UMR Silva


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The Silva Joint Research Unit brings together people from AgroParisTech, INRAE, and the Université de Lorraine to conduct multidisciplinary research on wood, trees and forest ecosystems. It is the result of the merge of the joint research units « Forest Ecology and Ecophysiology » [EEF] and « Laboratory of Wood Forest Resource Studies » [LERFoB] in January 2018. The main scientific goal of the UMR Silva is to develop pure and applied research to answer questions of society, including forest managers, about (1) the role and the future of forest ecosystems in the context of global changes, including climate change, and (2) the future of the timber industry, particularly in the Grand – Est region for which it is of major economic importance.


HAL : Dernières publications

  • [hal-04518775] A Novel Framework and a New Score for the Comparative Analysis of Forest Models Accounting for the Impact of Climate Change

    A broad consensus has been reached on the need to adapt the management of our forests to the context of the rapidly changing climate, which resulted in the development of numerous models capable of simulating the impact of the climate change on the forest. The primary goal of this specific endeavor is to propose a novel framework of comparative analysis which could lead to the unique and universal description and mapping of these models. This framework is based on the reduction of the model output to the relatively simplistic information about the presence of the tree species suitable for the forest management i.e. - a binary classifier, making it comparable with the largely available tree presence observations. The framework we propose comes along with a new score, based on the joint use of the Principal Component Analysis and the Co-inertia Analysis, which evaluates the model vis-`avis the corresponding observations with the focus on its phase space dynamics i.e. its dependence on external environmental variables, rather than its spatial precision. The pertinence of the proposed multi-scale approach, suitable for the multi-scale analysis, is demonstrated by conjointly using prototype binary classifiers, designed for this purpose, and two different examples of binary classifiers used in the forest management - climate-dependent tree species distribution models. This work has the ambition to serve as the basis for a potential combination of different models at different spatial scales in order to improve the decision making process in the forest management. (Nikola Besic) 24 Mar 2024
  • [hal-04199566] Microwave-Assisted Synthesis of Pd Nanoparticles into Wood Block (Pd@wood) as Efficient Catalyst for 4-Nitrophenol and Cr(VI) Reduction

    Palladium (Pd) nanoparticle catalysis has attracted increasing attention due to its efficient catalytic activity and its wide application in environmental protection and chemical synthesis. In this work, Pd nanoparticles (about 71 nm) were synthesized in aqueous solution by microwave-assisted thermal synthesis and immobilized in beech wood blocks as Pd@wood catalysts. The wood blocks were first hydrothermally treated with 10% NaOH solution to improve the internal structure and increase their porosity, thereby providing favorable attachment sites for the formed Pd nanoparticles. The stable deposition of Pd nanoparticle clusters on the internal channels of the wood blocks can be clearly observed. In addition, the catalytic performance of the prepared Pd@wood was investigated through two model reactions: the reduction of 4-nitrophenol and Cr(VI). The Pd@wood catalyst showed 95.4 g −1 s −1 M −1 of normalized rate constant k norm and 2.03 min −1 of the TOF, respectively. Furthermore, Pd nanoparticles are integrated into the internal structure of wood blocks by microwaveassisted thermal synthesis, which is an effective method for wood functionalization. It benefits metal nanoparticle catalysis in the synthesis of fine chemicals as well as in industrial wastewater treatment. (Zhao Zhang) 07 Sep 2023
  • [hal-04108113] Urea-Formaldehyde Resin Removal in Medium-Density Fiberboards by Steam Explosion: Developing Nondestructive Analytical Tools

    [...] (Sarah Troilo) 26 May 2023
  • [hal-04303411] Management-related energy, nutrient and worktime efficiencies of the wood fuel production and supply chain: modelling and assessment

    Bioenergy from wood can contribute to reach the goals of energy-transition policies. Use of wood as fuel should focus on low-quality wood, e.g. by-products from timber production, which production and supply is related to various management decisions. Reaching the policy objectives efficiently remains an issue. Aims The aims are (1) to develop a modelling approach that links local management decisions with indicators of the whole wood fuel production and supply chain and (2) to test the model in a case study. The study should further provide first insights on how indicators of energy, nutrient and worktime efficiency vary according to wood fuel chain characteristics and the related management decisions. Methods The model depicts the flow of wood (biomass, nutrients, moisture content, heating value) from the forest stand to the heating plant for each silvicultural intervention simulated with a growth and yield model. It further quantifies the energy and worktime spent on different wood fuel chain tasks (e.g. felling, forwarding) set by the user. We defined four scenarios according to the scale of energy production (large vs. small) and the demand for wood fuel (high vs. moderate). Results The case study revealed that the model outputs were plausible. Energy efficiency largely varied depending on the type of silvicultural intervention. Large-scale production associated with high demand was most favourable for energy and worktime efficiencies. In contrast, nutrient efficiency was best for small-scale production associated with moderate demand. Conclusions Local management decisions all along the wood fuel chain highly influenced efficiency indicators, and thus its relevance for energy-transition policies. Our model may contribute to strategic decision making in different forestry and energy production contexts. (Nicolas Bilot) 14 Dec 2023
  • [hal-04001980] Ellenberg‐type indicator values for European vascular plant species

    Aims: Ellenberg-type indicator values are expert-based rankings of plant species according to their ecological optima on main environmental gradients. Here we extend the indicator-value system proposed by Heinz Ellenberg and co-authors for Central Europe by incorporating other systems of Ellenberg-type indicator values (i.e., those using scales compatible with Ellenberg values) developed for other European regions. Our aim is to create a harmonized data set of Ellenberg-type indicator values applicable at the European scale.Methods: We collected European data sets of indicator values for vascular plants and selected 13 data sets that used the nine-, ten- or twelve-degree scales defined by Ellenberg for light, temperature, moisture, reaction, nutrients and salinity. We compared these values with the original Ellenberg values and used those that showed consistent trends in regression slope and coefficient of determination. We calculated the average value for each combination of species and indicator values from these data sets. Based on species' co-occurrences in European vegetation plots, we also calculated new values for species that were not assigned an indicator value.Results: We provide a new data set of Ellenberg-type indicator values for 8908 European vascular plant species (8168 for light, 7400 for temperature, 8030 for moisture, 7282 for reaction, 7193 for nutrients, and 7507 for salinity), of which 398 species have been newly assigned to at least one indicator value.Conclusions: The newly introduced indicator values are compatible with the original Ellenberg values. They can be used for large-scale studies of the European flora and vegetation or for gap-filling in regional data sets. The European indicator values and the original and taxonomically harmonized regional data sets of Ellenberg-type indicator values are available in the Supporting Information and the Zenodo repository. (Lubomír Tichý) 24 Feb 2023
  • [hal-04181161] Pre- and post-drought conditions drive resilience of Pinus halepensis across its distribution range

