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Summary: Climate warming advances the onset of tree growth in spring, but above‐ and belowground phenology are not always synchronized. These differences in growth responses may result from differences in root and bud dormancy dynamics, but root dormancy is largely unexplored.We measured dormancy in roots and leaf buds of Fagus sylvatica and Populus nigra by quantifying the warming sum required to initiate above‐ and belowground growth in October, January and February. We furthermore carried out seven experiments, manipulating only the soil and not air temperature before or during tree leaf‐out to evaluate the potential of warmer roots to influence budburst timing using seedlings and adult trees of F. sylvatica and seedlings of Betula pendula.Root dormancy was virtually absent in comparison with the much deeper winter bud dormancy. Roots were able to start growing immediately as soils were warmed during the winter. Interestingly, higher soil temperature advanced budburst across all experiments, with soil temperature possibly accounting for c. 44% of the effect of air temperature in advancing aboveground spring phenology per growing degree hour.Therefore, differences in root and bud dormancy dynamics, together with their interaction, likely explain the nonsynchronized above‐ and belowground plant growth responses to climate warming. [ABSTRACT FROM AUTHOR]

Key Message: Beech growth acclimated better during severe drought and recovered faster than spruce after drought ended. This was associated with a shift in performance along relative tree size towards small trees. The effects of several consecutive drought years and the recovery reaction of mature trees in particular after a long-term drought have been poorly studied so far. In this study, we demonstrate the growth reactions of mature trees during and after a five-year treatment of extended summer droughts, followed by controlled irrigation in a very productive mixed forest stand. We exposed 70-year-old Norway spruce (Picea abies [L.] Karst) and 90-year-old European beech (Fagus sylvatica [L.]) trees to reduced precipitation using automatic throughfall exclusion (TE) roofs during the growing seasons from 2014 to 2018, irrigated the trees in early summer 2019 and removed the roofs thereafter. From 2009 to 2022, we monitored annual tree growth and precipitation on 6 plots with throughfall exclusion and on 6 plots with ambient Control conditions (CO) of the KROOF canopy experiment. Norway spruce lost significant growth during drought, with some trees dying and others remaining at a low growth level without significant recovery from the effects of drought stress. European beech also significantly reduced growth at the beginning of the drought but emerged stronger in growth from the drought than the Control group. Spruce and beech showed a non-significant trend of increased inter-specific growth compared to intra-specific growth during drought. We found that spruce benefitted more from mixture than beech in the recovery phase after drought than during the drought phase itself. Most importantly, we observed a shift in growth performance along the relative tree size towards smaller trees in the TE plots for both species. This change in the relationship between diameter increment and tree size during and after drought is a major finding of our study and suggests a possible response mechanism to prolonged drought. This key observation requires further investigation and should be considered in future forest management strategies under changing climatic conditions. [ABSTRACT FROM AUTHOR]

Local survival of forest tree populations under climate change depends on existing genetic variation and their adaptability to changing environments. Responses to selection were studied in European beech (Fagus sylvatica) under field conditions. A total of 1087 adult trees, seeds, 1‐year‐old seedlings and established multiyear saplings were genotyped with 16 nuSSRs. Adult trees were assessed for phenotypic traits related to growth, phenology and reproduction. Parentage and paternity analyses were used to estimate effective female and male fecundity as a proxy of fitness and showed that few parents contributed to successful regeneration. Selection gradients were estimated from the relationship between traits and fecundity, while heritability and evolvability were estimated using mixed models and the breeder's equation. Larger trees bearing more fruit and early male flowering had higher total fecundity, while trees with longer growth season had lower total fecundity (directional selection). Stabilizing selection on spring phenology was found for female fecundity, highlighting the role of late frosts as a selection driver. Selection gradients for other traits varied between measurement years and the offspring cohort used to estimate parental fecundity. Compared to other studies in natural populations, we found low to moderate heritability and evolvability for most traits. Response to selection was higher for growth than for budburst, leaf senescence or reproduction traits, reflecting more consistent selection gradients across years and sex functions, and higher phenotypic variability in the population. Our study provides empirical evidence suggesting that populations of long‐lived organisms such as forest trees can adapt locally, even at short‐time scales. [ABSTRACT FROM AUTHOR]

The Ellenberg quotient (EQ) is a climate index defined as a ratio of the hottest month's temperature and the average annual precipitation sum. The quotient indirectly expresses the relationship between climate and vegetation, and its application is related to the ecological niche of Fagus sp. Although the quotient was curated on the grounds of field research primarily on German vegetation, the possibilities of its utilisation are not limited to the Central European region. The objective of this study is (i) to compare the EQ values calculated for the forest vegetation zones in the Czech Republic with the published data using the ecological niche of Fagus sylvatica; and (ii) to compare the new EQ-based vertical model with field empirical mapping. The study area is the Czech Republic, Central Europe. We used climate data from 1970-2000 and the data of the National Forest Inventory, 2nd cycle (2011-2015), representing an objective data design. Geospatial analytic methods, machine learning (boosting), and verification through statistical testing were performed. The results indicate higher EQ values between the two most substantial spatial frames - the Hercynicum and Carpaticum regions. By comparing empirical mapped units to their climatic potential (in the EQ), a match was found only within the Carpaticum region. The study presents a concretisation of the general climate index for a specific region, adds to the knowledge about the Fagus ecological niche in context with the Central European vegetation, and also points to the EQ's potential for evaluating the concept of vertical differentiation of forest communities, as well as a possible prediction tool for the vegetation migration in context with climate change.

Deadwood plays a key role for biodiversity in forests. A significant number of beetles from this group are currently listed as endangered in the Red List. In addition to other management recommendations, there have been recent efforts to enrich stands with dead wood to promote biodiversity. An important parameter for forestry enterprises is the optimization of these interventions. The study investigated the abundance, species richness, gamma diversity, conservation value and biomass of saproxylic beetles in natural forests using window traps. A total of 89 traps were used for saproxylic beetle monitoring, of which 29 were placed on lying logs, 30 on snags and 30 as controls in forest stand space. A total of 35,011 beetles were recorded in 564 species (61 families). Notably, 20,515 of these belong to saproxylic beetles (59%) in 311 species (55%), with 62 classified as Red-List species (20%). In the group of ‘all saproxylic beetles’, the results indicate that α diversity and γ diversity (q ​= ​0) remain consistent across various deadwood types, while β diversity showed significant differences. Significant differences were found in the Red-List species group, where α diversity and γ diversity differed, with higher values observed in snags. Rarefaction based total species richness of site was estimated to be 391 species, including 74 Red-Listed species. Comparing the sample coverage of the studied stand categories showed that all saproxylic species exhibit a pronounced preference for inhabiting areas featuring lying logs. Conversely, Red-List species mainly inhabit snags, with β diversity being more similar to snags and forest stand space. Notably, both the conservation value (weighted average by conservation status) and beetle biomass are significantly highest in snags, whereas stand space shows the lowest values across all measured saproxylic beetle indices. Furthermore, the use of traps set on the poles in forest stand space resulted in an underestimation of the actual stand richness by 20%–25%. Our results support the conclusion that snags are indispensable features in beech forests, playing a key role in promoting high species diversity, especially among Red-List species, and supporting the biomass of saproxylic beetles. Consequently, it becomes crucial to incorporate a higher percentage of standing deadwood in managed forests or actively create equivalent environments by introducing high stumps.

