Productions 2021

Publications dans HAL pour l'année 2021


HAL : Dernières publications

  • [hal-03516967] Retrieval and validation of forest background reflectivity from daily Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) data across European forests

    Information about forest background reflectance is needed for accurate biophysical parameter retrieval from forest canopies (overstory) with remote sensing. Separating under- and overstory signals would enable more accurate modeling of forest carbon and energy fluxes. We retrieved values of the normalized difference vegetation index (NDVI) of the forest understory with the multi-angular Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo data (gridded 500 m daily Collection 6 product), using a method originally developed for boreal forests. The forest floor background reflectance estimates from the MODIS data were compared with in situ understory reflectance measurements carried out at an extensive set of forest ecosystem experimental sites across Europe. The reflectance estimates from MODIS data were, hence, tested across diverse forest conditions and phenological phases during the growing season to examine their applicability for ecosystems other than boreal forests. Here we report that the method can deliver good retrievals, especially over different forest types with open canopies (low foliage cover). The performance of the method was found to be limited over forests with closed canopies (high foliage cover), where the signal from understory becomes too attenuated. The spatial heterogeneity of individual field sites and the limitations and documented quality of the MODIS BRDF product are shown to be important for the correct assessment and validation of the retrievals obtained with remote sensing.

    ano.nymous@ccsd.cnrs.fr.invalid (Jan Pisek) 07 Jan 2022

  • [hal-03261880] Global transpiration data from sap flow measurements: the SAPFLUXNET database

    Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The “sapfluxnetr” R package – designed to access, visualize, and process SAPFLUXNET data – is available from CRAN.

    ano.nymous@ccsd.cnrs.fr.invalid (Rafael Poyatos) 16 Jun 2021

  • [hal-03278925] Method comparison of indirect assessments of understory leaf area index (LAIu): A case study across the extended network of ICOS forest ecosystem sites in Europe

    Leaf area index (LAI) is a key ecological indicator for describing the structure of canopies and for modelling energy exchange between atmosphere and biosphere. While LAI of the forest overstory can be accurately assessed over large spatial scales via remote sensing, LAI of the forest understory (LAIu) is still largely ignored in ecological studies and ecosystem modelling due to the fact that it is often too complex to be destructively sampled or approximated by other site parameters. Additionally, so far only few attempts have been made to retrieve understory LAI via remote sensing, because dense canopies with high LAI are often hindering retrieval algorithms to produce meaningful estimates for understory LAI. Consequently, the forest understory still constitutes a poorly investigated research realm impeding ecological studies to properly account for its contribution to the energy absorption capacity of forest stands. This study aims to compare three conceptually different indirect retrieval methodologies for LAIu over a diverse panel of forest understory types distributed across Europe. For this we carried out near-to-surface measurements of understory reflectance spectra as well as digital surface photography over the extended network of Integrated Carbon Observation System (ICOS) forest ecosystem sites. LAIu was assessed by exploiting the empirical relationship between vegetation cover and light absorption (Beer-Lambert- Bouguer law) as well as by utilizing proposed relationships with two prominent vegetation indices: normalized difference vegetation index (NDVI) and simple ratio (SR). Retrievals from the three methods were significantly correlated with each other (r = 0.63–0.99, RMSE = 0.53–0.72), but exhibited also significant bias depending on the LAI scale. The NDVI based retrieval approach most likely overestimates LAI at productive sites when LAIu > 2, while the simple ratio algorithm overestimates LAIu at sites with sparse understory vegetation and presence of litter or bare soil. The purely empirical method based on the Beer-Lambert law of light absorption seems to offer a good compromise, since it provides reasonable LAIu values at both low and higher LAI ranges. Surprisingly, LAIu variation among sites seems to be largely decoupled from differences in climate and light permeability of the overstory, but significantly increased with vegetation diversity (expressed as species richness) and hence proposes new applications of LAIu in ecological modelling.

    ano.nymous@ccsd.cnrs.fr.invalid (Jan-Peter George) 06 Jul 2021

  • [hal-03123656] OSIP1 is a self‐assembling DUF3129 protein required to protect fungal cells from toxins and stressors

    Secreted proteins are key players in fungal physiology and cell protection against external stressing agents and antifungals. Oak stress-induced protein 1 (OSIP1) is a fungal-specific protein with unknown function. By using Podospora anserina and Phanerochaete chrysosporium as models, we combined both in vivo functional approaches and biophysical characterization of OSIP1 recombinant protein. The P. anserina OSIP1(Delta) mutant showed an increased sensitivity to the antifungal caspofungin compared to the wild type. This correlated with the production of a weakened extracellular exopolysaccharide/protein matrix (ECM). Since the recombinant OSIP1 from P. chrysosporium self-assembled as fibers and was capable of gelation, it is likely that OSIP1 is linked to ECM formation that acts as a physical barrier preventing drug toxicity. Moreover, compared to the wild type, the OSIP1(Delta) mutant was more sensitive to oak extractives including chaotropic phenols and benzenes. It exhibited a strongly modified secretome pattern and an increased production of proteins associated to the cell-wall integrity signalling pathway, when grown on oak sawdust. This demonstrates that OSIP1 has also an important role in fungal resistance to extractive-induced stress.

    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Valette) 25 Mar 2021

  • [hal-03423711] Quels besoins de connaissances pour le futur des forêts en France ? Au-delà du plan de relance

    Le plan France Relance lancé en septembre 2020 prévoit des mesures forestières sur 2 ans, avec un accent sur la reconstitution des peuplements forestiers sinistrés, affaiblis par les sécheresses ou attaqués par les scolytes. Cependant la crise forestière liée au changement climatique est partie pour durer et les efforts sur les connaissances à acquérir pour aider la forêt à s’adapter au changement climatique devront être poursuivis sur le long terme. Nous identifions quatre enjeux principaux, fortement liés à la préservation de la biodiversité : 1) S’assurer des conditions de succès d’établissement des forêts plantées. 2) Tirer parti des dynamiques naturelles et de la biodiversité pour limiter les risques. 3) Raisonner territorialement, impliquer davantage les acteurs. 4) Connecter les enjeux nationaux aux enjeux économiques mondiaux.

    ano.nymous@ccsd.cnrs.fr.invalid (Maya Leroy) 10 Nov 2021

  • [hal-03299186] Mixing beech with fir or pubescent oak does not help mitigate drought exposure at the limit of its climatic range

    In the context of climate change, it remains unclear whether mixed-species forests will help mitigate the impacts of future droughts and, if so, through which processes. As European beech (Fagus sylvatica L.) is one of the major European species, it is crucial to evaluate its response to drought when mixed with species with contrasted functional traits and in contrasted climatic conditions, particularly at the limit of its climatic range. This study aimed to (i) characterize the effects of tree species interactions on the drought exposure of beech in southeastern France, and (ii) determine whether belowground water uptake complementarity underlies these effects. We focused on beech-silver fir (Abies alba Mill.) and beech-pubescent oak (Quercus pubescens Willd.) forests across six sites in the French pre-Alps, a region at the limit of the climatic range for beech. We used a triplet approach to compare the tree-ring carbon isotope composition (δ 13 C) of these species in pure and two-species mixed stands during a period of dry years, and used water hydrogen isotope composition (δ 2 H) in the xylem to identify water uptake sources. Overall, we found no clear mixture effect pattern on beech physiological functioning among sites and triplets. In beech-fir sites, mixing beech with fir had no effect on beech δ 13 C values during dry years. In beech-oak sites, mixture effects on beech were mostly neutral, although sometimes beech suffered from a stronger exposure to drought in mixed stands. Our study emphasizes the impact of the tree sampling design on the outcome of studies on forest biodiversity-ecosystem functioning relationships. Limiting tree sampling to dominant trees when analyzing stand-level relationships may bias these outcomes. We evidenced differences in water uptake sources between beech and fir, but not between beech and oak during a dry summer. However, these patterns did not help explain the lack of species mixture effects, or existence thereof, at the triplet scale. Our study demonstrates that managing beech in mixed stands with silver fir or pubescent oak at the limit of beech climatic range does not buffer drought impacts on beech during dry years. In the long term, with more frequent extreme droughts, promoting beech-fir mixtures will not be detrimental to beech drought response, while beech may suffer in mixtures with pubescent oak.

    ano.nymous@ccsd.cnrs.fr.invalid (Soline Martin-Blangy) 09 Aug 2021

  • [hal-03137074] Shifts in soil and plant functional diversity along an altitudinal gradient in the French Alps

