@article{a1881850bec049daa82086e1e8a2281e,
title = "Ecological effects of nitrogen deposition in the western United States",
abstract = "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 = "Biotic communities, Eutrophication, Lichens, Nitrogen saturation, Streamwater nitrate",
author = "Fenn, {Mark E.} and Baron, {Jill S.} and Allen, {Edith B.} and Rueth, {Heather M.} and Nydick, {Koren R.} and Linda Geiser and Bowman, {William D.} and Sickman, {James O.} and Thomas Meixner and Johnson, {Dale W.} and Peter Neitlich",
note = "Funding Information: Figure 4. Locations of nitrophilous versus air-pollution-sensitive lichens in Oregon and Washington (left) are contrasted with locations in which percent nitrogen (N) in lichen tissue was above or below regional thresholds (right). Thresholds are the 97.5% quantiles for N concentration in samples from remote forest sites. Percent N values above thresholds indicate enhanced N accumulation; two species were tested at each site. Sensitive species were found in areas where percent N in lichen tissue was below thresholds (open circles); nitrophilous lichens were found in areas where percent N was above thresholds (red circles). Pink circles indicate intermediate sites. Together, the maps show that greatest N enhancement is present in urban areas, in the Columbia River Gorge National Scenic Area west of Portland, and in agricultural parts of western Oregon between Portland and Medford and eastern Oregon and Washington. This work was sponsored by the US Forest Service between 1993 and 2001. Highest sampling density occurred in selected national forests.",
year = "2003",
month = apr,
day = "1",
doi = "10.1641/0006-3568(2003)053[0404:EEONDI]2.0.CO;2",
language = "English (US)",
volume = "53",
pages = "404--420",
journal = "BioScience",
issn = "0006-3568",
publisher = "Oxford University Press",
number = "4",
}