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Summary: Biodiversity world‐wide has been under increasing anthropogenic pressure in the past century. The long‐term response of biotic communities has been tackled primarily by focusing on species richness, community composition and functionality. Equally important are shifts between entire communities and habitat types, which remain an unexplored level of biodiversity change.We have resurveyed > 2000 vegetation plots in temperate forests in central Europe to capture changes over an average of five decades. The plots were assigned to eight broad forest habitat types using an algorithmic classification system. We analysed transitions between the habitat types and interpreted the trend in terms of changes in environmental conditions.We identified a directional shift along the combined gradients of canopy openness and soil nutrients. Nutrient‐poor open‐canopy forest habitats have declined strongly in favour of fertile closed‐canopy habitats. However, the shift was not uniform across the whole gradients.We conclude that the shifts in habitat types represent a century‐long successional trend with significant consequences for forest biodiversity. Open forest habitats should be urgently targeted for plant diversity restoration through the implementation of active management. The approach presented here can be applied to other habitat types and at different spatio‐temporal scales. [ABSTRACT FROM AUTHOR]

Plant invasion science has made a substantial progress in documenting the impacts of aliens, but comparisons with the impacts of native dominants are still rare. Further, the impacts on larger spatial scales remain poorly understood. We recorded the impacts of 10 native and nine invasive dominant plants in the Czech Republic on species richness and Shannon diversity by comparing communities with high vs. low cover of the dominant species. To estimate the impacts at the (i) population level and (ii) between-population level, we compared the Jaccard dissimilarity, nestedness and turnover of high- and low-dominance plots. Further, we calculated the Jaccard dissimilarity, nestedness and turnover between the high- and low-dominance plots within each population to express the impacts on species composition. We tested whether (i) native and invasive dominants affect the populationand between population levels of diversity by making the vegetation more homogenous; (ii) whether these effects differ between the native and alien dominants; and (iii) whether the impacts at different spatial levels are related. At the population level, high-dominance plots (with both native and alien dominants) showed higher nestedness and lower turnover compared to the low-dominance plots. Further, all plots with native dominants, both with high- and low dominance, showed higher similarity but lower nestedness than plots with alien dominants. Most importantly, high-dominance plots with native dominants were more similar to each other but showed marginally significantly lower nestedness compared to high-dominance plots with alien dominants. At the between-population level, high-dominance plots with native dominants showed a marginally significantly lower turnover compared to high-dominance plots with alien dominants. The differences in Jaccard dissimilarity, nestedness and turnover between the low- and high-dominance plots at the population level showed strong positive relations to low- and high-dominance differences at the between-populations level. Further, compositional impacts, expressed as the dissimilarity between high- vs. low-dominance plots, positively related to the plot-level impacts on Shannon diversity. Our results show that (i) both native and invasive dominants tend to reduce the diversity over larger areas and that the effect of native dominants may be even stronger, and (ii) the effects on plot-level richness and diversity cannot be easily extrapolated to larger scales but the impacts at the population- and between-populations levels are positively related. [ABSTRACT FROM AUTHOR]

Forests cover more than one third of the area of Czechia and provide many environmental, economic, social and cultural benefits. Only a small part of the country´s forested area is left to nature. Most Czech forests are managed, with Norway spruce as the main tree species. The ongoing climate change progressively creates new conditions for the functioning of forests as important components of the landscape and providers of ecosystem services for society. Until recently, Czech forestry policy makers had not paid enough attention to climate change. As a result, Czech forests grapple with increasing instability caused by repeated windstorms, droughts and insect plagues. Traditionally applied management methods and rigid business models are not suitable for resolving the situation. Czech forestry thus takes an exceptional position within Europe. The responsibility for the development of the adaptation strategy and sustainable management policy lies in the hands of forestry policy makers. In order to restore stability and to ensure multifunctionality of forests under new climatic conditions, it will be necessary to introduce a new model of forest management. Compared to the traditional forestry model based on age classes, the new management model must be more flexible and better adapted to the new environmental situation. The principles of the new forestry policy should stem from agreement and cooperation of the forestry sector with scientific and nature protection institutions, as well as from an active discussion within society.