    Severe droughts limit tree growth and forest productivity worldwide, a phenomenon which is expected to aggravate over the next decades. However, how drought intensity and climatic conditions before and after drought events modulate tree growth resilience remains unclear, especially when considering the range-wide phenotypic variability of a tree species. We gathered 4632 Aleppo pine (Pinus halepensis Mill.) tree-ring width series from 281 sites located in 11 countries across the Mediterranean basin, representing the entire geographic and bioclimatic range of the species. For each site and year of the period 1950–2020, we quantified tree-growth resilience and its two components, resistance and recovery, to account for the impact of drought and the capacity to recover from it. Relative drought intensity of each year was assessed using SPEI (Standardized Precipitation Evapotranspiration Index), a climatic water deficit index. Generalized additive mixed models were used to explore the non-linear relationships between resilience and its two components and drought intensity, preceding and following years climatic conditions. We found that P. halepensis radial growth was highly dependent on the SPEI from September of the previous year to June of the current year. Trees growing under more arid bioclimates showed higher inter-annual growth variability and were more sensitive to drought, resulting in an increased response magnitude to pre-, during and post-drought conditions. In contrast to our expectations, drought intensity only slightly affected resilience, which was rather negatively affected by favorable preceding conditions and improved by favorable following conditions. Resilience and its components are highly dependent on preceding and following years climatic conditions, which should always be taken into account when studying growth response to drought. With the observed and predicted increase in drought frequency, duration and intensity, favorable conditions following drought episodes may become rare, thus threatening the future acclimation capacity of P. halepensis in its current distribution. (Léa Veuillen) 18 Aug 2023
  • [hal-04081509] Mapping territorial vulnerability to wildfires: A participative multi-criteria analysis

    The Mediterranean region is routinely affected by forest fires, with adverse consequences on ecological, infrastructural, and socioeconomic assets. In a context of climate change, it is crucial for fire prevention and suppression to be able to identify locations where assets are most at risk, due to environmental, physical or socioeconomic reasons. Besides, this knowledge needs to be developed together with operational services and field experts to ensure their application. So far, fire risk research has largely focused on fire behavior, effects, and model simulation. In this article, we show how the concept of vulnerability can provide a flexible and relevant framework for assessing fire risk and be evaluated using a spatial multicriteria decision analysis method (MCDA)-the Analytical Hierarchy Process (AHP)-based on both quantitative data and expert judgment gathered through a participative approach. We focus on SouthEastern France, a region characterized by high economic and environmental stakes and heavily affected by wildfires. We develop a series of spatialized indicators using ecological, land-use and sociodemographic data which we aggregate to produce vulnerability maps for three categories of assets: population, ecosystems and infrastructures. An ex-post workshop was organized with field experts to put both the approach and results into discussion. Results reveal significant differences in indicators' perceived contributions to risk and vulnerability and enable appraising the contribution of sociodemographic factors, often overlooked in the literature. We also reveal differences in spatial patterns across both vulnerability subcomponents and exposed assets, helping identify primary and secondary vulnerability hotspots and underlying drivers. Consideration of multiple subcomponents of risk and vulnerability may help local decision makers prioritize how and where measures should be implemented, while the use of MCDA favors experience and knowledge sharing and among stakeholders while providing a basis of discussion. (Miguel Rivière) 26 Apr 2023
  • [hal-04400932] Dynamique spontanée de régénération des peuplements du Nord-Est de la France au cours des 20 ans suivant la tempête de 1999

    Suite au passage de la tempête Lothar en 1999, deux observatoires ont été mis en place dans le Nord-Est de la France pour caractériser la dynamique spontanée de recolonisation forestière et aider les gestionnaires dans leur choix d’itinéraire sylvicole. Nous présentons ici l’évolution de la composition dendrologique, de la densité et des diamètres des tiges sur 20 ans, en fonction de la taille de la trouée, de la composition du peuplement pré-tempête et de l’acidité du sol. La régénération naturelle ligneuse dans les trouées post-tempête est satisfaisante en densité et en diversité en essences 20 ans après la tempête, 87 % des sites ayant plus de 2 500 tiges/ha et la strate supérieure à 2 m comptant 4,4 espèces en moyenne sur 314 m2. Les situations présentant une faible densité de tiges ont pu être identifiées trois ans après la tempête : ce sont d’anciens peuplements résineux, sur sol acide où une végétation concurrente s’est développée. (Lucie Dietz) 17 Jan 2024
  • [hal-04027770] Trade‐offs and synergies between ecosystem productivity and stability in temperate grasslands

    Aim: It is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity-stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity-stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora. (Lucie Mahaut) 14 Mar 2023
  • [hal-03866312] How drought events during the last century have impacted biomass carbon in Amazonian rainforests

    [...] (Yitong Yao) 23 Nov 2022
  • [hal-04233219] Temperature extremes of 2022 reduced carbon uptake by forests in Europe

    Abstract The year 2022 saw record breaking temperatures in Europe during both summer and fall. Similar to the recent 2018 drought, close to 30% (3.0 million km 2 ) of the European continent was under severe summer drought. In 2022, the drought was located in central and southeastern Europe, contrasting the Northern-centered 2018 drought. We show, using multiple sets of observations, a reduction of net biospheric carbon uptake in summer (56-62 TgC) over the drought area. Specific sites in France even showed a widespread summertime carbon release by forests, additional to wildfires. Partial compensation (32%) for the decreased carbon uptake due to drought was offered by a warm autumn with prolonged biospheric carbon uptake. The severity of this second drought event in 5 years suggests drought-induced reduced carbon uptake to no longer be exceptional, and important to factor into Europe’s developing plans for net-zero greenhouse gas emissions that rely on carbon uptake by forests. (Auke van der Woude) 31 Oct 2023
  • [hal-04093388] Soil organic carbon models need independent time-series validation for reliable prediction

    Abstract Numerical models are crucial to understand and/or predict past and future soil organic carbon dynamics. For those models aiming at prediction, validation is a critical step to gain confidence in projections. With a comprehensive review of ~250 models, we assess how models are validated depending on their objectives and features, discuss how validation of predictive models can be improved. We find a critical lack of independent validation using observed time series. Conducting such validations should be a priority to improve the model reliability. Approximately 60% of the models we analysed are not designed for predictions, but rather for conceptual understanding of soil processes. These models provide important insights by identifying key processes and alternative formalisms that can be relevant for predictive models. We argue that combining independent validation based on observed time series and improved information flow between predictive and conceptual models will increase reliability in predictions. (Julia Le Noë) 10 May 2023
  • [hal-04224631] Detection and attribution of an anomaly in terrestrial photosynthesis in Europe during the COVID-19 lockdown

    Carbon dioxide (CO2) uptake by plant photosynthesis, referred to as gross primary production (GPP) at the ecosystem level, is sensitive to environmental factors, including pollutant exposure, pollutant uptake, and changes in the scattering of solar shortwave irradiance (SWin) − the energy source for photosynthesis. The spring lockdown due to COVID-19 resulted in improved air quality and atmospheric transparency, providing a unique opportunity to assess the impact of air pollutants on terrestrial ecosystem functioning. However, detecting these effects can be challenging as GPP is influenced by other meteorological drivers and management practices. Based on data collected from 44 European ecosystem-scale CO2 flux monitoring stations, we observed significant changes in spring GPP at 34 sites during 2020 compared to 2015-2019. Among these, 14 sites showed an increase in GPP associated with higher SW in , 10 sites had lower GPP linked to atmospheric and soil dryness, and seven sites were subjected to management practices. The remaining three sites exhibited varying dynamics, with one experiencing colder and rainier weather resulting in lower GPP, and two showing higher GPP associated with earlier spring melts. Analysis using the regional atmospheric chemical transport model (LOTOS-EUROS) indicated that the ozone (O3) concentration remained relatively unchanged at the research sites, making it unlikely that O3 exposure was the dominant factor driving the primary production anomaly. In contrast, SW in increased by 9.4 % at 36 sites, suggesting enhanced GPP possibly due to reduced aerosol optical depth and cloudiness. Our findings indicate that air pollution and cloudiness may weaken the terrestrial carbon sink by up to 16 %. Accurate and continuous ground-based observations are crucial for detecting and attributing subtle changes in terrestrial ecosystem functioning in response to environmental and anthropogenic drivers. (Angela Che Ing Tang) 02 Oct 2023
  • [hal-04459758] Author Correction: Temperature extremes of 2022 reduced carbon uptake by forests in Europe

