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A precise merchantable stem volume model of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] is missing in the Czech Republic. The aim of this study was to fit a new model through the reparametrization of volume equations (used in the Czech Republic or in other countries). We tested four volume equations (two from the Czech Republic, one from France and one from British Columbia) in the form of a nonlinear least squares model (NLS), weighted least squares model (WLS), and nonlinear mixed effects model (NLME). In all the tested models, the diameter at breast height of a tree and the total height of a tree were used as independent variables. Models were fitted on a dataset of 185 felled sample trees from eleven research areas with ages between 19–113 years. We have found that the model according to Omule et al. (1987) fits the merchantable stem volume as the best in the version of WLS model. Median value of the relative error of the final model was only –0.53%, which is less than the errors of models which are still used in the Czech Republic today.

The ecological significance of Scots pine (Pinus sylvestris L.) in Europe, especially in areas devastated by bark beetles, has led to its consideration as a substitute for Norway spruce. This pioneering species boasts sun and drought tolerance, fast growth, and wood industry value. To gauge its potential, we examined two ecotypes across two test sites over two years, focusing on height and growth increment. Through statistical analysis employing R software and linear mixed models, we assessed heritability, genotype by environment interaction, and spatial correlations. Both ecotypes exhibited significant differences in height and increment, varying by year and site. Heritability was higher in the second year, with increment showing greater stability. Genetic correlations between sites were evident, suggesting stable increment ranking across locations. These findings underscore the role of ecotypic variation in Scots pine growth, advocating for its consideration in reforestation. Acknowledging such dynamics is vital for effective forest management and reforestation in Central Europe, promoting sustainability and informed decision-making. Further research will enhance this understanding of preserving and enhancing the region's tree populations.

Lymantria dispar, a well-known defoliating pest species, also presents a health challenge due to the allergenic potential of its hairs, making it interesting to study from various perspectives. As chemical control methods decline in popularity, the search for effective natural enemies of this pest, such as predators, parasites and parasitoids, are expanding. On this occasion, we report the discovery of the primary parasitoid Glyptapanteles liparidis and the secondary parasitoid Gelis areator for the fauna of Slovenia. Illustrations and a short biology are given for both species.

Castanea sativa is a type of cultivated chestnut tree found in the Czech Republic, growing in both lowland and midland regions. These trees are usually planted individually or in pairs, with over half of the plantings located in urban areas. One-fifth of chestnut trees thrive in parks, while chestnut orchards or forest stands make up only one-tenth of the areas where chestnut trees are located. In the Czech Republic, approximately 30 ha are covered by chestnut trees. Regeneration of chestnut trees occurs in only 6% of the localities due to regular lawn mowing. However, 40% of the surveyed forests showed signs of regeneration, demonstrating the species' ability to regenerate under Central European climate conditions.

Grey poplar (Populus × canescens) is a natural hybrid of white poplar (Populus alba L.) and Eurasian aspen (Populus tremula L.). It could play a significant role in the afforestation of marginal sites which stretch out on ever more areas due to the negative effects of local climate change. Based on stand structure analyses of grey poplar stands grown on the sandy sites of Hungary, the following relations were found: There is a strong relationship between tree height and stand volume (R² = 0.7256), as well as between basal area per ha and stand volume (R² = 0.9158). There is a moderate relationship between diameter at breast height and stand volume (R² = 0.6175). The results could contribute to a more accurate assessment of applied silvicultural technologies.

In forest protection, various types of trap systems are used against spruce bark beetles to treat the foci of infested areas. Traditionally, these include pheromone traps, treated trap trees, and recently also the application of Storanet insecticide nets used for the sanitation of infested wood (trees), which also serve as treated trap trees when pheromones are applied, and the Trinet P system, a variation to a treated trap tree – a tripod. On an aluminium tripod, there is a Storanet insecticide net baited with a pheromone dispenser similar to other types of trap systems. The sex ratio proves to be a significant aspect in the assessment of individual types of trap systems. It is more favourable to catch a larger number of female individuals given that they bear the future development of the population. With a higher number of captured male individuals, the number of females per one male in the insect gallery increases, and the population cannot be reduced sufficiently. The results show that all three types of measures can be characterised by a lower ratio of captured males (approximately 40%) and a higher representation of females (around 60%). Differences in individual types of trap systems are insignificant.

