Central European Beech Forests Research Articles

The biogeochemical model Biome-BGCMuSo v6.2 provides plausible and accurate simulations of the carbon cycle in central European beech forests

Abstract. Process-based ecosystem models are increasingly important for predicting forest dynamics under future environmental conditions, which may encompass non-analogous climate coupled with unprecedented disturbance regimes. However, challenges persist due to the extensive number of model parameters, scarce calibration data, and trade-offs between the local precision and the applicability of the model over a wide range of environmental conditions. In this paper, we describe a protocol that allows a modeller to collect transferable ecosystem properties based on ecosystem characteristic criteria and to compile the parameters that need to be described in the field. We applied the procedure to develop a new parameterisation for European beech (Fagus sylvatica L.) for the Biome-BGCMuSo model, the most advanced member of the Biome-BGC family. For model calibration and testing, we utilised multiyear forest carbon data from 87 plots distributed across five European countries. The initial values of 48 new ecophysiological parameters were defined based on a literature review. The final values of six calibrated parameters were optimised for single sites as well as for multiple sites using generalised likelihood uncertainty estimation (GLUE) and model output conditioning that ensured plausible simulations based on user-defined ranges of carbon stock output variables (carbon stock in aboveground wood biomass, soil, and litter) and finding the intersections of site-specific plausible parameter hyperspaces. To support the model use, we tested the model performance by simulating aboveground tree wood, soil, and litter carbon across a large geographical gradient of central Europe and evaluated the trade-offs between parameters tailored to single plots and parameters estimated using multiple sites. Our findings indicated that parameter sets derived from single sites provided an improved local accuracy of simulations of aboveground wood, soil, and litter carbon stocks by 35 %, 55 %, and 11 % in comparison to the a priori parameter set. However, their broader applicability was very limited. A multi-site optimised parameter set, on the other hand, performed satisfactorily across the entire geographical domain studied here, including on sites not involved in the parameter estimation, but the errors were, on average, 26 %, 35 % and 9 % greater for the aboveground wood, soil, and litter carbon stocks than those obtained with the site-specific parameter sets. Importantly, model simulations demonstrated plausible responses across large-scale environmental gradients, featuring a clear production optimum of beech that aligns with empirical studies. These findings suggest that the model is capable of accurately simulating the dynamics of European beech across its range and can be used for more comprehensive experimentations.

The White-backed Woodpecker (Dendrocopos leucotos) as an umbrella species for threatened saproxylic beetle communities in Central European beech forests

The umbrella species concept is a popular conservation planning tool which postulates that conservation schemes targeting a specific species will indirectly benefit many other sympatric species. In Scandinavia and Central Europe, the White-backed Woodpecker (Dendrocopos leucotos) is considered an umbrella species for woodland birds and cryptogam species of conservation concern. Whether this also applies to saproxylic beetles, a group of high conservation concern, remains open. Therefore, we tested that umbrella function in Central European beech forests that are currently recolonized by this woodpecker. Relying on radiotracking data, we compared saproxylic beetle communities within the breeding home ranges of White-backed Woodpeckers (high and low activity of the bird) against forests with ascertained absence of the bird (control). Bayesian inference for linear regressions identified that species richness of threatened saproxylic beetles was 1.51 (lower and upper 5 % PPCrI=[1.09; 2.01]) times higher in sites with high White-backed Woodpecker activity compared to the control. Community composition analyses on threatened saproxylic beetles showed a reduced β-diversity at low and high White-backed Woodpecker sites compared to the control. Finally, an indicator species analysis showed that 17 saproxylic beetle species, including 4 threatened species, were positively associated with White-backed Woodpecker’s breeding home ranges, while only 3 species, but no threatened species, were associated with the control sites. Overall, our results suggest that the White-backed Woodpecker plays the role of an umbrella species for threatened saproxylic beetle communities, opening new opportunities for conservation planning in European beech forests.

Adaptive monitoring in action—what drives arthropod diversity and composition in central European beech forests?

