The State of Microbial Communities in Paleosoils of the Solonetz Complex on the Severnye Yergeni Upland as Indicator of Climate Humidity in the Mid-Sarmatian Age (1st Century AD)

The total and live biomass, the abundance and ecological-trophic structure of microbial communities in the paleosoils of the solonetz complex buried beneath the mid-Sarmatian (1st century AD) kurgan, located in the dry steppe zone of the Severnye Yergeni Upland (Volgograd oblast), have been studied. The total biomass in paleosoils was comparable to and in some cases exceeded that of the recent background analogs. The share of microbial carbon in the total organic carbon of the paleosoils (40–58%) was higher than in recent soils (20–26%). The live cells in microbial communities of the paleosoils constituted 2.4–10.2%, which is comparable to recent soil parameters. The ecological-trophic structure of microbial communities and their olygotrophy indices were generally similar to the parameters of recent background soils. The impact of the degree of alkalinity on the changes in the values of microbiological parameters in different horizons of the sub-kurgan paleosoils was evident throughout the profile; however, in each soil horizon it significantly affected only a single trophic group of the microbial community. The microbiological data obtained show that in the first century AD, the climatic conditions in the dry steppes of the Severnye Yergeni Upland were more humid as compared to the recent conditions.