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Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study, dendrochronological and GIS technologies have been used to evaluate shifts in the upper distribution limits of trees and shrubs in the Eastern Sayan Mountains. The results show that upward expansion along the altitudinal gradient and increase in projective cover against the background of climate warming reach a maximum in shrubs (Betula spp., Salix spp.); then follow Siberian larch (Larix sibirica Ledeb.), Siberian stone pine (Pinus sibirica Du Tour), and Siberian fir (Abies sibirica Ledeb). The abundance of P. sibirica undergrowth in the mountain forest–tundra ecotone has increased, which is due to a rise in May–August air temperatures (r = 0.97). In zones with sufficient moisture supply (high mountains), warming stimulates radial growth of trees and shrubs and promotes their expansion to the mountain forest–tundra.

Abstract To assess the state of plants and their response to changes in soil properties, the elemental composition of leaves of widespread and pollution-tolerant species Betula pubescens Ehrh. and Salix caprea L. has been studied near the nonferrous metallurgy enterprises in the Kola Peninsula. The content of nutrients and heavy metals in the leaves of undergrowth on technogenic barrens and remediation sites differing in remediation technologies has been analyzed. According to the results of leaf diagnostics, both species under barren conditions are characterized by a noticeable deficiency of K, Ca, P, and, especially, Mn and Zn. The leaves of both species accumulate Ni, Cu, Co, As, Cr, Fe, Al, Pb, V, and S. Willow leaves contain more Cd, Co, Cr, Ni, Cu, Al, Fe, As, S, Ca, K and less Mn than birch leaves. Chemophytostabilization has little effect, and the covering of contaminated soils with a constructed fertile layer leads to the enrichment of birch and willow leaves with Ca, K, and P. Under conditions of continuing atmospheric emissions and gradual accumulation of bioavailable heavy metals in soils after the remediation, the accumulation of metals in leaves is largely determined by the distance from the pollution source, reflecting the possibility of both root and foliar uptake. The concentrations of Ni and Cu in leaves in 2018 did not decrease compared to 2011. The low, albeit varying, ratios of the contents of heavy metals in undergrowth leaves and in the soil and weak correlation of heavy metal contents in these media indicated that B. pubescens and S. caprea retain their ability to regulate their chemical composition even under extreme conditions of technogenic barrens. At the same time, supporting the protective capabilities of plants via optimizing mineral nutrition and soil acidity in combination with a reduction in atmospheric pollution is a prerequisite for efficient remediation of technogenic territories in the Far North.

Fungus spores resembling teliospores of the genus Nyssopsora (Pucciniales) were found in a sample of Sakhalinian amber. Morphological features of the spores in the examined amber sample in general correspond to description of teliospores of the extant species Nyssopsora trevesiae parasitizing host plants of the Araliaceae, Trevesia sundaica in Java and Sumatra and Brassaiopsis ciliata in Southern China. It can be assumed that the plant on which those teliospores formed most likely belongs to the Trevesia–Brassaiopsis group. Extant species of these genera are characteristic of the undergrowth in humid forests from the Himalayas to Indonesia, which supports paleofaunistic data on rather warm and humid climate of Sakhalinian amber forest.

A comparative assessment of carbon accumulation in the soils of pine forests in western Russia (the Republic of Karelia, the Karelian Isthmus, and Bryansk region) developed on coarse-textured parent materials has been made. The total carbon stock in the litter and upper soil layer (0–50 cm) varied from 47 t/ha in the soils of pine forests of Bryansk region to 116 t/ha in the soils of pine forests of the Karelian Isthmus. It has been shown that the main factors of carbon accumulation in the soils of pine forests in western Russia were the climate, parent materials, vegetation, agricultural activity, and fires. The influence of climatic conditions has been clearly manifested in the levels of carbon accumulation in the litter and in the upper humus-accumulative soil horizons. In the pine litter within the zone of mixed forests (Bryansk region), the level of carbon accumulation was the lowest, whereas the litter layer of pine forests in the northern taiga (Karelia) has the highest stock of carbon. At the same time, the lowest carbon stocks in the upper mineral soil layers has been noted for the soils of northern taiga forests, which had no humus-accumulative mineral horizon. The variability of carbon stocks in the litter layer was largely controlled by the C/N ratio, as well as by the fraction of deciduous undergrowth and grasses producing high-quality litter. The influence of agricultural activity on soil carbon stock in pine forests was especially pronounced on the Karelian Isthmus with the high agricultural activity in the past, as well as in Bryansk region, where pine forests are formed from pine plantations. The effect of fires on soil carbon stock was most pronounced in heather and lingonberry pine forests of the northern taiga of Karelia.