Recent studies suggest that arthropod diversity in German forests is declining. Currently, different national programs are being developed to monitor arthropod trends and to unravel the effects of forest management on biodiversity in forests. To establish effective long-term monitoring programs, a set of drivers of arthropod diversity and composition as well as suitable species groups have to be identified. To aid in answering these questions, we investigated arthropod data collected in four Hessian forest reserves (FR) in the 1990s. To fully utilize this data set, we combined it with results from a retrospective structural sampling design applied at the original trap locations in central European beech (Fagus sylvatica) forests. As expected, the importance of the different forest structural, vegetation, and site attributes differed largely between the investigated arthropod groups: beetles, spiders, Aculeata, and true bugs. Measures related to light availability and temperature such as canopy cover or potential radiation were important to all groups affecting either richness, composition, or both. Spiders and true bugs were affected by the broadest range of explanatory variables, which makes them a good choice for monitoring general trends. For targeted monitoring focused on forestry-related effects on biodiversity, rove and ground beetles seem more suitable. Both groups were driven by a narrower, more management-related set of variables. Most importantly, our study approach shows that it is possible to utilize older biodiversity survey data. Although, in our case, there are strong restrictions due to the long time between species and structural attribute sampling.

Impacts of climate warming, pollution, and management on the vegetation composition of Central European beech forests

Over the past century, climate warming, nitrogen deposition, acidic rain, widespread disturbance events, adaptive management, and natural stand maturation have substantially altered the composition and structure of forests. However, the absence of historical data on the environment makes it difficult to prove these long-term effects. Ecological indicator values based on plant species characteristics offer a promising approach to detect presumed changes at relevant spatial scales (i.e., site level). In this study, we discerned the shifts in taxa composition of principal Central European beech forests and their associated environmental drivers by integrating three data sources: (1) 254 historical (1937 – 1948) and resurveyed (2019 – 2022) vegetation relevés of beech-dominated forests sites in the Swiss Jura mountains, (2) derived ecological indicator values for vascular plants regarding temperature, soil moisture, micro-climatic conditions, soil nutrients, pH, humus layer, and light availability, and (3) related data on disturbance/management intensity in these forest sites over the past 75 years, categorized as ‘undisturbed’ and ‘disturbed’ sites. We found a significant decrease in alpha diversity (taxa richness per site) on ‘undisturbed’ sites (loss of 7.0 ± 1.48 taxa) but stability on ‘disturbed’ sites (gain of 2.1 ± 5.71 taxa). Both beta (Jaccard dissimilarity) and gamma diversity (overall taxa richness) increased over the study period. The average ecological indicator values per site (EIV‾s) consistently indicated climate warming impacts on all sites ranging from 390 to 1480 m a.s.l., while effects of acidic rain on soil pH and nitrogen deposition on soil fertility were negligible, except in densely populated lowland forest areas. The EIV‾s for light and micro-climatic conditions differed between ‘undisturbed’ and ‘disturbed’ sites, indicating darker and more oceanic, and more open and continental conditions, respectively. The decrease in alpha diversity on ‘undisturbed’ sites corresponded primarily with reduced light availability, suggesting that stand maturation is the main driver of taxa loss while climate warming and pollution mainly affected composition rather than taxa richness. In contrast, the rise in beta and gamma diversity likely stems from changes in forest management and disturbance regimes, which have increased structural diversity with various micro-climatic niches enriching the taxa pool. In conclusion, our study demonstrates the ability to differentiate the profound effects of climate warming and pollution agents on forest composition and underscores the critical role of adaptive management in mitigating these impacts. By fostering structural diversity and biodiversity, adaptive management enhances the resilience of forests, enabling them to better adapt to evolving environmental conditions.

