Nitrogen Saturation in Northern Forest Ecosystems

Abstract

Human actitity has greatly altered the biogeochemical cycles of the Earth, generally increasing pollutant concentrations in the atmosphere and deposition rates to the surface. The combustion of fossil fuels is amajor component of human impct on the atmosphere and biosfere. Acid deposition, or acid rain, is on importante phenomenon associated with the burning of coal, gasoline, and oil. Until recently, sulfur emissions have been focus of US regulation on acid rain. There is, however, increasing concern about the N components of emissions and its potencial effects on air qulaity, water quality, and the health of forest ecossistems.