Knowledge of forest recovery processes after severe disturbances, such as tropical cyclones, is essential for understanding the mechanisms maintaining forest diversity and ecosystem functioning. However, studies examining the impact of tropical cyclones on forest dynamics are still rare, especially in Northeast Asia. Here, we explore the complex responses of vegetation and soil chemistry to severe tropical cyclone disturbances in Hallasan National Park in South Korea. Vegetation and soil were examined five years before and five years after passages of tropical cyclones in 2012 in natural broadleaf and coniferous forests along an elevation gradient from 950 to 1770 m a.s.l., including the largest population of endemic Abies koreana. Tropical cyclones caused abundant tree mortality, resulting in a 46% decrease in stem basal area. Tropical cyclone disturbances triggered the spread of pioneer trees and shrubs and intense clonal propagation of graminoids, including dwarf bamboo, resulting in less diverse understory vegetation, especially in coniferous forests. In contrast, broadleaf forests at lower elevations experienced only minor disturbance. Opening of canopies after tropical cyclone disturbance led to the decrease in soil cations and doubling of available soil phosphorus stock, which likely contributed to the increased coverage of clonal graminoids, especially in coniferous forests (from 36 to 66%). Hence, increased competition of graminoids and reduction in seed fall and seedling recruitment prevented A. koreana regeneration. The subalpine forest dominated by A. koreana is forecasted to gradual loss due to the fact of temperature increases, intensified tropical cyclones and, particularly, due to the altered competition between dwarf bamboo and fir seedlings. [ABSTRACT FROM AUTHOR]

Questions: Long‐term legacies of historical human activities in temperate forests are increasingly recognised as an important driver of vegetation diversity and composition. To uncover centuries‐old legacies, novel approaches are, however, needed. Here, we combine anthracology of historical charcoal kilns and long‐term vegetation resurveys. We asked whether the historical coppicing oriented on charcoal production affected tree‐species composition and how the forest understorey vegetation changed after the coppicing was abandoned. Location: Temperate broadleaved forests in the Slovak Karst National Park, central Europe. Methods: To explore the historical forest structure and long‐term changes in tree composition, we sampled charcoal remains from 28 historical kilns, identified the burnt tree taxa and estimated the original diameter of the burnt wood. To analyse the vegetation changes over the last four decades, we resurveyed plant composition of 60 quasi‐permanent plots established in 1975. Results: Historical charcoal burning was associated with coppicing, which decreased Fagus sylvatica dominance and favoured Quercus spp. in the tree layer. Several decades after the abandonment of coppicing, we observed the decline of Quercus spp. and spread of shade‐casting tree species with nutrient‐rich litter. This probably triggered the identified demise of light‐demanding species, the spread of nitrophytes and taxonomic homogenisation of the forest understorey. Conclusions: The shift from historical coppicing to current high‐forest management was likely a main driver of the observed taxonomic homogenisation and decline of light‐demanding plants, as in other European lowland forests. Long‐term data from charcoal kilns showed, however, that closed‐canopy forests dominated by beech were historically more common and observed changes in vegetation thus represent a natural process. Findings also suggest that coppicing taking place over centuries enhanced diversity of forest understorey vegetation. Our novel approach combining a vegetation resurvey and charcoal kiln anthracology thus uncovered otherwise hidden links between current biological processes and the historical human legacies, with consequent important implications for nature protection and management. [ABSTRACT FROM AUTHOR]

