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[hal-05456757] Secondary Seed Dispersal by Hydrochory During Surface Runoff Inside a Mediterranean Vineyard
Water circulation within agroecosystems can contribute to the distribution of plant communities by inducing seed dispersal through a process known as hydrochory. As vegetation is currently intensively managed in Mediterranean agroecosystems, relying on seed dispersal to increase vegetation cover and limit soil erosion could be a cost-effective approach. However, hydrochory has rarely been studied when it occurs during surface runoff in agroecosystems. In addition, hydrochory has been observed to be an efficient dispersal agent that plays a key role in both maintaining and enhancing biodiversity. Studying the effect of simple soil surface features on seed mobilization and dispersal by hydrochory during surface runoff is thus a way to gain insight into the influence of agricultural practices on the natural seed dispersal process. Here, we used seeds marked with a UV powder to track seed mobilization and movement during a typical Mediterranean runoff event over a ploughed and a vegetated surface within interrows. Surface roughness was the main factor limiting seed remobilization after seed deposition, and buoyancy did not appear to facilitate secondary seed dispersal by hydrochory. Vegetation and surface roughness influenced seed dispersal and thus confirmed previous studies in permanent and quasi-permanent water streams. However, a slope was not associated with seed dispersal, suggesting that a certain degree of slope is required to observe an effect of the slope on seed dispersal. Our study showed that accounting for seed morphology revealed that round seeds were more sensitive to surface features such as surface roughness and vegetation cover than hooked or plumed seeds, which had an influence on patterns of seed deposit during surface runoff. In the face of climate change, our results contribute to the development of biodiversity-based mitigation strategies in Mediterranean regions and vineyards.
ano.nymous@ccsd.cnrs.fr.invalid (Martin Faucher) 13 Jan 2026
https://hal.inrae.fr/hal-05456757v1
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[hal-05311246] Physical constraints and environmental factors shape phloem anatomical traits in woody angiosperm species
Xylem trait studies have enhanced our understanding of how plants strategically adapt their morphological and anatomical features to diverse climates. Despite the importance of the phloem in plant functioning, similar studies of phloem traits are lacking. To tackle this knowledge gap, we analyzed phloem anatomical traits of woody angiosperm species in relation to climate and the distance of samples to the stem tip. We collected main stem or branch cross‐sections of 188 angiosperm woody species, which represent a wide range of climates and diverse families. Measurements of xylem vessel and phloem sieve element diameter, density, and lumen fraction were used in phylogenetic structural equation models to disentangle internal and climatic constraints on their morphological and anatomical features. Our results showed that distance‐to‐tip mainly affects sieve element and vessel diameter and density, while climate more strongly influenced conduit lumen fraction. Vessel size was positively correlated with temperature after correcting for the distance‐to‐tip, while sieve element diameter was correlated with water availability. Our results highlight the need to account for distance‐to‐tip when accessing anatomical variations linked to the environment, and show that sieve element traits respond to other climatic drivers than vessel traits rather than simply mirroring them.
ano.nymous@ccsd.cnrs.fr.invalid (Yan Wang) 13 Oct 2025
https://hal.inrae.fr/hal-05311246v1
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[hal-05418804] Réseau INRAE- RÉCRÈ (Réseau Évaluation multiCRitÈre)
Le réseau INRAE-RÉCRÈ (Réseau Évaluation multiCRitÈre) a été créé pour structurer une communauté autour de la diversité des approches d’évaluation multicritère (EMC) déjà présentes à l’INRAE, et en favoriser le développement. Dans un contexte d’enjeux croissants liés à l’aide à la décision publique (environnement, nutrition, etc.), d’opportunités via des appels à projets nationaux et internationaux, et de besoin de co-construction d’outils d’aide à la décision avec les acteurs des filières, le réseau ambitionne de renforcer l’interconnexion, le partage de connaissances et l’animation interdisciplinaire sur ces thématiques. RÉCRÈ vise à faire progresser les démarches EMC en travaillant sur quatre verrous méthodologiques majeurs : l’intégration des changements d’échelles spatiales et organisationnelles, la prise en compte des dynamiques temporelles, la gestion du risque et de l’incertitude, ainsi que l’articulation avec les dires d’acteurs dans les processus d’évaluation.
ano.nymous@ccsd.cnrs.fr.invalid (Geneviève Gésan-Guiziou) 17 Feb 2026
https://hal.inrae.fr/hal-05418804v1
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[hal-05200178] AgroforesTreeAdvice: a decision support tool combining heterogeneous knowledge resources for tree species selection in agroforestry systems
<div><p>different aspects of adaptation to local conditions or achieving specific farming objectives. In this context, we introduce a new framework for agroforestry tree species selection. Its goals are twofold: (i) to compile and organize the knowledge embedded in existing tree selection tools, and (ii) to offer an intuitive, userfriendly graphical interface-AgroforesTreeAdvice. This tool allows users to input local parameters such as soil type, climate, biotic factors, and farm-level or socio-economic constraints, alongside production goals (e.g., timber, fruits) and ecosystem service Abstract Selecting the right tree species is a crucial step in designing sustainable and effective agroforestry systems. To support this process, several decision support systems (DSS) have been developed in various countries to help farmers and advisors choose appropriate species. However, these tools are often limited in reach-typically used only within the country where they were created-and tend to focus on</p></div>
ano.nymous@ccsd.cnrs.fr.invalid (Marie Gosme) 05 Aug 2025
https://hal.inrae.fr/hal-05200178v1
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[hal-05121280] PHOREAU v1.0: a new process-based model to predict forest functioning, from tree ecophysiology to forest dynamics and biogeography
Climate change impacts forest functioning and dynamics, but large uncertainties remain regarding the interactions between species composition, demographic processes and environmental drivers. While the effects of changing climates on individual plant processes are well studied, few tools dynamically integrate them, which precludes accurate projections and recommendations for long-term sustainable forest management. Forest gap models present a balance between complexity and generality and are widely used in predictive forest ecology, but their lack of explicit representation of some of the processes most sensitive to climate changes, like plant phenology and water use, puts into question the relevance of their predictions. Therefore, integrating trait- and process-based representations of climate-sensitive processes is key to improving predictions of forest dynamics under climate change. In this study, we describe the PHOREAU model, a new semi-empirical forest dynamic model resulting from the coupling of a gap model (FORCEEPS), with two process-based models: a phenology-based species distribution model (PHENOFIT) and a plant hydraulics model (SurEAU), each parametrized for the main European species. The performance of the resulting PHOREAU model was then evaluated over many processes, metrics and time-scales, from the ecophysiology of individuals to the biogeography of species. PHOREAU reliably predicted fine hydraulic processes at both the forest and stand scale for a variety of species and forest types. This, alongside an improved capacity to predict stand leaf areas from inventories, resulted in better annual growth compared to ForCEEPS, and a strong ability to predict potential community compositions. By integrating recent advancements in plant hydraulic, phenology, and competition for light and water into a dynamic, individual-based framework, the PHOREAU model, developed on the Capsis platform, can be used to understand complex emergent properties and trade-offs linked to diversity-effects effects under extreme climatic events, with implications for sustainable forest management strategies.
