Résumé
Indispensables à la bonne santé des sols comme à la séquestration du carbone, hôtes d’une biodiversité aussi diverses que cryptiques, les feuilles mortes sont un véritable carburant des écosystèmes.
Auteurs, date et publication :
Auteurs Mathieu Santonja , Thierry Gauquelin
Date : 2024
Catégorie(s)
#CNRS #FORET O3HPRésumé
To improve our understanding of the carbon cycle, precise estimates of forest biomass are needed. High values of dense tropical forest biomass are particularly important, as they determine uncertainties in carbon stock assessment and carbon loss due to deforestation and forest degradation. However, estimating Above Ground Biomass (AGB) of tropical forests based on remote sensing systems remains challenging, most existing satellite systems are not sensitive to AGB in the high range. In this paper, we assess the use of P-band SAR tomography technique to provide AGB with reduced uncertainties in the range of 200-400 Mg.ha -1. We present the expected contribution of the BIOMASS mission in estimating the carbon loss from deforestation and from forest degradation , and in providing the Digital Elevation Model under dense forests.
Auteurs, date et publication :
Auteurs Thuy Le Toan , Ludovic Villard , Dinh Ho Tong Minh , Juan Doblas , Stephane Mermoz , Laurent Ferro-Famil , Thierry Koleck , Alexandre Bouvet , Milena Planells , Laurent Polidori
Publication : The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Date : 2024
Volume : XLVIII-3-2024
Pages : 287-293
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Phylogenomics reveals reticulate evolution to be widespread across taxa, but whether reticulation is due to low statistical power or it is a true evolutionary pattern remains a field of study. Here, we investigate the phylogeny and quantify reticulation in the Drosophila saltans species group, a Neotropical clade of the subgenus Sophophora comprising 23 species whose relationships have long been problematic. Phylogenetic analyses revealed conflicting topologies between the X chromosome, autosomes and the mitochondria. We extended the ABBA-BABA test of asymmetry in phylogenetic discordance to cases where no “true” species tree could be inferred, and applied our new test (called 2A2B) to whole genome data and to individual loci. We used four strategies, two based on our new assemblies using either conserved genes or ≥50 kb-long syntenic blocks with conserved collinearity across Neotropical Sophophora, and two consisted of windows from pseudo-reference genomes aligned to either an ingroup or outgroup species. Evidence for reticulation varied among the strategies, being lowest in the synteny-based approach, where it did not exceed ∼7% of the blocks in the most conflicting species quartets. High incidences of reticulation were restricted to three nodes on the tree that coincided with major paleogeographical events in South America. Our results identify possible technical biases in quantifying reticulate evolution and indicate that episodic rapid radiations have played a major role in the evolution of a largely understudied Neotropical clade.
Auteurs, date et publication :
Auteurs Carolina Prediger , Erina A Ferreira , Samara Videira Zorzato , Aurélie Hua-Van , Lisa Klasson , Wolfgang J Miller , Amir Yassin , Lilian Madi-Ravazzi
Publication : Molecular Biology and Evolution
Date : 2024
Volume : 41
Issue : 12
Pages : msae250
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Le virus Mayaro (MAYV) est un virus sud-américain proche du virus Chikungunya, de la famille des Togaviridae et du genre Alphavirus, généralement transmis par des moustiques forestiers du genre Haemagogus. La présentation clinique, proche de celle liée au chikungunya, associe de la fièvre, des arthralgies au premier plan et un exanthème. En Guyane, 17 cas seulement ont été rapportés entre 2003 et 2019, majoritairement après un séjour en forêt. Treize cas ont été détectés en 2020, sans lien épidémiologique entre eux, parmi lesquels 11 avaient été acquis sur l’île de Cayenne. Aucun cas n'a été rapporté depuis. Nous rapportons ici un cluster survenu début 2024 chez des personnes revenant de la réserve naturelle nationale (RNN) des Nouragues. Fin janvier 2024, 5 personnes dont 3 chercheurs de l'Union Européenne et 2 salariés de la RNN ont développé un tableau « chikungunya-like » au retour d'un séjour de la RNN de Nouragues. La médiane d’âge était 36 ans (min-max, 30-48). Parmi les 5 patients (2 femmes et 3 hommes), tous ont rapporté des arthralgies, 4 de la fièvre, 4 une éruption cutanée, 3 des œdèmes des pieds, et un des œdèmes des mains. Les articulations distales étaient les plus fréquemment touchées. La médiane de la durée de la fièvre était de 5 