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Aim: Tree mortality is increasing world-wide, leading to changes in forest composi-tion and altering global biodiversity. Nonetheless, owing to the multifaceted stochas-tic nature of tree mortality, large-scale spatial patterns of mortality across species ranges and their underlying drivers remain difficult to understand. Our main goal was to describe the geographical patterns and drivers of the occurrence of mortality (presence of a mortality event) and the intensity of tree mortality (amount of mortal-ity related to that mortality event) in Europe. We hypothesized that the occurrence of mortality represents background mortality and is higher in the margin than in core populations, whereas the intensity of mortality could have a more even distribution according to the spatial and temporal stochasticity of die-off events.Location: Europe (Spain, France, Germany, Belgium, Sweden and Finland).Major taxa studied: More than 1.5 million trees belonging to 20 major forest tree species.Methods: We developed binomial and truncated negative binomial models to tease apart the occurrence and intensity of tree mortality in National Forest Inventory plots at the range-wide scale. The occurrence of mortality indicated that at least one tree had died in the plot, whereas the intensity of mortality referred to the number of dead trees per plot.Results: The highest occurrence of mortality was found in peripheral regions and the climatic trailing edge linked with drought, whereas the intensity of mortality was driven by competition, drought and high temperatures and was scattered uniformly across species ranges.Main conclusions: We show that tree background mortality, but not die-off, is gener-ally higher in the trailing-edge populations. It remains to be explored whether other demographic traits, such as growth, reproduction and regeneration, also decrease at the trailing edge of European tree populations., Université de Bordeaux

International audience; Climate-smart forestry (CSF) is an emerging branch of sustainable adaptive forest management aimed at enhancing the potential of forests to adapt to and mitigate climate change. It relies on much higher data requirements than traditional forestry. These data requirements can be met by new devices that support continuous, in situ monitoring of forest conditions in real time. We propose a comprehensive network of sensors, i.e., a wireless sensor network (WSN), that can be part of a worldwide network of interconnected uniquely addressable objects, an Internet of Things (IoT), which can make data available in near real time to multiple stakeholders, including scientists, foresters, and forest managers, and may partially motivate citizens to participate in big data collection. The use of in situ sources of monitoring data as ground-truthed training data for remotely sensed data can boost forest monitoring by increasing the spatial and temporal scales of the monitoring, leading to a better understanding of forest processes and potential threats. Here, some of the key developments and applications of these sensors are outlined, together with guidelines for data management. Examples are given of their deployment to detect early warning signals (EWS) of ecosystem regime shifts in terms of forest productivity, health, and biodiversity. Analysis of the strategic use of these tools highlights the opportunities for engaging citizens and forest managers in this new generation of forest monitoring.

International audience; Phenotypic plasticity and local adaptation are the two main processes underlying trait variability. Under rapid environmental change, phenotypic plasticity, if adaptive, could increase the odds for organisms to persist. However, little is known on how environmental variation has shaped plasticity across species ranges over time. Here, we assess whether the portion of phenotypic variation of tree populations linked to the environment is related to the interannual climate variability of the last century and how it varies among populations across species ranges and age. To this aim, we used 372,647 individual tree height measurements of three pine species found in low elevation forests in Europe: Pinus nigra Arnold, P. pinaster Aiton and P. pinea L Measurements were taken in a network of 38 common gardens established in Europe and North Africa with 315 populations covering the distribution range of the species. We fitted linear mixed-effect models of tree height as a function of age, population, climate and competition effects. Models allowed us to estimate tree height response curves at the population level and indexes of populations' phenotypic variation, as a proxy of phenotypic plasticity, at 4,8 and 16 years old, and relate these indexes to the interannual climate variability of the last century. We found that phenotypic variation in tree height was higher in young trees than in older ones. We also found that P pinea showed the highest phenotypic variation in tree height compared with P pinasfer anti P nigra. Finally, phenotypic variation in tree height may be partly adaptive, and differently across species, as climate variability during the last century at the origin of the populations explained between 51 and 69% of the current phenotypic variation of P. nigra and P. pinea, almost twice of the levels of P. pinaster. Main conclusions: Populations' phenotypic variation in tree height is largely explained by the climate variability that the populations experienced during the last century, which we attribute to the genetic diversity among populations.

International audience; Forest social-ecological systems (FSESs) can play a major role in both the mitigation of climate change, as well as the adaptation of local communities to it. In Europe, however, forests are highly fragmented and located close to human populations. This means that maintaining forest sustainability implies not only increasing ecosystem adaptation but also developing social adaptation. Hence, there is a need to understand the current priorities and management goals of forestry stakeholders, as well as their capacity to achieve functional and sustainable FSES in the future. The present study uses an interdisciplinary approach to evaluate stakeholders’ capacity to deal with climate change and top-down policies in different FSESs. We selected five FSESs in France that exhibit a range of climatic threats and socio-economic characteristics to estimate their adaptive capacity and transformative potential. The estimation is based on an assessment of different types of capital (i.e. natural, social, resources, governance) that involves evaluating 70 indicators through more than 70 semi-structured interviews with local stakeholders. Our results highlight that forest management in France, and more broadly in Europe, is mainly based on technical approaches, which build stakeholders’ confidence in their capacity to maintain the status quo. We observe asymmetry in capital distribution in some FSES, mainly through the maximization of the resources capital, which can constraint FSESs in a robustness trap. To develop adaptive capacity for small perturbations as well as transformability, forestry stakeholders should be encouraged to compromises. More balanced capital distribution, with decreased economic benefits, along with new technical approaches and changes to the landscape composition could be necessary to ensure the long-term adaptability of FSES to climate change.

