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Aims: The accurate classification of habitats is essential for effective biodiversity conservation. The goal of this study was to harness the potential of deep learning to advance habitat identification in Europe. We aimed to develop and evaluate models capable of assigning vegetation‐plot records to the habitats of the European Nature Information System (EUNIS), a widely used reference framework for European habitat types. Location: The framework was designed for use in Europe and adjacent areas (e.g., Anatolia, Caucasus). Methods: We leveraged deep‐learning techniques, such as transformers (i.e., models with attention components able to learn contextual relations between categorical and numerical features) that we trained using spatial k‐fold cross‐validation (CV) on vegetation plots sourced from the European Vegetation Archive (EVA), to show that they have great potential for classifying vegetation‐plot records. We tested different network architectures, feature encodings, hyperparameter tuning and noise addition strategies to identify the optimal model. We used an independent test set from the National Plant Monitoring Scheme (NPMS) to evaluate its performance and compare its results against the traditional expert systems. Results: Exploration of the use of deep learning applied to species composition and plot‐location criteria for habitat classification led to the development of a framework containing a wide range of models. Our selected algorithm, applied to European habitat types, significantly improved habitat classification accuracy, achieving a more than twofold improvement compared to the previous state‐of‐the‐art (SOTA) method on an external data set, clearly outperforming expert systems. The framework is shared and maintained through a GitHub repository. Conclusions: Our results demonstrate the potential benefits of the adoption of deep learning for improving the accuracy of vegetation classification. They highlight the importance of incorporating advanced technologies into habitat monitoring. These algorithms have shown to be better suited for habitat type prediction than expert systems. They push the accuracy score on a database containing hundreds of thousands of standardized presence/absence European surveys to 88.74%, as assessed by expert judgment. Finally, our results showcase that species dominance is a strong marker of ecosystems and that the exact cover abundance of the flora is not required to train neural networks with predictive performances. The framework we developed can be used by researchers and practitioners to accurately classify habitats. [ABSTRACT FROM AUTHOR]

The first comprehensive phytosociological classification of all vegetation types in Europe (EuroVegChecklist; Applied Vegetation Science, 2016, 19, 3–264) contained brief descriptions of each type. However, these descriptions were not standardized and mentioned only the most distinct features of each vegetation type. The practical application of the vegetation classification system could be enhanced if users had the option to select sets of vegetation types based on various combinations of structural, ecological, and biogeographical attributes. Based on a literature review and expert knowledge, we created a new database that assigns standardized categorical attributes of 12 variables to each of the 1106 alliances dominated by vascular plants defined in EuroVegChecklist. These variables include dominant life form, phenological optimum, substrate moisture, substrate reaction, salinity, nutrient status, soil organic matter, vegetation region, elevational vegetation belt, azonality, successional status and naturalness. The new database has the potential to enhance the usefulness of phytosociological classification for researchers and practitioners and to help understand this classification to non‐specialists. [ABSTRACT FROM AUTHOR]

Aims: The Raunkiær's system classifies vascular plants into life forms based on the position of renewal buds during periods unfavourable for plant growth. Despite the importance of Raunkiær's system for ecological research, a study exploring the diversity and distribution of life forms on a continental scale is missing. We aim to (i) map the diversity and distribution of life forms in European vegetation and (ii) test for effects of bioclimatic variables while controlling for habitat‐specific responses. Location: Europe. Methods: We used data on life forms of 8883 species recorded in 546,501 vegetation plots of different habitats (forest, grassland, scrub and wetland). For each plot, we calculated: (i) the proportion of species of each life form and (ii) the richness and evenness of life forms. We mapped these plot‐level metrics averaged across 50 km × 50 km grid cells and modelled their response to bioclimatic variables. Results: Hemicryptophytes were the most widespread life form, especially in the temperate zone of Central Europe. Conversely, therophyte and chamaephyte species were more common in the Mediterranean as well as in the dry temperate regions. Moreover, chamaephytes were also more common in the boreal and arctic zones. Higher proportions of phanerophytes were found in the Mediterranean. Overall, a higher richness of life forms was found at lower latitudes while evenness showed more spatially heterogeneous patterns. Habitat type was the main discriminator for most of the responses analysed, but several moisture‐related predictors still showed a marked effect on the diversity of therophytes and chamaephytes. Conclusions: Our maps can be used as a tool for future biogeographic and macro‐ecological research at a continental scale. Habitat type and bioclimatic conditions are key for regulating the diversity and distribution of plant life forms, with concomitant consequences for the response of functional diversity in European vegetation to global environmental changes. [ABSTRACT FROM AUTHOR]

