• Energy Research

AbstractMotivationDetailed knowledge on the climatic tolerances of species is crucial to understand, quantify and predict the impact of climate change on biodiversity and ecosystem functions. However, quantitative data are limited; often, only expert‐based qualitative estimates are available. With the ClimPlant database, we capitalize on the link between species distribution ranges and macroclimate to infer the realized climatic niches of 968 European forest plant species.Main types of variables containedThe ClimPlant database contains information on the distribution of monthly, growing‐season and annual mean, minimum and maximum temperature and total precipitation within the distribution range of 968 European forest plants.Spatial location and grainEurope in 10 arc‐min grid cells; the study area has been cropped rectangularly at 15° W (Atlantic Ocean), 60° E (Ural Mountains), 25° N (Sahara) and 75° N (Arctic Ocean).Time period and grainThe distribution ranges of forest plant species are based on two renowned distribution atlases. The monthly mean, minimum and maximum temperature and precipitation between 1970 and 2000 were extracted from WorldClim v.2.Major taxa and level of measurementNine hundred and sixty‐eight vascular plant species of European forests, with taxonomy following the Euro+Med PlantBase nomenclature .Software formatData in 56 CSV files, with 1,000 values for monthly, growing season and annual observations of mean, minimum and maximum temperature and precipitation in the distribution range for every species. One summary CSV file with summary statistics (mean, median, fifth and 95th percentile), for every species, of each climatic variable, together with seven key geographical descriptors: area of the distribution range, latitude and longitude of the centroid, and northern, eastern, western and southern range limits within the study area.

The increasing prevalence of woody liana species has been widely observed across the neotropics, but observations from temperate regions are comparatively rare. On the basis of a resurvey database of 1814 (quasi‐)permanent plots from across 40 European study sites, with a median between‐survey interval of 38 years, and ranging from 1933 (earliest initial survey) to 2015 (most recent resurvey), we found that liana occurrence has also increased in the understories of deciduous temperate forests in Europe. Ivy (Hedera helix) is largely responsible for driving this increase across space and time, as its proportional occurrence has grown by an average of 14% per site. Enhanced warming rates, increased shade, and historical management transitions explain only some of the variation in ivy frequency response across the dataset, despite surveys coming from across continental gradients of environmental conditions. Uncovering the mechanisms underlying ivy expansion, and the potential consequences for forest structure and functioning, requires further research. Given the magnitude of increases in understory ivy frequency and its possible impacts, scientists, policy makers, and resource managers must be mindful of the patterns, processes, and implications of potential “lianification” of temperate forests.

Local factors restrain forest warming Microclimates are key to understanding how organisms and ecosystems respond to macroclimate change, yet they are frequently neglected when studying biotic responses to global change. Zellweger et al. provide a long-term, continental-scale assessment of the effects of micro- and macroclimate on the community composition of European forests (see the Perspective by Lembrechts and Nijs). They show that changes in forest canopy cover are fundamentally important for driving community responses to climate change. Closed canopies buffer against the effects of macroclimatic change through their cooling effect, slowing shifts in community composition, whereas open canopies tend to accelerate community change through local heating effects. Science , this issue p. 772 ; see also p. 711

AbstractForecasting the growth of tree species to future environmental changes requires a better understanding of its determinants. Tree growth is known to respond to global‐change drivers such as climate change or atmospheric deposition, as well as to local land‐use drivers such as forest management. Yet, large geographical scale studies examining interactive growth responses to multiple global‐change drivers are relatively scarce and rarely consider management effects. Here, we assessed the interactive effects of three global‐change drivers (temperature, precipitation and nitrogen deposition) on individual tree growth of three study species (Quercus robur/petraea, Fagus sylvatica and Fraxinus excelsior). We sampled trees along spatial environmental gradients across Europe and accounted for the effects of management forQuercus. We collected increment cores from 267 trees distributed over 151 plots in 19 forest regions and characterized their neighbouring environment to take into account potentially confounding factors such as tree size, competition, soil conditions and elevation. We demonstrate that growth responds interactively to global‐change drivers, with species‐specific sensitivities to the combined factors. Simultaneously high levels of precipitation and deposition benefitedFraxinus,but negatively affectedQuercus’growth, highlighting species‐specific interactive tree growth responses to combined drivers. ForFagus,a stronger growth response to higher temperatures was found when precipitation was also higher, illustrating the potential negative effects of drought stress under warming for this species. Furthermore, we show that past forest management can modulate the effects of changing temperatures onQuercus’growth; individuals in plots with a coppicing history showed stronger growth responses to higher temperatures. Overall, our findings highlight how tree growth can be interactively determined by global‐change drivers, and how these growth responses might be modulated by past forest management. By showing future growth changes for scenarios of environmental change, we stress the importance of considering multiple drivers, including past management and their interactions, when predicting tree growth.

AbstractOngoing 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.

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.

Globally, rising temperatures are increasingly favoring warm-affiliated species. Although changes in community composition are typically measured by the mean temperature affinity of species (the community temperature index, CTI), they may be driven by different processes and accompanied by shifts in the diversity of temperature affinities and breadth of species thermal niches. To resolve the pathways to community warming in Finnish flora and fauna, we examined multidecadal changes in the dominance and diversity of temperature affinities among understory forest plant, freshwater phytoplankton, butterfly, moth, and bird communities. CTI increased for all animal communities, with no change observed for plants or phytoplankton. In addition, the diversity of temperature affinities declined for all groups except butterflies, and this loss was more pronounced for the fastest-warming communities. These changes were driven in animals mainly by a decrease in cold-affiliated species and an increase in warm-affiliated species. In plants and phytoplankton the decline of thermal diversity was driven by declines of both cold- and warm-affiliated species. Plant and moth communities were increasingly dominated by thermal specialist species, and birds by thermal generalists. In general, climate warming outpaced changes in both the mean and diversity of temperature affinities of communities. Our results highlight the complex dynamics underpinning the thermal reorganization of communities across a large spatiotemporal gradient, revealing that extinctions of cold-affiliated species and colonization by warm-affiliated species lag behind changes in ambient temperature, while communities become less thermally diverse. Such changes can have important implications for community structure and ecosystem functioning under accelerating rates of climate change.