ano.nymous@ccsd.cnrs.fr.invalid (Tanguy Postic) 19 Jun 2025
https://hal.inrae.fr/hal-05121280v1
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[hal-05190147] Heurs et malheurs des démarches participatives. Retour sur une recherche-action hybride en territoires forestiers
Dans le cadre d’une recherche-action visant à accompagner la transition écologique, économique et sociale dans les territoires forestiers, nous avons mené des ateliers prospectifs avec les acteurs locaux pour faire émerger des actions collectives à développer. Deux démarches ont été hybridées : le « Jeu de Territoire », lequel vise à construire une vision partagée des dynamiques d’un territoire, et la démarche Living Lab qui permet de coconstruire des solutions innovantes tout en impliquant les futurs utilisateurs. Par une mise en récit de l’itinéraire méthodologique construit progressivement, nous revenons sur les heurs et malheurs du processus, en soulignant le potentiel et les limites du déploiement d’un dispositif participatif de recherche-formation-action pour l’accompagnement de la transition dans les territoires. Nous en tirons des enseignements génériques.
ano.nymous@ccsd.cnrs.fr.invalid (Sylvie Lardon) 28 Jul 2025
https://hal.inrae.fr/hal-05190147v1
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[hal-05468856] Plant Hydraulic Architecture for a Mechanistic Representation of Soil‐Plant‐Atmosphere Water Transfer in the Land Surface Model ORCHIDEE (r9107)
Land surface models (LSMs) typically represent soil moisture control on stomatal conductance through an empirical sensitivity function, without considering plant hydrology. This study proposes integrating water transfer representation within the soil-plant-atmosphere continuum in the ORCHIDEE land surface model. This new configuration includes vegetation hydraulic architecture and a stomatal control based on leaf water potential ψ leaf ) , along with a mechanistic representation of water absorption by roots via radial diffusion around the roots. An adaptive numerical scheme is implemented to prevent numerical instabilities during hydric stress, reducing hourly instabilities by a factor of 2. The implementation and the standard configuration of ORCHIDEE are calibrated and evaluated at FLUXNET sites with eddy-covariance flux measurements. A detailed assessment is carried out at two well-documented forest sites (FR-Hes and FR-Pue), where both configurations perform similarly regarding the seasonal dynamics of latent heat flux (RMSEs of 16.0 W/m 2 for the potential-based configuration and 15.8 W/m 2 for the standard configuration at FR-Hes). An evaluation of leaf water potential at FR-Pue shows correlations of 0.87 and 0.72 for predawn and midday ψ leaf respectively. A second evaluation across 135 sites from the FLUXNET2015 database highlights similar performances for both configurations. Finally, a global assessment of the differences between the two schemes emphasizes the good performance of the hydraulic architecture model. Overall, the new hydraulic architecture provides a more mechanistic description of stomatal conductance response to soil water stress and paves the way for incorporating physiological processes controlling tree mortality and using in situ observations to calibrate plant responses to water stress.<p>Plain Language Summary Land surfaces models (LSMs), which aim at representing the exchanges between the land surfaces and the atmosphere, usually represent the rate of water exchanges between the vegetation and the atmosphere according to soil water stress defined as an empirical function and without considering the plant water status. Here, we propose to represent the water transfers from the soil-root interface toward the leaves via a hydraulic architecture model, accounting for potential water storage in the plant. This model provides a more mechanistic description of the response of stomatal conductance to soil water stress and opens for the representation of important physiological processes such as cavitation. In order to evaluate the model, a detailed analysis has been performed at two forest sites. It enabled to understand the behavior of the new configuration and to verify its capacity to reproduce observations of water exchanges with the atmosphere. An extended analysis over 135 FLUXNET sites illustrated the overall good performances of the model. Finally, a study at global scale highlighted significant differences between the new hydraulic architecture and the standard model with respect to energy, water and carbon fluxes
ano.nymous@ccsd.cnrs.fr.invalid (Julien Alléon) 21 Jan 2026
https://hal.science/hal-05468856v1
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[hal-05345964] Species introductions shift seed dispersal potential more than extinctions across 120 island plant–frugivore communities
Oceanic islands are hotspots of both species extinctions and introductions, which led to marked changes in species composition. This may disrupt key ecological interactions, such as animal-mediated seed dispersal, with potential long-term impacts on ecosystem structure and functioning. While some recent studies on individual taxa and islands report functional shifts, there has been no globally comprehensive study of how these changes vary in intensity and direction across islands. Importantly, it remains unclear how changes in traits of animal communities actually translate to ecologically relevant mismatches with native plant species. We report widespread functional remodeling of frugivore communities based on frugivory-specific traits of all native, extinct, and introduced vertebrate frugivores (birds, mammals, reptiles) from 120 islands in 22 archipelagos. There is a trend for taxonomic and functional substitution, mainly of nonvolant terrestrial mammalian omnivores replacing large-gaped flying frugivores, which caused a mismatch between gape size and seed size. This shift in seed dispersal potential risks underestimation in single-taxon studies. Overall, vertebrate introductions outnumbered extinctions both in terms of species (44 vs. 23%) and islands affected (92 vs. 76%). Moreover, introductions have driven stronger shifts in frugivore trait space compared to extinctions. However, the general patterns are modulated by substantial spatial variation and idiosyncratic functional shifts within frugivore communities on some islands. This, coupled with differences in plant seed size distributions, leads to variability in realized functional mismatches among islands. These results emphasize challenges with predicting functional responses to anthropogenic activities, while highlighting that remodeling of ecosystem interactions is a global concern.
ano.nymous@ccsd.cnrs.fr.invalid (Julia Heinen) 11 Feb 2026
https://hal.science/hal-05345964v1
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[hal-05172724] Forest biodiversity and structure modulate human health benefits and risks
The benefits and risks of forests to human health are widely recognized. Yet, variation across forest types and their ecological characteristics driving health effects remain underexplored. Based on a continental-scale, interdisciplinary empirical database from 164 European forest stands, we constructed a Bayesian Belief Network to quantify seven causal pathways relating distinct forest types to physical and mental health. These forest–health pathways included mental well-being via visual or auditory stimuli, thermal comfort, polyphenol content of medicinal plants, mushrooms and nutrition, air quality, and ticks and Lyme disease. Results show that forests consistently provide net health benefits regardless of their ecological characteristics. Forest canopy density and tree species diversity emerge as key drivers, but their effect size and directionality are strongly pathway-dependent. Changes in forest canopy density can generate trade-offs. For example, forests optimized for heat buffering and air pollution mitigation may compromise medicinal plant yield and enhance Lyme disease prevalence. Tree diversity effects were weaker but more uniformly positive. Therefore, forest management should account for such trade-offs to tailor forest biodiversity and functioning to local public health priorities.
