HAL - La Rochelle Université, Archives Ouvertes
Not a member yet
19516 research outputs found
Sort by
Vers un outil web aidant les acteurs de l'aménagement du territoire (de la planification au design) à mieux intégrer les sols dans leurs processus et leurs pratiques.
No full textInternational audienceSoil is an essential part of the Earth continental surface, but it is submitted to a multitude of threats. The associated degradation is at risk for human being and ecosystems. That is why the integration of soil in spatial planning and design is essential. Spatial planners and designers however usually lack knowledge on soils. In addition, soils are not directly considered in current sectorial regulations. The European soil monitoring law should help increase awareness on soils and promote the use of the various tools and methods already developed to qualify soils. To fill the lack of tools to help planners and designers find out the right soil tools/methods to answer their needs along their process, the EU funded SPADES project is developing a webtool called Navigator. The objective of this abstract is to present the users’ need analysis to the soil community to get its feedback as a target group of the soil-planner Navigator. The users’ needs analysis is based on meetings with stakeholders from the pilots involved in the SPADES project, on a taskforce of stakeholders from the SPADES pilots and other volunteers. National and international events are also opportunities to interact directly with professionals and experts
Seasonal and interannual dynamics of the Aiguillon Bay salt marsh expansion
No full textInternational audienceCoastal salt-marsh/mudflat environments play a crucial role in capturing, sequestering, and storing CO₂ while protecting the coastline from extreme events. They are also essential habitats for biodiversity conservation, supporting both fauna and flora. Understanding and predicting their morphological evolution is crucial for assessing salt-marsh response to climate change and sea-level rise. Among these environments, salt marshes remain particularly challenging to monitor due to their complex spatial dynamics. Traditional approaches rely on historical cartography, aerial photographs, LiDAR surveys, or satellite imagery, where vegetation is most often delineated manually. However, several obstacles complicate the detection of salt marshes in coastal mudflat environments: regular mowing for livestock feeding and the presence of biofilms with spectral signatures similar to vegetation. While these approaches provide insights into long-term evolution, the availability of free multispectral satellite missions (Landsat, Sentinel-2) offers high-resolution data suitable for monitoring salt marsh dynamics at seasonal to multi-annual scales. This research is part of the La Rochelle Territoire Zéro Carbone (LRTZC) project, which aims to reach carbon neutrality at the scale of the La Rochelle urban area by 2040. We propose a semi-automatic approach to quantify both the trend and seasonality of salt marsh expansion in the Bay of Aiguillon from Landsat and Sentinel-2 imagery
Le chevalier qui fist les cons parler 2 - Édité et traduit d'après le ms. Harley 2253
No full textLe chevalier qui fist les cons parler 2 - Édité et traduit d'après le ms. Harley 225
Spatial models of cetacean density in European Atlantic waters based on SCANS-IV summer 2022 survey data
No full textThe 4th iteration of large-scale line-transect surveys of cetaceans in European Atlantic waters (SCANS) was conducted in the summer of 2022. SCANS-IV covered a 1.7 million km2 study area stretching from the Strait of Gibraltar to southern Norway, providing robust abundance estimates and trends for regularly occurring cetacean species. In this report, we summarise the development and results of predictive habitat-based models of cetacean density for seven species and two species groups using survey effort and sighting data from the SCANS-IV surveys conducted during summer 2022
Exposure to polycyclic aromatic hydrocarbons and phthalate diesters in a threatened freshwater turtle <i>Emys orbicularis:</i> effects of age, sex, and temporal variation
No full textInternational audienceFreshwater ecosystems constitute major sinks for organic contaminants, increasing pressure on already threatened environments and jeopardising the unique biodiversity they harbour. In addition to the persistence of legacy compounds, pollutants of various families are being released into the environment, such as polycyclic aromatic hydrocarbons (PAHs) and phthalate diesters (PAEs). Heretofore, these pollutants have received insufficient attention in freshwater vertebrates, particularly in reptiles, considering their potential to trigger detrimental effects on organisms. During two years (2019 and 2020), we quantified plasma levels of 46 compounds from 6 chemical families in two monitored populations of the European pond turtle (Emys orbicularis) in the Camargue wetland, France. PAHs and PAEs were often found concomitantly and with similar occurrences and levels in the two populations. We observed similar inter-annual variations in PAHs and PAEs with differences between males and females, highlighting the need for a better understanding of the role of sex in the exposure pathway and the toxicokinetics of contaminants, especially in turtles. The negative relationship between PAH levels and age, as well as the high intra-individual variation in levels of both contaminant families, provides further evidence of limited bioaccumulation of these pollutants in the blood of E. orbicularis. This could be explained by the metabolic biotransformation of parent compounds and the need to quantify the levels of PAH metabolites and phthalate monoesters. Finally, our work highlights the need for long-term monitoring and assessment of the potential maternal transfer of these contaminants in order to determine the risks for the conservation of turtle populations that are already exposed to a wide range of contaminants
Off target: herbicides applied in cereal fields exclude non-competitive species, while replacing them by competitive weeds
