A simple empirical model of salt marsh plant spatial distributions with respect to a tidal channel network

Previous work has shown that the distribution of plant species in a salt ma rsh near Petaluma, CA, is strongly influenced by the location and size of t idal channels. We developed a simple mathematical model to measure the "cha nnel influence" at each point as a cumulative function based on inverse squ ared distance to channel, length of potentially influential channel, and ch annel order (a surrogate for channel cross-sectional area.) Plant species d istributions predicted with this channel influence function compared favora bly to known distributions in Petaluma Marsh. Using this function and proba bilities estimated from transect vegetation data, we simulated the two-dime nsional pattern of species abundance across the entire site. Comparisons of predictions with independently generated field maps showed comparable patt erns of cover for most species. The results indicate that the distribution of vegetation in Petaluma Marsh, both major zones of marsh dominants and pa tches of minor species, can be described by a single, empirical factor: cum ulative distance from tidal channels of different size. (C) 2001 Elsevier S cience B.V. All rights reserved.