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Biogeochemical Influences Associated with Sedimentation in Riparian Forests of the Southeastern Coastal Plain

Rachel L. Jolley, B. Graeme Lockaby, Robin M. Governo
Soil Science Society of America journal 2010 v.74 no.1 pp. 326-336
riparian forests, biogeochemical cycles, mineralization, nitrogen, soil microorganisms, carbon, ephemeral streams, soil texture, soil pH, cation exchange capacity, soil density, bulk density, soil quality, soil temperature, soil water content, sand fraction, sediment transport, watersheds, Georgia
The importance of riparian forests in maintaining water quality through the retention of sediments and nutrients is well understood; however, little is known about how sediment deposition from upland erosion affects the integrity of these systems. The objectives of this study were to compare decomposition rates, net N mineralization rates, microbial biomass, and other soil properties along a gradient of sedimentation rates in headwater systems. These factors were measured in 17 plots situated within riparian forests of ephemeral streams at Ft. Benning, GA. The soils were analyzed for texture, pH, cation exchange capacity (CEC), and bulk density. A decline in soil quality was found with increasing sedimentation rates. Soils in plots with the highest sedimentation rates (highly disturbed or HD) exhibited decreased CEC, temperature, and moisture, and increased bulk density, sand content, and pH. The HD plots also had lower nutrient turnover from decomposition, net N mineralization rates, and microbial C and N. Declines in biogeochemical processes corresponded to sedimentation rates associated with HD plots (1.0 cm yr⁻¹). Shifts in biological indicators corresponding to annual variations in climate suggest that the stress of sedimentation may be further exacerbated by drought conditions. The results of this study imply that even low levels of erosional deposition in headwater riparian forests may significantly impact biogeochemical processes in these systems.