UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Litter decomposition and nutrient turnover in three ecosystem types of the coastal western hemlock biogeoclimatic… De Catanzaro, Jennifer Barbara 1979

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

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1979_A6_7 D43.pdf [ 5.86MB ]
Metadata
JSON: 831-1.0100225.json
JSON-LD: 831-1.0100225-ld.json
RDF/XML (Pretty): 831-1.0100225-rdf.xml
RDF/JSON: 831-1.0100225-rdf.json
Turtle: 831-1.0100225-turtle.txt
N-Triples: 831-1.0100225-rdf-ntriples.txt
Original Record: 831-1.0100225-source.json
Full Text
831-1.0100225-fulltext.txt
Citation
831-1.0100225.ris

Full Text

LITTER DECOMPOSITION AND NUTRIENT TURNOVER IN THREE ECOSYSTEM TYPES OF THE COASTAL WESTERN HEMLOCK BIOGEOCLIMATIC ZONE BY JENNIFER BARBARA DE CATANZARO B.Sc. (Hons), C a r l e t o n U n i v e r s i t y , 1977 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (FACULTY OF FORESTRY) We accept t h i s t h e s i s as conforming to the requ i r e d standards THE UNIVERSITY OF BRITISH COLUMBIA June, 1979 (c) J e n n i f e r Barbara deCatanzaro In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e 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 a n d s t u d y . I f u r t h e r a g r e e 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 o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s 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 o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t 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 . D e p a r t m e n t o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook Place Vancouver, Canada V6T 1W5 ABSTRACT R a t e s o f l i t t e r d e c o m p o s i t i o n , n u t r i e n t r e l e a s e , and t o t a l f o r e s t f l o o r t u r n o v e r were measured on two r e p l i c a t e s o f t h r e e e c o s y s t e m t y p e s i n t h e C o a s t a l W e s t e r n Hemlock Zone o f B r i t i s h C o l u m b i a , i n an a t t e m p t t o e s t a b l i s h whether o r n o t ecosystem t y p e s c o u l d be d i f f e r e n t i a t e d on t h e b a s i s o f f u n c t i o n a l p a r a m e t e r s . L i t t e r bags o f two mesh s i z e s and l e a f t e t h e r i n g were used t o compare w e i g h t l o s s e s and n u t r i e n t dynamics o f s p e c i f i c l i t t e r comp-o n e n t s . The d r y w e i g h t l o s s e s o f c o n i f e r n e e d l e s c o n f i n e d i n 1 mm mesh bags ranged f r o m 30 t o 40 % a f t e r one y e a r . T h e r e was no s i g n i f -i c a n t d i f f e r e n c e between s i t e s , Weight l o s s o f s a l a l l e a v e s on x e r i c s i t e s ranged f r o m 20 % a f t e r one y e a r f o r samples c o n f i n e d i n 1 mm mesh bags t o 45 % f o r t e t h e r e d l e a f samples. B i g - l e a f maple w e i g h t l o s s ranged from 15% f o r samples c o n f i n e d i n 1 mm mesh bags t o 60 % f o r t e t h e r e d samples. Twig samples l o s t 7 t o 21 % o f t h e i r w e i g h t on a l l s i t e s a f t e r s i x months, w i t h s l i g h t l y h i g h e r v a l u e s o c c u r r i n g on the h y g r i c s i t e s , C e l l u l o s e s t r i p s i n 4 mm mesh bags l o s t an a v e r a g e o f 23 % o f t h e i r w e i g h t on t h e - x e r i c , 21 % on t h e m e s i c , and 40 % on th e h y g r i c s i t e s . N u t r i e n t mass and c o n c e n t r a t i o n changes o v e r one y e a r v a r i e d somewhat between d i f f e r e n t t y p e s o f f o l i a g e l i t t e r . The t o t a l mass of K, Mg, and Ca d e c r e a s e d i n a l l l i t t e r t y p e s on a l l s i t e s , N and P mass changes were more v a r i a b l e , The r e l a t i v e m o b i l i t y o f n u t r i e n t s i i r e l e a s e d f r o m decomposing c o n i f e r l i t t e r was Ca> M g ? P > K > N , and from b r o a d - l e a f l i t t e r was C a > M g > K > P > N . The low m o b i l i t y o f K was c o n c l u d e d t o be due t o l e a c h i n g o f t h i s element from t h e l i t t e r p r i o r t o i t s c o l l e c t i o n f o r t h e s t u d y . Numbers o f f a u n a i n t h e f o r e s t f l o o r were compared on one r e p l i -c a t e o f each o f t h e ecosystem t y p e s a t s i x week i n t e r v a l s t h r o u g h o u t th e y e a r . M i c r o - f a u n a were more abundant on t h e x e r i c and m e s i c s i t e s , w h i l e macro- and meso-fauna were more numerous on t h e h y g r i c s i t e s . Numbers were l o w e s t on a l l s i t e s when f o r e s t f l o o r m o i s t u r e was l o w e s t i n A u g u s t . A t o t h e r t i m e s o f t h e y e a r p o p u l a t i o n f l u c t u a t i o n s were d i f f e r e n t f o r d i f f e r e n t f a u n a g r o u p s . F o r e s t f l o o r biomass was a l s o measured on one r e p l i c a t e o f each ecosystem t y p e . I t averaged 45,05 tonnes*-ha on t h e r x e r i c s i t e s , -1 1 45.68 tonnes *ha on t h e m e s i c s i t e s 5 , and 25,20 tonnes *ha r" x on t h e h y g r i c s i t e . A n n u a l f o r e s t f l o o r t u r n o v e r r a t e s were c a l c u l a t e d t o be .015 f o r t h e x e r i c , ,017 f o r t h e - m e s i c , and ,040 f o r t h e h y g r i c s a t e s , D i f f e r e n c e s i n t u r n o v e r r a t e s between s i t e s were a t t r i b u t e d •more t o d i f f e r e n c e s i n t h e q u a n t i t i e s - o f wood and herb a c e o u s f o l i a g e on t h e t h r e e s i t e s t h a n t o d i f f e r e n c e s i n t h e d e c o m p o s i t i o n r a t e s o f i n d i v i d u a l s u b s t r a t e s , i i i TABLE OF CONTENTS Page I n t r o d u c t i o n 1 L i t e r a t u r e Review/, 5 2.1 D e f i n i t i o n o f D e c o m p o s i t i o n 5 2.2 S o i l Organisms and D e c o m p o s i t i o n 5 2.3 E n v i r o n m e n t a l F a c t o r s and D e c o m p o s i t i o n 7 2.4 D i r e c t Methods o f M e a s u r i n g D e c o m p o s i t i o n R a t e s 10 2.5 I n d i r e c t Methods o f E s t i m a t i n g D e c o m p o s i t i o n R a t e s ; M a t h e m a t i c a l Models of D e c o m p o s i t i o n 12 S i t e D e s c r i p t i o n s 15 3.1 X e r i c S i t e s 15 3.2 M e s i c S i t e s - 17 3.3 H y g r i c S i t e s 18 Methods 19 4.1 F i e l d Methods 19 4.2 L a b o r a t o r y Methods 23 4.3 A u x i l i a r y S t u d i e s 24 R e s u l t s and D i s c u s s i o n 26 5.1 Weight L o s s 26 R e s u l t s - 26 D i s c u s s i o n 32 5.2 Changes- i n N u t r i e n t C o n c e n t r a t i o n and Mass 39. R e s u l t s 39. i v Page Discussion 50 5.3 Forest Floor Fauna 57 Results 57 Discussion 62 5.4 Forest Floor Biomass 64 Results 64 Discussion 66 General Discussion 69 References 72 Appendix 1 81 V LIST OF TABLES T a b l e Number T i t l e Page 1. S c h e d u l e f o r r e m o v a l of samples o f each l i t t e r t y p e f r o m each s i t e a t each c o l l e c t i o n t i m e . 22 2. P e r c e n t o f o r i g i n a l - W i g c h w e i g h t l o s t a f t e r f o u r months i n t h e f i e l d . 32 3. P e r c e n t o f o r i g i n a l c e l l u l o s e w e i g h t l o s t a f t e r s i x and t w e l v e months i n t h e f i e l d . 33 4. Comparison o f d e c o m p o s i t i o n p a r a m e t e r s o f c o n i f e r f o l i a g e w i t h v a l u e s f r o m o t h e r l i t t e r bag s t u d i e s i n t h e l i t e r a t u r e . 34 5. Comparison o f d e c o m p o s i t i o n p a r a m e t e r s o f b r o a d - l e a f f o l i a g e w i t h v a l u e s from o t h e r l i t t e r bag s t u d i e s i n t h e l i t e r a t u r e . 37 6. C o n c e n t r a t i o n s o f N, P, K, Ca, and Mg i n c o n i f e r l i t t e r on t h e s i x s i t e s a t eaeh!\sampling t i m e , e x p r e s s e d as p e r -c e n t o f d r y w e i g h t 0* s t a n d a r d deviation)... 40 7. P e r c e n t change i n n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass of n e e d l e s c o n f i n e d i n l i t t e r bags from t i m e 0 t o 12 months (% o f o r i g i n a l c o n c e n t r a t i o n o r m a s s). 41 8. C o n c e n t r a t i o n s o f n u t r i e n t s i n s a l a l l i t t e r on t h e two x e r i c s i t e s (100 and 400) a t each s a m p l i n g t i m e , e x p r e s s e d as p e r c e n t o f d r y w e i g h t (+ s t a n d a r d d e v i a t i o n ) . 43 9. P e r c e n t change o f s a l a l n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass from t i m e 0 t o 12 months (.% o f o r i g i n a l c o n c e n t r a t i o n or m ass). 44 v i T a b l e Number T i t l e Page 10, C o n c e n t r a t i o n s o f n u t r i e n t s i n b i g - l e a f maple l i t t e r on t h e two h y g r i c s i t e s a t each s a m p l i n g t i m e , e x p r e s s e d as p e r c e n t o f d r y w e i g h t (+ s t a n d a r d d e v i a t i o n ) . 46 11, P e r c e n t change i n n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass o f b i g - l e a f maple l i t t e r f r o m t i m e 0 t o 12 months (% o f o r i g i n a l c o n c e n t r a t i o n o r m a s s). 47 12, N u t r i e n t c o n c e n t r a t i o n s i n t w i g samples, e x p r e s s e d as p e r -c e n t o f d r y w e i g h t a t t i m e s 0 and 6 months (+ s t a n d a r d d e v i a t i o n ) . 49 13, P e r c e n t change i n n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t - m a s s o f t w i g s from t i m e 0 t o 6 months (% o f o r i g i n a l c o n c e n t r a -t i o n o r m ass), 50 14, Comparison of p e r c e n t change i n mass o f n u t r i e n t s f r o m decomposing c o n i f e r l i t t e r w i t h , v a l u e s from t h e l i t e r a t u r e , 51 15, Comparison o f p e r c e n t change i n mass o f n u t r i e n t s f r o m c decomposing b r o a d l e a f l i t t e r w i t h v a l u e s f r o m t h e l i t e r a t u r e , 52 16, Abundance o f m a j o r groups o f l i t t e r m i c r o - f a u n a p e r m^ a t each s a m p l i n g t i m e (+ s t a n d a r d d e v i a t i o n l , 59_ 17, Abundance o f major groups o f macro- and meso-fauna p e r m^ a t each s a m p l i n g t i m e s t a n d a r d d e v i a t i o n ) , 60 18, C a l c u l a t i o n of t h e d e c o m p o s i t i o n p a r a m e t e r , k., based on r a t e s o f l i t t e r i n p u t and f o r e s t f l o o r biomass f o r t h e l o w e r t r a n s e c t T c e r i c ( 1 0 0 ) , m e s i c ( 2 0 0 ) , and h y g r i c (300) s i t e s , 67. v i i L I ST OF FIGURES F i g u r e Number T i t l e Page 1. T o p o g r a p h i c sequence o f ecosystems i n t h e d r i e r subzone of t h e C o a s t a l W e s t e r n Hemlock B i o g e o c l i m a t i c Zone. 3 2. A e r i a l p h o t o g r a p h o f t h e southwest c o r n e r o f the'U,B.C. R e s e a r c h F o r e s t showing s i t e l o c a t i o n s . 16 3, A v e r a g e w e i g h t l o s s o f c o n i f e r f o l i a g e l i t t e r e x p r e s s e d as p e r c e n t o f o r i g i n a l w e i g h t r e m a i n i n g (+ s t a n d a r d dev-i a t i o n ) " f o r t h e l o w e r t r a n s e c t x e r i c ( 1 0 0 ) , m e s i c ( 2 0 0 ) , and h y g r i c (300) s i t e s . 27 4, A v e r a g e w e i g h t l o s s o f c o n i f e r f o l i a g e l i t t e r e x p r e s s e d as p e r c e n t o f o r i g i n a l w e i g h t r e m a i n i n g (+ s t a n d a r d dev-i a t i o n ) f o r t h e upper t r a n s e c t : x e r i c ( 4 0 0 ) , m e s i c (500)_, and h y g r i c (600).. s i t e s . 28 5. A v e r a g e w e i g h t l o s s - o f c o n f i n e d and u n c o n f i n e d s a l a l and b i g - l e a f maple l i t t e r e x p r e s s e d as p e r c e n t o f t h e o r i g i n a l w e i g h t r e m a i n i n g (+ s t a n d a r d d e v i a t i o n ) f o r t h e l o w e r t r a n s e c t x e r i c (100). and h y g r i c (300) s i t e s . 29 6, Average w e i g h t l o s s o f c o n f i n e d and u n c o n f i n e d s a l a l and b i g - l e a f maple l i t t e r e x p r e s s e d as p e r c e n t o f t h e o r i g i n a l w e i g h t r e m a i n i n g (± s t a n d a r d d e v i a t i o n ) f o r t h e upper t r a n s e c t - x e r i c (400) and h y g r i c (600) s i t e s , 30 v i i i F i g u r e Number T i t l e 7. T o t a l a v e r a g e meso- and macro-fauna numbers i n t h e f o r e s t f l o o r , and f o r e s t f l o o r m o i s t u r e c o n t e n t on t h e l o w e r t r a n s e c t x e r i c ( 1 0 0 ) , m e s i c ( 2 0 0 ) , and h y g r i c (300) s i t e s a t each s a m p l i n g t i m e . 8. Biomass o f t h e L, F, and H h o r i z o n s on t h e l o w e r t r a n s e c t x e r i c ( 1 0 0 ) , m e s i c ( 2 0 0 ) , and h y g r i c (300) s i t e s a t each; samp1ing t i m e . i x ACKNOWLEDGEMENT S I would l i k e to thank the many people who helped i n the planning and execution of the research presented i n t h i s t h e s i s . My advisor, Dr. Hamish Kimmins, was a great source of ideas and encouragement throughout. Min Tsze provided excellent technical assistance i n both f i e l d and l a b -oratory work. Special thanks go to Dr. Alan Carter f o r h i s generous prov-i s i o n of lab space and equipment f o r s o i l fauna extractions and f o r help-f u l discussion throughout that portion of the study, Jane Richards a s s i s t e d with f i e l d work and provided humour i n the early stages of the research, S t a t i s t i c a l analyses were planned with, the help of Denys deCatanzaro and much of the data was processed by computer with the help of Susan Phelps, F i n a l l y , I would l i k e to thank Dr, T.M. B a l l a r d and Dr, John McLean for th e i r guidance as -my committee members and for t h e i r h e l p f u l reviews of the thesis manuscript. INTRODUCTION The d e c o m p o s i t i o n o f p l a n t l i t t e r i s one o f t h e most c r u c i a l s t a g e s i n t h e dynamics o f n u t r i e n t c y c l i n g i n f o r e s t e c o s y s t e m s . I t d e t e r -mines the r a t e a t w h i c h n u t r i e n t s a r e m i n e r a l i z e d and become a v a i l a b l e f o r renewed u p t a k e by p l a n t s and o t h e r o r g a n i s m s , i n c l u d i n g decomposers. The r a t e o f l i t t e r d e c o m p o s i t i o n i s a l s o a major d e t e r m i n a n t o f t h e biomass and n u t r i e n t c o n t e n t o f t h e f o r e s t f l o o r , and i t has an i m p o r t a n t i n f l u e n c e on the p h y s i c a l and c h e m i c a l p r o p e r t i e s o f t h e s o i l . Knowledge o f t h e decom-p o s i t i o n p r o c e s s e s o f a p a r t i c u l a r e c o s y s t e m i s e s s e n t i a l f o r a t h o r o u g h u n d e r s t a n d i n g o f I t s f u n c t i o n a l dynamics. S t u d i e s o f n u t r i e n t c y c l i n g i n d i f f e r e n t f o r e s t s around t h e w o r l d i n d i c a t e t h a t t h e r e a r e b r o a d d i f f e r e n c e s i n t h e magnitude and c h a r a c t e r o f n u t r i e n t c y c l e s i n d i f f e r e n t c l i m a t i c r e g i o n s ( R o d i n and B a z i l e v i c h 1967). A c l a s s i f i c a t i o n s y s t e m w h i c h groups f o r e s t r e g i o n s w i t h s i m i l a r f u n c t i o n a l c h a r a c t e r i s t i c s c o u l d be v e r y u s e f u l f o r p r e d i c t i n g r a t e s o f biomass and n u t r i e n t a c c u m u l a t i o n and t u r n o v e r f o r a f o r e s t o f a p a r t i c u l a r r e g i o n . K r a j i n a (1965) has d e v e l o p e d an e c o l o g i c a l c l a s s i f i c a t i o n f o r B r i t i s h C o l u mbia. Under h i s system, t h e p r o v i n c e i s d i v i d e d i n t o t w e l v e b i o g e o c l i m a t i c z o n e s , w h i c h a r e l a r g e a r e a s w i t h s i m i l a r m a c r o c l i m a t e and c h a r a c t e r i s t i c p a t t e r n s o f v e g e t a t i o n and s o i l development. The zones a r e s u b d i v i d e d i n t o more homogeneous c l i m a t i c u n i t s , o r su b z o n e s , each of w h i c h i s c h a r a c t e r i z e d by a t o p o g r a p h i c s e r i e s o f e c o s y s t e m t y p e s ; t h e s e a r e r e l a t i v e l y homogeneous u n i t s o f s o i l and v e g e t a t i o n . I m p l i c i t i n K r a j i n a ' s s t r u c t u r a l and f l o r i s t i c c l a s s i f i c a t i o n s y s t e m i s t h e concept t h a t t h e u n i t s a l s o have a f u n c t i o n a l i d e n t i t y , and t h a t t h e y c o u l d be c l a s s i f i e d i n t o the. 2 same groupings on the basis of energy flow and nutrient c y c l i n g . The deve-lopment of forest management guidelines based on Krajina's system assumes that units i d e n t i f i e d on the basis of vegetation and s o i l s w i l l also be r e l a t i v e l y uniform i n terms of functional process. However, these assump-tions have not been tested and information on the f u n c t i o n a l c h a r a c t e r i s t i c s of forest ecosystem types i s lacking. This study examined one aspect of the functional c h a r a c t e r i s t i c s of three ecosystem types along a topographic sequence i n one of Krajina's subzones. Decomposition was compared on three ecosystem types i n the dry subzone of the Coastal Western Hemlock Biogeoclimatic zone. The three ecosystem types chosen for study are referred to as x e r i c , mesic, and hygric. Each i s assumed to have a d i f f e r e n t s o i l moisture regime which, i n the present study, was inferred from i t s p o s i t i o n along a topographic sequence (Figure 1 ) . The objective of the study was to test the hypothesis that l i t t e r breakdown, rates of nutrient release, and thus forest f l o o r turnover are s i g n i f i c a n t l y d i f f e r e n t on the three s i t e s ; slowest on the x e r i c and fa s t e s t on the hygric ecosystem type. This pattern of v a r i a t i o n i n decompo-s i t i o n was expected because the combination of b i o t i c and a b i o t i c factors determining decomposer a c t i v i t y should be l e a s t favourable on the x e r i c s i t e s and more favourable on the hygric s i t e s , which are moister and have more deciduous and herbaceous plant species. The factors determining decomposition rates are discussed i n the l i t e r a t u r e review section of t h i s t h e s i s . In order to determine rates of weight loss and nutrient release, both the l i t t e r bag and tethered l e a f methods were used. Also, annual decom-p o s i t i o n rate constants were calculated for each ecosystem type from e x i s t i n g data on l i t t e r input (Kimmins, unpublished) and forest f l o o r biomass. The 3 Figure 1. Topographic sequence of ecosystems i n the d r i e r subzone of the Coastal Western Hemlock Biogeoclimatic Zone (from Klinka, 1977), 3a S A L A L -DOUGLAS -F IR | M O S S - W E S T E R M | I H E M L O C K I MOSS-OREGON j JGRAPE- J I DOUGLAS-FIR- I j FOAM FLOWER- j J SWORD-FERN- 1 * WESTERN DEVIL'S C L U B -WESTERN I REDCEDAR 4 d i v e r s i t y and abundance of s o i l fauna were also measured on each ecosystem type because of t h e i r p o t e n t i a l l y important r o l e i n l i t t e r decomposition. Thus, the present study employed a comparative, ecosystem approach to the study of decomposition. 5 LITERATURE REVIEW 2.1 D e f i n i t i o n o f D e c o m p o s i t i o n L i t t e r d e c o m p o s i t i o n has been d e f i n e d as t h e m e c h a n i c a l and c h e m i c a l breakdown o f dead p l a n t s t r u c t u r e from t h e s t a g e where i t i s s t i l l a t t a c h e d t o the l i v i n g p l a n t t o t h e humus s t a g e where t h e g r o s s c e l l s t r u c t u r e i s no l o n g e r r e c o g n i s a b l e and t h e complex o r g a n i c mole-c u l e s a r e b r o k e n down t o m i n e r a l components ( S a t c h e l l - 1974). Decom-p o s i t i o n i s t h e r e s u l t o f t h r e e b a s i c p r o c e s s e s : l e a c h i n g , m e c h a n i c a l w e a t h e r i n g , and b i o l o g i c a l a c t i o n (Anderson- 1973a). L e a c h i n g i n v o l v e s t h e r e l a t i v e l y r a p i d l o s s o f s o l u b l e m a t e r i a l from t h e l i t t e r by t h e a c t i o n o f r a i n o r w a t e r f l o w . M e c h a n i c a l w e a t h e r i n g i s t h e breakdown o f l i t t e r due t o p h y s i c a l f a c t o r s s u c h as f r e e z i n g and d r y i n g . B i o l o -g i c a l a c t i o n i n v o l v e s the f r a g m e n t a t i o n and o x i d a t i o n o f l i t t e r by numerous h e t e r o t r o p h i c o r g a n i s m s . The c o m b i n a t i o n o f p r o c e s s e s and the e x t e n t t o w h i c h t h e y o p e r a t e a r e d e t e r m i n e d l a r g e l y by t h e f o r e s t f l o o r e nvironment on any p a r t i c u l a r s i t e . 