Climate change mitigation and biodiversity conservation are key forest functions, but how to pursue them jointly in timber-managed forests is still unclear. We use a Europe-wide dataset of forest multi-taxon diversity and stand structure to (i) evaluate the importance of aboveground carbon stocks in determining species richness of six taxonomic groups; (ii) assess relationships between species richness and carbon stocks; (iii) discuss the potential to jointly enhance carbon and biodiversity and policy implications. Carbon-diversity relationships are positive for several groups, but mostly when deadwood pools are considered. Forest policies should consider the complex relationship between different carbon pools and taxonomic groups. Environmental policies emphasizing carbon sequestration in aboveground living biomass may conflict with biodiversity conservation by promoting homogeneous, fast-growing forests that fail to support species diversity of multiple groups. Sustainable forest management should acknowledge that deadwood carbon instead may translate into positive outcomes for both carbon storage and biodiversity conservation. Forests are essential for both climate change mitigation and biodiversity conservation, yet how to balance these goals in managed forests remains unclear. Here, using a Europe-wide dataset, the authors find that biodiversity increases with carbon stocks, but mostly when deadwood is included.

Recent climatic changes are reshaping biological communities by shifting species distributions and favouring warm-affiliated over cold-affiliated species, a process referred to as thermophilisation. However, how this balance between the increase in warm-affiliated species versus decline in cold-affiliated species affects total species richness at multiple spatial scales remains poorly understood. Here, we resurveyed 54 temperate forest plots in Belgium (western Europe) after 25 years to assess how climate change altered carabid beetle communities over time and how this affects species richness at both local and regional spatial scales. Community composition changed consistently across plots, largely due to a significant decline in the relative abundance of cold-affiliated species, resulting in thermophilisation in 83% of sites and accounting for 22% of the change in community composition. Multi-scale analyses of species richness revealed a significant decline in overall carabid species richness across spatial scales, which was primarily driven by declines in the abundance of cold-affiliated species, with no compensatory increase in warm-affiliated species. Additionally, rarefied richness of cold-affiliated species declined markedly, indicating a reduction of this species pool, potentially due to local population extinctions. This was further supported by the absence of several previously abundant populations of cold-affiliated species with reduced dispersal capacities. Together, these patterns point towards recent climatic changes as a key driver of arthropod diversity loss in temperate forests, with pervasive effects across spatial scales.

Food forests are an emerging agroecosystem in the temperate zone, aimed at providing food while supporting high levels of biodiversity. How food forestry impacts belowground biodiversity is, however, largely unknown. We compared communities of 12 taxonomic groups of soil organisms between 15 food forests and nearby grasslands, croplands and forests in Northwest Europe. Food forest soil communities appeared to differ from communities in grass- and croplands and more closely resembled forest communities in terms of total biomass or number of individuals of most taxonomic groups, with especially higher numbers of most macroarthropods. In terms of composition, food forest communities of most groups were overall intermediate between those in grass- and croplands and those in forests. For microorganismal and microfaunal groups, food forest communities bore a greater resemblance to grass- and cropland communities than to forest communities. Besides a higher alpha-diversity for non-arbuscular mycorrhizal fungi and certain macroarthropod groups in food forests, differences in alpha- and beta-diversity were overall limited. As food forests appear to support different soil communities than grass- and croplands, planting food forests could increase soil biodiversity in agricultural landscapes.

