Betula Pendula Research Articles

Sensitivity of Eurasian Rear-Edge Birch Populations to Regional Climate and Local Hydrological Conditions

South rear-edge populations of widely distributed temperate and boreal tree species such as birches (Betula pubescens and Betula pendula) are considered particularly vulnerable to climate warming, and at the same time, they constitute genetic reservoirs of drought-adapted ecotypes. Here, we compared radial growth patterns and responses to climate, river, or reservoir flows and a drought index of rear-edge (southernmost) populations (Toledo Mountains, central-southern Spain) with populations located in northern Spain of B. pubescens and B. pendula. Then, we performed a comparative analysis across Europe of B. pendula populations. The main climatic constraint of birch growth was a high summer water deficit, although the effect of local hydrological conditions was particularly important in rear-edge populations. We found declining growth trends in rear-edge stands dating from the early 21st century, related to decreasing water availability and increasing aridity. Our results also suggested distinct growth patterns and climate-growth associations of B. pendula across Europe that show how populations further south and in warmer locations were more sensitive to drought stress. Drought-induced growth decline can be exacerbated by local human land uses, leading to reduced river inflow, thus endangering birch populations at their southern distribution limit. Protection of threatened rear-edge birch populations requires adequate management of local water resources.

Concentrations of chemical elements in the leaves of Populus suaveolens Fischer and Betula pendula Roth at the facilities of the gold deposit of Eastern Transbaikalia

The concentration of 50 chemical elements in the leaves of Populus suaveolens Fischer and Betula pendula Roth growing in tailings dumps and dumps of gold deposits in Eastern Transbaikalia (Baley) was studied. It was found that the highest concentration of most elements was in the leaves of plants growing at the ZIF-2 tailings dump, and the lowest was on the sands of the thorium tailings dump and sand–pebble soil at the dredge gold mining site. Populus suaveolens differed from Betula pendula by a higher concentration of most chemical elements. A feature of the elemental composition of birch was a significant concentration of Mn and Ba in relation to poplar. The concentration of a number of chemical elements significantly exceeded the clark of terrestrial plants, as well as the maximum permissible levels of concentration of elements established for feed and medicinal plant raw materials.

Forest Stands Formation on Exhausted Peat Bogs in the North-East of the European Part of Russia

It has been established that the directed construction of forest-meadow-bog agricultural landscapes in the place of territories that have been abandoned from industrial peat extraction is the most promising and environmentally friendly way to restore the biospheric functions of disturbed bog ecosystems. A special role in the ecological framework of the emerging agricultural landscape belongs to forest cultures. Long-term studies show that Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula) form the basis of future cultivated forest stands. With artificial reforestation, the best result was obtained on residual gley-degraded peat soils, where the peat layer does not exceed 20–30 cm, and the drainage rate is 80–100 cm. The most optimal conditions for the development of all the tree and shrub species were found to be near open reclamation canals. In this case, forest plantations are arranged in the form of shelterbelts 10–15 m wide. Natural reforestation as an alternative is possible, but it is characterized by slower dynamics and only a slight increase in commercial timber stocks. The process of self-recovery also largely depends on the degree of depletion of the residual deposit and the degree of its water content. In the structure of the post-bog forest-meadow landscape, the share of forest should be at least 20–30%.

Dead Wood Elements Composition in Different Tree Species and Stages of Decay in the Broad-Leaved Forests of the Kaluzhskie Zaseki Reserve

