Comprehensive Cooling Water Study Annual Report. Volume 5: Wetland Plant Communities, Savannah River Plant

摘要

Wetlands cover approximately 4% of the entire Savannah River watershed. The SRP contains 15,885 ha of wetlands of which 12,722 ha are bottomland hardwood and cypress-tupelo forest, predominantly along streams and in the Savannah River floodplain. The most obvious effect of cooling water releases on wetland plant communities is canopy loss by wetland tree species. About 770 ha of wetland tree canopy exhibits degree of alteration as a result of cooling water releases. Canopy loss continues at a rate of 10.5 to 11 ha/yr in river swamp areas associated with streams that currently receive reactor effluents (Pen Branch and Four Mile Creek). Closed canopy forest is replaced by a mixture of algal mat, thermally tolerant herbaceous, and scrub-shrub communities in the thermal streams and deltas. Following cessation of reactor effluent discharges, stream and delta areas are recolonized by a variety of herbaceous and scrub-shrub species, including many species that occur in the thermal deltas. Successional processes in the post-thermal areas result in a shift from herb dominated to shrub dominated communities. Limited data on primary production indicate that community biomass production rates recover to predistribution levels much faster than community structural parameters. Bald cypress trees in the nonthermal swamp areas do not appear to be replacing themselves, while water tupelo appears to be experiencing adequate regeneration. 65 refs., 52 figs., 45 tabs. (ERA citation 11:006308)