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International audience; Climate change affects forest ecosystem processes and related services due to climate variability. These might affect ecosystem functioning, especially productivity. Regarding management issues, mixed stands are considered a relevant option to maintain forest cover and ecosystem services under climate change. However, the possibility to maintain these mixed stands with management actions with positive effects on forest functioning under climate change remains uncertain and deserves further investigations. Relying on a simulation-based study with a forest gap model (ForCEEPS), we thus addressed the following questions: (1) Are monospecific stands vulnerable to climate change? (2) Would mixed stands significantly mitigate climate change effects on forest productivity and wood production under climate change? (3) Would conversion to mixed stand management affect significantly forest productivity and wood production under climate change compare to monospecific management? In this study, we quantified potential climate change effect (using RCP 8.5 and present climate) and management’s effect in the French Alps, focusing on five species (Fagus sylvatica, Abies alba, Picea abies, Pinus sylvestris, and Quercus pubescens). We tested different scenarios, with various composition, structure, or environmental conditions, under climate change. These simulations showed that monospecific stands currently growing in stressful conditions would be vulnerable to climate change. Managing mixed stands or conversion from pure to mixed stands would make it possible to maintain higher productivity in the long term than monospecific stands, depending on the species and the sites considered. Our results will feed into discussion on forest management in the context of climate change.

International audience; Landscapes are subject to ecological and socioeconomic forces of change that interact in complex ways. To cope with these changes, landscape planning of natural resource management integrates sociocultural, ecological, and economic considerations in an analytic and systemic way. In this regard, social-ecological system (SES) frameworks have been developed to help analyze key factors that drive the dynamics of such complex adaptive systems. For forests, multifunctional management, which also highlights the ecological and socioeconomic roles of forests for society, has become a central objective for several European countries (e.g., France, Italy, and Germany). However, further development of methods, tools, and conceptual approaches is needed to facilitate our understanding of the arrangements behind management practices that include complex human-environment interactions. This study adopts Ostrom's SES framework and Anderies' robustness framework to highlight how forestry institutions affect forest ecosystems, forest functions, and social arrangements. As an illustration, we apply both frameworks to the Quatre-Montagnes forest, located in the south-east of France, in which multifunctionality is a major objective of forest governance. We first apply the SES framework to construct an analysis of the Quatre-Montagnes forest, specifying the first-tier and second-tier variables. From this, we describe the importance of infrastructure-related variables in shaping the interactions between components of the SES. We then apply the robustness framework, developed by Anderies, because we believe this framework enables a better analysis of ecosystem functions for infrastructure governance than the SES framework, which provides a better descriptive capacity for the variables. We discuss insights, based on our infrastructure analysis, which can be used when establishing designs for efficient forest management with heavy infrastructure dependencies.

Recent institutional and policy frameworks prescribe the incorporation of ecosystem services (ES) into land use management and planning, favouring co-production of ES assessments by stakeholders, land planners and scientists. Incorporating ES into land management and planning requires models to map and analyze ES. Also, because ES do not vary independently, many operational issues ultimately relate to the mitigation of ES trade-offs, so that multiple ES and their interactions need to be considered. Using a highly accurate LULC database for the Grenoble urban region (French Alps), we mapped twelve ES using a range of models of varied complexity. A specific, fine-grained (less than 1 ha) LULC database at regional scale (4450 km²) added great spatial precision in individual ES models, in spite of limits of the typological resolution for forests and semi-natural areas. We analysed ES bundles within three different socio-ecosystems and associated landscape types (periurban, rural and forest areas). Such type-specific bundles highlighted distinctive ES trade-offs and synergies for each landscape. Advanced approaches combining remote sensing, targeted field data collection and expert knowledge from scientists and stakeholders are expected to provide the significant progress that is now required to support the reduction of trade-offs and enhance synergies between management objectives. ISSN:2639-5908 ISSN:2639-5916