AimBackground tree mortality is a complex demographic process that affects forest structure and long-term dynamics. We aimed to test how drought intensity interacts with interspecific and intraspecific competition (or facilitation) in shaping individual mortality patterns across tree species ranges.LocationEuropean latitudinal gradient (Spain to Finland).Time period1985 – 2014.Major taxa studiedScots pine (Pinus sylvestrisL.) and European beech (Fagus sylvaticaL.).MethodsWe performed logistic regression models based on individual tree mortality recorded in five European National Forest Inventories. We computed the relative importance of climatic drought intensity, basal area of conspecific and heterospecific trees (proxy of indirect intra- and interspecific competition or facilitation) and the effects of their interactions on mortality along the latitudinal gradient of both species range.ResultsIncrease in drought intensity over the study period was associated with higher mortality rates in both species. Drought was the most important driver of beech mortality at almost all latitudes while Scots pine mortality was mainly driven by basal area. High conspecific basal area was associated with high mortality rates in both species while high heterospecific basal area was correlated with mortality rates that were high in Scots pine but low in beech.Main conclusionsBeech mortality was directly affected by drought while Scots pine mortality was indirectly affected by drought through interactions with basal area. Despite their different sensitivity to drought and basal area, the highest predicted mortality rates for both species were at the ecotone between Mediterranean and cool temperate biomes, which can be explained by the combined effect of drought and competition. In the context of global warming, which is expected to be particularly strong in the Mediterranean biome, our results suggest that populations at the southern limit of species ranges may experience increased mortality rates in the near future.BIOSKETCHThe authors’ research is focused on functional trait ecology and global change, with special attention to mortality and demography processes. The authors use modelling multidisciplinary approaches to understand complex processes in ecology on a large geographical scale.

AimUnder rapid environmental change, phenotypic plasticity, if adaptive, could increase the odds for organisms to persist. Environmental variation over time is an important source of phenotypic plasticity. Likewise, phenotypic plasticity can vary with age in many organisms. However, little is known on phenotypic plasticity variation across species’ ranges. Our aims are: (i) to assess whether populations’ phenotypic plasticity is related to the inter-annual climate variation under which populations have evolved during the last century; (ii) to compare phenotypic plasticity among developmental classes; and (iii) to predict phenotypic plasticity across’ species ranges.LocationEurope and North-Africa.Time period1901-2014.Major taxa studiedPinus nigra, P. pinasterandP. pinea.MethodsWe used 372 646 individual tree height measurements at three developmental classes from a wide network of 38 common gardens in Europe and North Africa with provenances covering the distribution range of the species. With this data, we: i) build linear mixed-effect models of tree height as a function of tree age, population and climate; ii) estimate populations’ reaction norms from the fitted models; iii) calculate populations’ phenotypic plasticity indexes; iv) build models of populations’ phenotypic plasticity indexes as a function of inter-annual climate variation during the last century.ResultsWe found that i) most populations that have evolved under high inter-annual climate variation, in either maximum or minimum values in temperature or precipitation, exhibited high values of plasticity in tree height; ii) phenotypic plasticity for tree height was higher in young trees than in older ones, iii) phenotypic plasticity did not follow any particular geographical pattern across species’ ranges.Main conclusionsPhenotypic plasticity across the three Mediterranean pines’ ranges is related with the climate variation experienced over time and calls into question whether this plasticity could be adaptive and hence beneficial to cope with climate change in the short-term.

AimTo test whether adaptive and plastic trait responses to climate across species distribution ranges can be untangled using field observations, under the rationale that, in natural forest tree populations, long-term climate shapes local adaptation while recent climate change drives phenotypic plasticity.LocationEurope.Time period1901-2014.TaxaSilver fir (Abies alba Mill.) and sessile oak (Quercus petraea (Matt.) Liebl.).MethodsWe estimated the variation of individual tree height as a function of long-term and short-term climates to tease apart local adaptation, plasticity and their interaction, using mixed-effect models calibrated with National Forest Inventory data (in-situ models). To validate our approach, we tested the ability of in-situ models to predict independently tree height observations in common gardens where local adaptation to climate of populations and their plasticity can be measured and separated. In-situ model predictions of tree height variation among provenances (populations of different geographical origin) and among planting sites were compared to observations in common gardens and to predictions from a similar model calibrated using common garden data (ex-situ model).ResultsIn Q. petraea, we found high correlations between in-situ and ex-situ model predictions of provenance and plasticity effects and their interaction on tree height (r > 0.80). We showed that the in-situ models significantly predicted tree height variation among provenances and sites for Abies alba and Quercus petraea. Spatial predictions of phenotypic plasticity across species distribution ranges indicate decreasing tree height in populations of warmer climates in response to recent anthropogenic climate warming.Main conclusionsOur modelling approach using National Forest Inventory observations provides a new perspective for understanding patterns of intraspecific trait variation across species ranges. Its application is particularly interesting for species for which common garden experiments do not exist or do not cover the entire climatic range of the species.

