a n d i n s e c t d e n s i t i e s as w e l l . T h e o r e t i c a l l y , t h e r e e x i s t s some i n s e c t t r e e d e n s i t y a t which the e n e r g e t i c c o s t s of s e a r c h i n g the t r e e and removing i t s bark o u t w e i g h the c a l o r i c v a l u e of the l a r v a e i n the t r e e . S i m i l a r l y , t h e r e i s some b e e t l e s t a n d d e n s i t y a t which the e n e r g e t i c c o s t s of r e m a i n i n g i n a s t a n d w i t h a low i n s e c t d e n s i t y o u t w e i g h the c o s t s and r i s k s of moving t o a new s t a n d . Measurements of the amount of bark removed from a t r e e d u r i n g the w i n t e r i n r e l a t i o n t o measurements of t h e " i n i t i a l autumn l a r v a l d e n s i t y may h e l p i n u n d e r s t a n d i n g the woodpeckers' c r i t e r i a f o r f e e d i n g t r e e s e l e c t i o n . In a s i m i l a r manner, i t may be p o s s i b l e t o r e l a t e measurements of o v e r a l l s t a n d b e e t l e d e n s i t y t o woodpecker use of t h e s t a n d . I f so, a p a t t e r n s i m i l a r t o one of the forms of f u n c t i o n a l r e s p o n s e s may be o b s e r v e d . T h i s i n f o r m a t i o n would h e l p i n c r e a s e the a c c u r a c y of f u t u r e models on t h e impacts of b i r d s on the mountain p i n e b e e t l e , and o t h e r b a r k b e e t l e s as w e l l . REFERENCES CITED Anonymous. 1981. Kamloops Timber Supply Area Y i e l d A n a l y s i s R e p o r t . Kamloops F o r e s t R e g i o n . 60 pp. Amman, G.D. 1969. Mountain p i n e b e e t l e emergence i n r e l a t i o n t o d epth of l o d g e p o l e p i n e b a r k . U.S.D.A. f o r . S e r v . Res. Note INT-96. 8pp. Amman, G.D. 1972a. Some f a c t o r s a f f e c t i n g o v i p o s i t i o n b e h a v i o r of the mountain p i n e b e e t l e . E n v i r o n . Entomol. 1:691-695. Amman, G.D. 1972b. Mountain p i n e b e e t l e brood p r o d u c t i o n i n r e l a t i o n t o t h i c k n e s s of l o d g e p o l e p i n e phloem. J . Econ. Entomol. 65:138-140. Amman, G.D. 1973. P o p u l a t i o n changes of the mountain p i n e b e e t l e i n r e l a t i o n t o e l e v a t i o n . E n v i r o n . Entomol. 2:541-547. Amman, G.D. 1976. I n t e g r a t e d c o n t r o l of t h e mountain p i n e b e e t l e i n l o d g e p o l e p i n e f o r e s t s . XVI IUFRO World Congr. P r o c , D i v . I I , pp. 439-446. O s l o , Norway. Amman, G.D. 1978. The b i o l o g y , e c o l o g y , and causes of o u t b r e a k s of the mountain p i n e b e e t l e i n l o d g e p o l e p i n e f o r e s t s . Pages 39-53 In Berryman, A.A., G.D. Amman, and R.W. S t a r k , t e c h . eds. 1978. Theory and p r a c t i c e of mountain p i n e b e e t l e management i n l o d g e p o l e p i n e f o r e s t s : symposium p r o c e e d i n g s . U n i v . of Idaho, Moscow ID. G.D., B.H. Baker, and L.E. S t i p e . 1973. Lodgepole p i n e l o s s e s t o mountain p i n e b e e t l e r e l a t e d t o e l e v a t i o n . U.S.D.A. F o r . Serv. Res. Note INT-171. 8pp. G.D. and V.E. Pace. 1976. Optimum egg g a l l e r y d e n s i t i e s f o r the mountain p i n e b e e t l e i n r e l a t i o n t o l o d g e p o l e p i n e phloem t h i c k n e s s . U.S.D.A. F o r . Se r v . Res. Note INT-209. 8pp. G.D., M.D. McGregor, D.B. C a h i l l , and W.H. K l e i n . 1977. G u i d e l i n e s f o r r e d u c i n g l o s s e s of l o d g e p o l e p i n e t o t h e mountain p i n e b e e t l e i n unmanaged sta n d s i n t he Rocky Mou n t a i n s . U.S.D.A. F o r . Se r v . Gen. Tech. Rep. INT-36. 19pp. Amma n, Amma n, Amma n, 133 134 Amman, G.D. and W.E. C o l e . 1983. Mountain p i n e b e e t l e dynamics i n l o d g e p o l e p i n e f o r e s t s . P a r t I I : P o p u l a t i o n dynamics. U.S.D.A. F o r . S e r v . Gen. Tech. Rep. INT-145. 59pp. Amman,G.D. and L. S a f r a n y i k . 1985. I n s e c t s of l o d g e p o l e p i n e : Impacts and c o n t r o l . Pages 107-124 In Baumgartner, D.M., R.G. K r e b i l l , J.T. A r n o t t , and G.F. Weetman, eds. Lodgepole p i n e : the s p e c i e s and i t s management. Symposium p r o c e e d i n g s . 381 pp. Angove, K. and B. B a n c r o f t . 1983. A gu i d e t o some common p l a n t s of the s o u t h e r n i n t e r i o r of B r i t i s h C o lumbia. P r o v i n c e of B r i t i s h C o lumbia, M i n i s t r y of F o r e s t s , Land Management Handbook No.7. 225pp. Arno, S.F. 1980. F o r e s t f i r e h i s t o r y i n the n o r t h e r n R o c k i e s . J . F o r . l 78:460-465. A u s t i n , D.D. and M.L. P e r r y . 1979. B i r d s i n s i x communities w i t h i n a l o d g e p o l e p i n e f o r e s t . J . F o r . 77:584-586. B a l d w i n , P.H. 1960. O v e r w i n t e r i n g of woodpeckers i n bark b e e t l e - i n f e s t e d s p r u c e - f i r f o r e s t s i n C o l o r a d o . Pages 71-84 In P r o c . X I I I n t . O r n i t h o l . Congr., H e l s i n k i . B a l d w i n , P.H. 1968. Woodpecker f e e d i n g on Engelmann spruce b e e t l e i n windthrown t r e e s . U.S.D.A. F o r . S e r v . Res. Note RM-105. Rocky Mtn. F o r . and RAnge Exp. S t n . , F o r t C o l l i n s , CO. 4pp. Beaver, R.A. 1967. The r e g u l a t i o n of p o p u l a t i o n d e n s i t y i n t h e bark B e e t l e Scolytus scolytus ( F . ) . J . Anim. E c o l . 36:435-451. Beedy, E.C. 1981. B i r d communities and f o r e s t s t r u c t u r e i n t h e S i e r r a Nevada of C a l i f o r n i a . Condor 83:97-105. Bent, A.C. 1939. L i f e H i s t o r i e s of N o r t h American woodpeckers. U.S. N a t l . Mus. B u l l . 174. Washington, D.C. 334 pp. Berryman, A.A. 1976. T h e o r e t i c a l e x p l a n a t i o n of mountain p i n e b e e t l e dynamics i n l o d g e p o l e p i n e f o r e s t . E n v i r o n . Entomol. 5:1225-1233. Berryman, A.A. 1978. Towards a t h e o r y of i n s e c t e p i d e m i o l o g y . Res. P o p u l . E c o l . 19:181-196. 135 Berryman, A.A. 1981. P o p u l a t i o n systems: A g e n e r a l i n t r o d u c t i o n . Plenum P r e s s . New York, N.Y. 222pp. Berryman, A.A. 1982. B i o l o g i c a l c o n t r o l , t h r e s h o l d s , and pe s t o u t b r e a k s . Env. Ent. 11:544-549. Berryman, A.A. and R.W. S t a r k . 1985. A s s e s s i n g the r i s k of lo d g e p o l e p i n e s t a n d d e s t r u c t i o n by p e s t s . Pages 163-170 In Baumgartner, D.M., R.G. K r e b i l l , J.T. A r n o t t , and G.F. Weetman, eds. Lodgepole p i n e : the s p e c i e s and i t s management. Symposium p r o c e e d i n g s . 381 pp. Berryman, A.A., B. De n n i s , K.F. R a f f a , and N.C. S t e n s e t h . 1985. E v o l u t i o n of o p t i m a l group a t t a c k , w i t h p a r t i c u l a r r e f e r e n c e t o bark b e e t l e s ( Coleoptera: Scol yt idae). E c o l o g y 66:898-903. B e t t s , M.M. 1955. The food of t i t m i c e i n the oak woodland. J . Anim. E c o l . 24:282-323. B l a c k f o r d , J.L. 1955. Woodpecker c o n c e n t r a t i o n i n a burned f o r e s t . Condor 57:28-30. Blackman, M.W. 1931. The B l a c k H i l l s b e e t l e . Tech. P u b l . No. 36. Syracuse U n i v . , New York S t a t e C o l l e g e of F o r e s t r y . S y r a c u s e , N.Y. 82pp. B l a i s , J.R. and G.H. P a r k s . 1964. I n t e r a c t i o n s of eve n i n g grosbeak (Hesperiphona v e s p e r t i n a ) a n d the spruce budworm (Choristoneura fumiferana (Clem.) i n a l o c a l i z e d budworm outbreak t r e a t e d w i t h DDT i n Quebec. Can. J . Z o o l . 42:1017-1024. Bock, C.E. and J.F. Lynch. 1970. B r e e d i n g b i r d p o p u l a t i o n s of burned and unburned c o n i f e r f o r e s t s i n the S i e r r a Nevada. Condor 72:182-189. Borden, J.H., L . J . Chong, K.E.G. P r a t t , and D.R.Gray. 1983. The a p p l i c a t i o n of b e h a v i o r m o d i f y i n g c h e m i c a l s t o c o n t a i n i n f e s t a t i o n s of the mountain p i n e b e e t l e Dendroctonus ponderosae. F o r . Chron. 