Pure Beech Research Articles

Interactive effects of tree species mixture and climate on foliar and woody trait variation in a widely distributed deciduous tree

Abstract Despite increasing reports of severe drought and heat impacts on forest ecosystems, community‐level processes, which could potentially modulate tree responses to climatic stress, are rarely accounted for. While numerous studies indicate a positive effect of species diversity on a wide range of ecosystem functions and services, little is known about how species interactions influence tree responses to climatic variability. We quantified the intraspecific variation in 16 leaf and wood physiological, morphological and anatomical traits in mature beech trees (Fagus sylvatica L.) at six sites located along a climatic gradient in the French Alps. At each site, we studied pure beech and mixed stands with silver fir (Abies alba Mill.) or downy oak (Quercus pubescens Willd.). We tested how functional traits differed between the two species mixtures (pure vs. mixed stands) within each site and along the climatic gradient. We found significant changes in many traits along the climatic gradient as conditions progressively got drier and warmer. Independent of the mixture, reduced leaf‐level CO2 assimilation, stomatal size and thicker leaf cuticles, consistent with a more conservative resource use strategy, were found. At the drier sites, higher foliar stable carbon isotopic composition (δ13C), thicker mesophyll tissues and lower specific leaf area (SLA) in pure stands suggest that beech had more acquisitive traits there compared to mixed stands. At the wetter sites, trees in beech‐silver fir mixtures had higher chlorophyll concentration, lower δ13C, larger xylem vessels and higher SLA, suggesting a more acquisitive resource use strategy in mixed stands than in pure stands. Our work revealed that species interactions are significant modulators of functional traits, and that they can be just as important drivers of intraspecific trait variation as climatic conditions. We show that downy oak mixtures lead to an adaptive drought response by common beech in dry environments. In contrast, in milder climates, interactions with silver fir seem to increase beech resource acquisition and productivity. These findings highlight a strong context dependency and imply that incorporating local interspecific interactions in research on climate impacts could improve our understanding and predictions of forest dynamics. A free Plain Language Summary can be found within the Supporting Information of this article.

Shifting tree species composition affects biodiversity of multiple taxa in Central European forests

Central Europe's temperate forests are heavily shaped by centuries of human activity. Their natural vegetation, mainly consisting of beech-dominated (Fagus sylvatica) deciduous forests, has been widely replaced by more profitable species grown outside of their natural ranges. This has strongly influenced forest-dwelling communities. Necessary adaptations to changing climatic conditions and the increasing demand for forest ecosystem multifunctionality are reversing these shifts in tree species composition. Integrative approaches that seek to balance production and conservation goals promote mixed forests of beech with spruce (Picea abies), pine (Pinus sylvestris), or oak (Quercus spp.). These mixed forests more closely resemble the natural vegetation and have reduced vulnerability to disturbances compared to coniferous monocultures, but higher commercial value compared to pure beech forests. However, our understanding of how different levels of admixture of commercially relevant tree species to beech forests affect multi-trophic diversity and community composition remains limited.We investigated herbaceous plants, fungi, oribatid mites, springtails, true bugs, beetles, birds and bats in 41 mature forest stands differing in tree species composition. We assessed the effects of admixtures on abundances and alpha and gamma diversity, i.e. the total number of species per forest type, and a measure of multidiversity by comparing reference beech stands with stands containing varying proportions of admixed species. At the plot level, the proportion of admixtures was especially important regarding oak and pine. Increasing shares of oak positively affected birds, true bugs and herbivorous beetles. Increasing shares of pine benefitted herbivorous true bugs and understory plants but negatively affected other true bugs, bats, and litter-decomposing fungi. Spruce admixture resulted in higher saproxylic beetle and bird diversity. At the landscape level, admixture significantly increased gamma diversity in plants, mycorrhizal and litter decomposing fungi and herbivorous and saproxylic beetles. Only springtail gamma diversity decreased in the presence of admixture. Admixture also significantly altered community composition for six out of 13 taxa. Indicator species were found for all forest types, and seven species groups included species significantly associated with pure beech stands.Our results indicate that forestry decisions determine forest biodiversity across trophic levels via tree species composition, combining habitat heterogeneity effects and tree species-specific associations. Even low shares of admixed species affect local abundances and diversity. By displacing some species while benefitting others, admixing also alters community composition. This study provides a basis for estimating how altering tree species composition in Central European forests changes the diversity and composition of forest communities.

