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.

Biodiversity time series reveal global losses and accelerated redistributions of species, yet no net loss in local species richness. To better understand how these patterns are linked, we quantify how individual species trajectories scale up to diversity changes using data from 68 vegetation resurvey studies of seminatural forests in Europe. Herb-layer species with small geographic ranges are being replaced by more widely distributed species and our results suggest this is less due to species abundances than to species nitrogen (N) niches. N-deposition accelerates extinctions of small-ranged, N-efficient plants and colonization by broadly distributed, N-demanding plants including non-natives. Despite no net change in species richness at the spatial scale of a study site, losses of small-ranged species reduce biome-scale (gamma) diversity. These results provide one mechanism to explain the directional replacement of smallranged species within sites and thus patterns of biodiversity change across spatial scales.

Species turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller‐ by larger‐ranged species across habitats. Communities shifted in parallel towards more nutrient‐demanding species, with species from nutrient‐rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller‐ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community‐scale turnover to macroecological processes such as biotic homogenisation.

Comparison of spontaneous revegetation and forestry reclamation can provide valuable information about the trajectories and rate of vegetation development applicable to restoration practice over broader geographical scales. In the current study, we sampled terrestrial vegetation in spontaneously revegetated and forestry reclaimed spoil heaps after brown coal mining differing in age in three regions across Central Europe (Germany, the Czech Republic, and Hungary). The main objective was to compare the course of vegetation development and species richness between the two restoration methods over a large geographical scale. In all geographical regions, species richness was higher on spontaneously revegetated sites. Although the starting point differed across regions, trajectories to woodland development converged with time. In addition, spontaneous revegetation was comparably as fast as forestry reclamation in developing towards woodland. Spontaneous revegetation proved to be more valuable and cost‐effective in terms of nature conservation and should be considered as an alternative restoration strategy to forestry reclamation in Central Europe.

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Closely similar species may occupy similar niches, but usually divergence can be found in one or more traits when they inhabit the same habitat. In this study, we examined how two co-occurring gammarids — the nativeGammarus fossarumand the naturalizedG. roeselii — are distributed among microhabitats, depending on their sympatric or allopatric distribution. We hypothesized that the larger body-sized species (G. roeselii), exploiting their advantages in competition, restrict smaller species to microhabitats with smaller particle sizes. Four headwaters were sampled in the Mecsek Mountains (SW Hungary) in May, July and October 2009, and 37 local scale environmental variables at each site were measured. AlthoughG. fossarumis smaller in size, significantly more individuals were collected from the more favourable lithal and biotic microhabitats, whereas a strong negative association was observed between the two species.Gammarus roeseliioccurred at sites characterized by degraded riparian vegetation, which indicates stronger anthropogenic impacts, but still has a disadvantage in competition in mountainous streams under anthropogenic influence.

Ungulate populations are increasing across Europe with important implications for forest plant communities. Concurrently, atmospheric nitrogen (N) deposition continues to eutrophicate forests, threatening many rare, often more nutrient-efficient, plant species. These pressures may critically interact to shape biodiversity as in grassland and tundra systems, yet any potential interactions in forests remain poorly understood. Here, we combined vegetation resurveys from 52 sites across 13 European countries to test how changes in ungulate herbivory and eutrophication drive long-term changes in forest understorey communities. Increases in herbivory were associated with elevated temporal species turnover, however, identities of winner and loser species depended on N levels. Under low levels of N-deposition, herbivory favored threatened and small-ranged species while reducing the proportion of non-native and nutrient-demanding species. Yet all these trends were reversed under high levels of N-deposition. Herbivores also reduced shrub cover, likely exacerbating N effects by increasing light levels in the understorey. Eutrophication levels may therefore determine whether herbivory acts as a catalyst for the “N time bomb” or as a conservation tool in temperate forests.