Forests represent the most important source of ecosystem services (ES) on a global level both for the production of goods and for the provision of services and externalities, nevertheless scientific research in the economic field is lacking. Currently the number of documents relating to ES is 16 673, of which only 1 379 concern the forestry sector. The aim of this study is to provide an overview of scientific research trends in the field of economic evaluation of forest ecosystem services (FES). To this end, an on-line bibliographic survey was carried out on the main scientific search engines, which made it possible to quantify the works and at the same time to detect the main evaluation methods used for the different FES. This survey allowed to collect 93 articles meeting the search criteria: the most active continents were Europe and Asia, whereas most of the articles focused on the joint evaluation of provisioning, regulation and cultural services, even if a good number of them only concerned cultural services. The most widely used valuation methodologies were the contingent valuation among the stated preference techniques and the market price among direct observation criteria.

The exact determination of the rotation period is still a current and important essential issue of forestry. It attracts the attention of forest economists, managers and owners worldwide, not only of forest economists but also of forest managers. The rotation period is defined by physical, technical or financial parameters of forest management. Therefore, it is necessary to distinguish between the biological and the economic optimal rotation period. A fundamental challenge in forest management is the need for appropriate determination of the rotation period. The primary interest of our research was to compare the effective legislation for the determination of the rotation period in the Czech Republic and in the Slovak Republic. Scientific methods such as document analysis and questionnaire survey were applied. The results of the legislation analysis and other related documents were compared with the expert opinions of the relevant stakeholders. Those who affect the decision process related to the problem and those where are "affected" by the problem were involved in the study. Results show that respondents do not agree with the regulation of rotation period according to effective law. Moreover, they consider it as not usable as the conditions in forest ecosystems have changed recently, which is not considered in the legislation.

The aim of the study was to assess the current state of silver birch (Betula pendula Roth.) stands in Ukrainian Polissya, as well as to identify optimal composition resulting in productive and resilient mixed birch forests. It was found that in forests managed by the State Forest Resources Agency of Ukraine, birch stands grow on an area of 352 800 ha, covering 5.6% of the total area of forests in Ukraine. Within the study region of Ukrainian Polissya, birch stands cover 294 900 ha making 12.3% of the total forest area. Naturally originated birch stands were found to dominate in the study region, with 65.4% of vegetative stands and 25.2% of those grown from seeds. However, planted stands significantly prevail in terms of growing stock as compared to natural ones. In Ukrainian Polissya, silver birch trees grow as a part of mixed pine and birch forests on 632 400 ha. Our study found that mixed pine and birch stands with 80-90% of Scots pine and 20-10% of silver birch in the composition are the most productive.

Teak has been planted extensively by smallholders in Central America within reforestation programmes and has become one of the most valuable timbers. The five-year growth and mortality of teak cultivated in a plantation in central Nicaragua, representing sites at the low limit of teak ecological valence, were evaluated. From 2006 to 2010, 72 pure teak stands were established, with 48.93 ha in total. For afforestation, planting stock from five provenances was used and planted at 1 m × 1 m spacing to stimulate the height growth and reduce broad crowns formed by self-pruning. In the pure teak stands, 144 permanent sample plots of 0.01 ha in size were established in 2011. From 2011 until 2015, the tree height and stem girth of all individuals in the studied sample plots were measured, and mortality based on the stand density was assessed. Significant differences between the provenances were observed. The highest growth was noted in the Local provenance originated from the studied area, whereas the Semilla provenance from Costa Rica, characterised by the lowest growth ability, was characterized by lower radial increment and mean tree height with high mortality.

