Hamilton, S.K.
Presented at the All Scientist Meeting (1996-07-16 to 1996-07-17 )
Knowledge of factors regulating the uptake, retention, and cycling of nitrogen is integral to understanding stream ecosystem structure and function. Furthermore, because streams serve as key hydrologic and biogeochemical links between upland and downstream aquatic ecosystems, understanding how changes in climate or land use will affect the movement of materials across the landscape requires working models of the controls on the structure and function of streams. In this project we will employ simulation modeling, field tracer additions, and an intersite comparison approach to investigate the controls on stream nitrogen cycling and develop a generalized model of nitrogen dynamics in stream ecosystems.Specific experiments to be performed at each of the sites include stable isotope enrichments of the dissolved inorganic nitrogen, which will enable us to trace to flow of nitrogen through abiotic and biotic compartments, as well as short-term additions of conservative tracers, which will allow us to quantify the hydraulic characteristics of the experimental reaches. The experimental methods will be coordinated with those used at the other sites to facilitate eventual comparisons among sites.The proposed work is a subcontract comprising part of an intersite comparative study led by Virginia Polytechnic Institute and State University, and has recently been funded by NSF Ecosystems. Ten sites have been selected, most of which are associated with LTER projects. The research to be performed by MSU will be done in the Augusta Creek system, which is adjacent to the W.K. Kellogg Biological Station in southwestern Michigan. The Augusta Creek system is distinct from the other proposed sites because its waters are highly enriched in dissolved nitrogen (mainly as nitrate, presumably from agricultural sources), yet remain quite low in phosphorus. Stephen K. Hamilton is the senior participant in the MSU portion of this project. The MSU work is scheduled among the second round of sites to be investigated in the intersite comparison, and thus the experiments will be performed in summer 1998.
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