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Relationship Between Watershed Land Use and Denitrification Enzyme Activity in Headwater Streams
Citation:
BURKE, R. A., K. M. FRITZ, B. R. JOHNSON, S. FULTON, AND C. Barton. Relationship Between Watershed Land Use and Denitrification Enzyme Activity in Headwater Streams. Presented at Denitrification Research Coordination Network Workshop, Cambridge, MD, May 27 - 30, 2008.
Impact/Purpose:
Evaluate the relationship between watershed land use (e.g. poultry production, residential development, natural and managed forests, and MTM/VF) and DEA in headwater streams.
Description:
Headwater streams are the dominant land-water interface across much of the landscape. Denitrification is an important ecological service provided by headwater streams. Anthropogenic inputs of N to terrestrial ecosystems largely result from agricultural practices. Animal agriculture is the largest agricultural sector in the southeastern U.S. The South Fork Broad River (SFBR) watershed in Georgia covers approximately 600 km in an important poultry production area. Poultry wastes are disposed of by application to pastures. Appalachia accounts for over a third of US coal production. Mountaintop mining/valley fill (MTM/VF) is a common coal mining practice in Appalachia that physically devastates the areas in which it is employed. From 1992 to 2002, approximately1200 miles of small streams were impacted by MTM/VF in Appalachia. Due to high variability and methodological problems associated with measuring in situ denitrification rates, various measures of denitrification potential have been developed. The assay of denitrification enzyme activity (DEA) developed by Smith and Tiedje is a commonly used measure of denitrification potential. In the DEA assay, O is removed, C and nitrate are present in excess, and growth is inhibited by chloramphenicol so that only the enzymes originally present in the sample contribute to N gas production. Our observations of relatively high DEA in streams with low nitrate levels suggests that there is a reservoir of denitrification potential in many headwater streams that should be considered a valuable ecosystem service worthy of protection.