Forest structure is a key component of its management and assessment in every forest ecosystem. In the study, 23 plots were established to obtain data on the acacia forest community based on tree size. Results from the study indicated that the acacia community could be broadly divided into two groups based on tree-size variables. The diameter and height frequency distributions of Group 1 were right-skewed, while those of Group 2 were more complicated. In both groups, there were positive correlations between tree-size variables, nonetheless the relationship between diameter at breast height and total height was best described using the cubic equation. Further, the Weibull and Sinh-Arcsinh (SHASH) best simulated the diameter and height frequency distribution. High-quality trees were found in a large diameter (> 30 cm) and height groups (> 22 m). In contrast, low-quality plants often concentrated on the smallest sizes. Therefore, trees with a diameter of 2–10 cm and a height lower than 8 m should receive attention to tend. Carbon stock in the two groups was 61.48 Mg·ha^–1 and 64.21 Mg·ha^–1, respectively. Tending solutions and measurements should be carried out regularly to promptly propose silvicultural measures and improve forest quality in future.

Forest cover plays an important role in terms of biodiversity and the environment. The Beni Salah national forest in its part which is located in the Guelma province in the extreme northeast of Algeria is an illustrative example where forest fires represent the chronic phenomenon which weighs heavily on this forest. The present study comes after a forest fire that occurred in 2021, when 3 000 ha of this forest were ravaged by forest fires according to the conservation of forests of Guelma. The main objective of this research is to map the severity of burns and estimate the severely burned area using Sentinel-2 satellite images based on remote sensing indices such as Normalized Difference Vegetation Index (NDVI), Differenced Normalized Difference Vegetation Index (dNDVI), Normalized Burn Ratio (NBR), Differenced Normalized Burn Ratio (dNBR), Green Normalized Difference Vegetation Index (GNDVI), Differenced Green Normalized Difference Vegetation Index (dGNDVI), Burn Area Index (BAI) and Relativized Burn Ratio (RBR). The result obtained revealed that 28.23% of the study area represents a seriously burned area. The established burn severity map is a real decision-making tool, but it still has certain limitations.

Silver fir (Abies alba Mill.) is still counted among drought-tolerant tree species. However, its ability to cope with the recent extremely dry period has not yet been sufficiently studied. The objective of research was to analyse differences in the climate-growth response between silver fir, Norway spruce (Picea abies L. Karst.) and European larch (Larix decidua Mill.) growing in areas with large-scale disintegration of spruce stands. In 2019–2021, the increment cores were sampled at 16 sites along the altitudinal gradient of 340–775 m a.s.l. in different regions of the Czech Republic affected by bark beetle outbreak. The radial growth pattern of fir was compared with that of spruce or larch growing under the same site conditions. In fir, the missing rings were frequently recorded during the period of peak SO₂ pollution load in 1966–1985, but they were rarely identified in recent years. In spruce and larch, missing rings were less common and occurred mainly in the recent dry period after 2015. Fir was less sensitive to summer drought compared to larch and especially to spruce, which showed high sensitivity to summer drought regardless of the altitude. The significant positive response of fir to summer precipitation was recorded at sites up to 450 m a.s.l., however, its sensitivity to drought has increased in the last two decades. Hence, when considering the wider use of fir, it is necessary to respect its ecological requirements as much as possible in order to preserve its vitality and production potential in changing climatic conditions.

Litterfall of silver fir contributes to development of forest floor similarly like Norway spruce litterfall does. The nutrient return to soil can be intensified by mixing these conifers with other tree species whose effects on soil are positive; our study deals with European rowan. The study aimed at firs and rowans in alternating rows (Fi-Ro) compared to the monospecific plantation of fir (Fi) at two former meadow sites with the stands of 20 and 17 years of age, respectively. Both organic forest floor and its mineral subsurface were sampled. Rowan admixed to the silver fir plantation improved both the uppermost layer and the topsoil as higher pH, more favourable soil-sorption properties and higher plant available magnesium were found below Fi-Ro compared to Fi. Fine dry matter was higher below Fi, which was reflected in higher organic carbon (C_ox), combustible matter and nitrogen pools. Besides the effects of trees on the soil, silvicultural issues such as renewal costs and tree species performance in monospecific and mixed stands were presented and discussed.

