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[hal-04300713] Mediterranean vineyard soil seed bank characterization along a slope/disturbance gradient: Opportunities for land sharing
The Mediterranean region is predicted to experience more intense rainfall events separated by severe droughts due to climate change. In agrosystems, the intensification of rainfall on dry bare soils will lead to an increase in runoff and erosion rates, especially on slopes. A common method to reduce erosion is to cover the soil with vegetation. To save costs, this vegetation could be provided by the soil seed bank. Vineyards situated on slopes are part of the typical Mediterranean landscape; thus, developing vegetation cover inside vineyards could be a solution to fight growing erosion risks in addition to providing other valuable services. However, the relationship between slope, erosion and seed loss can vary. Another key ingredient in the development of spontaneous vegetation cover is the spatial dispersal of seeds from one place to another, but the amount of seeds displaced depends on their respective dispersal modes. In this study, we sampled the soil seed bank at two sites characterized by either a low or high frequency of vegetation removal. The soil seed bank was sampled along a transect starting upslope of the vineyards to the bottom of neighboring agricultural ditches. Germination trials were carried out to define the soil seed bank in terms of species and seed density. Each identified species was linked with a main dispersal mode. Our main objective was to assess the effect of vegetation cover on seed loss inside a vineyard, as well as the potential differences in the soil seed bank along our transect and the influence of dispersal mode on those differences. Despite previous contradictory literature, vegetation did not seem to protect interrows from seed loss caused by runoff. Overall, our results support the use of the soil seed bank to provide spontaneous vegetation cover to limit present and future erosion rates and advocate for relaxing vegetation removal operations.
ano.nymous@ccsd.cnrs.fr.invalid (Martin Faucher) 22 Nov 2023
https://hal.science/hal-04300713v1
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[hal-04718869] The Relationship between Maturation Size and Maximum Tree Size from Tropical to Boreal Climates
The fundamental trade-off between current and future reproduction has long been considered to result in a tendency for species that can grow large to begin reproduction at a larger size. Due to the prolonged time required to reach maturity, estimates of tree maturation size remain very rare and we lack a global view on the generality and the shape of this trade-off. Using seed production from five continents, we estimate tree maturation sizes for 486 tree species spanning tropical to boreal climates. Results show that a species' maturation size increases with maximum size, but in a non-proportional way: the largest species begin reproduction at smaller sizes than would be expected if maturation were simply proportional to maximum size. Furthermore, the decrease in relative maturation size is steepest in cold climates. These findings on maturation size drivers are key to accurately represent forests' responses to disturbance and climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Valentin Journé) 02 Oct 2024
https://hal.science/hal-04718869v1
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[hal-04858502] Contribution of oak tree-ring width and stable isotopes to reconstruct hydroclimate variability in central France over the last millennium
To better understand current global warming, it is crucial to document natural climate variability during the pre-industrial period. This helps to characterize the patterns of variability and identify the forcings driving it, assess the accuracy of the variability simulated by climate models, and determine the role of anthropogenic effects (IPCC 2021). In Europe, tree-ring width (TRW) and maximum latewood density (MXD) series have been widely used to reconstruct temperature variations over the past millennium, particularly in high-altitude or high-latitude regions (e.g. Briffa et al 1992; Corona et al 2010). At lower altitudes, tree growth is more controlled by drought and precipitation, making these records valuable for characterizing hydroclimate variability (e.g. Büntgen et al 2011, Cook et al 2016, Cooper et al 2013). However, these tree-ring series are affected by age-related effects and stand dynamics trends, requiring standardization procedures that can impact the low-frequency component of the signal (see Helama et al 2017, for a review). The dendroisotopic approach, which is based on the determination of the oxygen and carbon isotopic composition (δ18O and δ13C) in tree-ring cellulose, partly overcomes the issues associated with conventional tree-ring measurements. These isotopic proxies are highly sensitive to water stress, yet they are less affected, or even unaffected, by age-related growth effects. However, although numerous multi-century reconstructions exist across Europe (e.g. Büntgen et al 2021, Treydte et al 2024) and specifically in France (Etien et al 2008, Labuhn et al 2016), there are no millennial reconstructions based on stable isotopes or tree-ring widths at low altitudes in France. This is notable given that these areas have long been inhabited by human societies for centuries. Our goal is to deepen the understanding of past climate variability at the regional scale, where changes are more pronounced, by producing the first millennial scale tree-ring width chronology for central France. In parallel, we aim to construct a cellulose δ18O chronology covering the period 1200-1400 CE, which will help define the climatic transition between the relative warming of the Medieval Climate Anomaly (MCA; ∼950-1250 CE) and the cooling of the Little Ice Age (LIA; 1350-1850 CE). We present here the methodological framework of this work along with the initial findings on growth-climate relationships during the instrumental period. The climate sensitivity of the 3 proxies (TRW, δ18O and δ13C) has been evaluated. Notably, the strong correlation between the June-July SPEI and cellulose δ18O (r = -0.75), combined with model verification, indicates that δ18O is the most reliable proxy for reconstructing past hydroclimatic variability (Fig. 3). In contrast, TRW seems to be controlled more by the March-July SPEI and precipitation (r = 0.61). The observed correlations between the proxies and instrumental data indicate the potential to reconstruct past hydroclimatic variability. Dry and wet periods can be reconstructed over the last millennium from TRW using the vast corpus of archaeological wood studied, as well as from cellulose δ18O during the period 1200-1400 CE. This will provide new data on both climatic long-term variability and the MCA-LIA transition at low altitude in France.
ano.nymous@ccsd.cnrs.fr.invalid (Charlie Hureau) 29 Dec 2024
https://hal.science/hal-04858502v1
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[hal-04745820] Beech poles do not produce flexure wood after mechanical stimulation: does shifting from stress avoidance to stress tolerance matter?
Formation of a specific wood tissue called flexure wood often accompanies the thigmomorphogenetic syndrome in mechanically stimulated trees. Flexure wood exhibits high microfibril angle allowing for increase in the stem flexibility and higher resistance to post-elastic damage during repeated loadings. In this study, we examine the microstructure and the properties of wood produced by beech poles submitted to increased mechanical stimulus. Contrary to previous results obtained on poplar saplings, aside a little decrease in density no changes in the microstructure or the post-elastic properties of wood were observed in beech poles. While in saplings wood properties explained 25% of the resistive moment increase and 50% of the maximal curvature decrease, their relative contribution was of 6% for the resistive moment and 5% for the maximal curvature decrease in beech poles. These apparent discrepancies between our results and previous studies were explained by a possible combination of three factors: (i) experienced level of mechanical stimulus, (ii) tree size-dependent shift in the strategy to resist wind loads and (iii) the species sensitivity to thigmomorphogenetic syndrome. We further suggest the use of juvenile transition as an indicator of the species strategy to cope with environmental signals adopting a broader view of the adaptive capacity of a given species.