For proper management of invasive alien species (IAS), it is needed to know species persistence and spread capacity as ignoring them may significantly bias the estimates of species presence. We compared 50 years old historical and current distribution of Telekia speciosa to assess its population change in a restricted area of a chateau park. The aim of this study is to analyse factors that may have shaped the persistence on previous sites, as well as, the spread of the species from historical sites by using repeated sampling. We found that after 50 years Telekia speciosa persisted at 67% sites and has spread to another 381 new sites. Such a level of persistence and rate of spread over a fifty year period goes exceedingly beyond any known records for other IAS. [ABSTRACT FROM AUTHOR]

Ornamental plants are an important component of urban floras and a significant source of alien plant invasions to the surrounding landscapes. We studied ornamental flora across 174 settlements in the Czech Republic, Central Europe. The aims of the study were to (i) identify clusters of sites that are defined as distinctive groups of ornamental taxa reflecting environmental or socioeconomic factors and (ii) apply the classification approach which is traditionally used for spontaneous vegetation in order to evaluate the potential of different settlement types to act as source sites of invasive species. The inventories were classified in a similar manner that is generally applied to spontaneous vegetation using the COCKTAIL method. Diagnostic taxa were classified in a repeatable manner into 17 species groups, forming five dis- tinctive clusters with ~70% of sites attributed to one cluster. The species pools of the clusters differed in their representation of species with native or alien status and different life forms. The following clusters were distinguished, based on the prevailing type of settlement: (1) old villas neighbourhoods of towns, (2) upland settlements, (3) modern neighbourhoods, (4) old rustic settlements and (5) modern rustic settlements. Similar to spontaneous vegetation, the classification of ornamental flora reflects both basic natural gradients (i.e. altitude) and man-made factors (i.e. the preferences for certain plants and associated management practices). Alien taxa associated with modern neighbourhoods are characterised by a relatively higher invasion potential than those from, for example, old rustic settlements. This is especially true for woody species which can spread in ruderal habitats as a result of urban sprawl. Our results showed that the classification method, commonly used to analyse vegetation data, can also be applied to ornamental flora. [ABSTRACT FROM AUTHOR]

Ongoing climate change is expected to shift tree species distribution and therefore affect forest biodiversity and ecosystem services. To assess and project tree distributional shifts, researchers may compare the distribution of juvenile and adult trees under the assumption that differences between tree life stages reflect distributional shifts triggered by climate change. However, the distribution of tree life stages could differ within the lifespan of trees, therefore, we hypothesize that currently observed distributional differences could represent shifts over ontogeny as opposed to climatically driven changes. Here, we test this hypothesis with data from 1435 plots resurveyed after more than three decades across the Western Carpathians. We compared seedling, sapling and adult distribution of 12 tree species along elevation, temperature and precipitation gradients. We analyzed (i) temporal shifts between the surveys and (ii) distributional differences between tree life stages within both surveys. Despite climate warming, tree species distribution of any life stage did not shift directionally upward along elevation between the surveys. Temporal elevational shifts were species specific and an order of magnitude lower than differences among tree life stages within the surveys. Our results show that the observed range shifts among tree life stages are more consistent with ontogenetic differences in the species' environmental requirements than with responses to recent climate change. The distribution of seedlings substantially differed from saplings and adults, while the distribution of saplings did not differ from adults, indicating a critical transition between seedling and sapling tree life stages. Future research has to take ontogenetic differences among life stages into account as we found that distributional differences recently observed worldwide may not reflect climate change but rather the different environmental requirements of tree life stages. [ABSTRACT FROM AUTHOR]

