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Vegetation-environment relationships in the tidal marshes of the Fraser River Delta, British Columbia Porter, Glendon Leslie 1982

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VEGETATION-ENVIRONMENT RELATIONSHIPS IN THE TIDAL MARSHES THE FRASER RIVER DELTA, BRITISH COLUMBIA by GLENDON L E S L I E PORTER B . S c , U n i v e r s i t y Of B r i t i s h C o l u m b i a , 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department Of Botany We accept t h i s t h e s i s as conforming to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA October 1982 © Glendon L e s l i e P o r t e r , 1982 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y of B r i t i s h C o l u m b i a , I agree tha t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n for e x t e n s i v e c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s unders tood tha t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s for f i n a n c i a l ga in s h a l l not be a l l o w e d wi thout my w r i t t e n p e r m i s s i o n . Department of Botany The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver , Canada V6T 1W5 Date : October 7, 1982 i i ABSTRACT The l i t e r a t u r e on N o r t h American P a c i f i c Coast t i d a l marshes n o r t h of Mexico i s summarized. V e g e t a t i o n and e n v i r o n m e n t a l d a t a from F r a s e r D e l t a t i d a l marshes a t Ladner Marsh, Brunswick P o i n t , and Boundary Bay were a n a l y z e d u s i n g p r i n c i p a l components a n a l y s i s and r e c i p r o c a l a v e r a g i n g t o i n v e s t i g a t e q u a n t i t a t i v e r e l a t i o n s h i p s between s p e c i e s performance and d i s t r i b u t i o n , and s e l e c t e d e n v i r o n m e n t a l f a c t o r s . These were: s o i l t e x t u r e (percentage of sand, s i l t , and c l a y ) ; s o i l c o n c e n t r a t i o n of n i t r o g e n , p o t a s s i u m , c a l c i u m , magnesium, and sodium; and e l e v a t i o n ( s t a n d a r d i z e d by l o c a l t i d a l r a n g e ) . O r d i n a t i o n s were performed on both the v e g e t a t i o n and the e n v i r o n m e n t a l data s e t s . D i f f e r e n t methods of d a t a s t a n d a r d i z a t i o n (square r o o t t r a n s f o r m a t i o n , n o r m a l i z a t i o n , and c o r r e l a t i o n m a t r i x ) were t e s t e d f o r t h e i r u s e f u l n e s s i n e x p o s i n g e c o l o g i c a l g r a d i e n t s . . N o r m a l i z a t i o n and square r o o t t r a n s f o r m a t i o n of the d a t a were found t o be u s e f u l i n v e g e t a t i o n o r d i n a t i o n ; the c o r r e l a t i o n m a t r i x was n o t . R e c i p r o c a l a v e r a g i n g and p r i n c i p a l components a n a l y s i s gave r e s u l t s of e q u i v a l e n t q u a l i t y w i t h the v e g e t a t i o n d a t a , but p r i n c i p a l components a n a l y s i s was g e n e r a l l y s u p e r i o r t o r e c i p r o c a l a v e r a g i n g i n the e n v i r o n m e n t a l o r d i n a t i o n s . The marshes of the study a r e a s e p a r a t e c o n s p i c u o u s l y i n t o two types on both f l o r i s t i c and e n v i r o n m e n t a l c r i t e r i a : a f r e s h - t o - b r a c k i s h type a t Ladner Marsh and in n o r t h e r n and western Brunswick P o i n t , and a s a l i n e type i n s o u t h e a s t e r n Brunswick P o i n t and a t Boundary Bay . W i t h i n each a r e a , four main s p e c i e s - e n v i r o n m e n t sample groups were i n f o r m a l l y r e c o g n i z e d , dominated r e s p e c t i v e l y by: (1 . ) Carex l y n g b y e i and A g r o s t i s a l b a ; (2 . ) A g r o s t i s a l b a and S c i r p u s m a r i t i m u s ; (3 . ) S c i r p u s amer icanus ; (4 . ) E q u i seturn' f l u v i a t i l e , Sc i rpus  v a l i d u s , A g r o s t i s a l b a , and A l i s m a p l a n t a g o - a q u a t i c a ; (5 . ) A t r i p l e x p a t u l a ; (6 . ) Carex l y n g b y e i and D i s t i c h l i s s p i c a t a ; (7 . ) S a l i c o r n i a v i r g i n i c a and T r i q l o c h i n marit imum; (8 . ) S p e r g u l a r i a c a n a d e n s i s . P a t t e r n s of performance and d i s t r i b u t i o n of important t i d a l marsh s p e c i e s were shown to be r e l a t e d to l e v e l s of the measured e n v i r o n m e n t a l f a c t o r s . TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i i LIST OF FIGURES ix ACKNOWLEDGEMENT x i i i 1. INTRODUCTION 1 2. LITERATURE REVIEW: PACIFIC COAST TIDAL MARSHES 3 2.1 G e n e r a l Overview 3 2.2 C a l i f o r n i a 5 2.3 Oregon 8 2. 4 Washington 11 2.5 A l a s k a 12 2.6 B r i t i s h Columbia 14 3. THE STUDY AREA 24 3 . 1 L o c a t i o n 24 3.2 Format ion And Development Of The F r a s e r D e l t a . . . . 2 4 3.3 Exten t Of T i d a l Marshes In The F r a s e r D e l t a 26 3.4 P h y s i c a l Environment Of The F r a s e r D e l t a T i d a l Marshes 29 3 .4 .1 C l i m a t e 29 3 .4 .2 R i v e r And Mar ine I n f l u e n c e s 30 3 . 4 . 3 T i d e s 33 3 .4 .4 Sed imenta t ion And S u b s t r a t e 35 3.5 T r a n s e c t L o c a t i o n s And S i t e D e s c r i p t i o n s 38 3.5 .1 S e l e c t i o n Of L o c a t i o n s 38 3 . 5 . 2 Ladner Marsh 38 3 . 5 . 3 Brunswick P o i n t 40 3 . 5 . 4 Boundary Bay 42 4. SOME FACTORS AFFECTING SPECIES DISTRIBUTIONS 52 4.1 I n t r o d u c t i o n 52 4.2 T i d e s ...52 4.3 S a l i n i t y 56 4.4 S u b s t r a t e N u t r i e n t Regime 61 4.5 S u b s t r a t e T e x t u r e 65 5. SAMPLING METHODS AND DATA COLLECTION 68 5.1 V e g e t a t i o n 68 5.2 S o i l 69 5.3 L e v e l l i n g Survey 69 6. SOIL ANALYSIS 71 7. DATA ANALYSIS 73 7.1 O r d i n a t i o n Methods . . 73 7.2 Treatment Of The V e g e t a t i o n Data 75 7.3 Treatment Of The E n v i r o n m e n t a l Data . . . 8 6 8. DISCUSSION 100 8.1 Data S t a n d a r d i z a t i o n s 100 8.2 E c o l o g i c a l I n t e r p r e t a t i o n Of O r d i n a t i o n R e s u l t s .105 8 .2 .1 V e g e t a t i o n Data 105 8 .2 .2 E n v i r o n m e n t a l Data 110 8 .2 .3 S p e c i e s - E n v i r o n m e n t Diagrams 116 8.3 P l a n t Communities In The Study Area 118 v i 9. CONCLUSIONS 123 REFERENCES 126 APPENDIX A . NAMES OF SPECIES SAMPLED, WITH AUTHORITIES .140 APPENDIX B. ENVIRONMENTAL DATA 142 v i i LIST OF TABLES I. Environmental data summary for the study area: mean d a i l y temperature, mean da i l y maximum temperature, mean dai l y minimum temperature, mean t o t a l p r e c i p i t a t i o n 30 II. Typical concentrations (mg L" 1) of macronutrient cations plus Na+ and Cl~ in s o i l solution, seawater, and Fraser River water 62 III . F l o r i s t i c table: 64 species in 103 sample plo t s . Group at l e f t , mainly fresh-water influenced; group at r i g h t , mainly salt-water influenced 76 IV. Summary of results of PCA ordination on square roots of species cover data from a l l plots. Eigenvector elements in the range -0.1500 to +0.1500 not shown 106 V. Summary of results of PCA ordination on species cover data from freshwater pl o t s . Eigenvector elements in the range -0.150 to +0.150 not shown ..107 VI. Summary of results of PCA ordination on normalized species cover data from freshwater p l o t s . Eigenvector elements in the range -0.150 to +0.150 not shown 1 08 VII. Summary of results of PCA ordination on species cover data from saltwater p l o t s . Eigenvector v i i i elements in the range -0.150 to +0.150 not shown ..110 V I I I . Summary of resu l t s of PCA ordinat ion on environmental data from freshwater and saltwater p lo t s together 111 IX. Summary of resu l t s of PCA ordinat ion on environmental data from freshwater p lots 112 X. Summary of resu l t s of PCA ordinat ion on environmental data from saltwater p lots 113 X I . Product-moment c o r r e l a t i o n c o e f f i c i e n t s for env i -ronmental var iables (* = p < .05; ** = p < .01) 115 ix LIST OF FIGURES 1. Map of the study area 25 2. Ladner Marsh, v i c i n i t y of Transect J. Foreground: Lythrum s a l i c a r i a , Carex lyngbyei. Background: Populus trichocarpa. Right: Scirpus validus 39 3. Brunswick Point North, v i c i n i t y of Transect A. Carex  lyngbyei is dominant. Conspicuous inflorescences: Lythrum s a l i c a r i a (magenta); Sium suave (white) 43 4. Brunswick Point South, v i c i n i t y of Transect A. Triglochin mar i t imum forms isol a t e d clumps at marsh edge; clumps coalesce into continuous stand (right background) 44 5. Brunswick Point South, Transect B. Scene in late winter 45 6. A e r i a l photograph of Brunswick Point, showing c i r c u l a r patterning of marsh vegetation. Clumps are mainly Carex lyngbyei and Scirpus maritimus 46 7. Boundary Bay East, Transect E. Mixed grasses in foreground; Carex lynqbyei (yellow-green) in mid-portion of transect; Sali c o r n i a v i r g i n i c a , T riglochin mar itimum, Plantago maritima at far end of transect (dark green) 47 8. Boundary Bay East. Triglochin mar itimum and X S a l i c o r n i a v i r q i n i c a , with patches of filamentous green and blue-green algae. Black reducing mud i s covered by brownish diatom mat 49 9. Boundary Bay West, v i c i n i t y of Transect H. Atriplex  patula dominates the driftwood zone in foreground. Farther out, S a l i c o r n i a v i r q i n i c a i s infested by yellowish Cuscuta salina 50 10. Boundary Bay West. Grindelia i n t e g r i f o l i a flowers amid the driftwood 51 11. PCA ordination of samples using species cover data from freshwater plot group 78 12. PCA ordination of samples using species cover data from saltwater plot group 79 13. PCA ordination of samples using square roots of species cover data from freshwater plot group 80 14. PCA ordination of samples using square roots of species cover data from saltwater plot group 81 15. PCA ordination of samples using square r.oots of species cover data from a l l plots (freshwater group, Transects A, D, J; saltwater group, Transects B, C, E, F, G, H) 82 16. PCA ordination of samples using normalized species cover data from freshwater plot group 84 17. PCA ordination of samples using normalized species cover data from saltwater plot group 85 18. RA ordination of species and samples using species cover data from freshwater plot group 87 19. PCA ordination of samples using environmental data from freshwater (Transects A, D, J) and saltwater (Transects C, G, H) plot groups 91 20. PCA ordination of samples using environmental data from freshwater plots 92 21. PCA ordination of samples using environmental data from, saltwater plots 93 22. Plot of cover class codes of Agrostis alba on the ordination of environmental data from freshwater plo t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 94 23. Plot of cover class codes of Scirpus americanus on the ordination of environmental data from freshwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 95 24. Plot of cover class codes of Carex lyngbyei on the ordination of environmental data from freshwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 96 25. Plot of cover class codes of Salico r n i a v i r g i n i c a on the ordination of environmental data from saltwater plo t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 97 26. Plot of cover class codes of D i s t i c h l i s spicata on the ordination of environmental data from saltwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 98 P l o t of cover c l a s s codes of T r i g l o c h i n maritimum on the o r d i n a t i o n of environmental data from s a l t w a t e r p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent ACKNOWLEDGEMENT Many individuals have helped me with t h i s project, and I thank them a l l . Some I want to single out for special mention. Anna Scagel was my much-appreciated f i e l d a ssistant, and Andy Mackinnon aided me with the s o i l analysis. Marshall Cant and Ted Wickman brought their technical competence to the job of surveying the sample plots. Alard Ages of the Ins t i t u t e of Ocean Sciences gave valuable assistance with the t i d a l data. Dr. L.M. Lavkulich generously made available his laboratory f a c i l i t i e s in the U.B.C. S o i l Science Department, where Val Miles supplied very helpful technical assistance. I am indebted to the members of my M.Sc. advisory committee, Drs. G.E. Bradfield, W.B. Schofield, and J.R. Maze, for their helpfulness in many ways; and p a r t i c u l a r l y to Dr. Bradfield, my thesis supervisor, for his assistance, advice, in s t r u c t i o n , understanding, and patience. My parents have been very supportive throughout, for which I am especially g r a t e f u l . This study was supported by a grant from the Natural Sciences and Engineering Research Council of Canada. 1 1. INTRODUCTION Tida l marsh ecosystems, belonging as they do neither e n t i r e l y to the t e r r e s t r i a l environment nor to the marine, yet overlapping the fro n t i e r s of both, have long been a source of interest to ecologists -- even as man's ambition has led to the diking, draining, c u l t i v a t i n g , or f i l l i n g of coastal marshlands everywhere. Fortunately, the interactive relationships between i n d u s t r i a l a c t i v i t i e s and natural ecosystems have been the object in recent years of some c r i t i c a l examination, with the result that i t i s now possible to appreciate marshlands as an economic resource, and ecological considerations are no longer ignored in economic and p o l i t i c a l decision making. There i s hope, therefore, that remaining estuarine marshes w i l l be valued as important l i v i n g systems, rather than being treated as useless wastelands. The t i d a l marshlands of the Fraser estuary, as l o c a l hunters and na t u r a l i s t s have long known, are p r i n c i p a l nesting and feeding areas for migratory waterfowl; 1 recent research demonstrates their importance to the f i s h e r i e s resource 2 as well. Not the least importance of these marshlands, however, 1 Burgess 1970, Burton 1977, Campbell et a l . 1972, Habitat Work Group 1978, Hoos & Packman 1974, Leach 1972, Vermeer & Levings 1977. 2 Dorcey et a l . 1978, Dunford 1975, Levy & Northcote 1981, Levy et a l . 1979, V a l i e l a & K i s t r i t z 1980. 2 i s their value as wilderness. Here are vast areas very near the c i t y , teeming with b i r d l i f e and vibrant with f l o r a l splendor, in which the anxieties of a c i v i l i z e d existence seem to recede l i k e the f a l l i n g t i d e . The present study i s concerned with the elucidation of vegetation-environment relationships in the Fraser Delta. The objectives may be summarized as follows: ( 1 . ) To describe and compare the vegetation of three Fraser Delta t i d a l marshes; (2.) To relate performance and d i s t r i b u t i o n of vascular plant species to measured environmental variables; (3.) To assess the e f f e c t s of d i f f e r e n t types of data standardization in exposing ecological gradients, using p r i n c i p a l components analysis and reciprocal averaging. It i s hoped that any increased understanding of t i d a l marsh systems that may result from this study w i l l be helpful to researchers and managers concerned with t i d a l marsh establishment and r e h a b i l i t a t i o n . 3 2. LITERATURE REVIEW: PACIFIC COAST TIDAL MARSHES 2.1 General Overview The l i t e r a t u r e on t i d a l marsh ecosystems and their vegetation i s voluminous, and cannot be dealt with here in i t s enti r e t y . This review i s therefore r e s t r i c t e d geographically to the P a c i f i c Coast of Canada and the United States. For comprehensive, global treatments of s a l t marsh, t i d a l marsh, and other coastal vegetation, the reader i s referred to Chapman (1960, 1974, 1976, 1977) and Ranwell (1972). The area being reviewed i s mountainous for much of i t s extent, with a generally narrow continental shelf; the shoreline i s .usually steep-sloped and marked by rocky headlands. From Puget Sound north, the coast i s deeply dissected into fiords and archipelagos, and has been subjected to rather recent - g l a c i a l erosion and subsequent i s o s t a t i c u p l i f t (Mathews et a l . 1970). Such conditions do not favour coastal marsh development, with the result that our marshes tend to be quite small, young (Macdonald & Barbour 1974, Jefferson 1974), and isolated — commonly r e s t r i c t e d to small bays, estuaries and rive r mouths (Macdonald 1977a). The beach and salt marsh vegetation of the North American P a c i f i c coast between Point Barrow, Alaska and Cabo San Lucas, Baja C a l i f o r n i a was surveyed by Macdonald & Barbour (1974). 4 For the same area, Macdonald (1977a) summarized the knowledge to that date of s a l t marsh and mangal vegetation, and proposed a tentative phytogeographical c l a s s i f i c a t i o n of P a c i f i c Coast s a l t marshes, based on regional f l o r a s , into five major groups: a r c t i c , subarctic, temperate, dry mediterranean, and a r i d . These groups correspond roughly to: northern and western Alaska; southern and southeastern Alaska and the Queen Charlotte Islands; B r i t i s h Columbia, Washington, Oregon and northern C a l i f o r n i a ; southern C a l i f o r n i a ; and Baja C a l i f o r n i a , respectively. A numerical analysis of data from theoret i c a l sample si t e s (using "expected" species l i s t s ) broadly supported these groupings, but indicated a major break into northern and southern d i v i s i o n s at about 51 degrees north l a t i t u d e . The scheme thus assigns Fraser Delta marshes to the southern group. (It would be interesting to redo the analysis now, using data from actual sample locations.) Some directions in current marsh research are indicated in a compilation of abstracts 1 from papers delivered at the Sixth Biennial International Estuarine Research Conference, published in Estuaries, v o l . 4, 1981. In general, the published l i t e r a t u r e on t i d a l marsh vegetation in the review area is rather sparse. The marshes of C a l i f o r n i a and Alaska are the best-documented. Marshes of 1 e s p e c i a l l y E i l e r s 1981, Frenkel 1981, Mahall 1981, M i t c h e l l 1981, Oliver & R e i l l y 1981, Onuf 1981, Wolf & Fucik 1981, Zedler 1981. 5 the Oregon, Washington, and B r i t i s h Columbia coasts are described mainly in unpublished theses and government reports (frequently quite obscure ones). In the remainder of t h i s review, the l i t e r a t u r e i s surveyed geographically: C a l i f o r n i a , Oregon, Washington, Alaska, and B r i t i s h Columbia. 2.2 C a l i f o r n i a The f i r s t major published ecological investigation of t i d a l marsh vegetation in C a l i f o r n i a seems to be that of Purer (1942), who studied twelve coastal salt marshes in San Diego County, in the southern part of the state. She described at length the ecology and anatomy of the nine p r i n c i p a l vascular species in her study area. The marshes of Newport Bay, also in southern C a l i f o r n i a , were described by Stevenson (1954), Stevenson & Emery (1958), and Vogl (1966). Stevenson & Emery (1958) recognized fiv e plant communities in the marsh proper -- the Spartinetum, the Salicornietum, the Suaedetum, the Monanthochloetum, and the Distichlidetum -- and related the community zonation to t i d a l immersion and s o i l factors. Vogl (1966) sampled quantit a t i v e l y for frequency and cover, and found that the marsh could be separated into three zones: the lower zone dominated by Spart ina f o l i o s a , the middle one by Bat i s  maritima and Salic o r n i a v i r g i n i c a , and the upper one by S a l i c o r n i a v i r g i n i c a and Monanthochloe l i t t o r a l i s . He found 6 that the zones did not have discrete boundaries, but that f l o r i s t i c composition gradually changed along environmental gradients, consistent with the continuum concept sensu Curtis & Mcintosh (1951). Zedler (1977) investigated the vegetation of the Tijuana Estuary s a l t marsh, at the southern end of the C a l i f o r n i a coast, in r e l a t i o n to measured environmental factors over a one-metre elevation gradient. She found that dominance of vascular plants changed gradually with elevation; rigorous data analysis did not support the concept of i n t e r t i d a l zonation. She also studied species interactions and the role of competition in determining species d i s t r i b u t i o n s . Further north, Cooper (1926) provided a brief early description of the marshes near Palo Alto in San Francisco Bay. Also in the Palo Alto area, Hinde (1954) i d e n t i f i e d three major vegetation associations, describing them and their dominant species (Salicornia ambigua, D i s t i c h l i s spicata, and Spartina leiantha) in terms of their v e r t i c a l d i s t r i b u t i o n with respect to tide l e v e l s . The s a l t marsh at Bodega Head, north of San Francisco, was described by Barbour et a l . (1973), reporting on a study by Hamner (unpublished?), who sampled species cover along elevational transects. In a series of three papers, Mahall & Park (1976a, b, c) described the ecotone between Spart ina f o l i o s a and S a l i c o r n i a 7 v i r g i n i c a , corresponding to the le v e l of mean high water, in two marshes with d i f f e r e n t topographical c h a r a c t e r i s t i c s in northern San Francisco Bay. Their findings indicated: (1.) productivity of both species i s low at the ecotone, with frequent open spaces, suggesting that the boundary results not from competition, but from poor environmental conditions there for both species; (2.) Sa l i c o r n i a occupies a habitat having considerably higher s o i l s a l i n i t y than that of Spartina during the growing season; (3.) Spartina i s less tolerant than S a l i c o r n i a of rapid s a l i n i t y changes, and much less tolerant of higher root medium s a l i n i t i e s ; (4.) s o i l aeration is not an important factor a f f e c t i n g the d i s t r i b u t i o n s of the two species about the ecotone; (5.)