Urbanisation is a major driver of biodiversity change; however, its impact on soil macrodetritivore communities and their functional composition still remains overlooked. Terrestrial isopods, key soil macrodetritivores involved in decomposition processes, are increasingly used as model organisms to assess environmental change. In this study, we investigated the influence of landscape-scale urbanisation and local environmental variables on terrestrial isopod communities in Rome (Italy) to test three hypotheses: (H1) community composition vary along the urbanisation gradient, leading to biotic homogenisation; (H2) local factors contribute more to these changes than landscape-scale urbanisation; and (H3) species show non-random associations with the urban gradient. We examined variations in taxonomic and functional β-diversity, multivariate composition, and species-habitat association from 48 plots across 16 sites sampled in spring and autumn. Each plot was characterised in terms of landscape characteristics and local microhabitat and edaphic chemo-physical conditions. Overall, 42 species were collected in the study area. In accordance with H1, urbanisation affected isopod communities, increasing taxonomic and functional homogenisation. Taxonomic and functional β-diversity decreased with increasing urbanisation, driven by greater contributions of richness differences and loss of the most sensitive species. Local-scale variables accounted for a general larger proportion of community variation than landscape-scale variables, partially supporting H2. Finally, we found non-random associations between species and urbanisation, with habitat specialists thriving only in semi-natural and suburban forests, while urban areas were mostly dominated by tolerant generalist species, confirming H3. In summary, our study revealed that urbanisation filters isopod communities through the combined influence of landscape-scale gradients and local environmental conditions, especially soil properties and habitat structure, highlighting the conservation importance of structurally complex urban green spaces for soil macrodetritivores and related soil ecosystem functions.

The transferability of single or joint species distribution models ((j)SDMs) depends on their ability to predict beyond the observed environmental range and to remain consistent despite shifts in biotic interactions. Transfer accuracy may be improved by recent advances in the application of deep learning that provide greater flexibility and potentially superior predictive accuracy than traditional approaches. We implemented jSDMs with deep and machine learning algorithms and measured the transfer accuracy from continental to regional areas in communities with different species composition. We ran jSDMs with deep neural networks (DNN), elastic net (EN), and stacked SDMs (sSDM) with random forests (RF). We used 134 689 occurrence records representing 1776 species of six taxonomic groups (beetles, birds, bryophytes, fungi, lichens and plants) from 2387 forest plots in Europe. We employed an agnostic modelling approach that covered most of the environmental conditions by including more than 100 satellite-derived variables and 98 climatic variables. The predictive power of the models within the training continental area was evaluated using AUC, whereas the transfer accuracy in the regional area was evaluated with the Boyce index calculated with independent presence records. We found that the DNN-jSDMs outperformed other models at continental scale, but model transfer from continental to regional extent was less accurate. We found that the accuracy of regional predictions was higher for taxonomic groups with better representation in the continental data, such as birds, bryophytes and plants. Depending on the algorithm and the taxonomic group, we achieved acceptable (Boyce > 0) to accurate (Boyce > 0.5) transferability for 32-78% of the species. Our findings underscored the need of considering trade-offs among hyperparameter tuning, spatial scales and model complexity. Our findings also suggest that the varying biotic interaction structures and, particularly, the different species compositions of the transfer areas, may affect model transferability more than previously considered.

Temperate forests in Europe are experiencing increasingly hotter and drier summers. Because of increasing forest disturbances, canopies are also opening up, creating brighter, but also drier conditions at the forest floor. This can lead to a dominance of drought-resistant species, such as graminoids, potentially leading to a grassification of the understorey in the long term. It remains unclear how graminoid dominance is impacting tree seedling recruitment in forests because of a lack of experiments that allow disentangling the effects of different interacting drivers. Here we introduce a novel experimental platform and report the early-stage results on seedling growth and survival. We test two hypotheses: (1) light and recent forest soil promote graminoid growth, while drought has little effect at this very early stage; and (2) the presence of graminoid negatively affects tree seedling growth. We planted 12 tree seedlings within a matrix of monocultures of graminoids together in trays filled with forest soils and subjected to three two-level factorial treatments of light, rainfall, and land-use legacies. Graminoid shoot length significantly increased after exposure to light, which suppressed tree seedling height growth. Drought had no effect, but light and land use significantly influenced seedling growth through the mediation of graminoid shoot length. Light increased the height of Acer pseudoplatanus when growing alongside shorter Deschampsia cespitosa but decreased Acer pseudoplatanus and Quercus petraea height within mesocosm dominated by taller graminoid species, such as Calamagrostis epigejos. Recent forest soil only increased Acer pseudoplatanus height when grown in combination with Brachypodium sylvaticum, the shortest graminoid species within the studied species pool. This study presents a novel experimental platform where we demonstrate that light and post-agricultural soil promote graminoid growth more than tree seedlings, while their interaction with graminoids significantly affects seedling growth.