Non-random species loss and gain in local communities change the compositional heterogeneity between communities over time, which is traditionally quantified with dissimilarity-based approaches. Yet, dissimilarities summarize the multivariate species data into a univariate index and obscure the species-level patterns of change, which are central to understand the causes and consequences of the community changes., Here, we propose a model-based approach that looks for species-level effects of time period and construct a multiple-site metric as a sum across species to test the consistency of the individual species responses. Species fall into different response types, showing how they influence the changes in community heterogeneity., In a comparison with other multiple-site metrics, we illustrate the properties of our method and the differences and similarities with other approaches. For instance, our metric estimates the total variation in a community data set based on species-level contributions, not the compositional dissimilarities between particular sites. Similar to some other approaches, we can distinguish between heterogeneity derived from turnover or richness differences., Our approach was applied to a set of 23 forest understorey resurvey studies spread across Europe. We show the species gains and losses may as well decrease or increase levels of community heterogeneity. Although species occurrences and communities have not changed in a consistent way along continental-scale environmental gradients such as climatic conditions, several species shifted in a similar way across the different data sets., Testing the significance of shifts in species prevalence over time to infer corresponding changes in the compositional heterogeneity among sites provides a very intuitive tool for community resurvey studies. The main strengths of our framework are the explicit consideration of the relative roles of species gains and losses and the straightforward generalization to different sets of hypotheses related to community changes. [ABSTRACT FROM AUTHOR]

Soil acidification was assessed in the Eastern Sudetes Mountains (Czech Republic) between 1941 and 2003, i.e. before and after the period of major industrial pollution (1950s–1990s). The twenty sites included in our study were distributed along a gradient of altitude ranging 1000m. Values of pH have decreased in 80–90% of the pairs of samples after the six decades, on average by 0.7 for pH-H2O and 0.6 for pH-KCl. Organic matter increased in the topsoil, probably reflecting a change in decomposition conditions. The most important finding is that the acidification varies along the joint gradient of altitude/tree layer composition, and displays a changing pattern in three soil horizons (A, B and C). Contrary to expectations, most acidified were soils in beech forests at lower elevations. [Copyright &y& Elsevier]

Abstract: This paper explores potential biases due to recording effort in the species richness (number of vascular plant species) recorded in grid-mapping projects. In this study, we review 80 regional and national grid Central European Basic Area (CEBA) mapping projects on the vascular plant flora of Central Europe. The measures of recording effort used were the duration of the mapping project, resolution of the mapping grid and number of botanists involved. Furthermore, several environmental and geographic factors associated with the variation in species richness were used as covariables: the number of phytosociological units in the Map of Potential Natural Vegetation of Europe, altitudinal range, annual precipitation, mean January and June temperatures and geographical location of the study areas. The effects of individual factors on species richness were compared by multiple regression and hierarchical partitioning. Both methods indicated a bias in observed species richness due to recording effort. Multiple regression indicated a significant role of duration of study, and hierarchical partitioning revealed significant effects of duration, number of botanists and used resolution. Of the variation in the total number of species recorded, 8% was attributed to the duration of mapping, 9% to the used resolution, and 7% to the number of botanists involved in mapping. However, this bias was scale-dependent. Although the sampling effect can be neglected on a broad scale, on a finer scale a significant amount of the variation in plant species richness can be ascribed to recording effort. This indicates the need for a standard approach in mapping and analysing patterns of species richness. [Copyright &y& Elsevier]

Abstract: A geobotanical study was performed of the wild plants growing in the area of the old uranium mill tailings waste depot of a former uranium ore reprocessing factory in South Bohemia and the distribution of 226Ra in selected plants was determined. The distribution of 226Ra in contaminated soil was found to be extremely variable (from 7 to 32Bq 226Rag−1 of DW). The differences in plant distribution were caused by factors of disturbance, soil properties (nutrients and salt content, water supply), and successional stage. No direct relation was proved between plant species characteristics and their radioactivity content. The results showed a great range of variation in the accumulation of 226Ra by the plant species found. The highest activity of 226Ra was found in Potentilla reptans (4.09Bq 226Rag−1 of DW), Mentha arvensis (4.00Bq 226Rag−1 of DW), and Daucus carota (3.70Bq 226Rag−1 of DW). About half of the plant species are used as medicinal plants and some of them are accumulators of 226Ra. However, no plants suitable for phytoextraction of 226Ra contaminated substrates were discovered. [Copyright &y& Elsevier]

