Soil and Vegetation Cover and Biodiversity Transformation of Postagrogenic Soils of the Volga-Oka Interstream Area

Abstract

Based on the actual material, the state of the land, previously (more than 15 years ago) placed under cultivation and “neglected” to date, was assessed. Control sites within different landscape provinces of the Volga-Oka interstream area were compared by the state of soil cover and vegetative cover, as well as the type of anthropogenic transformation. The study identified three types of transformation of post-agrogenic lands characteristic of the initial and intermediate overgrowth stages of pre-climax communities: field overgrowth associated with a change in land use; field overgrowth with nearby forest; and field overgrowth without nearby forest. The soil cover state was assessed by acidity, pH, and humus content, and it generally corresponds to the area’s characteristics. Deterioration of these characteristics was noted on sod-podzolic soils overgrown with forest vegetation, as evidenced by low humus content of 0.96–1.46%. The results of research using statistical methods reliably showed that the overgrowth of most sites with herbaceous vegetation within different landscapes followed common successions, even on different soils (sod-podzolic and gray forest). With the leveling of landscape features of areas, there were similar plant species and communities. It was shown that as a result of agricultural overgrowing, the species richness of plant communities was sharply reduced. For example, the maximum value of the Shannon index on overgrown lands is 3.6, which is lower than the reference natural community, where this indicator is 4.1. The remediation of biodiversity in the foreseeable future is very problematic. Although post-agrogenic phytocenoses can gradually restore their productive potential to the level of natural phytocenoses (the maximum value of phytomass in overgrown lands is 10.2 mt/ha, for comparison, natural phytocenoses accumulate 6.3 mt/ha at reference sites), their productivity is provided by a different species composition of herbaceous plants with poor biodiversity. In order to preserve biodiversity, it seems advisable to intersperse croplands with uncultivated plots of sufficiently large size which can serve as a kind of natural ecosystem preservation bank.