California Sea Grant College Program

Sea Grant sponsorship to this program was used to establish the role of some of the many factors affecting vegetation distribution and zonation in San Francisco Bay-Delta marshes. Although much of the more recent research has emphasized species interactions, we emphasized physical factors in the belief that these were the principal factors that could be manipulated in early restoration. In particular, we found in our comparative studies of tidal marshes that seasonal changes in soil salinity were likely controlling distribution and biomass production in the vegetation. However, soil salinity itself is partly a function of tidal hydrology, since tidal input is capable of both increasing and decreasing salinity. As one of the principal accomplishments of this past year, we were able to develop a conceptual model of vegetation response to physical gradients in the marsh environment, for the major dominant vegetation species.