• i n h i b i t i o n of growth resulting from t i d a l immersion may be an important factor checking the seaward advance of S a l i c o r n i a . Some recent Ph.D. dissertations in C a l i f o r n i a have dealt with t i d a l marsh vegetation not from the point of view of community composition or ecological gradients, but rather in terms of energy budgets, chemistry, and nutrient c y c l i n g . Felton (1978) examined microclimatic conditions in a San Francisco Bay salt marsh in order to determine the detailed nature of the radiational and energy exchanges occurring in the marsh, and the extent to which vegetation differences can aff e c t the marsh microclimate. Winfield (1980) studied three functional aspects of a salt marsh-estuarine ecosystem in the Tijuana Estuary: primary productivity of the s a l t marsh vascular plants, organic carbon cycle, and inorganic nitrogen 8 cycle. Newby (1980) investigated the levels of f i f t e e n mineral nutrients and elements in tissues of Spart ina f o l i o s a and S a l i c o r n i a v i r g i n i c a with respect to the species d i s t r i b u t i o n s in a marsh in Humboldt Bay. She found that phosphorus correlated best with percent cover of the two species, and that nitrogen, sodium, calcium, and iron correlated only weakly. Macdonald (1977b) compiled a comprehensive and thorough summary of what was known to that date of the plant ecology of C a l i f o r n i a coastal salt marshes. 2.3 Oregon the e a r l i e s t published study of t i d a l marsh vegetation in Oregon -- and probably anywhere on the P a c i f i c Coast — seems to be the paper by House (1914), who described the marshes of the Coos Bay region. The p r i n c i p a l references, however, for Oregon t i d a l marsh vegetation are the unpublished Ph.D. dis s e r t a t i o n s of Jefferson (1975) and E i l e r s (1975). Jefferson (1975) surveyed the vegetation of 19 Oregon t i d a l marshes with the objectives of determining and describing the marsh communities, determining successional relationships, and quantifying the relationships of s a l i n i t y and t i d a l inundation to marsh species d i s t r i b u t i o n s . She determined previous plant communities at selected 9 s i t e s by examination of p a r t i a l l y decomposed plant material in the s o i l , enabling the construction of detailed successional diagrams. She found that the inferred successional sequences corresponded closely with the exi s t i n g zonation sequences. She obtained a time frame for marsh development by varve counting and radiocarbon dating (yielding dates of approximately 410 and 770 years for mature high marshes). Jefferson's approach to the vegetation was phytosociological, and she presented association tables for six marsh types comprising 29 discrete communities. She f e l t that the characterization of vegetation in terms of communities rather than continua was warranted by the existence of environmental d i s c o n t i n u i t i e s which precluded any manifestation of continuous gradients, leading rather to the formation of homogeneous stands with d i s t i n c t boundaries. (Nonetheless, her plots of species d i s t r i b u t i o n s along transects usually suggest species d i s t r i b u t e d independently of one another along continua.) E i l e r s (1975) described the marshes at Nehalem Bay, in northern Oregon, by considering the continuous v a r i a t i o n of vegetation along environmental gradients and by assessing community structure, together with an estimate of net primary productivity. He plotted species d i s t r i b u t i o n s along the elevational gradient for May, July, and September, using species dry weight as the index of plant performance. He i d e n t i f i e d communities, partly with the aid of a reference-10 stand ordination procedure; these communities were found to correspond cl o s e l y with major signature types recognized on colour and colour infra-red a e r i a l photographs, permitting the construction of a phytosociological map of the marsh. E i l e r s found that plant species d i s t r i b u t i o n s , species d i v e r s i t y , community location, seasonal development, net a e r i a l production, and amount of net a e r i a l production exported were a l l c l o s e l y related to elevation and associated t i d a l factors. Vascular plant primary production in six marshes in Coos Bay, on the central coast, was investigated by Hoffnagle (1980), who calculated productivity values ranging from 400 g nr 2 year" 1 (in disturbed marshes) to 1200 g n r 2 y e a r - 1 (in Sc irpus validus marshes). He found A p r i l root standing crop values on the order of 20 000 g n r 2 . Two recent studies have dealt with marsh establishment or restoration. McVay et a l . (1980) seeded and transplanted Deschampsia cespitosa and Carex obnupta on sandy dredge material in an i n t e r t i d a l location in the Columbia River estuary, under d i f f e r e n t f e r t i l i z a t i o n regimes and at d i f f e r e n t t i d a l heights. M i t c h e l l (1982) studied salt marsh reestablishment following dike breaching in the Salmon River estuary. 11 2.4 Washington The marshes of Grays Harbour, on Washington's P a c i f i c Coast, were described by Messmer et a l . (unpublished), using a c l a s s i f i c a t i o n system adapted from Jefferson (1975). They i d e n t i f i e d thirteen communities within seven marsh types, and presented graphs of species percent cover along an elevational gradient, indicating continuum-type d i s t r i b u t i o n s . (Rarely in the review area has a vegetation description system developed by one author been applied elsewhere by another, as was done here -- with the result that direct comparison of marshes described by different investigators is often d i f f i c u l t . ) The major published studies of Washington t i d a l marshes are those of Burg, Rosenberg & Tripp (1976), D i s r a e l i & Fonda (1979), and Burg, Tripp & Rosenberg (1980). D i s r a e l i & Fonda (1979) examined a brackish marsh in Bellingham Bay, north of Puget Sound, using a gradient analysis approach. They recorded species cover, frequency, and biomass estimates; measured water table depth, s a l i n i t y , and s o i l moisture; and determined s o i l texture. From elevation measurements and t i d a l data they calculated t i d a l submergence periods. Their results indicated that plant species d i s t r i b u t i o n s were related to a l l the environmental factors measured except s a l i n i t y (which was quite low). They noted a c r i t i c a l tide l e v e l at 274 cm above mean lower low water. Below this l e v e l , the marsh had over 70 submergence 12 days per year, had sandy, poorly drained s o i l s , and was dominated by Scirpus americanus; above 274 cm, the marsh had fewer than 50 submergence days per year, had s i l t i e r , better-drained s o i l s , and was dominated by Carex lyngbyei. (Notwithstanding t h i s apparent ecotone, their plot of species importance against elevation seems to indicate a continuum-type d i s t r i b u t i o n of species.) Burg, Rosenberg & Tripp (1976) and Burg, Tripp & Rosenberg (1980) studied the Nisqually marsh at the southern end of Puget Sound. They recorded species cover values and analyzed the data by means of a computer-programmed version of the polar ordination method of Bray & Curtis (1957). From f i e l d observation and ordination analysis, they recognized twelve plant associations, and prepared a detailed vegetation map of the delta showing the extent of each association. They obtained production estimates for eight of the associations. 2.5 Alaska A general description of the P a c i f i c Coast marshes of Alaska was provided by Crow (1977), who noted that out of hundreds of marshes in the region, few have been studied. The e a r l i e s t treatment of Alaskan t i d a l marshes seems to be that of Cooper (1931), who described the colonization of mudflats following recent g l a c i a l retreat at Glacier Bay. 13 P u c c i n e l l i a pumila was the primary c o l o n i s t , with Glaux  maritima appearing at s l i g h t l y higher elevations. Further up came a community dominated by Plantaqo maritima, Hordeum  brachyantherum, and T r i g l o c h i n maritimum. There was a meadow zone between the marsh proper and the forest, dominated by Elymus arenarius. Hanson (1951) i d e n t i f i e d and described marsh communities and their zonation sequences at s i t e s in Knik Arm and Kachemak Bay in south-central Alaska. Another Kachemak Bay marsh was described by Crow & Koppen (1977), who i d e n t i f i e d and described nine "community complexes". Net a e r i a l production was measured in each community complex, the highest being 661 g m~2 in the Elymus  mollis - P o t e n t i l l a anserina complex. Detritus removal was found to be close to 100%. A l i s t of the diatom f l o r a was included in the report. Crow (1968, 1971) described the vegetation of a large marsh complex in the delta of the Copper River, in south-central Alaska, which was u p l i f t e d almost 2 m by the earthquake of 1964. The raised marsh surface i s no longer flooded by even the highest tides, and the s o i l i s being desalinized, with a consequent invasion of what used to be lower marsh habitats by species c h a r a c t e r i s t i c of the higher marsh and upland zones. Stephens & B i l l i n g s (1967) reported a vegetation study of a t i d a l marsh on Chichagof Island in southeastern Alaska. Three major plant communities, quite discrete in appearance, 1 4 were subjectively i d e n t i f i e d , dominated (from lowest elevation to highest) by Carex lyngbyei, Deschampsia atropurpurea, and Elymus m o l l i s . The s o i l s of each community were described pedologically and chemically. The only published study of an Alaskan P a c i f i c Coast t i d a l marsh in which data are analyzed objectively i s that of del Moral & Watson (1978), who investigated an island marsh in the delta of the Stikine River, in the southeastern part of the state. They i d e n t i f i e d eight marsh community types by an agglomerative clustering method; these groupings were supported by discriminant analysis using species as the discriminating variables. The community types (with one exception) were recognizable on a e r i a l photographs and thus were mappable; boundaries drawn between them, however, were sometimes a r b i t r a r y because the types were often found to grade into one another imperceptibly. "While we treat the data as i f they are derived from vegetation consisting of a series of discrete units," say the authors, "such i s not always the case." 2.6 B r i t i s h Columbia The e a r l i e s t published l i t e r a t u r e source on B r i t i s h Columbia t i d a l marsh vegetation i s apparently that of Calder & Taylor (1968), who provided a q u a l i t a t i v e description of the sa l t marsh communities of the Queen Charlotte Islands. (To 15 date i t seems that no other work has been published on the marshes of this f l o r i s t i c a l l y interesting archipelago.) Pojar (1974), working in the Tofino area on the west coast of Vancouver Island, studied the reproductive biology of a s a l t marsh community in r e l a t i o n to community structure and function. The population structure of individual species was characterized by means of an aggregation index. Levels of i n t e r s p e c i f i c association were calculated for d i f f e r e n t quadrat sizes and the results presented in the form of a co n s t e l l a t i o n diagram. Polyploidy l e v e l s , flowering phenology, p o l l i n a t i o n and dispersal ecology, and various community parameters were determined, and the reproductive biology of each species was summarized. During the 1970's, information on t i d a l marsh vegetation was c o l l e c t e d in many locations by a variety of government agencies and private firms, and by several graduate students. Much of this information i s summarized in a series of Environment Canada publications which inventory the environmental knowledge from a l l available sources for B r i t i s h Columbia coastal estuaries. These publications contain species l i s t s , community descriptions, and maps, as available, for t i d a l marshes within the estuaries. The following estuaries have been surveyed so far in th i s series (more volumes are planned): Fraser (Hoos & Packman 1974), Squamish (Hoos & Void 1975), Skeena (Hoos 1975), Cowichan and Chemainus (Bell & Kallman 1976a), Nanaimo (Bell & Kallman 1976b), 16 Kitimat (Bell & Kallman 1976c), Campbell (Bell & Thompson 1977), Courtenay (Morris et a l . 1979), and Somass (Morris & Leaney 1980). The Squamish Delta marsh has been better studied than most. Lim & Levings (1973) recognized and mapped ten vegetation types, i d e n t i f y i n g Carex lynqbyei as the most important species in both geographical extent and standing crop. Levings & Moody (1976) made production measurements in d i f f e r e n t areas of the marsh, finding high values for net above-ground production of Carex: up to 1323 g dry weight m"2 season" 1, with growth rates up to 22.9 g m"2 day" 1 in late June. A recently published management plan for the Squamish Estuary includes a detailed environmental summary (Habitat Work Group 1981). The plant communities of 18 estuarine marshes on the east coast of Vancouver Island and one marsh on the mainland were described and mapped by Kennedy (1982), using a e r i a l photograph interpretation and associated ground truthing. Kennedy found that at higher lev e l s in both brackish and salt marshes, a f l o r i s t i c break occurred at Courtenay, with marshes north of Courtenay dominated more by brackish indicator species, and those south of Courtenay more by saline indicator species. This discontinuity she attributed to higher r a i n f a l l north of Courtenay. On the basis of community composition Kennedy c l a s s i f i e d the estuaries studied into eleven groups, which she believed resulted from the interaction of six 1 7 physical factors: time of maximum discharge, relationship between mean growing season discharge and size of delta, mean annual t o t a l p r e c i p i t a t i o n , r e l a t i v e protection from wind and wave energy, dir e c t i o n and frequency of t i d a l inundation, and substrate p a r t i c l e s i z e . She also determined standing crop and root reserves in monthly samples from eleven communities in f i v e estuaries. The largest t i d a l marsh syst-em in B.C. is found in the delta of the Fraser River, and i t is these marshes that are the most abundantly described. Some general reference works are: the ecological overview of the delta by Becker (1971), the comprehensive summary of published and unpublished sources on the estuarine environment by Hoos & Packman (1974), and the review of estuarine habitat in the context of a management plan by Habitat Work Group (1978). Vegetation studies done in the Fraser Delta area are here grouped for convenience into two categories: those directed towards measurement of productivity, biomass d i s t r i b u t i o n , or nutrient cycling; and those concerned with f l o r i s t i c , compositional, or synecological characterization. In the f i r s t group, Yamanaka (1975) measured primary productivity in the marshes of the Fraser Delta foreshore between Point Grey and Crescent Beach, and mapped the zones of dominance of the major species. He estimated dry matter yiel d s of up to 1819 g n r 2 year" 1, with an average y i e l d of 490 g n r 2 , or 4.9 tonnes ha" 1, per year. (This contrasts with 18 an average lower Fraser Valley hay crop of about 3.8 tonnes ha" 1 (Moody 1978).) Yamanaka found Carex lyngbyei to make the largest contribution to t o t a l standing crop (36%), with Scirpus americanus not far behind (32%). Burton (1977), studying the food resource for wintering snow geese, sampled below-ground biomass of Scirpus ameri-canus , a preferred food source, at various locations frequented by the geese. He then evaluated marsh areas for food producing c a p a b i l i t y on the basis of both rhizome density and crude protein l e v e l . He attempted to f i n d a r e l i a b l e method of estimating rhizome standing crop from objective above-ground parameters, but could not f i n d s i g n i f i c a n t c o r r e l a t i o n s . The Brunswick Point marsh was studied by Moody (1978), who was concerned with primary productivity, decomposition, and s p a t i a l and temporal d i s t r i b u t i o n s of the marsh vegetation. Moody harvested a e r i a l biomass p e r i o d i c a l l y through the growing season, and was able to relate growth rates, standing crops, shoot densities, reproductive shoot numbers and nitrogen contents for the major species to such variables as s a l i n i t y , temperature, elevation, and time of year. L i t t e r bag and laboratory studies indicated that soft, fleshy species such as Triglochin maritimum decomposed the fastest, and Carex lyngbyei decomposed the slowest. Transplantation experiments and h i s t o r i c a l and present observations suggested a successional sequence commencing with 19 Scirpus americanus and S. maritimus. Ogwang (1979) investigated phytomass production and dis p o s i t i o n in two brackish Fraser Delta marshes, at Iona Island and Brunswick Point, and also in a freshwater t i d a l marsh along the P i t t River (a tributary of the Fraser). He harvested a e r i a l vegetation sequentially during the growing season, and extended the sampling over a three-year period. He related variations in peak standing crop between species, s i t e s and years to such variables as climate, water regime, s a l i n i t y , and substrate nutrient status. He found large differences between species in the timing of peak production, which were related to such factors as the presence or absence of overwintered shoots. He found that belowground phytomass comprised a high proportion (up to 85%) of t o t a l phytomass; the proportion varied among species. He i d e n t i f i e d the main di s p o s i t i o n routes for the shoot phytomass as grazing ( f a i r l y unimportant), organic matter accumulation, and detritus export. He assayed the nutrient content of the emergent vegetation, and investigated aspects of nutrient leaching. A series of reports by K i s t r i t z and others has resulted from a program of studies on the Fraser Delta t i d a l marshes conducted by U.B.C.'s Westwater Research Centre. K i s t r i t z (1978) reviewed the l i t e r a t u r e on ecological processes in t i d a l marshes, concentrating on primary production, the role of phytodetritus, estuarine food webs, marsh biogeochemistry, and nitrogen c y c l i n g . K i s t r i t z & Yesaki (1979) and K i s t r i t z , 20 Hall & Yesaki (1983) reported on a study of primary productivity, detritus flux, and nutrient cycl i n g in a r i v e r marsh dominated by Carex lyngbyei. Monthly measurements of shoot growth, density, standing crop, root biomass, and tissue levels of carbon, nitrogen and phosphorus were made. Results indicated an annual net primary production estimate of 634 g ash-free dry weight (AFDW) per m2; net annual detritus production was estimated at 435 g AFDW m~2, of which 62% was exported into the estuary, and the balance buried by sediment. In the second category of studies, the e a r l i e s t detailed f l o r i s t i c description of the Fraser Delta marshes is probably that of Burgess (1970), who studied the vegetation of the delta front t i d a l marshes from Iona Island to Brunswick Point, as part of a study of duck habitat and feeding ecology. Based on a l i n e - i n t e r c e p t frequency sampling method, he described a lower and an upper marsh zone, f l o r i s t i c a l l y d i s t i n c t , divided by a low c l i f f . He mapped the d i s t r i b u t i o n s of the p r i n c i p a l marsh species and calculated seed production indices. He found the most important seed sources for ducks to be Carex  lyngbyei, Scirpus validus and S. americanus. Forbes (1972) conducted a vegetation survey of the foreshore marshes from Point Grey to Crescent Beach, providing subjective community descriptions, species abundance ratings and c h e c k l i s t s , and vegetation maps (not very d e t a i l e d ) . McLaren (1972) provided a similar treatment of the rive r marshes from Deas Island to Westham Island. 