This article presents the results of studies on the structural organization of the crown in Ulmus glabra. Knowledge of types of shoot systems regularly changing in the tree crown in the ontogenesis of a species is of both theoretical and practical importance. In our studies, we use an architectural (modular) approach that enables us to describe the spatiotemporal program of tree-crown development. The results show that the main structural unit of the tree crown, resistant to the changes in climatic factors, is a biennial shoot system (BSS). The choice of this unit is determined by the fact that zonality in maternal shoot can be detected only in the second year of the shoot lifespan. To identify the spatiotemporal structure of the BSS, we have compared the traits of 1- and 2-year-old shoots. The BSS of U. glabra undergrowth plants in the forest-steppe oak forest of the Belogorye Natural Reserve have been studied. The study involves 100 species of the same ontogenetic stage. The shoot systems in the studied trees have been differentiated into large (“growth”) and small (“basic”) ones with the same location within the crown. Based on the cross-correlation function, which depends on the internode number on the maternal shoot, a regression model of the length distribution of lateral shoots has been created. It is shown that, when numbering the internodes on the maternal shoot from the top downwards, the dependence of the lateral shoot length of both the growth and the basic BSS in U. glabra vs. the number of internodes is consistent with the exponential model. The development of the BSS is found to be dependent on the light conditions and positioning in the crown. The comparison of two samples allows us to introduce a shift parameter into the model, which defines a specific zone in the maternal shoot.

To identify features in natural reforestation after abandonment of land, this paper considers the current state of 21 tracts of fallow lands of the Tunka depression (Republic of Buryatia). On the basis of a geobotanical analysis, the species composition of tree and ground covers was revealed during the overgrowing of arable land on the basis of the geobotanical analysis. The landscape specificity of the main agrarian regions of the Tunka depression was reviewed, and directions for progressive successions occurring in different conditions of the functioning of geosystems were identified. By studying the dependence of demutation features on the state of the biogeocenoses surrounding the fallow lands, it was possible to single out the pine, birch, mixed and meadow varieties of vegetation after the termination of plowing. The dependence of the intensity of spread of tree undergrowth on the degree of remoteness from the forests surrounding the abandoned lands was confirmed. A decrease in overgrowth of tree species with an increase in the distance from the periphery of the deposit to its center was observed. Grazing and hay-mowing are the main factors complicating the process of reforestation. For determining the formation characteristics of the flora in the process of progressive successions, monitoring studies are appropriate.

The dynamics, structure, and functional activity of microbial biomass have been studied in soils of felling areas in southern taiga fir forests (the Yenisei Ridge, Krasnoyarsk krai), which are at different stages of natural regenerative successions. The top organomineral horizons of soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) of the after-felling regeneration succession (with the stage of secondary birch forests) is characterized by an increase in the content of carbon of microbial biomass (Cmic) and in the intensity of basal respiration from new felling to the stage of dense young forest. In the soil of the dense young-wood stage, the total reserves of Cmic (170 g C/m3) and microbial CO2 production (528 mg СО2–С/m3 per hour) are the highest and exceed the control by 80–85%. In the humus-accumulative soil horizon of the studied succession series, there is a tendency for a decrease in the portion of fungal substrate-induced respiration and in the fungi to bacteria ratio in comparison with the control. In the middle-aged deciduous forests with dark-coniferous undergrowth, all the considered parameters of microbial complexes decrease but remain higher than the control. A trend for a decrease in Cmic and basal respiration is revealed in the profile of soddy-podzolic soil of the regeneration series without species change over an eight-year period. At the stage of fir dense young forest, all ecological-functional parameters of the microbial complex become closer to the control small-grass–true-moss fir forest.