The content and mass concentration of eight chemical elements Al, Ca, Cu, K, Mg, Mn, P, and Zn were analysed in dead wood of eight tree species at five stages of decomposition. Wood samples were taken at the site of the mass windfall of 2006 in a multispecies broadleaved forest in the Kaluzhskie Zaseki nature reserve. Deadwood of seven deciduous trees species was studied: maple (Acer platanoides), birch (Betula pendula), common ash (Fraxinus excelsior), common aspen (Populus tremula), English oak (Quercus robur), linden (Tilia cordata), rough elm (Ulmus glabra), as well as one coniferous tree species – Norway spruce (Picea abies). A series of one-way analyses of variance was carried out to assess the influence of the species and the stage of deadwood decomposition (including the zero stage for control samples) on the density, content of elements and their mass concentration. Tree species most clearly differed in the content and mass concentration of Mn, Zn, Mg, Ca, and K: R2 varied from 50 to 23% for the content and from 53 to 19% for the mass concentration of elements of the indicated series. The leaders in the content of these elements were the following species: Mn – maple, birch, spruce, linden; Zn – birch and aspen; Mg – maple, elm; Ca – elm; K – linden, elm. The stages of wood decomposition turned out to be a significant factor of variation for the content of Mn, P, Cu, Zn and Ca: R2 varied from 22 to 16%. During the destruction of wood trunks, a significant increase in the content of these elements occurred. Maintenance of cycles of biophilic elements is more successfully implemented in the presence of deadwood of different species at different stages of decomposition.

Interactions of hydrophilic birch wood (Betula pendulaRoth) extractives with adhesives for load-bearing timber structures

This study investigated how water-soluble extractives of silver birch (Betula pendulaRoth) wood interact with the most common adhesives used for producing engineered wood products (EWPs), i.e., melamine-urea-formaldehyde (MUF) and one-component polyurethanes (PUR). Therefore, the extractives were characterized via various chromatographic techniques and mass spectrometry. The effects of extractives on the curing kinetics were investigated using rheometry. The impact of extractives on the chemical and mechanical properties of the cured adhesives was investigated with FTIR spectrophotometry and tensile stress-strain measurements, respectively. Moreover, a comparative study on the shear strength of birch wood with and without extractives was performed.The organic fraction of the water extractives of birch mainly consisted of phenolic glycosides, carboxylic (fatty) acids, and saccharides. The extractives decelerated the curing process of MUF, as observed in a rheological small-angle oscillatory shear experiment using wood substrates as the lower plate. This was indicated by a reduced gel time from 5 to 3.8 h on pristine vs. extracted wood. When measuring MUF on extracted wood, this deceleration was also reached by adding ∼1% (W/W) of the isolated extractives into the MUF resin. Similar experiments with PUR showed a slight acceleration when dispersing extract into the adhesive, indicated by a reduction of vitrification time of −0.9 ± 0.3 h per percent of extractives added. However, measurements with pure PUR on pristine and extracted wood showed no significant difference in curing kinetics due to the extractives’ limited mobility and solubility in PUR. Both PUR and MUF cured adhesive films showed a reduced stiffness, elastic stress limit and tensile strength in uniaxial tensile stress-strain measurements of adhesive films upon increasing the amount of hydrophilic birch extractives concentration. Comparative standard tensile shear strength measurements on pristine and extracted wood indicate a 7–19% strength increase due to extraction when bonding with MUF, while the bond strength of PUR bond lines was less affected by the extraction procedure.

Fine root morphological traits and production in coniferous- and deciduous-tree forests with drained and naturally wet nutrient-rich organic soils in hemiboreal Latvia

Fine root production is one of the key elements of carbon (C) turnover in soil in afforested peatlands and forest lands with organic soils. We estimated variability in fine root morphology traits and annual production in hemiboreal forests dominated by coniferous trees (Norway spruce) and deciduous trees (silver birch and black alder) with nutrient-rich organic soils in Latvia. In total, 23 research sites were established in drained and naturally wet forests of different ages, and ingrowth core techniques were used to sample fine roots and subsequently determine fine root morphology traits and annual production, and calculate C input through fine root litter. Significant differences in several fine root morphological traits between coniferous- and deciduous-trees-dominated stands were found. Fine root production tended to be higher in coniferous-trees-dominated stands and positively correlated with several forest stand characteristics: stand age, average tree diameter at breast height, basal area and average tree height, but negatively correlated with nitrogen and phosphorus content in soil. C input through fine root litter ranged up to 0.46 ± 0.16 t ha-1 yr-1. It is necessary to conduct further research, including multi-annual estimates in a wider set of forest stands with diverse dominant tree species and growing conditions, to improve estimates, patterns and understanding of C flows through fine root litter in drained and naturally wet organic soils.

