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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Biogeochemistry 2
Influence of Wood on Nitrate Uptake in Streams of Western Oregon, U.S.A.
D.J. Sobota1, S.V. Gregory1, S.L. Johnson2, and L.R. Ashkenas1.1Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon 97331, 2USDA Forest Service, Pacific NW Research Station, 3200 SW Jefferson Way, Corvallis, Oregon 97331
Wood has been envisioned to influence dynamics of nitrogen (N) in stream ecosystems, yet few reach-scale experiments have evaluated this hypothesis. We evaluated influence of wood on processing of nitrate (NO3−) in stream reaches of western Oregon as part of the Lotic Intersite Nitrogen eXperiment II (LINX II). Nine reaches were injected with NO3− for 24 hr during summer low flow. Uptake velocity of NO3−–N was not correlated to biomass or surface area of wood in the stream, but uptake on wood accounted for 1% to 56% of total N uptake by stream biomass. Uptake of NO3−–N on wood was as much as 1.3 to 4.2 times greater than expected based on fraction of wood comprising total stream biomass. Also, turnover times of N were 1.1 to 3.7 times longer for biofilms on wood than uptake by biofilms on inorganic substrates. Wood often is seen as an inert structure that primarily influences N dynamics in streams by altering physical retention properties of channels. These results indicate that wood also has a direct biologically-mediated effect on N dynamics in streams, influencing quantity and quality of N in transport and storage in these systems.
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