Microcosm Experiments for Simulation of Freeze-Thaw Cycles and Studying Methane Dynamics in Permafrost-Affected Soils

Abstract

Long-term methane flux studies in the Lena Delta (Siberia) indicated that back-stored methane adds to the emission of newly produced methane at the beginning of the vegetation period. Further field analysis showed that microbial methane production already occurred at in situ temperatures of around -6 °C in the perennially frozen ground. The microbial process of methane production during the back freezing of permafrost soils in autumn and the future fate of produced methane in the thawing phase of the following spring are not well understood so far. Therefore, a permafrost microcosm is developed to simulate the influence of the annual freezing-thawing cycles on the methane fluxes in the active layer of permafrost soils. Two cryostats ensure an independent freezing and thawing from the top and from the bottom of the microcosm to simulate different field conditions. The methane concentration, the soil temperature and the soil water content are analysed in different depth of the microcosm during the simulation as well as the concentration of emitted methane in the headspace of the microcosm. The simulation studies will contribute to the understanding of microbial processes and methane fluxes in permafrost environments in the scope of a warming Arctic.