    Altitude integrates changes in environmental conditions that determine shifts in vegetation, including temperature, precipitation, radiation and edaphogenetic processes. In turn, vegetation alters soil biophysical properties through litter input, root growth, microbial and macrofaunal interactions. The belowground traits of plant communities modify soil processes in different ways, but it is not known how root traits influence soil biota at the community level. We collected data to investigate how elevation affects belowground community traits and soil microbial and faunal communities. This dataset comprises data from a temperate climate in France and a twin study was performed in a tropical zone in Mexico.Data description: The paper describes soil physical and chemical properties, climatic variables, plant community composition and species abundance, plant community traits, soil microbial functional diversity and macrofaunal abundance and diversity. Data are provided for six elevations (1400 – 2400 m) ranging from montane forest to alpine prairie. We focused on soil biophysical properties beneath three dominant plant species that structure local vegetation. These data are useful for understanding how shifts in vegetation communities affect belowground processes, such as water infiltration, soil aggregation and carbon storage. Data will also help researchers understand how plant communitiesadjust to a changing climate/environment

    ano.nymous@ccsd.cnrs.fr.invalid (Alexia Stokes) 10 Feb 2021

  • [hal-03424361] Mixture effect on radial stem and shoot growth differs and varies with temperature

    The effect of species diversity on forest productivity and its temporal stability is known to be species-, climateand site-dependent and is mostly apprehended through stem diameter. Therefore, it remains largely unknown whether the mixture effect on the growth of tree crowns is similar to its effect on the growth of tree diameter. However, it is commonly accepted that changes in crown architecture are an important component of tree response to tree species diversity. Moreover, the mixture effect on species is often asymmetric, i.e. the effect of a species A on a species B is not equal to the effect of species B on A. It then appears that considering the effects of both species mixture and climate on shoot growth could contrast the results coming mainly from stem growth. We studied the effects of tree species mixture and temperature on the annual growth of shoots and basal area of stems in Fagus sylvatica-Quercus pubescens and Fagus sylvatica-Abies alba stands along a Mediterranean-Alpine gradient, for four years in five sites. The sample design was organized in 10 triplets: four triplets of mono-and bispecific plots of Quercus pubescens and Fagus sylvatica and six triplets of mono-and bi-specific plots of Abies alba and Fagus sylvatica along an altitudinal gradient ranging from 725 m to 1431 m. We found that the mixture effect on annual shoot volume increment (SVI) and on basal area increment (BAI) was asymmetrical in seven out of 10 cases and not significant in the three remaining cases. Mixture effect on SVI ranked from − 56% to 157% and on BAI it ranked from − 40% to 252%. Eventually we found that mixture effect was dependent on the type of limiting factor for growth, with at the driest sites a predominance of competition effects and at the coldest site a positive mixture effect on the two species studied. Branch growth appears as a variable that can be at least as informative as radial growth regarding the tree response to species interactions. This implies that considering only stem diameter in the diversity-productivity relationship can lead to biased conclusions on the global mixture effect on tree growth, which calls for a comprehensive approach of the tree response to tree species diversity. Our results are discussed in the light of the species stress tolerances and strategies to cope with competition.

    ano.nymous@ccsd.cnrs.fr.invalid (Maude Toïgo) 10 Mar 2023

  • [hal-03282821] The GenTree Platform: growth traits and tree-level environmental data in 12 European forest tree species

    Progress in the field of evolutionary forest ecology has been hampered by the huge challenge of phenotyping trees across their ranges in their natural environments, and the limitation in high-resolution environmental information;The GenTree Platform contains phenotypic and environmental data from 4,959 trees from 12 ecologically and economically important European forest tree species: Abies alba Mill. (silver fir), Betula pendula Roth. (silver birch), Fagus sylvatica L. (European beech), Picea abies (L.) H. Karst (Norway spruce), Pinus cembra L. (Swiss stone pine), Pinus halepensis Mill. (Aleppo pine), Pinus nigra Arnold (European black pine), Pinus pinaster Aiton (maritime pine), Pinus sylvestris L. (Scots pine), Populus nigra L. (European black poplar), Taxus baccata L. (English yew), and Quercus petraea (Matt.) Liebl. (sessile oak). Phenotypic (height, diameter at breast height, crown size, bark thickness, biomass, straightness, forking, branch angle, fructification), regeneration, environmental in situ measurements (soil depth, vegetation cover, competition indices), and environmental modeling data extracted by using bilinear interpolation accounting for surrounding conditions of each tree (precipitation, temperature, insolation, drought indices) were obtained from trees in 194 sites covering the species’ geographic ranges and reflecting local environmental gradients. The GenTree Platform is a new resource for investigating ecological and evolutionary processes in forest trees. The coherent phenotyping and environmental characterization across 12 species in their European ranges allow for a wide range of analyses from forest ecologists, conservationists, and macro-ecologists. Also, the data here presented can be linked to the GenTree Dendroecological collection, the GenTree Leaf Trait collection, and the GenTree Genomic collection presented elsewhere, which together build the largest evolutionary forest ecology data collection available.

    ano.nymous@ccsd.cnrs.fr.invalid (Lars Opgenoorth) 17 Nov 2021

  • [hal-02934522] Estimation of dairy goat body composition: A direct calibration and comparison of eight methods

    The objective was to compare eight methods for estimation of dairy goat body composition, by calibrating against chemical composition (water, lipid, protein, mineral and energy) measured post-mortem. The methods tested on 20 Alpine goats were body condition score (BCS), 3-dimension imaging (3D) automatic assessment of BCS or whole body scan, ultrasound, computer tomography (CT), adipose cell diameter, deuterium oxide dilution space (D 2 OS) and bioelectrical impedance spectroscopy (BIS). Regressions were tested between predictive variates derived from the methods and empty body (EB) composition. The best equations for estimation of EB lipid mass included BW combined with i) perirenal adipose tissue mass and cell diameter (R 2 = 0.95, residual standard deviation, rSD = 0.57 kg), ii) volume of fatty tissues measured by CT (R 2 = 0.92, rSD = 0.76 kg), iii) D 2 OS (R 2 = 0.91, rSD = 0.85 kg), and iv) resistance at infinite frequency from BIS (R 2 = 0.87, rSD = 1.09 kg). The D 2 OS combined with BW provided the best equation for EB protein mass (R 2 = 0.97, rSD = 0.17 kg), whereas BW alone provided a fair estimate (R 2 = 0.92, rSD = 0.25 kg). Sternal BCS combined with BW provided good estimation of EB lipid and protein mass (R 2 = 0.80 and 0.95, rSD = 1.27 and 0.22 kg, respectively). Compared to manual BCS, BCS by 3D slightly decreased the precision of the predictive equation for EB lipid (R 2 = 0.74, rSD = 1.46 kg), and did not improve the estimation of EB protein compared with BW alone. Ultrasound measurements and whole body 3D imaging methods were not satisfactory estimators of body composition (R 2 ≤ 0.40). Further developments in body composition techniques may contribute for high-throughput phenotyping of robustness.

    ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Lerch) 09 Sep 2020

  • [hal-03956007] Observatoire des peuplements dévastés et mités après tempête (1999). 2 - Éléments de diagnostic pour optimiser la reconstitution des peuplements sinistrés

    L’observatoire des peuplements dévastés et mités mis en place quelques années après la tempête de 1999 a permis le suivi pendant 20 ans de la reconstitution forestière en l’absence de travaux sylvicoles. Le travail d’analyse des données propose des éléments de diagnostic sur la façon de discriminer les situations où la régénération naturelle est suffisante pour assurer un objectif de reconstitution et les situations où des travaux de plantation (en plein ou en enrichissement) seraient nécessaires. Sur la base de cette étude, l’article présente plusieurs pistes de réflexion autour de la qualité de la reconstitution des parcelles sinistrées.

    ano.nymous@ccsd.cnrs.fr.invalid (Lisa Laurent) 25 Jan 2023

  • [hal-04155557] Les observatoires des peuplements dévastés et mités après tempête, 1re partie


    ano.nymous@ccsd.cnrs.fr.invalid (Lisa Laurent) 07 Jul 2023

  • [hal-04155358] Les observatoires des peuplements dévastés et mités après tempête, 2e partie


    ano.nymous@ccsd.cnrs.fr.invalid (Lisa Laurent) 07 Jul 2023

  • [hal-03048359] Tree species identity drives soil organic carbon storage more than species mixing in major two-species mixtures (pine, oak, beech) in Europe

    Mixed forests are usually associated with higher aboveground carbon storage compared to the corresponding monocultures but information on the impact of tree species mixing on soil organic carbon (SOC) is still limited. Yet, maximizing SOC storage is crucial for ecosystem C sequestration and many other ecosystem services. This study used a triplet approach (ie. two-species mixed stand and respective pure stands at the same site) to assess the impact of tree species identity and mixing on SOC storage in eight pine-oak, eight pine-beech and five beech-oak triplets in Europe. We sampled the forest floor (FF) and 0–40 cm in the mineral soil per 10 cm interval. For each triplet type, we fitted basal area (BA) proportion of one component species (for species identity) and a BA-based plot-level True Shannon Diversity index (for species mixing) as explanatory variables for SOC stocks in linear mixed effects models, which included stone content and plot BA as covariates, and site as a random intercept. Considering the total soil depth (FF + 0–40 cm), species identity effect on SOC stocks was only significant for pine-beech and pine-oak triplets but explained more variability in SOC stocks than species mixing across triplet types. Species mixing effect was not significant for any triplet type in the total soil depth. While species identity consistently drove SOC storage in the topsoil layers across triplet types, species mixing explained more variability in SOC stocks in the deeper soil layers except for pine-oak triplets. The results showed that species identity is a stronger driver of SOC storage than species mixing. While tree species identity effect was strongly related to a conifers vs broadleaves signature, the drivers behind mixing effects remained elusive. The results suggest that targeted selection of tree species could better enhance SOC storage in European forests than a mere increase in species richness.

