Create Content in MinutesGet Started For Free
Publications and reports about forest and climate change curated by the LIFE FORECCAsT project
Exposure of plants and animals to ultraviolet-B radiation (UV-B; 280–315 nm) is modified by stratospheric ozone dynamics and climate change. Even though stabilisation and projected recovery of stratospheric ozone is expected to curtail future increases in UV-B radiation at the Earth's surface, on-going changes in climate are increasingly exposing plants and animals to novel combinations of UV-B radiation and other climate change factors (e.g., ultraviolet-A and visible radiation, water availability, temperature and elevated carbon dioxide). Climate change is also shifting vegetation cover, geographic ranges of species, and seasonal timing of development, which further modifies exposure to UV-B radiation.
Here, we present results from a new forest carbon monitoring and modeling system that combines high-resolution remote sensing, field data, and ecological modeling to estimate contemporary above-ground forest carbon stocks, and project future forest carbon sequestration potential for the state of Maryland at 90 m resolution. Statewide, the contemporary above-ground carbon stock was estimated to be 110.8 Tg C (100.3–125.8 Tg C), with a corresponding mean above-ground biomass density of 103.7 Mg ha−1 which was within 2% of independent empirically-based estimates.
The paper assesses the impact of forestry practices on carbon balance in forest ecosystems the example of eleven regions fully or partly included in forest-steppe or steppe of European Russia (ER). Calculations made by the procedure «Regional evaluation carbon balance in forests», has shown, that yearly fires and other forest destruction causes harmed carbon stock by all pools of forest ecosystems the studied regions in amount of 2632,000 [tC year−1] (tons of carbon per year) (87.3 % of total loss of carbon by forest ecosystems). Forestry practices such as salvage felling harm carbon stock of forest ecosystems in amount of 288 thousand [tC year−1] (9.5 %). Improvement felling harmed it in amount of 108,000 [tC year−1] (3.58 %).
We revealed a significant positive effect of the sums of atmospheric precipitation in May-August on pine growth (correlation coefficient up to 0.39) and a weak effect of air temperatures. The prevailing cyclic components of the time series studied are established: a high-frequency cycle (about 3 years) and a Brikner cycle (about 33 years). We have constructed mathematical models by the method of singular-spectral analysis (SSA). In the mathematical models constructed by us, due to the use of combined time series of climatic factors (the sum of precipitation, hydrothermal coefficient and indices of the radial increment of pine stands, for the first time a very high coefficient of similarity between actual and theoretical series was achieved
Temperature and precipitation regimes in the East-European forest-steppe have been disrupted in response to the recent climatic changes. Particularly, (1) increased the range of day-night temperatures, especially during the spring – summer period, (2) increased the number and intensity of thaws in January – February, and (3) the timing, range and intensity of annual precipitation were distorted, thus making some periods of the year excessively dry or wet. Synergistically, these disturbances (1) increase environmental stress to fruit plants, and (2) alter conditions for their growth, development and crop bearing. Hence, we argue that current criteria for the selection of plant varieties for cultivation in that region are no longer valid
The significant reduction of shrubs and grass plants biodiversity between urban and reserved territory could be a biomarker of human impact and effect of urbanisation. We could conclude that trees are more resistant to climate change and anthropogenic pressure.The research of cytogenetic parameters for English oak seed progeny in the areas with different levels of anthropogenic pollution was carried out. High level of mitotic pathologies and mitotic activities of seed progeny plantlets from trees growing near freeway was observed. Also high level of variability indices, such as percentage of prophase cells, metaphase cells, mitotic pathologies were seen.
Climate-induced tree mortality became a global phenomenon during the last century and it is expected to increase in many regions in the future along with a further increase in the frequency of drought and heat events. However, tree mortality at the ecosystem level remains challenging to quantify since long-term, tree- individual, reliable observations are scarce. Here, we present a unique data set of monitoring records from 126 forest stands across Switzerland, which include five major European tree species (Norway spruce, Scots pine, silver fir, European beech, and sessile and common oak) and cover a time span of over one century (1898-2013), with inventory periods of 5 to 10 years.
By combining data from a network of forest plots with repeat airborne lidar, here we develop an approach to (i) map fine-scale variation in aboveground carbon density (ACD) and its change over time across the landscape, and (ii) link these changes in ACD to forest structural attributes, species composition, disturbance regimes and local topography. We tested this framework on a temperate forest in the Alps characterized by the presence of three dominant species: spruce (Picea abies), silver fir (Abies alba) and beech (Fagus sylvatica).
Globally, the increase in the climatic variability has led to adverse effects on the treeline species in the high-elevation mountain landscapes. Identifying the geographical space that supports the treeline species survival over time is essential for conservation biogeography. Increase in the global warming and snowmelt has made available the treeline species favourable niches in the higher elevations. Random Forest algorithm assuming non-parametric distribution was employed to predict the potential distribution of Betula utilis niche in the Hindu-Kush Himalayan (HKH) region. The potential distributions were simulated in the Last Inter-Glaciation (LIG), present (the year 1970–2000) and future (the year 2061–2080) environmental conditions.
The influence of climate change on the biomass of a tree species in the format of additive models for transcontinental hydrothermal gradients has not yet been studied. In the present study, the first attempt is made to model changes in the additive component composition of the stand biomass and NPP of two-needled pines along Trans-Eurasian hydrothermal gradients. In the process of modelling the database of pine stand biomass in a number of 2460 sample plots with the definitions of biomass and 760 plots with the definitions of biomass and annual NPP compiled by the authors, is used.
Relationships between forest cover and streamflow have been studied worldwide, but only a few studies have examined how gradual changes in forest structure and species composition due to logging and climate change affect watershed water yield (Q) and flow regimes. In this study, we analyzed long-term (45 years) hydrologic, climate and forest dynamics data from the subboreal Tahe watershed in northeastern China. Our purpose was to evaluate the effects of forest logging and regeneration on changes in forest biomass and species and to quantify the subsequent impact on mean annual streamflow and flow regime under a changing climate.
Climate influences vegetation directly and through climate-mediated disturbance processes, such as wildfire. Temperature and area burned are positively associated, conditional on availability of vegetation to burn. Fire is a self-limiting process that is influenced by productivity. Yet, many fire projections assume sufficient vegetation to support fire, with substantial implications for carbon (C) dynamics and emissions. We simulated forest dynamics under projected climate and wildfire for the Sierra Nevada, accounting for climate effects on fuel flammability (static) and climate and prior fire effects on fuel availability and flammability (dynamic).
Climate change-induced tree mortality is occurring worldwide, at increasingly larger scales and with increasing frequency. How climate change-induced tree mortality could affect the ecology and carbon (C) sink capacity of soils remains unknown. This study investigated regional-scale drought-induced tree mortality, based on events that occurred after a very dry year (2012) in the Carpathians mountain range (Romania), which caused mortality in three common conifer species: Scots pine, Black pine, and Silver fir. This resulted in hot-spots of biogenic soil CO2 emissions (soil respiration; Rs).
Selective logging causes at least half of the emissions from tropical forest degradation. Reduced-impact logging for climate (RIL-C) is proposed as a way to maintain timber production while minimizing forest damage. Here we synthesize data from 61 coordinated field-based surveys of logging impacts in seven countries across the tropics. We estimate that tropical selective logging emitted 834 Tg CO2 in 2015, 6% of total tropical greenhouse gas emissions. Felling, hauling, and skidding caused 59%, 31%, and 10% of these emissions, respectively. We suggest that RIL-C incentive programs consider a feasible target carbon impact factor of 2.3 Mg emitted per Mg of timber extracted.
Vegetation is known to have strong influence on evapotranspiration (ET), a major component of terrestrial water balance. Yet hydrological models often describe ET by methods unable to sufficiently include the variability of vegetation characteristics in their predictions. To take advantage of increasing availability of high-resolution open GIS-data on land use, vegetation and soil characteristics in the boreal zone, a modular, spatially distributed model for upscaling ET and other hydrological processes from a grid cell to a catchment level is presented and validated. An improved approach to upscale stomatal conductance to canopy scale using information on plant type (conifer / deciduous) and stand leaf-area index (LAI) is proposed by coupling a common leaf-scale stomatal conductance model with a simple canopy radiation transfer scheme.
The present study models the potential current and future distribution ranges of Taxus wallichiana based on its suitable climatic envelop developed under a baseline scenario (1960–1990) and climate change scenarios centred on representative concentration pathways (RCPs) for the year 2070, as provided in the Fifth Assessment Report (AR5) of the UNO’s Intergovernmental Panel on Climate Change (IPCC). The projected shrink in climatic niche of Taxus wallichiana by 28% (RCP 4.5) and 31% (RCP 8.5) highlights the vulnerability of the endangered species to climate change impacts and the perturbations on the structure of mountain ecosystem.
Deforestation and forest degradation are major drivers of global environmental change and tropical forests are subjected to unprecedented pressures from both.For most tropical zones, deforestation rates are averaged across entire countries,often without highlighting regional differentiation. There are also very few estimates of forest degradation, either averaged or localized for the tropics. We quantified regional and country-wide changes in deforestation and forest degradation rates for Madagascar from Landsat temporal data (in two intervals,1994–2002 and 2002–2014). To our knowledge, this is the first country-wide estimate of forest degradation for Madagascar.