2.2 S o i l Organisms and D e c o m p o s i t i o n The a c t i v i t y and n u t r i e n t demands o f l i t t e r h e t e r o t r o p h s , i n r e s p o n s e t o d i f f e r e n c e s i n t h e p a l a t a b i l i t y and n u t r i e n t c o n t e n t o f v e g e t a t i o n s p e c i e s , a r e l a r g e l y r e s p o n s i b l e f o r r a t e s o f l i t t e r b r e a k -down and n u t r i e n t r e l e a s e (Gosz e t a l . 1973). I t has been e s t a b l i s h e d t h a t t h e r e a r e g e n e r a l p a t t e r n s o f s u c c e s s i o n o f v a r i o u s h e t e r o t r o p h i c o r ganisms on decomposing l i t t e r . The organisms i n each s u c c e s s i v e s t a g e a t t a c k d i f f e r e n t s t r u c t u r a l components as t h e y become exposed o r more p a l a t a b l e w i t h t i m e . The r e s u l t i s r e c o g n i s a b l e p a t t e r n s o f 6 d e c o m p o s i t i o n . The o r g a n i s m s i n v o l v e d i n d e c o m p o s i t i o n and t h e i r p a t t e r n s o f s u c c e s s i o n have been e x t e n s i v e l y r e v i e w e d and w i l l o n l y be summarised h e r e . The s u c c e s s i o n o f m i c r o - o r g a n i s m p o p u l a t i o n s on c o n i f e r o u s and d e c i d u o u s l i t t e r have been r e v i e w e d i n d e t a i l by M i l l e r (1974) , Hayes ( 1 9 6 5 ) , Sherwood and C a r r o l l ( 1 9 7 4 ) , and J e n s e n ( 1 9 7 4 ) . F u n g a l p o p u l a t i o n s a r e a l r e a d y w e l l e s t a b l i s h e d on l i v i n g p l a n t s and a r e a l s o t h e i n i t i a l c o l o n i z e r s o f dead c o n i f e r l i t t e r . However, t h e i n i t i a l m i c r o b i a l i n v a s i o n i s c o n s i d e r e d by Edwards e t a l . (1970) t o be f a i r l y u n i m p o r t a n t i n d e g r a d a t i o n o f l i t t e r . An i n t e n s e f a u n a l i n v a s i o n u s u a l l y f o l l o w s w i t h i t s own c h a r a c t e r i s t i c s u c c e s s i o n p a t t e r n s ( f o r r e v i e w see S t y l e s 1967; Edwards e t a l . 1 9 7 0 ) . The l i t t e r f a u n a c o n t r i b u t e t o t h e breakdown o f o r g a n i c m a t t e r i n s e v e r a l ways (Edwards e t a l . 1970). They fragment p l a n t and a n i m a l t i s s u e s and make them more e a s i l y i n v a d e d by m i c r o -o r g a n i s m s . They i n c r e a s e t h e s u r f a c e a r e a a v a i l a b l e f o r b a c t e r i a l and f u n g a l a c t i o n , mix the o r g a n i c m a t t e r i n t o t h e upper l a y e r s o f t h e s o i l , and f o r m complex a g g r e g a t e s o f o r g a n i c m a t t e r w i t h t h e m i n e r a l p a r t s o f t h e s o i l . There i s a l s o some e v i d e n c e t h a t c h e m i c a l changes may o c c u r d u r i n g f r a g m e n t a t i o n by f a u n a , i n c l u d i n g breakdown o f s t a b l e s u b s t a n c e s s u c h as c e l l u l o s e , k e r a t i n , and c h i t i n ( G a s d o r f and G o o d n i g h t : 1963). As t h e l i t t e r decomposes f u r t h e r i t i s compressed by t h e f o r e s t f l o o r and m a t t e d by f u n g a l hyphae. L e v e l s o f c e l l u l o s e and l i g n i n d e c r e a s e and t h e m e s o p h y l l i s d e s t r o y e d . The a c t i v i t i e s o f t h e f a u n a and m i c r o - f l o r a a r e complementary and i n t r i c a t e l y i n t e r r e l a t e d t h r o u g h o u t d e c o m p o s i t i o n (Ausmus and Witkamp 1974; Edwards e t a l . 1 9 7 0 ) . 7 F r a g m e n t a t i o n by f a u n a a c c e l e r a t e s m i c r o b i a l i n v a s i o n , and c h e m i c a l and s t r u c t u r a l changes i n i t i a t e d by m i c r o f l o r a f a v o u r f u r t h e r a t t a c k by f a u n a . 2.3 E n v i r o n m e n t a l F a c t o r s and D e c o m p o s i t i o n The d i v e r s i t y and abundance o f t h e l i t t e r o r g a n i s m s i n v o l v e d i n t h e g e n e r a l s u c c e s s i o n a l p a t t e r n s d e s c r i b e d above a r e d e t e r m i n e d l a r g e l y by t h e p h y s i c a l and c h e m i c a l environment o f t h e f o r e s t f l o o r . T h i s , i n t u r n , i s i n f l u e n c e d by numerous f a c t o r s , i n c l u d i n g t h e amount and c h e m i c a l c o m p o s i t i o n o f t h e l i t t e r w h i c h f a l l s , s o i l t y p e and s o i l m o i s t u r e r e g i m e , and the macro and m i c r o - c l i m a t e o f a p a r t i c u l a r s i t e . C o n i f e r o u s f o l i a g e g e n e r a l l y decomposes much more s l o w l y t h a n d e c i d u o u s f o l i a g e ( W i l l i a m s and Gray 1 9 7 4 ) , a l t h o u g h c o n s i d e r a b l e v a r i a t i o n o c c u r s w i t h i n each group. The v a r i a t i o n i n r a t e s o f l i t t e r d e c o m p o s i t i o n between d i f f e r e n t p l a n t s p e c i e s was r e c o g n i z e d e a r l y i n t h e h i s t o r y o f d e c o m p o s i t i o n r e s e a r c h ( f o r example, see B r o a d f o o t and P i e r r e 1939; C o l d w e l l and deLong 1950). T h i s v a r i a t i o n i s l a r g e l y due t o d i f f e r e n c e s i n t h e c h e m i c a l c o m p o s i t i o n and p a l a t a b i l i t y o f l i t t e r t o o r g a n i s m s . F o r example, pH and base c o n t e n t a r e i m p o r t a n t v a r i a b l e s , w i t h c o n i f e r l i t t e r t e n d i n g t o be more a c i d i c t h a n h a r d -wood l i t t e r ( M i l l e r 1974). B o t h a c i d i t y and base c o n t e n t t e n d t o d e c r e a s e as o r g a n i c a c i d s a r e l e a c h e d from t h e l i t t e r ( N y k v i s t 1959a, 1959b). pH i s e x t r e m e l y i m p o r t a n t because many decomposer o r g a n i s m s a r e i n a c t i v e a t pH l e s s t h a n 5. The o r g a n i c c o n s t i t u e n t s o f p l a n t s a r e commonly d i v i d e d i n t o s i x b r o a d c a t e g o r i e s , t h e q u a n t i t i e s o f w h i c h v a r y c o n s i d e r a b l y between s p e c i e s and t o some e x t e n t w i t h i n s p e c i e s . The s i x c a t e g o r i e s 8 i n c l u d e : c e l l u l o s e , v a r y i n g from 15 t o 60 p e r c e n t o f t h e d r y w e i g h t ; h e m i c e l l u l o s e , commonly making up 10 t o 30 p e r c e n t of t h e w e i g h t ; l i g n i n , c o m p r i s i n g 5 t o 30 p e r c e n t o f t h e w e i g h t ; t h e w a t e r - s o l u b l e f r a c t i o n ( s i m p l e s u g a r s , amino a c i d s , a l i p h a t i c a c i d s ) , c o n t r i b u t i n g 5 t o 30 p e r c e n t of t h e w e i g h t ; e t h e r and a l c o h o l - s o l u b l e c o n s t i t u e n t s ( f a t s , o i l s , waxes, r e s i n s ) ; and p r o t e i n s ( A l e x a n d e r 1961). The m i n e r a l c o n s t i t u e n t s v a r y from 1 t o 13 p e r c e n t o f t h e t o t a l d r y t i s s u e w e i g h t . The q u a n t i t i e s o f many o f t h e s e o r g a n i c and i n o r g a n i c c o n s t i -t u e n t s i n l i t t e r d e t e r m i n e t h e p a l a t a b i l i t y o f t h e l i t t e r f o r s o i l o r g a n i s m s . The w a t e r - s o l u b l e o r g a n i c m a t t e r component p r o v i d e s a r e a d i l y a v a i l a b l e energy s o u r c e f o r decomposers, and i s t h e r e f o r e an i m p o r t a n t i n f l u e n c e i n t h e i n i t i a l s t a g e s o f d e c o m p o s i t i o n ( W i l l i a m s and Gray 1974). O r g a n i c n i t r o g e n i s a l s o a major f o o d s o u r c e f o r decomposers. B r o a d f o o t and P i e r r e (1939) d e t e r m i n e d n i t r o g e n c o n t e n t s f o r l i t t e r o f a number o f s p e c i e s and found them to range from .46% t o 2.06%. V o i g t (1965) found a v e r a g e v a l u e s f o r hardwood l e a v e s t o be s l i g h t l y g r e a t e r t h a n t h o s e f o r c o n i f e r s and n o t e d a h i g h c o r r e l a t i o n between r a t e o f d e c o m p o s i t i o n d u r i n g t h e f i r s t two months and i n i t i a l n i t r o g e n c o n t e n t . N i t r o g e n c o n t e n t d e t e r m i n e s t h e c a r b o n : n i t r o g e n r a t i o w h i c h has been used by Cromack (1973) t o f o r m u l a t e r e g r e s s i o n e q u a t i o n s f o r p r e d i c t i n g d e c o m p o s i t i o n r a t e s . F i n a l l y , p l a n t s c o n t a i n a number o f p o l y h y d r o x y - p h e n o l s w h i c h may be v e r y i m p o r t a n t i n c o n t r o l l i n g r a t e s of l i t t e r d e c o m p o s i t i o n . Minderman (1968) s u g g e s t e d t h a t i n l a t e r s t a g e s o f d e c o m p o s i t i o n , r a t e s o f l i t t e r a c c u m u l a t i o n a r e l a r g e l y d e t e r m i n e d by t h e s e components. D e c o m p o s i t i o n r a t e s have been found 9 t o be c l o s e l y c o r r e l a t e d w i t h l i g n i n c o n c e n t r a t i o n s ( F o g e l and Cromack 1 9 7 7 ) , o r l i g n i n c o n c e n t r a t i o n s i n c o m b i n a t i o n w i t h l o c a l e v a p o t r a n s p i r a t i o n r a t e s (Meentemyer 1978). M i c r o - c l i m a t i c v a r i a b l e s and s o i l m o i s t u r e a l s o have an i m p o r t a n t i m pact on t h e a c t i v i t y and s u r v i v a l o f decomposers, and t h u s on r a t e s o f d e c o m p o s i t i o n . Witkamp and van d e r D r i f t (1961) n o t e d s e a s o n a l t e m p e r a t u r e e f f e c t s on r a t e s o f m u l l and mor f o r e s t f l o o r breakdown. S t r o n g r e l a t i o n s h i p s between t e m p e r a t u r e and r a t e s o f c a r b o n d i o x i d e e v o l u t i o n (an i n d i c a t o r o f decomposer a c t i v i t y ) have a l s o been n o t e d (Edwards 1975; Yoneda 1975). I n c u b a t i o n s t u d i e s by I v a r s o n (1973) d e m o n s t r a t e d a 1.3 t o 2.3 p e r c e n t d e c r e a s e i n d e c o m p o s i t i o n r a t e f o r each 1°C drop i n t e m p e r a t u r e , w h i l e f i e l d s t u d i e s by Shanks and O l s o n (1961) and M i k o l a (1960) found a 1.8% d e c r e a s e f o r a 1°C t e m p e r a t u r e d r o p . However, Daubenmire and P r u s s o (1963) i n v e s t i g a t e d d e c o m p o s i t i o n r a t e s o f e l e v e n c o n i f e r s p e c i e s a t 10°C and 25°C. A l t h o u g h most s p e c i e s decomposed f a s t e r a t 25°C, some, i n c l u d i n g D o u g l a s - f i r , d i s a p p e a r e d f a s t e r a t t h e l o w e r tempera-t u r e . M o i s t u r e c o n t e n t and a e r a t i o n a r e b o t h i m p o r t a n t f a c t o r s i n f l u e n c i n g decomposer a c t i v i t y . D u r i n g p e r i o d s o f d r o u g h t , decom-p o s i t i o n r a t e s o f b o t h m u l l and mor l i t t e r a r e r e t a r d e d and numbers o f f a u n a i n t h e l i t t e r a r e r e d u c e d (van d e r D r i f t 1963) . Witkamp (1963) found w e i g h t l o s s e s o f s e v e r a l hardwood l i t t e r s t o be c o r r e -l a t e d w i t h m o i s t u r e c o n t e n t , w h i l e Wiant (1967) n o t e d a major i n f l u e n c e o f m o i s t u r e on f o r e s t f l o o r c a r b o n d i o x i d e e v o l u t i o n r a t e s . A e r a t i o n , w h i c h i s d i r e c t l y a s s o c i a t e d w i t h m o i s t u r e c o n t e n t , may 10 become a p r o b l e m when l i t t e r i s w a t e r l o g g e d and gaseous d i f f u s i o n i s i m p a i r e d ( W i l l i a m s and Gray 1974). The i n d i v i d u a l f a c t o r s d i s c u s s e d above do n o t o p e r a t e i n d e p e n -d e n t l y , and a c o n s i d e r a t i o n o f t h e i r i n t e r a c t i o n s i s n e c e s s a r y f o r a c o m p l e t e u n d e r s t a n d i n g o f d e c o m p o s i t i o n . F o r example, Witkamp (1966) and Ausmus and Witkamp (1974) found t h a t v a r i a t i o n s i n r a t e s o f CO^ e v o l u t i o n from decomposing l i t t e r c o u l d be a c c o u n t e d f o r by t h e i n t e r -a c t i o n o f t e m p e r a t u r e , m o i s t u r e c o n t e n t , and l i t t e r age. 2.4 D i r e c t Methods o f M e a s u r i n g D e c o m p o s i t i o n R a t e s R a t e s o f l i t t e r d e c o m p o s i t i o n can be measured by s e v e r a l methods. These i n c l u d e t h e use o f p a i r e d p l o t s , r a d i o i s o t o p e s , l i t t e r b a gs, and l i t t e r t e t h e r i n g . The p a i r e d - p l o t s method i n v o l v e s c o l l e c t i n g l i t t e r f r om one p l o t and w e i g h i n g i t a t the b e g i n n i n g o f a t i m e i n t e r v a l . The l i v i n g p l a n t s a r e removed from t h e second p l o t t o p r e v e n t l i t t e r i n p u t , and f o l l o w i n g a s p e c i f i c i n t e r v a l o f t i m e t h e l i t t e r i s removed and weighed. The d i f f e r e n c e between l i t t e r w e i g h t s on t h e two p l o t s o v e r t i m e g i v e s the breakdown r a t e o f l i t t e r ( f o r an example, see B i r k 1977). T h i s method i s n o t a p p r o p r i a t e i n f o r e s t ecosystems where l i t t e r i n p u t cannot be p r e v e n t e d d u r i n g t h e t i m e i n t e r v a l . A l s o , r e m o v a l o f p l a n t s may i n f l u e n c e t h e m o i s t u r e , c h e m i s t r y , and tempera-t u r e o f t h e l i t t e r , t h u s a l t e r i n g d e c o m p o s i t i o n r a t e s . R a d i o i s o t o p e s have o c c a s i o n a l l y been used i n d e c o m p o s i t i o n 14 s t u d i e s . Smith (1966) and J e n k i n s o n (1971) l a b e l l e d p l a n t s w i t h C, ground v a r i o u s p l a n t components t o a powder, and i n c u b a t e d them i n s o i l . The d e c o m p o s i t i o n r a t e s o f t h e d i f f e r e n t p l a n t components were 14 t h e n compared by m e a s u r i n g t h e r a t e o f e v o l u t i o n o f CO^. However, 11 t h i s method cannot be used f o r the study of turnover r a t e s of n u t r i e n t s that do not have a gaseous c y c l e . The most widely used procedure f o r the e s t i m a t i o n of decomposi-t i o n r a t e s i s the l i t t e r bag method, which y i e l d s i n f o r m a t i o n about both weight l o s s and changes i n n u t r i e n t concentrations. The procedure i n v o l v e s c o n f i n i n g known q u a n t i t i e s of l i t t e r i n nylon mesh bags which are placed on or i n the f o r e s t f l o o r and then r e t r i e v e d , weighed, and analysed a f t e r a known i n t e r v a l of time (see, f o r example, Bocock and G i l b e r t 1957, Crossley and Hoglund 1962, G i l b e r t and Bocock 1960). The method has been c r i t i c i z e d f o r s e v e r a l reasons. The bag a l t e r s the n a t u r a l environment of the l i t t e r by c r e a t i n g a homogeneous sub-s t r a t e , unnatural accumulations and aggregations of p l a n t m a t e r i a l , and d i f f e r e n t moisture contents w i t h i n the bags than are found outside them (Bocock 1964, L o u s i e r and Parkinson 1976). Anderson (1973a), working i n an oak-chestnut stand, noted that the species of mites which invaded l i t t e r bags were c h a r a c t e r i s t i c of the top of the n a t u r a l l i t t e r l a y e r . This suggested that a f t e r 31 months of decom-p o s i t i o n , l i t t e r i n the bags was a r t i f i c i a l l y maintained under environ-mental c o n d i t i o n s c h a r a c t e r i s t i c of f r e s h l y - f a l l e n l i t t e r . Another problem i s that small mesh s i z e s may r e s t r i c t the entry of some s o i l fauna, thereby c o n t r i b u t i n g to an underestimation of decomposition r a t e s (Bocock 1964, W i l l 1967, Anderson 1973a). L i t t e r bag s t u d i e s may not, t h e r e f o r e , r e f l e c t true patterns of decomposition and s o i l f a u n al feeding a c t i v i t i e s . Leaf t e t h e r i n g i n v o l v e s a t t a c h i n g leaves to lengths of s t r i n g or thread. Threads w i t h one or more pre-weighed leaves are placed 12 u n c o n f i n e d on t h e f o r e s t f l o o r and r e t r i e v e d a f t e r a known i n t e r v a l o f t i m e ( s e e , f o r example, Witkamp and O l s o n 1963, Hayes 1965). T h i s method can be used t o e l i m i n a t e t h e p r o b l e m o f t h e a r t i f i c i a l e n v i r o n -ment c r e a t e d by t h e l i t t e r bags. However, l o s s e s due t o p h y s i c a l f r a g m e n t a t i o n can be g r e a t , so t h e method u s u a l l y measures r a t e s o f comminution r a t h e r t h a n d e c o m p o s i t i o n . Bocock and G i l b e r t ( 1 9 5 7 ) , Witkamp and O l s o n (1963) and Anderson (1973a) have r e p o r t e d s i g n i f i -c a n t l y g r e a t e r w e i g h t l o s s e s from t e t h e r e d o r u n c o n f i n e d l e a f samples t h a n from l i t t e r c o n f i n e d i n l i t t e r bags. L i t t e r bags and t e t h e r i n g r e m a i n p o p u l a r methods f o r t h e s t u d y o f d e c o m p o s i t i o n f o r s e v e r a l r e a s o n s . The p r o c e d u r e i s s i m p l e and t h e l i t t e r i s u s u a l l y easy t o r e c o v e r . S e a s o n a l changes i n decompo-s i t i o n r a t e s can be o b s e r v e d and n u t r i e n t c o n c e n t r a t i o n changes i n t h e decomposing l i t t e r can be a s s e s s e d . 2.5 I n d i r e c t Methods o f E s t i m a t i n g D e c o m p o s i t i o n R a t e s : M a t h e m a t i c a l  M o d e l s o f D e c o m p o s i t i o n D e c o m p o s i t i o n r a t e s can be d e t e r m i n e d i n d i r e c t l y u s i n g mathe-m a t i c a l models such as t h o s e p r o p o s e d by Jenny e t a l . (1949) and O l s o n (1963). Such models can be used t o g e n e r a t e an a n n u a l f r a c t i o n a l w e i g h t l o s s c o n s t a n t , o r k v a l u e . A c o m p a r i s o n o f t h e k v a l u e s c a l -c u l a t e d m a t h e m a t i c a l l y w i t h w e i g h t l o s s e s measured i n t h e f i e l d can be u s e f u l f o r a s s e s s i n g t h e a p p r o p r i a t e n e s s o f a model and t h e a c c u r a c y o f f i e l d methods f o r a p a r t i c u l a r s i t e . The d e c o m p o s i t i o n model o f Jenny e t a l . (1949) i s based on t h e a s s u m p t i o n t h a t i n a s t e a d y - s t a t e f o r e s t f l o o r , t h e a n n u a l r a t e 13 o f a d d i t i o n o f o r g a n i c m a t t e r i s e q u a l t o t h e a n n u a l r a t e of l o s s , and t h a t t h i s l o s s r a t e i s p r o p o r t i o n a l t o t h e amount o f f o r e s t f l o o r a c c u m u l a t e d . I f X r e p r e s e n t s t h e b i o m a s s , n u t r i e n t , o r energy c o n t e n t o f t h e f o r e s t f l o o r p e r u n i t a r e a , t h e n t h e r a t e o f change o f X f o r a d i s c r e t e i n t e r v a l o f t i m e , A t , i s : Ax/At = L - kX, where L = r a t e o f l i t t e r i n p u t and k = a n n u a l d e c o m p o s i t i o n c o n s t a n t . Once t h e f o r e s t f l o o r r e a c h e s s t e a d y - s t a t e , t h e r a t e o f change o f f o r e s t f l o o r biomass i s e q u a l t o 0, and L = k X s s . Thus, t h e w e i g h t l o s s c o n s t a n t , k, can be c a l c u l a t e d i f b o t h the biomass o f t h e s t e a d y - s t a t e f o r e s t f l o o r and t h e r a t e of l i t t e r i n p u t a r e known, k v a l u e s can e a s i l y be c a l c u l a t e d and compared f o r many f o r e s t e d r e g i o n s o f t h e w o r l d . When l i t t e r bag e s t i m a t e s a r e used t o c a l c u l a t e k v a l u e s (see O l s o n 1963) t h e r e i s no l i t t e r i n p u t and t h e w e i g h t l o s s e q u a t i o n can be r e a r r a n g e d t o e x p r e s s w e i g h t l o s s as a f r a c t i o n o f t h e r e s i d u e X r e m a i n i n g , o r : 3x/x = - k 9 t . The f r a c t i o n r e m a i n i n g can t h e n be r e p r e s e n t e d as a n e g a t i v e e x p o n e n t i a l f u n c t i o n : x / x D = e A l t h o u g h t h e n e g a t i v e e x p o n e n t i a l model f i t s l o n g - t e r m d a t a m o d e r a t e l y w e l l , i t i s i n many ways o v e r l y s i m p l e and p r o v i d e s an i n a p p r o p r i a t e d e s c r i p t i o n of s h o r t - t e r m measured r a t e s o f l i t t e r d i s -a ppearance ( B u n n e l l and T a i t 1974; B i r k 1977). The c r i t i c a l assump-t i o n s a r e t h a t k remains c o n s t a n t o v e r l o n g p e r i o d s , a n d t h a t t h e r a t e o f l o s s i s p r o p o r t i o n a l t o t h e amount o f l i t t e r p r e s e n t . Minderman (1968) has s u g g e s t e d t h a t w h i l e i n d i v i d u a l b i o c h e m i c a l components o f t h e l i t t e r m i g ht be e x p e c t e d t o conform t o a n e g a t i v e e x p o n e n t i a l decay model, i t i s u n r e a s o n a b l e t o assume t h a t t h e sum o f t h e s e f r a c t i o n s s h o u l d f o l l o w t h e same r e l a t i o n s h i p . Minderman a l s o n o t e d 14 t h a t f o r a c o n s t i t u e n t s u c h as c e l l u l o s e , masking by o t h e r compounds may hamper d e c o m p o s i t i o n , so t h a t more c e l l u l o s e -may a c c u m u l a t e o v e r t i m e t h a n t h e e x p o n e n t i a l model p r e d i c t s . E x p e r i m e n t a l e v i d e n c e s u g g e s t s t h a t t h e f r a c t i o n a l decay r a t e o f l i t t e r d e c l i n e s w i t h , age of t h e f r a g m e n t s and hence w i t h fragment s i z e and d e p t h i n t h e f o r e s t f l o o r p r o f i l e (Anderson 1973a; H e a l and F r e n c h 19.74; L o u s i e r and P a r k i n s o n 1976). D e c o m p o s i t i o n r e s e a r c h has r e c e n t l y extended t o d e v e l o p i n g models w h i c h a r e more complex t h a n t h e s i m p l e n e g a t i v e e x p o n e n t i a l f u n c t i o n . Models have been d e v e l o p e d which, i n c l u d e t h e d i f f e r e n t components of l i t t e r o r v a r i o u s s t a g e s o f breakdown ( s e e , f o r example, B u n n e l l and T a i t 1974; B o l i n g e t a l . 