HR: 0800h
AN: B51D-0255    [Abstracts]
TI: Methanotroph community properties determine the sensitivity of soil methane oxidation to variation in soil moisture
AU: * von Fischer, J
EM: jcvf@lamar.colostate.edu
AF: Dept. of Biology & NREL, Colorado State University, Ft. Collins, CO 80523 United States
AB: Soil biogeochemical processes depend on aspects of physical and biological structure that are very fragile. This fragile nature has limited our ability to understand the relative importance of abiotic vs. biotic controls on biogeochemical processes. To overcome this limitation, I have applied a non-disruptive, in-situ method for studying the controls of a relatively simple biogeochemical process: methane consumption in upland soils. My work uses additions of an inert tracer gas (sulfur hexafluoride, SF₆) to the headspace of gas flux chambers that are coincident with methane flux measures. By measuring both methane flux and SF₆ transport at the same time, I simultaneously and uniquely measure the physical transport and biological transformations that collectively regulate methane flux on the Shortgrass Steppe LTER (SGS LTER) site in north central Colorado, USA. Study areas on the SGS LTER differed in soil texture and vegetation, but none had been tilled. My results reveal that the response of methane flux to changes in soil moisture differed among study areas such that some showed steep declines with increasing soil water content while other sites had minimal changes. Underlying this response, my data show that the methane uptake capacity, a property of the methanotroph community, is greatest in soils that show the least sensitivity to soil moisture. Using a methane reaction-diffusion model, I have constrained the potential importance of methanotroph population size, spatial distribution and enzymatic properties for structuring the observed differences in methane uptake capacity.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: Fall Meeting 2005