HYDROLOGY AND NUTRIENT GRADIENTS IN NORTH-CAROLINA PEATLANDS

Soil chemistry and hydrology gradients are closely associated with and have often been cited as the causative agents for changes in wetland plant community composition. We analyzed the biogeochemistry and hydro logy of three freshwater peatland communities on the North Carolina Co astal Plain-short pocosins, tall pocosins, and gum swamps. We compare this community gradient to the classical bog-fen gradient of northern peatlands. Short pocosins, in the ombrotrophic center of the raised bo g complex, have the highest summer water table, with a large part of t he peat profile remaining anaerobic throughout the year. They are high ly nutrient-deficient with low levels of total and extractable P, N, a nd basic cations. They additionally have the greatest peat depth, with an organic matter content of ca. 95%. Tall pocosins have a highly sea sonal water table, shallower peat depth, low soil nutrient levels, and an average soil organic matter content from 76 to 93% in the top 30 c m. Gum swamp forests have a highly seasonal water table and the shallo west peat depth. They are the most minerotrophic community, based on l ow organic matter and high N and P content of the soil, but have low l evels of exchangeable Ca and Mg and low percent base saturation. All c ommunities had low soil pH (< 4). Short pocosins and tall pocosins wer e effectively differentiated by seasonal hydrology and peat depth but not by soil characteristics, while the pocosins and swamp forest had l arge differences in seasonal hydrology, peat depth, percent organic ma tter, and soil nutrients. This community gradient contrasts sharply wi th the bog-fen gradient of northern peatlands, in which there is an in crease in soil pH, basic cations, percent base saturation, and ash con tent, and a decrease in extractable N, P, and K. This biogeographical comparison suggests a need for further study of the nutrients likely t o control plant growth in peatlands (i.e., P, N, and K), in addition t o the historical emphasis on basic cations and pH.