1975)., Models such a s t h e s e appear t o be more r e a l i s t i c b o t h i n terms o f i n c o r p o r a t i n g t h e o r y and f i t t i n g d a t a t h a n was t h e n e g a t i v e e x p o n e n t i a l m o d e l , However, th e e a r l i e r model i s s i m p l e and c o n v e n i e n t , r e q u i r e s v e r y l i t t l e d a t a , and i s a c c e p t a b l e as a f i r s t a p p r o x i m a t i o n o f a complex phenom-enon . 15 SITE DESCRIPTIONS The r e s e a r c h was c o n d u c t e d i n the s o u t h - w e s t c o r n e r o f t h e U n i v e r s i t y o f B r i t i s h C o l umbia r e s e a r c h f o r e s t n e a r Haney, B.C. The a r e a f a l l s i n t o t h e d r y subzone o f t h e C o a s t a l Western Hemlock B i o g e o -c l i m a t i c Zone as d e f i n e d by K r a j i n a (1965). The c l i m a t e o f t h e a r e a i s Cfb ( s y s t e m o f KSppen, 1936), w h i c h i s c h a r a c t e r i s e d as warm, temperate and m o i s t , w i t h no pronounced d r y s e a s o n . The J a n u a r y mean t e m p e r a t u r e i s 0°C and t h e J u l y mean i s 15°C. P r e c i p i t a t i o n a v e r a g e s 234 cm a n n u a l l y and ranges from 37 cm i n J a n u a r y t o 7.5 cm i n J u l y . C l i m a t i c d a t a a r e a v a i l a b l e from t h e Haney w e a t h e r s t a t i o n . The t h r e e e c o s y s t e m t y p e s i n v e s t i g a t e d i n t h i s s t u d y a r e r e f e r r e d t o as x e r i c , m e s i c and h y g r i c . The terms a r e used t o encompass th e g e n e r a l a b i o t i c and b i o t i c e c o s y s t e m c h a r a c t e r i s t i c s o c c u r r i n g i n a r e a s w h i c h a r e d r y e r , t h e same a s , o r m o i s t e r , r e s p e c t i v e l y , t h a n e x p e c t e d from t h e r e g i o n a l c l i m a t e . These can be most e a s i l y v i s u a l i z e d as o c c u r r i n g a l o n g a t o p o g r a p h i c sequence ( F i g u r e 1 ) . One s i t e r e p r e -s e n t a t i v e o f each e c o s y s t e m t y p e was chosen a l o n g each o f two t o p o g r a p h i c sequences, g i v i n g a t o t a l o f s i x s i t e s . The l o c a t i o n s o f t h e s i t e s a r e shown i n F i g u r e 2. 3.1 X e r i c S i t e s The x e r i c s i t e s a r e l o c a t e d on upper s l o p e s : one a t 240 m ( s i t e 400) and t h e o t h e r a t 140 m ( s i t e 100). On b o t h s i t e s the dominant 2 -1 t r e e s p e c i e s was D o u g l a s - f i r , w i t h a b a s a l a r e a o f 46.9 m -ha on s i t e 100 and 33.5 on s i t e 400. Western hemlock had a b a s a l a r e a o f 2 -1 7.6 m 'ha on s i t e 100 and 21.4 on s i t e 400, w h i l e w e s t e r n r e d c e d a r 16 Figure 2. A e r i a l photograph of the southwest corner of the U,B.C, Research Forest showing s i t e locations (photographed 1972) , Scale 1:12000, 17 b a s a l a r e a was 16.6 on s i t e 100 and 4.4 on s i t e 400. Tree h e i g h t a v e r a g e d 24.6 m on s i t e 100 and 23.9 m on 400. Canopy c l o s u r e was 86 t o 88% on b o t h s i t e s . There was a f a i r l y dense shrub l a y e r o f s a l a l on b o t h s i t e s (50 t o 75% c o v e r ) , and some ground c o v e r o f s t e p moss. A ; i i s t i r i g > m a f o r . . s p e c i e s and t h e i r l a t i n names i s p r e s e n t e d i n A p p e n d i x 1. The s o i l s on b o t h s i t e s were m i n i I f u m o - f e r r i c B o d z o l s d e v e l o p e d f r o m s h a l l o w a b l a t i o n t i l l - c o l l u v i u m . The f o r e s t f l o o r a v e r a g e d 9.2 cm deep and was c l a s s i f i e d as a f e l t y mor (Hoover and Lu n t 1952). 3.2 M e s i c S i t e s The m e s i c s i t e s were s i t u a t e d a t a p p r o x i m a t e l y mid s l o p e : one a t 120 m (200) and t h e o t h e r a t 220 m ( 5 0 0 ) . The dominant t r e e 2 -1 s p e c i e s was a g a i n D o u g l a s - f i r , h a v i n g a b a s a l a r e a o f 35.7 m -ha on s i t e 200 and 28.8 on 500. Western hemlock had a b a s a l a r e a o f 2 -1 24.0 m -ha on s i t e 200 and 22.5 on s i t e 500. The b a s a l a r e a o f . w e s t e r n r e d ce d a r was 7.0 on s i t e 200 and 10.4 on s i t e 500. Tree h e i g h t s a v e r a g e d 36.3 m on s i t e 200 and 29.3 m on s i t e 500. Canopy c l o s u r e was 85 t o 89% on b o t h s i t e s . There was a s p a r s e shrub l a y e r o f r e d h u c k l e b e r r y and young w e s t e r n hemlock. A l s o , on b o t h s i t e s t h e r e was a ground c o v e r o f mosses, p a r t i c u l a r l y f e a t h e r moss and s t e p moss. The s o i l s on b o t h s i t e s were m i n i J e r r o - H u m i c ©odzols d e v e l o p e d from m o d e r a t e l y deep a b l a t i o n t i l l o v e r b a s a l t i l l . The f o r e s t f l o o r a v e r a g e d 10.9 cm deep and was c l a s s i f i e d as a f e l t y mor (Hoover and L u n t 1952). 18 3.3 H y g r i c S i t e s The two h y g r i c s i t e s were l o c a t e d n e a r t h e bottoms o f s l o p e s : one a t 80 m (300) and t h e o t h e r a t 170 m (6 0 0 ) . D o u g l a s - f i r was 2 -1 dominant on b o t h s i t e s , h a v i n g a b a s a l a r e a o f 58.2 m *ha on s i t e 2 -1 300 and 40.6 m -ha on s i t e 600. Western r e d c e d a r had a b a s a l 2 -1 a r e a o f 45.4 m -ha on s i t e 300 and 20.6 on s i t e 600. Western 2 -1 hemlock had a b a s a l a r e a o f 14.8 m -ha on s i t e 300 and 5.2 on s i t e 600. These s i t e s a l s o had a component o f b i g - l e a f maple i n t h e 2 -1 o v e r s t o r y , w i t h a b a s a l a r e a o f 4.0 m .ha on s i t e 300 and 3.2 on s i t e 600. T r e e s a v e r a g e d 40.7 m i n h e i g h t on s i t e 300 and 43.8 m on s i t e 600. Canopy c l o s u r e was 87 t o 89% on b o t h s i t e s . There was a s p a r s e c o v e r o f v i n e maple on b o t h s i t e s and a dense herbaceous c o v e r o f sword f e r n and o t h e r s p e c i e s . S o i l s on b o t h s i t e s were ferro-Humic E o d z o l s d e v e l o p e d f r o m g l a c i o - m a r i n e m a t e r i a l s . The f o r e s t f l o o r a v e r a g e d 6.4 cm deep and was c l a s s i f i e d as a t h i c k d u f f m u l l (Hoover and Lunt 1952). 3.4 S i t e H i s t o r y Most o f t h e t r e e s on t h e s i t e s can be d a t e d back t o t h e l a s t f i r e w h i c h o c c u r r e d i n t h e a r e a about 120 y e a r s ago, However, on t h e 300 h y g r i c s i t e t h e r e a r e some t r e e s w h i c h s u r v i v e d t h e f i r e and a r e t h e r e -f o r e much o l d e r . These t r e e s a c c o u n t f o r t h e v e r y h i g h t o t a l b a s a l a r e a 2 1 2 — 1 on t h i s s i t e o f 122,4 m -ha" , compared w i t h 59.3 t o 71.1 m *ha ± f o r t h e o t h e r f i v e s i t e s . 19 METHODS 4.1 F i e l d Methods L i t t e r was c o l l e c t e d on November 22 and 23, 1977, from t h i r t y 2 1 m l i t t e r t r a p s l o c a t e d randomly on each o f t h e s i t e s used i n t h i s s t u d y . The t r a p s had been c o l l e c t i n g l i t t e r f o r about two months. The samples were a i r - d r i e d f o r two weeks and t h e n s e p a r a t e d i n t o t h e f o l l o w i n g components: a) mixed c o n i f e r o u s f o l i a g e from a l l s i t e s , b) s a l a l f o l i a g e from x e r i c s i t e s , and c) b i g - l e a f maple f o l i a g e from h y g r i c s i t e s . H u c k l e b e r r y f o l i a g e was s e p a r a t e d from t h e m e s i c s i t e l i t t e r b u t i t was n o t used i n t h e s t u d y because i n s u f f i c i e n t q u a n t i t i e s were c o l l e c t e d , r e f l e c t i n g t h e s p a r s e c o v e r o f t h e s h r u b s on t h e p l o t s . A second l i t t e r c o l l e c t i o n was made from a l l s i t e s i n June, 1978, i n o r d e r t o add w e s t e r n r e d c e d a r and D o u g l a s - f i r t w i g s t o t h e s t u d y . Both t h e l i t t e r bag and t h e t e t h e r i n g methods were used t o measure r a t e s o f l i t t e r breakdown and n u t r i e n t c o n c e n t r a t i o n changes. L i t t e r bags were made o f n y l o n mesh, 20 cm by 20 cm i n s i z e , w i t h edges s e a l e d by a h e a t p r e s s . Bags w i t h a mesh s i z e o f 1 mm were used f o r a l l l i t t e r t y p e s on a l l s i t e s , i n o r d e r t o a l l o w c o m p a r i s o n s t o be made o f l i t t e r t y p e s and s i t e s . T h i s s i z e was chosen because i t w i l l r e t a i n c o n i f e r o u s n e e d l e s w i t h m i n i m a l l o s s o r a d d i t i o n s . A d d i t i o n a l bags o f 4 mm mesh were used f o r t h e b r o a d - l e a f s p e c i e s i n o r d e r t o examine t h e e f f e c t o f l a r g e r (> 1 mm d i a m e t e r ) s o i l f a u n a on l i t t e r d e c o m p o s i t i o n . Leaves o f s a l a l and b i g - l e a f maple were a l s o t e t h e r e d on 50 cm l e n g t h s o f n y l o n t h r e a d t i e d t o t h e l e a f p e t i o l e o r t h r o u g h any n a t u r a l l y e x i s t i n g h o l e s i n t h e l e a f . On t h r e e s i t e s (100, 200, and 300) dead t w i g s , % t o 1 cm i n d i a m e t e r 20 o f D o u g l a s - f i r and w e s t e r n r e d c e d a r were c o l l e c t e d from l i t t e r t r a p s , d r i e d , weighed, and t e t h e r e d on l e n g t h s o f n y l o n t h r e a d . I n a l l c a s e s where t e t h e r i n g was used, t h e t h r e a d was a t t a c h e d t o a s t a k e o r t h e s t r i n g t h a t marked t h e p e r i m e t e r o f t h e s a m p l i n g b l o c k s . F i n a l l y , t o c o n t r o l f o r s u b s t r a t e d i f f e r e n c e s on t h e s i x s i t e s and t o a l l o w f o r c o m p a r i s o n w i t h o t h e r c l i m a t i c r e g i o n s , t h e decom-p o s i t i o n r a t e o f s q u a r e s c u t from a c e l l u l o s e s h e e t was measured on a l l s i t e s . Squares were 2 cm by 2 cm i n s i z e and 0.2 cm t h i c k . These were we i g h e d , p l a c e d i n 4 mm mesh bags and p l a c e d on t h e f o r e s t f l o o r . The q u a n t i t y o f each t y p e o f l i t t e r p l a c e d i n t h e bags was d e t e r m i n e d by t h e amount t h e bags c o u l d h o l d w i t h o u t r e p r e s e n t i n g an u n n a t u r a l a c c u m u l a t i o n o f l i t t e r . F o r c o n i f e r n e e d l e s t h i s was a p p r o x i m a t e l y 5 g p e r bag, and f o r b r o a d - l e a f s p e c i e s about 3 g. 5 g o f c e l l u l o s e was p l a c e d i n each bag. Twigs and b i g - l e a f maple l e a v e s were t e t h e r e d i n d i v i d u a l l y , w h i l e s a l a l l e a v e s were t e t h e r e d i n groups o f t h r e e . L i t t e r b a g s and t e t h e r e d l e a v e s were p l a c e d i n t h e f i e l d u s i n g a randomized complete b l o c k d e s i g n . T h i s was done i n an a t t e m p t to r e d u c e v a r i a n c e i n d a t a due t o g r a d i e n t s o f f o r e s t f l o o r m o i s t u r e and f e r t i l i t y . A t each s i t e a 50 m by 50 m s t u d y a r e a was s e l e c t e d t o be r e p r e s e n t a t i v e o f t h e e c o s y s t e m t y p e . F i v e p o i n t s were chosen randomly w i t h i n each s t u d y a r e a , and a s e r i e s o f 2 1 m a d j o i n i n g b l o c k s were marked out a t each p o i n t u s i n g wooden 21 s t a k e s and n y l o n s t r i n g . Each b l o c k c o n t a i n e d one l i t t e r t y p e , e i t h e r t e t h e r e d o r i n one bag t y p e . Thus, on t h e x e r i c s i t e s t h e r e 2 were seven 1 m b l o c k s a t each p o i n t , on t h e h y g r i c s i t e s s e v e n , and on t h e m e s i c s i t e s f o u r . S u f f i c i e n t l i t t e r samples were p l a c e d w i t h i n each o f t h e b l o c k s t o p e r m i t t h e d e s i r e d number o f c o l l e c t i o n s t o be made. The samples were p l a c e d randomly i n t h e b l o c k s , b u t r o c k s o r l o g s were a v o i d e d i f l i t t e r d i d n o t appear t o a c c u m u l a t e n a t u r a l l y on t h e s e . Bags were p l a c e d as f l a t as p o s s i b l e on t o p of t h e L h o r i z o n but b e n e a t h any t w i g s o r b r a n c h e s w h i c h would h o l d t h e l i t t e r i n t h e a i r o r t e a r t h e bags. Samples were p l a c e d on t h e f i r s t t o p o g r a p h i c sequence on Dec^ ember 27, 1977, and on t h e second ( l o w e r ) sequence on J a n u a r y 10, 1978. T e t h e r e d t w i g s - w e r e p l a c e d i n t h e p l o t s on June 21, 1978. S u f f i c i e n t samples were p l a c e d i n t h e p l o t s t o p e r m i t s a m p l i n g a c c o r d i n g t o t h e s c h e d u l e i n T a b l e 1. S ampling was p l a n n e d f o r t h r e e y e a r s a l t h o u g h o n l y t h e f i r s t y e a r o f d a t a i s used i n t h i s t h e s i s . T e t h e r e d t w i g s were n o t p l a c e d i n t h e f i e l d u n t i l s i x months a f t e r t h e b e g i n n i n g of t h e s t u d y , so t h a t o n l y s i x months o f d a t a a r e p r e s e n t e d h e r e . At each s a m p l i n g d a t e , one sample s e l e c t e d a t random was removed from each, b l o c k . Thus-, f i v e r e p l i c a t e s o f each sample type, were c o l l e c t e d a t each s a m p l i n g d a t e from each of two r e p l i c a t e s o f each ecosystem t y p e . The samples- were c a r e f u l l y e n c l o s e d i n r m d i y i d u a l paper bags.-and t r a n s p o r t e d t o t h e l a b . 22 TABLE 1. S c h e d u l e f o r r e m o v a l o f samples o f each l i t t e r t y p e from each s i t e a t each c o l l e c t i o n t i m e . Number o f samples t o be t a k e n a t each S i t e L i t t e r Type Method t i m e (months) a f t e r s t a r t o f s t u d y lh 3 6 9 12 18 24 36 100 and 400 C o n i f e r n e e d l e s bag 1 mm 5 5 5 5 5 5 5 5 S a l a l bag 1 mm 5 5 5 5 5 5 5 5 S a l a l bag 4 mm 5 5 5 5 5 5 - -S a l a l t e t h e r e d 15 15 15 15 15 15 - -C e l l u l o s e bag 4 mm - - 5 - 5 - 5 5 „ . a C o n x f e r t w i g s t e t h e r e d - - 10 - 10 10 10 10 200 and 500 C o n i f e r n e e d l e s bag 1 mm 5 5 5 5 5 5 5 5 C e l l u l o s e bag 4 mm - - 5 - 5 - 5 5 C o n i f e r t w i g s ^ t e t h e r e d - - 10 - 10 10 10 10 300 and 600 C o n i f e r n e e d l e s bag 1 mm 5 5 5 5 5 5 5 5 C o n i f e r n e e d l e s t e t h e r e d - - 5 - 5 B i g - l e a f maple bag 1 mm 5 5 5 5 5 5 5 5 B i g - l e a f maple bag 4 mm 5 5 5 5 5 5 - -B i g - l e a f maple t e t h e r e d 5 5 5 5 5 5 - -C e l l u l o s e bag 4 mm - - 5 - 5 - 5 5 C o n i f e r t w i g s 0 t e t h e r e d - - 10 - 10 10 10 10 a S i t e 100 o n l y . b S i t e 200 o n l y . ° S i t e 300 o n l y . 23 4.2 L a b o r a t o r y Methods Samples were o v e n - d r i e d a t 70°C f o r 48 h o u r s b e f o r e b e i n g weighed. Weight l o s s f o r each sample from t h e b e g i n n i n g o f t h e e x p e r i m e n t t o t h e d a t e o f s a m p l i n g was c a l c u l a t e d by a p p l y i n g an oven-dry w e i g h t c o r r e c t i o n f a c t o r t o t h e samples a t ti m e 0, and t h e n e x p r e s s i n g t h e l o s s i n w e i g h t as a p e r c e n t a g e o f o r i g i n a l o v e n - d r y w e i g h t . F o l l o w i n g w e i g h i n g , samples were ground t o pass a 1 mm s i e v e . F i v e r e p l i c a t e s o f each l i t t e r t y p e a t t i m e 0 were a l s o ground. The ground samples were t h e n s t o r e d i n s e a l e d p l a s t i c bags u n t i l n u t r i e n t a n a l y s e s were done. Samples were r e d r i e d p r i o r t o n u t r i e n t a n a l y s i s . F o r t o t a l n i t r o g e n and phosphorus d e t e r m i n a t i o n a p p r o x i m a t e l y 0.2 g o f each sample was used. Each sample was d i g e s t e d i n 5 ml o f d i g e s t i o n s o l u t i o n (100 g p o t a s s i u m s u l p h a t e and 1 g s e l e n i u m i n 1 1. concen-t r a t e d H^SO^), o v e r n i g h t a t about 300°C. The d i g e s t e d samples were t h e n d i l u t e d t o 100 ml w i t h d i s t i l l e d w a t e r and a n a l y s e d on a T e c h n i c o n A u t o a n a l y s e r . R e s u l t s were e x p r e s s e d as p e r c e n t o f t h e o r i g i n a l d r y w e i g h t . F o r the d e t e r m i n a t i o n o f p o t a s s i u m , magnesium, and c a l c i u m c o n c e n t r a t i o n s , about 1.0 g o f sample was ashed a t 400°C f o r t h r e e h o u r s and t h e ash d i s s o l v e d i n 7.5 ml o f 28% H'Cl by h e a t i n g g e n t l y on a h o t p l a t e . The s o l u t i o n was t h e n made up t o 100 ml w i t h d i s t i l l e d w a t e r and a n a l y s e d on a V a r i a n - T e c h t r o n A t o m i c A b s o r p t i o n S p e c t r o p h o t o m e t e r u s i n g an a i r - a c e t y l e n e f l a m e . A n a l y s i s f o r c a l c i u m c o n c e n t r a t i o n s were r e p e a t e d u s i n g a n i t r o u s 24 o x i d e - a c e t y l e n e f l a m e . R e s u l t s were e x p r e s s e d as p e r c e n t o f t h e o r i g i n a l sample d r y w e i g h t . A n a l y s i s of v a r i a n c e was used t o t e s t f o r s i g n i f i c a n t d i f f e r e n c e s i n t h e amount of l i t t e r w e i g h t l o s t on d i f f e r e n t s i t e s . The a n a l y s i s a l s o examined t h e c o n t r i b u t i o n of d i f f e r e n t t i m e s , methods and b l o c k s , as w e l l as i n t e r a c t i o n s i n t h e s e f a c t o r s i n a c c o u n t i n g f o r v a r i a t i o n i n p e r c e n t w e i g h t l o s t . Because w e i g h t l o s s i s e x p r e s s e d as a p e r -c e n t a g e w i t h many h i g h v a l u e s , an a r c s i n e t r a n s f o r m a t i o n was used t o n o r m a l i z e t h e d i s t r i b u t i o n o f t h e d a t a , 4.3 A u x i l i a r y S t u d i e s I n a d d i t i o n t o t h e c e n t r a l d e c o m p o s i t i o n s t u d y d e s c r i b e d above, a number of a u x i l i a r y i n v e s t i g a t i o n s were u n d e r t a k e n t o examine d i f f e r e n c e s between t h e t h r e e ecosystem t y p e s t h a t m i g h t c o n t r i b u t e to d i f f e r e n c e s i n r a t e s o f d e c o m p o s i t i o n . D i f f e r e n c e s i n t h e d e p t h and biomass o f t h e f o r e s t f l o o r o f t h e t h r e e ecosystem t y p e s were measured as f o l l o w s . A t s i x - w e e k i n t e r v a l s b e g i n n i n g on December 22, 1977, f i v e randomly l o c a t e d 1/16 q u a d r a t samples were t a k e n f r o m each o f t h e t h r e e ecosystem t y p e s a l o n g t h e l o w e r t r a n s e c t , Logs were i n c l u d e d i n t h e samples o n l y i f t h e y appeared t o be i n c o r p o r a t e d i n t o t h e f o r e s t f l o o r and were s o f t enough t o be e a s i l y c u t and removed. L a r g e , u n i n c o r p o r a t e d l o g s were a v o i d e d . L i v i n g r o o t s l a r g e r t h a n .5 cm d i a m e t e r were n o t i n c l u d e d i n t h e samples because t h e y a r e n o t t e c h n i c a l l y l i t t e r . The samples were d i v i d e d i n t o L, F, and H h o r i z o n s and t r a n s p o r t e d t o t h e l a b i n p l a s t i c b a g s. I n t h e l a b , each sample was weighed, o v e n - d r i e d a t 105° C f o r 48 h o u r s , and t h e n r e w e i g h e d . U s i n g t h e s e d a t a , t h e biomass and m o i s t u r e c o n t e n t o f t h e 25 forest f l o o r on the three ecosystem types were estimated and seasonal changes examined. In addition to the samples for biomass determination, a second quadrat sample and a 7.2 cm diameter core sample were taken at each sampling time at the f i v e sampling points on each s i t e for extraction of s o i l fauna. S o i l animals were extracted from the quadrat samples over a period of 120 hours i n dry Tullgren funnels using a 100 watt bulb as a heat source. Animals from core samples were extracted oyer a period of 80 hours i n dry Tullgren funnels using bulbs con-t r o l l e d by a rheostat. Major groups of macro- and meso-fauna extracted from the quadrat samples were i d e n t i f i e d and counted, Major groups of micro-fauna extracted from the core samples were also i d e n t i f i e d and counted. 