jours (min-max, 4-8), de la durée de l’éruption 6 jours (min-max, 5-21). Parmi les 5 patients, 3 ont eu des douleurs articulaires qui se sont amendées (11, 17 et 28 jours), et 2 avaient des arthralgies persistantes à plus 3 mois, l'un toujours sous AINS, l'autre sous prednisone avec persistance d'une cortico-dépendance. Le diagnostic d'infection par le virus Mayaro a été posé par RT-qPCR pour 2 patients, par sérologie (IgM Mayaro positives) pour 2 autres. Le 5e patient, avec pourtant un tableau clinique évocateur, n'a pas pu être confirmé biologiquement malgré 2 sérologies réalisées au Centre national Allemand de référence pour les pathogènes infectieux tropicaux respectivement à J19 et J31 des symptômes (persistants à 32 jours) qui sont restées négatives (techniques différentes de celles utilisées en Guyane). Dix-huit personnes ont séjourné aux Nouragues sur la période parmi lesquelles six ont bénéficié d'une sérologie MAYV, toujours revenue négative, démontrant l'absence de formes asymptomatiques. Par la suite, plus aucun cas n'a été signalé au retour de la RNN, y compris un groupe de 20 chercheurs qui y a séjourné dans les même conditions quelques semaines plus tard. À noter qu'un autre cas, sans aucun lien épidémiologique avec ce cluster a été identifié en février2024 à Saint Laurent du Maroni. Les résultats négatifs en sérologie de la 5e personne du groupe pourrait peut-être s'expliquer par une sensibilité différente de la technique utilisée en Allemagne comparée à celle de Guyane. L'infection par le MAYV est à évoquer devant un syndrome « chikungunya-like » associant des arthralgies distales fébriles avec ou sans éruption cutanée chez des personnes vivant ou revenant d'Amérique latine. Certains patients évoluent vers une maladie douloureuse/inflammatoire chronique comme observée au décours d'un chikungunya. Des explorations entomologiques sont prévues dans les mois à venir pour apporter des explications à la survenue de ce cluster. À noter que la période 2024 a été marquée par une circulation importante d'arbovirus divers en Amérique latine (dengue, Oropouche, virus de l'encéphalite équine, etc).
Auteurs, date et publication :
Auteurs L. Epelboin , A. Lavergne , P. Le Turnier , S. Talaga , S. Pavin , R. Naldjinan , C. Gaertner , A. Enfissi , M. Gertler , A. Zoufaly , J.-B. Duchemin , D. Rousset
Publication : Assises Guyanaises d'Infectiologie et de médecine Tropicale
Date : 2024
Volume : 3
Issue : 4, Supplement
Pages : S14-S15
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Mountains are particularly vulnerable to climate change, as they are warming at a rate that exceeds the global average, significantly impacting cold-adapted ecosystems. In these environments, soil organic matter (SOM) stocks are often considerably larger than at lower elevations. These stocks are therefore highly susceptible to global warming and the associated risk of greenhouse gas (GHG) (CO₂, CH₄, N₂O) emissions driven by temperature-induced increases in SOM mineralisation. In order to quantify these emissions and the change of mineralisation rates under warming, it is necessary to gain an understanding of the annual mineralisation balance. We investigated how warming impacts the duration and intensity of mineralisation in different seasons. The main aim of this study is to quantify alpine SOM mineralisation rates and GHG production under a range of seasonal conditions, including those associated with warming. An in vitro approach was employed to expose alpine topsoils (0–10 cm) to the conditions of key seasonal periods: snow cover, growing season and rainfall/snowmelt. This was achieved by experimentally varying temperature and inflow of precipitation water. Additionally, the soil samples were subjected to a temperature increase of 4°C. The short-term responses of carbon (C), nitrogen (N) and phosphorus (P) mineralisation and GHG production were monitored. The results demonstrated that alpine soil respiration rates exhibited a twofold increase with a 4°C warming, while the relative proportion of labile SOM demonstrated a decline with rising temperatures. Water saturation from simulated rain and snowmelt played a crucial role in organic matter mineralisation and increased the mineralisation of carbon (+12% to +53%), nitrogen (+20% to +80% of net ammonification) and phosphorus (+50% of net phosphate production). This suggests that nutrients present in the snowpack or the rain were added to the soil. In contrast, soil–water saturation decreased net nitrate production by between 10% and 90%. The results of this study highlight the potential for alpine soil warming to release labile SOM and demonstrate the influence of the snow regime on nutrient and carbon fluxes.