    [...] (Auke M van der Woude) 15 Feb 2024
  • [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. (Sébastien Albert) 01 Dec 2023
  • [hal-04188106] Biology and ecology of Pontederia crassipes in a Mediterranean river in Lebanon

    Invasive aquatic plants are considered the second cause of biodiversity loss in aquatic ecosystems. Pontederia crassipes Mart., formerly Eichhornia crassipes (Mart.) Solms (water hyacinth) is one of the most dangerous invasive species in the world. Since 2006, P. crassipes has invaded Lebanon's Al Kabir River, causing ecological and socioeconomic problems. To solve them, ecological and biological characteristics are important to understand the water hyacinth response to variations in environmental conditions. The aims of this study were (i) to analyze P. crassipes growth and (ii) physico-chemical parameters at two sites and (iii) to determine ecological relationships between P. crassipes and other plant species. The main results show the existence of different cohorts of water hyacinth at the two sites. Differences in growth between these cohorts are likely due to physico-chemical differences. In addition, P. crassipes coexist with other invasive and native plants. This ecological study can help ecologists and stakeholders map invasive plants in rivers and improve their control (Youssra Ghoussein) 25 Aug 2023
  • [hal-04028874] Within and between population phenotypic variation in growth vigor and sensitivity to drought stress in five temperate tree species

    Within-population variation in individual tree growth and response to climate has an impact on forest dynamics, resilience and adaptation to environmental change. Combining dendrochronological analyses with a process-based ecophysiological model simulating drought stress at the stand scale, we studied the phenotypic variation of two growth-related traits within 22 pure stands of five contrasted tree species sampled in the RENECOFOR network over a wide range of ecological conditions. First, we computed the annual stress level from soil, climate and stand inventory data. Second, we computed individual sensitivity as the quantitative growth response to drought stress level and individual vigor as the capacity to grow in favorable years relative to an average stand-level growth model. We analyzed within-population variation and covariation of individual vigor and sensitivity, their temporal changes during stand development, as well as the effect of environmental conditions on population-level means, variances and correlation. Our results show that within-population variances in sensitivity and vigor exceed the between-population variances for all species. The populations located in more stressful environments, i.e., low summer precipitation and extractable soil water, showed lower mean and variance of sensitivity, suggesting possible multiscale adaptation at the population level and within populations. None of the environmental factors considered had an effect on the average population vigor or on the within-population variance of vigor. We found a general positive correlation between individual growth sensitivity and vigor in 17 out of 22 populations, potentially revealing a growth performance trade-off. The correlation was more pronounced in low extractable soil water environments, which may be related to a need for stressful conditions to reveal the trade-off or be the consequence of adaptive processes, i.e., acclimation and selection. If high within-population stand phenotypic variation in growth traits contributes to the resilience and adaptive capacity of forests to climate change, a trade-off could represent a constraint on selection. We provide genetic and environmental arguments supporting the hypothesis of a trade-off, then we highlight the importance of integrating it into the management process, especially during selective thinning, to avoid indirectly increasing population sensitivity by selecting the most vigorous trees. (Victor Fririon) 20 Mar 2023
  • [hal-04569080] De la haie à l’arbre champêtre : réhabiliter l’arbre en milieu rural agricole

    À partir de l’exemple d’un programme de recherche participative, cet article se propose de discuter de la place des arbres champêtres dans deux territoires du sud lorrain. Ce programme, structuré par une succession de temps (recueil des représentations individuelles quant à la place et au rôle des arbres dans ces milieux ruraux agricoles, atelier de partage autour de ces représentations, sessions d’information basées sur des témoignages de terrain, construction de scénarios) a permis d’ouvrir les représentations et les perspectives depuis un centrage autour des haies vers l’intégration dans un projet de territoire des arbres champêtres dans leurs diversités de formes et d’usages. (Catherine Jondreville) 06 May 2024
  • [hal-04327124] AI chatbots can boost scientific coding

    Chatbots powered by artificial intelligence, such as ChatGPT, are ready to speed up monotonous coding tasks and teach you new skills. We highlight, with worked examples, some advantages and limitations of using generative artificial intelligence for scientific coding and argue that if you are willing to debug, you can get a head start on more challenging tasks. (Cory Merow) 06 Dec 2023
  • [hal-04195221] Identifying blocking behaviors in small‐scale group decision‐making and their impact on consensus outcomes: A case study on forest management

    Abstract Group decision‐making (GDM) problems usually include stakeholders with different views and opinions. In order to find a collective solution, it is necessary to achieve a consensus reaching process (CRP) that may lead to the emergence of non‐cooperative behaviors within the group. This article proposes to study how these non‐cooperative behaviors appear in a group of decision‐makers and what their level of impact is on the evolution of consensus and on the final decision. To provide some answers to this research problem, we propose a multi‐criteria decision‐making (MCDM) methodology implementing analytic hierarchy process (AHP) in order to provide a visualization of the CRP evolution and observe four non‐cooperative behaviors within small‐scale GDM: (1) collective agreement, (2) blocking behavior, (3) leadership demonstration, and (4) experts' coalition. We implement our methodology within a pedagogical framework, in 29 small‐scale groups of masters and engineering students, through a case study related to the implementation of forest management scenarios in France. Our results show the evolution of the four non‐cooperative behaviors within the groups, as well as their impact on the CRP outcomes. (Manon Enjolras) 04 Sep 2023
  • [hal-04454254] Measuring Photosynthesis of Entire Tree Crowns and Pulse Label Trees in Large Closed Chamber with 13CO2 in the Field: Design and Testing

    Measuring the photosynthesis of entire tree crowns and pulse labelling trees with 13CO2 are valuable approaches to study carbon acquisition, transfer, and allocation; however, it is challenging for trees in the field. The objective was to develop and field test large chambers (35 - 45 m3) that enclosed the entire crown of a tree, provided a reliable estimate of tree crown photosynthesis, and ensured efficient 13CO2 labelling. The chambers, made of transparent polyethylene film pulled tightly over a frame, were equipped with an air conditioner, fans, and air blowers. Air temperature, relative humidity, and photosynthetic photon flux density were measured outside and inside each chamber. Six of 4-year-old rubber trees (Hevea brasiliensis) were pulsed-labelled with 18 L of 13CO2 in June and October 2016. The mean air temperature inside the chambers was 1.2 °C higher and the relative humidity 8 % lower than the outside air. The crown photosynthesis, calculated from the decrease in the CO2 concentration inside the chamber, was in the range 140 - 249 µmol s–1 and was significantly related to photosynthetic photon flux density, total leaf area of the tree, and average net CO2 assimilation at leaf level. The labelling efficiency, estimated as the ratio of the amount of 13C recovered in the foliage immediately after labelling divided by the amount of 13C delivered to the tree, was in the range 43 - 68 %. The designed chamber was suitable to estimate crown photosynthesis and perform 13CO2 pulse labelling of 5-m-tall trees in the field. HIGHLIGHTS Measuring carbon acquisition, transfer, and allocation of entire trees in the field is a challenge The paper describes in detail the system including a 45 m3 chamber that was developed and tested to measure crown photosynthesis and to label trees 5 - 6 m tall with 13CO2 The system and methodology proved efficient in controlling the chamber temperature and providing appropriate conditions for leaf gas exchanges The rates of crown photosynthesis were consistent with measurements at the leaf and ecosystem levels, providing a clear relationship with photosynthetic photon flux density More than 1-half the injected 13CO2 was recovered in the leaves after the end of labelling, showing that the design of the chamber and the labelling protocol were effective for studying C allocation within the tree GRAPHICAL ABSTRACT (Ornuma Duangngam) 13 Feb 2024
  • [hal-04155899] Comment renouveler les forêts de production gérées selon les principes de la Sylviculture Mélangée à Couvert Continu (SMCC) ?

