2019

Productions 2019

Publications dans Hal pour l'année 2019

 

HAL : Dernières publications

  • [hal-02943204] Importance of Detoxification Processes in Ozone Risk Assessment: Need to Integrate the Cellular Compartmentation of Antioxidants?

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    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Dusart) 22 Jul 2024

    https://hal.science/hal-02943204
  • [hal-02629130] Identifying the tree species compositions that maximize ecosystem functioning in European forests

    1. Forest ecosystem functioning generally benefits from higher tree species richness, but variation within richness levels is typically large. This is mostly due to the contrasting performances of communities with different compositions. Evidencebased understanding of composition effects on forest productivity, as well as on multiple other functions will enable forest managers to focus on the selection of species that maximize functioning, rather than on diversity per se. 2. We used a dataset of 30 ecosystem functions measured in stands with different species richness and composition in six European forest types. First, we quantified whether the compositions that maximize annual above-ground wood production (productivity) generally also fulfil the multiple other ecosystem functions (multifunctionality). Then, we quantified the species identity effects and strength of interspecific interactions to identify the “best” and “worst” species composition for multifunctionality. Finally, we evaluated the real-world frequency of occurrence of best and worst mixtures, using harmonized data from multiple national forest inventories. 3. The most productive tree species combinations also tended to express relatively high multifunctionality, although we found a relatively wide range of compositions with high- or low-average multifunctionality for the same level of productivity. Monocultures were distributed among the highest as well as the lowest performing compositions. The variation in functioning between compositions was generally driven by differences in the performance of the component species and, to a lesser extent, by particular interspecific interactions. Finally, we found that the most frequent species compositions in inventory data were monospecific stands and that the most common compositions showed below-average multifunctionality and productivity. 4. Synthesis and applications. Species identity and composition effects are essential to the development of high-performing production systems, for instance in forestry and agriculture. They therefore deserve great attention in the analysis and design of functional biodiversity studies if the aim is to inform ecosystem management. A management focus on tree productivity does not necessarily trade-off against other ecosystem functions; high productivity and multifunctionality can be combined with an informed selection of tree species and species combinations.

    ano.nymous@ccsd.cnrs.fr.invalid (Lander Baeten) 27 May 2020

    https://hal.inrae.fr/hal-02629130
  • [hal-02384184] Les réponses observées des arbres aux variations du climat (croissance, phénologie foliaire et fructification)

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    ano.nymous@ccsd.cnrs.fr.invalid (François Lebourgeois) 16 Jul 2024

    https://agroparistech.hal.science/hal-02384184
  • [hal-03889618] Soil and climate differently impact NDVI patterns according to the season and the stand type

    Several studies use satellite-based normalized difference vegetation index (NDVI) to monitor the impact of climate change on vegetation covers. Good understanding of the drivers of NDVI patterns is hindered by the difficulties in disentangling the effects of environmental factors from anthropogenic changes, by the limited number of environmental predictors studied, and by the diversity of responses according to periods and land covers. This study aims to improve our understanding of the different environmental drivers of NDVI spatial variations for different stand type characteristics of mountain and Mediterranean biomes. Using NDVI values extracted from MODIS Terra time series, we calculated Spring Greenness (SG) and annual Relative Greenness (RGRE) to depict spring and summer vegetation activity, respectively, in a contrasted area of 10,255 km2 located in the south of France. We modeled SG and RGRE at different scales, using 20 environmental predictors characterizing available energy, water supply, and nutrient supply calculated for different periods of the year. In spring, high minimum temperatures, good nitrogen availability, and acidic or neutral pH turned out to be determining for greenness, particularly for stand types located in altitude. In summer, an important soil water reserve and low temperatures promoted vegetation dynamics, particularly for stands located in areas with a Mediterranean climate. Our results show that NDVI dynamics was not only driven by climatic variability, and should not be studied using only mean temperature and rainfall. They highlight that different environmental factors act complementarily, and that soil parameters characterizing water stress and soil nutrition should be taken into account. While the factors limiting NDVI values varied according to the season and the position of the stands along the ecological gradients, we identified a global temperature and water-stress threshold when considering the whole vegetation.

    ano.nymous@ccsd.cnrs.fr.invalid (Christian Piedallu) 08 Dec 2022

    https://hal.science/hal-03889618
  • [hal-02621961] Améliorer la qualité des plants et leur taux de reprise

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    ano.nymous@ccsd.cnrs.fr.invalid (Nathalie Ollat) 26 May 2020

    https://hal.inrae.fr/hal-02621961
  • [hal-02561718] On the need to consider wood formation processes in global vegetation models and a suggested approach

    Abstract• Key messageDynamic global vegetation models are key tools for interpreting and forecasting the responses of terrestrial ecosystems to climatic variation and other drivers. They estimate plant growth as the outcome of the supply of carbon through photosynthesis. However, growth is itself under direct control, and not simply controlled by the amount of available carbon. Therefore predictions by current photosynthesis-driven models of large increases in future vegetation biomass due to increasing concentrations of atmospheric CO2may be significant over-estimations. We describe how current understanding of wood formation can be used to reformulate global vegetation models, with potentially major implications for their behaviour.

    ano.nymous@ccsd.cnrs.fr.invalid (Andrew D. Friend) 04 May 2020

    https://hal.science/hal-02561718
  • [hal-02903210] Habitats forestiers et forêts habitées

    Les 26 et 27 mars 2019 se tenait, au sein du Domaine national de Chambord, un colloque international regroupant une centaine de participants originaires d’une dizaine de pays. Cet évènement scientifique venait conclure le projet de recherche interdisciplinaire COSTAUD « Contribution des ongulés sauvages au fonctionnement de l’écosystème et aux services rendus à Chambord », financé par la Région Centre-Val de Loire au titre de son Appel à Projets de Recherche d’Intérêt Régional (édition 2015). Intitulé Habitats forestiers et forêts habitées, il visait à questionner les interactions existant en forêt et ses habitats associés entre la faune et les usages, modes de gestion et pratiques sociales, en se structurant autour de quatre thèmes. Le thème 1 du colloque s’est intéressé aux facteurs environnementaux et humains à l’origine des populations animales actuelles Dans le thème 2, il s’agissait d’interroger l’influence de la faune, en l’occurrence des grands herbivores, sur le fonctionnement des écosystèmes. Le thème 3 a abordé les conséquences des modes de gestion des habitats forestiers, afin d’en identifier les impacts sur la faune, notamment sur sa distribution spatiale. Enfin le thème 4 s’est intéressé à la manière dont la faune pouvait être valorisée par la société, c’est-à-dire aux usages et pratiques sociales associés à la faune sauvage et aux milieux forestiers.

    ano.nymous@ccsd.cnrs.fr.invalid (Christophe Baltzinger) 24 Nov 2021

    https://hal.inrae.fr/hal-02903210
  • [hal-02311392] The functional trait spectrum of European temperate grasslands

    Questions What is the functional trait variation of European temperate grasslands and how does this reflect global patterns of plant form and function? Do habitat specialists show trait differentiation across habitat types? Location Europe. Methods We compiled 18 regeneration and non-regeneration traits for a continental species pool consisting of 645 species frequent in five grassland types. These grassland types are widely distributed in Europe but differentiated by altitude, soil bedrock and traditional long-term management and disturbance regimes. We evaluated the multivariate trait space of this entire species pool and compared multi-trait variation and mean trait values of habitat specialists grouped by grassland type. Results The first dimension of the trait space accounted for 23% of variation and reflected a gradient between fast-growing and slow-growing plants. Plant height and SLA contributed to both the first and second ordination axes. Regeneration traits mainly contributed to the second and following dimensions to explain 56% of variation across the first five axes. Habitat specialists showed functional differences between grassland types mainly through non-regeneration traits. Conclusions The trait spectrum of plants dominating European temperate grasslands is primarily explained by growth strategies which are analogous to the trait variation observed at the global scale, and secondly by regeneration strategies. Functional differentiation of habitat specialists across grassland types is mainly related to environmental filtering linked with altitude and disturbance. This filtering pattern is mainly observed in non-regeneration traits, while most regeneration traits demonstrate multiple strategies within the same habitat type.

    ano.nymous@ccsd.cnrs.fr.invalid (Emma Ladouceur) 26 May 2020

    https://hal.science/hal-02311392
  • [hal-02165403] Infiltration from the Pedon to Global Grid Scales: An Overview and Outlook for Land Surface Modeling

