Introduction

Seasonal and interannual ecophysiological responses of beech ( Fagus sylvatica) at its south-eastern distribution limit in Europe

Large-scale protein analysis of European beech trees following four vegetation periods of twice ambient ozone exposure.

Thinning decreases above-ground biomass increment in central European beech forests but does not change individual tree resistance to climate events

Key messageClimate-warming related replacement of beech by oak forests in the course of natural forest succession or silvicultural decisions may considerably reduce ecosystem carbon storage of central European woodlands.ContextClimate warming may change the carbon (C) storage in forest biomass and soil through future shifts in tree species composition. With a projected warming by 2–3 K over the twenty-first century, silvicultural adaptation measures and natural succession might lead to the replacement of European beech forests by thermophilic oak forests in drought- and heat-affected regions of central and south-eastern Europe, but the consequences for ecosystem C storage of this species shift are not clear.AimsTo quantify the change in C storage in biomass and soil with a shift from beech (Fagus sylvatica) to oak forest (Quercus petraea, Q. frainetto, Q. cerris), we measured the aboveground biomass (AGC) and soil C pools (SOC).MethodsAGC pools and SOC stocks to − 100 cm depth were calculated from forest inventory and volume-related SOC content data for beech, mixed beech-oak and oak forests in three transects in the natural beech-oak ecotone of western Romania, where beech occurs at its heat- and drought-induced distribution limit.ResultsFrom the cooler, more humid beech forests to the warmer, more xeric oak forests, which are 1–2 K warmer, AGC and SOC pools decreased by about 22% (40 Mg C ha−1) and 20% (17 Mg C ha−1), respectively. The likely main drivers are indirect temperature effects acting through tree species and management in the case of AGC, but direct temperature effects for SOC.ConclusionIf drought- and heat-affected beech forests in Central Europe are replaced by thermophilic oak forests in future, this will lead to carbon losses of ~ 50–60 Mg ha−1, thus reducing ecosystem carbon storage substantially.

Tree growth depends on tree-intrinsic attributes, synecological interactions, atmospheric conditions and soil properties. While the influence of tree factors and climate are analysed in detail in many studies, the effect of soil properties is less investigated and compensatory soil effects are often not quantified. In this study, we use a comprehensive dataset of 1659 tree increment cores from six common Central European tree species (Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus spp.) sampled at 1562 locations across large environmental gradients in the Eastern Alps. Soil data was available from an extensive soil survey including soil pits, laboratory analysis and the application of pedotransfer-functions. Up to three main tree species per site were sampled and the tree ring widths were dendrochronologically measured and synchronized. Topographic information from a high-resolution Digital Terrain Model, high-resolution climate data and biometric measures were available at each site. To determine the influence of soil water storage capacity and soil nutrient status, we used generalized additive models to expand standard models of well-known drivers of tree growth, including age, climatic water balance and temperature. For the time span of 38 years from 1981 until 2018, we found species-specific impacts of soil properties on tree ring growth. Specifically, soil water storage acted as a buffer to overcome drought periods, in particular for deep rooting tree species like Quercus spp. and Abies alba. In addition, we found species-specific growth reactions to soil nutrient status for nutrient-demanding species likes Fagus sylvatica but no effects for less demanding tree species like Pinus sylvestris. Our results show the magnitude of the effects of soil properties in relation to other growth factors on radial growth of six Central European tree species. Therefore, we posit that, while age and climate do have a stronger influence on tree growth, it is important to consider soil as a growth factor, particularly at the distribution margins along climatic gradients.

Effects of forest management on biodiversity in temperate deciduous forests: An overview based on Central European beech forests

This study investigated the influence of climate on the carbon isotopic composition (sigma13C) and oxygen isotopic enrichment (delta18O) above the source water of different organic matter pools in European beech. In July and September 2002, sigma13C and delta18O were determined in phloem carbohydrates and in bulk foliage of adult beech trees along a transect from central Germany to southern France, where beech reaches its southernmost distributional limit. The data were related to meteorological and physiological parameters. The climate along the transect stretches from temperate [subcontinental (SC)] to submediterranean (SM). Both sigma13Cleaf and delta18Oleaf were representative of site-specific long-term environmental conditions. sigma13C of leaves collected in September was indicative of stomatal conductance, vapour pressure deficit (VPD) and radiation availability of the current growing season. delta18O was mainly correlated to mean growing season relative humidity (RH) and VPD. In contrast to the leaves, sigma13Cphloem varied considerably between July and September and was well correlated with canopy stomatal conductance (Gs) in a 2 d integral prior to phloem sampling. The relationship between sigma13C and delta18O in both leaves and phloem sap points, however, to a combined influence of stomatal conductance and photosynthetic capacity on the variation of sigma13C along the transect. delta18Ophloem could be described by applying a model that included 18O fractionation associated with water exchange between the leaf and the atmosphere and with the production of organic matter. Hence, isotope signatures can be used as effective tools to assess the water balance of beech, and thus, help predict the effects of climatic change on one of the ecologically and economically most important tree species in Central Europe.