The objective of the present work was to evaluate the efficacy of use of the RITA^® temporary immersion system in the large-scale propagation of P. patula. The effects of four concentrations (0.00 µM, 4.50 µM, 9.00 µM, and 13.51 µM) of 6-benzylaminopurine (BAP) on 10 hypocotyl explants were studied using a completely randomised design with three replicates per treatment. Five hypocotyl explants were grown in 250 mL RITA^® containers of Woody Plant Culture Medium (WPM) supplemented with 20 g·L^–1 sucrose and 10 mg·L^–1 vitamins from Murashige and Skoog (MS) culture medium. The frequency of immersion of the explants into the culture medium was 2 min every 8 hours. The number of adventitious buds and calli formed, as well as shoot growth, were evaluated after 6 weeks of in vitro culture. The 4.50 µM concentration of BAP was the best treatment for shoot production (5 shoots per plant) and shoot length (1.32 cm). These results could help the widespread vegetative propagation of this important forest species.

While even-aged forestry is the dominating forest management system in Sweden, there is an increasing interest in Continuous Cover Forestry. Consequently, the conversion of even-aged stands into uneven-aged ones using e.g. selection cutting can be expected to become more common in Sweden. However, there are no up-to-date studies available on harvester productivity during selection cutting under Nordic conditions. Studying harvest intensity during selection cutting is of interest because lighter harvest intensities lead to higher volume growth and better-preserved forest ambience than heavier intensities. The objective of this study was to examine the effect of harvest intensity on harvester productivity during selection cutting. The field study entailed harvesting either 14%, 28% or 48% of a mature stand’s basal area. Harvester productivity was mainly explained by piece size (stem volume), while other factors, including harvest intensity, had only minor effects. This reality means that during selection cutting (thinning from above), piece size increases with decreasing harvest intensity, which in turn increases harvester productivity. Moreover, we observed a mild tendency that operators could select the stems’ felling directions and order more freely when fewer trees are harvested. This amelioration increases productivity additionally during lighter harvesting intensities.

Local people’s socio-economic and natural resources, especially forest resources, have been affected by land degradation in Ethiopia in the past years. To combat this problem, rehabilitation of community-based degraded land has been performed since 1979. Rehabilitation of degraded land (RDL) is important for forest management strategy regarding the regeneration of degraded forests and related resources through women’s empowerment. Because empowered women are key users and managers of resources from rehabilitated land such as forest resources, which leads to sustainable utilization of forest products. The aim of the study was to evaluate women’s participation and empowerment in decision-making regarding the rehabilitation intervention. A total of 120 women households (60 user and 60 non-user
women) were selected using a stratified random sampling method. Data were collected using a household survey, focus group discussion and key informant interviews. The results revealed that there is a significant difference between user and non-user women in fetching water and fuelwood collection time. Furthermore, RDL contributes to improving user women’s economic status and social relationships such as livelihood opportunity, social network, build-up of trust and changes in social assets. The result also indicated that women able to participate in forest-related meetings, land use management, use and control of assets, decision-making, and in soil and water conservation measures. Further, user women had greater awareness compared to non-users due to participation in different meetings and other decision-making activities. The findings suggest that consideration of women’s participation in decision-making regarding the community land rehabilitation program is important to empower women equally with men.

Designing and constructing a road network is one of the most critical steps of the development process in managing natural resources. The current research is going to investigate the application of network connectivity indices to the analysis of road networks in the forested watershed. First, the road network suitability map (RNSM) was created to emphasize the technical and physiographic criteria and integrated management scenarios using a weighted linear combination (WLC) and analytic network process (ANP). Subsequently, three road network alternatives (RNA) were assigned based on the priorities in the RNSM. In order to try to determine the appropriate alternative, the network connectivity of the designed alternatives looked into the forest and non-forest land uses, as well as the whole study area, using the values of alpha (α), beta (β), gamma (γ), eta (η), network density (ND) and detour indices (DI) in the context of the graph theory. Results show that the road density of the RNA2 variant (11.56 m·ha^–1) is shorter than the other alternatives and the existing road network (ERN). In addition, dealing with the whole study area, we realized that the index values which are related to the number two reflect a better status than the other alternatives of alpha, beta, gamma, eta and detour index, in which they were identified to be 0.44, 1.34, 1.16, 0.45 and 0.83, respectively. RNA2 is chosen as the appropriate road network according to the network connectivity, technical and physiographical criteria, along with integrated management scenarios. Further control measures and field surveys are recommended to achieve more relevant results.

