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Effects of microbial communities and organic matter quality on methane fluxes in different areas of a Siberian polygon tundra

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Wagner, D. , Gattinger, A. , Lipski, A. and Schloter, M. (2005): Effects of microbial communities and organic matter quality on methane fluxes in different areas of a Siberian polygon tundra , Second European Conference on Permafrost, EUCOP 2005, Potsdam, March 12- .
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Abstract:

Wet tundra environments of the Arctic are natural sources of the climate relevant trace gas methane. The underlying microbial and geochemical processes are not yet well understood. The field investigations were carried out on the island Samoylov (N 72°, E 126°) located in the Lena Delta, Siberia. The study site represented an area of typical polygonal patterned grounds with ice-wedges. For the understanding and assessment of recent and future carbon dynamics of permafrost soils the processes of CH4 production and oxidation, the microbial community structure and the quality of DOM were studied in two soils of a polygonal tundra.The mean flux rate of the depression was 53.2 ± 8.7 mg CH4 m-2 d-1, whereas the mean flux rate of the dryer rim part of the polygon was 4.7 ± 2.5 CH4 m-2 d-1. Activities of methanogens and methanotrophs differed significantly in their rates and distribution patterns among the two investigated profiles. Community structure analysis showed similarities between both soils for esterlinked PLFAs and differences in the fraction of unsaponifiable PLFAs and PLELs. Furthermore, a shift of the overall composition of the microbiota with depth at both sites was indicated by an increasing portion of iso- and anteiso-branched fatty acids related to the amount of straight chain fatty acids. The quantity of dissolved organic matter (DOM), which represents an important C pool for microbial communities, correlated significant with the total concentrations of phospholipid fatty acids and ether lipids (PLFA and PLEL) a measure for microbial biomass. Although permafrost soils represent a large carbon pool, it was shown, that the reduced quality of organic matter leads to a substrate limitation of the microbial metabolism. This is an important finding for modelling and calculating trace gas fluxes from permafrost environments, because the known models are consider only the total carbon amount.It can be concluded by the presented results firstly that microbial communities in permafrost environments are composed by members of all three domains of life at numbers comparable to temperate soil ecosystems and secondly that the permafrost microorganisms are well adapted to the extreme temperature gradient of their environment.

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