This paper presents the results of analyzing the state and dynamics of damaged vegetation from satellite images of high and ultrahigh spatial resolution. This study was conducted based on the example of the site of coniferous forests in the Lower Angara region (Krasnoyarsk krai), where a large outbreak of the Siberian moth took place in 1944–1995. The remote assessment of the state of dark coniferous forests revealed the trends of the SWVI (or NDMI) and NDVI indices that characterize long-term changes in the vegetation cover over the period 2000–2018. The SWVI index is the most informative indicator: a sharp decrease in average values and increase in the coefficient of variation of the index are noted for dead and severely damaged wood stands (crown defoliation of more than 75%). The area of dead forests was calculated according to the difference images of the indices (ΔSWVI) with the threshold criterion lσ (the standard deviation). In 2000, the area of forests that died under the impact of the Siberian moth was approximately 19 200 ha. Alter two major fires in 2004 and 2011 and as a result of destructive factors combination, the area of dead forests increased up to 20 400 ha by 2017–2018. Reforestation within the boundaries of dead stands was estimated from the classification of Landsat images (June 20, 2017; June 23, 2018) by the Random Forest algorithm using the selection of templates from detailed Resurs-P images with a spatial resolution of 1 m (Geoton-LI—July 22, 2015 and December 3, 2018), which were taken during different seasons. The classification proved to be highly reliable (Kappa index is more than 0.9). The areas of classified deciduous and coniferous stands, deciduous and mixed stands with mainly coniferous regrowth, grass–shrub vegetation, and barren soil were calculated. Natural regeneration of mainly coniferous undergrowth occurred in 17% of the damaged area, and deciduous regrowth occurred in approximately 10% of the area 23 years after damage by pests. The area damaged by the moth affected reforestation: the larger the area of the outbreak, the higher the share of open lands with grass and shrub vegetation (it accounts for more than half of the area for the large outbreak and approximately 45% for smaller outbreaks). Regrowth was found in proximity of patches of stands and deadwood in the sites unaffected by large fires. Frequent fires in the territory of moth infestation limit the process of reforestation; therefore, most of the vegetation was at the initial stage of the succession cycle.

Patterns of lateral intrabiogeocenotic (between separate elementary biogeoranges) and interbiogeocenotic variability in the content of secondary metabolites and nutritional elements in the different-age needles of spruce (Picea abies ssp. obovata (Ledeb.) Domin) have been studied along the geochemical transect in spruce forests in northern taiga (Kola Peninsula). The perennial needles of spruce undergrowth (30–40 years) are characterized by a higher concentration of carbon, lignin, high-molecular-weight phenolic compounds, bounded tannins, and wide ranges of lignin/cellulose and lignin/N ratios compared to trees older than 100 years. The needles of spruce trees older than 100 years have significantly more bounded tannins and low-molecular-weight phenols in transitional and accumulative sites than in automorphic locations. The concentration of lignin and lignin/N ratio was significantly higher in the 5–7-year-old needles of spruce trees growing in automorphic conditions, while spruce forests in transitional and accumulative sites have the maximum values of these indicators for the current-year needles. Changes in the chemical composition of spruce needles along the geochemical transect are determined by (1) different concentrations of nutritional elements and secondary metabolites in soils; (2) increased soil moisture from automorphic to accumulative sites; (3) the features of the microbiological activity of soils; and (4) environmental factors (light, temperature, etc.).

Acer negundo L., the invasive tree species of North American origin, is naturalizing in the floodplain forests of Orenburg oblast. Now A. negundo has created an extensive secondary range on the territory of Orenburg oblast and occupies an area of more than 20 000 ha. On the right and left sides of the Tok River in Krasnogvardeysky and Grachevsky districts in the northwest of Orenburg oblast, four test areas of 20 × 2000 m were laid, and inside each test area, 40 sample plots of 20 × 50 m were laid. Nine tree species were considered; the data of records were recalculated per 1 ha. In tree communities of the floodplain of the River Tok, an absolute dominance of A. negundo, which in abundance exceeded all other floodplain tree species (281.13 and 383.25 specimens/ha), was noted. The share of invasive species in the floodplain forests of this area on average was 66.39%. The performed calculation of natural renewal of woody vegetation showed the considerable superiority of undergrowth of A. negundo (130 833.50 and 178 831.50 specimens/ha). Naturalization of A. negundo in floodplains of Orenburg oblast influenced negatively the height, development, and renewal of local forest-forming species, leading to irreversible consequences of degeneration of the floodplain forests.

A comprehensive quantitative assessment of the state of vegetation, soil invertebrate complex, litter horizons, and soddy-podzolic soils (Albic Retisols) in Moscow forest parks (Bitsevskii Forest and Losinyi Ostrov) as dependent on the level of recreational loads is presented. The changes in the main components of forest ecosystems in the forest parks under study have a unidirectional character. At the fifth stage of the recreation-induced degradation, the portion of the trees in good condition decreases by 4–5 times; the canopy density, by 20–30%; and the abundance of undergrowth, by 3–4 times. This leads to an increase in illumination of the surface by more than 30 times. With an increase in recreational loads, the species diversity of herbs in the ground cover initially increases from 9–11 to 23 species owing to the invasion of forest-meadow, meadow, and ruderal plants; then, it decreases. The litter pool becomes lower, and its fractional composition changes: the portion of the active litter fractions decreases by 1.7–2 times, and the portion of mechanically comminuted fractions increases by 3.5–7 times. The density and biomass of mesopedobionts at this stage decreases by 2–2.5 times in the soil and by 4–7 times in the litter. The most pronounced changes in the soil properties take place in the uppermost mineral layer (0–5 cm); in the deeper horizons, they are weaker. According to the results of discriminant analysis, the major contribution to the discrimination of soils at different stages of the recreational degradation is made by the aggregation factor. Individual contributions of changes in other soil properties are small, though their cumulative effect of the discrimination of soils is significant.

