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Comparison of some growth characteristics between two different Douglas-fir ecosystems of the same age… Jaeger, Brigitte Maria 1983

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COMPARISON OF SOME GROWTH CHARACTERISTICS BETWEEN TWO DIFFERENT DOUGLAS-FIR ECOSYSTEMS OF THE SAME AGE AND SITE INDEX by BRIGITTE MARIA JAEGER Diploma Forest Engineer, University of Munich, 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Forestry) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April 1983 © Brigitte Maria Jaeger, 1983 \ \ I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t 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 make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r 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 o r h e r 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 fo<l£sr(toj  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 1956 Main Ma l l V a n c o u v e r , Canada V6T 1Y3 DE-6 (3/81) i i ABSTRACT This study compared growth characteristics of two naturally established, unmanaged, late-immature, Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands. Both stands were very similar in regards to age, site index, relative density and history, but represented two different ecosystems. The objective was to determine and explain differences in major growth characteristics between the two stands. The ecosystems were identified at all levels of the biogeoclimatic ecosystem classification. The analysis of the ecosystems confirmed that the selected stands were considerably different in their ecotope. The stand in which Douglas-fir was moderately shade-tolerant had a warm and drier mesothermal climate. The other stand in which Douglas-fir was shade-intolerant had a cold and wetter mesothermal climate. Comparing edatopic differences, the site of the first stand was drier and had a poorer nutrient status than that of the second stand. The classification and site indices of Douglas-fir determined for the stands were in agreement with those predicted by Krajina (1969). The stand in which Douglas-fir was moderately shade-tolerant had a multilayered stand structure and the associated growth characteristics resembled those of an uneven-aged stand of shade-tolerant tree species. The stand in which Douglas-fir was shade-intolerant had a uniform canopy and the associated characteristics were typical for an even-aged stand of shade-intolerant tree species. Adjusting for a six year difference in age, there was a 15 percent difference in volume in favour of the stand in which Douglas-fir was shade-intolerant. The analysis of stand structure and i i i relationship of density to a number of growth characteristics indicated consistent differences between the stands, which appeared to be correlated to shade tolerance of Douglas-fir. Despite the similar site index and relative density index, it was concluded that there was a disparity in stand structure and volume production, which was related to ecological differences. A small number of samples and unknown initial density levels however, limit the validity of conclusions reached. The described trends and relationships need to be verified by further integrated studies. If such studies can confirm the relationship between ecosystem taxa and growth characteristics as described in this study, the adoption of a selective ecosystem-specific approach to stand management and construction of yield tables for Douglas-fir should be recommended. This could help to fully utilize the production potential of a site and to accurately predict stand development. iv TABLE OF CONTENTS JJaae ABSTRACT i i TABLE OF CONTENTS iv LIST OF TABLES 1 vii LIST OF FIGURES ix ACKNOWLEDGEMENTS xii INTRODUCTION 1 ECOLOGICAL FUNCTION OF COASTAL DOUGLAS-FIR 4 THE STUDY AREA 16 METHODS 21 Selection of Ecosystems and Sample Plots 21 Methods of Ecosystem Analysis 22 Methods of Ecosystem Synthesis 23 Synthesis of Environmental and Vegetation Data 23 Species Importance and Ecological Spectra 24 Methods of Stand Analysis 29 Methods of Stand Synthesis 30 Age, Top Height and Site Index 30 Height/Diameter Regression Curves 31 Basal Area and Volume 31 Crown Maps and Stand Profiles 32 Statistical Methods and Computing Techniques 33 RESULTS AND DISCUSSION 34 Characterization of the Ecosystems 34 Description 34 V page Classification 41 Productivity and Functional Relationships 60 Characterization of the Stands 69 Age, Top Height and Site Index 69 Stand Structure 73 Stand Map 74 Stand Profile 78 Crown Class Distribution 80 Length of Live Crown-Total Height Relationship 82 Diameter Characteristics 86 Diameter and Basal Area Distribution 87 Height-Diameter Relationship 90 Density 93 Number of Stems 93 Stand Density Indices 94 Relationship between Density and some Stand Characteristics 97 Crown Class-Density Relationship 97 Effect of Density on Height 99 Top Height-Density Relationship 101 Effect of Density on Diameter 104 Diameter-Density Relationship 107 Effect of Density on Volume Production 111 Basal Area and Volume of the Studied Stands 114 Volume-Density Relationship 116 Timber Quality SUMMARY CONCLUSIONS LITERATURE CITED Appendix I. L i s t of Plant Species Present in the Study Plots Appendix I I . Description of the Soil Pedons Sampled Appendix I I I . Environment-Vegetation Tables, Part 2 Appendix IV. Summary Vegetation Table vii LIST OF TABLES Page Table 1. Criteria for differentiating values of plant species in characteristic combination of species. 25 Table 2. Species importance scale. 27 Table 3. Relationship between height and diameter for Douglas-fir, western hemlock and western redcedar in the two stands studied. 32 Table 4. Selected environmental and vegetation data for the study plots. 35 Table 5.. Synopsis of ecosystem taxa using four integration levels of the biogeoclimatic classification system. 42 Table 6. Common and differential combination of species in the study plots. 43 Table 7. Combinations of plant indicator species from the study plots in relation to hygrotope. 48 Table 8. Combinations of plant indicator species from the study plots in relation to trophotope. 49 Table 9. The plant species from the study plots found in characteristic combinations for the CDF and CWH zones. 53 Table 10. The plant species from the study plots found in characteristic combinations for three orders. 56 Table 11. The plant species from the Ladysmith study plots found in characteristic combinations for two alliances of the Gaultherio shallonis -Pseudotsugetalia Order. 59 Table 12. The plant species from the Chi 11iwack study plots found in characteristic combinations for two alliances of the Polysticho muniti - Thujetalia Order. 61 Table 13. Comparison of biogeocoenotic taxa and site indices for Douglas-fir between the study plots and those predicted by Krajina (1969). 62 Table 14. Selected climatic data for the study area. 65 Table 15. Mean values obtained from a tree-ring analysis for the selected study plots. 68 v i i i page Table 16. Basic growth characteristics of the study plots and stands. 70 Table 17. Diameter characteristics of the stand studied. 86 ix LIST OF FIGURES Page Figure 1. Edatopic grids showing isolines of site indices and shade tolerance for coastal Douglas-fir in the biogeocoenotic associations or types of four mesothermal biogeoclimatic subzones. 10 Figure 2. Location of the two study areas. 16 Figure 3. Charcoal on the remaining stump of western redcedar in the Chilliwack study area. 20 Figure 4. The understory vegetation of the forest community in the Ladysmith ecosystem (plot no. 3). 36 Figure 5. The representative pedon sampled in the Ladysmith ecosystem (plot no. 3). 36 Figure 6. The understory vegetation of the forest community in the Chilliwack ecosystem (plot no. 17). 39 Figure 7. The representative pedon sampled in the Chilliwack ecosystem (plot no. 17). 40 Figure 8. Ecological spectra indicating floristic affinity between successional associations. 44 Figure 9. Ordination of the study plots using principal component analysis. 45 Figure 10. Ecological spectra indicating floristic affinity of of the study plots to hygrotope. 50 Figure 11. Ecological spectra indicating floristic affinity of the study plots to trophotope. 50 Figure 12. Ecological spectra indicating floristic affinity of the study plots to the mesothermal biogeoclimatic zones. 54 Figure 13. Ecological spectra indicating floristic affinity of the study plots to plant orders. 57 Figure 14. The ecological spectrum indicating floristic affinity of the Ladysmith study plots to two alliances of the Gaultheria - PM Order. 58 Figure 15. The ecological spectrum indicating floristic affinity of the Chilliwack study plots to two alliances of the Polystichum - TP Order. 60 X page F i g u r e 1 6 . Wes te rn r e d c e d a r o f good v i g o r i s common i n t h e sh rub l a y e r o f t h e L a d y s m i t h e c o s y s t e m . 63 F i g u r e 1 7 . Annua l wa te r b a l a n c e f o r t h e L a d y s m i t h e c o s y s t e m . 67 F i g u r e 1 8 . Annua l w a t e r b a l a n c e f o r t h e C h i l l i w a c k e c o s y s t e m . 67 F i g u r e 1 9 . The s t a n d map o f t h e p l o t n o . 1 i n t h e L a d y s m i t h s t a n d . 75 F i g u r e 2 0 . The s t a n d map o f t h e p l o t n o . 17 i n t h e C h i l l i w a c k s t a n d . 76 F i g u r e 2 1 . A r e p r e s e n t a t i v e v i ew o f t h e h o r i z o n t a l s t r u c t u r e o f t h e L a d y s m i t h s t a n d showing an uneven canopy w i t h s c a n t y c r o w n s . 77 F i g u r e 2 2 . A r e p r e s e n t a t i v e v i ew o f t h e C h i l l i w a c k s t a n d show ing t h e h o r i z o n t a l s t r u c t u r e o f an u n i f o r m canopy w i t h dense c r o w n s . 77 F i g u r e 2 3 . The s t a n d p r o f i l e r e p r e s e n t a t i v e o f t h e L a d y s m i t h s t a n d . 79 F i g u r e 2 4 . The s t a n d p r o f i l e r e p r e s e n t a t i v e o f t h e C h i l l i w a c k s t a n d . 79 F i g u r e 2 5 . D i s t r i b u t i o n o f crown c l a s s e s i n r e l a t i o n t o number o f t r e e s f o r t h e L a d y s m i t h s t a n d ( F i g . 25a) and t h e C h i l l i w a c k s t a n d ( 2 5 b ) . 81 F i g u r e 2 6 . D i s t r i b u t i o n o f crown c l a s s e s i n r e l a t i o n t o b a s a l a r e a f o r t h e L a d y s m i t h s t a n d ( F i g . 26a) and t h e C h i l l i w a c k s t a n d ( F i g . 2 6 b ) . 81 F i g u r e 2 7 . R e l a t i o n s h i p between t h e r a t i o o f l e n g t h o f l i v e crown t o t o t a l h e i g h t and t o t a l h e i g h t f o r t h e L a d y s m i t h s t a n d . 84 F i g u r e 2 8 . R e l a t i o n s h i p between t h e r a t i o o f l e n g t h o f l i v e crown t o t o t a l h e i g h t and t o t a l h e i g h t f o r t h e C h i l l i w a c k s t a n d . 84 F i g u r e 2 9 . L i n e a r r e g r e s s i o n s show ing r e l a t i o n s h i p s between t h e r a t i o o f l e n g t h o f l i v e crown t o t o t a l h e i g h t and t o t a l h e i g h t f o r bo th s t a n d s . 85 F i g u r e 3 0 . D i a m e t e r d i s t r i b u t i o n f o r D o u g l a s - f i r i n t h e L a d y s m i t h s t a n d . 88 page Figure 31. Diameter distribution for Douglas-fir in the Chi 11iwack stand. 88 Figure 32. Basal area distribution for Douglas-fir in the Ladysmith stand. 89 Figure 33. Basal area distribution for Douglas-fir in the Chilliwack plot. 89 Figure 34. Relationship of height to diameter for Douglas-fir in the study plots. 90 Figure 35. Relationship between the percent of basal area of dominant and codominant trees and density. 98 Figure 36: Relationship between top height and density (all species) in the Ladysmith stand. 102 Figure 37. Relationship between top height and density (all species) in the Chilliwack stand. 102 Figure 38. Relationship between mean dbh and number of trees/ha of Douglas-fir in the Ladysmith stand. 108 Figure 39. Relationship between mean dbh and number of trees/ha of Douglas-fir in the Chilliwack stand. 108 Figure 40. Relationship between mean dbh and number of trees/ha including all species in the Ladysmith and Chilliwack stands. 110 Figure 41. The downslope oriented pattern of dead branches on the lower stem of a dominant tree in the Chilliwack stand. 119 xii ACKNOWLEDGEMENTS I wish to thank my supervisor Dr. K. Klinka for his thorough help and patience in the ecological part of the study, and for the generous amount of time and support during all phases of my study. I wish to express appreciation to my Supervisory Committee, Dr. G. Weetman, Dr. K. Mitchell and Dr. J . Demaerschalk for advice and assistance. I wish to acknowledge the help of the staff of the Research Section, Ministry of Forests, and the computer programmers at UBC, J . Emmanuel and B. Wong. Thanks also to C. Ray for assistance with the field work. I am thankful for the financial support provided by a scholarship from the Canadian National Research Council, McPhee Fellowship and VanDusen Graduate Fellowship. -1-INTRODUCTION The common approach of assessing site quality or forest productivity is to classify a stand according to its site index, that i s , the expected height of a tree species at an index age. Once the stand has been classified a number of growth and yield characteristics, such as height, number of trees, basal area and volume per unit area, can be predicted from yield tables. Assumptions inherent to yield tables based on site indices prescribe growth development as follows: even-aged stands with the same site index will have the same growth and yield characteristics at various ages, and at the end of the rotation period they will produce the same volume (Assman 1970). Foresters relate a stand to yield tables by determining its site index, and applying the yield tables, they make predictions and management decisions based upon the predicted values. If the above assumptions are not valid, the predicted values can be associated with errors of variable magnitude. It has been accepted that site index alone is an inadequate measure to assess or explain site quality and to accurately predict stand development for the purpose of intensive silvicultural management. The rationale to consider other ecosystem properties was advanced by Franz (1965) as follows: "The yield level describes a complex of primary factors, which is based on site quality and plant physiological properties. Mensurational measurements summarize the effect of this complex, but cannot explain causal relationships. As a consequence, the mensurational attributes can only yield secondarily derived values." -2-The main purpose of the ecological program developed by the British Columbia Ministry of Forests is to classify forest lands and to elucidate environment-vegetation relationships. The intent is to provide an ecosystem-specific framework and interpretations for forest management. This program was not designed to provide detailed and reliable growth' and yield characteristics for a multitude of forest stands found in different ecosystems. However, the information on the potential productivity of ecosystems for timber production and crop design is of particular importance to a forest manager. By comparing composition, structure and growth characteristics of fully-stocked, natural stands on a site-specific basis, information on the site-growth relationship can be obtained. This information is useful for the assessment of potential productivity of managed stands or for forest management in general (Franklin 1981). Ecologically based growth and yield studies should greatly enhance the value of the recognized ecosystem taxa and, in general, the understanding of site-specific, environmental- and community-growth relationships. Thus they should support current efforts of intensified silvicultural management. Available information on the ecological characteristics of forest trees in British Columbia (Krajina 1969) makes it possible to conclude: 1. That significantly different ecosystems can support stands of the same species and forest productivity as expressed by site index and 2. that these stands may differ in some growth characteristics because of differences in the ecological characteristics of species and function . of the ecosystems. Recently, the Inventory Branch of the Ministry of Forests has -3-i n i t i a t e d a program o f c l a s s i f y i n g g rowth and y i e l d p l o t s u s i n g t h e b i o g e o c l i m a t i c c l a s s i f i c a t i o n s y s t e m . The goa l o f t h i s program i s t o d e t e r m i n e t h e d e g r e e o f r e l a t i o n s h i p between t h e g rowth d a t a and t h e r e c o g n i z e d e c o s y s t e m s y n t a x a f o r t h e pu rpose o f an a c c u r a t e and i n t e g r a t e d p r e d i c t i o n o f s t a n d d e v e l o p m e n t . T h i s s t u d y i s an a t t e m p t t o c h a r a c t e r i z e and compare some g rowth a t t r i b u t e s o f n a t u r a l l y d e v e l o p e d , f u l l y s t o c k e d , and n e a r l y mature f o r e s t s t a n d s w h i c h a r e e c o l o g i c a l l y d i f f e r e n t . S p e c i f i c a l l y , t h e s t u d y t e s t s t h e h y p o t h e s i s t h a t t h e r e i s no d i f f e r e n c e i n g rowth c h a r a t e r i s t i e s between two d i f f e r e n t D o u g l a s - f i r [ P s e u d o t s u g a m e n z i e s i i ( M i r b . ) F r a n c o ] e c o s y s t e m s o f the same a g e , h e i g h t - s i t e i n d e x and h i s t o r y . The f i r s t p a r t o f t h e s t u d y d e s c r i b e s , c l a s s i f i e s and compares the s t u d i e d e c o s y s t e m s , and s u g g e s t s t h e c o m p e n s a t i n g e n v i r o n m e n t a l f a c t o r s r e s p o n s i b l e f o r t h e same h e i g h t as e x p r e s s e d by s i t e i n d e x . In t h e second p a r t o f t h e s t u d y d i f f e r e n c e s i n b a s i c g rowth and s t a n d c h a r a c t e r i s t i c s a r e i d e n t i f i e d , a n a l y z e d and r e l a t e d t o the e n v i r o n m e n t a l p r o p e r t i e s o f t h e e c o s y s t e m s . I t i s assumed t h a t t h e v a r i a t i o n s i n t h e s e c h a r a c t e r i s t i c s c a n be a t t r i b u t e d t o d i f f e r e n c e s i n t h e f u n c t i o n o f t h e e c o s y s t e m s s t u d i e d . -4-ECOLOGICAL FUNCTION OF DOUGLAS-FIR Douglas-fir is one of the world's most important and valuable timber trees. It is native to Western North America, with the range of the coastal variety extending from central British Columbia (lat. 55°N) to the central coast of California (lat. 36°N) (Fowells 1965). This tree species has been introduced and grown for over 100 years in Europe, Great Britain and New Zealand. Its autecological characteristics have been reported in numerous studies from all these areas. On some important aspects most of the studies agree: Douglas-fir grows in a cool, maritime climate with the precipitation ranging from 700 mm to 5000 mm in the Pacific Northwest (Shumway 1981). In central Europe, where the precipitation is evenly spread over the year Douglas-fir grows well with only 500 mm annual rainfall (Floehr 1958). The drought resistance of the species is rated intermediate in a comparison of the trees of the Pacific Northwest (Minore 1979). Elevation and latitude interact in a way that Douglas-fir extends in its southern range (northern California) to 1800 m, whereas in its extreme northern range in British Columbia the upper altitudinal limit is 800 m (Fowells 1965). Douglas-fir is reported to be sensitive to wind on exposed sites in Great Britain, causing die-back and breakage of the leader (Darrah et_ al_. 1965). Exposure is a limiting factor in New Zealand as well (New Zealand Forest Service 1971). Early and late frosts are causing severe damage in young Douglas-fir plantations in Germany (Schober 1963). Kirkland (1971) reported similar problems for New Zealand. The general frost resistance of Douglas-fir in -5-the Pacific Northwest is rated relatively high (Minore 1979). When assessing the relative shade-tolerance of several tree species Minore (1971) rated the position of Douglas-fir intermediate. When compared with its most common associates, Douglas-fir rates very high on the scale of intolerance (Fowells 1965). In humid climates these associates, typically western hemlock, western redcedar and Pacific silver f i r form the climax species. In drier areas, caused by topographic rain shade, soil and climatic characteristics pure Douglas-fir stands may exist as the climax stage and occasionally form uneven-aged stands (Williamson 1981). Under these conditions Douglas-fir apparently is tolerant to its own shade. Douglas-fir occupies a wide variety of sites throughout its native habitat (Revel 1 1974). Good drainage and aeration of the root zone are important for the growth of Douglas-fir (Williamson 1980). It will not thrive on poorly drained soils or soils with an impervious layer near the surface (Fowells 1965). Heavy clay soils and podzols support unsatisfactory growth in New Zealand (New Zealand Forest Service 1971). Best growth of Douglas-fir in Germany was found on areas of glacial outwash t i l l with clay influence, or morainic sites and on rich sandy sites (Floehr 1958). The best development of the species has been reported on soils with the pH between 5 and 5.5 (Fowells 1965). Floehr (1958) notes that in German Douglas-fir plantations the preferred pH range appears to be 5-6, with a decline in vigour for calcareous soils. Krajina (1969) and, more recently, Krajina et al_. (1982) presented autecological characteristics of forest trees in British Columbia. These characteristics were derived from the synecological studies carried out - 6 -d i r e c t l y i n t h e n a t u r a l e n v i r o n m e n t , e x p e r i m e n t a l s t u d i e s and f i e l d o b s e r v a t i o n s . As a r e s u l t , t h i s i n f o r m a t i o n can be r e l a t e d to s p e c i f i c s i t e s where t h e s e t r e e s may g r o w , t h u s p r o v i d i n g a b a s i s on wh i ch t o d e s c r i b e the e c o l o g i c a l f u n c t i o n o f e v e r y t r e e s p e c i e s . These s i t e s o r e c o s y s t e m s , when i n c l u d i n g b i o c o e n o s e s , a r e c l a s s i f i e d o r i d e n t i f i e d u s i n g the t a x o n o m i c c l a s s i f i c a t i o n p r o p o s e d by K r a j i n a ( 1 9 6 9 , 1972 , 1 9 7 7 ) . T h i s c l a s s i f i c a t i o n s y s t em has s e v e r a l i n t e g r a t i o n l e v e l s , w i t h each l e v e l h a v i n g s e v e r a l c a t e g o r i e s . In t h i s s t u d y , s y n t a x a a t t he b i o g e o c o e n o t i c , b i o g e o c l i m a t i c , p h y t o c o e n o t i c and e d a t o p i c ( f u n c t i o n a l ) l e v e l s a re a p p l i e d . The a u t e c o l o g i c a l c h a r a c t e r i s t i c s o f D o u g l a s - f i r were summar ized by K r a j i n a et a l _ . ( 1982 ) as f o l l o w s : ( a ) g e o g r a p h i c : W e s t e r n N o r t h A m e r i c a n ; P a c i f i c and C o r d i l l e r a n D i s t r i b u t i o n i n Wes te rn No r th A m e r i c a : c e n t r a l and s o u t h i n the P a c i f i c r e g i o n ; c e n t r a l and s o u t h i n the C o r d i l l e r a n r e g i o n (b) c l i m a t i c : [ s u b a l p i n e b o r e a l ( D f c ) - b o r e a l ( D f c ) -] c o o l t e m p e r a t e (D fb ) - warm temperTCe (D fa ) - [ s e m i a r i d ( B Sk ) ] - c o l d mesotherma l ( C f c ) - c o o l mesothermal ( C s b , C f b ) ( c ) o r o g r a p h i c : submontane - montane (- s u b a l p i n e ) (d) e d a t o p h i c : (1 ) h y g r o t o p e s : ( v e r y x e r i c -) x e r i c - s u b x e r i c -s u b m e s i c - m e s i c - s u b h y g r i c - h y g r i c (2 ) t r o p h o t o p e s : ( o l i g o t r o p h i c -) s u b m e s o t r o p h i c -m e s o t r o p h i c - p e r m e s o t r o p h i c - s u b e u t r o p h i c t o e u t r o p h i c ; g e n e r a l i z e d n u t r i t i o n a l t y p e : s u b e u t r o p h i c e u r y t r o p h o p h y t e The scope o f t h i s s t u d y was l i m i t e d to the c e n t r a l p a r t o f t h e P a c i f i c r e g i o n wh i ch s u p p o r t s t h e c o a s t a l p o p u l a t i o n o f D o u g l a s - f i r ( P s e u d o t s u g a  m e n z i e s i i v a r . m e n z i e s i i ) . In t h i s a r e a D o u g l a s - f i r i s f o u n d g r o w i n g i n mesotherma l c l i m a t e s ( v e r y r a r e l y i n a s u b a l p i n e - b o r e a l c l i m a t e ) f rom submontane t o montane ( v e r y r a r e l y s u b a l p i n e ) e l e v a t i o n s and on a g r e a t -7-variety of sites within the Coastal Douglas-fir (CDF) and Coastal Western Hemlock (CWH) (very rarely in the Mountain Hemlock) biogeoclimatic zones. ' The CDF and the CWH zones are characterized by a cool summer and a mild winter. A more complete climatic characterization of these zones is given by Krajina et al_. (1982). Frost resistance is not very high in the coastal variety which does not tolerate frost below -10°C for a period of more than about a week, even i f the ground is well protected against freezing by snow. Flood resistance of Douglas-fir is one of the lowest among the trees growing in British Columbia. This special characteristic is probably also reflected in the hydrosere gradient, because Douglas-fir does not grow on subhydric sites. It does not occur on recent floodplains because occasional flooding eliminates i t completely. Shade tolerance is considered to be moderate because the species is well adapted to subhumid or even dry climates. On mesic sites Douglas-fir is shade-tolerant only in the drier CDF subzones. In the wetter CDF subzones i t is shade-tolerant only on very xeric to submesic sites, whereas on mesic sites i t regenerates until the stands develop an open canopy. Krajina (1965) suggested that Douglas-fir in more humid climates becomes shade intolerant in many habitats, where i t takes up more water than it is able to transpire, due to its leaf stomata being closed and in the shade. In general, the nutritional requirements of Douglas-fir are moderate, but to achieve maximum growth nutritional requirements are considerable. Douglas-fir grows poorly on oligotrophic soils, where calcium, magnesium, nitrogen, phosphorus and potassium are in low supply. Phosphorus and potassium must be well balanced. -8-Krajina (1973) found in an experiment that Douglas-fir grows very poorly where it is dependent on ammonium compounds alone for its nitrogen supply. Root growth of Douglas-fir showed signs of intolerance towards pure ammonium nutrition (Bigg et al_. 1978). Results of other experiments showed that the growth of Douglas-fir seedlings and young trees, fertilized with nitrogen was superior for the nitrate treatment versus the ammonium one (Garm 1958, Ebell et al_. 1970, Radwan et al_. 1971, Bigg et al_. 