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A dust cloud rises from a field being
plowed in the Central Valley of California. © NPS photo |
Nitrogen is essential for all living
things. It is found in solid earth and in the
atmosphere. Small amounts of nitrogen move in a
dynamic cycle involving the atmosphere, oceans,
lakes, streams, plants, and animals. Depending on the
form and amount in the environment, nitrogen can
serve as a nutrient, enhancing growth and
productivity, or as a toxin, causing ecological
damage or harming human health.
Human activities (emissions from
vehicles, electric utilities, industrial plants and
agricultural activities) have added levels of
nitrogen rivaling or exceeding contributions from
natural sources.
There has been a slow, continuous increase in
atmospheric nitrogen deposition in park watersheds as
well as around the world. However, in spite of
increasing nitrogen deposition, there has been a
decrease in the dissolved nitrogen that has been
measured in the water flowing out of mid and
high-elevation park watersheds. The consequences of
increased nitrogen deposition and retention on
terrestrial plant communities are unknown.
For further information, visit the National
Atmospheric Deposition Program
web site.
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