Victor Fririon

Face au changement climatique, se pose la question de la capacité intrinsèque naturelle des forêts à y faire face et des impacts positifs ou négatifs de la gestion sylvicole. Luberon2, un modèle Démo-Génétique individus-centré (DG-ABM) qui intègre des régimes de perturbation stochastiques a été développé pour apporter des réponses.À partir du modèle Luberon2, deux plans de simulation sont analysés :1. Dans les écosystèmes forestiers, la sélection naturelle dépend étroitement de la compétition interindividuelle qui se manifeste notamment par le processus d’auto-éclaircie, c’est-à-dire la suppression des plus petits arbres lorsque la densité est élevée. Nous montrons une augmentation rapide de la vigueur et des performances de croissance des peuplement monospécifiques de cèdre en réponse à un environnement social compétitif sélectif. Nous montrons également qu’une gestion intensive, i.e. nombreuses éclaircies systématiques, en réduisant la compétition, limite la capacité d’évolution des peuplements, fait aggravé en présence de perturbations naturelles non sélectives. Les taux d’évolution observés sont dans une gamme empirique réaliste, ce qui représente un élément fort de validation du modèle.2. Une stratégie classique d'adaptation au changement climatique consiste à maintenir une faible densité d'arbres via une sylviculture intensive pour réduire le niveau de stress pendant les sécheresses et limiter les impacts directs. Néanmoins, nous montrons que la sélection naturelle pour une moindre sensibilité à le potentiel d'induire une réponse positive rapide en termes de croissance et de survie appréciable dès la première génération, et qu’une intensification de la sylviculture réduit ce potentiel adaptatif chez des peuplements monospécifiques de sapin Douglas. Dès lors qu'il y a de la diversité génétique, c'est-à-dire le cas réaliste, nous montrons qu’une sylviculture moins intensive, visant à favoriser l'adaptation spontanée, représente la meilleure stratégie pour favoriser la productivité et abaisser la vulnérabilité. En particulier, le maintien d'un niveau élevé de stress à un stade de peuplement juvénile semble être une stratégie prometteuse pour favoriser l'acclimatation et l'adaptation précoce.Le rôle de la diversité génétique et des processus évolutifs ainsi que l’impact de la gestion sont discutés en détail dans le cadre de diverses stratégies d’adaptation de la sylviculture au changement climatique et à la lumière de la large étude bibliographique effectuée sur les interactions entre perturbations, pratiques de gestion et diversité génétique.

In managed populations—whether for production or conservation—management practices can interfere with natural eco‐evolutionary processes, providing opportunities to mitigate immediate impacts of disturbances or enhance selection on tolerance traits. Here, we used a modelling approach to explore the interplay and feedback loops among drought regimes, natural selection and tree thinning in naturally regenerated monospecific forests. We conducted a simulation experiment spanning three nonoverlapping generations with the individual‐based demo‐genetic model Luberon2. Luberon2 integrates forest dynamics processes driving survival and mating success, including tree growth, competition, drought impacts and regeneration, with genetic variation in quantitative traits related to these processes. We focused on two variable traits: individual vigour, determining diameter growth potential without stress as the deviation from average stand growth, and individual sensitivity to drought stress as the slope of the relationship between diameter growth and drought stress level. We simulated simplified thinning scenarios, tailored to even‐aged stands. Considering plausible genetic variation and contrasting drought regimes, the predicted evolutionary rates for both traits aligned with documented rates in wild plant and animal populations. Thinning considerably reduced natural selective pressures caused by competition and drought compared to unthinned stands. However, the conventional thinning practice of retaining the larger trees resulted in indirect anthropogenic selection that enhanced genetic gain in vigour and lowered sensitivity by up to 30%. More intensive thinning aimed at reducing drought stress by reducing stand density hampered the selection against sensitivity to drought, potentially hindering long‐term adaptation. Conversely, avoiding the early, nonselective thinning step—thereby promoting both natural and anthropogenic selection—ultimately resulted in better stand performance while maintaining long‐term evolvability. This study emphasises the potential of evolution‐oriented forestry strategies to combine drought stress mitigation with genetic adaptation. It provides general insights into how population management, disturbance regimes and eco‐evolutionary responses interfere, aiding sustainable decision‐making amid environmental uncertainties.

Biological production systems and conservation programs benefit from and should care for evolutionary processes. Developing evolution‐oriented strategies requires knowledge of the evolutionary consequences of management across timescales. Here, we used an individual‐based demo‐genetic modelling approach to study the interactions and feedback between tree thinning, genetic evolution, and forest stand dynamics. The model combines processes that jointly drive survival and mating success—tree growth, competition and regeneration—with genetic variation of quantitative traits related to these processes. In various management and disturbance scenarios, the evolutionary rates predicted by the coupled demo‐genetic model for a growth‐related trait, vigor, fit within the range of empirical estimates found in the literature for wild plant and animal populations. We used this model to simulate non‐selective silviculture and disturbance scenarios over four generations of trees. We characterized and quantified the effect of thinning frequencies and intensities and length of the management cycle on viability selection driven by competition and fecundity selection. The thinning regimes had a drastic long‐term effect on the evolutionary rate of vigor over generations, potentially reaching 84% reduction, depending on management intensity, cycle length and disturbance regime. The reduction of genetic variance by viability selection within each generation was driven by changes in genotypic frequencies rather than by gene diversity, resulting in low‐long‐term erosion of the variance across generations, despite short‐term fluctuations within generations. The comparison among silviculture and disturbance scenarios was qualitatively robust to assumptions on the genetic architecture of the trait. Thus, the evolutionary consequences of management result from the interference between human interventions and natural evolutionary processes. Non‐selective thinning, as considered here, reduces the intensity of natural selection, while selective thinning (on tree size or other criteria) might reduce or reinforce it depending on the forester's tree choice and thinning intensity.

The study of eco‐evolutionary dynamics, that is of the intertwinning between ecological and evolutionary processes when they occur at comparable time scales, is of growing interest in the current context of global change. However, many eco‐evolutionary studies overlook the role of interindividual interactions, which are hard to predict and yet central to selective values. Here, we aimed at putting forward models that simulate interindividual interactions in an eco‐evolutionary framework: the demo‐genetic agent‐based models (DG‐ABMs). Being demo‐genetic, DG‐ABMs consider the feedback loop between ecological and evolutionary processes. Being agent‐based, DG‐ABMs follow populations of interacting individuals with sets of traits that vary among the individuals. We argue that the ability of DG‐ABMs to take into account the genetic heterogeneity—that affects individual decisions/traits related to local and instantaneous conditions—differentiates them from analytical models, another type of model largely used by evolutionary biologists to investigate eco‐evolutionary feedback loops. Based on the review of studies employing DG‐ABMs and explicitly or implicitly accounting for competitive, cooperative or reproductive interactions, we illustrate that DG‐ABMs are particularly relevant for the exploration of fundamental, yet pressing, questions in evolutionary ecology across various levels of organization. By jointly modelling the effects of management practices and other eco‐evolutionary processes on interindividual interactions and population dynamics, DG‐ABMs are also effective prospective and decision support tools to evaluate the short‐ and long‐term evolutionary costs and benefits of management strategies and to assess potential trade‐offs. Finally, we provide a list of the recent practical advances of the ABM community that should facilitate the development of DG‐ABMs.