We illustrate the value of ‘legacy’ mentalities, enthusiasm for trial and error, and prosaic restorative cultures among resource stewardship actors, focusing on those whose present experimentation responds to lived experience of industrial capitalism's failures. Insights arise on efforts we must all make to craft a world that can survive the future we have wrought. Unpremeditated experimental relations with nonhuman others, and with the future, unfold materially in time and space - not through official policy initiatives, but extemporaneously, on the fringes of formality.
Knowledge of the response of thinning implementation on forest soil–atmospheric greenhouse gas (GHG) (CO2, CH4, N2O) fluxes exchange system in Mediterranean region is limited because of the high heterogeneity of both soil properties and forest biomass. The novelty of this study is grounded predominantly in evaluating for the first time the response of annual GHG fluxes to thinning in a coniferous peri-urban forest soil in Greece, thus contributing significantly to the enrichment of the GHG fluxes database from the Mediterranean forest ecosystem. Results suggest that CH4 uptake increased with increasing thinning intensity.
Global concern about the restoration of vegetation ecosystems has recently increased. Potential natural vegetation (PNV) and climate adaptation concepts should be integrated into revegetation programs to achieve sustainable ecosystems. The Yanhe Basin in the Loess Plateau of China (7687 km2) has been subjected to intense human activity for centuries. It was selected as the study area because vegetation degradation and restoration are occurring there. The objectives of this study were to (1) evaluate whether the current vegetation pattern is appropriate, and (2) provide a restoration plan for future revegetation programs based on PNV and habitat suitability patterns simulated by the dynamic vegetation model LPJ-GUESS.
Our results demonstrate a large difference between the landscape’s potential to store carbon and the landscape’s current trajectory, assuming a continuation of the modern land-use regime. They also reveal aspects of the land-use regime that will have a disproportionate impact on the ability of the landscape to store carbon in the future, such as harvest regimes on corporate-owned lands. This information will help policy-makers and land managers evaluate trade-offs between commodity production and mitigating climate change through forest carbon storage.
Climate is the predominant constraint on the distribution and composition of forested ecosystems. Forest managers and policy makers need to consider the effects of potential future climates on important forest attributes, such as aboveground biomass (AGB) present in standing trees. The Forest Inventory and Analysis (FIA) program, which systematically collects forest data across all forested lands in the USA, is an integral component in large-scale forest management and policy. The Forest Vegetation Simulator (FVS) is a common forest growth and yield simulator used by forest resource managers.
Global and regional environmental disturbances, including harvesting and climate change, can have significant integrated and interactive effects on forest ecosystems, altering their structure and function, and therefore long-term sustainability. Process ecosystem models are useful tools to gain a better understanding of complex, interacting ecological process and their response to disturbance. The biogeochemical model, PnET-BGC was modified and tested using field observations from an experimentally whole-tree harvested northern hardwood watershed (W5) at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA.
Ecological-bioclimatic modeling projects substantial vegetation changes: biomes shift northwards; area of conifer forest decreases and grasslands increases. Fire and the thawing of permafrost would be the principal mechanisms to shape new biomes. The zone at risk of forest loss in Siberia would extend northwards. Accumulated surface fuel loads together with an increase in severe fire weather would lead to increases in large, high-severity fires, which are expected to facilitate vegetation progression towards equilibrium with the climate. To minimize negative consequences and benefit from climate change in Siberian forests we suggest potential adaptive measures depending on management goals.
Wildfires are a dominant and integral component of the Alaskan boreal zone that affect the species composition and age-structure of vegetation. Climate change within Alaska is likely to result in increased drought and longer fire seasons, as well as increases in the severity and frequency of fires. Post-fire regrowth has been shown to be highly dependent on pre-fire species composition and stand structure as well as post-fire soil conditions such as organic layer depth and soil moisture. Vegetation characteristics in turn can act to influence fire frequency and severity, through differences in fuel amount and flammability, as well as soil characteristics, through species-specific effects on litter quality and decomposition rate.
Boreal forests are currently experiencing rapid changes. CO2 enriched conditions and warming with longer growing seasons are anticipated to increase boreal forests' growth and productivity, yet the frequency and severity of droughts and disturbances is also expected to increase in these forests. Increased growth and productivity under CO2 enrichment may reduce the vulnerability of trees to extreme events such as drought. It, however, could also increase tree mortality through increased competition for light and soil resources, or through acceleration of tree lifecycle.
Northeastern U.S. ecosystems are experiencing warmer winters and declining seasonal snowpack. Site-level evidence from this region indicates that altered winter conditions with continued climate change will lead to a complex suite of changes to forest nutrient and carbon cycling. However, existing studies are limited in temporal and spatial extent. The northeast region experiences high variability in winter conditions across a relatively small latitudinal gradient, and it is likely that responses to winter climate change depend on the historic conditions to which plants and soil organisms are adapted. Therefore, the importance of winter for forest productivity may vary considerably across a latitudinal and winter climate gradient.
Forest management is one of the most extensive and continual drivers of ecosystem dynamics, yet little is known about how forest management decisions influence forest ecology at regional to continental scales. Our research uses a macrosystems approach to expand our understanding of these mechanisms in the face of a changing climate, and incorporate them into Earth system models (ESMs). We outlines an ongoing research project focusing on the forests of the continental US, which seeks to answer the question: "Does Forest management matter?" We describe a framework for mapping and scaling forest management for ESMs that can expand the geographic scale of analysis and depth of questions that could be asked.
Forest ecosystems of the Russian Federation are expected to face high risks under environmental dynamics related to climate change. Analyzing the likely impacts of climate change on forest ecosystems becomes crucial to understand the potential adaptation of forests, to guide management strategies, as well as to preserve their ecosystem services. With the aim to provide information on the possible modifications of geographic ranges, on the medium to long term, for some Russian dominant forest species under climate change, we applied a Cascade Ensemble System (CES) approach. This consists in combining an Ensemble Platform for Species Distribution Models (SDMs) to six bias-corrected Earth System Model (ESM) projections, in turn driven by two Representative Concentration Pathways (RCPs) proxy of greenhouse gas emission scenarios, in order to obtain maps of future suitability for forest species. The suitability information is then flagged with information about its ”likelihood”, adopting the IPCC terminology based on consensus among projections. Maps of aggregated changes were created in order to identify areas potentially more vulnerable to climate change. Results show that possible impacts of climate change (either gain or loss) were diversified across species with a pronounced Northward shift of the ranges. Further analyses were performed at sub-regional level revealing the potential for the Arctic Circle to become a refuge area for some conifer species. Species-aggregated c...
Isoprene and monoterpenes (MTs) are among the most abundant and reactive volatile organic compounds produced by plants (biogenic volatile organic compounds). We conducted a meta‐analysis to quantify the mean effect of environmental factors associated to climate change (warming, drought, elevated CO2, and O3) on the emission of isoprene and MTs. Results indicated that all single factors except warming inhibited isoprene emission. When subsets of data collected in experiments run under similar change of a given environmental factor were compared, isoprene and photosynthesis responded negatively to elevated O3 (−8% and −10%, respectively) and drought (−15% and −42%), and in opposite ways to elevated CO2 (−23% and +55%) and warming (+53% and −23%, respectively). Effects on MTs emission were usually not significant, with the exceptions of a significant stimulation caused by warming (+39%) and by elevated O3 (limited to O3‐insensitive plants, and evergreen species with storage organs). Our results clearly highlight individual effects of environmental factors on isoprene and MT emissions, and an overall uncoupling between these secondary metabolites produced by the same methylerythritol 4‐phosphate pathway. Future results from manipulative experiments and long‐term observations may help untangling the interactive effects of these factors and filling gaps featured in the current meta‐analysis.
Soil nitrogen (N) loss has been predicted to intensify with increased global precipitation changes. However, the relative contributions of leaching and gaseous N emissions to intensified N losses are largely unknown. Thus, we simulated intensified precipitation seasonality in a subtropical forest by extending the dry season via rainfall exclusion and increasing the wet‐season storms via irrigation without changing the total annual precipitation. Extending the dry season length increased the monthly mean soil NO3− content by 25%–64%, net N mineralization rate by 32%–40%, and net nitrification rate by 25%–28%. After adding water in the wet season, the monthly NO3− leaching was enhanced by 43% in the relatively dry year (2013, 2,094‐mm annual rainfall), but reduced by 51% in the relatively wet year (2014, 1,551 mm). In contrast, the monthly mean N2O emissions were reduced by 24% in 2013 but increased by 78% in 2014. Overall, the annual inorganic N content was decreased significantly by the precipitation changes. Decrease of soil inorganic N might be linked to the enhanced NO3− leaching in 2013, and be linked to the increased N2O emissions in 2014. However, in both years the annual total amount of N lost through leaching was significantly greater than that through N2O emissions. The enhanced N2O emissions driven by wet‐season storms were correlated with an increase in nirS abundance. Our results suggest that increased frequency of droughts and storms will decrease soil inorganic N content in warm and humid subtropical forests mainly through enhanced leaching losses.
