Current Climatic Trends in Evaporation and Soil Moisture Changes in the South of European Russia

The influence of climate parameters on evaporation during the period of active vegetation of plants in the forest-steppe, steppe, and semi-desert in the south of European Russia in the period 1980–2021 was studied. The linkage between evaporation and soil moisture have been considered. At the beginning of the growing season, the change in evaporation in the forest and steppe is largely determined by a positive linkage with temperature and wind stress. In the middle of the growing season, the role of precipitation and wind increases. From July, the linkage between evaporation and temperature becomes negative due to the increasing moisture deficit in the regions that are characterized by dry sub-humid and semi-arid climates. The linkage between evaporation and moisture content of the upper soil layer is negative at the beginning of the growing season with minimal evaporation from the still unheated soil cover in the forest-steppe and steppe, and is positive in the semi-desert due to already heated soil. From the middle to the end of the growing season the linkage between evaporation and soil moisture is positive from forest-steppe to semi-desert landscapes. At the beginning of the growing season, continued warming leads to an increase in evaporation; in the middle and at the end of the growing season, evaporation trends are significantly negative, since the lack of moisture at high temperatures leads to the drying of the soil cover and premature withering of vegetation. The greatest decrease in evaporation is observed in the steppe and dry steppe, which was affected by the drying up of the area with an increase in temperature, a decrease in the amount of precipitation and the average wind speed. Topsoil moisture trends are mostly negative throughout the south of European Russia, with the maximum moisture loss in the broad-leaved-forest and forest-steppe, which are more humid than dry-steppe and semi-desert. In the semi-desert, changes in soil moisture are minimal over the entire growing season.