Forest-forming Tree Research Articles

Constructive organization of forest-forming tree species growing in the middle zone of European Russia

Constructive organization of forest-forming tree species growing in the middle zone of European Russia

Driving Factors of Forest Typological Diversity in the Moscow Region

The identification of the main factors influencing forest diversity, including both direct and indirect effects, as well as the compatibility of different-level approaches, is a key topic in community ecology and biogeography. The aim of the current study is to assess the contributions of natural and anthropogenic factors to forest diversity in the Moscow region (Russia). This study is based on a quantitative analysis of the linkage between forest diversity and biotopic local factors (LFs) at a lower spatial level, using geobotanical relevés, and external factors (EFs) at an upper spatial level, based on global environmental databases. The classification of 1040 field relevés (including forest-forming tree species, moisture conditions, and soil nutrients) resulted in the identification of eight forest types. A nonmetric multidimensional scaling algorithm, ANOVA post hoc test, hierarchical clustering, and multiple regression analysis were used in data processing. LFs are calculated based on complete species lists using Ellenberg ecological scales. According to a Duncan’s test, LFs provided significant differences between the eight forest types (p < 0.05). At the upper spatial level, the linkage between forest diversity and EFs was most pronounced for climatic factors, soil properties, and topography, including annual mean temperature, soil carbon, clay particle content, and DEM (elevation and slope). The contribution of anthropogenic factors was significantly smaller compared to the natural EFs in the study region.

Temporal Patterns of Vegetation Greenness for the Main Forest-Forming Tree Species in the European Temperate Zone

In light of recently accelerating global warming, the changes in vegetation trends are vital for the monitoring of the dynamics of both whole ecosystems and individual species. Detecting changes within the time series of specific forest ecosystems or species is very important in the context of assessing their vulnerability to climate change and other negative phenomena. Hence, the aim of this paper was to identify the trend change points and periods of greening and browning in multi-annual time series of the normalised difference vegetation index (NDVI) and enhanced vegetation index (EVI) of four main forest-forming tree species in the temperate zone: pine, spruce, oak and beech. The research was conducted over the last two decades (2002–2022), and was based on vegetation indices data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). To this end, several research approaches, including calculating the linear trends in the moving periods and BEAST algorithm, were adapted. A pattern of browning then greening then constant was detected for coniferous species, mostly pine. In turn, for broadleaved species, namely oak and beech, a pattern of greening then constant was identified, without the initial phase of browning. The main trend change points seem to be ca. 2006 and ca. 2015 for coniferous species and solely around 2015 for deciduous ones.

Widespread breakdown in masting in European beech due to rising summer temperatures.

Climate change effects on tree reproduction are poorly understood, even though the resilience of populations relies on sufficient regeneration to balance increasing rates of mortality. Forest-forming tree species often mast, i.e. reproduce through synchronised year-to-year variation in seed production, which improves pollination and reduces seed predation. Recent observations in European beech show, however, that current climate change can dampen interannual variation and synchrony of seed production and that this masting breakdown drastically reduces the viability of seed crops. Importantly, it is unclear under which conditions masting breakdown occurs and how widespread breakdown is in this pan-European species. Here, we analysed 50 long-term datasets of population-level seed production, sampled across the distribution of European beech, and identified increasing summer temperatures as the general driver of masting breakdown. Specifically, increases in site-specific mean maximum temperatures during June and July were observed across most of the species range, while the interannual variability of population-level seed production (CVp) decreased. The declines in CVp were greatest, where temperatures increased most rapidly. Additionally, the occurrence of crop failures and low seed years has decreased during the last four decades, signalling altered starvation effects of masting on seed predators. Notably, CVp did not vary among sites according to site mean summer temperature. Instead, masting breakdown occurs in response to warming local temperatures (i.e. increasing relative temperatures), such that the risk is not restricted to populations growing in warm average conditions. As lowered CVp can reduce viable seed production despite the overall increase in seed count, our results warn that a covert mechanism is underway that may hinder the regeneration potential of European beech under climate change, with great potential to alter forest functioning and community dynamics.