Conifers and non-native tree species shift trophic niches of generalist arthropod predators in Central European beech forests

BackgroundFunctional diversity is vital for forest ecosystem resilience in times of climate-induced forest diebacks. Admixing drought resistant non-native Douglas fir, as a partial replacement of climate-sensitive Norway spruce, to native beech forests in Europe appears promising for forest management, but possible consequences for associated biota and ecosystem functioning are poorly understood. To better link forest management and functional diversity of associated biota, we investigated the trophic niches (∆13C, ∆15N) of epigeic generalist predators (spiders and ground beetles) in mixed and pure stands of European beech, Norway spruce and non-native Douglas fir in north-west Germany. We assessed the multidimensional niche structure of arthropod predator communities using community-based isotopic metrics.ResultsWhilst arthropod ∆13C differed most between beech (high ∆13C) and coniferous stands (low ∆13C), ∆15N was lowest in non-native Douglas fir. Tree mixtures mitigated these effects. Further, conifers increased isotopic ranges and isotopic richness, which is linked to higher canopy openness and herb complexity. Isotopic divergence of ground beetles decreased with Douglas fir presence, and isotopic evenness of spiders in Douglas fir stands was lower in loamy sites with higher precipitation than in sandy, drier sites.ConclusionsWe conclude that tree species and particularly non-native trees alter the trophic niche structure of generalist arthropod predators. Resource use and feeding niche breadth in non-native Douglas fir and native spruce differed significantly from native beech, with more decomposer-fueled and narrower feeding niches in beech stands (∆13C, isotopic ranges and richness). Arthropod predators in non-native Douglas fir, however, had shorter (∆15N) and simplified (isotopic divergence) food chains compared to native forest stands; especially under beneficial abiotic conditions (isotopic evenness). These findings indicate potential adverse effects of Douglas fir on functional diversity of generalist arthropod predators. As tree mixtures mitigated differences between beech and conifers, mixed stands including (non-native) conifers constitute a promising compromise between economic and conservational interests.

Suitability of Fagus orientalis Lipsky at marginal Fagus sylvatica L. forest sites in Southern Germany

European beech (Fagus sylvatica L.) is the most important tree species in Central Europe and is considered to be relatively resistant to climate warming. However, dry summers in the last five years led to considerable damage in beech stands in Southern Germany (SG). Assisted migration of drought resistant beech provenances including those of Oriental beech (Fagus orientalis Lipsky) may help to stabilise Central European beech forests under climate change. The focus of this study is to compare the climatic ranges of F. sylvatica and F. orientalis using quantile distribution of climatic variables based on WorldClim data at forest sites within their natural distribution area. Temperature, precipitation, and aridity quantile ranges showed that F. orientalis is better adapted to warmer and drier climate compared to F. sylvatica. The quantile distribution method was applied to the whole range of the species to map the habitat suitability for both species at marginal sites in the target region (SG) in the current climatic scenario (1970-2000) and in a warmer scenario (+2°C) using the climate marginality index (CMI), i.e., the distance of sites to the xeric edge at low-latitude and low-altitude distribution limits for the species. To this purpose we applied the simple BIOCLIM algorithm using annual temperature and precipitation as climatic variables. According to our results, F. orientalis seems a promising species with a high potential for future afforestation activities in Southern Germany, especially at marginal sites of European beech forests. However, before introducing F. orientalis on a larger scale in the study area, further research on the species ecology and genetics are needed. For further application of the quantile range method, we produced tables of the vigintiles of the climatic range for both species, which can be used for estimating CMI based on WorldClim data in other regions.

Forest management impact on soil organic carbon: A paired-plot study in primeval and managed European beech forests