ano.nymous@ccsd.cnrs.fr.invalid (Jana Dlouhá) 21 Oct 2024
https://hal.science/hal-04745820v1
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[hal-04736502] Modeling of street trees for urban micro-climatology in Strasbourg - The TIR4sTREEt project
Urban vegetation acts as a microclimate regulator through transpiration and by providing shade for pedestrians and facades, thereby reducing surface temperatures of buildings and ground. The intensity of this phenomenon depends on the characteristics of the tree (species, leaf density, size, crown geometry, proximity to buildings, isolated or park trees), the soil and the surrounding environment. Street trees can have a significant impact on air and surface cooling, with a potential decrease of 2°C to 3°C and more than 10°C respectively (Gillner et al., 2015). The project TIR4sTREEt (Thermal Infrared for Street Trees) aims to enhance our understanding and quantify the effect of three different species of street trees on urban climate, with a particular focus on surface temperature. To achieve this, the project's first objective is to conduct full-scale measurement campaigns of both seasonal street microclimate (soil, air, buildings) and tree functioning. The second objective is to develop a methodology for merging the geometry of an urban scene with the measured surface temperatures. The thermal 3D model can be used, in a third objective, to validate estimates produced by microclimatic simulation tools, currently being developed by the consortium, namely the LASER/F model (LAtent SEnsible Radiation Fluxes) adapted to the scale of a district (Kastendeuch et al., 2017) and the RATP model (Radiation Absorption, Transpiration and Photosynthesis), operating at the scale of an individual tree (Sinoquet et al., 2001). By coupling both, it is possible to analyse and model the impact of trees and urban morphology on the urban climate. In the long term, these findings will help urban planners to propose greening scenarios and thus improve the ambient climate.
ano.nymous@ccsd.cnrs.fr.invalid (Tania Landes) 15 Oct 2024
https://hal.science/hal-04736502v1
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[hal-04729697] Tree drought–mortality risk depends more on intrinsic species resistance than on stand species diversity
Increasing tree diversity is considered a key management option to adapt forests to climate change. However, the effect of species diversity on a forest's ability to cope with extreme drought remains elusive. In this study, we assessed drought tolerance (xylem vulnerability to cavitation) and water stress (water potential), and combined them into a metric of drought–mortality risk (hydraulic safety margin) during extreme 2021 or 2022 summer droughts in five European tree diversity experiments encompassing different biomes. Overall, we found that drought–mortality risk was primarily driven by species identity (56.7% of the total variability), while tree diversity had a much lower effect (8% of the total variability). This result remained valid at the local scale (i.e within experiment) and across the studied European biomes. Tree diversity effect on drought–mortality risk was mediated by changes in water stress intensity, not by changes in xylem vulnerability to cavitation. Significant diversity effects were observed in all experiments, but those effects often varied from positive to negative across mixtures for a given species. Indeed, we found that the composition of the mixtures (i.e., the identities of the species mixed), but not the species richness of the mixture per se, is a driver of tree drought–mortality risk. This calls for a better understanding of the underlying mechanisms before tree diversity can be considered an operational adaption tool to extreme drought. Forest diversification should be considered jointly with management strategies focussed on favouring drought‐tolerant species.
ano.nymous@ccsd.cnrs.fr.invalid (Renaud Decarsin) 17 Jun 2025
https://hal.inrae.fr/hal-04729697v1
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[hal-04765061] Tips & Tricks pour analyser un Hydrogel en CRYO MEB
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ano.nymous@ccsd.cnrs.fr.invalid (C Blavignac) 04 Nov 2024
https://hal.science/hal-04765061v1
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[hal-04429206] Climate anomalies and neighbourhood crowding interact in shaping tree growth in old‐growth and selectively logged tropical forests
Climate extremes and biotic interactions at the neighbourhood scale affect tropical forest dynamics with long‐term consequences for biodiversity, global carbon cycling and climate change mitigation. However, forest disturbance may change crowding intensity, and thus the relative contribution of climate extremes and neighbourhood interactions on tree growth, thereby influencing tropical forest resistance and resilience to climate change. Here, we aim to evaluate the separate and interactive effects of climate and neighbours on tree growth in old‐growth and disturbed tropical forests. We used 30 years of growth measurements for over 300 tropical tree species from 15 forest plots in French Guiana to investigate the separate and interactive effects of climate anomalies (in solar radiation, maximum temperature, vapour pressure deficit and climatic water deficit) and neighbourhood crowding on individual tree growth. Contrasting old‐growth and selectively logged forests, we also examined how disturbance history affects tree growth sensitivity to climate and neighbours. Finally, for the most abundant 100 species, we evaluated the role of 12 functional traits pertaining to water relations, light and carbon use in mediating tree growth sensitivity to climate anomalies, neighbourhood crowding and their interactions. Climate anomalies tied to heat and drought stress and neighbourhood crowding independently reduced tree growth, and showed positive interactive effects which attenuated their separate effects on tree growth. Their separate and interactive effects were stronger in disturbed than undisturbed forests. Fast‐growing species (i.e. higher intrinsic growth rates) were more abundant in disturbed forests and more sensitive to climate anomalies and neighbourhood crowding. Traits related to water relations, light and carbon use captured species sensitivities to different climate anomalies and neighbourhood crowding levels but were weak predictors of their interactions. Synthesis : Our results demonstrate that climate anomalies and neighbourhood crowding can interact to shape tropical tree growth, suggesting that considering the biotic context may improve predictions of tropical forest dynamics facing altered climate regimes. Furthermore, species traits can capture tree growth sensitivity to the separate effects of climate and neighbours, suggesting that better representing leading functional dimensions in tropical tree strategies offers a promising way towards a better understanding of the underlying ecological mechanisms that govern tropical forest dynamics.
ano.nymous@ccsd.cnrs.fr.invalid (Daniela Nemetschek) 20 Feb 2024
https://hal.inrae.fr/hal-04429206v1
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[hal-04329908] Microclimate, an important part of ecology and biogeography
Brief introduction: What are microclimates and why are they important?Microclimate science has developed into a global discipline. Microclimate science is increasingly used to understand and mitigate climate and biodiversity shifts. Here, we provide an overview of the current status of microclimate ecology and biogeography in terrestrial ecosystems, and where this field is heading next. Microclimate investigations in ecology and biogeography: We highlight the latest research on interactions between microclimates and organisms, including how microclimates influence individuals, and through them populations, communities and entire ecosystems and their processes. We also briefly discuss recent research on how organisms shape microclimates from the tropics to the poles. Microclimate applications in ecosystem management: Microclimates are also important in ecosystem management under climate change. We showcase new research in microclimate management with examples from biodiversity conservation, forestry and urban ecology. We discuss the importance of microrefugia in conservation and how to promote microclimate heterogeneity. Methods for microclimate science: We showcase the recent advances in data acquisition, such as novel field sensors and remote sensing methods. We discuss microclimate modelling, mapping and data processing, including accessibility of modelling tools, advantages of mechanistic and statistical modelling and solutions for computational challenges that have pushed the state-of-the-art of the field. What's next?We identify major knowledge gaps that need to be filled for further advancing microclimate investigations, applications and methods. These gaps include spatiotemporal scaling of microclimate data, mismatches between macroclimate and microclimate in predicting responses of organisms to climate change, and the need for more evidence on the outcomes of microclimate management.
ano.nymous@ccsd.cnrs.fr.invalid (Julia Kemppinen) 31 Oct 2024
https://hal.science/hal-04329908v2
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[hal-04574740] Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass‐loss rate and stabilization
The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large‐scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass‐loss rates and stabilization factors of plant‐derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy‐to‐degrade components accumulate during early‐stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass‐loss rates and stabilization, notably in colder locations. Using TBI improved mass‐loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early‐stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.
