Temporal pattern of CO2, CH4 and N2O fluxes and soil microbial structure from snow-covered Alpine plant communities

• Global warming is expected to have large effects on carbon exchange between the biosphere and the atmosphere in the Arctic. Arctic ecosystems, which can be a net sink in the summer, are often a net source of CO2 to the atmosphere on an annual basis. Few studies on winter CO2 and CH4 efflux have been conducted in the subarctic part of Sweden. So far, no integrated estimates of winter fluxes of CO2, CH4 or N2O has been reported from the alpine areas in the Scandinavian mountains. As much as 44 to 53% of the northern hemispheres landmass may be snow covered for parts of the year. The depth and spatial spread of snow cover is a result of moisture availability, duration of temperatures bellow 0ºC, storm frequency and the more local factors such as wind redistribution and compaction. In future climate scenarios, predictions of warmer climate and increased precipitations are often mentioned, but to which extent is more uncertain. However, the major changes in precipitation will occur over the North Pacific, North Atlantic and Scandinavia. The controlling factor for microbial activity in the organic layer during winter in alpine areas is the development of a consistent snow cover, which effectively decouples the soil from the atmospheric temperature. The air and soil temperature the days before snow cover development is important, as it sets the temperature conditions for the whole winter period. Soil microbial activity is markedly reduced below temperatures of 0 to -5°C, when the soil starts to freeze and free water becomes limited. Nitrogen mineralisation, nitrification and denitrification can, however, be maintained down to -4°C, and N2O production (from denitrification) in frozen soils has potential to affect annual dynamics and budgets of N (although the soil pore water content prior to freezing is an important regulating factor for winter N2O production). Snowbed communities are rarely, if ever, subjected to temperatures as low as -5°C, which implies that they may be favourable for microbial activity during the winter. Furthermore, tundra soil microbial biomass reaches its annual peak under snow, and fungi account for most of the biomass. However, how the microbial community changes during winter and snowmelt are poorly know and, in particular, in relation to trace gas fluxes. Flux of CO2, CH4 and N2O through a seasonal snowpack, using Fick’s law, from four plant communities with different snow regime and how it changes during snowmelt in the subarctic-alpine part of Sweden will be presented. We will also try to relate the trace gas fluxes to the soil microbial community composition using phospholipid fatty acid analysis.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Arctic

Greenhouse gases

Microbial communities

Snow

Tundra

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