The confinedness of undergrowth Picea obovata and Abies sibirica (Pinaceae) to tree-related microhabitats and their development features at various phases of post-fire succession in green-moss dark coniferous forests in the Northern Pre-Urals

Forest ecology frequently explores the role of microsite mosaics in forest communities for the regeneration of forest-forming tree species. The present study aims to find out whether the ontogenetic structure and differentiation of Siberian spruce (Picea obovata) and Siberian fir (Abies sibirica) undergrowth plants by the plant vitality are associated with their occurrence on various microsites. The study has been carried out in the Pechora-Ilych State Nature Biosphere Reserve, Russia. In green-moss fir-spruce forests, 23 temporary sample plots were established, including 1) forest communities of the intermediate phase of post-fire succession (in areas where fires happened in 1850–1900) and 2) forest communities of the late phase (in areas where there were no fires, at least since the mid-XIX century). On the study plots, P. obovata and A. sibirica undergrowth individuals were recorded indicating ontogenetic state, vitality and microsite substrate for each plant. Using the Z-criterion, a comparison of the occurrence frequencies (%) of various undergrowth groups of P. obovata and A. sibirica on various microsites has been carried out, i.e. within each species and between the studied species, as well as at each phase of post-fire succession and between the phases. The analysis showed that, in communities of both succession phases in both species, undergrowth plants of ontogenetic state im2 occurred on deadwood logs less frequently than the undergrowth plants of the earlier ontogenetic state im1. At the same time, in both species on the flat ground surface an opposite occurrence trend for these ontogenetic states was revealed. In communities of the late succession phase, A. sibirica undergrowth plants of the ontogenetic state im2 and normal vitality occurred on a flat ground surface within inter-crown sites more frequently than plants of reduced and low vitality. A comparison between the species showed that in forest communities of both succession phases, A. sibirica undergrowth plants of im1 and im2 ontogenetic states more frequently occupy flat ground surface than deadwood logs, whereas P. obovata undergrowth plants more frequently grow on deadwood logs than on the flat ground surface. In addition, in communities of the intermediate succession phase, A. sibirica undergrowth is more likely than P. obovata to be found in the under-crown sites (especially on a flat ground surface). In communities of the late succession phase, A. sibirica undergrowth more often grows in under-crown sites on the near-trunk elevations of living trees. In both species, 40–50% of im2 plants of low vitality grow in inter-crown sites. To clarify the influence of the microsite mosaics on the regeneration processes in the studied forests, more detailed and large-scale studies are further needed, which will allow us obtaining more representative samples of undergrowth plants at various ontogenetic states.

Географические особенности возобновления Pinus sibirica Du Tour

One of the main problems of forest ecology is to identify the patterns of the dynamics of natural populations of woody plants at the stage of their renewal, which programs the entire subsequent structure and development of plant ecosystems. The process of reforestation is determined by both the dynamics of seed production and the peculiarities of the seed distribution of forest-forming tree species. The renewal of five-needled pines of the Cembrae subsection with wingless seeds is due to their close trophic relationships with birds of the genus Nucifraga sp., which spread seeds, creating soil forage stocks. The purpose of this study is to reveal geographical features of the relationship between seed production and renewal of Siberian stone pine (Pinus sibirica Du Tour) with the intermediary participation of the thin-billed nutcracker (Nucifraga caryocatactes macrorhynchos Brehm C.L.). The research was carried out in 3 geographical regions of Pinus sibirica forests: in the forests of the Aldan Highlands in Southern Yakutia (59º40´ N., 125º24´ E.), the Northern Urals in the area of the Denezhkin Kamen mountain (60º25´ N., 59º32´ E.), and the Khamar-Daban Mountain range in the South-Eastern Baikal region (51º32´ N., 103º32´ E.). It is shown that each region of the Pinus sibirica growth differs in the dynamics of both seed production and renewal. It was found that the abundance of Pinus sibirica seedlings in the forests of the Aldan Highlands is positively associated (R2 = 0.46) with the yield of cones the previous year. The number of seedlings in the Northern Urals and Khamar-Daban is negatively related to the yield of cones of last year but is positively (R2 = 0.48–0.49) associated with the yield of cones of the year before last. We believe that seedlings in any case appear from the seeds of last year's yield. But the visible connection is due to the activity of the nutcracker. As a result of the stationary studies conducted in the Northern Urals, we identified a constant close (R2 = 0.81) positive relationship between the number of Pinus sibirica seedlings and the number of nutcrackers during the period of seed storage and dispersal in August-September of the previous year. It is assumed that the nature of the dynamics of seed production in the region affects the change in the number of nutcrackers during the seed harvesting period, which in turn determines the abundance of Pinus sibirica seedlings next year. This determines the revealed differences in the dynamics of Pinus sibirica renewal and its dependence on the yields of tree cones in the regions under consideration. For citation: Tantsyrev N.V., Sannikov S.N., Usoltsev V.А. Geographical Features of Pinus sibirica Du Tour Renewal. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 6, pp. 44–56. (In Russ.). https://doi.org/10.37482/0536-1036-2023-6-44-56

