Permafrost soils and sediments are unique systems in the context of biogeochemi-cal cycling of carbon, particularly due to the enormous amount of organic carbon stored in these environments. Recent studies demonstrate the close relationship between apparent methane fluxes and the modes and intensities of microbiological processes of methane production and oxidation in permafrost ecosystems. Methane-producing and -consuming microorganisms are widespread, highly active and abundant in permafrost soils, despite the harsh environmental conditions they are exposed to. The permafrost environment forces an adaptation of the methane-cycling communities to low-temperature conditions, often yielding species which have not been detected in temperate ecosystems so far. In addition to soil characteristics and climate conditions, the activity and physiology of these well-adapted microbial communities dictate trace gas fluxes in permafrost soils. The future development of permafrost environments as a source of methane, therefore, primarily depends on the response of the methanogenic and methanotrophic microorganisms to a changing environment.
Anticipating this response, however, is difficult, as the sensitivity of microbial communities to permafrost degradation is completely unknown. Firstly, there is lack of experimental and theoretic studies on what determines microbial stability in general and in particular in permafrost environments. Secondly, the consequences of thawing permafrost on hydrology and morphology that indirectly influence microbial communities and their activities are very difficult to predict.
International projects such as ACD (Arctic Coastal Dynamics) and CALM (Circumpolar Active Layer Monitoring), which examine the impact of global warming on permafrost environments, should thus be linked more closely to microbiological process studies and biodiversity research. Microbial parameters important for the assessment of carbon turnover (e.g., viable cell numbers, activities, biodiversity and stability of microbial communities) should be analysed at observation areas in the Arctic, where long-term monitoring programs are undertaken. The evaluation of microbial ecology and its correlation to climatic and geochemical data represent the basis for an understanding of the role of permafrost soils in the global system, in particular in terms of feedback mechanisms related to fluxes of material and greenhouse gases in the scope of a warming Earth.
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