Currently, there is no consensus on how growing conditions affect the heartwood formation in Scots pine. Comparing the results obtained by different authors is difficult due to methodology differences and poor descriptions of the objects used. We selected two sample plots in (1) a blueberry pine forest on nutrient-rich and moist soil and (2) a lichen pine forest on nutrient-poor and dry soil and performed their detailed characterization. The sample plots were located 22 km apart in the middle taiga subzone (Karelia Republic, northwest Russia). In each sample plot, we selected five dominant trees (model trees), from which we took cores at different trunk heights (0.3, 1.5, 4.5, 7.5 and 10.5 m). The cores were treated with 2,6-dichlorophenolindophenol to identify the heartwood zone. Additionally, samples were taken to study the structural features of the transition zone between sapwood and heartwood. In both forest types, the number of heartwood rings depended on the cambium age, and the patterns of parenchyma cell death did not differ in the transition zone. These facts point to a predominantly internal regulation of the heartwood formation in Scots pine. The heartwood radius and its proportion on the cross-sections were significantly higher in the blueberry pine forest than in the lichen pine forest, despite the relative values of the annual ring width. Further research is needed to develop successful Scots pine heartwood width models under a wide range of conditions.

Bilberry spruce forests are the most widespread forest type in the European boreal zone. Limiting the clear-cuttings size leads to fragmentation of forest cover and the appearance of large areas of ecotone complexes, composed of forest (F), a transition from forest to the cut-over site under tree canopy (FE), a transition from forest to the cut-over site beyond tree canopy (CE), and the actual clear-cut site (C). Natural regeneration of woody species (spruce, birch, rowan) in the bilberry spruce stand—clear-cut ecotone complex was studied during the first decade after logging. The effects produced by the time since cutting, forest edge aspect, and the ground cover on the emergence and growth of trees and shrubs under forest canopy and openly in the clear-cut were investigated. Estimating the amount and size of different species in the regeneration showed FE and CE width to be 8 m—roughly half the height of first-story trees. Typical forest conditions (F) feature a relatively small amount of regenerating spruce and birch. The most favorable conditions for natural regeneration of spruce in the clear-cut—mature bilberry spruce stand ecotone are at the forest edge in areas of transition both towards the forest and towards the clear-cut (FE and CE). Clear-cut areas farther from the forest edge (C) offer an advantage to regenerating birch, which grows densely and actively in this area.

В статье приведены данные о видовом составе сосудистых растений в экотонном комплексе «лес–опушка–вырубка» через десять лет после рубки ельника черничного в Архангельской области (подзона северной тайги). Выявлены различия в проективном покрытии и встречаемости видов напочвенного покрова в разных зонах экотонного комплекса. Рассмотрены изменения показателей обилия видов напочвенного покрова по сравнению с более ранними стадиями восстановления (2–5 лет после рубки). Виды сгруппированы по реакции на рубку и последующее восстановление древесного яруса. Первую группу составляют типичные лесные виды, фитоценотический оптимум которых соответствует условиям ельников черничных (Goodyera repens, Listera cordata, Vaccinium vitis-idaea, V. myrtillus). Вторая группа включает в себя лесные виды, отрицательно реагирующие на рубку и положительно на формирование древесного яруса на вырубке (Carex globularis, Chamaepericlymenum suecicum, Equisetum sylvaticum, Gymnocarpium dryopteris, Luzula pilosa, Maianthemum bifolium, Melampyrum pratense, Oxalis acetosella, Pleurozium schreberi, Rubus arcticus, Trientalis europaea). В третью группу вошли опушечно-лесные виды (Empetrum nigrum и Orthilia secunda). Четвертая группа – это типичные лесные апофиты, положительно реагирующие на рубку, но по мере формировании древесного яруса снижающие обилие (Avenella flexuosa и Chamaenerion angustifolium, Polytrichum commune). Отдельную группу составляют виды, реакция которых на рубку и последующее формирование древесного яруса не обнаруживается геоботаническими методами и не подтверждается статистически. Показано, что и через 10 лет после рубки, несмотря на формирование древесного яруса, в трех зонах экотонного комплекса (лес – опушка – вырубка) сохранились характерные особенности структуры напочвенного покрова.