This article is a Commentary on Mas et al. (2024), 241: 1021–1034. [ABSTRACT FROM AUTHOR]

Species-rich mixed silver fir (Abies alba Mill.) forests dominated in the northern Apennines, but climate and, mainly, anthropogenic land use provoked a sharp silver fir decline approximately 5000 years bp. The conservation of the silver fir in this region was mainly due to the establishment of monastic orders that preserved and even planted silver fir for its spiritual and economic value. In 1993, the best silver fir stands were included in the Parco Nazionale delle Foreste Casentinesi (FCNP), Monte Falterona e Campigna, and have been submitted to low-intensive management or strict protection regardless of past land use and cultural history. In this study, we have (1) analyzed the current structure of three silver fir forests that have had different ownership histories and (2) compared the structure of the three Italian forests among them and with two old-growth forests from the Dinaric Alps as a reference of naturalness. The results show that the current structures of the three Italian forests are very different among them and are strictly related to past land use and, mainly, to monastic legacies. Even if the Italian forests have experienced decades of low-intensity management or strict protection, they are currently structurally very different from Dinaric old-growth forests. Developing an old-growth structure in these forests can be very slow and, in some ways, unpredictable. The results also highlight the importance of recognizing protected areas as cultural landscapes that host an important biocultural diversity. The current risk is that by applying almost exclusive biodiversity-centered management and setting difficult or impossible-to-achieve biodiversity goals, total diversity will decrease, and biocultural diversity, the greatest richness of most European parks, will be lost.

Rear‐edge tree populations are experiencing a combination of higher temperatures and more intense droughts that might push individuals beyond their tolerance limits. This trend towards rising atmospheric [CO2] is concurrent with an increase in intrinsic water use efficiency (iWUE), which theoretically enhances photosynthesis and decrease evapotranspiration rates, consequently improving tree resistance to drought. However, it remains unclear whether iWUE is favouring tree growth under current climate conditions, particularly when climate and iWUE legacy effects are simultaneously considered.We evaluated this question with an extensive sampling along Iberian rear‐edge (dry) populations comprising four mountain ranges and two distinct altitudes. We simultaneously examined the effects of climate and iWUE on secondary growth using annually resolved basal area increments (BAIs) for the period 1901–2017. We used linear mixed models including second‐order autocorrelation and 1‐year legacy effects of iWUE and summer drought.BAI and iWUE increased across the studied period. iWUE increase was driven by changes in atmospheric CO2 concentration and water availability during the growing season. Climate and iWUE exerted direct and lagged effects on beech growth. Water availability during growing season was the main driver of tree growth, combining direct and indirect effects through its impact on iWUE. Legacy effects of water availability and iWUE were more important than growing season conditions. The net effect of iWUE shifted when lagged effects were considered, resulting in a net negative impact on tree growth.Synthesis: Our results reveal that climate and iWUE legacy effects must be considered to assess the net iWUE effect on secondary growth. Considering lagged effects, the current increase in iWUE is constraining tree growth. Modelling efforts of tree growth response to climate warming should include climate and iWUE legacy effects to adequately assess terrestrial ecosystem carbon balance. [ABSTRACT FROM AUTHOR]

Healthy soils are the second C sink on Earth, and this sink could last for hundreds or even thousands of years as stable soil organic matter (SOM). Forest soils, in particular, have the potential to store significant amounts of C, however, the amount of C sequestered and the carbon-to-nitrogen (C/N) ratio of soil organic matter (SOM) depend on the vegetation influencing the soil. In the last decades, mixed stands have aroused great interest among the scientific community, but it is still necessary to intensify research on its effect on soils and their C storage capacity. In this study, we assess soil C sequestration potential in soil and litter of mixed and pure stands of Scots pine and beech (Pinus sylvestris–Fagus sylvatica). Three triplets (9 forest plots), two located in Southern Poland and one in Southern Germany were studied. A total of 40 circular subplots of 5 m radius were selected within the triplets, covering a wide range of species mixture, and soil and litter were sampled. Data were analyzed at two scales (plot-level and microsite-level) to determine which option is more appropriate when studying the mixing effect on SOM. Cstock in forest floor ranged between 2.5 and 11.1 Mg C ha−1 and in mineral soil between 39.6 and 337.8 Mg ha−1. According to our findings, the percentage of species mixture primarily impacted the forest floor rather than the mineral soil. On the forest floor, stands with 25–50% pine in the mixture were found to have a C/N ratio between 20 and 30, which indicates an equilibrium state between mineralization and immobilization. In the mineral soil, total organic C was the only variable affected by mixture percentage (p < 0.1). Finally, microsite-level scale proved to be the most appropriate when studying tree stand composition effect on SOM, as the plot-level scale diluted or masked some effects. [ABSTRACT FROM AUTHOR]

In the light of ongoing climate change, European beech trees face a loss of vitality due to an expected increase in the frequency of droughts, exacerbated by prolonged periods of high temperatures and solar radiation. Such conditions increase the predisposition to European beech splendour beetle attacks, and trigger sunburn, fungal infections and complex diseases. As a result, European beech forests are seriously threatened by climate change. Following prolonged and repeated periods of exceptional drought since 2018, European beech decline have been observed in several regions of Germany and Europe. Vitality losses, in some cases severe, of due to the extraordinarily warm, dry summers of 2018 and 2019 have been observed and investigated in several regions of Germany. The first symptoms of vitality loss of European beech associated with severe signs of crown dieback were recorded in midsummer 2018. Mortality of branches and individual trees was often associated with sunburn, bark necrosis and bleeding spots of sap flux. The first signs of mortality were observed locally in predisposed stands in autumn 2018. The stem stability and break resistance of affected trees were significantly reduced. To elucidate the complex interactions involved, the occurrence of vitality loss of European beech and associated causative agents were examined in north-western Germany. Disease symptoms of individual trees were studied, associated fungi (endophytes, plant pathogens and saprobes) were isolated and identified. Frequent potentially severe pathogens included Neonectria coccinea, Diplodia corticola and D. mutila. The presented cases of disease were the first, where D. corticola was recorded on beech. In addition, inoculation tests were used to assess the potential roles of Botryosphaeria species in the observed symptomatology. [ABSTRACT FROM AUTHOR]

A change in tree species composition in Central Europe to increase the resilience of forests when coping with climate change effects is imminent. We evaluated the present and expected future role of the European beech, (Fagus sylvatica L.), with respect to the expansion of its habitat and its stem. We assessed the current relevance of beech from data of the Austrian Forest Inventory 2007/09, and analyzed forest policies promoting the establishment of beech forests. We simulated forest growth with the model CALDIS, linked with the timber-market model FOHOW2. We used a business-as-usual (BAU) forest management strategy under moderate (RCP 4.5 BAU) or extreme (RCP 8.5 BAU) climate change. We also simulated an extreme climate change scenario with a forced change in the tree species composition (RCP 8.5 Change Species). Beech occurs in Austrian forests over the elevational gradient of 250 to 1600 m a.s.l. In low elevation, it forms beech-dominated forests, often for the supply of the domestic fuelwood demand. In mountain regions, beech enriches the diversity of Norway spruce, (Picea abies (L.) H. Karst.)-dominated forests. In a BAU setting, the habitat of beech increases only slightly in both climate scenarios. The scenario 'RCP 8.5 Change Species' increases the habitat of beech in the next 60 years considerably. With progressing warming, other broadleaved tree species gain relevance. The vulnerability to drought and pathogens are limiting factors for Austrian beech forests. The future habitat depends on many factors such as the ability of forests to cope with climate change, the confidence to arising market opportunities of beech timber in the wake of technological progress, and financial and non-financial incentives for the implementation of adaptive forest management. [ABSTRACT FROM AUTHOR]

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The character of pure or mixed forest canopies and their litterfalls contribute to different forest-floor properties. These organic layers and also subjacent topsoil were studied at three study sites covered by mixed treatments such as beech–spruce, beech–fir, spruce–fir and two monospecific beech and spruce treatments. The age of the forest stands ranged from 11 to 15 years when sampled. All study sites were used as meadows when afforested; therefore, the forest floors were new, and the A-horizon topsoil properties were not influenced by older humus inherited from previous forest generations. The mineral soil was likely affected by different levels of former fertilization, which resulted in differences among the study sites. The early-developed forest floors showed differences between the treatments with beech and the others. The topsoil below beech with spruce had more nitrogen, oxidizable carbon and cations of exchangeable hydrogen as well as pH showing more acidic conditions and lower contents and saturation of base cations. Pure beech had more phosphorus. The nutrient pools did not differ among the treatments; significantly more matter was found below the oldest stands on the first afforested site, which also increased nutrient pools. [ABSTRACT FROM AUTHOR]

Key message The datasets describe bacterial and fungal communities of European beech (Fagus sylvatica) leaves collected along a vertical gradient in a gallery forest throughout the growing season. They also describe communities in the surrounding environment of beech trees. Dataset access is at https://doi.org/10.7910/DVN/FFHAQU , and associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f17fe848-fc3e-4297-be11-9871b35a1be4 . Both can be used to uncover the dynamics and assembly processes of phyllosphere microbial communities in forest ecosystems.