60:235-239. Brown, G.S. 1956. P o p u l a t i o n t r e n d s i n the mountain p i n e b e e t l e a t Windermere Creek, B r i t i s h Columbia. I n t e r i m Report 1954-56. Pac. F o r . Res. C e n t r e , V i c t o r i a , B.C. 20pp. Brown, J.K. 1973. F i r e c y c l e s and community dynamics i n l o d g e p o l e p i n e f o r e s t s . Pages 429-456 In D.M. Baumgartner, ed. 1973. Management of Lodgepole P i n e Ecosystems: Symposium P r o c e e d i n g s . Washington S t a t e U n i v . , C o o p e r a t i v e E x t e n s i o n S e r v i c e , Pullman, W.A. 495pp. 136 B u l l , E.L. 1983. B i r d response t o b e e t l e - k i l l e d l o d g e p o l e p i n e . The M u r r e l e t 64:94-96. B u r n e l l , D.G. 1977. A d i s p e r s a l - a g g r e g a t i o n model f o r mountain p i n e b e e t l e i n l o d g e p o l e p i n e s t a n d s . Res. P o p u l . E c o l . 19:99-106. B u r n e l l , D.G., N.L. C r o o k s t o n , and A.R. Stage. Computing a l g o r i t h m s used i n the mountain p i n e b e e t l e model: An e x t e n s i o n of the p r o g n o s i s model. In P r e s s . M a n u s c r i p t . 57 pp. Campbell, R.W., T.R. T o r g e r s e n , and N. S r i v a s t a v a . 1983. A suggested r o l e f o r predaceous b i r d s and a n t s i n the p o p u l a t i o n dynamics of the western spruce budworm. F o r . S c i . 29:779-790. C l a r k , W.C., D.D. Jon e s , and C.S. H o l l i n g . 1977. The development and e v a l u a t i o n of t h e o r y i n ecosystem a n a l y s i s : p e r s p e c t i v e s from a f o r e s t i n s e c t s t u d y . Working Paper W-19. I n s t , of Res. E c o l . , U n i v . of B r i t i s h Columbia, Vancouver, B.C. 36 PP. C o l e , D.M. 1973. E s t i m a t i o n of phloem t h i c k n e s s i n l o d g e p o l e p i n e . U.S.D.A. F o r . S e r v . Res. Paper INT-148. 10pp. C o l e , W.E. 1974. Competing r i s k a n a l y s i s i n mountain p i n e b e e t l e dynamics. Res. P o p u l . E c o l . 15:183-192. C o l e , W.E. 1978. Management s t r a t e g i e s f o r p r e v e n t i n g mountain p i n e b e e t l e e p i d e m i c s i n l o d g e p o l e p i n e s t a n d s — b a s e d on e m p i r i c a l models. Pages 87-97 In Berryman, A.A., G.D. Amman, and R.W. S t a r k , Eds. 1978. Theory and p r a c t i c e of mountain p i n e b e e t l e management i n l o d g e p o l e p i n e f o r e s t s . Symp. P r o c . C o l l e g e of F o r . , W i l d l . , and Range S c i . , U n i v . of Idaho, Moscow, ID. C o l e , W.E. 1981. Some r i s k s and causes of m o r t a l i t y i n mountain p i n e b e e t l e p o p u l a t i o n s : a l o n g term a n a l y s i s . Res. P o p u l . E c o l . 23:116-144. C o l e , W.E. and G.D. Amman. 1969. Mountain p i n e b e e t l e i n f e s t a t i o n s i n r e l a t i o n t o l o d g e p o l e p i n e d i a m e t e r s . U.S.D.A. F o r . S e r v . Res. Note INT-95. 7pp. 137 C o l e , W.E., G.D. Amman, and C.E. Jense n . 1976. M a t h e m a t i c a l models f o r the mountain p i n e b e e t l e - l o d g e p o l e p i n e i n t e r a c t i o n . Env. Ent. 5:11-19. C o l e , W.E. and G.D. Amman. 1980. Mountain p i n e b e e t l e dynamics i n l o d g e p o l e p i n e f o r e s t s . P a r t I : Course of an i n f e s t a t i o n . U.S.D.A. F o r . S e r v . Gen. Tech. Rep. INT-89. 56pp. C o l e , W.E., E.P. Guymon, and C.E. Jense n . 1981. Monoterpenes of l o d g e p o l e p i n e as r e l a t e d t o mountain p i n e b e e t l e s . U.S.D.A. F o r . S e r v . Res. Pap. INT-281. 10 pp. C o l e , W.E. and M.D. McGregor. 1983. E s t i m a t i n g the r a t e and amount of t r e e l o s s from mountain p i n e b e e t l e i n f e s t a t i o n s . U.S.D.A. F o r . Serv. Res. Paper. INT-318. 22 pp. Co p p e l , H.D. and N.F. S l o a n . 1970. A v i a n p r e d a t i o n an impor t a n t a d j u n c t i n the s u p p r e s i o n of the l a r c h c a s e b e a r e r and i n t r o d u c e d p i n e s a w f l y p o p u l a t i o n s i n W i s c o n s i n f o r e s t s . Second Annu. T a l l Timbers F i r e E c o l o g y Conf. P r o c , Pages 259-272. T a l l Timbers Res. S t n . T a l l a h a s s e e , F l . D e R u i t e r , L. 1952. Some ex p e r i m e n t s on the camouflage f o r s t i c k c a t e r p i l l a r s . B e h a v i o r . 4:222-232. D i c k s o n , J.G., R.N. Conner, and J.H. W i l l i a m s o n . 1983. Snag r e t e n t i o n i n c r e a s e s b i r d use of a c l e a r c u t . J . W i l d l . Manage. 47:790-804. E l s e t h , G.D. and K.D. Baumgardner. 1981. P o p u l a t i o n B i o l o g y . D. Van N o s t r a n d Company. New York, N.Y. 623 pp. E r i k s o n , R.D. and R.L. F e r r i s . 1983. F o r e s t I n s e c t and Di s e a s e C o n d i t i o n s . Kamloops F o r e s t R e g i o n . 1983. P a c i f i c F o r e s t Research C e n t r e F i l e R e p o r t . 35pp. F i d d i c k , R.L. and G.A. Van S i c k l e . 1980. F o r e s t i n s e c t and d i s e a s e c o n d i t i o n s . B r i t i s h Columbia and Yukon 1980. Can. F o r . S e r v . I n f o . Rep. BC-X-220. 23 pp. F r a n z , J.M. 1961. B i o l o g i c a l c o n t r o l of i n s e c t p e s t s i n Europe. Annu. Rev. Entomol. 6:183-200. F r a n z r e b , K.E. 1978. Tree s p e c i e s used by b i r d s i n lo g g e d and unlogged mixed c o n i f e r o u s f o r e s t s . W i l s o n B u l l e t i n 90:221-238. 1 38 F u r n i s s , M.M. and J.A. Schenk. 1969. S u s t a i n e d n a t u r a l i n f e s t a t i o n by the mountain p i n e b e e t l e i n seven new Pinus and Picea h o s t s . J . Econ. Entomol. 62:518-519. F u r n i s s , R.L. and V.M. C a r o l i n . 1977. Western f o r e s t i n s e c t s . U.S.D.A. F o r . S e r v . M i s c . P u b l . No. 1339. Gar a , R . I . , W.R. L i t t k e , J.K. Agee, D.R. G e i s z l e r , J.D. S t u a r t , and C.H. D r i v e r . 1985. I n f l u e n c e of f i r e , f u n g i , and mountain p i n e b e e t l e on development of a l o d g e p o l e p i n e f o r e s t i n s o u t h - c e n t r a l Oregon. Pages 163-170 In Baumgartner, D.M., R.G. K r e b i l l , J.T. A r n o t t , and G.F. Weetman, eds. Lodgepole p i n e : the s p e c i e s and i t s management. Symposium p r o c e e d i n g s . 381 pp. G o d f r e y , W.E. 1979. The B i r d s of Canada. N a t i o n a l Museum of N a t u r a l S c i e n c e s . N a t i o n a l Museum of Canada. Ottawa. 428pp. H e i n , D. 1980. Management of l o d g e p o l e p i n e f o r b i r d s . Pages 238-246 In R.M. D e G r a f f , Tech. Co-ord. 1980. Workshop p r o c e e d i n g s : Management of we s t e r n f o r e s t s and g r a s s l a n d s f o r nongame b i r d s . U.S.D.A. F o r . S e r v . Gen. Tech. Rep. INT-86. 535 pp. Hodgkinson R.S., M. F i n n i s , R.F. Shepherd, and J.C. Cunningham. 1979. A e r i a l a p p l i c a t i o n s of N u c l e a r P o l y h e d r o s i s v i r u s and Bacillus thuringensis a g a i n s t w e s t e r n spruce budworm. B.C. M i n . of For./Can. F o r . S e r v . CANUSA J o i n t R e p o r t No. 10. 19 pp. H o l l i n g , C S . 1959. The components of p r e d a t i o n as r e v e a l e d by a study of s m a l l mammal p r e d a t o r s of the European p i n e s a w f l y . Can. Ent o m o l . H o l l i n g , C S . 1965. The f u n c t i o n a l response of p r e d a t o r s t o p r e y d e n s i t y and i t s r o l e i n mimicry and p o p u l a t i o n r e g u l a t i o n . Mem. Entomol. Soc. Can. No. 45. H o l l i n g , C S . 1973. R e s i l i a n c e and s t a b i l i t y of e c o l o g i c a l systems. Ann. Rev. E c o l . S y s t . 4:1-23. H o l l i n g , C.S., D.D. J o n e s , and W.C. C l a r k . 1977. E c o l o g i c a l p o l i c y d e s i g n : A case s t u d y of f o r e s t and p e s t management. Pages 13-90 In N o r t o n , G.A. and C S . H o l l i n g , eds. P r o c e e d i n g s of a c o n f e r e n c e on pest management. I n t . I n s t . A p p l . S y s t . A n a l y s i s . Luxemburg, A u s t r i a . 