On the study of molecular markers of the genus <i>Picea</i> in Russia and Belarus

Currently, degradation of spruce stands is observed in various regions of Russia, which is associated with the transformation of climatic and environmental conditions of the environment. To ensure effective reforestation and afforestation of spruce forests, it is necessary to study the features of the population-genetic structure of plantations in order to preserve the genetic resources of valuable forest-forming tree species. The purpose of this work is to review modern achievements in the study of molecular markers of the genus Picea in Russia and Belarus. To characterize the genetic diversity of spruce populations, 9 ISSR primers with a high level of polymorphism (86,6%) were selected: (GA)9T, (AC)8C, (CA)6RY, (CA)6RG, (CA)6(GT), (CA)6(AC), (AG)8T, (GA)8C and (AG)8YT. The analysis of the mh44 locus of mitochondrial DNA revealed 13 allelic variants and is suitable for studying the genetic diversity of intra- and inter-population genetic variability of spruce. Experimental work with the mitochondrial Nad1 gene has shown the possibility of its application for phylogeographic studies of spruce. The assessment of the genetic variability of microsatellite loci Pt63718, Pt26081, Pt71936 revealed 19 allelic variants and is also suitable for phylogeographic studies. These results are very valuable and can form the basis for studying and characterizing the genetic structure of spruce plantations.

Выращивание березы на вырубках с применением гербицидов

Birch, being one of the main forest-forming tree species, has valuable and soughtafter timber. In production forest conditions, natural regeneration and crops of this species experience strong competition from both grass cover and undesirable hardwoods (aspen, gray alder and willow). Without carrying out high-quality maintenance (agrotechnical care, clearing), the formation of economically valuable birch forests is impossible. The most effective and economical is the chemical care method, which involves the use of modern environmentally friendly herbicides. However, if technological regulations and practical recommendations for the use of herbicides have already been developed for the care of coniferous species (pine, spruce and others), then there are currently no such recommendations for birch. The aim of the research is to develop a scientifically based method of caring for natural young birch stands (clearing, agrotechnical care) using selective herbicides on forest fund lands. The objects of research are seed and vegetative regeneration of birch in young stands formed in clear-cut areas, as well as undesirable herbaceous and tree-shrub vegetation. When laying the experiments and evaluating their results, we were guided by the generally accepted methodology for testing herbicides in agriculture. In field production and small-scale experiments with herbicides magnum, magnum super, mortira and anchor-85 in young stands with birch trees, the biological effectiveness of the action of the preparations on a wide range of undesirable vegetation was determined, as well as their selectivity with respect to birch. High efficiency of herbicides magnum (100–300 g/ha) and magnum super (100–200 g/ha) on dicotyledonous species of herbaceous vegetation and deciduous species – willow, aspen, gray alder and mountain-ash, as well as high resistance of birch to them at continuous spraying during the growing season was established. Herbicides mortira (100–200 g/ha) and anchor-85 (100 g/ha) were recognized as unsuitable for birch care. It was found that after a single application of herbicide magnum at rates of 100 and 200 g/ha in mixed young stands dominated by aspen, willow and gray alder and with participation of birch 1–2 composition units, stands dominated by the latter are formed. For citation: Egorov A.B., Postnikov A.M., Bubnov A.A., Pavluchenkova L.N., Partolina A.N. Growing Birch in Clear-cut Areas with Herbicide Application. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 58–74. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-58-74

Current state of trees and shrubs vegetation conditional references linden-ash oakwoods flood places of Dniprovsk Prisamarya