Limited sink but large storage: Biomass dynamics in naturally developing beech (Fagus sylvatica) and oak (Quercus robur,Quercus petraea) forests of north‐western Germany

AbstractCurrently, the dynamics underlying the storage and acquisition of biomass, and thus carbon, in naturally developing forests are under debate. A better understanding of the biomass dynamics of forests is needed to clarify the role played by naturally developing forests in the mitigation of climate change.Long‐term monitoring data from unmanaged strict forest reserves (SFRs) in north‐western Germany were used to analyse the biomass dynamics of pure beech, mixed beech and mixed oak forests. A complete balance of above‐ground woody biomass (biomass) and growth, density‐dependent and ‐independent mortality, as well as deadwood decay was derived. Density‐independent mortality served as a proxy for disturbance severity.After a time since abandonment (TSA) of 50 years, the average biomass ranged between 334 t/ha in mixed oak and 478 t/ha in pure beech stands. The net change in biomass was positive in all forest types. Density‐independent mortality and decay rates were much lower than the growth rates. Pure beech forests reached higher levels of biomass, a higher net change in biomass, and more growth than either of the mixed forest types. Biomass increased linearly with TSA in pure beech stands but followed an asymptotic course in the mixed forests. In the latter, the net change in biomass and growth were consistent with a unimodal development pattern. The development of biomass could not be explained by the ageing of the tree communities.Synthesis. We hypothesized that the observed biomass dynamics are a result of the interaction between resource supply within a limited growing space and the resource‐use efficiency of the tree stand in conjunction with disturbances. The still‐linear increase in the biomass of pure beech forests was assumed to reflect the high resource‐use efficiency of beech, especially its use of light. The above‐ground capacity of naturally developing broadleaved forests to store and acquire carbon is substantial. Accordingly, allowing broadleaved forests to develop naturally can contribute substantially to carbon storage and sequestration. However, our study also suggests that the above‐ground carbon sink decreases after several decades.

An Investigation of Flexural Behavior of Pure and Hybrid Wood Composite Panels Using Weibull Analyses

The production of inexpensive wood products compared to their strength is important both in terms of economy and meeting the expectations of users. For this purpose, the use of hybrid wood products is increasing in the furniture industry. With the hybridization process, relatively cheap and flimsy material is combined with a material that has a stronger structure. Thus, stronger bonded material is manufactured cheaper. In this study, the flexural behavior of pure and hybrid wood composite panels, which were prepared by applying longitudinal jointing techniques from different wood materials, was investigated. In this context, pure chipboard, pure medium density fiberboard (MDF), chipboard-east beech and MDF-east beech hybrid wood composite panels were produced. During the hybridization process, oriental beech was combined by using the self-grooving technique in three different numbers as one row, two rows, and three rows. Flexural test results were analyzed according to the Weibull distribution method. The results of the analyses showed that the hybridization process increased the flexural strength and flexural modulus of pure wood panels by up to 214 %, and 95 %, respectively.

Distribution of the timber quality attribute \u2018knot surface\u2019 in logs of Fagus sylvatica L. from pure and mixed forest stands

Research on mixed forests has mostly focused on tree growth and productivity, or resistance and resilience in changing climate conditions, but only rarely on the effects of tree species mixing on timber quality. In particular, it is still unclear whether the numerous positive effects of mixed forests on productivity and stability come at the expense of timber quality. In this study, we used photographs of sawn boards from 90 European beech (Fagus sylvatica L.) trees of mixed and pure forest stands to analyze internal timber quality through the quality indicator knot surface that was quantitatively assessed using the software Datinf® Measure. We observed a decrease in knot surface with increasing distance from the pith as well as smaller values in the lower log sections. Regarding the influence of neighborhood species identity, we found only minor effects meaning that timber qualities in mixed stands of beech and Norway spruce (Picea abies (L.) H. Karst.) tended to be slightly worse compared to pure beech stands.

