Climate aridization in the desert-steppe zone: the causes, results and impact on life of the ancient population

The reason for aridization in the desert-steppe zone lies in the strengthening of the winter Asian anticyclone, which prevents the Mediterranean and Caspian cyclones from passing into the zone of desert steppes. These conditions provoke cold and snowless winters. The impact of aridization on soils consists in the accumulation of salts in the upper layers, the increase of carbonates and gypsum proportion, and in the intensification of soil erosion. Such conditions were very favorable for ancient cattle breeders, since they could allow the livestock to graze throughout the year and did not have to store fodder. The reverse process - increased humidization is associated with the weakening of the Asian winter anticyclone and the penetration of precipitation cyclones into the region of desert steppes. In such periods, toxic salts are washed out from the soils, humus content increases, segregation of soil carbonate begins, and the reserve of moisture for plants is created. Winter precipitation, though, leads to the formation of a thick snow cover, icing of the plants and the creation of an ice crust. In these conditions grazing was impossible, and herds were subject to depletion and death. Thus, during the periods of aridization, the most favorable conditions for pasturing developed in the desert steppe, while in humid periods, which were previously considered to be the most favorable, there was no opportunity for traditional pastoral farming. So, in the conditions of sharply arid climate in the middle - second half of the 3rd millennium BC, the catacomb cultures and post-catacomb cultural communities prospered in the desert steppe. The increase in the atmospheric humidity in the 19th - 18th cc. BC resulted in the increase in winter precipitation, which made impossible the winter grazing. This was the reason for a well-known period of depopulation of the desert steppe in the Late Bronze Age. The presented material is the result of the authors’ joint research work: A. V. Borisov has developed the general conception of the research, reviewed literary sources and prepared the manuscript’s text; M. V. Eltsov has conducted paleoclimatic reconstructions for the investigated region; S. N. Udaltsov has carried out the chemicalanalytical studies of the selected paleo-soil samples, and the general editing of the manuscript; A. V. Bukhonov has taken an active part in the field part of the study and discussed the proposed conception.