Abstract Pulsed resources have prominent effects on community and ecosystem dynamics; however, there is little research on how resource pulses affect human–wildlife interactions. Tree masting is a common type of pulsed resource that represents a crucial food for many species and has important bottom‐up effects in food webs. In anthropogenic landscapes, years of food shortage after mast years can have negative outcomes for both people and wildlife, for instance when an increased use of anthropogenic foods by animals exacerbates human–wildlife conflicts. Here, we used novel remote sensing indicators of forest productivity and phenology, together with weather cues and ground measures of mast production, to assess whether years of masting and crop failures lead to changes in human–wildlife conflict occurrence. We used a unique 14‐year dataset including the production of European beech Fagus sylvatica seeds and brown bear Ursus arctos damage in the northeastern Carpathians as our model system. Linking these data in a panel regression framework, we found that temporal fluctuations in damage occurrence were sensitive to the year‐to‐year variation in beechnut production. Specifically, the number of damages during bear hyperphagia (i.e., September to December, when bears need to accumulate fat reserves prior to hibernation) was significantly higher in years with low beechnut production than in normal or mast years. Furthermore, we provide evidence that beech masting and failure can be predicted through a combination of remote‐sensing, weather, and field indicators of forest productivity and phenology. We demonstrate how pulsed resources, such as tree masting, can percolate through food webs to amplify human–wildlife conflict in human‐dominated landscapes. Given the recent range expansion of large carnivores and herbivores in many regions, including Europe, predicting years of natural food shortage can provide a pathway to proactive damage prevention, and thus to foster coexistence between wildlife and people.

Two provenance tests in North-Eastern Bulgaria have been studied, whose purpose is to test the response of beech provenances from Southern Germany to the drier and warmer climatic conditions in Bulgaria, in order to predict how they would perform in a warming and drying climate. The provenance tests were established in the spring of 2010 in the area of the Varbitza and Kipilovo Forest Services with 2-year-old seedlings in a 2 x 1 m scheme in 3 replications. Four provenances of common beech were studied - 2 German (Silberbach and Ebersdorf) and 2 Bulgarian (Petrohan and Berkovitza). On the 12th year after afforestation, an inventory and measurements of the height and root collar diameter were carried out. The results were processed statistically by applying one and two-factor analysis of variance, as well as Tukey’s test for multiple comparisons. A higher survival rate was found in the provenance test in Kipilovo. The Bulgarian provenances Petrohan and Berkovitza were characterized by better growth in height in both provenance tests, and in root collar diameter - provenance Petrohan. Provenance Ebersdorf could be recommended for use in drier and warmer places in Southern Germany.

The cerambycid beetle Rosalia alpinais associated with temperate, broadleaved (mainly beech) forests containing dead or decaying wood. This species is protected under the Habitats Directive of the European Union. Given its narrow ecological niche and limited dispersal abilities, habitat fragmentation is a conservation concern for populations of R. alpina. In order to maximise the effectiveness of habitat restoration, a scientifically sound procedure for patch selection is needed. In Gipuzkoa (N Spain), we used Light Detection and Ranging (LiDAR) images to search for 20x20-m cells matching the parameterisation of a predictive and local habitat model for R. alpinaat the tree level. The cells selected under quantitative criteria were clustered to identify potential habitat patches. Conefor Sensinode software was used to estimate the importance of each of those patches in terms of the connectivity of the population, based on dispersal distances of R. alpinaand the probabilities of dispersing events among patches. We identified 380 potential habitat patches, mostly in the south-eastern sector of the study area, which were classified into “core areas” and “connecting areas”. The performance of the model was tested in the field (61% of correct assignations), although the actual occurrence of R. alpinawithin the habitat patches should be assessed in the future. This model represents a step forward in guiding the cost-effective implementation of conservation activities, through a strict preservation of the current core habitat patches and an increase in the size of connecting patches.Therefore, we show that connectivity models combining remote sensing data and local habitat selection can be an aid in conservation planning and restoration actions, probably outperforming less efficient strategies, such as random or expert selection. RESUMEN: El escarabajo cerambícido Rosalia alpinaestá asociado a los bosques templados de frondosas (principalmente hayas) que albergan madera muerta o en descomposición. La especie está protegida bajo la Directiva de Hábitats de la Unión Europea. Dado su estrecho nicho ecológico y su limitada capacidad de dispersión, la fragmentación de su hábitat es un problema de conservación para las poblaciones de R. alpina. Para maximizar la efectividad de la restauración del hábitat, se necesita un procedimiento científicamente sólido para la selección de parches forestales sobre los que intervenir. En Gipuzkoa (norte de España) utilizamos imágenes LiDAR para buscar celdas de 20x20 m que se ajustaran a la parametrización de un modelo predictivo local de hábitat para R. alpinaa nivel de árbol. Las celdas seleccionadas bajo criterios cuantitativos fueron agrupadas para identificar parches de hábitat potencial. Se utilizó el software Conefor Sensinode para estimar la importancia de cada uno de estos parches en términos de conectividad para la población, con base en las distancias de dispersión de R. alpinay la probabilidad de eventos de dispersión entre parches. Se identificaron 380 parches de hábitat potencial, mayoritariamente en el sector sureste del área de estudio, que fueron clasificados como “áreas centrales” o “áreas de conexión”. La ejecutoria del modelo fue testada en campo (61 % de asignaciones correctas), si bien la presencia real de R. alpinaen los parches de hábitat debería ser confirmada en el futuro. Este modelo constituye un avance para guiar la implementación de actividades de conservación de manera eficiente, mediante la protección estricta de “áreas centrales” y el incremento del tamaño de las “áreas de conexión”. Por lo tanto, mostramos que los modelos de conectividad que combinan datos de detección remota y selección local del hábitat pueden asistir en la planificación de la conservación y en las acciones de restauración específicas, seguramente mejorando los resultados de estrategias menos eficientes, como la selección al azar o basada en criterio experto.

