Patterns of plant species diversity and composition in a semi-arid riparian ecosystem

Abstract

Understanding plant community structure is fundamental to successful restoration and conservation of riparian ecosystems. High plant species diversity is often cited as an important characteristic of riparian areas. Graphical summaries, principal components analysis, and analysis of variance were used on species composition and abundance data to determine community patterns in riparian areas and surrounding uplands. Woody plant composition varied with relative elevation above the primary channel, but herbaceous composition appeared unaffected by proximity to the riparian area. Alpha diversity indices, richness, Shannon's H', and Simpson's D, were not always higher within the riparian area. Alpha diversity of woody plants demonstrated no consistent pattern, however vertical structural diversity was highest near the stream. Herbaceous plants showed increased diversity in floodplain sites and decreased diversity in hillslopes sites, suggesting that topographical profile influenced diversity. Herbaceous richness was better predicted from overstory characteristics than herbaceous biomass and environmental variables.