Establishing the regularity of the impact of protective forest plantations and relief on agrophysical and biochemical properties of soils in the Volga uplands

Determination of patterns of humus content dynamics in southern chernozem and gray forest soils under the influence of protective forest plantations, relief, and water-permeability of soil aggregates on the basis of long-term observations was the purpose of the study. The research methodology was based on relevant GOSTs, recommendations of scientific institutions and scientists. It is important not only to establish the dynamics of agrophysical, physico-chemical and biochemical properties of soils under the influence of protective plantations, but also their compliance with normalized indicators. Normalized indices were proposed by the V.V. Dokuchaev Soil Institute (1996) and by the authors of this article, based on many years of research from 1964–2020 (2020). On treeless slopes there is a constant worsening of the above properties of soils, first of all the value of the water-tightness criterion (the ratio of the content of soil particles 10–0,25 mm in wet and dry sieving according to the generally accepted methodology): the decrease of the index depending on the value of the slope and the distance to protective forest plantations is 3.2–39.2 %. At the same time, decrease of actual value of watertightness criterion in comparison with normalized indices is 11.9–56.3 %. Under influence of forest plantations the criterion of water tightness of soil aggregates is higher than normalized one on 1,4–16,0 % that undoubtedly positively influences other properties of soil: the sum of exchangeable bases and the maintenance of calcium from capacity of a cation exchange having the same tendencies of improvement. The content of humus in the absolute value also increases under influence of protective forest plantations to 0,6 %, on slopes without forest protective plantations – decreases to 0,9 % depending on a size of a slope slope and distance from protective forest plantations. According to the carried out statistical analysis, the humus content in soil is 65–94 % connected with the criterion of water permeability, the slope slope and the degree of soil protection by forest protective plantations.