HR: 0800h
AN: B11A-1030    [Abstracts]
TI: Applications of Isotopomers to Apportion Nitrous Oxide Production From Tropical Rain Forest Soils to Nitrification and Denitrification
AU: * Ostrom, N E
EM: ostromn@msu.edu
AF: Department of Zoology, Michigan State University 203 Natural Sciences Building, East Lansing, MI 48824-1115 United States
AU: Ostrom, P H
EM: ostrom@msu.edu
AF: Department of Zoology, Michigan State University 203 Natural Sciences Building, East Lansing, MI 48824-1115 United States
AU: Silver, W L
EM: wsilver@nature.berkeley.edu
AF: Ecosystem Sciences Division Department of Environmental Science, Policy, and Management, 137 Mulford Hall #3114 University of California, Berkeley, CA 94720-3114 United States
AU: McDowell, W H
EM: Bill.McDowell@unh.edu
AF: Department of Natural Resources, University of New Hampshire, Durham, NH 03824 United States
AU: Gandhi, H
EM: gandhiha@msu.edu
AF: Department of Zoology, Michigan State University 203 Natural Sciences Building, East Lansing, MI 48824-1115 United States
AB: Within pure cultures of microbes our prior research has demonstrated that the isotopomer composition of nitrous oxide can provide a basis to apportion the origin of this important greenhouse gas to nitrification and denitrification. This approach is based on the observation that nitrous oxide derived from denitrification and nitrification have distinct values (approx. 0 and 30 ‰, respectively) in Site Preference (S.P.) (the difference in δ¹⁵N between the central and outer N atoms in the linear nitrous oxide molecule). In July of 2005 we conducted a series of flux chamber experiments to evaluate the isotopomer composition of nitrous oxide evolving from tropical rainforest soils at the Luquillo Long Term Ecological Research site within control and N-fertilized plots. Within one chamber collection, for example, δ¹⁵N, δ¹⁸O and S.P. changed from 1.0 to -1.2, 40.6 to 39.5, and 4.1 to 18.5 ‰, respectively. These shifts are consistent with mixing of soil-derived with atmospheric nitrous oxide and indicate the production of nitrous oxide from nitrification. Mass balance models (Keeling plots) are used to determine the isotopomer composition of the soil-derived nitrous oxide. These results have important implications for understanding how nitrous oxide production will change with increased N deposition.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: Fall Meeting 2005