[Departement_IRSTEA]Territoires; International audience; Physically and socially heterogeneous mountain landscapes support high biodiversity and multiple ecosystem services. But rapid landscape transformation from fast urbanisation and agricultural intensification around cities to abandonment and depopulation in higher and more remote districts, raises urgent environmental and planning issues. For anticipating their future in a highly uncertain socio-economic context, we engaged stakeholders of a dynamic urban region of the French Alps in an exemplary interactive Participatory Scenario Planning (PSP) for co-creating salient, credible and legitimate scenarios. Stakeholders helped researchers adapt, downscale and spatialize four normative visions from the regional government, co-producing four storylines of trend versus break-away futures. Stakeholder input, combined with planning documents and analyses of recent dynamics, enabled parameterisation of high-resolution models of urban expansion, agriculture and forest dynamics. With similar storylines in spite of stakeholders insisting on different governance arrangements, both trend scenarios met current local and European planning objectives of containing urban expansion and limiting loss and fragmentation of agricultural land. Both break-away scenarios induced considerable conversion from agriculture to forest, but with highly distinctive patterns. Under a commonly investigated, deregulated liberal economic context, encroachment was random and patchy across valleys and mountains. A novel reinforced nature protection scenario affecting primarily mountain and hilly areas fostered deliberate consolidation of forested areas and connectivity. This transdisciplinary approach demonstrated the potential of combining downscaled normative scenarios with local, spatially-precise dynamics informed by stakeholders for local appropriation of top-down visions, and for supporting land planning and subsequent assessment of ecosystem service trade-offs.

The overall demand for both agricultural and forest goods and services has strongly increased and is likely to continue to rise in the future, leading to more intensive practices in many managed ecosystems with potential negative effects for biodiversity and the environment (Cassman 1999; Tilman et al. 2002; Brussaard et al. 2010; Verkerk et al. 2014). Regarding agriculture, the challenge is to feed increasing numbers of people (food security) as well as to contribute to the development of bioenergy (Valentine et al. 2012). In the same vein, more forest products are required to satisfy new ambitious energy and construction policies (Jonsson 2013). Meanwhile, the concept of ecosystem services (ESs) has emerged and has been established in the environmental research and public spheres, exemplifying the complexity of ecosystems and their multiple relationships with human needs, including provisioning and regulating as well as social and cultural services (Tilman et al. 2002; Messier et al. 2015). Although conflicts or trade-offs between ESs have often been emphasized, positive interactions between, for example, regulating and provisioning ESs have paved the way to designing new management systems promoting ecological processes and reducing practices based on heavy mechanical or chemical means (Gaba et al. 2015). Overall, this is creating possibilities to reconcile production and the environment through a new type of ecologically driven intensification. According to Dore et al. (2011), ecological intensification (EI) consists in reducing artificial inputs while maintaining high production levels through biological regulation. It can thus be related to all practices that consist in intensifying the use of natural functions provided by ecosystems to support production (Chevassus au Louis and Griffon 2008). By nature, EI is closely related to biodiversity, which can directly or indirectly support production and other ESs through functional processes (Bommarco et al. 2013; Gaba et al. 2014). Although to date it has for the most part been mentioned in discussions on crop systems in agriculture, with some adjustments it can be generalized to other managed ecosystems dedicated to production (Rey et al. 2015). For instance, in forest science, concepts such as close-to-nature forestry, which explicitly integrates the reduction of inputs using natural processes, can fall under EI (Bauhus et al. 2013). As highlighted by Tittonell (2014), EI must be considered as designing ecosystem-based ‘‘[...] multifunctional agroecosystems that are both sustained by nature and sustainable in their nature.’’ From all these principles, it appears that EI contains all the ingredients to reconcile production and the environment (Fig. 1): (1) it aims at supporting and maximizing production; (2) it promotes practices that are based on functional ecological processes and that favor synergies between ESs (especially between regulating and provisioning ESs); and (3) it aims at reducing negative impacts of intensive management practices designed to increase productivity. So far, some important steps have been taken toward EI in both forestry and agriculture. For instance, in forestry, favoring species mixture in planted or natural forest stands may increase ecosystem productivity through temporal and spatial species niche complementarities (Forrester 2014). Silviculture practices based on natural processes (natural & Thomas Cordonnier thomas.cordonnier@irstea.fr