21 The salt marsh at Boundary Bay was the object of a study by Parsons (1975), who recognized and mapped six plant communities, r e l a t i n g the vegetation pattern to tide levels and s o i l conductivity. The Tsawwassen s a l t marsh was described by Hillaby & Barrett (1976), who assessed the degree of presence of each species in the marsh, but did not attempt to define or map communities. The most detailed studies of vegetation and environmental relations in Fraser Delta marshes are those recently reported by Hutchinson (1982) and Bradfield & Porter (1982). Hutchinson (1982) examined the brackish marshes along the delta foreshore of Lulu Island with the aim of re l a t i n g vegetation composition to environmental parameters. Species composition of plots was determined by biomass measurement, and plots were grouped by a cluster analysis procedure, from which seven main clusters or vegetation types were recognized. These types were mapped, and their d i s t r i b u t i o n s related s t a t i s t i c a l l y to variation in elevation, s a l i n i t y , and substrate texture. The lowest extent of marsh vegetation corresponded clo s e l y to the l e v e l of mean higher low water (MHLW). The l e v e l of mean lower high water (MLHW) appeared to separate a lower marsh, dominated by Scirpus americanus and Scirpus maritimus, from a higher marsh, dominated by Typha  l a t i f o l i a , Potent i11a p a l u s t r i s , Di st i c h l i s spicata, and Agrostis exarata. Zones dominated by Carex lyngbyei and T r i g l o c h i n mar itimum occurred at about MLHW. The low c l i f f 22 described by Burgess (1970) was found to occur at about th i s l e v e l . Bradfield & Porter (1982) investigated the vegetation structure of a rive r marsh under predominantly freshwater influence. Vegetation data consisting of cover class estimates were subjected to a cluster analysis procedure which permitted the recognition of seven subgroups, referred to as community types, within three main groups, corresponding to subjectively recognizable vegetation zones: a sedge zone in regularly flooded and drained areas, a grass-willow zone along the crests of levees, and a mixed forb zone in areas of poor drainage and high water table. For the seven community types, species mean percent cover and percent frequency were calculated and presented in tabular form, as were various d i v e r s i t y components, including t o t a l number of species found, species density or alpha d i v e r s i t y , beta d i v e r s i t y , and species evenness. The d i s t r i b u t i o n s of the community types were plotted along elevational. transect p r o f i l e s . In addition to being clustered, the plot data were subjected to ordination by means of p r i n c i p a l components analysis (PCA) and reciprocal averaging (RA). Ordination results suggested relationships between trends in compositional variation and p a r t i c u l a r environmental gradients. The p r i n c i p a l ordination axes appeared to be related to substrate drainage and to t o t a l period of inundation, suggesting that these two components of the hydrologic regime operate independently to control vegetation pattern. Elevation above chart datum was not found 23 to be a r e l i a b l e predictor of vegetation. 24 3. THE STUDY AREA 3.1 Location The Fraser Delta i s located on the southeastern shore of the S t r a i t of Georgia, in southwestern B r i t i s h Columbia, and extends from the c i t y of Vancouver southwards to the United States border. Its geographic centre i s at approximately 49° 07' N by 123° 05' W; the locations sampled in t h i s study are a l l within 12 km of that point (Fig. 1). 3.2 Formation and Development of the Fraser Delta Southern Georgia S t r a i t and the adjacent mainland lay buried beneath Pleistocene ice u n t i l about 13 000 years ago (Mathews et a l . 1970). Post-g l a c i a l i s o s t a t i c u p l i f t was e s s e n t i a l l y complete by 8000 years before present, and the shoreline has remained close to i t s present l e v e l during the past 5500 years (ibid.) The delta that exists today began to fan out from a gap in the highlands at what is now New Westminster about 8000 years ago, and now covers an area of about 380 square miles (980 km2), including submerged portions, with an average thickness (in areas where sediment accumulation i s complete) of probably about 380 feet (115 m) (Mathews & Shepard 1962). 25 Figure 1 - Map of the study area 26 The active front of the delta extends some 23 km along i t s western perimeter, between Point Grey and Point Roberts; an inactive front about 13 km long faces southward between Point Roberts and Crescent Beach. Along the western delta front, a very gently inclined i n t e r t i d a l zone extends about 6 km from the dikes almost to the edge of the much steeper delta fore-slope. The equivalent zone along the southern delta front i s about 4 km wide. The Fraser River i s currently depositing about 700 x 10s cubic feet (20 x 106 m3) of loose s i l t y sand and mud annually at the delta front, representing a load of about 21 x 106 tonnes (derived from Mathews & Shepard 1962 p. 1424). A zone of rapid advance occurs in the v i c i n i t y of the mouth of the main channel of the r i v e r ; there are areas, however, where the delta front i s retreating (Luternauer & Murray 1973). The measured rate of advance varies according to the depth below chart datum. A rate of 28 feet (8.5 m) per year at the 300 foot (91.4 m) contour over a 30-year period was determined by Mathews & Shepard (1962); the rate was much lower at shallower depths. 3.3 Extent of Tidal Marshes in the Fraser Delta The existing t i d a l marshlands of the Fraser Delta are found mainly in three areas: in a broad belt, averaging about 1 km wide, along the western delta foreshore; in a wide, 27 b r a i d e d p o r t i o n of the r i v e r ' s main c h a n n e l , c l o s e to i t s mouth; and in a r a t h e r narrow band, l e s s than 1 km at i t s w i d e s t , a l o n g the n o r t h shore of Boundary Bay. Narrow f r i n g e s of marsh v e g e t a t i o n are found e lsewhere a lon g the main channe l and i t s d i s t r i b u t a r i e s . The main ly a g r i c u l t u r a l and r e s i d e n t i a l d e l t a lands are surrounded by p r o t e c t i v e d i k e s ; the upper l i m i t of marshland i s g e n e r a l l y the base of the d i k e . The lower l i m i t seems to v a r y a c c o r d i n g to water s a l i n i t y : Swinbanks (1979) determined the lower marsh l i m i t a t s e v e r a l l o c a t i o n s from Westham I s l a n d around to Boundary Bay, and c o n c l u d e d that the lower l i m i t of b r a c k i s h marshes l i e s at l e a s t 1.0 to 1.5 m below tha t of s a l t marshes . V a r i a t i o n s i n t i d a l reg ime, however, may account for at l e a s t p a r t of t h i s d i f f e r e n c e . From an examinat ion of a e r i a l photographs , Medley & L u t e r n a u e r (1976) c o n c l u d e d that the marsh edge a l o n g the western d e l t a f r o n t had been g e n e r a l l y s t a b l e over the p r e c e d i n g 25 y e a r s , a l t h o u g h there were some l o c a l advances and r e t r e a t s . One area of a p p a r e n t l y r a p i d growth i s Brunswick P o i n t , where an area of sand f l a t s o c c u p y i n g about 90 ha f i r s t appeared on a e r i a l photographs i n 1948, and was d e n s e l y vege ta ted w i t h S c i r p u s americanus by 1969 (Moody 1978). At Boundary Bay, K e l l e r h a l s & Murray (1962) found ev idence ( i n the form of a s e r i e s of former beach r i d g e s marked by d r i f t w o o d ) tha t the marsh i s advanc ing over the t i d a l f l a t s in the western p a r t of the bay, but r e c e d i n g i n 28 the e a s t e r n p a r t , as i n d i c a t e d by an a c t i v e e r o s i o n a l c l i f f about 0.7 m h i g h . The r a t e of r e c e s s i o n i n t h i s a rea was e s t i m a t e d t o be a t l e a s t 0.75 mi. (1.2 km) over the l a s t 4350 y e a r s . The t o t a l a r e a of the d e l t a t i d a l marshes has been e s t i m a t e d a t 2683 ha, of which the western d e l t a f r o n t marshes account f o r 1664 ha, the Main Arm r i v e r marshes 782 ha, and Boundary Bay 237 ha (Yamanaka 1975, K i s t r i t z 1978). The marshes were more e x t e n s i v e b e f o r e the a r r i v a l of Europeans; d i k i n g of the d e l t a l a n d s f o r f l o o d c o n t r o l and r e c l a m a t i o n , m a i n l y d u r i n g the 1890's, e l i m i n a t e d about 221 ha of s a l t m a r s h and 629 ha of f r e s h w a t e r marsh (Romaine et a l . 1976). Other a c t i v i t i e s c o n t i n u e t o a l t e r the mar s h l a n d s . The c o n s t r u c t i o n , s i n c e the e a r l y 1900's, of s e v e r a l j e t t i e s , t r a i n i n g w a l l s and causeways, c o u p l e d w i t h d r e d g i n g of the r i v e r c h a n n e l s , has m o d i f i e d p a t t e r n s of e r o s i o n , s e d i m e n t a t i o n , and s a l i n i t y d i s t r i b u t i o n . These a c t i v i t i e s have l e d t o marsh growth i n some a r e a s , r e t r e a t i n o t h e r s , and changes i n s p e c i e s c o m p o s i t i o n . Some of the e f f e c t s of t r a i n i n g w a l l s and j e t t i e s i n the F r a s e r E s t u a r y were d e s c r i b e d i n d e t a i l by L e v i n g s (1980) and Tamburi & Hay (1978). Much of the t i d a l marsh a r e a of the F r a s e r D e l t a i s now p r o t e c t e d from development under some form of government r e s e r v e . Some a r e a s , though, . a r e d i r e c t l y t h r e a t e n e d , f o r example by a i r p o r t development. As i n d i c a t e d i n s e c t i o n 3.2, 29 however, the del ta i t s e l f i s growing r a p i d l y , so perhaps the long-term outlook for the marshes i s one of continuing expansion. 3.4 Phys ica l Environment of the Fraser Delta T i d a l Marshes 3.4.1 Climate Summers in the study area are mostly sunny, dry, and warm (seldom hot); winters are d u l l , ra iny , and usual ly quite mi ld . Some major c l i m a t i c var iables are summarized in Table I . 1 The area l i e s within the Csb (mediterranean subhumid) c l i m a t i c type in the c l a s s i f i c a t i o n system of Koeppen (1936). The mediterranean designation is a consequence of the pronounced summer drought; mean temperatures are considerably lower than in the mediterranean-climates of Europe (Hoos & Packman 1974). 1 The data are from a s tat ion about 2 km east of the Brunswick Point marsh. Rose (1975) has pointed out, however, that there are microcl imat ic di f ferences between coasta l wetlands and the adjacent drylands, with the wetlands exh ib i t ing a narrower range of temperatures both d i u r n a l l y and seasonal ly . Daytime maxima are lower as a resul t of evaporation and t r a n s p i r a t i o n , while night-time minima are higher because of the greater heat storage capacity of saturated s o i l . 30 Table I - Environmental data summary for the study area: mean d a i l y temperature, mean dai l y maximum temperature, mean d a i l y minimum temperature, mean t o t a l p r e c i p i t a t i o n dan . Feb Mar Apr May <Jun J u l Aug Sep Oct Nov Dec Year T 2 . 3 4 . 2 5 . 7 8 . 6 11.8 14.6 16.4 16 . 1 13.5 9.6 5.9 4 . 3 9 . 4 Tmax 5 . 2 7.6 9 . 5 12.6 16 . 7 19.2 21.6 2 1.2 18.4 13.6 9. 1 6 . 6 13.4 Tm i n -0.7 0.7 1 . 8 4 . 5 6 . 9 9.9 11.1 11.0 8.6 5 . 7 2 . 7 1 .9 5.3 P 1 15 99 83 52 38 45 24 3 1 50 99 125 142 903 T = mean d a i l y temperature (C) Tmax = mean d a i l y maximum temperature (C) Tmin = mean d a i l y minimum temperature (C) P = mean t o t a l p r e c i p i t a t i o n (mm) (Data s o u r c e : Environment Canada, Atmospheric Environment S e r v i c e , . Vancouver, B.C.; r e c o r d s f o r Ladner Monitor S t a t i o n . ) 3.4.2 River and Marine Influences The interacting and opposing influences of the Fraser River and Georgia S t r a i t produce complex geographical, ele v a t i o n a l , and seasonal variation in the s a l i n i t y regime of di f f e r e n t areas in the delta; t h i s v a r i a t i o n i s the p r i n c i p a l contributor to the very d i f f e r e n t character of the marshes in di f f e r e n t l o c a l i t i e s . The Fraser River drains an area of about 233 000 km2, within which about two-thirds of the pr e c i p i t a t i o n f a l l s in the form of snow (Ages & Woollard 1976). With the melting of the snow pack in spring and summer, the r i v e r ' s discharge ris e s rapidly during May with a pronounced peak, c a l l e d the 31 freshet, in late May or June; discharge remains high through July and August, decreasing to a low in December. Mean da i l y discharges (1912-1956 average at Hope) vary between 600 m 3s" 1 in winter and 8800 m3s~1 in summer; the peak flow recorded was 15 200 m 3s" 1 on May 31, 1948 ( i b i d . ) . Upon entering Georgia S t r a i t , the s i l t y brown river water fans out in a highly v i s i b l e plume over the clear marine water, spreading sometimes to the opposite side of the S t r a i t , 30 km away (Tabata 1972); the plume seldom i f ever enters Boundary Bay (Swinbanks 1979). Since.the fresh riv e r water i s less dense than sea water, i t f l o a t s . A certain amount of mixing takes place at the interface between the outflowing r i v e r water and the sea water beneath, so that the fresh surface water gradually becomes more brackish; in compensation for the entrainment of sea water in the outward-flowing water mass at the surface, salt water below flows upstream. This process gives r i s e to the phenomenon known as the s a l i n i t y wedge. The effect i s pronounced: for example, in a f a i r l y t y p i c a l observation at Sand Heads in August, s a l i n i t y to a depth of 3.1 m was measured as 0.0 parts per thousand (ppt); at 9 m depth, the s a l i n i t y was 25 ppt. The wedge has been observed as far upstream as Annacis Island, 10-15 km upstream from Ladner Marsh, when river discharge i s low (Ages & Woollard 1976). Detailed s a l i n i t y d i s t r i b u t i o n s in the Fraser Estuary were plotted by Ages (1979) from observations made in 1976 and 32 1977. The data i n d i c a t e that s u r f a c e waters i n the lower r i v e r at l e a s t as f a r as Steveston were almost i n v a r i a b l y f r e s h d u r i n g the p e r i o d mid-May to mid-August. Even as f a r out as Sand Heads, s u r f a c e s a l i n i t y seldom exceeded 0.0 ppt d u r i n g t h i s p e r i o d . Beginning i n August and September, s l i g h t l y b r a c k i s h waters o c c a s i o n a l l y penetrate the outer e s t u a r y at the s u r f a c e ; by December, the month of lowest d i s c h a r g e , s a l i n i t i e s i n the range of 0-4 ppt ( s t i l l only m i l d l y b r a c k i s h ) were being recorded at the s u r f a c e as f a r upstream as the v i c i n i t y of Ladner Marsh. Surface s u b s t r a t e and s u r f a c e water s a l i n i t i e s i n the Brunswick Point area were determined by Levings & C o u s t a l i n (1975) and Swinbanks (1979), whose r e s u l t s i n d i c a t e d a m i l d l y t b r a c k i s h environment (ca. 0-8 ppt s a l i n i t y ) i n northern and western p o r t i o n s of the marsh, and a moderately b r a c k i s h to m i l d l y s a l i n e environment (ca. 12-20 ppt s a l i n i t y ) i n the southern p o r t i o n . Swinbanks found that s u r f a c e s u b s t r a t e s a l i n i t i e s corresponded very c l o s e l y to s u r f a c e water s a l i n i t i e s at low t i d e on ebb. On the Boundary Bay mudflats, s a l i n i t y measurements taken at d i f f e r e n t times of the year i n t i d a l pools at low t i d e by O'Connell (1975) and Swinbanks (1979) i n d i c a t e that freshwater input from the F r a s e r River i s minimal or n o n e x i s t e n t , even du r i n g f r e s h e t . In the area of my Boundary Bay West t r a n s e c t they determined s a l i n i t y values ranging from 23 to 33 ppt (with one anomalous reading of 39 p p t ) ; the h i g h e s t readings 33 were obtained on warm days in June. S l i g h t l y lower values (20-24 ppt) were recorded along a transect 5 km further east, possibly r e f l e c t i n g the influence of the minor r i v e r s emptying into Mud Bay. 3.4.3 Tides The tides in the study area are described as "mixed, mainly semi-diurnal" (Ages & Woollard 1976, Canadian Hydrographic Service 1981), which means there are "two complete t i d a l o s c i l l a t i o n s d a i l y with in e q u a l i t i e s both in height and time reaching the greatest values when the declination of the moon has passed i t s minimum" (Canadian Hydrographic Service 1981). In summer, when the days are long and warm, the lowest tides occur during the day -- a b e n e f i c i a l combination of circumstances for the marsh plants (and for botanists). In winter the lowest tides occur at night. The detailed character of the t i d a l curve varies considerably from one sampling l o c a l i t y to another within the study area. Thus the t i d a l range for large tides i s 4.4 m at Crescent Beach in Boundary Bay, with a mean water l e v e l of 2.3 34 m above chart datum;1 at Sand Heads on the active edge of the delta the range i s 4.8 m, and the mean water l e v e l i s 2.9 m above chart datum (data source: Canadian Hydrographic Service 1981). Moreover, because of the strong summer peak in Fraser River discharge (Section 3.4.2), summer tide l e v e l s in the lower r i v e r are higher than the levels elsewhere at the same time, and are higher than winter tide levels in the same area. The effect i s most pronounced on low tides. For example, June high water levels at Deas Island (near Ladner Marsh) are higher than winter highs by about 0.4 m; June lows are higher than winter lows by about 1.4 m (data from Canadian Hydrographic Service 1977). The summer elevation of t i d a l heights i s less pronounced at Steveston, nearer the river mouth; at Boundary Bay i t i s not s i g n i f i c a n t . Winter low water leve l s are at about the same l e v e l throughout the study area, more or less as a consequence of the d e f i n i t i o n of chart datum. The considerable variation in t i d a l regime from one sampling location to another within the study area i s inconvenient, since i t precludes any di r e c t comparison with respect to elevation of sample plots from d i f f e r e n t areas. (My solution to th i s problem is explained in Section 7.3.) 1 Chart datum i s defined in Canada as the plane of lowest normal tides (Canadian Hydrographic Service 1981). This i s not the same as chart datum in the United States, where the l e v e l of mean lower low water i s used (Tide Tables 1976). Thus American chart datum is a l i t t l e higher than Canadian. 35 3.4.4 Sedimentation and Substrate As indicated in Section 3.2, the Fraser River c a r r i e s a very large load of sediment into the delta each year; most of th i s i s suspended load (Ages & Woollard 1976). Up to 10% of the suspended load may be clay, and the rest i s about equally sand and s i l t (Mathews & Shepard 1962). Most of this material reaches the delta during the freshet (Pretious, 1972). Presumably i t i s at t h i s time of year that most of the sediment deposition in the river and delta-front marshes takes place, the dense marsh vegetation acting as a sediment trap as tidewaters r i s e over the marsh. At Boundary Bay the sediment contribution from the Fraser River may be s l i g h t (Swinbanks 1979), but sediments are supplied by the smaller Serpentine and Nicomekl r i v e r s , depositing s i l t and clay, and by erosion of the c l i f f s at Point Roberts and even of the marsh i t s e l f (Kellerhals & Murray 1969). The d i f f e r i n g sedimentological regimes within the study area give r i s e to d i f f e r i n g rates of v e r t i c a l marsh accretion. Because of erosion, i t i s necessary to di s t i n g u i s h between the net or long-term accretion rate and the short-term rate. Several centimetres of mud may be deposited l o c a l l y in a single season, only to be subsequently eroded away. Burgess (1970) c i t e d the knowledge of l o c a l residents that the surface of the Westham Island marsh had risen by 4 feet (1.2 m) in 3 6 under 35 years; i . e . about 3.5 cm y e a r - 1 . Moody (1978) quoted the same figure (perhaps derived from the same sources) for Brunswick Point. Presumably these rates represent short-term accumulation. Using the known rate of l a t e r a l delta-front advance and assuming a constant average slope, Burgess (1970) calculated a long-term sedimentation rate of 0.004 feet (1.2 mm) per year. This c a l c u l a t i o n would be an average for the entire foreshore zone from the dike to the edge of the delta front; within the r e l a t i v e l y narrow s t r i p of t i d a l marsh, however, the rate could well be higher. At Boundary Bay, Kellerhals & Murray (1969) determined a short-term mean sedimentation rate of 5.0 mm year" 1, but they calculated a much lower long-term rate of 0.42 mm year" 1 over the l a s t 4350 years. Sediment accumulation within t i d a l marshes i s thought to be enhanced s i g n i f i c a n t l y by the plants and animals there; b i o t i c influences on sedimentation were reviewed by Frey & Basan (1978). Among the mechanisms they discussed were: the damping effect of vegetation on wind-generated waves; the impedance of current flow by vegetation, with resulting loss of current competence and s e t t l i n g out of suspended load; and the trapping by macroinvertebrates of suspended par t i c u l a t e matter, with subsequent deposition in the form of feces. The a l l u v i a l sediments of the Fraser Delta t i d a l marshes range in texture from sands to clayey s i l t s , with weak to nonexistent development of mineral horizons. The coarsest and 37 most highly sorted sediments are found at Boundary Bay, probably as a result of both reworking by winter storm, waves, and the absence of a major source of suspended mud (Swinbanks 1979). At the highest elevations, several centimetres of organic material may accumulate at the surface. The humus produced by decomposing marsh vegetation i s sometimes augmented by l o c a l accumulations of driftwood and by washed-up r a f t s of eelgrass (mainly Zostera marina) from offshore. Mineral sediments may incorporate a considerable amount of organic matter, consisting of decaying roots, rhizomes, shoot bases, and al g a l mats. In a waterlogged environment, reducing conditions p r e v a i l , and thi s material decomposes anaerobically, giving r i s e to coal-black sediments reeking of hydrogen sulphide. In some areas the substrate displays a pronounced varve-l i k e s t r a t i f i c a t i o n : alternating narrow horizontal layers of mineral and organic material. As discussed by Kellerhals & Murray (1962) for Boundary Bay, thi s s t r a t i f i c a t i o n results from the growth during summer and f a l l of filamentous green and blue-green a l g a l mats on the marsh surface, followed by winter storms which bury the a l g a l mats beneath a layer of sand. In spring and early summer the algae re-colonize the surface. Each varve thus represents an annual cycle of growth and deposition. S t r a t i f i c a t i o n observed in the marshes of the river mouth and delta foreshore, however, presumably r e f l e c t s 38 the rather d i f f e r e n t annual cycle prevailing there, in which sedimentation peaks with - the summer freshet. 