European Forest Ecosystems Research Articles

Tis červený (Taxus baccata L.) a jeho význam v přírodě blízkém obhospodařování lesů v podmínkách klimatické změny – review

European yew (Taxus baccata L.) is a key tree species in forest ecosystems, contributing to biodiversity and ecosystem stability. However, its populations have declined significantly due to historical overexploitation, habitat fragmentation, and increasing environmental pressures, particularly under ongoing climate change. This review provides a comprehensive analysis of the ecological characteristics, distribution, and silvicultural management of yew, emphasising its role in close-to-nature forest management. It discusses the species’ resilience to drought, shade tolerance and potential for adaptation to changing environmental conditions. Conservation strategies including natural and artificial regeneration, site-specific silvicultural interventions and the need for wildlife management to mitigate herbivore damage are also reviewed. The economic and pharmacological importance of yew, particularly as a source of taxanes for anticancer treatment, is also highlighted. The review also examines the sensitivity of the species to biotic and abiotic stressors and predicts its future distribution under climate change scenarios. The results highlight the need for targeted conservation measures, assisted migration, and adaptive forest management to sustain yew populations. Future research should integrate genetic diversity studies, climate modelling, and field-based silvicultural experiments to increase the species’ viability and ecological functions in European forest ecosystems.

Revisiting Ancient Forests: Insights From the Mid‐Pliocene to Predict Future Climate Impacts

ABSTRACTAimThe potential analogues in Earth's past may hold insight on how modern European forests will react to different levels of future warming. There is a lack of comparison between future warming and its most recent climate analogue 3.25 million years ago during the mid‐Piacenzian warm period. We have attempted to fill this knowledge gap by modelling the zonation of woody plant communities during the mid‐Pliocene and comparing it with their current distribution and predictions of their future distribution.LocationEurope.Time Period3.25–3 million years ago, 1970–2000, and 2081–2100.TaxonEuropean tree species.MethodsIn this study, we selected 15 European tree species from three main European forest ecosystems: Mediterranean, temperate and boreal species that had ancestors present in Europe during the mPWP. Then we applied an ensemble model using climatic data from the mPWP, modern and two future climate scenarios. In order to compare the models, we assessed the overlapped area as well as Dutilleul's modified t‐test in order to assess the spatial similarities in forest communities distribution between the mPWP and future warming.ResultsOur results showed that there is a clear northern trend in the northward shift of forest communities under all warming scenarios. Across all species, there is a clear drop in suitable area with the exception of Mediterranean species, where suitable area increased in all warm scenarios. When comparing the mPWP with future warming, there is evidence to support that RCP 4.5 will potentially exhibit similar conditions, while RCP 8.5 may result in highly novel habitats.Main ConclusionsAlthough mid‐Pliocene conditions are more analogous to the RCP 4.5, it raises an urgent ecological concern for adaptive forest management. Increasing temperatures and uncertain precipitation patterns have the potential to aid the expansion of Mediterranean forest communities while fragmenting temperate and boreal forest communities throughout central Europe.

Consequences of nitrogen deposition and soil acidification in European forest ecosystems and mitigation approaches

Consequences of nitrogen deposition and soil acidification in European forest ecosystems and mitigation approaches

Assessing the ecological complexity and uncertainty of predicting forest ecosystem services under climate change

Assessing the ecological complexity and uncertainty of predicting forest ecosystem services under climate change

Site conditions rather than provenance drive tree growth, climate sensitivity and drought responses in European beech in Germany

