Vegetation structure and diversity components of a Fraser estuary tidal marsh

Abstract

Vegetation data from a predominantly freshwater-influenced tidal marsh in the Fraser River estuary are analysed to investigate different properties of community structure. Three main vegetation zones are recognized, dominated respectively by Carex lyngbyei, Festuca arundinacea, and Menyanthes trifoliata. The zones occupy parts of the marsh which differ primarily in hydrological regime: the Carex zone occurs in regularly flooded and drained areas, mainly along tidal creeks; the Festuca zone occurs on infrequently flooded levees; the Menyanthes zone occurs in areas of impeded drainage, mainly between tidal creeks.Principal components analysis and reciprocal averaging gave similar results except for a 90° rotation of ordination axes. The combined results from cluster analysis and ordination give a useful summary of the marsh vegetation structure. The evaluation of various diversity measures including species richness, species density, beta diversity, and species evenness provided a useful basis for making comparisons and helped to focus attention on factors influencing community development.