ano.nymous@ccsd.cnrs.fr.invalid (Loïc Gillerot) 21 Jul 2025
https://hal.inrae.fr/hal-05172724v1
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[hal-04644460] A Benchmark of Neural Networks for Semantic Segmentation of Wood Log Ends
Neural networks have achieved significant performance in image segmentation tasks. This paper describes a benchmark of deep learning-based methods for segmenting log ends of several species in images. More precisely, we are interested in segmenting a cross-section of a log positioned approximately at the centre of the image. Other logs that may be present next to the log of interest in the image should not be segmented. This task of semantic segmentation is essential in various applications, such as biometric log tracking and log quality assessment. Different state-of-the-art Convolutional Neural Networks (CNNs) and Vision Transformers (ViTs) for segmentation were tested in this paper, including Mask R-CNN, U-Net, PointRend, YOLOv11 and OneFormer. Some of these, being among the most recent architectures, had never before been tested on this type of image. To compare efficiency of the networks, well-known metrics such as Precision, Recall, Accuracy, Dice, IoU and MCC were used. From the experiment results, PointRend found to produce the most accurate segmentations, while YOLOv11 was better suited to real-time processing. In addition, an original dataset consisting of 1345 manually segmented images of oak log ends was created for this study and made available. Oak is a new species in these segmentation approaches. This dataset was supplemented with 855 images of two softwood species (Douglas fir and spruce) in order to increase the genericity of the models. The images have been selected to represent real situations encountered in the field and a wide variety of acquisition conditions and cross-section appearance.
ano.nymous@ccsd.cnrs.fr.invalid (Dorian Martinetto) 11 Jul 2024
https://hal.science/hal-04644460v1
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[hal-05279911] TROLL 4.0: Representing water and carbon fluxes, leaf phenology, and intraspecific trait variation in a mixed-species individual-based forest dynamics model - Part 2: Model evaluation for two Amazonian sites
TROLL 4.0 is an individual-based forest dynamics model that jointly simulates the structure, diversity, and functioning of tropical forests, including their water balance, carbon fluxes, and leaf phenology, while accounting for intraspecific trait variation for a large number of species. In a companion paper, we describe how the model represents the physiological and demographic processes that control the tree life cycle in a 1 m resolution spatially explicit scene and uses plant functional traits measurable in the field to parameterize such processes across species and individuals (Maréchaux et al., 2025). Here we evaluate the performance of TROLL 4.0 for two Amazonian sites with contrasting soil and climate properties. We assessed the model's ability to represent forest structure, composition, and dynamics using lidar-derived spatial distribution of top canopy height and forest inventories combined with information on plant functional traits. We also evaluated the model's ability to represent carbon and water fluxes, as well as leaf area variation, at daily and fortnightly resolution over a decade, using detailed information from on-site eddy covariance towers, satellite data, and ground-based or airborne lidar data. We finally compared the responses of carbon and water fluxes to environmental drivers between simulated and observed data. Overall, TROLL 4.0 provided a realistic representation of forests at both sites. The simulated canopy height distribution showed a high correlation coefficient (CC) with observed aerial and satellite data (CC &gt; 0.92), while the species and functional composition were well represented (CC &gt; 0.75). TROLL 4.0 also realistically simulated the seasonal variability of carbon and water fluxes (CC &gt; 0.46) and their responses to environmental drivers, while capturing temporal variations in leaf area (CC &gt; 0.76) and its partitioning into leaf age cohorts. However, TROLL 4.0 overestimated annual gross primary productivity at both sites (mean RMSEP = 0.94 ± 0.67 kgC m−2 yr−1) and evapotranspiration at one site (mean RMSEP = 0.75 ± 0.63 mm d−1), likely due to an underestimation of the soil water depletion and stomatal control during the dry season. This evaluation highlights the potential of TROLL 4.0 to represent ecosystem fluxes and the structure, diversity, and dynamics of plant communities at a fine resolution, paving the way for model predictions of the effects of climate change, fragmentation, and forest management on forest structure and dynamics.
ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Schmitt) 24 Sep 2025
https://hal.science/hal-05279911v1
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[hal-05268156] Multiyear drought strengthens positive and negative functional diversity effects on tree growth response
Mixed-species forests are proposed to enhance tree resistance and resilience to drought. However, growing evidence shows that tree species richness does not consistently improve tree growth responses to drought. The underlying mechanisms remain uncertain, especially under unprecedented multiyear droughts. We used a network of planted tree diversity experiments to investigate how neighborhood tree diversity and species' functional traits influence individual tree responses to drought. We analyzed tree cores (948 trees across 16 species) from nine young experiments across Europe featuring tree species richness gradients (1–6 species), which experienced recent severe droughts. Radial growth response to drought was quantified as tree-ring biomass increment using X-ray computed tomography. We applied hydraulic trait-based growth models to analyze single-year drought responses across all sites and site-specific responses during consecutive drought years. Growth responses to a single-year drought were partially explained by the focal species' hydraulic safety margin (representing species' drought tolerance) and drought intensity, but were independent of neighborhood species richness. The effects of neighborhood functional diversity on growth responses shifted from positive to negative with increasing drought duration during a single growing season. Tree diversity effects on growth responses strengthened during consecutive drought years and were site-specific with contrasting directions (both positive and negative). This indicates opposing diversity effects pathways under consecutive drought events, possibly resulting from competitive release or greater water consumption in diverse mixtures. We conclude that tree diversity effects on growth under single-year droughts may differ considerably from responses to consecutive drought years. Our study highlights the need to consider trait-based approaches (specifically, hydraulic traits) and neighborhood scale processes to understand the multifaceted responses of tree mixtures under prolonged drought stress. This experimental approach provides a robust framework to test biodiversity-ecosystem functioning (BEF) relationships relevant for young, planted forests under increased drought stress.
ano.nymous@ccsd.cnrs.fr.invalid (Hernán Serrano-León) 19 Sep 2025
https://hal.science/hal-05268156v1
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[hal-05077558] Insights into the subdaily variations in methane, nitrous oxide and carbon dioxide fluxes from upland tropical tree stems
Summary Recent studies have shown that stem fluxes, although highly variable among trees, can alter the strength of the methane (CH 4 ) sink or nitrous oxide (N 2 O) source in some forests, but the patterns and magnitudes of these fluxes remain unclear. This study investigated the drivers of subdaily and seasonal variations in stem and soil CH 4 , N 2 O and carbon dioxide (CO 2 ) fluxes. CH 4 , N 2 O and CO 2 fluxes were measured continuously for 19 months in individual stems of two tree species, Eperua falcata (Aubl.) and Lecythis poiteaui (O. Berg), and surrounding soils using an automated chamber system in an upland tropical forest. Subdaily variations in these fluxes were related to environmental and stem physiological (sap flow and stem diameter variations) measurements under contrasting soil water conditions. The results showed that physiological and climatic drivers only partially explained the subdaily flux variations. Stem CH 4 and CO 2 emissions and N 2 O uptake varied with soil water content, time of day and between individuals. Stem fluxes decoupled from soil fluxes. Our study contributes to understanding the regulation of stem greenhouse gas fluxes. It suggests that additional variables (e.g. internal gas concentrations, wood‐colonising microorganisms, wood density and anatomy) may account for the remaining unexplained variability in stem fluxes, highlighting the need for further studies.