3.5 Transect Locations and Site Descriptions 3.5.1 Selection of Locations Sampling locations were selected at Ladner Marsh, Brunswick Point, and Boundary Bay, a l l in the Municipality of Delta, B r i t i s h Columbia (Fig. 1), with the objective of representing the wide range of vegetational and environmental va r i a t i o n in the delta marshes, from areas of mainly fresh- 1 water influence in and near the Fraser River to areas of mainly salt-water influence on Boundary Bay and Georgia S t r a i t . 3.5.2 Ladner Marsh Ladner Marsh (Fig. 2) was sampled near the north end of Ferry Road. A single transect perpendicular to the r i v e r , Transect J, extends 45 m from a swampy thicket dominated by cottonwood, willows and red osier dogwood to the bare mud of a slough. The dominant species along the transect are Equisetum  f l u v i a t i l e , Agrostis alba, and Carex lyngbyei. Somewhat less 39 i m p o r t a n t are S c i r p u s v a l i d u s , Typha l a t i f o l i a , E l e o c h a r i s  p a l u s t r i s , and Oenanthe sarmentosa. Lythrum s a l i c a r i a and Sium  suave are c o n s p i c u o u s by t h e i r showy i n f l o r e s c e n c e s i n the h i g h e r p a r t of the marsh, and s e v e r a l minor s p e c i e s a r e a l s o p r e s e n t . The bare mud a t the lower edge of the marsh i s b e i n g c o l o n i z e d by Equisetum f l u v i a t i l e . F i g u r e 2 - Ladner Marsh, v i c i n i t y of T r a n s e c t J . Foreground: Lythrum s a l i c a r i a , Carex l y n g b y e i . Background: Populus t r i c h o c a r p a . R i g h t : S c i r p u s v a l i d u s 40 3.5.3 Brunswick Point Brunswick Point i s a peninsular marshland bounded on the north by Canoe Pass, a minor d i s t r i b u t a r y of the Fraser River, and on the west and south by Georgia S t r a i t . Thus there i s a gradient from predominantly fresh-water influence on the north side to brackish or marine influence on the south. Transect D samples the high marsh vegetation on the north side of the point, where the community is mainly composed of Carex lyngbyei, P o t e n t i l l a pac i f i c a , Juncus balticus, Eleocharis p a l u s t r i s , Aqrostis alba, and scattered clumps of Typha l a t i f o l i a and Lythrum s a l i c a r i a . Other species also present include Sium suave, Bidens cernua, and Juncus  art iculatus. Transect A, the longest, runs 1420 m across the point from north to south. On the r i v e r side, bare mud i s being colonized mainly by Scirpus americanus, and also by Eleocharis  p a l u s t r i s ; these are the p r i n c i p a l species in the lowest fringe of t h i s marsh area. Higher up (Fig. 3), Carex lyngbyei and Aqrostis alba are the dominant species in an extensive community which also includes Triglochin maritimum, Sag i t t a r i a  l a t i f o l i a , Bidens cernua, Li l a e o p s i s occidentalis, P o t e n t i l l a  p a c i f i c a , and several other species. Ruppia maritima i s common in channels. Towards the south end of t h i s transect (Fig. 4), Scirpus maritimus becomes important. At the south end, the mudflats are being colonized by Sc i rpus amer icanus 41 and are covered by dense mats of filamentous algae. Floodwaters here are f a i r l y fresh, sweeping around the point from the r i v e r . Transect B runs perpendicular to the dike in an area of evidently marine influence on the south side of the point (Fig. 5). Nearest the dike the dominant species are D i s t i c h l i s spicata and Atriplex patula. Further out i s a community composed mainly of D i s t i c h l i s spicata, S a l i c o r n i a  v i r g i n i c a , and Tri g l o c h i n maritimum. At the lower end of the transect the marsh breaks up into clumps of Scirpus maritimus and Tr iglochin maritimum. The mud i s covered with an a l g a l mat and i s being colonized by Sperqularia canadensis. Further out on the t i d a l f l a t , well beyond the edge of the marsh proper, Scirpus americanus and S. maritimus are colonizing the mud. A fourth transect, Transect C, is located in the same general area as Transect B, but runs at an acute angle to the dike, from the area of salt-water influence towards the area of fresh-water influence. The f l o r a varies accordingly, from halophyte communities similar to those described for Transect B to a Scirpus maritimus - Sc i rpus amer icanus - Triglochin  maritimum community resembling that in the southern part of transect A. From the a i r , the Brunswick Point marsh (Fig. 6) displays a prominent pattern of c i r c u l a r blotches, which correspond to dense stands of mainly Carex lyngbyei or Scirpus maritimus. 42 Presumably these stands are colonies that have spread out rhizomatously. Johannessen (1964) considered such c i r c u l a r colonies at the edge of a marsh to be evidence of rapid marsh expansion. At Brunswick Point, where c i r c u l a r features are conspicuous in the higher, older parts of the marsh, they may be r e l i c t s of a previous episode of rapid expansion. 3.5.4 Boundary Bay The Boundary Bay marsh was sampled at two locations, here c a l l e d Boundary Bay East and Boundary Bay West. The Boundary Bay East study area is located near the foot of 112th Street, Delta, in an area where the predominantly marine influence is moderated by freshwater input from nearby streams (Fig. 7). Three transects, E, F, and G, extend south into the bay, more or less perpendicular to the dike. Here the ' highest part of the marsh, next to the dike, i s characterized by large driftwood deposits. The p r i n c i p a l species in the high marsh i s usually Atriplex patula; also important are Carex lyngbyei, S a l i c o r n i a v i r g i n i c a , P o t e n t i l l a  p a c i f i c a , Agrostis alba, and P u c e i n e l l i a n u t t a l l i a n a . Carex  lyngbyei, with occasional dense patches of Juncus q e r a r d i i , often dominates the middle l e v e l s . At s l i g h t l y lower elevations, D i s t i c h l i s spicata, Plantago maritima, Triglochin  maritimum, Glaux ma r i t i ma, Sperqularia canadensis, and S a l i c o r n i a v i r g i n i c a form a c h a r a c t e r i s t i c species assemblage. Figure 3 - Brunswick Point North, v i c i n i t y of Transect A. Carex lyngbyei is dominant. Conspicuous inflorescences: Lythrum s a l i c a r i a (magenta); Sium suave (white) 44 Figure 4 - Brunswick Point South, v i c i n i t y of Transect A. Triglochin maritimum forms isol a t e d clumps at marsh edge; clumps coalesce into continuous stand (right background) 45 Figure 5 - Brunswick Point South, Transect B. Scene in late winter Figure 6 - A e r i a l photograph of Brunswick Point, showing c i r c u l a r patterning of marsh vegetation. Clumps are mainly Carex lyngbyei and Scirpus maritimus 47 Figure 7 - Boundary Bay East, Transect E. Mixed grasses in foreground; Carex lyngbyei (yellow-green) in mid-portion of transect; Sali c o r n i a v i r g i n i c a , Triglochin maritimum, Plantago  maritima at far end of transect Tdark green) 48 Several other species are also found. The mudflats here, as in other saline-influenced areas, are being colonized by Spergularia canadensis and are covered by a l g a l mats. A summer diatom bloom colours the mud surface pinkish-brown (Fig. 8). Zostera americana and Ruppia maritima are p l e n t i f u l in channel bottoms and w a t e r - f i l l e d depressions. As noted by Kellerhals & Murray (1962), the marsh in thi s area i s eroding; I observed several centimetres of undercutting during one season of fieldwork. The Boundary Bay West study area, at the foot of 72nd Street, Delta, is probably the most marine-influenced of the t i d a l marshes in t h i s study. S a l i n i t i e s of 22 parts per thousand were determined for bay water sampled here at high tide in summer. The higher marsh here, along Transect H (Figs. 9, 10), i s characterized by old bleached driftwood, Atr i p l e x patula, S a l i c o r n i a v i r g i n i c a , Spergularia marina, and Grindelia  i n t e g r i f o l i a . At middle elevations, S a l i c o r n i a v i r q i n i c a , A triplex patula, and D i s t i c h l i s spicata predominate; the Sal i c o r n i a i s densely infested with Cuscuta s a l i n a . The lowest part of the contiguous marsh is characterized by Plantago mar i t ima, Salicorn ia v i r q i n i c a , Spergular ia  canadensi s, and Tr iglochin maritimum. Colonizing the sandflats are clumps of Sal i c o r n i a and Plantago. 49 Figure 8 - Boundary Bay East. Triglochin maritimum and Sal i c o r n i a v i r g i n i c a , with patches of filamentous green and blue-green algae. Black reducing mud i s covered by brownish diatom mat Figure 9 - Boundary Bay West, v i c i n i t y of Transect H. Atriplex patula dominates the driftwood zone in foreground. Farther out, Sa l i c o r n i a v i r g i n i c a is infested by yellowish Cuscuta salina 51 Figure 10 - Boundary Bay West. Grindelia i n t e g r i f o l i flowers amid the driftwood 52 4. SOME FACTORS AFFECTING SPECIES DISTRIBUTIONS 4.1 Introduction Chapman (1938), in a study of s a l t marshes, considered 10 environmental factors to be of major importance: tides, s a l i n i t y , drainage, aeration, water table, r a i n f a l l , s o i l , evaporation, temperature, and biota. Obviously these are a l l to some degree interdependent in their influence. Chapman's environmental categories seem applicable to t i d a l marshes in general. In the present study, I have c o l l e c t e d data from four of them: biota, tides, s a l i n i t y , and s o i l . Some of the other factors ( i . e . drainage, aeration) can be inferred from these. The the o r e t i c a l relevance of my environmental data to plant species d i s t r i b u t i o n s i s discussed in the following four sections. 4.2 Tides The unique phenomenon of t i d a l marsh habitats i s , of course, the tides. Daylight flooding reduces photosynthesis by reducing the supply of carbon dioxide and, mainly because of suspended sediment, l i g h t . T i d a l flooding during day or night may exclude oxygen from the rooting environment, a f f e c t i n g respiration. The flooding tide may bathe the marsh 53 plants in saline water and increase the s a l i n i t y of the substrate; after the ebb tide, r a i n f a l l or seepage may reduce substrate s a l i n i t y . Cool floodwaters may suddenly and sharply reduce the temperature of the marsh plants; the f a l l i n g tide may then expose the vegetation to sharply increased temperatures. Evaporation on warm days after the tide has receded may substantially increase the s a l i n i t y of surface pools and s o i l water. Evaporation of s i l t - l a d e n water commonly leaves a fine coating of light-blocking mud on photosynthetic surfaces. The flow of water on flooding and ebbing tides subjects plant shoots to mechanical stress. T i d a l a c t i v i t y a ffects sedimentation patterns, d i s t r i b u t e s propagules and ca r r i e s away d e t r i t u s . At the highest elevations in the marsh, flooding is a brief and infrequent event, perhaps occurring for a few minutes once a month; at the lowest l e v e l s , flooding i s d a i l y and prolonged, sometimes l a s t i n g most of the day. Differences in frequency and duration of t i d a l flooding give r i s e to a very pronounced environmental gradient in the marsh, corresponding to a rather s l i g h t gradient in elevation. A r e l a t i o n between t i d a l factors and the v e r t i c a l zonation of i n t e r t i d a l organisms has been postulated since at least the early 1800's (Doty, 1957). A pioneering study of the r e l a t i o n of t i d a l marsh plant species d i s t r i b u t i o n s to tide levels was that of Johnson & York (1915). In a monographic treatment of a Long Island (N.Y.) sa l t marsh, they 54 considered the effects of t i d a l o s c i l l a t i o n on transpiration, gas exchange, s o i l s a l i n i t y , l i g h t supply, and other factors. In p a r t i c u l a r , they related the v e r t i c a l d i s t r i b u t i o n s of marsh plant species to both the frequency and the duration of t i d a l flooding, and they summarized these parameters in the form of a r a t i o between t o t a l time exposed at a given elevation and t o t a l time submerged. They considered competitive interactions as well as autecological l i m i t s in explaining species d i s t r i b u t i o n s . On the A t l a n t i c coast, including the area of Johnson & York's study described above, successive semidiurnal t i d a l o s c i l l a t i o n s are nearly equal in range, but on the P a c i f i c coast there is a marked inequality in the range of successive tides (Frey & Basan 1978). Thus neither the frequency of inundation or exposure, nor the cumulative duration of inundation or exposure, nor the duration of single episodes of inundation or exposure, changes smoothly along an elevation gradient. Rather, there are certain c r i t i c a l elevations, defined by lev e l s in the t i d a l cycle, at which the values of these parameters jump abruptly. The result i s a v e r t i c a l series of several d i s t i n c t exposure zones, each (one might predict) with i t s own c h a r a c t e r i s t i c biota, within the i n t e r t i d a l region. This concept of c r i t i c a l tide levels was f i r s t published by Doty (1946) in connection with the v e r t i c a l d i s t r i b u t i o n s of marine algae in C a l i f o r n i a . Doty i d e n t i f i e d the c r i t i c a l tide levels as: the lowest tide l e v e l , or low lower low water (LLLW); the mean l e v e l of the lower of the two 55 d a i l y low tides, or mean lower low water (MLLW); the lowest l e v e l of the higher of the two d a i l y low t i d e s , or low higher low water (LHLW); the highest l e v e l of the two d a i l y low tides, or high higher low water (HHLW); the lowest l e v e l of the two d a i l y high t i d e s , or low lower high water (LLHW); the lowest l e v e l of the higher of the two d a i l y high tides, or low higher high water (LHHW); and the highest tide l e v e l , or high higher high water (HHHW). Swinbanks (1979) pointed out that the curve of t i d a l heights varies according to at least four cycles of progressively increasing wavelength, having p e r i o d i c i t i e s of 1 lunar day (24 h 50 min), 1 lunar month, 1 year, and 18.6 years. Each of these cycles gives r i s e to i t s own c r i t i c a l tide l e v e l s . Even the 18.6-year t i d a l cycle i s s i g n i f i c a n t , perturbing tide levels by about 0.5 m in the Fraser Delta area (hence the period over which t i d a l measurements have been recorded i s of considerable s i g n i f i c a n c e ) . The c r i t i c a l tide l e v e l s are universal, and can be used to cross-correlate very d i f f e r e n t types of t i d a l curves from geographically distant locations. Unfortunately, as Swinbanks noted, there are so many of them that any b i o t i c zone boundary stands a good chance of coinciding rather c l o s e l y with one. I have described the c r i t i c a l tide l e v e l concept at some length because of i t s obvious appeal and l i k e l y significance in explaining the observed zonation of vascular plants within the i n t e r t i d a l marsh zone. However, the concept seems to me 56 to be of doubtful p r a c t i c a l u t i l i t y , at least in the context of my own study, for a variety of reasons, including the following: (1.) as stated, there are a great many c r i t i c a l tide l e v e l s , some of which are bunched closely together: which of several c r i t i c a l tide levels i s a species responding to? (2.) the tide l e v e l data base i s not everywhere adequate to the task, since observations over at least 18.6 years may be required; (3.) species autecological l i m i t s and requirements are not well enough understood, and what information exists has mostly been inferred empirically from f i e l d observation, making i t useless for predicting correlations with f i e l d variables such as c r i t i c a l tide levels; (4.) interactions between t i d a l factors and other environmental variables (e.g. substrate texture, s a l i n i t y ) may be s i g n i f i c a n t in determining species d i s t r i b u t i o n a l l i m i t s ; (5.) interactions between species probably influence their d i s t r i b u t i o n a l l i m i t s . Largely because of these reservations, I have not attempted to u t i l i z e the c r i t i c a l tide level concept in t h i s study. 4.3 S a l i n i t y In the Fraser Delta, with i t s strong gradient from fresh water to sa l t water habitats, the effect of s a l i n i t y on t i d a l marsh plant species d i s t r i b u t i o n s i s readily apparent. 57 Phy s i o l o g i c a l l y , an excess of NaCl in the growth medium can produce various toxic effects in higher plants, including protoplasmic swelling and changes in enzyme a c t i v i t y , leading to interference in respiration, disturbance of nitrogen assimilation, and abnormalities of protein metabolism (Larcher 1980). Uptake of essential nutrient ions may be reduced in the presence of NaCl ( i b i d . , Waisel 1972). Yet some species tolerate l e v e l s of NaCl that would k i l l most plants. The adaptation of plant species to saline environments i s expressed in the phenomenon of halophytism, 1 which i s the subject of an extensive l i t e r a t u r e and i s discussed only b r i e f l y here. For comprehensive reviews of the physiological ecology of halophytes, see the volumes by Waisel (1972) and Poljakoff-Mayber & Gale (1975); a wider-ranging symposium treatment of halophyte ecology i s given in Reimold & Queen (1972). Useful, concise treatments of halophytism with respect s p e c i f i c a l l y to s a l t marshes are found in Chapman (1974) and Ranwell (1972). As Epstein (1969) pointed out, a plant, to function metabolically, must deal with i t s chemical environment in three ways: "It must s e l e c t i v e l y acquire essential nutrient elements from [the chemical environment], i t must cope with 1 I am using the term "halophytism" to mean adaptation to a saline environment, without implying the degree of adaptation, or whether the adaptation J.s f a c u l t a t i v e or . obligate. The opposite term is "glycophytism", meaning adaptation to a freshwater environment. 