Large live and dead trees promote saproxylic beetle diversity and White‐backed Woodpecker breeding territories

Colouration can affect predation risk through camouflage, signalling, or other mechanisms that shape predator perception and decision-making. The Rosalia longicorn (Rosalia alpina), a flagship longhorn beetle of European beech forests, has a bluish-grey exoskeleton with conspicuous black spots, yet the function of this colour pattern remains unclear. We tested whether its blue body colouration is consistent with background matching to beech bark and whether black spotting reduces predation risk beyond that provided by the blue body colouration alone. We measured reflectance spectra of the blue body colouration, black spots and beech bark, modelled chromatic contrasts under avian vision, and deployed plasticine beetle models in three colour variants: black, blue and a natural pattern with blue and black spots. Visual modelling showed that both beetle colours were chromatically distinguishable from beech bark, but black spots had lower chromatic contrast than blue body colouration, suggesting that the black component may match the bark background more closely than the blue component. In the field experiment, attack occurrence varied with colour, sampling session and their interaction. In September, blue and patterned models were less likely than black models to be attacked. Patterned models also received fewer marks than black models. By October, these colour differences had weakened or disappeared. These findings indicate that the blue body colouration and the natural colour pattern may reduce predation risk relative to an entirely black phenotype, particularly early in the season. However, we found no clear evidence that black spotting provides protection beyond that afforded by the blue body colouration alone. Alternative functions of the spots, including thermoregulation or signalling, remain plausible.

Nutrient and water supply are decisive limiting factors for trees and their productivity. Yet, the consequences of fertilization for drought responses, especially during the sensitive nursery stage, remain poorly understood. In this study, we exposed potted saplings of Pinus sylvestris, Fagus sylvatica, and Quercus robur to two levels of fertilization and three water regimes. The effects of fertilization, drought, and their interaction on gas exchange, hydraulic traits, and growth were examined. Fertilization generally promoted gas exchange, hydraulic conductance, and biomass accumulation but responses were species-specific and did not always persist under and after drought. While fertilized Q. robur maintained or even increased its biomass and physiological performance under drought, the benefits of fertilization for P. sylvestris and F. sylvatica diminished under increasing drought intensity. No consistent changes in drought resistance traits (e.g., turgor loss point, embolism resistance) were observed across species in response to fertilization, which may indicate limited plasticity or acclimation potential of saplings. Our findings highlight the species-specific fertilization effects on drought responses and post-drought performance of saplings, emphasizing the need to consider both factors in silvicultural practices under future climate scenarios.

Climate change is intensifying drought stress in temperate forests, but its effects on tree reproduction, central to forest regeneration and migration capability, remain poorly understood. Here, we analyze 221 time series of beech (Fagus sylvatica) seed production across Europe to test whether drought reduces seed output. We isolate drought exposure during the flowering, pollination, and seed maturation phases of reproduction, and test for legacy effects on future reproduction. Seed production was not impaired by summer drought, and dry spring conditions were associated with increased output, likely via enhanced pollen dispersal. Thus, once initiated, beech reproduction is not reduced by drought, with no suppression of reproduction the following year. Reproduction was not reduced at the driest sites during exceptional European summer droughts in 2003, 2018, and 2022. Considered alongside prior evidence that drought suppresses forest growth and elevates mortality, these findings indicate that vital rates can respond in opposite directions to the same stressor. Such contrasts may sustain forest reproduction during heat-drought events yet shift demographic balance toward higher mortality and turnover as climatic extremes intensify.

Seed production of European beech (Fagus sylvatica) is highly variable between years and synchronised between individual trees (i.e., masting), creating years with high seed crops, commonly separated by one or more years with little or no seed production. This pulsed reproduction has selective benefits for the trees, as it creates a cycle of predator satiation and starvation, through which masting drives population dynamics of dependent species. Masting is sensitive to climate change, making long-term data on annual seed production valuable for understanding changes in the masting patterns and their effects on seed consumers. This study presents a long-term dataset of 50 years containing annual, ground-plot beechnut counts for 81 individual trees in the Netherlands. Time series length of individual trees ranges from one year to the whole study period, with 21 trees having at least 40 years of data. Beechnut counts are categorized in sound, empty and predated, complemented by gross and net weights of individual nuts, allowing for detailed analyses of masting patterns and annual variation in food abundance for seed predators.

Pre-drought Conservative Xylem Hydraulic Architecture Is Associated With Enhanced Recovery From the 1976 Drought in European Beech (Fagus sylvatica L.).

Forest management and species identity shape climate sensitivity and drought resilience in temperate mountain forests.