Forest soils have been recognized as important reservoirs of older stable carbon (C) in the biosphere and thus play a key role in the global C cycle. While much research has addressed the consequences of forest conversion and forest use on soil organic carbon (SOC) stocks, some controversies remain as to whether primary forest soils store significantly more SOC than soils in managed forests. Here, we explore the effect of forest management on SOC stocks in European beech (Fagus sylvatica) forests through a paired-plot study in nearby primeval and managed forests in the western Carpathians, testing the hypotheses that primeval forests store significantly more SOC especially in the topsoil and that larger biomass and deadwood amounts are important drivers. The three primeval forests stored on average 15 % more SOC (∼1.8 kg C m−2) in the organic layers and mineral soil to 50 cm depth than the managed forests prior to harvest (difference marginally significant at p = 0.09). Contrary to expectation, the difference was significant in the subsoil (30–50 cm depth) but not in the topsoil. Consequently, the primeval forests had a greater proportion of their SOC pool located in the subsoil than the managed forests. Despite considerably larger wood biomass and deadwood amounts in the primeval forests, SOC pools were neither related to biomass nor deadwood mass. PCA and correlation analyses revealed a prominent negative effect of the availability of Ca, Mg, K and P on SOC stocks, suggesting that clear-cutting has slightly (but significantly) increased nutrient supply in the managed forests, likely stimulating soil biological activity and reducing SOC storage in comparison to the primeval forests. We conclude that the primeval forest reference is important for assessing forest management effects on SOC storage, and that a long history of management likely has significantly reduced the SOC stocks of Central European beech forests.

Animal diversity in beech forests – An analysis of 30 years of intense faunistic research in Hessian strict forest reserves

Under natural conditions beech forest would be the most widespread habitat in Central Europe. Therefore the knowledge of this vegetation type, including the animal communities dwelling there, as well as the mechanisms forming these communities are of high interest for biodiversity research and conservation in Central Europe. However, historically, Central European beech forests were thought to harbor only relatively few species. Here, faunistic data of five beech forest reserves, which were generated as part of the Hessian strict forest reserves program, are analyzed to investigate diversity patterns of Hessian beech forests of low mountain ranges. We focus on species-level data from six organism groups: Aculeata, Araneae, Coleoptera, Heteroptera, Lumbricidae, and Macrolepidoptera. We show that with 2552 forest-dwelling species from these organism groups an unexpectedly high number of species was found in Hessian beech forests, and that a higher species richness can be expected in these groups. Observed species diversity ranges from 1245 to 1556 forest dwelling species in the five individual forest reserves. Overall, 36 % of the forest dwelling species of the considered species groups known from Germany were found with all applied methods in the forest reserves. Different forest reserves share 40–50 % of the species, representing 50–70 % of the species of the individual reserves, indicating high levels of regional and habitat-structure based differentiation. Only 21 % of the species are found in all five reserves. The low percentage of species found in all five reserves is, in addition to differing local conditions, probably a result of the communities being composed of few highly abundant and many rare species, leading to a high percentage of species only found by chance in our surveys. We also observe differences in community heterogeneity among the five reserves. Patterns differ between organism groups, clearly indicating that a focus on single taxa or a single indicator group falls short of revealing meaningful patterns. In spider communities, beta diversity is linked to the spatial distance between traps. In other organism groups community heterogeneity within reserves rather depends on structural heterogeneity. Species richness was associated with percentage of reserve area not covered with the most dominant habitat type, the deadwood amount, and with survey year. Being the potential natural vegetation of Germany and considering the unexpectedly high diversity of their associated fauna, beech forests bear a great conservation value. However, their widespread occurrence and dominance is likely to push them out of focus of conservation efforts. Yet protecting diverse and richly structured beech forests can contribute greatly to preserving the native arthropod fauna and should play a central role in biodiversity conservation efforts in Central Europe.

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

European beech plays a prominent role in the adaptation of European forests to and mitigation of climate change. Forest management may increase the mitigation potential of beech forests by accelerating carbon accumulation in tree biomass, but little is known about the interaction between the rate of biomass expansion in beech and its sensitivity to climate variation or its resistance to extreme drought episodes. A 60-year thinning experiment in beech forests in Central Europe was used to generate tree-ring width series describing past radial growth of dominant, co-dominant and sub-dominant beech trees. Randomisation applied to daily climate data was used to find the period of the year during which climate best explains beech growth. Results show that carbon uptake by above-ground biomass is higher in unmanaged stands and that thinning does not affect beech growth sensitivity to climate. Further, this study shows that average daily temperature amplitude and precipitation in March-July are the best predictors of radial growth in beech at lower-elevation sites. In a key finding, this research shows that site quality and thinning intensity increase tree size, which in turn lowers their resistance to drought. Using forest management to increase the productivity of European beech may thus increase its vulnerability to climate change.

