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Arnica montana L. is a medicinal plant with significant conservation importance. It is crucial to monitor this species, ensuring its sustainable harvesting and management. The aim of this study is to develop a practical system that can effectively detect A. montana inflorescences utilizing unmanned aerial vehicles (UAVs) with RGB sensors (red–green–blue, visible light) to improve the monitoring of A. montana habitats during the harvest season. From a methodological point of view, a model was developed based on a convolutional neural network (CNN) ResNet101 architecture. The trained model offers quantitative and qualitative assessments of A. montana inflorescences detected in semi-natural grasslands using low-resolution imagery, with a correctable error rate. The developed prototype is applicable in monitoring a larger area in a short time by flying at a higher altitude, implicitly capturing lower-resolution images. Despite the challenges posed by shadow effects, fluctuating ground sampling distance (GSD), and overlapping vegetation, this approach revealed encouraging outcomes, particularly when the GSD value was less than 0.45 cm. This research highlights the importance of low-resolution image clarity, on the training data by the phenophase, and of the need for training across different photoperiods to enhance model flexibility. This innovative approach provides guidelines for mission planning in support of reaching sustainable management goals. The robustness of the model can be attributed to the fact that it has been trained with real-world imagery of semi-natural grassland, making it practical for fieldwork with accessible portable devices. This study confirms the potential of ResNet CNN models to transfer learning to new plant communities, contributing to the broader effort of using high-resolution RGB sensors, UAVs, and machine-learning technologies for sustainable management and biodiversity conservation. [ABSTRACT FROM AUTHOR]

Retention trees and retention tree groups are of great value for the conservation of biodiversity: They are home to plant and animal species that have almost disappeared from commercial forests due to forest management interventions. The common beech (Fagus sylvatica L.) is of particular importance here, as it is one of the most dominant deciduous tree species in Central European forests. The present study analyses the contribution of the different tree zones for the epiphytic biodiversity of old beech trees in the montane altitudinal belt zone in the southern Black Forest, SW Germany. Twenty-four large beech habitat trees from 24 different plots were systematically sampled from the base of the trunk to the canopy. All epiphytic plant species (bryophytes and lichens) as well as relevant environmental data were recorded representatively on sample plots of 20 × 30 cm in size, selected by means of specific criteria. A total of 170 species of epiphytes were recorded, including 88 lichens and 82 bryophytes. Using numerical classification, the sample areas were divided into six cluster groups. Five plant communities/associations could be identified: (1) Ulotetum crispae Ochsn. 1928, (2) Dicrano scoparii-Hypnetum filiformis Barkm. 1958, (3) Antitrichia curtipendula community - within the alliance Lobario-Antitrichion Wirth 1968, (4) Usnea dasopoga-Platismatia glauca community - within the alliance Usneion dasypogae Barkm. 1958, (5) Parmelietum furfuraceae Hilitzer 1925. In addition, there were sample plots of dominant bark. This study thus makes a holistic contribution to the knowledge of epiphyte species and their communities on old beech trees, especially by including the little-researched tree crowns. [ABSTRACT FROM AUTHOR]

Poor drought tolerance of European beech trees raised concerns in Europe. We hypothesized that beech could show an opposite physiological response to the same level of climatic drought with change in edaphic drought. We performed a combined analysis of δ13C and δ18O in tree rings to reveal retrospective temporal physiological responses of trees to drought. The edaphic drought was assessed by quantifying the capacity of soil to store water in plots (classified as "dry" and "less-dry") near the drought limit of the species in three near-natural oak-beech ecotones in Germany and Switzerland. Neighbourhood competition was quantified. A climatic drought index was calculated from meteorological records and related to the δ13C and δ18O values of the trees. Trees from dry plots showed a higher response to drought and climatic dependency than less-dry plots. Neighbourhood competetion increased δ18O values significantly. Dual isotope analysis shows a tendency of greater stomatal resistance in dry plots and higher stomatal conductance in less-dry plots. We conclude that beech trees belonging to the same population under changing soil water availability can show different physiological responses under climatic drought stress. Our finding indicates the high plasticity of the beech trees to survive drought stress with changing site conditions. [ABSTRACT FROM AUTHOR]

