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Does anthropogenic nitrogen enrichment increase organic nitrogen concentrations in runoff from forested and human-dominated watersheds?

Ecosystems

By:
, ,
DOI: 10.1007/s10021-006-0076-3

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Abstract

Although the effects of anthropogenic nitrogen (N) inputs on the dynamics of inorganic N in watersheds have been studied extensively, "the influence of N enrichment on organic N loss" is not as well understood. We compiled and synthesized data on surface water N concentrations from 348 forested and human-dominated watersheds with a range of N loads (from less than 100 to 7,100 kg N km-2 y-1) to evaluate the effects of N loading via atmospheric deposition, fertilization, and wastewater on dissolved organic N (DON) concentrations. Our results indicate that, on average, DON accounts for half of the total dissolved N (TDN) concentrations from forested watersheds, but it accounts for a smaller fraction of TDN in runoff from urban and agricultural watersheds with higher N loading. A significant but weak correlation (r 2 = 0.06) suggests that N loading has little influence on DON concentrations in forested watersheds. This result contrasts with observations from some plot-scale N fertilization studies and suggests that variability in watershed characteristics and climate among forested watersheds may be a more important control on DON losses than N loading from atmospheric sources. Mean DON concentrations were positively correlated, however, with N load across the entire land-use gradient (r 2 = 0.37, P < 0.01), with the highest concentrations found in agricultural and urban watersheds. We hypothesize that both direct contributions of DON from wastewater and agricultural amendments and indirect transformations of inorganic N to organic N represent important sources of DON to surface waters in human-dominated watersheds. We conclude that DON is an important component of N loss in surface waters draining forested and human-dominated watersheds and suggest several research priorities that may be useful in elucidating the role of N enrichment in watershed DON dynamics. ?? 2006 Springer Science+Business Media, Inc.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Does anthropogenic nitrogen enrichment increase organic nitrogen concentrations in runoff from forested and human-dominated watersheds?
Series title:
Ecosystems
DOI:
10.1007/s10021-006-0076-3
Volume
9
Issue:
5
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Ecosystems
First page:
852
Last page:
864
Number of Pages:
13