Herbivorous pests and arbuscular mycorrhizal fungi (AMF) coexist on the same host plant, having an indirect effect on one another. We established an experiment in a randomised complete block design with four treatments and six replications to examine the impact of AMF on the population and the damage caused to plane trees by the leafhopper Zyginella pulchra. Manure, manure plus fertiliser, manure plus fertiliser plus AMF, and non-inoculated plants (control) were all of the treatments. The findings revealed that while the nutritional content and soluble carbohydrate content were significantly enhanced by all treatments, they largely reached their peak in the AMF-inoculated plants. When compared to control trees that were not inoculated, the concentrations of N, P, and Zn were boosted by 39%, 81%, and 425%, respectively. AMF inoculation increased the population of Z. pulchra nymphs and adults compared to the control. However, the plants with AMF inoculation eventually suffered greater leaf loss as a result of this rise in the pest population. The findings show that while AMF enhance nutrient absorption and are necessary to improve the nutritional state of the host trees, they also enhance the absorption of pests that are thought to be harmful to plane trees. However, AMF colonisation improved the potential attractiveness of Z. pulchra to plane trees.

Abies hidalgensis is an endemic species from the state of Hidalgo, Mexico, that has been registered only in nine fragmented relict populations that have a total of 1 000 individuals among them. Intensive forest management takes place in five of the populations under specific programs focused on Pinus spp. Still, it is necessary to know the impact of these activities on the genetic diversity of the threatened species, if restoration and conservation strategies are to be proposed. The aim of this work was to estimate the effect of forest management on the genetic structure of A. hidalgensis using seven nuclear molecular markers developed for A. guatemalensis (Ab07, Ab08, Ab09, Ab12, Ab15, Ab20, Ab23). The species was sampled growing under two different conditions; (i) areas under forest management and (ii) conserved areas. Two indexes of genetic diversity were evaluated, observed and expected heterozygosity. The genetic structure was determined by an analysis of molecular variance and a Bayesian assignment model. A bottleneck analysis was also carried out. The populations were found to have a common genetic base (differen­tiation coefficient F_ST = 0.056, number of mi­grants per generation Nm = 43), which suggests recent fragmentation of the distribution, which in turn increases the bottleneck effect in managed areas (Wilcoxon probability Wp = 0.007 and 0.016). This explains the apparently high heterozygous level (H_e = 0.69) and low inbreeding. Our results are important as they may be used to design strategies for management and conservation of A. hidalgensis.

In some cases, it is difficult to promote climax tree species in the forest stand composition. In the Czech Republic, silver fir (Abies alba Mill.) is a typical example. This study offers an evaluation of the use of two improving compounds for tree plantations in the initial stage of growth in Central Bohemia. In the experiment, we measured the initial growth performance of a young fir plantation treated with a brassinolide compound (concentration 1 : 100 and 1 : 200) and Bio-Algeen^® prior to planting and compared it with control treatment: we assessed height, root collar diameter, vitality and mortality rate during the period 2014–2019. Cumulative mortality rate of the plantation reached 25% at the end of the monitoring period, without any significant differences between variants. Height increment of the variant treated with Bio-Algeen^® was significantly (P < 0.05) lower than the growth of brassinolide-treated variants, all treated variants were comparable with the control variant. The plantation underwent a drought-stress period in 2014 and 2015, which resulted in worsened vitality and colour across variants. As a result of the simple economic analysis, the most expensive inputs are planting stock and labour, therefore the price and application of additional substances should not affect decision-making.

