The influence of landscape conditions on the functioning of microbial communities of postagrogenic soils of the tundra zone
Microbial communities of postagrogenic soils of the tundra zone of the Komi Republic were studied. It has been established that the main part of functionally active microorganisms is concentrated in organogenic and humus-accumulative horizons of postagrogenic soils. In the upper horizons of postagrogenic soils, the number of living bacterial cells is 62-84%. The influence of landscape conditions on the quantitative and qualitative indicators of microbiocenoses of 13-16-year-old fallows occupying different positions in the landscape, is shown. It was revealed that in the series of postagrogenic soils, the watershed → the terrace above the floodplain → the floodplain, the number of bacteria changes slightly, and the number of fungi increases. Micromycetes dominate in the microbial biomass of the analyzed soils. The proportion of mycelium in the total microbial biomass in organic and humus-accumulative horizons varies from 36 to 71%. In mineral horizons, where fungal mycelium is not found, the main components of microbial biomass are fungal spores - up to 99% of the total microbial biomass. The proportion of living functionally active mycelium in the soil of the floodplain fallow (up to 100%) is higher than in the fallows located at the top of the watershed (up to 85%) and the terrace above the floodplain (up to 70%). In the series of postagrogenic soils, the watershed → the floodplain terrace → the floodplain, an increase in the reserves of microbial biomass from 2.20 to 8.44 t/ha was established. In the soils of the above-floodplain terrace and floodplain, the main share in the distribution of microorganism stocks belongs to the humus-accumulative soil horizons: 48 and 57%, respectively. In the postagrogenic soil at the top of the watershed, the main reserves of microbial biomass are concentrated in mineral horizons (70%).