    Infiltration in soils is a key process that partitions precipitation at the land surface into surface runoff and water that enters the soil profile. We reviewed the basic principles of water infiltration in soils and we analyzed approaches commonly used in land surface models (LSMs) to quantify infiltration as well as its numerical implementation and sensitivity to model parameters. We reviewed methods to upscale infiltration from the point to the field, hillslope, and grid cell scales of LSMs. Despite the progress that has been made, upscaling of local-scale infiltration processes to the grid scale used in LSMs is still far from being treated rigorously. We still lack a consistent theoretical framework to predict effective fluxes and parameters that control infiltration in LSMs. Our analysis shows that there is a large variety of approaches used to estimate soil hydraulic properties. Novel, highly resolved soil information at higher resolutions than the grid scale of LSMs may help in better quantifying subgrid variability of key infiltration parameters. Currently, only a few LSMs consider the impact of soil structure on soil hydraulic properties. Finally, we identified several processes not yet considered in LSMs that are known to strongly influence infiltration. Especially, the impact of soil structure on infiltration requires further research. To tackle these challenges and integrate current knowledge on soil processes affecting infiltration processes into LSMs, we advocate a stronger exchange and scientific interaction between the soil and the land surface modeling communities.

    ano.nymous@ccsd.cnrs.fr.invalid (Harry Vereecken) 25 Jun 2019

    https://hal.sorbonne-universite.fr/hal-02165403
  • [hal-02346487] Precipitation mediates sap flux sensitivity to evaporative demand in the neotropics

    Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate, atmospheric evaporative demand [i.e., vapor pressure deficit (VPD)] will be increasingly important for plant functioning, becoming the major control of plant water use in the twenty-first century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the maximum sap flux velocity (vmax) and the VPD threshold at which vmax is reached (VPDmax) vary with precipitation regime [mean annual precipitation (MAP); seasonal drought intensity (PDRY)] and two functional traits related to foliar and wood economics spectra [leaf mass per area (LMA); wood specific gravity (WSG)]. We show that, even though vmax is highly variable within sites, it follows a negative trend in response to increasing MAP and PDRY across sites. LMA and WSG exerted little effect on vmax and VPDmax, suggesting that these widely used functional traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse forests. This study demonstrates that long-term precipitation plays an important role in the sap flux response of humid tropical forests to VPD. Our findings suggest that under higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates.

    ano.nymous@ccsd.cnrs.fr.invalid (Charlotte Grossiord) 05 Nov 2019

    https://hal.umontpellier.fr/hal-02346487
  • [hal-02352504] The effect of tree diversity on the resistance and recovery of forest stands in the French Alps may depend on species differences in hydraulic features

    As climate change should lead to an increase in the vulnerability and the sensitivity of forests to extreme climatic events, quantifying and predicting their response to more severe droughts remains a key task for foresters. Furthermore, recent works have suggested that tree diversity may affect forest ecosystem functioning, including their response to extreme events. In this study we aimed at testing whether the growth response of forest stands to stressful climatic events varied between mixed and monospecific stands, under various environmental conditions. We focused on beech-fir forests (Fagus sylvatica [L.] and Abies albs [L.]) and beech-oak forests (F. sylvatica [L.] and Quercus pubescent [L.]) in the French Alps. We used a dendrochronological dataset sampled in forest plots organized by triplets (one mixture and two monospecific stands) distributed in six sites along a latitudinal gradient. We tested (1) whether stand diversity (two-species stands vs monospecific stands) modulates the stands' response to drought events in terms of productivity, (2) whether species identity may drive the diversity effect on resistance and recovery, and (3) whether this can be explained by interspecific interactions. We found that (1) interspecific differences in response to extreme drought events (possibly due to interspecific differences in hydraulic characteristics) can induce a mixture effect on stand growth, although it appeared (2) to be strongly depending on species identity (positive effect only found for beech-fir mixed stands), while (3) there were no significant non-additive effects of diversity on stand resistance and recovery, except for some specific cases. Overall, our study shows that promoting selected mixed stands management may buffer extreme drought effect on stand productivity.

    ano.nymous@ccsd.cnrs.fr.invalid (M. Jourdan) 20 Jul 2022

    https://hal.science/hal-02352504
  • [hal-02154568] Soil fertilization transiently increases radial growth in sessile oaks but does not change their resilience to severe soil water deficit

    The future climate is projected to become increasingly problematic for European forest ecosystems, likely leading to the decline of many tree species. Forest management must adapt to cope with the negative effects of these changes. Despite the close interactions between nutrients and water in plant physiology, very few studies have investigated the link between soil fertility and tree response to soil water availability and vapour pressure deficit. The objective of this study was to test whether fertilization would modify forest tree resilience to soil water deficit. The potential impact of fertilization on trees during soil water deficit was assessed in a fertilization experiment carried out on sessile oaks. Three fertilization treatments (NCa, NPKCaMg and an unfertilized control) were applied to 40-year-old oaks that were cored almost 40 years later. The responses to drought in the fertilized and control trees were compared by analysing the radial growth chronologies following two complementary approaches. Firstly, the relationships between radial growth and inter-annual climate variations were investigated through dendroclimatic modelling including water deficit indices computed with the daily soil water balance model Biljou(C). Secondly, resistance, recovery and resilience to drought-induced crises were evaluated from tree-ring width and compared among treatments. In addition, the carbon isotope composition (delta C-13) of the tree rings was measured to evaluate potential differential gas-exchange processes between fertilized and control trees. Fertilization had an immediate, strong positive effect on oak growth which disappeared after nine years. NCa and NPKCaMg fertilizations had similar effects, suggesting that adding P, K and Mg did not increase radial growth. Whatever the treatment, ring width variations appeared to be identically constrained by climate, especially by the summer water deficits of the current and previous years. Tree resistance to soil water deficit was negatively affected by the severity of the drought event but did not significantly differ between control and fertilized trees. Tree resilience was not affected by fertilization and remained stable across crises. The tree-ring delta C-13 clearly increased during the severe 1976 water deficit but did not vary among treatments. We discuss the possible mechanisms involved in changes in growth and the lack of any significant effect of fertilization on resilience to drought and conclude that, under the relatively dry conditions and moderately poor soil fertility of our study site, fertilization could temporarily stimulate aboveground growth without inducing imbalances that would modify resilience and resistance to severe drought episodes.

    ano.nymous@ccsd.cnrs.fr.invalid (Stéphane Ponton) 11 Sep 2023

    https://hal.science/hal-02154568
  • [hal-02628125] Are mixed-tree plantations including a nitrogen-fixing species more productive than monocultures?

    The inclusion of N2-fixing tree species in tree plantations has the potential to increase biomass production compared to monocultures. Both successes and failures have been described in the literature; however, it is still difficult to distinguish a general pattern and to disentangle the factors influencing the mixture effect. The first objective of this study was to provide an overview of the published data on the effect of the introduction of N2-fixing trees in tree plantations through a meta-analysis approach and to calculate a mean effect of mixed-tree plantations on biomass production compared to monocultures of the non N2-fixing species in stands 2–20 years of age. The second objective was to evaluate the effects of (1) climate zone (temperate vs. tropical), (2) the species used (eucalypts vs. other non N2-fixing species, and leguminous tree species vs. other N2-fixing species), (3) the proportion of N2-fixing species compared to the non-fixing species, and (4) plant developmental stage. A total of 148 case studies from 34 experimental plantations under tropical (68 case studies) and temperate (80 case studies) conditions were identified from the literature. The global mixture effect was significantly positive, mixed-tree plantations being 18% more productive than the non N2-fixing monocultures, and this effect was significantly different from zero under temperate conditions (24% more productive) but not under tropical conditions (12% more productive). Indeed, the sites where the positive mixture effect was significantly different from zero were mostly located in a temperate climate, where soil nitrogen is generally considered less available than in tropical latitudes. Intermediate and high proportions of N2-fixing species gave similar positive results (27% more productive), while low proportions had no significant impact. Neither plantation age nor type of N2-fixing species (legume trees vs. other N2-fixing species) had any significant effect. In conclusion, it appears that climate is the main factor influencing the success of the mixture; however, it also seems that the degree of mixture success is more marked on sites with low biomass production where the monoculture is the least productive.