Ongoing climate change and associated extreme events strongly impact the growth and vitality of forest ecosystems in Europe. Because of its’ high drought sensitivity, European beech, which is considered as climax tree species in large parts of Central Europe, may specifically suffer. Hence, recent studies increasingly focus on the resistance and resilience of beech growth to climate change. Intra-specific variations in growth responses by comparing different beech provenances, however, received less attention, as did the question whether provenance selection can be used to mitigate potential future negative impacts of climate change. Therefore, we here investigated 24 provenances belonging to the International Beech Provenance Trial growing at three sites in Germany along a latitudinal gradient (study sites are referred to as ’North’, ‘Center’, ‘South’). Specifically, we compared tree-ring width (TRW), diameter breast height (DBH), climate-growth relationships, as well as drought resistance and resilience in the extreme years 2003 and 2018. Large differences in growth performance were observed between the three study sites. At site North, beech trees showed the highest DBH and TRW. Tree growth was predominantly driven by previous-year October and current-year winter temperature, whereas growth at sites Center and South was significantly impacted by summer SPEI and constrained by precipitation in late winter and early June, respectively. Overall, drought responses in 2003 were less variable than in 2018. We found increasing resistance and decreasing resilience from the wetter North to the drier South, but with minimal differences between the Center and the South. Whereas differences between study sites were large, provenance differentiation within sites was comparably low, substantiating that beech is a highly plastic tree species. Even though some provenances were found to perform slightly better or worse, differences were not statistically significant and show unclear patterns. Hence, we conclude that climate change will affect beech forests in Europe mainly depending upon site conditions, and that provenance selection may not ensure superior growth performance.

Silicon Modifies Photosynthesis Efficiency and hsp Gene Expression in European Beech (Fagus sylvatica) Seedlings Exposed to Drought Stress.

Background: Climate change is leading to severe and long-term droughts in European forest ecosystems. can have profound effects on various physiological processes, including photosynthesis, gene expression patterns, and nutrient uptake at the developmental stage of young trees. Objectives: Our study aimed to test the hypothesis that the application of silica (SiO2) influences photosynthetic efficiency and gene expression in 1- to 2-year-old Fagus sylvatica (L.) seedlings. Additionally, we aimed to assess whether silicon application positively influences the structural properties of leaves and roots. To determine whether the plant physiological responses are genotype-specific, seedlings of four geographically different provenances were subjected to a one-year evaluation under greenhouse conditions. Methods: We used the Kruskal-Wallis test followed by Wilcoxon's test to evaluate the differences in silicon content and ANOVA followed by Tukey's test to evaluate the physiological responses of seedlings depending on treatment and provenance. Results: Our results showed a significantly higher Si content in the roots compared with the leaves, regardless of provenance and treatment. The most significant differences in photosynthetic performance were found in trees exposed to Si treatment, but the physiological responses were generally nuanced and provenance-dependent. Expression of hsp70 and hsp90 was also increased in leaf tissues of all provenances. These results provide practical insights that Si can improve the overall health and resilience of beech seedlings in nursery and forest ecosystems, with possible differences in the beneficial role of silicon application arising from the large differences in wild populations of forest tree species.

Complex imprint of air pollution in the basal area increments of three European tree species

Complex imprint of air pollution in the basal area increments of three European tree species

Archetypal typology of European forest ecosystems integrating management intensity and naturalness

The crises of climate change and biodiversity loss have pushed the aim for increasing the resilience of forest ecosystems high on the agenda of foresters and policymakers. At the same time, synergistic opportunities for restoring forests and biodiversity are emerging to safeguard these ecosystems. Naturalness is a key characteristic of forest ecosystems, which should be considered when estimating benchmarks for resilience and biodiversity conservation. The naturalness of forest ecosystems is highly dependent on the intensity of human activity, as different levels of management intensity can change the original traits of forest ecosystems. This paper presents an archetypal typology of forest ecosystems, describing the association between management and naturalness. Both features are represented as gradients covering the full spectrum observed in European forests. The array of forest ecosystem archetypes was verified using case studies across Europe. The typology provides useful information for setting targets for resilience and restoration of forest ecosystems.

