HR: 09:00h
AN: B41G-05 [Abstracts]
TI: Denitrification is the Primary Source of Soil-Derived Nitrous Oxide in a Terrestrial Ecosystem: Evidence From Isotopologues
AU: Opdyke, M
EM: mopdyke@pointpark.edu
AF: Point Park University, Department of Natural Resources
Point Park University
201 Wood Street, Pittsburg, PA 15222, United States
AU: Ostrom, P H
EM: ostrom@msu.edu
AF: Michigan State University, Biogeochemistry Environmental Research Initiative
Michigan State University
203 Natural Sciences Building, East Lansing, MI 48824-1115, United States
AU: * Ostrom, N E
EM: ostromn@msu.edu
AF: Michigan State University, Biogeochemistry Environmental Research Initiative
Michigan State University
203 Natural Sciences Building, East Lansing, MI 48824-1115, United States
AB:
Isotopologues were applied to address the origins of N2O released from soils at the W.K. Kellogg
Biological Station, a temperate agricultural field station in SW Michigan. Soils sampled included: unfertilized, tilled
fields in soybean (AGsoy); tilled fields in corn receiving fertilizer (AGcorn), and an early-successional (SUCC) field
abandoned in1989. Soil-derived N2O fluxes and isotopologues were measured in May, July, Sept. and Nov.
in 2006. Fluxes were greatest in AGcorn, with a maximum average in May of 46.9 g N2O-N ha-1 d-1. The
δ15N and δ15O values for N2O ranged between -16.1 and 9.7 ‰, and 22.2
and 57.3 ‰, respectively. Site Preference (SP), the difference between the δ15N of the central
and outer N atoms in N2O, values weighted by flux were 3.0, 10.6 and 14.9 ‰ at AGcorn, SUCC and
AGsoy, respectively. Based on SP values of 0 ‰ for denitrification and 33 ‰ for nitrification [Sutka et
al., 2006], between 55 and 91 % of soil-derived N2O was from denitrification in all three fields. We further
find that N2O reduction alters SP to a small extent and results in an overestimate of the importance of
nitrification. Thus, our overall finding that 85% of the N2O flux is from denitrification is an underestimate.
DE: 0402 Agricultural systems
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0469 Nitrogen cycling
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: 2007 Fall Meeting