139 H o p k i n s , A.D. 1920. The b i o c l i m a t i c law. J . Wash. Acad. S c i . 10:34-40. Hopping, G.R. and G. B e a l l . 1948. The r e l a t i o n of diameter of l o d g e p o l e p i n e t o i n c i d e n c e of a t t a c k by the bark b e e t l e Dendroctonus monticolae H o p k i n s . For Chron. 24:141-145. H u t c h i n s o n , F.T. 1951. The e f f e c t s of woodpeckers on the Engelmann spruce b e e t l e Dendroctonus engelmannii H o p k i n s . M.S. T h e s i s . C o l o . A&M C o l l e g e , F o r t C o l l i n s . 73 pp. Hynum, B.G. 1978. M i g r a t i o n phase i n t e r a c t i o n s between the mountain p i n e b e e t l e and l o d g e p o l e p i n e . Ph. D. D i s s e r t a t i o n . Washington S t . U n i v . , S e a t t l e , WA. I v l e v , V.S. 1961. E x p e r i m e n t a l E c o l o g y Of The Fe e d i n g Of F i s h e s . Y a l e U n i v . P r e s s . New Haven, Conn. Jackman, S.M. 1975. Woodpeckers of the P a c i f i c N o r t h w e s t : t h e i r c h a r a c t e r i s t i c s and t h e i r r o l e i n t h e f o r e s t s . M.S. T h e s i s . Oregon S t a t e U n i v . , C o r v a l l i s . 147 pp. Kendeigh, C.S. 1947. B i r d p o p u l a t i o n s t u d i e s i n the c o n i f e r o u s f o r e s t biome d u r i n g a s p r u c e budworm o u t b r e a k . Ont. Dept. of Lands and F o r e s t s . B i o l . B u l l e t i n No. 1. Kendeigh, C.S. 1970. Energy r e q u i r e m e n t s f o r e x i s t e n c e i n r e l a t i o n t o s i z e of b i r d . Condor 72:60-65. K i n g , J.R. and D.S. F a r n e r . 1961. Energy m e t a b o l i s m , t h e r m o r e g u l a t i o n and body t e m p e r a t u r e . Pages 215-288 In M a r s h a l l , A . J . , ed. 1961. B i o l o g y and c o m p a r a t i v e p h y s i o l o g y of b i r d s , V o l . I I . Academic P r e s s , New Yor k , N.Y. K l e i n , W.H., D.L. P a r k e r , and C.E. Jense n . 1978. A t t a c k , emergence, and s t a n d d e p l e t i o n t r e n d s of the mountain p i n e b e e t l e i n a l o d g e p o l e p i n e s t a n d d u r i n g an o u t b r e a k . Env. E n t . 7:732-737. K n i g h t , F.R. 1958. The e f f e c t s of woodpeckers on p o p u l a t i o n s of the Engelmann spruce b e e t l e . J . Econ. Entomol. 51:603-607. K o p l i n , J.R. 1967. P r e d a t o r y and e n e r g e t i c r e l a t i o n s of woodpeckers t o the engelmann spruce b e e t l e . Ph.D. d i s s e r t a t i o n . C o l o r a d o S t a t e u n i v e r s i t y . 187pp. 140 K o p l i n , J.R. 1969. The n u m e r i c a l response of woodpeckers t o i n s e c t p r e y i n a s u b a l p i n e f o r e s t i n C o l o r a d o . Condor 71:436-438. K o p l i n , J.R. 1972. Me a s u r i n g p r e d a t o r impact of woodpeckers on spruce b e e t l e s . J . W i l d l . Manage. 36:308-320. K o p l i n , J.R. and P.H. B a l d w i n . 1970. Woodpecker p r e d a t i o n on an endemic p o p u l a t i o n of Engelmann s p r u c e b e e t l e s . Am. M i d i . Nat. 83:510-515. K r a j i n a , V . J . , K. K l i n k a , and J . W o r r a l l . 1982. D i s t r i b u t i o n and 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 and shrubs of B r i t i s h Columbia. F a c u l t y of F o r e s t r y , U n i v . of B r i t i s h C o l u m b i a , Vancouver, B.C. 131pp. Lack, D. 1955. B r i t i s h t i t s {Parus spp.) i n n e s t boxes. Ardea 43:50-84. L a s i e w s k i , R.C. and W.R. Dawson. 1967. A r e - e x a m i n a t i o n of the r e l a t i o n between s t a n d a r d m e t a b o l i c r a t e and body weight i n b i r d s . Condor 69:13-23. L e s t e r , A.N. 1980. N u m e r i c a l response of woodpeckers and t h e i r e f f e c t on m o r t a l i t y of mountain p i n e b e e t l e s i n l o d g e p o l e p i n e i n n o r t h w e s t e r n Montana. M.Sc. T h e s i s . U n i v . of Montana, M i s s o u l a , MT. 103pp. L o f r o t h , E. and S. Wetmore. 1985. R e l a t i o n s h i p s between f o r e s t b i r d d e n s i t i e s and f o r e s t age i n s o u t h e r n B r i t i s h C o lumbia. Canadian W i l d l i f e S e r v i c e . M a n u s c r i p t R e p o r t , In P r e s s . M a c A r t h u r , R.H. 1958. P o p u l a t i o n e c o l o g y of some w a r b l e r s of n o r t h e a s t e r n c o n i f e r o u s f o r e s t s . E c o l o g y 39:599-619. Manning, G.H., L. S a f r a n y i k , G.H. Van S i c k l e , R.B. S m i t h , W.A. White, and E. H e t h e r i n g t o n . 1982. A r e v i e w of mountain p i n e b e e t l e problems i n Canada. Env. Can., Can. F o r . S e r v . , Pac. F o r . Res. C e n t r e . V i c t o r i a , B.C. 27pp. M a r c o t , G.B. 1983. Snag use by b i r d s i n a D o u g l a s - f i r c l e a r c u t . Pages 134-139 In D a v i s , J.W., G.A. Goodwin, and R.A. O c k e n f e l s , Tech. Coords. 1983. Snag h a b i t a t management: p r o c e e d i n g s of the symposium. U.S.D.A. F o r . S e r v . Gen. Tech. Rep. RM-99. 226 PP. 141 Massey, C.L. and N.D. Wygant. 1954. B i o l o g y and c o n t r o l of the engelmann spruce b e e t l e i n C o l o r a d o . U.S.D.A. F o r . S e r v . C i r c . 944. 35pp. McCambridge, W.F. and F.B. K n i g h t . 1972. F a c t o r s a f f e c t i n g s p ruce b e e t l e s d u r i n g a s m a l l o u t b r e a k . E c o l o g y . 53:830-839. M i t c h e l l , R.G., R.H. Waring, and G.B. Pit m a n . 1983. T h i n n i n g l o d g e p o l e p i n e i n c r e a s e s t r e e v i g o r and r e s i s t a n c e t o mountain p i n e b e e t l e . F o r e s t S c i . 29:204-211. Moeck, H.A. and L. S a f r a n y i k . 1984. Assessment of p r e d a t o r and p a r a s i t o i d c o n t r o l of bark b e e t l e s . I n f o . Rep. BC-X-248. Env. Can., Can. F o r . S e r v . Pac. F o r . Res. C e n t r e , V i c t o r i a , B.C. 24pp. Mook, L. 1963. B i r d s and the spruce budworm. Mem. Entomol. Soc. Can. 31:268-271. M o r r i s , R.F. 1963. The dynamics of epidemic spruce budworm p o p u l a t i o n s . Can. Entomol. Mem. 31. 332 pp. M o r r i s , R.F., W.F. C h e s h i r e , C.A. M i l l e r , and D.G. M o t t . 1958. The n u m e r i c a l response of a v i a n and mammalian p r e d a t o r s d u r i n g a g r a d a t i o n of the spruce budworm. E c o l o g y . 39:487-494. Murdoch, W.W. 1969. S w i t c h i n g • i n g e n e r a l p r e d a t o r s : e x p e r i m e n t s on p r e d a t o r s p e c i f i c i t y and s t a b i l i t y of prey p o p u l a t i o n s . E c o l . Monogr. 39:335-354. G t v o s , I.S. 1965. S t u d i e s on a v i a n p r e d a t o r s of De ndr oct onus brevicomis w i t h s p e c i a l r e f e r e n c e t o P i c i d a e . Can. Entomol. 97:1184-1189. Otvo s , I.S. 1969. V e r t e b r a t e p r e d a t o r s of Dendroct onus brevicomis w i t h s p e c i a l r e f e r e n c e t o P i c i d a e . Can. Entomol. b r e v i c o m i s LeConte ( C o l e p t e r a : S c o l y t i d a e ) w i t h s p e c i a l r e f e r e n c e t o Aves. Ph.D. D i s s e r t a t i o n . U n i v . C a l i f . , B e r k e l e y , CA. 202pp. Otvo s , I.S. 1970. A v i a n p r e d a t i o n of the western p i n e b e e t l e . Pages 119-127 In S t a r k , R.W. and D.L. D a h l s t e n , eds. 1970. S t u d i e s on the p o p u l a t i o n dynamics of the western p i n e b e e t l e , Dendr oct onus brevicomis Le Conte (Coleoptera: Scolyt idae). U n i v . of C a l . , D i v . of A g r i c . S c i e n c e s . 174 pp. 142 O t v o s , I.S. 1979. The e f f e c t s of i n s e c t i v o r o u s b i r d a c t i v i t i e s i n f o r e s t ecosystems: an e v a l u a t i o n . Pages 341-374 In D i c k s o n , J.G., R.N. Conner, R.R. F l e e t , J.C. K r o l l , and J.A. J a c k s o n , eds. 1979. The r o l e of i n s e c t i v o r o u s b i r d s i n f o r e s t ecosystems. Academic P r e s s , New Yor k , N.Y. 381pp. O t v o s , I.S. and R.W. S t a r k . 1985. A r t h r o p o d f o o d of some f o r e s t - i n h a b i t i n g b i r d s . Can. E n t . 