Arnica montana L. (AM , Asteraceae) is a perennial, herbaceous vascular plant species of commercial importance. The flower heads' pharmacological properties are attributed mainly to sesquiterpene lactones (SLs), with phenolic acids and flavonoids also considered of relevance. The botanical drug is still partly collected in different European mountain regions. The SL content can be influenced by genetic factors and environmental conditions (altitude, temperature and rainfall). Surprisingly, the influence of the soil on SL-content have rarely been investigated. However, the soil determines the occurrence, distribution and overall fitness of AM. Equally, environmental factors are crucial determinants for the biosynthesis and fluctuations in plant secondary metabolites. Therefore, different abiotic (pH, C/N ratio, base saturation, cation exchange capacity) and biotic (species richness, vegetation cover) parameters need to be assessed as potential drivers of the variable content of A M's secondary metabolites. Consequently, we developed an in situ experimental design aiming to cover a wide range of soil pH conditions. We detected and investigated different AM populations growing in grassland on acidic soils, on siliceous as well as calcareous geologies within the same geographical region and altitudinal belt. The total SL content and most single SL contents of the AM flower heads differed significantly between the two geologies. AM flower heads of plants growing on loam on limestone showed a significant higher total SL content than the flower heads of plants growing in siliceous grasslands. Furthermore, the SL contents were significantly correlated with geobotanical species richness and vegetation cover pointing toward an effect of species interactions on the production of SLs. Moreover, the ratios of the main SLs helenalin to dihydrohelenalin esters were significantly correlated to environmental parameters indicating that SL composition might be a function of habitat conditions. The findings of this study shed light upon the often ignored, complex interactions between environmental conditions and plant secondary metabolites. We highlight the importance of both abiotic and biotic habitat parameters for SLs in AM. [ABSTRACT FROM AUTHOR]

This report provides an overview of the forest vegetation and the status of its conservation in Romania. Due to a large range of climates and soils, and a long-lasting postglacial vegetation history, the Romanian forests are highly diverse and species-rich ecosystems. Approximately 150 natural types of forest ecosystems have been described. Seven zonal forest formations were distinguished: (1) forest steppes and dry oak forests; (2) forests with Oriental hornbeam (Carpinus orientalis); (3) forests with oaks (Quercus spp.) and hornbeam (Carpinus betulus); (4) beech forests: Fagus sylvatica and Fagus sylvatica mixed forests; (5) beech-fir (Abies alba)-spruce (Picea abies) mixed mountain forests; (6) spruce forests; (7) subalpine shrubland with dwarf pine (Pinus mugo subsp. mugo). On extreme sites, azonal forests occur, dominated by (8) black pine (Pinus nigra subsp. banatica); (9) Scots pine (Pinus sylvestris); (10) Carpathian larch (Larix decidua subsp. carpatica) and stone pine (Pinus cembra); (11) valuable broadleaf species, including maple (Acer spp.), ash (Fraxinus spp.), elm (Ulmus spp.), linden (Tilia spec). Along water courses with periodical inundations, riparian forests and shrublands occur, dominated by (12) black alder (Alnus glutinosa); (13) grey alder (A. incana); (14) tamarisk (Myricaria germanica) pioneer copse; (15) pioneer forest with poplar (Populus spp.) and willow (Salix spp.); (16) riparian hardwood forest with oak, elm (Ulmus spp.), ash (Fraxinus spp.). In the EU countries virgin (primeval) and old growth forests account for less than 3% of the total forest area. Most alarming is the situation of temperate virgin and old-growth forest. About 80% of them are situated in the Carpathians, mainly formed by beech, fir, and spruce. Estimations of virgin and quasi-virgin, old-growth forests in Romania range between 150,000 and 200,000 ha. Between 2001 and 2019 about 350,000 ha disappeared through illegal and legal logging. Legislation in Romania demands that production forests have to be managed sustainably, and virgin forests have to be protected. Romanian forests are also subject to European law, such as the Habitats and Birds Directives. However, there is a severe lack of enforcement at all administration levels, even in National Parks. Sanctioning activities by the EU authorities are hardly visible. It follows: (1) It must be in the interest of all of Europe to preserve and protect the last large areas of primeval forest in Europe. (2) The community of EU countries, the Parliament and the European Commission must provide clear guidelines and care for their implementation, connected with attractive, secure and long-term funding programs (compensation for non-use). (3) At a regional level, new creative ideas and concrete initiatives must integrate wilderness areas into regional value creation concepts. [ABSTRACT FROM AUTHOR]

Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests. [ABSTRACT FROM AUTHOR]

An increase in drought could cause shifts in species composition and vegetation structure. In forests it limits the occurrence of drought sensitive tree species which become replaced by drought tolerant tree species and forest communities. Under temperate macroclimatic conditions, European beech (Fagus sylvatica L.) naturally dominates the forested landscape, except on extremely shallow soil in combination with high irradiation. On these sites beech reaches its drought limit, and is replaced by forests dominated by species like downy oak (Quercus pubescens s.l.) and English oak (Quercus petraea L). Phytosociological and ecological data were collected in the transition (ecotone) between European beach stands and stands of more drought tolerant species in order to quantify the drought intensity threshold, above which beech is replaced by drought tolerant species. It was shown that favourable topographic and soil conditions partially compensated the unsuitable climatic conditions for beech. The ecotone between these forest types was found to be characterized by shallow soils with an available soil water storage capacity of 73 l/m² or less, and an irradiation intensity of 6000 MJ/m² or more during the growing season. This indicates that under conditions of climate change beech would naturally still remain the dominant tree species on the majority of central European forest sites. [ABSTRACT FROM AUTHOR]

Biomass equations for European beech (Fagus sylvatica L.) trees growing on dry sites have not been published, although such equations are needed for a proper estimation of the biomass of beech trees growing naturally at their drought limit in dry forests. We aimed to: (1) develop new allometric aboveground biomass equations for European beech trees growing on dry sites; (2) compare these equations with existing biomass equations. We harvested 86 plants, ranging from saplings to trees, from forest stands on south-facing slopes at 5 locations in Germany and Switzerland. Whole plant weights were measured in the field after felling, and samples from stem, branches and leaves of every harvested plant were brought to the laboratory. We developed diameter- and height-based regression equations for the total above-ground biomass, stem with bark biomass, and biomass of the branches with leaves and further compared them with the existing equations from the literature. Our results showed that the 5 current diameter-based equations available in the literature significantly overestimate the total above-ground biomass, the stem with bark biomass and the biomass of branches and leaves. With increasing tree size, the proportion of the biomass of branches and leaves to the total tree biomass decreased significantly. We also found that the inclusion of height in biomass models did not influence the prediction of total aboveground biomass, but significantly improved the prediction of stem biomass. We recommend that researchers and foresters use the equations developed in this study to quantify the biomass of beech trees growing under similar site conditions. [ABSTRACT FROM AUTHOR]

Tertiary-relict Hyrcanian (Caspian) forest along the shores of the southern Caspian Sea is a center of biodiversity. Still, there is little information on plant diversity patterns in this area. This study evaluated plant diversity, variation in life forms, and geographical distribution of the zonal vegetation types and their relationships with environmental variables, in the educational and experimental forest of Kheyrudkenar, an important protected area in the central Hyrcanian forest of northern Iran. For this purpose, 226 vegetation plots of 400 m2 were laid out along two altitudinal transects from the lowlands (100 m a.s.l.) to the timberline (2000 m a.s.l.). Four vegetation types were identified using modified TWINSPAN, indirect and direct gradient analyses. Species-related (species diversity indices, life form and phytogeographical elements) and environmental variables (climate, topographic and soil variables) were calculated and subjected to one-way ANOVA among the vegetation types. Both constrained (CCA) and unconstrained (DCA) ordination analyses showed an almost identical variation of the floristic composition along their axes and demonstrated that there are two main gradients in the Hyrcanian forest. Elevation together with annual precipitation and mean annual temperature were the most important factors controlling the floristic composition in the area. Topographic features such as slope inclination and heat index were found to be important within an elevation zone/vegetation type. Soil physical and chemical properties were of secondary importance for the separation of the vegetation types. This knowledge will be useful for forest management and conservation practices in the Hyrcanian area with its distinct and unique flora and vegetation. [ABSTRACT FROM AUTHOR]