Natural oakwoods are considered one of the main centers of biodiversity of flora and fauna in Europe and an important agent of providing a wide range of ecosystem, sociocultural and economic services. But in the modern period, there is a decrease in the share of common oak natural forests in the forest reserves of European countries and various manifestations of their degradation. Floodplain forests form a particular value among natural oakwoods. They’re not only play an important role in the formation of vegetation and biogeocenotic cover, but also have a significant positive environment-transforming effect on soil-hydrological and mesoclimatic conditions. That helps to regulate the hydrological regime of river floods. An analysis of the current state of the tree-shrub vegetation of conditional reference linden-ash oakwoods of the central floodplain of the Samara River was conducted. They are a complex of forest vegetation component of Prysamary Dniprovskyi, the territory of which is reserved for the creation of a national nature park. The forest valuation indicators of stands of the main forest-forming tree species have been determined. According to the obtained data, the species composition of tree-shrub vegetation and the type of stand correspond to typical fresh central floodplain linden-ash forests. An increase in the share of participation in the tree stand of Acer campestre and a decrease of Tilia cordata are characteristic. Quercus robur and Fraxinus excelsior take a leading part in the formation of stocks of stem wood. It is determined that in the natural linden-ash oak centropopulation Fraxinus excelsior, Acer platanoides, Acer campestre, Ulmus laevis, Tilia cordata, Ulmus glabra, Pyrus communis, Ulmus minor belong to the normal type and are stable and capable of self-maintenance. The most active self-regeneration is recorded in Acer campestre. The population of Quercus robur is characterized as regressive with signs of disruption of natural regeneration processes and the absence of healthy undergrowth. Fraxinus excelsior, Acer platanoides, Ulmus laevis, Pyrus communis are distinguished by the highest indicators of vitality ((Ln) and according to the index of relative vitality their tree stands belong to the “healthy” categoty. The tree stand of Quercus robur belongs to the “weakend” category. Deterioration of the vitality of Quercus robur tree stands and disruption of its self-regeneration processes can potentially lead to a decrease in the edifying role of oak in fresh linden-ash forets of the valley complex of the Samara River. Also, it can lead to a transformation of their type of wood composition and a decrease in productivity. Major of environmental significance of the forest vegetation of this area requires systematic comprehensive monitoring studies to update current data on the state of unique natural oakwoods. The presented results are a continuation of the monitoring studies of natural reference central floodplain linden-ash forests and can become the basis for the development of differentiated methods of their preservation and restoration.

Dendrochronological Analysis of the Response of Forest-Forming Tree Species of the Projected Mystygyegan Reserve (Vakh River Basin) to Climate Change in the XX-XXI Centuries

The purpose of this study is to identify the age-old dendroclimatic dynamics of the state of the forests of the Mestygyegan reserve, as a representative standard of zonal middle-taiga forests of the Vakh river basin under global warming conditions. The main tasks of the work: analysis of tree-ring chronologies of the most important forest growers of this territory (Pinus sibirica, P. sylvestris, Betula pendula), identification of responses of radial growth of trees to average monthly air temperatures and monthly precipitation of the growing season and the previous period (only 18 months), identification of trends and patterns of dendroclimatic responses. They adhered to the methods of wood sampling, cross-dating, standardization of ring width rows (radial gain), and calculation of the function of growth responses adopted in dendroclimatology. For the period 19372021, trends were revealed to increase the deficit/excess of heat and precipitation in certain months, in particular with signs of summer drought in recent years. There was a shift in the isolines of the growth responses to an earlier time in spring and later in autumn, showing an elongation of the growing season. There is a shift in the manifestation of dendroclimatic responses from the growth of the current year to the growth of the next year, which may indicate both increased opportunities for the accumulation and redistribution of plastic resources by trees and the influence of pathogens. Grass-roots fires amplify the marked trends. Dendroclimatic response patterns of different tree species have both similarities and differences. The smallest response to climate change in birch, the largest in Siberian pine, which requires the greatest measures to protect and protect cedar trees. In the future of further research a great detail of the results obtained on the taxational characteristics of the forest and accounting for anthropogenic factors.

On the Restoration of Azerbaijan Hyrcanian Forests

The processes of development of forest communities are considered, forest-forming species and main associations are identified. In mountainous areas, relief is one of the important factors affecting the distribution of forest-forming tree species along various slopes. The authors provide data on the main forest types. A brief summary characteristic of the forest-forming tree species of the Hyrcanian forests by height is presented. Regularities of change of soils and other ecological conditions of forests are determined. The state of forests has been assessed and the authors come to the conclusion that these communities need to be monitored and protected.