58 elements present in excess, and i t must acquire water." In a saline environment, then, a plant must overcome three main problems (Queen 1975): (1.) acquiring s u f f i c i e n t e s s e n t i a l nutrients from a medium with an unfavorable ionic mix (high NaCl), (2.) maintaining i t s internal ionic balance and concentration within narrow l i m i t s despite the high concentration of NaCl in the external medium, (3.) acquiring water from an external solution with a high osmotic pressure (low water p o t e n t i a l ) . With regard to the f i r s t problem, Queen (1975) c i t e d evidence that halophytes were better than glycophytes at discriminating between essential nutrient ions and their nonessential competitors (mainly Na + and CI"). ' The second problem, that of regulating the internal ionic balance and concentration within tolerable l i m i t s , may be dealt with in three main ways: (a.) by internal segregation of excessive or toxic ions (mainly NaCl) within the vacuole; (b.) by external segregation of such ions, i . e . t h e i r removal from the plant; (c.) by succulence, i . e . d i l u t i o n of s a l t s by increasing c e l l volume. Queen (1974, 1975) considered the evidence for method (a.), internal segregation, to be contradictory, but Flowers et a l . (1977) reviewed the evidence and found i t favorable, a view endorsed by Dainty (1979). As for method (b.), actually getting r i d of excess s a l t , several mechanisms may be c i t e d (Waisel 1972, Queen 1975): ( i . ) salt glands — highly 59 selective excretors of Na + and CI" (in e.g. Glaux); ( i i . ) leaching from leaves (in e.g. A t r i p l e x ) ; ( i i i . ) guttation; (iv.) shedding of salt-concentrated leaves or shoots (in e.g. Juncus g e r a r d i i , A t r i p l e x, S a l i c o r n i a ) ; (v.) secretion by roots of s a l t s translocated from shoots (in e.g. S a l i c o r n i a ) ; (vi.) accumulation of s a l t s in s a l t hairs or bladders (in e.g. A t r i p l e x ) . Method ( c ) , the succulence strategy, appears most conspicuously (in my study area) in S a l i c o r n i a , in which i t i s a s p e c i f i c response to NaCl (Poljakoff-Mayber 1975, c i t i n g Russian sources). The t h i r d problem, acquiring water from a saline medium, led early researchers to speculate that halophytes endured a water d e f i c i t , or "physiological drought". This idea i s now discredited; halophytes are able to maintain a favorable water potential gradient by osmoregulation, accomplished in various ways (Gale 1975), including NaCl uptake. Although a .halophyte may reduce i t s internal water potential by taking in s a l t , the need to maintain a favorable gradient must be balanced against the need to keep the NaCl concentration below toxic l e v e l s . One might speculate, then, that halophyte enzymes are more tolerant of high NaCl concentrations than glycophyte enzymes. Queen (1974, 1975) considered the evidence contradictory for t h i s , but Dainty (1979), c i t i n g Flowers et a l . (1977), was quite d e f i n i t e : "there i s no evidence that enzymes of halophytes are d i f f e r e n t , in their s e n s i t i v i t y to NaCl, from the enzymes of 60 other plants." J e f f e r i e s (1973) estimated the protoplasmic (not vacuolar) Na + concentration in Trig l o c h i n maritimum to be about 100 mM, which i s f a i r l y low. Various organic solutes, however, are found in halophyte protoplasm at about the right concentrations for osmoregulation; thus i t seems l i k e l y that osmoregulation in halophyte c e l l s involves the production of organic osmotica (Dainty 1979, Stewart et a l . 1979, J e f f e r i e s et a l . 1979). Some of these compounds may also serve somehow to protect s a l t - s e n s i t i v e enzyme systems against high levels of NaCl (Stewart et a l . 1979). Much evidence now shows that very few i f . any s a l t -tolerant species are actually obligate halophytes (Flowers et a l . 1977, Chapman 1977); most perform best at low or zero s a l i n i t y . Barbour (1970) reviewed the l i t e r a t u r e and found that very few species appeared to be r e s t r i c t e d to s a l i n i t i e s above 5 ppt. Some common t i d a l marsh halophytes for which maximum growth has been found experimentally to occur at minimum or zero s a l i n i t i e s are Juncus g e r a r d i i (Rozema 1976, 1979), Plantago maritima (Chapman 1977), and Triglochin  maritimum (Pigott 1969). (An anecdotal observation from my own study area i s that Tr iglochin maritimum plants appear to grow much larger in the less saline areas.) Other halophytes show optimal growth in brackish conditions: e.g. Atriplex  patula, Puce i n e l l i a n u t t a l l i a n a , D i s t i c h l i s spicata, and Ruppia maritima (Flowers et a l . 1977). Of genera found in my study area, only Sa l i c o r n i a may be an obligate halophyte, r e s t r i c t e d to saline habitats (Ranwell 1972, Chapman 1974); 61 even for thi s genus, though, there i s some evidence to the contrary (Flowers et a l . 1977). Although most halophytes perform best in fresh water conditions in the laboratory, few are found in fresh water habitats in nature. Presumably the various halophytic adaptations to a high-NaCI environment have a s i g n i f i c a n t energy cost, no doubt contributing to the poor competitive a b i l i t y of halophytes in glycophytic environments. 4.4 Substrate Nutrient Regime In t i d a l marshes, as elsewhere, the chemistry of the rooting medium may be expected to play a major role in determining the d i s t r i b u t i o n of plant species. Aside from carbon, hydrogen, and oxygen, six elements, c a l l e d macronutrients, are required in some abundance by higher plants: nitrogen, phosphorus, potassium, sulphur, calcium, and magnesium. Seven other elements, including chlorine, are required in trace amounts. The a v a i l a b i l i t y of these nutrient elements i s strongly influenced by environmental factors operating in t i d a l marsh habitats: the sa l t content of the floodwaters enriches the rooting medium in several ionic species, especially toxic sodium; and the high water table, with periodic flooding, excludes oxygen from the i n t e r s t i t i a l solution, giving r i s e to reducing conditions. In addition, there may be chemical gradients from the high marsh to the low 62 marsh resulting from the gradients in frequency and duration of flooding. The macronutrient cations C a + + , Mg + +, and K + are generally made available to t e r r e s t r i a l plants by the weathering of clay minerals (Etherington 1975). Potassium i s the nutrient cation required by plants in greatest quantity, yet i t s concentration in s o i l solution i s often very low (Epstein 1969). In sa l t marshes, however, the macronutrient cations, including K +, are supplied in high concentrations by the saline t i d a l floodwaters (Table I I ) . The fresh water of the Fraser River i s nutrient-poor by comparison. Table II - Typical concentrations (mg L" 1 ) of macronutrient cations plus Na + and C l " in s o i l solution, seawater, and Fraser River water I on spec ies S o i l solut ion 1Seawater 2 Lower Fraser River 3 Jan. June Ca + + 1 36-560 400 18 1 5 Mg+ + 46-168 1 300 44 3.6 K + 27-39 400 9 1 .4 Na + 23-667 1 1 000 222 2.0 C l " 39-710 20 000 373 3.9 1 Fried & Broeshart 1967. Ranges are from ac i d i c s o i l s to calcareous s o i l s . 2 Pigott 1969 and Larcher 1980. 3 Benedict, Hall & Koch 1973. Much the commonest ions in seawater are Na+ and C l " 63 (Table I I ) , which are not only toxic in their own right to most plants (Section 4.3), but also reduce the uptake of essential ions, p a r t i c u l a r l y K+ and C a + + (Waisel 1972, Larcher 1980). Halophytes obtain what they need from the s o i l in spite of high NaCl concentrations. The halophyte Triglochin  maritimum has been shown to respond to an increase in the external sodium l e v e l by a c t i v e l y increasing i t s potassium uptake (Parnham 1971), presumably for osmoregulation. Several studies have pointed to nitrogen as the l i m i t i n g nutrient for t i d a l marsh halophytes (Pigott 1969; Stewart et a l . 1972, 1973; V a l i e l a & Teal 1974). Nitrogen metabolism may be cl o s e l y related to salt tolerance; certain nitrogen-containing compounds, presumably osmoregulatory solutes, are present at high levels in many halophytes, p a r t i c u l a r l y when grown in saline conditions (Stewart et a l . 1979). Reported studies on nutrient l i m i t a t i o n in t i d a l marshes seem a l l to have dealt with salt marshes; in freshwater marshes there i s no s a l i n i t y stress to be dealt with, and the nitrogen requirement may therefore be le s s . An important source of nitrogen in t i d a l marshes i s fi x a t i o n of atmospheric nitrogen by blue-green algae and bacteria (Green & Edmisten 1974, Jones 1974, Patriquin & Keddy 1978). Nitrogen-fixing blue-green algae are abundant on the mud surface; nitrogen-fixing bacteria are found within the anaerobic muds and also in association with the root systems of many t i d a l marsh vascular plant taxa (Patriquin & Keddy 64 1978), at least 22 of which are present in the marshes of the Fraser Delta. To put matters in proportion, the l e v e l of root nitrogenase a c t i v i t y found by Patriquin & Keddy was one to three orders of magnitude greater in the legume Lathyrus  p a l u s t r i s than in any of the other marsh species they studied. On the other hand, Green & Edmisten (1974), who sampled water, surface mud, green plant shoots, and dead shoots in a Gulf of Mexico Spartina marsh, found t o t a l nitrogen f i x a t i o n rates of up to 1550 kg of nitrogen per hectare in one month, which i s an order of magnitude greater than the f i x a t i o n rate for commercial soybean or a l f a l f a crops. The nutrient status of t i d a l marsh s o i l s i s greatly influenced by the effects of waterlogging. The high water . table e f f e c t i v e l y excludes oxygen from the marsh sediments. This permits populations of anaerobic microorganisms to build up, leading to the development of chemically reducing conditions. In such an environment, iron i s present in i t s toxic ferrous form, and sulphur i s present as sulphide, bisulphide, or hydrogen sulphide, a l l highly toxic. Nitrogen i s found as ammonia or ammonium ion, forms which are unavailable to many species. A gradient in s o i l oxygen status from the high marsh, where the rooting medium may be e s s e n t i a l l y aerobic, to the lowest marsh, where only a thin surface layer is aerobic, presumably af f e c t s species d i s t r i b u t i o n s . Many marsh species are capable of anaerobic metabolism when under oxygen stress 65 (Armstrong 1975); many can assimilate nitrogen in either the ni t r a t e or the ammonium form. A common strategy of wetland plants i s the transport of oxygen via aerenchymatous tissue from the shoots to the roots, whence i t diffuses into the rhizosphere ( i b i d . ) ; thus toxic reduced ions approaching in the s o i l solution may be oxidized before they reach the plant. Some marsh species, e.g. Juncus spp., show xeromorphic adaptations, which presumably function not for water conservation as such, but rather to reduce the rate of water flow towards the roots, thus increasing the time available for oxidation of potential toxins in the rhizosphere ( i b i d . ) . The a v a i l a b i l i t y of s o i l nutrients to plants is affected considerably by the s o i l pH, since ionic e q u i l i b r i a s h i f t with changing pH. S o i l microflora also are affected by pH differences, with possible consequences for higher plants (Etherington 1975). Most vascular plants have broad pH optima in the range between weak a c i d i t y and weak a l k a l i n i t y (Larcher 1980)., The pH of saline s o i l s i s usually more or less neutral but may be affected by leaching, temperature, and ion concentration (Waisel 1972). 4.5 Substrate Texture Moody (1978) reported that the habitats of Scirpus  americanus and Scirpus maritimus, the two major colonizing species in the brackish Brunswick Point marshes, were 66 d i f f e r e n t i a t e d by substrate texture: S. amer icanus colonizes on sandy substrates, and S. maritimus in s i l t y areas. Once established on a sandy substrate, S. americanus may be replaced by S. maritimus in apparent response to increasing s i l t deposition. Substrate texture probably affects species d i s t r i b u t i o n s in several ways. Coarse-grained s o i l s are more permeable, so that the water table w i l l fluctuate more, perhaps r i s i n g to the surface on a flooding tide; t h i s does not happen in the less permeable fine-grained sediments (Clarke & Hannon 1969). Being more permeable, however, the coarse-grained s o i l s are better drained and aerated, so that oxidizing conditions may dominate. A more porous s o i l i s more subject to the e f f e c t s of leaching by p r e c i p i t a t i o n or groundwater; thus s a l i n i t y may fluctuate more. Presumably, with the o v e r a l l greater fluctuation between atmospheric and aquatic conditions in a coarse-grained s o i l , other factors such as temperature and pH may also fluctuate more. Cation exchange capacity increases with increasing fine-p a r t i c l e content; thus substrate texture may influence nutrient a v a i l a b i l i t y for marsh vegetation. As pointed out by J e f f e r i e s (1972), the matrix potential of fine-textured s o i l s may s i g n i f i c a n t l y reduce the external water p o t e n t i a l . Thus even though the osmotic potentials of 67 sandy and clayey s o i l s may be si m i l a r , the water potentials may be quite d i f f e r e n t . 68 5. SAMPLING METHODS AND DATA COLLECTION 5.1 Vegetat ion Areas of marshland were selected which appeared to exhibit some vegetational or environmental d i s s i m i l a r i t i e s to one another, and within these areas transects were l a i d out in the d i r e c t i o n of evident or assumed environmental gradients (high elevation to low elevation; fresh water to s a l t water). Metre-square quadrats were placed subjectively at intervals along the transects in a manner intended to sample the f u l l range of observed v a r i a t i o n . Each quadrat location was marked with a wooden stake. Within each quadrat, a l l vascular plant species were subjectively assigned coverage code values corresponding to a e r i a l coverage classes of <1%, 1-5%, 6-25%, 26-50%, 51-75%, 76-95%, and 96-100%. Data were recorded for a t o t a l of 64 species in 103 quadrats. Plant specimens were c o l l e c t e d for species i d e n t i f i c a t i o n and eventual deposition in the University of B r i t i s h Columbia Herbarium. 69 5.2 S o i l At each plot one or more small spadefuls of mineral sediment (roughly 500 g) were co l l e c t e d from the upper 15 cm for l a t e r physical and chemical analysis. Where a d i s t i n c t organic horizon had accumulated, a sample of t h i s material was co l l e c t e d as well. Vegetation and s o i l sampling were carried out during the summer of 1978. 5.3 Levelling Survey To obtain quadrat elevations and map locations, a l e v e l l i n g survey was performed in the winter following the sampling season. A e r i a l vegetation by this time had died down and v i s i b i l i t y was thus greatly improved. By means of a Kern DKM2 theodolite, the horizontal coordinates of the quadrats were obtained and the quadrat elevations were determined to an accuracy of approximately plus or minus one centimetre. The r e l a t i v e elevations thus obtained were later converted to elevations above l o c a l chart datum, using one of two methods: (1.) At Boundary Bay, engineering survey monuments of known geodetic elevation were found nearby. The quadrat lev e l s were t i e d to the leve l s of these benchmarks, and their geodetic elevations converted to heights above chart 70 datum at White Rock. (2.) At Ladner Marsh and Brunswick Point, observations were made of the times at which the water l e v e l rose above ar b i t r a r y benchmarks on successive days. By extrapolation from hourly tide l e v e l records, 1 the heights of the benchmarks above chart datum at Steveston (for Brunswick Point) and Deas Island (for Ladner Marsh) were determined. 1 Supplied for Ladner Marsh by Environment Canada, Water Resources Branch, Inland Waters Directorate, P a c i f i c and Yukon Region, Vancouver, B.C., and for Brunswick Point by Institute of Ocean Sciences, Sidney, B.C. 71 6. SOIL ANALYSIS S o i l samples were oven-dried at 100 C for 24 hours, then crumbled with a r o l l i n g pin. Coarse plant material was separated from mineral sediments by hand-picking or with a sieve. Some samples had very l i t t l e mineral material remaining after roots and rhizomes were removed. For t h i s reason and also for reasons of economy, some samples were only p a r t i a l l y analyzed. The following analyses were performed: • P a r t i c l e size analysis, i.e. determination of percent by weight of sand, s i l t , and clay, using the Bouyoucos hydrometer, method (Day 1965). • pH determination on 1:1 soil:water extract, using a Radiometer pH Meter 29 with a Radiometer combined glass/reference electrode. • E l e c t r i c a l conductivity determination on s o i l saturation paste, using a Radiometer type CDM2e conductivity meter with a Radiometer CDC 104 conductivity c e l l . • Total nitrogen determination, by acid digestion and colorimetric analysis, using a Technicon AutoAnalyzer II . • Determination of C a + + , K+, Mg + +, and Na+ in 1:1 soil:water extract, using a Perkin-Elmer 306 atomic absorption spectrophotometer. 72 Except as indicated, the procedures followed were as outlined in Lavkulich (1978). 73 7. DATA ANALYSIS 7.1 Ordination Methods The term "ordination" i s used in ecology to denote techniques in which given e n t i t i e s , such as vegetation releves, "are ordered according to one or several of their properties in such a manner that their arrangenent w i l l reveal some useful information about their relationships" (Orloci 1978b). The ordination methods used in t h i s study f a l l into the category which Whittaker (1967) c a l l e d " i n d i r e c t gradient analysis", in which samples are arranged along axes generated by vegetational v a r i a t i o n . P r i n c i p a l components analysis, f i r s t developed for interpretation of results of psychological tests, was introduced to ecology by Goodall (1954). The method reduces the redundancy in species-dimensional vegetation space by summarizing the variation on the o r i g i n a l vegetation axes, corresponding to species, on a smaller number of ordination axes. In geometric terms, i t f i t s l i n e s or planes to a cloud of points, representing individuals (e.g. sample p l o t s ) , whose coordinates in n-dimensional space are the scores for each of the n attributes (e.g. species). The f i r s t ordination axis then corresponds to the d i r e c t i o n of maximum variance in the point cloud; each subsequent axis i s aligned in the d i r e c t i o n of greatest remaining variance. Geometrically, then, the axes 74 are orthogonal. However, since certain s t a t i s t i c a l c r i t e r i a , e s p ecially the assumption of multivariate normality, are not met by ecological data (Beals 1973), the axes are not b i o l o g i c a l l y independent. An ecological gradient may thus not be represented l i n e a r l y by PCA; t h i s has given r i s e to a great deal of a c t i v i t y by mathematically-inclined ecologists to discover a better method. A possible replacement for PCA in ecological ordination is reciprocal averaging. Like PCA, th i s method was used e a r l i e r in the s o c i a l sciences; the e a r l i e s t English-language applications of this method in ecology were those by Hatheway (1971) and H i l l (1973). As described by H i l l , the procedure is one of successive reciprocal r e - c a l i b r a t i o n s of species and stand scores, in which both are defined and redefined in terms of each other. The method i s thus related to Whittaker's dire c t gradient analysis and to the weighted averages technique of the Wisconsin school (Whittaker 1978). Computationally, RA is similar to PCA; i t s chief d i s t i n c t i o n i s that i t yiel d s simultaneous paired species and stand ordinations, "neither of which has l o g i c a l pre-eminence" ( H i l l 1973). The PCA and RA programs employed in t h i s study were developed by Dr. G.E. Bradfield from descriptions in Orloci (1978a). 75 7.2 Treatment of the Vegetation Data Recognition of plot groups: I n i t i a l l y , the cover data values for 64 species in 103 quadrats were organized in a f l o r i s t i c table (Table I I I ) . This procedure was f a c i l i t a t e d by the use of a tabular sorting program written by Dr. G.E. Bradfield of the University of B r i t i s h Columbia Botany Department. It became evident that the plots f e l l rather neatly into two f l o r i s t i c a l l y d i s t i n c t main groups. The f i r s t group comprises the plots from western and northern Brunswick Point and from Ladner Marsh (transects A, D, and J ) , and was designated the "freshwater" group; the second group includes a l l the Boundary Bay plots plus the plots from southeastern Brunswick Point (transects B, C, E, F, G, and H), and was designated the "saltwater" group. PCA on unstandardized data: As previously noted, the complete species cover value data set displayed a marked discontinuity in species d i s t r i b u t i o n s , indicating a high l e v e l of between-habitat or beta d i v e r s i t y . Since PCA has been shown to produce highly distorted ordinations from data with high beta d i v e r s i t y (Swan 1970; Whittaker & Gauch 1973, 1978), the data set was s p l i t into the more homogeneous "freshwater" and "saltwater" subsets, i d e n t i f i e d previously, for most ordination procedures. Results of PCA ordinations on these freshwater and saltwater cover data sets are shown in 76 Table III - F l o r i s t i c table: 64 species in 103 sample pl o t s . Group at l e f t , mainly fresh-water influenced; group at right, mainly salt-water influenced A A J J J J J j j j J A A A A AA A D D D A D A D D D A A A A A A A A A A A A A A A A A A D A A B C C E E E E H H B E E E G G H H H H H F F B C C E G G G E G G F 3 H H C G S S 8 C C E F B E G B H H 8 B C G 5 9 6 9 7 1 5 : 3 - : 8 G 8 1 1 2 2 2 2 7 8 2 5 7 4 6 t .1 1 ) 1 1 2 2 2 1 1 2 13 1 1 2 2 0 3 3 2 1 7 8 8 1 3 6 7 8 5 2 7 8 2 3 6 9 1 1 5 3 4 3 3 4 5 6 5 4 9 8 9 5 7 4 1 1 1 1 2 J 5 P 4 1 9 8 7 6 2 3 1 12 1 0 8 0 1 2 2 4 6 7 3 G 7 5 9 5 1 3 4 8 0 9 2 O 1 0 0 1 E O U I S E T U M F L U V I A T I L E A L I S M A P L A N T A G O - A Q U A T I C A S C I R P U S V A L I O U S A G R O S T I S A L B A C A R E X L Y N G B Y E I E L E O C H A R I S P A L U S T R I S S A G I T T A R I A L A T I F O L I A S C I R P U S A M E R I C A N U S S C I R P U S MAR I T I M U S R U P P I A MAR I T I M A C H A R A B R A U N I I J U N C U S B A L T I C U S P O T E N T I L L A P A C I F I C A T Y P H A L A T I F O L I A L Y T H R U M S A L I C A R I A S I U M S U A V E B I D E N S C E R N U A C O T U L A C O R O N O P I F O L I A T R I G L O C H I N M A R 1 T I 1 A U M S A L I C O R N I A V I R G I N I C A D I S T I C H L I S 5 P I C A T A S P E R G U L A R I A C A N A D E N S I S A T R I P L E X P A T U L A P L A N T A G O M A R I T I MA S P E R G U L A R I A M A R I N A C U 5 C U T A S A L I N A P U C C I N E L L I A N U T T A L L I A N A G R I N D E L I A I N T E G R I F O L I A G L A U X MAR I T I MA L 1 L A 6 A S C I L L O I D E S H O R D E U M B R A C H Y A N T H E R U M J U N C U S G E R A R D I I S P A 13 . 