Greek fir (Abies cephalonica Loudon) grows in montane Mediterranean climates characterized by dry, warm summers. Drought is an important climatic feature of these montane ecosystems as it affects the floristic composition, structure and distribution of plant communities. The Oxia-North Vardousia mountain system is one of the few areas in Greece with an extensive, well-preserved Greek fir forest. This study aims at describing the Greek fir forest vegetation of such area and determining the drought-related factors affecting their floristic composition and differentiation. Vegetation relevés were classified and ordinated. The impact of drought-related variables on the vegetation composition was analyzed. A cluster analysis was used to reveal the most important factor for the discrimination of the main plant communities and to determine the drought threshold between them. Two plant communities that reflect the differentiation of the Greek fir forests in central Greece into xerophytic and mesophytic forest communities were described. Each community was divided into two subcommunities. The elevational distribution of Greek fir forests in the mountains of central Greece follows a drought gradient linked to the two main climatic components of drought, precipitation and potential evapotranspiration. The combination of these two drought-related variables into a suitable humidity index was found to adequately differentiate the xerophytic from the mesophytic forest communities and define their drought threshold. [ABSTRACT FROM AUTHOR]

The concept and implementation of a tn-national EU intensive Programme (IP) is presented and discussed. The objective is to improve the methods employed by the teachers and scientist of the staff concerning the classification and management of grasslands to students and to prepare them to be able to design, analyse, and evaluate grassland management strategies and to understand grasslands in land-use-system terms. The focus lies on the development of strategies for sustainable grassland use in the context of regional development. The innovative character if this romanian-swedish-german module is exemplified. [ABSTRACT FROM AUTHOR]

The traditional cultural landscape of the mountainous regions of the Apuseni Mountains, its land-use systems and future perspectives for sustainable development were studied during a transdisciplinary project (2000 - 2004). New for Romania was the participatory approach with the involvement of different stakeholders from local and regional level. The presentation focuses on the results of this transdisciplinary approach, which becomes more and more important for sustainable development and management of natural resources. In this context, elements and methods of participation as well as successful implementation in the project are presented. [ABSTRACT FROM AUTHOR]

European beech (Fagus sylvatica L.) trees are becoming vulnerable to drought, with a warming climate. Existing studies disagree on how radial growth varies in European beech in response to droughts. We aimed to find the impact of multiple droughts on beech trees' annual radial growth at their ecological drought limit created by soil water availability in the forest. Besides, we quantified the influence of competition and canopy openness on the mean basal area growth of beech trees. We carried out this study in five near-natural temperate forests in three localities of Germany and Switzerland. We quantified available soil water storage capacity (AWC) in plots laid in the transition zone from oak to beech dominated forests. The plots were classified as 'dry' (AWC < 60 mL) and 'less-dry' (AWC > 60 mL). We performed dendroecological analyses starting from 1951 in continuous and discontinuous series to study the influence of climatic drought (i.e., precipitation-potential evapotranspiration) on the radial growth of beech trees in dry and less-dry plots. We used observed values for this analysis and did not use interpolated values from interpolated historical records in this study. We selected six drought events to study the resistance, recovery, and resilience of beech trees to drought at a discontinuous level. The radial growth was significantly higher in less-dry plots than dry plots. The increase in drought had reduced tree growth. Frequent climatic drought events resulted in more significant correlations, hence, increased the dependency of tree growth on AWC. We showed that the recovery and resilience to climatic drought were higher in trees in less-dry plots than dry plots, but it was the opposite for resistance. The resistance, recovery, and resilience of the trees were heterogeneous between the events of drought. Mean growth of beech trees (basal area increment) were negatively impacted by neighborhood competition and positively influenced by canopy openness. We emphasized that beech trees growing on soil with low AWC are at higher risk of growth decline. We concluded that changes in soil water conditions even at the microsite level could influence beech trees' growth in their drought limit under the changing climate. Along with drought, neighborhood competition and lack of light can also reduce beech trees' growth. This study will enrich the state of knowledge about the ongoing debate on the vulnerability of beech trees to drought in Europe. [ABSTRACT FROM AUTHOR]