ano.nymous@ccsd.cnrs.fr.invalid (Judith M Sarneel) 14 May 2024
https://hal.inrae.fr/hal-04574740v1
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[hal-04619314] Bilan hydrique et suivi du cycle de l’eau à l’échelle de l’écosystème forestier : les mesures du réseau ICOS France
Une forêt échange de l’eau avec son environnement. Elle reçoit un apport d’eau liquide sous forme de précipitationset d’éventuelles remontées de nappes souterraines. Elle émet de la vapeur d’eau dans l’atmosphère par évaporation,et peut éventuellement perdre de l’eau par ruissellement (sur sols en pente) ou drainage profond. On appelle « bilanhydrique » de l’écosystème forestier la différence entre ces entrées et ces sorties d’eau. Les différents flux et stockd’eau déterminant le bilan hydrique sont mesurés de façon continue dans cinq sites forestiers français appartenant àl’infrastructure de recherche ICOS France. Ces cinq sites comprennent des forêts tempérées et méditerranéennes,feuillues ou résineuses, caducifoliées ou sempervirentes et partagent tous les mêmes protocoles de mesure. Dans cetarticle, nous évaluons les déterminants du bilan hydrique de ces sites et nous mettons l’accent sur les différencesentre le site méditerranéen à chêne vert de Puéchabon, dans l’Hérault, et le site caducifolié tempéré à chêne sessilede Barbeau, en Ile-de-France. Selon les sites et les années, l’évapotranspiration peut représenter entre 50% et 100%de la pluie reçue par l’écosystème. Toutefois, la transpiration des arbres ne représente que 50% à 60% de l’évapo-transpiration. Au cours de l’année, l’évapotranspiration de l’écosystème dépend à la fois de la demande évapora-toire de l’atmosphère et de la disponibilité en eau du sol. Le sol forestier joue un rôle de réservoir d’eau qui permetaux arbres de continuer à transpirer, même pendant les périodes sans pluie, d’autant que les arbres ont des racinesqui peuvent aller chercher l’eau jusqu’à plusieurs mètres de profondeur. L’analyse des données de l’infrastructureICOS permet de montrer que la consommation d’eau de l’écosystème forestier dépend (1) du climat (demande éva-poratoire), (2) de la réserve hydrique du sol à un moment donné et (3) des caractéristiques morphologiques desarbres du peuplement telles que la profondeur d’enracinement et la surface foliaire. Les principes déduits de l’ana-lyse de ces données permettent de développer des modèles représentant le fonctionnement des forêts, utiles pourquantifier l’évolution des stocks en eau des sols et des sous-sols forestiers, et la réponse des forêts au changementclimatique en cours.
ano.nymous@ccsd.cnrs.fr.invalid (Jean‐marc Limousin) 20 Jan 2025
https://hal.inrae.fr/hal-04619314v1
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[hal-04653766] AgroforesTreeAdvice: an advice aggregator for tree species selection for agroforestry systems
Tree species selection is a crucial step in the design of agroforestry systems, for which farmers expressed the need for decision support systems (DSS). A quick search among the partners of the DigitAF Horizon Europe project (https://digitaf.eu) allowed us to identify several such DSS, which had been developed independently, in different countries and for different agroforestry systems. These include DENTRO (tree selection for silvoarable and silvopastoral system in Flanders), ShadeTreeAdvice (shade tree selection for coffee and cocoa agroforestry systems), SCSM (soil and climate suitability models for a range of trees and shrubs worldwide), Deciduous (fruit tree rootstock selection in France) and a Czech trees characteristics database. In this presentation, we present our joint efforts to develop a common framework in which these tools could all fit, in order to increase their i) findability (all tools are gathered in the same place), ii) accessibility (a common interface allows users to query the tools with interfaces having the same look and feel), and iii) interoperability (API requests can be used to query all tools). Our hypothesis was that all tree selection tools work by matching tree traits to selection criteria defined by the user in order to provide a suitability score for each tree species, and that the selection criteria, although being different between different tools, could be organised in a structured way to make comparisons between tools possible. We considered that tree suitability depends on i) adaption to local conditions and ii) efficiency at providing the desired benefits (tree products and/or ecosystem services (ES). Based on the trait-function-service framework (Violle et al. 2007), we organized the data according to two types of tree traits: response traits (causing the response of the tree to its environment, and so driving its adaptation to local conditions) and effect traits (allowing the tree to perform functions leading to the production of ES, e.g. fulfilling the farmer’s objectives). Criteria linked to the provision of ES (and therefore the matching effect traits) were organized following the CICES 5.1 classification (Haines-Young and Potschin 2018) at the highest levels, and subsequent levels were added when more details were needed (e.g. distinguishing between different uses of wood). In the absence of internationally recognized classification of criteria linked to the adaptation to local conditions, these criteria were organized as adaptation to soil, climate, biotic context, constraints at plot scale, constraints at farm scale and constraints at socio-economic level. As for ES, we classified these criteria in a hierarchical manner, allowing different levels of details according to the focus of each tool. Finally, we developed a shiny app using this common framework to interface with several tree selection tools.Initial work on the five species/rootstock selection tools mentioned in the introduction proved that the idea is feasible: the criteria used in each tool were categorized according to the common framework. Table 1 shows the number of criteria of each top category in each tool. The shiny app aggregates the advice of these five tools. It allows users to define their site conditions and objectives, compute the adaptation and efficiency scores of each tree species and visualize the results in graph or table form; it also supports URL requests. It is available in six languages and can be tested at https://agroforestreeadvice.sk8.inrae.fr/. After the proof of concept is done, we aim at enlarging the tool contributors beyond the limits of the DigitAF project. Therefore, we created a repository under EURAF GitHub account. The code is open-source and we welcome contributions (adding new languages, adding new tools, improving code): https://github.com/euraf/agroforestreeadvice. The tool will be tested and further improved within DigitAF Living Labs.
ano.nymous@ccsd.cnrs.fr.invalid (Marie Gosme) 19 Jul 2024
https://hal.inrae.fr/hal-04653766v1
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[hal-04382723] Not all sweetness and light: Non-structural carbohydrate storage capacity in tree stems is decoupled from leaf but not from root economics
Non-structural carbohydrates (NSC) are considered as indicators of the balance between tree carbon sources and sinks and reflect functional strategies throughout different biomes. However, little is known about the contribution of NSC to tree economics, and in particular, whether leaf, stem and coarse root traits co-ordinate together into a whole-tree economics spectrum. Twenty-four functional traits (including NSC content) were measured in leaves, stem and coarse root xylem of up to 90 angiosperm tree species in temperate, Mediterranean and tropical climates. By performing principal component analysis and standardized major axis regression, we explored the relationships between NSC and other functional traits, as well as the effects of climate and phylogeny on these relationships. Our results revealed a covariation between leaf and coarse root NSC content and leaf economic traits, whereas stem NSC content was largely decoupled from the leaf economics spectrum that was mostly driven by leaf nitrogen content and leaf mass per area. Coarse root xylem traits were closely correlated with leaf traits, while most stem xylem traits were independent from the leaf economics spectrum but covaried with coarse root traits. Trade-offs among traits in tropical species opposed those from other climates. Evolutionary history affected relationships among certain traits but did not change overall patterns. We conclude that due to leaf habit, an extended growing season and heightened defences, tropical species form distinct conservative resource acquisition strategies. Across all climates, as the stem must provide an efficient transport route between roots and leaves, while maintaining the display of branch and leaf organs, stem xylem design and NSC storage capacity lead to a stem economics spectrum that is largely independent from the leaf spectrum, but is coupled with that of coarse roots due to anatomical continuity.