    [...] (Lisa Laurent) 07 Jul 2023
  • [hal-04210267] Ectomycorrhizal symbiosis prepares its host locally and systemically for abiotic cue signaling

    Tree growth and survival are dependent on their ability to perceive signals, integrate them, and trigger timely and fitted molecular and growth responses. While ectomycorrhizal symbiosis is a predominant tree‐microbe interaction in forest ecosystems, little is known about how and to what extent it helps trees cope with environmental changes. We hypothesized that the presence of Laccaria bicolor influences abiotic cue perception by Populus trichocarpa and the ensuing signaling cascade. We submitted ectomycorrhizal or non‐ectomycorrhizal P. trichocarpa cuttings to short‐term cessation of watering or ozone fumigation to focus on signaling networks before the onset of any physiological damage. Poplar gene expression, metabolite levels, and hormone levels were measured in several organs (roots, leaves, mycorrhizas) and integrated into networks. We discriminated the signal responses modified or maintained by ectomycorrhization. Ectomycorrhizas buffered hormonal changes in response to short‐term environmental variations systemically prepared the root system for further fungal colonization and alleviated part of the root abscisic acid (ABA) signaling. The presence of ectomycorrhizas in the roots also modified the leaf multi‐omics landscape and ozone responses, most likely through rewiring of the molecular drivers of photosynthesis and the calcium signaling pathway. In conclusion, P. trichocarpa‐L. bicolor symbiosis results in a systemic remodeling of the host's signaling networks in response to abiotic changes. In addition, ectomycorrhizal, hormonal, metabolic, and transcriptomic blueprints are maintained in response to abiotic cues, suggesting that ectomycorrhizas are less responsive than non‐mycorrhizal roots to abiotic challenges. (Maíra de Freitas Pereira) 18 Sep 2023
  • [hal-04303420] Annals of Forest Science promotes multidisciplinary research devoted to forests and wood in a changing world

    No abstract available (Erwin Dreyer) 12 Feb 2024
  • [hal-04001076] Multi-elemental and Strontium-Neodymium Isotopic Signatures in Charred Wood: Potential for Wood Provenance Studies

    The chemical composition of the wood reflects the composition of the soil over which the corresponding tree has developed. Multi-elemental and isotopic signatures, which are characteristic of the soil and underlying rock substrates, are potentially powerful tools for determining wood provenance. These tracers are of special interest for charred archaeological wood because they circumvent some limitations of dendrochronological provenancing linked to tree-ring loss. However, thermal degradation may introduce a significant bias in wood chemical and isotopic analyses. This experimental study focused on the effects of carbonization temperature on three geochemical wood markers: elemental signatures and isotopic signatures of strontium and neodymium (86Sr/87Sr and 143Nd/144Nd, respectively). Wood specimens from a variety of oak trees and stand locations were pyrolyzed at four temperatures (ranging from 200°C to 800°C) and analyzed using ICP-MS and µ-XRF (X-ray fluorescence) spectroscopy for elemental composition and with multiple collection ICP-MS (MC-ICP-MS) for strontium (Sr) and neodymium (Nd) isotope composition. The concentration of mineral nutrients generally increased with temperature, but the magnitude of the enrichment depended on the element, wood compartment (sapwood vs. heartwood), and geological substrate. The concentrations of rubidium, strontium, manganese, magnesium, potassium, and, to a lesser extent, calcium, were minimally affected by temperature, wood compartment, and substrate. The ratios between the concentrations of these elements, as well as the 86Sr/87Sr and 143Nd/144Nd isotope ratios, were stable over the entire temperature range. However, only 86Sr/87Sr and selected elemental ratios (calcium or magnesium normalized to manganese) were successful for site discrimination. Therefore, our multi-tracer approach provides promising new information to determine the provenance of charred archaeological wood (Anna Imbert Štulc) 22 Feb 2023
  • [hal-04172415] Dynamically simulating spruce budworm in eastern Canada and its interactions with wildfire

    Eastern Spruce Budworm (ESBW) is a major agent of disturbance in Eastern Canada’s boreal forests. Outbreaks have historically led to widespread defoliation of its preferred host trees, fir and spruce species, leading to high rates of mortality. This in turn can result in significant economic losses and enhancement of fire potential in the region. Representation of such biotic disturbance has rarely been included in Dynamic Global Vegetation Models (DGVM), which have become essential tools in understanding and predicting forest dynamics in present and future contexts. We present novel representation of host-specific defoliation in a DGVM (LPJ-LMfire), to better represent disturbance regimes in the boreal forest of eastern Canada. Using host foliage density to trigger outbreak, we were able to calibrate and simulate general spatial patterns of defoliation relative to historical aerial sketch map data. Return intervals were thus sensitive to the growth rates of host trees. Modeled return intervals tended to be significantly longer than 30 years, the approximate observed return interval. A factorial experiment was performed on the interactions of ESBW with wildfire, which was found to be slightly enhanced in terms of burned areas after outbreaks due to increased fuel loads. Interactions between ESBW and fire were found to have higher interaction strength in the drier Western region of the boreal forest. Our study demonstrates that biotic disturbance and its interaction with wildfire can be effectively simulated in a DGVM. We show that bottom-up climatic controls are sufficient to drive simulated spatiotemporal patterns of ESBW that can be calibrated to generally match historical observations. (Hiromitsu Sato) 28 Jul 2023
  • [hal-04347203] Interactions within the climate-vegetation-fire nexus may transform 21st century boreal forests in northwestern Canada

    Dry and warm conditions have exacerbated the occurrence of large and severe wildfires over the past decade in Canada's Northwest Territories (NT). Although temperatures are expected to increase during the 21st century, we lack understanding of how the climate-vegetation-fire nexus might respond. We used a dynamic global vegetation model to project annual burn rates, as well as tree species composition and biomass in the NT during the 21st century using the IPCC's climate scenarios. Burn rates will decrease in most of the NT by the mid-21st century, concomitant with biomass loss of fire-prone evergreen needleleaf tree species, and biomass increase of broadleaf tree species. The southeastern NT is projected to experience enhanced fire activity by the late 21st century according to scenario RCP4.5, supported by a higher production of flammable evergreen needleleaf biomass. The results underlie the potential for major impacts of climate change on the NT's terrestrial ecosystems. (Dorian M Gaboriau) 15 Dec 2023
  • [hal-04005898] Spatial vulnerability assessment of silver fir and Norway spruce dieback driven by climate warming

    Context: A significant forest decline has been noticed these last years in Europe. Managers need tools to better anticipate these massive events. Objectives: We evaluated the efficiency of easily available data about environmental conditions and stand characteristics to determine different levels of vulnerability. Methods: We combined remote sensing images, photo-interpretation, and digital models describing environmental conditions within a modelling approach to achieve spatial vulnerability assessment of the stands. We focused on silver fir and Norway spruce stands in the Vosges mountains (8,900 km², northeastern France), where severe symptoms of decline are visible. Results: Silver fir were predicted highly vulnerable on 7% of their area versus 33% for Norway spruce. Using an independent dataset, we observed ten-times (silver fir) and two-times (Norway spruce) higher mortality rates in the units with a high level of vulnerability than in the others. About half of the model deviance was directly or indirectly explained by variables related to water stress (soils displaying low water availability, having suffered severe drying events these last years). Furthermore, the stands acclimatised to drought conditions were more resilient. Stand characteristics also influenced dieback spread, suggesting that an evolution of silvicultural practices toward mixed stands with broadleaved species and uneven-aged trees can contribute to better adapt to future climate conditions. Conclusions: Vulnerability maps based on easily available geographic information describing climate, soil, and topography can efficiently discriminate canopy mortality patterns over broad areas, and can be useful tools for managers to mitigate the effects of climate change on forests. (Christian Piedallu) 27 Feb 2023
  • [hal-03689880] Drought tolerance traits in Neotropical trees correlate with the composition of phyllosphere fungal communities