Summary: Roots of forest trees are colonized by a diverse spectrum of ectomycorrhizal (EM) fungal species differing in their nitrogen (N) acquisition abilities. Here, we hypothesized that root N gain is the result of EM fungal diversity or related to taxon‐specific traits for N uptake.To test our hypotheses, we traced 15N enrichment in fine roots, coarse roots and taxon‐specific ectomycorrhizas in temperate beech forests in two regions and three seasons, feeding 1 mM NH4NO3 labelled with either 15NH4+ or 15NO3−.We morphotyped > 45 000 vital root tips and identified 51 of 53 detected EM species by sequencing. EM root tips exhibited strong, fungal taxon‐specific variation in 15N enrichment with higher NH4+ than NO3− enrichment. The translocation of N into the upper parts of the root system increased with increasing EM fungal diversity. Across the growth season, influential EM species predicting root N gain were not identified, probably due to high temporal dynamics of the species composition of EM assemblages.Our results support that root N acquisition is related to EM fungal community‐level traits and highlight the importance of EM diversity for tree N nutrition. [ABSTRACT FROM AUTHOR]

Transpiration and sap flow are physiologically interconnected processes that regulate nutrient and water uptake, controlling major aspects of tree life. They hold special relevance during drought, where wrecked sap flow can undermine overall tree growth and development. The present study encompasses five-year (2012–2015 and 2017) sap flow datasets on European beech (Fagus sylvatica). Four different techniques were used for sap flow modeling, namely, a linear model (LM), random forest (RF), extreme gradient boosting machine (XGBM), and neural networks (NN). We used six variants (Variants 1–6) differing in the captured conditions and the dataset size. The 'prediction power' was the ratio of the predicted and observed sap flow. We found the LM had the maximum prediction power for the overall sap flow in beech trees with 1 h shift of global radiation. In the reaming variants, the LM provided comparable prediction power to RF and XGBM. At the same time, NN exhibited relatively poor prediction power over other machine learning models. The study supports an easier-to-apply and computationally simpler approach (LM) to assess sap flow over more sophisticated machine learning approaches (RF, XGBM, and NN). [ABSTRACT FROM AUTHOR]

In forest communities, light competition is a key process for community assembly. Species' differences in seedling and sapling tolerance to shade cast by overstory trees is thought to determine species composition at late‐successional stages. Most forests are distant from these late‐successional equilibria, impeding a formal evaluation of their potential species composition. To extrapolate competitive equilibria from short‐term data, we therefore introduce the JAB model, a parsimonious dynamic model with interacting size‐structured populations, which focuses on sapling demography including the tolerance to overstory competition. We apply the JAB model to a two‐"species" system from temperate European forests, that is, the shade‐tolerant species Fagus sylvatica L. and the group of all other competing species. Using Bayesian calibration with prior information from external Slovakian national forest inventory (NFI) data, we fit the JAB model to short time series from the German NFI. We use the posterior estimates of demographic rates to extrapolate that F. sylvatica will be the predominant species in 94% of the competitive equilibria, despite only predominating in 24% of the initial states. We further simulate counterfactual equilibria with parameters switched between species to assess the role of different demographic processes for competitive equilibria. These simulations confirm the hypothesis that the higher shade tolerance of F. sylvatica saplings is key for its long‐term predominance. Our results highlight the importance of demographic differences in early life stages for tree species assembly in forest communities. [ABSTRACT FROM AUTHOR]

The increase in the frequency, intensity, and duration of drought periods in recent decades, with a significant impact on the state and functionality of the forest, requires an improvement in understanding the resilience and adaptability of forest species to environmental changes. Based on an extensive network of dendrochronological series from the Eastern Carpathians (150 spruce series, 41 fir series, and 40 beech series) with ages ranging from 30 to 160 years, distributed along an altitudinal gradient (470-1670 m), the resilience to the severe drought of 2003 was assessed. The results obtained, through resilience indices (resistance, recovery, resilience, and recovery period) applied to the mean growth series in basal area increment, suggest a higher resilience to the 2003 drought in beech compared to spruce and fir. Drought resistance increases with altitude, while recovery capacity decreases, especially for beech and spruce. In the case of fir, no significant variation in the resilience index was observed with the altitudinal gradient. Regarding the average cambial age in the year of the extreme climatic event, no statistically significant relationship was found. The research highlighted a high resilience to the 2003 drought among the main forest species in the Eastern Carpathians. In most cases, these species have the capacity to recover to their previous radial growth rates, even though the reduction in auxological processes was relatively large. [ABSTRACT FROM AUTHOR]

The quality of container-grown seedlings is influenced by the air and water properties of the substrate. These properties are closely tied to the amount and frequency of water supplied through sprinkler systems in nurseries, as well as the density of the substrate in the container cells. Throughout the entire growing season, this study examined how various parameters of Scots pine, Norway spruce, European beech, and pedunculate oak seedlings cultivated in HIKO V120SS and V265 containers were affected by two factors. Firstly, the study analyzed the impact of increased substrate density when filling the containers. Secondly, it explored the precise dosing of water applied by the sprinkler system, which was determined based on substrate sensors and meteorological conditions surrounding the seedlings. The results revealed that increased substrate compaction led to a long-term reduction in air capacity and an increase in water capacity within pine, spruce, and beech containers. However, oak seedlings were not affected by the increased substrate density. Additionally, the higher density of the compacted substrate positively influenced the growth parameters of pine seedlings but did not affect the other species. As a result, the current substrate compaction level used in the nursery where the measurements were taken appears to be optimal for spruce, beech, and oak seedlings. Furthermore, precise control over the amount of water applied during irrigation allowed for a reduction in water consumption by about 8%. This control also resulted in improved seedling sturdiness quotient and a more developed root system in the case of pine seedlings. However, no significant differences were observed for the other species. [ABSTRACT FROM AUTHOR]

Earth's forests are increasingly exposed to climate risks through climate change-related drought and heat waves. Here, we review the climate vulnerability of European beech (Fagus sylvatica), the most abundant tree species of Central Europe's temperate forests, and its adaptation potential to a hotter and drier climate in northern Germany, close to the center of the species' distribution range. About two-thirds of the studied beech forests show persistent negative growth trends of their dominant trees since the onset of rapid warming in the early 1980s, driven primarily by long-term deterioration of the climatic water balance (CWB) in summer and, locally, long-term decrease in June precipitation. Lower water storage capacity of the soil increases the climate sensitivity of growth. Even though beech populations of drier sub-regions reveal some acclimation to drought (reduced stomatal conductance, turgor loss point reduction, higher C allocation to roots), they are more climate-vulnerable than populations at moister sites, visible in larger growth decreases and greater CWB sensitivity of growth. Even though beech mortality is still lower in the study region than in other parts of Central Europe, our results identify beech forest regions with <350 mm growing-season precipitation as vulnerable to recent climate conditions, which refers to half of the study region. With further climate warming and aridification, most of northern Germany likely will become unfavorable for beech growth within the next tree generation, which suggests choosing in many production forests alternative, more drought- and heat-resistant timber species. [ABSTRACT FROM AUTHOR]

The Ellenberg quotient (EQ) is a climate index defined as a ratio of the hottest month's temperature and the average annual precipitation sum. The quotient indirectly expresses the relationship between climate and vegetation, and its application is related to the ecological niche of Fagus sp. Although the quotient was curated on the grounds of field research primarily on German vegetation, the possibilities of its utilisation are not limited to the Central European region. The objective of this study is (i) to compare the EQ values calculated for the forest vegetation zones in the Czech Republic with the published data using the ecological niche of Fagus sylvatica; and (ii) to compare the new EQ-based vertical model with field empirical mapping. The study area is the Czech Republic, Central Europe. We used climate data from 1970–2000 and the data of the National Forest Inventory, 2nd cycle (2011–2015), representing an objective data design. Geospatial analytic methods, machine learning (boosting), and verification through statistical testing were performed. The results indicate higher EQ values between the two most substantial spatial frames – the Hercynicum and Carpaticum regions. By comparing empirical mapped units to their climatic potential (in the EQ), a match was found only within the Carpaticum region. The study presents a concretisation of the general climate index for a specific region, adds to the knowledge about the Fagus ecological niche in context with the Central European vegetation, and also points to the EQ's potential for evaluating the concept of vertical differentiation of forest communi)ties, as well as a possible prediction tool for the vegetation migration in context with climate change. [ABSTRACT FROM AUTHOR]

