Factors of Microbial Biomass Variation in Recent and Buried Soils of the Steppe Zone

The article summarizes the results of long-term studies of microbial biomass in buried soils of archaeological sites and recent reference soils. Geographically, the objects of study are located in the southeast of the East-European Plain, the Caspian Lowland, the Western Caucasus, and the Crimea. A very representative data have been accumulated on the chronogeographic patterns of changes in microbial biomass in chernozems (Chernozem), chestnut soils (Haplic Kastanozems), light chestnut soils (Salic Cambisols), and solonetzes (Humic Solonetzes). Chronological framework is from the Latest Neolithic (Eneolithic) to the recent time (5700–300 years ago). The biomass of soil microbial communities has been assessed for the content of phospholipids in soil. It was found that the microbial biomass in buried soils does not depend on the soil as well as on the time of soil burial. The average content of phospholipids in buried soils was two times lower than that in modern ones, but no correlation of microbial biomass with the duration of soil buried state was found. To a greater extent, the content of phospholipids in buried soils depended on the content of silt; when it was less than 10%, the microbial biomass was minimal. Geomorphological position was a significant factor influencing the microbial biomass. Thus, the maximum values of microbial biomass are typical for soils of local watersheds and slopes of northern aspect. In solonetzes, an inverse correlation was noted between the microbial biomass and the thickness of the SEL horizon. In the cultural layers of ancient settlements, the microbial biomass exceeded the that in recent soils, and depended on land use and the volume of incoming anthropogenic substrates.