Assessment of Effects of Acidic Deposition on Forested Ecosystems in Great Smoky Mountains National Park using Critical Loads for Sulfur and Nitrogen.

摘要

The eastern U.S. has been severely impacted by elevated atmospheric deposition of sulfur (S) and nitrogen (N), which contribute to acidification of soils and surface waters, with detrimental effects on forest vegetation and aquatic biota. The decrease in emissions of sulfur dioxide in the U.S. since 1973, as a result of the Clean Air Act (CAA), has not coincided with widespread recovery of soil and surface waters from acidic deposition. Indeed, S and N deposition remain serious threats to forest health in the region. Excess acidic deposition may lead to depletion of nutrient base cations, while excess N deposition may lead to N saturation. Ultimately, both N and S deposition may lead to plant nutrient imbalances, increased susceptibility to pests and disease and other secondary stresses, and declines in forest productivity and health. The purpose of this assessment was to calculate critical loads of S and N deposition to forests in Great Smoky Mountains National Park (GSMNP) based on available data. Four sites within the park were selected for this assessment to represent the range of forest ecosystems within the Park.