1978). A study of van den Driessche (1971) where he grew Douglas-fir seedlings in a sand culture showed best growth for a combination of both the nitrate and the ammonium form. Gosz (1981) reviewed the various findings on this subject. Low nitrogen demanding species seem to prefer the nitrate form of nitrogen. Douglas-fir seems to be able to use both forms. He concluded that plants which have the ability to assimilate nitrate increase their level of nitrate reduction with increasing level of nitrate in the soi l . Havill et aj_. (1975) showed that calciphytic plants have a higher ability to produce nitrate reductase and therefore to utilize nitrate than calciphobic plants. Since nitrifying bacteria are dependent on a relatively high pH, nitrification is carried out mainly in Moders and Mulls of soils in which calcium is easily available and there is better growth of Douglas-fir in these than in acid Mors. The best growth of Douglas-fir was recorded on base-rich soils (Klinka et 1981a). To indicate the ecological function of Douglas-fir it is necessary to integrate forest communities and site components of the ecosystems in which it grows. Krajina (1969) proposed a method by which the ecological characteristics of a tree species can be assessed together with its growth performance and shade tolerance in relation to a site. This method is -9-based on the edatopic grid technique (Figure 1). This technique uses a matrix which is composed of a moisture gradient (hygrotope) and a nutrient gradient (trophotope). The hygrotope is applied on a vertical axis and the trophotope is applied on a horizontal axis. Within the geographic limits of a biogeocl imatic subzone, forest ecosystems with the same or a similar hygrotope and trophotope as indicated by the similarity in their f loristic composition, are grouped together into associations. Because each association, is characterized by a range of values of hygrotope and trophotope in turn, these values can be used to identify the sites that are characteristic for an association or a group of closely related associations. Coastal Douglas-fir is a component of various forest ecosystems classified into associations. The various associations supporting or having a potential to support the species, as well as all the other associations in the respective subzones, can also be shown on the edatopic grids. This is done by plotting the associations into individual cells (edatopes) according to the identified values of hygrotope and trophotope. Arabic numerals in the upper right corner of the grid cells identify these associations. On this basis tree species can be related to their sites or ecosystems. A tree symbol can be drawn in the individual cells indicating under which particular climatic and edatopic conditions coastal Douglas-fir grows or may grow. The symbol may be modified to indicate the species productivity and shade tolerance or any other chosen silvical attribute. The size of the symbols in Figure 1 indicates the species growth class (i.e. site index class); solid black symbols represent tolerance of shade Coastal Douglas-fir Drier Maritime Coastal Douglas-fir Subzone Wetter Maritime Coastal Douglas-fir Subzone n 17 II 10 10 17 17 11 V i • s ft> 1y %/ y f/ fi',: r r / !• 1 * <»: u I I 11 ti Drier Maritime Coastal Western Hemlock Subzone Wetter Maritime Coastal Western Hemlock Subzone A B C D E. Explanatory notes Hygrotopes (vertical axis): 0 - very xeric. 1 - xeric. 2 - subxeric. 3 - submesic. 4 - mesic. 5 - subhygric. 6 - hygric. 7 - subhydric Trophotopes (horizontal axis): A - oligotrophic. B - submesotrophic. C - mesotrophic. D - permesotrophic, E - subeutrophic to eutrophic Tree symbols end their sizes according to growth classes (site indices m/100 yrs) end tolerance to shade: { la(>54) llb(51) \ lla(48) 4 llb|45) 41118(42) 4 lllb(39) • IVa(36) t IVb(33) • Va(30) I Vb(22) «Vc(<15) 4 Shade-requiring or shade-tolerant Shade-intolerant F i g u r e 1. ETdatbpTcgr ids showing i s o l i n e s o f s i t e i n d i c e s and shade t o l e r a n c e f o r c o a s t a l D o u g l a s -f i r i n the b i o g e o c o e n o t i c a s s o c i a t i o n s o r t y p e s o f f o u r mesotherma l b i o g e o c l i m a t i c subzones ( a f t e r K r a j i n a 1 9 6 9 ) . Sma l l a r a b i c numbers i n t h e r i g h t uppe r c o r n e r s r e f e r t o a s s o c i a t i o n s o r t y p e s named i n K r a j i n a ( 1 9 6 9 , p . 4 1 - 4 4 ) . A _ 1 1 _ w h i l e c l e a r s ymbo l s r e p r e s e n t i n t o l e r a n c e o f shade . I s o l i n e s a re t h e n drawn between c e l l s w i t h t h e same s i t e i n d e x . The d i a g r a m s p r e s e n t e d i n F i g u r e 1 i n f o r m about t h e e c o l o g i c a l f u n c t i o n o f c o a s t a l D o u g l a s - f i r i n f o r e s t e c o s y s t e m s o f f o u r mesothermal b i o g e o c l i m a t i c s u b z o n e s . F o r e s t e c o s y s t e m s i n t h e s e subzones were s t u d i e d by K r a j i n a and S p i l s b u r y ( 1 9 5 2 , 1 9 5 3 ) , S c z a w i n s k i ( 1 9 5 3 ) , McMinn ( 1 9 5 7 , 1 9 6 0 , 1 9 6 5 ) , K r a j i n a ( 1 9 5 9 , 1 9 6 5 ) , M u e l l e r - D o m b o i s ( 1 9 5 9 , 1 9 6 5 ) , L e sko ( 1 9 6 1 ) , O r l o c i ( 1 9 6 1 , 1964 , 1 9 6 5 ) , E i s ( 1 9 6 2 ) , Kuramoto ( 1 9 6 5 ) , Wade ( 1 9 6 5 ) , C o r d e s ( 1 9 6 9 ) , K o j i m a ( 1 9 7 1 ) , K o j i m a and K r a j i n a ( 1 9 7 5 ) , K l i n k a (1976) and K l i n k a and K r a j i n a ( 1 9 8 3 ) . Based on t h e s e s t u d i e s a b r i e f summary o f the f u n c t i o n and p r o d u c t i v i t y o f t h i s t r e e s p e c i e s i n b i o g e o c l i m a t i c s y n t a x a r e l e v a n t t o t h i s s t u d y f o l l o w s . C o a s t a l D o u g l a s - f i r Zone T h i s i s t h e d r i e s t mesothermal zone o f B r i t i s h C o l u m b i a . I t i s f ound a l o n g t h e e a s t e r n s i d e o f Vancouve r I s l a n d , on t h e G u l f I s l a n d s and on t h e a d j a c e n t c o a s t a l m a i n l a n d between 48° and 50° 2 0 ' N l a t i t u d e . E l e v a t i o n may r ange f rom sea l e v e l t o 150 m i n t h e n o r t h and t o 450 m i n t h e s o u t h . T h i s zone e x t e n d s s o u t h i n t o Wash ing ton and O regon . D o u g l a s - f i r i s t h e m o s t common t r e e s p e c i e s i n t h e f o r e s t s t a n d s o f t h i s z o n e . I t can r e g e n e r a t e under the canopy o f ma tu re and p a r t l y open f o r e s t s t a n d s on most s i t e s . Wes te rn r e d c e d a r ( T h u j a p l i c a t a Donn eix D. Don vn L a m b . ) , g r a n d f i r [ A b i e s g r a n d i s ( D o u g l . ex D. Donn) L i n d l . ] , P a c i f i c madrone ( A r b u t u s m e n z i e s i i P u r s h ) , and G a r r y oak (Que rcus g a r r y a n a D o u g l . ex Hook . ) may f r e q u e n t l y accompany D o u g l a s - f i r , d e p e n d i n g on the - 1 2 -s o i l : m o i s t u r e and n u t r i e n t r e g i m e o f t h e s i t e . P r edominance o f s m a l l e r s h r u b s ( G a u l t h e r i a s h a l l o n and Mahom'a n e r v o s a ) , l o w p r e s e n c e o f h e r b s and m o s s e s , and t h e modera te shade t o l e r a n c e o f D o u g l a s - f i r a r e c h a r a c t e r i s t i c f l o r i s t i c f e a t u r e s o f z o n a l e c o s y s t e m s . Moder t o weak Mor f o r m a t i o n , m e l a n i z a t i o n , weak l a t e r i z a t i o n , and weak l e a c h i n g were d e s c r i b e d by K r a j i n a ( 1 9 5 9 , 1 9 6 5 , 1969 , 1978) as t h e c h a r a c t e r i s t i c s o i l p r o c e s s e s . The s o i l s o f zona l e c o s y s t e m s a r e D y s t r i c B r u m ' s o l s w i t h medium base s a t u r a t i o n g r a d i n g w i t h i n c r e a s i n g p r e c i p i t a t i o n i n t o Humo-Fe r r i c P o d z o l s w i t h Moders o r f r i a b l e M o r s . The h i g h p o t e n t i a l f o r f o r e s t p r o d u c t i o n i s l i m i t e d by a summer w a t e r d e f i c i t . W e t t e r M a r i t i m e CDF (CDFb) Subzone T h i s subzone i s c h a r a c t e r i z e d by a modera te s o i l m o i s t u r e d e f i c i e n c y , and hence has a h i g h e r f o r e s t p r o d u c t i v i t y than t h e d r i e r s u b z o n e . The e f f e c t o f g r e a t e r r a i n f a l l i s n o t i c e a b l e e s p e c i a l l y i n the a b i l i t y o f D o u g l a s - f i r t o become e s t a b l i s h e d on v e r y x e r i c s i t e s . D o u g l a s - f i r i s s h a d e - r e q u i r i n g o n l y on v e r y x e r i c and x e r i c s i t e s and s h a d e - t o l e r a n t on s u b x e r i c and submes i c s i t e s . On m e s i c s i t e s i t i s m o d e r a t e l y shade-t o l e r a n t , i . e . i t c an e s t a b l i s h i n an o v e r m a t u r e s t a g e a f t e r the s t a n d canopy has opened . On s u b h y g r i c and h y g r i c s i t e s D o u g l a s - f i r i s shade-i n t o l e r a n t . The most p r o d u c t i v e s t a n d s f o u n d on h y g r i c and s u b e u t r o p h i c s i t e s have a s i t e i n d e x i n t h e r ange f r om 4 9 . 6 t o 5 2 . 5 m/ lOOyrs . C o a s t a l Wes t e rn Hemlock Zone T h i s i s t h e w e t t e s t mesotherma l zone o f B r i t i s h C o l u m b i a . I t c o v e r s -13-much of Vancouver Island and the Coast Mountains. Upper elevations of the zone are 900 m on the windward and 1100 m on the leeward side of mountains in southwestern British Columbia. Outside of the rainshadow area, i t extends to sea level. Like the CDF Zone, the CWH Zone continues along the Pacific coast into Washington and Oregon. Western hemlock [Tsuga heterophylla (Raf.) Sarg.] is usually the most common species in the forest cover. It regenerates in abundance under the canopy of forest stands on zonal sites and elsewhere if there is enough accumulation of acid humus materials or decaying wood on the forest floor. Throughout the zone, Douglas-fir and western redcedar occur frequently, while amabilis f i r [Abies amabilis (Dougl. ex Loud.) Forbes] and yellow-cedar [Chamaecyparis nootkatensis (D.Don) Spach] are common only in the wetter CWH subzones. The predominance of several moss species (Hylocomium splendens, Rhytidiadelphus loreus, and Plagiothecium undulatum) along with the low presence of herbs and a high species significance of western hemlock are the characteristic floristic features of zonal ecosystems. Accumulation of acid decomposition products on the forest floor, leaching, eluviation, i l luviation, and gleization were described by Krajina (1959, 1965, 1969, 1978) as the characteristic soil forming processes. The soils of zonal ecosystems are Humo-Ferric Podzols with Mors grading with increasing precipitation into Ferro-Humic Podzols with Mors. Wetter Maritime CWH (CWHb) Subzone In this subzone, which is the wettest biogeoclimatic unit of British Columbia, Douglas-fir is less productive than in the CWHa Subzone, due to -14-the effective leaching of the soils caused by high precipitation. As a result, the loss of nutrients by leaching is detectable even on the most productive (subhygric to hygric/subeutrophic) sites which feature a site index in the range from 49.6 to 52.5 m/lOOyrs. Pacific Silver Fir , Sitka spruce [Picea sitchensis (Bong.) Carr.], western hemlock and yellow-cedar however, have the most productive growth in the CWHb Subzone. Douglas-fir is shade tolerant only on very xeric and xeric sites; on all other sites i t is shade-intolerant. It does not grow on very xeric/oligotrophic and subhydric sites. Figure 1 shows the predicted site indices for coastal Douglas-fir in different edatopes of different associations occurring in different biogeoclimatic subzones. Krajina (1969) admitted that the curves are idealized and need to be tested. It can be observed that: 1. The forest productivity (as measured by site index) of coastal Douglas-fir ecosystems of the same edatopes increases from the CDFa to CDFb or CWHa subzone, and then decreases in the CWHb subzone. 2. Within the same hygrotope the site index increases with increasing trophotope. 3. The same site index may be found for several ecosystems of different edatopes in the same or different biogeoclimatic subzones. The site index remains the same providing that the decrease in hygrotope is compensated by an increase in trophotope. If these predictions are valid, then it should be possible to find comparable Douglas-fir stands with the same site index but with contrasting -15-c o m b i n a t i o n o f c l i m a t e , h y g r o t o p e and t r o p h o t o p e . C o n s i d e r i n g t h e d e s c r i b e d v a r i a t i o n s i n t o l e r a n c e t o shade i t i s l i k e l y t h a t a l o n g w i t h s i t e d i f f e r e n c e s one c a n e x p e c t c o r r e s p o n d i n g d i f f e r e n c e s i n t h e c o m p o s i t i o n and d e v e l o p m e n t o f t h e s t a n d s , such as i n s t o c k i n g o r d e n s i t y , h o r i z o n t a l and v e r t i c a l s t r u c t u r e , and pe rhaps even i n volume p r o d u c t i o n . -16-THE STUDY AREA Location The study was carried out in two stands located in southwestern British Columbia - on Vancouver Island, near Ladysmith and in the Lower Mainland, near Chilliwack (Figure 2). The Douglas-fir stand on Vancouver Island was located about five km southwest of Ladysmith on the eastern side of Banon Creek and about five km north of the point where the creek joins the Chemainus River (48° 56' N latitude and 123° 49' W longitude). The Douglas-fir stand on the Lower Mainland was located on the western slopes of the Tamihi Creek Valley, about three km south from where the Tamihi Creek joins the Chilliwack River (49° 03' N latitude and 121° 48' W longitude). Figure 2. Location of the two study areas. -17-C1 imate At the general leve l the c l imate of the study area i s described as mesothermal (C) c l imate - a m i l d , ra iny c l ima te ; the mean temperature of the co ldes t month i s between 0°C and 18°C, the mean temperature of the warmest month i s over 10°C a f t e r Koppen and Trewartha (Trewartha 1968 as modif ied by Kra j ina et jil_. 1982). At the regional level however, there are profound c l ima t i c d i f fe rences between the study areas. The fo l lowing charac te r i za t ion of c l imates i s based on Court in et a V s. (1983) summary for b iogeoc l imat ic uni ts in southwestern B r i t i s h Columbia. The regional c l imate of the Ladysmith area i s described as t r a n s i t i o -nal between wetter Csb and d r i e r Cfb - a cool mesothermal c l imate with no d i s t i n c t dry season, p r e c i p i t a t i o n of the d r i e s t month greater than 30 mm, grading to that with dry summer, p r e c i p i t a t i on of the d r i e s t month of summer l e s s than 30 mm (the mean value for the area i s 32 mm), and the mean monthly temperature o f the warmest month below 22 °C . A long growing season with low p r e c i p i t a t i o n i s c h a r a c t e r i s t i c of t h i s c l imate . The regional c l imate of the Chi l l iwack area i s descr ibed as a milder Cfc - a co ld mesothermal c l imate with no d i s t i n c t dry season, p r e c i p i t a t i o n o f the d r i e s t month greater than 30 mm, and fewer than 4 months have a mean temperature greater than 10°C. A shor t , co ld and wet growing season i s c h a r a c t e r i s t i c of t h i s c l imate . - 1 8 -P h y s i o g r a p h y The L a d y s m i t h s t u d y a r e a i s l o c a t e d w i t h i n the e a s t e r n Vancouve r I s l a n d Ranges , wh i ch b e l o n g to t h e I n s u l a r M o u n t a i n s o f t h e Oute r M o u n t a i n A r e a ( H o l l a n d 1 9 6 4 ) . The s t u d y s t a n d i s p r e d o m i n a n t l y f l a t and i s s i t u a t e d 190 m above sea 1 e v e l . The C h i l l i w a c k s t u d y a r e a i s l o c a t e d w i t h i n the S k a g i t Range wh i ch b e l o n g s to the Cascade M o u n t a i n s ( H o l l a n d 1 9 6 4 ) . The s t u d y s t a n d i s s i t u a t e d on the upper p a r t o f a s t e e p , wes t f a c i n g s l o p e w i t h a s l o p e g r a d i e n t o f 67 p e r c e n t , a t an e l e v a t i o n o f 680 m e t r e s above sea l e v e l . S o i l P a r e n t M a t e r i a l s The L a d y s m i t h a r e a l i e s on a g l a c i o f l u v i a l t e r r a c e a d j a c e n t to Banon C r e e k . The m a t e r i a l s a r e o v e r 1 m t h i c k and v a r y i n p a r t i c l e s i z e and c o n t e n t o f c o a r s e f r a g m e n t s f rom sandy i n the upper so lum to s a n d y - s k e l e t a l i n the l o w e r s o l u m . A n g u l a r c o a r s e f r a g m e n t s d e r i v e d f rom v o l c a n i c r o c k s a r e p r e d o m i n a n t . The u n d e r l y i n g b e d r o c k i s a s i c k e r v o l c a n i c f o r m a t i o n , c o n s i s t i n g o f h o r n b l e n d e - a r g i t e a n d e s i t e ( G e o l o g i c a l Su rvey o f Canada 1 9 1 8 ) . The C h i l l i w a c k a r e a l i e s w i t h i n the C h i l l i w a c k s e r i e s , c o n s i s t i n g o f a r g i l l i t e , q u a r t z i t i c s a n d s t o n e , and l i m e s t o n e , w i t h i n t e r b e d s o f g r i t and c o n g l o m e r a t e ( G e o l o g i c a l map o f t h e N o r t h A m e r i c a n C o r d i l l e r a 1 9 1 3 ) . The s u r f i c i a l m a t e r i a l i n t h e a r e a i s a l o a m y - s k e l e t a l c o l l u v i a l v enee r u n d e r l a i n a t a d e p t h o f abou t 1 m by a wea the red s h a l e b e d r o c k wh i ch i s o r i e n t e d a t n e a r l y r i g h t a n g l e s t o t h e s l o p e . The c o n t e n t o f t h i n and f l a t -19-(shale derived) coarse fragments is over 60 percent. Hi story It is estimated that the old (more than 250 years) growth forest in both study areas was logged about 80 years ago. The Ladysmith area was apparently a part of timber exploitation which occurred within the limits of the Esquimalt-Nanaimo Grant on eastern Vancouver Island. The forest in the Chilliwack area was likely within the area of logging operations which included forested lands on Vedder Mountain and easily accessible parts of the Chilliwack River Valley. Identification of the remaining stumps and left-over cut timber indicates that western redcedar was a significant component of the tree species composition of old growth forest in both study areas (Figure 3). Charcoal on the stumps and timber debris and in the surface organic layer gave evidence of post-logging fire, but the degree of burning remains unknown. The present forest was established by natural regeneration within a relatively short period following the fire and has not been managed. A considerable amount of small, undecomposed wood debris in the Ladysmith area suggests continuing mortality up to the present developmental stage. In contrast there are no signs of recent wood debris on the forest floor in the Chilliwack area. It could be concluded that either this forest stand had init ial ly an open spacing or that mortality occurred in the very early stage of stand development due to the shade-intolerance of Douglas-fir in the climatic environment of the area. Figure 3. Charcoal on a remaining stump of western redcedar in the Chilliwack study area. -21-METHODS Selection of Ecosystems and Sample Plots To achieve the described objective of the study it was essential, to locate two stands of the same site index, but of contrasting sites. Specifically, the stands were required to be uniform in the following characteristics: 1. Age (preferably within the range from 60 - 100 years) 2. Height (based on the average height of the 100 largest diameter Douglas-fir trees per hectare) 3. Tree species composition (Douglas-fir comprising 90 percent or more of the total basal area) 4. Crown coverage (greater than 80 percent), 5. Vegetation and environment characteristics 6. History An additional requirement was to select stands large enough to allow the establishment of 10 sample plots. The sample plot size of 25 x 25 m or 0.0625 ha was chosen to contain a minimum of 30 trees. Ecologically, the objective was to select two stands that would represent two strongly contrasting ecosystems, i.e each being within a different biogeoclimatic subzone. The stand selection was done by using biogeoclimatic and forest cover maps of the Ministry of Forests and ground checks. Preliminary measurements were taken in selected stands to obtain information on the age and the site index. -22-Methods of Ecosystem Analysis This study employed an approach and methods which were described by Brooke et al_. (1970), Kojima and Krajina (1975), Inselberg et al_. (1982) — and Krajina et al_. (1982). Each sample plot used for stand analysis was also used for the ecosystem analysis. Each stand represented a sample of an individual ecosystem. On each plot the vegetation'was analyzed by phytosociological techniques. The vegetation analysis included the listing of all vascular plants, bryophytes and lichens present on the plot, as well as evaluation of species significance and vigor according to vegetation strata (Inselberg et al_. 1982). A l i s t of all plant species recorded in the two ecosystems is given in Appendix I. Sites (habitats) were described in terms of elevation, slope, exposure and parent materials. Description of soil pedons was limited to one selected plot in each stand. The description of the pedons sampled is given in Appendix II. Soil sampling and classification followed practices and terminology of the Canadian Soil Survey Committee (CSSC 1978). Classification of humus forms was done according to Klinka et aj_. (1981). Samples of individual soil horizons were collected and prepared for chemical analysis. Analyses were made for soil pH in CaCl2» total carbon by dry combustion, total nitrogen by Kjeldahl digestion and cation exchange capacity and exchangeable cations by NH4OAC (pH 7.0) extraction. The analytical methods employed were those described by Lavkulich (1981). -23-Methods of Ecosystem Synthesis Synthesis of Environmental and Vegetation Data Following an analysis of vegetation and its environment, the l ists of obtained values for each plot were compared for similarities and differences, using a tabular method (Klinka and Phelps 1979). Applying these methods, standardized tables and a differentiating table (Table 6) for the two ecosystems studied were prepared to supplement the description given. Principal component analysis (PCA) was used to complement the tabular methods. The PCA used a covariance matrix based on species coverage values altered by centering (Gauch 1977). Synthesis of the data revealed consistency of plots in each ecosystem studied - from these, the taxa at the biogeoclimatic, biogeocoenotic, phytocoenotic and functional level were identified. The identification was based mainly on the floristic attributes of ecosystems, i.e. on the charac-teristic combination of species proposed for the recognized taxa by various workers and on the indicative values of plants in relation to selected environmental factors, as interpreted by Krajina et al_. (1983). The characteristic combination of species was defined by Braun-Blanquet (1928) as a combination of plants more or less unique to a particular taxon. Thus, the taxa can be differentiated or identified by the presence (as well the absence) of these mutually exclusive combinations. A detailed discussion on this topic, including the principles for selection and the criteria used to assign a differentiating value, in relation to the biogeoclimatic classification was given by -24-Inselberg et al_. (1982) (Table 1). Species Importance and Ecological Spectra In all synecological studies, the question arises as to objective and reliable identification of the recognized taxa in order to permit their successful application for further ecosystem studies or practical application. In general, this question has been resolved by determining differentiating characteristics (usually a combination of environmental and floristic attributes of ecosystems) for the taxa or by taxonomic mapping or by a combination of both. The former approach, combined frequently with dichotomous keys, assumes that any random plot located in the classified area will fall into a described taxon or can be readily assigned to an intermediate position between two of the described taxa (McVean and Ratcliffe 1962). The latter approach fu l f i l l s directly the identification task, furthermore, it portrays a pattern of ecosystems in the landscape. Both approaches however, have weaknesses that may result in difficulties in identification. In general, the differentiation of ecosystem taxa predominantly on the basis of f loristic characteristics may be difficult and result in inconsistencies, where the flora is species-poor or where the vegetation pattern is found to reflect varying successional stages. Similar problems may be encountered in mapping; moreover, because of cartographic considerations, each map tends to generalize. This is the case at large map scales in particular. Of a special interest to forest management practitioners is the use of indicator plant species for the assessment of site quality. The plant -25-Table 1. Cr i ter ia for differentiating,values of plant species in character-i s t i c combination of species [after Inselberg et al.(1982)]. Symbol Name Description e exclusive A plant species whose distr ibut ion is exclusively or almost exclusively restricted to a particular taxon; presence class >_ IV, species significance is variable. s selective A plant species whose distr ibution indicates a strong association with a particular taxon, but may be in f re -quently associated with other taxa; presence class >_ IV, species significance is variable. p preferential A plant species whose distr ibut ion indicates a definite association with a particular taxon but may be associ-ated with several other taxa; presence class >_ IV, species significance is variable. d di f ferent ia l A plant species which has qual i f ied or may qualify as a character species at a higher level of generalization but at a lower level of generalization i t s distr ibution shows a definite association with a particular taxon. Presence class > IV, in other taxa under comparison, presence class is lower by two or more classes, species significance may be variable. The same species may be used as di f ferent ia l in more than one characteristic combination of species providing i t differentiates a particular taxon from other taxa under comparison. cd constant A plant species which has presence class V and mean dominant species significance >. 