Structure of microbial communities of peat soils in two bogs in Siberian tundra and forest zones

The structure and functional activity of microbial complexes of a forest oligo-mesotrophic subshrub- grass-moss bog (OMB, Central Evenkiya) and a subshrub-sedge bog in the polygonal tundra (PB, Lena River Delta Samoylovsky Island) was studied. Soil of the forest bog (OMB) differed from that of the polygonal tundra bog (PB) in higher productivity (C_org, N_total, P, and K reserves), higher biomass of aerobic chemoorganotrophs (2.0 to 2.6 times), and twice the level of available organic matter. The contribution of microorganisms to the carbon pool was different, with the share of C_mic in C_org 1.4 to 2.5 times higher in PB compared to OMB. Qualitative composition of the methane cycle microorganisms in PB and OMB soils differed significantly. Methanogenic archaea (Euryarchaeota) in the shrub-sedge PB of tundra were more numerous and diverse than in the oligo-mesotrophic bog (OMB) and belonged to six families (Methanomassiliicoccaceae, Methanoregulaceae, Methanobacteriaceae, Methanomicrobiaceaee, Methanosarcinaceae, and Methanotrichaceae), while members of only four families (Methanosarcinacea, Methanobacteriaceae, Methanotrichaceae, and Methanomassiliicoccaceae) were revealed in OMB. In both bogs, methane-oxidizing bacteria belonged to Alphaproteobacteria (II) and Gammaproteobacteria (I). Methanotroph diversity was higher in OMB than in PB. Microbial communities of PB soils had higher potential activity of methanogenesis and methanotrophy compared to those of OMB. Methanogenic and methanotrophic activities in PB were 20 and 2.3 times higher, respectively, than in OMB.