Local characteristics of the standing genetic diversity of European beech with high within-region differentiation at the eastern part of the range

Developing “climate smart forestry” (CSF) indicators in mountain forest regions requires collection and evaluation of local data and their attributes. Genetic resources are listed among the core indicators for forest biological diversity. This study is a report on the evaluation of the standing genetic diversity within and across 12 pure beech stands (Fagus sylvatica L.) established within the CLIMO (CLImate Smart Forestry in MOuntain Regions) project, using nuclear microsatellite markers. The sampling sites were set along the species’ distribution range, including the Balkan region and extending towards the Iberian Peninsula. Cores or leaves from 20 to 23 old, mature trees per plot were sampled for DNA analysis. Genetic diversity indices were high across the range (HE = 0.74−0.81) with the highest in the Bosnian Mountains. Genetic divergence increased significantly with the geographical distance (Mantel test: r = 0.81, p < 0.001). Most of the stands exhibited an excess of heterozygotes, with the highest value at the Hungarian site (HO/HE = 1.177), where beech persists close to the eastern xeric limit of the species’ distribution. STRUCTURE revealed within-region differentiation in the Balkan Peninsula, where the Bulgarian stand was the most outstanding. The genetic parameters of each stand could be assessed as a resource for CSF indicators interpreted especially at the local level.

Monoculture and mixture-planting of non-native Douglas fir alters species composition, but promotes the diversity of ground beetles in a temperate forest system

Planting non-native tree species, like Douglas fir in temperate European forest systems, is encouraged to mitigate effects of climate change. However, Douglas fir monocultures often revealed negative effects on forest biota, while effects of mixtures with native tree species on forest ecosystems are less well understood. We investigated effects of three tree species (Douglas fir, Norway spruce, native European beech), on ground beetles in temperate forests of Germany. Beetles were sampled in monocultures of each tree species and broadleaf-conifer mixtures with pitfall traps, and environmental variables were assessed around each trap. We used linear mixed models in a two-step procedure to disentangle effects of environment and tree species identity on ground beetle abundance, species richness, functional diversity and species assemblage structure. Contradictory to our expectations, ground beetle abundance and functional diversity was highest in pure Douglas fir stands, while tree mixtures showed intermediate values between pure coniferous and pure beech stands. The main drivers of these patterns were only partially dependent on tree species identity, which highlights the importance of structural features in forest stands. However, our study revealed distinct shifts in assemblage structure between pure beech and pure Douglas fir stands, which were only partially eased through mixture planting. Our findings suggest that effects of planting non-native trees on associated biodiversity can be actively modified by promoting beneficial forest structures. Nevertheless, integrating non-native tree species, even in mixtures with native trees, will invariably alter assemblage structures of associated biota, which can compromise conservation efforts targeted at typical species composition.

Dynamics of humus forms and soil characteristics along a forest altitudinal gradient in Hyrcanian forest

Humus forms are good indicators of environmental conditions and thus important in forest ecological processes. Altitudinal gradients are considered as natural laboratory for evaluating soil ecological processes and humus form distribution. The objective of this study was to evaluate the macromorphology of humus forms along an altitudinal gradient (0-2000 m a.s.l.) covered with plain forest, mixed and pure forests and forest-grassland ecotone, in Alborz Mountains in northern Iran. In total, 225 humus profiles were evaluated. Forest stand variables including tree density, basal area, crown density, and height, forest floor and soil physico-chemical properties along with biological features were measured. We found that altitudinal gradients influence both humus forms distribution and soil properties but with different mechanisms. While soil properties (i.e., temperature, pH, CaCO3, soil N content, soil C/N and microbial biomass N) were significantly correlated with altitude, the forest floor properties were more influenced by tree species composition. Particularly, the abundance of Mull was decreased in plain mixed forests compared to mountain pure forests, whereas the frequency of Amphi was increased. Moreover, Oligomull and Leptoamphi were abundant in mixed beech forests, while Eumacroamphi, Eumesoamphi and Pachyamphi were only observed in pure beech forests. Such a distribution influenced soil fertility where higher values of nitrogen (N), microbial biomass nitrogen (MBN) and pH were observed at lower altitudes under mixed forests compared to pure forests at higher altitudes.

