The influence of tidal channels on the distribution of salt marsh plant species in Petaluma Marsh, CA, USA

Tidal channels influence the distribution and composition of salt marsh veg etation in a San Francisco Bay salt marsh. Two channel networks in the Peta luma Marsh, Sonoma County, CA, were mapped and characterized using global p ositioning and geographic information systems. Plant species abundance was sampled on transects placed perpendicular to and extending away from the ch annel banks. The vegetation showed significant increases in species richnes s along channel banks and larger areas of effect which increased approximat ely linearly with channel size. Composition of species assemblages varies w ith distance from the channel bank and channel size. These results demonstr ate that salt marsh plant assemblages, composed of both major and minor spe cies, are distributed with respect to the channel network in Petaluma Marsh .