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


The literature on North American Pacific Coast tidal marshes north of Mexico is summarized. Vegetation and environmental data from Fraser Delta tidal marshes at Ladner Marsh, Brunswick Point, and Boundary Bay were analyzed using principal components analysis and reciprocal averaging to investigate quantitative relationships between species performance and distribution, and selected environmental factors. These were: soil texture (percentage of sand, silt, and clay); soil concentration of nitrogen, potassium, calcium, magnesium, and sodium; and elevation (standardized by local tidal range). Ordinations were performed on both the vegetation and the environmental data sets. Different methods of data standardization (square root transformation, normalization, and correlation matrix) were tested for their usefulness in exposing ecological gradients. Normalization and square root transformation of the data were found to be useful in vegetation ordination; the correlation matrix was not. Reciprocal averaging and principal components analysis gave results of equivalent quality with the vegetation data, but principal components analysis was generally superior to reciprocal averaging in the environmental ordinations. The marshes of the study area separate conspicuously into two types on both floristic and environmental criteria: a fresh-to-brackish type at Ladner Marsh and in northern and western Brunswick Point, and a saline type in southeastern Brunswick Point and at Boundary Bay. Within each area, four main species-environment sample groups were informally recognized, dominated respectively by: (1.) Carex lyngbyei and Agrostis alba; (2.) Agrostis alba and Scirpus maritimus; (3.) Scirpus americanus; (4.) Equisetum fluviatile, Scirpus validus, Agrostis alba, and Alisma plantago-aquatica; (5.) Atriplex patula; (6.) Carex lyngbyei and Distichlis spicata; (7.) Salicornia virginica and Triqlochin maritimum; (8.) Spergularia canadensis. Patterns of performance and distribution of important tidal marsh species were shown to be related to levels of the measured environmental factors.

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