Data characterizing forest restoration in Middle Taiga spruce forests after clear cutting are analyzed. Data on the biodiversity and carbon stocks in the phytomass and coarse woody debris were presented for a virgin spruce forest, the cutting area of a spruce forest, and a ripening birch forest that appeared after clear cutting of a spruce forest. The carbon stocks in the phytomass of the virgin spruce forest are 99.01 t/ha, in the cutting area of the spruce forest, they are 18.28 t/ha, and in the birch forest, 56.48 t/ha. The share in the total carbon stock of the stand, understory, undergrowth, ground cover plants, and coarse woody debris was calculated.

This paper presents the results of research into the role of various types of microsites (flat under- and intercrown areas, stumps, fallen logs, mounds, and pits) in the natural regeneration of trees in uneven-aged dark coniferous boreal tall-herb spruce–fir forests of the northern Urals. Areas of microsites of various types have been identified; a general description of natural tree regeneration is provided; the association of undergrowth of various tree species with different microsites was determined; and the undergrowth distribution by ontogenetic states has been assessed. The lowest undergrowth density was registered on flat sites occupying the major part of the community area, while the highest density was detected on elevated microsites (fallen logs, stumps, and mounds) the total area of which is pretty small. The highest density of the undergrowth of all species was observed on stumps. On mounds and fallen logs, it was 4.3 and 3.0 times lower, respectively. It is shown that elevated microsites (stumps, fallen logs, and mounds) are required for successful survival of the undergrowth of various tree species in boreal tall-herb forests.

We have tested management practices at monitoring plots of the Institute of Forest, Russian Academy of Sciences, in Ermakovo station (Western Sayan) to develop Siberian pine forests (Pinus sibirica Du Tour) from young coniferous–deciduous forests that were formed in the place of clearcuttings in tall-grass–fern fir and Siberian pine forests in the low-mountain dark Chern zone. The dynamics of all layers and structural elements of the communities were studied from 1966 to 2014 at two experimental monitoring plots (each with an area of 2500 m2) and compared to the control. The article considers the case of admitting the complete lighting of Siberian pine undergrowth at first thinning. This practice proved to be optimal for further forest-management recommendations. Siberian pine gained competitive advantages over aspen or fir after the first thinning for a short period until the dominant species (aspen, birch, or fir) started to actively regenerate. Repeated thinning made Siberian pine steadily dominant in stands. Our experiment has shown that highly productive Siberian pine forests can be formed for 50 years under the unique natural and climate conditions of the low-mountain Chern zone of the Western Sayan, while the natural course of succession could not yield this result even after 200 or more years. These forests are comparable to indigenous dark Siberian pine forests with respect to their density (0.4–0.6) and wood stock (182 m3/ha at the age of 70–80 years and 270 m3/ha at the age of 80–90 years); however, the managed stands yield many more nuts (about 300 kg/ha) at the age of 70–90 years. Thinning induced the growth of a stand dominated by Siberian pine, as well as the formation of a phytocenotic structure similar to indigenous dark Siberian pine forests, i.e., a structure with a high diversity.

To better understand the habitat requirements of sika deer in the Taohongling National Nature Reserve, transect lines were set out to collect data on bed sites used by sika deer during the autumn. The results showed that sika deer displayed a preference for bed sites with a moderate height of grass fallow and brush fallow, lower shrub density, higher herb density, lower canopy coverage, and higher undergrowth coverage. The bed sites were also characterized as being located on sunny slopes, gentle slopes, and upper slopes, with high elevation. In addition, most bed sites were located far away from human disturbance (more than 1000 m). A logistic regression analysis model indicated that undergrowth coverage, slope location, canopy coverage, and height of undergrowth were important factors that contributed to the difference between used and non-used plots. The habitat–animal relationship is one of the most important types of information, which could provide important references for the conservation and management of sika deer and their habitats in the Taohongling reserve.