    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Marron) 22 Oct 2021

    https://hal.inrae.fr/hal-02628125
  • [hal-02021420] More than climate? Predictors of tree canopy height vary with scale in complex terrain, Sierra Nevada, CA (USA)

    Tall trees and vertical forest structure are associated with increased productivity, biomass and wildlife habitat quality. While climate has been widely hypothesized to control forest structure at broad scales, other variables could be key at fine scales, and are associated with forest management. In this study we identify the environmental conditions (climate, topography, soils) associated with increased tree height across spatial scales using airborne Light Detection and Ranging (LiDAR) data to measure canopy height. The study was conducted over a large elevational gradient from 200 to 3000 m in the Sierra Nevada Mountains (CA, USA) spanning sparse oak woodlands to closed canopy conifer forests. We developed Generalized Boosted Models (GBMs) of forest height, ranking predictor variable importance against Maximum Canopy Height (CHMax)at six spatial scales (25, 50, 100, 250, 500, 1000 m). In our study area, climate variables such as the climatic water deficit and mean annual precipitation were more strongly correlated with CHMax (18-52% relative importance) than soil and topographic variables, and models at intermediate (50-500 m) scales explained the most variance in CHMax (R-2 0.77-0.83). Certain soil variables such as soil bulk density and pH, as well as topographic variables such as the topographic wetness index; slope curvature and potential solar radiation, showed consistent, strong associations with canopy structure across the gradient, but these relationships were scale dependent. Topography played a greater role in predicting forest structure at fine spatial scales, while climate variables dominated our models, particularly at coarse scales. Our results indicate that multiple abiotic factors are associated with increased maximum tree height; climatic water balance is most strongly associated with this component of forest structure but varies across all spatial scales examined (6.9-54.8% relative importance), while variables related to topography also explain variance in tree height across the elevational gradient, particularly at finer spatial scales (37.15%, 20.26% relative importance at 25, 50 m scales respectively).

    ano.nymous@ccsd.cnrs.fr.invalid (Geoffrey A. Fricker) 15 Feb 2019

    https://hal.science/hal-02021420
  • [hal-02628795] Acclimation and adaptation components of the temperature dependence of plant photosynthesis at the global scale.

    The temperature response of photosynthesis is one of the key factors determining predicted responses to warming in global vegetation models (GVMs). The response may vary geographically, owing to genetic adaptation to climate, and temporally, as a result of acclimation to changes in ambient temperature. Our goal was to develop a robust quantitative global model representing acclimation and adaptation of photosynthetic temperature responses. We quantified and modelled key mechanisms responsible for photosynthetic temperature acclimation and adaptation using a global dataset of photosynthetic CO2 response curves, including data from 141 C3 species from tropical rainforest to Arctic tundra. We separated temperature acclimation and adaptation processes by considering seasonal and common‐garden datasets, respectively. The observed global variation in the temperature optimum of photosynthesis was primarily explained by biochemical limitations to photosynthesis, rather than stomatal conductance or respiration. We found acclimation to growth temperature to be a stronger driver of this variation than adaptation to temperature at climate of origin. We developed a summary model to represent photosynthetic temperature responses and showed that it predicted the observed global variation in optimal temperatures with high accuracy. This novel algorithm should enable improved prediction of the function of global ecosystems in a warming climate.

    ano.nymous@ccsd.cnrs.fr.invalid (Dushan P Kumarathunge) 27 May 2020

    https://hal.inrae.fr/hal-02628795
  • [hal-02623598] Altered stomatal dynamics induced by changes in irradiance and vapour-pressure deficit under drought: impacts on the whole-plant transpiration efficiency of poplar genotypes

    Recent findings were able to show significant variability of stomatal dynamics between species, but not much is known about factors influencing stomatal dynamics and its consequences on biomass production, transpiration and water-use efficiency (WUE). We assessed the dynamics of stomatal conductance (g(s)) to a change of irradiance or vapour-pressure deficit (VPD) in two Populus euramericana and two Populus nigra genotypes grown under control and drought conditions. Our objectives were to determine the diversity of stomatal dynamics among poplar genotypes, and if soil water deficit can alter it. Physiological and morphological factors were investigated to find their potential links with stomatal morphology, WUE and its components at the whole-plant level. We found significant genotypic variability of g(s) dynamics to both irradiance and VPD. Genotypes with faster stomatal dynamics were correlated with higher stomatal density and smaller stomata, and the implications of these correlations are discussed. Drought slowed g(s) dynamics, depending on genotype and especially during stomatal closing. This finding is contrary to previous research on more drought-tolerant species. Independently of the treatment, faster stomatal dynamics were negatively correlated with daily whole-plant transpiration, presenting new evidence of a previously hypothesized contribution of stomatal dynamics to whole-plant water use.

    ano.nymous@ccsd.cnrs.fr.invalid (Maxime Durand) 26 May 2020

    https://hal.inrae.fr/hal-02623598
  • [hal-02622295] Massive postglacial gene flow between European white oaks uncovered genes underlying species barriers

    Oaks are dominant forest tree species widely distributed across the Northern Hemisphere, where they constitute natural resources of economic, ecological, social and historical value. Hybridisation and adaptive introgression have long been thought to be major drivers of their ecological success. Therefore, the maintenance of species barriers remains a key question, given the extent of interspecific gene flow. In this study, we made use of the tremendous genetic variation among four European white oak species (31 million single nucleotide polymorphisms (SNPs)) to infer the evolutionary history of these species, study patterns of genetic differentiation and identify reproductive barriers. We first analysed the ecological and historical relationships among these species and inferred a long-term strict isolation followed by a recent and extensive postglacial contact using approximate Bayesian computation. Assuming this demographic scenario, we then performed backward simulations to generate the expected distributions of differentiation under neutrality to scan their genomes for reproductive barriers. We finally identified important intrinsic and ecological functions driving the reproductive isolation. We discussed the importance of identifying the genetic basis for the ecological preferences between these oak species and its implications for the renewal of European forests under global warming.

    ano.nymous@ccsd.cnrs.fr.invalid (Thibault Leroy) 07 Dec 2023

    https://hal.inrae.fr/hal-02622295
  • [hal-01938609] Impact of vegetation on the methane budget of a temperate forest

    Upland forest soils are known to be the main biological sink for methane, but studies have shown that net methane uptake of a forest ecosystem can be reduced when methane emissions by vegetation are considered. We estimated the methane budget of a young oak plantation by considering tree stems but also the understorey vegetation. Automated chambers connected to a laser‐based gas analyser, on tree stems, bare soil and soil covered with understorey vegetation, recorded CH4 fluxes for 7 months at 3 h intervals. Tree stem emissions were low and equated to only 0.1% of the soil sink. Conversely, the presence of understorey vegetation increased soil methane uptake. This plant‐driven enhancement of CH4 uptake occurred when the soil was consuming methane. At the stand level, the methane budget shifted from −1.4 ± 0.4 kg C ha−1 when we upscaled data obtained only on bare soil, to −2.9 ± 0.6 kg C ha−1 when we considered soil area that was covered with understorey vegetation. These results indicate that aerenchymatous plant species, which are known to reduce the methane sink in wetlands, actually increase soil methane uptake two‐fold in an upland forest by enhancing methane and oxygen transport and/or by promoting growth of methanotrophic populations.

    ano.nymous@ccsd.cnrs.fr.invalid (Caroline C. Plain) 28 Nov 2018

    https://hal.univ-lorraine.fr/hal-01938609
  • [hal-02181076] Air temperature optima of vegetation productivity across global biomes.

    The global distribution of the optimum air temperature for ecosystem-level gross primary productivity ([Formula: see text]) is poorly understood, despite its importance for ecosystem carbon uptake under future warming. We provide empirical evidence for the existence of such an optimum, using measurements of in situ eddy covariance and satellite-derived proxies, and report its global distribution. [Formula: see text] is consistently lower than the physiological optimum temperature of leaf-level photosynthetic capacity, which typically exceeds 30 °C. The global average [Formula: see text] is estimated to be 23 ± 6 °C, with warmer regions having higher [Formula: see text] values than colder regions. In tropical forests in particular, [Formula: see text] is close to growing-season air temperature and is projected to fall below it under all scenarios of future climate, suggesting a limited safe operating space for these ecosystems under future warming.

    ano.nymous@ccsd.cnrs.fr.invalid (Mengtian Huang) 11 Jul 2019

    https://hal.science/hal-02181076
  • [hal-02384205] Améliorer la capacité du chêne sessile à répondre à des sécheresses extrêmes : Réduction de la densité des peuplements. Étude dendro-écologique de réseaux d’expérimentations sylvicoles à long terme

    Dans un contexte de changement climatique, les gestionnaires ont besoin de bases scientifiques pour adapter leurs itinéraires sylvicoles. Cela passe notamment par l’étude de l’influence de la compétition sur la réponse au climat et à ses variations.

