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1.
Understanding tropical forest succession is critical for the development of tropical forest conservation strategies worldwide, given that tropical secondary forests can be considered the forests of the future. Tropical dry forests (TDF) are among the most threatened tropical ecosystems, there are more secondary forests and forest restoration efforts that require a better understanding of successional processes. The main goal of this synthesis for this special issue on the ecology and management of tropical dry forests in the Americas is to present a summarized review of the current knowledge of the ecology and management implications associated to TDF succession. We explore specific issues associated to tropical dry forest succession with emphasis on the use of chronosequences, plant diversity and composition, plant phenology and remote sensing, pollination, and animal–plant interactions; all under the integrating umbrella of ecosystem succession. We also emphasize the need to conduct socio-ecological research to understand changes in land-use history and its effects on succession and forest regeneration of TDF. We close this paper with some thoughts and ideas associated with the strong need for an integrating dimension not considered until today: the role of cyberinfrastructure and eco-informatics as a tool to support sound conservation, management and understanding of TDF in the Americas.  相似文献   

2.
Forests in Africa support the livelihoods of millions of people through provision of timber and non-timber forest products, food and nutrition, energy and payment of environmental services. However, mismanagement of forests has resulted in deforestation and forest degradation, thereby contributing to the increased emission of carbon dioxide into the atmosphere. This special issue highlights some of the research outcomes presented at a pre-congress workshop organised by the African Forest Forum and partners at the 2015 World Forestry Congress. In this issue, the main drivers of land degradation are highlighted vis-à-vis population growth, agricultural expansion, climate variability, drought and energy needs. Promising traditional management practices are identified including age-old farmer-managed natural regeneration and exclosures. In addition, research presented indicates that age-old systems such as native non-browse shrubs in Ethiopia are important in that they facilitate regeneration of late-successional tree species. Furthermore, opportunities for using forests to mitigate climate change are highlighted with a case study on the economics associated with carbon markets. The issue also highlights the methodological challenges of quantifying carbon in African forests. The effect of climate change on threatened forest species and biodiversity in general is discussed, and the associated human disturbances impacting on the population structure of a threatened species, e.g. Afzelia africana in West Africa, is presented. The important role of non-timber forest products in income generation for the rural communities and the associated challenges of commercialisation is emphasised with examples from two important tree species: shea (Vitellaria paradoxa) and baobab (Adansonia digitata). Finally, the issue covers a people-centred approach in tree planting and management where studies demonstrated that there are still problems of poor participation of local communities due to poor implementation of enabling policies, lack of involvement in initial planning and subsequent lack of clear benefit-sharing mechanisms.  相似文献   

3.
With a predicted rise in average global surface temperature at an unprecedented rate, as well as changes in precipitation and disturbance regimes, climate change will bring forth new challenges for nature conservation in forest ecosystems. Species and habitats to be protected will be affected as well as related concepts and area specific objectives. Climate change impacts are likely to be aggravated by other anthropogenic stresses such as fragmentation, deposition or habitat destruction. To be reliable and effective, current objectives and guidelines of forest conservation need to be reassessed and improved. Our study analyses possible impacts of climate change on forests and identifies key future challenges for nature conservation in forests and ecosystem research. We reviewed 130 papers on climate change impacts on forest ecosystems and species published between 1995 and 2010. The geographical focus of the study is Central Europe. Papers were analysed accounting for direct and indirect impacts of gradual changes as well as stochastic disturbance events in forest ecosystems and their possible consequences for nature conservation.Even though broader aspects of nature conservation (protected areas, biodiversity) are frequently mentioned, little attention is given to forest-specific nature conservation. Particular aspects are insufficiently represented, such as the influence of climate change on different forest succession stages, the development of dead wood volume and quality, responses of secondary broadleaved species, azonal or extrazonal forests as well as ancient woodlands or remnants of historical silvicultural systems. Challenges arise in the context of great uncertainties about future developments. Nature conservation concepts and objectives in forests need to be adapted either within a permanent evaluation process or through the inclusion of further changes a priori, even if they are to some extent unpredictable. In some cases adaptation measures within nature conservation (e.g. adjusting protected areas) may conflict with interests of other stakeholders. Further research, particularly on interrelations between different impacts and the adaptive capacity of current forest ecosystems, associated species and existing genotypes is urgently needed. The scale and complexity of the task at hand calls for the establishment and further strengthening of international research networks.  相似文献   

4.