Investigations were carried out in June–August 2012 and 2013 in broadleaf forests and planted stands of the northern red oak Quercus rubra in Kiev. The ant visitation rates of 3–6 most abundant plant species within each vegetation layer were analyzed. In all, 16 species of ants were found in the broadleaf forest (Quercus robur + Acer spp. + Carpinus betulus), with the dominance of three species: Formica rufa, Lasius fuliginosus, and L. emarginatus. Eight ant species occurred in Q. rubra stands with the undergrowth of Acer campestre and A. platanoides; the dominant species were Lasius fuliginosus and L. emarginatus. The northern red oak stands with conspecific undergrowth had only four ant species with no dominants among them. Plants with the highest ant visitation rates in the herbage layer of the broadleaf forest were the invasive Impatiens parviflora and the native Aegopodium podagraria. Ants were rare or absent on the remaining herbs: Impatiens noli-tangere, Carex sylvatica, Stellaria holostea, and Galium odoratum. The herbage layer was mostly visited by influents, the dominants being represented only by Lasius emarginatus. Within the shrub layer, ants most frequently visited the undergrowth of the maple Acer platanoides, often harboring colonies of the aphid Periphyllus lyropictus; the highest visitation rates were recorded in the dominants L. emarginatus and L. fuliginosus. The arboreal layer had the highest visitation rate and was most often visited by the dominants Lasius fuliginosus, L. emarginatus, and F. rufa. The common oak Q. robur was the most visited tree in broadleaf forests. In addition to providing ants with food (colonies of the aphids Lachnus roboris and Stomaphis quercus, and also phytophagous insects and other invertebrates), these trees were used for nesting by the dominants L. fuliginosus and L. emarginatus. The presence of aphid colonies was also typical of ripe trees and undergrowth of the maple A. platanoides, the second-visited tree in broadleaf forests. The common hornbeam Carpinus betulus was the least frequently visited, though some ant species, usually L. emarginatus, nested in the trunks and branches of old trees. The vertical distribution of ants in broadleaf forests and red oak stands formed two clusters: the influents occupied the lower (herbage and shrub) vegetation layers, while the subdominants and dominants occupied the upper (shrub and arboreal) ones. The smallest number of ant species (1 or 2) in all the vegetation layers was recorded in the areas with F. rufa; areas with L. fuliginosus had twice as many species; the greatest numbers of ant species were found in the areas with L. emarginatus and in those without dominants. This pattern may result from different territoriality of the dominants: the strongest in F. rufa (defending the whole territory) and the weaker in the other two species (defending only a part of the territory). Plants of all the vegetation layers varied in their attractiveness to ants. As a result, the layers had a mosaic structure in their vertical (between-layer) and horizontal (between different plant species within one layer) arrangement. From 60 to 100% of plants of certain species were visited by ants while plants of other species were not visited at all. The main reason for visiting plants by ants was the presence of aphid colonies.

We have studied the natural regeneration of spruce (Picea abies L.) under a canopy of pine (Pinus sylvestris L.) on loamy soils. Spruce survival and growth depend on the duration of the regeneration period from the creation of the plantation and the local conditions formed as a result of uneven thinning of pine and spruce canopy. The formation of spruce population is mainly determined by trees that regenerated upon intensive thinning of 20- to 40-year-old pine trees. Spruce regeneration may be enhanced by timely cleaning cutting in pine plantations. The first one, done at the age of 15–20 years, favors pine growth and spruce regeneration. At the normal reproduction of spruce population under the canopy of 80-year-old pine plantations, the second spruce layer is formed. Trunk reserve in this layer is 20–25% of the reserves of the first layer. After its formation, the light regime in the forest depends greatly on the space volume occupied by spruce crowns. Their percentage is especially high at the relative height equal to 0.4–0.7 of the mean spruce height in the second layer. Smaller spruce trees may exist for a long time period, but their development is slowed down and they die at the undergrowth stage. When the plantation is 150 years old, the reserves of spruce trees regenerated under the canopy of pine comprise one-third of the total reserves of the plantation. If the growing conditions are favorable for spruce (C3), the stability and productivity of pine-spruce plantations exceed those of the pure spruce plantations. The reasonability of natural spruce regeneration for the creation of pine-spruce plantations under C3 conditions should be substantiated with the consideration of their designation, ages of cuttings, and the possibility of plantation creation and sanitary cuttings according to the valid regulations.

