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RELATIONS BETWEEN LAND USE AND STREAM NUTRIENT CONCENTRATIONS FOR SMALL WATERSHEDS IN THE GEORGIA PIEDMONT
Citation:
Molinero, J. AND R A. Burke Jr. RELATIONS BETWEEN LAND USE AND STREAM NUTRIENT CONCENTRATIONS FOR SMALL WATERSHEDS IN THE GEORGIA PIEDMONT. In Proceedings, 2003 Georgia Water Resources Conference, Athens, GA, April 23 - 24, 2003. University of Georgia, Athens, GA, 821-824, (2003).
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
Description:
We have been sampling nutrient concentrations in 17 headwater streams within the South Fork Broad River (SFBR) watershed on a monthly basis since November 2001. The streams were classified as either developed (n=4), agriculture/pasture (n=4), mixed land use (n=6) or forested (n=3) based on information from the National Land Cover Data (NLCD) database. The lowest mean nitrogen concentrations were observed in streams draining forested watersheds. A set of landscape indicators explained 93 % of the spatial variability in the total nitrogen concentrations which suggests that watershed land use has an important effect on stream nitrogen levels. Total phosphorus varied seasonally at some of the sites, with high concentrations observed during the summer and low concentrations in winter. Only 4 out of 14 non-forested sites showed higher mean total phosphorus concentrations and no relationships were found between the landscape indicators and the total phosphorus concentrations in the streams. We suggest that, in contrast to what was observed for nitrogen, in-stream sources (e. g. decaying plant material), in-stream cycling, or strong pollution sources (e. g. manure, septic tanks) are more important than watershed land use in determining the total phosphorus concentrations in these small streams.