Hydrophysical and thermophysical characteristics of leached chernozem in white-cedar agrocenosis in the arboretum

Abstract

To study the hydrothermal state of leached chernozem occupied by white-cedar (Thuja occidentalis ‘Danica’), field observations of its temperature were carried out in the summer of 2018 and 2019 to a depth of one meter every 10 cm in the arboretum of the Research Institute of Gardening of Siberia. The soil temperature regime was determined, first of all, by insolation and heat exchange in the soil-atmosphere system following the temperature state of the surface air layer. In the summer of 2018, during July and August, the accumulated temperature of soil profile fluctuated within 200°C. At the same time, the available moisture storage was much lower than in 2019. In early June, daily temperature fluctuations were observed to a depth of 20 cm. The accumulated temperature in the humus horizon was the maximum at 7 p.m., and the minimum was revealed in the morning. In August, daily temperature fluctuations in chernozem disappeared at a depth of 40 cm, so the temperature field in the underlying horizons acquired a stationary state. Warming of the soil profile in 2019 under the ornamental crop plantings began in the second ten-days of May. However, zero temperature was already observed at a depth of 20 cm, and below it remained negative. At the same time, winter cooling of the chernozem profile persisted until the third ten-days of June. The soil finally warmed up only at the beginning of July. Due to the small amount of snow accumulated in winter, soil moisture after its melting was satisfactory only in the humus horizon. The situation changed in mid-June when available moisture storage under the influence of atmospheric precipitation reached 263 mm. By mid-August, drying of the soil profile was observed when available moisture storage became “unsatisfactory”. Subsequent rains led to increase of soil moisture content.