    ano.nymous@ccsd.cnrs.fr.invalid (Richard Osei) 25 Oct 2023

  • [hal-03225001] Physiological and anatomical responses to drought stress differ between two larch species and their hybrid

    Abstract Key Message Hybrid saplings were more reactive to soil water deficit than Japanese and European larch. European larch had hydraulically safer wood and anisohydric behavior, Japanese and hybrid larch showed isohydric strategy. Abstract Deciduous larch species could be an alternative to evergreen conifers in reforestation, but little is known about drought sensitivity of their saplings. The effect of an experimental drought on hydraulics and quantitative wood anatomy was tested on saplings of European larch (EL, Larix decidua ), Japanese larch (JL, Larix kaempferi ) and their hybrid (HL). Across species, biomass, transpiration rate and relative water content were higher in controls than in drought stressed trees, but transpiration efficiency was lower. JL had the highest transpiration efficiency under drought, and EL the lowest, coinciding with slower growth of EL. Wood of EL formed before drought was hydraulically safer as shown by higher wall/lumen ratio and lower pit cavity area. EL neither had a significant increase in transpiration efficiency nor a reduction in transpiration rate under drought, suggesting that the stomata remained open under soil water deficit. HL saplings were the most reactive to water shortage, indicated by intra-annual density fluctuations and a decrease in relative water content of the sapwood. Significant reduction in transpiration by HL suggested a higher stomatal sensitivity, while the same leaf surface area was maintained and radial growth was still similar to its best parent, the JL. The latter showed a significantly lower leaf surface area under drought than controls. EL, with its hydraulically safer wood, followed an anisohydric behavior, while JL and HL revealed an isohydric strategy. Altogether, our results suggest species dependent acclimations to drought stress, whereby HL followed the strategy of JL rather than that of EL.

    ano.nymous@ccsd.cnrs.fr.invalid (Nadia Sasani) 25 Oct 2023

  • [hal-03880251] Climate sensitivity and drought seasonality determine post-drought growth recovery of Quercus petraea and Quercus robur in Europe

    Recent studies have identified strong relationships between delayed recovery of tree growth after drought and tree mortality caused by subsequent droughts. These observations raise concerns about forest ecosystem services and post-drought growth recovery given the projected increase in drought frequency and extremes. For quantifying the impact of extreme droughts on tree radial growth, we used a network of tree-ring width data of 1689 trees from 100 sites representing most of the distribution of two drought tolerant, deciduous oak species (Quercus petraea and Quercus robur). We first examined which climatic factors and seasons control growth of the two species and if there is any latitudinal, longitudinal or elevational trend. We then quantified the relative departure from pre-drought growth during droughts, and how fast trees were able to recover the pre-drought growth level. Our results showed that growth was more related to precipitation and climatic water balance (precipitation minus potential evapotranspiration) than to temperature. However, we did not detect any clear latitudinal, longitudinal or elevational trends except a decreasing influence of summer water balance on growth of Q. petraea with latitude. Neither species was able to maintain the pre-drought growth level during droughts. However, both species showed rapid recovery or even growth compensation after summer droughts but displayed slow recovery in response to spring droughts where none of the two species was able to fully recover the pre-drought growth-level over the three post-drought years. Collectively, our results indicate that oaks which are considered resilient to extreme droughts have also shown vulnerability when droughts occurred in spring especially at sites where long-term growth is not significantly correlated with climatic factors. This improved understanding of the role of drought seasonality and climate sensitivity of sites is key to better predict trajectories of post-drought growth recovery in response to the drier climate projected for Europe.

    ano.nymous@ccsd.cnrs.fr.invalid (Arun Bose) 02 Dec 2022

  • [hal-04226966] Drought elicits contrasting responses on the autumn dynamics of wood formation in late successional deciduous tree species

    Abstract Research on wood phenology has mainly focused on reactivation of the cambium in spring. In this study we investigated if summer drought advances cessation of wood formation and if it has any influence on wood structure in late successional forest trees of the temperate zone. The end of xylogenesis was monitored between August and November in stands of European beech and pedunculate oak in Belgium for two consecutive years, 2017 and 2018, with the latter year having experienced an exceptional summer drought. Wood formation in oak was affected by the drought, with oak trees ceasing cambial activity and wood maturation about 3 weeks earlier in 2018 compared with 2017. Beech ceased wood formation before oak, but its wood phenology did not differ between years. Furthermore, between the 2 years, no significant difference was found in ring width, percentage of mature fibers in the late season, vessel size and density. In 2018, beech did show thinner fiber walls, whereas oak showed thicker walls. In this paper, we showed that summer drought can have an important impact on late season wood phenology xylem development. This will help to better understand forest ecosystems and improve forest models.

    ano.nymous@ccsd.cnrs.fr.invalid (Inge Dox) 03 Oct 2023

  • [hal-03466115] A generic information framework for decision-making in a forest-based bio-economy

    Key message We present a methodological framework that both scientists and supply chain actors can mobilise to organise information at different scales of observation, and further make informed decisions regarding the supply and extraction of bio-molecules from forest biomass. We demonstrate its usefulness for extracting bio-molecules contained in silver fir growing in France. Context Numerous bio-active molecules can be extracted from trees at an industrial scale. Supply chain actors play a central role in this emerging bio-economy. However, they do not have enough information and tools to make informed decisions with respect to species, growing locations, or identities of potential suppliers of relevant wood biomass. Aims We explore and demonstrate an information chain and methodological framework that can help make three critical decisions regarding the selection of (1) the species containing the desired bio-molecules, (2) the locations where the resource is collected, and (3) the supply chain partners and types of industrial wood by-products necessary to obtain sufficient biomass for industrial extraction. Methods The methodological framework provides detailed guidelines and references to select the right combination of sampling protocol, allometric models, chemical analyses, GIS tools, and forest growth and supply chain models in order to produce information for the three decision steps within various regional contexts. Results We apply the framework within the context of supply chain actors who are interested in estimating the quantity and diversity of bio-molecules contained in silver fir (Abies alba Mill.) growing in the Grand Est region of France. We show how conflicting environmental, legal and economic constraints can affect the results. We discuss future challenges that need to be tackled to improve the methodological framework. Conclusion This study represents a highly detailed overview of the potential bio-molecules contained in a tree species, from its natural habitat or plantation to the end of the regional supply chain. It also represents a step towards the development of a generic knowledge infrastructure and methodology that is necessary to solve various decision-making problems regarding the industrial supply and extraction of high-value bio-molecules.

    ano.nymous@ccsd.cnrs.fr.invalid (Jean-Baptiste Pichancourt) 28 Sep 2022

  • [hal-03293479] The climatic debt is growing in the understorey of temperate forests: Stand characteristics matter

    Aim. Climate warming reshuffles biological assemblages towards less cold-adapted but more warm-adapted species, a process coined thermophilization. However, the velocity at which this process is happening generally lags behind the velocity of climate change, generating a climatic debt the temporal dynamics of which remain misunderstood. Relying on high-resolution time series of vegetation data from a long-term monitoring network of permanent forest plots, we aim at quantifying the temporal dynamics – up to a yearly resolution – of the climatic debt in the understorey of temperate forests before identifying the key determinants that modulate it. Location. France. Time period. 1995–2017. Taxa studied. Vascular plants. Methods. We used the community temperature index (CTI) to produce a time series of understorey plant community thermophilization, which we subsequently compared to a time series of mean annual temperature changes over the same period and for the same sites. The direction and magnitude of the difference (i.e., the climatic debt) was finally analysed using linear mixed-effect models to assess the relative contributions of abiotic and biotic determinants, including forest stand characteristics. Results. We found a significant increase in CTI values over time (0.08–0.09 °C/decade), whereas the velocity of mean annual temperature changes was three times higher over the same period (0.22–0.28 °C/decade). Hence, the climatic debt increased over time and was greater in forest stands with higher basal area or older trees as well as under warmer macroclimate. By contrast, a greater frequency of anthropogenic disturbances decreased the climatic debt, while natural disturbances and herbivory had no impact. Conclusions. Although often overlooked in understanding the climatic debt of forest biodiversity, changes in forest stand characteristics may modulate the climatic debt by locally modifying microclimatic conditions. Notably, the buffering effect of the upper canopy layer implies microclimate dynamics that may provide more time for understorey plant communities to locally adapt.

    ano.nymous@ccsd.cnrs.fr.invalid (Benoit Richard) 21 Jul 2021

  • [hal-03231137] Historical ecology and ancient forests: Progress, conservation issues and scientific prospects, with some examples from the French case