Microbial soil biodiversity in beech forests of European mountains

Fagus sylvatica L. is widely distributed across Europe thanks to its high adaptability in a wide variety of soils and climate. Microbial communities are essential for maintaining forest soil quality and are responsible for forest ecosystem functioning; the ability of soil microorganisms to respond to abiotic stressors (e.g., organic carbon losses, water scarcity, temperature changes) is crucial under ongoing environmental changes and also supports tree health. In this study, soil samples were collected from pure beech plots as part of the COST Action project CLIMO to find differences in microbial community characteristics and evaluate the effects of soil properties on microbial communities across gradients of elevation, latitude, and longitude. Positive relationships were found between organic carbon content and both microbial abundance and dehydrogenase activity. Dehydrogenase and catalase activities were elevation-correlated and microbial activities were longitude-correlated. In the most southern beech plot, the microbial community was abundant and displayed high activities. This shows that microbial communities could help tree populations to better adapt to predicted changes in environmental conditions in the future. We suggest that research into forest health and beech performance should also test soil microbial enzymatic activity, particularly under changing climate conditions, to assist in identifying adaptation strategies.

Analyzing the effect of silvicultural management on the trade-off between stand structural heterogeneity and productivity over time

This study combined an empirically based simulation with an analysis of the trade-off between structural heterogeneity and stand productivity depending on time, spatial scale, and silvicultural management, whereas volume growth and tree species diversity have been examined in detail, the role of forest structure and its interdependencies with stand productivity has only lately become a stronger research focus. We used the growth simulator SILVA to examine the development of stand structural heterogeneity and its trade-off with stand productivity in age-class versus uneven-aged pure and mixed spruce and beech stands at different spatial scales over 100 years. Those stands were based on typical forest types in Bavaria and were representative of forests in Central Europe. We examined how stand structure and its trade-off with productivity were modified by a multifunctional, a production-oriented, and a set-aside management scenario. The production-oriented management scenario applied to uneven-aged stands led to a reduction in structural heterogeneity per unit of productivity over time. In age-class stands, the production-oriented scenario was able to maintain the initial structural heterogeneity. The structural heterogeneity per unit of productivity increased more strongly with increasing spatial scale in age-class stands compared to uneven-aged stands. Combining forest stand simulation with scenario analyses is an exemplary method for testing the effect of silvicultural management alternatives on forest structure. This approach can later be connected to climate models considering long-term changes in growing conditions and support the planning of multifunctional forests.

Long-term tending effect on static stability of pure beech (Fagus sylvatica L.) stands

The production stability together with the provision of required functions are the key requirements for the future existence of stable forest stands. Sufficient mechanic stand stability could be developed by the early and long-term thinning where basic tree characteristics, such as stem and crown parameters play the decisive role. We compared selected parameters of static stability in pure beech stands, which have been exposed to heavy low thinning and free-crown thinning with control stands without interventions. Data from twenty-seven long-term research subplots at eight localities across Slovakia were involved in this study. In total 7 693 trees between 30 and 110 years were analysed. Slenderness (h/d ratio), crown length, crown width and crown ratio proved to be the most explanatory parameters for the defining mechanical stability on subplots with free-crown thinning. We found the least favourable results on control subplots. The differences between the subplots with tending (regardless of the tending method) and the control subplots were statistically significant in all studied parameters (P < 0.05).

Crown structure of European beech (Fagus sylvatica): a noncausal proxy for mechanical–physical wood properties

The current tendency towards the silvicultural promotion of mixed tree species has increased the variability in the crown structure within stands. This study shows how neighbouring trees can influence both the external crown features and internal wood properties of trees. Using terrestrial laser scanning, the crown features of 100 European beech trees (Fagus sylvatica L.) from pure beech stands and mixed stands of beech with Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) Karst.), sessile oak (Quercus petraea (Matt.) Liebl.), and Scots pine (Pinus sylvestris L.) were recorded. After felling and sawing, the dynamic modulus of elasticity was determined on 1623 boards from the two lowest 4.1 m logs. Significant differences were found between beech trees from pure stands and those from beech–pine mixed stands in terms of crown volume (415 vs 766 m3), crown ratio (50.0% vs 71.5%), crown projection ratio (0.182 vs 0.253 m·cm−1), and branch angle (30.7° vs 54.1°). Multiple regression mixed models revealed significant relationships between timber stiffness and crown volume (–1.7 N·mm−2·m−3), crown ratio (–28.4 N·mm−2·%−1), and crown projection ratio (–9835 N·mm−2·m−1·cm). Thus, the crown morphology of broad-leaved species reflects the tree’s long-term competitive status and suggests indicators for the assessment of mechanical–physical wood properties.