ABSTRACT When sorting highly stressed wood-hybrid composites made of laminated veneer and plywood, both density and fibre orientation must be considered due to the pronounced anisotropy of wood. For the accurate design and dimensioning of components made from defect-free veneers, strength and modulus of elasticity must be estimated as precisely as possible using non-destructive methods. These properties are primarily influenced by the in-plane and out-of-plane fibre orientation. In this study, fibre orientation was estimated indirectly via the dynamic modulus of elasticity, determined from stress-wave transition time and density. A total of 327 beech veneers (Fagus sylvatica), each 0.9 mm thick, were analyzed. The veneers originated from 12 trees supplied by four different manufacturers and exhibited fibre orientations between 0° and 32.4°. As a reference, fibre orientation was determined optically using five measurements per specimen with a reflected-light microscope at 20× magnification. Based on the experimental data, a predictive model using Hankinson’s equation was developed and validated with an independent sample set (N = 22) from a fifth supplier. The model achieved a coefficient of determination of R² = 0.93 for the training set and R² = 0.74 for the validation set, demonstrating strong potential for future technical applications.

Observation of drinking behaviour in the Ursus arctos marsicanus at a tree cavity (dendrotelm) in the central Apennines.

ABSTRACTMasting, highly synchronised but temporally variable seed production, is initiated by weather cues and is thus highly sensitive to climate change. Changes in these cues can lead to a masting breakdown, reducing the fitness benefits of masting through decreasing pollination efficiency and increasing predation risk for seeds. Here, we use 50 years of individual tree data on annual seed production of European beech (Fagus sylvatica) in the Netherlands to assess temporal changes in masting patterns and their consequences for the selective benefits of masting. Additionally, we use a novel approach to identify which weather cues initiate reproduction, assess their temporal changes, and test whether they account for the observed changes in masting. We show that synchrony and inter‐annual variation in beechnut production have declined, resulting in a masting breakdown in the late‐2000s, since which there has been constant, but low, seed production each year. Consequently, predation risk increased almost three‐fold, while pollination became less efficient, together reducing the fitness benefits of masting. Seed production was driven by precipitation and temperatures in the year of seed fall and the two preceding years, but the periods within the year in which trees respond to each climate variable differ in both timing and duration. Interestingly, only temperature, not precipitation, has changed over time, but this change only partly explained the observed changes in masting patterns. Masting breakdown is shown across the species range, but its fitness consequences remain understudied, because detailed, individual‐level, long‐term data are required but still rare. By using such a dataset, we here provide crucial evidence for the negative consequences of masting breakdown for beeches through reduced pollination efficiency and increasing predation risk. Using a new methodology, we further underline the strong effects of weather cues on reproduction, while showing that changing climate alone cannot be driving the masting breakdown and must interact with currently unidentified factors.

The persistence of organisms in changing climates depends on both phenotypic plasticity and adaptation. However, despite extensive research, it remains largely unclear how forest trees will genetically adapt or phenotypically acclimate to future climates. In this study, we investigated the genetic architecture of tree-ring and leaf traits in sessile oak (Quercus petraea) and European beech (Fagus sylvatica) and tested for signals of climate adaptation at loci controlling these traits. We combined trait data from common gardens established in the 1990s across the species' European ranges with climatic and genomic data. We conducted genome-wide association (GWA) analyses and tested the effects of temperature and precipitation transfer distances on associated loci. Our GWA analyses revealed a complex, multi-locus genetic architecture underlying functional traits in both species. Sessile oak displayed a greater number of trait associations than European beech and we found indications of pleiotropy, particularly in sessile oak. European beech showed limited plastic and adaptive responses to climate at the genomic level. In contrast, sessile oak showed signals of both adaptive plasticity and climate adaptation, particularly at loci associated with growth responses to extreme droughts and to long-term summer temperature. Our findings suggest that sessile oak possesses a stronger capacity to respond to climate change than European beech. This capacity may facilitate range expansion in sessile oak, while raising concerns about the sustainability of beech in European lowland forests under future climates.

