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Communication at the NABS Annual meeting, Keystone, 2000
(306) ESTIMATES OF NITROGEN LOADING TO STREAMS USING IN-STREAM PROCESSING RATES.
W.M. Wollheim1, B.J. Peterson2, P.J. Mulholland3, J.R. Webster4, J.L. Tank5, J.L. Meyer6, N.B. Grimm7, E. Marti8, W.B. Bowden9, J. Merriam10, H.M. Valett4, A.E. Hershey11, W.H. McDowell10, W.K. Dodds12, S.K. Hamilton13, S.L. Johnson14, L.R. Ashkenas14, and D.J. D'Angelo15. 1Complex Systems Research Center, University of New Hampshire, Durham NH 03824, 2Ecosystems Center, Marine Biological Lab. Woods Hole MA, 02543, 3Environmental Science Division Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6036, 4Department of Biology, Virginia Tech University, Blacksburg, VA 24061, 5Dept. Natural Resources and Env. Sciences, N-411 Turner Hall, University of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801, 6Institute of Ecology, University of Georgia, Athens GA, 30602-2602, 7Department of Biology, Arizona State University, Tempe, AZ 85287-1501, 8Centre d'Estudis Avangats de Blanes, Cami de Sta. Barbara s/n, Blanes (Girona) SPAIN , 17300, 9Landcare Research, PO Box 69, Lincoln 8152, New Zealand, 10Dept of Natural Resources, James Hall, Durham NH 03824, 11Dept of Biology, University of North Carolina - Greensboro, Greensboro, NC 27402, 12Ackert Hall, Division of Biology, Kansas St. University, Manhatten KS 66506, 13Kellog Biological Station, 3700 E. Gull Cr. Dr., Hickory Corners, MI 49060, 14Dept. of Fisheries and Wildlife, Oregon St. University, 15The Proctor and Gamble Co. , Experimental Stream Facility, 1003 Route 50, Milford, Ohio 45150-0356
Estimates of nitrogen loading to streams are difficult to obtain because in-stream or riparian processes may confound estimates of land-water transfers. We created a spreadsheet model using information from the Lotic Intersite Nitrogen Experiment (LINX) to estimate the ammonium and nitrate concentrations in lateral water inputs necessary to maintain observed N concentrations and DIN dynamics in streams. The model includes rates of in-stream ammonium and nitrate uptake, nitrification, and net nitrogen regeneration obtained from 15NH4 additions to the various LINX streams. Concentrations of ammonium and nitrate in lateral water inputs were then found that best fit observed DIN fluxes in channel water over distance downstream. Predicted nitrate concentrations in lateral inputs ranged from 44 μg/l in Walker Branch, TN, to 129 μg/l in E-1 outlet stream, AK, to 160 μg/L in Mack Cr. OR. In Walker Br., our estimate compared favorably with estimates of loading concentrations obtained from detailed studies of groundwater flow paths (35 μg/l). Model estimates of ammonium concentrations in lateral inputs were generally lower than nitrate concentrations. This recipient-ecosystem method of estimating DIN loading should be linked with land-based studies to determine factors controlling N export from watersheds.
Presented at 1:45 PM on Thursday, June 1, 2000 in Nutrient Dynamics I
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