Development of the steppe zone in southern Russia based on the reconstruction from the loess-soil formation in the Don-Azov Region

Herbaceous communities in forest ecosystems on the southern part of the Russian Plain appeared in the Middle Miocene (??10 Ma BP). In the Late Miocene (??7 Ma BP), feather-grass steppe associations appeared among them. In the time span of 2.7 to 2.1 Ma BP (i.e., in the Early Quaternary, according to the current chronostratigraphic scale), the steppe zone arose on the southern Russian Plain in the Don-Azov Region. Seven stages of this zone development here have been distinguished throughout the Quaternary. The first one (Eopleistocene-Early Pleistocene) was characterized by savanna-like subtropic ecosystems. Then, in the Middle Pleistocene, the temperate zone ecosystems (tallgrass prairie-like steppes) developed here and were followed by steppe ecosystems close to the modern ones in Central Europe. The ecosystems of rich-species forb steppes developed in the Late Pleistocene. Finally, in the optimum of the modern interglacial (Holocene), steppes became similar to the modern ones here, but with a slightly higher precipitation. The general trend is characterized by reduction in heat and water provision and increase in aridization progressing from earlier to later stages.