Response of Soils to Climate Change in the Steppe Zone of European Russia over the Past Decades

Soils of the steppe zone have been studied in natural grassland ecosystems of the Volga-Don interfluve and the Northern Caspian region. The objects of research are represented by chestnut soils and solonetzes (Calcic Cambic Kastanozems and Salic Gypsic Solonetz) in the areas of archaeological sites (burial mounds). The repeated surveys of the soils studied 20-40 years ago have not shown any noticeable changes in their properties. The distribution of carbonates, soluble salts, gypsum, organic carbon, and exchangeable Na+ in the solonetzic horizons of the soils remains almost unchanged. A tendency for an insignificant increase in salinity (by no more than 0.5% of total dissolved solids in the water extract) has been identified for the upper 1-m-thick soil layer. An increased grazing pressure on the Northern Yergeni Upland in the past two decades has caused the expansion of the area of microdepressions with crusty solonetzes. Modeling of the spatial distribution of the aridity index in the form of isolines has been performed, and the shift in the steppe zone boundaries in the Lower Volga region depending on the climate dynamics over the past 60 years has been analyzed. A tendency for a higher aridity at the beginning of the 21st century after the stage of increased moistening in the second half of the 20th century is revealed for almost the entire area of the south of the East European Plain.