Tuesday, November 6, 2007
215-3

Linking Nitrogen, Carbon and Phosphorus Mineralization in a North Florida Watershed dominated by Forests.

Aja Stoppe, Soil and Water Science, University of Florida, University of Florida, 2169 Mccarty Hall, Gainesville, FL 32611, Nicholas Comerford, PO Box 110290, University of Florida, University of Florida, Soil & Water Science Department, Gainesville, FL 32611-0290, Sabine Grunwald, 2169 McCarty Hall, PO Box 110290, University of Florida, University of Florida, Soil & Water Sci. Dept., Gainesville, FL 32611, and James Sickman, University of California, Riverside, Department of Environmental Sciences, Riverside, CA 92521.

Land management depends on a comprehensive understanding of the relevant transformations associated with land use and the nutrient flux changes resulting from alternations in land use. Nutrient cycling is a critical land use characteristic that influences not only soil nutrient bioavailability, but also the off-site consequences of management practices. The 358,500 ha Santa Fe River Watershed (SFRW), located in north Florida, was the focus of this study that evaluated the aerobic mineralization rates of carbon, nitrogen and phosphorus for over 140 locations that represent the range of land uses in the SFRW. This study correlated mineralization rates of carbon, nitrogen and phosphorus with soil and landscape variables. Mineralization measurements were performed on soils at field capacity at 35ºC during a period of 29 days. Net inorganic phosphorus, ammonium and nitrate release were evaluated. While C mineralization was linearly increasing throughout the time frame, N mineralization peaked prior to day 29 and P mineralization was often represented as net immobilization. Land use differences in mineralization patterns were noticed. For example, forest management was characterized by minimal to net immobilization of P, while N mineralization was dominated by NH4 production and virtually no nitrification. Annual crop management also saw low mineralization to net P immobilization; but while NH4 production dominated early in the process, nitrification quickly became the dominant output beyond 8 days. For this watershed, the data suggests that N is the linkage between C and P mineralization. While SOC and total N mineralization are related to each other, C is not related to P mineralization. P mineralization is highly variable and best explained by soil P and N parameters. Linking C, N and P will be necessary to better describe inorganic nutrient generation on a landscape level; and these data will be useful to that end.

Back to Soil Carbon and Nitrogen Dynamics
Back to S07 Forest, Range & Wildland Soils

Back to The ASA-CSSA-SSSA International Annual Meetings (November 4-8, 2007)