Large and severe disturbances may erode the resilience of temperate forest ecosystems and alter their recovery dynamics, especially under global change. We investigated mid-term recovery in mixed mountain forests in Slovenia after three independent severe windstorms in 2008 created large disturbed patches. Across a network of 102 permanent plots and three inventories over the 11-year post-disturbance period, we monitored trends in density, composition, and structure of regeneration, which are key indicators of forest resilience. Ecological drivers of regeneration, including topography, microsites, and biotic interactions, were analysed using linear mixed models. We quantitatively assessed physiognomic recovery by comparing regeneration densities with the restocking target used in forest practice, and compositional recovery by comparison with pre-disturbance stand composition. Regeneration densities and structure tended to converge among post-disturbance treatments (planting vs. natural regeneration) 11 years post-disturbance, as density of natural regeneration substantially dropped between the second and third inventory. Some drivers of recovery (i.e. ground vegetation and distance to the forest edge) varied over time, while the effect of elevation on regeneration density was consistently negative. The results indicate that the forest sites generally show adequate resilience to large-scale wind disturbances, in terms of physiognomic recovery, but not in terms of rapid compositional recovery, as pioneer and light-demanding tree species increased in share compared to the pre-disturbance stands.

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5.
The highest deforestation and forest degradation rates in Africa occur in the dry forests and woodlands where pressure for land is increasing, poverty is rampant, livelihood options are few and climate change effects are severe. This paper examines factors that cause land and forest degradation in the Sahel and dry forests and woodlands of eastern and southern Africa and highlights some successful restoration practices, technologies and approaches. In the Sahel, enclosures are used to protect young growing trees while in East Africa enclosures are implemented on degraded land as a mechanism for environmental rehabilitation with a clear biophysical impact. The choice of techniques for rehabilitating specific degraded areas depends first on the priorities and management objectives of stakeholders followed by the costs and benefits associated with available rehabilitation techniques and the economic, social, and environmental values of the land resources in their current and desired future states. In the Sahel, sustainable land management is considered to be an imperative for their sustainable development and the practices include soil and water conservation activities and structures. In all regions, natural forest rehabilitation has used both natural and assisted regeneration to promote the growth of especially indigenous species through coppice regrowth and root suckers rather than seeds. Assisted regeneration was especially prevalent in the Sahel where indigenous tree species have been identified to dominate the degraded sites during early stages of secondary forest succession. The success of any rehabilitation activities depends on community-based natural resources management. In addition, the forest policies and their related policies need to be enabling in order to address issues of concern, including (1) the full participation of communities, (2) clear land and tree tenure and (3) equitable benefit sharing.  相似文献   

6.
Forest change is of great concern for land use decision makers and conservation communities. Quantitative and spatial forest change information is critical for addressing many pressing issues, including global climate change, carbon budgets, and sustainability. In this study, our analysis focuses on the differences in geospatial patterns and their changes between federal forests and nonfederal forests in Alabama over the time period 1987–2005, by interpreting 163 Landsat Thematic Mapper (TM) scenes using a vegetation change tracker (VCT) model. Our analysis revealed that for the most part of 1990 s and between 2000 and 2005, Alabama lost about 2% of its forest on an annual basis due to disturbances, but much of the losses were balanced by forest regeneration from previous disturbances. The disturbance maps revealed that federal forests were reasonably well protected, with the fragmentation remaining relatively stable over time. In contrast, nonfederal forests, which are predominant in area share (about 95%), were heavily disturbed, clearly demonstrating decreasing levels of fragmentation during the time period 1987–1993 giving way to a subsequent accelerating fragmentation during the time period 1994–2005. Additionally, the identification of the statistical relationships between forest fragmentation status and forest loss rate and forest net change rate in relation to land ownership implied the distinct differences in forest cutting rate and cutting patterns between federal forests and nonfederal forests. The forest spatial change information derived from the model has provided valuable insights regarding regional forest management practices and disturbance regimes, which are closely associated with regional economics and environmental concerns.  相似文献   