    Plant-associated microorganisms have shown to aid plants in coping with drought. However, the underlying mechanisms are poorly understood and there is uncertainty regarding which microbial taxa and functions are mostly involved. We explored these issues in Neotropical rainforests and identified foliar microorganisms that may play a role in drought tolerance of trees. Our objectives were to (1) test the relationship between drought tolerance traits in Neotropical trees and the diversity and composition of their foliar fungal and bacterial communities and (2) identify leaf microbial taxa positively or negatively associated with drought tolerance traits. Our results showed that the composition of leaf fungal communities, but not bacterial communities, was related to drought tolerance. We identified 27 fungal Amplicon Sequence Variants (ASVs) whose relative abundance co-varied with drought tolerance traits. Most variants were assigned to fungal clades often described as plant pathogens and increased in abundance with drought susceptibility. This greater relative abundance of leaf pathogens in the most drought-susceptible trees might increase their vulnerability to climate change. Moreover, we identified the Strelitziana and Ochroconis fungal genera as potential candidates for future culture-dependent studies aimed at understanding and improving drought tolerance in Neotropical forests. (Marine Cambon) 07 Jun 2022
  • [hal-04443629] Monitoring and control of forest seedling quality in Europe

    The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increases with species richness, although the ecological fundamentals have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two‐species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between‐species asynchrony in mixtures in comparison to monocultures. Synthesis and applications . This study highlights the emergent properties associated with mixing two species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance this impact. The overyielding and temporal stability of growth addressed in this paper are essential for ecosystem services closely linked with the level and rhythm of forest growth. Our results underline that mixing two species can be a realistic and effective nature‐based climate solution, which could contribute towards meeting EU climate target policies. (Milan Mataruga) 21 Feb 2024
  • [hal-04211027] Tree species growth response to climate in mixtures of Quercus robur/Quercus petraea and Pinus sylvestris across Europe - a dynamic, sensitive equilibrium

    Quercus robur/Quercus petraea and Pinus sylvestris are widely distributed and economically important tree species in Europe co-occurring on mesotrophic, xeric and mesic sites. Increasing dry conditions may reduce their growth, but growth reductions may be modified by mixture, competition and site conditions. The annual diameter growth in monospecific and mixed stands along an ecological gradient with mean annual temperatures ranging from 5.5 ◦C to 11.5 ◦C was investigated in this study. On 36 triplets (108 plots), trees were cored and the year-ring series were cross-dated, resulting in year-ring series of 785 and 804 trees for Q. spp. and P. sylvestris, respectively. A generalized additive model with a logarithmic link was fit to the data with random effects for the intercept at the triplet, year and tree level and a random slope for the covariate age for each tree; the Tweediedistribution was used. The final model explained 87 % of the total variation in diameter increment for both tree species. Significant covariates were age, climate variables (long-term mean, monthly), local competition variables, relative dbh, mixture, stand structure and interactions thereof. Tree growth declined with age and local density and increased with social position. It was positively influenced by mixture and structural diversity (Gini coefficient); mixture effects were significant for P. sylvestris only. The influence of potential evapotranspiration (PET) in spring and autumn on tree growth was positive and non-linear, whereas tree growth sharply decreased with increasing PET in June, which proved to be the most influential month on tree growth along the whole ecological gradient. Interactions of PET with tree social position (relative dbh) were significant in July and September for Q. spp. and in April for P. sylvestris. Interactions of climate with density or mixture were not significant. Climatic effects found agree well with previous results from intra-annual growth studies and indicate that the model captures the causal factors for tree growth well. Furthermore, the interaction between climate and relative dbh might indicate a longer growth duration for trees of higher social classes. Analysis of random effects across time and space showed highly dynamic patterns, with competitive advantages changing annually between species and spatial patterns showing no large-scale trends but pointing to the prevalence of local site factors. In mixed-species stands, the tree species have the same competitivity in the long-term, which is modified by climate each year. Climate warming will shift the competitive advantages, but the direction will be highly site-specific. (Sonja Vospernik) 19 Sep 2023
  • [hal-04113176] Towards a Modeling of the Impacts of Road Verge Management on the Pollination Service Using System Dynamics: A Case Study in France

    Several research studies have proven that eliciting and predicting the impact of human activity on ecosystem services will be crucial to support stakeholders’ awareness and to decide how to interact with the environment in a more sustainable manner. In this sense, the ecosystems known as road verges are particularly important because of their length and surface at an international scale, and their role in mitigating the damage done by roads. Plant pollination by insects is one of the most important ecosystem services. Because of its nature and the fact that they extend across a variety of landscapes, roadside can contribute to the maintenance of healthy ecosystems, under the condition of adapted management practices. This research is the first attempt to develop a System Dynamics-based aiming to estimate the ecological and economic impact of maintenance on the road verge pollination service in France. Maintenance strategies of road verges are simulated to compare their performance. The results show that there are ways to improve current maintenance strategies in terms of pollination value, but also that the model needs to consider other ecosystem services and synergistic effects that could further affect pollination to obtain more accurate estimations. (Juan Pablo Ortega) 01 Jun 2023
  • [hal-04453144] Carbon sequestration and soil nitrogen enrichment in Robinia pseudoacacia L. post-mining restoration plantations

    Robinia pseudoacacia L. (black locust) has been extensively used for restoring degraded lands, following anthropogenic interventions like coal mining. Here we have addressed the contribution of black locust restoration plantations, established on overburden post-mining material, to carbon storage and to soil nitrogen enrichment at the largest lignite center in Greece. Carbon stocks and fluxes in all pools of the ecosystem, as well as the foliar nitrogen resorption efficiency and soil N stocks were quantified and the effect of plantations’ age was tested. The young age of the plantations (4–24 years) resulted in a relatively low total ecosystem C stock (56.7 t ha −1 ), which was partitioned among the different pools in the following order: above-ground biomass (50%) > black locust-derived SOC (24%) > coarse roots (14%) > deadwood (6%) > forest floor (5%) > fine roots (less than 1%). Litterfall started early in the growing season and together with fine roots that had a turnover rate of 0.62 yr −1 , fueled soil organic carbon. SOC accrual, referring to the accumulation of SOC derived by black locust, declined with age. However, further SOC accumulation is expected, based on the potential SOC storage capacity of soil at the area. C stocks in above- and below-ground biomass increased linearly with age. The same response was observed for soil N stock and NRE, indicating that despite the N 2 -fixing capacity of black locust, there was still a poor pedospheric N supply and a need for efficient N cycling. Overall, the studied restoration plantations have a considerable contribution to C and N accumulation at the degraded post-mining sites. These positive effects are expected to further increase at least until the plantations reach maturity. (Giorgos Xanthopoulos) 12 Feb 2024
  • [hal-04068603] Annals of Forest Science promotes multidisciplinary research on forests and wood in a changing world and is now a full Open Access journal

    [...] (Erwin Dreyer) 14 Apr 2023
  • [hal-03987049] Traceability and quality assessment of Norway spruce (Picea abies (L.) H.Karst.) logs: the TreeTrace_spruce database