This study investigates the climate sensitivity and resilience of radial growth in eight coniferous and deciduous tree species in the Vienna Woods, Austria. Using dendrochronological methods, we analyzed tree-ring width data from 63 forest plots to assess growth responses to meteorological variability over the period 1933-2023. Historic climate records were used to develop a water balance model, from which we derived seasonal growth factors. Linear mixed effects models were applied to quantify species-specific relationships between tree-ring width and climatic conditions during the current and preceding two years. Tree-ring width responded not only to climatic conditions of the current growing season but also strongly to those of the previous year. Soil moisture and air temperature emerged as the principal drivers of radial growth, with soil moisture positively and temperature negatively affecting ring width. Climatic conditions during June-July of the current year exerted the strongest impact on ring formation. Using regional climate trends and projected air temperature and precipitation trajectories for Central Europe under RCP4.5 and RCP8.5, we forecast future growing conditions for the region. Both scenarios predict an extended growing season, increased transpiration demand, and heightened drought risk - more pronounced under RCP8.5. However, projected increases in precipitation partly offset the drought risk. By combining historical climate sensitivity of radial increment with future climate projections, we modelled expected tree-ring growth for eight tree species. Most species are predicted to experience notable declines in radial growth, with the strongest reductions in conifers, including European larch (Larix decidua), Norway spruce (Picea abies), Austrian pine (Pinus nigra) and Scots pine (Pinus sylvestris). Deciduous species - Sycamore maple (Acer pseudoplatanus), European beech (Fagus sylvatica), and sessile oak (Quercus petraea) - show moderate declines. In contrast, Turkey oak (Quercus cerris) is projected to increase radial growth under future climate scenarios. These findings suggest that forest management in the Vienna Woods and adjacent regions should prioritize the promotion of warm- and drought-tolerant tree species such as Quercus cerris to enhance forest resilience and sustainability in the face of climate change.

Tree species can exert strong and species-specific controls on water infiltration in forest soils. However, the magnitude and meteorological sensitivity of these effects remain poorly quantified under standardised site conditions. We measured unsaturated hydraulic conductivity ( K ) and soil water repellency index ( R ) in the A horizon beneath seven single-species stands – lime ( Tilia cordata ), sycamore ( Acer pseudoplatanus ), maple ( Acer platanoides ), beech ( Fagus sylvatica ), oak ( Quercus robur ), larch ( Larix decidua ), and Douglas-fir ( Pseudotsuga menziesii ) – in a common-garden experiment on sandy Dystric Gleyic Cambisols. Measurements were conducted in five campaigns representing contrasting 10-day antecedent weather conditions. Broadleaved species such as lime, maple, and sycamore maintained low repellency and high K regardless of preceding weather, indicating low susceptibility to hydrophobicity. In contrast, conifers (Douglas-fir and larch) rapidly developed strong repellency and sharply reduced infiltration following dry spells. Beech and oak showed intermediate responses, with repellency emerging under drought but receding after wet periods. These patterns reveal that species differ not only in baseline hydraulic properties but also in the speed and magnitude of their response to short-term meteorological variability. Our study highlights the importance of species-specific functional traits in regulating soil hydraulic behaviour. Selecting species that sustain infiltration and resist the onset of hydrophobicity could help improve water retention, limit runoff, and enhance forest resilience under projected increases in drought frequency. • Unsaturated hydraulic conductivity and soil repellency were measured in humus-mineral soil horizon beneath seven tree species. • Five campaigns represented distinct 10-day antecedent weather conditions ranging from dry to wet. • Conifers (Douglas-fir, larch) rapidly developed high water repellency and infiltration loss after short dry spells. • Lime, maple, and sycamore remained wettable under all conditions, indicating resistance to drought-induced hydrophobicity. • Beech and oak showed intermediate sensitivity, with repellency peaking only after prolonged dryness.

Accurate projections of temperate tree growing seasons under climate change require representing developmental constraints that determine tree resource allocation. A phenological 'switch point' after the summer solstice (21 June) has been proposed, with pre-solstice warming advancing autumn phenology and post-solstice warming delaying it. We propose that this switch is flexible and occurs at the compensatory point between early-season development and late-season temperature effects. We performed trans-solstice climate manipulation experiments on potted European beech (Fagus sylvatica) saplings to test (i) how spring leaf-out timing and June-August temperatures influence end-of-season timing (bud set and leaf senescence) and (ii) whether daytime and nighttime temperatures before and after the solstice have distinct effects. Bud set and senescence were tightly coupled (R2=0.49), with stronger bud responses. Each day of delayed leaf-out postponed bud set by 0.24±0.06 days and senescence by 0.22±0.08 days. July full-day cooling delayed autumn phenology in late-leafing individuals (bud set +4.9±2.6 days; senescence +3.1± 2.8 days) but had a negligible impact on early-leafing trees. August full-day cooling advanced both stages. Pre-solstice daytime cooling had no effect, while post-soltice daytime cooling advanced autumn phenology. Nighttime cooling consistently delayed bud set. These findings support the Solstice-as-Phenology-Switch model and highlight the central role of developmental progression in constraining growing seasons. Faster early-season development - especially under nighttime warming - moves trees past the switch earlier, increasing sensitivity to late-season cooling and thereby triggering earlier autumn phenology. Phenology models should incorporate these developmentally-mediated and diel-specific temperature responses.

Assessing the potential effects of climate change on future forest composition in France.

