Knute Nadelhoffer
Atmospheric Nitrogen Deposition:
Implications for Nutrient Cycling, Acidification and Terrestrial Ecosystem Functioning

Unlike sulfate, rates of nitrate deposition in eastern North America are not decreasing. Further, other forms of nitrogen inputs from the atmosphere, such as ammonium ions, can have acidifying effects on terrestrial ecosystems. Biological assimilation of nitrate and ammonium plants and soil microbes partially determines the extent of acidification resulting from N deposition. Also, because plant growth and other biological processes are often partially limited by N availability, N deposition can lead to changes in plant community composition, net primary production, carbon gain or loss, and patterns of nutrient cycling in terrestrial ecosystems, as well as to increases in nitrate outputs to freshwater and estuarine ecosystems. This talk will summarize research into mechanisms by which terrestrial ecosystems retain or release N inputs and will develop predictions of long-term responses of the effects of N deposition on the composition and functioning of terrestrial ecosystems .