HR: 1340h
AN: B53A-0931    [Abstracts]
TI: Methane uptake in forest and agro-ecosystems in Australia
AU: * Arndt, S K
EM: sarndt@unimelb.edu.au
AF: The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia
AU: Livesley, S J
EM: sjlive@unimelb.edu.au
AF: The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia
AU: Fest, B J
EM: benedikt.fest@mytum.de
AF: The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia
AU: Weston, C J
EM: weston@unimelb.edu.au
AF: The University of Melbourne, 500 Yarra Boulevard, Richmond, VIC 3121, Australia
AU: Butterbach-Bahl, K
EM: Klaus.Butterbach@imk.fzk.de
AF: Forschungszentrum Karlsruhe, Kreuzeckbahnstresse 19, Garmisch-Partenkirch, 82467, Germany
AB: Oxidation of methane by methanotrophic bacteria in aerated soils does provide a considerable global sink for greenhouse gases (-30 Tg CH4/yr). The form of land-use can have a significant impact on the methane uptake capacity of a soil. We investigated the sink strength for methane uptake of forest ecosystems and agro- ecosystems in Australia using automated measurement systems and manual chamber methods. Our results demonstrate large differences in the methane uptake capacity of Australian soils. Data from Western Australia showed that CH4 uptake rates increased with stand age of plantations and were greatest in an undisturbed native forest and lowest in an improved pasture. Measurements in differently aged forest ecosystems indicated that sites with the most recent fire disturbance had the lowest methane uptake rates. Generally, native forest ecosystems showed the greatest methane uptake rates (up to 130 kg CO2-e ha yr). Plantations (eucalyptus/pine) showed significantly lower methane uptake rates (around 15 kg CO2-e ha yr). Grazed pastures in Australia had the lowest uptake rates (6 kg CO2-e ha yr) and were occasional methane sources. The methane uptake rates of soils were only marginally influenced by environmental parameters over the course of a year. Between sites the methane uptake rates were not related to soil parameters such as soil bulk density. Experiments with excavated soil cores demonstrated that diffusivity of methane through the upper soil layer was the rate limiting step. Our results indicate that the community structure of methanotrophic bacteria and substrate diffusivity are the most important factor influencing methane uptake rates in soils. Disturbance events such as change of land-use or vegetation structure can have significant impacts on the capacity of soils to take up methane.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: 2007 Fall Meeting