    The TreeTrace_spruce database contains images and measurements of 100 Norway spruce (Picea abies (L.) H.Karst.) logs from Northeastern France, each about 4.5 m long. The image database includes RGB images of large and small ends of the logs and hyperspectral and computed tomography (CT) images of wood discs sampled at both log ends. The 100 logs were also fully X-ray scanned with a CT device for roundwoods and their top surface was scanned with a terrestrial LiDAR device. The measurements performed on discs include wood local density, growth ring widths and pith location. This database is complementary to another one (TreeTrace_Douglas) resulting from the same ANR project TreeTrace, but if the objectives are similar, the protocols and conditions of acquisition are not the same for these two databases. TreeTrace_spruce dataset is available at and associated metadata are available at (Fleur Longuetaud) 19 Feb 2024
  • [hal-03930047] Monitoring the risk of Legionella infection using a general Bayesian network updated from temporal measurements in agricultural irrigation with reclaimed wastewater

    This paper presents a model for the risk assessment of pathogen inhalation from sprinkler irrigation using treated wastewater. Reuse of reclaimed wastewater for agricultural irrigation is an expanding practice worldwide. This practice needs to be monitored, partly because of pathogens that the water may contain after treatments. More particularly, sprinkler irrigation is known to generate aerosols which may lead to severe health risks to the population close to irrigated areas in case of the presence of Legionella bacteria in the water. A pilot experiment was conducted on two corn fields in South-Western France, irrigated with wastewater undergoing two different water treatments (ultra-filtration and UV). Water analyses have shown high levels of Legionella in the water even after a standard wastewater treatment plant (WWTP) cleaning process followed by the UV treatment (up to 106 GC per L in 2019). In this context, an updated general Bayesian network (GBN), using discrete and continuous random variables, in quantitative microbial risk assessment (QMRA) is proposed to monitor the risk of Legionella infection in the vicinity of the irrigated plots. The model's originality is based on i) a graphical probabilistic model that describes the exposure pathway of Legionella from the WWTP to the population using observed and non-observed variables and ii) the model inference updating at each new available measurement. Different scenarios are simulated according to the exposure time of the persons, taking into account various distances from the emission source and a large dataset of climatic data. From the learning process included in the Bayesian principle, quantities of interest (contaminations before and after water treatments, inhaled dose, probabilities of infection) can be quantified with their uncertainty before and after the inclusion of each new data collected in situ. This approach gives a rigorous tool that allows monitoring the risks, facilitates discussions with reuse experts and progressively reduces uncertainty quantification through field data accumulation. For the two pilot treatments analyzed in this study, the median annual risk of Legionella infection did not exceed the US EPA annual infection benchmark of 10−4 for any of the population at risk during the past few months of the pilot experiment (DALYs are estimated up to 10−5). The risk still bears watching with support from the method shown in this work. (Gaspar Massiot) 09 Jan 2023
  • [hal-04169477] Growth trajectories, better than organ-level functional traits, reveal intraspecific response to environmental variation

    1. Trait-environment relationships have been described at the community level across tree species. However, whether interspecific trait-environment relationships are consistent at the intraspecific level is yet unknown. Moreover, we do not know how consistent is the response between organ vs. whole-tree level. 2. We examined phenotypic variability for 16 functional leaf (dimensions, nutrient, chlorophyll) and wood traits (density) across two soil types, Ferralitic Soil (FS) vs. White Sands (WS), on two sites for 70 adult trees of Cecropia obtusa Trécul (Urticaceae) in French Guiana. Cecropia is a widespread pioneer Neotropical genus that generally dominates early successional forest stages. To understand how soil types impact resource use through the processes of growth and branching, we examined the architectural development with a retrospective analysis of growth trajectories. We expect soil types to affect both, functional traits in relation to resource acquisition strategy as already described at the interspecific level, and growth strategies due to resource limitations with reduced growth on poor soils. 3. Functional traits were not involved in the soil response, as only two traits-leaf residual water content and K content-showed significant differences across soil types. Soil effects were stronger on growth trajectories, with WS trees having the slowest growth trajectories and less numerous branches across their lifespan. 4. The analysis of growth trajectories based on architectural analysis improved our ability to characterise the response of trees with soil types. The intraspecific variability is higher for growth trajectories than functional traits for C. obtusa, revealing the complementarity of the architectural approach with the functional approach to gain insights on the way trees manage their resources over their lifetime. Soil-related responses of Cecropia functional traits are not the same as those at the interspecific level, suggesting that the effects of the acting ecological processes are different between the two levels. Apart from soil differences, much variation was found across sites, which calls for further investigation of the factors shaping growth trajectories in tropical forests. (Sébastien Levionnois) 24 Jul 2023
  • [hal-04169407] Functional trade‐offs are driven by coordinated changes among cell types in the wood of angiosperm trees from different climates

    Wood performs several functions to ensure tree survival and carbon allocation to a finite stem volume leads to trade-offs among cell types. It is not known to what extent these trade-offs modify functional trade-offs and if they are consistent across climates and evolutionary lineages. Twelve wood traits were measured in stems and coarse roots across 60 adult angiosperm tree species from temperate, Mediterranean and tropical climates. Regardless of climate, clear trade-offs occurred among cellular fractions, but did not translate into specific functional trade-offs. Wood density was negatively related to hydraulic conductivity (Kth) in stems and roots, but was not linked to nonstructural carbohydrates (NSC), implying a functional trade-off between mechanical integrity and transport but not with storage. NSC storage capacity was positively associated with Kth in stems and negatively in roots, reflecting a potential role for NSC in the maintenance of hydraulic integrity in stems but not in roots. Results of phylogenetic analyses suggest that evolutionary histories cannot explain covariations among traits. Trade-offs occur among cellular fractions, without necessarily modifying trade-offs in function. However, functional trade-offs are driven by coordinated changes among xylem cell types depending on the dominant role of each cell type in stems and roots. (Guangqi Zhang) 24 Jul 2023
  • [hal-03872564] Species-mixing effects on crown dimensions and canopy packing in a young pine–birch plantation are modulated by stand density and irrigation

    Mixed-species plantation forests are of high interest both because of their potentially superior productivity and multi-functionality benefits over monocultures. However, how trees of different species interact at the canopy level in mixed forests remains unclear, even at young growth stages. We tested whether crown shape and size and stand-level canopy packing were affected by stand composition and how mixture effects varied with stand density and irrigation. We measured crown attributes in pure and mixed plots of two light-demanding species, silver birch (Betula pendula Roth) and maritime pine (Pinus pinaster Ait.), in a 10-year-old tree diversity experiment (ORPHEE). This allowed us to estimate tree-level crown volumes and stand-level canopy packing. We found that (i) at the tree level, stand composition influenced crown-stem allometric relationships in pine but not in birch, (ii) mixture led to greater crown and tree dimensions in pine, but to the opposite for birch, (iii) the changes in crown volume resulted in a higher canopy packing in mixed stands, only at high density and with no irrigation, i.e., under highest constraints for light availability but also soil water availability, contrary to initial expectations. This study sheds light on the effects of water constraints on the aboveground mechanistic processes that explain greater productivity in young mixed plantations, and improves our understanding of canopy packing in mixed stands. (Soline Martin-Blangy) 25 Nov 2022
  • [hal-04211083] Climatic water availability is the main driver of contextdependency of tree functional diversity effects on top and subsoil carbon storage in European forests

