SummaryFor the understanding and assessment of recent and future carbon dynamics of arctic permafrost soils the processes of CH 4 production and oxidation, the community structure and the quality of dissolved organic matter (DOM) were studied in two soils of a polygonal tundra. 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 ester-linked phospholipid fatty acids (PLFAs) and differences in the fraction of unsaponifiable PLFAs and phospholipid ether lipids. 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. 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. It can be concluded from our and previous findings first that microbial communities in the active layer of an Arctic polygon tundra are composed by members of all three domains of life, with a total biomass comparable to temperate soil ecosystems, and second that these microorganisms are well adapted to the extreme temperature gradient of their environment.

Permafrost environments within the Siberian Arctic are natural sources of the climate relevant trace gas methane. In order to improve our understanding of the present and future carbon dynamics in high latitudes, we studied the methane concentration, the quantity and quality of organic matter, and the activity and biomass of the methanogenic community in permafrost deposits. For these investigations a permafrost core of Holocene age was drilled in the Lena Delta (72122 0 N, 126128 0 E). The organic carbon of the permafrost sediments varied between 0.6% and 4.9% and was characterized by an increasing humification index with permafrost depth. A high CH 4 concentration was found in the upper 4 m of the deposits, which correlates well with the methanogenic activity and archaeal biomass (expressed as PLEL concentration). Even the incubation of core material at À3 and À6 1C with and without substrates showed a significant CH 4 production (range: 0.04-0.78 nmol CH 4 h À1 g À1).The results indicated that the methane in Holocene permafrost deposits of the Lena Delta originated from modern methanogenesis by cold-adapted methanogenic archaea. Microbial generated methane in permafrost sediments is so far an underestimated factor for the future climate development.

Permafrost environments within the Siberian Arctic are natural sources of the climate relevant trace gas methane. In order to improve our understanding of the present and future carbon dynamics in high latitudes, we studied the methane concentration, the quantity and quality of organic matter, and the activity and biomass of the methanogenic community in permafrost deposits. For these investigations a permafrost core of Holocene age was drilled in the Lena Delta (72122 0 N, 126128 0 E). The organic carbon of the permafrost sediments varied between 0.6% and 4.9% and was characterized by an increasing humification index with permafrost depth. A high CH 4 concentration was found in the upper 4 m of the deposits, which correlates well with the methanogenic activity and archaeal biomass (expressed as PLEL concentration). Even the incubation of core material at À3 and À6 1C with and without substrates showed a significant CH 4 production (range: 0.04-0.78 nmol CH 4 h À1 g À1 ). The results indicated that the methane in Holocene permafrost deposits of the Lena Delta originated from modern methanogenesis by cold-adapted methanogenic archaea. Microbial generated methane in permafrost sediments is so far an underestimated factor for the future climate development.

CitationTraditional cattle manure application determines abundance, diversity and activity of methanogenic Archaea in arable European soil.

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