Document Type


Publication Date



One of the conclusions reached during the Congressionally mandated National Acid Precipitation Program (NAPAP) was that, compared to ozone and other stress factors, the direct effects of acidic deposition on forest health and productivity were likely to be relatively minor. However, the report also concluded “the possibility of long-term (several decades) adverse effects on some soils appears realistic” (Barnard et al. 1990). Possible mechanisms for these long-term effects include: (1) accelerated leaching of base cations from soils and foliage, (2) increased mobilization of aluminum (Al) and other metals such as manganese (Mn), (3) inhibition of soil biological processes, including organic matter decomposition, and (4) increased bioavailability of nitrogen (N).


This article first appeared in 2006, MB Adams, DR DeWalle, and J Hom, editors. The Fernow Watershed Acidification Study, Series: Environmental Pollution, Vol. 11, New York, NY: Springer and is reprinted with permission. The final publication is available at