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Reconstructing the freshwater paleoecosystems diversity of Toros-Menalla (Late Miocene, Chad) from an integrated faunal perspective
No full textAquatic environments are critical components of past ecosystems that shaped species distribution and survival. Yet in hominin-bearing fossil sites, they are often treated as uniform or poorly detailed elements of “mosaic” landscapes, failing to capture their ecological complexity. In the northern Chad Basin, the late Miocene Toros-Menalla area records vast perilacustrine systems where aquatic and terrestrial ecosystems were deeply interconnected. While terrestrial vertebrate assemblages have been well characterised as reflecting a heterogeneous landscape, the aquatic component remains poorly resolved. Variations in depositional settings, aquatic vertebrate diversity, stable isotope data, and field observations point to a more complex and dynamic network of freshwater habitats. An integrative study of aquatic and semi-aquatic vertebrate assemblages from five Toros-Menalla sites reveals distinct faunal structures reflecting different ecological preferences and depositional conditions, ranging from perilacustrine floodplains to swampy, vegetated, or marginal waters and large open waterbodies with current. These environments, distributed across several hundreds of meters up to 30 km, represent lateral habitat diversity rather than temporal succession, as most assemblages formed geologically instantaneously (except for TM266, where vertical mixing could be hypothesised). Comparison with the present-day Bol Archipelago on the northeastern shores of Lake Chad provides a suitable analogue for the Toros-Menalla paleoenvironment. There, interdunal water bodies of varying depth and connectivity create a dynamic network of aquatic habitats at a similar spatial scale. This study underscores the need for systematic, grid-based collection and sieving of fossils to capture representative aquatic biodiversity and structure, and to reconstruct freshwater paleoenvironments with greater ecological precision
Trait-dependent declines of threatened endemic trees following plant invasion on a tropical oceanic island
No full textInternational audienceBiological invasions are a leading cause of the ongoing biodiversity crisis, and particularly so on islands. However, the role of invasive alien plants (IAPs) as a driver of native plant declines and extinctions remains unclear. The inherently slow and gradual nature of plant extinctions, especially that of long-lived woody species, could be a reason. Here, we examined temporal trends in subpopulations of 28 threatened endemic tree (TET) taxa. We questioned the frequency with which they decline in association with IAPs on Reunion Island (South-West Indian Ocean), and asked whether the most susceptible TET taxa exhibit characteristics that could reveal the underlying ecological mechanisms. We resurveyed 182 historically described subpopulations and tested whether observed trends of juvenile and adult TETs correlate with the abundance in IAPs using path analyses, while distinguishing TET taxa with respect to their leaf–height–seed characteristics and extinction risk. The trend of adult TETs was not affected by IAPs but that of juvenile TETs was negatively correlated with the abundance of IAPs in the understory layer. This was particularly the case for TET taxa with conservative resource-use strategies (low specific leaf area or low maximum height), whose juveniles might be particularly susceptible to competition with IAPs, but not for TET taxa with large seeds, whose metabolic reserves make seedlings more likely to attain a critical size. These findings suggest that IAPs can significantly contribute to the extinction dynamics of trees, primarily by limiting regeneration through competitive exclusion, and that their impacts vary depending on the traits of the affected taxa
Effets du contrôle de corruption sur le développement économique en République Démocratique du Congo Démocratique du Congo : analyse empirique et pistes d'avenir
No full textInternational audienceAbstract This study examines the relationship between corruption control and economic development in the Democratic Republic of Congo (DRC) from 1996 to 2023. Using an ARDL (Auto-Regressive Distributed Lag) econometric model, the research evaluates how combating corruption influences economic development. The results demonstrate that, in the short term during the study period, corruption control (COCOR) has a significantly positive impact on the Human Development Index (HDI). Specifically, a 1-point increase in the corruption control indicator leads to a 0.000485 rise in the Human Development Index. In the long term, during the study period, corruption control (COCOR) also has a significantly positive impact on the Human Development Index (HDI). Indeed, a 1-point increase in the corruption control index (COCOR) results in a 0.004844-point increase in the Human Development Index (HDI).Cette recherche examine la relation entre le contrôle de corruption et le développement économique en République Démocratique du Congo (RDC) de 1996 à 2023. En utilisant un modèle économétrique ARDL (Auto Regressive Distributed Lag), l'étude évalue comment la lutte contre la corruption influence le développent économique. Les résultats de cette étude démontrent qu'à court terme, durant la période sous étude, le contrôle de corruption (COCOR) a un impact significativement positif sur l'indice de développement humain (IDH), En effet, la croissance de l'indicateur du contrôle de corruption de 1 point entraîne une augmentation de l'indice de développement humain de 0.000485; tandis qu'à long terme, durant la période sous étude, le contrôle de corruption (COCOR) a un impact significativement positif sur l'indice de développement humain (IDH). En effet, toute augmentation de l'indice de contrôle de corruption (COCOR) de 1 point entraine l'augmentation de l'indice du développement humain (IDH) de 0.004844 point