Monitoring of the condition of woody plants in the central part of the city of Donetsk

The dendroflora of Donetsk has been studied the species composition of trees in stands has been determined, the age structure of plantings has been analyzed, the life condition of green spaces has been assessed, as well as morphometric parameters of trees have been evaluated and models of age dependences of the allometric coefficient of trees, characterized by high indicators of adequacy to the initial data, have been proposed for the first time. As part of the linear plantings of the surveyed streets, 45 species of trees were identified, including 13 species of the indigenous fraction of the local flora belonging to 24 genera and 17 families. Dominant are Populus bolleana Lauche, Acer platanoides L., Betula pendula Roth, Acer pseudoplatanus L., Robinia pseudoacacia L., Aesculus hippocastanum L. and Picea pungens Engelm. The plantings are dominated by species of European (48,85%), North American (22,49%) and Central Asian (18,02%) origin. The most numerous in trees is the age group of 4049 years. The vital condition of 41% of trees with a fast and medium growth rate is assessed as good with minor signs of weakening, and 59% of plants are marked as severely weakened or dying. For slow-growing trees, 91% of the sample consists of healthy plants with minor signs of weakening.

Derivative-based time-adjusted analysis of diurnal and within-tree variation in the OJIP fluorescence transient of silver birch

The JIP test, based on fast chlorophyll fluorescence (ChlF) kinetics and derived parameters, is a dependable tool for studying photosynthetic efficiency under varying environmental conditions. We extracted additional information from the whole OJIP and the normalized variable fluorescence (Vt) transient curve using first and second-order derivatives to visualize and localize points of landmark events. To account for light-induced variations in the fluorescence transient, we present a time-adjusted JIP test approach in which the derivatives of the transient curve are used to determine the exact timing of the J and I steps instead of fixed time points. We compared the traditional JIP test method with the time-adjusted method in analyzing fast ChlF measurements of silver birch (Betula pendula) in field conditions studying diurnal and within-crown variation. The time-adjusted JIP test method showed potential for studying ChlF dynamics, as it takes into account potential time shifts in the occurrence of J and I steps. The exact occurrence times of J and I steps and other landmark events coincided with the times of significant differences in fluorescence intensity. Chlorophyll fluorescence parameters were linearly related to photosynthetic photon flux density (PPFD) at different times of day, and the values obtained by the time-adjusted JIP test showed a stronger linear regression than the traditional JIP test. For fluorescence parameters having significant differences among different times of day and crown layers, the time-adjusted JIP test resulted in more clear differences than the traditional JIP test. Diurnal ChlF intensity data indicated that differences between the southern and northern provenance were only evident under low light conditions. Taken together, our results emphasize the potential relevance of considering the time domain in the analysis of the fast ChlF induction.

The effect of short-term cold exposure on the change in the concentration of free proline in various birch species <i>in vitro</i>

In natural conditions of growth, forest woody plants constantly face negative environmental factors. Environmentally unfavorable impacts certainly affect the physiological and biochemical processes occurring in plants and lead to the activation of their own protective mechanisms. In recent years, methods of biotechnology (cell and tissue selection) have been increasingly used in the study of adaptive capabilities, as well as the degree of tolerance of plants to abiotic stress factors. In our work, we evaluated the specifics of the reaction of Betula pendula Roth, Betula pendula Roth var. carelica (Mercklin) L. Hmet-Ahti and Betula pubescens Ehrh. in vitro, in particular the change in the level of free proline to low-temperature stress (+4C) of different duration times. It was found that the highest value of the amino acid content in relation to the control was in the Betula pendula Roth var. carelica Merckl. clones and ranged from 163 to 206%, in the Betula pubescens Ehrh. and Betula pendula Roth clones ranged from 103 to 128% and from 101 to 131%, respectively. Uniformity was noted among the clones of Betula pendula Roth var. carelica Merckl. according to the degree of response to stress. The relationship between the ability of plants to produce more proline and successful adaptation to cold shock was revealed.