Most populations of Scots pine in Spain are locally adapted to drought, with only a few populations at the southernmost part of the distribution range showing maladaptations to the current climate. Increasing tree heights are predicted for most of the studied populations by the year 2070, under the RCP 8.5 scenario. These results are probably linked to the capacity of this species to acclimatize to new climates. The impact of climate change on tree growth depends on many processes, including the capacity of individuals to respond to changes in the environment. Pines are often locally adapted to their environments, leading to differences among populations. Generally, populations at the margins of the species&rsquo, ranges show lower performances in fitness-related traits than core populations. Therefore, under expected changes in climate, populations at the southern part of the species&rsquo, ranges could be at a higher risk of maladaptation. Here, we hypothesize that southern Scots pine populations are locally adapted to current climate, and that expected changes in climate may lead to a decrease in tree performance. We used Scots pine tree height growth data from 15-year-old individuals, measured in six common gardens in Spain, where plants from 16 Spanish provenances had been planted. We analyzed tree height growth, accounting for the climate of the planting sites, and the climate of the original population to assess local adaptation, using linear mixed-effect models. We found that: (1) drought drove differences among populations in tree height growth, (2) most populations were locally adapted to drought, (3) tree height was predicted to increase for most of the studied populations by the year 2070 (a concentration of RCP 8.5). Most populations of Scots pine in Spain were locally adapted to drought. This result suggests that marginal populations, despite inhabiting limiting environments, can be adapted to the local current conditions. In addition, the local adaptation and acclimation capacity of populations can help margin populations to keep pace with climate change. Our results highlight the importance of analyzing, case-by-case, populations&rsquo, capacities to cope with climate change.

International audience; Aim To better understand and more realistically predict future species distribution ranges, it is critical to account for local adaptation and phenotypic plasticity in populations' responses to climate. This is challenging because local adaptation and phenotypic plasticity are trait-dependent and traits covary along climatic gradients, with differential consequences for fitness. Our aim is to quantify local adaptation and phenotypic plasticity of vertical and radial growth, leaf flushing and survival across the range of Fagus sylvatica and to estimate the contribution of each trait to explaining the species' occurrence. Location Europe. Time period 1995-2014; 2070. Major taxa studied Fagus sylvatica L. Methods We used vertical and radial growth, flushing phenology and mortality of F. sylvatica L. recorded in the BeechCOSTe52 database (>150,000 trees). Firstly, we performed linear mixed-effect models that related trait variation and covariation to local adaptation (related to the planted populations' climatic origin) and phenotypic plasticity (accounting for the climate of the plantation), and we made spatial predictions under current and representative concentration pathway (RCP 8.5) climates. Secondly, we combined spatial trait predictions in a linear model to explain the occurrence of the species. Results The contribution of plasticity to intraspecific trait variation is always higher than that of local adaptation, suggesting that the species is less sensitive to climate change than expected; different traits constrain beech's distribution in different parts of its range: the northernmost edge is mainly delimited by flushing phenology (mostly driven by photoperiod and temperature), the southern edge by mortality (mainly driven by intolerance to drought), and the eastern edge is characterized by decreasing radial growth (mainly shaped by precipitation-related variables in our model); considering trait covariation improved single-trait predictions. Main conclusions Population responses to climate across large geographical gradients are dependent on trait x environment interactions, indicating that each trait responds differently depending on the local environment.

Raw data can be freely accessed online for French National Forest Inventories (http://inventaire-forestier.ign.fr), Quercus petraea (https://arachne.pierroton.inra.fr/QuercusPortal) and Abies alba common gardens (online repository, in progress). Climate data used for this study are available online (http://gentree.data.inra.fr/climate). R codes used for data analyses can be obtained from the corresponding author upon request.; International audience; Aim To test whether intraspecific trait responses to climate among populations across species distribution ranges can be untangled using field observations, under the rationale that, in natural forest tree populations, long-term climate shapes population responses while recent climate change drives phenotypic plasticity. Location Europe. Time period 1901-2014. Taxa Silver fir (Abies alba Mill.) and sessile oak [Quercus petraea (Matt.) Liebl.]. Methods We estimated the variation of individual tree height as a function of long-term and short-term climates to tease apart provenance effects (variation among populations of different geographical origin), plasticity and their interaction, using mixed-effect models calibrated with national forest inventory data (in-situ models). To validate our approach, we tested the ability of in-situ models to predict independently tree height observations in common gardens experiments where provenance and plastic effects can be measured and separated. In-situ model predictions of tree height variation among provenances and among planting sites were compared to observations in common gardens and to predictions from a similar model calibrated using common garden data (ex-situ model). Results In Q. petraea, we found high correlations between in-situ and ex-situ model predictions of provenance and plasticity effects and their interaction for tree height (r > .80). We showed that the in-situ models significantly predicted tree height variation among provenances and sites for A. alba and Q. petraea. Spatial predictions of phenotypic plasticity across species distribution ranges indicate decreasing tree height in populations of warmer climates in response to recent anthropogenic climate warming. Main conclusions Our modelling approach using national forest inventory observations provides a new perspective for understanding patterns of intraspecific trait variation across species ranges. Its application is particularly interesting for species for which common garden experiments do not exist or do not cover the entire climatic range of the species.

International audience; Improving our understanding of species ranges under rapid climate change requires application of our knowledge of the tolerance and adaptive capacity of populations to changing environmental conditions. Here, we describe an emerging modelling approach, ΔTraitSDM, which attempts to achieve this by explaining species distribution ranges based on phenotypic plasticity and local adaptation of fitness‐related traits measured across large geographical gradients. The collection of intraspecific trait data measured in common gardens spanning broad environmental clines has promoted the development of these new models – first in trees but now rapidly expanding to other organisms. We review, explain and harmonize the main findings from this new generation of models that, by including trait variation over geographical scales, are able to provide new insights into future species ranges. Overall, ΔTraitSDM predictions generally deliver a less alarming message than previous models of species distribution under new climates, indicating that phenotypic plasticity should help, to a considerable degree, some plant populations to persist under climate change. The development of ΔTraitSDMs offers a new perspective to analyse intraspecific variation in single and multiple traits, with the rationale that trait (co)variation and consequently fitness can significantly change across geographical gradients and new climates.