Aims: Ellenberg‐type indicator values are expert‐based rankings of plant species according to their ecological optima on main environmental gradients. Here we extend the indicator‐value system proposed by Heinz Ellenberg and co‐authors for Central Europe by incorporating other systems of Ellenberg‐type indicator values (i.e., those using scales compatible with Ellenberg values) developed for other European regions. Our aim is to create a harmonized data set of Ellenberg‐type indicator values applicable at the European scale. Methods: We collected European data sets of indicator values for vascular plants and selected 13 data sets that used the nine‐, ten‐ or twelve‐degree scales defined by Ellenberg for light, temperature, moisture, reaction, nutrients and salinity. We compared these values with the original Ellenberg values and used those that showed consistent trends in regression slope and coefficient of determination. We calculated the average value for each combination of species and indicator values from these data sets. Based on species' co‐occurrences in European vegetation plots, we also calculated new values for species that were not assigned an indicator value. Results: We provide a new data set of Ellenberg‐type indicator values for 8908 European vascular plant species (8168 for light, 7400 for temperature, 8030 for moisture, 7282 for reaction, 7193 for nutrients, and 7507 for salinity), of which 398 species have been newly assigned to at least one indicator value. Conclusions: The newly introduced indicator values are compatible with the original Ellenberg values. They can be used for large‐scale studies of the European flora and vegetation or for gap‐filling in regional data sets. The European indicator values and the original and taxonomically harmonized regional data sets of Ellenberg‐type indicator values are available in the Supporting Information and the Zenodo repository. [ABSTRACT FROM AUTHOR]

Riparian zones are the paragon of transitional ecosystems, providing critical habitat and ecosystem services that are especially threatened by global change. Following consultation with experts, 10 key challenges were identified to be addressed for riparian vegetation science and management improvement: (1) Create a distinct scientific community by establishing stronger bridges between disciplines; (2) Make riparian vegetation more visible and appreciated in society and policies; (3) Improve knowledge regarding biodiversity—ecosystem functioning links; (4) Manage spatial scale and context‐based issues; (5) Improve knowledge on social dimensions of riparian vegetation; (6) Anticipate responses to emergent issues and future trajectories; (7) Enhance tools to quantify and prioritize ecosystem services; (8) Improve numerical modeling and simulation tools; (9) Calibrate methods and increase data availability for better indicators and monitoring practices and transferability; and (10) Undertake scientific validation of best management practices. These challenges are discussed and critiqued here, to guide future research into riparian vegetation. This article is categorized under:Water and Life > Nature of Freshwater EcosystemsWater and Life > Stresses and Pressures on EcosystemsWater and Life > Conservation, Management, and Awareness [ABSTRACT FROM AUTHOR]

The importance of environmental difference among sites and dispersal limitations of species to the explanation of diversity differs among biological systems and geographical regions. We hypothesized that climate and then dispersal limitation will predominantly explain the similarity of alpine vegetation at increasing distances between pairs of regions at subcontinental extent. We computed the similarity of all pairs of 23 European mountain regions below 50° N after dividing the species lists of each region by calcareous or siliceous substrates. Distance decay in similarity was better fitted by a cubic polynomial than a negative exponential function, and the fit was better on calcareous than on siliceous substrate. Commonality analysis revealed that the proportion of explanation of beta diversity by climatic difference had unimodal patterns on a gradient of increasing distance between regions, while explanation by dispersal limitation had consistently rising patterns on both substrates. On siliceous substrate, dispersal limitation explained more of the variation in beta diversity only at longer distances, but it was predominant at all distances on calcareous substrate. The steeper response to distance at <1600 km and >2600 km may indicate dispersal limitation at different temporal scales, and the uptick in the response to distance at the longest distances may reflect how isolated some regions have been before and since the last glacial maximum. [ABSTRACT FROM AUTHOR]