Summary 1.Ecosystem services (ES) from mountain forests are highly relevant for human societies. ES with a direct economic support function (e.g. timber production), regulatory services (e.g. protection from natural hazards) and cultural services (e.g. recreation) are likely to be affected strongly by a rapidly changing climate. To evaluate whether adverse climate change effects on ES can be counteracted by adapting management, dynamic models and indicator-based assessments are needed. 2.We applied a forest dynamic model in case study areas of four European mountain regions and evaluated the future supply of four ES - timber production, carbon sequestration, biodiversity, and protection against natural hazards - using state-of-the-art ES indicators. Forest dynamics were simulated under three management scenarios (no management, business-as-usual, and alternative management) and five climate change projections for selected representative stand types in each region. We analysed potential trade-offs and synergies between ES, and evaluated future changes among regions, forest stands, climate and management scenarios. 3.Impacts of climate change on the provision of multiple ES were found to be highly heterogeneous and to depend on the region, site, and future climate. In the absence of large-scale natural disturbance (not considered), protection services, carbon stock and deadwood abundance (proxy for biodiversity) benefitted from no management in all regions. Negative impacts of climate change were evident for the provision of multiple ES but limited to the most severe climate scenarios and low-elevation stands. Synergies and trade-offs between the majority of ES were found to be sensitive to the choice of management strategy and – in some regions – to climate change. 4.Synthesis and applications. Management regimes in European mountain forests should be regionally adapted to stand and site conditions. Although in some cases alternative management regimes may be more suitable than current management for supporting multiple ecosystem services, adaptation options should be evaluated carefully at the local scale due to the highly different magnitude of the impacts of climate change in different regions and along elevation gradients. This article is protected by copyright. All rights reserved.

International audience; Mountain forests provide a multitude of services beyond timber production. In a large European project (ARANGE—Advanced multifunctional forest management in European mountain RANGEs), the impacts of climate change and forest management on ecosystem services (ES) were assessed. Here, we provide background information about the concept that was underlying the ARANGE project, and its main objectives, research questions, and methodological approaches are presented. The project focused on synergies and trade-offs among four key ES that are relevant in European mountain ranges: timber production, carbon storage, biodiversity conservation, and protection from gravitational natural hazards. We introduce the concept and selection of case study areas (CSAs) that were used in the project; we describe the concept of representative stand types thatwere developed to provide a harmonized representation of forest stands and forest management in the CSAs; we explain and discuss the climate data and climate change scenarios that were applied across the seven CSAs; and we introduce the linker functions that were developed to relate stand- and landscape-scale forest features from model simulations to ES provisioning in mountain forests. Finally, we provide a brief overview of the Special Feature, with an attempt to synthesize emerging response patterns across the CSAs.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Uneven-aged mountain forests are considered favourable for the continuous provisioning of multiple ecosystem services (ES). These ES may however exhibit trade-offs or synergies that can be modulated by forest management. Yet, our knowledge remains poor on both the relationships between ES and the way management practices can optimise and reconcile them. In this study, we aimed at (1) characterising trade-offs and synergies between timber production, biodiversity conservation and protection against natural hazards; (2) identifying efficient (i.e. Pareto-optimal) management scenarios for the joint provisioning of these ES; and (3) comparing them to “reference” management scenarios. Using a simulation framework that couples a forest dynamics model, a silviculture algorithm and linker functions relating ES indicators to stand structure, we predicted the response of different ES indicators to various uneven-aged management practices in the Western Alps. With a metamodeling approach and Pareto front techniques, we intensively explored and analysed relationships between ES indicators and found trade-offs between timber production and other ES, but synergies between protection and biodiversity. “Pareto-optimal” management scenarios were characterised by low thinning and harvesting intensities but exhibited gradients of total removals and deadwood and large tree retention along the Pareto front. They greatly differed from our set of production and biodiversity oriented reference scenarios, thus emphasising the strong impact of considering additional ES in scenario optimisation processes. This study highlighted the strengths and weaknesses of Pareto front techniques for both the analysis of trade-offs and synergies between ES and the identification of efficient management practices