Key message: A total of 45 aquaporins was identified in Fagus sylvatica, 35 of which were differentially expressed in spring and summer in the leaves, phloem and xylem of 11-year-old trees. European beech (Fagus sylvatica) has been widely studied in terms of its water relations and local adaptation. However, to date, the underlying basis conferring adaptation to differences in water availability are unknown. Therefore, we examined the expression of aquaporins in trees of four different beech provenances representing the southern and northern range margins, as well as core populations, grown in a common garden. We sampled their xylem, phloem and leaf tissue, when leaves had fully expanded, and in late summer. A total of 45 aquaporin isoforms were identified in the beech genome, of which 35 were detected across all sampled tissues. In our phylogenetic analysis, beech aquaporins clustered into the five subfamilies found in other woody species. Members of the plasma membrane intrinsic protein subfamily generally displayed the highest levels of expression, followed by tonoplast intrinsic proteins. Isoforms of the remaining subfamilies, Noduline-26-like intrinsic proteins, small basic intrinsic proteins and uncharacterised intrinsic proteins, were expressed at very low to moderate levels. The expression of most isoforms was stable or declined from spring to summer. Leaves followed a different expression profile from that of vascular tissues, whereas both phloem and xylem were found to express the same FsMIPs. Tissue-specific aquaporin expression was very similar amongst the four beech provenances, indicating that there is no inherent difference in the capability of these provenances to regulate aquaporin activity. The general decrease in FsMIP expression toward the end of the growing period indicates that aquaporins are involved in tree water relations and growth. [ABSTRACT FROM AUTHOR]

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow‐necked mice in beech forest after 2 mast and 2 non‐mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density‐dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance ("dilution," which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump‐shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation. [ABSTRACT FROM AUTHOR]

Temperature rise and more severe and frequent droughts will alter forest transpiration, thereby affecting the global water cycle. Yet, tree responses to increased atmospheric vapour pressure deficit (VPD) and reduced soil water content (SWC) are not fully understood due to long‐term tree adjustments to local environmental conditions that modify transpiration responses to short‐term VPD and SWC changes.We analysed sap flux density (SFD) of Fagus sylvatica, Picea abies, Pinus sylvestris and Quercus ilex from 25 sites across Europe to understand how daily variation in SWC affects the sensitivity of SFD to VPD (βVPD) and the maximum SFD (S95). Furthermore, we tested whether long‐term adjustments to site climatic conditions and stand characteristics affect βVPD and S95.The studied species showed contrasting βVPD and S95 with the largest values in F. sylvatica, followed by Q. ilex, which surpassed the two conifers that showed low βVPD and low S95. We observed that βVPD and S95 dropped during days of low SWC in F. sylvatica, P. sylvestris and Q. ilex, but not in P. abies. Both βVPD and S95 were driven by tree height, and the temperature and precipitation at the sites. However, stand basal area was the most important driver of βVPD and S95, explaining 30% of their total variance.Synthesis and applications: A future warmer and drier climate will restrict tree transpiration and thereby heavily affect the soil–plant‐atmosphere coupling. However, the effect of basal area, being the largest driver of tree transpiration sensitivity to vapour pressure deficit across a broad range of conditions, provides the opportunity to pre‐adapt European forests to future climate conditions. While stand thinning can increase the soil water availability for remaining trees, it also increases transpiration sensitivity to high air temperatures and may thereby amplify tree vulnerability to heat and drought. [ABSTRACT FROM AUTHOR]

Natural tree regeneration is a fundamental process in forest ecosystems ensuring the persistence and resilience of forest stands. Research on natural regeneration of European beech (Fagus sylvatica) in Central European forests has mainly focused on the impacts of abiotic processes, while little is known about the impact of pathogens. The aim of this study was to isolate Phytophthora species and identify the role that they may play in the decline of beech seedlings in Poland. A total of 1192 Phytophthora isolates were obtained from 300 symptomatic beech seedlings (60 seedlings from each of five stands): 638 isolates from seedlings exhibiting above‐ground symptoms and 554 isolates from seedlings that had roots with damping‐off symptoms. Based on morphological and molecular identification, the isolated species were Phytophthora cactorum, P. × cambivora, P. europaea, P. gonapodyides, P. plurivora and P. pseudosyringae. P. cactorum, P. × cambivora, P. europaea and P. plurivora were the most frequently isolated species from both above‐ and below‐ground organs. P. cactorum, P. × cambivora and P. plurivora were the most pathogenic species in the pathogenicity trials and caused 100% seedling mortality within 14 days of inoculation of the above‐ground organs. One single isolate of P. europaea was similarly pathogenic. P. gonapodyides, and P. pseudosyringae induced seedling mortality after inoculation of the cotyledons but not the roots. Our results demonstrate that Phytophthora may play an important role in reduction of naturally regenerated European beech seedlings. [ABSTRACT FROM AUTHOR]

Abstract Environmental DNA consists of species‐specific intracellular and extracellular fractions, whose content and information may not be similar in all environments. In forest soil, in particular, the biogeochemical fate of DNA originated by plant litter input has been extensively reviewed, but species‐specific persistence and distribution still await to be quantified. In the present work, based on the purification of extracellular and intracellular DNA fractions from forest soil samples representing 3 soil horizons at 36 randomized locations differing for stand composition (either beech‐ or spruce‐dominated, and mixed), followed by exDNA metabarcoding with the rbcL marker, we provide a clear picture of species‐specific plant DNA distribution, and explore plant community composition and diversity along the explored gradient and the soil profile. We did not find significant differences in intra‐ vs. extracellular total DNA distribution, with a progressive depletion with soil depth positively associated with soil organic C and N content and negatively associated with soil pH and mineral content. Species‐specific DNA distribution was horizontally dependent on beech and spruce basal area aboveground, while extracellular DNA showed peculiar species‐specific vertical patterns. Proportion of Fagus sylvatica DNA increased with depth in beech stand soil, and Picea abies DNA decreased in spruce stand soil, respectively, possibly linked to species‐specific differences in leaf litter decomposition dynamics and root litter contributions. Finally, our approach by metabarcoding provided a faithful, although incomplete, picture of the local plant diversity, suggesting that such technique could positively integrate traditional biodiversity inventory studies based on expert field assessments.

Key message: The datasets describe bacterial and fungal communities of European beech (Fagus sylvatica) leaves collected along a vertical gradient in a gallery forest throughout the growing season. They also describe communities in the surrounding environment of beech trees. Dataset access is at https://doi.org/10.7910/DVN/FFHAQU, and associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f17fe848-fc3e-4297-be11-9871b35a1be4. Both can be used to uncover the dynamics and assembly processes of phyllosphere microbial communities in forest ecosystems. [ABSTRACT FROM AUTHOR]

In forests, mycorrhizal fungi regulate carbon (C) and nitrogen (N) dynamics. We evaluated the interplay among ectomycorrhizas (ECM), ecosystem C fluxes, tree productivity, C and N exchange and isotopic fractionation along the soil‐ECM‐plant continuum in a Mediterranean beech forest. From bud break to leaf shedding, we monitored: net ecosystem exchange (NEE, a measure of the net exchange of C between an ecosystem and the atmosphere), leaf area index, stem growth, N concentration, δ13C and δ15N in rhizosphere soil, ectomycorrhizal fine root tips (ERT), ECM‐free fine root portions (NCR) and leaves. Seasonal changes in ERT relative biomass were strictly related to NEE and mimicked those detected in the radial growth. The analysis of δ13C in ERT, leaves and NCR highlighted the impact of canopy photosynthesis on ERT development and an asynchronous seasonal C allocation strategy between ERT and NCR at the root tips level. Concerning N, δ15N of leaves was negatively related to that of ERT and dependent on seasonal 15N differences between ERT and NCR. Our results unravel a synchronous C allocation towards ERT and tree stem driven by the increasing NEE in spring‐early summer. Moreover, they highlighted a phenology‐dependent 15N fractionation during N transfer from ECM to their hosts. This evidence, obtained in mature beech trees under natural conditions, may improve the knowledge of Mediterranean forests functionality. Summary Statement: The natural abundances of C and N stable isotopes along the soil‐ectomycorrhiza‐plant continuum in mature Fagus sylvatica trees revealed the key role of ectomycorrhizae in regulating source‐sink relationships and the close interchange between biogeochemical cycles in forest ecosystem. [ABSTRACT FROM AUTHOR]