This study provides an overview of mangrove forestations in Abu Dhabi and its numerous environmental benefits including the sequestering of atmospheric carbon dioxide (CO2) and climate change mitigation. It describes the efforts to increase mangrove plantation and the site selection criteria for mangrove establishment in the coastal land. It also discusses the natural regeneration and propagation of mangroves through seeds and seedlings, and the favorable conditions for the trees to reproduce and grow. Furthermore, the study describes the adaptation and occurrences of mangroves worldwide and in Abu Dhabi, the main anthropogenic and natural threats to mangroves ecosystems, and some of the biological & physiological characteristicsof mangrove trees such as the aerial roots “pneumatophore” and the salts glands that assist the trees to survive the harsh climate conditions. Finally, the study also highlights the importance of mangroves in climate change mitigation, carbon sequestration, and coastline protection. The valuable information presented can help in managing and preserving this unique ecosystem and support climate change mitigation and adaptation, and achieve environmental sustainability
Boreal forests form the largest and least disturbed forest biome in the northern hemisphere. However, anthropogenic pressure from intensified forest management, eutrophication, and climate change may alter the ecosystem functions of understory vegetation and services boreal forests provide. Swedish forests span long gradients of climate, nitrogen deposition, and management intensity. This makes them ideal to study how the species composition and functions of other, more pristine, boreal forests might change under increased anthropogenic pressure. Moreover, the National Forest Inventory (NFI) has collected systematic data on Swedish forest vegetation since the mid-20th century. We use this data to quantify changes in vegetation types between two periods, 1953-1962 and 2003-2012. The results show changes in forest understory vegetation since the 1950s at scales not previously documented in the boreal biome. The spatial extent of most vegetation types changed significantly. Shade-adapted and nutrient-demanding species (those with high specific leaf area) have become more common at the expense of light-demanding and nutrient-conservative (low specific leaf area) species. The cover of ericaceous dwarf shrubs decreased dramatically. These effects were strongest where anthropogenic impacts were greatest, suggesting links to drivers such as nitrogen deposition and land-use change. These changes may impact ecosystem functions and services via effects on higher trophic levels and faster plant litter decomposition in the expanding vegetation types. This, in turn, may influence nutrient dynamics, and consequently ecosystem productivity and carbon sequestration.
Climate-based predictions of species distributions provide information for understanding impacts of climate change. However, species distribution models do not include land management zones as input. Improving understanding of geographic shifts will require consideration of management zones where certain activities could facilitate or impede responses to climate change. For instance, assisted migration to overcome dispersal barriers could be challenged in areas designated for “untrammeled” character (e.g., wilderness). Alternatively, large tracts of land with uninterrupted disturbance regimes may offer opportunities for disturbance-facilitated establishment of species into new areas. We focused on current and future distributions of whitebark pine (Pinus albicaulis), a keystone species of treeline. Current and future “climate space” of whitebark pine were overlaid onto ecoregions and land management zones. We also used different thresholds of predicted presence to assess the sensitivity of patterns to varying levels of confidence.
Climate change is a major concern for forest managers involved in ecological restoration, in part because they are responsible for planting trees that will be components of a healthy and resilient ecosystem for the next 100 to 200 years. Anticipated changes in climate include changes in temperature, precipitation, and length of the growing season. Trees locally adapted to their native climate may not be able to survive or grow in novel climates. Current afforestation strategies may thus require the use of seeds from populations already adapted to future climates.
In some Rocky Mountain treeline ecotones, whitebark pine (Pinus albicaulis) serves as a tree island initiator more frequently than Engelmann spruce (Picea engelmannii) or subalpine fir (Abies lasiocarpa). Tree island initiation begins with a solitary krummholz tree, which provides sufficient leeward protection so that another tree may become established, resulting in a tree island. More trees may establish on the lee side over time. Whitebark pine mortality from white pine blister rust (pathogen: Cronartium ribicola) reduces opportunities for such facilitation. Will declines in whitebark pine alter treeline response to climate warming? We have surveyed various treeline communities from the Greater Yellowstone area (Wyoming, Montana, and Idaho, USA) to whitebark pine’s northern limit.
Simulations suggest that for both species the common phenological strategy of one generation annually (univoltine) will shift northward with warming throughout this century. As optimum habitat for I. typographus univoltinism shifts northward, habitat supporting a 2nd generation, a historically common strategy in warm European Picea forests, expands on both continents. In contrast, a 2nd D. ponderosae generation has been historically rare due to traits that evolved for phenological synchrony in its cool native habitats. As thermal habitat for D. ponderosae univoltinism shifts northward, suitability for a 2nd generation is limited to the warmest Pinus forests on both continents. In the near future (2011–2040), models project extensive thermal suitability for inter-continental establishment of both species, highlighting the need for effective mitigation policies and continued monitoring at ports in an era of climate change and increasing global trade. Throughout the century, thermal suitability remains high for I. typographus population success on both continents, for D. ponderosae in warm areas of Europe, and for D. ponderosae expansion into novel North American Pinus habitats. Portions of the historical D. ponderosae range, however, are projected to become thermally unsuitable.
FORMIT-M is a simple-to-use open-access forest management simulator for Europe. It combines process-based and data-based components. It uses standard forest inventory data and climate scenarios as input. Conventional and alternative management scenarios follow practices in European regions. Management had a greater impact on carbon stocks and harvest potential than climate change.
We assess various policy needs for biomass data and recommend a long-term collaborative effort among forest biomass data producers and users to meet these needs. A gap remains, however, between what can be achieved in the research domain and what is required to support policy making and meet reporting requirements. There is no single biomass dataset that serves all users in terms of definition and type of biomass measurement, geographic area, and uncertainty requirements, and whether there is need for the most recent up-to-date biomass estimate or a long-term biomass trend. The research and user communities should embrace the potential strength of the multitude of upcoming missions in combination to provide for these varying needs and to ensure continuity for long-term data provision which one-off research missions cannot provide. International coordination bodies such as Global Forest Observations Initiative (GFOI), Committee on Earth Observation Satellites (CEOS), and Global Observation of Forest Cover and Land Dynamics (GOFC‐GOLD) will be integral in addressing these issues in a way that fulfils these needs in a timely fashion. Further coordination work should particularly look into how space-based data can be better linked with field reference data sources such as forest plot networks, and there is also a need to ensure that reference data cover a range of forest types, management regimes, and disturbance regimes worldwide.
We carried out the first genome-wide population genomics study in a Neotropical tree, Handroanthus impetiginosus (Bignoniaceae), sampling 75,838 SNPs by sequence capture in 128 individuals across 13 populations. We found evidences for local adaptation using Bayesian correlations of allele frequency and environmental variables (32 loci in 27 genes) complemented by an analysis of selective sweeps and genetic hitchhiking events using SweepFinder2 (81 loci in 47 genes). Fifteen genes were identified by both approaches. By accounting for population genetic structure, we also found 14 loci with selection signal in a STRUCTURE-defined lineage comprising individuals from five populations, using Outflank. All approaches pinpointed highly diverse and structurally conserved genes affecting plant development and primary metabolic processes. Spatial interpolation forecasted differences in the expected allele frequencies at loci under selection over time, suggesting that H. impetiginosus may track its habitat during climate changes. However, local adaptation through natural selection may also take place, allowing species persistence due to niche evolution. A high genetic differentiation was seen among the H. impetiginosus populations, which, together with the limited power of the experiment, constrains the improved detection of other types of soft selective forces, such as background, balanced, and purifying selection. Small differences in allele frequency distribution among widespread populations and the low number of loci with detectable adaptive sweeps advocate for a polygenic model of adaptation involving a potentially large number of small genome-wide effects.
The international legal framework for valuing the carbon stored in forests, known as "Reducing Emissions from Deforestation and Forest Degradation' (REDD+), will have a major impact on indigenous peoples and forest communities. The REDD+ regime contains many assumptions about the identity, tenure and rights of indigenous and local communities who inhabit, use or claim rights to forested lands, the authors bring together expert analysis of public international law, climate change treaties, property law, human rights and indigenous customary land tenure to provide a systemic account of the laws governing forest carbon sequestration and their interaction, their work covers recent developments in climate change law, including the Agreement from the Conference of the Parties in Paris that came into force in 2016. The Impact of Climate Change Mitigation on Indigenous and Forest Communities is a rich and much-needed contribution to contemporary understanding of this topic.
We compare model results for vegetation cover and carbon dynamics over the period 1895–2100 assuming: 1) unlimited wildfire ignitions versus stochastic ignitions, 2) no fire, and 3) a moderate CO2 fertilization effect versus no CO2 fertilization effect. Carbon stocks decline in all scenarios, except without fire and with a moderate CO2 fertilization effect. The greatest carbon stock loss, approximately 23% of historical levels, occurs with unlimited ignitions and no CO2 fertilization effect. With stochastic ignitions and a CO2 fertilization effect, carbon stocks are more stable than with unlimited ignitions. For all scenarios, the dominant vegetation type shifts from pure conifer to mixed forest, indicating that vegetation cover change is driven solely by climate and that significant mortality and vegetation shifts are likely through the 21st century regardless of fire regime changes.
Notre étude se focalise sur les effets de l’abroutissement par les grands ongulés et du changement climatique sur la régénération du sapin, du hêtre et de l’épicéa en mélange. Nous utilisons pour cela diverses approches. Nous montrons que la germination et l’installation de semis de hêtres n’est pas affectée par l’éclairement au sol plus faible en situation de mélange. Nous mettons en évidence une quasi-inversion d’essences entre sapin et épicéa au niveau de la strate de régénération, bénéficiant à l’épicéa, lorsqu’ils sont soumis à une forte pression d’abroutissement. A l’échelle des traits foliaires, nous trouvons des réponses différentes entre les trois essences aux pressions du climat et de l’abroutissement, le sapin étant le seul à exprimer une réponse claire à l’abroutissement (tissus plus résistants, augmentation du rapport C/N foliaire). Nos résultats démontrent également une diminution de l’abroutissement avec l’augmentation de la température hivernale et un effet plus important de l’abroutissement que de la température printanière sur la croissance des semis de sapin, hêtre, érable. Enfin, via une approche de modélisation, nous avons simulé la dynamique d’un peuplement mélangé de sapin, hêtre et épicéa sur une durée de 100 ans, et montré une modification des seuils de tolérance à la sécheresse par l’abroutissement, et vaildé la possible disparition du sapin dans des scénarios comprenant abroutissement et changement climatique.