3.0; the species which is constant dominant in a l l or nearly a l l taxa under comparison should be selected and designated as con-stant dominant or otherwise at the higher level of generalization. c constant A plant species which has presence class V and mean species significance < 3.0; the species which is con-stant in a l l or nearly a l l taxa under comparison should be selected and designated as constant or otherwise at the higher level of generalization. i c important A plant species that does not meet the above c r i t e r i a companion but i t s distr ibut ion indicates an a f f in i t y to a pa r t i -cular taxon; presence class >^  I I I , species s i g n i f i -cance i s variable. unimportant A plant which does not meet the above c r i t e r i a ; the companion species should not be selected into a characteristic combination of species. Species with exclusive, selective and preferential values are referred to as character species, species with di f ferent ia l values as di f ferent ia l species, and the species with constant dominant, constant and important companion values are referred to as a companion species. -26-s p e c i e s a r e p r e c i s e i n d i c a t o r s o f t h e i n t e g r a t e d e f f e c t s o f e n v i r o n m e n t a l and b i o t i c f a c t o r s a f f e c t i n g the e c o s y s t e m s ( M a j o r 1 9 6 9 ) . V a r i o u s i n d i c a t i v e v a l u e s f o r p l a n t s o f t h e r e g i o n a l f l o r a have been p r o p o s e d f o r t h i s p u r p o s e , e . g . M e z e r a ( 1 9 5 2 ) , A i c h i n g e r ( 1 9 6 7 ) , P l i v a and P r u s a ( 1 9 6 9 ) , E l l e n b e r g ( 1 9 7 4 ) , Lando l t ( 1 9 7 7 ) , B a k u s i s ( 1 9 7 8 ) , and K r a j i n a e t a l . ( 1 9 8 3 ) . I n d i c a t o r p l a n t s p e c i e s have been employed to a s s e s s h y g r o t o p e and t r o p h o t o p e o f f o r e s t s i t e s i n t h e "Gu ide f o r T ree S p e c i e s S e l e c t i o n and P r e s c r i b e d B u r n i n g i n the Vancouve r F o r e s t D i s t r i c t " by K l i n k a ( 1 9 7 7 ) . The ma jo r weakness i n c o n s i s t e n t l y a s s e s s i n g f o r e s t s i t e s has been t h e l a c k o f an e a s i l y a p p l i e d method i n t e g r a t i n g d i f f e r e n t i n d i c a t i v e v a l u e s o f t he p i a n t s p e c i e s . To a d d r e s s t h e s e weaknesses a c o n c e p t o f s p e c i e s i m p o r t a n c e and e c o l o g i c a l s p e c t r a has been a p p l i e d and t e s t e d i n t h i s s t u d y i n an a t t e m p t t o p r o v i d e a more e x p l i c i t method to i d e n t i f y e c o s y s t e m t a x a and to a s s e s s s i t e q u a l i t y . In t h e sys tem o f b i o g e o c l i m a t i c e cosys t em c l a s s i f i c a t i o n , v e g e t a t i o n d a t a a r e r e c o r d e d and p r e s e n t e d i n a t a b u l a r f o r m . The t a b l e s p r e s e n t e d f o r t a x a u s u a l l y c o n t a i n p r e s e n c e ( c o n s t a n c y ) c l a s s and mean s p e c i e s s i g n i f i c a n c e f o r each s p e c i e s l i s t e d . S e v e r a l w o r k e r s p roposed s c a l e s t h a t comb ined b o t h p r e s e n c e o r p r e s e n c e c l a s s , abundance ( d e n s i t y ) and dominance ( c o v e r a g e ) ( t h e l a t t e r two c h a r a c t e r i s t i c s b e i n g combined i n t h e D o m i n - K r a j i n a s p e c i e s s i g n i f i c a n c e s c a l e i n a s i n g l e v a l u e ) , r e f e r r e d to as a s p e c i e s i m p o r t a n c e v a l u e ( P l i v a and P r u s a 1 9 6 9 ) , o r as an i m p o r t a n c e v a l u e i n d e x ( C u r t i s and M c i n t o s h 1 9 5 1 ) . In t h i s s t u d y t h e app roach u s i n g s p e c i e s i m p o r t a n c e was adap t ed t o f i t t he s p e c i e s s i g n i f i c a n c e s c a l e ( T a b l e 2 ) . The s p e c i e s i m p o r t a n c e v a l u e i s d e r i v e d f rom a m a t r i x f e a t u r i n g Table 2 a. Species Importance scale - combined values of species significance and presence (exponential/linear scales)(Jaeger and Klinka). Species significance Presence (class symbol and nominal value) Class Corresponding I II III IV V symbol cover value {%) 10 30 50 70 90 + 0.2 2 6 10 14 18 1 0.7 7 21 35 49 63 2 1.6 16 48 80 112 144 3 3.6 36 108 180 252 324 4 7.5 75 225 375 525 675 5 17.5 175 525 875 1775 1575 6 29.0 290 870 1450 2030 2610 7 41.0 415 1245 2075 2905 3735 8 62.5 625 1875 3125 4375 5625 9 87.5 875 2625 4375 6125 7875 I Table 2 b. Species Importance scale - combined values of species significance and presence 1 (exponential scales)(Jaeger and Klinka). Species significance Presence (class symbol and nominal value) Class Corresponding I II III IV V symbol cover value {%) 1 3 9 27 81 + 0.2 0.2 0.6 1.8 5.4 16.2 1 0.7 0.7 2.1 6.3 18.9 56.7 2 1.6 1.6 4.8 14.4 43.2 129.6 3 3.6 3.6 10.8 32.4 97.2 291.6 4 7.5 7.5 27.5 67.5 202.5 607.5 5 17.5 17.5 52.5 157.5 472.5 1417.5 6 29.0 29.0 87.0 261.0 783.0 2349.0 7 41.0 41.0 124.4 373.5 1120.5 3361.5 8 62.5 62.5 187.5 562.5 1687.5 5062.5 9 87.5 87.5 262.5 787.5 2362.5 7087.5 -28-products of multiplication between species significance (mid-points of corresponding cover values) and nominal values assigned to presence classes. The latter values were rated in two ways: 1. By using the mid-point values of presence classes yielding an exponential/linear scale (Table 2a). 2. By using values of the geometric expansion scale yielding exponential scales (Table 2b). The preliminary testing indicated only minor differences when evaluating ecological spectra obtained from the scales. Because the cover values increase exponentially and the exponential scale accentuates the presence of species more than the linear scale, the geometric expansion scale (Table 2b) was consistently applied. When the presence class and species significance values of the species present in a series of plots or in a single study plot are transformed to species importance values, i t then becomes possible to: 1. Characterize each taxon by the distribution of ecological species groups, each group indicating a certain set or sets of environmental factors, 2. to assess affinity of a plot or plots to the recognized taxa in the classification system, and 3. to assess quality of a site in relation to a number of environmental factors. This is done by computing the relative species importance values (the proportions of the species importance value of a species or a group of species to that of the plot, series of plots or taxon as a whole). The computed percentages may be expressed graphically in a variety of -29-histograms referred to as ecological spectra. The ecological spectra were used in this study to identify and compare the ecosystems studied. Methods of Stand Analysis Ten plots, each 25 x 25 m in size were established in each stand. In the Chilliwack area the slope distance of the uphill plot boundaries was calculated to equal the horizontal distance of 25 m. On each plot all live and dead trees with a diameter at height 1.3 m (dbh) greater than 7.5 cm were numbered. For each live tree the following parameters were measured: dbh, height of the lowest dead branch, and location using a coordinate system, whereby the plot boundaries were the x- and y- axes. Crown class (dominant, codominant, intermediate and suppressed) was estimated for each tree present on a plot. Dbh and location of dead trees were recorded providing they were higher than 1.3 m and their bark was intact. Heights of the seven largest diameter trees per plot to derive a top stand height and seven to ten more heights were also measured for height over diameter regressions. In addition, for all these trees the height of the live crown base was measured. In one of the plots in each stand the branch extensions of each tree into four cardinal directions was determined. On a 10 x 100 m strip in each stand, dbh, height, base of live crown and location of each live and dead tree were measured. On five plots in each stand increment cores were taken for the ten largest diameter trees. The increment cores were analysed on a tree-ring measuring instrument, which recorded the width of the early wood and latewood for each ring. -30-Methods of Stand Synthesis Age, Top Height and Site Index The stand age was derived as the arithmetic mean of ages of the ten largest diameter trees from five plots in each stand. Six years were added to the mean based on increment borings at a height of 1.3 m applying the Ministry of Forests (1981) age-correction tables. The top height was defined as the arithmetic mean of the heights of the 100 largest diameter trees/ha, corresponding to the seven largest diameter trees per plot. Using the stand age and height two different site indices were derived according to King's (1966) and B.C. Ministry of Forests (Hegyi et aK 1979) tables; King's tables use age at breast height and an index age of 50 years; the B.C. Ministry of Forests tables use the mean height, total age and an index age of 100 years. Mean height is defined as the arithmetic mean of the heights of 10 dominant and codominant trees (in a ratio 3:7). In this study the site index derived from King's tables was used as a measure of forest productivity for the following reasons: 1. Many plots did not feature dominant trees. 2. To preclude subjectivity in selecting dominant and codominant trees. 3. In research studies the top height is thought to be least influenced by the initial stand density, thus providing the best expression of site (ecosystem) productivity (Assman 1961, Braathe 1957). 4. King's site index uses the age at breast height of the site trees; this prevents errors which may result from the use of age-correction tables. -31-Height/Diameter Regression Curves For Douglas-fir in each stand a separate height/diameter regression curve was fitted to predict height values for the diameters measured. Firstly, the measured heights were plotted over the respective diameters. The scattergram suggested that three different curvilinear equations would yield a close f i t . To decide which one would give the closest f i t , the components of these three equations were combined into one equation. Through a procedure of stepwise elimination, using the MIDAS command REGRESSION this equation was reduced, until all remaining independent variables were significant at the 0.05 level. The final equation was tested logically by plotting it into the scattergram and statistically by plotting the residual values over the predicted values (Table 3). For western hemlock and western redcedar one height/diameter regression equation for each stand was derived applying the same procedure (Table 3). Basal Area and Volume The basal area for each plot was calculated as a sum of basal areas of all tree species present. The volume (total volume of entire stem, inside bark, including stump and top, without allowance for defect, trim or breakage) for each plot was computed as a sum of volumes of all trees present using the derived height/diameter regression equations and the volume equations of the B.C. Ministry of Forests (1976). The volume for red alder was derived applying the height/diameter regression equation for Douglas-fir and the volume equation for red alder of the B.C. Ministry of Forests. -32-Table 3. Relationships between height and diameter for Douglas-fir, western hemlock and western redcedar in the two stands studied. T r e e — — — Equation species Regression equation statistics SE The Ladysmith stand: Df h = - 30.229 - 0.0989 dbh + 43.108 log dbh .93 2.0 Hw and C h = 5.7135 + 0,0155 dbh3 .80 0.82 The Chilliwack stand: Df h = - 0.9778 + 1.2033 dbh - 0.0089 dbh2 .92 2.49 Hw and C h = 1.2641 + .6834 dbh .86 1.54 explanation of symbols: F = Douglas-fir, Hw = western hemlock, C = western redcedar h = height, dbh = diameter at breast height R2 = coefficient of determination, SE = standard error. Crown Maps and Stand Profiles A crown map is a horizontal projection of the crown extension to show crown size, crown size in relation to crown class, distribution of crown classes, clustering patterns, overshaded areas and deviations of crown shape. A stand profile is a vertical projection (cross-section) of a stand complementing the crown map. It shows the layering, crown extension and length of live crown and reveals clustering patterns. A crown map was plotted for the plot no. 1 and plot no. 17 using branch extension measurements and location of each tree in a selected plot. Two stand profiles were plotted using location, height and base of live -33-crown of trees in a 10 x 100 m strip. Statistical Methods and Computing Techniques Additional stand properties (stems per hectare, mean diameter, diameter of the stem of mean basal area stem) and descriptive statistics were computed for each plot and stand. All plot data were converted into per hectare values by multiplication with the factor 16 (625 m2 x 16 = 1 ha). All per hectare figures given refer to the horizontal projection. Statistical methods used in the study included basic statistics, t-tests, analysis of variance and simple and multiple regressions. These methods were used to compare descriptive growth characteristics of the stands and to determine the extent of differences in individual growth parameters. A principal component analysis was applied to the vegetational data set to identify clustering of the plots and to separate the two ecosystems. The statistical analysis was carried out at the University of B.C. Computing Centre, which is equipped with an AMDAHL 470V18 computer and a Houston plotter. The statistical package Midas (Fox et al_. 1970) was used to compute descriptive statistics, t-tests and regressions. Ordiflex (Gauch 1977), an ordination program was used for the principle component analysis. Environment-vegetation tables were printed using the program described by Klinka and Phelps (1979). Crown mapping and all other calculations and plottings were performed with Fortran programs written by John Emmanuel and Barry Wong, Faculty of Forestry, University of B.C. -34-RESULTS AND DISCUSSION Characterization of the Ecosystems The locations of two ecosystems suitable for conducting the study were selected after two months of survey work in the Vancouver Forest Region. Environmental and stand characteristics of the selected ecosystems approached very closely the specified requirements but the reqirement of the same age was not satisfied. The six year difference in age notwithstanding, i t is believed that the ecosystems finally chosen were satisfactory to meet the objective of this study. The ecosystems studied have developed under the influence of different climates, soil parent materials and physiography (relief). As a result they exhibit differences in their floristic composition and structure despite similarities in age, composition, density and some aspects of the history of the forest cover. Basic information about the location, climate, soil parent materials, physiography and history was given earlier. Standardized vegetation-environment tables are included in the text, while some detailed information on vegetation and soils of the ecosystems is given in Appendices. Description The Ladysmith Ecosystem (Table 4; Figure 4 and 5; Appendix II; Appendix III, Table 1; Appendix IV). This ecosystem was found on a flat fluvial terrace and the adjacent, Table 4. Selected environmental and vegetation data for the study plots. Study area Number of sample plots Biogeoclimatic subzone Elevation (m) , Slope gradient (%) , Aspect (degrees azimuth) Particle size (CSSC 1978) Volume of coarse fragments (%) Soil subgroup (CSSC 1978) Parent materials (landform) Lithology Soil moisture regime Soil nutrient regime Thickness of the LFH layer (cm) Humus form pH (CaCl?) of the LFH layer Total C (%) of the LFH layer C/N ratio of the LFH layer pH (CaCl?) of the B horizon! Total C \%) of the B horizon C/N ratio of the B horizonl Base saturation (%) of the B horizon' Site index of Douglas-fir (m/100 yrs )^  Strata coverage A layer! (%) B layer, C layer| 0 layer Ground coverage Humusl . (%) Mineral soil , Decaying wood , Rocks & stones Total number of plant species Ladysmi th 10 CDFb 190 1 flat(- 198) Sandy 30 Orthic Dystric Brunisol Alluvial terrace Mixed (mainly basaltic) Mesic (-subhygric) Mesotrophic Orthileptomoder 3.6 38.5 44.3 5.0 0.95 22.5 7.2 43 83 75 19 59 83 16 1 41 Chilliwack 10 (CWHa-) CWHb 680 67 250 Fine loamy-skeletal 75 Orthic Humo-Ferric Podzol Colluvial veneer Shale Submesic Eutrophic Mineroleptomoder 5.0 33.7 33.0 5.1 2.69 20.7 17.9 42 81 47 39 74 89 11 65 The values are means or weighted means. Figure 4. The understory vegetation of the forest community in the Ladysmith ecosystem (plot no. 3). Figure 5. The representative pedon sampled in the Ladysmith ecosystem (plot no. 3). -37-very gently sloping flanks of a moraine blanket ( t i l l ) at an elevation of 190 m above sea l e v e l . The tree layer had an average cover of 83 percent with minor canopy openings. Douglas-fir was the only tree species present i n the tree layers - a feature indic a t i n g moderate shade-tolerance of the species and hence, a moderate v e r t i c a l d i f f e r e n t i a t i o n of the stand canopy. Red alder and western hemlock occurred sporadically in the A3 layer. A few i n d i v i d u a l s of western redcedar, western hemlock and Douglas-fir were found scattered in the upper shrub layer. Vigor of western hemlock was poor - many i n d i v i d u a l s had dead tops. In contrast, vigor of western redcedar in the upper and lower shrub layer was good. Charcoaled stumps of western redcedar and Douglas-fir were conspicuous on the Ladysmith ecosystem. The lower shrub layer was very well developed with an average cover of 65 percent. It was dominated by Gaultheria shallon. Mahonia  nervosa and Vaccinium parvifolium were the associated constant species. Average cover of the herb layer was only 19 percent and the most prominent species were Achlys t r i p h y l l a , Polystichum munitum, Pteridium aquilinum and Linnaea b o r e a l i s . The moss layer on humus substrate had a coverage of 59 percent, forming a discontinuous carpet on the forest f l o o r . Hylocomium  splendens was dominant; the associated species were Kindbergia* oregana, Rhytidiadelphus loreus and Rhytidiadelphus t r i q u e t r u s . A total of 41 plant species were i d e n t i f i e d , suggesting a moderate f l o r i s t i c d i v e r s i t y which i s c h a r a c t e r i s t i c for amphimesic forest communities. Reconnaissance of the s o i l component indicated that with the exception of the uppermost layer the s o i l s are morphologically uniform. The *A new name f o r the genus S t o k e s i e l l a (Kind.) Robins., horn, i11 eg. (Ochyra 1981). -38-thickness of the LFH layer varied (the mean was 5 cm) as well as the presence of decaying wood both on the forest floor and within the organic surface layer. Based on morphological features, the humus form was identified as an Orthileptomoder; however, the high acidity and carbon/nitrogen ratio measured are more characteristic for Mors than for Moders. The incipient and discontinuous A horizon, either as an Ah, or Ae or both was present in the solum. The uppermost part of the master B horizon was identified as the podzolic Bf subhorizon; the remaining layer was formed by a series of brum*sol ic Bm subhorizons. The master B horizon contained less than 10 percent coarse fragments. The C horizon consisted of granular, coarse fragments and coarse sand and contained no roots. The pedon examined was identified as a sandy Orthic Dystric Brunisol, developed from fluvial (alluvial over glaciofluvial) materials. These materials contained both basaltic and granitic coarse fragments with the former prevailing over the latter. Considering both external and internal attributes, the hygrotope and trophotope were assessed as mesic and mesotrophic, respectively. The Chilliwack Ecosystem (Table 4; Figure 6 and 7; Appendix II; Appendix III, Table 2; Appendix IV). This ecosystem was found on a steep, west facing slope at the elevation of 680 m above sea level. The tree layer in all plots sampled had an average cover of 81 percent. Douglas-fir dominated the canopy and in most plots, western hemlock and occasionally red alder were found in the lower tree layers. The coverage of the A2 layer was much greater than Figure 6. The understory vegetation of the forest community in the Chilliwack ecosystem (plot no. 17). that of the Aj^  and A3 layers. The lack of Douglas-fir in the A 3 and lower layers was attributed to its shade-intolerance in this ecosystem. In the moderately developed shrub layers the average cover was 47 percent. Mahonia nervosa, Tsuga heterophylla and Acer circinatum were constant dominant species; other frequently occurring species were Vaccinium  parvifolium, Rosa gymnocarpa and Holodiscus discolor. Western hemlock was the only tree species found to regenerate on decaying wood under the stand canopy. Charcoaled stumps and cut timber debris of western redcedar and Douglas-fir were common in the Chilliwack ecosystem. Many ericaceous species and western hemlock have established on, or in the proximity of these materials. The diverse composition and well developed herb layer were the characteristic floristic features of the plots. A total of 65 -40-plant species were recognized in the sample plots with 54 percent being in the herb layer. The constant dominant species were Polystichum munitum, Achlys triphylla, Pteridium aquilinum and Smilacina stellata. The coverage of the moss layer on humus was high (the average value was 74 percent) but discontinuous. Hylocomium splendens, Kindbergia oregana and Rhytidiadelphus triquetrus were the constant dominant species. The associated soils were described using a pedon in the plot no. 17 (Figure 7). The forest floor varied in total thickness and thickness of Figure 7. The representative pedon sampled in the Chilliwack ecosystem (plot no. 17). -41-individual organic horizons however, Mi neroleptomoder was the p r e v a i l i n g humus form. The loose to f r i a b l e H horizon featured a large amount of dropping residues and incorporated inorganic materials. The colour of the master podzolic B horizon, e s p e c i a l l y of the uppermost subhorizon, was reddish brown due to a high content of organic matter. A l l recognized sub-horizons were i d e n t i f i e d as podzolic. The pedon examined was i d e n t i f i e d as f i n e loamy-skeletal (with 75 percent coarse fragments) Orthic Humo-Ferric Podzol developed from c o l l u v i a l veneer derived from and over shale bedrock. Based on both external and internal properties, the hygrotope and trophotope were assessed as submesic and eutrophic, r e s p e c t i v e l y . C l a s s i f i c a t i o n Following synthesis of environmental and vegetation data, the sample plots were c l a s s i f i e d as successional stages ( v a r i a t i o n s ) at the category of association and then i d e n t i f i e d , using the recognized taxa at the biogeoclimatic, biogeocoenotic, phytocoenotic and functional integration l e v e l s . A synopsis of the taxa i s given in Table 5. The study plots f e l l into two successional a s s o c i a t i o n s : the Hylocomium - Gaultheria - PM in the Ladysmith area and the Hylocomium -Mahonia - (TH) - PM in the Chilliwack area. Both tabular and numerical analyses were c a r r i e d out to determine s i m i l a r i t i e s , d i f f e r e n c e s , and r e l a t i o n s h i p s between these associations. The two types of analysis gave very s i m i l a r r e s u l t s . From Table 6 i t appears that the associations have a large number of both common and d i f f e r e n t i a l species. The former species suggest ecological relationships to be addressed at higher l e v e l s of Table 5. Synopsis of ecosystem taxa using four integration levels of the biogeoclimatic c lass i f i cat ion system. . Study area Ladysmi th Chilliwack Biogeocoenotic l eve l : Successional association Climax association Hylocomio (splendentis) - Gaultherio (shallonis) - PM Mahonio (nervosae) - Gaultherio (shallonis) - TP & PM Hylocomio (splendentis) - Mahonio (nervosae) - (TH) - PM Mahonio (nervosae) - Polysticho (muniti) - TH & TP Functional leve l : Hygrotope/trophotope Biogeoclimatic leve l : Biogeoclimatic subzone Mesic (-subhygric)/mesotrophic Wetter Maritime Coastal Douglas-fir Subzone (CDFb) Submesic/eutrophic Wetter Maritime Coastal Western Hemlock Subzone [CWHb, the lowest l im i t of the montane (CWHb^ ) variant] i -P» ro i Phytocoenotic l eve l : Plant all iance Mahonio (nervosae) - Thujo (plicatae) & Pseudotsugion menziesii Polysticho (muniti) - Thujion plicatae Plant order Gaultherio (shallonis) - Pseudotsugatalia menziesii Polysticho (muniti) - Thujetalia plicatae The tree species component in the nomenclature for associations is expressed by two capital le t ters . The following abbreviations are used: PM - Pseudotsuga menziesii, TH - rsuga heterophylla, TP - rhuja plicata. The complete names are derived by modifying species names according to standard phytosociological practice. In the text, for convenience, the anglicized names of biogeocoenotic and phytocoenotic taxa are used: tree species are abbreviated by two capital letters as described above and other species are referred to by their generic names. 