State and Stability of Forest Ecosystems of the Region with Extreme Anthropogenic Transformation (Evidence from the Oka River Basin)

Abstract

Using satellite sounding data on the forest cover of Russia and three GIS programs, mapping of forest cover and average crown density in the Oka river basin was carried out. Considering hydro-ecological role of forests, these parameters were differentiated according to water management areas. The progressive decline in the wooded areas, thinning and defoliation of forest stands confirm the validity of classifying the Oka river basin as a territory with a catastrophic environmental situation. This is especially true for the forest-steppe zone, where the forest cover ranges from 2.4 to 40%. The average canopy density of the forests in the basin is 50.7%, which makes a significant part of them approaching the state of sparse hemi-xerophytic forests. Using the methods developed by the authors, the indices of the resistance and elastic-plastic stability of forests were calculated and the corresponding maps for the Oka river basin were constructed. It was found that the replacement of primary mixed and broadleaf forests with secondary small-leaved forests leads to a general increase in the dynamism of forest communities: to an increase in their sensitivity to disturbing signals and to an acceleration of ecogenetic successional changes that tend to transfer them to their previous (or new) stable state. The ordination of forest formations of the Oka river basin was carried out according to the gradients of the indices of resistance and elastic-plastic stability. The overwhelming majority of forest formations are characterized by high sensitivity to the initial signals of external disturbances, but at the same time, by sufficiently developed mechanisms of ecogenetic successions, which represent their elastic-plastic stability. This indicates the high reforestation potential of the degraded lands of the Oka basin, which makes it possible to include its forest areas in the global system of biosphere reserves. Two opposite mechanisms exhibiting the known buffer properties of the forest litter have been revealed. In response to the unfavourable impacts, the forest community switches from some leading processes of its functioning to others – from the level of autotrophic biogenesis to the level of detrital metabolism.