ano.nymous@ccsd.cnrs.fr.invalid (Guangqi Zhang) 23 Jul 2025
https://hal.inrae.fr/hal-04382723v1
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[hal-04692350] Oak regeneration facing deer browsing: Can competition between saplings offset the diversion effect? A simulation experiment
The constraint caused by wild ungulates on forest regeneration is increasing worldwide. Hypotheses for plant association effects predict that species susceptible to herbivory can gain protection from other neighbouring plant species. In theory, such interactions could help limit the impact of browsing on the regeneration of specific tree species. However, the presence of neighbouring species can also result in increasing competition for resources between species. The resultant effects on forest regeneration of these interactions, both positive (protection against herbivores) and negative (inter-specific competition) are still unclear. To gain insight, we coupled models of browsing by roe deer (Capreolus capreolus) and of forest dynamics to simulate trajectories of oak (Quercus petraea (Matt.) Liebl.) regeneration admixed with species of contrasted palatability and growth rate under different scenarios of browsing pressure and initial sapling density. We also investigated how releasing oak saplings from all or specific neighbours during the simulation affect regeneration. We found that admixed species composition had a relatively weak effect on the density of oak recruits, but a strong effect on the duration of the regeneration phase. Oak regenerated faster when admixed with species of intermediate growth and low palatability (Fagus sylvatica) than with species of fast growth and high palatability (Carpinus betulus L.), except at intermediate sapling density and high browsing pressure where we found the opposite. Releasing oak from all competitors was most effective in promoting oak regeneration when admixed with both species together, although the benefit of competition release was much weaker at high browsing pressure. Lastly, we found that at low initial sapling density (i.e., 10 saplings/m2), oak regeneration was driven only by browsing and the effect of admixing species became negligible. Our study showed that admixing oak with palatable neighbours impedes rather than improves oak regeneration due to increased competition for resources. As such, we suggest that the benefits of herbivore diversion can be off-set by increased inter-specific competition.
ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 23 Sep 2024
https://ofb.hal.science/hal-04692350v1
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[hal-04334646] Distinct trait syndromes and plasticity maintain similar performance between seedlings populations of the riparian tree species Populus nigra L.
Riparian forests remain largely understudied in the context of climate change in comparison to other forest ecosystems although they serve multiple socio-ecological functions. We evaluated local adaptation and adaptive potential in Populus nigra L., an emblematic tree species of European riparian forests. We set up a reciprocal transplant experiment and measured 17 structural and functional traits among 10 progenies of two genetically differentiated populations. The populations originated from two separate watersheds differing in climate conditions and a total of 1200 seedlings were grown in 1-m3 mesocosms at both sites for one growing season. Traits measured were related to growth, leaf physiology and xylem water transport. The populations showed similar biomass suggesting no local adaptation for overall performance but displayed distinct trait syndromes and plastic abilities. The southern population primarily adjusted through changes in allocation and leaf water-use efficiency while the northern population primarily adjusted through changes in specific leaf area. Genetic variation within populations was most of the times equal or larger than between populations. This combined with the generally moderate to high heritability values and the observed plasticity suggested significant adaptive potential. Altogether, our findings reveal that although evolution may not lead to obvious differentiation between populations in global performance, integrated multi-trait approaches are highly valuable to shed light on how evolution may shape distinct underlying functional strategies among populations resulting in a similar outcome.
ano.nymous@ccsd.cnrs.fr.invalid (Régis Fichot) 11 Dec 2023
https://hal.inrae.fr/hal-04334646v1
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[hal-04602330] Carbon assimilation limitations during and after the European 2022 drought and heat wave
In 2022, Europe experienced a widespread severe summer edaphic drought and heat event. We explore how the gross primary productivity (GPP) was affected by this dry spell by contrasting 2022 with previous years, using high-frequency Eddy-Covariance and meteorological monitoring from 16 ICOS forest stations spanning across Europe. With the exception of Scandinavian forests, all monitored stations experienced a reduction of GPP ranging from 5 to 60% and a reduction of evapotranspiration ranging from 10 to 62% during summer. GPP reduction was predominantly attributed to a decrease in the maximum apparent carboxylation rate rather than a direct effect of soil water content limitation on stomatal aperture at the canopy scale. Some sites showed more GPP than usual after the drought due to abnormally hot and wet autumn conditions. However, most severely affected sites did not fully recover to normal GPP levels after the drought, suggesting a potential lagged effect of the adverse summer conditions.
ano.nymous@ccsd.cnrs.fr.invalid (Emilie Joetzjer) 05 Jun 2024
https://hal.inrae.fr/hal-04602330v1
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[hal-04841197] Phenology Across Scales: An Intercontinental Analysis of Leaf‐Out Dates in Temperate Deciduous Tree Communities
Aim: To quantify the intra-community variability of leaf-out (ICVLo) among dominant trees in temperate deciduous forests, assess its links with specific and phylogenetic diversity, identify its environmental drivers and deduce its ecological consequences with regard to radiation received and exposure to late frost. Location: Eastern North America (ENA) and Europe (EUR). Time Period: 2009-2022. Major Taxa Studied: Temperate deciduous forest trees. Methods: We developed an approach to quantify ICVLo through the analysis of RGB images taken from phenological cameras. We related ICVLo to species richness, phylogenetic diversity and environmental conditions. We quantified the intra-community variability of the amount of radiation received and of exposure to late frost.
ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Delpierre) 16 Dec 2024
https://hal.inrae.fr/hal-04841197v1
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[hal-04841046] Mechanical vulnerability of beech (Fagus sylvatica L.) poles after thinning: Securing stem or roots is risk dependent
In this study, we analysed how the tree growth in stem and roots reacts to thinning, focusing on the consequences for mechanical stability of the root-soil plate quantified by field mechanical bending tests. In order to disentangle the role of the biomechanical control of growth (thigmomorphogenesis) from other factors, half of the studied trees were guyed to remove mechanical stimulation due to the wind of living cells. Surprisingly, our results show a decrease in the root-soil plate mechanical performances for a given stem biomass after thinning. This decrease was however explained by boosted biomass allocation to the stem at the expense of the root system. Further, relationship between the initial stiffness and the strength (overturning moment) of the root-soil plate was modified by thinning. It is suggested that at this development stage (poles), as stem break is the weakest point of tree resistance to wind loads, the biomechanical control of growth strengthens preferentially the stem and not the anchorage. Further developments should study the diversity of behaviours between development stages and between species for a unified theory on the role of the thigmomorphogenetic syndrome in tree resistance to wind risk, with synergies and trade-offs with other processes and functions.