Density of Tree Wood and Bark in Climatic Gradients of Eurasia

Under the conditions of climate changing, the biospheric role of forest cover is increasing, as well as the relevance of research on the carbon depositing capacity of the world’s forests. These studies include an assessment of the trees’ and stands’ biological productivity, which includes not only phytomass, but also the basic density (BD) of stem wood and bark. In our study, allometric models of the BD of wood and bark of 9 forest-forming tree species of Northern Eurasia have been developed, including such independent variables as the tree age, the stem diameter, as well as the average temperature of January and average annual precipitation. The structure of a mixed-effects model is applied, in which the affiliation of the source data to each of the tree species is encoded by a set of dummy variables. Based on the space-for-time substitution principle, the obtained patterns of BD changes in spatial climatic gradients are used to predict their changes in temporal gradients. The effect of Liebig’s law of limiting factor in predicting BD in spatial and temporal climatic gradients has been confirmed. The revealed patterns of changes in the BD of wood and bark in temperature and precipitation gradients completely repeat the previously established patterns of changes in phytomass and net primary production of trees and stands of Eurasia in the same gradients. This means that the climatic conditionality of the studied indicators of biological productivity has a common nature for both quantitative and qualitative indicators of trees and stands.

A multi-trait assessment of selected provenances of Scots pine following 50 years of growth on a provenance experiment in Central Poland, in the light of climate change

The unpredictable nature of climate change impacts, e.g. warming producing a latitudinal shift in photoperiod, may modify trees’ rates of survival and capacities for growth. This is also true of the Scots pine (Pinus sylvestris L.), as one of Europe’s main forest-forming tree species. The best results in the study of tree responses to climate change can be obtained during long-term experiments carried out on provenance trials. Such objects make it possible to precisely determine the growth and adaptation reactions of offspring coming from different soil and climatic conditions to the conditions of the research area. Research of this kind has been conducted by analysing growth in the progeny of 16 different Polish provenances of Scots pine on a single provenance experiment located in the centre of Poland, in an area where annual precipitation is at the rather low average level of 580 mm. The experiment was established in 1966, using a randomised block design with five replicates for each of the tested provenances. In autumn 2015, trees present were monitored and analysis of variance was used for their heights and diameters at breast height, with estimates also made regarding straightness of the trunk, crown width and branching angle. At the same time, ecophysiographic features of the places of occurrence of parent stands for each of the provenances were also analysed, with a quantification of the relationship between the growth traits studied and ecophysiographic features also achieved using PCA, while Ward’s Method of clustering was used to establish provenance groups characterised by multi-trait similarity. In the light of what is known about forecast climate change, it would be possible to transfer progeny of different pine populations, if only from places where levels of precipitation are lower, along with values for the De Martonne aridity index. In practice, Central Poland might play host to the progenies of pines from the western part of the country—as represented here by the Bolewice, Rychtal, Karsko and Gubin provenances. On the other hand, the progenies of pines from stands at higher altitudes will not be suitable for cultivation in lowland locations in Central Poland.

Genetic Diversity and Population Structure of Scots Pine (Pinus sylvestris L.) in Middle Siberia

Scot pine (Pinus sylvestris L.) is one the main forest-forming tree species in Russia, and is of great ecological, economic and social value. In order to manage the genetic resources of this important forest tree species efficiently, knowledge of its genetic diversity and structure is needed. Here, we assessed the genetic variation of 17 populations representing different parts of Scots pine range in Russia by using nuclear microsatellite markers (nSSR). Specifically, 14 populations were chosen within the natural distribution range of the species in Middle Siberia and three distant populations were sampled from the European part of Russia, the West Siberia and the Russian Far East. All populations showed high values of genetic diversity (HE = 0.514) and AR = 4.150. However, the easternmost population has shown the lowest level of genetic diversity (HE = 0.433) and allelic richness (AR = 3.505). Five genetic groups could be detected that correspond to: the European part of Russia, the south of Middle Siberia, the northwest of Middle Siberia, West and Middle Siberia, and the Russian Far East. However, the European population was the most genetically distinct one. The variation among Scots pine populations accounted for only 5% of the total variance. The highest level of genetic differentiation was found only between westernmost and easternmost populations (FST = 0.097). Our genetic data may contribute to a better understanding of the pattern of genetic diversity of Scots pine populations in Middle Siberia and help the conservation efforts of these genetic resources.