The quantitative knowledge of global forest litterfall is very important for understanding the global biogeochemical cycle and evaluating of forest ecosystem services. Our aims are to show the spatio‐temporal patterns of forest litterfall and the variation in different forest types and climate zones in the world. We compiled the global forest litterfall dataset of 2347 total litterfall and 1507 leaf litterfall measurements by a survey of literature published. The total litterfall and leaf litterfall were estimated in 2000 and 2009, respectively, through raster and vector calculation based on remote sensing‐based global vegetation cover data.
Les régions alpines sont particulièrement sensibles aux changements climatiques en cours. Ainsi, l’ouest des Alpes s’est réchauffé deux fois plus vite que l’hémisphère Nord au cours du XXème siècle. Les rythmes saisonniers des arbres, comme beaucoup d’autres organismes, sont fortement modifiés par le réchauffement climatique. La phénologie et les variations temporelles fines du climat apparaissent comme des composantes incontournables à prendre en compte pour prédire la répartition des espèces. L’objectif principal de ce travail de thèse a été de comprendre la réponse de la phénologie des espèces arborées au réchauffement climatique dans les Alpes et de développer des outils pour évaluer cette réponse dans le futur. Pour atteindre cet objectif nous avons utilisé des données phénologiques (débourrement, floraison, senescence foliaire,) pour le noisetier, le frêne, le bouleau, le mélèze et l’épicéa, issues du programme de sciences participatives Phénoclim
The structure and composition of forest ecosystems are expected to shift with climate‐induced changes in precipitation, temperature, fire, carbon mitigation strategies, and biological disturbance. These factors are likely to have biodiversity implications. However, climate‐driven forest ecosystem models used to predict changes to forest structure and composition are not coupled to models used to predict changes to biodiversity. We proposed integrating woodpecker response (biodiversity indicator) with forest ecosystem models. Woodpeckers are a good indicator species of forest ecosystem dynamics, because they are ecologically constrained by landscape‐scale forest components, such as composition, structure, disturbance regimes, and management activities. In addition, they are correlated with forest avifauna community diversity. In this study, we explore integrating woodpecker and forest ecosystem climate models.
Belgian’s future climate is projected to be warmer, with a higher frequency of extreme precipitation events. Parental temperature influenced the germination success, bud phenology and growth of oak and beech seedlings, but we did not observe DNA methylationthat could help to explain the phenological change mediated by the parental temperature. Studies on both saplings and mature treessuggested that drought may influence ecosystem processes in young and mature forests, affecting the growth and vitality of trees. Despite the high awareness of climate change as an issue in forest management and the need to adjust management practices, we found a lack of knowledge on how to adapt forest management in order to mitigate the vulnerability of forests under changing climate conditions. The results of this project confirm that admixing tree species in oak and beech stands is a good adaptation measure across all forest development stages.
Economic consequences of altered survival probabilities under climate change should be considered for regeneration planning in Southeast Germany. Findings suggest that species compositions of mixed stands obtained from continuous optimization may buffer but not completely mitigate economic consequences. Mixed stands of Norway spruce ( Picea abies L. Karst . ) and European beech ( Fagus sylvatica L.) (considering biophysical interactions between tree species) were found to be more robust, against both perturbations in survival probabilities and economic input variables, compared to block mixtures (excluding biophysical interactions).
We show that current management policies are threatening biodiversity in Romania, and changes in forest management policies are urgently needed to halt the loss of habitats of protected species. Although recent management policies likely did lead to good tree species connectivity, habitats of protected species are becoming increasingly fragmented by logging. Adopting policies to protect forest habitats of protected species, limiting large-scale salvage logging within protected areas, and restricting road building to reduce forest fragmentation are crucial steps towards the long-term persistence of biodiversity hotspots in the Romanian Carpathians.
Reducing Emissions from Deforestation and forest Degradation (REDD+) has emerged as a promising climate change mitigation mechanism in developing countries. In order to identify the enabling conditions for achieving progress in the implementation of an effective, efficient and equitable REDD+, this paper examines national policy settings in a comparative analysis across 13 countries with a focus on both institutional context and the actual setting of the policy arena. The evaluation of REDD+ revealed that countries across Africa, Asia and Latin America are showing some progress, but some face backlashes in realizing the necessary transformational change to tackle deforestation and forest degradation. A Qualitative Comparative Analysis (QCA) undertaken as part of the research project showed two enabling institutional configurations facilitating progress: (1) the presence of already initiated policy change; and (2) scarcity of forest resources combined with an absence of any effective forestry framework and policies. When these were analysed alongside policy arena conditions, the paper finds that the presence of powerful transformational coalitions combined with strong ownership and leadership, and performance-based funding, can both work as a strong incentive for achieving REDD+ goals
Tropical forest management has a vital role to play in improving local adaptive capacity to climate change. Although forests are themselves often vulnerable to the consequences of climate change – such as the increased risk of fires or sea level rise – concerted management can also enhance the resilience of local communities to climate change-related events such as storm surges, coastal erosion, and landslides. This chapter explores the many ways that strategic forest management plays a role in climate change adaptation in Bangladesh, reviewing recent initiatives for conservation of the Sundarbans Reserve Forest, coastal afforestation, and reforestation of hill tract forests. Community-based social forestry, livelihood diversification, as well as disaster management are also key components of many of these programs. However, because baseline data and continual monitoring have been sparse, important uncertainties concerning long-term project effectiveness remain. Additional research is therefore necessary to evaluate the successfulness of forest-based adaptation in Bangladesh.
The objective of the FRESh LIFE project is to demonstrate the possible integration of remote sensing technologies, in order to provide high resolution spatial information on selected SFM indicators under Forest Europe process, at the forest management unit scale. In this study we present the activities of the FRESh LIFE project carried out in a Mediterranean study area (Central Italy) to create a Forest Information System (DSS). Forest inventory data and high resolution remote sensing data acquired by drones (UAV) were used to produced maps of SFM Indicators. These maps were implemented in the Forest Information System to support forest managers in the decision making process
We compared tree-ring parameters (RWI and the carbon isotope ratio: δ13C) and NDVI products with forest ecosystem CO2 fluxes estimated using the eddy covariance method, at a larch forest in eastern Siberia. The RWI and tree-ring δ13C correlated well with the ecosystem gross primary production (GPP), and their temporal stabilities were high during 2004–2014. However, the NDVI products did not show any temporally stable relationship with the GPP. This could be ascribed to significant changes in the understory vegetation in this forest, i.e., from dense cowberry to shrubs and moisture-tolerant grasses, because of an excessively moist environment during 2007–2008. Changes in the understory vegetation could be reflected by the NDVI products but not by the GPP. Our results indicate that it is more feasible to study forest carbon uptake using tree-ring parameters than using satellite-derived vegetation indices in such larch-dominated forest ecosystems in eastern Siberia.
Tree radial growth is widely found to respond differently to climate change across altitudinal gradients, but the relative roles of biotic factors (e.g. forest type, height and density) vs. climate gradient remain unclear. We sampled tree rings from 15 plots along a large altitudinal gradient in northeast China, and examined how climate gradient, forest type, height, tree size and density affect: (1) temporal growth variability [mean sensitivity (MS) and standard deviation (SD) of the chronologies], and (2) the relationship of ring width indices (RWI) with historical climate. We used BIC based model selection and variable importance to explore the major drivers of their altitudinal patterns.
Using the Random Forest ensemble learning classification tree system, we developed annual LULC maps in the CGE from 2002 to 2015 using a time series of cloud-free MODIS vegetation index products. The MODIS imagery was processed through a Gaussian weighted filter to further correct for cloud pollution and matched to visual interpretations of land cover and land use from available high spatial resolution imagery (WorldView-2, Quick Bird, Ikonos and GeoEye-1). Validation of LULC maps resulted in a Kappa of 0.87 (Sd = 0.008). We detected a gradual replacement of forested areas with agriculture (mainly grassland planted to support livestock grazing), and secondary vegetation (agriculture reverting to forest) across the CGE. Forest loss was higher between 2010–2015 when compared to 2002–2010. LULC change trends, deforestation drivers, and reforestation transitions varied according to administrative organization (countries: Panamanian CGE, Colombian CGE, and Ecuadorian CGE).
This section provides a summary of the implications of the developed 2.0 °C and 1.5 °C scenarios for global mean climate change. Specifically, we consider atmospheric CO2 concentrations, radiative forcing, global-mean surface air temperatures and sea level rise.
This paper examines the contributions of international forest governance to bilateral forest cooperation through a case study of the Republic of Korea (ROK). The ROK has shared its knowledge and experiences of successful reforestation in the context of the South-South Cooperation. The cooperation areas, activities, and structures determined in bilateral international forest agreements (memorandum of understanding) were analyzed in the context of the history of international forest governance. This paper examines the roles of voluntary agreements by focusing on global accountability and reciprocal interests in forest cooperation between the ROK and its partner countries when implementing global forest regimes. The findings provide information on bilateral forest cooperation agreements as an institutional policy instrument and contribute to solving global issues, such as deforestation, desertification, and climate change, and fulfilling the reciprocal interests among countries in the field of forestry.
