Microbiological methane emission in the boreal ecosystems of cryogenic Siberia zones

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Evgrafova, S. Y. , Grodnitskaya, I. D. , Krinisun, Y. O. and Wagner, D. (2010): Microbiological methane emission in the boreal ecosystems of cryogenic Siberia zones , Joint Russian-German Workshop on Research in the Laptev Sea Region, November 8-11, 2010, St. Petersburg, Russia. .
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Carbon dioxide is known to be the major contributor to the green-house effect;however, its annual increase in the atmosphere has slowed down markedly inrecent years. The methane (CH4) concentration in the atmosphere has morethan doubled over the last 300 years and is currently increasing at an annualrate of 0.8 to 1.0% per year [Dedysh , 2002].The arctic and sub-arctic zones of Siberia are considered to be among the mostactive atmospheric methane sources. The CH4 emission is controlled by thedegree of drowning, the temperature, the amount of organic matter, thevegetation and the methanogenesis and methanotrophic processes. As a ruleon the territory of Siberia the emission of modern biogenic methane, which isactive source of atmospheric methane occurred from the natural ecotopes[Galchenko, 2001]. A considerable amount of methane does not participate inthe contemporary biogeochemical cycle, since it is stocked in the permafrosttogether with living anaerobic microorganisms including methane-producingbacteria (Archaea). Methane production can occur at below-zero temperatures (down to 16.5oC) in permafrost depositions [Rivkina et al., 2006; Gilichinsky,2002; Wright et al., 1998]. We have carried out ourinvestigations in the two Siberian regions which are located in the permafrostzone. There are the Central Evenkia (forest ecosystem) and Lena Delta (tundraecosystem). The general aim is the estimation of microbial emission and theCH4 absorption of the cryogenic soils simultaneously using of the unifiedmethodology. We used the method of closed chambers (Wagner et al., 2003)for fixing the methane release with the surface of the soil during July andAugust.It was determined that from11.7 to 50.4 mg/m2/day of CH4 was risen with thesoil surface in the tundra ecosystem. The difference in the methane fluxesbetween of the polygon centre and rims was 1.7-2.8 times. The methane fluxvalue was from 8.9 to 34.7 mg/m2/day in the forest ecosystem and depended onthe amount of precipitations incoming from the atmosphere to the soil. Theobtained data permit to tell about the similarity of microbial processes ofmethane transformation, occurring in the mineral soil layer of the bothecosystems. The methane flux in tundra ecosystem was 2.2 times higher thanin the forest ecosystem.The presence of archaeabacteria was determined by the molecular geneticmethod. Methanogenic archaea belonging to the uncultivated Rice cluster II ofEuryarcheota was dominant in our samples and another big archaebacteriagroup belonged to the uncultivated Rice Cluster IV of Crenarcheota.

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