Interspecific Growth Reductions Caused by Wild Ungulates on Tree Seedlings and Their Implications for Temperate Quercus-Fagus Forests

Ungulate impacts on forest understory alter tree species composition, with cascading effects on forest functions and resilience against future climate conditions. Indeed, the ungulate browsing pressure on tree seedlings is species-specific and causes contrasted growth reductions that alter tree recruitment rates. Untangling the effects of browsing from the effects of the other factors driving regeneration success is required to guide the forest and ungulate management. In particular, Fagus sylvatica L. strongly dominates temperate Quercus-Fagus forests close to their climax, and it remains unclear if controlling ungulate populations can maintain tree species diversity in naturally regenerated forests. We addressed this question by monitoring 734 pairs of fenced and unfenced 6-m2 plots across a broad gradient of Cervus elaphus L. abundance in Belgian Quercus-Fagus forests managed by continuous cover forestry. Seedling height, density, and vegetation cover were monitored from 2016 to 2021. Species diversity and ecological affinity for light, temperature, and atmospheric humidity conditions were computed from these measures. With ungulates, the mean growth of Betula pendula Roth. and Sorbus aucuparia L. was negligible, whereas, without ungulates, their growth was higher than the growth of other species. With ungulates, the growth of Fagus sylvatica L. and Picea abies (L.) H. Karst was higher than other species. Quercus (Quercus petreae (Matt.) Liebl and Quercus robur L.) growth was the lowest in all conditions. Finally, Carpinus betulus L. was heavily browsed but still grew higher than its competitors with ungulates. Ungulate browsing can then severely affect seedling growth and likely reduce the diversity of future recruited trees. In the study area, browsing unfavored the regeneration of the species that are less shade tolerant, more-drought tolerant, and more-heat tolerant. It thus accelerates the natural succession and reduces forest resilience to heat and drought events. Such an observation was found valid over a wide study area encompassing contrasting levels of Cervus elaphus L. abundance. Combining further reductions of ungulate populations with foodscape improvement is likely required to maintain species diversity in these forests.

The natural regeneration characteristics in oak forests following different methods of clearcutting

An important task for Ukrainian foresters is to adapt forests to climate change and ensure sustainable forest management. One key measure for achieving this goal is the natural regeneration of tree species, which contributes to the biological resilience of forest stands. The purpose of this study is to assess the impact of different methods of main use fellings on the natural regeneration process of tree species in oak forests. The study was conducted within the territory of the Stradch Forestry Educational and Production Complex of the Ukrainian National Forestry University. Data on the quantity and height of oak seedlings and saplings, and other tree species, were collected through observation after various methods of main use fellings were applied in oak forests. An analytical method was applied to detect patterns and differences in quantitative and qualitative indicators of young trees of different species in sample plots. Statistical data analysis was employed to establish relationships and draw conclusions based on numerical data. Different success rates of natural regeneration of tree species were identified on plots subjected to various methods of main use fellings. Positive dynamics in the quantity of seedlings and saplings were observed due to first intervention of the uniform shelterwood felling, ranging from unsatisfactory to good levels. It is recognised that the distribution of seedlings and saplings of all tree species was uneven across the area. Hornbeam has the highest frequency of occurrence – 75.6%. Tree species like Scots pine, European birch, and goat willow exhibited occurrence frequencies ranging from 30.8% to 39.7%. In general, in all the studied areas, the undergrowth of tree species was dominated by a small fraction up to 20 cm of height. To ensure the prevalence of pedunculate oak in naturally formed young stands, silvicultural care for its saplings is necessary on all plots. The obtained results provide a basis for developing scientifically grounded forest management measures aimed at increasing the quantity and quality of valuable tree species’ saplings, particularly pedunculate oak

Состояние лиственничников и перспективы выращивания лиственницы сибирской в подзоне хвойно-широколиственных лесов