ano.nymous@ccsd.cnrs.fr.invalid (Laëtitia Bréchet) 21 May 2025
https://hal.inrae.fr/hal-05077558v1
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[hal-04979333] Canopy functional trait variation across Earth’s tropical forests
Tropical forest canopies are the biosphere’s most concentrated atmospheric interface for carbon, water and energy1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties3. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically4. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence—32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.
ano.nymous@ccsd.cnrs.fr.invalid (Jesús Aguirre-Gutiérrez) 06 Mar 2025
https://hal.inrae.fr/hal-04979333v1
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[hal-05050145] Love Thy Neighbour? Tropical Tree Growth and Its Response to Climate Anomalies Is Mediated by Neighbourhood Hierarchy and Dissimilarity in Carbon‐ and Water‐Related Traits
Taxonomic diversity effects on forest productivity and response to climate extremes range from positive to negative, suggesting a key role for complex interactions among neighbouring trees. To elucidate how neutral interactions, hierarchical competition and resource partitioning between neighbours' shape tree growth and climate response in a highly diverse Amazonian forest, we combined 30 years of tree censuses with measurements of water‐ and carbon‐related traits. We modelled individual tree growth response to climate and neighbourhood to disentangle the relative effect of neighbourhood densities, trait hierarchies and dissimilarities. While neighbourhood densities consistently decreased growth, trait dissimilarity increased it, and both had the potential to influence climate response. Greater water conservatism provided a competitive advantage to focal trees in normal years, but water–spender neighbours reduced this effect in dry years. By underlining the importance of density and trait‐mediated neighbourhood interactions, our study offers a way towards improving predictions of forest dynamics.
ano.nymous@ccsd.cnrs.fr.invalid (Daniela Nemetschek) 29 Apr 2025
https://hal.science/hal-05050145v1
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[hal-05369777] Quelle mobilisation des données du passé pour penser le futur des forêts ?
Les forêts sont des socio-écosystèmes façonnés par une longue coévolution avec les sociétés humaines. En les replaçant dans ce temps long, les sciences du passé (histoire environnementale, écologie historique, paléoécologie, archéologie, génétique) sont pertinentes pour éclairer leur fonctionnement actuel et accompagner les choix de gestion. Leurs apports sont multiples : soutien à la biologie de la conservation et à l’écologie de la restauration, participation aux changements de paradigmes, et mise en perspective des enjeux écologiques via l’histoire longue de la réflexivité environnementale et des controverses. De même, les modélisations climatiques et environnementales et les prospectives se nourrissent des données historiques pour construire une gamme de scénarii futurs et aider à la prise de décision. Pourtant, la pertinence des données passées et les modalités selon lesquelles elles sont mobilisées pour penser les forêts de demain ont peu été explorées. Cette communication questionne la place des données du passé dans la construction de récits du futur (modélisations, prospectives…) en identifiant pourquoi, comment, pour qui et par qui celles-ci sont mobilisées. Elle s’intéresse aux différences épistémologiques entre les récits de trajectoires et controverses passées étayés sur une analyse critique de données, et les récits rétrospectifs servant de base à la construction de prospectives. Elle s’interroge sur le rôle du chercheur en sciences du passé dans la mobilisation de ces données (simple passeur de savoir ou implication active à la prospective) et sur son positionnement vis-à vis de l’action. Nous nous appuierons sur les recherches inter- et transdisciplinaires du FOREST-HUB pour explorer l’hypothèse selon laquelle les récits sur les trajectoires socio-écologiques et les controverses passées peuvent favoriser le dialogue entre chercheurs et acteurs forestiers (propriétaires, gestionnaires, usagers), contribuer à dépasser certains blocages, modifier des perceptions, fournir de nouveaux leviers et innover pour penser d’autres futurs pour les forêts.
ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Burri) 17 Nov 2025
https://hal.science/hal-05369777v1
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[hal-05352852] Tracer la provenance du bois de sapin (Abies alba Mill.) : défis dendrochronologiques et apports à la compréhension des dynamiques passées d’exploitation des forêts montagnardes
Le projet régional Bosca du Défi Clé Occitanie ‘Sciences du Passé’, vise à détailler les différentes étapes de la production, du transport et de l’utilisation du bois en région Occitanie durant les périodes médiévale et moderne. Il s’intéresse notamment aux modes de gestion et d’exploitation des forêts à ces époques, dans le but de sensibiliser à l’importance de ces écosystèmes pour la préservation de la biodiversité. L’un des objectifs majeurs du projet consiste à poursuivre les recherches dendrochronologiques dans cette région, en exploitant les cernes de croissance pour déterminer l’origine du bois d’œuvre historique. En complément des chênes caducifoliés (Quercus robur L. et Quercus petraea (Matt.) Liebl.), le sapin (Abies alba Mill.) a été retenu comme l’une des essences principales de notre étude en raison de son importance dans la filière bois passée en Occitanie. Après deux années d’investigations, le projet a permis des avancées notables dans la compréhension de l’usage du sapin dans la région. En confrontant les données issues de bois présents dans des bâtiments de l’époque moderne avec celles provenant d’arbres vivants, nous avons pu révéler la complexité des études de dendroprovenance liées à cette essence. En effet, des recherches antérieures ont démontré que des arbres de sapin situés à des distances considérables mais à une altitude équivalente produisent de variations de croissance très similaires. Ainsi, bien que les largeurs de cernes permettent une caractérisation altitudinale, les méthodes classiques de dendroprovenance – qui utilisent le coefficient de corrélation de Pearson (R) et le test de Student (T) – ne permettent pas de localiser précisément la provenance géographique du bois de sapin. Cela souligne la nécessité d’une évaluation rigoureuse des approches statistiques employées, et l’importance d’étudier les séries issues d’arbres vivants pour identifier les méthodes les plus fiables dans l’analyse de provenance des bois anciens. Pour cela, nous avons d’abord testé des méthodes statistiques, telles que l’analyse de la corrélation spatiale des résidus, sur un corpus d’arbres vivants provenant des Pyrénées centrales, du Massif central et des Alpes. L’étude de provenance s’est ensuite focalisée sur la zone de confluence entre les rivières Tarn et Garonne, avec une attention particulière portée à la ville de Montauban et à sa cathédrale, qui constitue un cas d’étude emblématique. L’édifice présente deux principales phases de construction. Les bois datés des XVIIe / XVIIIe siècles montrent des signes évidents de flottage ainsi que des marques de marchands originaires des Pyrénées, révélant l’existence de circuits d’approvisionnement bien établis. En revanche, les bois utilisés au XIXe siècle présentent des caractéristiques techniques et typologiques distinctes, témoignant d’un changement des modes de transport et vraisemblablement des aires d’approvisionnement en bois. L’ensemble de ces observations met en lumière une chaîne opératoire complexe, dont les dynamiques ont pu être précisées grâce à l’analyse dendrochronologique et à l’utilisation de méthodes statistiques d’abord testés sur nos référentiels d’arbres vivants.
