期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 117, 期 -, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2011JG001740
关键词
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资金
- New York Energy Research and Development Authority
- U.S. Geological Survey New York Water Science Center
- National Science Foundation
- USGS
- Northern States Research Cooperative (USDA) [02CA11242343110]
- USDA [VT-PS-00912]
- Division Of Environmental Biology
- Direct For Biological Sciences [1114804] Funding Source: National Science Foundation
Nitrogen export from small forested watersheds is known to be affected by N deposition but with high regional variability. We studied 10 headwater catchments in the northeastern United States across a gradient of N deposition (5.4 - 9.4 kg ha(-1) yr(-1)) to determine if soil nitrification rates could explain differences in stream water NO3- export. Average annual export of two years (October 2002 through September 2004) varied from 0.1 kg NO3--N ha(-1) yr(-1) at Cone Pond watershed in New Hampshire to 5.1 kg ha(-1) yr(-1) at Buck Creek South in the western Adirondack Mountains of New York. Potential net nitrification rates and relative nitrification (fraction of inorganic N as NO3-) were measured in Oa or A soil horizons at 21-130 sampling points throughout each watershed. Stream NO3- export was positively related to nitrification rates (r(2) = 0.34, p = 0.04) and the relative nitrification (r(2) = 0.37, p = 0.04). These relationships were much improved by restricting consideration to the 6 watersheds with a higher number of rate measurements (59-130) taken in transects parallel to the streams (r(2) of 0.84 and 0.70 for the nitrification rate and relative nitrification, respectively). Potential nitrification rates were also a better predictor of NO3- export when data were limited to either the 6 sampling points closest to the watershed outlet (r(2) = 0.75) or sampling points <250 m from the watershed outlet (r(2) = 0.68). The basal area of conifer species at the sampling plots was negatively related to NO3- export. These spatial relationships found here suggest a strong influence of near-stream and near-watershed-outlet soils on measured stream NO3- export.
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