Forests are atmospheric CO₂ sinks, but their losses and degradation accelerate the emissions of carbon stored as a sink. Deforestation and forest degradation are widespread in Bangladesh, but their impact on greenhouse gas (GHG) emissions is unknown. We assess land use and land cover (LULC) change and forest loss in this study by classifying different Landsat satellite imagery with a focus on forest cover loss from 1989 to 2020. Tier 1 standards were used to estimate the carbon removal and emissions from a small-scale tropical forest. Over the last three decades, the forest area has decreased by 2.40%, 3.74% and 7.52%, respectively. The primary causes of forest loss are large-scale tea garden and homestead expansion, as well as increase in agricultural activities. Because of a reduction in the forest area, the annual gain of carbon in forest biomass has also decreased. Although overall carbon emission was a net gain for the Maulvibazar hill forest, it has decreased from 331.24 Gg·yr^–1 in the first decade (1989 to 2000) to 307.7 Gg·yr^–1 in the most recent decade (2011 to 2020), which is an alarming trend. As a result, this research will contribute to leaders’ commitment to “halt and reverse forest loss and land degradation by 2030” at the 26^th United Nations Climate Change Conference of the Parties (COP 26) in 2021 to improve carbon sequestration, combat climate change and conserve biodiversity.

According to the literature, forwarding productivity depends chiefly on log concentration, the number of assortments, mean log volume, load-size, slope, and extraction distance. However, there is not much scientific knowledge available on forwarding in continuous cover forestry (CCF) in boreal forests, nor whether the presence of remaining trees actually affects forwarding productivity. Thus, the objective of our study was to isolate the effect of remaining trees (i.e. stand density) on forwarding productivity during CCF, specifically selection cutting. The results showed that productivity was explained mainly by the log concentration, while other factors had at most minor effects. Most importantly, stand density did not significantly affect forwarding productivity, ceteris paribus. Thus, we conclude that remaining trees do not affect forwarding productivity in boreal forests. Although the study results from this CCF operation must only be cautiously applied to even-aged forestry, our results raise a general question: do we need separate productivity models for thinning and clearcut operations in boreal forests if remaining trees (stand density) do not affect forwarding productivity? Because of the small dataset, we consider our paper to be a pilot study whose findings need to be verified by studies based on larger datasets including several operators and stands.

The aim of the study was to compare the stock of essential nutrients and carbon in the aboveground biomass of mature stands of silver fir and Norway spruce. A comparison was carried out for 14 mixed stands of spruce and fir. The tree-level dendrometric characteristics were taken from experimental measurements or were generated using the SIBYLA growth simulator. The amount of biomass was calculated using allometric equations. Samples of stem wood, stem bark, and needles were taken and analysed for carbon, nitrogen, calcium, magnesium, potassium, phosphorus, and sulphur concentrations. Using biomass data, the concentrations of the elements were converted into the stock at the stand level. Overall, spruce fixes a greater amount of carbon. The difference is in the carbon allocation, where fir allocates more carbon in the crown and spruce in the stem. Fir needles contain a greater amount of nutrients than spruce needles. A higher supply of phosphorus, nitrogen, and especially potassium was found in the stem wood and bark of fir, the amount of which is more than twice that of spruce. The stem wood of spruce, on the other hand, fixes more calcium and magnesium. As part of the study, linear regression models predicting the stock of nutrients and carbon depending on the stand basal area were parameterised.

In this study, the first observation of Thanasimus femoralis was conducted in Türkiye. Adults of T. femoralis and Thanasimus formicarius were collected from pheromone traps together with Ips sexdentatus, Ips acuminatus, Ips mannsfeldi and Scolytus intricatus in forest nurseries located in the Western Black Sea Region, between 2021 and 2022. The clerid and bark beetles were morphologically described. The aedeagus and antennae of T. femoralis were observed by scanning electron microscopy.

