Chronic Nitrogen Additions to Forest Ecosystems: Effects of Nitrogen Cycling, Canopy Chemistry, and Trace Gas Emissions

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This research project will concentrate on continuing the Nitrogen additions in both the hardwood and red pine stands, and measuring basic N cycling parameters such as mineralization, nitrification, and plant uptake, including green foliar content. The project will also estimate N return to the system in litter fall and litter decay. As well, trace gas fluxes (CO2, N2O, CH4) will be measured. It is hypothesized that trace gas fluxes are controlled to a significant degree by short-term availability of carbon and nitrogen to soil microbes, and that these availabilities are, in turn, constrained by feedbacks between soil availability and plant demand. The effects of N additions on gross and net N immobilization and mineralization, on the production and consumption of available carbon during litter and soil organic matter decay, and on the available carbon and inorganic nitrogen content of throughfall will be investigated.