43 Table 6. Common and d study plots ' i f fe rent ia l combinations of species for the Study area Ladysmith Chilliwack Biogeoclimatic subzone CDFb CWHb Edatope 4/C 3/E Number of plots Plant species 10 10 Presence class and mean species significance 1. The combination of species common to both study areas: Achlys triphylla IV 4.8 V 4.9 Adenocaulon bicolor IV 2.0 I I I 1.3 Galium triflorum IV 1.8 V 2.2 Hylocomium splendens V 8.1 V 8.2 Mahonia nervosa V 5.1 V 6.6 Polystichum munitum V 3.0 V 5.7 Pseudotsuga menziesii V 8.5 V 8.5 Pteridium aquilinum V 4.3 V 3.2 Rhytidiadelphus loreus V 2.2 IV 1.4 Rhytidiadelphus triguetrus IV 1.6 V 3.6 Rosa gymnocarpa I I I 1.9 V 2.5 Rubus ursinus V 2.8 V 2.0 Kindbergia oregana v 4.6 V 5.0 Tsuga heterophylla V 2.7 V 5.3 Vaccinium parvifolium V 4.4 IV 3.2 2. The dif ferent ia l combination of species for the Ladysmith study plots [the Hylocomio (splendentis) - Gaultherio (shallonis) - PM Successional Association]: Festuca subuliflora III 1.3 I + .0 Gaultheria shallon V 7.9 Linnaea borealis V 3.2 III + .9 Listera cordata III + .8 Thuja plicata IV 2.3 Tiarella trifoliata III 1.4 3. The di f ferent ia l combination of species for the Chilliwack study plots [the Hylocomio (splendentis) - Mahonio (nervosae) - (TH) - PM Successional Association]: Acer circinatum V 3.5 Actaea rubra _ IV 1.3 Aruncus dioicus - IV 2.1 Chimaphila menziesii II + .0 IV 1.3 Disporum hookeri - V 2.2 Goodyera oblongifolia II + .0 IV 1.2 Holodiscus discolor - IV 3.0 Mycelis muralis I l l + .4 V 2.3 Rhytidiopsis robusta - V 2.4 Ribes lacustre - III 1.2 Smilacina racemosa - IV 1.2 Smilacina stellata - V 3.2 Symphoricarpos albus - IV 1.4 Trientalis l a t i f o l i a - V 2.2 Trillium ovatum II +.6 V 1.6 Viola orbiculata III 2.0 Viola sempervlEens II +.2 IV 2.6 These combinations include only the species that have presence class >^  I I I , and whose presence class is greater by 2 or more than that for the same species in the other unit under comparison. -44-general ization while the latter species provide for a distinct differentiation of one association from another. Transforming presence class and mean species significance of the species listed to species importance values, the sums of the importance values for each combination and associations are expressed on a relative basis in Figure 8. The plot of ecological spectra indicates a considerable similarity and a minor difference in the floristic composition between the two associations. There were differential species present in both ecosystems which belonged to the opposite association, but their species significance values were so low, that the corresponding relative importance values were below 0.00 percent. The Hylocomium - Gaul ther ia -PM Successional Association C (76%) LS (24%) The Hylocomium - Mahonia - (TH) - PM Successional Association C (92%) CH (8%) Explanation of symbols: C - the combination of species common to both study areas LS - the differential combination of species for the Ladysmith study plots CH - the differential combination of species for the Chilliwack study plots Figure 8. Ecological spectra indicating floristic affinity between successional associations. The result of a principle component analysis is presented in Figure 9. The ordination of the plots showed two groups the centroids of which were significantly different along the second axis which expressed approximately -45-Key to sample plot symbols © Hylocomium - Gaultheria - PM Successional Association Hylocomium - Mahonia - (TH) -PM Successional Association sample plot number F i g u r e 9. O r d i n a t i o n o f t he s t u d y p l o t s u s i n g p r i n c i p l e component a n a l y s i s . The c e n t r o i d s and s t a n d a r d d e v i a t i o n s f o r the a s s o c i a t i o n s a r e i n d i c a t e d . -46-10 percent of the variation in the data. The two groups and affinities recognized by this analysis are parallel to those derived by tabular analysis. To proceed with identification of ecosystem taxa beyond the category of successional association i t is logical to follow with the assessment of hygrotopes and trophotopes (i.e. edatopes) of the ecosystems. Tentative assessment of edatopes was done earlier on the basis of soil properties (Table 4). In the following discussion assessment of edatopes will be done on the basis of indicator plant analysis. The occurrence of a plant species signals that i t has competed successfully in a certain environment. The integrated effect of environmental and biotic factors in an ecosystem must be then within the tolerance limits of the species. Many plant ecologists have been using plant species as indicators of various properties of ecosystems. Recently, Krajina et aK (1983) compiled a matrix of vascular plants and some bryophytes, liverworts and lichens of British Columbia showing their affinities to selected ecosystem attributes. In relation to edatope, each species included was characterized by the range of hygrotope and trophotope using nominal relative scales of the edatopic grid. Grouping of species with the same or similar values of hygrotope or trophotope or both in a plot or set of plots makes i t possible to characterize these plots or ecosystem taxa by a pattern of these groups, referred to as ecological or indicator species groups. The patterns of indicator species groups should assist (within certain geographic limits) to assess the edatope and taxonomic affinity of ecosystems. The indicator plant analyses for the study plots in relation to -47-h y g r o t o p e and t r o p h o t o p e a r e p r e s e n t e d i n T a b l e s 7 and 8 , r e s p e c t i v e l y . The t a b l e s i n c l u d e o n l y s p e c i e s t h a t have the p r e s e n c e c l a s s y I I I f o r one o f t h e a s s o c i a t i o n s . Many s p e c i e s i n n e a r l y a l l i n d i c a t o r s p e c i e s g r o u p s were found to be common to b o t h a s s o c i a t i o n s . The absence o f some s p e c i e s i n t h e L a d y s m i t h e c o s y s t e m can be p a r t l y e x p l a i n e d e i t h e r by t h e i r i n t o l e r a n c e o f a d r i e r (Csb) mesothermal c l i m a t e ( e . g . R h y t i d i o p s i s  r o b u s t a ) o r t h e i r g e o g r a p h i c r ange ( e . g . A c e r c i r c i n a t u m ) , b u t most o f t h e s p e c i e s a r e a b s e n t be cause o f t h e e d a t o p i c q u a l i t y o f t h e s i t e . The c o n t e n t o f t h e t a b l e s i s complemented by e c o l o g i c a l s p e c t r a p r e s e n t i n g r e l a t i v e i m p o r t a n c e v a l u e s o f t h e i n d i c a t o r s p e c i e s g r o u p s ( F i g u r e 10 and 1 1 ) . E v i d e n t l y , each a s s o c i a t i o n d i s p l a y s a d i s t i n c t l y d i f f e r e n t p a t t e r n o f t h e s e g roups s u g g e s t i n g a c o r r e s p o n d i n g d i f f e r e n c e i n t h e i r e d a t o p e s . The absence o f c a l i b r a t e d s p e c t r a p r e c l u d e s however , i d e n t i f i c a t i o n o f e d a t o p e s on a r e l a t i v e b a s i s , i . e . r e l a t i v e t o a b i o g e o c l i m a t i c s u b z o n e . T h e r e f o r e , t h e e x a m i n a t i o n o f e c o l o g i c a l s p e c t r a w i l l be done on an a b s o l u t e b a s i s wh i ch i s t h o u g h t to be more m e a n i n g f u l f o r the pu rpose o f t h i s s t u d y . The ma in d i f f e r e n c e between the L a d y s m i t h and C h i l l i w a c k e cosy s t em i n r e l a t i o n t o h y g r o t o p e was f o u n d t o be between t h e p a t t e r n o f x e r o - t o mesophy t e s and h y g r o p h y t e s . The i m p o r t a n c e o f t h e f o r m e r g roup d e c r e a s e d f r o m 47 t o 28 p e r c e n t , and t h a t o f t h e l a t t e r g roup i n c r e a s e d f rom 5 t o 27 p e r c e n t . T h i s change i n p a t t e r n s u g g e s t s t h a t i n a b s o l u t e t e r m s , t h e C h i l l i w a c k e c o s y s t e m has a s u b s t a n t i a l l y h i g h e r s u p p l y o f a v a i l a b l e wa te r t h a n t h e L a d y s m i t h e c o s y s t e m . The p r e s e n c e o f t h r e e i n d i c a t o r s p e c i e s g r o u p s c o m p r i s i n g m e s o p h y t e s , wh i ch a c c o u n t f o r 95 p e r c e n t o f t he s p e c t r u m , s u g g e s t s an i n t e r m e d i a t e o r m e s i c h y g r o t o p e o f t h e L a d y s m i t h e c o s y s t e m . -48-Table 7. Combinations of plant indicator species from the study plots in relat ion to hygrotope. Group of indicator species Xero- to mesophytes Mesophytes Meso- to hygrophytes Hygrophytes Study area LS Species 1. Xero- to mesophytes: Chimaphila menziesii Gaultheria shallon Holodiscus discolor Mahonia nervosa Rhytidiopsis robusta Rosa gymnocarpa Kindbcrgia oregana 2. Mesophytes: Goodyera oblongifolia Linnaea borealis Listera cordata Pteridium aquilinum Rhytidiadelphus triquetrus Rubus ursinus Trientalis l a t i f o l i a Vaccinium parvifolium Viola orbiculata Viola sempervirens 3. Meso- to hygrophytes: Adenocaulon bicolor Hylocomium splendens Rhytidiadelphus loreus Ribes lacustre Smilacina racemosa Smilacina stellata Symphoricaxpos albus 4. Hygrophytes: Acer circinatum Achlys triphylla Actaea rubra Aruncus dioicus Disporum hookeri Festuca subuliflora Galium triflorum Mycelis muralis Polystichum munitum Tiarella trifoliata Trillium ova turn I I v V 5.1 I I I 1.9 V 4.6 CH LS CH LS CH LS IV 1.3 3.0 6.6 2.4 2.5 5.0 II +.0 IV 1.2 V 3.2 I I I +.9 I I I +.8 V 4.3 V 3.2 IV 1.6 V 3.6 V 2.8 V 2.0 - V 2.2 V 4.4 IV 3.2 - I I I 2.0 I I +.2 IV 2.6 IV 2.0 V 8.1 V 2.2 I I I 1.3 V 8.2 IV 1.4 I I I 1.2 IV 1.2 V 3.2 IV 1.4 CH Presence class and mean species s ignif icance V 3.5 IV 4.8 V 4.9 IV 1.3 IV 2.1 V 2.2 I I I 1.3 I +.0 IV 1.8 V 2.2 I I I +.4 V 2.3 V 3.0 V 5.7 I I I 1.4 -I I +.6 V 1.6 symbol LS refers to the Ladysmith study p lo ts , the symbol CH refers to the Chilliwack study pi -49-Table 8. Combinations of plant Indicator speciesfrom the study plots in relation to trophotope. Group of indicator species Study area Species Oxylophytes LS Mesotrophytes Eutrophytes CH LS CH LS CH Presence class and mean species significance 1. Oxylophytes: Gaultheria shallon V 7. 9 Coodyera oblongifolia II + , 0 IV 1. .2 Hylocomium splendens V 8. 1 V 8, .2 Listera cordata III +. 8 Rhytidiadelphus loreus V 2. 2 IV 1. .4 Rhytidiopsis robusta V 2. ,4 Rosa gymnocarpa III 1. 9 V 2. .5 Vaccinium parvifolium V 4. 4 IV 3. .2 Viola orbiculata III 2. .0 2. Mesotrophytes: Chimaphila menziesii II + .0 IV 1.3 Holodiscus discolor IV 3.0 Linnaea borealis V 3.2 III +.9 Mahonia nervosa V 5.1 V 6.6 Pteridium aquilinum V 4.3 V 3.2 Rubus ursinus V 2.8 V 2.0 Kindbergia oregana V 4.6 V 5.0 Trientalis l a t i f o l i a V 2.2 viola sempervirens II + .2 IV 2.6 3. Eutrophytes: Acer circinatum Achlys triphulla Actae,-> rubra? Adenocaulon bicolor? Aruncus dioicus^ Disporum hookeri Festuca subuliflora Galium triflorum^ Mycelis muralis^ Polystichum munitum^ Rhytidiadelphus triquetrus Ribes lacustre? Smilacina racemosa^ Smilacina stellata^ Symphoricarpos albus Tiarella trifoliate? Trillium ovatum^ V 3.5 IV 4. .8 V 4.9 IV 1.3 IV 2. .0 III 1.3 IV 2.1 V 2.2 III 1. .3 I + .0 IV 1. .8 V 2.2 III +, .4 V 2.3 V 3. .0 V 5.7 IV 1. .6 V 3.6 III 1.2 IV 1.2 V 1.3 IV 1.4 III 1. .4 II +, .0 IV 0.6 The symbol LS refers to the Ladysmith study plots, the symbol CH refers to the Chilliwack study plots. The suffix 2 denotes a nitrophyte. The suffix 3 denotes a species with nitrophytic inclinations. -50-Th e Ladysmith study plots: 1 X-M M M-H 1 (47%) (14%) (34%) The Chilliwack study plots: X. (1%) H (5%) II X-M M M-H H I II (28%) (8%) (36%) (27%) I Explanation of symbols: X - xerophytes X-M - xero- to mesophytes M - mesophytes M-H - meso- to hygrophytes H - hygrophytes Figure 10. Ecological spectra indicating floristic affinity of the study plots to hygrotope. The Ladysmith study plots: o M E (70%) (25%) (5%) The Chilliwack study plots: o M E (36%) (32%) (32%) Explanation of symbols: 0 - oxylophytes; the species found on strongly acid, base-poor soils with Mors. M - mesophytes; the species found on moderately acid and base saturated soil with Mors or Moders. E - eutrophytes; the species found on weakly acid to circumneutral, base-rich, melanized soils providing a balanced supply of nutrients with Moders to Mulls; this group includes also nitrophytes and nitrophytic species found on soils with a high availability of nitrogen. Figure 11. Ecological spectra indicating floristic affinity of the study plots to trophotope. -51-The considerable importance of xero- to mesophytes in the Chilliwack ecosystem suggests that the presence of hygrophytes could be partly due to a high nutrient supply. In relation to other ecosystems in the CWHb Subzone, the presence of three groups comprising mesophytes with the importance value of 73 percent suggests an amphimesic (submesic to mesic) hygrotope. The difference between the associations in relation to trophotope was found to be even more pronounced than that for the hygrotope. The importance of oxylophytes decreased from 70 to 36 percent and that of eutrophytes increased from 5 to 32 percent, when comparing the Ladysmith and Chilliwack ecosystem. Along with the increase of eutrophytes, there was a corresponding increase in the importance of nitrophytes and nitrophytic species. The relative percentage of these species increased from 12 percent in the Ladysmith to 88 percent in the Chilliwack ecosystem. This suggests that the Chilliwack ecosystem has a substantially higher supply of available nutrients than the Ladysmith ecosystem. The relatively high importance of oxylophytes for an eutrophic trophotope is somewhat surprising. It should be noted that Hylocomium splendens accounts for the major part of the oxylophyte group in the Chilliwack ecosystem. This may be due to the presence of acidic microsites (e.g. decaying wood accumulation) on the forest floor. The plant indicator analysis suggests that the Chilliwack ecosystem is considerably wetter and more nutrient rich than the Ladysmith ecosystem. Due to the lack of calibrated spectra for edatopes in different biogeoclimatic subzones, the analysis could not verify hygrotope and trophotope on the relative scales, but gave some support to their -52-identification inferred from the soil properties. Based on published biogeocl imatic maps (KI inka et al_. 1979, Courtin et al_. 1983), the study plots fell into two biogeocl imatic subzones: those in the Ladysmith area belonged to the CDFb Subzone, and those in the Chilliwack area belonged to the lowest limits of the CWHb Subzone, mohtane variant (CWHby). The identification was verified by a reconnaissance in the climax zonal ecosystems found in adjacent areas, using the differentiating characteristics for the' subzones described by several workers. To complement the above identification, f lorist ic affinities to CDF and CWH zones were evaluated using the ecological spectra, despite the fact that the study plots featured non-climax vegetation and the Chilliwack plots were azonal. Plant species, which are members of the characteristic combinations of species for the two zones, and their differentiating values were compiled in Table 9. The species listed included only those ones which were present in the study plots. Transforming presence class and mean species significance to species importance values, the sums of the importance values for each combination (with and without Douglas-fir) and study area were plotted in Figure 12. The spectra for the Ladysmith ecosystem display a strong affinity to the CDF Zone. This could be substantiated by the zonal character of the Ladysmith ecosystem, and a significant proportion of Douglas-fir in the tree species composition of climax stands on mesic and mesotrophic sites. The Chilliwack ecosystem displays a similar pattern. However, the increased importance of species characteristic for the CWH Zone is of significance. In this case one must consider f i rst ly, a great difference in vegetation between climax and -53-Table 9. The plant species from the study plots found in characteristic combinations for the CDF and CWH zones!. Study area Ladysmi th Chilliwack CDF Zone: Acer macrophyllum (P) Cornus nuttallii (p) Gaultheria shallon (p, Cd) Holodiscus discolor (p) Mahonia nervosa (p, cd) Pseudotsuga menziesii (p, cd) Rhytidiadelphus triquetrus (ic) Rosa gymnocarpa (p) Rubus ursinus (p, C) Kindbergia oregana (p, cd) Trachybryum megaptilum (p) Vaccinium parvifolium (cd) CWH Zone: Abies amabilis (d) Clintonia uniflora (d) Dryopteris expansa (ic) Menziesia ferruginea (ic) Oplopanax horridus (ic) Plagiothecium undulatum (p) Rhytidiadelphus loreus (p, cd) Rhytidiopsis robusta (d) Tsuga heterophylla (p, cd) . I + .0 I + .0 I + .0 V 7.9 IV 3.0 V 5.1 V 6.6 V 8.5 V 8.5 IV 1.6 V 3.6 III 1.9 V 2.5 V 2.8 V 2.0 V 4.6 V 5.0 I + .0 V 4.4 IV 3.2 I + .0 I + .0 I + .0 I + .0 II + .9 I + .0 I +.1 I + .0 V 2.2 IV 1.4 V 2.4 V 2.7 V 5.3 1 The source is Krajina (1959), Kojima and Krajina (1975), Klinka 'et al_ (1979), Courtinetal_. (1983) and Klinka and:Krajina (1983). -54-Figure 12a. Ecological spectra indicating floristic affinity of the study plots to the mesothermal biogeoclimatic zones. The Ladysmith study plots: CDF (97.3%) The Chilliwack study plots: CDF CWH (85.5%) (14.5%) | CWH (2.7%) Figure 12b. Ecological spectra indicating floristic affinity of the study plots to the mesothermal biogeoclimatic zones when Douglas-fir is excluded. The Ladysmith study plots: CDF (96%) The Chilliwack study plots: CDF CWH (73%) (27%) CWH (4%) Explanation of symbols: CDF - refers to the species listed in the characteristic combination of species for the CDF Zone. CWH - refers to the species listed in the characteristic combination of species for the CWH Zone. -55-non-climax forest communities in the CWHb Subzone and secondly the non-zonal character of the ecosystem. As a result, i t was not surprising that the serai vegetation present in the Chilliwack ecosystem did not reveal a strong affinity to the CWH Zone. The change of tree species composition to western hemlock , western redcedar and amabilis f i r (Orloci 1964, Krajina 1969, Klinka 1976) in the near-climax successional stage will result in profound changes in the composition of understory vegetation which then should express stronger affinity to CWH than to the CDF Zone. The identification of edatopes and biogeoclimatic subzones allows the relation of successional associations to the phytocoenotic taxa and climax associations. The successional associations are likely members of one of the three plant orders: Gaultheria - PM1, Rhytidiadelphus - TH2 or Polystichum - TP3 (Table 10). Using the available information, charac-teristic combinations of species for these orders were compiled and those species found in the study plots and listed in the combinations are presen-ted in Table 10. Thus, the presented combinations are incomplete, i.e. they do not include all the species listed. Also, i t should be noted that the presence and/or mean species significance of some species do not meet the specified differentiating values shown in parenthesis. Complementary ecological spectra in Figure 13 show the pattern of three combinations of ^ . n . ; Krajina (1969), Kojima (1971, 1975), Klinka and Krajina in Klinka (1976), Klinka and Krajina (1983). 2 n .n . ; Krajina (1969), Kojima and Krajina in Kojima (1971), Kojima and Krajina (1975), Klinka and Krajina in Klinka (1976), Klinka and Krajina (1983), Klinka et al_. (1980). 3 n .n . ; Krajina in Brooke (1965), Krajina (1965), Brooke et al . (1970), Klinka and Krajina in Klinka (1976), Klinka and Krajina~TOH3), Klinka et al . (1980, 1981), Inselberg et a l . (1982). — -56-T a b l e 1 0 . The p l a n t s p e c i e s f r o m t h e s t u d y p l o t s f o u n d i n c h a r a c t e r i s t i c c o m b i n a t i o n s f o r t h r e e o r d e r s . S t u d y a r e a L a d y s m i t h C h i l l i w a c k G a u l t h e r i a - PM O r d e r Chimaphila umbellata ( i c ) Gaultheria shallon ( p , Cd) Holodiscus discolor (p) Mahonia nervosa ( i c ) Pseudotsuga menziesii ( p , cd ) Rhytidiadelphus triguetrus (p ) Rosa gymnocarpa (p ) Rubus ursinus ( p , c ) Kindbergia oregana ( p , cd ) Trachybryum megaptilum ( s ) Vaccinium parvifolium ( cd ) R h y t i d i a d e l p h u s - TH O r d e r Dryopteris expansa ( i c ) Goodyera oblongifolia ( i c ) Linnaea borealis ( i c ) Listera cordata ( i c ) Menziesia ferruginea ( i c ) Plagiothecium undulatum ( p , c ) Rhytidiadelphus loreus ( p , cd ) Rhytidiopsis robusta ( i c ) Tsugaheterophylla ( p , cd ) P o l y s t i c h u m - TP O r d e r Achlys triphylla (p ) Festuca subuliflora ( s ) Galium triflorum ( s , c ) Leucolepis menziesii{s) Mycelis muralis (p ) Plagiomnium insigne ( s ) Polystichum munitum ( p , cd ) Rhytidiadelphus triguetrus ( i c ) Thuja plicata ( p , cd ) Tiarella t r i f o l i a t a ( s , c ) T r i l l i u m ovatum (p ) V 7 .9 V 5.1 V 8 .5 IV 1.6 I I I 1.9 V 2 . 8 V 4 . 6 V 4 . 4 I +.0 I I + . 0 V 3 .2 I I I + . 8 I +.1 V 2 .2 V 2 .7 IV 4 . 8 I I I 1.3 IV 1.8 I I I +.4 V 3 . 0 IV 1.6 I I I 2 .4 I I I 1.4 I I +.6 I +.0 IV 3 .0 V 6 . 6 V 8 .5 V 3 .6 V 2 .5 V 2 . 0 V 5 .0 I + . 0 IV 3.2 I + . 0 IV 1.2 I I I + . 9 I I + . 9 I + . 0 IV 1.4 V 2 .4 V 5.3 V 4 . 9 V 2 .2 I + . 0 V 2 . 3 I +.0 V 5.7 V 3 .6 I +.0 V 1.6 -57-Figure 13. Ecological spectra indicating floristic affinity of the study plots to plant orders. The Ladysmith study plots: G-PM R-TH P-TP (85%) (7%) (8%) The Chilliwack study plots: G-PM R-TH P-TP (46%) (17%) (37%) Explanation of symbols: G-PM - plants of the characteristic combination of species for the Gaultheria - PM Order R-TH - plants of the characteristic combination of species for the Rhytidiadelphus - TH Order P-TP - plants of the characteristic combination of species for the Polystichum - TP Order species for the orders. To reduce inherent problems arising from the successional character of ecosystems, Douglas-fir was excluded from the spectra for both ecosystems. The spectrum for the Ladysmith ecosystem shows overwhelming preponderance of species characteristic for the Gaultheria - PM Order, while that for the Chilliwack ecosystem displays a different pattern: The importance of characteristic species of the Polystichum - TP and Rhytidiadelphus - TH orders increased while that for the Gaultheria - PM Order decreased but is st i l l accounting for the major part of the spectrum. It could be concluded that the Ladysmith ecosystem is a member of the Gaultheria - PM Order, however, for the Chilliwack ecosystem this analysis did not indicate a definitive taxonomic affinity either to Gaultheria - PM or Polystichum - TP Order. The lack of -58-calibrated data might have prevented a proper interpretation. Considering the tabular information and the change in spectral pattern, but mainly the identified edatopes and biogeoclimatic subzones, this ecosystem was identified as a member of the Polystichum - TP Order. On submesic and eutrophic sites in the CWHb Subzone, Douglas-fir is shade-intolerant, therefore the major species in climax stands will be western redcedar as it had been in the past, along with some amabilis f i r . Such ecosystems in the maritime climate environment are considered to be members of the Polystichum -TP Order. The membership of the Ladysmith study ecosystem in one of the two alliances of the Gaultheria - PM Order is examined in Table 11 and Figure 14. Both tabular and spectral analysis indicated that this ecosystem be-longs to the Mahonia - TP & PM Alliance but showed a considerable affinity to the Gaultheria - PM Alliance, both being tentative taxa. Using the flo-r ist ic data and edatope these study plots are identified as members of the Mahonia - Gaultheria - TP & PM Climax Association (n.n., Krajina 1969). Figure 14. The ecological spectrum indicating floristic affinity of the Ladysmith study plots to two alliances of the Gaultheria - PM Order. G-PM (42%) M-TP*PM (58%) Explanation of symbols: G-PM - plants of the characteristic combination of species for the Gaultheria - PM Alliance M-TP - plants of the characteristic combination of species for the Mahonia - TP & PM Alliance - 5 9 -Table U . The plant species from the Ladysmith study plots found in characteristic combinations for two alliances of the Gaultheria - PM Order. Presence class and mean species significance V I I V V V V V I I I V V 7 .9 +.0 4 . 6 3.2 5.1 8 .5 2 .2 IV 1.6 1.9 2 . 8 4 . 4 IV V I I V V V V V V V I I I V I I I V 4 . 8 7 .9 +.0 8.1 4 . 6 3 .2 5.1 3 . 0 8 .5 2 .2 IV 1.6 1.9 2 . 8 2 . 3 4 . 4 Plant alliance The Gaultheria - PM Alliance: Gaultheria shallon (p, cd) Goodyera oblongifolia (ic) Kindbergia oregana (p, cd) Linnaea borealis (cd) Mahonia nervosa (ic) Pseudotsuga menziesii (p, cd) Rhytidiadelphus loreus (ic) Rhytidiadelphus triquetrus (p) Rosa gymnocarpa (p) Rubus ursinus (p, c) Vaccinium parvifolium (cd) The Mahonia - TP & PM Alliance: Achlys triphylla (d) Gaultheria shallon (p, cd) Goodyera oblongifolia (jc) Hylocomium splendens (cd) Kindbergia oregana (p, cd) Linnaea borealis (cd) Mahonia nervosa (i C , cd) Polystichum munitum (cd) Pseudotsuga menziesii (p, cd) Rhytidiadelphus loreus (ic) Rhytidiadelphus triquetrus (p) Rosa gymnocarpa (p) Rubus ursinus (p, c) Thuja plicata (ic, cd) Vaccinium parvifolium (cd) -60-The membership of the Chilliwack ecosystem in one of the two alliances of the Polystichum - TP Order is examined in Table 12 and Figure 15. Both tabular and spectral analysis suggest that they belong to the Polystichum -TP Alliance (n.n.; Kojima and Krajina 1971 in Kojima 1971, Kojima and 4 Krajina 1975; Klinka and Krajina in Klinka 1976, Klinka and Krajina 1983; Inselberg et al_. 1982). The presence of Mahonia nervosa (cd,ic), Trientalis lat i fol ia (ic) and Tsuga heterophylla (cd) identified the study plots as members of the Mahonia - Polystichum - TH & TP Climax Association (n.n.; Klinka and Krajina in Klinka 1976, Klinka and Krajina 1983; Inselberg et al_. 1982). Figure 15. The ecological spectrum indicating floristic affinity of the Chilliwack study plots to two alliances of the Polystichum - TP Order. 1 P-TP T-TP 1 (71%) (29%) Explanation of symbols: P-TP - plants of the characteristic combination of species for the Polystichum - TP Alliance T-TP - plants of the characteristic combination of species for the Tiarella - TP Alliance Productivity and Functional Relationships A comparison of taxa and site indices for Douglas-fir of this study and those predicted by Krajina (1969) is given in Table 13. It is concluded that the Mahonia - Gaultheria - TP & PM Climax Association is - 6 1 -T a b l e 1 2 . The p l a n t s p e c i e s f r o m t h e C h i l l i w a c k s t u d y p l o t s f o u n d i n c h a r a c t e r i s t i c c o m b i n a t i o n s f o r two a l l i a n c e s o f t h e P o l y s t i c h u m - TP O r d e r . P l a n t a l l i a n c e P r e s e n c e c l a s s and mean s p e c i e s s i g n i f i c a n c e The P o l y s t i c h u m - TP A l l i a n c e : Acer macrophyllum ( i c ) Achlys triphylla (p ) Chimaphila menziesii ( i c ) Galium triflorum ( s , C, cd ) Goodyera oblongifolia ( i c ) Leucolepis menziesii ( s , cd ) Mycelis muralis (p) Plagiomnium insigne ( s ) Polystichum munitum ( p , cd ) Pseudotsuga menziesii ( d , cd ) Rhytidiadelphus triguetrus ( i c ) Ribes lacustre ( i c ) Stokesiella oregana ( cd ) Tiarella trifoliata ( s , c ) Trillium ovatum (p ) The T i a r e l l a - TP A l l i a n c e : Achlys triphylla (p ) V 4 . 9 Adenocaulon bicolor ( i c ) I I I 1.3 Galium triflorum ( s , cd ) V 2 .2 Leucolepis menziesii ( s , Cd) I +.0 Mycelis muralis (p ) V 2 . 3 Plagiomnium insigne ( s ) I +.0 Polystichum munitum ( p , cd ) V 5 .7 Rhytidiadelphus triguetrus ( i c ) V 3 .6 Rubus parviflorus ( i c ) I +.0 Streptopus amplexifolius ( i c ) I +.0 Tiarella trifoliata ( s , Cd) I +.0 Trillium ovatum (p ) V 1.6 I +.0 V 4 . 9 IV 1.3 V 2 .2 IV 1.2 I +.0 V 2 . 3 I +.0 V 5 .7 V 8 .5 V 3 .6 I I I 1.2 V 5 .0 I +.0 V 1.6 T a b l e 1 3 . Compar i son o f b i o g e o c o e n o t i c t a x a and s i t e i n d i c e s f o r D o u g l a s - f i r between t h e s t u d y p l o t s and t h o s e p r e d i c t e d by K r a j i n a ( 1 9 6 9 ) . C l i m a x a s s o c i a t i o n Eda tope S i t e i n d e x (m/ lOOyrs ) The L a d y s m i t h s t u d y p l o t s , CDFb Subzone 1. P r e s e n t s t u d y : Mahon ia - G a u l t h e r i a - TP & PM 2. K r a j i n a ( 1 9 6 9 ) : Eu rhynch ium - Mahon ia - G a u l t h e r i a - PM ( b i o g e o c o e n o t i c u n i t n o . 5 ) mes i c ( - s u b h y g r i c ) / m e s o t r o p h i c 43 m e s i c ( - s u b h y g r i c ) / m e s o t r o p h i c 42 ( 4 0 . 6 - 4 3 . 5 ) The C h i l l i w a c k s t u d y p l o t s , CWHb Subzone 1. P r e s e n t s t u d y : Mahon ia - P o l y s t i c h u m - TH & TP 2 . K r a j i n a ( 1 9 6 9 ) : R h y t i d i a d e l p h u s - R h y t i d i o p s i s - V a c c i n i u m - PM - AA - TP ( b i o g e o c o e n o t i c u n i t n o . 3 5 ) submes i c / e u t r o p h i c submes i c / e u t r o p h i c m e s i c / e u t r o p h i c 42 39 ( 3 7 . 6 - 4 0 . 5 ) 42 ( 4 0 . 6 - 4 3 . 