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Competing effects of charge-carrier and impurity scattering limiting phonon heat conduction in heavily-doped silicon
No full textWith respect to undoped semiconductors, thermal transport by phonons is limited by two additional mechanisms when doping increases: charge-carrier and impurity scattering. Previous works provided contradicting conclusions on the dominant doping-induced scattering mechanism in silicon. In this work, we clarify the competing roles of impurity and charge-carrier scatterings of phonons in the reduction of the lattice thermal conductivity in n-and p-doped silicon, by comparing experimental results obtained with the 3ω method and predictive DFT-based calculations for a large set of doping concentrations and a wide temperature range. The analysis allows delimiting the doping and temperature ranges where (i) extrinsic scattering surpasses intrinsic (phonon-phonon and phonon-isotope) one and (ii) one of the two doping-induced mechanisms plays the dominant role. We observe that the experimental setup impacts both the thermal conductivity value and the critical doping concentration at which the thermal conductivity is reduced by half
Assessment of surface water storage in the Amazon floodplains by hydrological modelling and earth observation data
No full textInternational audienceInland surface waters in tropical regions are fundamental to global hydrological and biogeochemical cycles, yet the quantification of floodplain freshwater storage and its variability remains limited. This study provides a basin-wide assessment of the spatiotemporal dynamics of floodplain water storage in the Amazon Basin over the period 2000-2018. We developed an integrated framework combining in situ discharge measurements, multisensor remote sensing datasets, and process-based hydrological modelling to quantify daily floodplain hydrodynamics at high spatial resolution. Floodplain extent was derived from L-band passive microwave observations from Soil Moisture and Ocean Salinity (SMOS) satellite, while water surface elevation was constrained using altimetry data (Jason-2/3 and Sentinel-3). The hydrological model (SWAF-FP), specifically improved to represent floodplain-river interactions, was calibrated at eight gauging stations and evaluated using approximately 4,000 altimetry-based floodplain water level records. Model performance demonstrated high skill, with a mean R2 of 0.83 for discharge and R2 > 0.62 for floodplain water surface elevation. The results indicate a mean annual surface water storage of 1800 +/- 854 km3 across the Amazon Basin, with pronounced seasonal cycles and interannual stability at the basin scale. The Negro and Madeira sub-basins were identified as the dominant contributors to total floodplain storage, accounting for approximately 480 km3 (33.6 %) and 312 km3 (12.5 %), respectively. This study provides the first consistent long-term quantification of Amazonian floodplain water storage dynamics at daily resolution. The results emphasize the critical role of floodplains in regulating basinscale hydrological fluxes and offer a robust observational-modeling framework for improving large-scale hydrological and Earth system models in tropical regions
Understory plant indicator values poorly perform at monitoring temporal changes in French forest soil chemical properties
No full textInternational audienceUnderstory plant communities are widely used to infer soil conditions through species indicator values (IVs), scores reflecting species’ ecological preferences for factors such as soil acidity, moisture, or nutrient levels. While their reliability to describe soil conditions along spatial gradients is well established, their ability to capture temporal changes in soil chemistry remains largely untested at both temporal and geographical scales. We combined 26 years of vegetation monitoring with two French national soil surveys (1993–1997; 2007–2012) across 102 permanent forest plots to assess the reliability of community soil indices (CSIs) as bioindicators of soil pH, carbon-to-nitrogen ratio (C/N), and extractable phosphorus. CSIs were computed by averaging species IVs for each plot and survey. Temporal dynamics of measured soil properties and CSIs were analyzed using mixed-effects models at the national scale, while local trends were estimated separately for each plot to directly compare measured and vegetation-inferred changes. CSIs showed strong spatial correlations with measured pH and C/N, but weaker relationships for phosphorus. In contrast, no significant coupling was found between temporal changes in CSIs and measured soil parameters, with frequent mismatches in both direction and magnitude at the plot level. Measured soil dynamics were mainly driven by initial edaphic conditions and stand age, whereas CSI dynamics responded primarily to canopy openness and anthropogenic disturbances such tree harvesting. These findings confirm the value of IVs for spatial bioindication but highlight their limited sensitivity for detecting long-term soil changes, especially where soil changes remain modest
Microstructural and sorption properties evolution on leached geopolymers for strontium decontamination
No full textInternational audienceGeopolymers are promising materials to be used as strontium adsorbent in fixed-bed processes for nuclear wastewater decontamination. Nevertheless, geopolymer formulation parameters – SiO2/M2O, H2O/M2O molar ratios – influence microstructure and strontium sorption property evolution under water leaching. Increasing the SiO2/M2O ratio increases the geopolymer’s compressive strength (16 MPa to 35 MPa) and reduces silicon leaching in water (1.31 mmol.g−1 to 0.26 mmol.g−1). This resistance to leaching results from a silicon-richer structure, reinforcing hydrolysis resistance. An increase in H2O/M2O ratio reduces the material’s strength (59 MPa to 28 MPa), and increases leaching due to greater porosity. Then, water leaching lowers sorption properties of the geopolymers by releasing AlIV, which are exchange sites for cations. Nonetheless, the composition with the lowest AlIV concentration achieved the highest distribution coefficient (KD) and fastest kinetics. This highlights the critical role of the silicon environment for optimal cation trapping, outmatch the total concentration of AlIV sites
