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The results of a long-term study of changes in soils and vegetation during postagrogenic succession of sown meadows on reclaimed peat soils (Eutric Histosols) are presented. The study was performed on experimental plots in the Korzinskaya Lowland (Karelia); sowing of perennial grasses was accompanied by the application of mineral fertilizers. Observations over changes in the vegetation communities along with the reduction of the peat thickness were conducted. The soil samples were analyzed for the organic carbon, total nitrogen, and available phosphorus contents and for the pH of salt extracts. Vegetation was described using the Braun-Blanquet approach; the botanical composition and the biomass of herbs were assessed by their cutting and weighing. Nematode communities were characterized by their taxonomic diversity, population density, and eco-trophic structure. The analysis of soil profiles demonstrated that the thickness of the peat deposits decreased over 40 years of observation (1974–2015). The direction of vegetation succession on sown meadows was dictated by the type of fertilization. Two plant communities were formed: Deschampsieta caespitosae humidiherbosum developed on the plots treated with mineral fertilizers, and Elytrigeto magnograminosoherbosum community developed on the plots treated with mineral and organic fertilizers. The main changes in soil nematode communities during the long-term succession were related to their eco-trophic structure. Two trophic groups exhibited an obvious response: the relative abundance of nematodes associated with plants decreased, whereas the share of plant-parasitic nematodes increased. In addition, it was found that the species composition of herbs predetermined the ecological specialization of dominant plant-parasitic nematode taxa. [ABSTRACT FROM AUTHOR]

The results of two rounds of soil and geobotanic surveys of rangeland ecosystems in the steppe zone are presented. The same sites with southern chernozems (Calcic Chernozems) under steppe plant communities at different stages of pasture degradation were investigated at the end of the 1980s, when they suffered maximum anthropogenic loads, and in 2011-2013, after a long period of relative rest. In the 1980s, degradation of soil physical properties in rangeland ecosystems under the impact of long-term unsustainable management was noted. At the same time, it was found that the major qualitative and quantitative properties of humus in the chernozems were preserved independently from the level of pasture degradation. The following period of moderate grazing pressure had a favorable effect on the soil properties. Owing to the good characteristics of the soil humus, the restoration of the physical properties of chernozems-including their structural state, water permeability, and bulk density-took place in a relatively short period. It is argued that the soil bulk density is a natural regulator of the species composition of steppe vegetation, because true grasses (Poaceae)-typical representatives of the steppe flora-have a fibrous root system requiring the soils with low density values. The improvement of the properties of chernozems is related to the development of secondary ecosystems with a higher portion of grasses in place of damaged rangelands and to the increase in the area of nominal virgin phytocenoses. [ABSTRACT FROM AUTHOR]