5 ) -63-synonymous with Krajina's biogeocoenotic unit no. 5. The reconstruction of past tree species composition and advanced regeneration in the Ladysmith ecosystem suggests that western redcedar has been a significant component in the association's f loristic composition (Figure 16). The role of western redcedar is believed to increase gradually in the course of secondary succession. Thus, the inclusion of western redcedar into this association's climax composition and into the other ones related to permesotrophic and eutrophic trophotopes is considered to be a viable interpretation. The site index determined for the Ladysmith ecosystem is Figure 16. Western redcedar of good vigor is common in the shrub layer of the Ladysmith ecosystem. -64-within the limits of growth class Ilia (40.6 to 43.5 m/lOOyrs). The Chilliwack ecosystem can be related to Krajina's (1969) taxa through its edatopic and climatic characteristics. The edatopic grid in Figure 1 indicates that the submesic to mesic/eutrophic edatope in the CWHb Subzone is related to the biogeocoenotic unit no. 35. The corresponding unit in the CWHa Subzone is the biogeocoenotic unit no. 25: Hylocomium -Mnium - Achlys - Polystichum - PM - TP. On the basis of comparing constant dominant species, i t appears that the recognized Mahonia - Polystichum - TH - TP Climax Association cannot be readily assigned to any of these units. This conclusion is supported by two special circumstances; f irst ly the Chilliwack ecosystem is climatically transitional, and secondly i t is one of the ecosystem series developed on steep colluvial slopes. These ecosystems were classified into a special series of associations (Klinka 1976, Klinka and Krajina 1983), which has not yet been included in the grids. Thus, the identified climax association has an intermediate position between the unit 35 and 25. For both units the predicted site index on submesic edatopes is 39 (37.6-40.5) m/lOOyrs which is lower than that found on the study plots. The preceding discussion established that the Douglas-fir ecosystems studied differed in a number of properties but the estimated site index was similar. In consequence, the total effect of environmental factors controlling forest growth must also be similar but because of compensation, the individual factors responsible for this effect may be different in each ecosystem. Following a general characterization, selected data for regional climates affecting each ecosystem are presented in Table 14. As stated - 6 5 -T a b l e 14 : S e l e c t e d c l i m a t i c d a t a f o r the s t u d y a r e a . 1 S tudy a r e a L a d y s m i t h C h i l l i w a c k B i o g e o c l i m a t i c u n i t CDFb CWHb7 Mean Minimum/ Maximum Mean Min imum/ Maximum Number o f d a t a s e t s 19 12 C l i m a t e ( Koppen/T rewa r tha ) w e t t e r C s b - C f b w e t t e r ( C f b ) - C f c Mean annua l p r e c . (mm) 1305 958/1936 2236 1422/3774 Mean p r e c . A p r i l - S e p t . (mm) 301 2 2 7 / 422 615 4 2 5 / 939 Mean p r e c . o f d r i e s t month (mm) 32 2 2 / 45 62 5 1 / 89 Mean annua l t e m p e r a t u r e ( ° C ) 9 .1 8 . 0 / 9 . 8 5.6 4 . 6 / 6 . 5 Mean t emp , o f c o l d e s t month ( ° C ) 1.5 0 . 1 / 2.8 -2 .4 - 4 / -1 Mean temp, o f warmest month ( ° C ) 1 6 . 9 1 5 . 9 / 1 7 . 8 1 3 . 6 1 2 . 4 / 1 4 . 4 Number o f months w i t h mean t e m p e r a t u r e l e s s t han 0°C 0 0 / 0 2 .3 1 / 3 Number o f months w i t h mean t e m p e r a t u r e l a r g e r than 10°C 5 .2 5 / 6 3 .8 3 / 4 F r o s t f r e e p e r i o d (days ) 187 1 3 3 / 250 139 104/ 181 E f f e c t i v e g r o w i n g - d e g r e e days 980 881/1137 776 4 6 0 / 944 P o t e n t i a l e v a p o t r a n s p i r a t i o n (mm) 424 3 5 5 / 549 334 2 9 8 / 378 A c t u a l e v a p o t r a n s p i r a t i o n (mm) 341 3 0 8 / 439 334 2 9 8 / 378 A c t u a l e v a p o t r a n s p i r a t i o n / p o t e n t i a l e v a p o t r a n s p i r a t i o n .81 . 6 7 / . 99 1.0 1 . 0 / 1 .0 Water s u r p l u s (mm) 961 626/1540 1902 1123/3462 Water d e f i c i t (mm) 82 5/ 160 0 0 / 0 The s o u r c e i s C o u r t i n e t a l . ( 1 9 8 3 ) . -66-earlier each ecosystem was under the influence of different regional climate. Employing potential (PET) and actual (AET) evapotranspiration as indices of zonal plant activity under natural conditions as suggested by Major (1963), the potential for plant growth appears to be much greater in the CDF Subzone than in the CWHby variant. The reasons are the warm, temperature and long growing season of a wetter Csb - drier Cfb climate (Figure 17 and 18). However, due to the low summer precipitation in the CDFb Subzone a significant period of soil moisture deficiency is usually encountered. As a result only 81 percent of the PET is realized in the mesic ecosystem of this subzone. In contrast, there is no difference between PET and AET in the index ecosystem for the CWHb Subzone suggesting that all potential heat is used for plant growth because precipitation is more than adequate to cover PET. The difference of 7 mm between PET and AET is insignificant. On the flat, mesic and mesotrophic Ladysmith ecosystem the local physiography does not modify regional climate; however, the steep slope gradient and aspect, along with the soil properties of the Chilliwack ecosystem will likely be influential in modifying regional climate. The slope of 70% gradient and somewhat southerly aspect (250° azimuth) may be responsible for a minor increase in PET. The steep slope and a high volume of coarse fragments could result in a reduction of available soil water but the plant indicator analysis rejects this possibility; in fact, i t rather suggests that the Chilliwack ecosystem has a higher soil water supply than the Ladysmith ecosystem. The same analysis also assessed the former ecosystem to have a richer nutrient regime than the latter. A high pH, high C/N ratio and high values of total carbon and base saturation of Figure 17. Annual water balance for the mesic ecosystems in the CDFb Subzone (after Courtin et al_. 1983). Figure 18. Annual water balance for the mesic ecosystems in the CWHb Subzone (after Courtin et al_. 1983). -68-master B horizon determined for the Chilliwack ecosystem support this assessment. Thus, the more humid climate and greater availability of nutrients, particularly of nitrogen, of the Chilliwack ecosystem compensate for the warmer climate and longer growing season of the Ladysmith ecosystem. The longer growing season of the latter ecosystem appears to be reflected in its radial growth pattern. The tree-ring analysis showed that the mean latewood/total wood ratio was greater for the Ladysmith plots than for the Chilliwack plots. Although the difference between the plots is small, i t was found to be highly significant (p < 0.01)(Table 15). Table 15. Mean values obtained from a tree-ring analysis for the selected study plots. Standard deviations in parenthesis. Study area Latewood Total wood Latewood/ (cm) (cm) Total wood Ladysmith 5.43 18.10 0.30 (0.97) (3.29) (0.02) Ch illiwack 5.57 (0.65) 20.66 (3.02) 0.27 (0.02) -69-Characterization of the Stands While the analytical results will be presented and discussed from a number of viewpoints later in this section, major features of the stand analysis can be noted at this point. Selected growth properties for the study plots and the mean values for each stand are summarized in Table 16. All parameters listed are given for Douglas-fir only and for all tree species found in the study plots including red alder, western hemlock and western redcedar. A small difference in age results in a 1.9 m difference in site index on a 50 year basis between the two stands. Major differences between the stands were found in number of stems/ha, diameter, basal area and volume characteristics. Because density and structure are the key factors determining growth characteristics of a stand, their characterization and relationship were the focus of stand analysis. Age, Top Height and Site Index The arithmetic mean age was 72 years and 78 years for the Ladysmith and Chilliwack stands, respectively, with a significant difference (p < 0.01) of six years. This difference will affect to a certain degree a variety of growth characteristics, and therefore will be accounted for where possible. Both stands had an identical mean top height (height of the 100 largest diameter trees) of 39.6 m, with nearly identical ranges of 36.9 m to 41.5 m in the Ladysmith and 36.9 m to 41.1 m in the Chilliwack stand. Table 16. Basic growth characteristics of the study plots and stands. Top Si te Douglas-fir " o t Age height index ~ J®5 " 7~* n o - , . . . , Mean Mm. Max. NT/ha ° f l (yrs) (m) (m/50yrs) : f c i ] (mZ/ha) The Ladysmith study plots: 1 72 38.5 33.2 32.2 15.4 71.3 672 61.9 2 70 41.4 36.6 31.1 10.3 65.9 816 73.5 3 72 40.9 35.4 32.9 7.8 73.4 656 74.5 4 72 38.4 33.2 28.2 13.2 56.4 864 62.9 5 73 36.9 31.7 28.0 7.5 57.7 816 60.2 6 72 38.5 33.2 28.9 10.1 52.0 928 68.3 7 72 39.5 34.1 31.9 11.5 66.0 608 58.4 8 72 39.1 33.8 31.6 7.1 61.0 816 76.2 9 72 37.3 32.3 28.7 8.5 63.1 976 72.8 10 72 41.5 36.0 29.6 12.8 69.5 1008 84.9 Mean 72 39.2 34.0 30.3 10.4 73.4 816 69.4 The Chilliwack study plots: 11 78 39.3 32.3 41.2 14.0 70.1 461 70.8 12 77 38.9 32.3 39.7 18.2 62.5 569 76.3 13 78 39.1 32.3 41.4 15.1 65.0 496 75.4 14 78 36.9 30.5 38.6 21.2 54.6 544 68.0 15 78 41.2 34.1 44.6 16.8 65.5 448 76.4 16 79 38.3 31.4 43.5 18.8 69.3 512 83.2 17 78 39.1 32.0 48.8 24.4 75.7 400 80.0 18 78 39.6 32.3 38.4 9.0 69.4 592 78.9 19 80 38.5 29.9 42.0 13.5 76.3 533 83.8 20 78 41.1 33.8 46.8 27.7 71.1 464 85.6 Mean 78 39.2 32.1 42.5 17,9 76.3 502 77.9 All species V o i u m e Mean Mini! Max. NT/ha f Volume (m /ha) Tc¥) (mVha) (m3/ha) 755 31.2 8.0 71.3 704 62.2 756 900 29.4 8.2 65.9 896 74.8 908 946 30.6 7.8 73.4 736 75.4 951 745 25.8 7.7 56.4 992 63.8 748 717 25.3 7.5 57.7 960 61.3 721 804 25.7 7.5 52.0 1120 69.9 811 723 30.6 10.5 66.0 656 60.5 728 937 31.6 7.1 61.0 816 76.2 937 864 27.8 8.0 63.1 1024 73.3 868 1035 27.1 7.5 69.5 1152 86.1 1040 843 28.5 8.0 63.6 906 70.4 847 875 33.2 9.4 70.1 723 79.0 939 920 32.4 10.3 62.5 846 83.5 972 931 33.0 8.7 65.0 720 79.5 955 809 28.6 8.0 54.6 944 75.9 856 952 33.3 8.6 65.5 736 82.7 992 1026 36.2 9.8 69.3 704 87.6 1054 1012 45.6 16.0 75.7 448 81.4 1021 943 35.0 9.0 69.4 704 81.7 962 1095 34.1 7.8 76.3 957 92.4 1167 998 46.8 27.7 71.1 464 85.6 998 956 35.8 11.5 68.0 725 82.9 992 - 7 1 -The s i t e i n d e x a c c o r d i n g t o K i n g (1966) i s d e r i v e d from the 10 l a r g e s t d i a m e t e r t r e e s o u t o f 50 sample t r e e s , t h u s t h e number o f s i t e t r e e s s e l e c t e d i s n o t r e l a t e d to an a r e a b u t t o a f i x e d number o f t r e e s . S i n c e number o f t r e e s per ha and s t a n d s t r u c t u r e a r e d i f f e r e n t f o r each s t a n d t h e t r e e s s e l e c t e d may be i n c o m p a t i b l e i n r e l a t i o n t o crown c l a s s . I f , f o r i n s t a n c e , t r e e s w i t h a r e l a t i v e l y l o w e r c rown c l a s s were i n c l u d e d t h i s w o u l d r e s u l t i n a l o w e r s i t e i n d e x f o r the L a d y s m i t h s t a n d . A d o p t i n g K i n g ' s a p p r o a c h i n t h i s c a s e wou ld r e s u l t i n the s i t e h e i g h t as t h e a ve r age h e i g h t o f t h e 10 ( r a n g i n g f rom 8 t o 12) l a r g e s t d i a m e t e r t r e e s pe r p l o t i n t h e L a d y s m i t h s t a n d , b e i n g compared t o the s i t e h e i g h t as the ave rage h e i g h t o f t h e 6 ( r a n g i n g f rom 5 t o 8 ) l a r g e s t d i a m e t e r t r e e s pe r p l o t i n the C h i l l i w a c k s t a n d . To d e r i v e a more c o m p a r a b l e s i t e i n d e x , an a r e a - r e l a t e d s i t e h e i g h t ( i . e . t he t op h e i g h t o f t he 100 l a r g e s t d i a m e t e r s tems/ha ) was u s e d . T h i s gave v a l u e s i d e n t i c a l t o K i n g ' s s i t e h e i g h t a t a f i x e d d e n s i t y o f 500 t r e e s / h a . U s i n g t h i s a p p r o a c h , s i t e i n d i c e s o f 3 4 . 0 and 3 2 . 1 m/50yrs were d e r i v e d f o r the L a d y s m i t h and the C h i l l i w a c k s t a n d s , r e s p e c t i v e l y , and a p p l i e d i n f u r t h e r a n a l y s i s . The p r e d i c t e d s i t e h e i g h t s a t age 100 a r e 4 8 . 6 m and 4 6 . 1 m, r e s p e c t i v e l y . C u r t i s e t a l _ . 1974 examined whe the r the s i t e i n d e x c u r v e s by M c A r d l e e t a l _ . (1961) and K i n g (1966) wh i ch were d e v e l o p e d on t h e d a t a b a s e o f l o w l a n d D o u g l a s - f i r a r e a p p l i c a b l e f o r h i g h e l e v a t i o n D o u g l a s - f i r s t a n d s i n w e s t e r n Oregon and n o r t h e r n W a s h i n g t o n . They d e r i v e d h e i g h t g rowth and s i t e i n d e x e s t i m a t i o n c u r v e s f rom stem a n a l y s i s o f D o u g l a s - f i r t r e e s i n h i g h - e l e v a t i o n s t a n d s and found t h a t t h e r e s u l t i n g h e i g h t g rowth p a t t e r n d i f f e r s f rom t h a t o f l o w - e l e v a t i o n D o u g l a s - f i r ; t h e h e i g h t / a g e c u r v e o f -72-high-elevation Douglas-fir has the culmination point at a higher age, declines before the intersection point with Kings's site index curve and exceeds the growth of the low-elevation stand afterwards. Height over age growth could not be examined in this study to test the — results of Curtis et a]_. According to their classification cr i ter ia ' (altitude) however, the Chilliwack stand belongs to these high-elevation forests. The site index curve for the site index of 42 m (reference age of 100 yrs) intersects King's site index curve at age 90. In consequence we can expect King's and Curtis et a]_'s. site index values to be similar for the Chilliwack stand. The Curtis _et al_. site index was calculated for the Chilliwack stand as being 45.7 m/lOOyrs. Kings's predicted height value for age 100 was 46.1 m/lOOyrs. To compare growth and yield characteristics of the two stands at their present stage it was safe to apply King's site index for both stands. To compare the development of these parameters over time, King's site index is not applicable for the Chilliwack stand. Applying the site index curves of the B.C. Ministry of Forests (Hegyi et aK 1981) site indices of 43 and 42 m/lOOyrs were derived for the Ladysmith and Chilliwack stands, respectively. Since not all plots featured dominant trees, the top height as defined above was applied to derive the site height. In comparison with King's and Curtis et a l 's . predictions for the site height at age 100, the site index curve of the B.C. Ministry of Forests seems to underestimate the site index. A single site index curve set for coastal Douglas-fir must lead to erroneous conclusions for growth and yield characteristics i f the results of Curtis et al_. are applicable in British Columbia. In summary, the stands compared do not have the same site index as was -73-was desired for the objective of this study. The difference of 1.9 m (SI/50yrs) or 1.0 m (Sl/lOOyrs) is due to the difference in age. Considering this relatively small difference in relation to exactness of measurements taken and the purpose of the study, it is thought that its influence on comparing the majority of growth characteristics will be insignificant, and whenever possible, appropriate adjustments could account for the di fference. Stand Structure The stand composition is the arrangement of the elements constituting a forest stand. It is usually described in terms of species, age, structure and origin. The structure or the structural (spatial) composition of a stand refers to the horizontal and vertical distribution of trees (occasionally of other plant species) in a forest stand. The horizontal distribution is expressed either quantitatively by diameter distribution and crown coverage or qualitatively by a stand map showing location, diameter and crowns of individual trees. The vertical distribution or layering is expressed either quantitatively by coverage of layers (stories, strata), height distribution, crown class distribution, or graphically by stand map and stand profile. The structure of a stand is the result of the species' silvical characteristics, site quality and management practices under which the stand originated and developed. Despite some uncertainty in stand history, the differences in stand structure between the two stands will be related to the different ecological function of Douglas-fir in the two ecosystems. -74-The different ecological function likely resulted in a significant difference in the number of Douglas-fir trees between the two stands. However, variations in stand density and initial stand density might be also responsible for much of these differences in stand structure. The section on stand structure will describe structural differences between the stands and relate them to the ecological function of Douglas-fir. In the chapter on the influence of stand density some spacing and thinning studies, which show causative effects of density on some stand characteristics, will be reviewed, and the relationship between stand density and various stand characteristics will be examined. Stand Map To demonstrate the horizontal stand structure with elements of crown structure, size, shape and distribution, one representative plot in each stand was selected for stand mapping. Computer-plotted maps are presented in Figure 19 and 20. The maps are complemented by photographs of the canopy taken in each stand (Figure 21 and 22). The four solid interconnecting lines on the margins represent the plot boundaries. The crown class identified for each tree is printed inside its diameter ring using arabic numerals from 1 to 4. The four points of branch extension are connected - for Douglas-fir with solid lines and for western hemlock with dashed lines - to give a rough shape of crown circumference. The trees with stems located outside the plot boundaries were included providing their branches extended into the plot. The characteristic features of the horizontal stand structure for the -75-F i g u r e 19 . The s t a n d map o f t h e p l o t n o . l i n the L a d y s m i t h s t a n d a t t he s c a l e 1 : 222 . Figure 20. The stand map of the plot no.17 in the Chilliwack stand at the scale 1:222. Figure 2 1 . A representative view of the horizontal structure of the Ladysmith stand showing an uneven canopy with scanty crowns. Figure 2 2 . A representative view of the Chilliwack stand showing the horizontal structure of an uniform canopy with dense crowns. -78-Ladysmith stand are summarized as follows: a. the two dominant trees are free of competition for space from codominant trees. b. the codominant trees tend to form clusters, hence their crowns overlap but living branches are maintained. c. the intermediate and suppressed trees appear to be evenly distributed d. the crown shape is more or less a square. The characteristic features of the horizontal stand structure for the Chilliwack stand are summarized as follows: a. there are no dominant trees present. b. the codominant trees are evenly distributed and no overlapped crowns are apparent. c. there are very few intermediate and no suppressed Douglas-fir trees; those present are relatively l i t t l e overshaded. d. all trees tend to have a pronounced branch extension in the downslope direction as described earlier by Mitscherlich (1970). Stand Profile To illustrate the vertical structure of the stands a representative profile of each stand was plotted (Figure 23 and 24). Quantitatively, the differences between the stands in the coverage of the Aj_, A2, A3 and layers were discussed earlier when describing the floristic composition and structure of forest communities. Although the relationship -79-l " " ST ~ ~ ~ Son. Figure 23. The stand profile representative of the Ladysmith stand, (the horizontal scale is 1:606, the vertical scale is 1:606). Figure 24. The stand profile representative of the Chilliwack stand (the horizontal scale is 1:606, the vertical scale is 1:606), = Douglas-fir; ^ = western hemlock -80-between c rown c l a s s e s and t h e above l a y e r s i s o n l y a p p r o x i m a t e t h e a p p a r e n t d i f f e r e n c e s i n l a y e r i n g between t h e s t a n d s a r e comp lementa ry t o t h o s e d e s c r i b e d f o r t h e s t a n d maps. F o r an even-aged s t a n d t h e L a d y s m i t h s t a n d e x h i b i t s a c o n s i d e r a b l y d i v e r s i f i e d v e r t i c a l s t r u c t u r e . A h i g h number o f s u p p r e s s e d t r e e s i n t h e A3 and B2 l a y e r s and a l a r g e d i f f e r e n c e between h e i g h t s o f dominan t and s u p p r e s s e d t r e e s a r e t h e most c h a r a c t e r i s t i c f e a t u r e s o f t h i s s t a n d . In c o n t r a s t , t h e C h i l l i w a c k s t a n d has an u n i f o r m s t r u c t u r a l p a t t e r n wh i ch i s c h a r a c t e r i s t i c f o r an even-aged s t a n d o f a s h a d e - i n t o l e r a n t s p e c i e s . T h i s p a t t e r n f e a t u r e s t h e dominant A2 l a y e r c o m p r i s e d m a i n l y o f codominan t t r e e s , t h e A3 l a y e r i s l a c k i n g o r v e r y p o o r l y d e v e l o p e d c o m p r i s i n g b o t h i n t e r m e d i a t e and s u p p r e s s e d t r e e s . There i s o n l y a s m a l l d i f f e r e n c e between h e i g h t s o f dominant and s u p p r e s s e d t r e e s . Crown C l a s s D i s t r i b u t i o n The r e l a t i v e d i s t r i b u t i o n o f crown c l a s s e s e i t h e r i n r e l a t i o n t o number o f s tems o r b a s a l a r e a i s one o f t h e q u a n t i t a t i v e i n d i c a t o r s o f s t a n d s t r u c t u r e used i n t h e s t u d y . D i s t r i b u t i o n h i s t o g r a m s a r e p r e s e n t e d i n F i g u r e s 25 and 2 6 . The r o l e o f d e n s i t y w i t h r e s p e c t t o crown c l a s s d i s t r i b u t i o n w i l l be d i s c u s s e d i n t h e c h a p t e r on t h e i n f l u e n c e o f d e n s i t y on v a r i o u s s t a n d p a r a m e t e r s . The c o m p a r i s o n o f t h e d i s t r i b u t i o n o f crown c l a s s e s i n r e l a t i o n t o number o f t r e e s r e v e a l e d a c o n t r a s t i n g p a t t e r n . In t h e L a d y s m i t h s t a n d t h e f r e q u e n c y i n c r e a s e s i n t h e o r d e r f rom crown c l a s s I t o I V ; i n t h e C h i l l i w a c k s t a n d , when o m i t t i n g crown c l a s s I, t h e f r e q u e n c y d e c r e a s e d . -81-Ladysmith stand --I n nr nc Crown class 7 0 r Chilliwack stand 60 h 50 40 30 20 10 n n Crown class Figure 25a Figure 25a and b. Figure 25b D i s t r i bu t i on of crown c lasses in r e l a t i o n to number trees for the Ladysmith stand ( F i g . 25a) and the Chi l l iwack stand ( F ig . 25b). of 8 0 r Ladysmith stand 70 60 50 40 30 20 10 8 0 r Chilliwack stand n n r Crown class Figure 26a F igure 26a and b. 70 60 50 40 30 20 10 II m Crown class Figure 26b D i s t r i bu t i on of crown c lasses in r e l a t i on to basal area for the Ladysmith stand ( F ig . 26a) and the Chi l l iwack stand ( F ig . 26b). -82-The suppressed class is most frequent for the Ladysmith stand whereas the codominant class is most frequent for the Chilliwack stand. Somewhat different but informative patterns emerged in relation to basal area. The codominant trees accounted for 73% of the basal area in the Chilliwack stand which is nearly twice the value for the same class in the Ladysmith stand. The combined basal area for crown classes III and IV in the Ladysmith stand was nearly as large as that for class II. Thus, a large number of intermediate and suppressed trees remain alive under the main canopy and contribute considerably to the stand basal area, substantially more than in the Chilliwack stand. It could be safely inferred from the crown class distribution that crown competition is severe in the Chilliwack stand, particularly for the codominant component. The likely result of shading is early mortality because the frequency of intermediate and suppressed classes stays at a low level. On the other hand, the crown competition in the Ladysmith stand is believed to be less severe. There are fewer dominant and codominant trees to compete with the lower canopy layer and restrict the availability of 1ight. Length of Live Crown-Total Height Relationship The form and size of live crown is considered to be an expression of vigor and shade-tolerance of a tree species. Vigorously growing trees, such as those in the uppermost tree layer, and shade-tolerant tree species tend to have long and large crowns in relation to their total height (Worthington et a l . 1961, Mitscherlich 1970). To assess the difference in - 8 3 -shade t o l e r a n c e o f D o u g l a s - f i r i n the two s t a n d s , t h e r e l a t i o n s h i p between t h e r a t i o o f l e n g t h o f l i v e crown t o t o t a l h e i g h t (LCTH) and t o t a l h e i g h t (TH) was examined ( F i g u r e s 2 7 , 2 8 and 2 9 ) . When c o m p a r i n g the p l o t t e d d a t a , a h i g h d i s p e r s i o n f o r the L a d y s m i t h s t a n d i s a p p a r e n t ( F i g u r e 27 and 2 8 ) . T r ees w i t h v e r y s h o r t l i v e c rowns p e r s i s t i n n e a r l y a l l canopy l a y e r s . In c o n t r a s t , i n the C h i l l i w a c k s t a n d t h e r e a r e v e r y few l i v i n g t r e e s w i t h t h e LC/TH r a t i o be l ow 0 . 2 6 ; f u r t h e r m o r e t h e s e t r e e s b e l o n g e x c l u s i v e l y t o the l o w e r c a n o p y . The c o r r e s p o n d i n g v a l u e o f t h e LC/TH r a t i o i n t h e L a d y s m i t h s t a n d i s a p p r o x i m a t e l y 0 . 1 3 . These v a l u e s , shown i n F i g u r e 27 and 28 as p a r a l l e l l i n e s w i t h t h e x - a x i s , a r e s u g g e s t e d t o r e p r e s e n t the uppe r l i m i t o f zones o f i m m i n e n t m o r t a l i t y (Drew and F l e w e l l i n g 1 9 7 9 ) . To e v a l u a t e t h e e x t e n t and s i g n i f i c a n c e o f t h e s e t r e n d s two s e p a r a t e l i n e a r r e g r e s s i o n s a r e g i v e n ( F i g u r e 2 9 ) . In c o m p a r i s o n the s l o p e o f t h e r e g r e s s i o n f o r t h e C h i l l i w a c k s t a n d i s c o n s i d e r a b l y s t e e p e r than t h a t f o r t h e L a d y s m i t h s t a n d . T h i s i n d i c a t e s t h a t t h e d e c r e a s e o f t o t a l h e i g h t i s r e l a t e d to a r a p i d d e c r e a s e o f t h e LC/HT r a t i o . The s h o r t l i v e c rown o f s h o r t e r t r e e s p r e d i s p o s e s l o w v i g o r and m o r t a l i t y o f t h e s h a d e - i n t o l e r a n t D o u g l a s - f i r i n t h i s e c o s y s t e m . The r e g r e s s i o n l i n e f o r the L a d y s m i t h s t a n d l i e s i n the range f rom 12 t o 37 m o f t o t a l h e i g h t w e l l above t h a t f o r the C h i l l i w a c k s t a n d . Thus w i t h i n t h i s r a n g e , i n c l u d i n g s u p p r e s s e d , i n t e r m e d i a t e and some o f t h e c o d o m i n a n t c o m p o n e n t s , t r e e s p o s s e s s r e l a t i v e l y l o n g l i v e c r o w n s , a h i g h s t a n d d e n s i t y n o t w i t h s t a n d i n g . On a r e l a t i v e b a s i s , t h e c a p a b i l i t y o f D o u g l a s - f i r t o m a i n t a i n a l o n g e r l i v e c r o w n , e s p e c i a l l y i n t h e l o w e r t r e e l a y e r s , i s i n t e r p r e t e d as the e x p r e s s i o n o f a g r e a t e r s h a d e - t o l e r a n c e . CO c CD ro oo O (D r r —• CU Oi CD CO* a> cr 3 CD Q - r r o n> r r 3 Cu — ' r r ZTCD rt> - • • - $ CO Oi = T r r <-*•-•• O - h O O - s -t) 3 " f D CO O r r s: —• Cu _ • . O < CO O r r - s cu o Ratio of length of l i v e crown to t o t a l height 81 H O • • • » • • • • CQ C ~i CD ro r r TO O (D r r Cu cu 3 " O CD 3 _ i . cn CQ 3 -3 " - " • rfo cu cr 3 rt> Q - r r S. rt- CD O CD rt- 3 Cu — 1 r r 3 " 3 " CD CD ->• - s CQ CU 3 - r r r r O -ti o o r r — ' ZT CD CD 3 CQ r- <-r Cu 3 " Q -*< o CO -tt ZT < n> co r r O Cu -S 3 O Q - S Ratio of length of l i v e crown to t o t a l height 7 X 3 c fD g t3 § H O rt ro 09 3 * r r O CD 00 -85-10 20 30 40 50 Height Im) Figure 29. Linear regressions showing relationships between the ratio of length of live crown to total height and total height for the stands. Within the height range of 30 to 45. m most trees in the Chilliwack stand belong to the codominant crown class. In that crown class position trees have relatively more space than in an intermediate or suppressed position, and therefore their live crown ratio is relatively higher (Worthington et 1961). Within this same height range many trees in the Ladysmith stand have an intermediate crown class position (Fig. 25). As a result, the regression line of the Chilliwack stand lies above the one of the Ladysmith stand within that range, ack stand lies above the one of the Ladysmith stand within that range. -86-Diameter Characteristics Several mean diameters were computed for each plot (Table 17): 1. The arithmetic mean diameter of Douglas-fir and of all species. 