Vegetation landscape dynamics are derived from the relationships established between anthropic activities and climate conditions over time. Paleoenvironmental research in the Pyrenees range (north-eastern Iberian Peninsula) has revealed what these dynamics were like in some regions during the Holocene. However, some fields of biogeography still present questions that need to be addressed, such as the patterns of Fagus sylvatica and Abies alba and the importance of the fire regime during the Meghalayan (late Holocene). We present a multiproxy study performed in a sedimentary record from the Clots de Rialba peat bog, located at 2093 m a. s. l. (Lleida, southern slope of the Pyrenees mountain range), that covers the last c. 3500 years. Analyses were performed on the organic matter content, pollen, non-pollen palynomorphs, and sedimentary charcoals larger than 150 μm. The palynological spectra revealed a maximum extension of Abies alba at about 3500 cal yr BP in the Bronze Age, while Fagus sylvatica showed its maximum extent between 3300 and 2800 cal yr BP. A dominance of Pinus was detected throughout the studied period. Other taxa such as cereals, herbaceous plants, aquatic plants, and coprophilous fungi have also been discussed to identify anthropic pressure and climate pulses. In addition, the study of sedimentary charcoals reveals the main forest fire episodes and their recurrences, some of them linked to anthropogenic activities and/or climate variations. These anthropogenic activities would include the use of opening and maintaining forest fires in deforestation in order to obtain pastures and spaces dedicated to cereal agriculture and the appearance of some taxa linked to or introduced by human communities. [ABSTRACT FROM AUTHOR]

Genetic diversity influences the evolutionary potential of forest trees under changing environmental conditions, thus indirectly the ecosystem services that forests provide. European beech (Fagus sylvatica L.) is a dominant European forest tree species that increasingly suffers from climate change-related die-back. Here, we conducted a systematic literature review of neutral genetic diversity in European beech and created a meta-data set of expected heterozygosity (He) from all past studies providing nuclear microsatellite data. We propose a novel approach, based on population genetic theory and a min–max scaling to make past studies comparable. Using a new microsatellite data set with unprecedented geographic coverage and various re-sampling schemes to mimic common sampling biases, we show the potential and limitations of the scaling approach. The scaled meta-dataset reveals the expected trend of decreasing genetic diversity from glacial refugia across the species range and also supports the hypothesis that different lineages met and admixed north of the European mountain ranges. As a result, we present a map of genetic diversity across the range of European beech which could help to identify seed source populations harboring greater diversity and guide sampling strategies for future genome-wide and functional investigations of genetic variation. Our approach illustrates how to combine information from several nuclear microsatellite data sets to describe patterns of genetic diversity extending beyond the geographic scale or mean number of loci used in each individual study, and thus is a proof-of-concept for synthesizing knowledge from existing studies also in other species. [ABSTRACT FROM AUTHOR]

Pulsed resources have prominent effects on community and ecosystem dynamics; however, there is little research on how resource pulses affect human–wildlife interactions. Tree masting is a common type of pulsed resource that represents a crucial food for many species and has important bottom‐up effects in food webs. In anthropogenic landscapes, years of food shortage after mast years can have negative outcomes for both people and wildlife, for instance when an increased use of anthropogenic foods by animals exacerbates human–wildlife conflicts. Here, we used novel remote sensing indicators of forest productivity and phenology, together with weather cues and ground measures of mast production, to assess whether years of masting and crop failures lead to changes in human–wildlife conflict occurrence. We used a unique 14‐year dataset including the production of European beech Fagus sylvatica seeds and brown bear Ursus arctos damage in the northeastern Carpathians as our model system. Linking these data in a panel regression framework, we found that temporal fluctuations in damage occurrence were sensitive to the year‐to‐year variation in beechnut production. Specifically, the number of damages during bear hyperphagia (i.e., September to December, when bears need to accumulate fat reserves prior to hibernation) was significantly higher in years with low beechnut production than in normal or mast years. Furthermore, we provide evidence that beech masting and failure can be predicted through a combination of remote‐sensing, weather, and field indicators of forest productivity and phenology. We demonstrate how pulsed resources, such as tree masting, can percolate through food webs to amplify human–wildlife conflict in human‐dominated landscapes. Given the recent range expansion of large carnivores and herbivores in many regions, including Europe, predicting years of natural food shortage can provide a pathway to proactive damage prevention, and thus to foster coexistence between wildlife and people. [ABSTRACT FROM AUTHOR]

European beech (Fagus sylvatica L.) is an important tree species throughout Europe but shifts in its suitable habitats are expected in the future due to climate change. Finding provenances that are still economically viable and ecologically resilient is an ongoing field of research. We modelled the dominant tree heights of European beech as a trait reflecting growth performance dependent on provenance, climate and soil conditions. We derived dominant tree heights from national forest inventory (NFI) data from six European countries spanning over large ecological gradients. We performed function-on-scalar regression using hierarchical generalized additive models (HGAM) to model both the global effects shared among all provenances and the effects specific to a particular provenance. By comparing predictions for a reference period of 1981–2010 and 2071–2100 in a RCP 8.5 scenario, we showed that changes in growth performance can be expected in the future. Dominant tree heights decreased in Southern and Central Europe but increased in Northern Europe by more than 10 m. Changes in growth performance were always accompanied by a change in beech provenances, assuming assisted migration without dispersal limitations. Our results support the concept of assisted migration for the building of resilient future forests and emphasize the use of genetic data for future growth predictions. [ABSTRACT FROM AUTHOR]

In forest ecosystems, decomposition is essential for carbon and nutrient cycling and therefore a key process for ecosystem functioning. During the decomposition process, litter chemistry, involved decomposer organisms, and enzymatic activity change interdependently. Chemical composition of the litter is the most complex and dynamic component in the decomposition process and therefore challenging to assess holistically. In this study, we aimed to characterize chemical shifts during decomposition and link them to changes in decomposer fungal activity. We characterized the chemical composition of freshly fallen autumn leaves of European beech (Fagus sylvatica) and the corresponding leaf litter after 1 year of decomposition by proton nuclear magnetic resonance spectroscopy. We further tested the applicability of spiking experiments for qualitative and quantitative characterization of leaves and litter chemistry. The composition and transcriptional activity of fungal communities was assessed by high-throughput Illumina sequencing in the same litter samples. We were able to distinguish freshly fallen leaves from 1-year-old litter based on their chemical composition. Chemical composition of leaves converged among regions with progressing decomposition. Fungal litter communities differed in composition among regions, but they were functionally redundant according to the expression of genes encoding litter degrading enzymes (CAZymes). Fungi of the saprotrophic genera Mycena and Chalara correlated with transcription of litter-degrading CAZymes in 1-year-old litter. Forestry measures influenced the diversity and transcription rate of the detected CAZymes transcripts in litter. Their expression was primarily predicted by composition of the soluble chemical fraction of the litter. Environmental NMR fingerprints thus proved valuable for inferring ecological contexts. We propose and discuss a holistic framework to link fungal activity, enzyme expression, and chemical composition. [ABSTRACT FROM AUTHOR]