First evidence of deleterious effect of pesticide mixture on health status in semi-captive grey partridges
No full textInternational audiencePesticides are mainly used in agroecosystems to control pests. Due to their limited specificity, the resulting widespread contamination may cause unintended effects on non-target organisms that use these habitats. While increasing attention is paid to the relationship between single substances and phenotype on non-target species, their combined impacts are still largely unknown. Since interactions between pesticides may also impact organisms' health, studying them as complex mixtures is the more realistic approach. Here, we present the first experimental study testing the relationship between an environmentally relevant pesticide mixture and health biomarkers on a farmland avian non-target model. To do so, we used 40 semi-captive grey partridges (Perdix perdix) fed for five months with conventional grains. Their plant protection product (PPP) load (i.e., the number of PPPs, the total sum of scaled pesticide concentrations and the total toxicity index) in blood and proxies of health status (evaluated using behavioral and physiological features) were monitored at the end of the exposure period. We demonstrated, for the first time, concerning correlations between PPP load indexes and bird healthrelated features (physical activity, flight initiation distance, eye ring redness and acetylcholinesterase activity). Overall, we highlighted the urgent need to consider environmentally-relevant PPP mixture when biomonitoring non-target vertebrates in ecotoxicological studies.</div
Plan de Gestion de Données pour le projet BioLycTom Data Management Plan of BioLycTom project
No full textInternational audienceDMP of the BioLycTom project where two surveys were carried out among market gardeners in France.PGD du projet BioLycTom (Lutte biologique contre l'agent de l'acariose bronzée, Aculops lycopersici) où deux enquêtes ont été menées auprès de maraîchers en Franc
Tree Pólya Splitting distributions for multivariate count data
No full textInternational audienceIn this article, we develop a new class of multivariate distributions adapted for count data, called Tree Pólya Splitting. This class results from the combination of a univariate distribution and singular multivariate distributions along a fixed partition tree. Known distributions, including the Dirichlet-multinomial, the generalized Dirichlet-multinomial and the Dirichlet-tree multinomial, are particular cases within this class. As we will demonstrate, these distributions are flexible, allowing for the modeling of complex dependence structures (positive, negative, or null) at the observation level. Specifically, we present the theoretical properties of Tree Pólya Splitting distributions by focusing primarily on marginal distributions, factorial moments, and dependence structures (covariance and correlations). A dataset of abundance of Trichoptera is used, on one hand, as a benchmark to illustrate the theoretical properties developed in this article, and on the other hand, to demonstrate the interest of these types of models, notably by comparing them to other approaches for fitting multivariate data, such as the Poisson-lognormal model in ecology or singular multivariate distributions used in microbiome
Prevalence of mealybug wilt-associated viruses in pineapple 'Queen Victoria' cultivars in Reunion Island and the potential of virus-free vitroplants for disease management
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/615299/) * Autres projets (id;sigle;titre): ;;(REU) Dispositif de partenariat en santé et biodiversité//International audienceMealybug wilt disease of pineapple (MWP) poses a significant threat to global pineapple production, yet its etiology remains poorly understood. The disease is believed to involve mealybugs, multiple pineapple mealybug wilt-associated viruses (PMWaVs, genus Ampelovirus), and possibly other viruses from the Badnavirus, Secovirus, and Vitivirus genera. This study examines the distribution and prevalence of three ampeloviruses (PMWaV1, PMWaV2, PMWaV3) and two badnaviruses (PBERV, PBCOV), previously associated to MWP symptoms, across 15 pineapple plots of the 'Queen Victoria' cultivar in Reunion Island. A total of 450 symptomatic and asymptomatic leaf samples were analyzed using PCR and RT-PCR-based diagnostics. Globally, 93 % of samples were infected with at least one virus, and 76 % were co-infected with two to four viruses. PMWaV1 (78 %) and PBCOV (87 %) were the most prevalent, while PBERV was not detected. Virus presence was associated with leaf dieback, wilting, and curling. Leaf reddening and yellowing, commonly associated with MWP, were not associated with viral infection, suggesting that other biotic or abiotic factors may be responsible for these symptoms. Viral infections and MWP symptoms were significantly lower in plots planted with vitroplants (VPs) compared to those using suckers, highlighting the potential of VPs in reducing viral infections. These findings highlight the complexity of MWP and underscore the potential benefits of using virus-free VPs to manage the disease
Un partage d’expérience autour de la pratique de l’interdisciplinarité sur les feux : le projet EcoSoFI (2022-2024)