Impact of hygro-mechanical loading on crack initiation and propagation in orthotropic media : A numerical modeling approach
No full textInternational audienceMoisture content gradients play a crucial role in the mechanics of wood, significantly affecting its properties and overall behavior. Among the adverse effects induced by moisture content variations, crack initiation and propagation remain one of the major challenges in wooden structures. This paper presents an energy-based fracture mechanics approach that relies on the computation of invariant integrals to evaluate fracture parameters in orthotropic materials subjected to moisture content gradients. A new concept of crack initiation is introduced by an algorithm based on the bisection method, which leads to automatic crack propagation under hygro-mechanical loading. The fracture criteria are derived from the energy release rate through a novel formulation of the invariant integral Ain a moisture-coupled environment. The path-independence of this newly proposed integral is verified via finite element simulations under mixed-mode loading using the Mixed-Mode Crack Growth (MMCG) specimen. Both analytical and numerical formulations account for the combined effects of mechanical and moisture-induced pressure on the crack lips. The influence of these coupled pressures on crack initiation and propagation in wood under variable moisture content conditions is introduced and discussed. For all fracture modes, the initiation and propagation criteria are obtained through a moisture-driven propagation algorithm, which triggers automatic crack growth when a critical moisture content threshold is reached. The results demonstrate that the developed analytical tool, implemented within a finite element framework provides a reliable determination of the fracture parameters of wood under moisture content variations
Wealth and Solidarity Taxes in International Law : Constitutional Constraints and Policy Options
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Droit du commerce international et fiscalité: une perspective européenne
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Stearic acid fatty esters as biobased phase change materials for building applications: Structure–property relationships and climate-specific suitability
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To what extent are the IASI water vapour profiles representative of the conditions in the autumn before the HPE? Lessons learned from the WaLiNeAs campaign
No full textInternational audienceThe WaLiNeAs campaign took place along the north-western Mediterranean coast between October 2022 and January 2023. This period was marked by unusual weather conditions associated with dry autumn and winter. In such conditions and for the first time, eight ground-based stations equipped with water vapour Raman lidars were strategically deployed by four European countries. We studied the consistency of this network with the water vapour mixing ratio (WVMR) products derived from the Infrared Atmospheric Sounding Interferometer (IASI) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5), which assimilate IASI radiances. The statistical metrics used in the comparison are the mean bias (MB, defined as lidar -IASI or ERA5), the root mean square error (RMSE) and the correlation coefficient (COR). A positive MB of approximately 0.9 g kg -1 (respectively 0.6 g kg⁻¹) between 0.2 and 5 km above mean sea level (amsl) indicates a systematic underestimation of the WVMR by IASI (respectively ERA5). RMSE values range from 1 to 2 g kg -1 across all lidar stations for IASI and ERA5, while the measurement uncertainties of the lidars are typically below 0.4 g kg -1 . COR presents little variation between stations, it ranges from 0.7 to 0.8 and remains almost constant between 0.2 and 5 km amsl. Both the IASI and the ERA5 products appear to accurately reproduce the temporal variability of the vertical structure of water vapour in the low troposphere. Nevertheless, they show MB and RMSE significantly above the uncertainties of lidar measurements
Conclusion. L'empreinte singulière des sports olympiques d'hiver
No full textInternational audienceCe chapitre de conclusion referme l’aventure éditoriale vouée à explorer l’histoire des sports olympiques d’hiver. L’analyse souligne la singularité de ces sports et de l’évènement international qui les porte – soit les Jeux olympiques d’hiver. Elle revient en particulier sur la sécularisation paradoxale de la manifestation, le registre d’institutionnalisation spécifique des sports d’hiver, leur universalité discutable et leur avenir incertain au regard des bouleversements écologiques du XXIe siècle