0 6 N A N T H E S A R M E N T O S A J U N C U S A R T 1 C U L A T U S L I L A E O P S I S O C C I D E N T A L I S A G R O P V R O N R E P E N S C A L T H A A S A R I F O L I A L I M O S E L L A A Q U A T I C A C A L L I T R I C H E S P . S P C 2 S P G I O A C H I L L E A M I L L E F O L I U M H Y G R O H Y P N U M L U R I D U M L E P T O O I C T Y U M R I P A R I U M A S T E R E A T O N I I S O N C H U S A R V E N S I S M Y O S O T I S L A X A L A T H Y R U S S P . T R I F O L I U M O L I G A N T H U M J U N C U S B U F 0 N 1 U S M E N T H A A R V E N S I S D E S C H A M P S I A C E S P I T O S A E L Y M U S G L A U C U S E L Y M U S M O L L I S F E S T U C A A R U N O I N A C E A P U C C I N E L L I A N U T K A E N S I S S P C 3 S P 0 1 S P E 1 P O L Y G O N U M A V I C U L A R E S P J 1 A MI M U l . U S G U T T A T U S S P J 4 A 2 2 2 3 3 2 2 ; : 2 2 2 2 1 1 4 4 * 2 1 ) 1 + 4 5 5 3 2 2 3 35 12 1 5 5 5 2 2 3 2 1 1 + 1 1 * * 3 3 5 5 5 4 5 1 - * + * 1 4 4 6 5 * 4 6 2 6 6 2 3 1 5 6 2 * 13 1 * 1 * l 1 * * + 1 1 1 1 13 + 3 " 1 3 " 1+++ + 1 * 2 2 + 12+ 12 B + 5 3 - 3 2 1 2 2 1 1 5 2 2 1 6 4 2 + 1 + 1 4 + * 2 1 1 5 2 2 + 2 2 + 4 1 + 2 2 2 2 3 5 + + 5 1 2 2 + 3 5 + 1 2 2 2 2 1 2 2 14 111 + 2 2 + " 2 2 2 3 3 " + 2 1 5 +" 5 2 3 + 1 2 3 3 + 1 2 + 1 2 2 3 3 2 6 1 2 2 1 + 2 3 2 4 1 2 + - 4 2 1 " -+ + + 3 + 2 1 1 3 + 6 3 4 2 6 2 6 5 5 2 + * ' 2 5 5 2 5 5 2 6 1+ + + + 1 3 +3 3 3 + 1 + 3 3 4 2 2 1* + + 1 3 2 1 2 2 2 12 4 2 2 + 2 1 4+ + 2 2 3 2 2 2 2 3 2 Legend: " = s o l i t a r y i n d i v i d u a l , n e g l i g i b l e c o v e r ; + = s e v e r a l i n d i v i d u a l s , < 1% c o v e r ; 1 = 1-5% c o v e r ; 2 = 6-25% cover; 3 = 26-50% cover; 4 = 51-75% cover; 5 = 76-95% c o v e r ; 6 = 96-100% cover Nomenc1 a t u r e i s a c c o r d i ng w i t h a u t h o r i t i es. to H i t c h c o c k et a l 1969 See Appendix A f o r s p e c i e s names 77 Figs. 11 and 12. (Unless otherwise stated, a l l PCA ordinations are performed using a variance-covariance resemblance matrix.) A PCA ordination on the complete cover data set was performed, but results proved unsatisfactory, because many of the 103 plots were overprinted on one another. Data standardizations: The usefulness of an ordination method in exposing ecological gradients may be considerably affected by the data standardization or transformation employed; hence d i f f e r e n t standardizations and transformations were tested on the data in order to evaluate their e f f e c t s . These are described in the remainder of t h i s section. Square root transformation: It was noted that the high weightings on the p r i n c i p a l component axes were given to high-cover species, leading to the suspicion that the information supplied in lower cover values was being more or less ignored by PCA. Accordingly, a means was sought to even out somewhat the d i s p a r i t y between high and low cover values. Thus the percent cover values, ranging from 0 to 100, were transformed to their square roots, ranging from 0 to 10. Results of PCA ordinations on the square root transformed freshwater and saltwater cover data matrices are given in Figs. 13 and 14. Results of the PCA ordination on the square root transformed complete cover data matrix are shown in F i g . 15. Normalization: The lowest portions of the marsh, where 78 A 2 0 J 2 A17«* 1 0 + A 2 7 A 1 6 A 2 8 A 4 , A 9 A11 • A 7 J 6 • D3» . A 1 5 r £ \ « A 2 9 Aig'^o J 7 A X I S 1 e 5 A 3 J 5 • A 8 A6 A 1 B 07 • 08 A10 • D4» •D6 Figure 11 - PCA ordination of samples using species cover data from freshwater plot group 79 H4 G9 • • H 2 »H1 C 7 R 1 l / B 1 0 W^'E8,12 G1 C2» 6 f G2 G10 E6.*E8 E7»*G5» »H9 B5 H10 H8 FA E-2 B 7 G6" B6 E5 G8 H5 G3 • B8 »B9 -3+ C.S F1 • B2 B3» C 4 Figure 12 - PCA ordination of samples using species cover data from saltwater plot group 80 1.0 A 271 A 2 6 A 1 4 J 6 J 9 A 1 3 D 3 A , 2 3 J 1 . 4 2 0 A 1 7 »J2 D 2 J 5 J 3 A 1 8 - 0 . 5 A O J • A 2 9 s .3 ,0 A 9 A 5 A * 8 A 7 • A 2 4 0 . 5 0 7 J 4 - 0 . 5 + 0 8 D 5 A 6 D 4 A 1 0 0 6 Figure 13 - PCA ordination of samples using square roots of species cover data from freshwater plot group 81 1.0 C1 G 9 H1 0 . 5 B 1 0 • B11 % B 1 2 G 7 F5 E9» H11 V m C 2 • H 3 C 3 C 6 G 1 0 G 2 G 8 G5» B 8 B 9 * . * * B 7 E 7 H 1 0 • • G 6 * C 8 _ B 6 E 6 A X I S 1 H 9 0.5 H 6 1.0 E 4 H 8 E 2 C 4 G 4 F 2 B 4 G 3 B 2 - 0 . 5 + E 5 Figure 14 - PCA ordination of samples using square roots of species cover data from saltwater plot group 82 G 2 F 3 C 3 i f * C 6 • B3 H 6 F 1 C 5 0.4> G 3 E 5 F 4 » B4 -t-H 9 • G 9 . H 4 . H 3 H 8 Bp , m H 5 E 7 E 6 G 5 H11 G 7 A 2 9 J 8 | H 1 0 . G B B*9 % B . • F 5 E 6 E 9 C 8 B 1 2 -A 3 0 » * B B i t * C 7 » * ^ 5 ^ A 4 A 2 8 . | A 2 4 G 1 0 0.4 D 8 J 4 D 6 D 7 A 2 2 A 6 A 1 8 D 5 J 7 J 5 A X I S 1 0 . 4 " A 7 A l * ^ 1 3 A I 9 . • ^ • • A 1 3 »J6 » A 2 3 A 9 • »A11 A 1 4 A 1 6 A 2 0 . A 2 6 J 1 • A 1 7 A 27 A 2 3 Figure 15 - PCA ordination of samples using square roots of species cover data from a l l plots (freshwater group, Transects A, D, J; saltwater group, Transects B, C, E, F, G, H) 83 flooding effects are most severe, present a h o s t i l e environment for plant growth. Plant performance i s poor in such marginal habitats, and cover values are correspondingly low. Releves from such areas were lumped near the o r i g i n on the PCA scatter diagrams, rather than being grouped with stands of similar species composition but higher cover values. A means was therefore sought which would give equality to stands with low t o t a l cover. Normalization of the data accomplished t h i s objective. Each element in a quadrat vector ( i . e . each species cover value in the quadrat) was divided by the length of the quadrat vector ( i . e . the square root of the sum of the squared cover values in the quadrat). The consequence of this standardization is as i f the plants in a sparsely-vegetated quadrat were to extend themselves to cover a l l the bare areas, without changing the proportion of t o t a l cover represented by each species in the quadrat. Results of PCA ordinations on the normalized freshwater and saltwater cover data matrices are shown in Figs. 16 and 17. Correlation matrix: The variance-covariance resemblance matrix used in the preceding examples caused PCA to ignore rare, low-cover species. In contrast, a resemblance matrix generated by the product-moment correlation c o e f f i c i e n t gives stronger weighting to rare species. It was f e l t that rare species might p o t e n t i a l l y contribute useful information to an ordination, so the data were analyzed using a resemblance 8 4 . 0 8 + . 0 4 + ^ 5 J 9 , A 2 5 A 1 3 » « A l 9 D3 J 8 A 2 0 A 2 3 0 2 J 5 A 1 8 - . 1 2 A 1 1 • A 9 A 2 . 8 * VM A » A 7 3 0 . 0 8 A 5 A 2 9 - . 0 4 + . 0 4 D 5 A 3 0 7 A 2 2 .« D 8 D 4 • A 6 • 0 6 A 1 0 Figure 16 - PCA ordination of samples using normalized species cover data from freshwater plot group 85 .10 G 7 E9« • F 5 E 8 H 1 0 G 8 G 5 . 0 5 + C1 B 1 1 , ' C * B 1 2 H 3 H2»«G1 C2 G 9 H 4 G 1 0 C 3 C6» G 2 H 5 E 4 G 4 G 6 C 8 , B 6 B 8 V B S E 6 H 9 F 3 B 5 B 4 C 5 F l »B2 - . 0 5 G 3 E 2 » « B 3 Figure 17 - PCA ordination of samples using normalized species cover data from saltwater plot group 86 matrix of co r r e l a t i o n c o e f f i c i e n t s . The res u l t i n g ordinations (not shown) featured a very dense cluster of plots near the o r i g i n , with a few o u t l i e r s around the edges. Reciprocal averaging; This method may be regarded as a standardized version of PCA (Noy-Meir 1970, H i l l 1973), so i t is considered here as a standardization. It d i f f e r s from PCA mainly in that i t produces simultaneous species and stand ordinations. I n i t i a l results of RA ordinations on freshwater and saltwater cover data matrices showed an extreme s e n s i t i v i t y to certain data anomalies. T y p i c a l l y , one or a few quadrats (and species) would appear as o u t l i e r s at one edge of the scatter diagrams, with the other quadrats (and species) crowded along the opposite edge of the diagrams. By removing these outlying quadrats from the data matrices, greatly improved ordination results were obtained (Fig. 18). 7.3 Treatment of the Environmental Data Standardization of elevation data: Elevation as such has nothing to do with the performance or d i s t r i b u t i o n of species; rather i t i s a variable which conveniently estimates and summarizes the levels of influence of the factors which actually act on the organism. In the. t i d a l marshes, elevation is mainly an index of the degree to which a plant i s d i r e c t l y 87 I C h a b r a + • A 5 • A 3 0 > A 2 4 • A 2 8 K J 9 • + S c i v a l J 6 • A 1 4 C o t c o r A13« S a g l a t + R u p m a r + • A 9 A11 • • A 2 9 T r i m a r + »A4 > A O • A 1 5 + E l e p a l A 2 5 • J 8 + B i d c c r A l i p l a + E q u f l u + « A 2 7 A 1 7 A 2 3 » • » A 1 6 A 2 0 * _ » J 2 S c i m a r P u c n U t 4 + A 2 6 T y p l a t + A 1 2 « + L i r n a q u + , + C a l a s a D 3 J 7 + A g r a l b J 5 L i l o c c + + A n g a r g + P o t p a c + + S i u s u a • f L y t s a l D 2 • J 3 A 2 1 a A 1 8 < • J 4 D 5 • D 7 A 8 » A 2 2 . D 6 A S . C a r l y n + . A 1 0 * Legend: + = s p e c i e s • sampl e p i o t s s p e c i e s codes = f i r s t 3 l e t t e r s of genus name + f i r s t 3 l e t t e r s of s p e c i f i c e p i t h e t ; see Appendix A f o r f u l l names (Pucnut = P u c c i n e l l i a n u t k a e n s i s ) Figure 18 - RA ordination of species and samples using species cover data from freshwater plot group 88 or i n d i r e c t l y influenced by the l e v e l of the nearby water body. Unfortunately, water l e v e l fluctuations due to the t i d a l cycle and to variations in r i v e r flow do not follow the same pattern throughout the study area (Section 3.4.3). The result i s that absolute elevation i s not l i k e l y to be a very good predictor of plant performance when comparing data from d i f f e r e n t areas. To resolve t h i s problem, I standardized the elevation data according to l o c a l variations in t i d a l range. Thus the elevations above chart datum were divided by the t i d a l range for large tides at convenient t i d a l monitoring stations: Deas Island 1 for the Ladner Marsh plots, Steveston 2 for the northern and western Brunswick Point plots, Tsawwassen3 for the southeastern Brunswick Point plots, and Crescent Beach" for the Boundary Bay p l o t s . The standardized elevations are expressed in percentage units, and may range in theory from 0 (chart datum) to 100 (the highest l o c a l water l e v e l ) . The standardization procedure, however, depends for i t s r e l i a b i l i t y on the judiciousness of certain decisions -- such 1 Data obtained from printout of 1978 hourly water levels at Deas Island Tunnel, supplied by Environment Canada, Water Resources Branch, Inland Waters Directorate, P a c i f i c and Yukon Region, Vancouver, B.C. 2 Data obtained from printout of 1978 hourly water levels at . Steveston, supplied by Institute of Ocean Sciences, Sidney, B.C. 3 Data obtained from Canadian Hydrographic Service 1977, p. 18. • i b i d . 89 as which t i d a l monitoring station to use as a reference, and over what time period to determine the t i d a l range. Thus the values obtained should be regarded as approximations. Ordination; Eight s o i l variables and a s i t e elevation variable were selected for ordination. The s o i l variables were: percentage by weight of sand, s i l t , clay, and nitrogen; and concentration in parts per m i l l i o n (ppm, or mg kg" 1) of potassium, calcium, magnesium, • and sodium. The elevation variable was the standardized elevation above chart datum described above. I n i t i a l l y , a l l plots for which any data values were missing were removed from the data set. The environmental data set thus d i f f e r e d in character from the vegetation data set, in which most of the values were zero ( i . e . species not present). With species data, this i s almost unavoidable, and tends to cause distorted ordinations, es p e c i a l l y with PCA (Swan 1970; Whittaker & Gauch 1973, 1978). The environmental data ordinations, therefore, were free of at least this one source of confusion. The environmental data set was s p l i t into "freshwater" and "saltwater" subsets on the same basis as for the vegetation data, and PCA and RA ordinations were performed on a l l three data sets. Since the variables were not a l l measured by the same units, a co r r e l a t i o n matrix was used in the PCA. The PCA results are shown in Figs. 19, 20, and 21. The RA results were f a i r l y s i m i l a r , but were not as easy to 90 interpret and are not shown here. Display of spec ies cover values on environmental  ordinations: A major assumption of th i s study was that plant species d i s t r i b u t i o n s and performance values could be shown to be related to the level s of selected environmental factors. To demonstrate such a relationship, cover class values for some important species were plotted on the environmental ordination diagrams. Results are shown for Agrostis alba, Sc i rpus amer icanus, and Carex lyngbyei on the freshwater ordination (Figs. 22, 23, 24), and for Sal i c o r n i a v i r g i n i c a , D i s t i c h l i s spicata, and Triglochin maritimum on the saltwater ordination (Figs. 25, 26, 27). 91 A17 A25»* • B8 A14 B.6 D10 AS D6 D8 A24 A5 B12 A19 J6 J4 D2 04 A6 AO Al A2 A26» A 28 A 21 D1 A23 A3 J2 J1 C 8 Q5 B2 B4 63 :AXIS 1 G2 G5 H1 H*8 H10 G6 H11 F i g u r e 19 - PCA o r d i n a t i o n of samples u s i n g e n v i r o n m e n t a l da ta from freshwater ( T r a n s e c t s A , D, J ) and s a l t w a t e r ( T r a n s e c t s C , G , H) p l o t groups , 92 ^ 2 5 A5 A24 A23 A14 A17 •A10 A19 A26 A2B A1 A2 J1 0 8 A11 A8 D6 AXIS 1 A 21 D2 D4 A6 • J6 DI J4 J2 F i g u r e 20 - PCA o r d i n a t i o n o f s a m p l e s u s i n g e n v i r o n m e n t a l d a t a from f r e s h w a t e r p l o t s 93 C 8 C5 B4 G 3 B1 H8 H1 H10 G2 G5 B2 AXIS 1 B8 B10 B12 B6 G6 H11 F i g u r e 21 - PCA o r d i n a t i o n of samples u s i n g e n v i r o n m e n t a l d a t a from s a l t w a t e r p l o t s 94 4 1 A X I S 1 1 1 Figure 22 - Plot of cover class codes of Agrostis alba on the ordination of environmental data from freshwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 =76-100%; • = absent A X I S 1 Figure 23 - Plot of cover class codes of Scirpus  americanus on the ordination of environmental data from freshwater pl o t s . 1 = <25% cover; 2 = 26-50%; 3 =51-75%; 4 = 76-100%; • = absent 96 4 A X I S 1 Figure 24 - Plot of cover class codes of Carex lyngbyei on the ordination of environmental data from freshwater plots, 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 =76-100%; • = absent 97 X < 2 2 AXIS 1 Figure 25 - Plot of cover class codes of Salico r n i a  v i r g i n i c a on the ordination of environmental data from saltwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 98 AXIS 1 Figure 26 - Plot of cover c lass codes of D i s t i c h l i s  spicata on the ordinat ion of environmental data from saltwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 4 A X I S 1 1 1 Figure 27 - Plot of cover class codes of Triglochin  maritimum on the ordination of environmental data from saltwater p l o t s . 1 = <25% cover; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%; • = absent 100 8. DISCUSSION 8.1 Data Standardizations Square root transformation; As may be seen by comparing Fig . 11 with F i g . 13 and F i g . 12 with F i g . 14, the general result of using square root transformed data was that the points on the scatter plots were spread out more evenly. A p r a c t i c a l benefit of thi s was a reduction in the number of plots which were overprinted by the computer. This effect made l e g i b l e the ordination of the complete cover data set, as shown in F i g . 15. The use of thi s transformation may thus be helpful for improving the rea d a b i l i t y of highly congested ordination diagrams. The square root transformation made previously d i s t i n c t clumps of plots i n d i s t i n c t , but trends in the data, i . e . the relationships between clumps, became more evident. The over a l l s p a t i a l pattern was preserved with r e l a t i v e l y minor d i s t o r t i o n , at least on the f i r s t and second axes. The percent of t o t a l variance accounted for by the p r i n c i p a l axes is a l i t t l e lower with square root transformed data; e.g. 61% for the f i r s t . three axes (transformed freshwater data) compared with 70% (untransformed). The variable weightings on the ordination axes corresponded well with those obtained from untransformed data, 101 at least on the f i r s t two axes; on higher axes, the important species were sometimes weighted in quite d i f f e r e n t proportions. In the untransformed data, there was a tendency for a single species to greatly dominate the weightings, whereas with transformed data the weightings were somewhat more equitable. In the freshwater ordinations, the increased weighting of less important species resulted in easier ecological interpretation of the t h i r d axis. Normalization: By amplifying the e f f e c t i v e information content of low-cover quadrats, normalization resulted in the plots being grouped together according to their s i m i l a r i t y with respect to the proportionate representation of their dominant species. As with the square root transformation, - the broad patterns of the ordinations were not changed (cf. Figs. 11 and 16, 12 and 17), at least for the f i r s t and second axes. The percent variance accounted for on the f i r s t three axes was s l i g h t l y reduced. The species showing strongest correlations with the f i r s t and second axes were the same, though differences appeared in the t h i r d axis. In F i g . 16, several d i s t i n c t groups of quadrats are apparent; these groups constitute f l o r i s t i c a l l y d i s t i n c t e n t i t i e s characterized by their r e l a t i v e abundance of three important species (Agrostis alba, Carex lyngbyei, and Scirpus  americanus). A similar pattern of plots is found in the ordination of non-normalized data (Fig. 11), but there the 1 02 groups are not d i s t i n c t l y separated. The same p r i n c i p a l species govern the axis orientations in either case, but plot position i s influenced by r e l a t i v e species abundance in the ,case of normalized data, and absolute abundance with non-normalized data. For example, F i g . 16 shows a cluster of plots just below the l e f t end of the f i r s t axis: these are a l l proportionately high in Scirpus americanus. In plots A29 and A30, however, the absolute cover of Scirpus americanus is very low; they are located far out on a mudflat where only Scirpus  amer icanus and Ruppia maritima occur, very sparsely. In F i g . 