Mind the gaps: Comparison of representative vs opportunistic assessment of tree regeneration in Central European beech forests

Tree regeneration (TR) in canopy gaps is a key process to understand how forest ecosystems might adapt to future environmental changes. Since successful TR is the result of a complex interplay of several stochastic events such as gap formation, seed production, ungulate pressure and diseases, some of the processes have been neglected or strongly reduced for model applications. Most empirical data on TR originate from (national) forest inventories based on statistically optimized designs for timber resource estimations and use geographically fixed permanent plots. Consequently, these representative samples record TR both in gaps as well as under closed canopy conditions. In this study, we compared TR in 63 representative plots of the Swiss National Forest Inventory (‘NFI sampling’), located in beech and silver fir-beech forests along an elevation gradient in the Jura Mts., with an opportunistic ‘gap sampling’ strategy targeting TR-clusters. We analyzed quantitative (e.g., number of individuals) and qualitative (e.g., species diversity, similarity to surrounding canopy) differences between the ‘NFI sampling’ and ‘gap sampling,’ as well as the environmental factors (e.g., gap size, cluster age, elevation) influencing the composition of TR in small canopy gaps. The ‘gap sampling’ recorded higher median TR densities (+62%, stems ha−1) and species richness (4.0 ± 2.1, mean ± sd) than the ‘NFI sampling’. More importantly, the ‘gap sampling’ provided much more consistent results among sites (i.e., 4x lower variance). Consequently, the ‘gap sampling’ revealed not only general but also species-specific patterns across TR size classes and along elevational gradients in contrast to the lack of patterns in the ‘NFI sampling’. Species richness decreased as TR grew taller, and the tallest TR size class (>130 cm) was almost solely comprised of the dominant species in the surrounding canopy (direct ingrowth). The high amount of direct ingrowth in TR indicates that small canopy gaps might offer only limited management potential to alter forests and that extensive disturbances or management at early TR stages (sapling) would be necessary to promote species better suited to the expected future site conditions. We raise the question of whether a forest monitoring that is statistically optimized for timber resource estimation is best suited to detect adaptation effects to quickly changing environments best visible at the regeneration stage, or whether forest inventory tools should be extended by methods that focus on disturbed parts of forests where changes and adaptations take place. We propose the implementation of an opportunistic gap-based monitoring of TR that essentially serves to identify the best forest management strategies (e.g. gap size, intervention intervals) in forests adapting to environmental change.

Nine decades of major compositional changes in a Central European beech forest protected area

Lowland forests in Europe went through dramatic changes in the last century. Data accumulated from the nature reserve Buky u Vysokeho Chvojna in the Czech Republic provide a unique opportunity to follow beech forest development using a time series consisting of five points in time from 1926 to 2019. Our goal was to reconstruct changes in plant species richness and plant community composition over this period. Based on the available data, we concluded that vascular plant species richness per plot declined by at least 50%, possibly by 75% since 1951. Compositional dissimilarities between the first survey and subsequent resurveys revealed a directional trajectory of vegetation changes. Treating time as an environmental factor and tree canopy cover as a covariable (and vice versa) in canonical correspondence analysis permutation tests where only the herbaceous layer was used, time turned out to be much more important. Variance partitioning revealed that time explained 28.1% and tree canopy 4.2% of the variation in the species data. The two variables together explained 36.8% of the variance, revealing that the shared effect of these two variables was 4.5%. Ellenberg-type indicator values point to a possible role of increasing nitrogen and decreasing pH. Several other factors potentially responsible for observed vegetation changes are discussed.