ano.nymous@ccsd.cnrs.fr.invalid (Jana Dlouhá) 16 Dec 2024
https://hal.inrae.fr/hal-04841046v1
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[hal-04608174] Residual water losses mediate the trade-off between growth and drought survival across saplings of 12 tropical rainforest tree species with contrasting hydraulic strategies
Knowledge of the physiological mechanisms underlying species vulnerability to drought is critical for better understanding patterns of tree mortality. Investigating plant adaptive strategies to drought should thus help to fill this knowledge gap, especially in tropical rainforests exhibiting high functional diversity. In a semi-controlled drought experiment using 12 rainforest tree species, we investigated the diversity in hydraulic strategies and whether they determined the ability of saplings to use stored non-structural carbohydrates during an extreme imposed drought. We further explored the importance of water- and carbon-use strategies in relation to drought survival through a modelling approach. Hydraulic strategies varied considerably across species with a continuum between dehydration tolerance and avoidance. During dehydration leading to hydraulic failure and irrespective of hydraulic strategies, species showed strong declines in whole-plant starch concentrations and maintenance, or even increases in soluble sugar concentrations, potentially favouring osmotic adjustments. Residual water losses mediated the trade-off between time to hydraulic failure and growth, indicating that dehydration avoidance is an effective drought-survival strategy linked to the ‘fast–slow’ continuum of plant performance at the sapling stage. Further investigations on residual water losses may be key to understanding the response of tropical rainforest tree communities to climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Camille Ziegler) 06 Jan 2025
https://hal.inrae.fr/hal-04608174v1
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[hal-04521727] La simulation d’abroutissement : un outil pour mieux comprendre l’effet de l’herbivorie par les cervidés sur les jeunes plants de Chênes
Le renouvellement de nombreuses essences d’intérêts économique et écologique est remis en cause par une hausse généralisée des populations de cervidés et des dégâts qu'ils occasionnent. La simulation d’abroutissement est une méthode expérimentale consistant à combiner la section mécanique de la plante et l’application de salive de cervidés sur la zone sectionnée qui permet de contrôler précisément les épisodes d'abroutissement auxquels sont soumis les plants. Nous illustrons ici, par deux exemples, les possibilités offertes par cette technique pour comprendre les effets des abroutissements de chevreuil sur la croissance et survie des plants de Chêne. Messages clés• La simulation d’abroutissement consiste à imiter l’herbivorie en combinant section mécanique et application de salive sur la plante.• L’abroutissement simulé réduit de 50 % la survie des semis de Chêne.• Les semis répondent en investissant dans les traits fonctionnels favorisant la croissance (teneur foliaire en azote et chlorophylle).
ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 26 Mar 2024
https://hal.inrae.fr/hal-04521727v1
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[hal-04564702] Multimodal imaging analysis in silver fir reveals coordination in cellulose and lignin deposition
Despite lignin being a key component of wood, the dynamics of tracheid lignification are generally overlooked in xylogenesis studies, which hampers our understanding of environmental drivers and blurs the interpretation of isotopic and anatomical signals stored in tree rings. Here, we analyzed cell wall formation in silver fir (Abies alba Mill.) tracheids to determine if cell wall lignification lags behind secondary wall deposition. For this purpose, we applied a multimodal imaging approach combining transmitted light microscopy (TLM), confocal laser scanning microscopy (CLSM), and confocal Raman microspectroscopy (RMS) on anatomical sections of wood microcores collected in northeast France on 11 dates during the 2010 growing season. Wood autofluorescence after laser excitation at 405 and 488 nm associated with the RMS scattering of lignin and cellulose, respectively, which allowed identification of lignifying cells (cells showing lignified and nonlignified wall fractions at the same time) in CLSM images. The number of lignifying cells in CLSM images mirrored the number of wall-thickening birefringent cells in polarized TLM images, revealing highly synchronized kinetics for wall thickening and lignification (similar timings and durations at the cell level). CLSM images and RMS chemical maps revealed a substantial incorporation of lignin into the wall at early stages of secondary wall deposition. Our results show that most of the cellulose and lignin contained in the cell wall undergo concurrent periods of deposition. This suggests a strong synchronization between cellulose and lignin-related features in conifer tree-ring records, as they originated over highly overlapped time frames.
ano.nymous@ccsd.cnrs.fr.invalid (Gonzalo Pérez-De-Lis) 30 Apr 2024
https://hal.science/hal-04564702v1
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[hal-05302359] Analyses pour étudier la dépolymérisation des protéines par les micro-organismes du sol
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ano.nymous@ccsd.cnrs.fr.invalid (Stutzmann Charlotte) 07 Oct 2025
https://hal.science/hal-05302359v1
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[hal-04818390] Gross rates of protein depolymerization and microbial amino acid uptake in soil
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ano.nymous@ccsd.cnrs.fr.invalid (Charlotte Stutzmann) 04 Dec 2024
https://hal.science/hal-04818390v1
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[hal-04370436] Forest management and former land use have no effect on soil fungal diversity in uneven-aged mountain high forests
Key message: Metabarcoding analysis of soil fungal communities in French mountain forests revealed that harvesting intensity, time since last harvest and former land use had no effect on fungal community composition compared to key abiotic factors. Low-intensity management in these uneven-aged mountain forests therefore has limited effects on soil fungal community composition which is mainly driven by elevation and edaphic properties. Context: Past and current human activities are known to affect forest biodiversity. However, the effects of former land use and forest management have been studied much more extensively on higher plants than on fungi. Aims: Our objectives were to assess the effects of harvesting intensity, duration since last harvest and former land use on soil fungal communities in uneven-aged mountain high forests. Methods: On the basis of historical land-use maps drawn between 1862 and 1864 and on historical forest management archives, we selected 62 sites in the French Alps with contrasting land-use histories (ancient forests, which were already forested on historical maps vs recent forests, which have recovered following abandonment of pastures) and different durations since last harvest (from 1 to over 50 years). We carried out soil sampling and assessed fungal diversity by metabarcoding analysis. We analysed soil fungal molecular operational taxonomic units (MOTU) diversity as a whole and for the main lifestyle groups (such as wood saprotrophic or ectomycorrhizal fungi) using multiple linear regressions on Shannon’s diversity index and fungal taxonomic composition using canonical correlation analysis. Results: We found no significant effect of harvesting intensity, time since last harvest or land-use history on total fungal MOTU diversity, fungal lifestyle diversity or taxonomic composition. In contrast, we observed significant effects of elevation, pH, organic carbon and available phosphorus content on the taxonomic and functional composition of soil fungal communities. Conclusions: The structure of soil fungal communities (i.e. diversity and species composition) was mainly determined by elevation and edaphic factors, indicating a high-context dependency, as previously found in similar studies. Our study in mountain forests shows that recent forests established on former pastures had no legacy effect on soil conditions and fungal communities, in contrast to previous results in lowland areas, where recent forests were mainly established on former cropland. Uneven-aged forest management had no effect on fungal diversity, in contrast to previous results observed in even-aged high forests.
ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Mollier) 03 Jan 2024
https://hal.science/hal-04370436v1
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[hal-04991153] Intransitive competition: an important mechanism?
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ano.nymous@ccsd.cnrs.fr.invalid (Laure Gallien) 14 Mar 2025
https://hal.univ-grenoble-alpes.fr/hal-04991153v1
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[hal-04904203] Projections comparées de la répartition et de la croissance du Chêne pubescent face au changement climatique : apports et limites de la modélisation
Essentiels à la filière forêt-bois française, les Chênes sessile et pédonculé sont menacés par l'intensification des événements climatiques extrêmes tandis que le Chêne pubescent, plus résistant à la sécheresse, offre une alternative prometteuse. La modélisation est un divergences de leurs projections concernant la survie et la productivité des peuplements donnent un ordre de grandeur possible des incertitudes associées, et sont discutées afin de fournir une analyse critique de la modélisation forestière en tant qu'outil d'aide à la décision. Cette analyse illustre l'importance d'utiliser des modèles différents pour déterminer si des conclusions similaires émergent malgré des approches variées, c'est-à-dire quantifier à minima et réduire les incertitudes afin de produire des résultats plus robustes.