The population structure of common juniper (Juniperus communis L.) growing in the Cis-Urals and Southern Urals has been studied using 17 morphological traits of generative and vegetative organs. A multivariate analysis of ten coenopopulations has recognized three phenotypically different local populations: Cis-Ural, forest Cis-Ural forest-steppe, and Southern Ural mountain populations. The Cis-Ural forest population is strictly associated with lowland pine forests of the northwestern part of the Bashkir Cis-Urals. The Cis-Ural forest-steppe population is located in the northwestern part of the Bashkir Cis-Urals and the southeastern part of the Udmurt Cis-Urals. The Southern Ural mountain population is located in the central part of the Southern Urals and is associated mainly with mountain pine and dark coniferous forests. The last population is divided into forest and forest-edge subpopulations; the first one is represented by typical undergrowth locations, whereas the second is associated with open steppelike slopes and forest edges. In general, based on morphological traits of generative organs, the revealed local subpopulations hold an intermediate position between the Eastern European and Siberian populations of common juniper. Based on the morphological traits of vegetative organs, Cis-Ural populations are considered related to the populations of the European part of Russia, whereas the mountain Southern Ural population resemble Siberian populations. Concerning morphological traits of generative organs, the intrapopulation phenotypic diversity of common juniper is higher for mountain habitats; in the case of vegetative organs, the maximum diversity is observed for lowland habitats. The character of phenotypic differentiation determines the need to conserve the gene pool of common juniper of the Cis-Urals and southern Urals on a population basis.

Transformation of ecological factors on dumps of coal mines under the effect of Pinus sylvestris L. results in formation of three-zone phytogenous fields. The under-crown zone is characterized by a leveled temperature regime, low illumination, forest litter accumulation, and formation of abundant undergrowth. In the sufficiently moistened transitional zone, well-developed moss cover is formed, and the undergrowth occurrence is very low. The external zone, transitional to the background meadow communities, is characterized by well-formed grass cover, an abundance of species, and a group pattern of the undergrowth of P. sylvestris L. The reaction of herbaceous plants on the effect of phytogenous pine fields may be positive (adaptive) or negative. Most species are characterized by a negative reaction.

In the summer of 2010, thermal damages to birch in cultures reached 4.2–4.8 points according to the authors’ five-point scale. In 2011, the stands of birch trees were weakened to variable degrees, but some healthy stands remained. High-density forest massifs and birch forest belts are more drought-resistant. The grass cover is weakly developed therein. Thinned birch cultures become overgrown with herbs and die out after droughts. The root exudates of shrubs depress the intensity of photosynthesis of steppe plants by 10–25%. In vegetation experiments, various species of shrubs stimulate or slow down the growth of shoots and roots and the intensity of photosynthesis of the birch by 10–30%, on average. It is recommended to cultivate birch trees in forest belts using shrubby borders with high allelopathic activity for biological defense of the soil from overgrowth with weedy and steppe plants.

The role of Polygraphus proximus Blandf., an invasive bark beetle of Far Eastern origin, in the transformation of taiga ecosystems of the plains of Western Siberia is evaluated. It is shown that this species is currently one of the main factors of degradation of the Siberian fir forests and various changes in their ecosystems. The consequences of invader outbreaks in fir forests of the region are massive mortality of forest stands, reduction in the number of and deterioration in the vitality of fir undergrowth, and significant changes in the species composition and structure of the vegetation cover and xylophilous insect fauna.

The purpose of the research was to study the invasions of plants into communities of initial stages of regenerative successions in landscapes of the southeast of Belarus (by the example of Solidago canadensis L.). Intrusion of Solidago canadensis L. into the plant succession had the following consequences: decrease in specific abundance, suppression of arboreal undergrowth, long preservation of high level of synanthropization, and inhibition of the directed changes in plant communities.

A set of characters has been used to evaluate transformations in forest phytocenoses and their small mammal communities affected by urbanization, compared to conditionally undisturbed phytocenoses (communities). In park forests of the city of Yekaterinburg, the understory and subordinate shrub and herb- dwarf shrub layers of phytocenosis are transformed to a greater extent. The undergrowth of conifer forest� forming species is as a rule sparse or absent, and that of deciduous trees often consists mainly of invasive spe� cies. Small mammal communities in pine forests transformed under the effect of urbanization also undergo changes leading to the formation of relatively stable (for an urbanized environment) zoocenoses differing both in species composition and in parameters characterizing community diversity.

The state of food resources for Eurasian beavers (Castor fiber Linnaeus, 1758) after several cycles of habitat colonization and abandonment has been analyzed in three beaver settlements on small rivers of Novgorod oblast. It has been shown that tree stands surrounding the settlements differ in composition and degree of damage but are similar in that they contain no forage for beavers: aspen is absent, and birch trees are large and require great efforts to cut them down and utilize. The undergrowth and understory also contain no aspen, while abundant willows and birch are represented by young, thin-stemmed plants unevenly distributed over the area. Tree species prevailing in abandoned settlements are not favored by beavers, implying that the animals must have expended extra energy for foraging. Supposedly, populations of beavers on small rivers in the southern taiga subzone, in habitats modified by their activities, will maintain their abundance far below the maximum possible level, depending on the rate of forage plant regrowth against the background of deteriorating habitat quality.