Decadal effects of landscape‐wide enrichment of dead wood on saproxylic organisms in beech forests of different historic management intensity

AbstractAimEuropean temperate forests have lost dead wood and the associated biodiversity owing to intensive management over centuries. Nowadays, some of these forests are being restored by enrichment with dead wood, but mostly only at stand scales. Here, we investigated effects of a seminal dead‐wood enrichment strategy on saproxylic organisms at the landscape scale.LocationTemperate European beech forest in southern Germany.MethodsIn a before–after control–impact design, we compared assemblages and gamma diversities of saproxylic organisms in strictly protected old‐growth forest areas (reserves) and historically moderately and intensively managed forest areas before and a decade after starting a landscape‐wide strategy of dead‐wood enrichment.ResultsBefore enrichment with dead wood, the gamma diversity of saproxylic organisms in historically intensively managed forest stands was significantly lower than in reserves and historically moderately managed forest stands; this difference disappeared after 10 years of dead‐wood enrichment. The species composition of beetles in forest stands of the three historical management intensities differed before the enrichment strategy, but a decade thereafter, the species compositions of previously intensively logged and forest reserve plots were similar. However, the differences in fungal species composition between historical management categories before and after 10 years of enrichment persisted.Main conclusionsOur results demonstrate that intentional enrichment of dead wood at the landscape scale is a powerful tool for rapidly restoring saproxylic beetle communities and for restoring wood‐inhabiting fungal communities, which need longer than a decade for complete restoration. We propose that a strategy of area‐wide active restoration combined with some permanent strict refuges is a promising means of promoting the biodiversity of age‐long intensively managed Central European beech forests.

Forest as a place for recreation but also the source of allergenic plant pollen: to come or avoid?

For many years, we have observed a significant rise in urban population, the spatial development of cities, and an increase in urbanized areas. More and more people feel the need to have contact with nature. The interest in forest recreation is growing, though the forest is a serious source of allergenic plant pollen. The aim of the present study was to compare two forest types in the context of their recreational potential and the effect strength of aeroallergens. This study was conducted in SE Poland in a Nemoral Scots pine forest (RB) and in a Central European submountainous beech forest (TH). Their recreational potential was assessed. Samples of moss containing plant pollen were collected under the canopy, from forest clearings and forest edges as well as in an open area. Based on the number of pollen grains deposited in moss pollsters, the forest impact on humans was calculated. The recreational potential values for both sites studied are evidence of the high recreational suitability of these forests, but the recreational capacity of RB is lower compared to TH. Palynological analysis showed that the pollen deposition is higher in BR and that the plant pollen risk is lowest under the canopy, regardless of the forest type. The beech forest was found to be characterized by greater recreational potential and a weaker actual effect of pollen allergens than the pine forest. In assessing forest recreational potential, palynological data should form the basis for modification of the degree of recreational suitability. Such information would also be useful in controlling recreational traffic since, as we have proved, visiting appropriate places in a forest allows the exposure of allergen sensitive people to be reduced.

The impact of even‐aged and uneven‐aged forest management on regional biodiversity of multiple taxa in European beech forests

Abstract For managed temperate forests, conservationists and policymakers favour fine‐grained uneven‐aged (UEA) management over more traditional coarse‐grained even‐aged (EA) management, based on the assumption that within‐stand habitat heterogeneity enhances biodiversity. There is, however, little empirical evidence to support this assumption. We investigated for the first time how differently grained forest management systems affect the biodiversity of multiple above‐ and below‐ground taxa across spatial scales. We sampled 15 taxa of animals, plants, fungi and bacteria within the largest contiguous beech forest landscape of Germany and classified them into functional groups. Selected forest stands have been managed for more than a century at different spatial grains. The EA (coarse‐grained management) and UEA (fine‐grained) forests are comparable in spatial arrangement, climate and soil conditions. These were compared to forests of a nearby national park that have been unmanaged for at least 20 years. We used diversity accumulation curves to compare γ‐diversity for Hill numbers 0D (species richness), 1D (Shannon diversity) and 2D (Simpson diversity) between the management systems. Beta diversity was quantified as multiple‐site dissimilarity. Gamma diversity was higher in EA than in UEA forests for at least one of the three Hill numbers for six taxa (up to 77%), while eight showed no difference. Only bacteria showed the opposite pattern. Higher γ‐diversity in EA forests was also found for forest specialists and saproxylic beetles. Between‐stand β‐diversity was higher in EA than in UEA forests for one‐third (all species) and half (forest specialists) of all taxa, driven by environmental heterogeneity between age‐classes, while α‐diversity showed no directional response across taxa or for forest specialists. Synthesis and applications. Comparing EA and uneven‐aged forest management in Central European beech forests, our results show that a mosaic of different age‐classes is more important for regional biodiversity than high within‐stand heterogeneity. We suggest reconsidering the current trend of replacing even‐aged management in temperate forests. Instead, the variability of stages and stand structures should be increased to promote landscape‐scale biodiversity.

