Vegetation–environment relations in a brackish marsh, Lulu Island, Richmond, B.C.

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Abstract
A study of plant–environment relations was conducted on the foreshore marshes of Lulu Island in the Fraser River delta. Analysis of tidal records indicated that the marsh platform could be subdivided into three elevational zones: a low marsh dominated by Scirpus americanus and S. maritimus; a middle marsh dominated by Carex lyngbyei, Triglochin maritimum, and S. maritimus; and a high marsh community of Agrostis exarata, Potentilla pacifica, Distichlis spicata, and Typha latifolia. This is interpreted as a successional sequence. The low marsh experiences a maximum continuous submergence of 21–16 h, the middle marsh a maximum of 8 h, and the high marsh a maximum continuous exposure of > 200 h. ANOVA results demonstrate the overwhelming importance of elevation (Typha, Potentilla, Distichlis) and elevation–salinity interactions (Scirpus spp., Carex, Agrostis) as controls on plant distribution. In addition substrate texture and moisture content are significantly associated with variations in species abundance. The Lulu Island marshes are floristically and ecologically similar to estuarine and deltaic marshes of Washington and Oregon. Variations in vegetation and successional pattern within this group are likely a function of fluvial regimes, which influence salinity and sediment characteristics.