This article shows the phytocoenotic role of individual postfire trees of the Gmelin larch under conditions of the permafrost zone of Central Siberia. On the basis of the vital state of the trees, the limits of their influence on the recovery of the species of the lower layers of phytocenosis are defined and the formation of the new stand generation is shown.

The effects of two exogenous factors, ground fires and industrial air pollution, on natural regeneration of Scots pine (Pinus sylvestris L.) cenopopulations have been studied in the Transural region. It has been found that an increased level of air pollution leads to a decrease in the abundance and occurrence frequency of pine undergrowth; as the intensity of ground fire increases, these parameters of the postfire generation of undergrowth increase as well, especially in background areas. As shown by two-way ANOVA, either of these factors and their interaction have a significant effect on the density of pine undergrowth, with this effect being stronger in the case of ground fires.

To analyze and quantitatively estimate the contribution of different factors of competition from the edificator tree stand to its effect on plants comprising the lower forest vegetation layer, a set of ecophysiologically based indices of root, light, and integrated competition has been proposed and tested. The results obtained in pine and spruce forests forests of Western Siberia and the Urals show that the growth of the conifer undergrowth is more closely correlated with the index of root competition, and that of heather (Calluna vulgaris (L.) Hull.), with the index of light competition from the edificator tree stand. Moreover, the correlation of their growth with the integrated competition index is 15–25% stronger than the correlation with the indices of root and light competition, irrespective of forest type.

The spatial structure of the fir undergrowth vs. to the fir, aspen, and birch trees in the climax community of the fir-aspen-birch forest was analyzed by the method of R-functions. The analysis showed that the fir undergrowth is primarily concentrated near old fir trees, but near the fir stumps it is more rare than expected. This distribution of the fir undergrowth should have resulted in the decrease in area and number of fir population. The fir undergrowth concentrates the most near the small-leaved species, where dense fir clumps are formed. The populations of the small-leaved species are a stabilizing factor of the dominant population in the fir-aspen-birch forests.

The paper presents the results of the studying of the parameters of post-fire structure and seed-bearing capacity of tree stands, factors of surface medium (thickness of burnt duff, projective cover of herb and moss vegetation) as well as number, vitality, and age structure of self-seeded Scots pine (Pinus sylvestris L.) and accompanying small-leaved species in the Lower Selenga pine forest massif of the forest-steppe in Southwestern Transbaikalia. The seed harvests were 1.5-2 times higher than in the geographically replacing forest types in the forest-steppe of West Siberia, and vitality of the undergrowth of the pine under the canopy of fire-affected stands was extremely low. It is shown that the pine reforests successfully on the fire-sites in the zone of insemination from the forest walls and on the thin fire-sites in the cowberry-rhododendron pine forests, where it is 2-3 times more abundant than in forest-steppe of the West Siberia. The reforestation is insufficient on the fire-sites in the bearberry-lichen pine forests.

Correlations between the structure of phytocenoses representing different stages of the process of forest formation in the Polar Urals and moistening of ecotopes, as well as between the lower layers and forest tree stand are considered. Current density of trees and undergrowth is not exhaustive of the ecotope capacity, and therefore open woodland can be transformed into closed forest. Perspectives of such a transformation within a certain plot may be assessed by percentage of mesophilic and relatively thermophilic (hypoarctic + boreal) species in the herb-dwarf shrub layer.

Parameters of reproduction of the Siberian stone pine (Pinus sibirica), including radial and apical tree increments, the age structure of stands, the amount of young growth, and its distribution along an altitudinal gradient, have been studied in the forest-tundra ecotone of the Western Sayan. The results show that, over the past 30 years, P. sibirica undergrowth has expanded to the mountain tundra belt, the apical and radial tree increments and stand density have increased, and the life form of many P. sibirica plants has changed from prostrate to erect (single-or multistemmed). These changes correlate with the dynamics of summer temperatures and monthly (in May and June) and annual precipitation. The rise of summer temperatures by 1°C promotes the expansion of P. sibirica undergrowth for approximately 150 m up the altitudinal gradient.

