Pacific Southwest

Title: Ecological effects of nitrogen deposition in the western United States

Author: Fenn, Mark E.; Baron, Jill S.; Allen, Edith B.; Rueth, Heather M.; Nydick, Koren R.; Geiser, Linda; Bowman, William D.; Sickman, James O.; Meixner, Thomas; Johnson, Dale W.; Neitlich, Peter

Date: 2003

Source: BioScience 53(4):404-420

Description: In the western United States vast acreages of land are exposed to low levels of atmospheric nitrogen (N) deposition, with interspersed hotspots of elevated N deposition downwind of large, expanding metropolitan centers or large agricultural operations. Biological response studies in western North America demonstrate that some aquatic and terrestrial plant and microbial communities are significantly altered by N deposition. Greater plant productivity is counterbalanced by biotic community changes and deleterious effects on sensitive organisms (lichens and phytoplankton) that respond to low inputs of N (3 to 8 kilograms N per hectare per year). Streamwater nitrate concentrations are elevated in high-elevation catchments in Colorado and are unusually high in southern California and in some chaparral catchments in the southwestern Sierra Nevada. Chronic N deposition in the West is implicated in increased fire frequency in some areas and habitat alteration for threatened species. Between hotspots, N deposition is too low to cause noticeable effects or has not been studied.

Keywords: Nitrogen saturation, streamwater nitrate, eutrophication, lichens, biotic communities

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Citation

Fenn, Mark E.; Baron, Jill S.; Allen, Edith B.; Rueth, Heather M.; Nydick, Koren R.; Geiser, Linda; Bowman, William D.; Sickman, James O.; Meixner, Thomas; Johnson, Dale W.; Neitlich, Peter  2003.  Ecological effects of nitrogen deposition in the western United States.   BioScience 53(4):404-420.