ano.nymous@ccsd.cnrs.fr.invalid (Marion Carme) 04 Feb 2025
https://hal.science/hal-04904203v1
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[hal-04782273] Surprisingly wide climatic niche breadth of a relict mountain species raises hope for survival under climate change
Aims: We assessed the juvenile climatic niche breadth of a relict mountain species by comparing field observations and transplant experiments within and beyond the elevational limits of its distribution range. Location: Lebanon – Near East – Mediterranean region. Methods: We studied the survival and growth of the Cedar of Lebanon (Cedrus libani) to determine the lower and upper elevational range limits of its juvenile stage through an experimental setup with and without water supplementation and with potentially competing species as a control. The experiment included eight common gardens at elevations ranging from 110 to 2330 m, within and far beyond the warm and cold limits of Cedar distribution observed under natural conditions. Results: We observed unexpectedly high survival and growth rates of Cedar at elevations well below the range of its natural distribution in Lebanon. Below the observed warm limit, water stress at very low elevations and competition at low and medium elevations limited juvenile survival. In contrast, cold temperature and water stress limited survival at elevations slightly above the observed upper natural limit. The experimental setup demonstrated that the elevation range suitable for Cedar growth and survival was twice as wide as the range within which Cedar is observed under natural conditions. Main Conclusions: High survival rates experimentally observed beyond the warm limit of the natural distribution range of the Cedar of Lebanon raise hope for its resilience to ongoing climate warming. If this pattern were frequent among montane species, it would challenge predictions of massive extinction with climate change and pave the way for promoting adaptive actions such as competition management to improve their survival.
ano.nymous@ccsd.cnrs.fr.invalid (Yaacoub Nassif) 11 Sep 2025
https://hal.science/hal-04782273v1
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[hal-04746259] A model of the within-population variability of budburst in forest trees
Spring phenology is a key indicator of temperate and boreal ecosystems' response to climate change. To date, most phenological studies have analyzed the mean date of budburst in tree populations while overlooking the large variability of budburst among individual trees. The consequences of neglecting the within-population variability (WPV) of budburst when projecting the dynamics of tree communities are unknown. Here, we develop the first model designed to simulate the WPV of budburst in tree populations. We calibrated and evaluated the model on 48 442 budburst observations collected between 2000 and 2022 in three major temperate deciduous trees, namely, hornbeam (Carpinus betulus), oak (Quercus petraea) and chestnut (Castanea sativa). The WPV model received support for all three species, with a root mean square error of 5.7 ± 0.5 d for the prediction of unknown data. Retrospective simulations over 1961–2022 indicated earlier budburst as a consequence of ongoing climate warming. However, simulations revealed no significant change for the duration of budburst (DurBB, i.e., the time interval from BP20 to BP80 (with BP representing budburst percent), which respectively represent the date when 20 % and 80 % of trees in a population have reached budburst), due to a lack of significant temperature increase during DurBB in the past. This work can serve as a basis for the development of models targeting intra-population variability of other functional traits, which is of increasing interest in the context of climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Jianhong Lin) 22 Oct 2024
https://hal.science/hal-04746259v1
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[hal-04602394] Growth is not just about wood : investigating the link between ecosystem carbon uptake and net primary productivity in three European forests
A body of work published over the past two decades shows that there is a partial decoupling between the fixation of carbon by photosynthesis and the formation of wood in forests. Years of high photosynthesis are not necessarily accompanied by large wood production. In this contribution, we explore the link between photosynthesis, estimated using eddy covariance fluxes and the productivity of the various forest compartments (leaves, wood, fruit, roots) measured over 12 to 21 years on three forest sites in France belonging to the European ICOS network (two temperate sites, one oak forest and one beech forest, and one Mediterranean oak forest). Annual wood productivity was not significantly correlated with carbon fixation, neither GPP nor NEP, at any of the three sites. On the other hand, annual above-ground net primary productivity was significantly correlated with GPP at all sites and with NEP at two of the three sites, i.e. the Mediterranean and the temperate oak forests. In these oak forests, years of high productivity are masting years, supporting the hypothesis that reproduction is limited by the availability of recent photo-assimilates. These results remind us that wood growth is not necessarily representative of tree productivity, and invites us to investigate the causes of the inter-annual variability of carbon allocation to the different organs and tissues of trees.
ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Delpierre) 05 Jun 2024
https://hal.inrae.fr/hal-04602394v1
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[hal-04984386] Monitoring forest biodiversity at a national scale: how to build upon existing monitoring networks
Due to the scarcity of rigorous species monitoring across several taxonomic groups, sustainable forest management indicators related to the biodiversity criterion in Europe are mainly indirect indicators based on tree-related data. Direct monitoring of species, however, often permit more thorough monitoring of the status of biodiversity and its dynamics, with a more rapid assessment of the impact of forest management and forest policies. Using French metropolitan forests as a case study, the PASSIFOR2 project combined the use of direct forest biodiversity indicators as well as associated dendrometric and management-related variables in designing monitoring templates. The project was developed based on (i) the specification of refined monitoring objectives, (ii) a broad consultation of existing networks for collecting biodiversity data in forests and (iii) some methodological research to improve the quality of sampling and data analysis. We present our lessons learned as well as the four main advances that have been made: (i) a method and a protocol for building multi-network biodiversity monitoring templates; (ii) an objective choice of taxa to be favored in monitoring in French forests, based on a multicriteria analysis, and associated protocols to monitor them (direct biodiversity indicators); (iii) proposals for dendrometric and management variables to be documented and be related to the direct biodiversity indicators; and (iv) statistical results to guide the choices in terms of sampling schemes and data analysis.
ano.nymous@ccsd.cnrs.fr.invalid (Frédéric Gosselin) 10 Mar 2025
https://hal.inrae.fr/hal-04984386v1
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[hal-04592906] Does long-term drought or repeated defoliation affect seasonal leaf N cycling in young beech trees?
Abstract Forest trees adopt effective strategies to optimize nitrogen (N) use through internal N recycling. In the context of more recurrent environmental stresses due to climate change, the question remains whether increased frequency of drought or defoliation threatens this internal nitrogen recycling strategy. We submitted 8-year-old beech trees to two years of either severe drought (Dro) or manual defoliation (Def) to create a state of N starvation. At the end of the 2nd year before leaf senescence, we labeled the foliage of the Dro and Def trees, as well as that of control (Co) trees, with 15N-urea. Leaf N resorption, winter tree N storage (total N, 15N, amino acids, soluble proteins) and N remobilization in spring were evaluated for the three treatments. Defoliation and drought did not significantly impact foliar N resorption or N concentrations in organs in winter. Total N amounts in Def tree remained close to those in Co tree, but winter N was stored more in the branches than in the trunk and roots. Total N amount in Dro trees was drastically reduced (−55%), especially at the trunk level, but soluble protein concentrations increased in the trunk and fine roots compared to Co trees. During spring, 15N was mobilized from the trunk, branches and twigs of both Co and Def trees to support leaf growth. It was only provided through twig 15N remobilization in the Dro trees, thus resulting in extremely reduced Dro leaf N amounts. Our results suggest that stress-induced changes occur in N metabolism but with varying severity depending on the constraints: within-tree 15N transport and storage strategy changed in response to defoliation whereas a soil water deficit induced a drastic reduction of the N amounts in all the tree organs. Consequently, N dysfunction could be involved in drought-induced beech tree mortality under the future climate.