International audience; How populations of long-living species respond to climate change depends on phenotypic plasticity and local adaptation processes. Marginal populations are expected to have lags in adaptation (i.e. differences between the climatic optimum that maximizes population fitness and the local climate) because they receive pre-adapted alleles from core populations preventing them from reaching a local optimum in their climatically marginal habitat. Yet, whether adaptation lags in marginal populations are a common feature across phylogenetically and ecologically different species and how lags can change with climate change remain unexplored. To test for range-wide patterns of phenotypic variation and adaptation lags of populations to climate, we (a) built model ensembles of tree height accounting for the climate of population origin and the climate of the site for 706 populations monitored in 97 common garden experiments covering the range of six European forest tree species; (b) estimated populations' adaptation lags as the differences between the climatic optimum that maximizes tree height and the climate of the origin of each population; (c) identified adaptation lag patterns for populations coming from the warm/dry and cold/wet margins and from the distribution core of each species range. We found that (a) phenotypic variation is driven by either temperature or precipitation; (b) adaptation lags are consistently higher in climatic margin populations (cold/warm, dry/wet) than in core populations; (c) predictions for future warmer climates suggest adaptation lags would decrease in cold margin populations, slightly increasing tree height, while adaptation lags would increase in core and warm margin populations, sharply decreasing tree height. Our results suggest that warm margin populations are the most vulnerable to climate change, but understanding how these populations can cope with future climates depend on whether other fitness-related traits could show similar adaptation lag patterns.

This datapaper collects individual georeferenced tree height data from Pinus nigra Arn., P. pinaster Aiton, and P. pinea L. planted in common gardens in France, Germany, Morocco, and Spain. The data can be used to assess genetic variation and phenotypic plasticity with further applications in biogeography and forest management. The three datasets are available at (Vizcaino-Palomar et al. 2018a), (Vizcaino-Palomar et al. 2018b), and (Vizcaino-Palomar et al. 2018c), and the associated metadata are available at , and for P. nigra, P. pinaster and P. pinea, respectively.

One of the most widespread consequences of climate change is the disruption of trees’ phenological cycles. The extent to which tree phenology varies with local climate is largely genetically determined, and while a combination of temperature and photoperiodic cues are typically found to trigger bud burst (BB) in spring, it has proven harder to identify the main cues driving leaf senescence (LS) in autumn. We used 925 individual field-observations of BB and LS from six Fagus sylvatica provenances, covering the range of environmental conditions found across the species distribution, to: (i) estimate the dates of BB and LS of these provenances; (ii) assess the main drivers of LS; and (iii) predict the likely variation in the growing season length (GSL; defined by BB and LS timing) across populations under current and future climate scenarios. To this end, we first calibrated linear mixed-effects models for LS as a function of temperature, insolation and BB date. Secondly, we calculated the GSL for each provenance as the number of days between BB and LS. We found that: i) there were larger differences among provenances in the date of LS than in the date of BB; ii) the temperature through September, October and November was the main determinant of LS in beech, although covariation of temperature with daily insolation and precipitation-related variables suggests that all three variables may affect LS timing; and iii) GSL was predicted to increase in northern beech provenances and to shrink in populations from the core and the southern range under climate change. Consequently, the large differences in GSL across beech range in the present climate are likely to decrease under future climates where rising temperatures will alter the relationship between BB and LS, with northern populations increasing productivity by extending their growing season to take advantage of warmer conditions.

Impacts of climate change are likely to be marked in areas with steep climatic transitions. Species turnover, spread of invasive species, altered productivity, and modified processes such as fire regimes can all spread rapidly along ecotones, which challenge the current paradigms of ecosystem management. We conducted a literature review at a continental-wide scale of South-Western European forests, where the drier and warmer conditions of the Mediterranean have been widely used as examples of what is expected in more temperate areas. Results from the literature point to: (a) an expansion of slow-growing evergreen hardwood trees; (b) increased dieback and mortality episodes in forests (both natural and planted) mostly related to competition and droughts, and mainly affecting conifers; and (c) an increase in emergent diseases and pests of keystone-trees used in agroforestry zones. There is no consensus in the literature that fire regimes are directly increasing due to climate change, but available satellite data of fire intensity in the last 17 years has been lower in zones where agroforestry practices are dominant compared to unmanaged forests. In contrast, there is agreement in the literature that the current spread of fire events is probably related to land abandonment patterns. The practice of agroforestry, common in all Mediterranean countries, emerges as a frequent recommendation in the literature to cope with drought, reduce fire risk, and maintain biodiverse landscapes and rural jobs. However, it is unknown the extent to which the open vegetation resulting from agroforestry is of interest to forest managers in temperate areas used to exploiting closed forest vegetation. Hence, many transitional areas surrounding the Mediterranean Basin may be left unmanaged with potentially higher climate-change risks, which require active monitoring in order to understand and help ongoing natural adaptation processes., This research was funded by a small network grant provided by the LabEx-BASC French research consortium granted to J.F.-M., S.D., and H.L. M.A.Z. and P.R.-B. were supported by the grant FUNDIVER (MINECO, CGL2015-69186-C2-2-R). P.R.-B. was funded by the Talent Attraction Grant of the Madrid Community grant number 2016-T2/AMB-1665. V.P. was funded by FCT—The Foundation for Science and Technology grant number SFRH/BPD/80726/2011.