    ano.nymous@ccsd.cnrs.fr.invalid (Anna Schmitt) 28 Nov 2019

    https://agroparistech.hal.science/hal-02384205
  • [hal-02095574] Background mortality drivers of European tree species : climate change matters

    Increases in tree mortality rates have been highlighted in different biomes over the past decades. However, disentangling the effects of climate change on the temporal increase in tree mortality from those of management and forest dynamics remains a challenge. Using a modelling approach taking tree and stand characteristics into account, we sought to evaluate the impact of climate change on background mortality for the most common European tree species. We focused on background mortality, which is the mortality observed in a stand in the absence of abrupt disturbances, to avoid confusion with mortality events unrelated to long-term changes in temperature and rainfall. We studied 372 974 trees including 7312 dead trees from forest inventory data surveyed across France between 2009 and 2015. Factors related to competition, stand characteristics, management intensity, and site conditions were the expected preponderant drivers of mortality. Taking these main drivers into account, we detected a climate change signal on 45% of the 43 studied species, explaining an average 6% of the total modelled mortality. For 18 out of the 19 species sensitive to climate change, we evidenced greater mortality with increasing temperature or decreasing rainfall. By quantifying the mortality excess linked to the current climate change for European temperate forest tree species, we provide new insights into forest vulnerability that will prove useful for adapting forest management to future conditions.

    ano.nymous@ccsd.cnrs.fr.invalid (Adrien Taccoen) 14 Dec 2020

    https://hal.science/hal-02095574v2
  • [hal-03085685] Partition idéalisée et régionalisée de la composition en espèces ligneuses des forêts françaises

    Forest tree species strongly influence forest dynamics and management. French forests have the greatest compositional diversity in Europe, which constrains the quantitative analysis of associated wood resources. A partition of French forests according to dominant tree species composition and stratified by biogeographical regions (GRECO) was developed in order to handle this diversity. The partition relies on forest composition as measured by the national forest inventory (2006-2015, > 65,000 plots). It builds on the J-shaped distribution of elementary composition abundance, identifies dominant compositions describing at least 50% of the GRECO's area, and groups minor compositions. An ecological assessment of this partition and its application to the analysis of the growing stock are developed. The partition describes 61.4% of the forest area (66% of the growing stock) according to 29 dominant compositions, demonstrating its efficiency. These compositions revealed the importance of broadleaved mixtures, and of neglected forest strata (pine species in Northern France). Growing stock density appeared lowest in broadleaved compositions (Mediterranean oaks), and highest in some coniferous compositions (silver fir/Norway spruce mixture in mountains). Partitioning highlights the role of ecological contexts and forest management on tree diversity.

    ano.nymous@ccsd.cnrs.fr.invalid (Jean-Daniel Bontemps) 21 Dec 2020

    https://hal.science/hal-03085685
  • [hal-02356964] Alpha diversity of vascular plants in European forests

    Aim. The former continental‐scale studies modelled coarse‐grained plant species‐richness patterns (gamma diversity). Here we aim to refine this information for European forests by (a) modelling the number of vascular plant species that co‐occur in local communities (alpha diversity) within spatial units of 400 m2; and (b) assessing the factors likely determining the observed spatial patterns in alpha diversity. Location. Europe roughly within 12°W–30°E and 35–60°N. Taxon. Vascular plants. Methods. The numbers of co‐occurring vascular plant species were counted in 73,134 georeferenced vegetation plots. Each plot was classified by an expert system into deciduous broadleaf, coniferous or sclerophyllous forest. Random Forest models were used to map and explain spatial patterns in alpha diversity for each forest type separately using 19 environmental, land‐use and historical variables. Results. Our models explained from 51.0% to 70.9% of the variation in forest alpha diversity. The modelled alpha‐diversity pattern was dominated by a marked gradient from species‐poor north‐western to species‐rich south‐eastern Europe. The most prominent richness hotspots were identified in the Calcareous Alps and adjacent north‐western Dinarides, the Carpathian foothills in Romania and the Western Carpathians in Slovakia. Energy‐related factors, bedrock types and terrain ruggedness were identified as the main variables underlying the observed richness patterns. Alpha diversity increases especially with temperature seasonality in deciduous broadleaf forests, on limestone bedrock in coniferous forests and in areas with low annual actual evapotranspiration in sclerophyllous forests. Main conclusions. We provide the first predictive maps and analyses of environmental factors driving the alpha diversity of vascular plants across European forests. Such information is important for the general understanding of European biodiversity. This study also demonstrates a high potential of vegetation‐plot databases as sources for robust estimation of the number of vascular plant species that co‐occur at fine spatial grains across large areas.

    ano.nymous@ccsd.cnrs.fr.invalid (Martin Večeřa) 18 Nov 2019

    https://hal.science/hal-02356964
  • [hal-02052715] Compositional response of Amazon forests to climate change

    Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO2 concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.

    ano.nymous@ccsd.cnrs.fr.invalid (Adriane Esquivel-Muelbert) 28 Feb 2019

    https://hal.umontpellier.fr/hal-02052715
  • [hal-02111822] Soils Drowned in Water Impoundments: A New Frontier

    Water impoundments have major impacts on biogeochemical cycles at the local and global scales. However, although reservoirs flood soils, their biogeochemical evolution below water and its ecological consequences are very poorly documented. We took advantage of the complete emptying of the Guerlédan Reservoir (Brittany, France) to compare the composition of soils flooded for 84 years with that of adjacent non-flooded soils used as reference, in 3 situations contrasted by their soil type (Cambisol and Podzol) and initial land-use (forest or grassland). In the annual drawdown zone, upper horizons of submerged soils are eroded, especially near the upper shore and on slopes. In the permanently drowned area, silty sediments cover drowned soils. Compared to reference soils, forest soils drowned for 84 years maintain their original morphological differentiation, but colors are dull, and the humus (O horizons) have virtually disappeared. Spodic horizons are depleted in poorly crystallized iron minerals while the accumulation of amorphous aluminum compounds remains unchanged. Soil bulk density increases as well as pH while total phosphorus content is almost unchanged. On the other hand, the pH of drowned grassland soils is lower by almost one unit, and the total phosphorus content was halved compared to reference soils. In this context, in addition to the effects of flooding, differences are attributed to post-1950 changes in agricultural practices i.e., liming and fertilization. Organic matter stocks decrease by almost 40%. This rate is similar in Cambisols and Podzols. Assuming that carbon was lost as CO2 and CH4, the corresponding flux averaged over the reservoir’s life is close to global areal estimates of CO2 emissions in temperate reservoirs and offsets a significant proportion of the carbon burial in reservoir sediments. Hence, flooded soils contribute significantly to the GHG budget of reservoirs, provide original long-term experimental sites to measure the effects of anoxia on soils and contain archives of past soil properties.

    ano.nymous@ccsd.cnrs.fr.invalid (Jim Félix-Faure) 26 Apr 2019

    https://hal.science/hal-02111822
  • [hal-02149053] Water and nutrient uptake capacity of leaf-absorbing trichomes vs. roots in epiphytic tank bromeliads

    The water and nutrient uptake mechanisms used by vascular epiphytes have been the subject of a few studies. While leaf absorbing trichomes (LATs) are the main organ involved in resource uptake by bromeliads, little attention has been paid to the absorbing role of epiphytic bromeliad roots. This study investigates the water and nutrient uptake capacity of LATs vs. roots in two epiphytic tank bromeliads Aechmea aquilega and Lutheria splendens. The tank and/or the roots of bromeliads were watered, or not watered at all, in different treatments. We show that LATs and roots have different functions in resource uptake in the two species, which we mainly attributed to dissimilarities in carbon acquisition and growth traits (e.g., photosynthesis, relative growth rate, non-structural carbohydrates, malate), to water relation traits (e.g., water and osmotic potential, relative water content, hydrenchyma thickness) and nutrient uptake (e.g., 15N-labelling). While the roots of A. aquilega did contribute to water and nutrient uptake, the roots of L. splendens were less important than the role played by the LATs in resource uptake. We also provide evidence for a synergistic effect of combined watering of tank and root in the Bromelioideae species. These results call for a more complex interpretation of LATs vs. roots in resource uptake in bromeliads.

    ano.nymous@ccsd.cnrs.fr.invalid (Céline Leroy) 22 Oct 2021

    https://hal.umontpellier.fr/hal-02149053
  • [hal-02264373] Additive effects of high growth rate and low transpiration rate drive differences in whole plant transpiration efficiency among black poplar genotypes