Assessing multi-taxon biodiversity is crucial to understand forests’ response to environmental changes and to inform management strategies. In Europe, forest biodiversity monitoring is still scattered and heterogeneous, although a long-term monitoring network has long been advocated. Given the monitoring aims reported in various EU policies, this network should be accurately designed also through the estimation of its sampling effort, here intended as the number of sampling plots and sites.We used a novel database of forest multi-taxon biodiversity for a pilot study to: estimate the minimum sampling effort needed to: assess variation in species richness and composition; compare these estimates with the efforts invested in the pilot database; discuss estimates’ differences across taxonomic groups and forest categories.We focused on six taxonomic groups (vascular plants, birds, epiphytic lichens and bryophytes, wood-inhabiting fungi and saproxylic beetles) across six forest categories. Based on 6,165 plots at 2,084 different locations across Europe, we benchmarked the effort to achieve: a complete species richness estimate through interpolation/extrapolation curves, and a precise evaluation of species composition variation through multivariate standard error.Our estimates differed widely, especially among taxonomic groups. For species richness, estimates range from 3 to 147 plots per site across 3 to 29 sites per forest category, with birds and epiphytic bryophytes requiring the least effort. For species composition, estimates range from 5 to over 25 plots per site across 5 to 20 sites per forest category, with saproxylic beetles, vascular plants, and fungi displaying the highest estimates.The taxonomic groups requiring an effort comparable to existing data were the least diverse, all the others need greater efforts, either for species richness (e.g., saproxylic beetles), or species composition (e.g., vascular plants), or both (e.g., wood-inhabiting fungi). An effective monitoring network of European forests’ biodiversity should thoroughly account for these benchmarks and for their taxon-dependency.

Wild animals sold as pets are at a higher risk of extinction than animals that are not traded. Invertebrates are often overlooked in national and international laws designed to control the global pet trade. Among these invertebrates, terrestrial isopods-which function as detritivores-have traditionally been kept to clean terraria housing vertebrates and other arthropods. Over the past 2 decades, they have gained popularity among hobbyists due to their ease of care, vibrant colors, minimal space requirements, and harmlessness to humans. Many traded species have limited distribution areas, sometimes only a single locality. Collecting these species in the wild poses a threat to local populations. Species are continuously being added to the online market. Many of these species, especially from tropical regions in Southeast Asia, Central America, and South America, have not been described scientifically. In addition to threatening native populations, this trade in live specimens increases the probability of non-native species introductions and invasions to new regions. Given this growing interest, we advocate for including terrestrial isopods in national and international regulations. We encourage scientists to assess the scale of the terrestrial isopod pet trade, scientifically describe traded species, and collect distribution and ecological data. We ask the International Union for Conservation of Nature to establish a terrestrial isopod specialist group to assess the status of traded species, which would facilitate their inclusion in the Convention on International Trade in Endangered Species of Wild Fauna and Flora. We urge policy makers to make conservative lists of species that can be traded applying the precautionary principle in regulating the trade in species with an unknown conservation status and invasion risk.

