HR: 08:55h
AN: H21F-04    [Abstracts]
TI: Topographic metrics for predicting dissolved inorganic and organic N export from catchments
AU: * Creed, I F
EM: icreed@uwo.ca
AF: Department of Biology, University of Western Ontario, London, ON N6A 5B7 Canada
AU: Beall, F D
EM: fbeall@nrcan.gc.ca
AF: Natural Resources Canada, Canadian Forest Service, Sault Ste. Marie, ON P6A 2E5 Canada
AB: Topographic controls on the natural variation in the export of dissolved inorganic nitrogen (DIN) (nitrate-N and ammonium-N) and dissolved organic N (DON) among catchments within a forested landscape in the Algoma Highlands of Ontario were explored. The annual average DIN output was 3.35 kg N/ha/yr, with individual catchments ranging from 0.79 to 5.59 kg N/ha/yr, and the annual average DON output was 1.07 kg N/ha/yr, with individual catchments ranging from 0.73 to 1.42 kg N/ha/yr based on water years from 1981 to 1996. Natural variations were also expressed in the speciation of N output, with the ratio of DIN:DON ranging from 1:1 to 5:1 among the catchments, a ratio achieved predominantly by a smaller DIN output. Topographic metrics were derived to represent hypothesized flushing controls on N export. DIN residuals in catchment specific versus catchment average export were significantly related to metrics representing variation in hydrologic flushing potential. In contrast, DON residuals were significantly related to metrics representing topographic flats and depressions. The implication of this study is that natural variations in the export of dissolved N species within a single forest homology can be substantial and that simple topographic metrics of hydrologically mediated N export can be used to predict N export of all catchments within a landscape.
DE: 0400 BIOGEOSCIENCES
DE: 1800 HYDROLOGY
SC: Hydrology [H]
MN: Fall Meeting 2005