For the sustainable development of society, timely and high-quality reproduction of forests is necessary with the preservation of ecosystem functions at the expense of economically valuable species, such as Larix sibirica Led. The aim of the work is to study the composition and structure of artificially created larch forests in the subzone of broadleafconiferous forests of the Kirov Region to find out the possibility, expediency and features of them for the conservation and maintenance of biodiversity, as well as timber resources. Communities were characterized from these positions by traditional silvicultural, geobotanical, ecological, and cenotic characteristics. The state of the stand was evaluated in comparison with normal stands according to M.M. Orlov. It was found that: 1) Larch stands mainly correspond to the values of normal stands of this age and are distinguished by a greater stock of wood than forests of the main forest-forming species of the region. 2) There is a tendency of natural transformation of larch forests into forests with greater participation of spruce: large undergrowth of Picea abies L., Abies sibirica Ledeb., Betula pendula L.; presence of boreal species in underbrush: Sorbus aucuparia L., Rubus idaeus L.; prevalence of boreal ecological and cenotic group (EEC) among herbs; moss cover of taiga species. 3) The main reason for community change is high density of stands. 4) Presence of non-moral ECG species, including Convallaria majalis L., which is protected in Kirov region. Increase of resource, supporting and preserving functions of forest ecosystems in the sub-zone of broadleaf-coniferous forests of Kirov region is possible and expedient by using L. sibirica in forest reproduction. To prevent transformation of larch forests into forests with spruce it is necessary to maintain illumination, for which purpose it is expediente carry out a full complex of forest maintenance cuts, especially thinning and pass logging.

ISOLATION, CHEMICAL AND SPATIAL CHARACTERIZATION OF ACIDIC POLYSACCHARIDES FROM SOME PLANTS OF SIBERIAN FLORA WITH IMMUNOTROPIC ACTIVITY

Plant polysaccharides have a wide range of biological activity, including an immunotropic effect, the degree and magnitude of which depends on the composition and tertiary structure of the macromolecule. Acidic polysaccharides (APS) were isolated by extraction with an acidic aqueous solution (pH=3) and characterized From the rhizomes of Acorus calamus L., the aerial part of Centaurea pseudomaculosa Dobrocz., the herb Conium maculatum L., and the leaves of Betula pendula Roth. The content of total carbohydrates was determined for all samples (>90%), uronic acids (24.56–53.70%) and a small amount of impurity substances (protein and nucleic acids 0.81–1.02% and 0.016–0.035%, respectively); molecular weight distribution (Mn, Mw). Structural features were studied using physicochemical and instrumental methods, such as UV and IR spectroscopy, reaction with Congo red, and scanning electron microscopy. The polysaccharides of Acorus calamus, Conium maculatum, and Betula pendula have a triple-helical conformation and bulky ultrastructure; the polysaccharides of Centaurea pseudomaculosa are characterized by the absence of a triple-helical conformation and an amorphous ultrastructure.

Chemical constituents from the bark of Betula pendula and their chemotaxonomic significance

Phytochemical investigation of the bark of Betula pendula led to the isolation of three triterpenoids (1–3), seven fatty acid derivatives (4–10), two butylbenzene derivatives (11–12), one phenylpropanoid (13), one phenolic acid (14), and one diarylheptanoid (15). The structures of these compounds were elucidated using spectroscopic methods. Compounds 3–6, 8–10, 12 and 14 serve as valuable chemotaxonomic markers for B. pendula in the Betulaceae family since there are no reports of their isolation in Betulaceae species. Additionally, compound 13 was isolated from B. pendula for the first time.

Comparison of Bioactive Secondary Metabolites and Cytotoxicity of Extracts from Inonotus obliquus Isolates from Different Host Species

