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Hydropedology: Genesis, Properties, and Distribution of Hydromorphic Soils
Department of Plant and Soil Sciences
Physical, chemical, and morphological indicators of hydric soils vary across the region as a function of hydrological gradients, landscape-vegetation relationships, and changes in land use. Wetland identification and functionality assessments require the application of consistent criteria based on reliable research information. The purpose of this project is to develop improved guidelines for identification of wet soils that do not display typical hydromorphic features, thus making difficult the implementation of proper land use interpretations. Also, to provide better estimates of carbon sequestration and carbon cycling in wetland ecosystems under variable hydrological gradients.
2009 Project Description
Redox potentials (Eh) were monitored bimonthly and pore water chemistry was analyzed seasonally at three slightly-acidic, high-elevation Kentucky wetlands that differed in hydrology, parent materials, and vegetation. At all sites, Eh values were below 300 mV which indicated that reducing conditions persisted within the upper 90 cm and fluctuated mainly within the range of iron and sulfate reduction. Significant relationships of Eh values with depth were observed only at the Martins Fork wetland where precipitation was the primary water source. The strongest and most stable reducing conditions, observed at the Kentenia site, reflected consistently high water levels which were sustained by ground water. The third wetland (Four Level) was distinguished by irregular Eh fluctuations coinciding with strong seasonal ground-water upwelling. Although Fe3+ and SO42- were the primary terminal electron acceptors in all wetlands, pore water chemistry also varied significantly by season and soil depth in response to piezometric water level fluctuations.
Additional factors that influenced pore water chemistry included: (1) the presence of limestone parent materials that affected pore water pH, Ca2+, and Mg2+; and (2) the prevalence of sphagnum moss or graminoid species that influenced dissolved organic carbon, CO2, and CH4. Results from this study indicated the diverse range and importance of multiple factors in controlling biogeochemical processes and properties in small, high-elevation Appalachian wetlands.
Information generated by this project will be of general utility in better understanding the formation, distribution, and management of these soils and develop more consistent criteria for their identification.
Thompson, Y.L., B. C. Sandefur, A.D. Karathanasis and E.M. D Angelo. 2009. Redox Potential and Seasonal Porewater Biogeochemistry of Three Mountain Wetlands in Southeastern, Kentucky, USA. Aquatic Geochem. (DOI 10.1007/s10498-008-9042-3). 15: 349-370.