The bark beetle Taphrorychus bicolor primarily inhabits Fagus sylvatica forests. Its populations increase after periods of drought. Due to the limited knowledge of factors affecting its abundance, we conducted a large-scale sampling. Beetles were captured using three Theysohn traps lured with bicolorin at 26 study sites in mature homogeneous beech forests distributed throughout the Czech Republic. The traps were checked, and beetles were sampled weekly or biweekly in 2022. Using Generalized Linear Mixed Models (GLMMs), the impact of selected environmental and management variables on the abundance of T. bicolor was analyzed. The species occurs at elevations ranging from 150 m a.s.l. to 1300 m a.s.l. throughout the Czech Republic. This represents its entire host range, e.g., beech, although in the lowest elevations it is also found on other deciduous trees. In 2022, the flight activity lasted from late April to early September, and two generations were recorded, with the filial generation starting to fly in late June. In many study sites, more than 10,000 beetles were captured per trap. The number of females trapped was higher than males, consistent with the species' polygamous strategy, where females move toward increasing concentrations of pheromones. The number of beetles in the traps was influenced by elevation, with the highest abundance observed at around 600 m a.s.l. Abundances were higher in areas with more extensive beech forest complexes. Lower beetle abundances were found in stands where the studied forest bordered with meadows, pastures, or crop fields, indicating the species' reluctance to fly outside the forest habitat. The abundance of the filial generation was higher when there was a larger area of beech forests within a 1000 m radius, suggesting a median dispersal flight distance of approximately 1 km for the filial generation. [Display omitted] • Taphrorychus bicolor primarily inhabits Fagus sylvatica forests. • Both sexes of T. bicolor are easily caught in traps baited with bicolorin. • Catching >10,000 beetles per trap does not indicate an outbreak. • Abundances of T. bicolor are higher in larger beech forest complexes. [ABSTRACT FROM AUTHOR]

In the present work, single- and double-dowel joints following different geometric configurations are experimentally and numerically investigated to derive the splitting behaviour of beech wood (Fagus sylvatica L.), one of the most widespread hardwood species in Europe for structural purposes. The influence of the spacing between dowels, their distance to the supports, and the slenderness of the beams is analysed. The correlation of the experimental failure loads with those predicted numerically by cohesive zone finite element-based models using the fracture properties of the species is discussed. The experimental results are also compared with those obtained from the normative expression included in Eurocode 5 and two other design models reported in the literature. The splitting failure loads predicted by both the analytical and numerical models were found to be conservative, the latter being closer to the experimental values.

Forest management has a direct influence on the structure and stability of forests. In this study, we used the 3D data from mobile laser scanning in real forest stands dominated by European beech (Fagus sylvatica L.) to simulate different silvicultural treatments and assess their impact on the structural complexity and short-term economic return. For the structural assessment, we used the box-dimension (Db), a holistic measure of structural complexity in forest. The expected net revenues of the silvicultural treatments were used as a proxy for short-term economic gain. We simulated six different treatments in 19 different real-world forest stands. The results showed that each treatment had a negative impact on the structural complexity of the stands but with varying severity. The treatments with the smallest effect on stand structural complexity showed the highest net revenue, indicating no trade-offs if a forest owner strives for small stand structural changes and high economic return. The approach used here allows quantifying the structural and economic consequences of different treatments in forest stands prior to the actual application in the real world. This holds large potential for decision making according to the forest owner's objective.

Leaf cuticular waxes play an important role in reducing evapotranspiration via diffusion. However, the ability of mature trees to regulate the biosynthesis of waxes to changing conditions (e.g., drought, light exposition) remain an open question, especially during the late growing season. This holds also true for one of the most widely distributed trees in Central Europe, the European beech tree (Fagus sylvatica L.). In order to investigate the ongoing formation of wax constituents like alkanes and fatty acids, we conducted a 13CO2 pulse-chase labelling experiment on sun-exposed and shaded branches of a mature beech tree during the late summer 2018. The 13C-label was traced via compound-specific δ13C isotope analysis of n-alkanes and fatty acids to determine the denovo biosynthesis within these compound classes. We did not observe a significant change in lipid concentrations during the late growing season, but we found higher n-alkane concentrations in sun-exposed compared to shaded leaves in August and September. The n-alkane and fatty acid composition showed ongoing modifications during the late growing season. Together with the uptake and following subsequent decrease of the 13C-label, this suggests ongoing de-novo biosynthesis, especially of fatty acids in European beech leaves. Moreover, there is a high variability in the 13C-label among individual branches and between sun-exposed and shaded leaves. At the same time, sun-exposed leaves invest more of the assimilated C into secondary metabolites such as lipids than shaded leaves. This indicates that the investigated mature beech tree could adjust its lipid production and composition in order to acclimate to changes in microclimates within the tree crown and during the investigated period. [ABSTRACT FROM AUTHOR]

European beech is one of the most common tree species in Europe and is generally suggested to play even more of a prominent role in forestry in the future. It seems to have the potential to partially replace Norway spruce, as it is less sensitive to expected warmer and drier conditions. It is, however, not well known in which regions these new plantings would be particularly favourable and if specific provenances may be better adapted to the new conditions than others. Therefore, we estimated the potential early height growth under climate conditions in 2040–2060 for 20 beech provenances across a region covering the Czech Republic and Slovakia. This Central European region is expected to experience considerably drier and warmer conditions in the future. For this exercise, we implemented a new neural network model developed from height growth information obtained from the open-access BeechCOSTe52 database. The simulations are driven by past and future climate data obtained from the WorldClim database of historical climate data and future climate projections. Simulations revealed that provenances originating from drier regions performed on average significantly better than those from regions with good water supply. Moreover, provenances originating from drier regions had a particularly large advantage in the relatively arid regions of Central Czechia and Southern Slovakia. We can also confirm that all provenances showed a high phenotypic plasticity of height growth across the whole investigated region. [ABSTRACT FROM AUTHOR]

During the particularly severe hot summer drought in 2018, widespread premature leaf senescence was observed in several broadleaved tree species in Central Europe, particularly in European beech (Fagus sylvatica L.). For beech, it is yet unknown whether the drought evoked a decline towards tree mortality or whether trees can recover in the longer term.In this study, we monitored crown dieback, tree mortality and secondary drought damage symptoms in 963 initially live beech trees that exhibited either premature or normal leaf senescence in 2018 in three regions in northern Switzerland from 2018 to 2021. We related the observed damage to multiple climate‐ and stand‐related parameters.Cumulative tree mortality continuously increased up to 7.2% and 1.3% in 2021 for trees with premature and normal leaf senescence in 2018, respectively. Mean crown dieback in surviving trees peaked at 29.2% in 2020 and 8.1% in 2019 for trees with premature and normal leaf senescence, respectively. Thereafter, trees showed first signs of recovery. Crown damage was more pronounced and recovery was slower for trees that showed premature leaf senescence in 2018, for trees growing on drier sites, and for larger trees. The presence of bleeding cankers peaked at 24.6% in 2019 and 10.7% in 2020 for trees with premature and normal leaf senescence, respectively. The presence of bark beetle holes peaked at 22.8% and 14.8% in 2021 for trees with premature and normal leaf senescence, respectively. Both secondary damage symptoms occurred more frequently in trees that had higher proportions of crown dieback and/or showed premature senescence in 2018.Our findings demonstrate context‐specific differences in beech mortality and recovery reflecting the importance of regional and local climate and soil conditions. Adapting management to increase forest resilience is gaining importance, given the expected further beech decline on dry sites in northern Switzerland. [ABSTRACT FROM AUTHOR]

We evaluated three estimation methods for fitting the three-parameter Weibull distribution to even-aged European beech (Fagus sylvatica) forests by using experimental tree diameter data collected in 3709 sample plots (500 m² each). The maximum likelihood estimation method (MLE), the method of moments (MOM) and the method of modified moments type 1 (MM1 ) were applied for fitting the Weibull function. The goodness-of-fit of stand parameters (total tree number, stand basal area, dominant stand diameter and mean quadratic diameter) was tested by MAE and RMSE, and the probability and cumulative density functions of trees per 5 cm diameter classes were additionally tested by the Kolmogorov-Smirnov test and compared with Kolmogorov-Smirnov's D statistic. All three methods are suitable for estimating stand parameters based on the fitted Weibull function. Fitting the diameter distribution per 5 cm diameter classes at the plot level was less accurate due to the low number of trees or irregular diameter distribution of trees. The MM1 method was found to be the most suitable for fitting the three-parameter Weibull distribution to beech forests represented by data derived from small plots. [ABSTRACT FROM AUTHOR]