    Forest area has dramatically increased since the beginning or middle of the 19th century in European countries. At least half of the forests present today have grown on formerly cultivated lands, pastures or heathlands. However, net forest expansion largely masks a slow but irretrievable erosion of ancient forests. Meanwhile, forest resource harvesting (biomass, litter) has fundamentally changed during the last two centuries, moving from intensive biomass removal to increased growing stocks in different European countries. This article reviews the current knowledge on the long-term legacies of past land use and forest management practices and their effects on the functions, diversity and composition of understory vegetation of current forest ecosystems. First, we define the concepts of forest continuity and ancient forest. Then, based on the French case, we present the advances in historical sources, which make it possible to better reconstruct the change in land use and forest management practices over the last two hundred years. We review how understory plant communities and their traits respond to forest continuity and to different types of former agricultural uses, both at local and landscape scales. We then address three important issues for conservation and management: the conservation value of ancient forests, the impact of forest management on the ecological integrity of ancient forests, and the under-explored legacies of former forest management practices on soil and understory vegetation. Lastly, we propose five main fronts for future research efforts: (a) explore all types of cartographic, written sources and environmental markers; (b) develop modelling approaches to understand how past land use shapes plant communities; (c) better define the conservation value of ancient forests in conservation and management policies; (d) investigate how drivers of global change interact with forest management and land use legacies and (e) explore land use legacies in mountain and Mediterranean socio-ecological systems.

    ano.nymous@ccsd.cnrs.fr.invalid (Laurent Bergès) 20 May 2021

  • [hal-03363269] Mapping species richness of plant families in European vegetation

    Aims. Biodiversity is traditionally studied mostly at the species level, but biogeographical and macroecological studies at higher taxonomic levels can provide valuable insights into the evolutionary processes at large spatial scales. Our aim was to assess the representation of vascular plant families within different vegetation formations across Europe. Location. Europe. Methods. We used a data set of 816,005 vegetation plots from the European Vegetation Archive (EVA). For each plot, we calculated the relative species richness of each plant family as the number of species belonging to that family divided by the total number of species. We mapped the relative species richness, averaged across all plots in 50 km × 50 km grid cells, for each family and broad habitat groups: forests, grasslands, scrub and wetlands. We also calculated the absolute species richness and the Shannon diversity index for each family. Results. We produced 522 maps of mean relative species richness for a total of 152 vascular plant families occurring in forests, grasslands, scrub and wetlands. We found distinct spatial patterns for many combinations of families and habitat groups. The resulting series of 522 maps is freely available, both as images and GIS layers. Conclusions. The distinct spatial patterns revealed in the maps suggest that the relative species richness of plant families at the community level reflects the evolutionary history of individual families. We believe that the maps and associated data can inspire further biogeographical and macroecological studies and strengthen the ongoing integration of phylogenetic, functional and taxonomic diversity concepts.

    ano.nymous@ccsd.cnrs.fr.invalid (Martin Večeřa) 07 Oct 2021

  • [hal-03168867] Historical ecology of Mediterranean forests: Land use legacies on current understorey plants differ with time since abandonment and former agricultural use

    Questions: Land use legacies in current forest understorey vegetation, thoroughly studied in temperate regions, were investigated in a Mediterranean context. We tested the effect of three historical variables on current forest plant communities and traits: forest temporal continuity (ancient: forested before 1860, recent: reforested after 1860, and very recent forest: reforested after 1958) and type of land use in 1860 and 1958 (forest, pasture or arable land). Location: The Regional Natural Park of Luberon (southeastern France). Methods: We used a comprehensive vegetation plot database (473 species in 1,429 plots). Species’ response to historical variables was tested with logistic regressions, and the relationship between plant traits and historical variables was analysed with RLQ and fourth‐corner analyses. Results: Among all studied species, 250 responded to forest temporal continuity, 208 to 1860 land use, and 246 to 1958 land use. Species associated with ancient forests were more frequently forest specialists or forest edge species, shade‐tolerant and perennials, while species associated with recent and very recent forests were more frequently annuals, anemochorous and heliophilous species. Species exhibited different traits and ecological preferences according to the type of land use prior to forest: therophytes were more frequent on former arable land while chamaephytes were more frequent on former pasture. Trait responses to 1860 and 1958 land uses were globally consistent. Conclusions: The effect of forest temporal continuity and past land use on forest understorey communities was consistent with other studies in northern Europe or northern America, which suggests that the same ecological processes apply in temperate lowland and Mediterranean regions. This study highlights a succession of plant communities in the long term and different trajectories of succession according to the type of former agricultural use. The long‐term legacies of past land use in current forest plant communities highlight the importance to preserve ancient forests, where typical forest species can be maintained.

    ano.nymous@ccsd.cnrs.fr.invalid (Juliet Abadie) 19 Apr 2021

  • [hal-03013971] Scientific and human errors in a snow model intercomparison

    Twenty-seven models participated in the Earth System Model - Snow Model Intercomparison Project (ESM-SnowMIP), the most data-rich MIP dedicated to snow modelling. Our findings do not support the hypothesis advanced by previous snow MIPs: evaluating models against more variables, and providing evaluation datasets extended temporally and spatially does not facilitate identification of key new processes requiring improvement to model snow mass and energy budgets, even at point scales. In fact, the same modelling issues identified by previous snow MIPs arose: albedo is a major source of uncertainty, surface exchange parametrizations are problematic and individual model performance is inconsistent. This lack of progress is attributed partly to the large number of human errors that led to anomalous model behaviour and to numerous resubmissions. It is unclear how widespread such errors are in our field and others; dedicated time and resources will be needed to tackle this issue to prevent highly sophisticated models and their research outputs from being vulnerable because of avoidable human mistakes. The design of and the data available to successive snow MIPs were also questioned. Evaluation of models against bulk snow properties was found to be sufficient for 15 some but inappropriate for more complex snow models whose skills at simulating internal snow properties remained untested. Discussions between the authors of this paper on the purpose of MIPs revealed varied, and sometimes contradictory, motivations behind their participation. These findings started a collaborative effort to adapt future snow MIPs to respond to the diverse needs of the community

    ano.nymous@ccsd.cnrs.fr.invalid (Cecile Menard) 19 Nov 2020

  • [hal-04528777] Improvement of modeling plant responses to low soil moisture in JULESvn4.9 and evaluation against flux tower measurements

    Drought is predicted to increase in the future due to climate change, bringing with it myriad impacts on ecosystems. Plants respond to drier soils by reducing stomatal conductance in order to conserve water and avoid hydraulic damage. Despite the importance of plant drought responses for the global carbon cycle and local and regional climate feedbacks, land surface models are unable to capture observed plant responses to soil moisture stress. We assessed the impact of soil moisture stress on simulated gross primary productivity (GPP) and latent energy flux (LE) in the Joint UK Land Environment Simulator (JULES) vn4.9 on seasonal and annual timescales and evaluated 10 different representations of soil moisture stress in the model. For the default configuration, GPP was more realistic in temperate biome sites than in the tropics or high-latitude (cold-region) sites, while LE was best simulated in temperate and high-latitude (cold) sites. Errors that were not due to soil moisture stress, possibly linked to phenology, contributed to model biases for GPP in tropical savanna and deciduous forest sites. We found that three alternative approaches to calculating soil moisture stress produced more realistic results than the default parameterization for most biomes and climates. All of these involved increasing the number of soil layers from 4 to 14 and the soil depth from 3.0 to 10.8 m. In addition, we found improvements when soil matric potential replaced volumetric water content in the stress equation (the "soill4_psi" experiments), when the critical threshold value for inducing soil moisture stress was reduced ("soil14_p0"), and when plants were able to access soil moisture in deeper soil layers ("soil14_dr*2"). For LE, the biases were highest in the default configuration in temperate mixed forests, with overestimation occurring during most of the year. At these sites, reducing soil moisture stress (with the new parameterizations mentioned above) increased LE and increased model biases but improved the simulated seasonal cycle and brought the monthly variance closer to the measured variance of LE. Further evaluation of the reason for the high bias in LE at many of the sites would enable improvements in both carbon and energy fluxes with new parameterizations for soil moisture stress. Increasing the soil depth and plant access to deep soil moisture improved many aspects of the simulations, and we recommend these settings in future work using JULES or as a general way to improve land surface carbon and water fluxes in other models. In addition, using soil matric potential presents the opportunity to include plant functional type-specific parameters to further improve modeled fluxes.

    ano.nymous@ccsd.cnrs.fr.invalid (Anna B Harper) 02 Apr 2024

  • [hal-03208693] Assessment of the efficiency of three sampling methods for the recovery of soil charcoals in tropical anthropogenic sites