Beyond species means – the intraspecific contribution to global wood density variation
No full textInternational audienceWood density is central for estimating vegetation carbon storage and a plant functional trait of great ecological and evolutionary importance. However, the global extent of wood density variation is unclear, especially at the intraspecific level. We assembled the most comprehensive wood density collection to date, including 109 626 records from 16 829 plant species across woody life forms and biomes (GWDD v.2, available here: doi: 10.5281/zenodo.16919509 ). Using the GWDD v.2, we explored the sources of wood density variation within individuals, within species and across environmental gradients. Intraspecific variation accounted for c . 15% of overall wood density variation (SD = 0.068 g cm −3 ). Variance was 50% smaller in sapwood than heartwood, and 30% smaller in branchwood than trunkwood. Individuals in extreme environments (dry, hot and acidic soils) had higher wood density than conspecifics elsewhere (+0.02 g cm −3 , c . 4% of the mean). Intraspecific environmental effects strongly tracked interspecific patterns ( r = 0.83) but were 70–80% smaller and varied considerably among taxa. Individual plant wood density was difficult to predict (root mean square error > 0.08 g cm −3 ; single‐measurement R 2 = 0.59). We recommend (1) systematic sampling of multiple individuals and tissues for local applications, and (2) expanded taxonomic coverage combined with integrative models for robust estimates across ecological scales.La densidad de la madera es fundamental para estimar el almacenamiento de carbono vegetal y constituye un rasgo funcional de gran importancia ecológica y evolutiva. Sin embargo, el alcance global de la variación de la densidad de madera no está claramente descrito, especialmente a nivel intraespecífico. Recopilamos la colección más completa de densidad de madera hasta la fecha, que incluye 109 626 registros de 16 829 especies de plantas leñosas de diversas formas de vida y biomas (GWDD v.2, disponible aquí: doi: 10.5281/zenodo.16919509 ). Utilizando la GWDD v.2, exploramos las fuentes de variación en la densidad de la madera entre individuos y especies, así como a través de gradientes ambientales. La variación intraespecífica representó aproximadamente el 15% de la variación total de la densidad de la madera (SD = 0.068 g cm −3 ). La varianza fue un 50% menor en la albura que en el duramen, y un 30% menor en la madera de ramas que en la del tronco. Los individuos en ambientes extremos (secos, cálidos, suelos ácidos) presentaron una densidad de madera mayor que sus congéneres en otros lugares (+0.02 g cm −3 , ~4% de la media). Los efectos ambientales intraespecíficos siguieron estrechamente los patrones interespecíficos ( r = 0.83), sin embargo, resultaron entre un 70% y un 80% menores y variaron considerablemente entre los taxones. La densidad de madera por individuo fue difícil de predecir (RMSE >0.08 g cm −3 ; R 2 de medición única = 0.59). Recomendamos (1) el muestreo sistemático intraespecífico de múltiples individuos para aplicaciones locales y (2) una cobertura taxonómica ampliada combinada con modelos integradores para obtener estimaciones robustas a través de las escalas ecológicas.La densité du bois est essentielle pour estimer le stockage de carbone de la végétation et constitue un trait fonctionnel d’une grande importance écologique et évolutive. Cependant, l’ampleur de la variation globale de la densité du bois reste mal caractérisée, en particulier au niveau intraspécifique. Nous avons rassemblé la base de données la plus complète à ce jour sur la densité du bois, comprenant 109 626 mesures provenant de 16 829 espèces de plantes ligneuses appartenant à diverses formes de vie et biomes (GWDD v.2, disponible ici: doi: 10.5281/zenodo.16919509 ). À l’aide de la GWDD v.2, nous avons exploré les sources de variation de la densité du bois au sein des individus, au sein des espèces et le long de gradients environnementaux. La variation intraspécifique représentait environ 15% de la variation totale de la densité du bois (SD = 0,068 g cm −3 ). La variance était 50% plus faible dans l’aubier que dans le duramen, et 30% plus faible dans le bois des branches que dans celui du tronc. Les individus vivant dans des environnements extrêmes (secs, chauds, sols acides) présentaient une densité du bois plus élevée que leurs congénères ailleurs (+0,02 g cm −3 , soit ~4% de la moyenne). Les effets environnementaux intraspécifiques reflétaient les tendances interspécifiques ( r = 0,83), mais étaient 70 à 80% plus faibles et variaient considérablement entre taxons. La densité du bois à l’échelle individuelle était difficile à prédire (RMSE >0,08 g cm −3 ; R 2 = 0,59). Nous recommandons (1) un échantillonnage systématique de plusieurs individus et tissus pour les applications locales et (2) un élargissement de la couverture taxonomique combiné à des modèles intégratifs afin d’obtenir des estimations robustes à travers les échelles écologiques