Soil temperature field and dynamics of freezing-thawing processes in the south of the Vitim Plateau (Transbaikal region)

Abstract

The results of geographic and stationary studies of temperature, water and permafrost regimes and soil properties in the south of the Vitim Plateau (Transbaikal region) are discussed. Instrumental data on soil temperature regimes indicate the dynamics of soil freezing–thawing processes and attest to changes in the thawing depth of permafrost-affected soils. The revealed spatiotemporal patterns of soil freezing/thawing reflect the distribution of heat and cold (permafrost) in the soils of the studied cryoarid landscapes. Seasonal, annual and long-term differences in the soil temperature field cause a great heterogeneity of soil toposequences with contrasting soils on the north– and south–facing slopes. An increase in the soil thawing depth has been observed over the past 50 years. In the relatively wet and cold 1970–1990 years, its rate varied from 1.0 to 1.5 cm/year with higher values typical for Haplic Chernozems under meadow-steppe vegetation, and lower values for Phaeozems under forest vegetation. Over the recent 25 years, the rate of the increase in the soil thawing depth for the same soils has intensified by 2.5– 3.0 times in relation to aridization and climate warming.