117:971-990. Peterman, R.M. 1974. Some a s p e c t s of the p o p u l a t i o n dynamics of the mountain p i n e b e e t l e , Dendroctonus ponder os ae, i n l o d g e p o l e p i n e f o r e s t s of B r i t i s h C o l umbia. Ph. D. T h e s i s . U n i v . of B.C., Vancouver, B.C. 208 pp. P e t e r s o n , S.R. 1982. A p r e l i m i n a r y survey of f o r e s t b i r d communities i n n o r t h e r n Idaho. Northwest S c i . 56:287-298. P f i s t e r , R.D., B.L. K o v a l c h i k , and S.F. Arno. 1977. F o r e s t h a b i t a t t y p e s of Montana. U.S.D.A. F o r . S e r v . Gen. Tech. Rep. INT-34. 174pp. Pynnonen, A. 1939. B e i t r a g e z u r K e n n t n i s der B i o l o g i e f i n n i s c h e r S p e c h t e . In O t v o s , I.S. 1969. V e r t e b r a t e p r e d a t o r s of Dendroctonus brevicomis LeConte ( C o l e o p t e r a : S c o l y t i d a e ) w i t h s p e c i a l r e f e r e n c e t o Aves. Ph.D. D i s s e r t a t i o n . U n i v . C a l i f . , B e r k e l e y , CA. 202pp. K.F. and A.A. Berryman. 1980. F l i g h t r e s p o n s e s and ho s t s e l e c t i o n by bark b e e t l e s . Pages 213-233 In Berryman, A.A. and L. S a f r a n y i k , eds. 1980. P r o c e e d i n g s of t h e second IUFRO c o n f e r e n c e on d i s p e r s a l of f o r e s t i n s e c t s : e v a l u a t i o n , t h e o r y , and management i m p l i c a t i o n s . S a n d p o i n t , ID. 278 pp. K.F. and A.A. Berryman. 1983. The r o l e of host p l a n t r e s i s t a n c e i n the c o l o n i z a t i o n b e h a v i o r and e c o l o g y of bark b e e t l e s {Coleoptera:Scolyl i dae). E c o l . Monogr. 53:27-49. Rasmussen, L.A. 1974. F l i g h t and a t t a c k b e h a v i o r of mountain p i n e b e e t l e s i n l o d g e p o l e p i n e of n o r t h e r n Utah and s o u t h e r n Idaho. U.S.D.A. F o r . Se r v . Res. Note INT-180. 7pp. R a f f a , R a f f a , 143 Reid, R.W. 1962a. Biology of the mountain pine beetle, Dendroctonus monticolae Hopkins, in the east Kootenay region of B r i t i s h Columbia. I. L i f e cycle, brood development, and f l i g h t periods. Can. Entomol. 94:531-538 Reid, R.W. 1962b. Biology of the mountain pine beetle, Dendr oct onus monticolae Hopkins, in the east Kootenay region of B r i t i s h Columbia. I I . Behavior in the host, fecundity, and internal changes in the female. Can. Entomol. 94:605-613. Reid, R.W. 1963. Biology of the mountain pine beetle, Dendroct onus monticolae Hopkins, in the east Kootenay region of B r i t i s h Columbia. I I I . Interaction between the beetle and i t s host, with emphasis on brood mortality and s u r v i v a l . Can. Entomol 95:225-238. Reid, R.W. and H. Gates. 1970. Effe c t of temperature and resin on hatch of eggs of the mountain pine beetle (Dendroct onus ponderosae ). Can. Entomol. 102:617-622. Roppe, J.A. 1974. E f f e c t s on w i l d l i f e of a f i r e in a lodgepole pine f o r e s t . M.Sc. Thesis. Col. St. Univ., Ft. C o l l i n s , C o l . 100 pp. Rust, H.J. 1929. Relation of insectivorous birds to the mortality of the mountain pine beetle during the f l i g h t period. U.S.D.A. Bur. of Entomol. Forest Insect F i e l d Station. Couer d'Alene, Idaho. Unpublished report. Spp. Rust, H.J. 1930. Relation of insectivorous birds to the mortality of the mountain pine beetle during the f l i g h t period. U.S.D.A. Bur. of Entomol. Forest Insect F i e l d Station. Couer d'Alene, Idaho. Unpublished report. 11pp. Safranyik, L. 1968. Development of a technique for sampling mountain pine beetle populations in lodgepole pine. Ph. D. Thesis. University of B r i t i s h Columbia, Vancouver, B.C. 197 pp. 144 Safranyik, L. 1978. Effects of climate and weather on mountain pine beetle populations. Pages 77-84 In A.A. Berryman, G.D. Amman, and R.W. Stark, eds. 1978. Theory and practice of mountain pine beetle management in lodgepole pine forests, Symposium proceedings. C o l l . For., Wildl., Rauge S c i . , Univ. of Idaho, Moscow, Idaho. Safranyik, L., D.M. Shrimpton, and H.S. Whitney 1974. Reprinted 1982. Management of lodgepole pine to reduce losses from the mountain pine beetle. Environ. Canada, Canadian For. Serv., For. Tech. Rep. 1. 25pp. Safranyik, L., D.M. Shrimpton, and H.S. Whitney. 1975. An interpretation of the interaction between lodgepole pine, the mountain pine beetle and i t s associated blue stain fungi in western Canada. Pages 406-428 In D.M. Baumgartner, ed. 1973. Management of Lodgepole Pine Ecosystems: Symposium Proceedings. Washington State Univ., Cooperative Extension Service. Pullman, WA. 495pp. Safranyik, L., G.A. Van Sickle, and G.H. Manning. 1961. Position paper on mountain pine beetle problems with special reference to the Rocky Mountain Parks Region. Env. Can., Can. For. Serv., Pac. For. Res. Centre, V i c t o r i a , B.C. 27pp. Salt, G.W. 1957. An analysis of avifaunas in the Teton Mountains of Jackson Hole, Wyoming. Condor 59:373-393. Schmid, J.M. and R.H. Frye. 1977. Spruce beetle in the Rockies. U.S.D.A. For. Serv. Gen. Tech. Rep. RM-49. 38 pp. Schmidt, W.C. and R.R. Alexander. 1985. Strategies for managing lodgepole pine. Pages 201-210 In Baumgartner, D.M., R.G. K r e b i l l , J.T. Arnott, and G.F. Weetman, eds. Lodgepole pine: the species and i t s management. Symposium proceedings. 381 pp. Schmitz, R.F. and A.R. Taylor. 1969. An instance of lightning damage and infestation of ponderosa pines by the pine engraver beetle in Montana. U.S.D.A. For. Serv. Res. Note INT-88. 8 pp. 145 Schwab, F.E. 1979. E f f e c t of v e g e t a t i o n s t r u c t u r e on b r e e d i n g b i r d communities i n the d r y zone D o u g l a s - f i r f o r e s t o f s o u t h e a s t e r n B r i t i s h C o lumbia. M.Sc. T h e s i s . U n i v e r s i t y of B r i t i s h C o l u m b i a , Vancouver, B.C. 117pp. V.E. 1979. B i r d r e s p o n s e s t o snag removal i n ponderosa p i n e J . F o r . 77:26-28. V.E. and J.L. Oldemeyer. 1983. C a v i t y - n e s t i n g b i r d r e q u i r e m e n t s and re s p o n s e s t o snag c u t t i n g i n ponderosa p i n e . Pages 19-23 In J.W. D a v i s , G.A. Goodwin, and R.A. O c k e n f e l s , Tech. Coords. 1983. Snag h a b i t a t management: p r o c e e d i n g s of the symposium. U.S.D.A. F o r . S e r v . Gen. Tech. Rep. RM-99. 226pp. S c o u l l a r , K.A. 1980. U s i n g l a n d r e s o u r c e maps t o d e f i n e h a b i t a t f o r f o r e s t b i r d s . M.Sc. T h e s i s . U n i v . of B r i t i s h C olumbia, Vancouver, B.C. 295pp. Shepherd, R.F. 1965. D i s t r i b u t i o n of a t t a c k s by Dendroctonus ponder os ae Hopk. on Pinus contort a D o u g l . v a r . latifolia Engelm. Canad. E n t . 97:207-215. Shepherd, R.F. 1966. F a c t o r s i n f l u e n c i n g the o r i e n t a t i o n and r a t e s of a c t i v i t y of Dendroctonus ponderosae Hopkins (Coleopt era: Scolytidae). Can. Entomol. 98:507-518. Shook, R.S. and P.H. B a l d w i n . 1970. Woodpecker p r e d a t i o n on bark b e e t l e s i n Engelmann spruce l o g s as r e l a t e d t o s t a n d d e n s i t y . Can. Entomol. 102:1345-1354. Smith, K.G. 1980. Nongame b i r d s of the Rocky Mountain s p r u c e - f i r f o r e s t s and t h e i r management. Pages 258-279 In R.M. D e G r a f f , Tech. Coord. Workshop P r o c e e d i n g s , Management of Western F o r e s t s and G r a s s l a n d s f o r Nongame B i r d s . U.S.D.A. F o r . Se r v . Gen. Tech. Rep. INT-86. 535pp. Solomon, M.E. 1949. The n a t u r a l c o n t r o l of a n i m a l p o p u l a t i o n s . J . Anim. E c o l . 18:1-35. S t a l l c u p , P.L. 1963. A method of i n v e s t i g a t i n g a v i a n p r e d a t i o n on the a d u l t B l a c k H i l l s b e e t l e . M.Sc. T h e s i s . C o l . S t a t e U n i v . , F o r t C o l l i n s , CO. 60pp. S c o t t , S c o t t , 146 S t a r k , R.W. and F.W. Cobb, J r . 1969. Smog injury, root diseases, and bark beetle damage in ponderosa pine. Cal. A g r i c , September, 1969, 13-15. Szaro, R.C. and R.P; Balda. 