2. The diameter of the mean basal area stem as the diameter of the (theoretical) tree with the arithmetic mean basal area for Douglas-fir only. This mean basal area stem is commonly preferred because in even-aged and uniform stands its diameter corresponds approximately to that of the stem with the mean volume (Gehrhardt 1901). This was applied when deriving Reineke's stand density index. 3. The arithmetic mean diameter of the 100 largest diameter stems/ha. As could be expected on the basis of diameter-density relationships, all diameter characteristics for the Chilliwack stand have significantly greater values (p < 0.01) than those of the Ladysmith stand. The possible effect of density will be discussed in the section on the influence of density on stand structure and parameters. Table 17. Diameter characteristics of the stands studied. Stand Ladysmith Chilliwack Diameter (cm) The mean dbh of Douglas-fir 30.3 42.5 The mean dbh of all species 28.5 35.8 The dbh of the mean basal area stem 32.9 44.5 The mean dbh of the 100 largest diameter trees 53.7 60.1 -87-Diameter and Basal Area Distribution Distribution of diameters was the third quantitative analysis conduc-ted to characterize structural differences between the stands (Figures 30 and 31). This analysis was complemented by the distribution of basal area showing number of trees in 0.02 m^  classes (Figures 32 and 33). Contrasting distribution patterns were expected on the basis of crown class distribution. The Ladysmith stand features a pattern which is strongly skewed to the left. A significant preponderance of the small diameter component in the Ladysmith stand is interpreted as the expression of the moderate tolerance to shade of Douglas-fir. The Chilliwack stand seems to approximate a normal distribution pattern, which is slightly skewed to the right. Since the basal area is a function of the squared diameter, a tree with a smaller diameter at the left side of the diameter distribution has a relatively smaller basal area than a tree with a larger diameter. In consequence, the basal area ranging from 0.01 to 0.03 m^  comprises all trees with a diameter of 11.2 to 19.5 cm, whereas the basal area class ranging from 0.41 to 0.43 comprises the trees with the diameter between 72.3 and 74.0 cm. In consequence the culmination point of the basal area distribution is skewed to the left in relation to the diameter distribution. A large number of small trees in the Ladysmith stand explains a nearly J-shaped basal area distribution which further accentuates the distinct culminating pattern as seen in the diameter distribution. In contrast, the basal area distribution of the Chilliwack stand reveals an even distribution pattern throughout the range of the basal area. -88-90 80 70 60 01 i : 50 1 40 5£ 30 20 10 _L _L J _ _L 10 15 20 25 30 35 40 45 50 55 60 65 70 75 dbh class (cm) Figure 30. Diameter distribution for Douglas-fir in the Ladysmith stand. 4 6 50 40 30 20 10 _L _L _L -L 10 15 20 25 30 35 40 45 dbh class (cm) 50 55 60 65 70 75 Figure 31. Diameter distribution for Douglas-fir in the Chilliwack stand. -89-110 100 90 80 70 60 1 50 40 30 20 10 I I l I I < 01 .02 .06 .10 .14 .18 .22 .26 Basal area class Im2) .30 .34 .38 .42 Figure 32. Basal area distribution for Douglas-fir in the Ladysmith stand. 40 30 20 10 J_ <.01 .02 .06 .10 .14 .18 .22 .26 Basal area class Im2) .30 .34 .38 .42 .46 Figure 33. Basal area distribution for Douglas-fir in the Chilliwack stand. -90-Height-Diameter Re lat ionship The two stands studied had an ident i ca l top height but the correspon-ding diameters were cons i s t en t l y d i f f e r e n t . Therefore, height/diameter (h/d) r a t i o s must be a lso d i f f e r e n t for each stand. Interpret ing height-diameter r e l a t i onsh ips (Figure 34) , the regress ion curve for the Ladysmith stand i s located on the average about 2 m above that for the Chi l l iwack stand. In consequence, the h/d ra t i o s for the Ladysmith stand must be cons i s t en t l y higher than those for the Chi l l iwack stand. 40 10 ^^^^^S^^^^^^ Chill iwack stand y 0.978 + 1.203x - 0.00892x2 x - 0.96 jT^r P * 001 Ladysmith stand ' y - -30.2-0.0989x + 43.1 log x r - 0.97 P < 0.01 I I I I I I i 10 20 30 40 SO 60 dbh (cm) Figure 34. Re lat ionship of height to diameter for Douglas-f i r in the study p l o t s . The h/d ra t i o was ca l cu la ted for a l l trees for which heights had been measured. For short trees the h/d ra t i o was in the range from 1.0 to 1.5 (the l a t t e r value re fe r s to a tree with the dbh of 13.5 cm). The mean h/d r a t i o for the 100 l a rges t diameter trees in the Ladysmith stand was 0.74 -91-(ranging from 0.64 to 0.80). The corresponding values for the Chilliwack stand were significantly lower than those above; the mean h/d ratio was 0.65 (ranging from 0.57 to 0.70) and the highest ratio of 1.2 was calculated for a tree with dbh of 18.8 cm. In this stand h/d ratios equal to or greater than 1 were rare. The h/d ratio is commonly used in Europe as an indicator of shade tolerance, taper and windfirmness. On a relative basis, shade-tolerant species tend to form high density stands (Mayer 1970). At high density levels diameter growth decreases in relation to height growth, hence the h/d ratio for shade-tolerant species is higher than that for less shade-tolerant or shade-intolerant species. The above results corroborate further the converging evidence on tolerance to shade as the underlying cause of structural differences found in the studied stands. Under low density levels diameter growth increases in relation to height growth. It has been documented that the diameter increment at breast height is larger in relation to that higher on the stem (Assman 1970). In consequence, there is a corresponding increase in taper. Since trees in low density stands have also relatively low h/d ratios, taper and this ratio are negatively correlated. Thus, the h/d ratio is expected to be different between the two stands. In this respect the application of volume equations using a single value for taper may result in a considerable systematic error. Further study determining the variation of different ecosystems could be informative. Windfirmness of even-aged stands is a desirable silvicultural attribute. A well developed root system is one of the several factors influencing windfirmness. In general, the development of root systems is -92-inhibited by dense spacing. Large crowns and diameters develop under competition-free density levels, which are indicated by relatively low h/d ratios. Critical values of h/d ratios have been derived in Europe to guide stand density management in areas and for species prone to windthrow. The qualitative and quantitative differences in horizontal and vertical structure described above suggest a distinct structural pattern for each stand: the diversified structure is characteristic for the Ladysmith stand while uniform structure is characteristic for the Chilliwack stand. In this respect the Ladysmith stand resembles an uneven-aged stand of a shade-tolerant species whereas the Chilliwack stand is typical for an even-aged stand of a shade-intolerant species. These structural arrangements are believed to reflect Douglas-fir activity in relation to local heat and water supply (cf. Major 1963). The strongly vertically diversified structure of the Ladysmith stand is attributed to a moderate shade-tolerance of Douglas-fir in this climatic and edaphic environment. As a result, a multilayered canopy with scanty crowns has developed in which the lower tree layers are relatively free of shading. In contrast, the slightly vertically diversified structure of the Chilliwack stand is attributed to the shade-intolerance of Douglas-fir in this more humid and edaphically wetter environment. Thus, i t is not surprising that a nearly single-layered canopy with dense crowns has developed in which shading causes a rapid reduction of live crown and mortality. These interpretations agree with the varying shade tolerance of Douglas-fir in different ecosystems discussed earlier. It was suggested that Douglas-fir in humid and perhumid climates and on sites where i t takes up more water than i t requires must not be shaded i f the excess water is to -93-be removed effectively by transpiration (Krajina 1965, Krajina et al . 1982). It is concluded that the tolerance of Douglas-fir to shade has been the main factor determining the structure of the stands studied. Density Number of Stems Approximately 90 percent of the total number of stems/ha, 99 percent of the total basal area and 100 percent of the total volume in the Ladysmith study plots are constituted by Douglas-fir; the corresponding values for the Chilliwack study plots are 69, 94 and 96 percent, repectively. The relatively high percentage of other tree species in the Chilliwack study plots is due to a large number of western hemlock trees in the upper shrub layer and the lower tree layer. However, they contribute only 6% to the total basal area and 4% to the total stand volume. The western hemlock component is considerably uneven-aged and young as it has followed the pattern of secondary succession. If it was included in the following analyses where density is correlated with other stand characteristics, the results might be distorted. It is suggested that this minor and subordinate component has had relatively l i t t le influence on the growth characteristics of the major Douglas-fir component. Therefore some analyses e.g. those involving number of stems/ha, are concerned with Douglas-fir only. The comparison of number of trees per hectare (NT/ha) produced an -94-overwhelming difference between the stands. The values of NT/ha for plots and stands were given in Table 16. Comparing the Douglas-fir component only, the difference between the stand means was found significant at p < 0.01 level; when all trees were considered this difference was found also significant at p < 0.05 level. These results are consistent with respect to the overwhelming role of shade tolerance on the structure of the stands as discussed above. Under relatively dry conditions, considering interaction of climate and hygrotope, both shade-tolerant and shade-intolerant tree species grow in high density stands (Assman 1961). In relation to the shade-tolerance of a species, the shade-intolerant species however, grow in less dense stands than the shade-tolerant species (Mayer 1970). It is concluded that the number of trees in relation to the structure reported for each stand reflects approximately the maximum density level at this developmental stage. Stand Density Indices An important parameter, which determines yield characteristics is the stand density. Quantitative information on stand density is therefore important in relation to tree size and stand yield. Various workers have developed a number of density indices, whereby a given stand is compared to a reference stand, either at crown closure or in maximum stocking conditions. Curtis (1970) reviewed these indices and concluded that they have approximately equal uti l ity. A simple density index was proposed by Reineke (1933). It is based on -95-the relationship between ,the maximum number of trees/ha (Nmax/ha) (this maximum number of stems/ha refers to his database from plantations) and the corresponding mean diameter (meandbh). log Nmax/ha = - 1.605 log(meandbh) + Jk This relationship is believed to be independent of age and site index, the constant is species-speciftc and was computed from Reineke's reference curve for Douglas-fir as 5.02928. This value for J< and the mean diameter (Table 17) were entered into the above equation to solve it for Nmax/ha. The percentage stocking value was derived as the ratio between the actual number of stems/ha (N/ha) and the Nmax/ha. This calculation resulted in a percentage stocking value of 0.74 and 0.78 for the Ladysmith and the Chilliwack stands, respectively, with a relative difference of 5%. Using the diameter of the mean basal area stem which corresponds closely to that of the stem with the mean volume instead to derive the percentage stocking value resulted in an identical percentage stocking value of 0.84 for both stands. The corresponding stand-density index is 500 for both stands. This stand-density index refers to the number of trees per acre at the intersection of a line parallel to the reference curve with the 10-inch ordinate. The reference curve as given by Reineke to derive the density index is valid only for even-aged stands of a single species. Therefore if all species were included to derive the percentage stocking value it should be interpreted with caution. To get an overall percentage stocking value for the two stands however, it was calculated. Applying the diameter of the -96-mean basal area stem resulted in percentage stocking values of 0.87 and 0.95 for the Ladysmith and Chilliwack stands, respectively, this is a difference of 9%. Drew and Flewelling (1979) proposed a relative stand density index, defined as the ratio of actual stand density to the maximum stand density attainable in a stand with the same mean tree volume. This index is independent of age, site quality and other factors. Applying the value of mean tree volume and number of Douglas-fir trees/ha to the diagram of relative density indices for Douglas-fir (cf. Drew and Flewelling, p. 525), the identical value of 0.74 was determined for both stands. The corresponding values, i f all species are included, are 0.80 and 0.84 for the Ladysmith and the Chilliwack stands, respectively. This also implies that both stands are under conditions of imminent competition mortality (cf. Drew and Flewelling, p. 521). The derived relative density indices are of considerable significance in indicating the same relative density, and hence comparability, for the stands studied. This is supportive of the previous conclusion suggesting that the present density levels of the stands approximate the carrying capacity of each site. The implied imminent competition mortality appears to be predicted correctly for shade-intolerant Douglas-fir in the Chilliwack stand. However, the agent for mortality is believed to be the density itself by causing excessive shading. In the Ladysmith stand mortality appears to be an environmental agent, which affects primarily the suppressed tree component having a reduced vigor. To elucidate the influence of density on stand structure the relationship of density to crown class, top height, diameter and volume were examined. -97-Relationship between Density and some Stand Characteristics Crown Class-Density Relationship The dominant and codominant component comprises the crop trees produced in a stand. Thus, the information on the influence of density on this stand component and stand structure could be useful for stand management. Using basal area, the ratio of crown class I and II to all crown classes was calculated for each plot and applied as an independent variable in a regression analysis. The results are given in Figure 35. In general, the basal area of the upper canopy component decreases with increasing stand density. This suggests that a highly competitive environment in high density plots has suppressed the growth of dominant and codominant trees. Under the same density conditions dominant and codominant trees in the Chilliwack stand contribute consistantly more to basal area than those in the Ladysmith stand. This is to be expected in view.of differences in stand structure discussed above. However, the differential rate of this relationship is of considerable significance. The slope of the regression line for the Ladysmith stand is steeper than that for the Chilliwack stand (0.0509 and 0.0164, respective-ly). Therefore, increasing density in the Ladysmith stand does not result in an increase in mortality, but in an increase of the lower canopy compo-nent apparently due to the shade-tolerant nature of Douglas-fir. Growth of the upper canopy component is suppressed, its advantageous position notwithstanding, mainly due to the available water supply being shared by all trees present in the stand. In contrast, an increase in density in the -98-Figure 35. Relationship between the percent of basal area of dominant and codominant trees and density. Chilliwack stand has r e l a t i v e l y l i t t l e influence on the contribution of the upper canopy component to the stand's basal area. High density conditions however, appear to reduce diameter growth of dominant and codominant trees. -99-With respect to the shade-intolerant nature of Douglas-fir, an increase in density results in an increased mortality, hence a poorly differentiated vertical stand structure. The suppressed and in part intermediate stand component is comprised mainly of shade-tolerant western hemlock whose contribution to the stand's basal area is negligible. Effect of Density on Height Braathe (1957), Sjolte-Jorgensen (1967) and Evert (1971,1973) reviewed literature on the effect of initial spacing on height, diameter, basal area and volume growth. Results from spacing experiments in Norway spruce plantations in Europe indicated that differing spacing had l i t t le influence on the height growth of trees (Braathe 1957). Sjolte-Jorgensen (1967) concluded, that for many studies he cited, in experiments with Picea abies, Pinus ssp. and other conifers, the mean height of the stand increased with increasing spacing. The spacing trials for which he showed this influence of spacing on height were generally denser than the ones Braathe referred to. Both authors agree that on dry and poor sites the development of height appears to be retarded by high initial spacing. However, most of the studies refer to mean height, which can be expected to be lower in denser stands with a larger number of small and suppressed trees. They also define mean height in various ways, and therefore results may vary according to the definition applied. Consequently caution is necessary when drawing conclusions about the effect of initial spacing on height growth and site index. Summarizing results of a fity-year Douglas-fir spacing trial on a poor -100-site (site index IV), Reukema (1979) reported that increasing number of stems/unit area had a definite negative impact on the height growth. The resulting site index (height of the 100 largest trees per acre) was found to be 50% higher at the widest spacing than at the dense spacing. Analyzing data from an 11-year-old .Douglas-fir spacing trial in France, Bartoli ^t al_. (1971) did not find any influence of spacing on top height. Results from the 20-year-old Douglas-fir spacing trial in the U.B.C. research forest on a high-quality site .(SI is 55m/age 100) show no difference in total height and height growth for the plots ranging from 0.9 m to 4.60 m in initial spacing (Smith 1977). An increase in height growth after thinning on a poor site (top height of 21 m at age 50) was reported in the Shawnigan Lake Experiment (Barclay et aj_. 1982), whereby trees in the smallest and largest diameter classes had the highest relative height increase. First results of a cooperative 1 evels-of-growing-stock study show no difference in height growth between thinned plots and control plots (Williamson 1976, Berg et aj_. 1979). 21 years of repeated thinning had no effect on height growth in the Voight Creek study (Reukema 1972). From a review of yield tables (1972) Curtis concluded, excluding lodgepole and ponderosa pine, that the effect of stand density on height growth and site index estimates is usually small. In contrast Reukema and Bruce (1977) suggested that a high initial spacing causes a reduction in height growth and consequently affects the site index. It can be expected that additional results of Douglas-fir spacing trials in Germany (Abetz 1971), France (Bartoli et al_. 1971) and the Pacific Northwest (Warrack 1964, Warrack et al_. 1964, Revell 1970, -101-Diggle 1972, Smith 1977) will show a variable reaction of Douglas-fir to init ial density. In summary, no general statement about the influence of density on height can be made. The influence of variables like stand age, site quality and envionmental factors has to be assessed to allow valuable predictions about the interaction of spacing and height growth. Top Height-Density Relationship Comparability of the two stands measured in terms of site index is essential to the study. If the stand density in either of the two stands has influenced height growth, then the site index as a measure of the productivity potential of a site will be affected. For this purpose, the top height-density relationships were examined (Figure 36 and 37). Linear regression lines were derived for both data sets and drawn into the scattergrams. The linear regression for the Ladysmith plots was not signi-ficant and the slope coefficient was close to zero (0.00023). Thus it can be concluded that the density is not correlated with the top height in the Ladysmith stand. The regression line for Chilliwack however, is signif i -cant (p < 0.1), 34 percent of the total variation in the top height is explained by the regression. The trend of the regression line (slope coefficient is 0.00434) indicates that the top height decreases with in-creasing density. When the number of Douglas-fir was used as the indepen-dent variable in another regression analysis, a steeper slope coefficient of 0.00893 was obtained, but the regression analysis was not significant. The variable density could be a result of differing site quality, whereby a better site is correlated with less trees/ha and a poorer site with a higher density. To examine this hypothesis site index was used -102-41 h 40 •c ~ 39 38 37 Ladysmith stand 19 600 700 N - 10 y - 39.0 + 0.000233x f - 0.02 _1_ 800 900 1000 Density (number of trees I ha) 1100 1200 Figure 36. Relationship between top height and density (all species) in the Ladysmith stand. 41 h 40 f 39 38 37 Chilliwack stand 400 MO N - 10 y - 42.3 - 0.00434x r - 0.58 P < 0.1 _l_ •00 700 800 Density (number of trees!ha) 900 1000 Figure 37. Relationship between top height and density (all species) in the Chilliwack stand. -103-instead of height as the dependent variable in another set of regression analyses. The resulting equations, r-values and significance were similar to the ones where height was used. No correlation between site index and density was found for the Ladysmith stand, with either Douglas-fir/ha or total stems/ha as the independent variable. For the Chilliwack stand-, using the total number of stems/ha resulted in a significant (p < 0.1) relationship between this parameter and site index with a slope coefficient of 0.00466. Again this slope was steeper (0.00887) when the number of Douglas-fir/ha was used, but this regression was not significant. These results indicate that when trees on the more productive sites in the Chilliwack stand become tal ler, the smaller trees, left with less light, cannot survive. However, no correlation between site index and density is apparent in the Ladysmith stand. Therefore, i f some trees on better sites become taller, the smaller trees manage to stay alive in a suppressed position - an indication for their relative shade-tolerance. If however, the difference found in top height is not due to a variable site quality and, i f the variability in stand density (stems/ha) as measured in this study reflects differences in initial spacing, then the lower spacing could have resulted in greater heights in the Chilliwack stand. Because of the contrasting relationships found in this study I propose the hypothesis, that the top height of some tree species may be affected under certain conditions by stand density. It is suggested that this could be a function of shade tolerance of a species, which may vary in relation to regional climate and hygrotope (Krajina et ^1_. 1982). In the Ladysmith stand where Douglas-fir is moderately shade-tolerant the dominant and -104-codominant trees have crowns relatively free of shading. Even i f the lower crowns of these trees are shaded, the shading is believed to have a minor effect on height growth and a slow effect on mortality. In the Chilliwack ecosystem however, where Douglas-fir functions as a shade-intolerant tree, increased stand density results in excessive shading of large parts of the live crowns of dominant but mainly codominant trees causing in this case a rapid reduction of live crown, and hence growth. Effect of Density on Diameter A stimulating effect of low initial spacing on the diameter growth rate has been reported in all spacing trials cited by Braathe (1957). Sjolte-Jorgensen (1967) confirms these results for young stands. In compa-rison initial spacing did not influence the diameter increment of a stand between age 29 and age 62. The difference in mean diameter at breast height (dbh) of plots with varying spacing did not increase after age 28 and therefore was due to the differing diameter increment during the first 28 years. Sjolte-Jorgensen concludes for conifers that the poorer the site, the longer it will take until the difference in mean dbh may be considered to remain constant with increasing age. Evert (1971) shows a similar effect of age in a graph (cf. Figure 13), where the mean dbh increment for a 5-year period is plotted over spacing for four stands at different ages. The steepness of slope for this relationship decreases with stand age. For an 11-year-old Douglas-fir stand Bartoli et al_. (1971) reports an increased mean dbh for the plots at wider spacing. In the Wind River spacing trial (Reukema 1970, Reukema 1979) the mean dbh was found to be -105-twice as large at wider spacing as at denser spacing. The analysis of the U.B.C. spacing trial showed the mean dbh to be twice as large for the 4.60 m spacing as for the 0.9 m spacing, and the respective dbh increment eight times as large (Smith 1977). While sampling a wide range of spacing levels — in unthinned plantations in New Zealand, James et aK (1974) reported-that the mean ring width (defined as the mean dbh divided by age) decreased linearly with increasing spacing up to a spacing level of 1000 trees per hectare. For higher densities however,-mean ring width and spacing were not correlated. In various thinning trials the mean dbh and dbh increment were reported to increase for the thinned plots in comparison with the control plots and furthermore to increase with heavier thinning levels (James et a l . 1974, Barclay et aj_. 1982). A considerable part of the increase in mean dbh however, may be due to the removal of trees with diameters smaller than the average dbh. The thinning rules for the "1evels-of-growing-stock" studies (Williamson 1976, Berg et a]_. 