Composition of soil bacterial and fungal communities in relation to vegetation composition and soil characteristics along an altitudinal gradient.

The objective of the present study was to evaluate how altitudinal gradients shape the composition of soil bacterial and fungal communities, humus forms and soil properties across six altitude levels in Hyrcanian forests. Soil microbiomes were characterized by sequencing amplicons of selected molecular markers. Soil chemistry and plant mycorrhizal type were the two dominant factors explaining variations in bacterial and fungal diversity, respectively. The lowest altitude level had more favorable conditions for the formation of mull humus and exhibited higher N and Ca contents. These conditions were also associated with a higher proportion of Betaproteobacteria, Acidimicrobia, Acidobacteria and Nitrospirae. Low soil and forest floor quality as well as lower bacterial and fungal diversity characterized higher altitude levels, along with a high proportion of shared bacterial (Thermoleophilia, Actinobacteria and Bacilli) and fungal (Eurotiomycetes and Mortierellomycota) taxa. Beech-dominated sites showed moderate soil quality and high bacterial (Alphaproteobacteria, Acidobacteria, Planctomycetes and Bacteroidetes) and fungal (Basidiomycota) diversity. Particularly, the Basidiomycota were well represented in pure beech forests at an altitude of 1500m. In fertile and nitrogen rich soils with neutral pH, soil quality decreased along the altitudinal gradient, indicating that microbial diversity and forest floor decomposition were likely constrained by climatic conditions.

Microclimatic Tipping Points at the Beech–Oak Ecotone in the Western Romanian Carpathians

European beech (Fagus sylvatica) is a drought-sensitive species that likely will retreat from its xeric distribution edges in the course of climate warming. Physiological measurements indicate that the species may not only be sensitive to soil water deficits, but also to high temperatures and elevated atmospheric vapor pressure deficits (vpd). Through microclimatological measurements in the stand interior across near-natural beech forest–oak forest ecotones, we searched for microclimatic tipping points in the contact zone with the aim to define the thermic and hydrometeorological limits of beech more precisely. In three transects in the foothills of the Romanian western Carpathians, we measured in mid-summer 2019 air temperature, relative air humidity, and vpd at 2 m height in the stand interior across the ecotone from pure oak to pure beech forests, and compared the readings to the microclimate in forest gaps. Mean daytime temperature (T) and vpd were by 2 K and 2 hPa, respectively, higher in the oak forests than the beech forests; the extremes differed even more. Especially in the second half of the day, the oak forests heated up and were more xeric than the beech forests. Part of the differences is explained by the elevation difference between oak and beech forests (200–300 m), but species differences in canopy structure, leaf area, and canopy transmissivity enhance the microclimatic contrast. Our T and vpd data point to thresholds at about 30 °C and 25 hPa as maxima tolerated by beech in the lowermost shade canopy for extended periods. In conclusion, the rather sharp stand microclimatic gradient demonstrated here for the xeric distribution limit of beech may well be the decisive factor that hinders the spread of beech into the warmer oak forests.

Comparison of different bonding parameters in the production of beech and combined beech-spruce CLT by standard and optimized tests methods

