thumbnail

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

Scientific World Journal
By:
https://doi.org/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.
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
Google Analytic Metrics Metrics page
Additional publication details