Remote Sensing Data Using for Mesorelief Depressions Monitoring in the Desolate Steppe Zone

In the arid conditions of the southern European part of Russia, located in the dry steppe and semi-desert zones, there has been a tendency to reduce arable land and use it as pastures in recent decades. Intensification of semi-nomad animal husbandry leads to excessive stress on natural communities, degradation of vegetation cover and desertification. Creation of forest plantations may be effective for preventing a negative impact on landscapes. In areas of dry steppes and semi-deserts, it is advisable to carry out forest reclamation measures in terrain lowering areas, which are characterized by the best soil and hydrological characteristics and are favorable for tree growth. The purpose of the work is to identify the sites in the study area that are most suitable for forest reclamation. The region of the Alexandrovo-Gaisky district of the Saratov Region was chosen as the research object as the most representative site. The determination of forest-suitable areas was carried out by negative landforms (depressions filled with water in the spring) mapping based on Sentinel-2 and Landsat-5,7,8 satellite images and MNDWI index calculating. In the semi-desert zone, mesorelief depressions are classified into large (estuaries), medium (padinas) and microrelief (for example, zapadinas). Weather data from the AISORI system, as well as official statistics, were also used to identify characteristics affecting the hydrological regime of depressions. 7.1 thousand hectares of arable land and 254.6 thousand hectares of non-arable land, which are mainly used as pastures, were mapped. The assessment of forest-suitable sites, the area of which is 18.8 thousand hectares, has been carried out. As a result of the data obtained on the flooding areas and meteorological data analysis, it was found that the hydrological conditions of relief depressions depend on the surface runoff of meltwater, the depth of soil freezing in winter and the thickness of snow cover. An increase in the average annual air temperature in the study area leads to a decrease in the water content of depressions, which must be taken into account during forest reclamation.