HR: 1340h
AN: B43C-0298    [Abstracts]
TI: Nitrous Oxide and Methane Fluxes from Urban Lawns to the Atmosphere in Denver, Colorado
AU: * Thienelt, T
EM: canyon62@gmx.de
AF: U.S. Geological Survey/WRD, M.S. 413, Bldg. 53 Federal Center, Denver, CO 80225 United States
AU: Anderson, D E
EM: deander@usgs.gov
AF: U.S. Geological Survey/WRD, M.S. 413, Bldg. 53 Federal Center, Denver, CO 80225 United States
AB: In 1996, urban land occupied 3-4% of the total surface area of the United States and urban counties, which include cities, covered nearly 25%. Both of these areas are rapidly expanding, particularly in the west and south. Using remote sensing imagery for Denver, we calculate that urban lawns cover approximately 30% of the surface. Urban lawns likely differ markedly from rangeland vegetation and cropland which they replace through human induced landuse change. Urban lawns are an intensely managed component of urban ecosystems and their impact on urban greenhouse gas emissions needs to be understood. They are typically well-watered and well-fertilized and experience warmer, longer growing seasons due to the urban heat island effect. Methane (CH₄) and nitrous oxide N₂O fluxes were measured over 12 lawns in the Denver urban ecosystem during the 2005 growing season using 6-liter surface chambers. Preliminary analysis indicates that fluxes were heavily dependent on irrigation frequency, especially during mid-summer when evaporative demand was high (Denver experiences a semi-arid climate). Over the course of the growing season, there was an average CH₄ flux uptake of 0.08 ± 0.09 g C m^-2 yr^-1 from the atmosphere while N₂O fluxes indicated an emission of 0.013 ± 0.02 g N m^-2 yr^-1. Fluxes varied considerably from site to site in the city but tended to be more self-consistent with time within sites. CH₄ flux was typically downward over moist to saturated soils, near zero over un-irrigated (dry) soils, and upward over saturated soils. N₂O fluxes were almost always upward, particularly over moist to saturated, fertilized soils. Downward N₂O fluxes were weak and may have been an artifact of measurement methodology.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0490 Trace gases
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: Fall Meeting 2005