Problems of Estimation of Microbial Biomass in Soddy-Podzolic Soils (Forests of the Protected Areas of Moscow Region)

The carbon content of microbial biomass in soil serves as one of the indicators of its biological activity and is often used in assessing the impact of anthropogenic activity and natural changes on the soil microbiome. Significant spatial and temporal variation of the indicator at the level of ecosystems, soil typological units, land use types, etc., makes it difficult to interpret the data obtained during mass monitoring. The aim of the study was to determine the background values of microbial biomass content in the surface sub-litter layer of soils in protected forests of the Moscow region. A reconnaissance survey of various podzolic soils typical for the region and differing in their genesis and texture and formed under mixed southern taiga forests in four protected natural territories was carried out. The soils of autonomous positions and the soils experiencing slight additional moistening were studied. The microbial biomass carbon was estimated by two methods: by the content of phospholipids and by substrate-induced respiration of microbial communities. Significant spatial variability of microbial biomass was noted both at the site level and at the ecosystem level. For the autonomous soils of similar classification positions and textures, it was comparable with the local variability at the experimental sites. The value of microbial biomass depended mainly on the character of soil water regime and soil texture, which largely determined the sorption capacity of the soil and its provision with biophilic elements, and also correlated with the richness of the ground cover providing the soil microbiome with nutrients. In order to obtain correct results of monitoring soil biological activity, unification of the methodology and depth of sampling in soils of background and anthropogenically transformed ecosystems is of great importance.