Impacts of fire on plant species diversity in two brackish tidal wetlands along the upper San Francisco Bay Estuary.
Vasey, Michael 1, Schile, Lisa1, Parker, V. Thomas1, Callaway, John2, Tuxen, Karin3, 1 San Francisco State University, San Francisco, CA2 University of San Francisco, San Francisco, CA3 University of California, Berkeley, CA
ABSTRACT- As tidal wetlands have disappeared in the San Francisco Bay Estuary, concern about the loss of species diversity in this region has increased. While large-scale wetland restoration focuses on the long-term recovery of these species, the dynamics that stimulate and maintain species diversity in the Estuary are poorly understood. These tidal wetlands are dominated by long-lived species in genera such as Scirpus, Typha, Spartina, and Salicornia. Restoration activities generally promote these dominants rather than less common, more specialized plants that are also part of tidal wetland assemblages. Two wetland sites, Browns Island, a remnant historic wetland, and Lower Sherman Island, a naturally restored wetland, are located at the junction of the western Delta and eastern Suisun Bay in a species-rich, brackish salinity zone. In fall 2003, we used 162 burned and 196 unburned randomly-located 3-m diameter vegetation relevés to sample a large spring 2002 burn from Browns Island. In spring 2004, another fire burned a large area of Sherman Island. Similar random, plot-based surveys were conducted in burned and unburned areas, both before and after the burn. Based on these data, burned areas host significantly higher species diversity and enhance the frequency and abundance of one group of annual and short-lived perennial species. These species appear to opportunistically exploit the post-fire conditions of reduced thatch and increased nutrients. Dominant species in these areas survived, however, and are already returning to their former status. These findings suggest that fire could be used as a management tool to promote species diversity in restored and historic brackish tidal wetlands in the upper Estuary.
Key words: Impact of fire on plant species diversity, Brackish tidal wetlands in San Francisco Bay
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