Diversity and ecological significance of modern fungal non-pollen palynomorphs in a European lowland forest ecosystem

Fungal non-pollen palynomorphs (fNPPs) are microscopic structures occurring in various sediments. In paleoecological studies, they can serve as reliable indicators of vegetation types, grazing activities, and human impact, enriching the interpretation of fossil data. This study explores the composition and taxonomic richness of fNPPs in 85 moss samples from a European lowland forest. We found rich fungal diversity, with 95 morphological types, predominantly saprotrophs, favoring specific substrates, like wood, decaying bark, herbaceous plant remains, litter, and freshwater habitats. Key taxa, such as type HdV-96A, and cf. Hypoxylon (EMA-24), were prevalent across different forest types, especially in deciduous forests. We identified two primary gradients of fNPP composition. The first axis delineated samples by taxonomic richness, Shannon index, and canopy openness, showing similarities among deciduous forests. The second axis ordered samples by the proportion of fNPPs, volume of stumps, coarse woody debris, and herbs pollen richness, highlighting their connections. Forest management intensity had minimal influence on fNPP composition, indicating consistent composition along both ordination axes. Forest type and herbs pollen richness, significantly affected the taxonomic richness and Shannon diversity of fNPPs. Deciduous forests exhibited higher fNPP richness, compared to coniferous forests, linked to increased herbs pollen richness. However, fNPPs decreased with increasing volume of stumps, coarse woody debris, and canopy openness, demonstrating the complexities of forest management’s influence on fungal diversity. This study pioneers fNPP investigation in an old-growth temperate forest ecosystem, emphasizing the interplay of forest characteristics, herbs diversity, and dead wood components in shaping their composition and richness. It also reveals differences in fNPP assemblages between deciduous and coniferous forests, underscoring the importance of forest type in shaping fungal diversity. These findings highlight the need for detailed studies on microhabitats, dead wood decomposition rates, and specific forest impacts to comprehensively understand forest ecosystem dynamics.

Tracking effects of extreme drought on coniferous forests from space using dynamic habitat indices

Terrestrial ecosystems such as coniferous forests in Central Europe are experiencing changes in health status following extreme droughts compounding with severe heat waves. The increasing temporal resolution and spatial coverage of earth observation data offer new opportunities to assess these dynamics. Dense time-series of optical satellite data allow for computing Dynamic Habitat Indices (DHIs), which have been predominantly used in biodiversity studies. However, DHIs cover three aspects of vegetation changes that could be affected by drought: annual productivity, minimum cover, and seasonality. Here, we evaluate the health status of coniferous forests in the federal state of Hesse in Germany over the period 2017–2020 including the severe drought year of 2018 using DHIs based on the Normalized Difference Vegetation Index (NDVI) for drought assessment. To identify the most important variables affecting coniferous forest die-off, a series of environmental variables together with the three DHIs components were used in a logistic regression (LR) model. Each DHI component changed significantly across non-damaged and damaged sites in all years (p-value 0.05). When comparing 2017 to 2019, DHI-based annual productivity decreased and seasonality increased. Most importantly, none of the DHI components had reached pre-drought conditions, which likely indicates a change in ecosystem functioning. We also identified spatially explicit areas highly affected by drought. The LR model revealed that in addition to common environmental parameters related to temperature, precipitation, and elevation, DHI components were the most important factors explaining the health status. Our analysis demonstrates the potential of DHIs to capture the effect of drought events on Central European coniferous forest ecosystems. Since the spaceborne data are available at the global level, this approach can be applied to track the dynamics of ecosystem conditions in other regions, at larger spatial scales, and for other Land Use/Land Cover types.

The Role of the Intraspecific Variability of Hydraulic Traits for Modeling the Plant Water Use in Different European Forest Ecosystems