The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of the historic Emperor’s Beech (Fagul Împăratului) from Muncel, Baia de Arieş, Romania. Two wood samples were collected from the large tree, out of which four segments were extracted and analysed by AMS radiocarbon. The oldest dated sample segment had a radiocarbon date of 233 ± 18 BP, which corresponds to a calibrated age of 365 ± 5 years. This value suggests an age of 420 ± 20 years for the Emperor’s Beech. Thus, the historic beech started growing around the year 1600. [ABSTRACT FROM AUTHOR]

Temperature (T) and vapour pressure deficit (VPD) are important drivers of plant hydraulic conductivity, growth, mortality, and ecosystem productivity, independently of soil water availability. Our goal was to disentangle the effects of T and VPD on plant hydraulic responses. Young trees of Fagus sylvatica L., Quercus pubescens Willd. and Quercus ilex L. were exposed to a cross‐combination of a T and VPD manipulation under unlimited soil water availability. Stem hydraulic conductivity and leaf‐level hydraulic traits (e.g., gas exchange and osmotic adjustment) were tracked over a full growing season. Significant loss of xylem conductive area (PLA) was found in F. sylvatica and Q. pubescens due to rising VPD and T, but not in Q. ilex. Increasing T aggravated the effects of high VPD in F. sylvatica only. PLA was driven by maximum hydraulic conductivity and minimum leaf conductance, suggesting that high transpiration and water loss after stomatal closure contributed to plant hydraulic stress. This study shows for the first time that rising VPD and T lead to losses of stem conductivity even when soil water is not limiting, highlighting their rising importance in plant mortality mechanisms in the future. [ABSTRACT FROM AUTHOR]

The importance of veteran trees is well recognised nowadays. The sudden breakage of some of these plants in Trentino (Italy), mainly due to Kretzschmaria deusta, prompted a survey of the veteran beeches reported in this area. Visual tree assessment was carried out in 40 sites with either single trees or groups of beeches, for a total of 115 trees evaluated. Most trees showed serious defects or problems in need of management and 19 had a high level of risk of breakage because of the presence of several structural problems. The presence of K. deusta was recorded on 50.4% of the examined trees. The pathogen was also identified in the proximity of investigated trees at 29 sites. Laboratory tests confirmed the identity of K. deusta by microbiological and molecular approaches and also identified Cosmopora berkeleyana as mycoparasite on K. deusta fruiting bodies. Isolates obtained from declining trees and old stumps showed the same pattern of growth at different temperatures. The risk evaluation emphasised how the fungus could affect the survival and safety of these veteran trees; this was confirmed by the collapse of four of the investigated trees in the last years. Therefore, K. deusta, which has been considered as a facultative parasite up to now, could play a more incisive role both in the decline of old beech trees and the natural evolution of aging beech woods.

Wood use in bio-building should be considered as one of the main pillars of sustainability. According to international standards, beech wood (Fagus sylvatica L.) is a rather less durable species as it is subject to degradation due to weathering, though it is abundantly available to a more intense use. Service life of beech products and wood products in general can be enhanced by different methods, such as heat treatments, but new chances are offered by coating technologies. However, to ensure protection from wood-destroying organisms, most commercial coatings include components that could harm human health, other organisms and the environment. Therefore, coating industry has to develop more eco-friendly solutions in order to decrease its impact on human health and environment. The objective of this article was to modify commercial acrylic varnish by adding cellulose nanocrystals (CNC) and lignin (LN) extracted from beech wood and investigate their effect on water sorption, additive dispersion in the coating matrix and coating resistance to bacterial attack. Contact angle, weight gain and colour difference were analysed and FT-IR mapping was applied. The performance of CNC was promising, as it enhanced water sorption of the modified coating. However, protection against bacterial attack was not satisfying. On the other hand, chemically unmodified lignin did not show positive effects as component in the coating formulation. Nevertheless, the currently limited usage of these two renewable and abundant resources urgently calls for their more efficient utilization, in order to create additional value with industry side-streams producing novel bio-based materials. Further experiments are needed in order to obtain better dispersion of the particles and higher resistance to bacterial attacks.

Abstract Background The tick Ixodes ricinus is an important vector of tick-borne diseases including Lyme borreliosis. In continental Europe, the nymphal stage of I. ricinus often has a bimodal phenology with a large spring peak and a smaller fall peak. There is consensus about the origin of the spring nymphal peak, but there are two alternative hypotheses for the fall nymphal peak. In the direct development hypothesis, larvae quest as nymphs in the fall of the same year that they obtained their larval blood meal. In the developmental diapause hypothesis, larvae overwinter in the engorged state and quest as nymphs one year after they obtained their larval blood meal. These two hypotheses make different predictions about the time lags that separate the larval blood meal and the density of questing nymphs (DON) in the spring and fall. Methods Inter-annual variation in seed production (masting) by deciduous trees is a time-lagged index for the density of vertebrate hosts (e.g., rodents) which provide blood meals for larval ticks. We used a long-term data set on the masting of the European beech tree and a 15-year study on the DON at 4 different elevation sites in western Switzerland to differentiate between the two alternative hypotheses for the origin of the fall nymphal peak. Results Questing I. ricinus nymphs had a bimodal phenology at the three lower elevation sites, but a unimodal phenology at the top elevation site. At the lower elevation sites, the DON in the fall was strongly correlated with the DON in the spring of the following year. The inter-annual variation in the densities of I. ricinus nymphs in the fall and spring was best explained by a 1-year versus a 2-year time lag with the beech tree masting index. Fall nymphs had higher fat content than spring nymphs indicating that they were younger. All these observations are consistent with the direct development hypothesis for the fall peak of I. ricinus nymphs at our study site. Our study provides new insight into the complex bimodal phenology of this important disease vector. Conclusions Public health officials in Europe should be aware that following a strong mast year, the DON will increase 1 year later in the fall and 2 years later in the spring. Studies of I. ricinus populations with a bimodal phenology should consider that the spring and fall peak in the same calendar year represent different generations of ticks. Graphical Abstract

Leaf cuticular waxes play an important role in reducing evapotranspiration via diffusion. However, the ability of mature trees to regulate the biosynthesis of waxes to changing conditions (e.g., drought, light exposition) remain an open question, especially during the late growing season. This holds also true for one of the most widely distributed trees in Central Europe, the European beech tree (Fagus sylvatica L.). In order to investigate the ongoing formation of wax constituents like alkanes and fatty acids, we conducted a 13CO2 pulse-chase labelling experiment on sun-exposed and shaded branches of a mature beech tree during the late summer 2018. The 13C-label was traced via compound-specific δ13C isotope analysis of n-alkanes and fatty acids to determine the de-novo biosynthesis within these compound classes. We did not observe a significant change in lipid concentrations during the late growing season, but we found higher n-alkane concentrations in sun-exposed compared to shaded leaves in August and September. The n-alkane and fatty acid composition showed ongoing modifications during the late growing season. Together with the uptake and following subsequent decrease of the 13C-label, this suggests ongoing de-novo biosynthesis, especially of fatty acids in European beech leaves. Moreover, there is a high variability in the 13C-label among individual branches and between sun-exposed and shaded leaves. At the same time, sun-exposed leaves invest more of the assimilated C into secondary metabolites such as lipids than shaded leaves. This indicates that the investigated mature beech tree could adjust its lipid production and composition in order to acclimate to changes in microclimates within the tree crown and during the investigated period.