Biological invasions are globally recognised as a significant threat to native biodiversity, as they can change the structure, composition, and functioning of the native ecological system. The riparian forest is considered a habitat highly invaded by invasive plants since rivers serve as corridors for alien species through the terrestrial ecosystem or may simply harbour exotic species that cannot survive elsewhere. The riparian forest, as a high conservation value forest, is an important part of the lowland forests of Georgia. These forests are distributed along large rivers, including the Mtkvari, Alazani, Iori, Aragvi, Ksani, Algeti, and Great and Little Liakhvi rivers. Here, we present a case study that was part of the scientific project titled 'Survey of Potential Invasive Alien Woody Species (PIAWS) in the Protected Areas of Georgia'. Protected areas (PAs) in Georgia play an important role in conserving native biodiversity, including forest ecosystems of distinguished biodiversity. We focused on the lowland riparian forest (LRF) distributed along the Mtkvari and Iori rivers within two PAs – Korugi and Gardabani Managed Reserves (MRs). Six main alien woody species (AWS) were identified in the study areas: Robinia pseudoacacia, Gleditsia triacanthos, Ailanthus altissima, Acer negundo, Amorpha fruticose and Morus alba. Among these AWS, the local status of R. pseudoacacia, G. triacanthos, A. altissima, and A. fruticosa is invasive, while that of A. negundo and M. alba is naturalised. The environmental impact of AWS on LRF habitat was evaluated using the Environmental Impact Classification for Alien Taxa (EICAT) classification system. A major or moderate impact of AWS on the LRF habitat is evident, which, according to EICAT impact mechanisms, is expressed as apparent competition and physical, structural and indirect impacts. The study revealed that the impact levels of three AWS, R. pseudoacacia, G. triacanthos, and A. altissima, were classified as major or moderate ('harmful' impact), while the remaining AWS, A. negundo and A. fruticosa, were of minor or minimal concern. AWS in the invaded areas of the LRF are found as an understorey layer or, otherwise, they have already formed the main canopy and replaced native dominant woody species. Therefore, undesirable structural and succession processes in invaded LRFs are evident.

This paper is focused on the description of the black mulberry (Morus nigra), its ecology and the possibilities of its in vitro propagation for quick and efficient obtaining of a large quantity of clones in a relatively short time for subsequent planting or sale. Due to ongoing climate change, it is considerable to use mulberry trees in horticulture, agroforestry and forestry under the conditions of Central Europe. The use of the mulberry is conditioned by the availability of planting stock. A proven and successful method of mulberry propagation is in vitro cultivation. Based on literature review, the recommended composition of planting media and other procedures for in vitro cultivation of mulberries are presented. The aim of the article is to inform foresters about the possibilities of using the black mulberry tree in our conditions and, using its example, to point out the possibility of using non-standard species of trees both as part of adaptation measures to the expected climate change and as one of the options for increasing the biodiversity of the landscape.

Tree height is one of the most important variables in describing forest stand structure. However, due to difficulty in height measurement, especially in dense and mountainous forests, the common approach is to invoke the height-diameter (H-D) models. The oriental beech (Fagus orientalis Lipsky) is one of the most important species of Hyrcanian forests, over the mid to high-altitudes (400–1 800 m a.s.l.), in northern Iran. In this study, the H-D relationship of beech trees was investigated separately for mid-altitude and high-altitude in Shafaroud forests of Guilan using 14 nonlinear H-D models and an artificial neural network model (ANN). To collect data, a systematic random sampling method within a 100 × 100 m regular randomized grid was applied. In total, 3 243 individual trees in 255 circular plots with 0.1 ha were measured. For comparing the results, performance criteria including root mean square error (RMSE), R²_adj, Akaike's information criterion (AIC), and mean absolute error (MAE) were used. In high and mid altitudes, Meyer (1940) and Bates and Watts (1980) models had the best performance, while Watts (1983) model and Burkhart-Strub (1974) model had the worst performance in high-altitude and in mid-altitude, respectively. On the other hand, the ANN model had the best accuracy and performance in both sites. Since the performance of the ANN model is superior and consistent compared to the common nonlinear models, here it is preferred for both regions.

In this paper, empirical relationships between diameter at breast height (DBH), crown diameter (CD), and stem number per hectare (N) were improved in a Paulownia Shan Tong plantation. Various functions of these variables were defined, focusing on growing space (G_s) and stem number per hectare. The linear crown index between CD and DBH seems to be particularly important in predicting stem number per hectare. Based on an analysis of the relationships, a CD-DBH (R² = 0.7254) and a DBH-N graphic model (R² = 0.7302) can be applied widely in plantation forestry. Under suitable site conditions, the investigated Paulownia hybrid can provide a higher increment in DBH than most of poplar hybrids at a certain age. The aim of this study was to explore the relationships between the G_s based on CD and DBH. These types of investigations are of fundamental importance in terms of the growing technology of tree plantations.