AbstractThe drought resilience of forest ecosystems is generally believed to depend on the dominant tree species' hydraulic traits. These traits define the maximum water transport capacity and the degree of vulnerability to hydraulic failure of a tree species. This work evaluates the effect of the intraspecific variability of hydraulic traits on the simulated tree water use in the Community Land Model (CLM, version 5.0). We selected two contrasting broadleaved tree species and performed a series of numerical experiments by modifying the parameters of the plant vulnerability curve and the maximum xylem hydraulic conductance accounting for the variability within each species. Our prescribed parameter sets represent vulnerable and resistant tree responses to the water deficit. At sites with an ample water supply, the resistant configuration simulates reduced water stress and increased transpiration compared to the vulnerable configuration. Meanwhile, the model results are counter‐intuitive at temporarily dry sites when water availability is the limiting factor. The numerical experiments demonstrate the emergent role of the maximum xylem conductance as a modulator of the plant water use strategy and the simulated transpiration within the model. Using the default value for maximum xylem conductance, the model tends to overestimate the early summer transpiration at drier sites, forcing the vegetation to experience unrealistic water stress later in the year. Our findings suggest that the parameterization of maximum xylem conductance is an important yet unresolved problem in the CLM and similar land surface models.

Invasive Pest and Invasive Host: Where Might Spotted-Wing Drosophila (Drosophila suzukii) and American Black Cherry (Prunus serotina) Cross Paths in Europe?

Both spotted-wing drosophila (SWD, Drosophila suzukii) and American black cherry (ABC, Prunus serotina) are invasive species with major deleterious effects on forest ecosystems in Europe. ABC, a host of SWD, can sustain large populations of SWD, and SWD in turn can constrain the regeneration of its host. Here, we examined the range shifts of SWD, ABC, and their range overlap under future scenarios using range shift models. In the current–future scenarios, both SWD and ABC were predicted to undergo potential range expansions in Europe, suggesting that their invasion risks might increase in the future. Climate change might be the major driver of range shifts of both the pest and host, followed by land-use and host availability changes; therefore, mitigating future climate change might be key for controlling their future invasions in Europe. The relative contribution of climate and host availability to shaping the potential ranges of invasive species might not only vary with their feeding habitats (polyphagy/oligophagy) but also with the relative abundance of hosts among available host reservoirs. Range overlap under current and future scenarios was mainly observed in the UK, Germany, France, Switzerland, Italy, and Eastern Europe; this area is of high and low priority for the control of SWD and ABC, respectively.

The Range Potential of North American Tree Species in Europe

European forest ecosystems are projected to change severely under climate change especially due to an anticipated decline in the distribution of major tree species in Europe. Therefore, the adaptation of European forests appears necessary and urgent. While spontaneous adaptation mechanisms bear a large self-guided potential, we focus on quantifying the potential of management-guided mechanisms. Besides other possible tree species groups for adaptation, non-native tree species from North America have a long tradition in Europe, yet their full distribution potential is not completely revealed. We applied an ensemble species distribution model approach to six North American species, using combined occurrence data from the native and naturalized ranges to gain more insights into the species suitability in the introduced area in 2070 (2061–2080) under the emission scenarios RCP 4.5 and 8.5. Our findings support the assumption that there is unreported species potential in the introduced area beyond their current distribution. Next to northeastern range shifts projected for all species, we identified Abies grandis, Liriodendron tulipifera, Quercus rubra, and Robinia pseudoacacia with increasing range potentials in the future. P. ponderosa and P. menziesii var. menziesii are projected to show a steady and decreased range potential under RCP 4.5 and 8.5, respectively.

Potential of hydrogel treatment in forest regeneration: impact on growth and vitality of Central European tree species

IntroductionDrought negatively affects the growth and yield of plants. Several measures have been employed to improve the drought tolerance of plants, including the application of superabsorbent hydrogel (SAH) to soil. However, studies on the effect of SAH on trees in Central Europe, which has a temperate climate, are scarce.MethodsHere, the effects of SAH treatment on the cultivation of four key tree species in Central European forest ecosystems—European beech, sessile oak, Scots pine, and Norway spruce—were evaluated. Field and greenhouse experiments were conducted; the greenhouse conditions served as the reference for the absence of water stress.Results and DiscussionSAH treatment reduced seedling mortality by 1%–9% in the field experiment. The morphological parameters of the control and SAH-treated seedlings did not significantly differ. Among the tree species, oak seedlings exhibited a positive response to SAH treatment. Spruce, pine, and beech did not respond to SAH treatment; the proline content of SAH-treated conifer leaves was three times higher than that of oak leaves but still very low, revealing no drought stress. The results highlight the significance of employing an individual approach in the application of SAH in forestry, rather than relying on generic measures.