ИНДУКЦИЯ РИЗОГЕНЕЗА У ОСИНЫ ТРИПЛОИДНОЙ (POPULUS TREMULA L.) IN VITRO

Triploid aspen (Populus tremula L.) is a valuable woody species. Triploid aspen is a valuable tree species. Unlike diploid forms of aspen, it is not subject to core rot, has rapid growth and forms a large phytomass. Plantation cultivation of triploid aspen is important for enriching the gene pool of the main forestforming tree species in the Republic of Bashkortostan and obtaining high-quality wood raw materials. Valuable properties and qualities of tree species are most fully transmitted in the offspring during their vegetative cultivation, especially during microclonal reproduction. The article presents methodological aspects of rooting aspen triploid on artificial nutrient media. The methodology has been worked out and the optimal composition of the nutrient medium for rooting micro-plants of aspen triploid under in vitro conditions has been developed.

Fungi of the Russulaceae family in the conditions of natural monuments of the Penza region and the influence of environmental factors on their distribution

The relevance of the study of fungi of the Russulaceae family is determined by the fact that they play an important role in the life of temperate forest ecosystems as mycorrhizal symbionts of the main forest-forming tree species. In addition, this group of fungi is of great practical importance, as they are edible fungi. Despite this, they are one of the little studied groups of Agaricomycetes. The information about the fungi of the studied family in the conditions of the Russian Federation is limited, and therefore the data on their ecology are contained mainly in foreign literature. The purpose of this work is to study the species composition of fungi of the Russulaceae family and to establish the influence of the main environmental factors on the distribution of this group of fungi on the territory of some forest natural monuments of regional significance (Burchikhinsky slopes, Zasursky blueberry forest, Kichkleysky pine forest with oak, Nikonovsky forest and Floodplain oak forest) in the conditions of the Penza region. The studies were carried out in 20162022 by methods of route and stationary studies. When determining fungi, the method of light microscopy was used. As a result, the species composition of fungi of the Russulaceae family of the studied natural monuments located in the Penza region was studied. Within the studied protected areas, 78 species of fungi of the Russulaceae family were identified. As a result of the taxonomic analysis of mycobiota, it was found that it included 24 species from the genus Lactarius, 3 from the genus Lactifluus, and 51 from the genus Russula. All of them belong to the ecological-trophic group of symbiotrophs. 19 species form mycorrhiza with various tree species, and 59 species have a narrow specialization in relation to partners in symbiosis (29 species are associated with Quercus robur, 15 with Betula pendula, 10 with Pinus sylvestris, 2 with Populus tremula, 1 with Tilia cordata, 1 with Alnus glutinosa and 1 with Corylus avellana). It has been established that the leading factors determining spatial distribution and productivity of fruiting bodies of fungi of the studied family are soil fertility and moisture. In megatrophic habitat conditions, acidity also has a significant effect on the distribution of fungi of the family under consideration. The species composition of fungi of the Russulaceae family for habitat types was determined in accordance with the edaphic grid. For different ecotopes, the composition of indicator species was revealed. An estimate of the yield of fruiting bodies of fungi of the Russulaceae family in various types of forests, depending on fertility and soil moisture, is given.

Modelling bark thickness for Scots pine (Pinus sylvestris L.) and common oak (Quercus robur L.) with recurrent neural networks.

Variation of the bark depends on tree age, origin, geographic location, or site conditions like temperature and water availability. Most of these variables are characterized by very high variability but above of all are also affected by climate changes. This requires the construction of improved bark thickness models that take this complexity into account. We propose a new approach based on time series. We used a recurrent neural network (ANN) to build the bark thickness model and compare it with stem taper curves adjusted to predict double bark thickness. The data includes 750 felled trees from common oak and 144 Scots pine-trees representing dominant forest-forming tree species in Europe. The trees were selected across stands varied in terms of age and site conditions. Based on the data, we built recurrent ANN and calculated bark thickness along the stem. We tested different network structures with one- and two-time window delay and three learning algorithms-Bayesian Regularization, Levenberg-Marquardt, and Scaled Conjugate Gradient. The evaluation criteria of the models were: coefficient of determination, root mean square error, mean absolute error as well as graphical analysis of observed and estimated values. The results show that recurrent ANN is a universal approach that offers the most precise estimation of bark thickness at a particular stem height. The ANN recursive model had an advantage in estimating trees that were atypical for height, as well as upper and lower parts on the stem.