1979. Effects of Harvesting Ponderosa Pine on Non-game Bird Populations. U.S.D.A. For. Serv. Res. Paper RM-212. 8pp. Takahashi, F. 1964. Reproduction curve with two equilibrium points: A consideration of the fluctuation of insect populations. Res. Popul. E c o l . 6:28-36. Takekawa, J.Y., E.O. Garton, and L.A. Langelier. 1982. B i o l o g i c a l control of forest insect outbreaks. Transactions; 47th Nor. Am. Wildl. and Nat. Res. Conf. 1982. Pages 393-409. Takekawa, J.T. and E.O. Garton. 1984. How much i s an evening grosbeak worth? J . For. 82:426-428. Taylor, D.L. 1969. B i o t i c succession of lodgepole pine forests of f i r e o r i g i n in Yellowstone National Park. Ph.D. Thesis, Univ. of Wyoming, Laramie, Wy. Thomas, J.W. Tech. Ed. 1979. W i l d l i f e habitats in managed forests: the Blue Mountains of Oregon and Washington. U.S.D.A. Agric. Handb. No. 533. 512pp. Tinbergen, L. i960. The natural control of insects in pinewoods. I. Factors influencing the intensity of predation by songbirds. Arch. Neer. Zool. 13:265-343. Torgersen, T.R. and R.W. Campbell. 1982. Some effects of avian predators on the Western Spruce Budworm in North Central Washington. Env. Ent. 11:429-431. Verner, J.E., C. Beedy, S.L. Granholm, L.V. R i t t e r and E.T. Toth. 1980. Birds. Pages 75-302 In C a l i f o r n i a W i l d l i f e and their Habitats: Western Sierra Nevada. U.S.D.A. For. Serv. Gen. Tech. Rep. PSW-37. 439 pp. V i t e , J.P. and G.B. Pitman. 1968. Bark beetle agregation: effects of feeding on the release of pheromones in Dendroct onus and Ips. Nature 218:169-170. Volland, L.A. 1985. Ecological c l a s s i f i c a t i o n of lodgepole pine in the United States. Pages 63-76 In Baumgartner, D.M., R.G. K r e b i l l , J.T. Arnott, and G.F. Weetman, eds. Lodgepole pine: the species and i t s management. Symposium proceedings. 381 pp. 147 Waring, R.H., W.G. T h e i s , and D. Muscato. 1980. Stem growth per u n i t l e a f a r e a : a measure of t r e e v i g o r . F o r e s t S c i . 26: 1 12-117. Wood, C.S. and H.A. Woensdregt. 1981. F o r e s t I n s e c t and D i s e a s e C o n d i t i o n s . Kamloops F o r e s t R e g i o n . 1981. P a c i f i c F o r e s t Research C e n t r e F i l e R e p o r t . 38pp. Wood, C.S., G.A. Van S i c k l e , and T.L. Shore. 1985. F o r e s t I n s e c t and D i s e a s e C o n d i t i o n s : B r i t i s h Columbia and Yukon 1984. Can. F o r . S e r v . I n f o . Rep. BC-X-259. 32 pp. Wood, S.L. 1963. A r e v i s i o n of the bark b e e t l e genus Dendroctonus E r i c h s o n (Coleoptera: Scolytidae). G r e a t B a s i n Nat. 23:1-117. Zach, R. and J.B. F a l l s . 1976. B i a s and m o r t a l i t y i n the use of t a r t a r emetic t o de t e r m i n e the d i e t of oven b i r d s (Aves:Parulidae). Can. J . Z o o l . 54:1599-1603. APPENDIX 1 COMMON AND crTF.NTIFIC NAMES 148 F u n g i B l u e s t a i n f u n g i Cerat ocyst i s montia Rumbold B l u e s t a i n f u n g i Europhium clavi gerum Robinson and Davidson T r e e s Lodgepole p i n e Pinus contort a Douglas v a r . I at i folia Engelmann I n s e c t s Mountain p i n e b e e t l e Dendr oct onus ponder osae Hopkins B i r d s Common nighthawk P i l e a t e d woodpecker H a i r y woodpecker Downy woodpecker B l a c k - b a c k e d woodpecker T h r e e - t o e d woodpecker Western wood pewee O l i v e - s i d e d f l y c a t c h e r C l a r k ' s n u t c r a c k e r Mountain c h i c k a d e e W h i t e - b r e a s t e d n u t h a t c h R e d - b r e a s t e d n u t h a t c h Chordei I es minor F o r s t e r Dryocopus pi I eat us L i n n a e u s Picoides villosus L i n n a e u s Picoides pubescens L i n n a e u s Picoides arcticus Swainson Picoides tri dactyl us L i n n a e u s Contopus sordidulus S c l a t e r Contopus boreal is Swainson Nucifraga Columbiana W i l s o n Parus gambeli Ridgway Sitta carol inens is Latham Sitta canadensis L i n n a e u s 1 4 9 150 APPENDIX 1 Pygmy n u t h a t c h Brown c r e e p e r American r o b i n Townsend's s o l i t a i r e • Mountain b l u e b i r d Yellow-rumped w a r b l e r c o n t i n u e d Si it a pygmaea V i g o r s Cert hi a americana L i n n a e u s Turdus migratorius L i n n a e u s Myadest es t ownsendi i Audubon Si alia currucoides B e c h s t e i n Dendroica coronata L i n n a e u s APPENDIX 2 KEY REFERENCES USED IN MODEL CONSTRUCTION 151 1 : Hut c h i n s o n 1951, B a l d w i n 1960, K o p l i n 1967, L e s t e r 1980 B u l l 1983 2 : Beaver 1967, Amman 1973, Schmidt and Frye 1977, L e s t e r 1980 3 : B u r n e l l 1977 B u r n e l l et el In P r e s s . 4 : Amman 1972b, Co l e and Amman 1980 5 : Rust 1929 and 1930, S a l t 1957, S t a l l c u p 1963, T a y l o r 1969, Bock and Lynch 1970, Roppe 1974, Schwab 1979, A u s t i n and P e r r y 1979, Hein 1980 6 : R e i d 1962a, Rasmussen 1974, Peterman 1974, Hynum 1978 7 : Hopping and B e a l l 1948, Shepherd 1966, C o l e and Amman 1969, S a f r a n y i k et al 1974 8 : Rasmussen 1974, K l e i n el al 1978, C o l e and Amman 1980, L e s t e r 1980 9 : R e i d 1962b, Co l e and Amman 1969, S a f r a n y i k et. al. 1975, R a f f a and Berryman 1983 10: C o l e et. al. 1976, Amman and C o l e 1983 11: R e i d 1962b, Peterman 1974, S a f r a n y i k et al 1974 12: R e i d 1963, R e i d and Gates 1970, Amman and C o l e 1983 152 r 153 13: R e i d 1963, Amman 1973, C o l e 1974, C o l e et al 1976, C o l e 1981, Amman and C o l e 1983 14: S a f r a n y i k el al 1974, Amman and C o l e 1983, S a f r a n y i k 1985 p e r s o n a l communication 15: S a f r a n y i k el al 1974, K l e i n et al 1978, S a f r a n y i k 1985 p e r s o n a l communication 16: C o l e el al 1976, C o l e 1978, C o l e and Amman 1980 17: R e i d 1963, Shepherd 1965, C o l e and Amman 1969, Peterman 1974, S a f r a n y i k el al 1974, K l e i n et al 1978, R a f f a and Berryman 1983, Berryman et al 1985, Schmitz 1985 p e r s o n a l c o m m u n i c a t i o n , S a f r a n y i k 1985 p e r s o n a l communication 18: K o p l i n 1967, Otvos 1969, Otvos 1984 p e r s o n a l communication 19: S a l t 1957, S t a l l c u p 1963, K o p l i n 1969, Otvos 1969, Bock and Lynch 1970, 20: Massey and Wygant 1954, K o p l i n 1967, Otvos 1969, Otvos 1984 p e r s o n a l communication 21: Pynnonen 1939, K o p l i n 1967, Otvos 1969, Otvos 1984 p e r s o n a l communication 22: S a l t 1957, S t a l l c u p 1963, K o p l i n 1969, Otvos 1969, Bock and Lynch 1970 23: K i n g and Fa r n e r 1961, L a s i e w s k i and Dawson 1967, K o p l i n 1967, Kendeigh 1969 and 1970 154 24: Rust 1929 and 1930, S t a l l c u p 1963 25: S t a l l c u p 1963, K o p l i n 1967, communication, Otvos 1984 p e r s o n a l Moeck 1984 p e r s o n a l communicat i o n APPENDIX 3 BASIC MOUNTAIN PINE BEETLE SIMULATION MODEL 1 5 5 L i s t i n g of Ml at 04:38:07 on SEP 18. 1985 for CCtd=AVES Page 1 1 SUBROUTINE UMODEL(ITIME) 2 ^CONTINUE WITH MCI RETURN 3 TREES=0. 4 TTRHA =0. 5 ATTR=0. 6 ALLBET=0. 7 ALLATT=0. 8 TEGS=0. 9 TTEGS-O. 10 TSLRV=0. 11 TTSLRV=0. 12 WSLRVT-O. 13 TWLRV'O. 14 WLRT=0. 15 TCATS=0. 16 TBETS=0. 17 ALLEM=0. 18 AVDBH=0. 19 DM2»0. 