Holocene vegetation and fire history of the mountains of Northern Sicily (Italy)

Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixe, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests (Quercus pubescens, Q. cerris, Fraxinus ornus, Ulmus), that included a substantial portion of evergreen broadleaved species (Q. suber, Q. ilex, Hedera helix), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees (Fagus sylvatica, Ilex aquifolium) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc, at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc. Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus-Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adapted Fagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.

Drivers of nitrogen leaching from organic layers in Central European beech forests

Background and Aims The response of forest ecosystems to continuous nitrogen (N) deposition is still uncertain. We investigated imports and exports of dissolved N from mull-type organic layers to identify the controls of N leaching in Central European beech forests under continuous N deposition. Methods Dissolved N fluxes with through fall and through mull-type organic layers (litter leachate) were measured continuously in 12 beech forests on calcareous soil in two regions in Germany over three consecutive growing seasons. Results Mean growing season net (i.e. litter leachate – throughfall flux) fluxes of total dissolved N (TDN) from the organic layer were low (2.3 ± 5.6 kg ha⁻¹) but varied widely from 12.9 kg ha⁻¹ to–8.3kgha⁻¹. The small increase of dissolved N fluxes during the water passage through mull-type organic layers suggested that high turnover rates coincided with high microbial N assimilation and plant N uptake. Stand basal area had a positive feedback on N fluxes by providing litter for soil organic matter formation. Plant diversity, especially herb diversity, reduced dissolved N fluxes. Soil fauna biomass increased NO−3 -N fluxes with litter leachate by stimulating mineralization. Microbial biomass measures were not related to dissolved N fluxes. Conclusions Our results show that dissolved N exports from organic layers contain significant amounts of throughfall-derived N (mainly NO−3 -N) that flushes through the organic layer but also highlight that N leaching from organic layers is driven by the complex interplay of plants, animals and microbes. Furthermore, diverse understories reduce N leaching from Central European beech forests.

A review on plant diversity and forest management of European beech forests

The impact of historical and present drivers on forest biodiversity is poorly understood. A better understanding is mandatory to ensure conservation and appropriate management of biodiversity and ecosystem functions in the face of climate warming and increasing demand for wood products. Here, we assess forest management strategies for maintaining plant biodiversity in Central European beech forests, with a focus on Germany. We show that (1) diversity of the German vascular plant flora increased exponentially during the Holocene reaching 3874 species mainly through apomictic and hybrid speciation. Vascular plant species confined to forests comprise about 10 % of this flora. No loss in vascular plants restricted to forests occured over the past 250 years despite of forest management; (2) the indigenous arboreal flora has a low diversity (64 tree species) compared with other continents due to environmental changes in the last 2 million years; (3) forest management has maintained a high plant diversity in the past. It should be an aim of silviculture to ensure this in the future; and (4) only 22 of the indigenous tree species are commercially used; nine of these commercially used species are threatened by diseases. We introduce the concept of palaeo-neophytes to address genera that existed in Central Europe during the latest Cenozoic. The introduction of species of palaeo-neophytic genera and sub-Mediterranean species is discussed as a measure to buffer negative effects on native species caused by climate change and spread of novel diseases.

Can rove beetles (Staphylinidae) be excluded in studies focusing on saproxylic beetles in central European beech forests?