In Siberia, pine forests are widespread and grow in diverse habitats. Under zonal conditions, pine shows a wide amplitude of ecological flexibility, being an edificator species in areas with different soils, from shallow podzols with a low base exchange capacity to soddy calcareous soils. The expansion of pine forests far beyond the limits of the zone with a true forest (boreal) climate is apparently explained by the ability of pine to take full advantage of local edaphic conditions, thereby alleviating the impact of adverse climatic factors and broadening its potential climatic range. In this respect, pine is superior to other conifers (Shumilova, 1962). The range of pine forests in Siberia is mainly confined to the Angara basin in its upper and lower reaches and to the watershed separating it from the upper reaches of the Podkamennaya Tunguska, Lena, and Nizhnyaya Tunguska rivers. These forests are typologically diverse, but forest types with green mosses, lichens, and mesoxerophytic herbs dominating in the ground vegetation are more widespread. Fires in boreal forests are a permanent natural factor accounting for the formation of their structure and species diversity. In pine forests, they have always been a factor of evolutionary significance, since these forests are characterized by a high fire frequency. The vegetation of pine forests had been exposed to selection by fires for many millennia, which provided for the development of a variety of adaptations to the impact of fires in pine and produced a significant effect on the composition and properties of its ecobiomorphs, species, and biotypes (Sannikov, 1973). The frequency of fires in pine forests depends on their zonal location and the degree of landscape isolation. In pine forests of Central Siberia, the average interval between fires was estimated at 38.5 years (McRae et al., 2006). A relatively simple structure, ecological flexibility, and high fire frequency in pine forests make them a convenient object for studying the dynamics of postfire succession. The purpose of this study was to reveal changes in the species diversity and structure of ground vegetation at early stages of pyrogenic succession after fires of different intensities. Studies were performed in a dwarf shrub‐lichen‐ green moss pine forest growing on an island in a bog located on the right bank of the Togulan River, which flows into the Yenisei in its middle reaches. This forest occupies a low ridge with a depression in the middle, at an elevation of 60 m a.s.l. The uneven-aged pine stand (10P) is of quality classes 4 and 5, with tree diameter and height averaging 26 cm and 22 m. The undergrowth (10P) is also uneven-aged, up to 0.5 m high; its distribution is uniform. The shrub layer is sparse and consists of Rosa acicularis and Salix caprea . Ground vegetation is differentiated according to microenvironmental conditions. The moss layer is dominated by Pleurozium schreberi , with its coverage ranging from 60 to 100%. In the lichen layer (20‐100% coverage), Cladina arbuscula, Cl. rangiferina, and Cl. stellaris are dominant. The herb‐dwarf shrub layer is 20‐35 cm high, and its coverage varies from 15‐20% to 40%. Dominance belongs to mesophytic dwarf shrubs. The main dominants are Vaccinium vitis-idaea in relatively welldrained biotopes, Vaccinium myrtillis in mesotrophic biotopes, and Ledum palustre and Vaccinium uliginosum in overmoistened sites.

Natural regeneration and the height-age structure of small-leaved linden (Tilia cordata Mill.) under a forest canopy were studied with regard to specific features of forest typology on the Ufa Plateau. For the first time, the height-age structure of linden undergrowth was analyzed by an anatomical method, which allowed accurate determination of the actual plant age and linear increment. The results of this analysis made it possible to reveal three periods in the development of linden undergrowth with respect to the linear growth rate and abundance of plants. More successful regeneration of linden was observed in open elements of relief.

Climate-related changes that occurred in the Ary-Mas larch forests (the world’s northernmost forest range) in the last three decades of the 20th century have been analyzed. An analysis of remote-sensing images made by Landsat satellites in 1973 and 2000 has provided evidence for an increase in the closeness of larch forest canopy (by 65%) and the expansion of larch to the tundra (for 3–10 m per year) and to areas relatively poorly protected from wind due to topographic features (elevation, azimuth, and slope). It has also been shown that the radial tree increment correlates with summer temperatures (r = 0.65, τ = 0.39) and the amounts of precipitation in summer (r = −0.51, τ = 0–41) and winter (r = −0.70, τ = −0.48), decreases with an increase in the closeness of forest canopy (r = −0.52, p > 0.8; τ = −0.48, p > 0.95), and increases with an increase in the depth of soil thawing (r = 0.63, p > 0.9; τ = 0.46, p > 0.9). The density of undergrowth depends on temperatures in winter (τ = 0.53, p > 0.8) and summer (r = 0.98, p > 0.99, τ = 0.9, p > 0.99) and the date of the onset of the growing period (r = −0.60, p > 0.99; τ = −0.4, p > 0.99) and negatively correlates with the amount of precipitation in summer (r = −0.56, p > 0.99, τ = −0.38, p > 0.99).