No full textInternational audienceLes collaborations inter/transdisciplinaires autour de la compréhension des feux et de leur gestion sont plébiscitées, mais leur mise en œuvre ne va pas pour autant de soi. A partir du partage d’expériences de plusieurs scientifiques et gestionnaires, le présent article restitue la démarche que nous avons adoptée pour comprendre ces difficultés ; et tire quelques constats et propositions. Onconstate notamment la dominance des sciences biophysiques et le poids de la modélisation dans les interfaces entre recherche et gestion. Au sein des SHS, on observe également des partitions entre disciplines et sous-disciplines, ainsi qu’une « interdisciplinarité inachevée » dans l’analyse des changements de régimes de feux. La spécialisation disciplinaire a conduit à une autonomisation du questionnement et des méthodes, qui ne sont plus explicitées ni interrogées au regard des autres approches et du terrain. Nos propositions consistent à remettre en question les catégories implicites concernant les pratiques et les savoirs liés aux feux et à définir des protocoles de recherche permettant des problématisations communes à partir d’études de cas localisées et « concrètes »
A narrative review of the impact of anthropogenic light and noise on owls
No full textInternational audienceToday, owls are exposed to increasingly brightly lit nights and noisy environments because of human activities. To understand the impacts of artificial light at night (ALAN) and anthropogenic noise we performed an evidence synthesis. We searched four literature databases and Google Scholar and we collected 39 relevant articles (1945-2024) providing 125 cases (64 on light pollution and 61 on noise pollution), targeting 25 species (c. 10% of owl species). We found harmful effects of both sensory pollutants on several outcomes. First, ALAN tends to reduce acoustic communication and to be associated with a lower occurrence of owl species, although it is difficult to confirm whether ALAN leads to silent or absent owls. Moreover, ALAN disturbs owl-prey interactions. Although light probably improves owl vision, the light-avoidance behaviour of small mammals could result in poorer hunting success of owls feeding on mammals. Conversely, ALAN enhances food provisioning and even breeding of owls feeding on insects that are attracted by light, to the detriment of these prey populations. Second, human-induced noise clearly tends to reduce owl vocalization, yet that vocalization may be essential to communication between individuals. The ability of owls to detect prey (hunting success) is also reduced under noise exposure (even at low amplitude), probably as the result of masking and distraction. Studies also demonstrate that anthropogenic noise can cause physiological and behavioural stress and disturbance to owls. Such adverse effects may contribute to declines in reproduction and occurrence of owls observed in noisy areas. As a result, we recommend reduction of both sensory stressors as much as possible, for owls and for ecosystem stability, for example by maintaining and restoring quiet and dark areas. We also recommend more consideration of owls in sensory ecology research to fill knowledge gaps.De nos jours, les rapaces nocturnes sont exposés à des nuits de plus en plus lumineuses et à un environnement de plus en plus bruyant en raison des activités humaines. Pour comprendre l'impact potentiel de la lumière artificielle nocturne et du bruit anthropique, nous avons réalisé une revue de littérature. Nous avons interrogé 4 bases de données bibliographiques et Google scholar et nous avons collecté 39 articles pertinents (1945–2024) fournissant respectivement 125 cas (64 sur la pollution lumineuse et 61 sur la pollution sonore), ciblant en tout 25 espèces (~10% des Strigiformes ). Nous avons trouvé plusieurs effets néfastes des pollutions lumineuse et sonore. Tout d'abord, la lumière artificielle tend à diminuer la communication acoustique et est associée à une occurrence plus faible, bien qu'il soit difficile de confirmer si les chouettes sont plus silencieuses ou absentes. Il est indéniable que l'éclairage nocturne perturbe les interactions entre les rapaces nocturnes et leurs proies, ce qui peut expliquer en partie cette situation pour les espèces qui se nourrissent de rongeurs, selon les effets documentés de la luminosité de la lune: alors que la lumière améliore la vision des chouettes/hiboux, le comportement d'évitement de la lumière des petits mammifères pourrait entraîner un moins bon succès de chasse. Inversement, l'éclairage artificiel améliore l'approvisionnement en nourriture et même la reproduction des chouettes insectivores, probablement au détriment des populations de proies attirées par la lumière. Deuxièmement, les sons artificiels tendent clairement à diminuer la vocalisation des chouettes, pourtant essentielle à la communication (par exemple entre partenaires). La capacité des Strigiformes à détecter leurs proies (succès de chasse) est également réduite en cas d'exposition au bruit (même à faible amplitude), sûrement par un effet de masquage et de distraction. Les données démontrent également que le bruit anthropique provoque du stress et des perturbations, tant au niveau physiologique que comportemental. Ces effets négatifs peuvent être responsables de la tendance à la baisse de la reproduction et de l'occurrence des rapaces nocturnes qui est également observée dans les zones bruyantes. Par conséquent, nous recommandons de réduire autant que possible les deux facteurs de stress sensoriel—pour les chouettes/hiboux et pour la stabilité des écosystèmes—par exemple en maintenant et en rétablissant des zones calmes et sombres. Nous demandons également que les Strigiformes soient davantage pris en compte dans la recherche en écologie sensorielle afin de combler les lacunes en matière de connaissances