Monitoring saproxylic beetle diversity, though challenging, can help identifying relevant conservation sites or key drivers of forest biodiversity, and assessing the impact of forestry practices on biodiversity. Unfortunately, monitoring species assemblages is costly, mainly due to the time spent on identification. Excluding families which are rich in specimens and species but are difficult to identify is a frequent procedure used in ecological entomology to reduce the identification cost. The Staphylinidae (rove beetle) family is both one of the most frequently excluded and one of the most species-rich saproxylic beetle families. Using a large-scale beetle and environmental dataset from 238 beech stands across Europe, we evaluated the effects of staphylinid exclusion on results in ecological forest studies. Simplified staphylinid-excluded assemblages were found to be relevant surrogates for whole assemblages. The species richness and composition of saproxylic beetle assemblages both with and without staphylinids responded congruently to landscape, climatic and stand gradients, even when the assemblages included a high proportion of staphylinid species. At both local and regional scales, the species richness as well as the species composition of staphylinid-included and staphylinid-excluded assemblages were highly positively correlated. Ranking of sites according to their biodiversity level, which either included or excluded Staphylinidae in species richness, also gave congruent results. From our results, species assemblages omitting staphylinids can be taken as efficient surrogates for complete assemblages in large scale biodiversity monitoring studies.

Dynamics of Hedera helix L. in Central European beech forests on limestone: results from long-term monitoring and experimental studies

A spread of Hedera helix L. into beech forests has been observed during the last 20 years in Central Europe. As this species is susceptible to intensive frost, it is believed that climate change with mild winters is the responsible driver. Other factors can, however, be equally important including forest management, eutrophication, and browsing. We compared old (sampled 1955–1967) and recent (sampled 2000–2012) releves as well as managed/unmanaged, fenced/unfenced, and fertilized (N, P and a combination of both)/unfertilized plots sampled in two beech forest communities of the Gottinger Wald (Lower Saxony, Germany), and addressed these potential drivers and their effect on H. helix. The H. helix abundance significantly increased in the last 50 years, accompanied by a general temperature increase and a reduction in severe frost events suggesting an influence of climate change. Inter-annual changes in H. helix cover correlated with climate variables reveal an interplay between low minimum temperatures and snow cover. The spread of H. helix, however, also goes along with higher nitrogen availability and a reduction in browsing pressure. A fertilization experiment underlines a positive impact of N and P on the H. helix abundance, whereas fencing and management reduced it by promoting a competing shrub layer. Thus, climate change could not be identified as the main driver of a H. helix spread in the Gottinger Wald. It is rather caused by a complex interaction of changing abiotic (climate change and eutrophication) and biotic (browsing, competition) conditions, that is not fully understood yet.

Fagus sylvatica forests and their faunal diversity: A regional and European perspective

While the postglacial history of European beech (Fagus sylvatica) and the plant species composition of beech forests in Central Europe are fairly well understood, the faunal biodiversity has been less well investigated. We studied three groups of mostly sedentary organisms in beech forest at regional and European scales by combining field studies with a compilation of existing literature and expert knowledge. Specifically, we examined the relationship between host tree genera and saproxylic beetles, and the diversity and composition of forest ground-dwelling molluscs and ground beetles in relation to the abundance of beech. At a west central European scale (Germany), where beech has a “young” ecological and biogeographical history, we found 48 primeval forest relict species of saproxylic beetles associated with beech, 124 ground beetles and 91 molluscs inhabiting beech forest, yet none exclusive of west central European beech forests. High levels of faunal similarity between beech and other woodland trees suggested that many of the beech forest dwelling species are euryoecious and likely to originate from mid-Holocene mixed broadleaf forests. Beech forests of the mountain ranges in southern and east central Europe, which are ecologically and biogeographically “old”, were found to harbour distinct species assemblages, including beech forest specialists (such as 10 carabid species in the Carpathians) and narrow-range endemics of broadleaf forest. The observed biodiversity patterns suggest differentiated conservation priorities in “young” and “old” European beech forest regions.