The aim of this paper is to explore the nexus of climate change, land use, and conflict. A particular focus is placed on the human security risks associated with the three elements. Climate change has been perceived as a “threat multiplier,” directly aggravating human security risks, such as food and water insecurity, as well as indirectly contributing to (violent) conflict in regions vulnerable to climate change. In addition to climate change–related environmental risks, such as droughts and floods, land and land use can be affected by climate mitigation and adaptation measures. These include, for instance, large-scale renewable energy plants and relocation efforts. It is not only important for decision-makers to take climate change impacts into account but also to assess the indirect risks associated with climate change mitigation and adaptation measures. For further research, it is hence promising to explore how conflict-sensitive approaches to climate change adaptation and mitigation can be developed.
We reviewed five forest policies and three climate change related plans and policies regarding integration of forest and climate change issues in respective policies. Our review reveals that forest policies contain notable provisions in regard to the contribution of forestry to climate change mitigation and adaptation. However, new and emerging issues such as climate refugia and invasive species are least concerned in forest policies. Climate change policies also contain provisions for forest management focusing on the mobilization of forest user groups for carrying out adaptation activities at the local level. However, the implementation of both polices seems poor due to lack of legal framework. Therefore, formulation of legal framework for implementation of these policies is essential. Similarly, we suggest both policies need to be revised incorporating the provisions based on scientific findings and field experience.
This study characterises spectral features of structurally diverse mountain treeline ecotones. Variation in above-ground woody biomass is defined with an R2 up to 0.723. Simplified classes improve the discrimination of areas indicative of forest advance. We advance our ability to quantify environmental change impacts in mountain systems.
This is the first work to describe plant’s early life stages in the context of species distribution modeling and phenological adjustments. We discuss how plant responses to water availability during early life stages influence species range formation and abundance. We highlight the variation in drought sensitivity of various life stages and propose ways to incorporate this into species distribution models.
Our findings show that coverage of forest issues in the media is dominated by fires, while discussion of pest outbreaks and forest sustainability are far less prevalent. While climate change is a topic that is covered in these newspapers as frequently as forest-related issues, there is very little overlap in this coverage and the articles that do discuss both forests and climate change are not associated with extreme events. In subsequent thematic analysis, we find that forest fire coverage tends to be restricted to discussion of single themes, particularly, risk or the economy, while avoiding discussion of multiple themes and their interactions. Mention of the causes of climate change is rare in coverage of either of these forest-related issues. Possible explanations for avoidance of climate change discussion in forest fire media coverage are discussed.
Here, we review this approach by first providing a basic background regarding the major trait axes generally of interest. We then discuss how these axes may be or have been applied from ecosystem to community and population studies. In doing so, we highlight where the functional trait research program has failed in tropical tree ecology and where it can be improved or strengthened. Finally, we provide a perspective regarding how functional trait and emerging ‘omics approaches can be integrated to address large questions facing the field. Our intention throughout is to provide an entryway into this literature for an early career researcher rather than a comprehensive review of all possible studies that have taken place in tropical forests.
Our results suggest that reports about bird decline in forests should separate between migratory and non-migratory bird species. Efforts to mitigate the general decline in bird abundance should focus on land-use systems other than forests and support sustainable forest management independent of economic conditions.
Recent articles show that climate-change science lacks multi-scale ecosystem demographics and dynamics data to test, improve and validate its models and recommendations. This is a major drawback, one that leads to skepticism from managers, policy makers and the public. It may be at least, partially compensated if the scientific community has access to, and analyzes data from, natural habitat management, particularly forest management.
There are 30,379 ha of restored active-fire forest in the Sierra Nevada. Eighty-one percent of active-fire forests are in National Parks. Variation in structure and pattern follows climatic and topographic templates. Climate and topography interact in complex, context-dependent ways. Restoration should create heterogeneous structure congruent with physiography.
The tree census, paleopollen, fossil charcoal, human population, and climate data presented here provide unique support for important anthropogenic influences on fire over the last 2000 years in the eastern USA. This includes multiple instances of climate fire anomalies that may be best explained by the role of human-caused burning.
Energy and water limitations of tree growth remain insufficiently understood at large spatiotemporal scales, hindering model representation of interannual or longer-term ecosystem processes. By assessing and statistically scaling the climatic drivers from 2710 tree-ring sites, we identified the boreal and temperate land areas where tree growth during 1930–1960 CE responded positively to temperature (20.8 ± 3.7 Mio km2; 25.9 ± 4.6%), precipitation (77.5 ± 3.3 Mio km2; 96.4 ± 4.1%), and other parameters. The spatial manifestation of this climate response is determined by latitudinal and altitudinal temperature gradients, indicating that warming leads to geographic shifts in growth limitations. We observed a significant (P < 0.001) decrease in temperature response at cold-dry sites between 1930–1960 and 1960–1990 CE, and the total temperature-limited area shrunk by −8.7 ± 0.6 Mio km2. Simultaneously, trees became more limited by atmospheric water demand almost worldwide. These changes occurred under mild warming, and we expect that continued climate change will trigger a major redistribution in growth responses to climate.
A record 1.2 million ha burned in British Columbia, Canada's extreme wildfire season of 2017. Key factors in this unprecedented event were the extreme warm and dry conditions that prevailed at the time, which are also reflected in extreme fire weather and behavior metrics. Using an event attribution method and a large ensemble of regional climate model simulations, we show that the risk factors affecting the event, and the area burned itself, were made substantially greater by anthropogenic climate change. We show over 95% of the probability for the observed maximum temperature anomalies is due to anthropogenic factors, that the event's high fire weather/behavior metrics were made 2–4 times more likely, and that anthropogenic climate change increased the area burned by a factor of 7–11. This profound influence of climate change on forest fire extremes in British Columbia, which is likely reflected in other regions and expected to intensify in the future, will require increasing attention in forest management, public health, and infrastructure.
The resilience, health, and stability of forest ecosystems are crucial to a large set of Forest Ecosystem Services (FES), intended as the direct and indirect contributions to human well-being by ecosystems, such as timber and non-timber products, habitats for wildlife, sinks to regulate and mitigate biogeochemical and hydrological cycles, and cultural and historical heritages. In this context, the report “Mediterranean forest ecosystem services and their vulnerability” by CMCC researchers Sergio Noce and Monia Santini (IAFES Division) aims at providing a synthetic overview about the existing key forest ecosystem services in the Mediterranean area, and about how they seem currently impacted by climate and, in some cases, by land use changes, human pressures and/or wrong management. Attention is paid to known risk hot spots and drivers of these risks, by relying on scientific evidence from available literature and existing datasets.
According to climate projections, global warming is associated with increasing temperatures and dry spells in some parts of the world, especially the Mediterranean area. This climate change has already triggered increases in wildfire danger and fire season length in Southern Europe and is expected to amplify in the forthcoming decades. However, it is quite challenging for the scientific community to assess the intensity of these changes, because (i) the trend relies on the greenhouse gases (GHG) emission scenario and (ii) fire occurrence depends on multiple factors (including climate, but not only). A proper assessment of the trend in terms of fire occurrence and of uncertainties associated with this increasing trend, still lacks, especially for the French territory. Our study refines traditional approaches of fire risk projection under climate change on two aspects: (i) the impact of climate prediction uncertaintieson the prediction of fire danger, and (ii) the translation of a danger index into a fire occurrence (per size classes).
A century of fire suppression across the Western United States has led to more crowded forests and increased competition for resources. Studies of forest thinning or stand conditions after mortality events have provided indirect evidence for how competition can promote drought stress and predispose forests to severe fire and/or bark beetle outbreaks. Here, we demonstrate linkages between fire deficits and increasing drought stress through analyses of annually resolved tree‐ring growth, fire scars, and carbon isotope discrimination (Δ13C) across a dry mixed‐conifer forest landscape. Although disturbance legacies contribute to local‐scale intensity of drought stress, fire deficits have reduced drought resistance of mixed‐conifer forests and made them more susceptible to challenges by pests and pathogens and other disturbances.
Tree communities have become increasingly dominated by large‐statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry‐affiliated genera have become more abundant, while the mortality of wet‐affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry‐affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate‐change drivers, but yet to significantly impact whole‐community composition. The Amazon observational record suggests that the increase in atmospheric CO2 is driving a shift within tree communities to large‐statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.
Potential fire intensity (PFI) is among the main drivers of fire–vegetation interactions, but how it varies across species ranges is unknown. We test whether PFI and crown fire likelihood (CFL) increase preferentially towards the warm/dry range margins of mountain trees.
Terrestrial ecosystems will be transformed by current anthropogenic change, but the extent of this change remains a challenge to predict. Nolan et al. looked at documented vegetational and climatic changes at almost 600 sites worldwide since the last glacial maximum 21,000 years ago. From this, they determined vegetation responses to temperature changes of 4° to 7°C. They went on to estimate the extent of ecosystem changes under current similar (albeit more rapid) scenarios of warming. Without substantial mitigation efforts, terrestrial ecosystems are at risk of major transformation in composition and structure.
