期刊
BIOGEOCHEMISTRY
卷 93, 期 3, 页码 219-233出版社
SPRINGER
DOI: 10.1007/s10533-009-9299-7
关键词
Nitrogen budgets; Nutrient inputs; Riverine export; Watersheds; West coast
资金
- Georgia Coastal Ecosystems LTER Project [OCE-0620959]
- Coastal Incentive [NA170Z2331]
This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km(-2) year(-1), with an overall area-weighted average of 1,870 kg N km(-2) year(-1). In 2002, the range of inputs was 490-10,875 kg N km(-2) year(-1), averaging 2,158 kg N km(-2) year(-1). Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km(-2) year(-1) (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km(-2) year(-1) (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km(-2) year(-1) (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated with variations in streamflow (export = 0.94 x streamflow - 5.65, R (2) = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 x streamflow + 0.06 x input - 227.78, R (2) = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 x streamflow - 2.61, R (2) = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes that control watershed N export are not yet completely understood.
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