Aims: Biodiversity is traditionally studied mostly at the species level, but biogeographical and macroecological studies at higher taxonomic levels can provide valuable insights into the evolutionary processes at large spatial scales. Our aim was to assess the representation of vascular plant families within different vegetation formations across Europe. Location: Europe. Methods: We used a data set of 816,005 vegetation plots from the European Vegetation Archive (EVA). For each plot, we calculated the relative species richness of each plant family as the number of species belonging to that family divided by the total number of species. We mapped the relative species richness, averaged across all plots in 50 km × 50 km grid cells, for each family and broad habitat groups: forests, grasslands, scrub and wetlands. We also calculated the absolute species richness and the Shannon diversity index for each family. Results: We produced 522 maps of mean relative species richness for a total of 152 vascular plant families occurring in forests, grasslands, scrub and wetlands. We found distinct spatial patterns for many combinations of families and habitat groups. The resulting series of 522 maps is freely available, both as images and GIS layers. Conclusions: The distinct spatial patterns revealed in the maps suggest that the relative species richness of plant families at the community level reflects the evolutionary history of individual families. We believe that the maps and associated data can inspire further biogeographical and macroecological studies and strengthen the ongoing integration of phylogenetic, functional and taxonomic diversity concepts. [ABSTRACT FROM AUTHOR]

Aim: Alpine habitats support unique biodiversity confined to high‐elevation areas in the current interglacial. Plant diversity in these habitats may respond to area, environment, connectivity and isolation, yet these factors have been rarely evaluated in concert. Here we investigate major determinants of regional species pools in alpine grasslands, and the responses of their constituent species groups. Location: European mountains below 50° N. Time period: Between 1928 and 2019. Major taxa studied: Vascular plants. Methods: We compiled species pools from alpine grasslands in 23 regions, including 794 alpine species and 2,094 non‐alpines. We used species–area relationships to test the influence of the extent of alpine areas on regional richness, and mixed‐effects models to compare the effects of 12 spatial and environmental predictors. Variation in species composition was addressed by generalized dissimilarity models and by a coefficient of dispersal direction to assess historical links among regions. Results: Pool sizes were partially explained by current alpine areas, but the other predictors largely contributed to regional differences. The number of alpine species was influenced by area, calcareous bedrock, topographic heterogeneity and regional isolation, while non‐alpines responded better to connectivity and climate. Regional dissimilarity of alpine species was explained by isolation and precipitation, but non‐alpines only responded to isolation. Past dispersal routes were correlated with latitude, with alpine species showing stronger connections among regions. Main conclusions: Besides area effects, edaphic, topographic and spatio‐temporal determinants are important to understand the organization of regional species pools in alpine habitats. The number of alpine species is especially linked to refugia and isolation, but their composition is explained by past dispersal and post‐glacial environmental filtering, while non‐alpines are generally influenced by regional floras. New research on the dynamics of alpine biodiversity should contextualize the determinants of regional species pools and the responses of species with different ecological profiles. [ABSTRACT FROM AUTHOR]

Aim: Plant functional traits summarize the main variability in plant form and function across taxa and biomes. We assess whether geographic range size, climatic niche size, and local abundance of plants can be predicted by sets of traits (trait syndromes) or are driven by single traits. Location: Eurasia. Methods: Species distribution maps were extracted from the Chorological Database Halle to derive information on the geographic range size and climatic niche size for 456 herbaceous, dwarf shrub and shrub species. We estimated local species abundances based on 740,113 vegetation plots from the European Vegetation Archive, where abundances were available as plant species cover per plot. We compiled a complete species‐by‐trait matrix of 20 plant functional traits from trait databases (TRY, BiolFlor and CLO‐PLA). The relationships of species’ geographic range size, climatic niche size and local abundance with single traits and trait syndromes were tested with multiple linear regression models. Results: Generally, traits were more strongly related to local abundances than to broad‐scale species distribution patterns in geographic and climatic space (range and niche size), but both were better predicted by trait combinations than by single traits. Local abundance increased with leaf area and specific leaf area (SLA). Geographic range size and climatic niche size both increased with SLA. While range size increased with plant height, niche size decreased with leaf carbon content. Conclusion: Functional traits matter for species’ abundance and distribution at both local and broad geographic scale. Local abundances are associated with different combinations of traits as compared to broad‐scale distributions, pointing to filtering by different environmental and ecological factors acting at distinct spatial scales. However, traits related to the leaf economics spectrum were important for species’ abundance and occurrence at both spatial scales. This finding emphasizes the general importance of resource acquisition strategies for the abundance and distribution of herbaceous, dwarf shrub and shrub species.We studied whether single traits or sets of traits matter for species’ abundance and distribution at both local and broad geographic scale. Traits related to the leaf economics spectrum were important for abundance and occurrence at both spatial scales. This finding emphasizes the general importance of resource acquisition strategies for the abundance and distribution of herbaceous, dwarf shrub and shrub species. [ABSTRACT FROM AUTHOR]