    The recovery and identification of wood charcoals from soil not associated to archaeological excavation is called pedoanthracology. Researchers in this field use different sampling methods, and only one study, in a temperate context, has compared their efficiency so far. In this paper, we compare the efficiency of three sampling methods on charcoal concentration (> 4 mm) and on taxonomic representativeness in a tropical environment for the first time. These methods are pit sampling, auger sampling and opportunistic handpicking of charcoal on tree uprooted mounds or in the soil excavated during the digging of a pit. Our results suggest that the two digging methods (pit and auger) allow to recover similar charcoal concentrations whatever the site and the depth under consideration. But as expected, the charcoal concentration of a site depends on its history (e.g. type of activity). We also show that the estimation of the minimal sampling effort required to obtain taxonomically representative assemblages, in terms of number of charcoals and of auger samplings, varied greatly depending on the site and on the presence of overrepresented taxa. Finally, our results show that auger cores were often monospecific (34 %). Nevertheless, they allowed to recover different taxa from the pit method, with 18 to 21 % of the taxa exclusive to the first method and 30 to 40 % of the taxa exclusive to the second one in the sites under consideration. Charcoals from opportunistic handpicking also allowed to improve the taxonomic diversity of the whole assemblage of a site with 5 to 15 % of the taxa being exclusive to this method. The three methods are therefore complementary and we suggest to use the three of them to obtain the best taxonomic diversity in an anthracological assemblage and to overcome the specific biases of each method. With this study, we hope that we will help tropical (pedo)anthracologists to optimize charcoal sampling in anthropogenic sites were the sampling design cannot benefit from archaeological excavations.

    ano.nymous@ccsd.cnrs.fr.invalid (Stéphanie C Bodin) 27 Apr 2021

  • [hal-03926049] Canopy openness and exclusion of wild ungulates act synergistically to improve oak natural regeneration

    Abstract Key message Fifteen species are most susceptible to require vegetation control during tree regeneration in the range of our study. Among these 15 species, Rubus fruticosus , Pteridium aquilinum , and Molinia caerulea cover each more than 300,000 ha of open-canopy forests. Context Vegetation control, i.e., the reduction of competitive species cover, is often required to promote tree seedling establishment during the forest regeneration stage. The necessity to control understory vegetation largely depends on the species to be controlled. In order to plan forest renewal operations, it is critical to identify which species require vegetation control during the regeneration stage and to quantify the forest area affected by these species. Aims We aimed at identifying the main species requiring vegetation control and at estimating the forest area they cover at the national level. Methods Using National Forest Inventory data, we created four indicators based on two levels of plant cover, cross-referenced with two levels of canopy opening, and compared them to the outcome of a survey of forest manager practices. Results The best indicator was the one that represented the proportion of forests with open canopy where the species was present with a large cover in the understory. In non-Mediterranean France, according to the indicator, a total of 15 species were found to frequently require vegetation control during the tree regeneration stage. Pteridium aquilinum , Molinia caerulea , and Rubus fruticosus were the main species, and each covered more than 300,000 ha of forest with open canopies, representing about 13% of the total forest area with open canopies outside of the Mediterranean area. Conclusions Forests covered by species requiring vegetation control according to forest managers represent a large share of the forest area undergoing regeneration. This study provides the first list of species that require vegetation control based on a methodological protocol that makes it possible to calculate the area associated with each species.

    ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 22 Mar 2023

  • [hal-03146559] Slow recovery from soil disturbance increases susceptibility of high elevation forests to landslides

    Natural hazards such as shallow landslides are common phenomena that disturb soil and damage forests. Quantifying the recovery of forest vegetation after a hazard is important for determining the window of susceptibility to new disturbance events, especially at high elevations, where extreme weather events are frequent and the growing season is short. Plant roots can reduce the size of this window on unstable hillslopes, by adding mechanical reinforcement (cr) to soil and increasing its matric suction, termed here as hydrological reinforcement (ch). These data are used in landslide models to calculate the Factor of Safety (FoS) of a hillslope. We calculated temporal variations in cr and ch in naturally regenerated mixed, montane forests in the French Alps. In these closed-canopy forests, open-canopy gaps were present, with understory vegetation comprising herbs, forbs and shrubs. At three altitudes (1400, 1700 and 2000 m), we dug small trenches as proxies for shallow landslide events and calculated cr before soil disturbance in both open gaps and closed forests. Then, using monthly tree root initiation and mortality data measured in rhizotrons, we calculated monthly cr for four years after the disturbance. To compare results with cr, ch was estimated using matric suction data that were measured in trenches at 1400 m for >1 year. Temporal FoS was then calculated using an infinite slope stability model.Results showed that finer, short-lived roots contributed little to soil reinforcement compared to thicker, long-lived roots. After disturbance, mean cr (over the entire soil profile) never fully recovered to the initial value at any site, although >90% recovery was observed in open gaps at 1400 m. Mean cr was slow to recover in closed forests, especially at 2000 m, where only 19% recovery occurred after 41 months. The ch in closed forests was considerable during the summer months, but marked increases in soil water moisture resulted in lower FoS, especially during December to April, when soil was near saturation. As cr changed little throughout the year, it was a more reliable contributor to slope stability. Our results show therefore, that particular attention should be paid to high elevation forests after a disturbance. Also, during the process of recovery, the highly variable soil water dynamics in closed forest can result in seasonal hotspots of vulnerability. Therefore, when tree transpiration is low, our results highlight a need for careful monitoring on steep or unstable slopes, especially in disturbed closed-canopy forests

    ano.nymous@ccsd.cnrs.fr.invalid (Hongxi Liu) 13 Feb 2023

  • [hal-02976274] Growth dynamics of fast-growing tree species in mixed forestry and agroforestry plantations

    In recent years, plantations of fast-growing tree species have emerged as a possible way to meet the increasing demand for biomass for renewable energy in Europe. Agroforestry plantations including fast-growing tree species could be an attractive option because they reduce land competition for biomass and food production while providing forest benefits. Today, the species interactions that determine whether a given mixture will be more productive than the corresponding monocultures are still poorly understood. Our objective was to assess the performance of fast-growing trees, i.e. poplar (Populus nigra × P. deltoides) and alder (Alnus glutinosa), in association with herbaceous species either N 2-fixing species (succession alfalfa (Medicago sativa) and clover (Trifolium pratense)) or graminoids (succession of wheat (Triticum aestivum)-triticale (Triticosecale)-temporary grassland consisting of mixtures of perennial ryegrass (Lolium perenne) and fescue (Festuca ovina)), respectively, and in association together. We compared tree growth in mixed stands to growth in the respective tree monocultures. An experimental plantation composed of three blocks including the different treatments was set up in 2014 in northeastern France. In the forest mixture, poplar and alder were planted in alternating rows, and in the agro-forestry plots, every second line of trees was replaced by the crops. No fertilizers (of any kind) were used during the experiments. During six growing seasons, tree growth (height and diameter at breast height) was monitored monthly in the agroforestry stands, the forest mixture stand and the two tree monocultures. By the end of 2019, poplar stem height in association with N 2-fixing crops (alfalfa, then clover) was higher than in the forest mixture and the monoculture. During the warmest growing season with a marked dry period in June-July (2018), poplar height growth rate in the agroforestry treatment was between three and five times higher than for the poplars in the monoculture and the forest mixture. A facilitation process in the agroforestry plantations could explain this result due to a significant enrichment of the soil in nitrogen by the N 2-fixing crops. This result only appeared several years after tree planting, and management actions were necessary in order to control the strong competition between crops and trees during the early stages. In the forest mixture, poplars associated with alders were smaller than in their monoculture, in spite of a stratification of the canopies of the two species. For alders, tree growth did not appear to be affected by either an association with graminoids or with poplar.

    ano.nymous@ccsd.cnrs.fr.invalid (Anaïs Thomas) 24 Oct 2022

  • [hal-03889520] Climate change impact on tree mortality differs with tree social status

    Changes in temperature and rainfall linked to recent climate change increase the mortality rates of European temperate tree species. The economic importance of trees and the ecosystem services they provide differ according to their social status (dominant or suppressed trees) and their size. The extent to which climate change impacts these different categories in different ways remains little explored. Ecophysiological differences between tree size and status suggest different sensitivities to climate change. Dominant trees are exposed to more evapotranspiration than suppressed trees that benefit from buffered climatic conditions. Large trees are able to develop a network of fine roots that allow deeper water and nutrient uptake during water shortage periods, but that have higher water requirements and more physical constraints than small trees due to the fact that they must lift water to greater heights. We used 207,100 trees from the French forest inventory data (including 3,514 dead trees), representing eight common European tree species. For each species, we separated the tree population into three subsets of suppressed, small dominant and large dominant trees. For each subset, we modelled the mortality observed in a stand in the absence of disturbances (background mortality), with a focus on the differences in sensitivity to recent changes in temperature and rainfall. After having taken the main mortality drivers related to competition into account, as well as stand characteristics including logging intensity effect, we assessed the over-mortality linked to the recent changes in temperature and rainfall for each of the three subsets. When considering both changes in temperature and rainfall, the climate change related to over-mortality was greater for suppressed than for small or large dominant trees, for all the species. Over-mortality of suppressed trees was related to temperature increase, whereas a maximum vulnerability related to rainfall decrease was observed for large dominant trees. Over-mortality driven by climate change not only concerns large and dominant trees, but small and especially suppressed ones as well. These results suggest that in addition to wood production, forest renewal and ecosystem services associated with understorey vegetation are threatened by the recent changes in temperature and rainfall in European temperate forests.

    ano.nymous@ccsd.cnrs.fr.invalid (Adrien Taccoen) 24 Jan 2024

  • [hal-03037249] Mixing has limited impacts on the foliar nutrition of European beech and Scots pine trees across Europe

