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Methanotrophy potential versus methane supply by pore water diffusion in peatlands
E. R. C. Hornibrook, H. L. Bowes, A. Culbert, and A. V. Gallego-Sala
Bristol Biogeochemistry Research Centre, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK
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Abstract. Low affinity methanotrophic bacteria consume a significant quantity of
methane in wetland soils in the vicinity of plant roots and at the
oxic-anoxic interface. Estimates of the efficiency of methanotrophy in peat
soils vary widely in part because of differences in approaches employed to
quantify methane cycling. High resolution profiles of dissolved methane
abundance measured during the summer of 2003 were used to quantify rates of
upward methane flux in four peatlands situated in Wales, UK. Aerobic
incubations of peat from a minerotrophic and an ombrogenous mire were used
to determine depth distributions of kinetic parameters associated with
methane oxidation. The capacity for methanotrophy in a 3 cm thick zone
immediately beneath the depth of nil methane abundance in pore water was
significantly greater than the rate of upward diffusion of methane in all
four peatlands. Rates of methane diffusion in pore water at the
minerotrophic peatlands were small (<10%) compared to surface emissions
during June to August. The proportions were notably greater in the
ombrogenous bogs because of their typically low methane emission rates.
Methanotrophy appears to consume entirely methane transported by pore water
diffusion in the four peatlands with the exception of 4 of the 33 gas
profiles sampled. Flux rates to the atmosphere regardless are high because
of gas transport through vascular flora, in particular, at the minerotrophic
sites. Cumulative rainfall amount 3-days prior to sampling correlated well
with the distance between the water table level and the depth of 0 μmol l−1
methane, indicating that precipitation events can impact methane
distributions in pore water. Further work is needed to characterise the
kinetics of methane oxidation spatially and temporally in different wetland
types in order to determine generalized relationships for methanotrophy in
peatlands that can be incorporated into process-based models of methane
cycling in peat soils.
Discussion Paper (PDF, 1921 KB) Interactive Discussion (Final Response, 4 Comments)
Citation: Hornibrook, E. R. C., Bowes, H. L., Culbert, A., and Gallego-Sala, A. V.: Methanotrophy potential versus methane supply by pore water diffusion in peatlands, Biogeosciences Discuss., 5, 2607-2643, 2008. Bibtex EndNote Reference Manager
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