It has been established by research on plant invasions that soil biota and availability of nutrients affect the processes of alien species establishment and spread. So far, attention was mainly on alien invaders, although some native species (expansive), vigorously spread in human-influenced landscapes and also transform the habitats they colonize. Based on indirect gradient ordination analysis of vegetation relevés dominated by five native (Calamagrostis epigejos, Filipendula ulmaria, Phalaris arundinacea, Rubus idaeus, Urtica dioica) and five alien taxa (Impatiens glandulifera, Lupinus polyphyllus, Telekia speciosa, Reynoutria sp., Solidago canadensis agg.) in the Czech Republic, Central Europe, we identified pairs of species differing by origin (native vs alien) and growing in similar habitats. In the resulting 10 pairs, we tested the net effect of species origin on the following soil characteristics: (i) physical properties, (ii) nutrient availability, and (iii) biological activity. We found that the impact of alien invasive and native expansive species on soil cannot be explained simply by species' origin as a factor. Regardless of the origin, a statistically significant effect was recorded only for factors expressing nitrogen supply at the peak of the vegetation season and soil biological activity. Differences in impacts attributable to origin were only verified for individual pairs, being most pronounced between the alien Lupinus and its native counterparts Calamagrostis and Filipendula , and least between Solidago vs Calamagrostis, and Telekia vs Rubus. Both invasive alien and expansive native dominant plants can alter the rate of decomposition by changing the litter quality and availability of nutrients, mainly inorganic nitrogen. Therefore, management actions to preserve or restore diversity and mitigate the negative impacts of dominant species should be focused both on native and alien species. • We tested the impact of native and alien plants on a wide range of soil properties. • The levels of impact were not associated with the origin of dominant species. • The level of impact was context- and species-dependent. • The most different pairs were Lupinus polyphyllus vs Calamagrostis epigejos or Filipendula ulmaria. • The least differences were found between Solidago canadensis agg. vs Calamagrostis epigejos. [ABSTRACT FROM AUTHOR]

Abstract: Mountainous areas of the Korean Peninsula are among the biodiversity hotspots of the world''s temperate forests. Understanding patterns in spatial distribution of their species richness requires explicit consideration of different environmental drivers and their effects on functionally differing components. In this study, we assess the impact of both geographical and soil variables on the fine-scale (400 m2) pattern of plant diversity using field data from six national parks, spanning a 1300 m altitudinal gradient. Species richness and the slopes of species–area curves were calculated separately for the tree, shrub and herb layer and used as response variables in regression tree analyses. A cluster analysis distinguished three dominant forest communities with specific patterns in the diversity–environment relationship. The most widespread middle-altitude oak forests had the highest tree richness but the lowest richness of herbaceous plants due to a dense bamboo understory. Total richness was positively associated with soil reaction and negatively associated with soluble phosphorus and solar radiation (site dryness). Tree richness was associated mainly with soil factors, although trees are frequently assumed to be controlled mainly by factors with large-scale impact. A U-shaped relationship was found between herbaceous plant richness and altitude, caused by a distribution pattern of dwarf bamboo in understory. No correlation between the degree of canopy openness and herb layer richness was detected. Slopes of the species–area curves indicated the various origins of forest communities. Variable diversity–environment responses in different layers and communities reinforce the necessity of context-dependent differentiation for the assessment of impacts of climate and land-use changes in these diverse but intensively exploited regions. [Copyright &y& Elsevier]