Plant structural diversity is usually considered as beneficial for ecosystem functioning. For instance, numerous studies have reported positive species diversity-productivity relationships in plant communities. However, other aspects of structural diversity such as individual size inequality have been far less investigated. In forests, tree size inequality impacts directly tree growth and asymmetric competition, but consequences on forest productivity are still indeterminate. In addition, the effect of tree size inequality on productivity is likely to vary with species shade-tolerance, a key ecological characteristic controlling asymmetric competition and light resource acquisition. Using plot data from the French National Geographic Agency, we studied the response of stand productivity to size inequality for ten forest species differing in shade tolerance. We fitted a basal area stand production model that included abiotic factors, stand density, stand development stage and a tree size inequality index. Then, using a forest dynamics model we explored whether mechanisms of light interception and light use efficiency could explain the tree size inequality effect observed for three of the ten species studied. Size inequality negatively affected basal area increment for seven out of the ten species investigated. However, this effect was not related to the shade tolerance of these species. According to the model simulations, the negative tree size inequality effect could result both from reduced total stand light interception and reduced light use efficiency. Our results demonstrate that negative relationships between size inequality and productivity may be the rule in tree populations. The lack of effect of shade tolerance indicates compensatory mechanisms between effect on light availability and response to light availability. Such a pattern deserves further investigations for mixed forests where complementarity effects between species are involved. When studying the effect of structural diversity on ecosystem productivity, tree size inequality is a major facet that should be taken into account.

International audience; An objective of mountain forest management is to increase the ability of forest stands to protect human activities against natural hazards such as rock-falls and snow avalanches in a sustainable way. The challenge is to find a compromise between efficient instantaneous protection, favoured by dense stands, and continuous renewal, minimizing time periods of low protection efficiency. We used a Norway spruce stand dynamics model to compare the respective advantages of individual tree and gap selection silviculture in this context. We simulated stand dynamics over 800 years with either individual tree or gap thinning every 20 years with several thinning intensities. At each time step, we evaluated stand resilience, protection efficiency against rock-falls, protection efficiency against avalanches, and structural complexity with four indicators based on stand structure. Every scenario produced short time periods with low stand resilience and protection efficiency. Such periods can be tolerated if they are sufficiently rare compared to the local disturbance regime. We characterized the permanence of resilience and protection of a forest stand as its ability to remain within boundary values of the different indicators, without going out of them during continuous time periods longer than fixed maximum durations. Permanence of resilience and permanence of protection decreased with thinning intensity. Efficient protection against rock-falls was obtained with gap thinning of intermediate intensity while protection against avalanches was obtained only for very low thinning intensities. For our ecological context, the best compromise between resilience and protection was obtained with three 10 m radius gaps per hectare every 20 years (9.5% of the area of a stand). This strategy led to uneven-aged stand structures with a high diversity of diameters classes. Our results suggest that small gap silviculture may be a good way to combine forest renewal and protection efficiency in mountain regions.

International audience; When harvesting activities stop, forest stands become steadily richer in very large trees and deadwood, maturity attributes that are crucial for forest dwelling species. On the other hand, the maturation process, associated with large trees and large gaps between trees, has traditionally been thought to be detrimental to the protective function of the forest against gravitational hazards such as rockfall. However, the findings of recent studies have contested this belief, first because they showed that natural dynamics in aging stands is rather gradual in space and time, and second because they highlighted that deadwood may play an important role in protection forests. In this study, we assessed the protection efficiency of the forest along a maturity gradient in uneven aged stands, using a network of permanent sample plots in the French Alps. Plots were selected according to management plans to represent four successive stages along the maturity gradient: young stands, adult stands just after logging, post-adult stands that escaped one to two rotations, and mature stands. We checked that stands gradually matured using the total number of very large trees (dbh > 77.5 cm), the total volume of deadwood, and the total volume of degraded large logs. We then developed a specific module to integrate deadwood into the Rockyfor3D rockfall simulation model and assessed the rockfall protection of the plots. Mature stands, although not having reached the protection efficiency of young and dense stands, can provide adequate protection against rockfall. First, because mature stands are rather dense (more than 500 stems ha1). Second, because large logs increase the surface roughness of the forest floor and act as additional obstacles to the propagation of rocks. Consequently, mature stands originating from aging irregular stands play a fitting role in protection forests, thereby reconciling biodiversity conservation objectives with protective functions. When mature stands originate from aging regular stands dominated by a cohort of very large trees, a cautious approach to management will better initiate a progressive irregularization process before promoting patches of mature stands.