26 RESULTS AND DISCUSSION 5.1 Weight L o s s 5.1.1 R e s u l t s C o n i f e r n e e d l e s . Weight l o s s e s o f c o n i f e r n e e d l e s c o n f i n e d i n 1 mm mesh bags a r e shown i n F i g u r e s 3 and 4. On a l l s i x s i t e s about 35 t o 40 p e r c e n t o f t h e o r i g i n a l w e i g h t was l o s t a f t e r one y e a r i n t h e f i e l d . Time a c c o u n t e d f o r a s i g n i f i c a n t p o r t i o n o f t h e v a r i a n c e (F prob < .001). There was no : s i g n i f i c a n t e f f e c t o f b l o c k i n g o f t r e a t m e n t s on the s i t e s (F prob = .43), i n d i c a t i n g f a i r l y u n i f o r m c o n d i t i o n s f o r d e c o m p o s i t i o n i n l i t t e r bags on t h e f o r e s t f l o o r s u r f a c e o f each s i t e . The d e c o m p o s i t i o n p a r a m e t e r , k, f o r c o n f i n e d c o n i f e r f o l i a g e was o b t a i n e d u s i n g the n e g a t i v e e x p o n e n t i a l w e i g h t l o s s f u n c t i o n : - k t x / x 0 = e , where x / X Q = p r o p o r t i o n o f t h e o r i g i n a l w e i g h t r e m a i n -i n g i n t h e bags. F o r c o n i f e r f o l i a g e l i t t e r on a l l s i t e s x/xo = 0.65 and k = 0.43 B r o a d l e a f f o l i a g e . Weight l o s s o f t h e two b r o a d l e a f s p e c i e s , u s i n g t h r e e methods o f measurement, a r e summarized i n F i g u r e s 5 and 6. Weight l o s s e s o f t h e c o n f i n e d l i t t e r o f b o t h s p e c i e s on a l l s i t e s were i n t h e range o f 25 t o 40 p e r c e n t a f t e r one y e a r . However, w e i g h t l o s s p a t t e r n s o f t h e t e t h e r e d l e a f samples were more v a r i a b l e . On t h e 100 ( l o w e r x e r i c ) and 300 ( l o w e r h y g r i c ) s i t e s b o t h s a l a l and b i g -l e a f maple f o l i a g e l i t t e r e x h i b i t e d a sudden w e i g h t l o s s d u r i n g t h e 27 Figure 3. Average weight loss of conifer f o l i a g e l i t t e r expressed as percent of original weight remaining (± standard deviation) for the lower t r a n s e c t f x e r i c (100), -mesic C200), and hygric (300) s i t e s , P e r c e n t off O r i g i n a l W e i g h t R e m a i n i n g M O CO 0 O O O O O 28 Figure 4. Average weight loss of conifer f o l i a g e expressed as percent of o r i g i n a l weight remaining (+ standard deviation) for the upper transect rxeric (400), mesic (_500), and hygric (600) sites-, 29 Figure 5. Average weight loss of confined and unconfined s a l a l and b i g -le a f maple f o l i a g e expressed as percent of the o r i g i n a l weight remaining (+ standard deviation) for the lower transect x e r i c (100) and hygric (300) s i t e s , 29a 30 Figure 6. Average weight loss of confined and unconfined s a l a l and b i g ^ le a f maple l i t t e r expressed as percent of the o r i g i n a l weight remaining (+ standard deviation) for the upper transect x e r i c (400) and hygric (600) s i t e s . c o E (D 0) D C *5> O o e <D u 4) •© 9 1 m m A- - - -A - * 6 0 0 M S salal E^3 T i m e ( m o n t h s ) 31 f i n a l t h r e e months (September t o December) r e s u l t i n g i n a t o t a l w e i g h t l o s s o f 80 p e r c e n t o v e r one y e a r i n b o t h c a s e s . On t h e 400 (upper x e r i c ) and 600 (upper h y g r i c ) s i t e s , however, t h e two s p e c i e s e x h i b i t e d d i f f e r e n t t r e n d s . Weight l o s s o f t h e t e t h e r e d samples was g r e a t e r a t e v e r y s a m p l i n g t i m e t h a n was w e i g h t l o s s o f c o n f i n e d samples, b u t s a l a l l o s t about 50% of i t s o r i g i n a l w e i g h t a f t e r one y e a r , w h i l e b i g - l e a f maple l e a v e s l o s t an a v e r a g e o f 95%. Due t o t h e d i f f e r e n t b e h a v i o r o f t h e u n c o n f i n e d samples on t h e f o u r s i t e s , t h e a n a l y s i s o f v a r i a n c e r e v e a l s a s t r o n g t h r e e -way i n t e r a c t i o n amongst s i t e s , methods, and t i m e (F prob < .001), w h i c h makes f u r t h e r s t a t i s t i c a l i n t e r p r e t a t i o n s q u e s t i o n a b l e . The d e c o m p o s i t i o n p a r a m e t e r , k, was c a l c u l a t e d f o r b o t h b r o a d l e a f s p e c i e s u s i n g t h e n e g a t i v e e x p o n e n t i a l w e i g h t l o s s f u n c t i o n d e s c r i b e d above. F o r s a l a l , k v a r i e d from .54 i n c o n f i n e d l i t t e r t o .69 f o r t e t h e r e d l i t t e r on s i t e 100 ( l o w e r x e r i c ) and 1.20 f o r t e t h e r e d l i t t e r on s i t e 400 (upper x e r i c ) . k v a l u e s f o r b i g - l e a f maple ranged from .33 f o r c o n f i n e d l i t t e r t o 1.61 f o r u n c o n f i n e d f o l i a g e on s i t e 300 ( l o w e r h y g r i c ) and 2.30 f o r uncon-f i n e d f o l i a g e on s i t e 600 (upper h y g r i c ) . C o n i f e r Twigs. Weight l o s s e s o f b o t h D o u g l a s - f i r and w e s t e r n r e d c e d a r t w i g s e x h i b i t e d s i m i l a r p a t t e r n s on t h e 100 ( l o w e r x e r i c ) , 200 ( l o w e r m e s i c ) and 300 ( l o w e r h y g r i c ) s i t e s ( T a b l e 2)".. Twigs o f b o t h s p e c i e s a t t a i n e d t h e i r g r e a t e s t w e i g h t l o s s on t h e 300 s i t e . W estern r e d c e d a r t w i g s appeared t o decompose more q u i c k l y t h a n D o u g l a s - f i r t w i g s on a l l t h r e e s i t e s . Because d a t a a r e a v a i l a b l e from o n l y one c o l l e c t i o n p e r i o d , no s t a t i s t i c a l a n a l y s e s were 32 TABLE 2. P e r c e n t o f o r i g i n a l b r a n c h w e i g h t l o s t a f t e r f o u r months i n t h e f i e l d . % w e i g h t l o s t S i t e Cedar D o u g l a s - f i r 100 13.6 8.2 200 11.4 7.8 300 21.9 11.2 a t t e m p t e d and t h e d e c o m p o s i t i o n p a r a m e t e r , k, was n o t c a l c u l a t e d . C e l l u l o s e . C e l l u l o s e w e i g h t l o s s e s were f a i r l y s i m i l a r on t h e two x e r i c and two m e s i c s i t e s ( T a b l e 3 ) . However, w e i g h t l o s s p a t t e r n s were v e r y d i f f e r e n t on t h e two h y g r i c s i t e s . On s i t e 300 ( l o w e r h y g r i c ) about 56% o f t h e o r i g i n a l c e l l u l o s e w e i g h t was l o s t a f t e r 12 months. However, on s i t e 600 (upper h y g r i c ) o n l y about 30% was l o s t a f t e r 12 months. T h i s i s r e f l e c t e d i n a s i g n i f i c a n t (F prob = .04) i n t e r -a c t i o n between s i t e and t i m e i n a n a l y s i s o f v a r i a n c e . Newman-Keul's m u l t i p l e range t e s t i n d i c a t e s t h a t t h e t w e l v e month mean w e i g h t l o s s f o r s i t e 300 ( l o w e r h y g r i c ) was s i g n i f i c a n t l y d i f f e r e n t from a l l o t h e r means. 5.1.2 D i s c u s s i o n C o n i f e r f o l i a g e . The r a t e s o f c o n i f e r f o l i a g e w e i g h t l o s s on t h e s i x s i t e s , e x p r e s s e d as a k v a l u e , can be compared w i t h r e s u l t s from o t h e r 33 TABLE 3. P e r c e n t o f o r i g i n a l c e l l u l o s e w e i g h t l o s t a f t e r s i x months and 12 months i n t h e f i e l d . % w e i g h t l o s t S i t e 6 months 12 months 100 7.5 12.8 200 6.8 21.4 300 6.2 5 6 . l a 400 4.6 20.3 500 3.2 16.6 600 3.6 29.6 S i g n i f i c a n t l y d i f f e r e n t from a l l o t h e r means u s i n g Newman-Keul's m u l t i p l e range t e s t . l i t t e r bag s t u d i e s ( T a b l e 4 ) . k v a l u e s measured i n t h e p r e s e n t s t u d y were s i m i l a r t o t h o s e c a l c u l a t e d f o r P i c e a s i t c h e n s i s and A b i e s g r a n d i s i n E n g l a n d (Hayes 1965). However, t h e y a r e somewhat h i g h e r t h a n t h o s e measured f o r D o u g l a s - f i r i n Oregon ( F o g e l & Cromack 1977). T h i s d i f f e r e n c e may have o c c u r r e d because t h e c o n i f e r l i t t e r i n t h e bags o f t h e p r e s e n t s t u d y c o n t a i n e d a m i x t u r e o f s p e c i e s , i n c l u d i n g w e s t e r n r e d c e d a r , w h i c h may have decomposed a t a f a s t e r r a t e t h a n D o u g l a s - f i r , t h u s i n c r e a s i n g t h e measured k v a l u e f o r t h e bag c o n t e n t s . The v e r y s i m i l a r r a t e s o f c o n i f e r o u s f o l i a g e w e i g h t l o s s on th e s i x s i t e s i s s u r p r i s i n g , c o n s i d e r i n g t h e p h y s i c a l and c h e m i c a l d i f f e r e n c e s between t h e s i t e s . T h i s c o u l d be a c c o u n t e d f o r by two TABLE 4. Comparison o f d e c o m p o s i t i o n parameters o f c o n i f e r f o l i a g e w i t h o t h e r l i t t e r bag s t u d i e s i n the l i t e r a t u r e . Study R e g i o n Tree S p e c i e s D u r a t i o n % Weight L o s s k R e f e r e n c e N. C a r o l i n a P i n u s s t r o b u s 12 Tennessee P i n u s t a e d a 12 New B r u n s w i c k P i n u s b a n k s i a n a 12 En g l a n d P i n u s s y l v e s t r i s 12 P i c e a s i t c h e n s i s 12 A b i e s g r a n d i s 12 F i n l a n d " P i n e l i t t e r " 12 Tennessee P i c e a 12 Tsuga 12 P i n u s 12 Oregon P s e u d o t s u g a menz. 24 B r i t i s h C o l u m b i a M i x e d c o n i f e r 1 12 2 12 3 12 36.9 .46 Cromack & Monk 1975 44 .580 Thomas 1968 24.5 - 29.9 .307 - .355 MacLean.1978 48 .654 Hayes 1965 37 .462 37 .462 32.7 .396 M i k o l a 1960 29 .342 Shanks and O l s o n 1961 34 .415 40 .515 35 .33 - .31 F o g e l & Cromack 1977 35 .43 P r e s e n t s t u d y 35 .43 35 .43 1 2 3 = x e r i c = m e s i c = h y g r i c 35 p o s s i b l e f a c t o r s : 1) the e f f e c t of the bags a r t i f i c i a l l y s e p arating the c o n i f e r f o l i a g e from the other l i t t e r of the f o r e s t f l o o r and the s o i l fauna, which might otherwise have created c o n d i t i o n s more favourable f o r decomposition and which would vary between the three ecosystem types, or 2) the o v e r r i d i n g i n f l u e n c e of sub s t r a t e chemical composition i n determining r a t e s of l i t t e r breakdown. Studies by Kawahara (1975) and Thomas (1968) have compared decomposition r a t e s of c o n i f e r needles w i t h an without the a d d i t i o n of hardwood leaves to the l i t t e r bags. Both s t u d i e s reported that the presence of hard-wood leaves d i d not make a s i g n i f i c a n t d i f f e r e n c e to the r a t e of c o n i f e r decomposition. Thomas (1968) ex t r a c t e d fauna from c o n i f e r l i t t e r bags w i t h and without hardwood leaves and found s i g n i f i c a n t l y greater numbers i n the bags of mixed l i t t e r . The fauna were e v i d e n t l y c o n f i n i n g t h e i r feeding a c t i v i t y to the hardwood leaves. Thus, i t i s p o s s i b l e that on the h y g r i c s i t e s i n the present study, the greater numbers and d i v e r s i t y of s o i l fauna found on these s i t e s are a l s o r e s t r i c t i n g t h e i r feeding to non-coniferous l i t t e r . I t t h e r e f o r e appears that the chemical composition of the c o n i f e r l i t t e r i n e a r l y stages of decomposition may:/override! d i f f e r e n c e s i n p h y s i c a l and chemical p r o p e r t i e s between the s i t e s i n determining r a t e s of l i t t e r decomposition. Broadleaf l i t t e r . The k values of .33 f o r confined and 1.6 to 2.3 f o r tethered b i g - l e a f maple f o l i a g e i n d i c a t e the important r o l e which p h y s i c a l breakdown and comminution played i n the disappearance of l i t t e r of t h i s species on the h y g r i c s i t e s . Leaves were observed to be 36 very fragmented at the end of the twelve month period i n the l i t t e r bags of both mesh s i z e s , and most of the fragments would have been l o s t had they not been confined. Thus, most of the difference between k values of confined and unconfined l i t t e r was probably due to fragmentation and not a difference i n rates of c a t a b o l i c degra-dation. Fragmentation of s a l a l l i t t e r on the x e r i c s i t e s was not nearly so great, and the k values for confined and unconfined leaves were more s i m i l a r . Both confined and unconfined leaves appeared to decom-pose nearly i n t a c t , gradually becoming thinner u n t i l only a skeleton remained. Because fragmentation was minimal the slower weight loss rate of the confined leaves was an unexpected f i n d i n g . However, some fragmentation did appear to occur because of alternate drying and wetting over the summer and t h i s may have helped to account for the difference. The f a s t e r weight loss of confined s a l a l l i t t e r than of con-fined b i g - l e a f maple l i t t e r i s also an unexpected r e s u l t . However, the confined s a l a l l i t t e r lay much f l a t t e r and was more completely and n a t u r a l l y incorporated into the forest f l o o r than was the b i g -l e a f maple f o l i a g e , which tended to c u r l up so that large portions of the leaves were not i n contact with the forest f l o o r . k values of confined l i t t e r of both species f e l l i n the general range of those measured for other broadleaf species (Table 5), varying from 0.3 to 0.6. The k value for confined b i g -l e a f maple i s considerably lower than the values reported for other maple species, such as .85 for Acer saccharum (Gosz et a l . 1973) and TABLE 5. Comparison o f k parameter o f b r o a d l e a f f o l i a g e l i t t e r w i t h o t h e r l i t t e r bag s t u d i e s i n the l i t e r a t u r e . R e g i o n T r e e S p e c i e s Decomp. Time (mos.) % Weight L o s s k R e f e r e n c e A l b e r t a P o p u l u s t r e m u l o i d e s 12 26.2 .303 L o u s i e r & P a r k i n s o n 1976 P o p u l u s b a l s a m i f e r a 12 21.2 .283 Quebec P o p u l u s spp. 10 35.1 .519 C o l d w e l l & DeLong 1950 A c e r saccharum 10 41.0 .633 B e t u l a p o p u l i f o l i u m 10 41.6 .645 New B r u n s w i c k A c e r rubrum 12 51.2 - 54.9 .718 - . 868 MacLean .1978 P r u n u s p e n s y l v a n i c a 12 55.7 - 56.4 .813 - . 905 P o p u l u s t r e m u l o i d e s 12 38.3 .483 B e t u l a p a p y r i f e r a 12 50.4 .702 A l a s k a P o p u l u s t r e m u l o i d e s 12 38.3 .483 Van C l e v e 1971 B e t u l a p a p y r i f e r a 12 40.6 .520 New Hampshire B e t u l a a l l e g h a n i e n s i s 12 42 .51 Gosz e t a l . 1973 A c e r saccharum 12 60 .85 N. C a r o l i n a A c e r rubrum 12 53.7 .77 Cromack & Monk 1975 Tennessee A c e r rubrum 12 55 .799 Thomas 1970 Quercus a l b a 12 . .700 Witkamp and O l s o n 1963 A c e r rubrum 12 .708 F i n l a n d " B i r c h l i t t e r " 12 37.2 .465 M i k o l a 1960 B r i t i s h C o l umbia A c e r m a c r o p h y l l u m 12 25 .33 P r e s e n t s t u d y G a u l t h e r i a s h a l l o n 12 40 ..54 38 .77 f o r A c e r rubrum (Cromack and Monk 1975). T h i s , a g a i n , may be e x p l a i n e d i n p a r t by t h e c u r l i n g o f c o n f i n e d b i g - l e a f maple, w h i c h would p r o b a b l y n o t o c c u r t o much e x t e n t i n s p e c i e s w i t h s m a l l e r l e a v e s . Twig l i t t e r . There have been few s t u d i e s w h i c h measure t w i g o r b r a n c h d e c o m p o s i t i o n , and most o f t h e s e have been i n hardwood f o r e s t s . However, t w i g d r y w e i g h t l o s s o f 14 t o 24% d u r i n g t h e f i r s t s i x months o f d e c o m p o s i t i o n i n t h e p r e s e n t s t u d y i s somewhat h i g h e r t h a n t h e range o f v a l u e s r e p o r t e d by most e x i s t i n g s t u d i e s . Decay p a t t e r n s o f t w i g s and b r a n c h e s a r e d i f f i c u l t t o p r e d i c t beyond t h e t i m e of t h e e x p e r i m e n t due t o t h e i r v e r y s l o w decay r a t e s and t h e d i f f e r e n t i a l decay t i m e s o f wood and b a r k (MacLean 1978). Thus, k v a l u e s c a l c u l a t e d from t h e d a t a a t t h i s p o i n t i n t h e p r e s e n t s t u d y a r e q u e s t i o n a b l e . A l s o , S w i f t e t a l . ( 1 9 7 6 ) e s t i m a t e d t h a t f a l l e n b r a n c h e s have a l r e a d y l o s t up t o 40% o f t h e i r o r i g i n a l d r y w e i g h t a t t h e time o f f a l l , and i t i s t h u s d i f f i c u l t t o a s s e s s t h e i r s t a g e o f d e c o m p o s i t i o n . C e l l u l o s e . The w e i g h t l o s s o f c e l l u l o s e s h e e t s was c o n s i d e r a b l y g r e a t e r on t h e h y g r i c s i t e s ( p a r t i c u l a r l y 300) t h a n on t h e d r y e r s i t e s a f t e r one y e a r i n t h e f i e l d . On t h e h y g r i c s i t e s , the c e l l u l o s e bags appeared t o become more t h o r o u g h l y i n c o r p o r a t e d i n t o t h e f o r e s t f l o o r , w h i c h p r o b a b l y improved c o n d i t i o n s f o r d e c o m p o s i t i o n . A l s o , t h e p h y s i c a l changes i n t h e c e l l u l o s e on t h e h y g r i c s i t e s 39 were d i f f e r e n t from those observed on the other two s i t e s , which may i n d i c a t e that d i f f e r e n t processes were operating. I n d i v i d u a l squares were o f t e n reduced to h a l f t h e i r o r i g i n a l s i z e on the h y g r i c s i t e s , w i t h small holes appearing i n s i d e them. This appeared to be the r e s u l t of removal by s o i l fauna. Weight l o s s of c e l l u l o s e on a l l s i t e s i n the present study was greater than the 8% l o s s i n one year reported by Piene and van Cleve (1978) f o r c e l l u l o s e i n a black spruce stand i n Alaska. 