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Abstract
To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites.
Publication Date
3-12-2013
Publisher
IOP Science
Journal Title
Environmental Research Letters
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Argerich, A., Johnson, S.L., Sebestyen, S.D., Rhoades, C.C., Greathouse, E., Knoepp, J.D., ... & Ice, G.G. (2013). Trends in stream nitrogen concentrations for forested reference catchments across the USA, Environmental Research Letters, 8(1), 1-8. doi: 10.1088/1748-9326/8/1/014039
Comments
This is an Open Access article published by IOP Science in Environmental Research Letters in 2013, available online: https://dx.doi.org/10.1088/1748-9326/8/1/014039