Inonotus obliquus, a wood-decaying mushroom, has been used as a health-promoting supplement and nutraceutical for centuries. It is a source of bioactive compounds accumulated in both the conks (pseudosclerotia/sclerotia) and the biomass obtained in vitro. This study aimed to qualitatively and quantitatively analyze the bioelements and selected metabolites produced in mycelial cultures obtained from different host species. The mycochemical potential of mycelial cultures isolated from pseudosclerotia grown in Betula pendula, Alnus glutinosa, and Carpinus betulus was compared. Parent cultures were obtained in two types of medium (malt extract agar substrates without and with birch wood). Experimental cultures were developed in 2 L bioreactors for 10 days. The content of bioelements was determined using FAAS and FAES methods. Organic compounds were estimated using the RP–HPLC–DAD method. The cytotoxicity of the extracts was evaluated in human keratinocytes HaCaT, human skin fibroblasts BJ, human liver cancer HepG2, human melanoma A375, and mouse melanoma B16-F10. The extracts showed the presence of bioelements: sodium, potassium, magnesium, calcium, zinc, manganese, iron, and copper; phenolic acids: p-hydroxybenzoic, caffeic, p-coumaric, and protocatechuic; sterols: lanosterol, ergosterol, ergosterol peroxide; triterpene compounds: betulin, betulinic acid, inotodiol; indole compounds: L-tryptophan, tryptamine, 5-methyltryptamine, melatonin. The content of bioactive substances in the biomass was dependent on both the origin of the host species of the fungus isolate and the type of culture medium. Based on the results of this study, mycelial cultures can be proposed as a potential source of bioactive compounds and are promising naturally derived cytotoxic agents.

Histomorphological changes in the organs of the immune system of broiler chickens when using drug Betulin

Currently, much attention is paid to maintaining the health of poultry and in this regard, the role of the immune system can hardly be overestimated. Specific protective reactions are carried out by immunocompetent cells that are located in the central and peripheral organs of the immune system. The purpose of the research was to study histomorphological changes in the thymus and Bursa fabricii of broiler chickens when using the phytodrug Betulin. The histomorphological changes in the central organs of the immune system (thymus and fabricius sac) of broiler chickens when using Betulin have been presented in the article. Betulin is a natural pentacyclic triterpenoid of the lupan series. It is found in a large number of plants (hazel, calendula, licorice), but it does not occur in free form. On an industrial scale, it is extracted from birch bark – the outer layer of the bark of white birch (Betula alba), hanging (Betula pendula). Its biological activity has been confirmed in the course of scientific research in more than forty international scientific centers. The effectiveness of using triterpene compounds as direct regulators of the activity of the body’s enzymatic systems has been demonstrated. The research was carried out in the veterinary department of poultry at Siberian Scientifi c and Research Institute of Poultry – a branch of the Federal State Budget Scientific Institution “Omsk Agrarian Scientific Center” on broiler chickens of the cross Sibiryak. The chickens of the experimental groups were used Betulin from 7–21 days, the 1st experimental group at a dose of 2,5 mg/kg of live weight, the 2nd – 5,0 mg/kg, the 3rd – 10,0 mg/kg and the 4th – 15,0 mg/kg of live weight. The poultry of the control group did not receive the phytodrug Betulin. Vaccination of chickens was carried out at the age of 7 days against Newcastle disease viruses and infectious bronchitis of chickens, at 14 days against infectious bursal disease. It was found on the base histological studies that Betulin in doses of 10,0 and 15,0 mg/kg of live weight stimulated the proliferation of lymphocytes and differentiation of the central organs of the immune system of broiler chickens.

Extractable Compounds in a Birch Tree—Variations in Composition and Yield Potentials

Extractives from silver birch (Betula pendula) can play an important role in the future bioeconomy by delivering the feedstock, for instance, for antioxidative applications. It is, therefore, inevitable to gain knowledge of the distribution of extractive content and composition in the different tissues of the tree for estimating the potential volumes of valuable extractable compounds. This study examines the extractable compound distribution of different tree tissues such as outer and inner bark and wood, respectively, considering the original height of the stem and comparing the yields after Soxhlet and accelerated solvent extraction (ASE). Eleven parts of the model tree (seven stem discs and four branches) were separated into primary tissues and extracted with a ternary solvent system. The investigated extraction methods resulted in a comparable performance regarding yields and the composition of the extractives. The extractives were divided into single compounds such as betulin, lupeol, γ-sitosterol, and lupeone and substance groups such as carbohydrates, terpenes, aromatics, and other groups. The distribution of single substances and substance groups depends on the location and function of the examined tissues. Furthermore, the evidence for the correlation of a single substance’s location and original tree height is stronger for lupeol than for betulin. Primary betulin sources of the calculated betulin output are the outer bark of the stem and the branches. By using small branches, further potential for the extraction of betulin can be utilized. A model calculation of the betulin content in the current birch tree revealed a significant potential of 23 kg of betulin available as a valuable chemical resource after by-product utilization.