Interest in the use of beech wood in construction is growing steadily. Considering its high mechanical performance, it has a large potential to be used for the production of glued timber structural products. However, the issue of structural bonding remains to be solved before effective production and safe use of beech wood in these products can be achieved. Three adhesives (one-component polyurethane – PUR, PUR + primer and melamine-urea–formaldehyde – MUF) and two press systems (hydraulic and vacuum press) were explored in the production of pure beech and combined beech-spruce-beech cross laminated timber (CLT). An evaluation of the bonding quality was performed with both standardized and optimized (the specimen layers were oriented with the wood grain forming an angle of 45° with respect to the load application) delamination and shear test methods.None of the adhesives that were tested met the requirements for delamination tests provided by the current standard for softwood. Specifically, PUR yielded the poorest performance in the production of the CLT panels entirely made of beech; the addition of a primer improved the bonding, achieving results comparable to those observed for MUF. On the contrary, in the production of beech-spruce panels, the three adhesives showed similar results. The press system was not a relevant factor in terms of bonding quality.In regard to testing, a size effect was noticed in the delamination test: the larger the specimen the greater the delaminations that were observed. The shear tests on dry specimens proved to be less efficient in determining the influence of the several bonding parameters, even if a 45° grain orientation seemed to reduce the rolling shear during the shear test and to improve the response of the test in this regard. Combining delamination pretreatment and shear made the test more sensitive and objective.

Structural and ecological characteristics of mixed broadleaved old-growth forest(Biogradska Gora - Montenegro)

Biogradska Gora National Park in Montenegro is part of the Dinaric Mountains mixed forest, which belongs to the montane region of the Dinaric Alps. This paper presents some of the main structural and ecological characteristics of the mixed broadleaved old-growth forest with beech [Fagus moesiaca (Domin, Maly) Czecz.], sycamore maple (Acer pseudoplatanus L.) and European ash (Fraxinus excelsior L.) from the preserve area of the Biogradska Gora. These forest ecosystems are characterized by the high species richness and potential productivity. In the study area, 58 vascular plant species were recorded in 4 sample plots of 0.25 ha each. The average timber volume found in the sample plots was 814 m(3)/ha. This value is twice as high as that of similar pure beech forests in the same preserve area. The results are confirmed the biodiversity and production potential of mixed broadleaved forests, which rarely occur spontaneously. A better understanding of the processes of the pristine forest ecosystems could form a realistic basis for close-tonature management of similar stands. The obtained data provides overview of the structural characteristics of these forests, which have developed without anthropogenic influence. Exploring the structure of forests in permanent preservation areas could be an excellent basis for close-to-nature forest management.

Foliar P nutrition of European beech (Fagus sylvatica L.) depends on the season but remains unaffected by co-cultivation with silver fir (Abies alba Mill.)

Beech (Fagus sylvatica) and silver fir (Abies alba) are often cultivated in mixed stands and, hence, compete for water and nutrients. Besides nitrogen (N), also phosphorus (P) is an important nutrient for growth and development. Beech trees in Central Europe grow on both P-poor and P-rich soils, thereby showing similar growth and low variation in foliar P. The central aim of the present study was to test the hypothesis that variations in foliar P contents of beech are driven by seasonal changes rather than by the competition with silver fir. It was further hypothesized that P contents in silver fir needles depend on needle age and forest site. To test these hypotheses, P contents and P fractions, i.e. organic-bound P (Porg) and inorganic phosphate P (Pi), were measured in the foliage of beech trees from pure beech and mixed beech/silver fir plots as well as in needles of silver fir of the mixed plots. The forest sites investigated are located in Central Europe in the Black Forest, Germany, and in Croatia near the south-eastern distribution limit of beech and are all poor in plant-available soil P. The analyses showed that the main driver of P contents and P fractions in beech leaves at all forest sites is the season and that competition with silver fir had no effect. Hence, the present results demonstrate the high plasticity of beech trees to adapt to both poor plant-available soil P and competition with silver fir. Total P contents of silver fir needles were higher at the Croatian site compared to the Black Forest sites and originated from higher foliar Pi contents. One third of the P present in current-year needles in late summer was remobilized and exported until the needles reached the age of 1 year. The difference in P contents between current-year and 1-year-old needles can be seen as the amount of P resorbed from 1-year-old needles in summer during the generation of new needles to support the P demand of current-year needles for growth and development.

