THE TEMPERATURE REGIME OF UMBRIC LEPTOSOLS IN THE ELBRUS REGION

Abstract

The annual temperature dynamics of humus-rich soils in the alpine zone of the Central Caucasus were studied depending on slope aspect and steepness, soil skeleton, plant projective cover, and the composition of phytocenoses. The studied sites are located on north- and south-facing slopes at altitudes of 2,680, 2,940, and 3,100 m.  It has been found that on the south-facing slope, the altitudinal gradient does not affect soil temperature: the determining factor is the species composition of the vegetation and the height of the grass stand. The dominance in the vegetation of the graminoid group with a dense projective cover leads to a decrease in the maximum soil temperature in the summer and a reduction in the number of days with negative temperatures in the cold season. On the north-facing slope, mean annual soil temperatures decrease with increasing absolute altitude. The differences between air and soil temperatures (at a depth of 10 cm) on the north-facing slope are less pronounced compared to the south-facing slope. Soil temperature extremes in the summer and winter periods are closely related to soil skeleton: a high proportion of stones and sparse projective cover cause the greatest variability in the temperature regime. In the lower part of the slope, the annual variation in soil temperature is less influenced by the slope's exposure, while in the upper part, this dependence is more pronounced. For the summer period, synchronous dynamics of the daily course of air and soil temperatures have been revealed, which was not registered in the cold season.