ano.nymous@ccsd.cnrs.fr.invalid (Roberta D’Andrea) 07 Nov 2025
https://hal.science/hal-05352852v1
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[hal-05454980] Dynamics and environmental drivers of methane and nitrous oxide fluxes at the soil and ecosystem levels in a wet tropical forest
Tropical forests are critical for maintaining the global carbon balance and mitigating climate change, yet their exchange of greenhouse gases with the atmosphere remains understudied, particularly for methane (CH 4 ) and nitrous oxide (N 2 O). This study reports on continuous measurements of CH 4 and N 2 O fluxes at the ecosystem and soil levels, respectively through eddy covariance and an automated chamber technique, in a wet tropical forest in French Guiana over a period of 26 months. We studied the magnitude of CH 4 and N 2 O fluxes and their drivers (climatic variables) during the driest and wettest seasons. Seasonal ecosystem fluxes showed near-zero net CH 4 uptake during the driest season and emissions during the wettest season that were larger in magnitude than the uptake. Meanwhile, N 2 O emissions were of similar magnitudes in both seasons. Upland soils within the footprint of the eddy covariance tower emitted N 2 O in both seasons, although these fluxes were particularly small. In contrast, upland soils were characterised by CH 4 uptake. Overall, seasonal ecosystem and soil CH 4 and N 2 O fluxes were partially explained by seasonal variations in soil water content, soil temperature and global radiation. The magnitude and sign of the net ecosystem fluxes of CH 4 and N 2 O were likely due to outgassing from aboveground biomass and the presence of seasonally flooded areas within the footprint of the eddy covariance system. Further studies of other ecosystem compartments in different forest habitats are needed to better understand the temporal variations in CH 4 and N 2 O fluxes in wet tropical forests.
ano.nymous@ccsd.cnrs.fr.invalid (Laëtitia M Bréchet) 12 Jan 2026
https://hal.science/hal-05454980v1
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[hal-05088722] Effect of climate on traits of dominant and rare tree species in the world’s forests
Species’ traits and environmental conditions determine the abundance of tree species across the globe. The extent to which traits of dominant and rare tree species differ remains untested across a broad environmental range, limiting our understanding of how species traits and the environment shape forest functional composition. We use a global dataset of tree composition of &gt;22,000 forest plots and 11 traits of 1663 tree species to ask how locally dominant and rare species differ in their trait values, and how these differences are driven by climatic gradients in temperature and water availability in forest biomes across the globe. We find three consistent trait differences between locally dominant and rare species across all biomes; dominant species are taller, have softer wood and higher loading on the multivariate stem strategy axis (related to narrow tracheids and thick bark). The difference between traits of dominant and rare species is more strongly driven by temperature compared to water availability, as temperature might affect a larger number of traits. Therefore, climate change driven global temperature rise may have a strong effect on trait differences between dominant and rare tree species and may lead to changes in species abundances and therefore strong community reassembly.
ano.nymous@ccsd.cnrs.fr.invalid (Iris Hordijk) 28 May 2025
https://hal.inrae.fr/hal-05088722v1
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[hal-04769801] TROLL 4.0: representing water and carbon fluxes, leaf phenology, and intraspecific trait variation in a mixed-species individual-based forest dynamics model – Part 2: Model evaluation for two Amazonian sites
TROLL 4.0 is an individual-based forest dynamics model that jointly simulates the structure, diversity and functioning of tropical forests, including their water balance, carbon fluxes and leaf phenology, while accounting for intraspecific trait variation for a large number of species. In a companion paper, we describe how the model represents the physiological and demographic processes that control the tree life cycle in a one-metre-resolution spatially-explicit scene and uses plant functional traits measurable in the field to parameterize such processes across species and individuals (Maréchaux et al., submitted companion paper). Here we evaluate the performance of TROLL 4.0 for two Amazonian sites with contrasting soil and climate properties. We assessed the model's ability to represent forest structure and composition using lidar-derived canopy height distributions and forest inventories combined with information on plant functional traits. We also evaluated the model's ability to represent carbon and water fluxes, as well as leaf area variation, at daily and fortnightly resolution over a decade, using detailed information from on-site eddy covariance towers, satellite data and ground-based or air-borne lidar data. We finally compared the responses of carbon and water fluxes to environmental drivers between simulated and observed data. Overall, TROLL 4.0 provided a realistic representation of forests at both sites. The simulated canopy height distribution showed a high correlation coefficient (CC) with observed aerial and satellite data (CC&gt;0.92), while the species and functional composition were well represented (CC&gt;0.75). TROLL 4.0 also realistically simulated the seasonal variability of carbon and water fluxes (CC&gt;0.46) and their responses to environmental drivers, while capturing temporal variations in leaf area (CC&gt;0.76) and its partitioning in leaf age cohorts. However, TROLL 4.0 overestimated annual gross primary productivity at both sites (mean RMSEP=0.94 kgC m-2 yr-1) and evapotranspiration at one site (mean RMSEP=0.75 mm day-1), likely due to an underestimation of the soil water depletion and stomatal control during the dry season. This evaluation highlights the potential of TROLL 4.0 to represent ecosystem fluxes and the structure and diversity of plant communities at a fine resolution, paving the way for model predictions of the effects of climate change, fragmentation and forest management on forest structure and dynamics.
ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Schmitt) 06 Nov 2024
https://hal.inrae.fr/hal-04769801v1
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[hal-05428690] Forêts françaises et changement climatique : entre écologisation, climatisation et matérialités
Les forêts françaises font face aujourd’hui aux manifestations du changement climatique, induisant une prise de conscience des enjeux d’adaptation des pratiques sylvicoles. En parallèle, les forêts sont mises en avant comme élément central d’une stratégie nationale d’atténuation. Cet enjeu climatique vient s’ajouter à des dynamiques antérieures autour de la multifonctionnalité forestière et de l’écologisation de la société. Dans ce contexte, notre étude analyse les recombinaisons en termes de coalitions, pratiques et discours, à l’interface entre écologisation, climatisation et matérialités territoriales et climatiques vécues par les acteurs, dans trois parcs naturels régionaux. D’un côté, notre enquête montre une forme de stabilité dans les coalitions et les pratiques défendues : entre des sylvicultures dites douces ou industrielles. De l’autre, nous montrons aussi comment les matérialités territoriales et les expériences vécues du changement climatique peuvent façonner et modifier coalitions, discours et pratiques ; la gestion de la crise climatique induisant des changements de pratiques et d’alliances. Nous mettons enfin en avant que la climatisation des discours n’est pas forcément corrélée avec l’apparition de signes évidents des effets du changement climatique. Nous concluons sur le décalage entre des débats nationaux centrés autour de l’atténuation, tandis que les territoires se posent davantage la question de l’adaptation pour maintenir des forêts.
ano.nymous@ccsd.cnrs.fr.invalid (Vanessa Cholez) 22 Dec 2025
https://hal.science/hal-05428690v1
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[hal-05111798] Soil secrets and tree tales: an in-depth comparison of carbon storage in mixed and pure stands of pine and birch
<div><p>With climate change intensifying droughts, pest outbreaks and fire risks, forest management practices are increasingly focused on stabilizing soil carbon (C) stocks, which are essential for long-term ecosystem productivity and climate change mitigation. Planting more species-rich forests has been proposed as a potential solution, but the impact of species selection and planting density on carbon stocks remains largely unknown, particularly in mixed-species plantations, where local water availability plays a key role. In this study, our objective was to examine the effects of tree diversity, water availability, and tree density on carbon stocks and fluxes. Using a 10-year-old tree diversity experiment, we investigated how pure monocultures of pine (Pinus pinaster) and birch (Betula pendula), as well as mixed pine-birch stands, influence carbon dynamics under contrasting water conditions and different tree densities. Our results indicated that tree species mixtures slightly increased total C stocks, primarily through enhanced soil C storage due to niche partitioning and greater root turnover. However, pine monocultures showed higher aboveground biomass productivity than birch monocultures and mixed stands, regardless of water availability. Overall, increased soil moisture enhanced both tree biomass and soil carbon stocks, especially in mixed stands, likely by alleviating drought stress for birch. In contrast, higher water availability accelerated litter decomposition, reducing C stocks in the litter layer. Tree density was a key driver of C storage, with denser stands of pine monocultures showing increased aboveground biomass but reduced understory C stocks. These findings highlight the context-dependent benefits of mixed stands: while species mixtures can enhance soil C storage and adaptability to drought, they may be inferior to pine monocultures in aboveground C storage, at least under the specific environmental conditions and temporal scale covered by our study. This study underscores the need for site-specific forest management strategies that balance productivity and C sequestration goals, offering guidance for climate change mitigation through alternative planting schemes adjusting tree density and species composition while maintaining ecosystem services.</p></div>
ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Fanin) 13 Jun 2025
https://hal.inrae.fr/hal-05111798v1
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[hal-05252221] 19th-century afforestation policies have predisposed mountain slopes to forest expansion under recent climate warming in the southern French Alps
This interdisciplinary study investigates the long-term interplay between forests, human societies, and climate in Abriès-Ristolas (Queyras massif, southern French Alps) over the past 200 years. Drawing on archival records, dendrochronology, satellite-derived vegetation indices, and climate data, we trace the historical legacies that have shaped contemporary land cover and forest dynamics. Our findings show that recent forest expansion and land greening – often attributed solely to climate change – are also the outcome of 19th-century socio-economic shifts and environmental policies. Specifically, we find that spatial variability in greening trends aligns with the historical structure of cadastral parcels, highlighting persistent land-use effects. The 1860 Mountain Reforestation Law, locally implemented by an 1864 decree, combined with rural depopulation and a decline in pastoral activities, significantly reduced anthropogenic pressure, facilitating natural forest regeneration in this area. These historical transformations have predisposed the landscape to continued forest expansion, with recent climate warming further amplifying this trajectory over the past four decades. This case study underscores the importance of incorporating land-use legacies into interdisciplinary approaches for understanding present-day ecological change.
ano.nymous@ccsd.cnrs.fr.invalid (Arthur Bayle) 12 Sep 2025
https://hal.inrae.fr/hal-05252221v1
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[hal-05398655] Un observatoire dédié au suivi de la biodiversité
La biodiversité poursuit-elle son érosion en France ? Les écosystèmes forestiers sont-ils particulièrement concernés ? Quelles sont les principales pressions, menaces et réponses apportées aujourd'hui ? L'Observatoire national de la biodiversité fournit les éléments clés pour comprendre et objectiver ces grandes questions sociétales. L'Observatoire national de la biodiversité est un dispositif mettant à disposition des informations précises et documentées sur la biodiversité en France. Divers indicateurs et synthèses sont publiés régulièrement sur le portail naturefrance. Un groupe de travail "biodiversité et forêt" développe des indicateurs spécifiques aux milieux forestiers.
ano.nymous@ccsd.cnrs.fr.invalid (Thomas Brusten) 04 Dec 2025
https://hal.inrae.fr/hal-05398655v1
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[hal-05223935] Sentinel-2 time series reveal species-specific responses in temperate conifer dieback
Silver fir (Abies alba Mill.), Norway spruce (Picea abies (L.) H. Karst) and Scots pine (Pinus sylvestris L.) tare major European conifers undergoing severe dieback. Large-scale, high-frequency monitoring with multispectral satellites using Sentinel-2 images and ground observations (2018-2023) over the French mountains for 742 pure and 949 mixed stands, we investigated the interest of analysing dieback detection at the species level. We used time series analysis from seven raw bands and eight vegetation indices and integrated spectral anomalies for different periods prior to the ground survey. Results differed among species: silver fir was best detected with a 15-month period and Inverted Red-Edge Chlorophyll Index (IRECI), Norway Spruce with a 1-month period and Continuum removal of the shortwave-infrared spectrum (CRSWIR), and Scots pine with a 4-month period and red-edge (CRRE). In pure stands, dieback detection was most accurate for Norway spruce (R2 = 0.54, OA = 77%) followed by silver fir (R2 = 0.34, OA = 61%) and Scots pine (R2 = 0.16, OA = 64%). Dieback was difficult to detect in its early stages and in mixtures, mainly for Norway spruce and Scots pine. This study highlights the importance of developing species-specific methods for large-area monitoring of dieback.