ano.nymous@ccsd.cnrs.fr.invalid (Catherine Massonnet) 29 May 2024
https://hal.inrae.fr/hal-04592906v1
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[mnhn-04778806] De la forêt à la charpente. Etudier la provenance des bois médiévaux par le croisement des données dendrochronologiques, chimiques / isotopiques, archéologiques et historiques
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ano.nymous@ccsd.cnrs.fr.invalid (Anne Poszwa) 12 Nov 2024
https://mnhn.hal.science/mnhn-04778806v1
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[hal-05189855] Spatio-temporal analysis of the growth of a poplar root to an axial mechanical resistance and to its relaxation
<div>Spatio-temporal analysis of the growth of a poplar root to an axial mechanical resistance and to its relaxationContext Materials and methods Results Conclusion Context Materials and methods Results Conclusion</div>
ano.nymous@ccsd.cnrs.fr.invalid (Amélia Léonoff Noël) 28 Jul 2025
https://hal.inrae.fr/hal-05189855v1
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[hal-04997458] Force generation by a cylindrical cell under stationary osmolyte synthesis
Turgor is the driving force of plant growth, making it possible for roots to overcome soil resistance or for stems to counteract gravity. Maintaining a constant growth rate while avoiding cell content dilution, which would progressively stop the inward water flux, imposes the production or import of osmolytes in proportion to the increase of volume. We coin this phenomenon stationary osmoregulation. The article explores the quantitative consequences of this hypothesis on the interaction of a cylindrical cell growing axially against an obstacle. An instantaneous axial compression of a pressurized cylindrical cell generates a force and a pressure jump, which both decrease towards a lower value once water has flowed out of the cell to reach the water potential equilibrium. In the first part, the article derives analytical formulae for these forces and over-pressure both before and after relaxation. In the second part, we describe how the coupling of the Lockhart growth law with the stationary osmoregulation hypothesis predicts a transient slowdown in growth due to contact before a re-acceleration in growth. We finally compare these predictions with the output of an elastic growth model which ignores the osmotic origin of growth: models only match in the early phase of contact for a high-stiffness obstacle.
ano.nymous@ccsd.cnrs.fr.invalid (Weiyuan Kong) 19 Mar 2025
https://hal.inrae.fr/hal-04997458v1
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[hal-04405701] 202 years of changes in Mediterranean fire regime in Pinus nigra forest, Corsica
Wildfires are critical socio-ecological features in the Mediterranean basin. In a context of global changes (climate, land use), we questioned whether the wildfire regime was altered in the mountains of Corsica, France. Using tree- ring analysis of fire-scarred trees, we tested for changes in frequency, seasonality, and area. We hypothesized that the fire regime changed during the middle-20th century due to human activities, as observed elsewhere in the Mediterranean. We sampled fire-scarred trees, geolocated for mapping fire areas, in a forest of black pine (Pinus nigra laricio). The oldest fire was in 1684 but the fire chronology with adequate sample depth for analysis covered 202 years [1820–1921]. Between 1820–2012, 15 fires were recorded, 8 of which scarred at least 25% of the sampled trees. The mean fire interval was 14 years, corresponding to a high fire frequency with 4 major fires per century. Most fires occurred between 1931–1970. On average, about 50% of trees were scarred by fires before 1931, but this percentage decreased thereafter. The exception was the 2000 fire that impacted 100% of living trees. Mapping showed spatially heterogenous fire areas. These results match other Mediterranean studies showing longer fire intervals since the late-20th century, and wildfires generally occurred during the period of late-earlywood or latewood formation, i.e., summer or early autumn, which is the season of contemporary fires. Although fires were recurrent for more than 200 years with no change in the fire season, the regime changed twice in frequency. These changes likely result from a combination of land use and warmer summer conditions. While pines survived most past fires of low intensity through the last large fire in the 1970’s, the severe fire of 2000, following ca 30 years of fire suppression, killed large patches of mature trees. Such chronology provides rational arguments for black pine ecosystem management, notably to consider seeking to recover the sustainable fire regime of the 19th century, for instance by using prescribed fires to manage surface fuel.
ano.nymous@ccsd.cnrs.fr.invalid (Justin Badeau) 19 Jan 2024
https://hal.science/hal-04405701v1
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[hal-04959057] Assessment of Pinus halepensis Forests’ Vulnerability Using the Temporal Dynamics of Carbon Stocks and Fire Traits in Tunisia
Carbon stocks provide information that is essential for analyzing the role of forests in global climate mitigation, yet they are highly vulnerable to wildfires in Mediterranean ecosystems. These carbon stocks’ exposure to fire is usually estimated from specific allometric equations relating tree height and diameter to the overall amount of aboveground carbon storage. Assessments of vulnerability to fire additionally allow for specific fire resistance (bark thickness, crown basal height) and post-fire recovery traits (cone mass for regeneration, and fine branches or leaves mass for flammability) to be accounted for. These traits are usually considered as static, and their temporal dynamic is rarely assessed, thus preventing a full assessment of carbon stocks’ vulnerability and subsequent cascading effects. This study aimed to measure the pools of carbon stocks of individual trees varying between 30 and 96 years old in the Djbel Mansour Aleppo pine (Pinus halepensis) forest in semi-arid central Tunisia in the southern range of its distribution to fit a sigmoid equation of the carbon pools and traits recovery according to age as a vulnerability framework. Allometric equations were then developed to establish the relationships between fire vulnerability traits and dendrometric independent variables (diameter at breast height, height, and live crown length) for further use in regional vulnerability assessments. The total carbon stocks in trees varied from 29.05 Mg C ha−1 to 92.47 Mg C ha−1. The soil organic carbon stock (SOC) at a maximum soil depth of 0–40 cm varied from 31.67 Mg C ha−1 to 115.67 Mg C ha−1 at a soil depth of 0–70 cm. We could identify an increasing resistance related to increasing bark thickness and basal crown height with age, and enhanced regeneration capacity after 25 years of age with increasing cone biomass, converging toward increasing vulnerability and potential cascading effects under shorter interval fires. These results should be considered for rigorous forest carbon sequestration assessment under increasing fire hazards due to climate and social changes in the region.
ano.nymous@ccsd.cnrs.fr.invalid (Fatma Rezgui) 24 Feb 2025
https://cnrs.hal.science/hal-04959057v1
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[hal-04671999] Inferred drought‐induced plant allocation shifts and their impact on drought legacy at a tropical forest site
While droughts predominantly induce immediate reductions in plant carbon uptake, they can also exert long‐lasting effects on carbon fluxes through associated changes in leaf area, soil carbon, etc. Among other mechanisms, shifts in carbon allocation due to water stress can contribute to the legacy effects of drought on carbon fluxes. However, the magnitude and impact of these allocation shifts on carbon fluxes and pools remain poorly understood. Using data from a wet tropical flux tower site in French Guiana, we demonstrate that drought‐induced carbon allocation shifts can be reliably inferred by assimilating Net Biosphere Exchange (NBE) and other observations within the CARbon DAta MOdel fraMework. This model‐data fusion system allows inference of optimized carbon and water cycle parameters and states from multiple observational data streams. We then examined how these inferred shifts affected the duration and magnitude of drought's impact on NBE during and after the extreme event. Compared to a static allocation scheme analogous to those typically implemented in land surface models, dynamic allocation reduced average carbon uptake during drought recovery by a factor of 2.8. Additionally, the dynamic model extended the average recovery time by 5 months. The inferred allocation shifts influenced the post‐drought period by altering foliage and fine root pools, which in turn modulated gross primary productivity and heterotrophic respiration for up to a decade. These changes can create a bust‐boom cycle where carbon uptake is enhanced some years after a drought, compared to what would have occurred under drought‐free conditions. Overall, allocation shifts accounted for 65% [45%–75%] of drought legacy effects in modeled NBE. In summary, drought‐induced carbon allocation shifts can play a substantial role in the enduring influence of drought on cumulative land‐atmosphere CO 2 exchanges and should be accounted for in ecosystem models.
