Winter Temperature Regime of Thufur Soils on Gazha Sediments in Orenburg Oblast

Winter temperature regime was studied for soils of thufur formed on gazha sediments within the first terrace above the floodplain and for dark humus soil formed under the conditions which were more similar to the zonal ones. A temperature of atmospheric air, soil surface under the snow, and soil at the depths of 5–120 cm was measured with autonomous temperature recorders. A surface temperature of soil under the snow depended on a snow depth. In the thufur center, the sum of surface temperatures reached –387°C in the period from December 10 to March 30; in the microdepression, this sum was smaller by absolute value and reached –170°C. A soil temperature in the thufur microelevation at different depths was lower than that in the microdepression between thufurs; a soil temperature in zonal conditions was intermediate. A zero-isotherm penetration depth was 55 cm within thufur, 25 cm in the microdepression, and 45 cm in the zonal soil. The thufur microtopography is a factor of snow redistribution and heterogeneous snow depth resulting in regular differences in the zero-isotherm penetration depth in different areas and spatial heterogeneities in the temperature field of the studied soils in winter.