Auteurs, date et publication :
Auteurs Nicolas Bonfanti , Jean-Christophe Clement , Annie Millery-Vigues , Tamara Münkemüller , Yves Perrette , Jérôme Poulenard
Publication : European Journal of Soil Science
Date : 2025
Volume : 76
Issue : 1
Pages : e70050
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Aim Land surface models (LSMs) currently represent each plant functional type (PFT) as an average phenotype, characterised by a set of fixed parameters. This rigid and constant representation is a limit in understanding the dynamics of highly diverse ecosystems, such as permanent grasslands, and their response to global change. Location France. Time Period 2001–2019. Major Taxa Grassland plant species. Methods We incorporated spatially explicit trait variability at the France scale in the ORCHIDEE land surface model to assess how the net primary productivity (NPP) will spatially vary over the years. More precisely, we focused on three key functional traits that govern the NPP of grassland ecosystems: specific leaf area (SLA) and leaf nitrogen content (LNC), as measured traits, and leaf lifespan (LLS) as an estimated trait. Community-weighted means (CWM) were implemented in various combinations with prescribed and spatially varying traits. We compared the outcomes of each NPP simulation to remotely sensed proxies of productivity by using the MODIS satellite-driven NPP products. Results The sensitivity of NPP to traits depends on climate conditions, such as temperature and water limitation. Considering trait variability decreases the NPP in the most productive regions (plains) and increases the NPP in the less productive regions (mountains) compared to the case with constant trait values. This leads to a more homogenous NPP across France. Compared to the observed MODIS NPP and FLUXCOM GPP, the simulation using varying traits improves the spatial NPP and GPP variations in several regions and most climate conditions. Main Conclusions Based on the existing trait data, we revealed that incorporating the CWM of traits in an LSM such as ORCHIDEE can be effectively performed. Improving the modelling and predictions by considering the relationships between biodiversity, functional biogeography, and ecosystem functioning is essential in current and future ecological research.
Auteurs, date et publication :
Auteurs Sara Chebbo , Cyrille Violle , Lucie Mahaut , Jens Kattge , Marc Peaucelle , Philippe Choler , Nicolas Viovy
Publication : Journal of Biogeography
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Photosynthesis, electron transport to carbon assimilation, photorespiration and alternative electron transport, light absorption of the two photosystems, antioxidative protection and pigment contents were investigated in S. alpina leaves. S. alpina is an alpine snow-bed plant which can be found with green leaves after snowmelt. At least 24% of the leaves were formed at the beginning of the vegetation period in the previous year and survived two consecutive vegetation periods under contrasting environmental conditions. In leaves still covered by snow (SNOW), the parameters of antioxidative protection and carbon assimilation were lower than in leaves from the previous vegetation period (NEW) or several weeks after snowmelt (OLD). Directly after snowmelt, antioxidative protection was strongly but transitionally increased. The senescence of leaves did not depend on antioxidative scavenging capacity. Lower carbon assimilation was not related to increases in alternative electron flow (ETRalt) in SNOW leaves. In the second vegetation period, light absorption by PSII decreases in favour of PSI in OLD leaves. This allows OLD leaves to keep the electron transport chain more oxidised and to support photorespiration with increased ATP synthesis by cyclic electron transport around PSI. This study describes how the leaves of a unique plant can cope with contrasting environmental conditions.