Forest loss and fragmentation are major threats to biodiversity and associated ecosystem services worldwide. Forest fragmentation leads to the creation of forest edges, which experience contrasting environmental conditions compared to forest interiors, inducing a strong change in biological communities. In addition, forest management interventions, such as thinning influence canopy opening, microclimate and strongly alter the structural environment of vegetation. Moths are a species-rich and functionally important taxonomic group because of their role in plant pollination and as bulk food for other species. Here we studied the effects of canopy structure and edge-to-interior gradients on macro-moth communities using light traps in Belgium and northern France. We found that forest edges had lower abundance of moths (a modeled reduction of 46 %) and lower species richness (-29 %) than forest interiors. Open stands had an overall lower abundance of moths compared to more closed stands (-17 %). Moreover, the interaction between forest structure and edge effect was significant, indicating stronger reductions of moth abundance towards the edge in open forest (-57 % vs -37 % in dense forest). Both local environmental variables and landscape variables explained the observed patterns, e.g., nighttime temperature of the plot and forest cover in the surrounding landscape both had a positive effect on moth activity density and species richness. We found limited evidence that moth species traits explained the observed edge-to-interior disparities, although species with larvae feeding on shrubs and trees tended to be more associated with forest cores than grass and herb feeders. Our results indicate the importance of functional forest interior habitat and relatively undisturbed forests with a high structural complexity for moth conservation.

The species richness of vascular plants in forests can have contrasting effects on the occurrence of non‐native insects. The establishment of non‐native insect populations may be facilitated by low plant species richness, which reflects the availability of few but easily accessible resources, or hampered by high plant species richness due to spatial dilution of resources or biotic resistance (i.e., resistance against biological invasions). The relationship between the species richness of plants and non‐native insects is likely influenced by disturbance regimes, which, in European forests, mostly consists of timber harvesting. We investigated this relationship considering two major forest attributes: (i) species richness of non‐native vascular plants and (ii) forest management. From 1101 forest plots in Europe, we gathered occurrences of 1212 vascular plant species, including 160 non‐native species, and of 2404 beetle species, including 29 non‐native species. We tested the relationship between the species richness of non‐native beetles and plants using non‐linear quantile regressions. We disentangled the effect of non‐native plant species richness from that of management on the species richness of non‐native beetles, while accounting for forest structural variables, using structural equation models. We found clear evidence of a hump‐shaped relationship between non‐native beetle and plant species richness. The general shape of the relationship persisted when considering only woody or non‐woody plants, as well as only non‐native plants. The relationship was also similar between managed and unmanaged forests. However, the proportion of non‐native beetles in managed forests was higher than in unmanaged forests at the same plant species richness. Management had a direct negative effect on non‐native beetle species richness, whereas non‐native plant species richness had a direct positive effect. When considering all direct and indirect effects, management facilitated the occurrence of non‐native beetles indirectly via non‐native plants rather than directly. Synthesis and applications . Species richness of native and non‐native vascular plants modulates the species richness of non‐native beetles through relationships with opposite signs. The interplay with management regimes and forest structures determines whether non‐native beetles are promoted. Forest management aimed at reducing the intensity of disturbance while encouraging native plant species richness could promote the dominance of dilution effects and biotic resistance and could moderate the establishment of non‐native insects.

Chaetophiloscia sicula Verhoeff, 1908 (Philosciidae) is a small terrestrial isopod of Mediterranean origin which was first reported in North America in 2000 in an urban forest in Baltimore, Maryland, and it was thought to be a recent introduction, with a restricted range. Here we report the current state of knowledge of C. sicula distribution in North America. Since the original observation, the species has been reported by citizen scientists from eight additional states. Standardized field surveys in Maryland and Washington D.C. revealed a strong habitat preference towards anthropogenic and coastal areas. The affinity of C. sicula to urban environments, including residential areas and urban parks, is reinforced by citizen-science data and is most likely key to its fast spread throughout North America. Keeping isopods as pets and trading them among hobbyists may also play a role especially in establishing core populations in urban centers. The species is likely to expand in the USA in the coming decade. This study highlights that thorough, systematic surveys, using a variety of collecting techniques, are essential to address existing knowledge gaps on terrestrial isopod distribution and spread in North America and elsewhere.