5.2 Changes i n N u t r i e n t Concentration and N u t r i e n t Mass 5.2.1 Results Conifer needles. The concentration of N, P, K, Ca, and Mg i n c o n i f e r needles confined i n l i t t e r bags on a l l s i t e s at a l l sampling times are shown i n Table 6. The percent change i n co n c e n t r a t i o n and percent change i n t o t a l mass over twelve months are presented i n Table 7. The f o l l o w i n g trends are revealed by an i n s p e c t i o n of the data: 1. On a l l s i t e s , N c o n c e n t r a t i o n increased w i t h time by 100% or more, g e n e r a l l y from about .5% N to greater than 1.0% N. N concentration was at a l l times higher on the h y g r i c s i t e s than on the other s i t e types. When weight l o s s of the needles was considered, i t was observed that there was al s o an increase i n N mass over time, u s u a l l y between 20 and 32%. However, on the upper h y g r i c s i t e (600) there was a 97% incr e a s e . Table 6. Concentrations of N, P, K, Ca, and Mg of conifer l i t t e r on the six sites at each sampling time, expressed as percent of dry weight (+ standard deviation). Site Xeric" 100 A00 Mesic 200 500 Hygric 300 600 Time % Ash N P * K Ca Mg 0 5.82 (.78) .52 (.07) .110 (.010) .070 (.010) .88 (.07) .080 (.018) 1.5 5.56 (.58) .59 ;.o8) .073 (.010) .043 (.016) .94 (.07) .053 (.018) 3 5.54 (.60) .58 [.04) .068 (.005) .059 (.039) .91 (.19) .043 (.007) 6 6.34 (.91) .76 [.06) .093 (.012) .079 (.019) .86 (.07) .047 (.007) 9 4.70 (1.25) .71 [.09) .091 (.017) .088 (.016) .70 (.43) .047 (.002) 12 5.74 (.76) 1.05 [.45) .084 (.040) .083 (.010) .38 (.10) .056 (.008) 0 4.69 (.42) .52 [.03) .100 (.010) .072 (.010) .74 (.03) .060 (.010) 1.5 5.48 (.70) .52 [.08) .071 (.010) .032 (.006). .69 (.13) .046 (.009) 3 5.20 (.33) .58 [.06) .073 (.006) .042 (.008) .84 (.05) .048 (.003) 6 5.20 (.45) .69 [.04) .092 (.011) .072 (.016) .83 (.03) .047 (.004) 9 4.02 (1.90) .64 : . o 7 ) .091 (.009) .099 (.012) .82 (.06) .062 (.019) 12 5.97 (.53) 1.06 '.21) .109 (.020) .098 (.024) .79 (.11) .065 (.024) 0 5.80 (,72) .50 '.04) .100 (.011) .075 (.010) .74 (.03) .060 (.001) 1.5 4.90 (.52) .53 '.08) .070 (.016) .040 (.007) .72 (.02) .052 (.007) 3 5.12 (.74) .58 '.13) .078 (.016) .056 (.012) .75 (.04) .051 (.009) 6 4.94 (.51) .77 ',05) .097 . (.006) .072 (.006) .83 (.17) .046 (.004) 9 3.22 (1.64) .68 '.18) .086 (.024) .076 (.016) .79 (.12). .043 (.009) 12 5.16 (.55) .97 '.15) .099 (.028) .079 (.002) .87 (.04) .053 (.011) 0 5.22 (.47) .53 '.01) .100 (.007) .071 (.009) '.83 (.12) .070 (.005) 1.5 4.96 (.50) .60 ',07) .076 (.013) .042 (.009) .87 (.08) .052 (.004) 3 5.61 (.97) .63 [.06) .083 (.013) .053 (.017) .85 (.07) .055 (.003) 6 4.94 (.63) .71 MO) .091 (.023) .064 (.014) .86 (.04) .048 (.010) 9 3.66 (1.72) .75 '.07) .105 (.015) .091 (.021) .86 (.06) .056 (.016) 12 4.86 (.34) 1.16 '.47) .107 (.018) .088 (.023) .40 (.26) .064 (.013) 0 5.20 (.46) .53 ,01) .080 (.010) .080 (.010) .85 (.09) .080 (.010) 1.5 5.00 (1.14) .78 .16) .077 (.007) .047 (.026) .90 ( . 1 1 ) .071 (.008) 3 5.06 (1.08) .98 .11) .091 (.012) .078 (.018) .99 (.35) .070 (.006) 6 5.51 (.48) 1.11 .11) .101 (.012) .075 (.017) .90 (.23) .072 (.012) 9 4.04 (1.39) 1.18 .21) .104 (.021) .084 (.019) .70 (.36) .068 (.009) 12 5.41 (.72) 1.09 .40) .100 (.034) .068 (.009) .66 (.38) .075 (.013) 0 5.17 ( . 2 2 ) .50 .04) .105 (.012) .075 (.008) .94 (.04) .071 (.008) 1.5 5.85 (.38) .74 .03) .062 (.003) .044 (.017) 1.13 (.12) .065 (.013) 3 5.62 (.98) .83 .05) .074 (.008) .047 (.007) 1.04 (.08) .058 (.003) 6 5.52 (.57) 1.04 .13) .090 (.021) .059 (.009) .98 (.13) .049 (.011) 9 4.88 (1;03) 1 .11 .09) .101 (.012)" .083 (.005) .34 (.25) .063 (.042) 12 5.63 (.74) 1.45 .33) .105 (.016) ,063 (.004) .18 (.07) .069 (.007) o 41 TABLE 7. P e r c e n t change i n n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass o f n e e d l e s c o n f i n e d i n l i t t e r bags from time 0 t o 12 months (% o f o r i g i n a l c o n c e n t r a t i o n o r mass). N P K Ca Mg S i t e Cone. Mass Cone. Mass Cone. Mass Cone. Mass Cone. Mass 100 +104 +26 -24 -53 +19 -26 -57 -73 -30 -57 400 +104 +26 + 9 -32 +36 -13 + 7 -34 + 8 -33 200 + 94 +20 + 9 -38 + 5 -30 +15 -28 -12 -43 500 +119 +42 + 7 -31 +24 -24 -52 -71 - 9 -45 300 +106 +24 +25 -19 -15 -45 -21 -59 - 6 -40 600 +190 +97' 0 -32 -16 -46 -82 -85 - 3 -32 2. C o n c e n t r a t i o n s of P i n c o n i f e r n e e d l e s were g e n e r a l l y much l o w e r t h a n t h o s e o f N. P c o n c e n t r a t i o n s d e c r e a s e d m a r k e d l y i n th e f i r s t s i x weeks o f d e c o m p o s i t i o n , and t h e n i n c r e a s e d . The r e s u l t was a v a r i a b l e n e t change i n P c o n c e n t r a t i o n a t t h e end of one y e a r , r a n g i n g from +25 t o -24%. However, sample w e i g h t l o s s r e s u l t e d i n a d e c r e a s e i n the mass o f P i n a l l c a s e s . 3. K c o n c e n t r a t i o n s showed a s i m i l a r t r e n d o f i n i t i a l d e c r e a s e f o l l o w e d by an i n c r e a s e . K c o n c e n t r a t i o n s o f samples on t h e two x e r i c and m e s i c s i t e s i n c r e a s e d 5 t o 36% a f t e r 12 months, and d e c r e a s e d on t h e two h y g r i c s i t e s . However, t h e mass o f K i n t h e bags d e c r e a s e d i n a l l c a s e s from 13 t o 46%. 4. Ca and Mg c o n c e n t r a t i o n s were much more v a r i a b l e o v e r t i m e , u s u a l l y d e c r e a s i n g b u t sometimes i n c r e a s i n g a f t e r 12 months. I n a l l c a s e s t h e r e was a c o n s i d e r a b l e l o s s o f n u t r i e n t mass, 42 ranging between 28 and 85% for Ca and 32 to 57% for Mg. S a l a l l e a f l i t t e r . Nutrient concentrations of s a l a l leaves at each c o l l e c t i o n time on the 100 and 400 s i t e s are shown i n Table 8. The percent change i n concentration and nutrient mass over twelve months ige shown i n Table 9. The following trends are revealed by an inspec-t i o n of the data: 1. N concentrations of the s a l a l l i t t e r were generally somewhat higher than those of the conifer l i t t e r , but they showed the same consistent increasing trend. However, the percent increase was generally le s s than that measured i n conifer l i t t e r , ranging from +19 to +100%. The combination of weight and N concentration changes resulted i n a decrease i n the mass of N a f t e r 12 months i n most cases. However, i n the 1 mm mesh bags on both s i t e s there was an increase i n N mass. 2. Concentrations of P i n s a l a l l i t t e r were generally s i m i l a r to those of conifer l i t t e r . However, unlike P.in conifer l i t t e r , concentration of P i n the s a l a l l i t t e r showed a consistent increasing trend, ranging from 13 to 80% a f t e r one year. Total mass of P decreased with time i n the tethered samples on both s i t e s , and i n other samples increased or decreased s l i g h t l y . 3. K concentrations of s a l a l l i t t e r were generally somewhat higher than those of conifer l i t t e r , but they showed the same general temporal v a r i a t i o n : a decrease over the f i r s t s i x weeks followed by an increase. This resulted i n v a r i a b l e TABLE 8. Concentrations of nutrients in Salal l i t t e r on the two xeric sites at each sampling time, expressed as percent of dry weight (+ standard deviation). B = 1 mm bag C = A mm bag E = tethered Site Method Time % Ash Ca Mg 300 400 0 4.40 (.45) .77 (.07) .070 (.004) .091 (.020) .92 (.11) .150 (.010) ih 4.38 (.86) .88 (.48) .076 (.025) .077 (.021) .92 (.20) .136 (.007) 3 4.70 (.93) .97 (.16) .088 (.008) .078 (.016) .97 (.17) .136 (.017) 6 5.59 (.64) 1.15 (.26) .091 (.013) .078 (.011) 1.12 (.07) .135 (.007) 9 9.37 (1.43) 1.19 (.22) .112 (.014) .079 (.010) .57 (.45) .103 (.009) 12 6.86 (1.87) 1.25 (.52) .102 (.056) .086 (.014) .34 (.47) .099 (.019) lh 5.06 (1.03) .73 (.19) .074 (.016) .072 (.024) 1.11 (.18) !l48 (.019) 3 5.18 (.91) .96 (.12) .087 (.010) .067 '(.007) .96 (.12) .118 (.035) 6 6.24 (1.51) 1.04 (.22) .094 (.017) .075 (.019) 1.12 (.11) .125 (.009) 9 4.90 (2.03) 1.07 (.22) .104 (.021) .089 (.012) .38 (.35) .089 (.009) 12 6.07 (.90) 1.54 (.15) .126 (.016) .084 (.011) .54 (.36) .087 (.009) lk 3.97 (2.30) .69 (.05) .062 (.009) .045 (.024) .83 (.40) .121 (.063) 3 4.80 (0.41) .74 (.15) .065 (.007) .079 (.059) .99 (.32) .145 (.043) 6 4.88 (.51) 1.04 (.16) .102 (.013) .070 (.019) .94 (.15) .111 (.032) 9 4.38 (1.92) .97 (.23) .097 (.022) .084 (.013) .58 (.37) .104 (.023) 12 6.12 (.41) 1.55 (.26) .124 (.016) .075 (.012) .23 (.09) .103 (.013) 0 4.96 (.83) .99 (.05) .090 (.007) .083 (.014) . .93 (.10) .162 (.011) lh 5.35 (.62) .68 (.21) .067 (.021) .064 (.013) 1.04 (.10) .162 (.009) 3 4.87 (.69) .80 (.24) .079 (.013) .057 (.007) .98 (.17) .132 (.020) 6 4.88 (.51) 1.04 (.16) .102 (.013) .070 (.019) .94 (.15) .111 (.032) 9 4.38 (1.92) .97 (.23) .097 (.022) .084 (.013) .58 (.37) .104 (.023) 12 6.12 (.41) 1.55 (.26) .124 (.016) .075 (.012) .23 (.09) .103 (.013) lk 4.85 (.46) .73 (.14) .069 (.013) .046 (.009) 1.03 (.74) .154 (.006) 3 5.32 (1.83) .84 (.13) .076 (.009) .059 (.009) .95 (.92) .117 (.026) 6 5.36 (.98) 1.20 (.30) .097 (.023) .078 (.017) 1.06 (.07) .104 (.006) 9 5.65 (1.90) 1.12 (.08) .113 (.009) .095 (.014) .23 (.15) .110 (.027) 12 5.90 (.69) 1.19 (.34) .102 (.032) .083 (.007) .25 (.16) .093 (.010) lh 6.64 (4.46) .68 (.05) .073 (.005) .107 (.093) 1.02 (.23) .154 (.027) 3 4.99 (1.08) .83 (.13) .078 (.010) .075 (.047) 1.08 (.08) : .138 (.018) 6 4.96 (.88) .96 (.23) .096 (.011) .063 (.013) .93 (.11) .099 (.007) 9 6.19 (4.83) 1.00 (.91) .079 (.029) .079 (.018) 1.11 (.57) .101 (.029) 12 11.62 (2.67) 1.18 (.42) .109 (.020) .098 (.031) 1.69 (.61) .102 (.065) 44 TABLE 9. P e r c e n t change o f s a l a l l i t t e r n u t r i e n t c oncen-t r a t i o n s and n u t r i e n t mass from t i m e 0 t o 12 months. B = 1 mm bag C = 4 mm bag E = t e t h e r e d . N P K Ca Mg S i t e Method Cone. Mass Cone. Mass Cone. Mass Cone. Mass Cone. Mas; 100 B + 62 + 5 +45 - 6 - 5 -47 -63 -76 -34 -57 C +100 +20 +80 + 8 - 8 -45 -41 -65 -41 -65 E +100 -40 +77 -47 -17 -75 -75 -92 -31 -79 400 B + 56 +17 +37 + 3 +10 -32 -75 -82 -36 -52 C + 20 -10 +13 -15 0 -27 -73 -80 -42 -55 E + 19 -30 +21 -27 +18 -29 -26 -56 -37 -62 change i n c o n c e n t r a t i o n a f t e r one y e a r , r a n g i n g from +18 t o -17%. N e i t h e r c o n f i n e m e n t nor mesh s i z e appeared t o i n f l u e n c e t h i s t r e n d . However, i n a l l c a s e s t h e r e was a c o n s i d e r a b l e d e c r e a s e i n K mass o v e r t h e y e a r . 4. Ca c o n c e n t r a t i o n s a l s o tended to be somewhat h i g h e r i n t h e s a l a l l i t t e r t h a n i n t h e c o n i f e r l i t t e r . A l t h o u g h t h e r e was no c o n s i s t e n t t r e n d i n c o n c e n t r a t i o n changes w i t h t i m e , i n a l l c a s e s c o n c e n t r a t i o n changes a t t h e end o f one y e a r were 41 t o 75% l o w e r t h a n a t the b e g i n n i n g . As a r e s u l t t h e r e was a v e r y marked d e c r e a s e i n Ca mass (56 t o 92% l o s s ) . 5. Mg c o n c e n t r a t i o n s i n s a l a l l i t t e r t e nded t o be about d o u b l e t h o s e i n c o n i f e r l i t t e r . There was a f a i r l y c o n s i s t e n t t r e n d o f d e c r e a s i n g Mg c o n c e n t r a t i o n o v e r t i m e , r a n g i n g from a 31 45 t o 42% d e c r e a s e o v e r one y e a r . I n a l l c a s e s t h e r e was a l o s s i n Mg mass from 52 t o 79%. There was no a p p a r e n t e f f e c t o f c o n f i n e m e n t o r mesh s i z e on n u t r i e n t changes. B i g - l e a f maple l i t t e r . N u t r i e n t c o n c e n t r a t i o n s o f b i g - l e a f maple l i t t e r a t each s a m p l i n g t i m e a r e shown i n T a b l e 10. R e s u l t s from t e t h e r e d l e a f samples a r e o n l y p r e s e n t e d t o n i n e months because r e t r i e v e d samples were g e n e r a l l y too s m a l l a f t e r t w e l v e months t o p e r m i t n u t r i e n t a n a l y s i s . The p e r c e n t change i n n u t r i e n t c o n c e n t r a t i o n and mass a f t e r t w e l v e months a r e p r e s e n t e d i n T a b l e 11. 1. N c o n c e n t r a t i o n s i n t h e i n i t i a l samples were c o n s i d e r a b l y g r e a t e r t h a n t h o s e o f s a l a l o r c o n i f e r l i t t e r . A l t h o u g h t h e r e was a p a t t e r n o f i n c r e a s i n g c o n c e n t r a t i o n w i t h t i m e , t h e c o n c e n t r a t i o n i n c r e a s e d o n l y 18 t o 66% i n one y e a r . Con-c e n t r a t i o n changes were g r e a t e r on t h e 300 s i t e and r e s u l t e d i n an i n c r e a s e o f N mass i n the bags on t h i s s i t e . On t h e 600 s i t e , t h e s m a l l e r c o n c e n t r a t i o n change and s i m i l a r w e i g h t l o s s r e s u l t e d i n a d e c r e a s e i n N mass. Mesh s i z e a ppeared t o have l i t t l e e f f e c t on n u t r i e n t changes on t h e 600 s i t e . However, on s i t e 300, l a r g e r mesh bags', .ftad a much g r e a t e r i n c r e a s e i n N c o n c e n t r a t i o n and N mass t h a n s m a l l mesh. 2. P c o n c e n t r a t i o n o f t h e b i g - l e a f maple l i t t e r was s i m i l a r t o t h a t o f t h e o t h e r l i t t e r t y p e s . I n a l l c a s e s c o n c e n t r a t i o n s t ended t o i n c r e a s e f o r t h e f i r s t t h r e e t o s i x months, and t h e n d e c r e a s e d . However, i n a l l c a s e s t h e r e was a n e t i n c r e a s e TABLE 10. Concentration of nutrients in big-leaf maple l i t t e r on the two hygric sites at each sampling time, expressed as percent ot dry weight (+ standard deviation). B = 1 mm bag C = 4 mm bag E = tethered Site Method Time % Ash 300 600 6.21 (.82) 3 6 9 12 15s 3 6 9 12 Ik 3 6 9 lk 3 6 9 12 ik 3 6 9 12 lk 3 6 9 86 10 67 80 11 A.82 3.44 5.22 4.66 7.40 (.57) (1.15) (2.21) (.07) (2.02) (.46) (2.33) (.31) (1.40) (1.51) 6.14 (1.58) 6.09 (.33) 5.93 (1.51) 3.11 (1.07) (1.52) (.46) (5.40) (2.29) (.74) (1.40) (1.48) (.88) (1.00) (.50) 6.83 (.93) 7.47 (2.30) 8.31 (.51) 7.99 (1.80) 7.40 6.83 8.38 5.88 7.20 7.50 7.36 7.26 7.23 6.96 .99 (.05) (.11) (.03) (.19) (.07) (.51) (.13) (.23) (.18) (.19) (.09) (.07) (.16) (.13) (.07) 1.10 1.18 1.42 1.32 1.31 .98 .97 1.28 1.39 1.65 .94 1.02 1.35 1.36 7.54 (1.62) 1.02 (.05) 1.08 1.04 1.35 1.60 1.21 1.20 1.13 1.36 1.41 1.20 1.02 1.05 1.40 .95 (.24) (.10) (.08) (.24) (.53) (.18) (.13) (.11) (.29) (.58) (.09) (.06) (.04) (.34) .069 (.007) .071 .083 .114 .101 .087 .066 .073 .100 .114 .118 .065 .076 .108 .110 (.009) (.007) (.029) (.006) (.037) (.009) (.018) (.018) (.034) (.017) (.005) (.014) (.017) (.005) .069 (.006) .083 .080 .102 .135 .087 .089 .088 .109 .119 .100 .075 .085 .116 .094 (.027) (.009) (.010) (.024) (.053) (.014) (.008) (.015) (.023) (.042) (.014) (.010) (.019) (.041) .090 (.010) (.006) (.031) (.031) (.003) (.019) (.016) (.018) (.007) (.004) (.025) (.017) (.087) (.016) (.014) .082 (.004) .061 .084 .106 .099 .074 .067 .063 .088 .096 .072 .071 .142 .111 .104 .077 .076 .094 .104 .065 .067 .077 .101 .097 .064 .081 .077 .103 .162 (.018) (.014) (.009) (.011) (.007) (.004) (.008) (.010) (.006) (.009) (.008) (.020) (.017) (.153) Ca 1.46 (.19) (.12) (.28) (.31) (.37) (.27) (.09) (.25) (.11) (.46) (.42) (.54) (.55) (.17) (.58) (.11) (.53) (.14) (.31) (.26) (.18) (.17) (.37) (.15) (.36) (.24): (.12) (.31) (.17) (.20) 1.11 1.18 1.04 .36 .63 1.04 .85 .87 .58 .42 1.44 1.51 .88 1.05 1.42 1.29 1.34 1.33 .40 .38 1.33 1.16 1.28 .40 .38 29 10 30 56 Mg .160 (.005) .130 .117 .104 .092 .093 .126 .109 .106 .094 .113 .139 .125 .069 .095 .119 .111 .093 .095 .088 .123 .096 .077 .067 .091 .105 .066 .058 .057 (.004) (.006) (.009) (.006) (.020) (.006) (.022) (.009) (.008) (.015) (.024) (.045) (.016) (.015) .151 (.010) (.022) (.021) (.015) (.002) (.014) (.013) (.021) (.010) (.010) (.009) (.016) (.015) (.021) (.056) 47 TABLE 11. P e r c e n t change o f n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass i n b i g - l e a f maple l e a v e s from 0 to 12 months. B = 1 mm bag C = 4 mm bag. N P K Ca Mg S i t e Method Cone. Mass Cone. Mass Cone. Mass Cone. Mass Cone. Mass 300 B +31 + 2 +26 - 4 -18 -32 -57 -66 -42 -56 C +66 +29 +71 +32 -20 -30 -71 -77 -29 -46 600 B +19 - 8 +26 - 6 -21 -38 -73 -80 -42 -57 C +18 -14 +44 + 3 -28 -42 -74 -81 -40 -60 i n P c o n c e n t r a t i o n o v e r t h e y e a r , r a n g i n g from 26 t o 71%. On b o t h s i t e s , c o n c e n t r a t i o n i n c r e a s e s were g r e a t e r i n t h e r 4 mm mesh b a g s , w h i c h r e s u l t e d i n an i n c r e a s e i n P mass f o r t h e s e samples. P mass i n 1 mm mesh bags d e c r e a s e d s l i g h t l y . 3. K c o n c e n t r a t i o n s had a l e s s c o n s i s t e n t p a t t e r n o v e r t h e y e a r t h a n d i d o t h e r n u t r i e n t s . I n a l l c a s e s t h e r e was an i n i t i a l d e c r e a s e , f o l l o w e d by an i n c r e a s e , w h i c h i n some c a s e s was f o l l o w e d by a d e c r e a s e o v e r the f i n a l t h r e e months. A l l samples had a c o n c e n t r a t i o n d e c r e a s e o v e r t h e y e a r o f 18 t o 28%. K mass d e c r e a s e d s l i g h t l y l e s s on s i t e 300 (30-32%) t h a n on s i t e 600 ( 3 8 - 4 2 % ) . Mesh s i z e had no e f f e c t . 4. Ca c o n c e n t r a t i o n s o f b i g - l e a f maple were c o n s i d e r a b l y h i g h e r t h a n t h o s e o f o t h e r s p e c i e s . There was a v e r y s t r o n g t r e n d o f d e c r e a s i n g c o n c e n t r a t i o n s w i t h t i m e , w i t h n e t d e c r e a s e s o f 57 t o 73% a f t e r one y e a r . T o t a l mass l o s s e s o v e r t h e y e a r r e a c h e d 66 t o 81%, and were s l i g h t l y g r e a t e r on t h e 48 600 s i t e . Mesh s i z e had no e f f e c t on s i t e 600. C o n c e n t r a t i o n and mass d e c r e a s e s were s l i g h t l y g r e a t e r i n l a r g e mesh bags on s i t e 300. 5. Mg c o n c e n t r a t i o n s a l s o e x h i b i t e d a d e c r e a s i n g t r e n d w i t h t i m e , d e c r e a s i n g 29 t o 42% o v e r one y e a r . The l o s s o f Mg mass amounted t o 46 t o 60%, w i t h l o s s e s a g a i n b e i n g s l i g h t l y h i g h e r on t h e 600 s i t e . As w i t h most of t h e n u t r i e n t s , Mg c o n c e n t r a -t i o n was n o t i n f l u e n c e d by mesh s i z e . Twige:. l i t t e r . The r e s u l t s from t h e s i n g l e c o l l e c t i o n o f " t w i g r l i t t e r a r e p r e s e n t e d i n T a b l e 12. The i n i t i a l c o n c e n t r a t i o n s o f a l l t h e n u t r i e n t s i n i>twi;g'st"->E o f b o t h w e s t e r n r e d c e d a r and D o u g l a s - f i r were about h a l f t h e c o n c e n t r a t i o n s found i n t h e f o l i a g e . Changes i n c o n c e n t r a t i o n and mass o v e r s i x months were v e r y v a r i a b l e ( T a b l e 1 3 ) . N c o n c e n t r a t i o n s i n c r e a s e d c o n s i d e r a b l y i n some samples and de c r e a s e d s l i g h t l y i n o t h e r s . P c o n c e n t r a t i o n s g e n e r a l l y i n c r e a s e d , b u t i n most samples t h e i n c r e a s e was s m a l l and r e s u l t e d i n a d e c r e a s e i n P mass. K c o n c e n t r a t i o n changes were t h e most c o n s i s -t e n t , d e c r e a s i n g i n a l l samples and r e s u l t i n g i n a d e c r e a s e i n mass i n a l l samples. Ca c o n c e n t r a t i o n s d e c r e a s e d i n most samples. How-e v e r , i n t h e ce d a r ';tv±ghee o f t h e two l o w e r s i t e s i t i n c r e a s e d c o n s i d e r a b l y . Mg c o n c e n t r a t i o n s d e c r e a s e d i n a l l samples e x c e p t one, where i t remained c o n s t a n t . D e c r e a s e s were g r e a t e r i n t h e c e d a r twigs::.3'? t h a n D o u g l a s - f i r " t w i g s . " o f a l l s i t e s . TABLE 12. N u t r i e n t c o n c e n t r a t i o n s i n t w i g samples (% of d r y wt.) a t t i m e s 0 and 6 months (+ s t a n d a r d d e v i a t i o n ) . S i t e S p e c i e s Time N P K Ca Mg 100 Douglas-• f i r 0 .50 (.04) .035 (.026) .066 (.020) .55 (.07) .034 (.005) 6 .90 (.87) .070 (.077) .028 (.011) .32 (.22) .028 (.021) Cedar 0 .48 (.06) .038 (.003) .045 (.010) .61 (.25) .037 (.009) 6 .56 (.44) .035 (.035) .020 (.010) .53 (.13) .015 (.010) 200 Douglas- f i r 0 .42 (.05) .036 (.021) .058 (.010) .57 (.06) .034 (.004) 6 .38 (.04) .037 (.006) .048 (.042) .49 (.07) .034 (.009) Cedar 0 .47 (.06) .038 (.004) .045 (.010) .60 (.12) .038 (.008) 6 1.29 (1.00) .082 (.055) .025 (.005) .84 (.23) .031 (.010) 300 Douglas- f i r 0 .46 (.21) .040 (.020) .048 (.008) .53 (.03) .032 (.010) 6 .49 (.05) .042 (.003) .015 (.007) .16 (.10) .030 (.012) Cedar 0 1.35 (.30) .050 (.031) .031 (.015) .31 (.11) .041 (.009) 6 1.30 (.62) .050 (.021) .019 (.017) .50 (.09) .028 (.018) 50 TABLE 13. P e r c e n t change I n n u t r i e n t c o n c e n t r a t i o n and n u t r i e n t mass o f twigs' from 0 t o 6 months. N P K Ca Mj y S i t e Cone. Mass Cone. Mass Cone. Mass Cone. Mass Cone. Mass 100 D o u g - f i r +80 +65 +100 +84 -57 -61 -42 -47 -18 -25 Cedar +17 -2 +8 -9 -55 -72 -3 -19 -58 -76 200 D o u g - f i r -10 -17 +3 -5 -17 -24 -14 -21 0 -8 Cedar +174 +144 +54 +37 -45 -61 +40 +25 -18 -27 300 D o u g - f i r -13 -23 +5 -7 -69 -72 -70 -74 -6 -16 Cedar -4 -25 0 -22 -39 -53 +61 +45 -32 -47 5.2.2 D i s c u s s i o n I n t e r p r e t a t i o n o f n u t r i e n t d a t a e x p r e s s e d b o t h as changes i n concen-t r a t i o n and changes i n t o t a l mass o f t h e element i n t h e sample i s i m p o r -t a n t . The l a t t e r t a k e s i n t o a c c o u n t t h e p a t t e r n o f n u t r i e n t c o n c e n t r a -t i o n change as w e l l as t h e l o s s i n d r y w e i g h t o c c u r r i n g o v e r t i m e . N u t r i e n t mass changes o b s e r v e d i n t h i s s t u d y a r e compared w i t h t h o s e from o t h e r s t u d i e s ( T a b l e s 14 and 1 5 ) . N i t r o g e n . The v e r y l a r g e i n c r e a s e s i n b o t h N c o n c e n t r a t i o n and N mass p r o b a b l y o c c u r r e d f o r s e v e r a l r e a s o n s . N i n f o r e s t l i t t e r t e n d s t o be i n s h o r t s u p p l y and most o f i t i s t h e r e f o r e r e t a i n e d , p r i m a r i l y by t h e m i c r o -organisms (Gosz e t a l . 