20 ACATS'O. 21 DO 10 1=1.6 22 C Total number of trees per hectare 23 TTRHA=TTRHA+TRHA<I) 24 C Total number of trees In each DBH class 25 TOTTR( I )•TRHA(I ) * S TAR 26 10 TREES = TREES+TOTTR( I ) 27 DO 15 1-1.6 28 C Average diameter of stand 29 DM1(I)=TRHA(I)*DIAM(I) 30 15 DM2=DM2+DM1(I) 31 AVDBH=DM2/TTRHA 32 33 DO 20 1=1,6 34 C Proportion of total trees represented by each DBH class 35 20 PR0ST<I )=T0TTR(I l/TREES 36 00 30 1=1.6 37 C Relative 'attractiveness' of trees In each DBH class in the stand 38 TRELAT(I)-RELAT(I)/0.95 39 C Total 'attractiveness' of trees In each DBH class In the stand 40 T0TAT(I )»TRELAT(I )*PR0ST(I) 41 IF(T0TAT(I).E0.0)PR0BET(I)=0 _ 42 C Sum of 'attractiveness' for a l l DBH classes ^ 43 30 ATTR = ATTR+TOTAT ( I ) CT> 44 45 C Total number of mountain pine beetles in the stand 46 ALLBET*PBPOP*STAR 47 PFR=PBP0P/10O0 48 49 50 DO 40 1=1,6 51 C Percentage of MPB population per DBH class 52 PR0BET(I )=TOTAT(I )/ATTR 53 C Total number of MPB per DBH class in the stand 54 T0TBET(I )»PROBET(I ) *ALtBET 55 C Percentage of MPB population that 1s female 56 PROFEMfI)»0.6919-(0.0035*DIAM(I)) 57 C Total number of attacking MPB per DBH class In the stand 58. TOTTAT(I )=TOTBET(I)*PROFEM(I) 59 C Total number of attacks in the stand 60 61 C Attacked surface area (square meters) per tree for each DBH c l a s s 62 A5RF(I)'-3.78+(0.3221*DIAM(I)) 63 AMOD«TH(PFR,1.0.10.0.1.0.1.1) 64 ATSA(I)=ASRF(I)*AM0D 65 C Mountain pine beetle attack density 66 ATDN=52.33+(7.56*PFR) 67 IF(PFR.GE.3.0)ATDN=75.0 6B ATMD»TH(PFR,1.0.10.0.1.0.1.1) 69 AT0EN«ATDN*ATMD 70 C Total number of attacks per tree 71 TATT(I )>ATSA(I )*ATDEN 72 73 C Total number of trees k i l l e d for each DBH c l a s s 74 TREKILU )*T0TTAT< I )/TATT( I ) 75 C Number of trees k i l l e d per hectare for each DBH c l a s s 76 TREKHA(I )«TREKIL(I)/STAR 77 78 C Phloem thickness for trees In each DBH c l a s s 79 PHTH(I>«0.3072*(0.0523*DIAM(I)) 80 C Number of eggs per female 81 EGFM(I )»62.878-(37 027*PHTH(I)) + ( 15.529*(PHTH(I )**2 ) ) 82 C Percent of females mated 83 FMTR(I)«0.95*TATT(I) 84 C Number of eggs per tree 85 EGTR( I )»FMTRU )*EGFM( I) 86 C Number of eggs per hectare 87 EGHA(I)=EGTR(I)*TREKHA(I) 88 TEGS = TEGS+EGHA(I ) 89 C Percentage of eggs that hatch 90 EGGA«TH(AVDBH,23.5,24.5,0.90,0.98) 91 GMD(1)=0.92+(0 002*DIAM(I)) 92 EGHCH(I)=GMO(I)* EGGA 93 C Number of small larvae per tree 94 SLRV(I)=EGTR(I)*EGHCH(I) 95 SLRVH(I)=SLRV(I)* TREKHA(I) 96 97 C Autumn mortality 98 AMRT(I)*C 30052*(0.02031*DIAM(I))-(0.0005035•(DIAM( I)**2)) 99 DM0D«DSP(AVDBH,23.5.24.0.1.2.1.0) 100 AUTMRT(I ) =AMRT(I)*DM0D 101 WWSLRV(I)»SLRV(I)•(1.0-AUTMRT(I)) 102 TRMRT(I)*(TRH(I)-TRHA(I))/TRH(I) 103 104 C I n i t i a l winter mortality 105 WNMRT(I)«0.30052*(0.02031*DIAM(I))-(0.0005035*(DIAM(I)•*2)) 106 WMOD-DSP(PFR.10.0,20.0.1.0.1.2) 107 WINMR T( I ) = WNMR T(I)* WMOD 108 WSLRV(I)»WWSLRV(I)•(1 0-WINMRT(I)) 109 WSLRVH(I)*WSIRV(I)*TREKHA(I) 110 C Total number of larvae a l i v e per hectare (woodpecker food source) 111 40 WSLRVT»WSLRVT+W5LRVH(I) 112 C 113 WS«WSLRVT**0.3333 114 C Number of woodpeckers per 10O hectares for the winter 115 WPHHA«-38.953*(2.6661*WS)-(0.027628*WS«*2) 116 IF(WS.LT.20.0)WPHHA=2.0 117 IF(WS.GT.45.0)WPHHA = 25.0 118 C Number of woodpeckers per hectare for the winter 119 WPHA=WPHHA/100.0 120 C Number of woodpeckers In the stand for the winter 121 C Kcals required per gram of woodpecker weight 122 WKGD=0.64-(0.008*TEMP) 123 C Kcals required per woodpecker per day 124 WPKD=WKGD*WPWT 125 C Proportion of MPB larvae in woodpeckers' diets 126 DIET=4.6734-(0.49062*WS)+(0.01608*WS**2)-(0.0001558*WS+*3) 127 IF(WS.GT.45.0)DIET=0.95 128 IF(WS.LT.25.0)DIET=0.02 129 C Number of larvae required per woodpecker per day 130 CATWPO=(WPKD*DIET)/CALRV 131 CATWPW=CATWPD*WINTER 132 C Number of larvae required per hectare per day by woodpeckers 133 CATWWH*WPHA*CATWPW 134 WNM=CATWWH/WSLRVT 136 C Percentage of larvae available per tree 137 UNVL=UNV/AMOD 138 AVL»TH(WS.25.0.50.0.0.20.0.80) 139 SVD-1.0-(AVL+UNVL) 140 DO 50 1=1.6 141 C Number of larvae per tree a v a i l a b l e to woodpeckers 142 A VA IL (I )=AVL*WSLRV(I) 143 AVLHA(I)=AVAIL(I)*TREKHA( I ) 144 C Number of larvae per tree protected by snow 145 UNAVAL(I)"UNVL*WSLRV(I) 146 UNVLH(I)*UNAVAL(I)'TREKHA( I ) 147 C Number of larvae per tree unavailable to woodpeckers 148 SAVED(I )=SVD*WSLRV(I) 149 50 SVDH(I)=SAVED(I)*TREKHA(I) 150 151 DO 60 1*1.6 152 DSTWPF(I)=WSLRVH(IVWSLRVT 153 C Larvae consumed per hectare during winter for each DBH class 154 CCWPH(I)=CATWWH*DSTWPF(I) 155 C Number of 'woodpeckered' trees per hectare In each DBH class 156 . WPTRHA(I)=CCWPH(I)/AVAIL(I ) 157 IF (WPTRHA(I).GT.TREKHA(I))WPTRHA(I)=TREKHA(I) 158 IF(WPTRHA(I).GT.TREKHA(I))UWPTHA(I ) =0 159 IF(WPTRHA(I) LE.0.)WPTRHA(I)=0. 160 C Number of 'non-woodpeckered' trees per hectare In each DBH class 161 UWPTHA(I)=TREKHA(1 )-WPTRHA(I) 162 IF(UWPTHA(I) LE.0.)UWPTHA(I)=0. 163 164 C Larval mortality due to cold for each DBH class 165 CLDU)=0.30052 + (0.02031 *DIAM(I))-(0.0005035*(DIAM(I)* *2)) 166 CM0D=0SP(PFR,10.0.50.0.1.0.1.1) 167 C0LD<I)»CLD(I)*CM00 168 C Larval mortality due to desslcatlon for each DBH class 169 DSC(I)=O.44-(0.006 *DIAM( I )) 170 OSCMD=DSP(PFR.10.0.50.0.1.0.1.2) 171 DESC(I)=DSC(I)*DSCMD 172 C Numbar of larvae per 'woodpeckered' tree dying during the winter 173 DWTRS(I) = AVAIL(I ) + (DESC(I)*UNAVAL(I)) + (CCLD(')*SAVED(I)) 174 C Number of larvae per 'non-woodpeckerac" tree dying during the wlnte,-175 DNWTRS(I)«(DESC(I)*UNAVAL(I)) + ((C0LD(I)*DESC(I))MSAVED( I ) . 176 1 +AVAIL(I>)) 177 C Number of larvae that survived winter per 'woodpeckered' tree 178 CWTAW(I)"=WSLRV(I)-DWTRS(I) ^ 179 IF(CWTAW(I).LT 0)CWTAW(I)=0 VD 180 C Number of larvae that survived winter per 'non-woodpeckered' tree 181 CNWTAW(I)*WSLRV(I)-DNWTRS(I) 182 CAWTAW(I)'WPTRHA(I)*CWTAW(I) 183 CANWTW(I)»UWPTHA(I)*CNWTAW(I) 184 TCATAW(I)«CAWTAW(I)+CANWTW(I) 185 C Total number of larvae a l i v e at end of winter 186 ACATS=ACATS+TCATAW(I) 187 188 C Spring mortality 189 SPMR(I)=0.30052+(0.02031*DIAM(I))-(0.0005035*(DIAM(I)**2)) 190 SPMOD»DSP(AVOBH,23.5.24.0,1.3.1.0) 191 SPMRT(I)»SPMR(I )*SPM0D 192 SSWT(I )«CWTAW(I ) *( 1 .0-(SPMRT(I)*DSCM0D)) 193 SSNWT(I)«CNWTAW(I)*(1.0-SPMRT( I )) 194 195 C Early summer mortality 196 ESMR(I)=0.84-(0.016*DIAM(I)) 197 SMM0D=DSP(AVDBH,23.5.24.0.1.3.1.0) 198 ESMRT(I)=ESMR(I)*SMM0D 199 200 C Number of MPB adults emerging per 'woodpeckered' tree 201 TBEWTR(I)=SSWT(!)*(1.0-ESMRT(I)*DSCM0D) 202 TBEWH(I)*TBEWTR(I)•WPTRHA(I) 203 WEAR(I) = TBEWTR(I)/TATT( I ) 204 C Number of MPB adults emerging per 'non-woodpeckered' tree 205 TBENWT(I)=SSNWT(I)*(1.0_ESMRT(I)) 206 TBENH(I)«TBENWT(I)*UWPTHA(I) 207 WEARN(I)«TBENWT(I)/TATT( I) 208 C Total number of MPB adults emerging from each DBH class 209 TBETEM(I)*TBEWH(I)+TBENH(I) 210 IF(TBETEM(I).LT.O)TBETEM(I)=0 211 TBETS=TBETS+TBETEM(I) 212 C Total number of MPB adults emerging In the stand 213 60 ALLEM=TBETS*STAR 214 215 DO 70 I»1.6 216 70 TRHA(I)=(TOTTR(I)-TREKIL(I))/STAR 217 218 TB'TBETS/lOOOO.O 219 C Summer b i r d species d e n s i t i e s per 100 hectares 220 HAWPN=0.54972+(2.4594•TB)-(0.32531*TB* *2) 221 IF(TB.GT.3.0)HAWPN=5.0 222 BRCRN-3.4162+(8.8138*TB)-(1.1294*TB**2) 223 IF(TB.GT.3.0)BRCRN=20.0 224 RBNHN-4.3156+(11 099*TB)-(1.435B*TB**2) 225 IF(TB.GT.3.0)RBNHN=25.0 226 227 C Percentage of MPB adutts in summer b i r d s ' d i e t s 228 HAWPD=0.010919-1.005405*TB) +(0.08968*TB**2)-(0.013995*TB**3) 229 IF(TB.GT.3.0)HAWP0=0.50 230 BRCRD=0.0174 19-(0.004630*TB)+(0.051552*TB**2)-(0 0079595*TB**3) 231 IF(TB.GT.3.0)BRCR0=0.30 232 RBNHD=0.015068 -(0.0058746*TB) + (0.03099* TB* *2)-(0.0050352*TB* *3) • 233 IF(TB.GT.3.0)RBNH0»0.20 234 235 C Kcals required per b i r d species per day 236 CAIHW«0.5404*(HAWPW**0.7545>* 1 .5 237 CALBC-1.5720*<BRCRW**0.6210)*1 .5 238 CALRB-1 . 5720*(RBNHW**0.6210)«1.5 239 240 C Total number of MPB adults consumed per b i r d species 241 TPBHWM(CALHW*HAWPD)/CALAD)'DAYAV*(HAWPN/100.0) 242 HWA«TPBHW/TBETS 243 TPBBC=((CALBC*BRCRD)/CALAD)*0AYAV*(BRCRN/100.0) 244 BRA=TPBBC/TBETS 245 TPBRB"((CALRB *RBNHD)/CALAD)*DAYAV*(RBNHN/100.0) 246 RBA=TPBRB/TBETS 247 248 C Total number of MPB adults consumed by a l l b i r d species 249 BBIF»TPBHW+TPBBC+TPBRB 250 BBA«BBIF/TBETS 251 C Total number of MPB adults k i l l e d 'in f l i g h t ' by other causes 252 BOIF«ALLEM*OIFMRT 253 C Total number of MPB adults k i l l e d 'in f l i g h t ' by a l l causes 254 BKIF =BBIF*B0IF 255 PBHA=(ALLEM-BKIF)/STAR 256 257 C Proportion of MPB adults dispersing from the stand 258 DISP»DSP(AVDBH.23.5.24.0.0.40.0.01) 259 ALDISP-PBHA*DISP 260 C New mountain pine beetle population 261 PBPOP-(PBHA-ALDISP) 262 C Ratio of Increase: population t/populatlon t-1 263 R0I=PBP0P/BLAST 264 BLAST-PBPOP 265 RETURN 266 END 267 SUBROUTINE UIN1T 268 CALL CMREADI 'MCI ' ) 269 RETURN 270 END 27« FUNCTION TH(X.X1.X2.V1.