The logging of mature tree stands, where part of the forest is clear-cut, results in the formation of an ecotone complex (EC) consisting of the forest (F), a transition from forest to a clear-cut site under canopy cover (forest edge—FE), a transition from forest to a clear-cut site outside of canopy cover (clear-cutting edge—CE), and the clear-cut site per se (C). Ground vegetation descriptions (percentage cover of dominants and height of subshrubs) were carried out on the sampling subplots along the transects running from spruce forest into the clear-cut site. We studied the effects of the time since logging and some microhabitat factors (aspect, coniferous and deciduous regeneration, downed deadwood, microrelief, and the abundance of subshrubs, grasses, and forbs) on the abundance of the main ground vegetation dominants of the bilberry-type spruce stands and the clear-cut sites: Vaccinium myrtillus, V. vitis-idaea, Deschampsia flexuosa, and Epilobium angustifolium, in different EC zones. The factor found to have the greatest modifying effect on the abundance of all the species in the CE and C zones was the time since clear-cutting. The clear-cutting pioneer species Deschampsia flexuosa and Epilobium angustifolium preferred open areas in the clear-cut site, whereas the abundance of V. myrtillus and V. vitis-idaea positively correlated with the amount of coniferous and deciduous regeneration. Some factors (downed deadwood, microrelief, coniferous regeneration) were found to act similarly on subshrubs both under the tree canopy (F and FE) and in clear-cut microhabitats (CE and C). The shoot height of subshrubs as well as its percentage cover varied depending on the time since clear-cutting and the microhabitat conditions.

When the forest is clear-cut, there forms an ecotone complex (EC) made up of the forest, the transition from the forest to the clear-cut area under the tree stand canopy and beyond the canopy, and the clear-cut area per se. Our surveys were carried out in North Russian boreal forests (64.4° N, 41.8° E). We studied how the abundance of vascular plants in the forest—clear-cutting EC changed during the first ten years after logging. The abundance of Vaccinium myrtillus and V. vitis-idaea declined immediately after tree stand removal both in the open clear-cut area and in the EC transitional zones. The projective cover of bilberry declined gradually from the forest towards the clear-cut site. The abundance of cowberry in the transitional zones grew throughout the period of observations. As the tree layer regenerated in the clear-cut area, the abundance of the dwarf shrubs also recovered. The average projective cover of Deschampsia flexuosa remained stable in the forest part of the EC and in the transitional zones, not exceeding 2%. In the clear-cut site, its abundance grew slightly in the second year after tree stand removal and reached a maximum in 5-year-old clear-cut area. By the time of canopy closure 10 years after logging, its abundance had declined notably. Epilobium angustifolium in the forest part was very rare, its contribution to the ground cover not exceeding 1%. Its abundance in the forest edge impact area was also extremely low. Fireweed abundance in the clear-cut area reached its maximum 3–5 years after logging and had declined in 10-year-old clear-cuts.

The article aims to describe the patterns of changes in the number of vascular plant species in communities at different stages of forest regeneration after clearcutting using the space-for-time substitution method. Large-scale logging in boreal forests leads to a simplification of the territory’s forest cover (the formation of even-aged stands), which in turn leads to a decrease in the diversity of forest communities and species diversity. These tendencies have been confirmed for many groups of organisms, especially those associated with old trees and dead wood; however, this is not so clear for vascular plants. We investigated plant communities at different stages of regeneration. We used the so-called space-for-time substitution (chronosequence) method of building dynamic series for four forest ecotopes, where industrial clearcuts are most actively carried out. We showed that the fertility of forest ecotopes determines the species pool—the richer the conditions, the more species that can potentially inhabit the community. At the same time, the structure of the tree stand significantly affects the composition and number of species in the community. The lowest species richness was in old-growth forests characterized by the dominance of one species in the tree stand and one or two vascular plant species in the ground cover. With insignificant fluctuations in the average number of species between stages of forest regeneration after logging, some communities at clearcuts in bilberry (Vaccinium myrtillus L.) pine (Pinus sylvestris L.) and spruce (Picea abies (L.) H.Karst.) forests have high species diversity due to the occupation of the site by species of open habitats. These clearcuts are located not far from settlements and close to roads.