Pacific Southwest

Title: A case study of nitrogen saturation in western U.S. forests

Author: Fenn, Mark E.; Poth, Mark A.

Date: 2001

Source: The Scientific World 1:1-7

Description: Virtually complete nitrification of the available ammonium in soil and nitrification activity in the forest floor are important factors predisposing forests in the San Bernardino Mountains of southern California to nitrogen (N) saturation. As a result, inorganic N in the soil solution is dominated by nitrate. High nitrification rates also generate elevated nitric oxide (NO) emissions from soil. High-base cation saturation of these soils means that soil calcium depletion or effects associated with soil acidification are not an immediate risk for forest health as has been postulated for mesic forests in the eastern U.S. Physiological disturbance (e.g., altered carbon [C] cycling, reduced fine root biomass, premature needle abscission) of ozone-sensitive ponderosa pine trees exposed to high N deposition and high ozone levels appear to be the greater threat to forest sustainability.

Keywords: Nitrogen saturation, California, western forests, mixed conifer forests, nitrate, nitrification, nitrogen mineralization, trace gas emissions, nitric oxide, nitrogen excess, nitrogen deposition, soil solution

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Citation

Fenn, Mark E.; Poth, Mark A.  2001.  A case study of nitrogen saturation in western U.S. forests.   The Scientific World 1:1-7.