International audience; Greater demand for wood material has converged with greater demand for biodiversity conservation to make balancing forest ecosystem services a key societal issue. Forest managers, owners, or policymakers need new approaches and methods to evaluate their ability to adapt to this dual objective. We analyze the ability of forest owners to define sustainable forest management options based on viability theory and a new flexibility index. This new indicator gauges the adaptive capacity of forest owners based on the number of sustainable actions available to them at a given time. Here we study a public forest owner who regulates harvest intensity and frequency in order to meet demand for timber wood at forest scale and to meet a biodiversity recommendation via a minimum permanently maintained volume of deadwood per hectare at stand scale. Dynamical systems theory was used to model uneven-aged forest dynamics-including deadwood dynamics-and the dynamics of timber wood demand and tree removals. Uneven-aged silver fir forest management in the "Quatre Montagnes region" (Vercors, France) is used as an illustrative example. The results explain situations where a joint increase in wood production and deadwood retention does not reduce the flexibility index more than increasing either one dimension alone, thus opening up ecological intensification options. To conclude, we discuss the value of the new flexibility index for addressing environmental management and ecological intensification issues.

Ecological models are increasingly used as decision-making tools and their reliability is becoming a key issue. At the same time, the sophistication of techniques for model development and analysis has given rise to a relative compartmentalization of model building and evaluation tasks. Several guidelines invite ecological modelers to follow an organized sequence of development and analysis steps and have coined the term "evaludation" for this process. The objective of this paper is to assess the feasibility and the value of a structured evaludation process, based on the working example of the Samsara2 model, a spatially explicit individual-based forest dynamics model. We implemented the six steps of model design, process level calibration, qualitative evaluation, quantitative evaluation, global sensitivity analysis, and partial recalibration using approximate Bayesian computing. We then evaluated how the evaludation process revealed model strengths and weaknesses, specified the model's conditions of use, clarified how the model works, and provided insights into forest ecosystem functioning. Finally, the efficiency/cost ratio of the process and future improvements are discussed.

Simulating the dynamics of heterogeneous forests calls for spatially explicit radiation transmission models at the scale of individual trees and requiring only a short computing time. Such a model was developed for spatially heterogeneous coniferous forest canopies. Based on the interception of light rays by parabolic crowns, it simultaneously calculates the radiation intercepted by each tree and the distribution of irradiance on the ground. For every sky direction, parallel rays aim at ground cell centres and are intercepted by tree crowns on their way. Slope and exposure are taken into account eliminating rays coming from above the slope. Optimisation in computing time is obtained by pre-selecting for each ray direction a rectangular cell neighbourhood around the target cell in such a way that potentially intercepting trees can only be found in this neighbourhood. Model evaluation was done by comparing hemispherical photographs with model predictions in a spatially heterogeneous Norway spruce (Picea abies, L. Karst) stand at the upper montane level in the Alps. Thanks to a satisfactory fit between model and data and a reasonably short computing time (about 2 min for 0.25 ha), the model can be considered for integration into a forest dynamics simulator. In the reference stand, 42% of incident radiation was intercepted by the highest trees (132 ha−1). Due to the clumped structure, 23% of incident radiation reached the soil. Interception by individual trees varied considerably as a function of tree size and location (from 0 to 60% of the potential interception of a tree growing in isolation). Irradiance at ground level was also extremely variable (between 0 and 50% of irradiance above the canopy), illustrating the need for spatial models in heterogeneous stands. The interception of radiation by trees was not affected by slope and exposure, unlike irradiance at ground level, which increased for southern exposures. Therefore, in terms of dynamics, regeneration should be the most sensitive to changes in these factors. Because the model produces precise radiation values at the ecosystem level, it allows analysis of the links between the structure of a forest stand and its energetic functioning synthetically.