Aim: A fundamental question in macroecology centres around understanding the relationship between species' local abundance and their distribution in geographical and climatic space (i.e. the multi‐dimensional climatic space or climatic niche). Here, we tested three macroecological hypotheses that link local abundance to the following range properties: (a) the abundance–range size relationship, (b) the abundance–range centre relationship and (c) the abundance–suitability relationship. Location: Europe. Taxon: Vascular plants. Methods: Distribution range maps were extracted from the Chorological Database Halle to derive information on the range and niche sizes of 517 European vascular plant species. To estimate local abundance, we assessed samples from 744,513 vegetation plots in the European Vegetation Archive, where local species' abundance is available as plant cover per plot. We then calculated the 'centrality', that is, the distance between the location of the abundance observation and each species' range centre in geographical and climatic space. The climatic suitability of plot locations was estimated using coarse‐grain species distribution models (SDMs). The relationships between centrality or climatic suitability with abundance was tested using linear models and quantile regression. We summarized the overall trend across species' regression slopes from linear models and quantile regression using a meta‐analytical approach. Results: We did not detect any positive relationships between a species' mean local abundance and the size of its geographical range or climatic niche. Contrasting yet significant correlations were detected between abundance and centrality or climatic suitability among species. Main conclusions: Our results do not provide unequivocal support for any of the relationships tested, demonstrating that determining properties of species' distributions at large grains and extents might be of limited use for predicting local abundance, including current SDM approaches. We conclude that environmental factors influencing individual performance and local abundance are likely to differ from those factors driving plant species' distribution at coarse resolution and broad geographical extents. [ABSTRACT FROM AUTHOR]

Abstract: Questions: Which major syntaxa of dry grasslands supported by carbonate bedrock occur in the central and southern Balkans? What is their position along major ecological gradients and in the context of phytogeographic patterns of the region? Location: Central and southern Balkans, including western Bulgaria, northern Greece, Kosovo, Macedonia (FYROM) and Serbia. Methods: We compiled a matrix of 660 relevés of dry grasslands over lime‐rich bedrock, previously classified in the Festuco‐Brometea. We applied clustering techniques to classify separately synoptic and relevé data, and applied NMDS with passive projection of indicator values, climatic data and biogeographic geo‐elements onto ordination diagrams to assist interpretation of the syntaxonomic patterns. We constructed elevation distribution profiles for alliances and classes of grasslands of several grassland classes from a broader study area to elucidate the relationship of the elevational sorting of the syntaxa in relation to latitude. Results: The analysis revealed six major vegetation types, classified into four orders: (1) Stipo pulcherrimae‐Festucetalia pallentis, incl. (sub)montane rocky steppic grasslands of the Saturejion montanae of central Balkans, and the Koelerio‐Festucion dalmaticae – submontane rocky grasslands of southern Serbia and Kosovo; (2) Astragalo onobrychidis‐Potentilletalia represented by the Saturejo‐Thymion (low‐elevation steppic grasslands of southern Balkans); (3) Festucetalia valesiacae represented by grasslands on deep soil and low elevation of northern Greece, and finally (4) high‐elevation rocky grasslands of southern Balkans, classified as a new alliance – Diantho haematocalycis‐Festucion hirtovaginatae, that might belong to a new, yet undescribed, syntaxonomic order. Ordination suggests that the major differentiation of the high‐rank syntaxa follows north–south geographic and low–high elevation gradients. Conclusions: Because of the transitional biogeographic position of the studied region, as well as considerable large elevation span across latitudes, the diversity of vegetation types is high. The indication a putative new dry grassland order, the mid‐high altitudes of the southern Balkans points to a need to re‐assess the Balkan vegetation occupying the community niche between the low‐elevation dry grasslands (Festuco‐Brometea) and those typical of high elevations (Elyno‐Seslerietea and Daphno‐Festucetea), seeking parallels to patterns described from the western Alps, Pyrenees, and Apennines. This syntaxonomic unit is poised to expand the concept of the Festuco hystricis‐Ononidetea striatae to the Balkans. [ABSTRACT FROM AUTHOR]