Expected increase of temperature over France will alter the grapevine development. The rate of warming depends on the season and on the specific region. Simulation of future budburst strongly depends on the phenological model adopted. Most likely, climate change will induce a significant precocity of budburst day. The risk of tardive frost will likely increase in the continental regions of France
The adaptive capacity of long-lived organisms such as trees to the predicted climate changes, including severe and successive drought episodes, will depend on the presence of genetic diversity and phenotypic plasticity. Here, the involvement of epigenetic mechanisms in phenotypic plasticity toward soil water availability was examined in Populus×euramericana.
Forest canopies buffer climate extremes and promote microclimates that may function as refugia for understory species under changing climate. However, the biophysical conditions that promote and maintain microclimatic buffering and its stability through time are largely unresolved. We posited that forest microclimatic buffering is sensitive to local water balance and canopy cover, and we measured this effect during the growing season across a climate gradient in forests of the northwestern United States (US).
The approaches to assessing vulnerability can be categorized according to the focus they each provide. Contextual vulnerability addresses current issues of climate and is usually evaluated using participatory techniques with people who live in, or work with, forests. Outcome vulnerability looks at the biophysical vulnerability of forests; it is often used to assess the cause-and-effect of climate change on a biological system. Vulnerability assessments can be highly technical and quantitative, using advanced computer programs and geographic information systems, or they can be based on social science approaches to obtaining qualitative information from people.
Seedlings displayed substantial drought tolerance with most seedlings surviving for more than 2 wk under protracted drought. Seed size in combination with SLA predicted seedling growth under well-watered conditions and seed size predicted survival under drought. In contrast to our expectations, seedlings with lower SSD survived for longer without water. Our results suggest that dry-forest species will be differentially affected by the predicted increases in the duration of growing-season droughts, and detrimental effects will be more severe for species with smaller seeds.
Worldwide, trees are confronting increased temperature and aridity, exacerbating susceptibility to herbivory. Long-term studies comparing patterns of plant performance through drought can help identify variation among and within populations in vulnerability to climate change and herbivory. We use long-term monitoring data to examine our overarching hypothesis that the negative impacts of poor soil and herbivore susceptibility would be compounded by severe drought. We studied pinyon pine, Pinus edulis, a widespread southwestern tree species that has suffered extensive climate-change related mortality. We analyzed data on mortality, growth, male reproduction, and herbivory collected for 14-32 years in three areas with distinct soil-types. We used standardized precipitation-evapotranspiration index (SPEI) as a climate proxy that summarizes the impacts of drought due to precipitation and temperature variation on semi-arid forests. Overall, chronically water-stressed and herbivore-susceptible trees had smaller declines in performance relative to less-stressed trees during drought years. These long-term findings support the idea that stressed trees might be more resistant to drought since they may have adapted or acclimated to resist drought-related mortality.
This study uses the dynamic forest ecosystem model ForSAFE to estimate the combined effect of changes in temperature and precipitation on forest carbon stocks in Sweden. The model is used to simulate carbon stock changes in 544 productive forest sites from the Swedish National Forest Inventory. Forest carbon stocks under two alternative climate scenarios are compared to stocks under a hypothetical scenario of no climate change (baseline). Results show that lower water availability in the future can cause a significant reduction in tree carbon compared to a baseline scenario, particularly expressed in the southern and eastern parts of Sweden. In contrast, the north-western parts will experience an increase in tree carbon stocks. Results show also that summer precipitation is a better predictor of tree carbon reduction than annual precipitation. Finally, the change in soil carbon stock is less conspicuous than in tree carbon stock, showing no significant change in the north and a relatively small but consistent decline in the south. The study indicates that the prospect of higher water deficit caused by climate change cannot be ignored in future forest management planning.
In this study, we apply dendroclimatological methods to investigate the growth response of the main forest species present in Moncayo Natural Park to climate to assess their current relationship and to model these responses over the potential distribution of each species across the study area. Our results revealed large differences in the response of beech, pine and Pyrenean oak to prevailing climate factors and indicated species-specific patterns of climate sensitivity. The general importance of summer conditions for tree growth was confirmed. In addition, we found directional trends in correlation with specific climate factors along spatial gradients; these results are consistent with the autoecology of the studied species. Based on these findings, we present a new model approach that can serve as a key tool for forest managers to design forest communities that are more stable during climatic change.
Forest conservation and carbon sequestration efforts are on the rise, yet the long‐term stability of these efforts under a changing climate remains unknown. We generate nearly three decades of remotely‐sensed canopy water content throughout California, which we use to determine patterns of drought stress. Linking these patterns of drought stress with meteorological variables enables us to quantify spatially explicit biophysical drought resistance in terms of magnitude and duration. These maps reveal significant spatial heterogeneity in drought resistance, and demonstrate that almost all forests have less resistance to severe, persistent droughts. By identifying the spatial patterning of biophysical drought resistance, we quantify an important component of long‐term ecosystem stability that can be used for forest conservation, management, and policy decisions.
As the simulation results indicates significant warming under even under mid emission trajectory RCP 4.5, further enhanced research is required to understand how different predominant endemic species behave under the drastic or slow alterations in the climate and growing conditions in future. This study also attempted to evaluate the existing adaptive conservation plans in the forest sector in the state and the need for strengthening its resilience.
Climate scenarios for Slovenia suggest an increase in the mean annual temperature by 2 °C over the next six decades, associated with changes in the seasonal distribution of precipitation. European beech is an ecologically and economically important forest species in Europe, so it is important to understand the influence of changing conditions on its phenology and productivity for the upcoming years. We hypothesise that the ongoing warming and reduction in precipitation during the growing season will shorten the period of xylem development, thus limiting beech growth in the next decades.
Climate and disturbance alter forest dynamics, from individual trees to biomes and from years to millennia, leaving legacies that vary with local, meso‐ and macroscales. Motivated by recent insights in temperate forests, we argue that temporal and spatial extents equivalent to that of the underlying drivers are necessary to characterize forest dynamics across scales. We focus specifically on characterizing mesoscale forest dynamics because they bridge fine‐scale (local) processes and the continental scale (macrosystems) in ways that are highly relevant for climate change science and ecosystem management. We revisit ecological concepts related to spatial and temporal scales and discuss approaches to gain a better understanding of climate–forest dynamics across scales.
Forest transitions occur when net reforestation replaces net deforestation in places. Because forest transitions can increase biodiversity and augment carbon sequestration, they appeal to policymakers contending with the degrading effects of forest loss and climate change. What then can policymakers do to trigger forest transitions? The historical record over the last two centuries provides insights into the precipitating conditions.
The carbon isotope composition (δ13C) in tree rings were used to derive the intrinsic water-use efficiency (iWUE) of Araucaria araucana trees of northern Patagonia along a strong precipitation gradient. It is well known that climatic and ontogenetic factors affect growth performance of this species but little is known about their influence in the physiological responses, as iWUE. Thus, the main objective of this study was to assess the physiological reactions of young and adult trees from two open xeric and two moderately dense mesic A. araucana forests to the increases in atmospheric CO2 (Ca) and air temperature during the 20th century, and to relate these responses with radial tree growth.
This special issue of Journal of Agricultural Meteorology is dedicated to the original articles derived from the organized sessions of the 28th IUFRO Biennial Conference of Research Group 7.01 as follows: (1) Asian forest ecosystem under changing environment, (2) Developing detection, monitoring and evaluation, (3) Ecophysiological and genetic understanding of plant responses, (4) Water and nutrient cycles in forest ecosystems, (5) Modelling and risk assessment, and (6) Forest ecosystems under multiple stressors.
Forest ecosystems in the United States (U.S.) are facing major challenges such as climate change, exotic species invasions, and landscape fragmentation. It is widely believed that forest composition in the eastern U.S. is transitioning from shade-intolerant, fire-tolerant species to shade-tolerant, fire-intolerant species, but most evidence is anecdotal or localized. No comprehensive studies exist to quantify the shifts in forest composition across multiple genera at a regional scale. Here, we examined the genus-level compositional changes in eastern U.S. forests to: (1) quantify the extent and magnitude of this transition, and (2) assess the influence of shade and fire tolerance traits on abundance change.
Cet article s’intéresse à la relation entre le Hêtre (Fagus sylvatica L.) et son environnement à l’échelle de la Belgique. L’accroissement radial a été utilisé pour évaluer l’effet des changements globaux, et plus particulièrement du changement climatique, sur le développement et la vitalité du Hêtre depuis le début du XXe siècle. L’accroissement moyen du Hêtre à l’échelle de la Belgique a diminué et sa variabilité a augmenté. Le climat a eu une influence grandissante sur l’accroissement, devenue prépondérante à partir du début des années 1990. Les accroissements de l’ensemble des arbres se sont synchronisés, principalement sous l’effet de l’augmentation de la fréquence et de l’intensité des canicules estivales et des sécheresses printanières. Les résultats sont interprétés sur la base des connaissances sur l’écophysiologie du Hêtre et les conséquences du changement climatique en cours et futur sont discutées.
We compared the responses of two broadleaved tree species (Fagus sylvatica and Quercus petraea) and two conifer tree species (Pinus sylvestris and Picea abies) to climatic transfers by fitting models containing the same climatic variables. We used published data from European provenance test networks to model the responses of individual populations nested within species. A mixed model approach was applied to develop a response function for tree height over climatic transfer distance, taking into account the climatic conditions at both the seed source and the test location.