11, however, the two plots appear in a tight c l u s t e r , below and to the l e f t of the o r i g i n , along with several plots with which they have no species at a l l in common -- e.g. D3, a dense stand of Typha l a t i f o l i a , and AO, containing only Eleocharis p a l u s t r i s • Normalization thus emphasized f l o r i s t i c s i m i l a r i t y , regardless of species performance. (Refer to Table III for the species composition of the plots.) The normalization procedure can be c r i t i c i z e d ~ on the grounds that i t causes important ecological differences between s i t e s to be overlooked — i . e . s i t e productivity differences, as expressed in o v e r a l l plant performance. However, the purpose of the ordination may be to assess the relationships among samples on the basis of their resemblance in f l o r i s t i c composition, not on the basis of their resemblance in s i t e productivity. Normalization of data is a procedure that enables the most e f f e c t i v e use to be made of f l o r i s t i c information, while s a c r i f i c i n g s i t e productivity 1 03 information. An optimal ordination strategy might thus involve the analysis of both normalized and non-normalized data. Correlat ion matrix: The corr e l a t i o n matrix i s a standardized variance-covariance matrix: each covariance value for a species pair i s divided by the standard deviations of the two species. In e f f e c t , the variables are standardized to zero mean and unit variance. The effect of t h i s procedure was that the highest c o r r e l a t i o n values corresponded to the rarest species, which had many zero values in common. The p r i n c i p a l components solution then gave the highest axis weightings to the rarest species, resulting in ordinations in which the great majority of plots were clustered t i g h t l y around the o r i g i n . When the rarest species (those present in only one or two quadrats) were removed from the data, improved ordinations were obtained, but I found the results d i f f i c u l t to interpret. Use of the corr e l a t i o n matrix decreased the amount of variance accounted for on the major axes. With the freshwater data, the f i r s t three axes accounted for only 34% of t o t a l variance. The co r r e l a t i o n matrix does not seem appropriate for use with vegetation data, although sat i s f a c t o r y results might perhaps be obtained with data from very homogeneous stands. Under such favourable conditions, the corr e l a t i o n matrix might 1 04 be recommended, i f axis generation on the basis of maximum variance did not produce e c o l o g i c a l l y meaningful results (Austin 1969). Rec iprocal averaging: As noted in Section 7.2, the i n i t i a l species and quadrat ordinations obtained with RA were disappointing, with one or two quadrats appearing as o u t l i e r s on the f i r s t axis, and a l l the other quadrats crowded together towards the other end (although with a good spread along the second a x i s ) . Examination of the raw data revealed that the anomalous outlying quadrats had very high cover values for uncommon species, which were themselves separated out in the corresponding species ordinations. When outlying plots (and species unique to those plots) were removed from the data, acceptable ordinations were obtained (Fig. 18). This d i s t o r t i o n by o u t l i e r s is a c h a r a c t e r i s t i c problem with RA (Gauch, Whittaker & Wentworth 1977), but i t is ea s i l y dealt wi th. Reciprocal averaging has been found superior to PCA by some investigators (Austin 1976; Gauch, Whittaker & Wentworth 1977; Robertson 1978; del Moral 1980) for the ordination of ecological data. RA has been found to produce an e f f i c i e n t ordination in one dimension (del Moral 1980), and H i l l (1973) stated that when there i s a long f l o r i s t i c gradient, i t would always be presented l i n e a r l y on the f i r s t axis. With PCA, by contrast, stands extreme on the f i r s t axis are not necessarily extreme on the f l o r i s t i c gradient, and vice versa. Although 105 RA may y i e l d spurious results on the second axis, with plot position r e f l e c t i n g only the degree of displacement from the f i r s t axis (Gauch, Whittaker & Wentworth 1977), this is not always the case, and the second RA axis can sometimes be ec o l o g i c a l l y meaningful. Del Moral (1980) suggested that t h i s w i l l usually be the case when beta d i v e r s i t y is low. Gauch, Whittaker & Wentworth (1977) found RA much superior to PCA at high beta d i v e r s i t i e s , and generally preferable at low beta d i v e r s i t i e s . 8.2 Ecological Interpretation of Ordination Results 8.2.1 Vegetation Data The PCA ordination of square root transformed cover data from a l l 103 plots (scatter diagram, F i g . 15; eigenvectors, Table IV) produced a good f i r s t - a x i s separation, accounting for 23% of t o t a l variance, of the freshwater plots (Transects A, D, J) on the right, and the saltwater plots (Transects B, C, E, F ,G, H) on the l e f t , on the basis of a f l o r i s t i c gradient related to high cover values of community dominants in both plot groups (Carex lyngbyei and Agrostis alba in the freshwater plots; D i s t i c h l i s spicata, Tr iglochin maritimum, and S a l i c o r n i a v i r g i n i c a in the saltwater p l o t s ) . The second axis, however (14% of t o t a l variance), loaded p o s i t i v e l y with 106 Carex lyngbyei, D i s t i c h l i s spicata, and Atriplex patula, and negatively with Scirpus americanus, Scirpus maritimus, and Agrostis alba, does not lend i t s e l f to such ready interpretation, and may largely r e f l e c t the d i s t o r t i o n resulting from high beta d i v e r s i t y . Table IV - Summary of results of PCA ordination on square roots of species cover data from a l l pl o t s . Eigenvector elements in the range -0.1500 to +0.1500 not shown A x i s % v a r i a n c e Ranked e i g e n v e c t o r S p e c i e s e l e m e n t s 1 22.93 0.562 A g r o s t i s a l b a 0.513 C a r e x l y n g b y e i -0.179 A t r i p l e x p a t u l a -0.249 T r i g l o c h i n maritimum -0.283 S a l i c o r n i a v i r g i n i c a -0.407 D i s t i c h l i s s p i c a t a 2 14.47 0.695 C a r e x l y n g b y e i 0.610 D i s t i c h l i s s p i c a t a 0.150 A t r i p l e x p a t u l a -0.116 A g r o s t i s a l b a -0.124 S c i r p u s m a r i t i m u s -0.238 S c i r p u s americanus The PCA ordinations on the freshwater plots (scatter diagrams,, Figs. 11, 13; eigenvectors, Table V) separate the plots on the f i r s t axis (accounting for 32% of t o t a l variance in the ordination of the untransformed data) between those high in Carex lyngbyei on the right and those high in Scirpus  americanus on the l e f t . Inspection of the environmental data reveals that this f l o r i s t i c gradient corresponds strongly to 107 elevation; i t is in fact highly conspicuous in the f i e l d at Brunswick Point, where a broad belt dominated by Carex  lyngbyei in the upper and middle part of the marsh gives way to a wide fringe of Scirpus americanus at the lower l e v e l s . On the second axis (28% of t o t a l variance), the f l o r i s t i c gradient runs from high cover values of Agrostis alba (top) to high values of Carex lyngbyei (bottom). This does not correspond with any of the environmental gradients sampled, though i t may be related to l o c a l variations in topography and drainage, with the hiqh-Agrostis group being located in more poorly drained areas where the community i s f l o r i s t i c a l l y r i cher, and where Scirpus maritimus tends to replace Carex  lyngbyei. Table V - Summary of results of PCA ordination on species cover data from freshwater plots. Eigenvector elements in the range -0.150 to +0.150 not shown Axis % variance Ranked eigenvector Species elements 1 31.59 0.912 Carex lyngbyei 0.232 Agrostis alba -0.309 Scirpus americanus 2 27.50 0.893 Agrostis alba 0.229 Scirpus maritimus -0.219 Scirpus americanus -0.293 Carex lyngbyei In the PCA ordination on normalized freshwater data (scatter diagram, F i g . 16; eigenvectors, Table VI), three 108 f l o r i s t i c nodal groups may be distinguished. At the top of the second axis i s a group of plots r i c h in Agrostis alba and, usually, Scirpus maritimus; at the l e f t end of the f i r s t axis is a group of plots r i c h in Scirpus americanus; and in the lower right corner is a group of plots high in Carex lyngbyei. The other plots either are dominated by some combination of these species, or are not r i c h in any of them (the group just above and to the l e f t of the o r i g i n ) . Table VI - Summary of results of PCA ordination on normalized species cover data from freshwater pl o t s . Eigenvector elements in the range -0.150 to +0.150 not shown A x i s % v a r i a n c e Ranked e i g e n v e c t o r S p e c i e s e l e m e n t s 1 27.89 - 0.576 Ca r e x l y n g b y e i 0.359 A g r o s t i s a l b a -0.719 S c i r p u s a m ericanus 2 22.04 0.688 :- A g r o s t i s a l b a 0.161 S c i r p u s m a r i t i m u s -0.184 S c i r p u s americanus -0.661 Carex l y n g b y e i The PCA ordinations on saltwater data (scatter diagrams, Figs. 12, 14; eigenvectors, Table VII) separated D i s t i c h l i s  spicata-dominated plots (right) from plots dominated by Triglo c h i n maritimum, S a l i c o r n i a v i r g i n i c a , and Spergularia  canadensis ( l e f t ) on the f i r s t axis, and plots dominated by Atriplex patula (top) from those dominated by Salico r n i a 109 v i r g i n i c a , Triglochin maritimum, Carex lyngbyei, and/or D i s t i c h l i s spicata (bottom) on the second axis. The f l o r i s t i c gradient on the f i r s t axis does not seem to correspond with a gradient in any of the measured environmental factors, whereas the second axis shows a strong relationship to elevation. The ordination on normalized saltwater data (Fig. 17) added more plots to the Atriplex group at the top and to the D i s t i c h l i s group in the lower right, while revealing greater d e t a i l in the group of plots at l e f t , in p a r t i c u l a r by i s o l a t i n g a group of f i v e plots which were d i s s i m i l a r to a l l other plots (including each other). Taken together, these ordination results suggest four nodal groups of plots: a group dominated by Atriplex patula; a group dominated by Atriplex and D i s t i c h l i s spicata; a group dominated by D i s t i c h l i s and other species -- Carex lyngbyei, Tr iglochin maritimum, Sa l i c o r n i a  v i r g i n i c a , and Spergularia canadensis; and a group dominated by S a l i c o r n i a , Tr iglochin, and Spergularia• The' RA ordination of freshwater plots (Fig. 18) i s similar in part to the PCA ordination, with a strong f i r s t -axis separation of the Scirpus americanus-dominated plots at l e f t from the plots dominated by Carex lyngbyei and Agrostis  alba at r i g h t . The strong separation on both axes of Scirpus  validus-dominated plots would not have been predicted from the PCA ordination, in which these plots f a l l into or near the central swarm. More interesting i s the arch-shaped sequence extending from lower l e f t to lower rig h t , which follows a f l o r i s t i c gradient from high-Carex plots at lower right (high-110 Table VII - Summary of results of PCA ordination on species cover data from saltwater p l o t s . Eigenvector elements in the range -0.150 to +0.150 not shown Axis % variance Ranked eigenvector Species elements 1 35.73 0.941 D i s t i c h l i s s p i cata 0.186 A t r i p l e x patula -0.168 S a l i c o r n i a v i r g i n i c a -0.176 T r i g l o c h i n maritimum 2 15.77 0.869 A t r i p l e x patula -0.200 S a l i c o r n i a v i r g i n i c a -0.264 D i s t i c h l i s s p i cata -0.329 T r i g l o c h i n maritimum elevation) through a f l o r i s t i c a l l y - r i c h series of plots in which Agrostis i s prominent (high to medium elevations) to low-elevation plots dominated by Scirpus americanus. (The dense clu s t e r at right centre i s formed by uncommon, low-cover species.) A linear f l o r i s t i c gradient i s curved here into the second ordination dimension, but i s displayed somewhat more e f f e c t i v e l y than by PCA. 8.2.2 Environmental Data The PCA ordination on environmental data from the freshwater and saltwater plots together (scatter diagram, F i g . 19; eigenvectors, Table VIII) c l e a r l y separated the freshwater group from the saltwater group on the f i r s t (horizontal) axis, accounting for 51% of t o t a l variance, with the two groups 111 appearing on opposite sides of the o r i g i n . S i l t and clay were weighted negatively on th i s axis; the other seven variables were weighted p o s i t i v e l y , especially sodium and potassium. The second ( v e r t i c a l ) axis, accounting for 23% of variance, i s b a s i c a l l y textural and n u t r i t i o n a l , with sandy plots toward the bottom, and plots high in cations, s i l t , and clay toward the top. Table VIII - Summary of results of PCA ordination on environmental data from freshwater and saltwater plots together E i g e n v e c t o r 1 2 3 4 5 6 7 8 Sand 0 .3717 -o .3914 -o . 1685 -0. 1389 -0. 0476 0. . 2370 -0. .0058 -0. .0114 S i l t -0 .3813 0 . 3462 0 .0916 O. 1077 0. 1934 -0. . 5785 0 .0119 0. .0123 C 1 ay -0 . 2781 0 . 4306 0 . 3282 0. 1907 -0. .3240 0. .6578 -0 .0108 0 .0073 N 0 .3101 0 .0361 0 . 5272 0. 1239 0. 7287 0. .1634 -0 . 2248 0. .0314 K 0 . 4059 0 . 158 1 -0 .0439 0. 4342 -0. . 3708 -0. .2311 -0 .6181 0 .2164 Ca 0 . 1967 0 . 5224 -0 . 2366 -0. 5998 0. 1060 0. .0787 -0. .0591 0 .5018 Mg 0 . 35 13 0 . 4409 -o . 1332 -0. 1276 -0. .0109 -0. .0332 0 .0006 -0 .8044 Na 0 . 4095 0 .2021 -0 .0470 0. 4424 0. .0028 -0. .053 1 0 . 7334 0 . 2299 E l e v o . 2203 -0 . 0839 o . 7069 -0. 3964 -0. .4189 -0. . 2936 0 . 1605 O .0140 % v a r i a n c e 50.67 22.87 13 . 24 5 . 76 4 . 40 1 .97 0.95 0.13 The ordination of the freshwater plots (scatter diagram, Fig . 20/ eigenvectors, Table IX) separated plots along the f i r s t axis (39% of t o t a l variance) mainly on the basis of texture and cation concentration: high-sand, low-cation plots at r i g h t , low-sand, high-cation plots at l e f t . (For the values of the environmental variables at each plot, consult the environmental data table in Appendix B.) Only sand was weighted p o s i t i v e l y ; the strongest negative weighting was for 1 12 T a b l e IX - Summary of r e s u l t s of PCA o r d i n a t i o n on e n v i r o n m e n t a l da ta from freshwater p l o t s E i g e n v e c t o r 1 2 3 4 5 6 7 8 Sand 0. 3991 0 . 3262 0 . 3623 0. 0492 -o. .0243 -0. 1250 -o. 0108 -0.0037 S i l t -0.3430 -0 . 2394 -o .5115 0. 0649 -0. . 4639 0. 2153 -0. 0857 0.0032 C l a y -0.3396 -0 . 3398 -0 .0040 -0. 2048 0. .7581 -0. 0579 0. 1543 0.0040 N -0.2509 -0 . 3406 0 .4635 0. 4157 -0, . 2788 -0. 1804 0. 5621 0.0848 K -0.4242 0 . 1729 0 .0628 0. 4202 0. .0740 -0. 5161 -0. 5461 -0.1989 Ca -O.3551 0 . 3753 0 .0744 -0. .4735 -0. . 1884 -0. 0981 ' 0. . 3226 -0.5951 Mg -0.3980 0 . 3706 0 . 1222 -0. 3039 -0. .0996 -0. 0719 -0. 0166 0. 7626 Na -0.2598 0 . 3928 0 . 1392 0. . 4248 0. .221 1 0. 7216 0. 0467 -0.0815 E l e v -0.1139 -0 . 3775 0 . 5903 -0. .3241 -0. . 1787 0. 3167 -0. .4980 -0.1040 % v a r i a n c e 39 . 34 28 . 14 13 . 42 7.18 5.15 4 . 42 2 . 22 0.13 p o t a s s i u m . On the second a x i s (28% Of t o t a l v a r i a n c e ) , sodium, c a l c i u m , magnesium, and sand c o n t r i b u t e d s t r o n g p o s i t i v e w e i g h t i n g s ; e l e v a t i o n , n i t r o g e n , and c l a y were s t r o n g l y weighted n e g a t i v e l y . The r e s u l t was a s e p a r a t i o n of g e n e r a l l y sandy, c a t i o n - r i c h , l o w - e l e v a t i o n p l o t s at top from g e n e r a l l y h i g h - e l e v a t i o n , f i n e - t e x t u r e d p l o t s r i c h in o r g a n i c matter a t bottom. ( E c o l o g i c a l i n t e r p r e t a t i o n i s not f a c i l i t a t e d by the l o a d i n g of sand and c a t i o n s at o p p o s i t e ends of the f i r s t a x i s , and at the same end of the second . ) In the o r d i n a t i o n of s a l t w a t e r p l o t s ( s c a t t e r d i a g r a m , F i g . 21; e i g e n v e c t o r s , T a b l e X ) , the f i r s t a x i s (45% of t o t a l v a r i a n c e ) was de termined by t e x t u r e and e l e v a t i o n , wi th sandy, h i g h - e l e y a t i o n p l o t s at r i g h t , and l o w e r - e l e v a t i o n p l o t s r i c h in s i l t and c l a y at l e f t . The Boundary Bay p l o t s are thus s e p a r a t e d out on the r i g h t ( T r a n s e c t s G and H) from the Brunswick P o i n t p l o t s on the l e f t ( T r a n s e c t s B and C ) . The second a x i s (30% of t o t a l v a r i a n c e ) i s l a r g e l y n u t r i t i o n a l , w i t h c a l c i u m and magnesium c o n t r i b u t i n g the s t r o n g e s t p o s i t i v e 1 13 loadings and sand the only negative loading. The sandy, cation-poor plots H11 and G6 were thus separated out at the bottom, and the s i l t y , c a t i o n - r i c h C8 was isolated at the top. The t h i r d ordination axis (11% of t o t a l variance; not shown) strongly separated high-nitrogen, high-elevation, low-potassium plots from low-nitrogen, low-elevation, high-potassium plots -- b a s i c a l l y an elevation gradient. Table X - Summary of results of PCA ordination on environmental data from saltwater plots E i g e n v e c t o r 1 2 3 4 5 6 7 8 Sand 0 . 4426 -0 .2213 -0 . 1654 -0. 2426 0. 1037 0. 0290 0. 1939 -0. 0603 S i l t -0 . 4370 0 . 2216 0 . 1803 0. 19 11 -0. 2035 -0. 1 178 -0. 5296 0. .1415 C l a y -O . 4275 0 . 2057 0 . 1 152 0. .361 1 0. 1651 •o. 2056 0. 6990 -0. 1561 N 0 . 2881 0 .0081 0 . 7873 0. .026 1 -0. 1397 -0. 4808 0. .2117 0. .0299 K 0 .3022 0 . 2344 -0 . 4748 0. . 5839 -0. 1266' -0. 464 1 0. . 1061 0. .2113 Ca -0 .01 13 0 . 5576 -0 .0103 -0. .4274 0. 3720 -0. 0586 0. 1 133 0. . 5929 Mg 0 . 1406 0 . 5742 -0 .0438 -0. . 1288 0. . 1920 -0. 1616 -0. .1712 -0 . 7346 Na 0 .2817 0 .4010 0 .0498 -0 .0550 -0. .6965 0. .5053 0. . 1030 0 , 0569 E l e v O . 3960 0 .056 1 0 . 2777 0. . 4800 0. 4739 0. . 4599 -0. . 2907 0 . 1093 % v a r i a n c e 45 . 37 29 . 79 10. 74 6 . 75 4 . 19 2 .48 0.64 0.03 An examination of the cor r e l a t i o n matrices (Table XI) may be h e l p f u l . In a l l the datasets, sand and s i l t / c l a y are strongly or very strongly negatively correlated. The nutrient cations are p o s i t i v e l y correlated, especially calcium with magnesium and potassium with sodium. Elevation and nitrogen do not show such strong correlations as the other variables, but their strongest correlations are with each other (p o s i t i v e ) , r e f l e c t i n g the greater accumulation of humic matter and peat at high elevations. In the freshwater 1 14 dataset, sand i s negatively correlated with everything else --r e f l e c t i n g the difference between the sandy, cation-poor, nitrogen-poor, lower-elevation plots along the Fraser River and the finer-textured plots, richer in cations and organic matter, that occur at higher elevations in northern Brunswick Point and Ladner Marsh and in the more brackish marsh in southern Brunswick Point. In the saltwater dataset, however, sand is p o s i t i v e l y correlated with elevation, potassium, sodium, and nitrogen, suggesting a gradient from sandy, ca t i o n - r i c h , nitrogen-rich plots at high elevations to finer-textured, cation-poor, nitrogen-poor plots at lower elevations. This i s somewhat misleading, r e f l e c t i n g as i t does mainly the geographical v a r i a t i o n between the finer-textured, perhaps more brackish, lower-elevation Brunswick Point marshes and the sandier, s a l t i e r , higher-elevation marshes at Boundary Bay. In the Brunswick Point marshes, texture does become finer towards the lower elevations; at Boundary Bay, however,- the opposite is true. The trends in nitrogen and cations with elevation are not c l e a r , but generally the highest values do occur at higher elevations. Apparently the p r i n c i p a l "gradient" exposed by the saltwater PCA ordination was geographical. This implies that beta d i v e r s i t y was too high; the ordination results would probably be improved by ordinating the Brunswick Point and Boundary Bay plots separately. It i s important to r e a l i z e that the results of an 1 15 Table XI - Product-moment co r r e l a t i o n c o e f f i c i e n t s for environmental variables (* = p < .05; ** = p < .01) 1. Combined f r e s h w a t e r and s a l t w a t e r p l o t s . Sample s i z e = 44. Sand 1 .000 S i l t - O . 9 7 9 * * 1 .000 C l a y - 0 . 8 6 4 * * 0 . 7 4 4 * * 1 .000 N 0 . 3 7 4 * - 0 . 4 1 0 * * -0.2 16 1 000 K 0 . 5 3 5 * * - 0 . 5 7 8 * * - 0 . 3 2 7 * 0 484** 1 000 Ca 0 .004 -0 .029 0 .057 0 163 0 396** 1 000 Mg 0 . 275 - 0 . 3 1 5 * -0.12 1 0 433* * 0 772 * * 0 860** 1 000 Na 0 . 5 0 6 * * - 0 . 5 4 2 * * - 0 . 3 2 2 * 0 578** 0 889** 0 457* * 0 815* * 1 .000 E l e v 0 . 3 2 3 * - 0 . 3 8 9 * * -0 .097 O 59 1 ** 0 3 19* 0 008 0 194 O. 258 Sand S i l t Cl ay N K Ca Mg Na F r e s h w a t e r p l o t s . Sample s i z e = 27. Sand 1.000 S i l t - 0 . 9 0 9 * * 1.000 C l a y - 0 . 7 7 4 * * 0 . 4 4 1 * 1.000 N - 0 . 4 0 8 * 0 .277 0 . 4 6 1 * K - 0 . 3 8 9 * 0 .338 0 .326 Ca -0 .167 0.164 0.112 Mg -0 .207 0 .185 0 .165 Na -0 .006 0 .022 -0 .020 E l e v -0 .237 0 .062 0 . 4 1 6 * 0 . 6 1 4 * * -0 .053 -0.091 -0.043 -0.192 1.000 Sand S i l t C l a y N K Ca Mg Na E l e v 1 ooo 0 34 1 1 OOO 0 027 0 554** 1 000 0 037 0 697* * 0 9 6 1 * * 1 000 0 008 0 542** 0 538** 0 6 4 0 * * 1.000 0 614** -0 053 -0 091 -0 043 -0.192 N K Ca Mg Na 3. S a l t w a t e r p l o t s . Sample s i z e = 17. Sand 1 .000 S i l t - 0 . 9 9 2 * * . 1.000 C1 ay - 0 . 9 5 0 * * 0 . 9 0 7 * * 1 .000 N 0 . 380 -0 .352 -O.427 1 K 0 . 3 9 0 -0.396 -0 .348 0 Ca -0.271 O. 269 0. 257 -0 Mg -0 .055 0 .062 0.036..- 0 Na 0 .248 -0.224 -0.293 0 E l e v O . 5 8 5 * * -0 .608** ' - 0 . 4 8 5 * 0 Sand S i l t C 1 ay OOO 066 1 000 027 0 178 1 000 147 0 514* 0 912** 1 000 360 0 538* 0 496* 0 7 11** 1 .000 608** 0 494*. -0 003 0 284 0. 438 N K Ca Mg Na 1 1 6 ordination depend on the choice of variables (Austin 1969). In a vegetation ordination, the variables (species) are pre-selected; in an environmental ordination, however, the investigator makes a subjective decision as to which variables to use. Thus a d i f f e r e n t choice of variables might have produced very d i f f e r e n t ordination r e s u l t s . 