THE TEMPERATURE REGIME OF SANDY SOILS OF THE FOREST-TUNDRA ZONE OF THE FAR NORTH
According to many authors, when the living ground cover is disturbed, the heat exchange between the soil and the atmosphere increases which leads to thawing and degradation of permafrost, and thus erosion processes on sandy soils are inevitable. Therefore, the study of the features of the temperature regime of sandy soils of the forest-tundra zone of the Yamalo-Nenets Autonomous District is of great importance due to the large-scale violations of natural ecosystems there. This paper discusses the results of long-term (2016-2018) studies of the temperature regime of sandy soils of the forest-tundra zone of the Yamalo-Nenets Autonomous District. It is shown that the average temperature during the growing season in 0.2 m of the layer does not exceed 7.8-10.6°C. In July, the temperature of the sandy soil reaches the maximum value (8.6-14.0°C). Violent temperature fluctuations are an important feature of the northern sandy soils which negatively affects the growth and development of perennial grasses. It has been found that the transition of the ground temperature through +5°C at a depth of 0.1 m occurs at the beginning of the first ten-days of June; 0.2 m - by 2-4 days later. Low air temperature, close occurrence of permafrost to the surface and relatively high soil moisture are the reasons for the late spring temperature transition through +5°C. Every year during the growing season in the forest-tundra conditions, the ground temperature drops below +5°C. The sandy soils of the Far North that are subject to reclamation are characterized by a very short and unstable period with a temperature of +10°C or higher. At a depth of 0.05 m, it is 23-57 days, and decreases to 18-24 days at a depth of 0.15-0.20 m. The low ground temperature and its delay with the transition time through +10°C causes the accumulation of a small amount of active temperatures: from 307.1-350.7°C at a depth of 0.1 m; up to 105.1-198.1°C at a depth of 0.2 m. The acute deficiency of heat for the active growth of perennial grasses determines the need for careful selection of grasses when forming a reclamation grass mixture.