International audience; & Context Uneven-aged management systems based on selec-tion silviculture have become popular in European mountain forests and progressively replace other silvicultural practices. In time, this trend could lead to a homogenisation of the forest mosaic with consequences on structural indices recognised as beneficial to forest biodiversity. & Aims This study was conducted to investigate the potential effects of a generalisation of the selection silvicultural system on structural diversity in the forest landscape with conse-quences for forest biodiversity conservation. & Methods We compared four structural indices (tree species richness, diameter heterogeneity, deadwood volume and basal area of mature trees) in five different stand types typical of the northern French Alps, using forest plot data in the Vercors mountain range. Through virtual landscape simulations, we then calculated predicted mean proportions of stand types under two different conservation strategies: (i) maximising mean index values at the landscape level and (ii) maximising the number of plots in the landscape with index values above given thresholds. & Results Multi-staged forests did not maximise all indices, the best solution being to combine the five stand types in uneven proportions to improve biodiversity conservation. & Conclusion The expansion of selection silviculture in Euro-pean heterogeneous forest landscapes could enhance biodi-versity conservation if other stand types with complementary structural characteristics are maintained.

International audience; Mixed uneven-aged forests are considered favorable to the provision of multiple ecosystem services and to the conciliation of timber production and biodiversity conservation. However, some forest managers now plan to increase the intensity of thinning and harvesting operations in these forests. Retention measures or gap creation are considered to compensate potential negative impacts on biodiversity. Our objectives were to assess the effect of these management practices on timber production and biodiversity conservation and identify potential compensating effects between these practices, using the concept of ecological intensification as a framework. We performed a simulation study coupling Samsara2, a simulation model designed for spruce-fir uneven-aged mountain forests, an uneven-aged silviculture algorithm, and biodiversity models. We analyzed the effect of parameters related to uneven-aged management practices on timber production, biodiversity, and sustainability indicators. Our study confirmed that the indicators responded differently to management practices, leading to trade-offs situations. Increasing management intensity had negative impacts on several biodiversity indicators, which could be partly compensated by the positive effect of retention measures targeting large trees, non-dominant species, and deadwood. The impact of gap creation was more mitigated, with a positive effect on the diversity of tree sizes and deadwood but a negative impact on the spruce-fir mixing balance and on the diversity of the understory layer. Through the analysis of compensating effects, we finally revealed the existence of possible ecological intensification pathways, i.e., the possibility to increase management intensity while maintaining biodiversity through the promotion of naturebased management principles (gap creation and retention measures).

National audience; Mountain forests produce a large number of ecosystem services that are going to be affected by climate change. We are expecting an increase in high altitude species that could result in the decrease in resinous and subalpine species. These changes in species could adversely affect biodiversity and timber production. However, we also observe an increase in productivity that favours the production of energy wood and, at least temporarily, timber, as well as carbon storage. Given the possible rise in extreme climatic events, changes in vegetation could be marked by periods of decline, which will be very detrimental to the economic system, protection against natural hazards and biodiversity. Climate change will also have an indirect effect on the forest by increasing the demand for renewable energy and carbon storage. There is a lot of uncertainty about vegetation change predictions and this makes it difficult to define forest management adaptation strategies. Effective crisis management, monitoring of natural transformations of the forest based on the interaction between research and management (adaptive management) and the explicit factoring in of the concept of uncertainty appear to be essential to the maintenance of the ecosystem services provided by the forest.; La forêt de montagne produit de nombreux services écosystémiques qui vont être affectés par les changements climatiques. On attend une remontée des essences en altitude qui pourrait conduire à une diminution des résineux et des espèces du subalpin. Ces changements d'essences pourraient avoir un impact négatif sur la biodiversité et sur la production de bois d'½uvre. On observe cependant également une augmentation de la productivité favorable à la production de bois énergie et au moins temporairement de bois d'½uvre, ainsi qu'au stockage de carbone. Face à une augmentation possible des évènements climatiques extrêmes, les changements de végétation pourront être marqués par des épisodes de dépérissements, très négatifs pour la filière économique, la protection contre les risques naturels et la biodiversité. Le changement climatique affectera la forêt également de manière indirecte en augmentant la demande en énergie renouvelable et en stockage de carbone. Les incertitudes sur les prédictions de changements de végétation sont élevées, ce qui rend délicate la définition de stratégies d'adaptation de la gestion forestière. Une gestion de crises efficace, un accompagnement des évolutions naturelles de la forêt basé sur une interaction recherche-gestion (gestion adaptative), et la prise en compte explicite de la notion d'incertitude paraissent des éléments essentiels au maintien des services écosystémiques fournis par la forêt.