7.
Mediterranean ecosystems are global hotspots of biodiversity threaten by human disturbances. Growing evidence indicates that regeneration of Mediterranean forests can be halted under certain circumstances and that successional stages can become notoriously persistent. The Mediterranean sclerophyllous forest in central Chile is been largely transformed into savannas dominated by the invasive legume tree Acacia caven as result of interacting management and ecological factors. We used multi-temporal satellite imagery to study the transition dynamics of these major vegetation types over the last four decades (1975-2008). Vegetation changes were related to indicators of resource availability (topography, water availability, solar radiance), potential propagule availability (distance to forest remnant patches) and disturbance regimes (grazing, fire occurrence and distance to roads and cities). During this study period, forests were mostly converted into Acacia savannas (46.1%). Acacia savanna was the most persistent natural vegetation type. The probability of sclerophyllous forest degradation into Acacia savanna increased on drier northern-exposed slopes, close to roads and further away from forest remnants. In contrast, forest regeneration from Acacia savanna was higher on moister southern-exposed slopes and closer to forest remnants. Acacia savannas are increasingly being converted into cultivated land on the moister locations or switching into a bare soil state in locations close to cities and further away from forest remnants. These results highlight the vulnerability of diverse sclerophyllous forests and its increasing conversion into persistent Acacia savannas in the Mediterranean region of central Chile and identify the ecological conditions for successful conservation and restoration of the native sclerophyllous forest vegetation that can be used for sensible land use planning.  相似文献   

8.
霍妍  郑云龙 《防护林科技》2013,(1):15-17,20
以大黑山水土保持生态修复工程示范区为研究区域,运用典型植物群落物种组成和群落物种多样性指数方法,对大黑山水土保持生态修复区典型植物群落物种多样性变化特征进行了研究,结果表明,生态修复区内天然次生林植物群落形成了乔灌草相结合的稳定的植物群落结构。人工林植物群落按生长型可以划为明显的乔木层和草本层2层群落结构类型;典型植物群落物种多样性指数的排序为:蒙古栎+蒙椴植物群落(Ⅱ)>山杏+黄榆植物群落(Ⅰ)>蒙古栎植物群落(Ⅲ)>油松+山杏混交植物群落(Ⅴ)>油松纯林植物群落(Ⅳ)>油松+沙棘混交植物群落(Ⅵ)>油松疏林植物群落(Ⅶ)。天然次生林植物群落的物种多样性要大于人工林植物群落。天然次生林植物群落由于远离人类活动区,长期以来受人为干扰较小,逐渐形成了相对比较发达的草本层植物群落。  相似文献   

9.
A number of forests in agroforestry environments are at risk due to urban development or agricultural expansion. These forests often consist of patches of wooded areas scattered in the agricultural and urban grid, and often constitute green corridors that enable a flow between animal and plant species (migration corridors). This study evaluates the composition and structure of riparian forests in agroforestry areas that are subject to various natural and anthropogenic disturbances. This study aims to understand the dynamics of these riparian forest populations and evaluate the effects of the disturbances on the tree stands (e.g. floods, partial cutting), while taking into account their development over space and time based on a diachronic assessment from 1945 to 2010. Although these woodlands are subject to various disturbances, a fairly large diversity of tree species can be noted, and the regeneration of the saplings and small trees follows a normal growth curve (asymmetric) with a high contingency of young tree population comparable to a typical reverse-J distribution. However, lower densities are observed for riparian stands subject to frequent flooding, which could over time compromise recruitment and forest regeneration for some tree species (e.g. woody plants with weak adaptive strategies). The multivariate analyses (Redundancy Analysis and Canonical Correspondence Analysis) conducted over all the soil, environmental and forest data reveal that some variables are more strongly related to the composition of the forest populations, including pH, ground litter and soil drainage. However, these variables must still be considered as being part of a set of interacting soil conditions. Lastly, the future of these woodlands may appear uncertain because there are no government policies or measures to ensure their protection and preservation.  相似文献   