International audience; The adaptation of social-ecological systems such as managed forests depends largely on decisions taken by forest managers who must choose among a wide range of possible futures to spread risks. We used robust decision theory to guide management decisions on the translocation of tree populations to compensate for climate change.We calibrated machine learning correlational models using tree height data collected from five common garden tests in France where Abies alba provenances from 11 European countries are planted. Resulting models were used to simulate tree height in the planting sites under current and 2050 climates (regional concentration pathway scenarios (RCPs) 2.6, 4.5, 6.0 and 8.5). Our results suggest an overall increase in tree height by 2050, but with large variation among the predictions depending on the provenance and the RCPs. We applied maximin, maximax and minimax decision rules to address outcomes under five uncertain states of the world represented by the four RCPs and the present climate (baseline). The maximin rule indicated that for 2050, the best translocation option for maximising tree height would be the use of provenances from Northwest France into all target zones. The maximax and minimax regret rules pointed out the same result for all target zones except for the ‘Les Chauvets’ trial, where the East provenance was selected. Our results show that decision theory can help management by reducing the number of options if most decision rules converge. Interestingly, the commonly suggested recommendation of using multiple provenances to mitigate long-term maladaptation risks or from ‘pre-adapted’ populations from the south was not supported by our approach.

International audience; Aim: The aim was to examine whether recent mortality can be explained by hydraulic failure linked to water deficit. Location: Western Europe. Time period: 1986-2014. Major taxa studied: Forty-four tree species. Methods: We modelled the hydraulic safety margin (HSM) across the ranges of 44 tree species at their driest margin (n=193,261 plots), defined as the difference between the estimated minimal soil water potential of each plot and the species water stress threshold, which corresponds to the hydraulic failure of the vascular system. Soil water potential was estimated by applying Campbell's equations on the minimal and maximal soil water contents estimated from 1979 to 2010 in the top 289 cm of soil and five soil textures across the species ranges. For each species, we modelled the amount of average mortality derived from plots of the Spanish and French National Forest Inventories to the variation in modelled hydraulic safety margin and environmental drivers across the species ranges using hurdle models. Results: We did not identify any global convergence of modelled HSM within the species distribution ranges, finding instead a rather large variability in modelled HSM for most of the studied species. Fifteen species, out of 25 for which the models were practicable, showed significantly higher mortality in populations with negative HSM in comparison to those showing positive HSM, with positive and negative interaction along the aridity index. Main conclusions: The combination of competition, average climate and modelled HSM explained average tree mortality. Most of the species presented at least one population that had already experienced a negative HSM and many other populations a positive but narrow HSM, suggesting that climate change is likely to push some populations towards a higher risk of hydraulic failure in the drier conditions projected for Western Europe.

Aim To analyse global patterns of climate during the mid-Holocene and conduct comparisons with pre-industrial and projected future climates. In particular, to assess the exposure of terrestrial biomes and ecoregions to climate-related risks during the Holocene–Anthropocene transition starting at the pre-industrial period. Location Terrestrial ecosystems of the Earth. Methods We calculated long-term climate differences (anomalies) between the mid-Holocene (6 ka cal bp, mH), pre-industrial conditions and projections for 2100 (middle-strength A1B scenario) using six global circulation models available for all periods. Climate differences were synthesized with multivariate statistics and average principal component loadings of temperature and precipitation differences (an estimate of climate-related risks) were calculated on 14 biomes and 766 ecoregions. Results Our results suggest that most of the Earth's biomes will probably undergo changes beyond the mH recorded levels of community turnover and range shifts because the magnitude of climate anomalies expected in the future are greater than observed during the mH. A few biomes, like the remnants of North American and Euro-Asian prairies, may experience only slightly greater degrees of climate change in the future as compared with the mH. In addition to recent studies that have identified equatorial regions as the most sensitive to future climate change, we find that boreal forest, tundra and vegetation of the Equatorial Andes could be at greatest risk, since these regions will be exposed to future climates that are well outside natural climate variation during the Holocene. Conclusions The Holocene–Anthropocene climate transition, even for a middle-strength future climate change scenario, appears to be of greater magnitude and different from that between the mH and the pre-industrial period. As a consequence, community- and biome-level changes due to of expected climate change may be different in the future from those observed during the mH.

Restoration programs need to increasingly address both the restitution of biodiversity and ecosystem services and the preparation of habitats for future climate change. One option to adapt habitats to climate change in the temperate zone is the translocation of southern populations to compensate for climate change effects - an option known as assisted migration (AM). Although AM is widely criticized for endangered species, forest managers are more confident that tree populations can be translocated with success because of previous experiences within native ranges. Here, we contend that translocations of tree populations are also subject to uncertainties, and we extract lessons for future programs of AM within species ranges from a well-documented failed case of population translocation of Pinus pinaster Ait. in Europe. The failure of these translocations originated from the unawareness of several unpredictable ecological and social events: cryptic maladaptation of the introduced populations, underestimation of climate variability differences between the source and target sites and complexity in the management schemes, postponing decisions that could have been undertaken earlier. Under the no-analog conditions that are expected with climate change, management decisions need to be made with incomplete data, implying that a certain degree of maladaptation should always be expected when restoring plant populations from local or external seed sources.

