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Abstract
Recent studies in the transverse ranges (including Class I Wilderness areas) of southern California have emphasized the strong linkage between levels of air pollution-related atmospheric nitrogen (N) inputs into montane watersheds and levels of nitrate in surface and subsurface drainage waters (fig. 1). Nitrate concentrations in streamwater in southern California are the highest in North America for wildland watersheds. High nitrate concentrations in runoff are a result of excessive ecosystem enrichment with N from atmospheric deposition. When N enrichment results in the removal of biological N limitation and the N retention capacity of the system is exceeded, the ecosystem is described as "N saturated." Nitrogen-saturated forests are analogous to over-fertilized agricultural fields with high nitrate runoff. The primary symptom of an N-saturated ecosystem is high nitrate concentrations in the soil solution, in soil leachate, and in groundwater and streamwater (Fenn and others 1998). Vegetation in N-saturated ecosystems contains high levels of N, and excess N also builds up in litter and soil organic matter, especially under fire suppression regimes. Stand densification is likely to be exacerbated by N deposition.
Parent Publication
Citation
Fenn, Mark; Poth, Mark; Meixner, Thomas. 2005. Atmospheric nitrogen deposition and habitat alteration in terrestrial and aquatic ecosystems in southern California: implications for threatened and endangered species. In: Kus, Barbara E., and Beyers, Jan L., technical coordinators. Planning for Biodiversity: Bringing Research and Management Together. Gen. Tech. Rep. PSW-GTR-195. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 269-271