    Tree species-mixing has been suggested as one option to counteract the adverse effects of global change on tree mineral nutrition, yet the effect of mixing on nutrient availability remains poorly documented. We therefore analyzed the current foliar nutrient (N, P, K, Ca, Mg) quantities and ilr balances (isometric log transformed ratios between elements or groups of elements) for 261 European beech and 248 Scots pine trees from 15 sites, each consisting of one beech-pine mixed stand and the respective monocultures, across a gradient of environmental conditions in Europe. We hypothesized an overall positive effect of mixing on tree foliar nutrient content, and that this mixing effect would be stronger on nutrient-poor sites. Using linear mixed models and multivariate linear regression models, we first tested for the effects of species (beech/pine) and composition (pure/mixed) across all sites; we then investigated whether the species-mixing effect was related to site fertility. The nutrient composition of beech leaves and pine needles differed significantly for all ilr balances. For both species, significant mixing effects were detected for some nutrients and ilr balances; those effects, however, could not be consistently related to contrasted nutrient composition between species. For most nutrients and ilr balances, the mixing effect was influenced by the site nutritional status, but the pattern differed from expectation: absence or minor differences between monocultures and mixtures at the lower end of the chemical fertility gradient, and maximum differences in rich soils. The contrasting foliar nutrient composition of pine and beech trees and the site nutrient status only partly explained the mixing effects on tree mineral nutrition. Our results claim for a better understanding of nutrientrelated mechanisms associated with complementarity and points towards the need to further expand the existing frameworks to account for the multivariate nature of tree nutrition.

    ano.nymous@ccsd.cnrs.fr.invalid (Géraud de Streel) 25 Oct 2023

  • [hal-04219519] Cutting tree rings into time slices: how intra‐annual dynamics of wood formation help decipher the space‐for‐time conversion

    Tree-ring anatomy, microdensity and isotope records provide valuable intra-annual information. However, extracting signals at that scale is challenged by the complexity of xylogenesis, where two major processescell enlargement and wall thickeningoccur at different times and rates. We characterized the space-for-time association in the tree rings of three conifer species by examining the duration, overlapping, inter-tree synchronicity and interannual stability during cell enlargement and wall thickening across regular tree-ring sectors (portions of equal tangential width). The number of cells and cell differentiation rates determined the duration of sector formation, which augmented more rapidly throughout the ring for wall thickening than for enlargement. Increasing the number of sectors above c. 15 had a limited effect on improving time resolution because consecutive sector formation overlapped greatly in time, especially in narrow rings and during wall thickening. Increasing the number of sectors also resulted in lower synchronicity and stability of intermediate-sector enlargement, whereas all sectors showed high synchronicity and stability during wall thickening. Increasing the number of sectors had a stronger effect on enhancing time-series resolution for enlargement-than for wall-thickening-related traits, which would nevertheless produce more reliable intra-annual chronologies as a result of the more similar calendars across trees and years in wall thickening.

    ano.nymous@ccsd.cnrs.fr.invalid (Gonzalo Pérez‐de‐lis) 27 Sep 2023

  • [hal-03265612] Turgor – a limiting factor for radial growth in mature conifers along an elevational gradient

    A valid representation of intra-annual wood formation processes in global vegetation models is vital for assessing climate change impacts on the forest carbon stock. Yet, wood formation is generally modelled with photosynthesis, despite mounting evidence that cambial activity is rather directly constrained by limiting environmental factors. Here, we apply a state-of-the-art turgor-driven growth model to simulate 4 yr of hourly stem radial increment fromPicea abies(L.) Karst. andLarix deciduaMill. growing along an elevational gradient. For the first time, wood formation observations were used to validate weekly to annual stem radial increment simulations, while environmental measurements were used to assess the climatic constraints on turgor-driven growth. Model simulations matched the observed timing and dynamics of wood formation. Using the detailed model outputs, we identified a strict environmental regulation on stem growth (air temperature > 2 degrees C and soil water potential > -0.6 MPa). Warmer and drier summers reduced the growth rate as a result of turgor limitation despite warmer temperatures being favourable for cambial activity. These findings suggest that turgor is a central driver of the forest carbon sink and should be considered in next-generation vegetation models, particularly in the context of global warming and increasing frequency of droughts.

    ano.nymous@ccsd.cnrs.fr.invalid (Richard L Peters) 21 Jun 2021

  • [hal-03465112] Nutrient supply modulates species interactions belowground: dynamics and traits of fine roots in mixed plantations of Eucalyptus and Acacia mangium

    Aims : Belowground interactions are still poorly understood in mixed-species forests. We investigated the effects of soil fertility on belowground processes in mixed planted forests. Methods : The dynamics and traits of Eucalyptus and Acacia mangium fine roots (diameter < 2 mm) in plantations with 50% of each species were studied in a randomized block design established in a nutrient depleted soil. Stands with NPK fertilization applied at planting (F+) were compared to unfertilized stands (F-). Results : In the 0–15 cm soil layer, Eucalyptus root mass density (RMD) was higher than Acacia RMD by 50% in F+ and 10% in F-, considering both ages. At 34 months of age, Eucalyptus RMD was 94% higher near Acacia trees than near Eucalyptus trees in F-. In this layer, Eucalyptus specific root length (SRL) was 21% higher than Acacia SRL at 16 months of age and was 10% higher in F- than in F+ at 34 months of age. The cumulative Eucalyptus fine root length production between 16 and 34 months was 66% higher in F- than in F+ in the 0–1 m soil layer. Conclusions : Fertilization increased the competition between species and led to a partial exclusion of Acacia fine roots from the nutrient-rich topsoil. Soil exploration by Eucalyptus roots in the vicinity of Acacia trees was higher in F- than in F+, which suggests that unfertilized trees benefited from facilitation through higher soil N availability and direct N transfer from Acacia trees.

    ano.nymous@ccsd.cnrs.fr.invalid (Bruno Bordron) 03 Dec 2021

  • [hal-03167847] Recent increase in European forest harvests as based on area estimates (Ceccherini et al. 2020a) not confirmed in the French case

    A recent paper by Ceccherini et al. (2020a) reported an abrupt increase of 30% in the French harvested forest area in 2016–2018 compared to 2004–2015. A re-analysis of their data rather led us to conclude that, when accounting for the singular effect of storm Klaus, the rate of change in harvested area depended on the change year used to separate the two periods to compare. Moreover, the comparison with data on harvested volumes from different sources brought contrasted results depending on the source. Therefore, it cannot be concluded that wood harvest increased in France in 2016–2018 compared to 2004–2015. The discrepancy between Ceccherini et al.’s data and other data on harvested volumes points out the difficulty of reconciling different approaches to estimate wood harvest at a country level.

    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Picard) 01 Dec 2022

  • [hal-03155739] Developing the persona method to increase the commitment of non-industrial private forest owners in French forest policy priorities

    In Europe, 60% of the forest area is privately owned, with a significant proportion of nonindustrial private forest (NIPF) being highly fragmented with, in particular, low intensity forest management. Numerous typologies have therefore been developed to provide detailed guidance to policy makers for the design of policy instruments to involve these owners in forest management approaches. However, these policy instruments fail to involve all categories of owners and there is no method made by and with people locally in charge of policy implementation to increase the commitment of NIPF owners. The main objective of this study is to adapt the persona method, which is a central user-centered design tool, to design typologies of NIPF owners as future users of policy instruments. We have designed our personas in the Vosges territory (France), in the context of the main French forest policy objective of increasing timber harvesting and NIPF sustainable management. Our results designed eight types of personas as well as a six-part composition of the persona sheet. The main interest is to provide a general methodology to forest policy and forest managers based on rigorous concepts of usercentered design processes and co-creation, to implement operational tools for NIFP management. Finally, both future developments and methodological limitations are discussed in a global research perspective.

    ano.nymous@ccsd.cnrs.fr.invalid (Maxence Arnould) 16 Feb 2023

  • [hal-03516955] Shifts in the Abundances of Saprotrophic and Ectomycorrhizal Fungi With Altered Leaf Litter Inputs

    Ectomycorrhizal (EcM) and saprotrophic fungi interact in the breakdown of organic matter, but the mechanisms underlying the EcM role on organic matter decomposition are not totally clear. We hypothesized that the ecological relations between EcM and saprotroph fungi are modulated by resources availability and accessibility, determining decomposition rates. We manipulated the amount of leaf litter inputs (No-Litter, Control Litter, Doubled Litter) on Trenched (root exclusion) and Non-Trenched plots (with roots) in a temperate deciduous forest of EcM-associated trees. Resultant shifts in soil fungal communities were determined by phospholipid fatty acids and DNA sequencing after 3 years, and CO2 fluxes were measured throughout this period. Different levels of leaf litter inputs generated a gradient of organic substrate availability and accessibility, altering the composition and ecological relations between EcM and saprotroph fungal communities. EcM fungi dominated at low levels of fresh organic substrates and lower organic matter quality, where short-distances exploration types seem to be better competitors, whereas saprotrophs and longer exploration types of EcM fungi tended to dominate at high levels of leaf litter inputs, where labile organic substrates were easily accessible. We were, however, not able to detect unequivocal signs of competition between these fungal groups for common resources. These results point to the relevance of substrate quality and availability as key factors determining the role of EcM and saprotroph fungi on litter and soil organic matter decay and represent a path forward on the capacity of organic matter decomposition of different exploration types of EcM fungi.