Impact of species mixture on the stiffness of European beech (Fagus sylvatica L.) sawn timber

European beech (Fagus sylvatica L.) is the most commonly occurring deciduous tree species in Central Europe. Because of its competitiveness and (morphological) variability, it occurs in different species mixtures. The aim of the present study was to determine whether, and to what extent, the internal wood properties of European beech are affected by species mixture. Logs obtained from 100 beech trees from the low-mountain Spessart region in Germany were sampled and subdivided into five equal groups representing different mixture types: pure beech stands and four beech stands with the following tree species, respectively: Pseudotsuga menziesii, Picea abies, Pinus sylvestris and Quercus petraea. After logging and sawing, the boards were graded according to strength. For this purpose, the dynamic modulus of elasticity (MOEdyn) was determined. The MOEdyn, which is a relevant property for wood quality in the construction sector, was regressed against various independent variables, such as cambial age or mixture type. Relevant differences in wood quality were observed between mixture types. Beech trees in monocultures had the highest stiffness. In particular, species mixture with the light-demanding Quercus petraea or Pinus sylvestris yielded a significant reduction in the stiffness of the beech timber (–10% and –14%, respectively). Therefore, beech glued laminated timber of higher strength classes (≥GL 40c) was not viable using beech from these mixture types. The findings of this study also revealed significant effects of axial board position and cambial age on MOEdyn. The present transformation of forests into mixed forests affects the quality of the wood. Future research should focus on the dependencies between varying growth conditions—also caused by climate change—and wood formation.

Evaluating different spatial interpolation methods and modeling techniques for estimating spatial forest site index in pure beech forests: a case study from Turkey.

Spatial interpolation methods are widely used to estimate some ecological and environmental parameters that are difficult to measure. One of these parameters is forest site index, which is a demonstration of forest productivity. The aim of this study was to estimate forest site index in a beech forest ecosystem in Turkey. In this context, soil characteristics, stand parameters, and topographic features were measured in 70 temporary sample plots of beech forest stands. Forest site index of beech forest stands was predicted using different modeling techniques such as multiple regression analysis (MLR), multilayer perceptron (MLP), radial basis function (RBF), multiple regression kriging (MLRK), multilayer perceptron kriging (MLPK), and radial basis function kriging (RBFK). The results showed that the RBFK (R2 = 0.98) and MLRK (R2 = 0.96) outperformed the others to predict forest site index in the study area. The greatest improvement occurred when krigged residual used with MLR, which increase from 0.23 to 0.96. Thus, MLRK method significantly improved the prediction accuracy for site index. The models combined with krigged residuals were more successful than those used without krigged residuals. The results of this study suggest that the combined methods may help obtaining improved site index maps for forest management.

Старовікові ліси та праліси Українських Карпат: геопросторова структура та перспективи збереження

The article presents the results of geospatial analysis of natural forests of the Ukrainian Carpathians, among which two categories are distinguished – virgin forests and old-growth forests. Field identification of natural forests was carried out in accordance with the criteria and indicators defined by the Carpathian Convention. In total, such forests cover almost 95 thousand hectares in the region, most of which grow within the Zakarpattia region. Most of the natural forests are preserved in the ecoregions of the Polonyny Borzhavy-Krasnoi (17.6 thousand ha) and Central Gorgany (13.2 thousand ha). At the same time, the largest share of natural forests in the total forested area (more than 20 %) was revealed within the ecoregions of Polonyny Borzhavy-Krasnoi, Rakhiv crystalline polonyny and Chyvchyn crystalline polonyny. About 58 % of all identified natural forests are beech-dominated stands, 70 % out of which are pure beech stands. About one-third of the virgin and old-growth forests are spruce stands, which are attributed to the middle-mountain ecoregions. About 5 % of the total area is covered by mountain pine forests, which are mostly monodominant. It was found that currently less than half of the natural forests occur within different types of protected areas, and therefore are protected. About 49 % of all virgin and old-growth forests grow within the 22 sites of the Emerald Network in the Ukrainian Carpathians. At the two key study areas we analyzed the possibility of improving the connectivity of the Emerald Network using natural forest massifs. In some places this possibility is limited by the significant intensity of forest cover loss in the region, including some due to the cuttings. In general, within the identified natural forests, the loss of forest cover was recorded on an area of about 1 800 ha. It was found out also that in 2016–2018, the volume of losses in natural forests increased, while within all forested areas of the Ukrainian Carpathians, it has decreased. Key words: virgin forests, old-growth forests, geospatial analysis, Emerald Network, Ukrainian Carpathians.