European beech (Fagus sylvatica L.) is one of the most widespread and ecologically significant broadleaf tree species in Central Europe and is highly sensitive to drought and climatic extremes. Monitoring canopy water status is therefore critical for understanding plant hydraulic functioning, ecosystem resilience, and responses to environmental stress. Satellite-derived Vegetation Optical Depth (VOD) quantifies microwave signal attenuation by vegetation, serves as a proxy for vegetation water content, and provides valuable large-scale information for global vegetation monitoring and climate studies. However, well-characterized ground-based observations are required to resolve canopy-scale processes and hydraulic dynamics and to validate and improve satellite VOD retrievals.To address this need, we employ Global Navigation Satellite System Transmissometry (GNSS-T) as an in situ remote sensing approach to observe canopy water content dynamics in a mature European beech forest in eastern Austria. GNSS-T exploits signals of opportunity from navigation satellites operating at L-band frequencies comparable to microwave radiometers by comparing simultaneous signal reception at paired open-sky reference and below-canopy receivers, with differences in received signal power attributable to vegetation. Using a stationary, multi-frequency, multi-constellation GNSS-T setup operated continuously for one and a half years, VOD was retrieved using a simplified tau–omega radiative transfer model as a function of GNSS system, frequency band, and ranging code type.Retrieved VOD magnitudes are generally consistent across systems and frequency bands. GNSS-T-derived VOD resolves spatial canopy structure as well as pronounced diel and seasonal dynamics and shows sensitivity to meteorological drivers. Comparisons with camera-based vegetation proxies (in situ LAI- and NDVI-proxies) and satellite-derived vegetation indicators (AMSR2 X- and Ku-band VOD, MODIS LAI, Sentinel-1 cross-polarization ratio) support the physical interpretability of these observations. A systematic, azimuth-independent decrease of VOD toward the horizon might point to limitations of the implemented radiative transfer framework.Overall, the results demonstrate the potential of GNSS-T to provide continuous, non-destructive in situ observations of canopy-scale hydraulic dynamics.

The European beech (Fagus sylvatica) is one of the most important and widespread tree species in Central Europe and is widely managed for its valuable hard wood. We assembled and characterized the complete chloroplast genome of F. sylvatica to serve as a valuable resource in future genetic studies. The complete plastome sequence is 158,462 bp in length and contains 131 genes including 83 protein-coding genes, 40 tRNA genes, and 8 rRNA genes. A phylogenetic analysis of 21 Fagaceae plastome sequences shows that the three available Fagus sequences form a cluster, suggesting that the genus Fagus represents a monophyletic clade within the Fagaceae.

The cumulative impacts of droughts and N deposition on Norway spruce (Picea abies) in Switzerland based on 37 years of forest monitoring

Key messageClimate envelope analysis of nine tree species shows that Fagus sylvatica L. and Picea abies H. Karst could lose 58% and 40% of their current distribution range. Quercus pubescens Willd and Quercus cerris L. may win areas equal with 47% and 43% of their current ranges. The ratio of poorly predictable areas increases by 105% in southern and south-eastern Europe.ContextClimate change requires adaptive forest management implementations. To achieve climate neutrality, we have to maintain and expand forest areas. Impact assessments have great importance.AimsThe study estimates the potential climate envelopes of nine European tree species for a past period (1961–1990) and for three future periods (2011–2040, 2041–2070, 2071–2100) under two emission scenarios (RCP4.5 and RCP8.5) based on the current species distribution.MethodsClimate envelopes were estimated simultaneously using the random forest method. Multi-resolution segmentation was used to determine the climatic characteristics of each species and their combinations. Models were limited to the geographical area within which the climatic conditions correspond to the climatic range of the training areas.ResultsResults showed remarkable changes in the extent of geographic areas of all the investigated species’ climate envelopes. Many of the tree species of Central Europe could lose significant portions of their distribution range. Adhering to the shift in climate, these tree species shift further north as well as towards higher altitudes.ConclusionEuropean forests face remarkable changes, and the results support climate envelope modelling as an important tool that provides guidelines for climate adaptation to identify threatened areas or to select source and destination areas for reproductive material.

We studied the immediate effects of two successive storms in 1983 and 2004 in an old-growth Fagus sylvatica L. – Abies alba Mill. forest in the Dinaric Alps, southeastern Slovenia. In the 1983 and 2004 storms the density and basal area of wind-killed trees were 27.4·ha–1 and 5.98 m2·ha–1 and 11.2·ha–1and 4.02 m2·ha–1, respectively. In both storm events, mid-sized to large stems were more prone to wind mortality than small stems, and A. alba was more susceptible than F. sylvatica. In the 2004 storm, 70% of wind-killed trees were uprooted and 30% were snapped. Tree size (diameter at breast height) was more important than species in determining damage type, smaller stems being more prone to uprooting and larger stems to snapping. The combined mortality due to the two storms was similar to a decade of baseline mortality, and wind-killed trees were larger than trees that died from background mortality processes. In both storms, wind-killed trees had a clumped spatial distribution, which resulted in the formation of many multiple-tree-fall gaps up to 1500 m2 in size. We suggest that intermediate wind disturbance occurs at time intervals similar to or less than the life expectancy of most canopy tree species in central Europe, and may play a more important role in forest dynamics than previously thought.

