Change in the Components of Steppe Geosystems in the Southwestern Transbaikal Region with Climate Warming

摘要

Climate change due to increased temperature, which has become a challenge for societal development around the world, has been and remains uneven for different regions. The work reports the results of an analysis of long-term data on air temperature, atmospheric precipitation, and moisture of deep freezing, mealy-textured calcareous chernozems (black-earth soils) of the Onon-Argun' steppe of the southwestern Transbaikal region. It has been shown that the next successive dry period of 1999-2020 differs from the preceding one of 1965-1981 by a substantial increase in temperature and an uneven annual amount of atmospheric precipitation. Based on these parameters, the former is divided into two parts: a very dry, warm period and a wet, very warm period. For most of the driest period (2001-2011), the soil-moisture reserve was at a wilting level or lower. Environmental catastrophic events, such as a ubiquitous drying of tree stands and the disappearance of lakes, including the large Lake Barun-Torei, were observed. Beginning in 2012, the amount of atmospheric precipitations had increased, but this had little effect on the soil-moisture reserve and lakes in terms of the replenishment of their waters. As a result, the water area of another large lake, Lake Zun-Torei in the Torei Depression, had almost entirely disappeared by 2018. The bottoms of the desiccating lakes transformed into alkaline-sulfate sodium and alkaline-chloride-sulfate sodium solonchaks. Xerophiles were observed to enter the community composition in the herbaceous plant ground cover of the steppes, and the height and density of the latter decreased. The above-ground phytomass decreased by a factor of 1.5-2.