    Poplar plantations, widely used for the production of woody biomass, might be at high risk from the climate change-induced increase in the frequency of drought periods. Therefore, selecting improved genotypes, which are highly productive but with a high water use efficiency (WUE), is becoming a major target. The use of automated weighing systems in controlled environments facilitates the estimation of cumulated water loss and whole plant transpiration efficiency (TE). Differences in TE and leaf level intrinsic WUE as well as the contribution of underlying ecophysiological traits were determined in three contrasting P. nigra genotypes. Strong differences in TE among the selected genotypes were congruent with differences in leaf level intrinsic WUE. Our data show that a high total leaf area was overcompensated by a low per leaf area transpiration rate, leading to higher TE in highly productive genotypes originating from cool locations. Nocturnal water loss was relatively low but contributed to variations in TE among genotypes. In response to drought, leaf level WUE increased but not TE, suggesting that carbon losses due to whole plant respiration could offset the drought-induced increase in intrinsic WUE.

    ano.nymous@ccsd.cnrs.fr.invalid (Marie-Béatrice Bogeat-Triboulot) 06 Aug 2019

    https://hal.science/hal-02264373
  • [hal-02625305] Chilling and forcing temperatures interact to predict the onset of wood formation in Northern Hemisphere conifers

    The phenology of wood formation is a critical process to consider for predicting how trees from the temperate and boreal zones may react to climate change. Compared to leaf phenology, however, the determinism of wood phenology is still poorly known. Here, we compared for the first time three alternative ecophysiological model classes (threshold models, heat-sum models and chilling-influenced heat-sum models) and an empirical model in their ability to predict the starting date of xylem cell enlargement in spring, for four major Northern Hemisphere conifers (Larix decidua, Pinus sylvestris, Picea abies and Picea mariana). We fitted models with Bayesian inference to wood phenological data collected for 220 site-years over Europe and Canada. The chilling-influenced heat-sum model received most support for all the four studied species, predicting validation data with a 7.7-day error, which is within one day of the observed data resolution. We conclude that both chilling and forcing temperatures determine the onset of wood formation in Northern Hemisphere conifers. Importantly, the chilling-influenced heat-sum model showed virtually no spatial bias whichever the species, despite the large environmental gradients considered. This suggests that the spring onset of wood formation is far less affected by local adaptation than by environmentally driven plasticity. In a context of climate change, we therefore expect rising winter-spring temperature to exert ambivalent effects on the spring onset of wood formation, tending to hasten it through the accumulation of forcing temperature, but imposing a higher forcing temperature requirement through the lower accumulation of chilling.

    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Delpierre) 04 Apr 2024

    https://hal.inrae.fr/hal-02625305
  • [hal-02627690] From xylogenesis to tree rings: wood traits to investigate tree response to environmental changes

    It is noteworthy that the largest part of global vegetation biomass depends on a thin layer of cells: the vascular cambium. Understanding the wood formation processes and relationships with environmental factors is a crucial and timely research question requiring interdisciplinary efforts, also to upscale the information gained and to evaluate implications for tree growth and forest productivity. We provide an overview of wood formation processes up to tree-ring development, bearing in mind that the combined action of intrinsic factors and environmental drivers determines the anatomical traits of a tree ring formed at a specific time and position within the tree’s architecture. After briefly reviewing intrinsic factors, we focus attention on environmental drivers highlighting how a correct interpretation of environmental signals in tree rings must be grounded in a deep knowledge of xylogenesis and consequent wood anatomical traits. We provide guidelines on novel methods and approaches recently developed to study xylem formation. We refer to existing literature on established techniques for retrospective analyses in tree-ring series of anatomical and isotopic traits, to assess long-term ecophysiological responses to environmental variations, also giving advice on possible bias because of interand within-tree variability. Finally, we highlight that, once the temporal axis of intra-annual tree-ring variability of xylem traits is established by xylogenesis analysis, a multidisciplinary approach linking classical dendro-ecology, wood functional traits (dendro-anatomy) and eco-physiology (here focusing on dendro-isotopes) allows a better interpretation of past environmental events hidden in tree rings, and more reliable forecasts of wood growth in response to climate change.

    ano.nymous@ccsd.cnrs.fr.invalid (Veronica de Micco) 26 May 2020

    https://hal.inrae.fr/hal-02627690
  • [hal-04492051] Analyse de l'évolution de la production de truffe noire du Périgord (Tuber Melanosporum Vitad.) de 1903-1904 à 1988-1989 dans le Vaucluse

    [...]

    ano.nymous@ccsd.cnrs.fr.invalid (Meili Baragatti) 06 Mar 2024

    https://hal.inrae.fr/hal-04492051
  • [hal-02629182] Phenology of wood formation in larch (Larix decidua Mill.) trees growing along a 1000-m elevation gradient in the French Southern Alps

    center dot Key message Spring temperature increase is the main driver of larch tree wood formation onset along a 1000-m elevation gradient in the Southern Alps, while its cessation is more probably controlled by water stress at the lowest elevation and photoperiod at higher ones. center dot Context The survival of perennial plants depends on their adaptation to changing environment and specially temperature, which in trees is notably implemented through wood formation process. center dot Aims Our main objective is to understand how the phenology of wood formation is related to environmental factors and to temperature in particular. center dot Methods We monitored the xylogenesis of 60 larch trees, distributed in four stands along an elevation gradient of 1000 m in the French Southern Alps. center dot Results Cambial activity started around mid-May at the lowest site (1350 m) and around mid-June at the highest one (2300 m), showing a delay of 5.4 days per degrees C. The onset of wall-thickening and mature phenophases followed the same linear trend with a delay of 5.2 and 3 days per degrees C, respectively. Phenophase cessations followed a parabolic trend with trees from the lowest site finishing their growth the first, while those from 1700 m finished the last. Our results show that the onset of xylem formation is mainly driven by spring temperature increase, while its cessation is more related to photoperiod, with water shortage being able to hasten it. center dot Conclusion Future climatic changes will most probably increase growing season length (but not necessarily wood production) and shift upwards the optimal elevation for larch growth in the Southern Alps.

    ano.nymous@ccsd.cnrs.fr.invalid (Seyedeh Masoumeh Saderi) 27 May 2020

    https://hal.inrae.fr/hal-02629182
  • [hal-02154444] Biomechanical control of beech pole verticality (Fagus sylvatica) before and after thinning: theoretical modelling and ground-truth data using terrestrial LiDAR

    Premise of the Study Thinning is a frequent disturbance in managed forests, especially to increase radial growth. Due to buckling and bending risk associated with height and mass growth, tree verticality is strongly constrained in slender trees growing in dense forests and poor light conditions. Tree verticality is controlled by uprighting movements implemented from local curvatures induced by wood maturation stresses and/or eccentric radial growth. This study presents the first attempt to compare the real uprighting movements in mature trees using a theoretical model of posture control. Methods Stem lean and curvature were measured by Terrestrial LiDAR Scanner (TLS) technology before and 6 years after thinning and compared to unthinned control poles. Measures for several tree and wood traits were pooled together to implement a widely used biomechanical model of tree posture control. Changes in observed stem lean were then compared with the model predictions, and discrepancies were reviewed. Key Results Even under a highly constrained environment, most control poles were able to counterbalance gravitational curvature and avoid sagging. Thinning stimulated uprighting movements. The theoretical uprighting curvature rate increased just after thinning, then slowed after 2 years, likely due to the stem diameter increase. The biomechanical model overestimated the magnitude of uprighting. Conclusions Most suppressed beech poles maintain a constant lean angle, and uprighting movements occur after thinning, indicating that stem lean is plastic in response to light conditions. Acclimation of posture control to other changes in growth condition should be investigated, and lean angles should be measured in forest inventories as an indicator of future wood quality.

    ano.nymous@ccsd.cnrs.fr.invalid (Estelle Noyer) 12 Jun 2019

    https://hal.science/hal-02154444
  • [hal-02184245] Time shifts in height and diameter growth allocation in understory European beech (Fagus sylvatica L.) following canopy release