We compared vegetation activities of two typical natural reserves (Gongbu natural reserve, GNR, and Yarlung zangbo river grand canyon natural reserve, YNR) and their surroundings in southeastern Tibet (outside of the natural reserves, ONR) using long-term satellite NDVI dataset. Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.
The contribution of plasticity to intra-specific 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 characterised by decreasing radial growth (mainly shaped by precipitation-related variables in our model); considering trait co-variation improved single-trait predictions. Population responses to climate across large geographical gradients are trait-dependent, indicating that multi-trait combinations are needed to understand species' sensitivity to climate change and its variation across distribution ranges.
Forests are Europe’s biggest carbon sinks and forestry the sector with the greatest potential to remove carbon dioxide from the atmosphere in the quantities needed to meet the bloc’s objectives under the Paris Agreement. Can EU forests mitigate climate change? In this Special Report, EURACTIV looks at how the forestry sector can help meet the EU’s goal of slashing net emissions by 40% by 2030, compared to 1990 levels.
Forests played an important role in carbon sequestration during the past two decades. Using a model tree ensemble method (MTE) to regress the seven reflectance bands of EOS-Terra-MODIS satellite data against country level forest biomass carbon density (BCD) of 2001–2005 provided by United Nations’s Forest Resource Assessment (FRA), we developed a global map of forest BCD at 1 km×1 km resolution for both 2001–2005 and 2006–2010.
This study examines the effects of future climate changes on watershed hydroecology, including runoff, evapotranspiration, soil moisture content, gross primary production (GPP), and photosynthetic productivity (PSNnet), by applying the Regional Hydroecological Simulation System model to the Seolmacheon catchment (8.5 km2).
Through comparative analyses across Gcm versions, we identified tree species meta-groups, which are more adapted than ecological guilds to describe the diversity of tree species dynamics and their responses to climate change. Projections under constant climate were consistent with a forest ageing phenomenon, with a slowdown in tree growth and a reduction of the relative abundance of short-lived pioneers. Projections under climate change showed a general increase in growth, mortality and recruitment. This acceleration in forest dynamics led to a strong natural thinning effect, with different magnitudes across species. These differences caused a compositional shift in favour of long-lived pioneers, at the detriment of shade-bearers. Consistent with other field studies and projections, our results show the importance of elucidating the diversity of tree species responses when considering the general sensitivity of Central African forests dynamics to climate change.
We analyzed tree rings from four conifers (Picea abies, Abies alba, Larix decidua, Pseudotsuga menziesii) regarding their intra-specific adaptation potential when trees are growing at the warm and dry margins of species distributions. Our study comprises data from four common garden experiments (45 provenances and a total of 743 trees) and assessed growth response at different temporal scales from decades (long-term) to only a few event years (short-term) and finally for density fluctuations within one year (sudden response). We observed significant variation among provenances at all time-scales, but with varying degree among species. However, variation in short-term response (drought years) was remarkably unstable across all species, when the seasonal variation of drought occurrence was considered. Silver-fir and Douglas-fir showed significant associations between seed-source climate and growth response as well as trade-offs between early- and latewood growth reaction which strongly suggests that growth responses are adaptive. Intra-specific variation in conifers in response to drought will probably be sufficient to mitigate climate change consequences on forest growth, but growth-environment interactions as well as dependencies between temporal scales could create major pitfalls for adaptive forest management in the future.
ere we report on biomass production in a typical nitrogen-limited boreal Picea abies forest, exposed to 18 years of soil warming manipulation (+5 °C) at a plot scale (100 m2). We show that two decades of soil warming elicited only short-duration growth responses, thus not significantly increasing aboveground biomass accumulation. Furthermore, in combination with published work from this forest, our results suggest that increased decomposition is slight and ephemeral, and increased fine root production and turnover in deeper soil may be greater than increased decomposition, netting slightly more biomass, perhaps conserving the soil carbon stock. Thus, this long-term study does not support the notion that the projected increase in soil temperatures will cause either an increased carbon loss with decomposition or a compensatory growth increase from nitrogen mineralization.
A l’instar de tout écosystème, la forêt va devoir s’adapter au changement climatique. Des chercheurs du centre Irstea de Nogent-sur-Vernisson s’appuient sur le site expérimental OPTMix, installé en pleine forêt, pour étudier les pressions subies par l’écosystème forestier, mais aussi tester des solutions de gestion qui permettront d’en atténuer les effets.
The articles published in this special issue cover a wide range of topics on the field of forest cover dynamics such as disturbance mapping, biomass change and forest health, using innovative approaches to study the rich information content of EO time-series datasets. It also stresses the potential as well as the challenges of EO data to monitor the different forest ecosystem dynamics efficiently and transparently.
In this study, we propose to assess climate impact on forest cover (represented by EVI) at multiple scales in areas undergoing substantial land cover change, using Landsat imagery with human-induced land cover change effect excluded. The findings should provide scientific supports for local forest management and ecosystem services, and should also support the hydrological effect assessment of vegetation cover change under climate change for the study area.
Functional traits directly link the performance of organisms to the environment and are used to scale up to effects on the overall structure, function, and diversity of ecosystems. Therefore, examining how the community composition of functional traits changes with the environment is key to understanding the role of climate in ecology. We provide a comprehensive assessment of relationships between climate and the functional composition of forests throughout the world. We identify the primary climatic drivers of functional composition/diversity across broad geographic gradients and show that forests may be experiencing functional shifts in response to global warming. These results illuminate important trait–climate relationships that help us understand the distribution of organisms throughout the world and anticipate ecosystem responses to future climate change.
Although several studies provide valuable insights into potential risks of prominent European tree species, we yet lack a comprehensive assessment on how and to which extent the composition of European forests may change. To overcome this research gap, we here project future tree-species compositions of European forests. We combine the concept of climate analogs with national forest inventory data to project the tree-species composition for the 26 most important European tree species at any given location in Europe for the period 2061–2090 and the two most relevant CMIP5 scenarios RCP 4.5 and RCP 8.5.
A growing body of research documents how individuals respond to local impacts of global climate change and a range of policy efforts aim to help individuals reduce their exposure and improve their livelihoods despite these stressors. Yet there is still limited understanding of how to determine whether and how adaptation is occurring. Through qualitative analysis of focus group interviews, I evaluated individual behavioral responses to local forest stressors that can arguably be linked to global climate change among landowners in the Upper Midwest, USA.
Future vegetation shifts under changing climate are uncertain for forests with infrequent stand-replacing disturbance regimes. These high-inertia forests may have long persistence even with climate change because disturbance-free periods can span centuries, broad-scale regeneration opportunities are fewer relative to frequent-fire systems, and mature tree species are long-lived with relatively high tolerance for sub-optimal growing conditions. Here, we used a combination of empirical and process-based modeling approaches to examine vegetation projections across high-inertia forests of Washington State, USA, under different climate and wildfire futures.
Climate−tree growth relationships recorded in annual growth rings have recently been the basis for projecting climate change impacts on forests. However, most trees and sample sites represented in the International Tree-Ring Data Bank (ITRDB) were chosen to maximize climate signal and are characterized by marginal growing conditions not representative of the larger forest ecosystem.
The ability of beech (Fagus sylvatica L.) populations to adapt to the ongoing climate change is especially important in the southern part of Europe, where environmental change is expected to be more intense. In this study, we tested the existing adaptive potential of eight beech populations from two provenances in N.E. Greece (Evros and Drama) that show differences in their environmental conditions and biogeographical background. The results showed that beech seedlings were generally able to survive under climate change conditions and showed adaptive differences among provenances and populations.
There has been growing interest in achieving multiple Sustainable Development Goals (SDGs) by identifying effective interactions or synergy potential among measures/policies on sustainable development. The simultaneous implementation of climate change mitigation (SDG 13) and forest protection (SDG 15) is an example of an interaction where the measures/policies that contribute to both goals can be identified and the overlaps eliminated. However, there are limited studies that quantitatively evaluate the synergy potential in the forest sector. This study is the first attempt to examine the synergy potential in the forest sector in Indonesia focusing on climate change mitigation and forest protection.
Climate change affects land use patterns all over the world. This study describes the present condition of vegetation in the Seyhan and Ceyhan basins, in the Eastern Mediterranean Region of Turkey, to estimate the impacts of climate change on the species composition and vegetation productivity. We estimated that the vegetation would be strongly impacted by global warming and a drier climate in the future, based on the data produced by the climate group of ICCAP (Kimura et al. 2007).
Rapid climate/weather severities which significantly enhance the forest fire events were observed in the month of April and May. The analysis of the Pearson Correlation Coefficient (PCC) values of climate parameters showed a significant correlation with forest fire events. The analysis of predicted (2050) climate anomalies data (RCP-6) for the month of April and annual precipitation manifest the significant rise in April temperature and reduction in annual precipitation observed over large part of high forest fire grids will certainly impact adversely to the future forest fire scenario.
On the basis of this documented experience we conclude that in the commercial sector of British forestry, where production is the main objective, there are strong arguments for undertaking a programme of rigorous testing and domestication of a very limited number of the most promising novel exotics which, in addition to good timber and growth, also have attributes that will allow the development of more naturalistic silvicultural systems and a move away from current clear-fell regimes. However this must be undertaken within a comprehensive risk assessment framework, where candidate species are rigorously screened both for any biosecurity threats, and their potential for causing ecological damage if they become invasive outside their initial planting sites.