Aim Woodlands make up a third of European territory and carry out important ecosystem functions, yet a comprehensive overview of their invasion by alien plants has never been undertaken across this continent. Location Europe. Methods We extracted data from 251,740 vegetation plots stored in the recently compiled European Vegetation Archive. After filtering (resulting in 83,396 plots; 39 regions; 1970-2015 time period), we analysed the species pool and frequency of alien vascular plants with respect to geographic origin and life-forms, and the levels of invasion across the European Nature Information System ( EUNIS) woodland habitats. Results We found a total of 386 alien plant species (comprising 7% of all recorded vascular plants). Aliens originating from outside of and from within Europe were almost equally represented in the species pool (192 vs. 181 species) but relative frequency was skewed towards the former group (77% vs. 22%) due, to some extent, to the frequent occurrence of Impatiens parviflora (21% frequency among alien plants). Phanerophytes were the most species-rich life-form (148 species) and had the highest representation in terms of relative frequency (39%) among aliens in the dataset. Apart from Europe (181 species), North America was the most important source of alien plants (109 species). At the local scale, temperate and boreal softwood riparian woodland (5%) and mire and mountain coniferous woodland (<1%) had the highest and lowest mean relative alien species richness (percentage of alien species per plot), respectively. Main conclusions Our results indicate that European woodlands are prone to alien plant invasions especially when exposed to disturbance, fragmentation, alien propagule pressure and high soil nutrient levels. Given the persistence of these factors in the landscape, competitive alien plant species with a broad niche, including alien trees and shrubs, are likely to persist and spread further into European woodlands. [ABSTRACT FROM AUTHOR]

Questions What are the main floristic patterns in European beech forests? Which classification at the alliance and suballiance level is the most convincing? Location Europe and Asia Minor. Methods We applied a TWINSPAN classification to a data set of 24 605 relevés covering the whole range of Fagus sylvatica forests and the western part of Fagus orientalis forests. We identified 24 'operational phytosociological units' (OPUs), which were used for further analysis. The position of each OPU along the soil pH and temperature gradient was evaluated using Ellenberg Indicator Values. Fidelity of species to OPUs was calculated using the phi coefficient and constancy ratio. We compared alternative alliance concepts, corresponding to groups of OPUs, in terms of number and frequency of diagnostic species. We also established formal definitions for the various alliance concepts based on comparison of the total cover of the diagnostic species groups, and evaluated alternative geographical subdivisions of beech forests. Results The first and second division levels of TWINSPAN followed the temperature and soil pH gradients, while lower divisions were mainly geographical. We grouped the 22 OPUs of Fagus sylvatica forests into acidophytic, meso-basiphytic and thermo-basiphytic beech forests, and separated two OPUs of F. orientalis forests. However, a solution with only two ecologically defined alliances of F. sylvatica forests (acidophytic vs basiphytic) was clearly superior with regard to number and frequency of diagnostic species. In contrast, when comparing groupings with three to six geographical alliances of basiphytic beech forests, respectively, we did not find a strongly superior solution. Conclusions We propose to classify F. sylvatica forests into 15 suballiances - three acidophytic and 12 basiphytic ones. Separating these two groups at alliance or order level was clearly supported by our results. Concerning the grouping of the 12 basiphytic suballiances into ecological or geographical alliances, as advocated by many authors, we failed to find an optimal solution. Therefore, we propose a multi-dimensional classification of basiphytic beech forests, including both ecological and geographical groups as equally valid concepts which may be used alternatively depending on the purpose and context of the classification. [ABSTRACT FROM AUTHOR]