    Understory trees experience a succession of canopy opening and closure events during their lifetime. Preferential allocation of their biomass to height or diameter growth is part of the acclimation process to their immediate environment. In this study, we investigated annual height and diameter increments in Fagus sylvatica understory trees submitted to canopy release. Annual height and diameter increments were obtained from retrospective stem analysis from the top of the tree to the stump on 39 understory trees. The relationship between height and diameter increments was investigated and temporal correlations among successive annual height and diameter increments were analyzed. An asymptotic relationship between annual height and diameter increment indicates that stem height growth was limited in understory trees. The intercept significantly differed from zero suggesting that height growth never stopped even when diameter growth was null. Following canopy release events, immediate diameter growth increase was observed while the height growth response was delayed, resulting in a time shift in the growth allocation strategy. Strong and asymmetric temporal correlations between annual height and diameter increments were observed: past annual diameter growth was positively correlated to present height growth. In understory trees, tree height is the main factor determining their potential growth since it determines their access to above-canopy light. However, the precedence of diameter growth over height growth suggests that tree growth is driven by diameter instead of height. This apparent discrepancy may be explained by the fact that, under closed canopy conditions, stem allometry reaches a functional threshold that forces tree to grow in diameter before growing in height.

    ano.nymous@ccsd.cnrs.fr.invalid (Estelle Noyer) 15 Jul 2019

    https://hal.science/hal-02184245
  • [hal-02147493] Climatic controls of decomposition drive the global biogeography of forest-tree symbioses

    The identity of the dominant root-associated microbial symbionts in a forest determines the ability of trees to access limiting nutrients from atmospheric or soil pools1,2, sequester carbon3,4 and withstand the effects of climate change5,6. Characterizing the global distribution of these symbioses and identifying the factors that control this distribution are thus integral to understanding the present and future functioning of forest ecosystems. Here we generate a spatially explicit global map of the symbiotic status of forests, using a database of over 1.1 million forest inventory plots that collectively contain over 28,000 tree species. Our analyses indicate that climate variables—in particular, climatically controlled variation in the rate of decomposition—are the primary drivers of the global distribution of major symbioses. We estimate that ectomycorrhizal trees, which represent only 2% of all plant species7, constitute approximately 60% of tree stems on Earth. Ectomycorrhizal symbiosis dominates forests in which seasonally cold and dry climates inhibit decomposition, and is the predominant form of symbiosis at high latitudes and elevation. By contrast, arbuscular mycorrhizal trees dominate in aseasonal, warm tropical forests, and occur with ectomycorrhizal trees in temperate biomes in which seasonally warm-and-wet climates enhance decomposition. Continental transitions between forests dominated by ectomycorrhizal or arbuscular mycorrhizal trees occur relatively abruptly along climate-driven decomposition gradients; these transitions are probably caused by positive feedback effects between plants and microorganisms. Symbiotic nitrogen fixers—which are insensitive to climatic controls on decomposition (compared with mycorrhizal fungi)—are most abundant in arid biomes with alkaline soils and high maximum temperatures. The climatically driven global symbiosis gradient that we document provides a spatially explicit quantitative understanding of microbial symbioses at the global scale, and demonstrates the critical role of microbial mutualisms in shaping the distribution of plant species.

    ano.nymous@ccsd.cnrs.fr.invalid (B. Steidinger) 04 Jun 2019

    https://hal.science/hal-02147493
  • [hal-01972724] Influence of annual climatic variations, climate changes, and sociological factors on the production of the Périgord black truffle (Tuber melanosporum Vittad.) from 1903–1904 to 1988–1989 in the Vaucluse (France)

    From 1903–1904 to 1988–1989, the two World Wars and sociological factors as rural desertification and changes in land uses mainly explained the decline of black truffle production in the Vaucluse department, which well reflects that of the whole of France. These can be correlated with the annual climatic variations as well as, from 1924–1925 to 1948–1949, the raw production rates of the managed truffle orchard of Pernes-les-Fontaines located in Vaucluse. The two methods used (correlation coefficients and Bayesian functional linear regression with Sparse Step functions) gave consistent results: the main factor explaining the annual variations of truffle production was the summer climatic water deficit of the year n. A general model including the rural exodus and the cumulated climatic water deficit of summer months both allowed to well explain the evolution of truffle production from 1903–1904 to 1988–1989 in the Vaucluse and its huge decrease. During that period, global warming had little effect. However, in the twenty-first century, all the scenarios predict increased summer water stress for the Mediterranean region, which could greatly affect black truffle production.

    ano.nymous@ccsd.cnrs.fr.invalid (Meïli Baragatti) 07 Jan 2019

    https://hal.science/hal-01972724
  • [hal-03328388] Un outil en ligne pour accompagner le choix des essences forestières dans un contexte de changement climatique.

    [...]

    ano.nymous@ccsd.cnrs.fr.invalid (Sophie Bertin) 30 Aug 2021

    https://hal.science/hal-03328388
  • [hal-02263853] Annotation data about multi criteria assessment methods used in the agri-food research: The French national institute for agricultural research (INRA) experience

    This data article contains annotation data characterizing MultiCriteria Assessment (MCA) Methods proposed in the agri-food sector by researchers from INRA, Europe's largest agricultural research institute (INRA, http://institut.inra.fr/en). MCA can be used to assess and compare agricultural and food systems, and support multi-actor decision making and design of innovative systems for crop production, animal production and processing of agricultural products. These data are stored in a public repository managed by INRA (https://data.inra.fr/; https://doi.org/10.15454/WB51LL).

    ano.nymous@ccsd.cnrs.fr.invalid (Geneviève Gésan-Guiziou) 05 Aug 2019

    https://hal.science/hal-02263853
  • [hal-02964786] Le processus d'innovation technologique en sylviculture - Exemple des outils mécaniques de préparation du sol avant plantation

    Un changement de pratiques sylvicoles s’impose pour assurer le renouvellement des forêts face aux changements globaux présents et à venir. C’est d’autant plus vrai avec la plantation qui doit subir des printemps au climat très contrasté. Assurer le transfert aux praticiens et propriétaires est essentiel pour garantir leur réussite.

    ano.nymous@ccsd.cnrs.fr.invalid (Catherine Collet) 14 Oct 2020

    https://hal.science/hal-02964786
  • [hal-02168619] Nondestructive and Fast Vibration Phenotyping of Plants

    The frequencies of free oscillations of plants, or plant parts, depend on their geometries, stiffnesses, and masses. Besides direct biomechanical interest, free frequencies also provide insights into plant properties that can usually only be measured destructively or with low-throughput techniques (e.g., change in mass, tissue density, or stiffness over development or with stresses). We propose here a new high-throughput method based on the noncontact measurements of the free frequencies of the standing plant. The plant is excited by short air pulses (typically 100 ms). The resulting motion is recorded by a high speed video camera (100 fps) and processed using fast space and time correlation algorithms. In less than a minute the mechanical behavior of the plant is tested over several directions. The performance and versatility of this method has been tested in three contrasted species: tobacco (Nicotiana benthamian), wheat (Triticum aestivum L.), and poplar (Populus sp.), for a total of more than 4000 data points. In tobacco we show that water stress decreased the free frequency by 15%. In wheat we could detect variations of less than 1 g in the mass of spikes. In poplar we could measure frequencies of both the whole stem and leaves. The work provides insight into new potential directions for development of phenotyping.

    ano.nymous@ccsd.cnrs.fr.invalid (Emmanuel de Langre) 28 Jun 2019

    https://hal.science/hal-02168619
  • [hal-02411666] The commonness of rarity: Global and future distribution of rarity across land plants

    A key feature of life’s diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant diversity to quantify the fraction of Earth’s plant biodiversity that are rare. A large fraction, ~36.5% of Earth’s ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth’s plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.

    ano.nymous@ccsd.cnrs.fr.invalid (Brian Enquist) 31 May 2021

    https://hal.science/hal-02411666
  • [hal-02399726] The cost of deer to trees: changes in resource allocation from growth-related traits and phenolic content to structural defence

    Background and aims-Plants may use various defence mechanisms to protect their tissues against deer browsing and the allocation of resources to defence may trade-off with plants' growth. In a context of increasing deer populations in European forests, understanding the resource allocation strategies of trees is critical to better assess their ability to face an increasing browsing pressure. The aim of this study was to determine how deer removal affects the resource allocation to both defensive and growth-related traits in field conditions for three tree species (Abies alba, Picea abies and Fagus sylvatica). Methods-We compared eight pairs of fenced-unfenced plots to contrast plots with and without browsing pressure. The pairs were set up in 2005 and 2014 to compare different fencing duration. We measured leaf and shoot traits related to the defence against herbivores (phenolic content, structural resistance, C:N ratio) and to the investment in plants' growth and productivity (specific leaf area and nutrient content). Key results-For the three species, the structural resistance of leaves and shoots was negatively correlated with SLA, nutrient content and phenolic content. For Abies alba, exclusion of deer decreased shoot structural resistance in favour of higher nutrient content, SLA and phenolic content. The fencing duration had no effect on the different measured traits. Conclusions-Our results support the assumption of a trade-off between structural defence and growth-related traits at the intraspecific scale for the three studied species. We also confirmed the hypothesis that exposure to deer browsing is involved in the resource allocation of woody species. For Abies alba, fencing led to a change in resource allocation from structural defence to growth-related traits and chemical defence.

    ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 09 Dec 2019

    https://hal.science/hal-02399726
  • [hal-02320571] Quelle pertinence du modèle diversité-productivité-perturbations pour analyser l’influence des pratiques agricoles sur la diversité des prairies permanentes du Massif central ?

    Un modèle a été réalisé pour évaluer l’impact des pratiques agricoles sur la diversité des prairies. Pour tester les prédictions d’un modèle théorique d’écologie, le modèle d’équilibre dynamique, nous avons suivi 18 prairies permanentes du Massif central aux pédoclimats et modes de gestion variés. Nous avons mis en évidence une diminution de la richesse spécifique liée à l’augmentation de la quantité de biomasse exportée (pâturée ou fauchée) et une diminution de la richesse fonctionnelle liée à l’augmentation de la productivité. Ces effets n’expliquent toutefois qu’une faible part de la variabilité observée entre sites. La quantité de biomasse exportée dépend du nombre de fauches et du chargement animal annuel ; la productivité était avant tout dépendante des précipitations durant la période d’étude, et non de la fertilisation. Nous discutons de l’intérêt et des limites de l’utilisation du modèle pour la gestion de la diversité des prairies.

    ano.nymous@ccsd.cnrs.fr.invalid (Rémi Perronne) 18 Oct 2019

    https://hal.science/hal-02320571
  • [cea-02363571] Sustainable bioenergy for climate mitigation: developing drought-tolerant trees and grasses

    Background and Aims Bioenergy crops are central to climate mitigation strategies that utilize biogenic carbon, such as BECCS (bioenergy with carbon capture and storage), alongside the use of biomass for heat, power, liquid fuels and, in the future, biorefining to chemicals. Several promising lignocellulosic crops are emerging that have no food role-fast-growing trees and grasses-but are well suited as bioenergy feedstocks, including Populus, Salix, Arundo, Miscanthus, Panicum and Sorghum. • Scope These promising crops remain largely undomesticated and, until recently, have had limited germplasm resources. In order to avoid competition with food crops for land and nature conservation, it is likely that future bio-energy crops will be grown on marginal land that is not needed for food production and is of poor quality and subject to drought stress. Thus, here we define an ideotype for drought tolerance that will enable biomass production to be maintained in the face of moderate drought stress. This includes traits that can readily be measured in wide populations of several hundred unique genotypes for genome-wide association studies, alongside traits that are informative but can only easily be assessed in limited numbers or training populations that may be more suitable for genomic selection. Phenotyping, not genotyping, is now the major bottleneck for progress, since in all lignocellulosic crops studied extensive use has been made of next-generation sequencing such that several thousand markers are now available and populations are emerging that will enable rapid progress for drought-tolerance breeding. The emergence of novel technologies for targeted genotyping by sequencing are particularly welcome. Genome editing has already been demonstrated for Populus and offers significant potential for rapid deployment of drought-tolerant crops through manipulation of ABA receptors, as demonstrated in Arabidopsis, with other gene targets yet to be tested. • Conclusions Bioenergy is predicted to be the fastest-developing renewable energy over the coming decade and significant investment over the past decade has been made in developing genomic resources and in collecting wild germplasm from within the natural ranges of several tree and grass crops. Harnessing these resources for climate-resilient crops for the future remains a challenge but one that is likely to be successful.

    ano.nymous@ccsd.cnrs.fr.invalid (G. Taylor) 14 Nov 2019

    https://cea.hal.science/cea-02363571
  • [hal-02265924] Altered stomatal dynamics of two Euramerican poplar genotypes submitted to successive ozone exposure and water deficit

    The impact of ozone (O3) pollution events on the plant drought response needs special attention because spring O3 episodes are often followed by summer drought. By causing stomatal sluggishness, O3 could affect the stomatal dynamic during a subsequent drought event. In this context, we studied the impact of O3 exposure and water deficit (in the presence or in the absence of O3 episode) on the stomatal closure/opening mechanisms relative to irradiance or vapour pressure deficit (VPD) variation. Two genotypes of Populus nigra x deltoides were exposed to various treatments for 21 days. Saplings were exposed to 80 ppb/day O3 for 13 days, and then to moderate drought for 7 days. The curves of the stomatal response to irradiance and VPD changes were determined after 13 days of O3 exposure, and after 21 days in the case of subsequent water deficit, and then fitted using a sigmoidal model. The main responses under O3 exposure were stomatal closure and sluggishness, but the two genotypes showed contrasting responses. During stomatal closure induced by a change in irradiance, closure was slower for both genotypes. Nonetheless, the genotypes differed in stomatal opening under light. Carpaccio stomata opened more slowly than control stomata, whereas Robusta stomata tended to open faster. These effects could be of particular interest, as stomatal impairment was still present after O3 exposure and could result from imperfect recovery. Under water deficit alone, we observed slower stomatal closure in response to VPD and irradiance, but faster stomatal opening in response to irradiance, more marked in Carpaccio. Under the combined treatment, most of the parameters showed antagonistic responses. Our results highlight that it is important to take genotype-specific responses and interactive stress cross-talk into account to improve the prediction of stomatal conductance in response to various environmental modifications.

    ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Dusart) 25 Oct 2021

    https://hal.science/hal-02265924
  • [hal-02624939] Using stable isotope approach to quantify pond dam impacts on isotopic niches and assimilation of resources by invertebrates in temporary streams: a case study

    Fishponds built across streams can greatly affect their functioning, especially through loss of ecological continuity but also changes in water availability and trophic resources. Yet, their consequences on communities and stream functioning remain largely understudied. We investigated effects of fishpond dams on the trophic ecology of macroinvertebrate communities in temporary low-order streams using C and N stable isotopes. Food resources and macroinvertebrates were sampled in one upstream and one downstream site of two temporary streams, one stream without (reference stream) versus one with a fishpond (impacted stream) and used for isotopic analyses. Results suggested moderate effects of fishponds on the upstream tributaries. In contrast, at the downstream impacted site, ten times higher macroinvertebrate biomass and modifications in the trophic niches were recorded, likely due to changes in resource availability/quality and dam-related hydrology. By modifying the food sources as well as water fluxes, fishpond dams tend to alter macroinvertebrate communities but also shift the trophic dynamics downstream. This assessment stresses the need for exploring their impacts on food webs and nutrient fluxes at larger downstream distances to better understand their effects before drawing conclusions in regard to their management.

    ano.nymous@ccsd.cnrs.fr.invalid (Brian Four) 16 Jun 2022

    https://hal.inrae.fr/hal-02624939
  • [hal-02011754] Explaining the larger seed bank of an invasive shrub in non-native versus native environments by differences in seed predation and plant size

    •Background and aims - Large, persistent seed banks contribute to the invasiveness of non-native plants, and maternal plant size is an important contributory factor. We explored the relationships between plant vegetative size (V) and soil seed bank size (S) for the invasive shrub (Ulex europaeus) in its native range and in non-native populations, and identified which other factors may contribute to seed bank variation between native and invaded regions. •Methods - We compared the native region (France) with two regions where Ulex is invasive, one with seed predators introduced for biological control (New Zealand) and another where seed predators are absent (La Réunion). We quantified seed bank size, plant dimensions, seed predation, and soil fertility for six stands in each of the three regions.•Key results - Seed banks were 9 to 14 times larger in the two invaded regions compared to native France. We found a positive relationship between current seed bank size and actual plant size, and that any deviation from this relationship was probably due to large differences in seed predation and/or soil fertility. We further identified three possible factors explaining larger seed banks in non-native environments: larger maternal plant size, lower activity of seed predators and higher soil fertility. •Conclusions - In highlighting a positive relationship between maternal plant size and seed bank size, and identifying additional factors that regulate soil seed bank dynamics in non-native ranges, our data offer a number of opportunities for invasive weed control. For non-native Ulex populations specifically, management focusing on 'S' (i.e. the reduction of the seed bank by stimulating germination, or the introduction of seed predators as biological control agents), and/or 'V' (i.e. by cutting mature stands to reduce maternal plant biomass) offers the most probable combination of effective control options.