Background:In response to the ongoing biodiversity crisis amongst arthropods, it is essential to implement efficient conservation strategies to safeguard both species diversity and the vital ecosystem services they provide. Developing such strategies requires reliable predictive models that can identify the species that are the most vulnerable to current and future threats, including those posed by climate and land-use change. Species life histories are central to these models, as they influence both population dynamics and spread rates. New information:To support this effort, we compiled a dataset with key traits for arthropods based on several literature sources and expert knowledge. The dataset contains data on body size, life history, thermal niche and ecology for 4874 northwestern European species across 10 different orders. By gathering these essential trait data, we aim to create a robust foundation for predicting species vulnerability and anticipating shifts in arthropod communities in response to global change.

Urban areas can support diverse communities of plants and animals. Yet, urbanisation can affect functionally important species traits, potentially impacting population dynamics. The saproxylic beetle Elater ferrugineus L. is associated with large trees and is often used as an indicator of species‐rich saproxylic communities. It is an important target for conservation and it is listed as a near‐threatened species on the European Red List. Few studies have quantified the impact of urbanisation on the ecology and intraspecific variation in functional traits of arthropods, other than pollinators. We studied how the local abundance of E. ferrugineus and functionally important response traits (e.g., width of the pronotum, length of the elytron and wing, wing area, body mass and wingload) changed along urbanisation gradients in eight European cities using pheromone traps installed on large solitary trees. We analysed the effects of the surrounding built‐up area and tree cover on our response variables while accounting for potential confounding effects due to tree size and the availability of microhabitats. Urbanisation had a strong negative effect on the local abundance of E. ferrugineus , while the amount of tree cover had a positive influence. We found no significant impact of urbanisation on the functional traits of this species, except for a significantly higher wingload in city centres. Our results provide a better understanding of the ecological processes impacting this saproxylic beetle and underpin the importance of future research on urbanisation's impact on arthropods.

Terrestrial isopods (Isopoda: Oniscidea), commonly known as woodlice, are among the most recognisable soil-dwelling invertebrates and are crucial for soil functioning. They are widely distributed from temperate to equatorial ecosystems, and their distribution is strongly influenced by environmental factors, such as soil type, temperature and humidity. Terrestrial isopods have fascinated taxonomists for centuries, with over 4,100 described species across 568 genera and 38 or 39 families. These animals contribute significantly to key ecosystem processes, such as litter decomposition, nutrient cycling, and carbon sequestration. However, data on patterns of their diversity, abundance, or biomass, which are crucial for assessing their importance in ecosystem functioning worldwide, are lacking. This is partly due to the incomplete taxonomy in regions such as the tropics and the scattered nature of local georeferenced datasets. To better understand the global taxonomic patterns, species distributions, and functional roles of terrestrial isopods, we call for the compilation of a comprehensive global database that integrates taxonomy, georeferenced species records, and trait data. This database would help answer fundamental questions about the response of terrestrial isopods to environmental changes and their role in ecosystem functioning and soil health. OniscidBase, a recently launched initiative, aims to consolidate such data, facilitating the analysis of taxonomic gaps and assessing the distribution and functional importance of terrestrial isopods. The database aims to include georeferenced data on the distribution, abundance and biomass of terrestrial isopod species, and metadata on environmental parameters. Our main goals are to strengthen the taxonomic backbone for terrestrial isopods, make distribution data available for macroecological studies, and collect trait data to understand species responses to environmental changes and effects on soils. Using these data leads to a deeper understanding of the importance of terrestrial isopods as components of terrestrial ecosystems and, at the same time, highlights future research directions.