Aim Tree growth may be enhanced by carbon dioxide fertilization unless drought stress becomes too severe, yet the likely increase in tree growth under a warmer climate is still controversial. Tree mortality has increased in some regions, but its multifactorial nature makes the prediction of likely global trends difficult. The aims of this work are: (1) to assess which abiotic, structural and competition factors influence tree growth and tree mortality in mainland Spain, and (2) to evaluate whether these processes would drive species distributions and would improve current niche model predictions. Location Continental Spain. Methods We projected species distributional models by integrating nonparametric tree growth and tree mortality models based on repeated surveys of diameter at breast height and mortality for 40,721 trees distributed in 45,301 plots, which include the 11 most common canopy tree species in continental Spain, as measured in the second and third National Forest Inventories, with a mean lag time of 11 years. Results Tree growth and tree mortality were explained by an assemblage of many factors, among which climate and competition played a key role. The accuracy of models including tree growth and tree mortality in predicting tree habitat suitability was comparable to classical niche models based on species occurrence. Projections under climate change showed for 9 out of 11 species, a likely increase in tree growth that would be counteracted by an increase in tree mortality, suggesting that even if growth rates increase, mortality would limit the species ranges under global warming expectations. Main conclusions Growth and mortality are major determinants of species distributions. Under future climate change expectations, our model suggests that growth may increase for some Iberian species, but even in this case, species ranges at the rear edge would be limited by an increase in mortality rates.

Climate change is expected to increase the frequency and intensity of droughts and heatwaves in Europe, leading to effects on forest growth and major forest dieback events due to hydraulic failure caused by xylem embolism. Inter-specific variability in embolism resistance has been studied in detail, but little is known about intra-specific variability, particularly in marginal populations. We evaluated 15 European beech populations, mostly from geographically marginal sites of the species distribution range, focusing particularly on populations from the dry southern margin. We found small, but significant differences in resistance to embolism between populations, with xylem pressures causing 50% loss of hydraulic conductivity ranging from −2.84 to −3.55 MPa. Significant phenotypic clines of increasing embolism resistance with increasing temperature and aridity were observed: the southernmost beech populations growing in a warmer drier climate and with lower habitat suitability have higher resistance to embolism than those from Northern Europe growing more favourable conditions. Previous studies have shown that there is little or no difference in embolism resistance between core populations, but our findings show that marginal populations have developed ways of protecting their xylem based on either evolution or plasticity.

Tree height-diameter allometry, the link between tree height and trunk diameter, reflects the evolutionary response of a particular species’ allocation patterns to above and belowground resources. As a result, it differs among and within species due to both local adaptation and phenotypic plasticity. These phenotypic variations in tree height-diameter allometry determine tree productivity, resistance and resilience to climate variation and, ultimately, the success of plant material used in restoration projects. We tested the effect of climate change and population origin on the phenotypic variation of tree allometry in four pine species at an early stage of development (ca. 11 years old) based upon data originated from multi-site provenance tests and planted along a wide climatic range in south-western Europe. For a representative sample of populations from each species, we used already-developed species-specific height-diameter allometric models to assess changes in allometry between present and future climatic conditions. We found that Pinus halepensis and Pinus pinaster were the most plastic species, while Pinus sylvestris and Pinus nigra showed negligible plastic responses. In addition, our models stressed that pine tree height-diameter allometry will change and phenotypic variation could increase, except in P. sylvestris, under future environmental conditions. For some of the species, this might allow the selection of phenotypes better suited to novel climatic conditions. These foreseeable changes in tree height-diameter allometry (among and within-species) could entail eco-evolutionary effects on the early forest plantation dynamics. Therefore, restoration and reforestation plans should consider these effects, as they may interfere with production and/or environmental goals. © 2016, Springer Science+Business Media Dordrecht.

The present work proposes new boundaries for the current submediterranean territories of the Iberian Peninsula, defining them at the smallest scale attempted to date. The boundaries proposed are not sharp divisions but somewhat ‘gradual’, reflecting the transitional nature of the territories they encompass. Climate change predictions were used to estimate how the distribution of these submediterranean regions might change in the near future. The maps constructed are based on the distribution of marcescent Quercus species—trees that characterise the submediterranean plant landscape where they form the main forest communities. To determine their climatic range, the distribution of different types of Iberian oak forest was represented in ‘climate diagrams’ (ordination diagrams derived from principal components analysis), both in terms of individual species and groups of species based on leaf ecophysiological type, i.e. marcescent (Submediterranean), sclerophyllous (Mediterranean), semideciduous (Mediterranean) and deciduous (Eurosiberian). The climate range of each type of forest was determined, and the means of representative climate variables are analysed by one way ANOVA. The variables differentiating the forest groups were also examined by discriminant analysis. The range of the climate variables found to be associated with the majority of marcescent forests was used to determine the distribution of territories throughout the Peninsula with the same conditions (i.e. whether marcescent forests were present or not), thus providing a map of the Iberian submediterranean territories. Predictions of climate change were used to investigate possible climate-induced modifications in the boundaries of these territories in the near future. The patterns obtained show dramatic reductions in the extension of the Iberian submediterranean environment. Submediterranean conditions will probably disappear from the areas where they currently reign, and it seems unlikely that any new, large submediterranean areas will form by displacement towards higher altitudes. The outlook for the unique submediterranean vegetation of the Iberian Peninsula is gloomy.