• Five vegetation types reflect an oceanity-continentality gradient in South Europe. • Robinia stands have specific species composition and high structural diversity. • The main drivers of invasion is large-scale and long-term cultivation. • The most invaded habitats are human-made, e.g. urban, agrarian and mining areas. • Stratified management on regional and local scales should be favoured. Knowledge of the species composition of invaded vegetation helps to evaluate an ecological impact of aliens and design an optimal management strategy. We link a new vegetation analysis of a large dataset to the invasion history, ecology and management of Robinia pseudoacacia stands across Southern Europe and provide a map illustrating Robinia distribution. Finally, we compare detected relationships with Central Europe. We show that regional differences in Robinia invasion, distribution, habitats and management are driven both by local natural conditions (climate and soil properties, low competitive ability with native trees) and socioeconomic factors (traditional land-use). Based on the classification of 467 phytosociological relevés we distinguished five broad vegetation types reflecting an oceanity−continentality gradient. The stands were heterogeneous and included 824 taxa, with only 5.8% occurring in more than 10% of samples, representing mainly hemerobic generalists of mesophilous, nutrient-rich and semi-shady habitats. The most common were dry ruderal stands invading human-made habitats. Among native communities, disturbed mesic and alluvial forests were often invaded throughout the area, while dry forests and scrub dominated in Balkan countries. Continuous, long-term and large-scale cultivation represent a crucial factor driving Robinia invasions in natural habitats. Its invasion should be mitigated by suitable management taking into account adjacent habitats and changing cultivation practices to select for native species. Robinia invasion has a comparable pattern in Central and Southern Europe, but there is a substantial difference in management and utilization causing heterogeneity of many South-European stands. [ABSTRACT FROM AUTHOR]

Biological nitrogen fixation is a fundamental part of ecosystem functioning. Anthropogenic nitrogen deposition and climate change may, however, limit the competitive advantage of nitrogen-fixing plants, leading to reduced relative diversity of nitrogen-fixing plants. Yet, assessments of changes of nitrogen-fixing plant long-term community diversity are rare. Here, we examine temporal trends in the diversity of nitrogen-fixing plants and their relationships with anthropogenic nitrogen deposition while accounting for changes in temperature and aridity. We used forest-floor vegetation resurveys of temperate forests in Europe and the United States spanning multiple decades. Nitrogen-fixer richness declined as nitrogen deposition increased over time but did not respond to changes in climate. Phylogenetic diversity also declined, as distinct lineages of N-fixers were lost between surveys, but the "winners" and "losers" among nitrogen-fixing lineages varied among study sites, suggesting that losses are context dependent. Anthropogenic nitrogen deposition reduces nitrogen-fixing plant diversity in ways that may strongly affect natural nitrogen fixation.

Climate change is commonly assumed to induce species' range shifts toward the poles. Yet, other environmental changes may affect the geographical distribution of species in unexpected ways. Here, we quantify multidecadal shifts in the distribution of European forest plants and link these shifts to key drivers of forest biodiversity change: climate change, atmospheric deposition (nitrogen and sulfur), and forest canopy dynamics. Surprisingly, westward distribution shifts were 2.6 times more likely than northward ones. Not climate change, but nitrogen-mediated colonization events, possibly facilitated by the recovery from past acidifying deposition, best explain westward movements. Biodiversity redistribution patterns appear complex and are more likely driven by the interplay among several environmental changes than due to the exclusive effects of climate change alone.

Global change has accelerated local species extinctions and colonizations, often resulting in losses and gains of evolutionary lineages with unique features. Do these losses and gains occur randomly across the phylogeny? We quantified: temporal changes in plant phylogenetic diversity (PD); and the phylogenetic relatedness (PR) of lost and gained species in 2672 semi-permanent vegetation plots in European temperate forest understories resurveyed over an average period of 40 yr. Controlling for differences in species richness, PD increased slightly over time and across plots. Moreover, lost species within plots exhibited a higher degree of PR than gained species. This implies that gained species originated from a more diverse set of evolutionary lineages than lost species. Certain lineages also lost and gained more species than expected by chance, with Ericaceae, Fabaceae, and Orchidaceae experiencing losses and Amaranthaceae, Cyperaceae, and Rosaceae showing gains. Species losses and gains displayed no significant phylogenetic signal in response to changes in macroclimatic conditions and nitrogen deposition. As anthropogenic global change intensifies, temperate forest understories experience losses and gains in specific phylogenetic branches and ecological strategies, while the overall mean PD remains relatively stable., (© 2023 The Authors. New Phytologist © 2023 New Phytologist Foundation.)