1979) try to avoid this "false" effect by prescribing that the quadratic mean dbh of cut trees should approximate that of trees available for cutting. Since crop trees (usually the largest diameter trees!) are excluded from cutting, there will remain some small difference between the mean dbh before and after thinning, which is not due to growth. The reported differences in the mean dbh between the different thinning levels are however much larger than could be attributed to this effect. In the McClearly Experiment Forest thinning trial larger than average trees were removed during the initial thinning. After 15 years the residual trees were not appreciably larger in the thinned stand than in the unthinned stand, in spite of the fact that the 15-year dbh -106-increment of the residual trees in the thinned stand was measured to be 29% greater (Reukema jit aj_. 1973). In the Voight Creek study the removal of trees in all diameter classes did not result in an increase in the mean dbh (Reukema 1972). Miller .et aj_. (1977) did not find an increased dbh — increment in the thinned stands versus the control stands during a five-year observation period. The growth of future crop trees (a specified largest number of trees per unit area) is of particular importance to forest managers. Therefore some studies additionally assess the influence of spacing on the mean dbh of these crop trees. In the spacing trials the mean dbh of the 100 largest trees/ha (Bartoli et al_. 1971) and 250 largest trees/ha (Reukema 1979) was significantly greater. It is interesting to note that in the Wind River spacing trial the difference between the mean diameter growth of wider and denser spaced plots was slightly decreasing in the last 10-year period (Reukema 1979). From some thinning trials an increase in mean dbh for crop trees in the thinned stands in comparison with the control plots is reported (Worthington 1966, Berg et al_. 1979, Barclay et !]_. 1982). Dbh increment of the 100 largest diameter trees per hectare was not significantly greater in thinned stands than in unthinned stands in the Voight Creek study (Reukema 1972). Therefore the mean diameter of these crop trees did not increase for the thinned plots. Some authors note that thinning seems to favor the growth of intermediate and suppressed trees rather than dominant trees (Miller et al.. 1974, Miller et a]_. 1979, Barclay et al_. 1982). In summary the stimulation of diameter increment by low stocking levels is a generally accepted fact. The degree of this impact however, -107-seems to vary. This is graphically shown in Figure 3 of Sjolte-Jorgensen's (1967) report. The mean diameter as the dependent variable is plotted over spacing as the independent variable and regression lines are drawn. The slopes of this regressions differ for trials with the same tree species (Picea abies). This indicates that other factors, possibly age and site quality, initial stocking and kind and degree of thinning may influence this relationship. As a consequence of larger diameter growth per tree the diameter distribution of low stocking plots is shifted to the right. In general the height-diameter regression curves of wider spaced plots tend to l ie above the ones for closer spacing, because at low stocking levels height does not at all or slightly increase while the diameter increment increases considerably. Both effects can be observed in a comparison between the two stands (Figures 30,31 and 34). Di ameter-Densi ty Rel ationshi p To test whether density has a similar effect on the mean diameter, mean diameter/density regressions were computed for each stand (Figure 38 and 39). A clear relationship for both stands emerged: the mean diameter decreases with an increasing number of Douglas-fir/ha. In addition there is a marked difference in the steepness of slope between the two ecosystems. The slope coefficient for the Chilliwack stand is more than five times as steep as that for the Ladysmith stand. This indicates that the Chilliwack stand responds to a change in density with a relatively -108 34 33 32 31 h p 30 29 28 27 600 J_ Ladysmith stand: N - 10 y - 38.5 -O.OIOOx r P - 0.74 < 0.05 700 800 900 Density (number of trees!ha) 1000 1100 Figure 38. Relationships between mean dbh and number of trees/ha of Douglas-fir in the Ladysmith stand. 49 r 48 h Density (number of trees!ha) Figure 39. Relationships between mean dbh and number of trees/ha of Douglas-fir in the Chilliwack stand. -109-larger change in the mean diameter than the Ladysmith stand. If these trends could be confirmed then it would be safe to conclude that the same increase in diameter growth in response to decrease in stand density cannot be expected for the Ladysmith stand. Since the density ranges in the above figures do not overlap, i t must be questioned whether the relationship between mean dbh and density is adequately represented by a linear regression. Therefore, two more regressions including all species were calculated (Figure 40). Both regressions were again significant (p < 0.01) and a threefold difference in steepness of slope remained. Examining the scattergram i t may be possible that the relationship between the two variables is curvilinear, e.g. a hyperbola. But since there are no datapoints between the values of 450 and 550 stems/ha in either stand, this can only be a speculation. If a hyperbolic relationship was established, then the curve for the Chilliwack stand would st i l l l ie a considerable distance above the one for the Ladysmith stand. When all species were included the relative density index for the Chilliwack stand was somewhat above that for the Ladysmith stand. The decrease in slope steepness of the Chilliwack stand from the first regression analysis to the second one is likely due to this higher density. At the same relative density the mean diameter measured for the Chilliwack stand seems to be much greater than can be attributed to the small difference in age. -110-Figure 40. Relationship between mean dbh and number of trees/ha including all species in the Ladysmith and Chilliwack stand. -Ill-Effect of Density on Volume Production Three growth parameters referred to in this chapter have to be clearly distinguished: Total production as the accumulated growth throughout stand age, growth as the increment per unit area for a specific time period and growth percent as the increment per unit of growing stock (residual growing stock) for a given time period. Whenever the term "gross" is useds mortality is included, "net" indicates that mortality is not considered. To test the response of thinning the following ratio maybe derived for any growth parameter: Thinned stand/thinned stand growing stock divided by control stand/control stand growing stock. A ratio of one or below means no response or depression of growth, a ratio greater than one indicates a positive response. The terms "growth" and "increment" are used interchangeably in this chapter. It was previously shown that diameter increment increased with increasing spacing in most studies cited. The number of trees producing however decreases with increasing spacing. The growth per unit area, which is dependent on both, the number of trees and the increment per tree, will be reduced, i f the basal area increment of these fewer trees (or the residual trees in the case of thinning) does not compensate. In general, basal area growth and volume growth will be similar, i f height is not influenced by spacing. In almost all experiments reviewed by Braathe (1957), Sjolte-Jorgensen (1967) and Evert (1971,1973) total basal area and volume production somewhat decreased with increasing spacing. Braathe (1957) explained this by the incomplete utilization of the soil space up to the period of crown -112-closure, which occurs latest for the widest spacing. With increasing age, the difference in total production decreases (Evert 1971). Fries (1978) concluded for Norway spruce that increased spacing at the time of establishment and lowered density of the stand due to random effects will decrease the production; furthermore lowered density caused by selective low thinning has l i t t l e impact on the volume production at least up to a difference in basal area of 40% (a reduction by means of thinnings down to 60% of the maximum basal area). Evert .(1971) summarizes the influences of spacing on basal area and volume growth and growth percent. While growth percentage increased with increasing initial spacing in all studies he reviewed, the basal area and volume growth has sometimes increased and sometimes decreased. Results of the 11-year-old spacing trial in France (Bartoli et a l . 1971) and the 20-year-old U.B.C. trial (Smith 1977) show decreasing volume growth and decreased total volume production with increasing spacing. In contrast, the widest spaced plots at age 53 in the Wind River spacing trial (Reukema 1979) grew at double the rate of the more densely spaced plots, and their total volume production was nearly double as high. This superiority of the wider spacing levels however, is solely due to the considerably better height growth in these plots, while the basal area production is only loosely associated with spacing. Miller et al_. (1979) summarized some recent short-term results of thinning and ferti l izing trials in the Pacific Northwest. The stands ranged from 15 to 68 years in age and from site II to IV in site quality. In all cases but one the volume growth per unit area was reduced. The percentage growth per unit growing stock increased in all cases. When -113-incltiding studies which observe the growth response for an extended period of time, we can summarize: There seems to be a general tendency that growth after thinning is init ial ly reduced (Williamson et al_. 1971, Reukema 1972, Reukema et al_. 1973, Williamson 1976, Berg et al_. 1979, Miller et al_. 1979, Barclay et al_. 1982). Thinning opens the crown canopy and trees are essentially free growing for a short period of time. During these years the growth of the thinned stand seems to be nearly proportional to the reduced thinning stock. After the canopy closes and the space is fully utilized the volume growth of unthinned stands approaches that for thinned stands (Wi 11 iamson et aj_. 1971, Reukema et al_. 1973, Miller et al_. 1979, Barclay et aj_. 1982, Williamson 1982). Length of time for this process depends on the age and growth rate of the stand (site index), and on the amount of growing stock removed during thinning. This is illustrated by the 30-year growth response of a 60-year-old stand on a site IV, as reported by Worthington (1966). In the first 15-year period the lightly thinned stand (31-37% of initial basal area removed) grew 82% of the control stand's volume increment, in the second 15-year period the volume growth was equal for thinned and unthinned stands. In contrast the respective figures for the heavily thinned stand (44-50% of initial basal area removed) are 66% and 82% of the control stand's growth. Comparison of various studies on thinning trials however, indicates that there is additional variability in basal area and volume growth rate which becomes evident when trials with similar age, site index and treat-ment are compared. Thus comparing thinning series in various geographical areas Braathe concludes: The results imply that the nature of the basal area growth differs somewhat with the length of growing season and climate. -114-Basal Area and Volume of the Studied Stands Earlier it was suggested that the initial density in the Chilliwack stand was relatively lower than in the Ladysmith stand. Considering the reviewed studies on the effect of initial spacing and differences in the stocking level, we would expect the Ladysmith stand with a higher number of Oouglas-fir/ha than the Chilliwack stand to have a somewhat higher total basal area and volume production. Since past mortality is unknown however, the total production cannot be assessed. The increment cores showed that the diameter growth for dominant trees was nearly identical for both stands. Therefore it is unlikely that the Ladysmith stand grew under extremely dense conditions which could have resulted in a considerable mortality. Thus the standing basal area and volume (net) are expected to be higher for the stand with the higher number of stems. Testing the basal areas and volumes of the two stands for differences, they were found to be significantly different. Opposite to what was expected the Chilliwack stand exceeded the Ladysmith stand by 18% in basal area and 17% in volume when including all trees (p < 0.01) or by 12% in basal area and 13% in volume when including Douglas-fir only (p < 0.05). To account for the difference in site index, the site index for the Ladysmith stand was adjusted by excluding the three highest site index plots. The resulting average volume is 796 n r . A draft copy of the interim managed stand yield tables for coastal Douglas-fir (Tass-simulation model, Mitchell et _al_. 1982) was used to estimate the volume increment in the Ladysmith stand for the next 6 years. The model predicted for a comparable stand a volume increment of approximately 67 m3/ha for the -115-p e r i o d between age 72 and age 7 8 . Thus a t age 78 t h e mean volume wou ld be 863 nvfyha, r e d u c i n g t h e volume d i f f e r e n c e t o 15% i n f a v o r o f t h e C h i l l i w a c k s t a n d . A c o n s i d e r a b l e v a r i a b i l i t y i n t h e volume p r o d u c t i o n o f s t a n d s w i t h t h e same s i t e i n d e x has been r e p o r t e d by Assmann ( 1 9 6 1 ) , B r a d l e y e t a l . ( 1 9 6 6 ) , K i n g (1970) and Chambers ( 1 9 7 1 ) . Assman d e f i n e d t h e " y i e l d l e v e l " o f a s t a n d as t h e t o t a l c r o p y i e l d a c h i e v e d f o r a g i v e n h e i g h t and showed t h a t t h e y i e l d l e v e l v a r i e d c o n s i d e r a b l y w i t h i n one s i t e i n d e x . T h i s v a r i a b i l i t y i s due t o a d i f f e r i n g maximum b a s a l a r e a p r o d u c t i o n o f s t a n d s . The c a p a b i l i t y o f p r o d u c i n g and m a i n t a i n i n g a c e r t a i n b a s a l a r e a t h r o u g h o u t t h e l i f e t i m e o f a t r e e s p e c i e s i s s i t e - s p e c i f i c . I t i s a l s o an e x p r e s s i o n f o r s i t e q u a l i t y not a c c o u n t e d f o r by t h e s i t e i n d e x . K i n g (1970) s t u d i e d t h e v a r i a b i l i t y i n b a s a l a r e a p r o d u c t i o n o f D o u g l a s - f i r s t a n d s on permanent g rowth and y i e l d p l o t s i n t h e P a c i f i c N o r t h w e s t . He d e v e l o p e d a s e t o f " G r o w i n g S tock I n d e x " c u r v e s t o a c c o u n t f o r t h i s v a r i a b i l i t y . W i th t h e a d d i t i o n a l know ledge o f t h e y i e l d l e v e l o r t h e g r o w i n g s t o c k i n d e x o f a s i t e more a c c u r a t e p r e d i c t i o n s o f f o r e s t p r o d u c t i v i t y and t h e e x p e c t e d y i e l d s a t t h e end o f a r o t a t i o n p e r i o d a r e p o s s i b l e . F r i e s ( 1978 ) showed t h a t b e s i d e t h e s i t e i n d e x , f rom a l l f a c t o r s s t u d i e d v e g e t a t i o n e x p l a i n e d most o f t h e v a r i a b i l i t y i n volume p r o d u c t i o n . The d i f f e r e n c e s i n b a s a l a r e a and volume p r o d u c t i o n o f t h e s t a n d s a r e s m a l l but s i g n i f i c a n t . The ' s h a d e - i n t o l e r a n t ' C h i l l i w a c k s t a n d , r e c e i v i n g an adequa te m o i s t u r e and n u t r i e n t s u p p l y seems t o have a h i g h e r b a s a l a r e a g rowth and t h e r e f o r e h i g h e r volume p r o d u c t i o n t h a n t h e s t a n d w i t h a s u s p e c t e d m o i s t u r e d e f i c i e n c y and r e l a t i v e l y p o o r e r n u t r i e n t s u p p l y . D e c r e a s e d d i a m e t e r g rowth w i t h i n c r e a s e d w a t e r s t r e s s (measured as s o i l -116-water deficit) has been reported by*Zaerr (1970) and Spittlehouse (1982) for studies in the CDF Biogeoclimatic Zone. Since the volume lost through mortality which has occured prior to this study is not known, the mean annual increment can only be computed using the present volume (as measured). It is 11.2 m3/ha for the Ladysmith and 12.7 m3/ha for the Chilliwack stand. The contrasting pattern for the basal area distributions of the two stands was shown earlier (Figure 32 and, 33). When computing tree volumes, the basal area of each tree in the Chilliwack stand is multiplied by a slightly smaller height value than that of a tree with the same basal area in Ladysmith (Figure 34). In consequence the volume distribution shifts slightly to the left for the Chilliwack stand in comparison to that of the Ladysmith stand. The basic shape of the volume distribution however, resembles the corresponding basal area distribution closely for both stands. Volume-Density Relationship Scattergrams were plotted to examine the relationship between volume and density. To account for a possible influence of the site index, this parameter was included in a multiple regression analysis with the volume as the dependent and site index and Douglas-fir/ha as the independent variables. The regression analysis for the Chilliwack stand was not significant, in a stepwise backward selection both variables were excluded. With an R2 value of 0.04 these two variables explain practically no variation of the volume. In contrast the multiple regression analysis for -117-the Ladysmith stand was significant (p < 0.05), site index and density accounted for 66% of the variation in volume, whereby the addition of density accounted for 20%. The average value for the site index was entered into the equation to standardize the effect of site index. With increasing density the volume clearly increased. The resulting range, of predicted volume values was between 770 m^  at a density of 608 Oouglas-fir/ha and 914 m^  at a density of 1008 Douglas-fir/ha. A comparison of the two stands, considering the different trend for the volume-density relationship and the difference in slope of the mean diameter-density relationship, suggests that with increasing density in the Chilliwack stand the growth of a smaller number of dominant Douglas-fir trees is sufficient to compensate for less trees producing. In contrast, in the Ladysmith stand it appears that lower density is correlated with less volume, and the mean diameter does not increase as rapidly as in the Chilliwack stand. A possible explanation for this is given in the results of a study by Black (1980) on the effects of understory removal on the soil surface energy balance in a thinned Douglas-fir stand. The study stand of Black (1980) was younger than the Ladysmith stand, but comparable in all other vegetation and environmental properties. It was reported that after the stand was thinned, salal growth became very vigorous. About one half of the extractable soil moisture was consumed by the salal understory, while the thinned stand density was slightly less than one-half that of the unthinned stand, the diameter growth rate in the thinned stand was only slightly greater than that in the unthinned stand. Consequently the total volume production of the thinned stand was below that of the unthinned -118-stand. Turner (1979) analyzed the relationship beween salal biomass and the biomass of the overstory stand and found that the amount of foliar biomass clearly decreased with increasing salal biomass. A similar explanation could be provided by the results of a study by Lin (1982) in which the effect of 4 different spacing levels on the growth of the remaining trees was tested. The plots in which competing trees were removed but trees smaller than 1.3 m were left showed a significantly larger percentage height growth than the other spacing levels and the control plots. When low initial spacing and precommercial thinning are suggested for management the common assumption is that this will result in the concentration of growth onto trees which will reach merchantable size (Reukema and Bruce 1977). If the above results are valid however, this assumption does not apply, or only apply to a certain degree for stands similar to the Ladysmith stand of this study. In this case fewer trees would not compensate for lower stand density by increases in dimeter growth and some loss in total volume production would be expected. Timber Quality Douglas-fir has been used mainly for lumber and related products. In order to produce high quality products, i t is imperative that logs are clear and free from defects (e.g. excessive number of coarse knots). The conspicuous difference observed between the stands was in the pattern of dead branches on the lower stem. To determine consistency and extent of this pattern, the height of the lowest dead branch was -119-measured. In the Chilliwack stand the mean value was 50 cm (ranging from 33 to 65 cm), whereas that for the Ladysmith stand was 150 cm (ranging from 133 to 180 cm). The means were found statistically different (p < 0.01). Although a one meter difference does not appear to be impressive, one should consider that the lowest dead branch in the Chilliwack stand was usually a part of the whorl of branches extending for a considerable distance downslope. Most trees in this stand did not feature clear lower stems (Figure 41). Figure 41. The downslope oriented pattern of dead branches on the lower stem of a dominant tree in the Chilliwack stand. -120-Such a pattern seems to be characteristic for shade-intolerant species on steep, south facing slopes, perhaps also provoked by a low initial density level (Mitscherlich 1970). In contrast, in the Ladysmith stand the lowest dead branch was usually a single branch or a short stub. However, most stems were clear of branches for several meters. The described branching patterns may have an impact on the quality of lumber produced. -121-SUMMARY The purpose of this study was to examine growth characteristics of two different Douglas-fir ecosystems of the same age and site index. The underlying objective was to test the hypothesis that there are no signif i -cant growth differences between such ecosystems. Two naturally established, unmanaged, late-immature stands of Douglas-fir, each representing a different ecosystem in coastal south-western British Columbia were selected for the study. Both stands were nearly of the same age (72 and 78 years, respectively), identical top height (39.2 m), relative density and similar history; they were different in climatic and edatopic characteristics. The methods used for ecosystem analysis and synthesis (sensu Krajina) included an indicator plant analysis. The ecosystems studied were identified at all levels of the biogeoclimatic ecosystem classification (sensu Krajina). The climate of one ecosystem was drier and warmer mesothermal (Csb - Cfb) whereas that of the other ecosystem was colder and perhumid mesothermal (Cfc). A comparison of edatopes indicated that the former ecosystem was relatively drier and had a poorer nutrient status than the latter ecosystem. Tolerance of Douglas-fir to shade was also found to be different between the ecosystems: Douglas-fir was shade-tolerant in the ecosystem with the Csb - Cfb climate but shade-intolerant in that with the Cfc climate. This difference in shade- tolerance was identified as the major underlying factor responsible for the described disparity in the growth and yield characteristics of the two stands. -122-The stand structure was described using stand maps, stand profiles and distribution patterns of crown classes, diameter and basal area; live crown-total height and height-diameter relationships were also examined. Despite the similar site index and relative density index, there was a disparity in most of the growth characteristics examined. For the • purposes of a full utilization of site productivity and accurate prediction of stand development i t is recommended that a selective, ecosystem-specific approach to stand management and construction of yield tables for Douglas-fir be adopted. This analysis is based on 20 samples in two stands only. General conclusions must therefore be tentative. Further studies involving random sampling of a larger amount of plots per ecosystem should be conducted to assess whether the shown differences and their suggested relationship with the ecological function of Dougals-fir will be consistent. -123-CONCLUSIONS Based on the results of this study the following conclusions have n reached: . Indicator plant analysis was found helpful in quantifying ecological attributes and relationships. It confirmed the identification of hygrotope, trophotope and taxonomic units. 2. Krajina's predictions of biogeocoenoses, ecological function and site indices for Douglas-fir were found to agree with those of this study. 3. Despite an identical density index the two stands had a very different number of stems/ha. Independent of whether this may be due to differing initial regeneration density or due to mortality of trees in the initial stage I suggest that the difference in shade-tolerance of Douglas-fir would have resulted in any circumstance in some difference in number of stems/ha. 4. Considerable structural differences were found between the stands correlated apparently to shade-tolerance of Douglas-fir. The stand in which Douglas-fir was moderately shade-tolerant had a multilayered vertical structure and the associated characteristics resembled those of uneven-aged stands of a shade-tolerant species. The stand in which Douglas-fir was shade-intolerant had a uniform canopy, and the associated characteristics were typical for even-aged stands of a shade-intolerant species. 5. After adjusting for the difference in age and site index, there was a 15% difference in gross volume in favor of the 'shade-intolerant' stand. -124-6. While the top height in the moderately shade-tolerant stand was independent of density, i t seemed to be negatively correlated with density in the other stand. It i s suggested that high density l e v e l s r e s u l t i n excessive shading, which leads to the death of the lower l i v e crown and then possibly to a reduction of height growth. ' 7. If i t i s implied that managed stands in which the density i s regulated by i n i t i a l spacing and thinning behave l i k e the lower density plots in t h i s study, then'stands at lower density in a s i m i l a r ecosystem as the Ladysmith one w i l l have a smaller mean diameter than stands i n conditions l i k e the Chilliwack stand. This makes i t questionable whether a corresponding increase in the mean diameter in the shade-tolerant stand can be expected, i f stand density i s decreased by management. 