thumbnail

Ecosystem processes and nitrogen export in northern U.S. watersheds.

Scientific World Journal

By:
DOI: 10.1100/tsw.2001.328

Links

Abstract

There is much interest in the relationship of atmospheric nitrogen (N) inputs to ecosystem outputs as an indicator of possible "nitrogen saturation" by human activity. Longer-term, ecosystem-level mass balance studies suggest that the relationship is not clear and that other ecosystem processes may dominate variation in N outputs. We have been studying small, forested watershed ecosystems in five northern watersheds for periods up to 35 years. Here I summarize the research on ecosystem processes and the N budget. During the past 2 decades, average wet-precipitation N inputs ranged from about 0.1 to 6 kg N ha(-1) year(-1) among sites. In general, sites with the lowest N inputs had the highest output-to-input ratios. In the Alaska watersheds, streamwater N output exceeded inputs by 70 to 250%. The ratio of mean monthly headwater nitrate (NO3-) concentration to precipitation NO3- concentration declined with increased precipitation concentration. A series of ecosystem processes have been studied and related to N outputs. The most important appear to be seasonal change in hydrologic flowpath, soil freezing, seasonal forest-floor inorganic N pools resulting from over-winter mineralization beneath the snowpack, spatial variation in watershed forest-floor inorganic N pools, the degree to which snowmelt percolates soils, and gross soil N mineralization rates.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Ecosystem processes and nitrogen export in northern U.S. watersheds.
Series title:
Scientific World Journal
DOI:
10.1100/tsw.2001.328
Volume
1
Issue:
Suppl 2
Year Published:
2001
Language:
English
Publisher:
Hindawi Publishong
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
581
Last page:
588
Number of Pages:
8