Volatile organic compounds (VOCs) facilitate aboveground plant communication, but belowground signaling remains less understood. This study explored root-root interactions between Picea abies and Fagus sylvatica saplings in monospecific (Fagus-Fagus) and heterospecific (Picea-Fagus) pairs (n=6), excluding shoot-level VOC communication. Sender plants were treated with jasmonic acid (JA) to simulate herbivory and labeled with 13CO2 and 15NH4NO3 to trace nutrient transfer in a split-root design. VOC emissions and gas exchange were measured over ten days using PTR-TOF-MS and 13CO2-spectroscopy and 13C and 15N were analyzed in roots and shoots via EA-IRMS. Our findings reveal, that (i) JA treatment induced strong de novo terpenoid emissions from P. abies and enhanced emissions of oxygenated VOCs and benzenoids from F. sylvatica, (ii) F. sylvatica receiver plants responded similarly to JA-treated neighbors, indicating belowground signaling, and (iii) responses of receiver plants were more pronounced in the heterospecific treatment. Furthermore, formic acid emissions from soils increased following JA treatment, suggesting altered soil microbial activity. Isotopic analysis revealed C exudation into the rhizosphere and N transfer to receiver plants. These results suggest that belowground signaling enables early upregulation of herbivore-induced defenses in neighboring plants, and that the response intensity is modulated by species identity.

Heatwaves are intensifying worldwide, often coinciding with high vapour pressure deficit (VPD) and soil drought. Yet, how temperate tree species tolerate these combined stresses remains elusive. Using single-tree gas-exchange chambers, we examined the response of leaf gas exchange and thermoregulation of three broadleaved tree species to a stepwise increase in air temperature (25°C-45°C) along with VPD (2.5-7.9 kPa) under well-watered and moderate drought conditions, followed by a 2-day recovery at 25°C. Across species, heat stress increased transpiration but reduced net assimilation, leading to sharp declines in water-use efficiency. Alongside, leaf cooling intensified, driving leaf temperatures below air temperature. Under moderate drought, restricted stomatal conductance reduced transpirational cooling, causing leaf temperatures to exceed air temperature and increasing heat-related damage. Species differed markedly in their heat responses along the isohydric-anisohydric spectrum. Isohydric Acer platanoides showed early stomatal closure, limited cooling, severe leaf damage, and poor recovery. Anisohydric Quercus robur maintained gas exchange, exhibited minimal leaf damage and recovered rapidly, while Fagus sylvatica showed intermediate responses. Together, these results highlight that the ability of temperate trees to withstand future heatwaves will depend on the interplay between water availability, transpirational cooling, as well as species-specific hydraulic strategy and heattolerance.

Mast-seeding trees can vary seed output by orders of magnitude among years, but it remains unclear whether high seed production reduces per-seed investment, as predicted by fixed-budget allocation models. We quantified individual seed production with seed mass in European beech across 2792 trees and 123 populations spanning the species' range and quantified seed protein and lipid content in 35 populations. Seed mass increased with seed production, with seeds from high-seeding years being 14% heavier than those from low-seeding years, providing no evidence for a seed size-number trade-off and instead supporting variable reproductive allocation. By contrast, protein content decreased by 31% with increasing seed production, whereas lipid content increased (by 14%), indicating that nitrogen becomes constraining at high reproductive output while carbon-based provisioning is maintained. Climate further structured provisioning: seed mass and protein content were the lowest at climatic range margins, being 28% and 32% lower, respectively, than at the center of the climatic range. European beech can increase seed output without reducing per-seed biomass, but that nitrogen limitation and climatic constraints may strengthen regeneration bottlenecks at both trailing and leading margins, especially as climate warming intensifies.

ABSTRACT This study investigates the influence of mechanical surface preparation on the bonding quality of European beech, Douglas fir, and larch, species increasingly utilized for glulam production. The bondability of these woods, often challenged by extractives and altered swelling behavior, was assessed following various treatments: planing (sharp/dull cutting edges), sanding, fining, and a novel face milling process with straight and rounded cutting edges. Bonding was performed with a phenol-resorcinol-formaldehyde (PRF) resin and a one-component polyurethane (1C-PUR) adhesive. Tensile shear strength was tested according to EN 302-1 after storage sequences A1, A4, and A5. Results demonstrate that face milling with a rounded cutting edge tends to yield significantly higher tensile shear strengths across all wood species and storage conditions. SEM analysis confirmed this method produces an open-pored surface with minimal deformation of the cell structure, in contrast to the compaction observed after planing. This enhanced surface topography facilitates better adhesive penetration and mechanical anchoring. The findings underscore the potential of rounded face milling to improve the reliability and stability of the bonding process for challenging wood species. It provides a basis for more controllable results in industrial applications.

High terrestrial laser scanning: An accessible method for tree crown characterization