¥2) 272 TH'VI 273 IFCX.LT.XI)RETURN 274 TH«Y2 275 IF(X.GE.X2 )RETURN 276 TH«(V 1-V2 )/(X « - X 2 X - X 2 ) * Y 2 to 277 RETURN 278 END APPENDIX 4 GLOSSARY OF SIMULATION MODEL VARIABLES 1 6 3 164 ACATS: T o t a l number of l a r v a e t h a t s u r v i v e d the w i n t e r ALDSP: T o t a l number of b e e t l e s d i s p e r s i n g out of the s t a n d ALLBET: T o t a l number of b e e t l e s i n the s t a n d i n e a r l y autumn ALLEM: T o t a l number of emerging b e e t l e s i n the s t a n d i n e a r l y summer AMOD: A t t a c k m o d i f i e r (based on b e e t l e p o p u l a t i o n d e n s i t y ) AMRT: I n i t i a l autumn m o r t a l i t y ASRF: I n i t i a l a t t a c k e d s u r f a c e a r e a (m 2) per t r e e ATDEN: F i n a l b e e t l e a t t a c k d e n s i t y ( a t t a c k s / m 2 ) ATDN: I n i t i a l a t t a c k d e n s i t y ( a t t a c k s / m 2 ) ATMD: A t t a c k m o d i f i e r (based on b e e t l e p o p u l a t i o n d e n s i t y ) ATSA: F i n a l a t t a c k e d s u r f a c e (m 2) a r e a per t r e e ATTR: Sum ' a t t r a c t i v e n e s s ' of t h e s t a n d AVAIL: Number of l a r v a e per t r e e a v a i l a b l e t o w i n t e r woodpeckers AVDBH: Average DBH of the s t a n d AVL: p e r c e n t i f b e e t l e brood p e r t r e e a v a i l a b l e t o w i n t e r woodpeckers AVLHA: Number of l a r v a e per h e c t a r e a v a i l a b l e t o w i n t e r woodpeckers AUTMRT: T o t a l autumn m o r t a l i t y ( p e r c e n t ) of l a r v a l p o p u l a t i o n k i l l e d per t r e e ) BBA: P e r c e n t of emerging a d u l t b e e t l e p o p u l a t i o n k i l l e d d u r i n g f l i g h t p e r i o d by a l l b i r d s BBIF: Number of emerging a d u l t b e e t l e s k i l l e d d u r i n g f l i g h t p e r i o d by a l l b i r d s BKIF: T o t a l number of emerging a d u l t b e e t l e s k i l l e d d u r i n g f l i g h t p e r i o d by a l l causes BLAST: Mountain p i n e b e e t l e p o p u l a t i o n a t time t-1 BOIF: Number of emerging a d u l t b e e t l e s k i l l e d d u r i n g f l i g h t p e r i o d by causes o t h e r than b i r d s 165 BRA: p e r c e n t of emerging a d u l t b e e t l e p o p u l a t i o n consumed by a l l brown c r e e p e r s BRCRD: p e r c e n t of brown c r e e p e r s ' d i e t r e p r e s e n t e d by a d u l t mountain p i n e b e e t l e s BRCRN: Number of brown c r e e p e r s per 1 0 0 . 0 h e c t a r e s d u r i n g the summer BRCRW: Weight i n grams of one brown c r e e p e r CALAD: V a l u e i n K i l o c a l o r i e s of one a d u l t mountain p i n e b e e t l e CALBR: Number of K i l o c a l o r i e s per day r e q u i r e d by one brown c r e e p e r CALHW: Number of K i l o c a l o r i e s per day r e q u i r e d by one h a i r y woodpecker CALRB: Number of K i l o c a l o r i e s per day r e q u i r e d by one r e d - b r e a s t e d n u t h a t c h CALRV: V a l u e i n K i l o c a l o r i e s of one mountain p i n e b e e t l e l a r v a CANWTW: Number of l a r v a e i n a l l non-woodpeckered t r e e s a l i v e a t the end of w i n t e r CATWPD: Number of l a r v a e consumed by one woodpecker i n one day CATWPW: Number of l a r v a e consumed by one woodpecker d u r i n g the w i n t e r CATWWH: Number of l a r v a e consumed per h e c t a r e d u r i n g the w i n t e r by a l l woodpeckers CAWTAW: Number of l a r v a e i n a l l woodpeckered t r e e s a l i v e a t the end o f t h e w i n t e r CCWPH: Number of l a r v a e consumed per h e c t a r e d u r i n g t he w i n t e r by a l l woodpeckers f o r each t r e e d i a m e t e r c l a s s CLD: I n i t i a l l a r v a l m o r t a l i t y due t o c o l d t e m p e r a t u r e s 166 CMOD: M o d i f i e r f o r m o r t a l i t y due t o c o l d t e m p e r a t u r e s (based on p o p u l a t i o n d e n s i t y ) CNWTAW: Number of l a r v a e per non-woodpeckered t r e e a l i v e a t the end of w i n t e r COLD: F i n a l m o r t a l i t y due t o c o l d t e m p e r a t u r e s ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d per t r e e ) CWTAW: Number of l a r v a e per woodpeckered t r e e a l i v e a t the end of w i n t e r DAYAV: Number of days i n a d u l t b e e t l e f l i g h t / a t t a c k p e r i o d DESC: F i n a l m o r t a l i t y due t o d e s i c c a t i o n ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d p er t r e e ) DIAM: Mean d i a m e t e r (cm a t DBH) of the di a m e t e r c l a s s e s DIET: p e r c e n t of w i n t e r woodpeckers' d i e t r e p r e s e n t e d by mountain p i n e b e e t l e l a r v a e DISP: p e r c e n t of b e e t l e p o p u l a t i o n d i s p e r s i n g out of the s t a n d DMOD: DM1: Sum o f t r e e d i a m e t e r s per h e c t a r e f o r each d i a m e t e r c l a s s DM2: Sum of t r e e d i a m e t e r s per h e c t a r e f o r a l l d i a m e t e r c l a s s e s DNWTRS: Number of l a r v a e d y i n g d u r i n g t he w i n t e r per non-woodpeckered t r e e DSC: I n i t i a l m o r t a l i t y due t o d e s i c c a t i o n DSCMD: M o d i f i e r f o r m o r t a l i t y due t o d e s i c c a t i o n (based on p o p u l a t i o n d e n s i t y ) DSCMOD: S p r i n g and e a r l y summer d e s i c c a t i o n m o d i f i e r ( b a s e d on l a r v a l p o p u l a t i o n d e n s i t y ) DSTWPF: D i s t r i b u t i o n of woodpecker f e e d i n g DWTRS: Number of l a r v a e d y i n g d u r i n g t he w i n t e r per woodpeckered t r e e EGFM: Number of eggs p e r female b e e t l e EGGA: I n i t i a l p e r c e n t a g e o f eggs t h a t h a t c h 1 6 7 EGHA: Number of eggs per h e c t a r e i n each d i a m e t e r c l a s s EGHCH: F i n a l p e r c e n t a g e of eggs t h a t h a t c h EGTR: Number of eggs l a i d per t r e e i n each d i a m e t e r c l a s s ESMR: I n i t i a l e a r l y summer m o r t a l i t y per d i a m e t e r c l a s s ESMRT: F i n a l e a r l y summer m o r t a l i t y per d i a m e t e r c l a s s FMTR: Number of female b e e t l e s p e r t r e e GMD: Egg h a t c h m o d i f i e r HAWPD: p e r c e n t of h a i r y woodpeckers d i e t r e p r e s e n t e d by a d u l t mountain p i n e b e e t l e s HAWPN: Number of h a i r y woodpeckers per 100.0 h e c t a r e s d u r i n g the summer HAWPW: Weight i n grams of one h a i r y woodpecker HWA: p e r c e n t of emerging a d u l t b e e t l e p o p u l a t i o n consumed by a l l h a i r y woodpeckers OIFMRT: p e r c e n t of emerging a d u l t p o p u l a t i o n k i l l e d d u r i n g f l i g h t p e r i o d by causes o t h e r t h a n b i r d s PBHA: Number of b e e t l e s per h e c t a r e r e m a i n i n g i n the s t a n d a f t e r d i s p e r s a l PBPOP: Number of b e e t l e s per h e c t a r e i n e a r l y autumn PFR: PBPOP/1000.0 PHTH: Tree phloem t h i c k n e s s (mm) PROBET: p e r c e n t of b e e t l e p o p u l a t i o n ' a s s i g n e d ' t o each d i a m e t e r c l a s s PROFEM: p e r c e n t of b e e t l e p o p u l a t i o n t h a t i s female PROST: p e r c e n t of t r e e s i n the s t a n d r e p r e s e n t e d by each d i a m e t e r c l a s s RBA: p e r c e n t of emerging a d u l t b e e t l e p o p u l a t i o n consumed by a l l r e d - b r e a s t e d n u t h a t c h e s 168 RBNHD: p e r c e n t of r e d - b r e a s t e d n u t h a t c h s ' d i e t r e p r e s e n t e d by a d u l t mountain p i n e b e e t l e s RBNHN: Number of r e a d - b r e a s t e d n u t h a t c h e s p e r 100.0 h e c t a r e s d u r i n g t h e summer RBNHW: Weight i n grams of one r e d - b r e a s t e d n u t h a t c h RELAT: ' I n i t i a l a t t r a c t i v e n e s s ' of t r e e s i n each d i a m e t e r c l a s s ROI: R a t i o of b e e t l e p o p u l a t i o n a t time t t o p o p u l a t i o n a t time t-1 SAVED: F i n a l number of l a r v a e per t r e e u n a v a i l a b l e t o woodpeckers but not p r o t e c t e d by snow SLRV: I n i t i a l number of l a r v a e per t r e e a l i v e a t the b e g i n n i n g of autumn SLRVH: I