Traditionally managed Central European mountain grasslands have high nature conservation value because of their high species diversity. Whether these grasslands and their diversity can be preserved will depend on many factors, including how plant species composition responds to changes in climate conditions. To differentiate between fluctuations and directional succession in the herbaceous layer composition of a Romanian Festuca rubra L. and Agrostis capillaris L. grassland in Apuseni and whether any compositional changes can be related to climate. The vegetation of permanent plots was recorded annually between 2004 and 2012. Temperature and precipitation were measured by an automatic weather station at the study site. Cluster analysis, Indicator Species Analysis and the co-dominance ratio between F. rubra L. - A. capillaris were analysed. The compositional data was related to the climate variables. Thresholds of relevant climate variables differentiating between clusters of plots with similar vegetation composition were determined using classification tree methods. The vegetation composition in our plots within the years 2004, 2005 and 2008 were different from each other. From 2004 to 2006 directional succession could be identified; however the major patterns to emerge were fluctuations which occurred over the whole study period. Compositional shifts included A. capillaris L. and F. rubra L exchanging co-dominance with each other. The most important variables differentiating clusters were temperature during the dormant and vegetation periods and water balance during the vegetation period. It can be concluded that compositional shifts among years were largely a consequence of year to year climatic fluctuations; however, there is some evidence for a directional shift during the early years of the study. [ABSTRACT FROM AUTHOR]

Owing to the growing sensitivity of forests to drought under the warming climate, more attention should be paid to the role of soil drought, plant–plant interactions, tree species and structural diversity, and other abiotic factors on the crown die-back of trees. We studied how permanent soil water stress had impacted on crown die-back of beech trees ( Fagus sylvatica L.) at their drought limit in near-natural temperate forests of Germany and Switzerland. Crown die-back was quantified by the proportion of dead above-ground biomass to total biomass for the individual beech tree. We quantified the available soil water storage capacity as a measure of soil drought stress in combination with other biotic (e.g., plant–plant interactions, tree species diversity, stand structural diversity, plant height and proportion of oak trees) and abiotic (e.g., light availability, soil pH, soil bulk density, potential evapotranspiration) factors to determine the influence of those stressors on crown die-back. We found increases in soil water storage capacity, neighbourhood interactions, plant height and light decreased crown die-back of the beech trees. These stressors differently influenced the die-back among different parts of tree crown. Soil water storage capacity, light availability, intra- and interspecific interactions, plant height and tree species diversity had the strongest influence on die-back in the upper part of the crown. Permanent death of beech trees occurred when the amount of dead above-ground biomass exceeded a 58% mortality threshold. We conclude that vitality of beech trees in drought stressed forests is related to soil water storage capacity, light availability, neighbourhood interactions and tree species diversity. [ABSTRACT FROM AUTHOR]

Growth and survival of young European beech (Fagus sylvatica L.) is largely dependent on water availability. We quantified the influence of water stress (measured as Available Soil Water Storage Capacity or ASWSC) on vitality of young beech plants at a dry site. The study site was located in a semi-natural sessile oak (Quercus petraea (Mattuschka) Liebl.) stand adjacent to beech stands on a rocky gneiss outcrop in southwestern Germany. Plant vitality was measured as crown dieback and estimated by the percentage of dead above ground biomass. The magnitude of crown dieback was recorded in different vertical parts of the crown. Biomass was calculated from the harvested plants following allometric regression equations specifically developed for our study site. Stem discs from harvested plants were used for growth analysis. We found that soil depth up to bedrock and skeleton content significantly influenced ASWSC at the study site. A significant negative correlation between ASWSC and crown dieback was found. Highest rates of crown dieback were noticed in the middle and lower crown. The threshold of crown dieback as a function of drought stress for young beech plants was calculated for the first time in this study. This threshold of crown dieback was found to be 40% of above ground biomass. Beyond 40% crown dieback, plants eventually experienced complete mortality. In addition, we found that the extremely dry year of 2003 significantly hampered growth (basal area increment) of plants in dry plots (ASWSC < 61 mm) in the study area. Recovery in the plants' radial growth after that drought year was significantly higher in less dry plots (ASWSC > 61 mm) than in dry plots. We concluded that a decrease in ASWSC impeded the vitality of young beech causing partial up to complete crown dieback in the study site.