Ecosystem processes and nitrogen export in northern U.S. watersheds.
Scientific World Journal
By: R. Stottlemyer
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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.
Suggested Citation
Stottlemyer, R., 2001, Ecosystem processes and nitrogen export in northern U.S. watersheds.: Scientific World Journal, v. 1, no. Suppl 2, p. 581-588, https://doi.org/10.1100/tsw.2001.328.
| 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 |
| Larger Work Title | Scientific World Journal |
| First page | 581 |
| Last page | 588 |