Winter temperature regime of thufur soils on gazha sediments in Orenburg oblast

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