Abstract

Ecosystem acidification and eutrophication resulting from increased deposition of dissolved inorganic nitrogen (DIN) are issues of increasing global concern. Consequently, costly policy decisions are being implemented to decrease nitrogen oxide (NO (x) ) emissions. Although declining DIN deposition along with rapid declines of DIN in surface waters have been reported in parts of Europe, the same observation is just emerging in North America. Here we find a significant decline in bulk deposition NO3 (-) during the later part of a 28-year record in southcentral Ontario, Canada. Despite high N retention and substantial inter-annual variability in the long-term record due to periods of drought, we find significant declines in annual NO3 (-) concentrations and export at six out of 11 streams that drain upland-dominated catchments. In contrast, five streams draining primarily wetland-dominated catchments with lower levels of NO3 (-) show no decreasing trend in NO3 (-) concentration or export. The rapid response in stream NO3 (-) to declining atmospheric inputs was observed at sites with historically moderate inputs of DIN (similar to 870 mg m(-2) y(-1)) in bulk deposition. Topographic features such as slope, and related catchment features including wetland cover, appear to influence which catchments will respond positively to declining DIN deposition. These findings force us to revise our original conceptualization of the N saturation status of these catchments.

Keywords

nitrate deposition; stream nitrate; long-term trends; forest catchments; nitrogen saturation; nitrogen cycling; biogeochemical cycles

Published in

Ecosystems
2011, Volume: 14, number: 2, pages: 274-286
Publisher: SPRINGER

SLU Authors

• Futter, Martyn

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Associated SLU-program

SLU Future Forests


UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use


Publication identifier

DOI: https://doi.org/10.1007/s10021-011-9422-1

Permanent link to this page (URI)

https://res.slu.se/id/publ/58986