8.2.3 Species-Environment Diagrams The projections of cover class codes of important marsh species on the freshwater and saltwater environmental ordinations (Figs. 22-27) reveal clear patterns that can be interpreted e c o l o g i c a l l y . Considering f i r s t the freshwater series, one sees that Agrostis alba (Fig. 22) performs evenly along the f i r s t (textural) axis, but seems to form three performance zones along the second axis (cationic, elevational, t e x t u r a l ) . The pattern for Sc i rpus amer icanus (Fig. 23) i s more or less the inverse of the Agrostis pattern. The d i s t r i b u t i o n pattern of Carex lyngbyei (Fig. 24) i s similar to that of Agrostis, but' i t s performance pattern i s d i f f e r e n t . These ordination patterns r e f l e c t patterns of species zonation in the marsh i t s e l f . Scirpus americanus i s found at low elevations (top of diagrams) on both the north and south sides of Brunswick Point, extending lower than Carex or 1 1 7 Agrostis. At middle and upper l e v e l s , Carex and Agrostis co-dominate, but Carex outperforms Agrostis at higher elevations (finer-textured, lower in cations, higher in nitrogen; bottom of diagrams). In the saltwater series, S a l i c o r n i a v i r g i n i c a (Fig. 25) shows i t s e l f to be mostly absent from the Brunswick Point plots at l e f t , but present in a l l the Boundary Bay plots at r i g h t . The f i r s t - a x i s gradient was based on texture and elevation. Examination of the data suggests that texture i s probably not the factor c o n t r o l l i n g Salicornia d i s t r i b u t i o n here; however, the two Brunswick Point plots in which S a l i c o r n i a does occur are the two highest Brunswick Point .plots in the environmental dataset, suggesting a possible role for elevation in r e s t r i c t i n g the d i s t r i b u t i o n of Salic o r n i a at Brunswick Point. D i s t i c h l i s spicata (Fig. 26) seems to show an avoidance of axis extremes, which corresponds to i t s d i s t r i b u t i o n in the marsh. An important component of the s a l t marsh f l o r a at middle l e v e l s , D i s t i c h l i s i s outcompeted by Atriplex patula at the highest elevations, and does not extend i t s e l f to the low leve l s where colonization of the unvegetated f l a t s is taking place. T r i g l o c h i n maritimum (Fig. 27) shows a broad ecological amplitude, apparently tolerant of a l l major ordination gradient extremes. This corresponds to the d i s t r i b u t i o n observed in the marsh: Trigl o c h i n was found on a l l transects 118 except Transect J, at Ladner Marsh. However, the figure reveals an interesting pattern: f a i r l y low, uniform cover in the Boundary Bay plots; more variable performance, with some high cover values and some absences, at Brunswick Point. It may be that the Brunswick Point marsh, closer to the influence of the Fraser River, is more susceptible to environmental fluctuations which may not have been detected by my sampling program. This might also be an explanation for the poorer performance of S a l i c o r n i a at Brunswick Point. 8.3 Plant Communities in the Study Area In this study, I have emphasized the continuous nature of vegetational v a r i a t i o n , rather than attempting to define plant associations, because I feel that the vegetation of the Fraser Delta t i d a l marshes i s best understood by using t h i s approach. A number of other t i d a l marsh studies have attempted to f i t plant associations, rather than individual species, to ecological gradients, with results that tend not to be supported by available data. Some such instances were mentioned in the Literature Review. A very d i s t i n c t i v e zonation pattern, with d i f f e r e n t species forming successive elevational bands of dominance, i s nonetheless a conspicuous and f a i r l y universal feature of t i d a l marshes, including the Fraser Delta marshes. Moreover, there i s a very clear vegetational and environmental 1 19 disjunction between the fresh and brackish Fraser Delta marshes on one hand and the salt marshes on the other.. Thus i t does not seem inappropriate to describe the vegetation in terms of important species-environment nodes that are suggested by ordination results and can be observed in the f i e l d . Such a description also f a c i l i t a t e s comparisons with t i d a l marshes elsewhere that have been described in terms of plant associations. Four of these nodal groups of samples may be informally recognized by analysis of the freshwater data: (1.) a Carex  lyngbyei - Agrostis alba group on better-drained s i t e s at high to medium elevations on s i l t y loams, sometimes nitrogen-rich; (2.) an Agrostis alba - Scirpus maritimus group on less well drained s i t e s , tending to be more brackish, at high to medium elevations on s i l t y loams; (3.) a Scirpus americanus group at low elevations in f a i r l y fresh to brackish areas on nitrogen-poor s i l t y clay loams to sandy loams; (4.) a group dominated by Equisetum f l u v i a t i l e , Scirpus validus, Agrostis alba, and Alisma plantago-aquatica at medium to low elevations on s i l t loams in the very fresh Ladner Marsh area. From the saltwater data, four more groups emerge: (1.) an Atriplex patula group at the highest elevations, often with high s o i l nitrogen and also often with driftwood, on sandy to s i l t y clay loams. In a variant of this group at somewhat lower elevations, D i s t i c h l i s spicata co-dominates; (2.) a Carex lyngbyei - D i s t i c h l i s spicata group at higher medium 120 elevations on loamy sediments with high to medium nitrogen concentrations; (3.) a S a l i c o r n i a v i r g i n i c a - Tr iglochin maritimum group at lower medium elevations, displaying two variants: a S a l i c o r n i a - Tr iglochin - D i s t i c h l i s variant at higher elevations, and a S a l i c o r n i a - Triglochin - Spergularia  canadensis variant at lower elevations; (4.) a Spergularia  canadensis group at low elevations on sandy loams to loamy sands. S a l i n i t y does not seem to play an important role in distinguishing these groups. To place the Fraser Delta marshes in a regional context, the above species-environment nodal groups were compared with published descriptions of nearby marshlands in the Fraser Delta and neighbouring Washington State. In the Nisqually s a l t marsh at the southern end of Puget Sound, Burg, Rosenberg & Tripp (1976) and Burg, Tripp & Rosenberg (1980) described twelve plant associations, the d i s t r i b u t i o n s of which they related to topographical and drainage features. Their f l o r i s t i c table and ordination results suggest that these associations are not discrete units, but can be interpreted as species dominance phases along an elevational gradient. Their sequence i s similar to that observed in my saltwater plots, with Spergular ia mar ina pioneering at the lowest elevations, zones dominated by S a l i c o r n i a v i r g i n i c a , D i s t i c h l i s spicata, Carex lyngbyei, and other species (some not found in the Fraser Delta) at intermediate l e v e l s , and a zone dominated by Festuca rubra and 121 Carex lyngbyei at the highest l e v e l s . Atriplex patula, important in the Fraser Delta s a l t marshes, was not present. Two important species i d e n t i f i e d in the Nisqually s a l t marsh occur in the Fraser Delta only in the freshwater marshes: Juncus balticus and Deschampsia cespitosa. Assuming that their and my species i d e n t i f i c a t i o n s are correct, t h i s i l l u s t r a t e s the fact that the ecological roles of species are not necessarily the same at di f f e r e n t s i t e s ; d i f f e r e n t community and habitat conditions a l t e r the rea l i z e d niche. Farther north, at Bellingham Bay, D i s r a e l i & Fonda (1979) described a brackish marsh similar f l o r i s t i c a l l y to the Brunswick Point marsh, with a lower zone dominated by Scirpus  americanus and an upper zone dominated by Carex lyngbyei• On the western side of Lulu Island in the Fraser Delta, Hutchinson (1982) also described a marsh of a similar type to the Brunswick Point marsh. He i d e n t i f i e d seven plant communities by a hi e r a r c h i c a l c l u s t e r i n g procedure, r e l a t i n g their d i s t r i b u t i o n s to elevation and substrate texture. As at Brunswick Point, the Lulu Island marsh has a lower zone dominated by Scirpus americanus and S. maritimus, and a higher, finer-textured, lower-cation zone dominated by Carex  lyngbyei and other species. Bradfield & Porter (1982) sampled much more extensively at Ladner Marsh than I did in t h i s study, and were able to recognize seven community types (about equal in l e v e l of 122 discrimination to my nodal group variants) from cluster analysis. The d i s t r i b u t i o n s of these types were related to physiographic and drainage factors. Only one of these types, the Carex - Agrostis type, would be recognizable in my own data -- a result of the presence of several major species within the area of the Bradfield & Porter study that were not found in my own study area. This i l l u s t r a t e s that the freshwater marshes of the lower Fraser River are quite d i f f e r e n t in character from the marshes at the delta front. I have not found descriptions in the l i t e r a t u r e of similar marshes outside of the lower Fraser River. 1 23 9. CONCLUSIONS (1.) Transforming species cover data values to their square roots prior to ordination can lead to more readable ordination diagrams by spreading out the points. Reduction of the bias from overemphasis of high-cover species may expose data trends not otherwise evident, without causing major change in plot scores on the f i r s t two PCA axes, though higher axes may be considerably changed. (2.) Normalization of species cover value data prior to ordination exposes sample relationships based on r e l a t i v e rather than absolute species abundances. E f f e c t i v e use i s thus made of f l o r i s t i c information, while s i t e productivity information i s s a c r i f i c e d . As an optimal ordination str.ategy for vegetation data, the analysis of both normalized and non-normalized data is recommended. (3.) Use of the c o r r e l a t i o n matrix for ordination of vegetation data is not recommended for general purposes. (4.) Reciprocal averaging i s highly sensitive to anomalous samples, but may produce good vegetation ordinations, at least along the f i r s t axis, when such samples are removed from the data. RA and PCA produced vegetation ordinations of equivalent quali t y , but the RA ordinations of environmental data were i n f e r i o r . 124 (6.) Ordination of environmental data exposes environmental gradients d i r e c t l y ; the results can be a worthwhile aid to the interpretation of vegetation ordinations. The projection of species data on an environmental ordination can suggest relationships between species performance and environmental factors. (7.) The performance and d i s t r i b u t i o n of dominant plant species in the Fraser Delta t i d a l marshes were shown to be related to substrate texture, substrate nitrogen and cation l e v e l s , and s i t e elevation. (8.) On the basis of f l o r i s t i c and environmental factors, the sample plots were separated into two main groups: one representing the brackish marshes of northern and western Brunswick Point and the freshwater marshes of Ladner Marsh; the other representing the s a l t marshes of southeastern Brunswick Point and Boundary Bay. Each group may be subdivided by f l o r i s t i c and environmental differences: the Ladner Marsh plots from the north and west Brunswick Point plots, and the southeast Brunswick Point plots from the Boundary Bay pl o t s . (9.) Based on f l o r i s t i c and environmental d i s t i n c t i o n s , eight field-recognizable species-environment sample groups, with variants, are informally recognized. These are dominated respectively by: (i) Carex lyngbyei and Agrostis alba; ( i i ) Agrostis alba and Scirpus maritimus; ( i i i ) Scirpus americanus; (iv) Equisetum f l u v i a t i l e , Scirpus validus, Agrostis alba, and 1 25 A l i sma plantaqo-aquat i c a ; (v) Atriplex patula (variant: Atriplex patula - D i s t i c h l i s spicata); (vi) Carex lyngbyei and D i s t i c h l i s spicata; ( v i i ) S a l i c o r n i a v i r g i n i c a and Triglochin  maritimum (variants: S a l i c o r n i a v i r g i n i c a - Triglochin  maritimum - D i s t i c h l i s spicata, and S a l i c o r n i a v i r g i n i c a -Tr iglochin maritimum - Spergularia canadensis); ( v i i i ) Spergularia canadensis. (10.) The marshes of the study area are similar to other brackish and salt marshes that have been described in the Fraser Delta and in Washington, but are mostly d i s s i m i l a r to the fresh Fraser River marshes. 1 26 REFERENCES Ages, A. 1979. 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Equisetum f l u v i a t i l e L. Festuca arundinacea Schreb. Glaux mar i t ima L. Grindelia i n t e g r i f o l i a DC. var. macrophylla (Greene) Cronq. Hordeum brachyantherum Nevski Hygrohypnum luridum CHedw.) Jenn. Juncus a r t i c u l a t u s L. Juncus balticus Willd. Juncus bufonius L. Juncus gerardi i L o i s e l . Lathyrus L. sp. Leptodictyum riparium (Hedw.) Warnst. Lila e a s c i l l o i d e s (Poir.) Hauman Lila e o p s i s occidentalis Coult. & Rose .Limosella aquat ica L. Lythrum s a l i c a r i a L. Mentha arvensis L. Mimulus guttatus DC. var. guttatus Myosotis laxa Lehm. Oenanthe sarmentosa Presl Plantago maritima L. Polygonum aviculare L. Potent i 1 1 a pac i f ica Howell P u c c i n e l l i a nutkaensis (Presl) Fern. P u c c i n e l l i a n u t t a l l i a n a (Schult.) A. S. Hitchc. Ruppia maritima L. S a g i t t a r i a l a t i f o l i a Willd* 141 Sali c o r n i a v i r g i n i c a L. Scirpus americanus Pers. Scirpus maritimus L. Scirpus validus Vahl Sium suave Wa1t. Sonchus arvensis L. Spergularia canadensis (Pers.) G. Don Spergularia marina (L.) Griseb. T r i f o l i u m oliqanthum Steud. Triglochin maritimum L. Typha l a t i f o l i a L. Zostera americana den Hartog Nomenclature is according to Hitchcock et a l . 1969, except: Chara braun i i Gm. (a green alga), Hygrohypnum luridum (Hedw.) Jenn. and Leptodictyum r i pa r i um (Hedw.) Warnst. (mosses), and Zostera amer icana den Hartog (which keys to Z. nana Roth in Hitchcock et a l . ) . 1 42 APPENDIX B. ENVIRONMENTAL DATA Explanation of abbreviations: SAMPL = sample plot ( i n i t i a l l e t t e r designates transect); SAND = percent by weight of sand in s o i l sample; SILT = percent by weight of s i l t in s o i l sample; CLAY = percent by weight of clay in s o i l sample; TXTCLASS = textural c l a s s i f i c a t i o n of s o i l sample (L = loam, LS = loamy sand, S = sand, SCL = sandy clay loam, SiCL = s i l t y clay loam, SiL = s i l t loam, SL = sandy loam); COND = e l e c t r i c a l conductivity of s o i l sample in mS cm"1; N = percent by weight of nitrogen (total) in s o i l sample; K = parts per m i l l i o n of potassium in s o i l sample; CA = parts per m i l l i o n of calcium in s o i l sample; MG = parts per m i l l i o n of magnesium in s o i l sample; NA = parts per m i l l i o n of sodium in s o i l sample; PH = pH of s o i l sample; ELEV = elevation of sample plot above l o c a l chart datum; %ELEV = standardized sample plot elevation as described in section 7.3. SAMPL SAND SILT CLAY TXTCLASS COND N K CA MG NA PH ELEV %ELEV A 0 27 , . 5 60 12 . 5 S i L 5 . 4 .04 31 . .6 105 1 10 290 1 .82 44 .9 A 1 25 . 60 15 . S i L 10 . 4 .05 30. 155 280 700 2 . 22 54 . 7 A 2 27 . . 5 57 . 5 15 . S i L 8 . 4 .06 45 . 137 .5 245 550 2 . 53 62 .6 A 3 27 . . 5 57 . 5 15 . S i L 5 .0 . 10 50. 82 .5 160 365 2 .71 67 .0 A 4 2 .73 67 . 5 A 5 25 . 60 15 . S i L 9 . 4 .06 67 , . 5 280 580 625 2 . 59 63 .9 A 6 15 . 52 . . 5 32 . . 5 S iCL 4 . 5 . 1 1 37 . . 5 40 120 425 2 .92 72 . 1 A 7 2 .80 69 . 1 A 8 7 . 5 60 32 . . 5 S iCL 5 . 6- . 14 72 . .5 140 275' ' 560 2 .88 67 . 9 A 9 2 ,84 70 . 1 A10 5 . 65 . 30. S i C L 8 .8 . 14 77 . . 5 272 . 5 710 855 2 .88 71 . 1 A1 1 7 . . 5 65 . 27 . . 5 S i L - S i C L 7 . 8 . 12 45 , 285 525 325 2 . . 92 72 .0 A12 3 . .00 74 . 2 A13 3 . .00 74 . 2 A 14 12 . 5 62 . . 5 25 . S i L 9 .  1 . 13 57 . . 5 • 372 .5 735 625 3 . . 1 1 76 . .7 A15 3 . . 10 76 . . 6 A 16 3 . . 20 79 . .0 A 17 7 . 5 67 . . 5 25. S i L 8 . 1 . 14 57 . . 5 460 825 415 3 . . 15 77 . .9 A 18 •i 1 1 , 4 . 14 39 . 9 209 37 1 703 3 . . 20 79 . . 1 A19 30. 47 . . 5 22 . 5 L 12 . . 12 39 . 335 608 608 3 . .09 76 . 4 A20 1 1 . . 12 91 . . 7 231 . 6 405 7 14 3 .08 76 . .0 A21 22 . 5 57 . , 5 20. S i L 10. . 17 35. . 9 135 . 2 31 1 877 3 . . 10 76. . 4 A22 14 . 2 . 13 51 . . 3 295 . 1 599 1001 3 . .03 74 . . 9 A23 25 . 55 . 20. S i L 12 . . 12 67 . 5 237 . 5 540 1380 5 . 1 2 . . 99 73 . . 9 A24 20. 57 . 5 22 . . 5 S i L 21 . .08 61 . . 3 254 578 1356 4 . 4 2 . .68 66 . . 2 A25 7 . 5 70. 22 . 5 S i L 18 . . 1 1 82 . . 5 4 15 915 1335 4 . 7 2 . 81 69 . .4 A26 22 . . 5 55 . 22 . .5 S i L 14 . . 12 40. 240 464 864 2 . 91 7 1 . .9 A27 15 . 4 . 1 1 50. . 2 301 . 3 59 1 837 2 .08 51 . 3 A28 32 . . 5 50. 17 . 5 S i L - L 16 . .06 42 . .6 246 .8 485 706 5.3 2 . . 37 58 . .4 A29 57 . . 5 32 . 5 10. SL 23 . .02 57 . .5 72 .5 165 1 130 6 .6 A30 62 . . 5 27 . . 5 10. SL .25 . .02 70. 162 . 5 125 5 10 6 .0 B 1 27 . . 5 52 . 5 20. S i L 46 . . 24 250. 315" 1115 8400 3 . . 75 80. . 4 B 2 15 . 65 . 20. S i L 39 . . 24 180. . 6 249 . 2 867 5272 3 . . 50 75 . . 1 B 3 39 . 19 217 . .5 22.5 840 7 100 3 . 39 72 . .8 B 4 20. 55 25 . S i L 42 .21 405 . . 5 224 . 5 905 6372 3 . 24 69 . . 5 B 5 40. . 13 148 . 4 16 896 3240 3 . . 29 70. .6 B 6 7 .5 65 27 . . 5 S i L - S i C L 35 . 14 250. 187 . 5 670 5450 3 . 19 68 . . 4 1 43 SAMPL SAND SILT CLAY TXTCLASS COND N K CA MG NA PH ELEV %ELEV B 7 B 8 0. 70. 30. S iCL 33 . . 15 B 9 B 10 17 . 5 57 . 5 25 . S i L 32 . 5 .08 B1 1 B12 27 . 5 50 . 22 . 5 L 30. .05 C 1 1 2 . 5 70 . 17 . 5 S i L C 2 27 . 5 52 . 5 20. S i L 26 . C 3 17 . 5 62 . 5 20. SIL 30. . 13 C 4 4 1 . . 28 C 5 12 . 5 57 . 5 30. S iCL 36 . . 19 C 6 38 . .21 C 7 46 . . 18 C 8 5 . 65 . 30. S iCL 40. . 14 D 1 17 . 5 65 . 17 . 5 S i L 3 . 5 . 24 D 2 2 . 5 72 . 5 25 . S i L 2 .3 . 10 D 3 D 4 5 . 67 . 5 27 . 5 S i L - S i C L 3 . 1 . 14 D 5 3 . 3 . 26 D 6 5 . 65 . 30. S iCL 3 . 8 . 26 D 7 4 . 7 . 23 D 8 10. 65 . 25 . S i L 5. . 14 E 1 35 . . 20 E 2 50. 37 . 5 12 . 5 L 31 . . 16 E 3 28 . . 13 E 4 30. 50. 20. S i L - L 28 . .21 E 5 48 . . 32 & 6 42 . 5 42 . 5 15 . L 52 . . 35 E 7 46 . . 30 E 8 75 . 15 . 10. SL 33 . .07 E 9 60 . 27 . 5 12 . .5 SL 47 . . 19 F 1 57 . 5 30. 15 . SL 29 . . 17 F 2 28 . 5 .07 F 3 75 . 20. 5 , LS 32 . . 1 1 F 4 41 . . 20 F 5 80 . 17 . 5 2 . 5 LS 28 . .09 G 1 57 . 5 32 . 5 10. SL 38 . . 28 G 2 60 . 30. 10. SL 46 . . 23. G 3 55 . 35 . 10, SL 58 . . 38 G 4 48 . . 26 G 5 72 . 5 20. 7 . 5 SL • 58 . . 14 G 6 72 . .5 17 . 5 10. SL 56 . . 23 G 7 60. 25 . 15 . SL 49 . G 8 85 . 10. 5 LS 40 . G 9 38 . . 1 1 G10 25 . .09 H 1 62 . . 5 22 . 5 15 SL 39 . .43 H 2 55 . 22 . 5 22 . 5 SCL H 3 67 . . 5 10. 22 . 5 SCL H 4 . 72 H 5 70. 15 , 15 SL H 6 83 . .84 H 7 60. 22 . 5 17 .5 SL .61 H 8 70. 17 . 5 12 . 5 SL 62 . . 18 H 9 57 . . 26 H10 82 . 5 7 . 5 10 LS 58 . . 13 H1 1 87 . 5 5 7 . 5 S 52 . . 3 1 J 1 50 35 15 L 1 . 3 .06 J 2 45 40 15 L '1 .9 • . 10 d 3 2 . 2 .01 J 4 5 67 . 5 27 . 5 S i L - S i C L 2 . 2 .08 J 5 1 . 8 . 13 0 6 2 . 5 72 . 5 25 S i L 3 . 2 .08 u 7 . 2 . 4 .06 J 8 10 72 . 5 17 . 5 S i L 2.8 .03 J 9 1 . .05 3 . 20 68 . 7 265 . 190. 690 5250 3 . 1 1 66 . 8 3. 18 68 . 2 185 . 272 . 5 775 4650 2 . 59 55 . 6 2 . 59 55 . 6 157 . 5 227 . 5 660 4250 2 . 59 55 . 5 3 . 92 84 . 1 152 . 5 2 12. 5 700 2080 3 . 64 78 . 0 3 . 66 78 . 6 221 . 4 278 . 8 951 6421 3 . 61 77 . 4 255 . 322 . 5 965 6000 6 . 3 3 . 54 75 . 9 166 . 2 253 . 3 823 5082 3 . 53 75 . 6 210. 8 450 . 4 1236 6143 3 . 37 72 . 3 285 . 577 . 5 1625 7500 5 . 6 3 . 27 70. 2 31 . 25 . 58 400 3. 40 83 . 9 38 . 7 54 . 1 129 156 3 . 33 82 . 1 3 . 24 80. . 1 36 . 9 62 . 7 140 280 3 , 48 85 . 9 600. 56 . 3 1 13 390 3 . 19 78 . 8 76: 6 119. 5 196 319 5. . 2 3 . 07 75 , .9 83 . 3 154 . 2 258 408 3 . 06 75 , . 5 92 . 5 235 . 640 300 4 . 2 2 . 95 72 , . 8 152 . 3 132 . 9 486 3403 77 . 5 102 . 5 395 3150 4 . 2 101 . 3 138 . 8 593 3900 252 . 5 167 . 5 645 4900 625. 320. 1285 9950 370. 145. 575 4350 5 . 5 390. . 4 233 . 974 8413 220. 205 . 830 3890 3 . 9 252 . 5 220. 395 2600 142 . 5 132 . 5 495 3950 5 . •0 98 . 4 84 . , 8 299 23 14 143 . 3 100. 367 2620 218 . . 7 • 109 . 3 820 496 1 84 . . 8 45 . 1 4 14 2705 590. 507 . 5 825 5500 3 . 9 3 . 53 80 .0 315, 315 . 1030 7500 4 . 2 3 , • 22 . 72 .9 440. 332 . 5 1250 9650 4 , . 7 3 . 26 73 .6 4 12. . 5 375 . 1523 10800 3 . 13 70 . 9 415. 290. 1035 8500 4 , .5 3 . 20 72 . 5 177 . 5 175 585 3550 4., , 4 3 . 13 70 . 8 600. 350. 1350 10800 4 . 1 2 .87 64 . 9 382 , . 5 192 , 5 735 6995. 5 . 6 3 .05 69 . 1 142 , . 5 150. 600 4200 3, . 54 80 . 1 86 . 3 127 , . 5 405 2610 3 .50 79 . 2 282 , . 5 292 . 5 1060 8500 5 . 7 4 . 24 95 . 9 6 .0 4 . 26 96 .4 5 . 6 4 . 28 96 . 8 4 . 22 95 .5 5 . 3 4 . 14 93 .7 865 598 . 2697 29906 4 . 15 93 .9 5 . 3 4 . 10 92 . 7 622 .5 267 . 5 1 140 5450 5 . 8 4 .07 92 . 2 799 364 1 193 10425 4 .01 90 .7 490 250 1040 9550 3 . 93 88 . 9 182 . 5 125 5 15 4600 5 .O 3 . 76 84 . 8 6 60 60 17 3 . 45 77 . 2 8 . 5 70 70 65 5 . 5 3 .50 78 . 3 6 . 2 71 . 3 86 20. 3 . 43 76 .6 6 .6 60 45 1 10 5 . 4 3 . 42 76 .6 8 . 1 72 72 54 3 .04 68 .0 •10 142 . 5 130 1 10 6 . 3 2 .91 65 . 1 8 . 7 191 . 3 131 4 1 2 . 39 53 . 5 14 . 1 192 . 5 65 55 6 . 8 5 . 1 75 5 1 38 2 . 48 55 .5 

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