ano.nymous@ccsd.cnrs.fr.invalid (Hélène Carletti) 26 Aug 2025
https://hal.science/hal-05223935v1
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[hal-05178612] Graft union formation involves interactions among bud signals, carbon availability, dormancy release, wound responses and non‐self‐communication in grapevine
<div><p>Grafting plants uses intrinsic wound-healing mechanisms to join together different organisms, yet the processes underpinning graft union formation remain poorly understood. To further our understanding of the molecular reprogramming triggered by grafting and wounding in a perennial plant, we characterised the transcriptome and metabolome of intact and wounded un-grafted scions and rootstocks, and homo-and hetero-grafts at 0 and 14 days after grafting/wounding in grapevine. We show that grafting triggered the coordinated activation of gene expression and the accumulation of lipids and phenolic compounds in comparison with intact tissues. We highlight an asymmetry in gene expression above and below the graft interface, which is in part not only due to carbon status, but also to intrinsic differences in gene expression between un-grafted scions and rootstocks, and their differential responses to wounding. We found that b-1,4-glucanases were differentially expressed in response to both wounding and grafting and demonstrated that exogenous b-1,4-glucanase application increased grafting success rate. Grafting, wounding, homo-graft and hetero-graft-specific transcriptome responses were characterised. The comprehensive experimental design of the dataset containing all necessary control samples allowed the identification of genes and metabolites potentially involved in wounding and grafting responses in an iconic grafted fruit crop. This is important because knowledge of genes regulating graft union formation could be leveraged for the selection of new, highly graft-compatible cultivars in the future.</p></div>
ano.nymous@ccsd.cnrs.fr.invalid (Grégoire Loupit) 23 Jul 2025
https://hal.inrae.fr/hal-05178612v1
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[hal-04644450] A new approach to biometric wood log traceability combining traditional methods and deep learning
This paper focuses on the biometric traceability of oak logs using images of cross-sections. The images were acquired in two temporally separated image acquisition sessions, and we want to find the correct matches for the images of the second session from the pool of images of the first session. No biometric traceability method has yet been proposed for oak logs and they differ greatly from softwood logs. In this context, we present a new method consisting of two steps. The first one involves extracting visible features from log-end images using the Scale-Invariant Feature Transform (SIFT) method and the SuperPoint architecture. Then, in the second step, the extracted features are matched to verify whether two images correspond to the same log. For this, we consider the deep neural network LightGlue that is well-known for efficiently matching sparse local features between pairs of images. This new approach was compared with two recent state-of-the-art methods, including a significant evolution of one of them. The experiments were carried out on two datasets, including a new and large dataset of almost 25k images. The results show the performance of the new method for identifying oak logs, significantly outperforming the most recent ones. Source code and pre-trained models are available at https://github.com/Braquemarok/ATECH2024, while the image database is accessible at https://doi.org/10.57745/9DBCL4.
ano.nymous@ccsd.cnrs.fr.invalid (Dorian Martinetto) 11 Jul 2024
https://hal.science/hal-04644450v1
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[hal-05244373] Corrigendum to “Oak regeneration facing deer browsing: Can competition between saplings offset the diversion effect? A simulation experiment” [Ecological Modelling 489 (2024) 110608]
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 08 Sep 2025
https://hal.inrae.fr/hal-05244373v1
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[hal-05307661] Bayesian model averaging of climate-dependent forest models using Expectation–Maximization
In the context of rapid climate change, climate-dependent models are essential for assessing species vulnerability. However, variation in model structure and divergence in their predictions introduce substantial uncertainty. Rather than selecting a single “best” model, a more robust strategy is to integrate predictions across models. Bayesian model averaging with Expectation–Maximization (BEM) provides an alternative to simple model averaging (SMA) and weighted model averaging (WMA) for combining ensemble predictions. To date, BEM has been rarely applied to tree species distribution models. We developed a BEM framework for models predicting either species occurrence or proxy variables linked to occurrence. The approach was applied to European beech (Fagus sylvatica) in France, using an ensemble of six models: four species distribution models, one model predicting the probability of hydraulic failure, and one model predicting juvenile productivity. In contrast to SMA and WMA, which assigned similar weights across models, BEM concentrated 85% of the weight on two models. Furthermore, BEM enabled spatially explicit decomposition of model weights, allowing us to identify regions where predictions diverged most strongly. The resulting probability maps revealed a specific zone in environmental space where model agreement on beech occurrence was particularly limited. Focusing on this zone may help refine projections and shed light on the ecological mechanisms that enable local persistence.
ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Picard) 10 Oct 2025
https://hal.inrae.fr/hal-05307661v1
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[hal-04918197] Remote-sensing-based forest canopy height mapping: some models are useful, but might they provide us with even more insights when combined?
The development of high-resolution mapping models for forest attributes based on remote sensing data combined with machine or deep learning techniques has become a prominent topic in the field of forest observation and monitoring. This has resulted in the availability of multiple, sometimes conflicting, sources of information, but, at face value, it also makes it possible to learn about forest attribute uncertainty through the joint interpretation of multiple models. This article seeks to endorse the latter by utilizing the Bayesian model averaging approach to diagnose and interpret the differences between predictions from different models. The predictions in our case are forest canopy height estimations for metropolitan France arising from five different models. An independent reference dataset, containing four different definitions of forest height (dominant, mean, maximum, and Lorey's) was established based on around 5500 plots of the French National Forest Inventory (NFI), distributed across the entire area of interest. In this study, we evaluate models with respect to their probabilities of correctly predicting measurements or estimations obtained from NFI plots, highlighting the spatial variability in respective model probabilities across the study area. We observed sig-nificant variability in these probabilities depending on the forest height definition used, implying that the different models inadvertently predict different types of canopy height. We also present the respective inter-model and intra-model variance estimations, enabling us to grasp where the employed models have comparable contributions but contrasting predictions. We show that topography has an important impact on the models spread. Moreover, we observed that the forest stand vertical structure, the dominant tree species, and the type of forest ownership systematically emerge as statistically significant factors influencing the model divergences. Finally, we observed that the fitted higher-order mixtures, which enabled the presented analyses, do not necessarily reduce bias or prevent the saturation of the predicted heights observed in the individual models.
ano.nymous@ccsd.cnrs.fr.invalid (Nikola Besic) 29 Jan 2025
https://hal.science/hal-04918197v1
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[hal-04644900] Traceability of oak (Quercus petraea (Matt.) Liebl. and Quercus robur L.) logs: the Biomtrace database
The Biomtrace database contains 33390 RGB images of the bottom cross-section of 5135 French oak logs. Each log was photographed four or five times at different camera orientations during an initial shot. In most cases, additional photos were taken at least three weeks after the first shot. The cross-sections were segmented on all the images using the PointRend convolutional neural network. Spatial calibration was carried out by a specific algorithm using a checkerboard pattern present in each image. Biomtrace dataset is available at https://doi.org/10.57745/9DBCL4. Pending publication of the database, a private URL will provide access to it: https://entrepot.recherche.data.gouv.fr/privateurl.xhtml?token=e71c17c0-11cb-4d80-86d2-5a91ce2de13b.