Global pollinator decline threatens food security, especially in regions with intensive agriculture and habitat loss. Agroforestry, a sustainable agricultural diversification practice, could mitigate these issues by providing diverse habitats and floral resources for pollinators, yet its effects on pollination services and crop yields in tropical Africa remain undocumented. This study examined the impact of tree density and landscape-level tree cover at various spatial scales on pollinator visitation and pollination success of the common bean in Rwandan smallholder agroforestry systems. We used two bean varieties from 18 farms with varying plot-level tree density and landscape-level tree cover for the study. Bean plants were subjected to two treatments: bagged (pollinator exclusion) and open (natural pollination). Pollinator surveys were conducted in 15-min intervals. We found that open-pollinated flowers had significantly higher yields than bagged flowers, highlighting the critical role of insect-mediated pollination in bean production. Insect pollination increased crop dry matter yield by 120.63

Forest canopies play a vital role in buffering macroclimatic conditions, creating stable microclimates that support species unable to survive under the surrounding climate. However, disturbances driven by climate change alongside management interventions can disrupt canopy cover, altering forest microclimates and, consequently, forest-related biodiversity. To investigate these dynamics, we monitored forest floor temperature, soil moisture and macroarthropod communities along a canopy cover gradient in the National Park Brabantse Wouden, Belgium. Forest microclimate was recorded using TMS4-loggers throughout the 2022-2023 growing seasons. Macroarthropod activity-density and species richness were sampled using pitfall traps during the 2022 summer. Generalized linear mixed models and piecewise structural equation modelling were used to assess the influence of forest structure. As canopy cover decreased, microclimate temperatures became more similar to macroclimate temperatures, reducing the forest's thermal buffering capacity. Once canopy cover dropped below 50%, temperatures were amplified rather than buffered. Additionally, lower stand densities were linked to higher soil moisture levels. Microclimatic conditions significantly affected both the activity-density and species richness of macroarthropod communities. Woodlice profited from temporarily elevated forest floor temperatures if soil moisture was sufficient, while prolonged high temperatures negatively affected ground beetles. Ground beetles benefited from reduced canopy cover and increased deadwood, while woodlice preferred oak-dominated stands. Synthesis and applications. To sustain a stable and well-buffered microclimate, we recommend maintaining canopies as closed as possible. Even small openings reduce the forest's ability to buffer temperature, with canopy covers below 50% leading to temperature amplification. Closed canopies should be combined with isolated canopy gaps to promote habitat heterogeneity. Additionally, deadwood amounts should increase to provide shelter during droughts. This balanced management approach fosters stable forest microclimates and diverse habitats, supporting long- and short-term macroarthropod biodiversity in temperate broadleaf forests.

Global changes are forcing forest management toward more resilient and more structurally complex forests, thereby creating a more attractive habitat for their associated biodiversity. However, the assessment of forest structural complexity and its relation to biodiversity is challenging. In this work, we applied the structural complexity index (SCI), which is designed for forest managers to quickly and easily assess structural complexity. Studies comparing the predictive value of this index with taxonomic biodiversity monitoring are rare. Herein, we focus on wild pollinators, which could potentially benefit from this shift toward more structurally complex forests. We used elevated pan traps in 19 forest plots varying in structural complexity and dominant tree species to address the following aims: First, we investigated how predictive the SCI is for wild bee and syrphid abundance and diversity. Second, we studied their communities and how these could be shaped by the SCI. We found that the SCI was not predictive for either the abundance or diversity. We found that some tree species exhibit effects on abundance and diversity, stressing the importance of maintaining multiple tree species. However, no differences between wild pollinator communities among different forest types and SCI levels were observed. Our results show that tools such as the SCI, which allows forest managers to quickly assess the potential biodiversity of forest stands, are not necessarily predictive for each taxonomic group. However, combining collection methods across multiple years and taxonomic groups should provide additional insight for an overall assessment of the predictive value of the SCI for pollinators in forests.

