Litter Decomposition Rates in the Seasonally Flooded Great Dismal Swamp

Litter decomposition rates, measured by the litter bag technique, and nutrient dynamics were monitored for 2 yr in four plant communities in the seasonally flooded nonriverine Great Dismal Swamp. The cypress and maple—gum communities were more extensively flooded and had less acid soils than the cedar and mixed—hardwood communities. The highest decay rates for mixed litter, representing an average species composition on each site, were recorded on the cypress and maple—gum sites. Site controls indicated that litter quality, as affected by species importance, was primarily responsible for site variation in total litter decomposition rates. The flooded sites had a predominance of species that were more subject to rapid decay (higher P concentrations, low C:N ratios, and low lignin and tannic acid content). Nitrogen and phosphorous were accumulated, with a few exceptions, in the decomposing litter; calcium and magnesium were released; and potassium was accumulated following initial losses. Accumulations were probably a result of immobilization of external nutrient sources (e.g., throughfall) by microbes. In general, decomposition in the Great Dismal Swamp appears to be nitrogen and phosphorus limited.