| The Role of Atmospheric Nitrogen in N Cycling in Forests
by Prof. Steve Bertman |
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An important issue in biosphere-atmosphere interactions is the relationship between atmospheric nitrogen deposition and forest ecosystem functioning, since ecosystem structure, diversity, and productivity are largely controlled by the availability of nitrogen. There is a need to determine the atmospheric input of nitrogen to each part of a forest ecosystem (soils, leaves, stems). Measurements of wet deposition of nitrate and ammonium have been made nationwide for the last several decades as part of the National Acid Deposition Program (NADP). Much less is known about the chemistry of dry deposition. In particular, the actual detailed fate, in terms of incorporation into biomass, of atmospherically deposited nitrogen to ecosystems is something that is only beginning to be explored. In addition, the current NADP network of deposition measurements does not consider the potential impact of forest canopy interactions on deposited nitrogen, since the measurements are made in clearings some distance away from forests. We are interested in assessing the impact of forest surfaces and canopy processes on atmospheric chemistry and of atmospheric nitrogen on forest ecosystems. For this we need to know about deposition of ALL atmospheric nitrogen species, and we need to understand processes that impact the rate at which biologically active forms are made available for uptake.