On temperature and moisture field formation in ordinary chernozem profile under plantations of mountain ash ‘Alaja krupnaja’

Abstract

The soil temperature regime determined by temperature distribution in the soil depth and its change over time under the influence of weather conditions and vegetation. In order to study the features of the hydrothermal regime formation, in 2018 and 2019, observations were made on temperature and soil moisture dynamics in the profile of ordinary chernozem under plantations of mountain ash ‘Alaja Krupnaja’ belonging to a tree species of moderate growth. In May 2019, positive temperatures after snow melting penetrated into the soil only to a depth of 40 cm, while in the underlying horizons, permafrost processes persisted and were observed until the end of June. Over time, the temperature profile demonstrated active penetration of heat throughout the entire soil depth. The maximum accumulated positive temperature here was confined to mid-August. The carbonate illuvial horizon had negative accumulated temperature until the end of June, and then it actively absorbed a large amount of heat from the upper part of the profile. In mid-May 2019, moisture distribution in one meter soil layer was quite uniform. In the process of plant respiration and drying out, there were losses of moisture content in the humus horizon. The end of June and July were characterized by lack of precipitation; consequently, the moisture content of the chernozem in the horizons A and AB dropped to wilting moisture. The drying out period turned out to be short. In general, during the growing season, the available moisture storage in one meter profile of ordinary chernozem did not fall below 176 mm. In May, the available moisture storage in the humus-accumulative horizon corresponded to the “good” level, and in the first ten-days of June it reached 150 mm. The dry weather in July sharply reduced soil moisture to wilting moisture. The situation changed only in mid-August after the rains.