Auteurs, date et publication :
Auteurs Peter Streb , Philippine Dubertrand , Gabriel Cornic , Kamel Soudani , Giovanni Finazzi
Publication : Physiologia Plantarum
Date : 2025
Volume : 177
Issue : 1
Pages : e70045
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Revealing the effects of multiple global change drivers on ecosystem dynamics and functioning is a crucial endeavour, which necessitates the use of appropriate tools. Here, we present the Aquatic Metatron, a unique mesocosm facility providing a large-scale experimental resource to study the combined effects of global change components, in particular climate change and habitat fragmentation, on the ecological and evolutionary dynamics of aquatic ecosystems. The Aquatic Metatron consists of 144 mesocosms of 2 m3 each that can be connected to each other with aquatic corridors, and—for a subset of them—with aerial corridors. This enables effective control of dispersal across meta-ecosystems. In addition, the temperature in each mesocosm is supervised and precisely controlled, either through a heating (all mesocosms) or a cooling (72 mesocosms) system. All mesocosms can be monitored automatically for abiotic and biotic factors (pH, dissolved oxygen, conductivity, turbidity and chlorophyll a) allowing for long-term experimentation. We tested the platform by conducting three experiments involving the manipulation of various components of global change: climate warming, biodiversity loss, eutrophication and aquatic/aerial fragmentation. The technical innovations of the platform have been validated, in particular its capacity to accurately recreate multiple climatic scenarios (e.g. heatwaves, warming, cooling) and the possibility of using aerial and water corridors to simulate fragmented landscapes. The Aquatic Metatron is located in the south-west of France (https://sete-moulis-cnrs.fr/fr) and is part of AnaEE France and AnaEE-ERIC (https://www.anaee.eu/), which are large-scale research infrastructures. The Aquatic Metatron is a research facility accessible to external researchers and projects.
Auteurs, date et publication :
Auteurs Murielle Richard , Alexandre Garreau , Elvire Bestion , Julien Cucherousset , Jose M. Montoya , Simon Blanchet
Publication : Methods in Ecology and Evolution
Date : 2025
Volume : 16
Issue : 1
Pages : 57-65
Catégorie(s)
#CNRS #Metatron aquatiqueRésumé
Agricultural intensification reduces not only biodiversity in agroecosystems but also key ecosystem functions such as soil fertility. By reintroducing biological diversity in fields, weeds may enhance soil biological fertility through their influence on crop microbiota. However, letting weeds grow in crop fields will depend on weed competitiveness, farmers’ perception and acceptance, and on crop management, which influences the occurrence and the abundance of weeds in the field. This study assessed the use of eight weed species to modify wheat plant root endospheric mycobiota, and the applicability of using these plants for mycobiota enrichment in the field. By combining controlled lab experiments and field studies, we demonstrated that weeds act either as a refuge for a high diversity of fungi or as a vector for transferring fungi to the crop, particularly symbionts. Weeds differed in their competitive effect on wheat growth and only three species significantly reduced wheat growth. Interviews with farmers’ revealed that weed species were better known and more appreciated in crop fields by organic farmers than by conventional farmers. Floristic surveys confirmed that both weed occurrence and cover were higher in organic fields than in conventional fields. A multicriteria analysis showed that Trifolium repens and V. persica had the highest potential for promoting wheat plant mycobiota. Among the weed species tested, these two are worth considering as auxiliaries to improve soil biological fertility in crop fields. Their use with the goal of selecting appropriate crop mycobiota should be relatively easier in organic farms where weeds are better accepted, whereas their use in conventional farms would require raising farmers’ awareness of the benefits of weeds for soil fertility.
Auteurs, date et publication :
Auteurs Claire Ricono , Jie Hu , Philippe Vandenkoornhuyse , Audrey Alignier , Cendrine Mony
Publication : Agriculture, Ecosystems & Environment
Date : 2025
Volume : 379
Pages : 109357
Catégorie(s)
#CNRS #EcoGenO #Université de RennesAuteurs, date et publication :
Auteurs Ciaran Laverty , Kyle D. Green , Jaimie T. A. Dick , Daniel Barrios-O’Neill , Paul J. Mensink , Vincent Médoc , Thierry Spataro , Joe M. Caffrey , Frances E. Lucy , Pieter Boets , J. Robert Britton , Josephine Pegg , Cathal Gallagher
Publication : Biological Invasions
Date : 2025
Volume : 19
Issue : 5
Pages : 1653-1665