Regeneration dynamics in mixed mountain forests at their natural geographical distribution range in the Western Rhodopes

Mixed mountain forests consisting of Norway spruce (Picea abies (L.) Karst.), European beech (Fagus sylvatica L.), and silver fir (Abies alba Mill.) are among the most productive and stable forest ecosystems in Europe. Their southeasternmost geographical distribution range is located in the Western Rhodopes, where they have high economic, recreational, and ecological value. In the past, shelterwood cuttings dominated forest management practices in these forests and were mainly aimed at maintaining and reproducing conifers. During the past two decades, single-tree and group-tree selection systems have been promoted as alternative management approaches to support the conversion of spruce-dominated stands to close-to-nature mixed forests of fir, beech, and spruce. However, the natural regeneration dynamics in these stands are barely known, and their dependence on microsite and management effects needs to be better understood.The objective of this study was to investigate ecological factors under management regimes of different intensity (“single-tree”-selection and “group-tree”-selection) that influence the regeneration processes in mixed mountain forests in the Bulgarian Rhodopes. Data on regeneration and microsite conditions were collected on 105 systematically distributed plots (25 m2/100 m2) in four 100–120 years old stands located in the regional forest district of Smoljan, Bulgaria (1580–1650 m a.s.l.). We relied on generalizeds linear mixed models to analyse for each species the (1) size-dependent regeneration density and (2) height increment in dependence on management practices, competing vegetation, as well as soil and light conditions.Our study revealed an overall high potential for recruitment in the Western Rhodopes. Regeneration density was highest in fir (median 12800 N ha-1), followed by spruce (median 1600 N ha-1) and beech (median 1200 N ha-1). Fir benefited most from “single-tree” selection cuttings, while “group-tree” selection cutting tended to promote beech and fir but also spruce. Competing ground vegetation was detrimental for seedling density of all species. Annual height increment increased with plant size, was lowest in spruce, and similar in fir and beech. Sapling increment was driven by light, whereas seedlings did not react to increased radiation. Browsing was species-specific and was highest in beech (15–30 %), followed by fir (5–10 %) and spruce (<1 %). It was not a crucial factor in impeding tree recruitment. We conclude that frequent harvest activities of low intensity which consider advanced regeneration are a promising approach to successfully convert the formerly spruce-fir-dominated forests to climate-adapted fir-beech-(spruce)-mixed stands.

Timing of autumnal leaf senescence in a common shrub species depends on the level of preceding summer drought symptoms

Timing of autumnal leaf senescence in a common shrub species depends on the level of preceding summer drought symptoms

Microbial biomarkers of tree water status for next-generation biomonitoring of forest ecosystems.

Next-generation biomonitoring proposes to combine machine-learning algorithms with environmental DNA data to automate the monitoring of the Earth's major ecosystems. In the present study, we searched for molecular biomarkers of tree water status to develop next-generation biomonitoring of forest ecosystems. Because phyllosphere microbial communities respond to both tree physiology and climate change, we investigated whether environmental DNA data from tree phyllosphere could be used as molecular biomarkers of tree water status in forest ecosystems. Using an amplicon sequencing approach, we analysed phyllosphere microbial communities of four tree species (Quercus ilex, Quercus robur, Pinus pinaster and Betula pendula) in a forest experiment composed of irrigated and non-irrigated plots. We used these microbial community data to train a machine-learning algorithm (Random Forest) to classify irrigated and non-irrigated trees. The Random Forest algorithm detected tree water status from phyllosphere microbial community composition with more than 90% accuracy for oak species, and more than 75% for pine and birch. Phyllosphere fungal communities were more informative than phyllosphere bacterial communities in all tree species. Seven fungal amplicon sequence variants were identified as candidates for the development of molecular biomarkers of water status in oak trees. Altogether, our results show that microbial community data from tree phyllosphere provides information on tree water status in forest ecosystems and could be included in next-generation biomonitoring programmes that would use in situ, real-time sequencing of environmental DNA to help monitor the health of European temperate forest ecosystems.

