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Thursday, May 21, 2009 - 8:45 AM
505
How does the study of agricultural streams enrich our understanding of nutrient spiraling?
Jennifer L. Tank1, Robert O. Hall Jr.2, Stephen K. Hamilton3, Patrick J. Mulholland4, Bruce J. Peterson5, Linda R. Ashkenas6, Clifford N. Dahm7, Walter K. Dodds8, Stuart Findlay9, Stanley V. Gregory6, Nancy B. Grimm10, Sherri L. Johnson11, William H. McDowell12, Judy L. Meyer13, Geoffrey C. Poole14, H. Maurice Valett15, Jackson R. Webster16, Clay P. Arango17, Jake J. Beaulieu18, Melody J. Bernot19, Amy J. Burgin20, Chelsea Crenshaw7, Ashley M. Helton13, Laura T. Johnson21, Bobbie R. Niederlehner22, Jonathan M. O'Brien23, Jody D. Potter12, Richard W. Sheibley24, Daniel J. Sobota25, and Suzanne M. Thomas5. (1) Department of Biological Sciences, University of Notre Dame, Galvin Life Sciences, Notre Dame, IN 46556, (2) Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, (3) Kellogg Biological Station, Michigan State University, 3700 East Gull Lake Drive, Hickory Corners, MI 49060, (4) Environmental Sciences Division, Oak Ridge National Laboratory, Bethel Valley Road, PO Box 2008, Oak Ridge, TN 37831-6036, (5) Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, (6) Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331, (7) Department of Biology, University of New Mexico, MSC03 2020, Albuquerque, NM 87131, (8) Division of Biology, Kansas State University, 104 Ackert Hall, Manhattan, KS 66506, (9) Inst. of Ecosystem Studies, Millbrook, NY 12545, (10) School of Life Sciences, Arizona State University, Tempe, AZ 85287, (11) Pacific NW Research Station, US Forest Service, 3200 SW Jefferson Way, Corvallis, OR 97331, (12) Department of Natural Resources, University of New Hampshire, Durham, NH 03824, (13) Odum School of Ecology, University of Georgia, Athens, GA 30602, (14) Dept. of Land Resources and Environmental Sciences, Montana State University, 819 Leon Johnson Hall, P.O. Box 173120, Bozeman, MT 59717, (15) Biological Sciences, Virginia Polytechnic Institute and State University, 2119 Derring Hall, Blacksburg, VA 24061, (16) Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, (17) Depts of Biological Sciences/Geography, Central Washington University, Science Building, Room 236A, 400 E. University Way, Ellensburg, WA 98926-7537, (18) US EPA, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, (19) Biology, Ball State University, 1024 W. Bethel Ave Apt 7, Muncie, IN 47303, (20) Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, (21) School of Public and Environmental Affairs, Indiana University - Bloomington, Bloomington, IN 47405, (22) Department of Biological Sciences, Virginia Polytechnic Institute and State University, 2119 Derring Hall, Blacksburg, VA 24061, (23) Kellogg Biological Station, 3700 East Gull Lake Drive, Hickory Corners, MI 49060, (24) Washington Water Science Center, U. S. Geological Survey, Tacoma, WA 98402, (25) School of Earth and Environmental Sciences, Washington State University, Vancouver Campus, Vancouver, WA 98686
The role of agricultural streams in processing and retaining nutrients has been understudied considering the recent focus on how agriculture influences export of excess nitrogen to downstream ecosystems. Empirical measurements of nutrient spiraling in agricultural streams are few in contrast to “pristine” streams. Data from the LINXII project quantifying 15N-nitrate removal from streams of varying land use helps fill this knowledge gap. Combining data from 23 LINXII agricultural streams with a meta-analysis of 170 previously published nitrate uptake measurements, we found substantial variation in spiraling metrics among agricultural streams likely reflecting the variability in agriculture practices across sites. Uptake lengths (Sw) in agricultural streams spanned the entire range of those from the meta-analysis and nitrate Sw increased significantly with increasing discharge. The coefficient of variation in Sw was similar between LINXII and meta-analysis streams while nitrate concentrations were significantly higher in agricultural streams. Meta-analyses can identify major drivers controlling nutrient uptake. For example, we observed that agricultural practices resulting in stream channel exposure to sunlight, in an otherwise forested landscape, makes streams more "alive" (i.e. bioreactive). Effective stream management should optimize the capacity for nutrient uptake while recognizing that the type of agriculture may differentially influence potential nutrient retention.