Question: Will the predicted climate changes affect species distribution in the Iberian Peninsula?Location: Iberian Peninsula (Spain and Portugal).Methods: We modelled current and future tree distributions as a function of climate, using a computational framework that made use of one machine learning technique, the random forest (RF) algorithm. This algorithm provided good predictions of the current distribution of each species, as shown by the area under the corresponding receiver operating characteristics (ROC) curves. Species turnover, richness and the change in distributions over time to 2080 under four Intergovernmental panel on climate change (IPCC) scenarios were calculated using the species map outputs.Results and Conclusions: The results show a notable reduction in the potential distribution of the studied species under all the IPCC scenarios, particularly so for mountain conifer species such as Pinus sylvestris, P. uncinata and Abies alba. Temperate species, especially Fagus sylvatica and Quercus petraea, were also predicted to suffer a reduction in their range; also sub-mediterranean species, especially Q. pyrenaica, were predicted to undergo notable decline. In contrast, typically Mediterranean species appeared to be generally more capable of migration, and are therefore likely to be less affected.

International audience; Four North American trees are becoming invasive species in Western Europe: Acer negundo, Prunus serotina, Quercus rubra, and Robinia pseudoacacia. However, their present and future potential risks of invasion have not been yet evaluated. Here, we assess niche shifts between the native and invasive ranges and the potential invasion risk of these four trees in Western Europe. We estimated niche conservatism in a multidimensional climate space using niche overlap Schoener's D, niche equivalence, and niche similarity tests. Niche unfilling and expansion were also estimated in analogous and nonanalogous climates. The capacity for predicting the opposite range between the native and invasive areas (transferability) was estimated by calibrating species distribution models (SDMs) on each range separately. Invasion risk was estimated using SDMs calibrated on both ranges and projected for 2050 climatic conditions. Our results showed that native and invasive niches were not equivalent with low niche overlap for all species. However, significant similarity was found between the invasive and native ranges of Q. rubra and R. pseudoacacia. Niche expansion was lower than 15% for all species, whereas unfilling ranged from 7 to 56% when it was measured using the entire climatic space and between 5 and 38% when it was measured using analogous climate only. Transferability was low for all species. SDMs calibrated over both ranges projected high habitat suitability in Western Europe under current and future climates. Thus, the North American and Western European ranges are not interchangeable irrespective of the studied species, suggesting that other environmental and/or biological characteristics are shaping their invasive niches. The current climatic risk of invasion is especially high for R. pseudoacacia and A. negundo. In the future, the highest risks of invasion for all species are located in Central and Northern Europe, whereas the risk is likely to decrease in the Mediterranean basin.

We present a modelling framework for predicting forest areas. The framework is obtained by integrating a machine learning software suite within the GRASS Geographical Information System (GIS) and by providing additional methods for predictive habitat modelling. Three machine learning techniques (Tree-Based Classification, Neural Networks and Random Forest) are available in parallel for modelling from climatic and topographic variables. Model evaluation and parameter selection are measured by sensitivity-specificity ROC analysis, while the final presence and absence maps are obtained through maximisation of the kappa statistic. The modelling framework is applied at a resolution of 1 km with Iberian subpopulations of Pinus sylvestris L. forests. For this data set, the most accurate algorithm is Breiman's random forest, an ensemble method which provides automatic combination of tree-classifiers trained on bootstrapped subsamples and randomised variable sets. All models show a potential area of P. sylvestris for the Iberian Peninsula which is larger than the present one, a result corroborated by regional pollen analyses.

International audience; One approach to compensating for rapid climate change and protecting biodiversity is assisted migration (AM) of key tree species. However, tools for evaluating the sensitivity of target sites and identifying potential sources have not yet been developed. We used the National Forest Inventories of Spain and France to design scenarios for AM between and within both countries. We characterized sensitivity to climate change as the expected changes in volume and mortality of Pinus halepensis Miller and Pinus pinaster Aiton between the present and 2050. Target zones were selected from provenances with high sensitivity and seed zones from provenances with low sensitivity to climate change; the latter can be considered “seed refugia” as the climate changes. Three plausible scenarios for translocation to the target zone were developed on the basis of volume simulations calibrated with different planting strategies: (1) seeds only from foreign provenances; (2) foreign provenances plus local seeds; and (3) only local seeds. The results for both species show that models based on foreign “top-three” provenances always increased the standing volume of the target zone. Models run with only local seeds predicted increased volume for P. halepensis but not for P. pinaster. Our results suggest that volume and mortality trends are not always correlated with seed sources and targets, that projected provenances mortality do not follow always a southern–northern pattern and that seed refugia, if any, may be useful for compensating for the effects of climate change only in a subset of provenances. © 2015 Springer Science+Business Media Dordrecht

