Functional diversity of microbial communities in permafrost affected peat soils of forest-tundra peatlands

The paper is devoted to functional diversity of microbial communities in peat soils of forest-tundra peatland studied by the method of multi-substrate testing. In profile metabolic activity changes of prokaryote communities in permafrost peats have been identified. Amount of assimilated carbon sources, their consumption intensity, metabolic activity of microbial associations differ among the active layer (AL), permafrost layer (PL), and on the border between these two layers. Upper AL (0-4 cm deep) includes remnants of Dicranum mosses, lichens of the Cladonia, Cetraria, Flavocetraria genera, fragments of Betula nana L., Ledum decumbens L., Empetrum hermaphroditum L., Vaccinium vitis-idaea L. leaf blades, shoots, and roots. It is best-warmed in summer and is marked through a high functional diversity (the Shannon index H=4.63) and metabolic activity (W=2472) values. Downwards at a depth of 4-10 cm, bacterial communities decrease in functional diversity (Н=3.33) and seven-fold in metabolic activity (W=727) though concentration of revivable (with save membrane) bacterial cells is similar to that in upper AL (1.04±0.13 and 1.67±0.20 milliard/g a.d.s., relatively). The in-between layer (47-55 cm deep) includes weakly-decomposed remnants of Sphagnum mosses with excessive moisture content (360±18%) and high actual acidity (рНwater=3.85±0.10). It contains few revivable prokaryotic cells (0.56±0.19 milliard/g а.d.s.), marks through a low functional diversity (Н=2.41) and metabolic activity (W=363) values. In spite of ice condition, the PL sections (55-115 cm) are characterized by a relatively high content of bacteria with save cell membrane (1.48-1.82 milliard/g а.d.s.) which is similar to that in upper AL. Natural cryo-conservation of prokaryotic life vitality in PL responds for a high functional diversity of microbial communities (the Shannon index H=4.37-4.51) and metabolic activity (W=1556-2108) values after defrosting. Microbial communities in AL and PL greatly differ by both quantity and qualitative composition of organic carbon assimilated sources. The difference is most prominent in case of in-between peat layer. Microbial communities in this layer and taken from depth of 4-10 cm are highly instable systems (d>1). Bacterial communities at depths of 0-4 and 55-115 cm are comparatively stable and resistant to critical situations due to high functional diversity.