Influence of Climate Change on Soil Degradation in Arid Zones of the Volga Region

Abstract

The goal of the research was to establish the impact of climate change on the processes of soil degradation and desertification in arid regions of the Volga region. The study material was the observational data for 1971–2020 on 20 meteorological stations, as well as the results of soil-ecological and hydrogeological monitoring at research stations of the Federal Center of Agriculture Research of the South-East Region in the prevailing soil and climatic zones on the territory of Saratov oblast (forest–steppe, steppe, dry steppe and semidesert). The signs accompanying aridization, desertification, and land degradation were revealed and differentiated by natural zones. In particular, the average annual air temperature increased in comparison with the climatic norm by 1.0–1.2°C, and the greatest increase (by 2.0–2.2°C) was observed in August. The average temperature of the soil surface during the warm period increased by 1.1–1.5°C. The risks of severe atmospheric droughts during the entire growing season increased throughout the entire territory, most notably in the semidesert zone (from 55 to 82%). The amount of precipitation increased by 10–25% in the spring and decreased by 23–30% in the summer. The boundaries of the semidesert zone have shifted to the north and northwest. The tendency of changes in the hydrological regime of zonal soils from nonleaching to periodically leaching in 20–40% of years is outlined. The values of the aridity indices of the territory calculated for the period from 2001 to 2020 increased in comparison with the climatic norm for 1971–2000 by 3–6%. This is an indicator of growing climate aridity during its current warming. As a result, high rates of dehumification (a decrease in the relative content of humus by 21–35%) and changes in the structural state of the arable layer and particle-size distribution (a decrease in water-resistant aggregates of >0.25 mm from 39% to 31.8% and the absolute content of physical clay by 7.5%). At the same time, there is an increase in the mineralization of groundwater from 2500 to 7000 mg/L, as well as an increase in the content of toxic salts in the soil solution. Thus, the content of Cl– ions $${\text{SO}}_{4}^{{2 - }}$$ in places of recharge by groundwater increased from 0.27 to 0.56 mg/eq and from 0.27 to 13.27 mg/eq respectively. The cation values also increased: Ca2+ increased from 0.30 to 4.41 mg/eq and Mg2+ increased from 0.12 to 5.59 mg/eq, The amount of K+ and Na+ rose from 0.09 to 0.28 mg/eq The development of processes of local salinization and waterlogging is noted in the lower relief elements.

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