10.
指出了矮林由于质量差、长势差、应对气候变化的能力差,急需通过森林经营提高林分质量。提出了老龄矮林由于其已失去天然更新的能力,主要依靠渐进式人工造林的方式,逐步改造为乔林;中龄矮林则主要依靠天然更新进行转变经营,逐步转化为乔林;幼龄矮林可先采用目标树经营法进行经营,并同时促进天然更新,并在天然更新成功后逐步转变为乔林。探讨了在矮林向乔林转变的过程中,需持续关注乡土树种和珍贵阔叶树种的培育、野生动物生存环境的保护以及生物多样性的恢复。  相似文献   

11.
A protective forest,including shelterbelt,windbreak,and shelter forest as its synonyms,is characterized by the protective functions of various forest types distributed or planted on ecologically fragile areas or nearby the objects that need to be protected using the ecological effects of forests.Ecological mechanisms for management practices of protective forests is one of the disciplinary orientations in forest ecology and management.Most protective forest studies are dependent on forestry eco-engineering,such as the Great Plains Shelterbelt Project in the United States,the Great Plan for the Transformation of Nature in the Soviet Union,and the Three-North Afforestation Program in China.The development of sustainable management of protective forests has been given increasing attention by governments,scientists,and media due to their impacts on environment conservation and global change.We introduce forestry ecoengineering and provide a review of their main ecological mechanisms for management practices of protective forests.Ecological mechanisms for management systems currently applied are emphasized,i.e.,the theory of protection maturity and phase-directional management;the relationship between structure and protective functions and structural optimization measures;and,the decline mechanism and ecological restoration strategies.In addition,several unresolved problems in management practices of protective forests are discussed as well as the prospects for ecological mechanisms for management practices of protective forests in the future,which include:(1) theories and technologies for management practices of protective forests at the landscape or regional scale;(2) the decline mechanisms and corresponding ecological restoration approaches across multiple scales;and,(3) the comprehensive assessment of forestry eco-engineering at large-scales based on ecosystem principles.  相似文献   

12.
In the last 10 years the Sri Lankan government has changed its policy regarding its remaining rain forest from one that promoted commercial exploitation to one of conservation. The growing importance of uplands as catchments for water production, biodiversity conservation and other downstream services has been recognized by the Sri Lankan government. It is therefore timely that we review 15 years of research investigating rain forest dynamics of southwest Sri Lanka with the objective of using this knowledge for forest restoration. We provide six common principles for understanding the integrity of rain forest dynamics in southwest Sri Lanka. The principles are: (i) disturbances provide the simultaneous initiation and/or release of a new forest stand; (ii) that disturbances are generally non-lethal to the groundstory vegetation; (iii) disturbances are variable in severity, type and extent across rain forest topography; (iv) guild diversity (habitat diversity) is dependent upon “advance regeneration”; (v) tree canopy stratification is based on both “static” and “dynamic” processes; and (vi) canopy dominant late-successional tree species are site specialists restricted to particular topographic positions of the rain forest. These principles are applied to determine effects of two rain forest degradation processes that have been characterized as chronic (continuous detrimental impacts) and acute (one-time detrimental impacts). Restoration pathways are suggested that range from: (i) the simple prevention of disturbance to promote release of rain forest succession; (ii) site-specific enrichment planting protocols for canopy trees; (iii) sequential amelioration of arrested fern and grasslands by use of plantation analogs of old field pine to facilitate secondary succession of rain forest, and plantings of late-seral rain forest tree species; and (iv) establishment and release of successionally compatible mixed-species plantations. We summarize with a synthesis of the restoration techniques proposed for reforestation using native vegetation on cleared conservation areas and parks, and for the stabilization of eroded upland watersheds. We conclude with a comparative analysis with restoration work done in other tropical forest regions.  相似文献   

13.