ano.nymous@ccsd.cnrs.fr.invalid (Fleur Longuetaud) 11 Jul 2024
https://hal.science/hal-04644900v1
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[hal-05328365] La technologie LiDAR pour explorer ce que les sols forestiers doivent à leur usage agricole antique
Le LiDAR (Light Detection And Ranging) permet de cartographier sous couvert forestier les microreliefs du sol, ce qui en fait un outil révolutionnaire pour identifier les traces d’usages anciens des sols dans un milieu jusqu’alors peu prospecté par les archéologues. En France, un des premiers vols LiDAR pour des recherches archéologiques en contexte forestier a été effectué pendant l’hiver 2006-2007 et a couvert le massif de Haye (Meurthe-et-Moselle, 54). Les données LiDAR ont rendu possible la cartographie de 647 km linéaires de structures anciennes, identifiées comme des vestiges de systèmes agraires et de voies gallo-romaines, mais aussi près d’une centaine de bâtiments. Sur le plan archéologique, cette étude a mis en évidence une sous-estimation majeure des surfaces occupées et cultivées à la période antique et remis en cause le schéma classique d’usage du territoire par des grandes villas romaines. Elle amène aussi à repenser à grande échelle les conséquences de ces usages anciens sur les propriétés des sols. Les pratiques agricoles antiques sont en effet connues pour avoir un impact résiduel à très long terme sur les propriétés chimiques des sols forestiers ainsi que sur la biodiversité floristique qui s’y exprime. Le programme national LiDAR-HD, mené par l’IGN met actuellement à la disposition du public une couverture LiDAR pour l’ensemble du territoire français, que nous analysons dans les massifs forestiers du Grand Est. Des parcellaires géométriques denses couvrant plus de 100 km2, de géométrie semblable à ceux de la forêt de Haye, ont été relevés dans les massifs de Mittersheim et de Paroy, sur les sols lourds développés sur les marnes du Keuper. Une première prospection archéologique en février 2025 a permis de confirmer sur le terrain les interprétations des données LiDAR, en identifiant des habitats enclos et des voies de circulation datés de la période romaine. En parallèle de ce parcellaire, un vaste réseau de mares forestières, datant de la même période et d’origine probablement anthropique, a également été mis en évidence grâce au LiDAR. Ces données LiDAR permettent ainsi une prospection rapide et à large échelle, facilitant considérablement la sélection de sites d’étude, nombreux et géographiquement distants. En outre, la possibilité d’exploiter ces données pour entrainer des modèles d’intelligence artificielle permettrait de mener ces réflexions au niveau national. Ceci devrait permettre de répondre à des questions multiples : (i) Quelles étaient les modes d’occupations et les usages antiques des territoires actuellement forestiers ? (ii) Ces populations se sont-elles installées préférentiellement sur certains types de sols, et comment les ont-elles modifiés ? (iii) L’ancien usage agricole de ces sols s’exprime-t-il encore aujourd’hui sous la forme d’une fertilité, d’une composition chimique ou d’une biodiversité remarquables ? (iv) Existe-t-il encore, en France, des sols et des écosystèmes forestiers réellement exempts d’activité humaine, qui constitueraient alors une référence de « naturalité » pédologique et écologique ?
ano.nymous@ccsd.cnrs.fr.invalid (Marie Neri) 23 Oct 2025
https://hal.science/hal-05328365v1
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[hal-05054453] Plant diversity dynamics over space and time in a warming Arctic
The Arctic is warming four times faster than the global average 1 and plant communities are responding through shifts in species abundance, composition and distribution 2–4 . However, the direction and magnitude of local changes in plant diversity in the Arctic have not been quantified. Using a compilation of 42,234 records of 490 vascular plant species from 2,174 plots across the Arctic, here we quantified temporal changes in species richness and composition through repeat surveys between 1981 and 2022. We also identified the geographical, climatic and biotic drivers behind these changes. We found greater species richness at lower latitudes and warmer sites, but no indication that, on average, species richness had changed directionally over time. However, species turnover was widespread, with 59% of plots gaining and/or losing species. Proportions of species gains and losses were greater where temperatures had increased the most. Shrub expansion, particularly of erect shrubs, was associated with greater species losses and decreasing species richness. Despite changes in plant composition, Arctic plant communities did not become more similar to each other, suggesting no biotic homogenization so far. Overall, Arctic plant communities changed in richness and composition in different directions, with temperature and plant–plant interactions emerging as the main drivers of change. Our findings demonstrate how climate and biotic drivers can act in concert to alter plant composition, which could precede future biodiversity changes that are likely to affect ecosystem function, wildlife habitats and the livelihoods of Arctic peoples 5,6 .
ano.nymous@ccsd.cnrs.fr.invalid (Mariana García Criado) 23 May 2025
https://u-picardie.hal.science/hal-05054453v1
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[hal-05224580] The addition of chemical compounds extracted from leaf litter leachates enhances short term methane uptake by forest soils
Upland forest soils are recognized as the primary biological sink for methane. The influence of litter on soil methane uptake has not been clearly elucidated: litter could reduce methane uptake, have no influence or enhance it. Until now, the role of litter has only been studied for the diffusion of gases. The chemical influence of leachate compounds from litter is a dominant process in forest ecosystems. In this study, we investigated this influence on soil methane fluxes. We extracted leaf litter compounds from four temperate tree species (beech, oak, pine and spruce) and determined their biochemical composition by spectrophotometry. The leachates, or pure water for the control treatment, were added to three different types of sieved forest soil (alocrisol, cambisol and luvisol) to determine their influences on methane fluxes. The methane fluxes were monitored for 48-h. We found that the chemical compounds leached from leaf litter enhanced methane uptake by 8.2 % with no significant effect of the species from which the leachates were extracted. The enhancement depended on the type of soil and was correlated to initial methane uptake. These results indicate that the role played by litter in the methane balance of forest soils, which has so far been thought to affect only the availability of the substrate (methane and dioxygen), is more complex than that.
ano.nymous@ccsd.cnrs.fr.invalid (Vincent Arricastres) 26 Aug 2025
https://hal.inrae.fr/hal-05224580v1
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[hal-05012488] High host density promotes ash dieback
<div><p>Ash dieback, induced by Hymenoscyphus fraxineus, a pathogenic ascomycete native to East Asia, has severely affected ash stands in Europe, raising questions about the future of the species. Reports on the relationship between host density and disease incidence are contradictory. Although the most recent studies indicate a reduction in disease severity at lower host densities, the evidence remains largely correlative, with the only study experimentally manipulating host density concluding that no effect of host density on ash dieback can be demonstrated. We investigated the impact of host density and tree species mix on the evolution of ash dieback and subsequent radial growth of affected trees. Data were extracted from a network of permanent thinning trials comprising pure and mixed stands of even-aged ash and a progeny trial where ash dieback was monitored from 2010 to 2015 (39 plots at 7 sites). We showed that host density, estimated from ash basal area, has a significant impact on the evolution of ash dieback and subsequent growth of affected stands. Large ash trees at low densities suffered little from the disease. The impact on ash growth is mainly due to the reduction in disease severity, although a significant effect of tree species mixing on ash growth also occurs for healthy trees. As ash trees are often present at low densities in mixtures, this should mitigate ash dieback.</p></div>
ano.nymous@ccsd.cnrs.fr.invalid (Marie-Laure Martin) 31 Mar 2025
https://hal.science/hal-05012488v1
