The influence of forest vegetation on the physical properties of chernozems in the steppe zone of Ukraine

Targeted changes in the physical properties of soils, including through afforestation, are an important component of land use practices that are aimed at obtaining sustainable crop yields, which is especially important for potentially highly fertile chernozem soils. The physical properties of ordinary chernozems under steppe vegetation (used as a control) and plantings of Robinia pseudoacacia L. and Quercus robur L., as well as chernozem luvosol under natural forest vegetation, were studied in the field, as well as in laboratory conditions using soil samples taken from 12 areas established within Dnipropetrovsk region (Ukraine). As a result of the study, it was established that the studied ordinary chernozems and luvic chernozems are classified as silty loam according to their granulometric composition. The growth of acacia and oak plantations led to an increase in sand content and a decrease in silt content, and the growth of natural forest vegetation contributed to an increase in sand and silt content and a decrease in clay content in black soils. The influence of forest vegetation on chernozems led in the 0–20 cm layer to an increase in the content of aggregates of fractions > 2 mm and water-resistant aggregates of fractions > 0.5 mm and a decrease in the content of aggregates of fractions < 1 mm and water-resistant aggregates of fractions < 0.5 mm compared to chernozems under steppe vegetation. The growth of forest vegetation caused a decrease in the density and density of the solid phase, and an increase in the total porosity of chernozems in the layers of 0–20 and 20–40 cm. The influence of forest vegetation on ordinary chernozems and luvic chernozems contributed to an increase in the content of available water for plants and an increase in their water permeability compared to ordinary chernozems under steppe vegetation. Ordinary chernozems under acacia and oak plantations are characterized by increased electrical resistivity, and luvic chernozems under natural forest vegetation are characterized by reduced electrical resistivity compared to ordinary chernozems under steppe vegetation. The growth of forest vegetation contributed to a decrease in the dielectric constant of chernozems. The influence of natural forest vegetation leads to more pronounced changes in the physical properties of chernozems compared to the influence of acacia and oak plantings.