Punctelia borreri and P. subrudecta (Parmeliaceae) associate with a partially overlapping pool of Trebouxia gelatinosa lineages

AbstractAn increasing number of studies are describing the diversity of lichen phycobionts, which is leading to a better understanding of how lichen communities are assembled at different taxonomic, evolutionary and geographical scales. The present study explores the identity and genetic diversity of the microalgal partners of Punctelia borreri and P. subrudecta, two tropical and temperate parmelioid lichen fungi that often grow in temperate and Mediterranean forest ecosystems in Europe. Based on a specimen sampling distributed in two climatically divergent regions in the Iberian Peninsula, we found that these mycobionts are associated with Trebouxia gelatinosa, whose identity was also confirmed by an ultrastructural study of the pyrenoid. The bipartite network analysis indicated that each Punctelia species was associated with a different set of low frequency T. gelatinosa infraspecific lineages, whereas the two most abundant phycobiont lineages were shared between both mycobionts. Based on the current sampling, these two algal lineages occur exclusively in one of the two studied regions, which might point towards climate-driven, fine-tuned fungal-algal interactions. Finally, we documented visible symptoms of injury on the thalli in areas likely to have been impacted by air pollution.

Accounting for forest condition in Europe based on an international statistical standard

Covering 35% of Europe’s land area, forest ecosystems play a crucial role in safeguarding biodiversity and mitigating climate change. Yet, forest degradation continues to undermine key ecosystem services that forests deliver to society. Here we provide a spatially explicit assessment of the condition of forest ecosystems in Europe following a United Nations global statistical standard on ecosystem accounting, adopted in March 2021. We measure forest condition on a scale from 0 to 1, where 0 represents a degraded ecosystem and 1 represents a reference condition based on primary or protected forests. We show that the condition across 44 forest types averaged 0.566 in 2000 and increased to 0.585 in 2018. Forest productivity and connectivity are comparable to levels observed in undisturbed or least disturbed forests. One third of the forest area was subject to declining condition, signalled by a reduction in soil organic carbon, tree cover density and species richness of threatened birds. Our findings suggest that forest ecosystems will need further restoration, improvements in management and an extended period of recovery to approach natural conditions.

Future Range Dynamics Suggest Increasing Threats of Grey Squirrels (Sciurus carolinensis) against Red Squirrels (Sciurus vulgaris) in Europe: A Perspective on Climatic Suitability

Interactions between the introduced gray squirrel (Sciurus carolinensis) and the native red squirrel (S. vulgaris) play an important role in the ecological equilibrium of European forest ecosystems. However, the range dynamics of the grey squirrel and red squirrel under future climate change scenarios remain unknown. The present study examined the range dynamics of grey squirrels and red squirrels in Europe and their range overlap now and in the future based on climate change. Under the most optimistic climate change scenario (SSP126), expansion of the grey squirrel’s range was mainly predicted in Germany, France, Croatia, Serbia, and Bulgaria. Under the most pessimistic climate change scenario (SSP585), expansion of the grey squirrel’s range was predicted in vast and scattered regions. Additionally, France, Italy, and Germany were overlapping ranges for the grey squirrel and red squirrel in the future under the SSP126 scenario but not under the current conditions, suggesting that there will be new regions where grey squirrels may threaten red squirrels in the future under SSP126. The range overlaps under the SSP585 scenario but not under the current conditions were vast and scattered, suggesting that there will be new regions in the future where grey squirrel may displace red squirrels under SSP585. Despite considerable variation, we detected expansions in the grey squirrel and red squirrel ranges and an increase in overlapping ranges between grey squirrels and red squirrels in the future. Therefore, our prediction suggests increasing threats of grey squirrels toward red squirrels in Europe in the future under climate change, which may impact the ecological equilibrium of European forest ecosystems.