Temporal variation in soil microbial communities and the influence of snow cover

• Global climate change is projected to have a large impact in arctic and alpine areas. Future projections with increased temperature also include increased precipitation, but to which extent is uncertain. However, the major changes in precipitation will occur over the North Pacific, North Atlantic and Scandinavia. As much as 44 to 53% of the northern hemispheres landmass may be snow covered for parts of the year and in higher alpine terrain the increased precipitation will lead to a greater snow accumulation. 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 could potentially affect the annual dynamics and budgets of N. 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 is poorly known and, in particular, in relation to trace gas fluxes. The objective of our study was, therefore, to investigate the temporal pattern of soil microbial structure in four plant communities with contrasting snow cover and nitrogen turnover. This study was conducted at Latnjajaure Field Station (LFS) located in the midalpine region in northern Sweden. The study includes four different plant communities, heath snowbed, heath meadow, meadow snowbed, and mesic meadow. To characterize the soil microbial community we used phospholipid fatty acid analysis (PLFA), which is a method targeting the fatty acid profiles of membrane phospholipids microorganisms. The results show that at each individual sampling occasion the four plant communities’ exhibits different soil microbial structure. However, the temporal variation is larger than the difference across plant communities. This temporal shift in microbial structure seems to be partially related to the fatty acid 18:2ω6, indicative of fungi, which show a high proportion in soils protected by snow and decreases after snow melt. Furthermore, the shift in microbial structure during the season is more modest in snowbeds than the mesic heath and meadow.

Ämnesord

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

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

Nyckelord

Arctic

Microbial communities

PLFA; Snow

Tundra

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