n i t i a l number of l a r v a e per h e c t a r e a l i v e a t t h e b e g i n n i n g of autumn SMMOD: M o d i f i e r f o r e a r l y summer m o r t a l i t y (based on l a r v a l p o p u l a t i o n d e n s i t y ) SPMOD: M o d i f i e r f o r s p r i n g m o r t a l i t y ( b a s e d on p o p u l a t i o n d e n s i t y ) SPMR: I n i t i a l s p r i n g m o r t a l i t y ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d p er t r e e ) SPMRT: F i n a l s p r i n g m o r t a l i t y ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d p er t r e e ) SSNWT: Number of l a r v a e per non-woodpeckered t r e e a l i v e a t the end of s p r i n g SSWT: Number of l a r v a e per woodpeckered t r e e a l i v e a t t h e end of s p r i n g STAR: Sta n d a r e a ( h e c t a r e s ) SVD: I n i t i a l number of l a r v a e per t r e e u n a v a i l a b l e t o woodpeckers but not p r o t e c t e d by snow SVDH: F i n a l number of l a r v a e per t r e e u n a v a i l a b l e t o woodpeckers but not p r o t e c t e d by snow 169 TATT: T o t a l number of a t t a c k s per t r e e TB: TBETS/10,000.0 TBENH: Number of b e e t l e s p e r h e c t a r e emerging from non-woodpeckered t r e e s TBENWT: T o t a l number of b e e t l e s emerging from non-woodpeckered t r e e s TBETEM: T o t a l number of b e e t l e s emerging from t h e e a r l y summer per di a m e t e r c l a s s TBETS: T o t a l number of b e e t l e s emerging i n t h e e a r l y summer TBEWH: Number of b e e t l e s per h e c t a r e emerging form woodpeckered t r e e s TBEWTR: T o t a l number of b e e t l e s per h e c t a r e emerging from woodpeckered t r e e s TCATAW: T o t a l number of l a r v a e a l i v e a t the end of w i n t e r TEGS: T o t a l number of eggs h a t c h i n g per h e c t a r e TEMP: Mean w i n t e r temperature (°C) TOTAT: ' T o t a l a t t r a c t i v e n e s s ' of t r e e s i n each d i a m e t e r c l a s s TOTBET: T o t a l number of b e e t l e s ' a s s i g n e d ' t o each d i a m e t e r c l a s s TOTTAT: T o t a l number of a t t a c k s per di a m e t e r c l a s s TOTTR: T o t a l number of t r e e s i n each d i a m e t e r c l a s s TPBBR: T o t a l number of a d u l t b e e t l e s consumed per h e c t a r e i n summer by brown c r e e p e r s TPBHW: T o t a l number of a d u l t b e e t l e s consumed per h e c t a r e i n summer by h a i r y woodpeckers TPBRB: T o t a l number of a d u l t b e e t l e s consumed per h e c t a r e i n summer by r e d - b r e a s t e d n u t h a t c h e s TREES: T o t a l number of t r e e s (>12.7 cm DBH) i n t h e s t a n d TREKHA: Number of t r e e s k i l l e d per h e c t a r e per y e a r i n each d i a m e t e r c l a s s TREKIL: Number of t r e e s k i l l e d per year i n each d i a m e t e r c l a s s 170 TRELAT: ' R e l a t i v e a t t r a c t i v e n e s s ' of t r e e s i n each diameter c l a s s TRH: Number of t r e e s per h e c t a r e i n each d i a m e t e r c l a s s TRHA: Number of t r e e s p e r h e c t a r e i n each d i a m e t e r c l a s s TRMRT: C u m u l a t i v e t r e e m o r t a l i t y f o r each d i a m e t e r c l a s s TTRHA: T o t a l number of t r e e s per h e c t a r e UNAVAL: Number of l a r v a e per t r e e p r o t e c t e d by snow UNV: I n i t i a l p e r c e n t of b e e t l e brood per t r e e p r o t e c t e d by snow UNVL: F i n a l p e r c e n t of b e e t l e brood per t r e e p r o t e c t e d by snow UNVLH: Number of l a r v a e per h e c t a r e p r o t e c t e d by snow UWPTHA: Number of non-woodpeckered t r e e s per h e c t a r e WEAR: R a t i o of emerging b e e t l e s t o a t t a c k i n g b e e t l e s f o r woodpeckered t r e e s WEARN: R a t i o of emerging b e e t l e s t o a t t a c k i n g b e e t l e s f o r non-woodpeckered t r e e s WINMRT: F i n a l g e n e r a l w i n t e r m o r t a l i t y ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d p er t r e e ) WINTER: Number of days i n woodpecker w i n t e r f e e d i n g p e r i o d WKGD: Energy r e q u i r e m e n t ( K i l o c a l o r i e s per gram body weight) f o r w i n t e r woodpeckers WMOD: M o d i f i e r f o r g e n e r a l w i n t e r m o r t a l i t y (based on p o p u l a t i o n d e n s i t y ) WNW: p e r c e n t of l a r v a l p o p u l a t i o n consumed by a l l woodpeckers d u r i n g t h e w i n t e r WNMRT: I n i t i a l g e n e r a l w i n t e r m o r t a l i t y ( p e r c e n t of l a r v a l p o p u l a t i o n k i l l e d p er t r e e WPKD: Woodpecker e n e r g e t i c r equirement i n k i l o c a l o r i e s per day WPHA: Number of woodpeckers per h e c t a r e WPHHA: Number of woodpeckers per 100.0 h e c t a r e s 171 WPSTD: Number o f woodpeckers i n t h e s t a n d WPTRHA: Number of woodpeckered t r e e s per h e c t a r e i n each d i a m e t e r c l a s s WPWT: Mean w i n t e r woodpecker weight (grams) WS: (WSLRVT)**0.33333 WSLRB: Number o f l a r v a e per t r e e a l i v e a f t e r g e n e r a l w i n t e r m o r t a l i t y WSLRVH: Number of l a r v a e per h e c t a r e a l i v e a f t e r g e n e r a l w i n t e r m o r t a l i t y WSLRVT: T o t a l number of l a r v a e p e r h e c t a r e a l i v e a f t e r g e n e r a l w i n t e r m o r t a l i t y WWSLRV: Number of l a r v a e per t r e e a l i v e a t the b e g i n n i n g of w i n t e r APPENDIX 5 INITIAL VALUES OF SELECTED MODEL PARAMETERS 172 173 11. INITIAL VALUES OF SELECTED MODEL PARAMETERS St a n d a r e a : 20 h e c t a r e s I n i t i a l mountain p i n e b e e t l e d e n s i t y : 750 b e e t l e s per h e c t a r e I n i t i a l w i n t e r woodpecker d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 2 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 0.2 i n d i v i d u a l s p e r 100 h e c t a r e s I n i t i a l summer h a i r y woodpecker d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 1 i n d i v i d u a l per 100 h e c t a r e s (Thinned s t a n d ) : 0.1 i n d i v i d u a l per h e c t a r e I n i t i a l summer brown c r e e p e r d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 4 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 0.4 i n d i v i d u a l per h e c t a r e I n i t i a l summer r e d - b r e a s t e d n u t h a t c h d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 5 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 0.5 i n d i v i d u a l per h e c t a r e Maximum summer h a i r y woodpecker d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 5 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 0.5 i n d i v i d u a l s per 100 h e c t a r e s 174 Maximum summer brown c r e e p e r d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 20 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 2 i n d i v i d u a l per h e c t a r e Maximum summer r e d - b r e a s t e d n u t h a t c h d e n s i t y ( C o n t r o l and Senescent s t a n d s ) : 25 i n d i v i d u a l s per 100 h e c t a r e s (Thinned s t a n d ) : 2.5 i n d i v i d u a l per h e c t a r e C a l o r i c v a l u e of one mountain p i n e b e e t l e l a r v a : 0.062 k i l o c a l o r i e s C a l o r i c v a l u e of one mountain p i n e b e e t l e a d u l t : 0.098 k i l o c a l o r i e s I n i t i a l r a t e of mountain p i n e b e e t l e e m i g r a t i o n : 1% Maximum r a t e of mountain p i n e b e e t l e e m i g r a t i o n : 40% I n i t i a l C o n t r o l s t a n d s t r u c t u r e ( t r e e s per h e c t a r e ) i n t he 15, 25, 30, 35, and 40-cm DBH c l a s s e s : 385 495 440 330 205 90 I n i t i a l Senescent s t a n d s t r u c t u r e ( t r e e s per h e c t a r e ) i n the 15, 25, 30, 35, and 40-cm DBH c l a s s e s : 100 150 225 325 550 350 I n i t i a l T h i n n e d s t a n d s t r u c t u r e ( t r e e s per h e c t a r e ) i n the 15, 25, 30, 35, and 40-cm DBH c l a s s e s : 385 495 22 17 10 5 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0096698/manifest

Comment

Related Items