1973). D u r i n g d e c o m p o s i t i o n the amount o f c a r b o n TABLE 14. Comparison o f p e r c e n t change i n mass of n u t r i e n t s f rom decomposing c o n i f e r l i t t e r w i t h v a l u e s from the l i t e r a t u r e . R e g i o n S p e c i e s Time i n f i e l d (mos.) % o f o r i g i n a l n u t r i e n t mass R e f e r e n c e N P K Ca Mg N. C a r o l i n a P i n u s s t r o b u s 12 ^100 ^100 18 ^100 32 Cromack and Monk 1975 New B r u n s w i c k P i n u s banks. 12 85 148 22 47 43 MacLean 1978 12 103 188 17 80 63 B r i t i s h C o l u m b i a M i x e d c o n i f e r 1 12 126 58 80 47 55 P r e s e n t Study 2 12 113 61 73 50 51 3 12 157 64 74 32 63 1 = x e r i c s i t e 2 = me s i c s i t e 3 = h y g r i c s i t e TABLE 15. Comparison o f p e r c e n t change i n mass o f n u t r i e n t s from decomposing b r o a d l e a f l i t t e r w i t h v a l u e s from the l i t e r a t u r e . „ m . % o f o r i g i n a l n u t r i e n t mass n - f . . . . . . R e g i o n S p e c i e s Time i n _ Reference f i e l d (mos.) N P K Ca Mg New Hampshire B e t u l a a l l e g h e n . 12 118 26 47 12 Gosz e t a l . 1973 Fagus g r a n d i . 12 147 34 53 37 A c e r saccharum 12 166 18 75 61 N. C a r o l i n a M i x e d hardwood 12 88 66 17 71 23 Cromack & Monk 1975 F r a n c e Fagus s y l v a t i c a 12 103 77 30 66 63 Lemee.et B i c h a u t 1973 Quercus p e t r a e a 12 137 63 45 84 45 C a r p i n u s b e t u l u s 12 93 87 34 74 84 A u s t r a l i a E u c a l y p t u s o b l i q u a 12 75 12 82 57 . A t t i w i l l 1968 New B r u n s w i c k A c e r rubrum 12 77 25 6 41 26 MacLean 1978 Prunus p e n s y l u . 12 74 26 3 65 26 P o p u l u s t r e m u l . 12 82 50 7 69 54 B e t u l a p a p y r i f . 12 80 38 7 72 44 B r i t i s h C o l umbia A c e r m a c r o p h y l . 12 115 106 65 24 46 P r e s e n t s t u d y G a u l t h e r i a s h a l l o n 12 98 88 65 25 49 P r e s e n t s t u d y 53 i s reduced and N c o n c e n t r a t i o n t h e r e f o r e i n c r e a s e s . Increases i n N mass probably occurred due to inputs of N i n p r e c i p i t a t i o n , i n s e c t f r a s s , n i t r o g e n f i x a t i o n , and l e a c h i n g from new l i t t e r (Bocock 1964), and p o s s i b l y from fungal i m m o b i l i z a t i o n and t r a n s l o c a t i o n (Gosz et a l . 1973). At d i f f e r e n t times of year and under d i f f e r e n t micro-environmental c o n d i t i o n s , any or a l l of the above f a c t o r s may have co n t r i b u t e d to observed increases i n N mass i n the present study. S i m i l a r increases i n N concentration and N mass during decomposition have been noted by L o u s i e r and Parkinson (1978), Howard and Howard (1974), Anderson (1973b), Bocock (1964), G i l b e r t and Bocock (1960) and Gosz et a l . (1973). In the two broadleaf species of the present study, N concen-t r a t i o n s increased but N mass changes were more v a r i a b l e , r e f l e c t i n g the d i f f e r e n c e s i n weight l o s s . Decreases i n N mass i n the i n i t i a l stages of decomposition have been noted by MacLean (1978), Cromack and Monk (1975), and Hayes (1965). Phosphorus. Although P concentrations i n c o n i f e r f o l i a g e f l u c t u a t e d w i t h time, l o s s e s i n P mass at the end of one year were s i m i l a r to l o s s e s i n weight. The i n i t i a l r a p i d decrease i n P c o n c e n t r a t i o n suggested a high s u s c e p t i b i l i t y of P to l e a c h i n g processes (Lousier and Parkinson 1978). This was followed by an increase i n P concentration which may have r e s u l t e d from a t e r m i n a t i o n of l e a c h i n g and a r e t e n -t i o n of P as carbon was l o s t . P mass decreased throughout the study and there was t h e r e f o r e no evidence of e x t e r n a l P i n p u t . How-ever, i n the broadleaf samples, P concentrations increased, and P 54 mass tended to i n c r e a s e s l i g h t l y i n some samples, p a r t i c u l a r l y b i g -l e a f maple i n l a r g e mesh bags. I t i s p o s s i b l e t h a t t h e l a r g e r mesh a l l o w e d s e v e r a l s o u r c e s o f e x t e r n a l P i n p u t , such as p l a n t r e p r o d u c -t i v e m a t e r i a l s , w h i c h may have been e x c l u d e d from s m a l l e r mesh ( L o u s i e r and P a r k i n s o n 1978). MacLean (1978) and Gosz e t a l . (1973) a l s o found P mass t o i n c r e a s e i n some decomposing samples. However, L o u s i e r and P a r k i n s o n ( 1 9 7 8 ) , Cromack and Monk ( 1 9 7 5 ) , Lemee and B i c h a u t (1973) and A t t i w i l l (1968) a l l found P mass t o d e c r e a s e , and g e n e r a l l y c o n c l u d e d t h a t t h e l o s s of P was a s s o c i a t e d w i t h t h e l o s s o f d r y m a t t e r t h r o u g h o u t d e c o m p o s i t i o n . P o t a s s i u m . K c o n c e n t r a t i o n s f o l l o w e d d i f f e r e n t p a t t e r n s o f change i n each t y p e o f l i t t e r , d e p e n d i n g on t h e i r i n i t i a l v a l u e s . I n c o n i f e r l i t t e r , i n i t i a l K c o n c e n t r a t i o n s were v e r y low and i n c r e a s e d w i t h t i m e . The i n i t i a l c o n c e n t r a t i o n s were much l o w e r t h a n t h o s e r e p o r t e d by o t h e r r e s e a r c h e r s ( f o r example L o u s i e r and P a r k i n s o n 1978; Gosz e t a l . 1973; MacLean 1978). T h i s was p r o b a b l y due t o l o s s e s by l e a c h i n g w h i l e t h e l i t t e r was i n l i t t e r t r a p s and p r i o r t o i t s i n c l u -s i o n i n t h i s s t u d y . Other s t u d i e s have r e p o r t e d t h a t t h e r e i s a r a p i d d e c r e a s e i n K c o n c e n t r a t i o n d u r i n g t h e f i r s t months o f decom-p o s i t i o n due t o l e a c h i n g . The o b s e r v e d i n c r e a s e i n K c o n c e n t r a t i o n may i n d i c a t e t h a t some h e t e r o t r o p h i c i m m o b i l i z a t i o n o f K does o c c u r (Gosz e t a l . 1973; L o u s i e r & P a r k i n s o n 1978). I n b i g - l e a f maple l i t t e r , i n i t i a l K c o n c e n t r a t i o n s were somewhat h i g h e r t h a n i n c o n i f e r l i t t e r b u t d e c r e a s e d w i t h t i m e . I n a l l c a s e s , mass o f t h e element 55 d e c r e a s e d o v e r t h e y e a r . However, the d e c r e a s e i n K mass was much l o w e r t h a n v a l u e s r e p o r t e d i n any o t h e r s t u d i e s . The v e r y l a r g e l o s s e s from b i g - l e a f maple i n d i c a t e t h a t t h e i o n i s p r o b a b l y l e a c h e d t o a g r e a t e r e x t e n t from t h i s s p e c i e s . I n t h e c o n i f e r and s a l a l l i t t e r , l o s s e s appeared t o be m a i n l y due t o f r a g m e n t a t i o n and c a t a -b o l i c d e g r a d a t i o n . C a l c i u m . The marked d e c r e a s e i n Ca c o n c e n t r a t i o n and mass from a l l l i t t e r t y p e s a f t e r one y e a r was g r e a t e r t h a n l o s s e s r e p o r t e d i n o t h e r s t u d i e s ( T a b l e s 14 and 1 5 ) . W i l l ( 1 9 6 7 ) , A t t i w i l l ( 1 9 6 8 ) , Thomas (1970) and Gosz e t a l . (1973) i n d i c a t e d t h a t Ca was n o t v e r y s u s c e p t i b l e t o l e a c h i n g and t h a t t h e l o s s p a t t e r n o f Ca was s i m i l a r t o w e i g h t l o s s p a t t e r n s o f l e a f t i s s u e . L o u s i e r and P a r k i n s o n ( 1 9 7 8 ) , on t h e o t h e r hand, found a c c u m u l a t i o n o r v e r y s l o w r e l e a s e o f Ca w i t h t i m e i n an Aspen woodland, and a poor c o r r e l a t i o n between Ca w e i g h t l o s s and d r y w e i g h t l o s s . R e s u l t s from t h e p r e s e n t s t u d y appear t o i n d i c a t e t h a t l e a c h i n g p l a y s an i m p o r t a n t r o l e i n Ca r e m o v a l from decomposing l i t t e r i n c o a s t a l D o u g l a s - f i r f o r e s t s . Magnesium. Mg c o n c e n t r a t i o n s a l s o tended t o d e c r e a s e w i t h t i m e i n t h e p r e s e n t s t u d y , a l t h o u g h a t a s l o w e r r a t e t h a n Ca. The p a t t e r n o f c o n c e n t r a t i o n and Mg mass change was s i m i l a r t o t h a t r e p o r t e d i n o t h e r s t u d i e s ( T a b l e s 14 and 1 5 ) . However, A t t i w i l l (1968) r e p o r t e d p a t t e r n s o f Mg mass l o s s s i m i l a r t o t h o s e o f l i t t e r 56 w e i g h t , and L o u s i e r and P a r k i n s o n (1978) r e p o r t e d i n c r e a s e s i n Mg c o n c e n t r a t i o n o v e r t i m e . The p r e s e n t s t u d y s u p p o r t s r e p o r t s t h a t Mg i s r e l a t i v e l y l e a c h a b l e ( A t t i w i l l 1968) and i s n o t r e a d i l y i m m o b i l i z e d . R e l a t i v e M o b i l i t y . The r e l a t i v e m o b i l i t y o f the n u t r i e n t s i n decomposing c o n i f e r f o l i a g e i n t h e p r e s e n t s t u d y can be summarized a s : Ca >Mg >P >K >N. T h i s i s s i m i l a r t o t h e o r d e r r e p o r t e d by MacLean (1978) f o r P i n u s f o l i a g e n u t r i e n t l o s s w i t h t h e e x c e p t i o n o f t h e r e l a t i v e p o s i t i o n o f K (MacLean r e p o r t e d K > Ca > Mg>P > N). However, i n i t i a l K concen-t r a t i o n s i n t h e P i n u s f o l i a g e l i t t e r were about f o u r t i m e s t h o s e measured i n t h e c o n i f e r f o l i a g e i n t h e p r e s e n t s t u d y . T h i s may i n d i -c a t e t h a t a c o n s i d e r a b l e amount o f K was l e a c h e d from t h e f o l i a g e p r i o r t o i t s c o l l e c t i o n f rom t h e l i t t e r t r a p s f o r t h e p r e s e n t e x p e r i m e n t . The o r d e r o f l o s s o f n u t r i e n t s from decomposing b r o a d l e a f l i t t e r i n t h e p r e s e n t s t u d y was Ca >Mg >K >P >N. T h i s can be com-p a r e d w i t h t h e o r d e r e s t a b l i s h e d by MacLean (1978) Lemee and B i c h a u t ( 1 9 7 3 ) , Rochow ( 1 9 7 5 ) , and v a n C l e v e and Noonan (1975) f o r v a r i o u s hardwood s p e c i e s o f : K > M g > P > C a > N . A g a i n , K i n t h e p r e s e n t s t u d y i s l e s s m o b i l e , p o s s i b l y due t o e a r l i e r l e a c h i n g . The v e r y h i g h m o b i l i t y o f Ca i n t h e p r e s e n t s t u d y i s s u r p r i s i n g because c o n c e n t r a t i o n s o f Ca i n t h e o r i g i n a l samples were v e r y c l o s e t o th o s e r e p o r t e d i n o t h e r s t u d i e s . 57 5.3 F o r e s t F l o o r Fauna 5.3.1 R e s u l t s The t o t a l numbers o f f o r e s t f l o o r meso and macro-fauna and f o r e s t f l o o r m o i s t u r e " c o n t e n t a t each c o l l e c t i o n t i m e on each s i t e a r e shown i n F i g u r e 7. Numbers o f f a u n a on a l l t h r e e s i t e s showed th e same g e n e r a l t i m e t r e n d s , b e i n g h i g h e s t i n t h e w i n t e r (September t o A p r i l ) and l o w e s t i n t h e summer (June t o A u g u s t ) . The h y g r i c s i t e had t h e h i g h e s t peaks i n f a u n a l abundance w i t h up t o d o u b l e t h e numbers found on t h e o t h e r two s i t e s a t t h e same t i m e s o f y e a r . F o r e s t f l o o r m o i s t u r e c o n t e n t o f t h e t h r e e s i t e s e x h i b i t e d much t h e same t r e n d as f a u n a l abundance e x c e p t on t h e h y g r i c s i t e where August m o i s t u r e c o n t e n t d i d n o t match t h e d e c l i n e i n f a u n a l abun-dance. The m o i s t u r e c o n t e n t o f t h e f o r e s t f l o o r on t h e t h r e e s i t e s was v e r y s i m i l a r t h r o u g h o u t t h e w i n t e r . The abundance o f major groups o f s o i l f a u n a a t each s a m p l i n g t i m e i s shown i n T a b l e s 16 and 17. M i c r o f a u n a , i n c l u d i n g C o l l e m b o l a and A c a r i tended t o be more numerous on t h e x e r i c and m e s i c s i t e s t h a n on t h e h y g r i c s i t e , p a r t i c u l a r l y d u r i n g t h e w i n t e r . A l l groups on a l l s i t e s were v e r y s c a r c e a t t h e August s a m p l i n g . Most groups o f macro and meso-fauna tended t o be more numerous on t h e h y g r i c s i t e t h a n on t h e d r y e r s i t e s a t a l l t i m e s . D i p t e r a n l a r v a e , m i l l i -p edes, i s o p o d s , and p s e u d o s c o r p i o n s i n p a r t i c u l a r showed t h i s t r e n d . C e n t i p e d e s and s y m p h y l l i d s o c c u r r e d i n g r e a t e s t number on t h e m e s i c s i t e . Some g e n e r a l t i m e t r e n d s f o r major f a u n a l groups on each s i t e can a l s o be o b s e r v e d i n T a b l e s 16 and 17. On t h e x e r i c s i t e , 58 Figure 7!- Total average meso- and macro- fauna numbers i n the fo r e s t f l o o r , and forest f l o o r moisture content on the lower transect x e r i c (100), mesic (200)., and hygric (300) s i t e s at each sampling time, TABLE 16. Abundance of major groups of l i t t e r microfauna per m 2 at each sampling time on the three s i t e s (j- standard d e v i a t i o n ) . C o l l e m b o l a 2 2 S i t e Time 1 1 3 1 2 3 ' 4 T o t a l 100 1 2417+3232 3493+4256 451+386 880+ 938 21089+8703 4533+1754 369+ 491 1' • 33232 X e r i c 2 5161+7246 12727+9177 377+210 1032+1102 21598+2103 5946+2103 526+ 416 ' 47370 3 5666+2521 22422+8148 0 2211+1793 12531+4948 3529+2153 82+ 142 , • 46441 4 371+ 461 6404+5839 2367+2568 2413+2568 18328+19390 5615+5062 139+ 207 35637-5 0 46+104 0 46+ 104 0 0 . 0 . 92 6 1530+1535 3248+4019 93+127 1346+1327 15513+10281 3306+2971 93+ 127 25129 200 1 4054+ 522 18319+4669 492+694 2088+ 870 51807+4385 8561+5858 2211+1310 87532 Mesic 2 2651+3857 14792+9792 0 4813+4036 15185+8898 5159+1714 690+ 670 43290 3 10504+6721 10195+7947 1473+1179 1290+ 875 28175+8750 6466+5997 1843+1642 ' 59946 4 1207+1882 31970+37010 2089+2565 2227+3466 14756+14323 4547+1569 371+ 588 57167 5 46+ 104 186+415 0 185+ 312 882+1244 46+104 139+ 208 1484 6 418+ 448 4640+4083 394+400 1903+2077 20926+13593 2274+1649 139+ 311 30694 300 1 144+ 265 2771+3780 246+491 1781+1696 10871+8779 4421+2261 3500+4568 23734 H y g r i c 2 1363+2090 3611+3382 62+123 5282+3994 10921+7012 3985+1579 4938+3874 30162 3 2043+4945 6122+2098 0 3559+3197 10484+5373 3357+2158 2895+1999 28460 4 417+ 474 4779+3602 1762+1742 1903+1201 12157+13515 6311+2751 4070+5675 31399 5 0 93+127 0 278+ 254 1670+1698 46+104 185+311 769 6 185+ 311 1411+2236 394+400 2610+1990 16704+13226 2330+2964 1040+1643 24674 2) Collembola 1 = l a r g e , pigmented, with s p r i n g 2 = s m a l l , non-pigmented, s p r i n g l e s s 3 = s m a l l , w i t h s p r i n g 3) A c a r i 1 = Dark, h e a v i l y - s c l e r i t i z e d O r i b a t i d 2 = m i s c e l l a n e o u s mites 3 = chewing mouth p a r t s 4 = pink, s o f t body, withdraws head 1) Time 1 = Dec, 1977 2 = Feb, 1978 3 = A p r i l , 1978 4 = June, 1978 5 = Aug, 1978 6 = Sept, 1978 TABLE 17 . Abundance o f m a j o r g roups o f l i t t e r macro and m e s o - f a u n a p e r m a t each s a m p l i n g t i m e on t h e t h r e e s i t e s (+ s t a n d a r d d e v i a t i o n ) . S i t e ' T i m e 1 1 2 • D i p t e r a -2 3 1 3 C o l e o p t e r a 2 3 C e n t i -pedes M i l l i -pedes S y m p t i -y l l i d s I sopods Pseudo S c o r p . T o t a l X e r i c 1 194+127 29+44 39+44 78+89 0 0 6+14 16+36 61+102 0 9+35 432 100 2 188+150 131+101 32+39 38+65 162+90 48+62 10+14 45+70 128+146 3+7 65+49 850 3 178+156 52+73 23+42 131+123 102+76 38+76 61+44 16+151 170+151 0 38+67 809 4 35+64 65+73 25+56 57+59 24+32 6+14 10+14 29+44 76+109 3+7 36+46 366 5 3+7 9+21 0 6+14 0 0 0 0 0 0 0 18 6 118+148 40+49 45+40 16+28 121+96 48+54 16+16 13+21 25+28 3+7 3+7 448 7 133+259 54+69 9+16 20+40 24+48 8+16 6+14 25+35 83+124 3+7 54+67 419 M e s i c 200 H y g r i c 300 1 80+66 68+87 65+81 61+65 74+78 16+20 3+7 13+21 29+49 0 2 233+135 90+63 109+104 83+103 110+49 35+54 19+22 6+9 108+189 0 3 136+138 17+21 55+98 26+40 98+80 165+201 65+74 6+14 233+302 16+28 4 61+130 70+71 64+103 86+82 93+120 39+42 80+83 9+21 108+143 3+7 5 0 3+7 0 3+7 0 0 0 0 0 0 6 3+7 6+14 22+29 13+21 79+111 59+80 35+48 12+28 13+28 0 7 26+29 44+42 61+77 71+68 28+52 19+26 22+24 17+27 16+20 0 1 352+111 23+26 52+82 145+106 70+78 6+9 6+9 13+28 0 9+16 2 231+149 36+40 33+36 51+93 80+67 6+14 6+9 42+59 18+35 41+87 3 94+83 26+26 48+96 556+383 164+100 12+24 36+49 108+86 20+40 24+38 4 57+77 70+100 55+92 45+58 20+35 6+14' 19+30 71+67 3+9 9+21 5 3+7 6+9 0 0 3+7 0 0 0 0 0 6 208+251 6+9 52+53 28+39 6+9 26+34 25+34 68+76 3+7 28+46 7 298+329 32+48 29+49 84+100 22+32 61+58 17+22 223+151 36+44 28+46 7+15 67+107 59+83 58+95 0 16+35 0 180+105 144+105 116+193 118+131 0 198+133 243+198 416 860 877 671 6 258 304 856 698 1204 473 12 648 1073 o 1) Time 1 = D e c , 1977 2 = F e b , 1978 3 = A p r i l , 1978 4 = J u n e , 1978 5 = A u g , 1978 6 = S e p t , 1978 7 = Nov , 1978 2) D i p t e r a 1 = C h i r o n o m i d a e 2 = M y c e t o p h y l i d a e ( ? ) 3 = M i s c e l l a n e o u s o t h e r s 3) C o l e o p t e r a 1 = S t a p h y l l i n i d a e 2 = Unknown l a r v a - y e l l o w 3 = M i s c e l l a n e o u s o t h e r 61 numbers of Diptera larvae i n the forest f l o o r exhibited seasonal v a r i a t i o n s : low i n August then increasing to a winter maximum. Coleoptera on the x e r i c s i t e appeared to have two population peaks, one i n early spring and another i n December. Pseudoscorpions showed a s i m i l a r trend. Other fauna groups usually reached maximum abundance i n winter or early spring. An o v e r a l l trend of s o i l fauna numbers showed a large population peak i n spring and another, smaller peak i n l a t e f a l l . On the mesic s i t e , a l l three Diptera groups had a population peak i n spring, with Coleoptera groups showing a s i m i l a r cycle. Centipedes and symphyllids were i n greatest abundance i n A p r i l and June; however, centipede numbers were very low i n both August and December. Isopods only appeared i n A p r i l and June samples. Other faunal groups had varying population cycles, but generally reached a peak i n early spring. Microfauna showed varying trends, with Collembola being most abundant i n June, but A c a r i having maximum numbers i n December. On the hygric s i t e , populations of Diptera peaked at d i f f e r e n t times than on the other two s i t e s . Numbers of Diptera 1 (Chirono-midae) %ere highest i n December, but maintained high l e v e l s throughout the winter. Other Diptera groups had population peaks i n early summer. Coleoptera numbers were highest i n early A p r i l but also increased i n November, as did 6entipede populations. M i l l i p e d e and isopod numbers were greatest i n November. Pseudoscor-pion numbers were high throughout the year except August, and 62 s y m p h y l l i d numbers were g e n e r a l l y v e r y low. C o l l e m b o l a numbers were h i g h e s t i n s p r i n g and e a r l y summer. A c a r i p o p u l a t i o n s r e a c h e d h i g h l e v e l s i n b o t h s p r i n g and f a l l . O v e r a l l , f a u n a on t h e h y g r i c s i t e r e a c h e d h i g h numbers i n b o t h s p r i n g and f a l l w i t h some drop o v e r t h e w i n t e r . 