8. As a result of t h i s d i f f e r e n c e in the diameter-density r e l a t i o n s h i p s contrasting pattern for the density-volume relationship was found. While in the shade-intolerant stand volume and density were not c o r r e l a t e d , in the shade-tolerant stand basal area and volume seemed to increase with increasing density. A small number of samples and unknown i n i t i a l density l e v e l s however, l i m i t the v a l i d i t y of these conclusions. Further studies are needed to v e r i f y these r e l a t i o n s h i p s . Considering the trends described and the ecological relationships involved, in r e l a t i o n to stand management i t appears that the 'shade-i n t o l e r a n t ' ecosystem possesses a s e l f - r e g u l a t i n g mechanism producing the maximum gross volume attainable on a s i t e in a stand with mainly large t r e e s . In contrast, such a mechanism appears to be absent in the -125-moderately 'shade-tolerant' stand. Trees of a small individual size will comprise a significant component of the volume produced in the course of natural development. However, it is uncertain whether lower density levels will result in greater growth of dominant and codominant trees with respect to the limited supply of soil water during the growing season, particularly where there is an effective competitor for soil water. Despite the similar site index and relative density, there was a disparity in most of the growth characteristics examined. The described relationships should be examined in further research. If these studies verify the conclusions I have reached, then it is recommended that a selective, ecosystem-specific approach to stand management and construction of yield tables for Douglas-fir be adopted. Such an approach would assist in accurately predicting stand development as well as utilizing site productivity. -126-LITERATURE CITED Aichinger, E. 1967. Pflanzen als forstliche Standortsanzeiger. Forstliche Bundesversuchsanstalt Wien, Oesterreichischer Agrarverlag, Wien. 367p. Assman, E. 1961. Waldertragskun.de. BLV Verlagsgesel 1 schaft Muenchen -Bonn - Wien. 490p. Assman, F. 1970. The Principles of Forest Yield Study. Pergamon Press, Oxford. 506p. Barclay, H., H. Brix and CR. Layton. 1982. 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University of British Columbia, Faculty of Forestry. 131 p. Krajina, V.J., K. Klinka and S. Kojima. 1983. Ecology of vascular plants in British Columbia. (Manuscript in preparation). -132-Kuramato, R.T. 1965. Plant associations and succession in the vegetation of the sand dunes of Long Beach, Vancouver Island. M. Sc. thesis, Dept. Botany, University of British Columbia. 87p. Landolt, E. 1977. Oekologische Zeigerwerte zur Schweizer Flora. Veroeffentlichungen des Geobotanischen Institutes der Eidg. Techn. Hochschule, Stiftung Rubel, Zuerich. 64. Heft. 45p. Lavkulich, L.M. 1981. Methods Manual. (4th ed.) Pedology Laboratory, Soil Science Dept., University of B.C. 211p. Lesko, G.L. 1961. Ecological study of soils in the Coastal Western Hemlock Zone. Thesis, University of British Columbia, Vancouver, B.C. 114p. Lin, J.Y. 1982. Competition of understory trees in a juvenile spaced stand. Crown Zellerbach Corporation, Forestry Research Division, Interim Rep. No.8. 20p. Long, J.N. and J . Turner. 1975. Aboveground biomass of understory and overstory in an age sequence of four Douglas-fir stands. J . Appl. Ecol.12:179-188 Major, J . 1963. A Climatic index to vascular plant activity. Ecol. 44: 485-498. Major, J . 1969. Historical development of the ecosystem concept. pp. 9-22 in G. H. Van Dyne (ed.) The ecosystem concept in natural resource management. Academic Press, New York & London. Mayer,H. 1970. Waldbau. BLV Verlagsgesel1schaft Muenchen. 482p. McArdle, R.E. Meyer, W.H. and Bruce, D. 1961. The yield of Douglas-fir in the Pacific Northwest. Techn. Bull. No.201 USDA, Washington, D.C. McMinn, R.G. 1957. Soils and forest growth in the Douglas-fir region on Vancouver Island. Paper presented at Agricultural Inst, of Canada, Annual Meeting & Convention. University of British Columbia. McMinn, R.G. 1960. Water relations in the Douglas-fir region on Vancouver Island. Ph. D. Thesis, Dept. Geol. and Bot., University of British Columbia 114p. McMinn, R.G. 1965. Water relations of phytocoenoses in the coastal Douglas-fir zone of British Columbia. Ecol. of Western N.A. 1:35-37. McVean, D.N. and D.A. Ratcliffe. 1962. Plant communities of the Scottish Highlands. A study of Scottish mountain moorland and forest vegetation. Monog. Nature Conservancy, No. 1, London. 445p. Mezera, A. 1952. Rostliny nasich lesu. Nakladatelstvi Brazda. Praha. 502p. -133-Mil1er, R.E. and R.L. Williamson. 1974. Dominant Douglas-fir respond to ferti l izing and thinning in southwest Oregon. USDA For. Serv. Res. Note PNW-216. Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 8p. Miller, R.E. and D.L. Reukema. 1977. Urea ferti l izer increases growth of 20-year-old, thinned Douglas-fir on a poor quality site. USDA For. Serv. Res. Note PNW-291, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 8p. Miller, R.E., Reukema, D.L. and R.L. Williamson. 1979. Reponse to fertilization in thinned and unthinned Douglas-fir stands. vn_ Gessel, S.P., Kennedy, R.M. and W.A. Atkinson (eds.). 1979. Proceedings of forest fertilization conference. Univ. of Washington, College of Forest Resources, Inst, of For. Res. Contr. No. 40. Minore, D. 1979. Comparative autecological characteristics of north-western tree species. A literature refiew. USDA For. Serv. Gen. Tech. Rep. PNW-87, Pac. Northwest For. and Range Exp. Stn., Portland, Oreg. 72p. Mitchell, K. and I.R. Cameron. 1982. Interim managed stand yield tables. Coastal Douglas-fir. Establishing density and juvenile spacing. Draft copy. B.C. Ministry of Forests, Research Branch, Victoria, B.C. 27p. Mitscherlich, G. 1970. Wald, Wachstum und Umwelt. J.D. Sauerlaender Verlag, Frankfurt am Main. Mueller-Dombois, D. 1959. The Douglas-fir forest-associations on Vancouver Island in their initial stages of secondary succession. Ph. D. Thesis, Univ. of British Columbia, Vancouver, B. C. 570p. Mueller-Dombois, D. 1965. Initial stages of secondary succession in the Coastal Douglas-fir and Coastal Western Hemlock Zones. Ecol. of Western N.A. 1:38-41. Ochyra, R. 1981. Kindbergia (Brachytheciaceae, Musci), a new name for Stokesiella (Kindb.) Robins., horn, i11 eg. Lindbergia 8:53-54 Orloci, L. 1961 Forest types of the Coastal Western Hemlock Zone. M.Sc. thesis, Dept. Biol.& Bot., Univ. of B.C. 206p. Orloci, L. 1964. Vegetation and environmental variations in the ecosystems of the Coastal Western Hemlock Zone. Ph.D. Thesis, University of British Columbia. 199p. Orloci, L. 1965. The Coastal Western Hemlock Zone on the southwestern British Columbia mainland. Ecol. of Western North America 1:18-37. PIiva, K. and E. Prusa. 1969. Typologicke podklady pestovani Lesu. Statni zemedelske nakladatelstvi, Praha. 401 p. -134-Radwan, M.A., Crouch, G.L. and Ward, H.S. 1971. Nursery fertilization of Douglas-fir seedlings with different forms of nitrogen. USDA For. Serv. Res. Pap. PNW-113, Pac. Northwest For and Range Exp. Stn. 8p. Reineke, L.H. 1933. Perfecting a stand density index for even-aged forests. Journ. Agric. Res. 46:627-638. Reukema, D.L. 1970. Forty-year development of Douglas-fir stands planted at various spacings. USDA For. Serv. Res. Pap. PNW-100, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. Reukema, D.L. 1972. Twenty-one year development of Douglas-fir stand repeatedly thinned at varying intervals. USDA For. Serv. Res. Pap. PNW-141, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 23p. Reukema, D.L. 1979. Fifty-year development of Douglas-fir stands planted at various spacings. USDA For. Serv. Res. Pap. PNW-253, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 21p. Reukema, D.L. and L.V. Pienaar. 1973. Yields with and without repeated commercial thinnings in a high-site quality Douglas-fir stand. USDA For. Serv. Res. Pap. PNW-155, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 15p. Reukema, D.L. and D. Bruce. 1977. Effects of thinning on yield of Douglas-fir: Concepts and some estimates by simulation. USDA For. Serv. Gen. Techn. Rep. PNW-58j Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 36p. Revell, D.H. 1974. The site limitations of Douglas-fir. pp.173-200 in James, R. N. and E. H. Bunn (eds.). 1978. A review of Douglas-fir in New Zealand. Proceedings of a symposium arranged by the Forest Research Institute, New Zealand For. Serv. Symposium No.15. 455p. Schober, R. 1963. Experiments with Douglas-fir in Europe. FAO World Consultation on Forest Genetics, Stockholm. 415p. Sczawinski, A. 1953. Corticulous and lignicolous plant communities in the forest associations of the Douglas-fir forest on Vancouver Island. Ph.D. Thesis, Dept. of Biology and Botany, University of British Columbia. Sedjo, R.A. 1982. Intensive management options in the Pacific Northwest in comparison with opportunities in other regions and countries. The H.R. MacMillan Lectureship in Forestry, Vancouver, B.C. 20p. Shumway, S.E. 1981. Climate, p.87-91 in Heilman, P.E., Anderson, H.W. and D.M. Baumgartner (eds.). Foresfsoils of the Douglas-fir region. Washington State University, Cooperative Extension Service, Pullman, Washington. 298p. -135-Sjolte - Jorgensen, J . 1967. The influence of spacing on the growth and development of coniferous plantations, pp.43-94 j_n International review of forest research, Vol.2. Academic Pres, New York. Smith, J.H.G. 1977. Results of U.B.C. spacing trials to age 20. Univ. of B.C., Fac. of For., 16p. under review. Spittlehouse, D.L. 1982. Determination of the frequency and intensity of growing season water deficits using a forest water balance model. Paper presented at the Can. Soc. of Soil Sci. meeting at U.B.C, Vancouver, B.C. July 12-14, 1982. 6p. Stanley, A.C and G.M. de Oliveira Castro. 1959. Manual of vegetation analysis. Harper & Brothers, Publishers, New York. 319p. * Trewartha, G.T. 1968. An introduction to climate. 4th edition. McGraw-Hill Book Co., New York 408p. Turner, J . 1979. Effects of fertilization on understory vegetation. pp.168-173 j_n Gessel, S.P., Kennedy R.M. and W.A. Atkinson (eds.). 1979. Proceedings forest fertilization conference. Union Washington. Contr. 40, Seattle, WA, Univ. of Washington, College of For. Res. Van den Driessche, R. 1971. Response of conifer seedlings to nitrate and ammonium sources of nitrogen. Plant and Soil 34: 421-439 Wade, L.K. 1965. Vegetation and history of the Sphagnum bogs of the Tofino area, Vancouver Island. Univ. of B.C., Vancouver, B.C. 125p. Williamson, R.L. 1976. Levels-of-growing-stock study in Douglas-fir. USDA For. Serv. Res. Pap. PNW-210, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. 39p. Williamson, R.L. 1980. Pacific Douglas-fir. pp.106-107 in Eyre, F.H. (ed.). Forest cover types of the United States. S."ATF. Williamson, R.L. 1982. Response to commercial thinning in a 110-year-old Douglas-fir stand. USDA For. Serv. Res. Pap. PNW-296, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. Williamson, R.L. and F.E. Price. 1971. Initial thinning effects in 70-150-year-old Douglas-fir in western Oregon and Washington. USDA For. Serv. Res. Pap. PNW-117, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. Worthington, N.P. 1961. Some observations on yield and early thinning in a Douglas-fir plantation. J . For. 59:331-334 Worthington, N.P. 1966. Response to thinning 60-year-old Douglas-fir. USDA For. Serv. Res. Note PNW-35, Pac. Northwest For. and Range Expt. Stn., Portland, Oregon. -136-Worthington, N.P. and G.R. Staebler. 1961. Commercial thinning of Douglas-fir in the Pacific Northwest. USDA Tech. Bull. 1230. 124p. Zaerr, J.B. 1970 Effects of Plant Moisture Stress on Growth of Douglas-fir trees, pp. 3-6 vn Univ. of B.C. Fac. of For., Bull. No7, Vancouver B.C. -137-APPENDIX I List of Plant Species1 Abies amabilis (Dougl. ex Loud.) Forbes Acer circinatum Pursh Acer glabrum Torr. Acer macrophyllum Pursh Achlys triphylla (Sm.) DC. Actaea rubra (Ait.) Wi11d. Adenocaulon bicolor Hook. Alnus rubra Bong. Aruncus dioicus (Walt.) Fern. Asarum caudatum Lindl. Calypso buibosa (L.) Oakes in Thomps. Chimaphila menziesii (R. Br. ex D. Don) Spreng. Chimaphila umbellata (L.) Barton Circaea alpina L. Claytonia sibirica L. Clintonia uniflora (Schult.) Klinth Corallorhiza maculata Raf. Cornus nuttallii Audub. ex Torr. & Gray Disporum hookeri (Torr.) Nicholson Dryopteris assimilis (Jacq.) Woynar Scheinz & Thell Festuca subuiifiora Scribn. in Macoun Fragaria vesca L. Galium triflorum Michx. Gaultheria shallon Pursh Goodyera oblongifolia Raf. Hieracium albiflorum Hook. Hoiodiscus discolor (Pursh) Maxim. Hylocomium splendens (Hedw.) B.S.G. Ilex aquifolium L. Kindbergia oregana (Sull.) Ochyra Leucolepis menziesii (Hook.) Steere ex L. Koch Lilium columbianum Hanson ex Baker Linnaea borealis L. Listera cordata (L.) R. Br. in Ait. Lonicera ciliosa (Pursh) DC. Nomenclature of the vascular plants follows Krajina e_t a l . (1983), Schofield (1968 ) for mosses and liverworts, and Hale and-Culberson (1970) for lichens. -138-APPENDXX I (Continued) Mahonia nervosa (Pursh) Nutt. Menziesia ferruginea Sm. Mycelis muralis (L.) Dumort Oplopanax horridus (Sm.) Miq. Orthilia secunda (L.) House Osmorhiza chilensis Hook. & Am. Pinus monticoia Dougl. ex D. Don in Lamb. Plagiomnium insigne (Mitt.) Koponen Plagiothecium undulatum (Hedw.) B.S.G. Platanthera obtusata (Banks ex Pursh) Lindl. Polystichum munitum (Kaulf.) Presl Pseudotsuga menziesii (Mirb.) Franco Pteridium aquilinum (L.) Kuhn in Decken Pyrola asarifolia Michx. Pyrola pieta Sm. in Rees Ranunculus uncinatus D. Don in G. Don. Rhytidiadelphus loreus (Hedw.) Warnst. Rhytidiadelphus triquetrus (Hedw.) Warnst. Rhytidiopsis robusta (Hedw.) Broth. Ribes lacustre (Pers.) Poir. Rosa gymnocarpa Nutt. in Torr. & Gray Rubus parviflorus Nutt. Rubus spectabilis Pursh Rubus ursinus Cham. & Schlecht. Smilacina racemosa (L.) Desf. Smilacina stellata (L.) Desf. Spiraea betulifolia Pall. Streptopus amplexifolius (L.) DC. Symphoricarpos albus (L.) Blake Taxus brevifolia Nutt. Thuja plicata Donn ex D. Don in Lamb. Tiarella laciniata Hook. Tiarella trifoliata L. Tolmiea menziesii (Pursh) Torr. & Gray Trachybryum megaptilum (Sull.) Robins. Trientalis l a t i f o l i a Hook. Trillium ovatum Pursh Tsuga heterophylla (Raf.) Sarg. Vaccinium parvifolium Sm. in Rees Viola orbiculata Geyer ex Hook. Viola sempervirens Greene -139 -APPENDIX II Description of the Pedons Sampled Plot no.: 03 Location: Ladysmith Soil taxon: Sandy Orthic Dystric Brunisol with Orthileptomoder Horizon Depth Description (cm) L,F & H 5 - 0 coniferous l i tter (1cm) underlain by a thin (1cm), discontinuous F horizon containing yellow-grayish mycelia; H horizon is mainly granular with commonly occurring worms and arthropods, yellow and white my-celia and abundant charcoal fragments; abrupt, wavy boundary. Bf 0 - 8 dark brown (7.5YR 4/4); sandy loam; moderate, fine, subangular blocky; 5% gravel; very friable; abundant, very fine, fine and medium roots; clear, irregular boundary. Bml 8-43 dark yellowish brown (10YR 3/6); loamy sand; moderate, fine to medium, subangular blocky; 5% gravel; very friable; abundant, very fine, fine and medium roots; many dead root channels; abrupt, wavy boundary. Bm2 43 - 73 dark yellowish brown (10YR 4/6); medium sand; weak, very fine to fine granular; 5% gravel; very friable; few, fine, very fine and medium roots within peds; abrupt, wavy boundary. Bmj 73 - 85 light olive brown (2.5Y 5/4); coarse sand; 60% gravel, 10% cobbles; abrupt, wavy boundary. II C 85 - 100+ light olive brown (2.5Y 5/4); coarse sand; 25% gravel, 30% cobbles, 30% stones; massive when undisturbed, single grain when disturbed; firm, when undisturbed, loose when disturbed, weak cementation by sil ica -possibly an incipient "duric" horizon partly restricting water movement and roots penetration; very few, medium roots. - 1 4 0 -APPENDIX II (Continued) Plot no.: 17 Location: Chilliwack Soil taxon: Fine-Loamy-Skeletal Orthic Humo-Ferric Podzol with K.i nerol eptomoder. Horizon Depth Description (cm) L,Fa & Hi 3 - 0 loose, discontinuous coniferous l i t ter (1cm); underlain by a thin (0.5cm), discontinuous loose, Fa horizon containing very few mycelia but numerous droppings; loose, Hi horizon (2.5cm) is granular, very friable and contains 10% coarse fragments; abrupt, wavy boundary. Bfl 0-15 dark reddish brown (5YR 3/3-4); laom; moderate, fine to medium granular to subangular blocky; 65% shale; very friable; abundant, very fine to fine roots; clear, wavy boundary. Bf2 15 - 38 reddish brown (5YR 4/4); loam; weak, very fine, granular; 75% shale; very friable; abundant, very fine to fine roots; gradual, wavy boundary. Bf3 38 - 56 yellowish red (5YR 4/6); loam; weak, very fine to fine, granular; 75% shale; very friable; plentiful, very fine to medium roots; gradual, wavy boundary. Bf4 56 - 76+ yellowish red (5YR 4/6); loam; weak fine, subangular blocky; 90% shale; very friable; plentiful, very fine to medium roots, in cracks many fungi mycelia; clear, irregular boundary. Appendix I I I , Table 1. Environment-vegetation table for the Ladysmith study plots, part 2. Climax association: Mahonio (nervosae) - Gaultherio (shallonis) - TP & PM Successional association: Hylocomio (splendentis) - Gaultherio (shallonis) - ™ Plot number St. No. Species Al A2 A3 Bl B2 1 Pseudotsuga menziesii Pseudotsuga menziesii Pseudotsuga menziesii Tsuga heterophylla Thuja plicata Gaultheria shallon 7 Mahonia nervosa Vaccinium parvifolium Tsuga heterophylla 8 Rubus ursinus Thuja plicata 9 Rosa gymnocarpa 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 DH 39 40 001 002 003 004 005 006 007 008 009 010 Pteridium aquilinum Linnaea borealis Polystichum munitum Achlys triphylla Adenocaulon bicolor Galium triflorum Tiarella trifoliata Listera cordata Festuca subuliflora Mycelis muralis Tiarella laciniata Trillium ovatum Viola sempervirens Goodyera oblongifolia Chimaphila menziesii Hylocomium splendens Kindbergia oregana Rhytidiadelphus loreus Rhytidiadelphus triquetrus MSS RS SPECIES SIGNIFICANCE AND VIGOR 100.0 5.3 4-5 4 3 5. 2 5. 2 5.2 4.2 5.2 4. 2 5.2 5.3 5.2 100.0 8.5 8-8 8 2 8 2 8 2 8.2 8.2 8.2 8 2 8.2 8.2 8.2 100.0 5.6 5-7 5 1 5 + 5 2 5.1 5.2 5.1 5 2 5.1 7.1 5.2 90.0 4.6 0-6 1 + 4 1 3 2 4.2 4.2 6.2 3 2 4.2 5.2 60.0 2.4 •0-4. 1 2 1 2 4 2 3.2 2 2 2.2 100.0 7.9 3-9 7 2 3 2 8 2 7.2 7.2 6.2 8 3 9.3 9.3 7.2 100.0 5.1 3-6 5 2 3 2 5 2 5.2 6.2 3.2 3 2 3.2 3.2 5.2 100.0 4.4 2-5 4 2 4 2 5 2 4.3 4.2 4.2 3 2 2.1 4.2 3.2 100.0 2.7 1-3 1 1 3 1 2 2 2.1 2.1 3.2 2 2 3.2 1.1 2.2 . 90.0 2.8 0-3 2 1 2 2 2 2 3.2 3.2 3.2 2 1 1.1 3.2 80.0 2.3 0-3 2 1 2 2 3 2 1.1 2.1 2 2 1.1 3.2 60.0 1.9 0-3 1 1 1 2 3 2 2.2 2 J 2.2 100.0 4.3 3-5 3 2 5 2 3 2 3.2 4.2 3.2 4 2 4.2 3.2 4.2 100.0 3.2 1-4 2 2 4 2 3 2 3.2 2.2 3.2 3 2 2.2 1.1 3.2 90.0 3.0 0-3 2 2 3 2 3 2 3.2 2.2 3.2 2 2 2.2 3.2 80.0 4.8 0-5 5 2 4 2 4 2 4.2 5.2 5.2 1 1 5.2 70.0 2.0 0-3 1 1 3 2 1 2 2.2 2.2 1.2 2.2 70.0 1.8 0-2 1 2 2 2 2 2 1.2 2.2 2.2 2.2 60.0 1.4 0-2 1 2 1 2 2.2 1.1 2.2 1.2 60.0 + .8 0-1 1 2 1.2 + .2 1 2 + ! l +.+ 50.0 1.3 0-2 2 2 1 2 2^ 2 1.2 1.2 50.0 + .4 0-1 + 1 1.1 1.2 +!i + 3 40.0 1.7 0-3 1 2 3 2 1.2 3.2 40.0 + .6 0-1 1 2 1 1 1.2 + .2 30.0 +.2 0-1 1 1 1.1 + .1 1 30.0 +.0 0-1 1.2 + .1 + 30.0 + .0 0-+ + + + 1 + .+ 100.0 8.1 3-9 8 .3 8 2 5 2 9.2 8.2 8.2 5 2 9.2 3.2 8.2 100.0 4.6 2-5 4 .2 5 2 4 2 4.2 3.1 5.2 4 2 2.2 3.2 4.2 100.0 2.2 1-3 3 . + 1 .2 2 2 2.2 1.+ 1.2 2 2 1.2 1.2 2.2 70.0 1.6 0-2 1 2 1' 2 2 2 1.2 2.2 2 2 1.2 I I—1 1—' I SPORADIC SPECIES WITH PRESENCE < A3 Bl 2 Alnus rubra 3 Tsuga heterophylla Pseudotsuga menziesii 5 Vaccinium parvifolium 6 Gaultheria shallon B2 10 Pinus monticola 11 honicera ciliosa 12 Acer macrophyllum 13 R u b u s s p e c t a £ > i l i s 14 Taxus brevifolia 30 C o r a l l o r n i z a maculata 31 T i a r e l l a u n i f o l i a t a 32 Circaea alpina 33 Claytonia sibirica 34 Dryopteris assimilis Lonicera ciliosa 35 P y r o l a asarifolia 36 R a n u n c u l u s u n c i n a t u s 20.0 1.0 0-2 2.2 20.0 1.0 0-2 2 J 20.0 1.5 0-3 3.2 20.0 + .6 0-2 2!2 10.0 + .0 0-1 r.3 20.0 +.1 0-1 1.1 20.0 + .0 0-1 1.+ 10.0 + .0 0-1 1.1 10.0 + .0 0-1 1.1 10.0 + .0 0-1 20.0 +.0 0-1 10.0 1.0 0-3 3^2 10.0 +.0 0-1 i!+ 10.0 +.0 0-1 10.0 + .0 0-1 K 2 10.0 + .0 0-1 10.0 + .0 0-1 K 2 10.0 + .0 0-+ + . DH 41 Plagiothecium undulatum 20.0 +.1 0-1 1.2 Appendix I I I , Table 2. Environment-vegetation table for the Chilliwack study plo t s , part 2. Climax association: Hahonio (nervosae) - Polysticho (munitl) - TH & TP Successional association: Hylocomio (splendentis) - Mahonio (nervosae) -(TH)- PM Plot number Oil 012 013 014 015 St. No. Species MSS RS Al A2 A3 BI B2 1 Pseudotsuga menziesii 7 8 9 10 11 12 13 14 22 23 24 25 26 27 28 29 30 Pseudotsuga menziesii Pseudotsuga menziesii Tsuga heterophylla Alnus rubra Tsuga heterophylla Acer circinatum Pseudotsuga menziesii Mahonia nervosa Tsuga heterophylla Acer circinatum Rosa gymnocarpa Rubus ursinus Vaccinium parvifolium Holodiscus discolor Symphoricarpos mollis Ribes lacustre Lqnicera ciliosa Henziesia ferruginea Acer glabrum Polystichum munitum Achlys triphylla Pteridium aquilinum Smilacina Stellata Mycelis muralis Disporum hookeri Galium triflorum Trientalis latifolia Trillium ovatum 30.0 3.3 0-5 4.2 100.0 8.5 7-9 8.2 100.0 5.0 2-6 3.1 70.0 4.1 0-5 5.1 30.0 2.3 0-4 3.1 100.0 5.3 1-7 4.2 60.0 3.6 0-5 2.2 30.0 + .9 0-2 100.0 6.6 5-7 5.2 100.0 3.7 1-5 3.2 100.0 3.5 1-4 2.2 100.0 2.5 1-3 1.1 90.0 2.0 0-2 1.+ 80.0 3.2 0-4 3.2 80.0 3.0 0-3 2.2 70.0 1.4 0-2 1.+ 60.0 1.2 0-2 2.1 30.0 + .9 0-2 30.0 + .9 0-2 1.2 30.0 + .2 0-1 100.0 5.7 4-7 7.2 100.0 4.9 3-5 3.2 100.0 3.2 +-5 + .+ 100.0 3.2 1-4 2.1 100.0 2.3 +-4 + .+ 100.0 2.2 +-3 1.2 100.0 2.2 1-3 2.2 100.0 2.2 1-2 1.1 100.0 1.6 1-2 1.2 5.2 4.2 1.2 4.2 1.1 1.1 2.2 1.2 1.2 6.2 4.2 2.1 2.1 1.1 2.1 2.2 1.2 1.2 5.2 8.2 8.2 8.2 8.2 5.2 4.1 5.2 4.2 4.2 4.1 4.2 4.1 5.2 6.1 5.1 7.1 4.2 6.2 7.2 6.2 6.2 2.2 2.1 2.2 2.1 3.2 3.1 2.2 3.2 2.2 2.1 2.2 2.2 2.+ 1.1 2.1 3.2 3.1 3.2 2.2 3.2 1.2 l!2 1.+ 1.+ 2'.2 1.1 l ' . l 5.2 4.2 2.2 2.2 1.1 + .+ 3.2 2.2 1.2 016 017 018 019 ! AND VIGOR 4.2 8.2 9.2 7.2 8.2 2.1 4.2 6.2 4.2 2.1 4.2 3.2 4^ 2 5.2 4.2 3.1 4.2 3.2 5.3 4.2 l'.2 2.+ 5.2 6.2 7.2 7.2 5.2 1.2 4.2 3.2 3.2 3.2 4.2 4.2 ! 3.2 1.2 2.2 1.+ 2.+ 2.2 1.+ 2.2 3.2 3.2 3'.2 3.2 3.2 3" 2 ! 2.1 1.2 l ! l 1.2 2^ 3 1.1 1.+ 5.2 3.2 2.2 3.2 1.2 2.2 1.2 2.2 1.2 2.3 1.1 7.2 4.2 2.2 3.2 1.1 2.1 1.1 2.2 1.1 6.2 5.2 3.2 3.2 2.2 1.2 1.2 2.2 1.2 4.2 5.2 1.1 2.2 1.2 2.1 1.2 2.2 2.2 4.2 4.2 2.2 1.2 1.2 2.2 1.2 2.2 1.2 020 8.3 4.1 1.1 2.2 1.1 6.1 3.1 1.2 3.2 1.+ 4.2 3.2 1.1 1.2 V.2 + .1 4.2 5.2 5.2 3.2 4.2 3.2 2.2 2.2 1.2 CO DH 31 Viola sempervirens 80 0 2 6 0-3 32 Chimaphila menziesii 80 0 1 3 0-2 1'. 1 33 Goodyera oblongifolia 80 0 1 2 0-1 1.2 34 Aruncus dioicus 70 0 2 1 0-3 + .+ 35 Actaea rubra 70 0 1 3 0-2 36 Smilacina racemosa 70 0 1 2 0-1 K 2 37 Viola orbiculata 60 0 2 0 0-3 2.2 38 Adenocaulon bicolor 60 0 1 3 0-3 39 Linnaea borealis 50 0 + 9 0-1 40 Calypso bulbosa 30 0 + 2 0-1 + .1 41 Claytonia sibirica 30 0 + 2 0-1 1.2 42 Osmorhilo cbilenis 30 0 + 6 0-2 57 Hylocomium splendens 100 0 8 2 6-9 6.2 58 Kindbergia oregana 100 0 5 0 3-7 3.1 59 Rhytidiadelphus t r i g u e t r u s 100 0 3 6 2-4 3.2 60 Rhytidiopsis robusta 100 0 2 4 1-3 1.1 61 Rhytidiadelphus loreus 70 0 1 4 0-2 2.2 2.2 3.2 2.2 2.2 2.2 2.2 3.2 3.2 1.+ 2.2 + .1 1.1 1.2 1.2 +.1 }'.2 1.2 + .2 1.2 K 2 1.2 1.2 1.2 3.2 2!2 2.2 3.2 1.2 1.2 2.2 + .2 1.2 1.2 +ll 2!2 1.2 1.2 1.2 1.2 1.2 1.2 2.2 2!2 3.2 2.2 \'.2 +.1 + .2 1.2 ' + ! l 1.2 3!2 + .2 1^ 2 1.2 1.2 1.2 1.2 1.2 + .2 r.2 1.1 2!2 9.2 8.2 7.2 8.2 7.2 8.2 8.2 8.2 7.2 3.2 4.2 4.2 4.2 7.2 3.2 4.2 4.2 5.2 3.2 4.2 3.2 2.2 3.2 2.2 3.2 3.2 4.2 1.2 2.2 3.2 2.2 2.2 2.2 1.2 1.2 3.2 2.2 1.1 1.2 1.2 1.2 1.2 SPORADIC SPECIES WITH PRESENCE < 20% A2 BI B2 2 A l n u s r u i r a 10. 0 1 0 0-3 3 Tsuga heterophylla 10. 0 1 0 0-3 5 Vaccinium parvifolium 10.0 + 0 0-+ + .2 15 Oplopanax horridus 20 0 + 0 0-1 1 2 16 Acer macrophyllum 20 0 + 0 0-+ 1 17 Abies amabilis 10 0 + 0 0-1 + 18 Cornus nuttallii 10 0 + 0 0-+ 1 19 Ilex aquifolium 10 0 + 0 0-+ + 20 Rubus parviflorus 10 0 + 0 0-+ 21 Spiraea betulifolia 10 0 + 0 0-+ 43 Fragaria vesca 20 0 + 1 0-1 44 Asarum caudatum 20 0 + 0 0-1 45 Festuca subuliflora 20 0 + 0 0-1 i i i + 1 46 Lilium columbianum 20 0 + 0 0-+ +.+ 47 Streptopus amplexifolius 20 0 + 0 0-+ 48 Tiarella trifoliata 20 0 + 0 0-+ + .+ 49 Dryopteris assimilis 10 0 + 2 0-2 2.2 50 Chimaphila umbellata 10 0 + 0 0-+ + 2 51 Clintonia uniflora 10 0 + 0 0-+ + .+ 52 Hieracium albiflorum 10 0 + 0 0-+ 3.2 3.2 1.1 +.1 + .1 + .1 + .1 DH 53 Orthilia secunda 10.0 + 0 0-+ +.1 54 Platanthera obtusata 10.0 + 0 0-+ + .'l 55 Pyrola asarifolia 10.0 + 0 0-+ 56 Pyrola pieta 10.0 + 0 0-+ + .2 Rubus parviflorus 10.0 + 0 0-+ +.+ 62 Plagiothecium undulatum 20.0 + 0 0-1 1.2 63 Trachybryum megaptilum 20.0 + 0 0-1 +.2 64 Plagiomnium insigne \ 10.0 + 0 0-1 K 2 65 - Leucolepis menziesii 10.0 + 0 0-+ - 1 4 6 -APPENDIX IV Summary V e g e t a t i o n T a b l e S t u d y a r e a L a d y s m i t h C h i l l i w a c k Number o f p l o t s 10 10 S p e c i e s P r e s e n c e c l a s s and mean s p e c i e s s i g n i f i c a n c e Abies amabilis I + . 0 Acer circinatum V 3.5 Acer glabrum I I + .2 Acer macrophyllum I + . 0 I + . 0 Achlys triphylla IV 4 . 8 V 4 . 9 Actaea rubra IV 1.3 Adenocaulon bicolor IV 2 . 0 I I I 1.3 Alnus rubra I 1 .0 I I 2 .3 Aruncus dioicus IV 2.1 " Asarum caudatum I + . 0 Calypso bulbosa I I +.2 Chimaphila menziesii I I + . 0 IV 1.3 Chimaphila umbellata I + . 0 Circaea alpina I + . 0 Claytonia sibirica I +.0 I I +.2 Clintonia uniflora I + . 0 Corallorhiza maculata I + . 0 Cornus nuttallii I + . 0 Disporum hookeri V 2 .2 Dryopteris assimilis I + . 0 I + .2 Festuca subuliflora I I I 1.3 I + . 0 Fragaria vesca I +.1 Galium triflorum IV 1.8 V 2 .2 Gaultheria shallon V 7 .9 Goodyera oblongifolia I I + . 0 IV 1.2 Hieracium albiflorum I + . 0 Holodiscus discolor IV 3 .0 Hylocomium splendens V 8.1 V 8 .2 Ilex aquifolium I +.0 Kindbergia oregana V 4 . 6 V 5 .0 Leucolepis menziesii I +.0 Lilium columbianum I +.0 Linnaea borealis V 3.2 I I I + . 9 Listera cordata I I I + . 8 Lonicera ciliosa I +.0 I I +.9 - 1 4 7 -APPENDIX IV ( C o n t i n u e d ) S t udy a r e a Ladysmi t h Chi 11 iwack Number o f p l o t s 10 10 S p e c i e s P r e s e n c e c l a s s ; and mean s p e c i e s s i g n i f i c a n c e Mahonia nervosa V 5.1 V 6 . 6 Menziesia ferruginea I I + . 9 Mycelis muralis I I I + .4 V 2 .3 Oplopanax horridus I + . 0 Orthilia secunda I + . 0 Osmorhiza chilensis I + .6 Pinus monticola I + .1 Plagiomnium insigne I +.1 I + . 0 Plagiothecium undulatum I + . 0 Platanthera obtusata I +.0 Polystichum munitum V 3 .0 V 5.7 Pseudotsuga menziesii V 8 .5 V 8 .5 Pteridium aquilinum V 4 . 3 V 3.2 Pyrola asarifolia I + . 0 I +.0 Pyrola pieta • I + . 0 Ranunculus uncinatus I + . 0 Rhytidiadelphus loreus V 2 .2 IV 1.4 Rhytidiadelphus triquetrus IV 1.6 V 3 .6 Rhytidiopsis robusta V 2 .4 Ribes lacustre I I I 1.2 Rosa gymnocarpa I I I 1.9 V 2 .5 Rubus parviflorus I I + . 0 Rubus spectabilis + . 0 Rubus ursinus V 2 . 8 V 2 . 0 Smilacina racemosa IV 1.2 Smilacina stellata V 3 .2 Spiraea betulifolia I + . 0 Streptopus amplexifolius I + . 0 Symphoricarpos albus IV 1.4 Taxus brevifolia I +.0 Thuja plicata IV 2 .3 Tiarella laciniata I I 1.7 Tiarella trifoliata I I I 1.4 I + . 0 Tolmiea menziesii I 1.0 I Trachybryum megaptilum + . 0 Trientalis l a t i f o l i a V 2 .2 Trillium ovatum I I + .6 V 1.6 Tsuga heterophylla V 2 .7 V 5 .3 Vaccinium parvifolium V 4 . 4 IV 3 .2 Viola orbiculata I I I 2 . 0 Viola sempervirens I I + .2 IV 2 .6 

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