Some aspects of forest vegetation dynamics in the European north of Russia

The article summarizes some previously published data on the dynamics of forest vegetation with emphasis on the scientific work of the Forest Research Institute of the Karelian Research Centre of the Russian Academy of Sciences. A cautious forecast of climatogenic dynamics of the forest cover of the taiga zone is made, and information on studies of climate and human influence on fire events in the European North in the last 700 years is given. Based on the research of T. K. Yurkovskaya and G. A. Elina (2009), it can be predicted that with climate warming in the middle taiga subzone, the taiga forests will naturally transform into temperate plant communities. Deciduous trees and nemoral plant species are likely to dominate in the tree layer and ground cover. In the Northern taiga subzone, there may be a shift towards middle taiga communities, with an increase in the productivity of coniferous stands. Fire activity (the frequency and intensity of fires) is another factor in the dynamics of forest vegetation. An international team of researchers has summarized the results of studies on the history of fires in the North-West of Russia, using dendrochronological methods and archival materials related to settlement development. The relationship between fire frequency, settlement formation, and human activity has been explored, and has been found that the area burned per unit time in forests is determined by climate factors (Drobyshev et al., 2022). In recent decades, forest dynamics is mainly related to logging, which determines the coenotic and species diversity of ecosystems. Modern forest typology, focused on scientific justification of biodiversity conservation and development of sustainable forest management practices, can no longer ignore issues related to forest dynamics. This is because secondary stands now dominate, and the problem of forest fragmentation is becoming more significant. The problems of classifying forest communities that arose after logging were pointed out by A. Cajander (Cajander, 1926) and V. N. Sukachev described the situation with the classification of secondary stands as “chaos” (Sukachev, 1930). The scale of the spread of communities after continuous logging can be illustrated by the ordination of hundreds of relevѐs of forest communities of different ages under four types, as shown in Figure 1. Here, is well seen how the relevѐs of forests older than 120 years are concentrated in a small area and close to each other, while the spread of relevѐs of deforested and young forests is very wide. “Chaos” could be reduced by unifying indigenous and secondary stands within forest conditions and considering dynamics (Fedorchuk et al., 2005; Rysin & Saveleva, 2007). Based on the analysis of hundreds of relevѐs entered into the “Habitats of Eastern Fennoscandia” database, we have constructed ecological and dynamic models of cenotic diversity on automorphic soils (Kryshen et al., 2018a; Kryshen et al., 2021). These models represent the stages of forest community development (clear-cut–young stand–middle-aged stand–mature forest–subclimax–climax) and the diversity of plant associations, which is determined by the ecotope and anthropogenic influence (Fig. 2 and Fig. 3). In applied terms, knowledge of dynamics (regularities of post-harvest reforestation) is necessary for the development of close-to-nature management. Instead of continuous and intensive logging, more gentle methods of logging began to be used. These methods only slightly disturb the ground cover and soil, while preserving the forest environment to the greatest extent possible. This is due to the small scale of deforestation and the preservation of the untreated forest sites and separate standing trees. A new field of forestry, called “variable retention forestry”, has emerged (Beese et al., 2019). In this context, studies of the dynamics of communities in transitional states (both in space and time) are particularly important. Our research has shown that after logging a part of a stand, an ecotone complex of four zones is formed: the forest, the transition to the clear-cut site under tree canopy, the transition to the clear-cut site outside of tree canopy, and the clear-cut per se. In both pine and spruce forests, we have determined the length of the transition zone based on various microclimatic and coenotic parameters to be approximately 8–10 meters (Genikova, Mamontov, 2023), however, the intensity of these differences varied. In bilberry pine forests, illuminance in the undisturbed area adjacent to the clear-cut site did not change as much as it did in bilberry spruce stands. This affected the similarity of the species composition and the dominant species in the ground cover between the two plant communities and the transition zone. The article also presents data on changes in the species diversity of plant communities during the restoration of forests at clear-cuts, for the four types of forest conditions previously described. In poor dry lichen (P. s.–Cl.) and lingonberry (P. s.–V. v.-i.) pine forests, the number of species on the clearing varies slightly. However, in total (Fig. 7) and across all communities (Fig. 8), these conditions show the greatest species diversity of vascular plants at the clear-cut stage. Number of species changes in another way in bilberry pine forests (P. s.–V. m.). Here, restoration of the original community usually occurs through the stage of dominance by birch or aspens. The maximum species diversity of vascular plants is observed both in general across all age stages and on average, observed at the stage of the middle-aged community, is characterized by a mixed coniferous and deciduous stand composition. Bilberry spruce forests differ from pine ones in terms of soils, dominant tree layers, and reforestation traits after logging. Without human intervention, forest regeneration occurs through the stages of dominance by deciduous species, such as Betula spp. and Populus tremula. In general, deforestation is highly diverse due to individual site relevѐs in agricultural areas. Two main factors contribute to an increase in diversity after logging: the removal of “pressure” from the tree layer, allowing neighboring species to colonize the clear-cut site, and the appearance of different microhabitats suitable for plants with different coenotic properties.