Plant communities are being exposed to changing environmental conditions all around the globe, leading to alterations in plant diversity, community composition, and ecosystem functioning. For herbaceous understorey communities in temperate forests, responses to global change are postulated to be complex, due to the presence of a tree layer that modulates understorey responses to external pressures such as climate change and changes in atmospheric nitrogen deposition rates. Multiple investigative approaches have been put forward as tools to detect, quantify and predict understorey responses to these global-change drivers, including, among others, distributed resurvey studies and manipulative experiments. These investigative approaches are generally designed and reported upon in isolation, while integration across investigative approaches is rarely considered. In this study, we integrate three investigative approaches (two complementary resurvey approaches and one experimental approach) to investigate how climate warming and changes in nitrogen deposition affect the functional composition of the understorey and how functional responses in the understorey are modulated by canopy disturbance, that is, changes in overstorey canopy openness over time. Our resurvey data reveal that most changes in understorey functional characteristics represent responses to changes in canopy openness with shifts in macroclimate temperature and aerial nitrogen deposition playing secondary roles. Contrary to expectations, we found little evidence that these drivers interact. In addition, experimental findings deviated from the observational findings, suggesting that the forces driving understorey change at the regional scale differ from those driving change at the forest floor (i.e., the experimental treatments). Our study demonstrates that different approaches need to be integrated to acquire a full picture of how understorey communities respond to global change., (© 2023 John Wiley & Sons Ltd.)

Schall and Heinrichs question our interpretation that the climatic debt in understory plant communities is locally modulated by canopy buffering. However, our results clearly show that the discrepancy between microclimate warming rates and thermophilization rates is highest in forests where canopy cover was reduced, which suggests that the need for communities to respond to warming is highest in those forests., (Copyright © 2020, American Association for the Advancement of Science.)

Climate warming is causing a shift in biological communities in favor of warm-affinity species (i.e., thermophilization). Species responses often lag behind climate warming, but the reasons for such lags remain largely unknown. Here, we analyzed multidecadal understory microclimate dynamics in European forests and show that thermophilization and the climatic lag in forest plant communities are primarily controlled by microclimate. Increasing tree canopy cover reduces warming rates inside forests, but loss of canopy cover leads to increased local heat that exacerbates the disequilibrium between community responses and climate change. Reciprocal effects between plants and microclimates are key to understanding the response of forest biodiversity and functioning to climate and land-use changes., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Aim: Alien plant species can cause severe ecological and economic problems, and therefore attract a lot of research interest in biogeography and related fields. To identify potential future invasive species, we need to better understand the mechanisms underlying the abundances of invasive tree species in their new ranges, and whether these mechanisms differ between their native and alien ranges. Here, we test two hypotheses: that greater relative abundance is promoted by (a) functional difference from locally co-occurring trees, and (b) higher values than locally co-occurring trees for traits linked to competitive ability., Location: Global., Time Period: Recent., Major Taxa Studied: Trees., Methods: We combined three global plant databases: sPlot vegetation-plot database, TRY plant trait database and Global Naturalized Alien Flora (GloNAF) database. We used a hierarchical Bayesian linear regression model to assess the factors associated with variation in local abundance, and how these relationships vary between native and alien ranges and depend on species' traits., Results: In both ranges, species reach highest abundance if they are functionally similar to co-occurring species, yet are taller and have higher seed mass and wood density than co-occurring species., Main Conclusions: Our results suggest that light limitation leads to strong environmental and biotic filtering, and that it is advantageous to be taller and have denser wood. The striking similarities in abundance between native and alien ranges imply that information from tree species' native ranges can be used to predict in which habitats introduced species may become dominant., (© 2019 The Authors. Global Ecology and Biogeography published by John Wiley & Sons Ltd.)