    The interplay of stand and environmental factors shape soil organic C (SOC) storage in forest ecosystems but little is known about their relative impacts in different soil layers. Moreover, how environmental factors modulate the impact of stand factors, particularly species mixing, on SOC storage, is largely unexplored. In this study conducted in 21 forest triplets (twospecies mixed stand and respective monocultures nearby) distributed in Europe, we tested the hypothesis that stand factors (functional identity and diversity) have stronger effects on topsoil (FF+0-10 cm) C storage than environmental factors (climatic water availability, clay+silt content, oxalate-extractable Al-Al ox) but that the opposite occurs in the subsoil (10-40 cm). We also tested the hypothesis that functional diversity improves SOC storage under high climatic water availability, clay+silt contents, Al ox. We characterized functional identity as the proportion of broadleaved species (beech and/or oak), and functional diversity as the product of broadleaved and conifer (pine) proportions. The results show that functional identity was the main driver of topsoil C storage while climatic water availability had the largest control on subsoil C storage. Contrary to expectations, functional diversity decreased topsoil C storage under increasing climatic water availability but the opposite was observed in the subsoil. Functional diversity effects on topsoil C increased with increasing clay+silt content, while its effects on subsoil C was negative at increasing Al ox content. This suggests that functional diversity effect on SOC storage along environmental gradients depends on the specific environmental factor and the soil depth under consideration. (Richard Osei) 19 Sep 2023
  • [hal-04327097] Ante- and post-mortem cellular injury dynamics in hybrid poplar foliage as a function of phytotoxic O3 dose

    After reaching phytotoxic levels during the last century, tropospheric ozone (O 3 ) pollution is likely to remain a major concern in the coming decades. Despite similar injury processes, there is astounding interspecific–and sometimes intraspecific–foliar symptom variability, which may be related to spatial and temporal variation in injury dynamics. After characterizing the dynamics of physiological responses and O 3 injury in the foliage of hybrid poplar in an earlier study, here we investigated the dynamics of changes in the cell structure occurring in the mesophyll as a function of O 3 treatment, time, phytotoxic O 3 dose (POD 0 ), leaf developmental stage, and mesophyll layer. While the number of Hypersensitive Response-like (HR-like) lesions increased with higher O 3 concentrations and POD 0 , especially in older leaves, most structural HR-like markers developed after cell death, independent of the experimental factors. The pace of degenerative Accelerated Cell Senescence (ACS) responses depended closely on the O 3 concentration and POD 0 , in interaction with leaf age. Changes in total chlorophyll content, plastoglobuli and chloroplast shape pointed to thylakoid membranes in chloroplasts as being especially sensitive to O 3 stress. Hence, our study demonstrates that early HR-like markers can provide reasonably specific, sensitive and reliable quantitative structural estimates of O 3 stress for e . g . risk assessment studies, especially if they are associated with degenerative and thylakoid-related injury in chloroplasts from mesophyll. (Benjamin Turc) 28 Feb 2024
  • [hal-04454262] Phénologie des bourgeons de l’Aulne et du Peuplier en plantations mélangées forestière et agroforestière

    La durée de la saison de végétation est importante à considérer puisqu’elle va directement impacter l’absorption photosynthétique saisonnière qui va conditionner la croissance des arbres. Cette étude avait pour objectifs de proposer une échelle de notation visuelle pour les processus de débourrement et d’entrée en dormance chez l’aulne glutineux et de déterminer l’effet de l’association de l’aulne avec le peuplier hybride, entre eux et avec des cultures herbacées, sur la durée de la saison de végétation des espèces ligneuses, comparativement à leurs monocultures respectives. Bien que la durée de la saison de végétation n’était pas significativement différente entre les arbres en mélange et leurs monocultures respectives, les aulnes agroforestiers ont eu tendance à débourrer plus tard et à entrer en dormance plus tôt, tandis que le contraire a été observé pour les peupliers agroforestiers. Messages clés• Le mélange d’espèces n’a pas eu d’influence sur la phénologie du bourgeon de l’Aulne et du Peuplier.• Les Aulnes agroforestiers ont eu tendance à débourrer plus tard et à entrer en dormance plus tôt par rapport à leur monoculture.• Les Peupliers agroforestiers ont eu tendance à débourrer plus tôt et à entrer en dormance plus tard par rapport à leur monoculture. (Anaïs Thomas) 13 Feb 2024
  • [hal-04217872] A method for estimating tree ring density by coupling CT scanning and ring width measurements: application to the analysis of the ring width–ring density relationship in Picea abies trees

    Key Message: The original method proposed provides useful data for the analysis of ring density variations in stems, highlighting the particular behaviour observed at the base of the tree. Abstract Tree growth in volume and wood density are the two factors that determine tree biomass. They are important for assessing wood quality and resource availability. Analysing and modelling the relationships between these two factors are important for improving silvicultural practices of softwoods like Norway spruce, for which a negative relationship is generally observed between ring width and ring density. We describe an original method for obtaining ring density data (RD) by coupling conventional ring width measurements (RW) and air-dry density measurements obtained with X-ray computer tomography at high-speed but with lower resolution than the RW data. The method was applied to 200 discs of Norway spruce trees sampled in a plantation to assess its relevance. The RW-RD relationship was analysed as a function of cambial age and disc height in the stem. Descriptive statistical models were developed and compared to models in the literature. These models made it possible to analyse the variations of RD as a function of height in the tree at a given cambial age or for a given calendar year and also to observe a shift in the juvenile wood-mature wood boundary between the bottom of the tree and the rest of the stem. The RD-RW relationship was observed in the juvenile wood at the base of the stem but not in the juvenile wood higher up. Furthermore, the juvenile wood formed at the base of the tree was denser than the juvenile wood formed higher up and the mature wood formed at the same height. In conclusion, the proposed method was found to be relevant, especially when wood discs are readily available, and the results obtained highlighted the importance of distinguishing juvenile wood formed at the base of the tree from that formed higher up. (Tojo Ravoajanahary) 26 Sep 2023
  • [hal-04047069] Large leaf hydraulic safety margins limit the risk of drought‐induced leaf hydraulic dysfunction in Neotropical rainforest canopy tree species

    The sequence of key water potential thresholds from the onset of water stress to mortality, and the timing of stomatal closure with regard to leaf xylem embolism formation are essential to characterizing plant adaptive strategies to drought. This constitutes a critical knowledge gap for tropical rainforest species, which may be less vulnerable to drought than previously thought. We recorded key leaf and stem water potential thresholds, leaf hydraulic safety margins (HSMleaf), leaf stomatal safety margins (SSMleaf) and estimated native embolism levels during a normal-intensity dry season across 18 Neotropical rainforest tree species. We also solved a sequence of key water potential thresholds. Additionally, we provide a cross-biome analysis of SSMleaf encompassing 97 species from four major biomes based on a literature survey. In the studied rainforest species, leaf turgor loss point, used as a surrogate for stomatal closure, typically occurred before the onset of leaf xylem embolism. Most species exhibited positive HSMleaf and SSMleaf, with contrasting values across species and nearly absent embolism levels during the dry season irrespective of the experienced midday leaf water potentials. Our results point out that leaf xylem embolism is not routine for Neotropical rainforest tree species. Based on our proposal of the water potential sequence for tropical rainforest trees, we argue that leaf xylem embolism is a rare event for these species. This was supported by the literature survey, indicating that across biomes, most woody species have rather large SSMleaf and that leaves of tropical rainforest trees are not necessarily more vulnerable than in other biomes. However, we found evidence that some tropical rainforest species may be more vulnerable than others to ongoing climate change. Our data provide an opportunity to parametrize tree-based or land-surface models for tropical rainforests. Read the free Plain Language Summary for this article on the Journal blog. (Camille Ziegler) 27 Mar 2023
  • [hal-04133784] Thresholds for persistent leaf photochemical damage predict plant drought resilience in a tropical rainforest