The Paris Agreement and the latest IPCC Assessment Report (2018) emphasize urgent and efficient actions for climate change mitigation. This means that we must rapidly reduce global greenhouse gas emissions and, therefore, also the use of fossil-based raw materials, energy and products. Climate Smart Forestry (CSF) is one approach for achieving these goals in forests and the forest sector. It is more than just storing carbon in forest ecosystems. It builds upon three main objectives: first, reducing the net emissions of greenhouse gases into the atmosphere; second, adapting and building forest resilience to climate change; and third, sustainably increasing forest productivity and economic welfare based on forestry. CSF can help to mitigate the EU’s CO2 emissions up to 20% by 2050.
With climate change becoming an increasingly hot topic globally, the EU-funded project IMPRESSIONS launches a new online resource to provide a scientifically robust and policy-relevant understanding of the nature and scale of more extreme and long-term consequences of climate and socioeconomic change, and guide the use of this knowledge by decision-makers working on adaptation, mitigation and sustainable development.
Selon un nouveau rapport de la FAO et du Centre d’activités régionales du Plan d’action pour la Méditerranée (Plan Bleu) « La situation des forêts en Méditerranée », entre 2010 et 2015, les zones forestières ont augmenté de deux pour cent dans la région Méditerranée, soit 1,8 million d’hectares supplémentaires, ce qui représente à peu près la superficie de la Slovénie. Selon le rapport, dans la région Méditerranée, les forêts ont connu une forte dégradation et sont de plus en plus menacées par le changement climatique, la croissance démographique, les feux de forêts et les pénuries d’eau.
Local natural forests are the role model in the forestry method the Lübeck model. This forestry method is one example of a method that provides conditions to face the changes that a warmer climate entails
The County Administrative Board of Västra Götaland is working to climate adapt protection and care of natural areas. A template with proposals on climate-adapted measures in the care of nature reserves was developed. The county’s salt wet meadows have been analysed in relation to the rising sea level and the need to enable relocation inland. The County Administrative Board also provides information on invasive species and holds courses on how trees worthy of protection can limit climate impact.
L’objectif de cette contribution est d’aborder l’intégration de la notion de résilience à la gestion du risque incendie de forêt sur le territoire du massif des Landes de Gascogne. La résilience est ici définie comme la capacité d’un système social à assurer sa pérennité en accompagnant les changements. Or, la forêt des Landes a connu de nombreuses catastrophes, en particulier des incendies de grande ampleur dans les années 1940. Cet épisode a donné naissance à un dispositif de gestion du risque original. Depuis sa mise en place, ce dispositif basé sur l’équipement des forêts et l’intervention rapide des secours, semble très efficace. Il a cependant pour défaut de s’attaquer aux symptômes et non aux causes d’incendies.
Le DSF propose une nouvelle méthode d’estimation simplifiée de l’état des houppiers des arbres, nommée DEPERIS, utilisable par tous et en toutes saison
The future climate is projected to become increasingly problematic for European forest ecosystems, likely leading to the decline of many tree species. Forest management must adapt to cope with the negative effects of these changes. Despite the close interactions between nutrients and water in plant physiology, very few studies have investigated the link between soil fertility and tree response to soil water availability and vapour pressure deficit. The objective of this study was to test whether fertilization would modify forest tree resilience to soil water deficit.
La fertilisation et les amendements sont des pratiques courantes en agronomie dont l’intérêt a été prospecté dans le domaine forestier. Des dispositifs expérimentaux de fertilisation ont été mis en place et étudiés par le passé. Le but de ces dispositifs était de déterminer si l’apport d’éléments nutritifs dans des milieux forestiers initialement pauvres ou acides pouvait augmenter la croissance voire restaurer l’état des cimes des arbres en situation de dépérissement.
Pour relever le défi du changement climatique, il est nécessaire d’anticiper les impacts environnementaux, économiques et sociaux pouvant affecter les territoires et les secteurs d’activité grâce à une stratégie coordonnée s’appuyant à la fois sur des mesures d’adaptation et d’atténuation. Et pour favoriser la prise de conscience de tous autour des enjeux d'adaptation au changement climatique, le CRID de la MRES et le Pôle Climat du Cerdd ont sélectionné de premières ressources incontournables sur la thématique "Nature et Adaptation au changement climatique".
France is highly covered by forests, upon which rely numerous jobs and natural habitats. Therefore, the country adopted a strategy of adaptation to climate change, leaning on a rich silviculture history to offer foresters various means to adapt (rotation shortening, species mixes, …). Still, different adaptations can be interesting in a given forest, depending on the trade-off between ecosystem services: timber production, biodiversity conservation, water quality preservation, …
Long-term effects of forest density management on total aboveground C are not well understood, especially for precommercial thinning (PCT) implemented very early in stand development. To assess the climate change mitigation potential of PCT, as well as tradeoffs with climate change adaptation, we examined total aboveground C stores in a 54-year-old western larch (Larix occidentalis Nutt.) precommercial thinning experiment
Low soil moisture may reduce, or even reverse, the potential benefits of climate warming on photosynthesis in mesic, seasonally cold environments, both during drought and in regularly occurring, modes
Du 2 au 7 juillet, Irstea intervenait à la deuxième école d’été des Objectifs du Développement durable dédiée, cette année, à la lutte contre les effets du changement climatique. L'occasion pour les scientifiques du centre d’Aix-en-Provence de faire le point sur les tendances d’évolution des incendies et sur les solutions concrètes et durables pour en atténuer les effets. Points clés à retenir
Drought is a source of stress affecting forest growth and resulting in financial losses for forest owners and amenity losses for society. Due to climate change, such natural event will be more frequent and intense in the future. In this context, the objective of the paper is to compare, from an economic perspective, different forest adaptation strategies towards drought-induced risk of decline.
The aim of the study is to analyze different forest management practices (selective and traditional thinning) in black pine peri-urban forest in Central Italy, by investigating their contribution in terms of provisioning (wood production), cultural (recreational benefits), regulating (climate change mitigation) Ecosystem Services.
Alors que les effets du changement climatique sont de plus en plus perceptibles, il est important d’en mesurer les conséquences sur la végétation et de définir des conseils de gestion adaptés. Ce sont les buts du projet SYLFORCLIM coordonné par le Centre Régional de la Propriété Forestière (CRPF) PACA, dont Irstea est partenaire, qui s’est intéressé à la vulnérabilité du pin sylvestre aux changements climatiques en région PACA.
La France a été touchée ces 20 dernières années par plusieurs épisodes de tempêtes (« Lothar et Martin » en 1999, « Klaus » en 2009) dont l’impact sur les peuplements forestiers a été particulièrement important. Fort de l’expertise acquise lors de la gestion de ces crises, le ministère de l’agriculture et de l’alimentation a souhaité capitaliser sur les expériences passées pour anticiper les mesures à prendre en cas de tempête.
Chaque individu d’une espèce est unique, il diffère toujours plus ou moins de ses congénères : c’est ce que l’on appelle la variabilité inter-individuelle. Elle permet aux écosystèmes de fonctionner et aux populations de s’adapter au changement. En écologie, où l’on travaille communément avec des moyennes, peu d’études sont consacrées à cette variabilité. Au CREA Mont-Blanc, nous nous sommes intéressés à cette question chez le mélèze.
Climate change affects ecosystem functioning directly through impacts on plant physiology, resulting in changes of global productivity. However, climate change has also an indirect impact on ecosystems, through changes in the composition and diversity of plant communities. The relative importance of these direct and indirect effects has not been evaluated within a same generic approach yet. Here we took advantage of a novel approach for disentangling these two effects in European temperate forests across a large climatic gradient, through a large simulation-based study using a forest succession model.
During the summers of 2003 and 2016 large parts of Europe suffered from extreme wildfire events. Experts questioned how changing drought conditions might affect the activity of these types of fires. For Mediterranean France, for instance, several fires became particularly large and devastating during these summers despite growing efforts in fire management and suppression capacities implemented since the beginning of the 1990s.
Forests provide a number of important ecosystem services to society. They provide timber and protect against floods, mudflows, and other natural hazards by regulating water flows. Another important service is the accumulation of carbon. The more carbon is accumulated in the trees of a forest, the more this forest contributes to the mitigation of climate change. Global warming will change the composition of forests, and this will affect the provision of ecosystem services. This is not just due to the direct impact of higher temperatures and changing precipitation patterns. In particular bark beetle infestations will also likely increase due to more favourable thermal conditions and higher susceptibility of host trees due to stronger drought stress.
Les cycles forestiers, souvent proches du siècle, s'accommodent mal de la vitesse des changements climatiques. Alors que la forêt, second puits de carbone mondial, serait susceptible de ralentir le réchauffement, elle risque d'en être l'une des premières victimes. Une politique audacieuse est nécessaire pour que les évolutions actuelles soient l'occasion de redynamiser une activité essentielle pour notre environnement et notre économie.
Les impacts du changement climatique sur les forêts de montagne sont déjà perceptibles et les prévisions nous montrent, par leurs contradictions, la complexité des phénomènes en jeu. L’objectif de cette étude bibliographique est d’abord de caractériser les principaux effets du changement climatique, principalement dans les forêts alpines, puis de présenter différentes options d’adaptation devant permettre de conserver les services actuellement fournis par la forêt. L’épicéa, le sapin et le hêtre, dominants dans les Alpes françaises, y sont privilégiés