ano.nymous@ccsd.cnrs.fr.invalid (Matthew Worden) 19 Feb 2025
https://hal.inrae.fr/hal-04671999v1
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[hal-04665597] Social-ecological modelling as a boundary object to implement inter- and transdisciplinary approaches of forests in transitions
French forests are at the crossroads of multiple dynamics and expectations: while they are supposed to be managed to ensure multifunctionality, national policies mostly focus on their role of carbon sink as a remedy for climate change mitigation. Simultaneously, French forests are increasingly impacted by on-going climate change (droughts, heat waves, bio-aggressors, fires), which alters their functioning and survival – and raises adaptation issues. As a result, forest management is currently facing a key challenge: how can we promote forests’ ability to maintain wood production and carbon sequestration, without impacting their other contributions (such as providing biodiversity habitats, air and water filtering, soil protection, leisures…), while also considering their sensitivity to climate change? This is the question addressed by the FISSA project (ForecastIng forest Socio-ecosystems’ Sensitivity and Adaptation to climate change) – whose ultimate aim is to test complex forest management scenarios at national and local levels within three regional natural parks (Pyrénées Ariégeoises, Luberon and Morvan) – in a context of climate change. FISSA has been designed to enlighten ongoing controversy, in this context of tensions between mitigation and adaptation strategies, between our multiple expectations regarding forests’ roles, and regarding the practices to promote to respond to such a challenge. To do so, it relies on an interdisciplinary approach: while social sciences inform dynamics of discourses and practices through social surveys at both national and local levels, natural sciences assess the effects of different forest management and climate scenarios on forests’ contributions through process-based models of forest dynamics and functioning. At the interface, transdisciplinary approaches are implemented to collectively define the management scenarios to be implemented both at local and national levels. In this presentation, we highlight how inter- and transdisciplinarity are promoted in the project, and how they can shape the original assumptions of modelers. First, we discuss how this project ensures the inter- and transdisciplinary dialogue through diverse boundary objects, both conceptual (social-ecological system), methodological (participatory modelling) and practical (common field work and promotion of dialogue among the participants). Second, we illustrate the changes in the modelling process brought by inter- and transdisciplinary contributions. Qualitative surveys, focus groups and dialogue have shown that expectations towards modelling are multiple depending on the territories, the stakeholders involved and the considered scale: (i) nourish a scientific and societal debate and controversy around adaptation and mitigation, but also (ii) respond to an extreme and unknown event such as major forest diebacks; or (iii) anticipate a shift from traditional sylvicultural practices and inherited forests towards more desirable practices in the face of environmental and climate urges. We conclude on the interests and limits of participatory social-ecological modelling approaches to promote collective action in a context where uncertainties and tensions are unavoidable.
ano.nymous@ccsd.cnrs.fr.invalid (Clara Therville) 31 Jul 2024
https://hal.science/hal-04665597v1
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[hal-05023204] Allelochemical interactions of Sphagnum mosses under climate changes: from physiological responses to peatland functioning
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ano.nymous@ccsd.cnrs.fr.invalid (Genevieve Chiapusio) 07 Apr 2025
https://hal.science/hal-05023204v1
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[hal-04318256] Defaunated and invaded insular tropical rainforests will not recover alone: recruitment limitation factors disentangled by hierarchical models of spontaneous and assisted regeneration
1. Most tropical forests are now severely degraded and their ability to recover is highly dependent on frugivores which ensure seed dispersal for most woody plants. The global collapse of large vertebrates therefore raises major concerns about tropical forest succession, but few field studies have been conducted to disentangle recruitment limitations during disrupted succession. 2. This study took place on Réunion (Mascarenes) where all large native frugivores have been extinct since human colonisation in 1665 and where multiple invasions threaten native ecosystems. We set up 20 experimental blocks on a lava flow dated back to 1800, in plant-impoverished post-defaunation vegetation bordered by old-growth forests. We assessed fecundity, seed dispersal and seedling recruitment of the complete fleshy-fruited plant community and used Bayesian analyses to disentangle the impact of multiple factors on these key processes. In the same blocks, we sowed four native trees assumed to be disperserless to test their capacity to establish, controlling for two additional post-dispersal limitations (seed predation and competition with invasive plants). 3. On the flow, small-seeded native plants were fairly dispersed but did not recruit, probably due to strong competition with invasive plants; the few native species that recruited somehow were mostly medium-seeded plants that were still dispersed; large-seeded plants were absent from seed rain (which shows that invasive frugivores did not replace extinct ones) and subsequently from spontaneous recruitment. Instead, some alien plants, notably the tiny-seeded highly-dispersed <i>Clidemia hirta</i> and the medium-seeded <i>Psidium cattleianum</i> largely dominated seedling recruitment. Native plants recruited better at the forest margin, including some large-seeded species nearby mother trees. 4. Sown large-seeded species were able to emerge and survive in all plots whatever the treatment, which demonstrates that dispersal loss was the primary cause of regeneration failure on the flow. Synthesis. The strong modulation of the establishment capacity of native plants by seed mass shows that invasive plants win by forfeit of large-seeded plants after native frugivores loss. Our study emphasises the fundamental role of dispersal loss and competition with invasive plants in the disruption of ecological succession, as well as the urgency of restoring seed dispersal and strengthening biosecurity regulations.
ano.nymous@ccsd.cnrs.fr.invalid (Sébastien Albert) 01 Dec 2023
https://hal.science/hal-04318256v1
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[hal-04874159] No Future Growth Enhancement Expected at the Northern Edge for European Beech due to Continued Water Limitation
<div><p>With ongoing global warming, increasing water deficits promote physiological stress on forest ecosystems with negative impacts on tree growth, vitality, and survival. How individual tree species will react to increased drought stress is therefore a key research question to address for carbon accounting and the development of climate change mitigation strategies. Recent tree-ring studies have shown that trees at higher latitudes will benefit from warmer temperatures, yet this is likely highly species-dependent and less well-known for more temperate tree species. Using a unique pan-European tree-ring network of 26,430 European beech (Fagus sylvatica L.) trees from 2118 sites, we applied a linear mixed-effects modeling framework to (i) explain variation in climate-dependent growth and (ii) project growth for the near future (2021-2050) across the entire distribution of beech. We modeled the spatial pattern of radial growth responses to annually varying climate as a function of mean climate conditions (mean annual temperature, mean annual climatic water balance, and continentality). Over the calibration period (1952-2011), the model yielded high regional explanatory power (R 2 = 0.38-0.72). Considering a moderate climate change scenario (CMIP6 SSP2-4.5), beech growth is projected to decrease in the future across most of its distribution range. In particular, projected growth decreases by 12%-18% (interquartile range) in northwestern Central Europe and by 11%-21% in the Mediterranean region. In contrast, climate-driven growth increases are limited to around 13% of the current occurrence, where the historical mean annual temperature was below ~6°C. More specifically, the model predicts a 3%-24% growth increase in the high-elevation clusters of the Alps and Carpathian Arc. Notably, we find little potential for future growth increases (-10 to +2%) at the poleward This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.</p></div>
ano.nymous@ccsd.cnrs.fr.invalid (Stefan Klesse) 08 Jan 2025
https://hal.inrae.fr/hal-04874159v1
