Remote sensing of tidal freshwater marsh elevation, channels, and vegetation structure

Abstract

I mapped three elevation classes in a Mid-Atlantic tidal freshwater marsh using QuickBird multi-spectral imagery and field measurements of elevation and channel networks. The elevation map reveals heterogeneous surfaces at a 2.4 m pixel scale. Field collected vegetation cover data differed among the three elevation classes. Species richness and the number of positive associations among species were higher in the mid- and high-marsh than the low marsh. The number of negative associations among species increased with rising elevation. Random forest classification of elevation class using species cover vectors selected only Impatiens capensis and Nuphar luteum and had an out of box predictive error of 26%. My research shows that the vegetation of freshwater tidal marshes is diverse with ill-defined boundaries between distinct communities. Yet vegetation shifts beyond the traditional low and high marsh communities could be detected, which should provide a useful tool for restoration and management.