Competitive effects of dense herbaceous vegetation (ground cover) can inhibit forest restoration on mine sites. Here we review the evidence of ground cover interactions with planted tree seedlings on coal surface mines of the eastern US, discuss recent research into these interactions, and draw conclusions concerning ground cover management when restoring forests on reclaimed coal mines. Reclaimed mine sites have a high potential to support productive forests, however forest establishment is inhibited by reclamation practices that included soil compaction, and the seeding of competitive ground covers. In the first few years after tree planting, a dense ground cover of grass and legume species commonly seeded on mine sites often affect growth and survival negatively. Herbaceous vegetation providing less extensive and competitive ground coverage may either facilitate or inhibit tree establishment, depending on site conditions. The use of quality planting stock promotes the competitive ability of seedlings by improving nutrient status and the ability to capture available resources. Herbaceous species have contrasting functional characteristics, and thus compete differently with trees for available resources. Negative interactions with trees are more frequently reported for non-native cool-season grasses than for native warm-season grasses, while the effects of legumes change over time. Further research is needed to fully understand the mechanisms of tree/ground cover interactions. The development of seeding mixes that can control erosion, facilitate survival and growth of planted trees, and allow establishment by unplanted native species would aid forest restoration on eastern US, coal mines.

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14.
Dry forests across the United States have become subject to declining resilience and, consequently, increased vulnerability to catastrophic wildfires. These disturbances cause severe environmental and social damages and may dislodge the forest into a different ecological regime. Forests provide many valuable services, such as the provisioning of timber and the sequestering of carbon that would otherwise contribute to climate change. The high-severity conflagrations that have become regular occurrences in many dry forests impinge the delivery of such benefits, particularly in the event of a regime shift. Sustainable forest management should take these risks into account. This article analyzes the economics of resilience in dry forests with respect to catastrophic fires and ecological thresholds. We illustrate how to price ecosystem resilience for the fire-prone ponderosa pine forests of the western United States. This analysis demonstrates that pricing forest resilience also establishes the economic value of ecological restoration with respect to ecosystem services, thereby operationalizing forest management as an investment in natural capital.  相似文献   

15.
Rotational swidden cultivation systems, with fallow periods long enough for the regeneration of secondary forests are capable of maintaining forest cover and plant diversity in a dynamic balance in swidden cultivation landscapes. Regeneration of secondary forests through several successional stages and by a combination of coppicing and seedling development is still poorly understood, especially the influence of different swiddening practices and the role of animals as seed dispersers. Swidden cultivators possess a vast knowledge of plants growing in swidden fallows and of fallow dynamics as well. Forest restoration in Thailand has been carried out mainly on the basis of experimental research on the potential of indigenous tree species to promote natural forest regeneration and biodiversity recovery; the so-called framework species. Another viable source of knowledge for forest restoration can be the study of the semi-natural revegetation processes in fallows and the indigenous knowledge of swiddeners of these processes. The research presented here was carried out to attain a better understanding of forest regeneration on fallow swiddens under different swiddening regimes and how it may be applied to practical forest restoration, We investigated the vegetation characteristics of from various stages of secondary succession in fallow swiddens of the Karen and Lawa ethnic groups in the Mae Chaem watershed, Chiang Mai province, northern Thailand. Indigenous knowledge on the use of species and traditional ecological processes in swiddening was recorded by questioning key informants. The data were analyzed and discussed with respect to their application in forest restoration and participatory forest management.  相似文献   

16.
Comparisons of Mayan forest management, restoration, and conservation   总被引:1,自引:0,他引:1  
Numerous communities associated with at least five distinct ethnic Mayan groups in southern Mexico and Central America continue to rely upon forested areas as integral components of their agricultural systems. They carefully manage these areas so that forests provide food, raw materials, and animals. Management practices include removing and planting of woody and herbaceous species, apiculture, and seed harvest. Mayan agroforestry systems in geographically and ecologically distinct areas of Mesoamerica were evaluated to better understand traditional agroforestry system components and how indigenous Mayan agroforestry could be a part of regional forest conservation and restoration. Systems were within Mexican land grant areas (ejidos) or on contested land. Although these systems rely upon different woody species and management techniques, common among them are: (1) the use of multi-stage and successional pathways with forest as a part of the larger system, (2) species that are believed by traditional ecological knowledge (TEK) to accelerate forest regeneration - more than 30 tree species are recognized and managed as potential facilitators of forest regeneration and (3) direct human consumption of forest products at all stages of regeneration.  相似文献   

