Ecological Effects of Contemporary Global Warming in Forest Geosystems of the Volga River Basin

Abstract

Using literature data and material from this author’s large-scale landscape-ecological research, an analysis is made of the impact of global anthropogenic warming over the last 100 years on the state of the forest geosystems of the Volga basin. In mixed forests, a nemoralization of the grass stand was revealed, with a decrease in the number of boreal species, and in oak forests—a massive desiccation of oak. It is found that on the southern border of the forest zone there occurs a partial replacement of forest-steppe vegetation with northern-steppe vegetation, this latter being substituted by dry-steppe vegetation. As a result, gray forest soils and common chernozems have persisted as northern relics. In the A1 soil horizon, the fractional composition of humus has changed, which indicates a change of the podzolic soil-forming process by the sodding process. At the main landscape line of the Russian Plain along the Oka and Volga valleys, a peculiar three-dimensional biogeographic ecotone was formed as a result of the transgression of different vegetation types: the taiga, nemoral forest and steppe types, along different biological horizons. Significant changes in the structure of hydrothermal niches of forest biogeocoenoses occurred on zonal ecotones of forests and steppes: the shift of dominants to an arid critical state of forests as well as the emergence of negative excesses and even “gaps” in the structure of niches. All these signs point to the beginning of massive structural and functional restructuring of forest geosystems in the Volga basin. Within the next 100 years, we can assume a certain “savanization” of mesophilic deciduous forests and their closure with a common mosaic complex of light forests, meadows and steppes of typical forest-steppe. This will occur against the background of instability of zonal boundaries.