5.3.2 D i s c u s s i o n D i f f e r e n c e s o b s e r v e d i n t h e s p e c i e s and abundance o f l i t t e r f a u n a on t h e t h r e e s i t e s were p r o b a b l y a r e f l e c t i o n o f d i f f e r e n c e s i n s i t e v e g e t a t i o n w h i c h i n f l u e n c e t h e c h e m i c a l p r o p e r t i e s o f t h e f o r e s t f l o o r , i n a d d i t i o n t o p h y s i c a l f a c t o r s s u c h as s o i l m o i s t u r e , t e m p e r a t u r e , and l i g h t i n t e n s i t y . The dominance o f C o l l e m b o l a and A c a r i on t h e x e r i c and m e s i c s i t e s p r o b a b l y r e s u l t e d from t h e d r y e r ' s,ummer c o n d i t i o n s and the l o w e r pH c r e a t e d by t h e dominant c o n i f e r l i t t e r . Many s p e c i e s o f C o l l e m b o l a and A c a r i a r e fungus f e e d e r s and may be abundant on t h e x e r i c and m e s i c s i t e s due t o t h e dominance of f u n g i on low pH, mor f o r e s t f l o o r s ( W allwork 1976). A l s o , c o n i f e r l i t t e r g e n e r a l l y has a h i g h t a n n i n c o n t e n t and h i g h C:N r a t i o ( M i l l e r 1974), f a c t o r s w h i c h r e n d e r i t r e l a t i v e l y u n p a l a t a b l e t o many t y p e s o f s o i l o r g a n i s m s . The g r e a t e r numbers o f a l l f a u n a groups i n t h e F and H h o r i z o n s o f t h e x e r i c and m e s i c s i t e s p r o b a b l y r e f l e c t e d t h e u n p a l a t a b i l i t y o f t h e f r e s h l y f a l l e n l i t t e r . A l s o , t h e upper l i t t e r l a y e r s d r y out more f r e q u e n t l y , c r e a t i n g c o n d i t i o n s u n s u i t a b l e f o r t h e f a u n a . Thus, f a u n a would be e x p e c t e d t o p l a y a r e l a t i v e l y m inor r o l e i n e a r l y s t a g e s o f d e c o m p o s i t i o n on t h e s e s i t e s . On t h e h y g r i c s i t e s , t h e i n p u t of hardwood and c e d a r l i t t e r w i t h l o w e r t a n n i n c o n c e n t r a t i o n s , l o w e r C:N r a t i o s , and h i g h e r base 63 c o n t e n t c r e a t e d c o n d i t i o n s w h i c h were more s u i t a b l e f o r t h e s u r v i v a l o f l i t t e r macro and meso-fauna ( W i l l i a m s and Gray 1974). The l o w e r numbers o f m i c r o f a u n a may have r e f l e c t e d t h e r e l a t i v e s c a r c i t y o f f u n g i on t h i s s i t e ( W allwork 1976). Those s p e c i e s o f m i c r o f a u n a w h i c h d i d o c c u r tended t o be l e s s h e a v i l y s c l e r i t i z e d t h a n most s p e c i e s on t h e o t h e r s i t e s , and t h u s more s u s c e p t i b l e t o d r y i n g . The r e l a t i v e l y h i g h abundance o f f a u n a i n t h e L h o r i z o n on t h e h y g r i c s i t e p r o b a b l y r e s u l t e d from t h e g r e a t e r p a l a t a b i l i t y o f t h e f r e s h l i t t e r . T h i s may i n d i c a t e t h a t f a u n a p l a y a more i m p o r t a n t r o l e i n e a r l y s t a g e s o f d e c o m p o s i t i o n on t h i s s i t e . The s e a s o n a l t r e n d s i n faunalnumbers o b s e r v e d on a l l s i t e s p r o b a b l y r e s u l t e d f r o m a c o m b i n a t i o n o f s e v e r a l f a c t o r s . W e t t i n g and d r y i n g o f t h e f o r e s t f l o o r h o r i z o n s may have caused movement up and down o f many s p e c i e s , w i t h some b e i n g more s e n s i t i v e t o d r y i n g t h a n o t h e r s . Temperature v a r i a t i o n s may a l s o have caused some up and down movements o r i n d u c e d s t a t e s o f dormancy i n some s p e c i e s w h i c h made them l e s s e a s i l y e x t r a c t e d . The c h e m i c a l c o m p o s i t i o n o f t h e l i t t e r i n d i f f e r e n t h o r i z o n s a t d i f f e r e n t t i m e s of y e a r may have v a r i e d t h e p a l a t a b i l i t y o f t h e l i t t e r t o d i f f e r e n t groups o f s o i l o r g a n i s m s , t h u s c a u s i n g v a r i a t i o n s i n p o p u l a t i o n d i s t r i b u t i o n . F i n a l l y , t h e l i f e c y c l e s o f d i f f e r e n t s p e c i e s may have caused them t o o c c u r i n d i f f e r e n t h o r i z o n s o f t h e f o r e s t f l o o r o r i n an u n e x t r a c t a b l e form (eggs, f o r example) a t d i f f e r e n t t i m e s o f y e a r . The v e r y s h a r p d e c r e a s e i n f a u n a numbers i n t h e August samples from a l l s i t e s a p p e ars t o have r e s u l t e d from t h e v e r y d r y c o n d i t i o n s of t h e f o r e s t f l o o r a t t h a t t i m e . I t i s p o s s i b l e t h a t f a u n a were e i t h e r k i l l e d by d e s s i c a t i o n , o r moved deeper i n t o t h e s o i l t o a v o i d 64 d e s s i c a t i o n . I n e i t h e r c a s e , t h e y were ho l o n g e r a c t i v e i n decom-p o s i t i o n i n t h e upper l a y e r s o f t h e l i t t e r where t h e l i t t e r bags were l o c a t e d . A l t h o u g h L and F h o r i z o n s on t h e h y g r i c s i t e r e t a i n e d about 50% m o i s t u r e c o n t e n t , t h i s was a p p a r e n t l y n o t ade-quate f o r o r g a n i s m a c t i v i t y o r s u r v i v a l . There were s e v e r a l m e t h o d o l o g i c a l problems w i t h t h e f a u n a s t u d y , w h i c h must be t a k e n i n t o a c c o u n t i n i n t e r p r e t a t i o n o f t h e r e s u l t s . The d r y T u l l g r e n f u n n e l i s n o t an e f f i c i e n t e x t r a c t o r o f a l l groups o f f a u n a , and i s p a r t i c u l a r l y poor f o r e x t r a c t i n g nematodes and a n n e l i d s . A l s o , many s p e c i e s o f f a u n a have a v e r y clumped d i s t r i b u t i o n i n t h e f i e l d , and t h e few s m a l l samples w h i c h were t a k e n a t each s a m p l i n g t i m e may n o t have p r o v i d e d a v e r y a c c u r a t e e s t i m a t e o f a c t u a l numbers. 5.4 F o r e s t F l o o r Biomass 5.4.1 R e s u l t s The biomass o f t h e L, F, and H h o r i z o n s o f t h e f o r e s t f l o o r o f t h e t h r e e s i t e s on t h e l o w e r t r a n s e c t ( x e r i c 100, m e s i c 200, h y g r i c 300) i s shown i n F i g u r e 8. The v a l u e o f H f o r t h e h y g r i c s i t e was d e t e r m i n e d by m u l t i p l y i n g t h e w e i g h t o f t h e Ah h o r i z o n t i m e s t h e p e r c e n t o r g a n i c m a t t e r i n t h e h o r i z o n . F o r e s t f l o o r biomass. on t h e x e r i c and m e s i c s i t e s was v e r y s i m i l a r , r a n g i n g from 50 up t o 60 " t .ha Most o f t h e between s i t e d i f f e r e n c e s appeared t o be due t o t h e F and H h o r i z o n s w h i c h had a c o n s i d e r a b l e a c c u m u l a t i o n on t h e x e r i c and m e s i c s i t e s . The L and F h o r i z o n s showed some s e a s o n a l v a r i a t i o n on a l l s i t e s . 65 Figure 8. Biomass of the L, F, and H horizons on the lower transect x e r i c (100), mesic (200),, and hygric (300) s i t e s at each sampling time. F o r e s t F l o o r B i o m a s s ( t o n n e s / h a a ro TI oo' > CO GO CD o rO O CO o o o _1 a o ••••••••linn........ E I |*'*'"*****'***''**^  'llf* : : " ^ * i i i J i U ! ! ! " " " j i ; * « i ; v v v 1 llllllllllillllllllllll=;=llllllllllf=ly.^ w I X llilillillllllli wmmmm\\ - £ iiiitiiiii - ^ iiiiiiiiP IlllUljllJIIIIIIIIlililiilJiilf \ \ \j X X Jlillililllilill - £ lliiiiiii i i i i n i k x v iHiiii!!ilA\\\1 3 o cn egg 66 On t h e h y g r i c s i t e , L biomass was g r e a t e s t i n November (6.3 t - h a ) and remained a t a c o n s i s t e n t l y low l e v e l (4.5 t -ha from A p r i l t o September. On t h e x e r i c and m e s i c s i t e s , t h e L h o r i z o n biomass was l o w e s t i n August. I t was h i g h e s t on t h e x e r i c s i t e t h r o u g h o u t t h e e a r l y w i n t e r (7.2 t . h a ^  ) , and on t h e m e s i c s i t e i n s p r i n g (10.5 t . h a ^  ). The F h o r i z o n s a l s o showed some s e a s o n a l v a r i a t i o n , w i t h t h e h i g h e s t biomass b e i n g r e a c h e d on a l l s i t e s between F e b r u a r y and June. On t h e h y g r i c s i t e F biomass was l o w e s t i n A u g u s t , and on the x e r i c and m e s i c s i t e s i t was l o w e s t i n November and December. Tu r n o v e r r a t e s f o r t h e f o r e s t f l o o r and L h o r i z o n o f s i t e s 100, 200, and 300 were e s t i m a t e d from t h e biomass o f t h e f o r e s t f l o o r , measured i n t h i s s t u d y , and r a t e s o f l i t t e r i n p u t measured by Kimmins ( u n p u b l i s h e d ) ( T a b l e 1 8 ) . By t h i s method k = L / X s s where L = a n n u a l l i t t e r i n p u t and X s s = biomass o f t h e f o r e s t f l o o r a t s t e a d y s t a t e . 5.4.2 D i s c u s s i o n The biomass o f the f o r e s t f l o o r measured on t h e t h r e e s i t e s i n i t h i s s t u d y compares w e l l w i t h v a l u e s r e p o r t e d f o r o t h e r s i t e s o f s i m i l a r c o m p o s i t i o n . W i l l i a m s and D y r n e s s (1967) r e p o r t e d f o r e s t f l o o r biomass under D o u g l a s - f i r - h e m l o c k s t a n d s i n t h e Cascade mountains t o be 68.79' " t *ha ^ f o r mor f o r e s t f l o o r s and 33.61 f o r f i n e m u l l . Youngberg (1966) found f o r e s t f l o o r s under D o u g l a s - f i r i n Oregon t o v a r y from 22.40 t o 33.60 t 'ha ^ on m u l l s i t e s . However, G e s s e l and B a l c i (1963) found much h i g h e r b i o m a s s , r a n g i n g from 103.35 , t o 157.88 , " t - h a " 1 on o l d growth s t a n d s i n t h e Cascade and Olympic m o u n t a i n s . 67 TABLE 18. C a l c u l a t i o n o f the d e c o m p o s i t i o n p a r a m e t e r , k, b a s e d on r a t e s o f l i t t e r i n p u t and f o r e s t f l o o r b i omass. To.tal, l i t t e r Ave. F o r e s t F o r e s t Ave. L H o r i - L S i t e I n p u t F l o o r B i o - F l o o r zon Biomass H o r i z o n ( I . h a - 1 . a - 1 ) mass ( f f . h a - 1 ) k ( t . h a - 1 ) k 100 ( x e r i c ) .684 45.04 .0152 5.69 .121 200 ( m e s i c ) .762 45.68 .0167 7.10 .107 300 ( h y g r i c ) 1.017 25.20 .0403 4.67 .218 D i f f e r e n c e s i n o v e r a l l t u r n o v e r r a t e s o f the t h r e e s i t e s , as c a l c u l a t e d u s i n g l i t t e r i n p u t and f o r e s t f l o o r b i o m a s s , can be a c c o u n t e d f o r i n s e v e r a l ways. The l a r g e number o f l o g s on t h e x e r i c and m e s i c e c o s y s t e m t y p e s decompose v e r y s l o w l y and may t e n d t o c o n t r o l o v e r a l l s i t e t u r n o v e r r a t e s . Most f o r e s t f l o o r samples on t h e x e r i c and m e s i c s i t e s i n c l u d e d l o g m a t e r i a l i n some s t a g e o f d e c o m p o s i t i o n . On t h e h y g r i c s i t e s l o g s were r a r e l y e n c o u n t e r e d , and t h o s e w h i c h d i d e x i s t were v e r y l a r g e and t h e r e f o r e a v o i d e d i n f o r e s t f l o o r s a m p l i n g . R a t e s o f l o g d e c o m p o s i t i o n have been e s t i m a t e d i n r e c e n t s t u d i e s by G r i e r ( 1 9 7 8 ) and M a c M i l l a n e t a l . ( u n p u b l i s h e d ) . G r i e r found l o g s o f w e s t e r n hemlock t o have k v a l u e s r a n g i n g from .009 t o .014. D o u g l a s - f i r l o g d e c o m p o s i t i o n p a r a m e t e r s e s t i m a t e d by M a c M i l l a n e t a l . ranged from .043 f o r r e c e n t l y f a l l e n l o g s t o .004 f o r o l d e r l o g s . N u t r i e n t c o n c e n t r a t i o n s o f l o g s i n b o t h s t u d i e s were much l o w e r t h a n t h o s e measured f o r f o l i a g e o r t w i g s i n t h i s s t u d y . 6 8 A s p i n a l l ( 1 9 7 4 ) , w o r k i n g on t h r e e o f t h e s i t e s i n c l u d e d i n t h i s s t u d y (100, 200, 300) found c o n c e n t r a t i o n s o f N, K, Ca, and Mg t o be s i g n i f i c a n t l y h i g h e r i n t h e f o r e s t f l o o r o f t h e h y g r i c s i t e t h a n o f t h e o t h e r two s i t e s . T h i s p r o b a b l y r e f l e c t s b o t h t h e l a r g e r amounts o f wood on t h e x e r i c and m e s i c s i t e s , and t h e i n p u t o f hardwood l i t t e r and s w o r d f e r n t o t h e h y g r i c s i t e s . Hardwood l i t t e r a c c o u n t s f o r about 20% o f t h e l i t t e r i n p u t t o the h y g r i c s i t e , b u t o n l y f o r 5 t o 7% o f t h e i n p u t t o t h e d r y e r s i t e s (Kimmins, u n p u b l i s h e d ) . T h i s i n p u t , w i t h i t s f a s t e r d e c o m p o s i t i o n r a t e w o u l d h e l p a c c o u n t f o r t h e f a s t e r t u r n o v e r r a t e o f t h e f o r e s t f l o o r on t h e h y g r i c s i t e . 69 GENERAL DISCUSSION The r a t e a t w h i c h f o r e s t f l o o r a c c u m u l a t e s on any s i t e s h o u l d be d e t e r m i n e d by t h e r a t e o f l i t t e r f a l l on t h a t s i t e and t h e r a t e a t w h i c h d e c o m p o s i t i o n o c c u r s . Because o f the v e r y d i f f e r e n t v e g e t a t i o n and p h y s i c a l c o n d i t i o n s on t h e t h r e e e c o s y s t e m t y p e s used i n t h i s s t u d y , v e r y d i f f e r e n t r a t e s o f d e c o m p o s i t i o n were e x p e c t e d . However, r e s u l t s o f t h e p r e s e n t s t u d y i n d i c a t e t h a t d e c o m p o s i t i o n r a t e s f o r c o n i f e r f o l i a g e i n l i t t e r bags were t h e same on a l l t h r e e e c o s y s t e m t y p e s . A l s o , v e r y l a r g e d i s c r e p a n c i e s were found between k v a l u e s c a l c u l a t e d from l i t t e r i n p u t and f o r e s t f l o o r biomass d a t a , and t h o s e measured i n l i t t e r bag w e i g h t l o s s . S i m i l a r d i s -c r e p a n c i e s have been found i n s e v e r a l o t h e r s t u d i e s ( f o r example see B i r k 1977). I n t h e p r e s e n t s t u d y , t h e c a l c u l a t e d k v a l u e s based on l i t t e r i n p u t and f o r e s t f l o o r biomass r e p r e s e n t e d t h e ave r a g e r a t e o f w e i g h t l o s s f o r c o m p l ete t r a n s f e r o f m a t e r i a l out o f t h e f o r e s t f l o o r . T h i s i n c l u d e d wood and b a r k l i t t e r , as w e l l as f o l i a g e , t h r o u g h a l l s t a g e s o f decomposi-t i o n . The measured k v a l u e s from t h e l i t t e r b a g s , on t h e o t h e r hand, o n l y a c c o u n t e d f o r t h e p a r t i a l t r a n s f e r o f a s i n g l e component ( f o l i a g e ) o ut of t h e l i t t e r l a y e r . Because f o l i a g e decomposes r e l a t i v e l y r a p i d l y , p a r t i c u -l a r l y d u r i n g t h e f i r s t months, t h e l i t t e r - b a g k v a l u e s would be e x p e c t e d t o be h i g h e r t h a n k v a l u e s based on t o t a l f o r e s t f l o o r t u r n o v e r , as was found i n t h e p r e s e n t s t u d y . When k v a l u e s f o r t h e L h o r i z o n a l o n e were c a l c u l a t e d , t h e s e were found t o be much c l o s e r t o t h e l i t t e r bag k v a l u e s . There were a l s o some s o u r c e s o f e r r o r a s s o c i a t e d w i t h t h e c a l c u -l a t e d k v a l u e s w h i c h s h o u l d be c o n s i d e r e d : 1) t h e sys t e m may n o t have been i n s t e a d y - s t a t e . G e n e r a l l y , t h e e r r o r i n e s t i m a t i n g k dr o p s exponen-t i a l l y as a sys t e m approaches s t e a d y - s t a t e ( B i r k 1 9 77), 2) f o r e s t f l o o r 70 biomass may have been overestimated, p a r t i c u l a r l y on the hygric s i t e where much of the humus was mixed into mineral s o i l , and 3) l i t t e r input was underestimated because root l i t t e r was not included. If root l i t t e r i s assumed to be equal to above ground l i t t e r input, k.values would be double those calculated. Probably the greatest factor accounting for the discrepency between measured and calculated k values i n the present study was the i n c l u s i o n of logs i n c a l c u l a t i n g forest f l o o r biomass. Because.-logs were very important as a component of the forest f l o o r on the x e r i c and mesic s i t e s , i t i s l i k e l y that calculated k values are much closer to the true turnover rates of forest f l o o r s on these s i t e s . Results of the present study support the hypothesis that rates of forest f l o o r turnover are d i f f e r e n t on the three ecosystem types. Turnover rates calculated for the hygric ecosystem type were much f a s t e r than those calculated f o r the x e r i c or mesic types. This was probably due to the amounts and chemical composition of the fo r e s t f l o o r components on each ecosystem type.rather than differences i n the decomposition rate of a s p e c i f i c substrate. The x e r i c and mesic s i t e s were generally found to be very s i m i l a r i n f o r e s t f l o o r biomass, turnover rate, and fauna populations. This probably occurred because the main differ e n c e i n vegetation composition, and thus l i t t e r input, was i n the shrub species. This difference may have been too minor to influence forest: f l o o r properties on the two ecosystem types. Rates of disappearance of needles confined i n l i t t e r bags did not d i f f e r on the three ecosystem types. However, t h i s may have been an a r t i f a c t of confinement, and i t i s possible that unconfined needle l i t t e r may have 71 decomposed a t d i f f e r e n t r a t e s due t o f r a g m e n t a t i o n and t h e a c t i o n o f l i t t e r f a u n a . P r e l i m i n a r y w e i g h t l o s s r e s u l t s f o r c e l l u l o s e and u n c o n f i n e d decomp-o s i n g t w i g s appear t o s u p p o r t t h i s h y p o t h e s i s . However, i t i s a l s o p o s s i b l e t h a t even though f a u n a p o p u l a t i o n s were q u i t e d i f f e r e n t on t h e h y g r i c ecosystem t y p e , t h e y would c o n f i n e t h e i r f e e d i n g t o b r o a d l e a f f o l i a g e and o t h e r h i g h n i t r o g e n s u b s t r a t e s even when n e e d l e l i t t e r i s a c c e s s i b l e t o them, T h i s may be p a r t i c u l a r l y t r u e d u r i n g e a r l y s t a g e s o f d e c o m p o s i t i o n , when c o n i f e r l i t t e r t ends t o have a h i g h t a n n i n and p o l y p h e n o l c o n t e n t and i s thus u n p a l a t a b l e t o -many s p e c i e s o f f a u n a , On t h e b a s i s o f a one y e a r l i t t e r -bag s t u d y i t i s t h e r e f o r e d i f f i c u l t t o form a s t r o n g c o n c l u s i o n about t h e e f f e c t o f ecosystem t y p e on r a t e s o f n e e d l e l i t t e r d e c o m p o s i t i o n . L i t t e r - b a g s t u d i e s o f t h e b r o a d l e a f s p e c i e s , w h i c h can be c o n f i n e d i n l a r g e r mesh bags o r t e t h e r e d , m ight have been more u s e f u l had t h e r e been a s i n g l e s p e c i e s w h i c h c o u l d have been compared on a l l ecosystem t y p e s . The f o r e s t f l o o r dynamics of t h e s i t e s i n t h i s s t u d y can be put i n t o a b r o a d e r , g l o b a l p e r s p e c t i v e . W i t h i n t h e t e n p o i n t c l a s s i f i c a t i o n s c a l e o f w o r l d ecosystems c r e a t e d by R o d i n and B a z i l e v i c h ( 1 9 6 7 ) , t h e h y g r i c ecosystem t y p e has s u f f i c i e n t l y l e s s f o r e s t f l o o r a c c u m u l a t i o n and f a s t e r d e c o m p o s i t i o n t o f a l l i n t o a s e p a r a t e c a t e g o r y from t h e x e r i c and m e s i c ecosystem t y p e s . The h y g r i c s i t e f a l l s i n t h e 7 t h h i g h e s t c a t e g o r y f o r f o r e s t f l o o r a c c u m u l a t i o n , and t h e x e r i c and m e s i c s i t e s t h e 8 t h . These v a l u e s a r e s i m i l a r t o t h o s e o b s e r v e d i n temperate c o n i f e r f o r e s t s o f t h e USSR and B r i t a i n b u t a r e much h i g h e r t h a n t h o s e o f g r a s s l a n d s o r t r o p i c a l f o r e s t s . The decay r a t e o f t h e h y g r i c s i t e f a l l s i n t o c a t e g o r y 2 and t h a t o f the x e r i c and m e s i c s i t e s i n t o c a t e g o r y 1 B o t h o f t h e s e a r e d e s c r i b e d as s t a g n a n t and a r e much l o w e r t h a n v a l u e s f o r b r o a d l e a f and t r o p i c a l f o r e s t s . 