Existing approaches for the assessment of forest management intensity lack a widely accepted, purely quantitative measure for ranking a set of forest stands along a gradient of management intensity. We have developed a silvicultural management intensity indicator (SMI) which combines three main characteristics of a given stand: tree species, stand age and aboveground, living and dead wooden biomass. Data on these three factors are used as input to represent the risk of stand loss, which is a function of tree species and stand age, and stand density, which is a function of the silvicultural regime, stand age and tree species. Consequently, the indicator consists of a risk component (SMIr) and a density component (SMId). We used SMI to rank traditional management of the main Central European tree species: Norway spruce (Picea abies [Karst.] L.), European beech (Fagus sylvatica L.), Scots pine (Pinus sylvestris L.), and oak (Quercus robur L. and Quercus petraea L.). By analysing SMI over their whole rotation period, we found the following ranking of management intensity: oak<beech<pine≪spruce. Additionally, we quantified the SMI of actual research plots of the German Biodiversity exploratories, which represent unmanaged and managed forest stands including conifer forests cultivated outside their natural range. SMI not only successfully separate managed from unmanaged forests, but also reflected the variability of forest management and stand properties across the entire sample and within the different management groups. We suggest using SMI to quantify silvicultual management intensity of stands differing in species composition, age, silvicultural system (even-aged vs. uneven-aged), thinning grade and stages of stand conversion from one stand type into another. Using SMI may facilitate the assessment of the impact of forest management intensity on biodiversity in temperate forests.

Process-based forest models are important tools for predicting forest growth and their vulnerability to factors such as climate change or responses to management. One of the most widely used stand-level process-based models is the 3-PG model (Physiological Processes Predicting Growth), which is used for applications including estimating wood production, carbon budgets, water balance and susceptibility to climate change. Few 3-PG parameter sets are available for central European species and even fewer are appropriate for mixed-species forests. Here we estimated 3-PG parameters for twelve major central European tree species using 1418 long-term permanent forest monitoring plots from managed forests, 297 from un-managed forest reserves and 784 Swiss National Forest Inventory plots. A literature review of tree physiological characteristics, as well as regression analyses and Bayesian inference, were used to calculate the 3-PG parameters.The Swiss-wide calibration, based on monospecific plots, showed a robust performance in predicting forest stocks such as stem, foliage and root biomass. The plots used to inform the Bayesian calibration resulted in posterior ranges of the calibrated parameters that were, on average, 69% of the prior range. The bias of stem, foliage and root biomass predictions was generally less than 20%, and less than 10% for several species. The parameter sets also provided reliable predictions of biomass and mean tree sizes in mixed-species forests. Given that the information sources used to develop the parameters included a wide range of climatic, edaphic and management conditions and long time spans (from 1930 to present), these species parameters for 3-PG are likely to be appropriate for most central European forests and conditions.

Beech forests in Central Europe are frequently the focus of entomological studies targeting saproxylic beetle species that depend on deadwood. However, considerably less attention has been paid to non‐saproxylic beetle species. Our research aimed to address this gap by focusing on the diversity and abundance of functional guilds of non‐saproxylic beetles. General analyses based only on total species richness can be misleading, as they may overlook fundamental ecological processes. Thus, the primary objective was to evaluate species richness and abundance of non‐saproxylic beetles in relation to species' habitat types, larval habitat types, and larval trophic feeding guilds. Data were collected over a three‐year period using window traps placed on permanent monitoring plots. Regarding species habitat, the highest proportion of both species (46%) and individuals (61%) belonged to an opportunistic group that inhabits both open landscapes and forest habitats equally. The second largest group, in terms of species (23%) and individuals (32%), consisted of species preferring forest environments. When categorized by larval habitat—belowground, epigeic, and aboveground—the number of species was relatively balanced. However, the highest number of species had epigeic (41%) or belowground (34%) larval stages. In contrast, the majority of individuals (63%) belonged to species whose larvae develop belowground. From the perspective of trophic guilds, most species were classified as mycetophagous (35%) or carnivorous (21%). Other trophic groups (rhizophagous, phytophagous, and saprophagous) were evenly represented. In terms of abundance, carnivorous species were dominant, comprising 40% of all individuals recorded. The results indicate that the composition of mainly flying, non‐saproxylic beetles is derived largely from the soil and epigeic layers of pure beech stands, with a community structure dominated by opportunistic species primarily associated with carnivorous and mycetophagous trophic guilds. This study contributes new insights into beech forest beetle assemblages, expanding the focus beyond the frequently studied saproxylic species.