Formation of spring moisture reserves in the Central Left Bank Forest Steppe

Abstract

Goal. To determine the peculiarities of the formation of spring reserves of productive moisture in the chornozem layer against the background of their intra-century climatic variability for the conditions of the left-bank part of the Central Forest-Steppe of Ukraine. Methods. Field (for the selection of samples in the chornozem layer in different research periods), laboratory (for thermogravimetric determination of productive moisture reserves during the research period), mathematical, statistical and comparative calculation (for substantion of the reliability of the obtained moisture reserves in the soil and development of statistical models of relationships). Results. In 1947–1965, the dynamics of the reserves of productive moisture in the meter-thick layer of chornozem in the spring had shown a slowly declining character. This was evidenced by the negative sign of the indicators of the power function of the trends of changes in spring reserves in the layers of chornozem 0–100 and 0–150 cm. In general, from 1947 to 2023, the reserves of productive moisture were decreasing, compared to 1947–1965. For 76 years of observations (according to regression coefficients of exponential equations) they decreased 16 times more intensively. At the same time, in 2005–2023, they decreased by 26 mm. In 1947–2023, the reserves of productive moisture in a meter thickness decreased by 35 mm in the 0–100 cm layer, 29 (0–50 cm), and in the 50–100 cm layer remained increasing and amounted to almost 6 mm. In 2013–2023, the trends of changes in the reserve of productive moisture in layers 0–50 cm, 50–100, and 0–100 cm were downward, and the minimum reserves of productive moisture decreased to 145 (2017) and 130 mm (2020), reserves of productive moisture in the spring decreased 14 times compared to 1947–1965. Conclusions. It was established that the reduction of productive moisture reserves in the spring in the meter layer began in 1947–1956 (weakly growing intensity), it gained increasing intensity in 1993–1999; of intensively increasing intensity — in 2005–2023. This should be perceived as a pattern stable over time, associated with the formation of a non-flushing regime of moistening in the spring within the limits of a periodically flushing water regime. However, the parameters of the humidification regime do not acquire the values characteristic of the steppe zone regime.