THE CURRENT STATE AND DYNAMICS OF GEOSYSTEMS IN THE SOUTH-EAST OF THE RUSSIAN PLAIN (BY THE EXAMPLE OF THE NATURAL PARKS IN VOLGOGRAD REGION)

Abstract. Aim. The current state, variability, dynamics of natural and natural-anthropogenic landscapes of dry steppes and desert steppe of the south-east of the Russian plain were studied. Methods. Methods of field complex landscape studies, remote methods of decoding space images and estimating the state of geosystems based on NDVI were used. Results. On the basis of long-term landscape-ecological monitoring on the territory of the Donskoy and Eltonsky natural parks of the Volgograd region, it is established that the main causes of disturbance of geosystems and desertification are fires, spontaneous livestock raising, overgrazing. After the impact of fire, the biological diversity of geosystems is reduced, the processes of self-regulation are weakened, and resistance to external influences is reduced. The structure is simplified, the homogeneity of the vegetation cover increases, the height of the grass stand is reduced 2-3 times and the total projective cover is reduced 1,5-2 times, the tree and shrub vegetation dies, the proportion of polynia and weeds grows. For a long term (3-5 years), the bioproductiveness of geosystems is significantly reduced 1,5-3 times. The upper layer (2-4 cm) of the humus horizon burns out, the fertility of soils decreases. The local climate of pyrogenic geosystems is aridized, evaporation increases, soil moisture deficit increases, groundwater level decreases, springs run out. The processes of wind and water erosion are activated. Fires destroy places of reproduction, recreation, feeding of animals, habitats of rare and endangered species. Conclusions. Pyrogenic transformation is the most serious real threat to the biological and landscape diversity of the steppes