1. Wild pollinators are crucial for ecosystem functioning and human food production and often rely on floral resources provided by different (semi-) natural ecosystems for survival. Yet, the role of European forests, and especially the European forest herb layer, as a potential provider of floral resources for pollinators has scarcely been quantified. 2. In this study, we measured the potential nectar production (PNP) of the forest herb layer using resurvey data across 3326 plots in temperate forests in Europe, with an average time interval of 41 years between both surveys in order to assess (i) the importance of the forest herb layer in providing nectar for wild pollinators, (ii) the intra-annual variation of PNP, (iii) the overall change in PNP between survey periods and (iv) the change in intra-annual variation of PNP between sur-vey periods. The PNP estimates nectar availability based on the relative cover of different plant species in the forest herb layer. Although PNP overestimates actual nectar production, relative differences amongst plots provide a valid and informative way to analyse differences across time and space. 3. Our results show that the forest herb layer has a large potential for providing nec-tar for wild pollinator communities, which is greatest in spring, with an average PNP of almost 16 g sugar/m2/year. However, this potential has drastically declined (mean plot- level decline >24%). 4. Change in light availability, associated with shifts in canopy structure and canopy composition, is the key driver of temporal PNP changes. 5. Synthesis. Our study shows that if management activities are carefully planned to sustain nectar- producing plant species for wild pollinators, European forest herb layers and European forests as a whole can play key roles in sustaining wild pol-linator populations.

Woodlice (Isopoda: Oniscidea) constitute a diverse and ecologically significant group inhabiting a great variety of ecosystems with a crucial role for ecosystem functioning, but strongly overlooked in conservation efforts and threats to species and populations are hardly studied. In this study, we evaluate for the first time the potential impact of an emerging unregulated trade on the woodlice of Spain. We conducted a search for all Spanish species nationally and internationally traded via online shops and studied various aspects of the nature of this market and its tendency. We found 56 species currently traded in international stores, and an additional 30 species through transactions on social media. Furthermore, the amount and number of species are increasing and far from stabilising, with higher prices paid for endemic than non-endemic species. This situation puts pressure on local populations, potentially inducing local extinctions, affecting ecosystem functioning. Other potential future threats such as genetic contamination of native populations and the introduction of alien species cannot be ruled out. The conservation of woodlice faces significant challenges due to a lack of assessments of species conservation status and conservation action plans for the most affected species. We propose preventive measures, such as the creation of whitelists or blacklists, essential to protect (endemic) species and mitigate the threat of invasive species.

QuestionsHow do local forest conditions and characteristics at the forest patch - scale and landscape - scale affect plot-scale plant diversity in Europe? Do these patterns vary between forest specialists and generalists? Do community saturation patterns differ between forests varying in their surrounding landscape type?LocationDeciduous forests sampled along a European gradient from southwest to northeast comprising eight regions in five countries (France, Belgium, Germany, Sweden, Estonia).MethodsWe examined the effects of local conditions assessed by means of Ellenberg indicator values (soil moisture, soil nitrogen, soil pH, light availability), patch-scale characteristics (patch-scale plant diversity, forest patch age, forest patch size) and a landscape-scale variable (representing low and high connectivity of forest patches) on plot-scale plant diversity, separately for forest specialist and generalist species. Additionally, we ran regression models to examine community saturation patterns.ResultsWe found patterns of niche partitioning among forest specialists and generalists. Low light availability and medium soil moisture favored forest specialists, while generalists were mostly present at higher light availability and medium and high soil moisture. In general, we found the highest plot-scale diversity at medium soil pH. Patch-scale diversity showed a positive impact on plot-scale diversity and plots in the high-connectivity landscape had a higher diversity than plots in the low-connectivity landscape. Further, we observed a high degree of community saturation in both landscape types.ConclusionThe positive impact of a high connectivity of forest patches on local plant diversity emphasizes the importance of small semi-natural habitats like tree lines, unused field margins and hedgerows to enhance the potential dispersal of forest plants across agricultural landscapes. Community saturation patterns revealed the increasing relevance of local conditions and processes for plot-scale diversity when patch-scale diversity increases.