    Water stress can cause declines in plant function that persist after rehydration. Recent work has defined ‘resilience’ traits characterizing leaf resistance to persistent damage from drought, but whether these traits predict resilience in whole-plant function is unknown. It is also unknown whether the coordination between resilience and ‘resistance’ – the ability to maintain function during drought – observed globally occurs within ecosystems. For eight rainforest species, we dehydrated and subsequently rehydrated leaves, and measured water stress thresholds for declines in rehydration capacity and maximum quantum yield of photosystem II (Fv/Fm). We tested correlations with embolism resistance and dry season water potentials (ΨMD), and calculated safety margins for damage (ΨMD – thresholds) and tested correlations with drought resilience in sap flow and growth. Ψ thresholds for persistent declines in Fv/Fm, indicating resilience, were positively correlated with ΨMD and thresholds for leaf vein embolism. Safety margins for persistent declines in Fv/Fm, but not rehydration capacity, were positively correlated with drought resilience in sap flow. Correlations between resistance and resilience suggest that species' differences in performance during drought are perpetuated after drought, potentially accelerating shifts in forest composition. Resilience to photochemical damage emerged as a promising functional trait to characterize whole-plant drought resilience. (Claire Fortunel) 20 Jun 2023
  • [hal-04294652] 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 5.6 ± 0.3 days. 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, 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. (Jianhong Lin) 20 Nov 2023
  • [hal-04321793] High landscape‐scale forest cover favours cold‐adapted plant communities in agriculture–forest mosaics

    Aim The ongoing climate warming is expected to reshuffle understorey plant community composition by increasing the occurrence of warm‐adapted species at the expense of cold‐adapted species. This process has been evidenced before by a warming community temperature index (CTI) over time. However, data indicate that the local tree canopy can partly explain an observed lag between understorey plant CTI and climate warming rates, though landscape‐scale forest cover effects have not yet been investigated. Here, we test the hypothesis that the amount of forest cover in the landscape lowers local CTI. Location Temperate forests in France. Time period 2005–2019. Major taxa studied Forest vascular plants. Methods We compared 2,012 pairs of neighbouring French forest inventory plots with contrasting percentages of forest cover within a 1‐km radius area (landscape forest cover). We computed the difference in the CTI of the understorey communities for each pair and tested the contributions of the landscape‐scale forest cover, local canopy cover, and soil conditions to the differences in CTI. Results Plots located in highly forested areas (> 80% in the 1‐km area) had an average CTI 0.26 °C lower (0.81 °C SD ) than plots in sparsely forested areas (< 30% in the 1‐km area). Fifty percent of this difference was explained by landscape‐scale forest cover. Bioindicated soil conditions such as pH and available nutrients, which correlated with cold‐adapted species preferences, explained the remaining 50%. Main conclusions Highly forested landscapes allow cold‐adapted species to survive in given macroclimatic conditions. These landscapes meet cold‐adapted species’ soil requirements and may cool the regional climate. Further microclimatic studies are needed to confirm the cooling capacity of landscape‐scale forest cover. (Jeremy Borderieux) 18 Jan 2024
  • [hal-04305505] Ambiguity in the altitude effect of precipitation isotopes for estimating groundwater recharge elevation and paleoelevation reconstruction in the leeward side of a mountain

    The altitude effect of isotopes in precipitation is not as significant on the leeward side of a mountain as it is on the windward side, which makes it difficult to use isotopes at leeward sites, especially if estimating elevation of groundwater recharge or reconstructing paleoelevations. Samples of precipitation were taken at three stations with different elevations-2,306-3,243 m above mean sea level (asl)-on the leeward side of the Meili Snow Mountains on the southeastern Tibetan Plateau from August 2017 to July 2018. The isotope vs. altitude gradients were calculated based on two adjacent stations at the daily, monthly, and annual scales. Most of the gradients are beyond the global ranges of -0.5 to -0.1 parts per thousand per 100 m for delta O-18 and -5 to -1 parts per thousand per 100 m for delta H-2, and some of the gradients are even positive. Local processes of sub-cloud evaporation and mixing with recycled moisture are identified for the ambiguous altitude effect, while regional atmospheric circulation processes dominate the major patterns of stable isotope variation at the three stations. The groundwater recharge elevation is estimated to be in a very large range, 2,562-6,321 m asl, which could be caused by the differences in isotope vs. altitude gradient in the studied catchments. Considering the complex atmospheric processes affecting precipitation isotopes, sampling of event-based/monthly precipitation at more than two altitudes for at least one complete hydrological year is a minimum requirement to establish a reasonable isotope vs. altitude gradient. (Yanlong Kong) 24 Nov 2023
  • [hal-04246795] Crown morphology of Populus deltoides × P. nigra and Alnus glutinosa growing in agroforestry and forest mixture plantations

    Many studies have highlighted the value of mixed plantations and their advantages over monocultures. The success of mixed plantations is usually assessed by measuring the increase in biomass and/or plant production compared to the corresponding monocultures. Among the structural determinants of growth, the vertical distribution of branches and crown shape are important to take into account because they directly impact access to light, which conditions tree growth. We evaluated the effect of two types of species mixtures in northeastern France (agroforestry and a forest mixture) on the crown architecture of poplars (Populus deltoides × P. nigra) and alder (Alnus glutinosa) after seven growing seasons and compared the mixtures to their respective onocultures. Four tree architecture variables (height, crown depth, crown projection area, crown volume) were evaluated. Our study shows that the poplars in the agroforestry plot altered their crown morphology through a true mixture effect due to the presence of clover, an N2-fixing species, as well as to reduced competition for light due to larger spacing compared to the monoculture. In the forest mixture, despite a stratification of the canopy suggesting an optimized sharing of the aerial niche, thus possibly creating an additive effect, poplar crown morphology was not different compared to the monoculture. Finally, the different types of mixtures did not affect alder crown morphology. From an agronomic perspective, the more important crown development that occurred when the poplar was associated with an N2-fixing crop makes this type of mixture a very promising way to increase the contribution of biomass to the renewable energy mix in Europe. (Anaïs Thomas) 17 Oct 2023
  • [hal-04245468] Soil Microbial Communities Involved in Proteolysis and Sulfate-Ester Hydrolysis Are More Influenced by Interannual Variability than by Crop Sequence

    Proteases, catalysing protein hydrolysis, and arylsulfatases, catalysing sulfate-ester hydrolysis, are key microbial enzymes for N and S mineralization in soil. However, knowledge gaps remain regarding the effect of crop successions and seasonal and interannual meteorological variations on microbial communities responsible for those activities. Here, we compared the effect of six cropping sequences on the abundance and activity of microbial communities involved in proteolysis and sulfate-ester hydrolysis in northern France over four years, with two sampling dates per year. Crop sequences impacted soil microbial communities involved in proteolysis but not those involved in sulfate-ester hydrolysis. Oilseed rape following wheat presented a higher abundance of fungal 18S rDNA, culturable bacteria and alkaline metalloprotease genes and higher protease activity than other crop sequences (wheat following oilseed rape or pea, barley following wheat and pea following barley). Net N and S mineralization was not impacted by the cropping sequence. However, interannual variability of microbial parameters was large, and largely overcame the effect of crop sequences. Precipitation variability between years was the likely cause of this effect. In conclusion, the interaction between current crop, previous crops and yearly meteorology can strongly impact the soil microbial communities in agroecosystems. (Nicolas Romillac) 17 Oct 2023