17.
A review of the roles of forest canopy gaps   总被引:5,自引:0,他引:5  
Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and pedo-diversity, influencing nutrient cycles, and maintain- ing the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics consid- ered critical to develop ecologically sustainable forest management sys- tems and to conserve native biodiversity. Specifically, we addressed the question: how do gaps influence forest structure? From the literature re- viewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade- tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summa- rizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.  相似文献   

18.
Abstract

Climatic warming may lead to increased or decreased future forest productivity. However, more frequent heat waves, droughts and storms and accompanying pathogen attacks are also expected for Europe and are considered to be increasingly important abiotic and biotic stress factors for forests. Adaptive forestry can help forest ecosystems to adapt to these new conditions in order to achieve management goals, maintain desired forest ecosystem services and reduce the risks of forest degradation. With a focus on central Europe, this paper presents the following management strategies: (1) conservation of forest structures, (2) active adaptation, and (3) passive adaptation. The feasibility and criteria for application of the different strategies are discussed. Forest adaptation may entail the establishment of “neonative” forests, including the use and intermixing of native and non-native tree species as well as non-local tree provenances that may adapt better to future climate conditions. An integrative adaptive management concept is proposed that combines (1) species suitability tests and modelling activities at the international scale, (2) priority mapping of adaptation strategies at the national to regional scale, and (3) implementation at the local scale. To achieve this, an international experimental trial system is required to test suitable adaptive measures throughout Europe and worldwide.  相似文献   

19.
In two related field studies: (1) a multiscale riparian forest inventory and (2) a comparative study of natural forest gap and nongap environments, we explored regeneration patterns of native riparian trees in relation to large- and small-scale ecological drivers in four western Oregon watersheds spanning a climatic gradient from dry to wet. Twenty-three tree species were classified by life history traits into five functional groups that differed in shade and drought tolerance; distribution and abundance of tree regeneration were analyzed by group. For most groups, seedling abundance varied substantially across the large scale climate gradient. In particular, drought tolerant species decreased sharply in abundance from the drier to wetter watersheds. Overall seedling frequency and diversity also decreased from the driest to wettest watersheds, while nurse log use increased. Regeneration of most, but not all, species was greater in gaps.Principal conclusions are that life history information was useful for categorizing species and quite predictive of regeneration behavior overall, yet for many species contextual factors such as climate, forest structure, and adjoining species were also very important. Species appeared to regenerate opportunistically wherever local conditions fell within their environmental tolerances and competitive abilities. Management or restoration of riparian forests, therefore, requires knowledge of site conditions, the life history of the riparian trees present, and in particular an understanding of the species’ environmental tolerances, disturbance responses, and competitive abilities relative to one another.  相似文献   

20.

We examined the association between habitat variables and the relative impacts of topographic microclimates as a valuable tool for restoration and conservation of Abies pinsapo in southern Spain. We used presence–absence data from A. pinsapo and 79 environmental variables and biomod species distribution models to describe the current and future species habitat across the Sierra de las Nieves Natural Park (southern Spain). A. pinsapo habitat was most strongly associated with microtopographic (solar incidence) and temperature variables, indicating climate-driven changes in microhabitat use. Most of the temperature variation among the study site was attributable to topographic microclimates rather than regional temperature differences, such that differences in microhabitat associations occurred principally between north- and south-facing slopes within the same region. The current potential distribution suggests that around 8.7% (56.44 km2) of the study area is highly suitable for A. pinsapo, with 9.7% (62.84 km2) being moderately suitable. Under different global circulation models and climate change scenarios, the net decrease in suitable habitat is predicted to be 93% of the current distribution by 2040, disappearing altogether by 2099. Our findings also show a sharp reduction of potential restoration areas (1.8% of the current areas). Microclimatic variation generated by the topography offers the microclimate-driven locations of habitat suitability which could shape species’ distribution restoration actions and their responses to environmental change. The approach presented here can provide a rapid assessment of the future conservation status of other important forest tree species in Spain, improving our understanding of the vulnerability of endangered species under climate change, and can be an effective tool for biodiversity conservation, restoration, and management.

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