    ano.nymous@ccsd.cnrs.fr.invalid (Mark Bakker) 13 Feb 2019

    https://hal.science/hal-02011754
  • [hal-02624918] LiDAR-derived topography and forest structure predict fine-scale variation in daily surface temperatures in oak savanna and conifer forest landscapes

    In mountain landscapes, surface temperatures vary over short distances due to interacting influences of topography and overstory vegetation on local energy and water balances. At two study landscapes in the Sierra Nevada of California, characterized by foothill oak savanna at 276–481 m elevation and montane conifer forest at 1977–2135 m, we deployed 288 near-surface (5 cm above the surface) temperature sensors to sample site-scale (30 m) temperature variation related to hillslope orientation and vegetation structure and microsite-scale (2–10 m) variation related to microtopography and tree overstory. Daily near-surface maximum and minimum temperatures for the 2013 calendar year were related to topographic factors and vegetation overstory characterized using small footprint LiDAR imagery acquired by the National Ecological Observatory Network (NEON) Airborne Observation Platform (AOP). At both landscapes we recorded large site and microsite spatial variation in daily maximum temperatures, and less absolute variation in daily minimum temperatures. Generalized boosted regression trees were estimated to measure the influence of tree canopy density, understory solar radiation, cold-air drainage and pooling, ground cover and microtopography on daily maximum and minimum temperatures at site and microsite scales. Site-scale models based on indices of understory solar radiation and landscape position explained an average of 61–65% of daily variation in maximum temperature; site-scale models based on tree canopy density and landscape position explained 65–83% of variation in minimum temperatures. Models explained <15% of variation in microsite-scale maximum temperatures but within-site heterogeneity was significantly correlated with within-site heterogeneity in modeled understory radiation at both landscapes. Tree canopy density and slope explained 33% of microsite-scale variation in minimum temperatures at savanna sites. Our results demonstrate that it is feasible to model site-scale variation in daily surface temperature extremes and within-site heterogeneity in surface temperatures using LiDAR-derived variables, supporting efforts to understand cross-scale relationships between surface microclimates and regional climate change. Improved understanding of topographic and vegetative buffering of thermal microclimates across mountain landscapes is key to projecting microclimate heterogeneity and potential species’ range dynamics under future climate change.

    ano.nymous@ccsd.cnrs.fr.invalid (Frank W. Davis) 26 May 2020

    https://hal.inrae.fr/hal-02624918
  • [hal-02485053] Effet de la chalarose (Hymenoscyphus fraxineus) sur la croissance radiale du frêne et sur son déterminisme climatique dans le nord de la France

    La chalarose du frêne (Hymenoscyphus fraxineus) est apparue dans le nord de la France entre 2010 et 2012. Afin de juger de l’effet du champignon sur la croissance radiale et sur la sensibilité au climat des frênes, 181 arbres adultes (âge et diamètre moyens : 100 ans et 50 cm) issus de 9 peuplements ont été échantillonnés en 2017 selon cinq niveaux de défoliation. Les peuplements sont purs et correspondent à des conditions sylvicole et écologique optimales pour l’essence (sols chimiquement riches et réserve utile en eau élevée autour de 150 mm). Sur la période 1920-2017, la croissance radiale a été d’en moyenne 2,3 } 0,4 mm par an. Pour les arbres peu défoliés en 2017 (≤ 25 %), la croissance est restée stable entre 2 et 2,5 mm par an après 2010 alors que, pour les autres catégories (> 25 %), elle a chuté d’autant plus que le niveau de défoliation était élevé (autour de 1 mm par an pour les défoliations supérieures à 75 %). Il est également apparu que les arbres défoliés à plus de 25% en 2017 avaient déjà une croissance plus faible depuis la fin des années 1990 et systématiquement plus faible depuis 2003 (différence de 15 à 25 %). Ces périodes ayant été particulièrement sèches dans la région étudiée, on peut émettre l’hypothèse d’une sensibilité plus forte au pathogène des arbres déjà affaiblis par des stress hydriques forts. Les modèles climatiques expliquent entre 50 et 60 % de la variation de la croissance des frênaies sauf pour les arbres les plus défoliés en 2017 (> 75 %) qui sont apparus peu sensibles au climat depuis toujours (taux d’explication des modèles climatiques de 25 %). Ainsi, dans le nord de la France et sur des stations très favorables, une bonne croissance correspond à des automnes pluvieux et des hivers doux bien arrosés suivis par un mois de mai chaud et pluvieux (facteur central pour la croissance). Depuis l’arrivée de la chalarose, les arbres les plus défoliés (> 25 %) répondent néanmoins de moins au moins au climat sauf aux conditions de fin d’été (pluies du mois d’août) ; période qui n’apparaissait pas déterminante sur le plus long terme. Des modifications du fonctionnement physiologique des arbres sont évoquées pour expliquer ces comportements. Finalement, notre étude a montré que les frênes étaient très réactifs au climat et que la chalarose a affecté préférentiellement les arbres déjà affaiblis par une succession de crises climatiques passées (sécheresses). Même si les frênes adultes semblent pouvoir tolérer un certain niveau de défoliation sans compromettre leur croissance, l’augmentation de la variabilité du climat et la récurrence des sécheresses pourraient déstabiliser les frênaies rendant leur gestion future encore plus complexe.

    ano.nymous@ccsd.cnrs.fr.invalid (François F. Lebourgeois) 19 Feb 2020

    https://hal.science/hal-02485053
  • [hal-02384139] Fructification du Hêtre et des Chênes en France : rôle des températures, du pollen et du bilan de carbone et relation avec la croissance des peuplements

    Dans cette étude, nous avons analysé les déterminants environnementaux de la variabilité spatiale et temporelle de la fructification des trois espèces feuillues européennes majeures : Quercus robur, Quercus petraea et Fagus sylvatica. Nous avons étudié les relations entre la production de fruits, l’émission de pollen, les ressources carbonées et hydriques et les conditions climatiques sur la période 1994-2007 (14 ans) à partir de 48 peuplements du réseau RENECOFOR. La production moyenne des fruits est de 251 kg/ha/an pour les Chênes et de 174 kg/ha/an pour le Hêtre. Pour le Hêtre, la production suit un rythme bisannuel très net et est synchrone entre les sites. Elle apparaît beaucoup plus variable pour les Chênes sans synchronisme net. Pour les Chênes, la fructification dépend très fortement des conditions thermiques durant la période d’émission du pollen (début avril) confirmant l’hypothèse du synchronisme pollinique pour ces espèces. Pour le Hêtre, la production dépend très fortement des écarts de température estivale entre les années. Pour les deux espèces, les relations entre la production de fruits et les différents déterminants suivent des lois non linéaires avec des forts effets seuil et des interactions complexes. Enfin, pour le Hêtre, la croissance radiale est réduite en cas de forte fructification alors que les années de bonne glandée sont aussi des années de forte croissance pour les Chênes. Les deux espèces présentent donc deux comportements opposés concernant les stratégies d’allocation entre la croissance radiale et la production de fruits.

    ano.nymous@ccsd.cnrs.fr.invalid (François F. Lebourgeois) 28 Nov 2019

    https://agroparistech.hal.science/hal-02384139
  • [hal-02154447] First evidences that the ectomycorrhizal fungus Paxillus involutus mobilizes nitrogen and carbon from saprotrophic fungus necromass

    Fungal succession in rotting wood shows a surprising abundance of ectomycorrhizal (EM) fungi during the late decomposition stages. To better understand the links between EM fungi and saprotrophic fungi, we investigated the potential capacities of the EM fungus Paxillus involutus to mobilize nutrients from necromass of Postia placenta, a wood rot fungus, and to transfer these elements to its host tree. In this aim, we used pure cultures of P. involutus in the presence of labelled Postia necromass (15N/13C) as nutrient source, and a monoxenic mycorrhized pine experiment composed of labelled Postia necromass and P. involutus culture in interaction with pine seedlings. The isotopic labelling was measured in both experiments. In pure culture, P. involutus was able to mobilize N, but C as well, from the Postia necromass. In the symbiotic interaction experiment, we measured high 15N enrichments in all plant and fungal compartments. Interestingly, 13C remains mainly in the mycelium and mycorrhizas, demonstrating that the EM fungus transferred essentially N from the necromass to the tree. These observations reveal that fungal organic matter could represent a significant N source for EM fungi and trees, but also a C source for mycorrhizal fungi, including in symbiotic lifestyle.

    ano.nymous@ccsd.cnrs.fr.invalid (Emila Akroume) 12 Jun 2019

    https://hal.science/hal-02154447

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