Population structure and genetic variation of fragmented mountain birch forests in Iceland.

Betula pubescens Ehrh. (mountain birch) is the only forest-forming tree in Iceland. Since human settlement (874 AD), the continuous 25,000 to 30,000 km2 forest has shrunk to 1.200 km2 of fragmented patches, making it a good object to study population genetic consequences of habitat fragmentation and disturbance. Further, genetic studies have also shown that hybridization between the tetraploid (2n = 56) B. pubescens and the diploid (2n = 28) Betula nana L. (dwarf birch) occurs among Iceland's natural populations. This study assessed the genetic variation within and among 11 birch forests remaining across Iceland. Genotype-by-sequencing methodology provided a total of 24,585 single nucleotide polymorphisms (SNP´s), with a minor allele frequency >5% for genetic analyses. The analysis showed similar diversity within forests, suggesting that fragmentation and hybridization have had a limited effect on the genetic variation within sites. A clear genetic divergence is found among forests from the different regions of Iceland that may reflect historical isolation; the differentiation between forests increased with geographic distances reflecting isolation by distance. Information on the distribution of genetic variation of birch in Iceland is essential for its conservation and to establish genotype-phenotype associations to predict responses to new environmental conditions imposed by climate change and novel biotic/abiotic stressors.

Stem volume by height classes of immature, mature and overmature stands of the main forest-forming species of Ukraine

Generally, it is impossible to measure diameters and heights of all trees in a forest stand. Therefore, models of relationships between heights (h) and diameters (d) of trees are commonly used in practice for stem volume estimation. This study aimed at developing models of tree height-diameter (h-d) relationships as well as corresponding models of the tree stem volume for immature, mature and overmature stands of the main forest-forming species of Ukraine. This paper is a aggregation of long-term studies of the stem volume, which are based on the results of measuring about 10 thousand sample trees. Modelling of the tree height-diameter relationships was performed using relative height values. The methodology used in this study allowed generalising the measurements of sample trees collected in stands of various forest site types, productivity levels, and age categories. The average height of trees with a diameter of 24 cm was taken as the reference during modelling relative heights, while the diameter of 40 cm was chosen as the reference for overmature Scots pine stands. As a result, the parameters of a unified mathematical model of relative heights for immature, mature, and overmature stands of the main forest-forming tree species of Ukraine were established. Based on these models, height-diameter relationships in forest stands of different height classes were predicted. The authors demonstrated that the developed mathematical models substantially simplify the methodology of field work during timber surveys. The paper also presents models of the tree stem volume. These models predict the stem volume outside the bark based on diameters and heights of trees or using the developed models of h-d relationships. In this study, a unified system of mathematical models of stem volume by height classes were created for immature, mature, and overmature stands of the main forest-forming species of Ukraine. The results of the study are introduced to the National Forest Inventory of Ukraine for growing stock volume calculation at sample plot level using measurements of individual trees. The developed models can be used both by operation forestry (estimation of the timber volume during harvesting), and forest management (forecasting the future structure of forests and estimating the growing stock volume), as well as in the forest ecology

Population dynamics of forest-forming tree species on landslide-scree slopes of the right bank of the Kuibyshev reservoir (Tatarstan)

The dynamics of forest-forming tree populations under conditions of landslide slopes makes it possible to assess the impact and the anthropogenic regulation of the Kuibyshev reservoir on the forest vegetation state. The Shannon index characterizes the phanerophytes diversity in the structure of forests by landslide elements. The integral signs of the activity/stability of landslide processes on the slopes are the trees functional parameters – the trunks height, the dynamics of cross-sectional areas and wood volumes, reflecting not only the different trees populations state and productivity according to the landslide elements, but also the stage of phytocenoses reforestation of along the right bank of the Kuibyshev reservoir.