Susceptibility of silver birch and black alder to several Phytophthora species isolated from soils in declining broadleaf forests in western Ukraine

AbstractIn declining broadleaf forests in western Ukraine, several Phytophthora species including P. plurivora, P. bilorbang, P. polonica, P. gonapodyides and P. cactorum were recovered using soil baiting assays and identified using morphological and molecular methods. Pathogenicity tests of selected isolates were performed on black alder (Alnus glutinosa (L.) Gaerth.) and silver birch (Betula pendula Roth.) to assess susceptibility of these two tree species to the newly detected Phytophthora species. Phytophthora plurivora, P. bilorbang and P. polonica showed higher pathogenicity in both alder and birch compared to the other tested Phytophthora species.

Group variability of the morphological features of the leaf of <i>Betula pendula</i> Roth (Betulaceae, Magnoliópsida) in the gradient of weather conditions and technogenic soil transformation

The group variability of morphological features of the leaves of Betula pendula Roth was studied in the gradients of adverse weather conditions and technogenic soil transformation. The studies were carried out on the territory of the Tagil zone of the Middle Urals in 2016–2019. It has been revealed that most of the studied leaf traits have an average level of variation, while a high one is characteristic of the shape index, and a low one is characteristic of the leaf blade index and the angles between the main and lateral vein of the first order, located in the middle and upper parts of the leaf. In the gradient of deterioration of weather conditions, the variability of the features increases, whilst it decreases in the gradient of technogenic soil transformation. The morphological features making the greatest contribution to the variability of the size and shape of the leaf were identified by the method of principal component analysis. Leaf variability is mainly determined by dimensional features. Allometric features are more stable. To assess the resistance of an organism to adverse factors, it is proposed to use the stability coefficient, which reflects the number of trait transitions from one level of variability to another one. This indicator increases both in the gradient of technogenic soil transformation and in the gradient of unfavorable weather.

Does shading and ground cover of moss and litter improve germination and establishment of Betula pendula Roth, Salix caprea L. and Populus tremula L. seedlings during drought stress in climate change? – A greenhouse study

The climate change is leading to a significant increase in temperatures and dry periods in spring, for example in parts of middle and north Europe. Thus, the important factor for tree growth, the water availability, decreases on forest sites. It is to be expected that the successful establishment of pioneer tree species as pre-forests on large damaged areas will considerable be limited in the future. The phases of germination and establishment are the most dangerous phase in the life of trees. In this greenhouse study, we tested how different microsite conditions (open soil, moss and litter cover as well as different shading) under reduced water availability influence establishment success and growth of Betula pendula, Populus tremula and Salix caprea.The initial high germination success were reduced to 14%, 7% and 12% for Populus tremula, Salix caprea and Betula pendula, respectively, and the growth were significantly slower when the relevant soil water resource was just above the permanent wilting point. Therefore, in the first year the germination and establishment is linked to persistent moist conditions. If the soil dries out during germination, e.g. if there is no watering for more than 3 weeks, all seedlings died. Equivalent germination microsites (shading or ground cover) with comparable possible seedling densities to the moist open soil does not exist under water stress. Although moss and litter cover retain longer soil moisture under extremely dry conditions and guarantee significantly better seedling development than on open soil, initially significantly fewer seeds germinate on these substrate types.Radiation shows no influence on germination and seedling survival. The seedlings are able to survive radiation conditions of 3% and 27% of open area radiation. This makes establishment possible under (remaining) light canopy, at the edge of damaged areas or in small islands of remaining shelter trees on damaged areas. However, radiation had a significant effect on growth. With increasing radiation, shoot lengths and above ground biomasses are higher and the root collar diameter larger.Overall, Betula pendula is the most drought stress resistant of the tested tree species. While Populus tremula and Salix caprea already had problems establishing themselves on dry sites, the problem will become more serious under climate change. The lack of moist, vegetation-free open soils will result in a significant reduction of establishment success for tested pioneer tree species in climate change.