    ano.nymous@ccsd.cnrs.fr.invalid (Sara Marañón-Jiménez) 07 Jan 2022

  • [hal-03363005] Climate and socio-economic factors explain differences between observed and expected naturalization patterns of European plants around the world

    Aim The number of naturalized (i.e. established) alien species has increased rapidly over recent centuries. Given the differences in environmental tolerances among species, little is known about what factors determine the extent to which the observed size of the naturalized range of a species and hence the extent to which the observed richness of naturalized species of a region approach their full potential. Here, we asked which region- and species-specific characteristics explain differences between observed and expected naturalizations. Location Global. Time period Present. Major taxa studied Vascular plants. Methods We determined the observed naturalized distribution outside Europe for 1,485 species endemic to Europe using the Global Naturalized Alien Flora (GloNAF) database and their expected distributions outside Europe using species distribution models. First, we investigated which of seven socio-economic factors related to introduction pathways, anthropogenic pressures and inventory effort best explained the differences between observed and expected naturalized European floras. Second, we examined whether distributional features, economic use and functional traits explain the extent to which species have filled their expected ranges outside Europe. Results In terms of suitable area, more than 95% of expected naturalizations of European plants were not yet observed. Species were naturalized in only 4.2% of their suitable regions outside of Europe (range filling) and in 0.4% of their unsuitable regions (range expansion). Anthropogenic habitat disturbance primarily explained the difference between observed and expected naturalized European floras, as did the number of treaties relevant to invasive species. Species of ornamental and economic value and with large specific leaf area performed better at filling and expanding beyond their expected range. Main conclusions The naturalization of alien plant species is explained by climate matching but also by the regional level of human development, the introduction pressure associated with the ornamental and economic values of the species and their adaptation to disturbed environments.

    ano.nymous@ccsd.cnrs.fr.invalid (Robin Pouteau) 02 Oct 2021

  • [hal-03145053] Intraspecific variability of quantity and chemical composition of ethanolic knotwood extracts along the stems of three industrially important softwood species: Abies alba , Picea abies and Pseudotsuga menziesii

    Knotwood of softwood species is rich in secondary metabolites, especially lignans. These metabolites can be extracted with organic solvents, and are known to be valuable sources of natural bioactive molecules. Here, we examine the intraspecific variability of the yield and compositions of ethanol extracts from knotwood along the stems of three economically significant softwoods Abies alba, Picea abies and Pseudotsuga menziesii in view of further valorisation. Extractive yields from all three species were higher from knots at the base of the living crown than at the top. Lignans and terpenes were abundant in A. alba and P. abies extracts, and lignans were present in the highest concentrations at the crown base. Secoisolariciresinol and hydroxymatairesinol were the most abundant lignans in A. alba and P. abies, respectively. P. menziesii extract composition was more diverse than those of the other species, containing taxifolin, small amounts of the lignan nortrachelogenin, and smaller amounts of secoisolariciresinol. A cyclitol, D-pinitol, was found in high concentrations in extracts from knots at the very top of the crown, particularly in A. alba and P. menziesii. Lignans, taxifolin and D-pinitol are reported to have anti-tumour properties, and valuable food-supplement markets exist for these compounds suggesting possibilities of further valorisation.

    ano.nymous@ccsd.cnrs.fr.invalid (Maree Brennan) 18 Feb 2021

  • [hal-04214003] Dynamiques forestières à l'ère anthropocène : mise au point sémantique et proposition de définitions écologiques

    Dans cette mise au point sémantique, nous proposons de formaliser une série de définitions des termes les plus fréquemment utilisés pour qualifier une forêt selon son degré d’anthropisation. La forêt est appréhendée ici sous sa dimension écosystémique, incluant biotope et biocœnose. Dans un souci de robustesse conceptuelle, nous nous appuyons sur quatre théories scientifiques : la théorie des communautés végétales, la théorie des successions écologiques, la théorie des perturbations et la théorie de la hiérarchie, dont les contributions sont brièvement analysées. Sur cette base, nous reprenons un certain nombre de définitions et en proposons de nouvelles, de manière à qualifier une forêt selon quatre attributs fondamentaux : son origine et sa genèse ; son degré de naturalité ; son historicité et sa morphologie. Chaque définition est explicitée, argumentée et illustrée à l’aide d’exemples concrets. Nous concluons par une réflexion ouverte sur le concept d’état de référence pour une forêt.

    ano.nymous@ccsd.cnrs.fr.invalid (Guillaume Decocq) 21 Sep 2023

  • [hal-03369095] Is vulnerability segmentation at the leaf-stem transition a drought resistance mechanism? A theoretical test with a trait-based model for Neotropical canopy tree species

    Key message: Leaf-stem vulnerability segmentation predicts lower xylem embolism resistance in leaves than stem. However, although it has been intensively investigated these past decades, the extent to which vulnerability segmentation promotes drought resistance is not well understood. Based on a trait-based model, this study theoretically supports that vulnerability segmentation enhances shoot desiccation time across 18 Neotropical tree species. Context: Leaf-stem vulnerability segmentation predicts lower xylem embolism resistance in leaves than stems thereby preserving expensive organs such as branches or the trunk. Although vulnerability segmentation has been intensively investigated these past decades to test its consistency across species, the extent to which vulnerability segmentation promotes drought resistance is not well understood. Aims: We investigated the theoretical impact of the degree of vulnerability segmentation on shoot desiccation time estimated with a simple trait-based model. Methods We combined data from 18 tropical rainforest canopy tree species on embolism resistance of stem xylem (flow-centrifugation technique) and leaves (optical visualisation method). Measured water loss under minimum leaf and bark conductance, leaf and stem capacitance, and leaf-to-bark area ratio allowed us to calculate a theoretical shoot desiccation time ( t crit ). Results: Large degrees of vulnerability segmentation strongly enhanced the theoretical shoot desiccation time, suggesting vulnerability segmentation to be an efficient drought resistance mechanism for half of the studied species. The difference between leaf and bark area, rather than the minimum leaf and bark conductance, determined the drastic reduction of total transpiration by segmentation during severe drought. Conclusion: Our study strongly suggests that vulnerability segmentation is an important drought resistance mechanism that should be better taken into account when investigating plant drought resistance and modelling vegetation. We discuss future directions for improving model assumptions with empirical measures, such as changes in total shoot transpiration after leaf xylem embolism.

    ano.nymous@ccsd.cnrs.fr.invalid (Sébastien Levionnois) 07 Oct 2021

  • [hal-04229676] A comprehensive framework for seasonal controls of leaf abscission and productivity in evergreen broadleaved tropical and subtropical forests

    Three climate-phenology regimes are identified across tropical and subtropical forest biomes-Where light and water limit plant in dry season, litterfall and productivity peak in sunny wet season-Where light or water alternately limits plant, productivity peaks in wet season with low litterfall-Where water does not limit plant, litterfall and productivity peak in sunny dry season ll www.cell.com/the-innovation

    ano.nymous@ccsd.cnrs.fr.invalid (Xueqin Yang) 05 Oct 2023

  • [hal-03134066] C-STABILITY an innovative modeling framework to leverage the continuous representation of organic matter

    The understanding of soil organic matter (SOM) dynamics has considerably advanced in recent years. It was previously assumed that most SOM consisted of recalcitrant compounds, whereas the emerging view considers SOM as a range of polymers continuously processed into smaller molecules by decomposer enzymes. Mainstreaming this new paradigm in current models is challenging because of their ill-adapted framework. We propose the C-STABILITY model to resolve this issue. Its innovative framework combines compartmental and continuous modeling approaches to accurately reproduce SOM cycling processes. C-STABILITY emphasizes the influence of substrate accessibility on SOM turnover and makes enzymatic and microbial biotransformations of substrate explicit. Theoretical simulations provide new insights on how depolymerization and decomposers ecology impact organic matter chemistry and amount during decomposition and at steady state. The flexible mathematical structure of C-STABILITY offers a promising foundation for exploring new mechanistic hypotheses and supporting the design of future experiments.

    ano.nymous@ccsd.cnrs.fr.invalid (Julien Sainte-Marie) 08 Feb 2021

  • [hal-03596873] Étude du choix de lieu de ponte par le hanneton forestier dans les Vosges du Nord

    Le hanneton forestier est une espèce importante de coléoptère à potentiel ravageur des forêts mixtes et feuillues européennes. Afin de mieux comprendre son écologie, nous avons étudié le comportement de ponte des femelles dans les Vosges du Nord. Nous avons mis en évidence qu’une strate arbustive dense est négativement corrélée à la densité de pontes et d’œufs dans le sol. Au contraire, l’ouverture de la canopée et la proportion de surface terrière de chêne dans le peuplement alentour étaient toutes deux positivement corrélées avec les densités de pontes et d’œufs. Nous émettons l’hypothèse qu’une couche arbustive dense crée une barrière physique pour les femelles. D’autre part, une canopée ouverte pourrait améliorer les conditions pour les larves dans le sol, tout comme une proportion élevée de chênes dans la zone environnante peut fournir une bonne source de nourriture pour les larves et les adultes.

    ano.nymous@ccsd.cnrs.fr.invalid (Jérémy Cours) 04 Mar 2022

  • [hal-03533462] Maladie des bandes rouges : le pin laricio souffre mais ne rompt pas !