72 Most other conifer forests considered by Rodin and B a z i l e v i c h also f a l l into category 2. In conclusion, differences i n rates of f o r e s t f l o o r turnover and accumulation are s u f f i c i e n t l y large to separate the hygric from the x e r i c and mesic ecosystem types. However, on the x e r i c and mesic s i t e s , f o rest f l o o r turnover rates are so s i m i l a r that the s i t e s would not be, d i f f e r e n t i a t e d by a c l a s s i f i c a t i o n system based on t h i s functional process even on a l o c a l l e v e l . 73 REFERENCES A l e x a n d e r , M. 1961. I n t r o d u c t i o n t o S o i l M i c r o b i o l o g y . John W i l e y & Sons, I n c . , New Y o r k , pp.128-147. Ander s o n , J.M. 1973a. The breakdown and d e c o m p o s i t i o n o f sweet c h e s t n u t ( C a s t a n e a s a t i v a M i l l . ) and beech (Fagus s y l v a t i c a L.) l e a f l i t t e r i n two d e c i d u o u s woodland s o i l s . I . Breakdown, l e a c h i n g , and d e c o m p o s i t i o n . O e c o l o g i a 12:251-274. A n d e r s o n , J.M. 1973b. The breakdown and d e c o m p o s i t i o n o f sweet c h e s t n u t ( C a s t a n e a s a t i v a M i l l . ) and beech (Fagus s y l v a t i c a L.) l e a f l i t t e r i n two d e c i d u o u s woodland s o i l s . I I . Changes i n t h e c a r b o n , h y d r o g e n , n i t r o g e n , and p o l y p h e n o l c o n t e n t . O e c o l o g i a 12:275-288. A s p i n a l l , W.A. 1974. Some b i o c h e m i c a l p r o p e r t i e s of f o r e s t f l o o r s found under t h r e e e c o s y s t e m t y p e s i n t h e d r y e r subzone o f t h e c o a s t a l w e s t e r n hemlock zone. B.F. T h e s i s , F a c u l t y o f F o r e s t r y , U n i v e r s i t y o f B r i t i s h C o l u mbia. A t t i w i l l , P.M. 1968. The l o s s o f elements from decomposing l i t t e r . E c o l o g y 49:142-145. Ausmus, B.S. and M. Witkamp. 1974. L i t t e r and s o i l m i c r o b i a l dynamic's i n a d e c i d u o u s f o r e s t s t a n d . Ph.D. T h e s i s , U n i v e r s i t y o f Tennessee. B i r k , E.M. 1977. L i t t e r a c c e s s i o n , a c c u m u l a t i o n , and d i s a p p e a r a n c e i n an A u s t r a l i a n e u c a l y p t f o r e s t . M . P h i l . T h e s i s , G r i f f i t h U n i v e r s i t y , Nathan, Queensland, A u s t r a l i a . 117 p. Bocock, K.L. 1964. Changes i n t h e amounts o f d r y m a t t e r , n i t r o g e n , c a r b o n , and energy i n decomposing woodland l e a f l i t t e r i n r e l a t i o n t o a c t i v i t i e s o f s o i l f a u n a . J . E c o l . 52:273-284. 74 Bocock, K.L. and O.W.J. G i l b e r t . 1957. The d i s a p p e a r a n c e o f l e a f l i t t e r under d i f f e r e n t woodland c o n d i t i o n s . P l a n t and S o i l 9 ( 2 ) : 1 7 9 - 1 8 5 . B o l i n g J r . j R . H . , E.D. Goodman, J.A. van S i c k l e , J.O. Zimmer, K.W. Cummins, R.C. P e t e r s o n , and S.R. R e i c e . 1975. Toward a model o f d e t r i t u s p r o c e s s i n g i n a woodland s t r e a m . E c o l o g y 56:141-151. B r o a d f o o t , W.M. and W.H. P i e r r e . 1939. F o r e s t s o i l s t u d i e s : I . R e l a t i o n o f r a t e o f d e c o m p o s i t i o n o f t r e e l e a v e s t o t h e i r a c i d - b a s e b a l a n c e and o t h e r c h e m i c a l p r o p e r t i e s . S o i l S c i e n c e 48:329-348. B u n n e l l , F,L, and D.E.N, T a i t . 1974. M a t h e m a t i c a l s i m u l a t i o n models o f d e c o m p o s i t i o n p r o c e s s e s , I n ; S o i l Organisms and D e c o m p o s i t i o n i n  Tundra. A . J . H o l d i n g , D.W. H e a l , S.F. MacLean, J r . , and P.W. F l a n a g a n , eds. Tundra Biome S t e e r i n g Committee, S t o c k h o l m , pp. 207-225. C o l d w e l l , B.B. and W.A- deLong, 1950. S t u d i e s o f t h e c o m p o s i t i o n o f d e c i d u o u s f o r e s t t r e e l e a y e s b e f o r e and a f t e r p a r t i a l d e c o m p o s i t i o n , S c i . A g r i c , 30:456-466. Cromack, K, J r , .1973. L i t t e r p r o d u c t i o n and d e c o m p o s i t i o n i n a mixed hardwood w a t e r s h e d and a w h i t e p i n e w a t e r s h e d a t Coweeta H y d r o l o g i c S t a t i o n , N o r t h C a r o l i n a . Ph.D, T h e s i s , U n i v e r i s i t y o f G e o r g i a , Athens G e o r g i a , 160 p. Cromack, K. J r . and C D . Monk. 1975. L i t t e r p r o d u c t i o n , d e c o m p o s i t i o n , •. and n u t r i e n t c y c l i n g i n a mixed hardwood w a t e r s h e d and a w h i t e p i n e w a t e r s h e d . I n : F.G. H o w e l l , J.B. G e n t r y , and M.H. S m i t h , eds. M i n e r a l C y c l i n g i n S o u t h e a s t e r n E c o s y s t e m s , Conf.-740513, W a s h i n g t o n , pp. 609-624. 75 C r o s s l e y , D.A. J r . , and M.P. Hoglund. 1962. A l i t t e r - b a g method f o r t h e s t u d y o f m i c r o a r t h r o p o d s i n h a b i t i n g l e a f l i t t e r . E c o l o g y 4 3 ( 3 ) : 5 7 1 -573. Daubenmire, R. and D.C. P r u s s o . 1963. S t u d i e s o f t h e d e c o m p o s i t i o n r a t e s o f t r e e l i t t e r . E c o l o g y 44:589-592. Edwards, N.T. 1975. E f f e c t s o f t e m p e r a t u r e and m o i s t u r e on c a r b o n d i o x i d e e v o l u t i o n i n a mixed d e c i d u o u s f o r e s t f l o o r . S o i l Sc. Soc. Amer. P r o c . 39:361-365. Edwards, C.A., D.E. R e i c h l e , and D.A. C r o s s l e y , J r . 1970. The r o l e o f s o i l i n v e r t e b r a t e s i n t u r n o v e r o f o r g a n i c m a t t e r and n u t r i e n t s . I n : A n a l y s i s o f Temperate F o r e s t E c o s y s t e m s , D.E. R e i c h l e , ed. S p r i n g e r -V e r l a g , New Yor k . pp. 147-172. F o g e l , R. and K. Cromack, J r . 1977. E f f e c t o f h a b i t a t and s u b s t r a t e q u a l i t y on D o u g l a s - f i r l i t t e r d e c o m p o s i t i o n i n w e s t e r n Oregon. Can. J . B o t . 55:1632-1640. G a s d o r f , E.C. and C.J. G o o d n i g h t . 1963. S t u d i e s on t h e e c o l o g y o f s o i l a r a c h n i d s . E c o l o g y 44:261-268. G e s s e l , S.P. and A.N. B a l c i . 1963. Amount and c h e m i c a l c o m p o s i t i o n o f f o r e s t f l o o r s under Washington c o n i f e r o u s f o r e s t s . I n : F o r e s t S o i l R e l a t i o n - s h i p s i n N o r t h A m e r i c a , C T . Youngberg, ed. , Oregon S t a t e U. P r e s s , pp. 11-23. G i l b e r t , 0. and K.L. Bocock. 1960. Changes i n l e a f l i t t e r when p l a c e d on t h e s u r f a c e o f s o i l s w i t h c o n t r a s t i n g humus t y p e s . J . S o i l Sc. 11:10-19. Gosz, J.R., C E . L i k e n s , and F.H. Bormann. 1973. N u t r i e n t r e l e a s e from decomposing l e a f and b r a n c h l i t t e r i n t h e Hubbard Brook F o r e s t , New Hampshire. E c o l . Mono. 43:173-191. G r i e r , C.C. 1978. A Tsuga h e t e r o p h y l l a - P i c e a s i t c h e n s i s e c o s y s t e m o f c o a s t a l Oregon: d e c o m p o s i t i o n and n u t r i e n t b a l a n c e s o f f a l l e n l o g s . Can. J . F o r . Res. 8(2):198-206. Hayes, A . J . 1965. S t u d i e s on t h e d e c o m p o s i t i o n o f c o n i f e r o u s l e a f l i t t e r . I . P h y s i c a l and c h e m i c a l changes. J . o f S o i l Sc. 16(1):121-140. H e a l , W.O. and D.D. F r e n c h . 1974. D e c o m p o s i t i o n o f o r g a n i c m a t t e r i n Tundra. I n : S o i l Organisms and D e c o m p o s i t i o n i n Tundra. A . J . H o l d i n g D.W. H e a l , S.F. MacLean, J r . , and P.W. F l a n a g a n , eds. Tundra Biome S t e e r i n g Committee, S t o c k h o l m , pp. 279-310. Hoover, M.D. and H.A. L u n t . 1952. A key f o r t h e c l a s s i f i c a t i o n o f f o r e s t humus t y p e s . S o i l Sc. Soc. Amer. P r o c . 17:368-370. Howard, P.J.A. and D.M. Howard. 1974. M i c r o b i a l d e c o m p o s i t i o n o f t r e e and shrub l e a f l i t t e r . 1. Weight l o s s and c h e m i c a l c o m p o s i t i o n o f decom-p o s i n g l i t t e r . O i k o s 25:341-352. I v a r s o n , K.C. 1973. F u n g a l f l o r a and r a t e of d e c o m p o s i t i o n o f l e a f l i t t e r a t l ow t e m p e r a t u r e s . Can. J . S o i l Sc. 53:79-84. J e n k i n s o n , D.S. 1971. S t u d i e s on t h e d e c o m p o s i t i o n o f C l 4 l a b e l l e d o r g a n i c m a t t e r i n s o i l . S o i l Sc. I l l ( 1 ) : 6 4 - 6 9 . Jenny, H., S.P. G e s s e l , and F.T. Bingham. 1949. C o m p a r a t i v e s t u d y of decom-p o s i t i o n r a t e s of o r g a n i c m a t t e r i n temperate and t r o p i c a l r e g i o n s . S o i l Sc. 68:419-432. J e n s e n , V. 1974. D e c o m p o s i t i o n o f a n g i o s p e r m t r e e l e a f l i t t e r . I n : B i o l o g y o f P l a n t L i t t e r D e c o m p o s i t i o n , C.H. D i c k e n s o n and G.J.F. Pugh, ed s . , Academic P r e s s , London and New Y o r k , pp. 69-104. Kawahara, T. 1975. Decomposition of l i t t e r on the f o r e s t f l o o r . I I . E f f e c t s of the mixture of two kinds of l e a f l i t t e r on t h e i r decomposition r a t e s . Jap. J . E c o l . 25:71-76. Kendrick, W.B. and A. Burges. 1962. B i o l o g i c a l aspects of the decay of Pinus s y l v e s t r i s l e a f l i t t e r . Nova Hedwigia 4:313-342. K l i n k a , K. 1977. B r i e f i n t e r p r e t a t i o n s f o r major f o r e s t ecosystems i n the C o a s t a l Western Hemlock B i o g e o c l i m a t i c Zone i n the U.B.C. Research Forest. B.C. Forest Service unpublished manuscript. Koppen, W. 1936. Das Geographische System der Rlimate. V o l . 1 , P a r t C. In: Handbuch der K l i m a t o l o g i e , Gebr., Borntraeger, B e r l i n . K r a j i n a , V.J. 1965. B i o g e o c l i m a t i c zones and c l a s s i f i c a t i o n of B r i t i s h Columbia. Ecology of Western North America 2:1-147. Lemee, G. and N. Bichaut. 1973. Recherches sur l e s ecosystemes des reserves b i o l o g i q u e s de l a f o r e t de Fontanebleau. I I . Decomposition de l a l i t i e r e de f e u i l l e s des arbres et l i b e r a t i o n des bioelements. Oecol. P l a n t . 8(2):153-174. L o u s i e r , J.D. and D. Parkinson. 1976. L i t t e r decomposition i n a c o o l temperate deciduous f o r e s t . Can. J. Bot. 54:419-436. L o u s i e r , J.D. and D. Parkinson. 1978. Chemical element dynamics i n decom-posing l e a f l i t t e r . Can. J . Bot. 56:2795-2812. MacLean, D.A. 1978. Fine and the n u t r i e n t c y c l e of New Brunswick pine and hardwood stands: f i e l d s t u d i e s and computer s i m u l a t i o n s t u d i e s . Ph.D. Thesis, U n i v e r s i t y of New Brunswick. MacMillan, P.C., J.E. Means, K. Cromack, J r . , and G.M. Hawk. Unpublished. D o u g l a s - f i r l o g decomposition, biomass and n u t r i e n t c a p i t a l i n the western Cascades, Oregon. 78 Meentemyer, V. 1978. Macroclimate and l i g n i n c o n t r o l of l i t t e r decom-p o s i t i o n r a t e s . Ecology 59 (3):465-472. M i k o l a , P. 1960. Comparative experiments on decomposition r a t e s of f o r e s t l i t t e r i n southern and northern F i n l a n d . Oikos 11:161-166. M i l l e r , • C . S . 1974. Decomposition of coniferous l e a f l i t t e r . In: Bi o l o g y  of P l a n t L i t t e r Decomposition, C.H. Dickenson and G.J.F. Pugh, eds. Academic Press, London and New York, pp. 105-128. Minderman, G. 1968. A d d i t i o n , decomposition, and accumulation of organic matter i n f o r e s t s . J . E c o l . 56:355-362. N y k v i s t , N. 1959a. Leaching and decomposition of l i t t e r . I . Experiments on l e a f l i t t e r of Fraxinus e x c e l s i o r . Oikos 10:190-211. N y k v i s t , N. 1959b. Leaching and decomposition of l i t t e r . I I . Experiments on needle l i t t e r of Pinus s y l v e s t r i s . Oikos 10:212-224. Olson, J.S. 1963. Energy storage and the balance of producers and decom-posers i n e c o l o g i c a l systems. Ecology 44(2):327-332. Piene, H. and K. van Cleve. 1978. Weight l o s s of l i t t e r and c e l l u l o s e bags i n a thinned white spruce f o r e s t i n i n t e r i o r Alaska. Can. J . For. Res. 8(l):42-46. Rochow, J . J . 1975. M i n e r a l n u t r i e n t pool and c y c l i n g i n a M i s s o u r i f o r e s t . J . E c o l . 63:985-994. Rodin, L.E. and N.I. B a z i l e v i c h . 1967. Production and M i n e r a l C y c l i n g i n T e r r e s t r i a l Vegetation. O l i v e r and Boyd, Edinburgh and London, 135 p. S a t c h e l l , J.E. 1974. I n t r o d u c t i o n : L i t t e r - I n t e r f a c e of animate/inanimate matter. In: Biology of Pl a n t L i t t e r Decomposition, C.H. Dickenson and G.J.F. Pugh, eds. Academic Press, London and New York, pp. 3-36. 79 Shanks, R.E. and J.S. O l s o n . 1961. F i r s t - y e a r breakdown of l e a f l i t t e r i n s o u t h e r n A p p a l a c h i a n f o r e s t s . S c i e n c e 134:194-195. Sherwood, M. and G. C a r r o l l . 1974. F u n g a l s u c c e s s i o n on n e e d l e s and young t w i g s o f o l d growth D o u g l a s - f i r . M y c o l o g i a 66:499-506. S m i t h , J.H. 1966. Some i n t e r r e l a t i o n s h i p s between d e c o m p o s i t i o n o f v a r i o u s p l a n t r e s i d u e s and l o s s o f s o i l o r g a n i c m a t t e r as measured by c a r b o n - 14 l a b e l l i n g . I n : The Use o f I s o t o p e s i n S o i l O r g a n i c  M a t t e r S t u d i e s (F.A.0./I.A.E.A. T e c h n i c a l M e e t i n g ) , Pergamon P r e s s , O x f o r d , pp. 223^224. S t y l e s , J.H. 1967. D e c o m p o s i t i o n o f P i n u s r a d i a t a l i t t e r on t h e f o r e s t f l o o r . P a r t 2. Changes i n m i c r o f a u n a p o p u l a t i o n s . N.Z. J . S c i . 10:1045-1060. S w i f t , M.J., I.N. H e a l e y , J.K. H i b b e r d , J.M. S y k e s , V. Bampoe, and M.E. N e s b i t t . 1976. The d e c o m p o s i t i o n o f branchwood i n t h e canopy and f l o o r o f a mixed d e c i d u o u s woodland. O e c o l o g i a 26:139-149. Thomas, W.A. 1968. D e c o m p o s i t i o n o f l o b l o l l y p i n e n e e d l e s w i t h and w i t h o u t a d d i t i o n s of dogwood l e a v e s . E c o l o g y 49(3):568-571. Thomas, W.A. 1970. Weight and c a l c i u m l o s s e s from decomposing t r e e l e a v e s on l a n d and i n w a t e r . J . A p p l . E c o l . 7:237-241. van C l e v e , K. 1971. Energy and w e i g h t l o s s f u n c t i o n s f o r decomposing f o l i a g e i n b i r c h and aspen f o r e s t s i n i n t e r i o r A l a s k a . E c o l o g y 52: 720-723. van C l e v e , K. and L.L. Noonan. 1975. L i t t e r f a l l and n u t r i e n t c y c l i n g i n t h e f o r e s t f l o o r o f b i r c h and aspen s t a n d s i n i n t e r i o r A l a s k a . Can. J . F o r . Res. 5:626-639. 80 van der D r i f t , J . 1963. The d i s a p p e a r a n c e o f l i t t e r i n m u l l and mor i n c o n n e c t i o n w i t h weather c o n d i t i o n s and t h e a c t i v i t y o f macrofauna. I n : S o i l Organisms Doeksen, J . and J . van d e r D r i f t , eds. Amsterdam. N o r t h H o l l a n d P u b l . Co. pp. 125-133. V o i g t , G.K. 1965. N i t r o g e n r e c o v e r y from decomposing t r e e l e a f t i s s u e and f o r e s t humus. S o i l Sc. Soc. Amer. J . 29(1):756-759. W a l l w o r k , J.A. 1976. The D i s t r i b u t i o n and D i v e r s i t y o f S o i l Fauna. Academic P r e s s , London, 355 p. Wia n t , H.V. J r . 1967. I n f l u e n c e o f m o i s t u r e c o n t e n t on " s o i l r e s p i r a t i o n " . J . F o r . 65:902-903. W i l l , G.M. 1967. D e c o m p o s i t i o n o f P i n u s r a d i a t a l i t t e r on t h e f o r e s t f l o o r . P a r t 1. Changes i n d r y m a t t e r and n u t r i e n t c o n t e n t . N.Z. J . S c i . 10:1030-1044. W i l l i a m s , C.B. and G.T. D y r n e s s . 1967. Some c h a r a c t e r i s t i c s o f f o r e s t f l o o r s and s o i l s under t r u e f i r - h e m l o c k s t a n d s i n t h e Cascade r a n g e . U.S. F o r e s t S e r v i c e R e s e a r c h Paper PNW 37, 19 p. W i l l i a m s , S.T. and T.R.G. Gray. 1974. D e c o m p o s i t i o n o f l i t t e r on t h e s o i l s u r f a c e . I n : B i o l o g y o f P l a n t L i t t e r D e c o m p o s i t i o n , C.H. D i c k e n s o n and G.J.F. Pugh, e d s . , Academic P r e s s , London and New Y o r k , pp. Witkamp, M. 1963. M i c r o b i a l p o p u l a t i o n s o f l e a f l i t t e r i n r e l a t i o n t o e n v i r o n m e n t a l c o n d i t i o n s and d e c o m p o s i t i o n . E c o l o g y 44(2):370-377. Witkamp, M. 1966. D e c o m p o s i t i o n o f l e a f l i t t e r i n r e l a t i o n t o e n v i r o n m e n t , m i c r o - f l o r a , and m i c r o b i a l r e s p i r a t i o n . E c o l o g y 47(2):194-201. Witkamp, M. and J.S. O l s o n 1963. Breakdown o f c o n f i n e d and n o n - c o n f i n e d oak l i t t e r . O i k o s 14(11):138-147. 81 Witkamp, M. and J . v a n der D r i f t . 1961. Breakdown o f f o r e s t l i t t e r i n r e l a t i o n t o e n v i r o n m e n t a l f a c t o r s . P l a n t and S o i l 1 5 (4):295-311. Yoneda, T. 1975. S t u d i e s on t h e r a t e o f decay o f wood l i t t e r on t h e f o r e s t f l o o r . I I . Dry w e i g h t l o s s and CC^ e v o l u t i o n o f d e c a y i n g wood. Jap . J . E c o l . 25:139-140. Youngberg, C T . 1966. F o r e s t f l o o r s i n D o u g l a s - f i r f o r e s t s : I . Dry w e i g h t and c h e m i c a l p r o p e r t i e s . S o i l Sc. Soc. Amer. P r o c . 30:406-409. 82 APPENDIX I LIST OF COMMONLY OCCURRING PLANT SPECIES Douglas-fir Western red cedar Western Hemlock Big-leaf maple Vine maple Pseudotsuga menziesii (Mirb.) Franco Thuja p l i c a t a Donn ex D.Don i n Lamb. Tsuga heterophylla (Raf.) Sarg. Acer macrophyllum Pursh. Acer circinatum pursh. S a l a l Red huckleberry Salmonberry T r a i l i n g blackberry Gaultheria shallon Pursh. Vaccinium parvifolium Smith i n Rees Rubus s p e c t a b i l i s Pursh. Rubus ursinus Cham, & Schlecht, Swordfern Lady f e r n Deer fern Bracken fern Polystichum muniturn (Kaulf,) P r e s l Athyrium felix-femina (L,) Roth, Blechnum spicant (L.) Roth, Pteridium aqujlinum (L.) Kuhn V a n i l l a l e a f Foam flower T r i l l i u m Twin flower Achlys t-riphylla (Smith) DC. T i a r e l l a t r i f o l i a t a L. T r i l l i u m ovaturn Pursh. Linnaea b o r e a l i s L. 83 Hylocomium splendens (Hedw.) B.S.G. Plagiothecium undulatum (Hedw.) B.S.G. Rhytidiadelphus l o r l u s (Hedw.) Warnst. Rhacomitrium canescens (Hedw.) B r i d . Rhyzomnium glabrescens (Kindb,) Koponen Plagiomnium insigne (Mitt.) Koponen S t o k e s i e l l a oregana (Sull.) Robins Dicranum fuscescens Turn, Leucolepus menzlesii (Hook.) Steere ex L, Koch Scapania undvilata (L, ) Dura, 

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}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            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:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0100225/manifest

Comment

Related Items