Cet article tente de faire le point sur les interactions entre changement climatique et mélange d’espèces dans les peuplements forestiers. Les changements climatiques vont affecter la composition des peuplements, non seulement par la modification du climat moyen, mais aussi par la modification du régime des perturbations, ou encore indirectement par les effets induits sur la filière forêt-bois et les stratégies des sylviculteurs. Ces effets, complexes, pourraient notamment s’opérer au bénéfice des pionnières et des espèces déplacées par l’homme, et aboutir à des dynamiques inédites. Mais le mélange des espèces peut également être mis à profit par le gestionnaire pour atténuer les impacts du changement climatique, et adapter progressivement et souplement la composition des peuplements. Les situations de mélange méritent d’ailleurs d’être mieux analysées, pour alimenter cette réflexion technique, mais également pour mieux comprendre les effets de changement en cours en jouant sur la différenciation des réponses des composants du mélange., This article attempts to provide an overview of the interaction between climate change and species mixture in forest stands. Climate change affects stand composition not only because average climate is changed but also due to the change in the disturbance regime, as well as indirectly through the induced effects on the forestry and forest-based industries and forest management strategies. These complex effects could be favourable to pioneer species and ones that have been displaced by man, possibly leading to unprecedented dynamics. However, forest managers too may use species mixtures to reduce the impact of climate change by gradually and flexibly adapting stand composition. Mixed species sites in fact deserve more extensive research so as to inform these technical decisions, but also to gain a better understanding of the effects of ongoing changes through the differentiated response of the species entering into the composition.

L’évolution des cadres institutionnels et politiques autour de la question des Services Ecosystémiques (SE), notamment avec la nouvelle loi Biodiversité en 2016 en France, amène à une obligation de leur prise en compte dans la gestion territoriale. Cela nécessite l’utilisation d’informations spatialement explicites, et par conséquent le développement de modèles permettant de cartographier les SE. La plupart des modèles se basent sur ou utilisent comme proxy des cartes d’Occupation ou d’Utilisation des Sols (OS/US). À partir d’une base de données spatialisée extrêmement précise, nous avons appliqué ou adapté des modèles permettant de cartographier 15 SE. Les résultats montrent que selon l’implication de la base de données d’OS/US en entrée dans les modèles, le type de modèle choisi (proxy vs. processus) et les processus modélisés, les patrons spatiaux résultants sont plus ou moins dépendants de la carte d’OS/US d’entrée. L’analyse critique des limites et incertitudes inhérentes à la constitution des cartes d’OS/US (en général et la notre en particulier), ainsi que l’utilisation de ces cartes à des fins de modélisation de SE a montré : 1- les apports notamment dans les milieux agricoles d’une description précise des dynamiques interannuelles de l’OS/US pour la quantification de SE d’approvisionnement ; 2- l’implication de limites typologiques d’OS/US pour la quantification de SE, notamment dans notre travail pour les milieux forestiers et semi-naturels. L’usage de la télédétection apparait alors comme une piste sérieuse d’amélioration à la fois typologique pour mieux caractériser l’OS/US et également à utiliser comme donnée d’entrée indépendante dans les modèles de SE., The evolution of institutional and policy frameworks for Ecosystem Services (ES), especially the new 2016 biodiversity legislation in France, make accounting for ES in land use management mandatory. This requires the use of spatially explicit information, and therefore the development of models to map ES. Most models are based on or use Land Use or Land Cover maps (LU/LC) as a proxy. Using a highly accurate spatialized LU/LC database, we applied or adapted models to map 15 ES. We show that depending on the implication of the LU/LC database as input to the models, the type of model (proxy vs. process based) and the processes modeled, the resulting spatial patterns are more or less dependent on the LU/LC database. The critical analysis of limits and uncertainties in the LU/LC mapping process (in general and for our database in particular), and the use of these maps for modelling ES showed : 1 - the benefits, especially in agricultural areas, of precise description and monitoring of LU/LC inter-annual dynamics for the quantification of ES supply ; 2- the consequences of LU/LC typological limits for the quantification of ES, especially in our work in forest and semi-natural areas. The use of remote sensing should support a serious typological improvement to better characterize the LU/LC and also use as independent input data in ES models.