    L’investissement de longue date des organismes forestiers de recherche et de développement dans l’installation et le suivi de réseaux d’expérimentation sylvicole, comme le GIS Coopérative des données sur la croissance des peuplements forestiers, permet d’étudier le lien entre sylviculture et maladie des bandes rouges sur un large panel de dispositifs de pins laricio en France. L’impact de la maladie des bandes rouges sur la mortalité et la croissance a été suivi pendant 3 ans. L’étude montre que la mortalité est très faible mais que la croissance est fortement réduite, proportionnellement aux niveaux de dégâts dans les houppiers causés par la maladie. Elle montre également qu’en gérant les peuplements de manière dynamique, on limite les symptômes de la maladie et donc la perte de production. Cet article a été publié dans le cadre d’un dossier intitulé « Le pin laricio, toujours d’actualité : résultats du programme Dolar » paru dans le n° 259/2021 de Forêt entreprise.

    ano.nymous@ccsd.cnrs.fr.invalid (Sandrine Perret) 18 Jan 2022

  • [hal-03955976] Observatoire des peuplements dévastés et mités après tempête (1999). 1 - Analyse des dynamiques naturelles forestières après deux décennies

    L’observatoire des peuplements dévastés et mités a été mis en place après la tempête de 1999 pour caractériser les différentes dynamiques de reconstitution des peuplements touchés par la tempête. 20 ans de suivi ont permis de montrer que la régénération naturelle s’installe en quantité suffisante dans de nombreux sites. L’étude de la dynamique de reconstitution naturelle a permis de mettre en évidence l’importance de la taille de la trouée et de la composition du peuplement antécédent dans la modulation de la succession forestière.

    ano.nymous@ccsd.cnrs.fr.invalid (Lisa Laurent) 25 Jan 2023

  • [hal-03965160] Quelles sont les limites climatiques de survie et de croissance du cèdre du Liban au stade juvénile en région méditerranéenne ?

    Dans un contexte de forte vulnérabilité du cèdre du Liban liée à des pressions anthropiques historiques et aux risques engendrés par le réchauffement climatique, nous avons cherché à évaluer la gamme climatique réelle de survie et de croissance du cèdre au stade juvénile. Nous avons relevé la présence du cèdre dans 1241 placettes situées dans l’aire naturelle de l’espèce au Liban pour préciser sa gamme altitudinale dans les conditions naturelles. Nous avons également établi dans cette région un dispositif de 8 sites expérimentaux régulièrement répartis entre 110 et 2320 m d’altitude en étudiant dans chaque site les effets de la densité de plantation, du mélange des essences et de l’arrosage. Nous avons mesuré la croissance et la survie à 3 ans des 1360 cèdres plantés dans le dispositif. Dans les conditions naturelles, la répartition du cèdre s’étend entre 1240 et 1850 m d’altitude. L’étude a mis en évidence le poids très important du stress hydrique comme déterminant de la marge altitudinale chaude mais aussi de la marge froide de distribution du cèdre. L’absence d’arrosage conduit ainsi à une forte baisse de survie et de croissance aux altitudes inférieures à 500 m et à une baisse moindre au-delà de 1900 m. L’effet de l’arrosage est nul pour les altitudes intermédiaires où la croissance et la survie de l’espèce sont optimales. Les résultats mettent en évidence une extension possible importante de l’aire de distribution du cèdre à basse altitude et une extension moindre à haute altitude ouvrant la voie à des tests d’élargissement de la zone de plantation de cette espèce au Liban et dans les régions aux climats comparables.

    ano.nymous@ccsd.cnrs.fr.invalid (Yaacoub Nassif) 31 Jan 2023

  • [hal-04211446] Caractérisation et variabilité des propriétés physiques et structurelles du bois du kevazingo, Guibourtia tessmannii, et de l’okoumé, Aucoumea klaineana, provenant des forêts naturelles du Gabon

    La caractérisation et l’analyse de la variabilité des paramètres structuraux et des propriétés physiques du bois ont été réalisées chez le Kevazingo et l’Okoumé, deux espèces gabonaises à fort potentiel économique. En parallèle aux caractéristiques technologiques telles que le retrait ou le point de saturation des fibres, une caractérisation fine de la structure du bois (angle des microfibrilles, angle de fil, microdensité) a été réalisée. Chez les deux espèces les valeurs moyennes observées pour chaque propriété ont été comparées aux valeurs de la littérature. L’analyse de la variabilité des différentes propriétés permet d’identifier la position radiale (effet de la distance à la moelle) comme principale source de variabilité des propriétés du bois chez le Kevazingo, alors que pour l’Okoumé la variabilité des propriétés provient non seulement de la distance à la moelle mais aussi de la variabilité entre les rayons et entre les arbres.

    ano.nymous@ccsd.cnrs.fr.invalid (Jean Leon Zue Ondo) 10 Oct 2023

  • [hal-03533278] Le climat et la station influencent-ils le développement de la maladie des bandes rouges dans le grand quart Nord-Ouest de la France ?

    Pour mesurer les effets des conditions pédoclimatiques sur le développement de la maladie des bandes rouges, 149 placettes de plantation de pins laricio de Corse en régions Centre-Val de Loire et Pays de la Loire ont été sélectionnées et mesurées. Les résultats de l’étude montrent que le développement de la maladie est fortement corrélé aux événements climatiques. Les périodes humides et chaudes lui sont favorables, alors que les sécheresses estivales le freinent. Les peuplements âgés et les sols pauvres sont également plus sévèrement atteints. L’installation des pins laricio sur les meilleures stations favorisera leur résistance. Cet article a été publié dans le cadre d’un dossier intitulé « Le pin laricio, toujours d’actualité : résultats du programme Dolar » paru dans le n° 259/2021 de Forêt entreprise.

    ano.nymous@ccsd.cnrs.fr.invalid (Dominique Balay) 18 Jan 2022

  • [hal-03334205] Numerical classification of the Carici caryophylleae-Genistetea lobelii in Corsica (France)

    The class ‘Carici caryophylleae-Genistetea lobelii Klein 1972’ corresponds to Cyrno-Sardian oromediterranean cushion-scrubs and related grasslands. In France, this class is only present in Corsica and the syntaxonomic scheme is debated among phytosociologists. This paper aims to highlight the main plant associations of the Carici caryophylleae-Genistetea lobelii Klein 1972 and to define the diagnostic species for each phytosociological unit. Diagnostic species are defined as species with a distinct concentration of occurrence or abundance in a particular vegetation unit. We compiled 519 vegetation plots and we applied the EuroVegChecklist expert system for the classes of European vegetation to only retain vegetation plots belonging to the Carici caryophylleae-Genistetea lobelii. We obtained a dataset with 189 vegetation plots, and we classified them using the Modified TWINSPAN classification. Our analyses identified six plant associations and three sub-associations that have already been described in the literature; and we were able to describe a new alliance corresponding to supramediterranean plant communities (Genistion salzmannii). For each of them, we identified diagnostic, constant, and dominant species and produced their distribution map. Formal definitions were then written for each phytosociological unit (from sub-association to class) and grouped in an expert system to classify the plant communities of the Carici caryophylleae-Genistetea lobelii.

    ano.nymous@ccsd.cnrs.fr.invalid (P. Delbosc) 27 Jan 2023

  • [hal-03516934] Growth resistance and resilience of mixed silver fir and Norway spruce forests in central Europe: Contrasting responses to mild and severe droughts

    Extreme droughts are expected to increase in frequency and severity in many regions of the world, threatening multiple ecosystem services provided by forests. Effective strategies to adapt forests to such droughts require comprehensive information on the effects and importance of the factors influencing forest resistance and resilience. We used a unique combination of inventory and dendrochronological data from a longterm (>30 years) silvicultural experiment in mixed silver fir and Norway spruce mountain forests along a temperature and precipitation gradient in southwestern Germany. We aimed at examining the mechanisms and forest stand characteristics underpinning the resistance and resilience to past mild and severe droughts. We found that (i) fir benefited from mild droughts and showed higher resistance (i.e., lower growth loss during drought) and resilience (i.e., faster return to pre-drought growth levels) than spruce to all droughts; (ii) species identity determined mild drought responses while species This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

    ano.nymous@ccsd.cnrs.fr.invalid (Alessandra Bottero) 07 Jan 2022


Date de modification : 29 août 2023 | Date de création : 25 avril 2023 | Rédaction : Corinne Martin