International audience; Recently, Pedlar et al. (2012) stated that assisted migration in forestry (forestry AM) differs from species-rescue-assisted migration (species rescue AM) because the risks of invasiveness, hybridization with local species, and spread of diseases are minimized in managed forests. The rationale behind this assertion for forestry AM is that it involves the translocation of populations within the existing geographic range of the species, whereas species rescue AM involves the introduction of exotic species. However, while we agree that forestry AM is less risky than species rescue AM for the recipient ecosystem, forestry AM can not only fail but can also incur enormous financial costs. The failure of efforts that involved planting maritime pine (Pinus pinaster Aït) trees in Southwest France (Aquitaine) with seeds from more southerly populations from Portugal for production purposes is a textbook case. The climate variability in Aquitaine includes periods of intense frost that are sufficiently rare (every 10 to 20 years) to be overlooked when establishing tree populations. The frost of the winter of 1985, the most intense frost event since records began with temperatures dropping as low as -22 °C (Boisseaux, 1986), affecting about 350 km2 of tree plantations in the region (Doré & Varoquaux, 2006). The highest mortality related to frost was observed in populations harvested from Leiria in Portugal, for which nearby records show that the absolute minimum temperature was only -7.8 °C in the last 60 years. Climate averages over the last 30 years differ only slightly between Leiria and Aquitaine, which would erroneously suggest that samples from Portugal would have survived in the Aquitaine region. Newly emerging climates (Williams et al. 2007) and the uncertainty related to climate change extreme events (Easterling, 2000) will make the search for southern locations with climatic conditions similar to those of northern populations of trees extremely difficult. Policies of forest adaptation to climate change should account for extreme cold events in the target populations even if climate change will likely decrease the number of extreme cold events (Easterling, 2000), that remain in our opinion, the hidden element behind the maladaptation of southern populations to northern locations.

We model the past and future distribution of Pinus sylvestris in the Iberian Peninsula using the random forest algorithm, a machine learning technique that implements an automatic combination of tree predictors. In order to model the past, we chose two of the most climatically significant events recognized affecting the species distribution: the last glacial maximum (LGM, 21 000 cal. BP), and the mid Holocene (6000 cal. BP). In order to model the distributions, we based the future scenarios of climate change upon the four storylines projected by the Intergovernmental Panel on Climate Change (A1, A2, B1 and B2). The results obtained for the past show a contraction in the distribution area during the LGM and a subsequent expansion, coinciding with an improvement in climate in the mid Holocene. The presence of isolated populations of Pinus sylvestris at low altitudes could support the existence of refuges for Northern European taxa. The results obtained for the future, even in the least aggressive scenario, show a rapid decrease in this species' distribution and a vertical migration as a response to climate change. Pinus sylvestris populations would be restricted in the future to the higher altitudes of the mountains in the north of the Iberian Peninsula (mainly the Pyrenees), and the species would disappear from the central and southern mountain ranges. These results identify a risk to high-mountain forest species in the Iberian Peninsula from the effects of global warming.

This paper reports a bioclimatic envelope model study of the potential distribution of 19 tree species in the Iberian Peninsula during the Last Glacial Maximum (LGM; 21 000 yr BP) and the Mid-Holocene (6000 yr BP). Current patterns of tree species richness and distributions are believed to have been strongly influenced by the climate during these periods. The modelling employed novel machine learning techniques, and its accuracy was evaluated using a threshold-independent method. Two atmospheric general circulation models, UGAMP and ECHAM3 (generated by the Palaeoclimate Modelling Intercomparison Project, PMIP), were used to provide climate scenarios under which the distributions of the 19 tree species were modelled. The results obtained for these scenarios were assessed by agreement measure analysis; they differed significantly for the LGM, but were more similar for the Mid-Holocene. The results for the LGM support the inferred importance of pines in the Iberian Peninsula at this time, and the presence of evergreen Quercus in the south. Important differences in the altitude at which the modelled species grew were also predicted. During the LGM, some normally higher mountain species potentially became re-established in the foothills of the Pyrenees. The warm Mid-Holocene climate is clearly reflected in the predicted expansion of broad-leaved forests during this period, including the colonization of the northern part of the Iberian Peninsula by evergreen Quercus species.

Phenomena of hybridization can affect the ecology and evolution of the species involved in the process, as well as their communities. Although numerous papers focus upon the problem of taxonomy, few of these have attempted to study hybrid zones in relation to the analysis of their communities. On the Iberian Peninsula, hybridization phenomena among different oak species are frequent. It is, however, between Quercus faginea Lam. and Quercus pubescens Willd. where the most noteworthy hybridization phenomenon occurs. In this respect, we are familiar with the existence of different introgression levels but we are unaware of whether these hybrids are the transitory result of the interspecific genetic flow or whether these are maintained by means of extrinsic selection processes. Study of plant communities’ flora and environment might shed light upon this issue. Comparison between plant communities dominated by one of the parental species and those dominated by individuals of hybrid origin might enable us to establish the presence or absence of an environment that is potentially selective in favour of the hybrids. Thus the possible existence of extrinsic selection. Furthermore, this information will help us to understand plant community distribution in an area␣that is difficult to interpret. To this purpose, we used multivariate ordination techniques (DCA and CCA) based upon a total of 395 floristic releves covering the whole range of the parental species on the Iberian Peninsula and upon climatic and edaphic variables for each of these releves. We also compared the groups obtained in relation to floristic similarity (Jaccard index), richness and diversity (Shannon–Weaver index). Forests associated with Quercus pubescens are related to heavy summer precipitation, whereas Quercus faginea forests correspond to lower values of this variable and higher ones for continentality. Between both formations, there is a broad hybrid zone, with diffused borders that are related to an environmental gradient of Mediterranean influence. In this region, two types of forest communities were distinguished, which enabled us to divide the hybrid zones into two territories. Our results allowed us to locate the hybrid zone in an ecotone. The differentiation between habitats appears to indicate models of ecological selection. These models require, by definition, the presence of an environmental gradient between the parental zones. We are, however, aware of the need for future experiments in order to establish whether the hybrids are better adapted than the parental species. Only with availability of all this information can intrinsic selection be rejected.