No full textInternational audienceWeed diversity plays an important role in maintaining resilient agroecosystems, yet agricultural practices, such as pesticide applications, significantly shape weed communities. Previous studies have primarily focused on comparing organic and conventional farming, with a particular emphasis on landuse intensification, with less attention on the impact of pesticides. Our study examined the impact of herbicide, fungicide, and insecticide use -both in terms of Treatment Frequency Index (TFI), i.e. intensity of application, and quantity -on weed communities in 96 non-organic cereal fields over 4 years. Interestingly, our results indicate that fungicide application intensity decreased weed abundance by 11.6% and species richness by 14.6% for each one-standard-deviation (1-SD) increase in TFI, whereas the total quantity applied (QA) did not. In contrast, for herbicides, QA had a stronger negative impact on weed communities than TFI, with a 14.3% decrease in weed abundance and a 12.4% decrease in species richness for each 1-SD increase in QA. This suggests that TFI of fungicide, which may reflect low-dose but frequent applications, could exert indirect and long-term effects on weed suppression, potentially by altering symbiotic arbuscular mycorrhizal fungi in the soil. In comparison, QA of herbicide more directly reflects the toxic load delivered to weeds and is therefore a better predictor of their suppression. Based on a combination of multivariate and univariate analyses and the study of underlying mechanisms in community changes, our results reveal that herbicides are the main factor shaping weed communities by decreasing the abundance of non-target/non-competitive species while replacing them by problematic, competitive to crops, weed species. These findings point out the potential ineffectiveness of herbicides application on problematic weeds and emphasize the need to reconsider the use of herbicides to maintain weed diversity in agricultural landscapes
Mesopelagic Fish Traits: Functions and Trade‐Offs
No full textInternational audienceFishes inhabiting the mesopelagic zone of the world's oceans are estimated to account for the majority of the world's fish biomass. They have recently attracted new attention because they are part of the biological carbon pump and have been reconsidered as a contribution to food security. Hence, there is an urgent need to understand how environmental conditions and species interactions shape their assemblages, and how they contribute to the functioning of marine ecosystems. Trait‐based approaches are valuable for addressing these types of questions. However, the biology and ecology of mesopelagic fishes are understudied compared to fishes in shallow and epipelagic waters. Here, we synthesise existing knowledge of traits of mesopelagic fishes and relate them to their role in survival, feeding and growth and reproduction, the key functions that contribute to fitness. Vertical migrations, specialised vision and the use of bioluminescence are among the most striking adaptations to the conditions in the mesopelagic realm. Many traits are interrelated as a result of trade‐offs, which may help to understand selection pressures. While morphological traits are straightforward to observe, major knowledge gaps exist for traits that require frequent sampling, assessment under experimental conditions or age determination. The unique adaptations of mesopelagic fishes need to be included in management strategies as well as fundamental research of the habitat
Crop yield loss under high insecticide regime driven by reduction in natural pest control
No full textInternational audienceCurrent agricultural pest management mainly relies on the use of synthetic insecticides with strong adverse impacts on the environment or humans. Decreasing crop productivity in the case of pesticide-use reduction has been a prominent argument against such reductions. However, the relationship between insecticide use and crop yields is complex. Through long-term monitoring of yields, farming practices, pest populations and natural pest control across 383 fields of oilseed rape—one of the most insecticide-intensive crops in Europe—we reveal a negative relationship between yield and insecticide use when application rates exceed 36.2 g ha −1 of active ingredients. Our analyses indicate that this negative effect of insecticide use is primarily driven by its adverse impacts on natural pest control, affecting both insect pests and weed seed regulation. This leads to increased pest abundance levels and, consequently, greater yield losses. Our study demonstrates that beyond a certain threshold, insecticides not only impose adverse environmental impacts and additional application costs for farmers, but also negatively affect overall crop production levels. Our results highlight the need for solutions that extend beyond the farm level, since we also demonstrate that landscape elements such as meadow and crop diversity play a crucial role in regulating pest populations
Influence of process parameters on flexural properties of composites reinforced with continuous fiber produced by material extrusion
No full textInternational audienceAdditive manufacturing revolutionized the production of personalized objects from 3D models across various industries, including medical, aerospace and automotive, primarily through the widely accessible material extrusion process. Despite additive manufacturing advantages, the parts fabricated using additive manufacturing often exhibit lower elastic properties compared to conventionally injection-molded thermoplastic components. Adding fiber-reinforced polymer composites during printing has a significant influence both on tensile and flexural strength, as well as on the overall quality of resulting composite structure. Adding a low volume of reinforcement (<15%) to a sample is advantageous without increasing the stiffness of the sample significantly. This study aims at investigating the impact of low reinforcement volume and placement on the flexural properties of samples while assessing the repeatability of the printing process through 3-point bending tests. A finite element model of the test is also proposed in order to predict the flexural properties of samples. Process induced defects such as voids are modeled in the samples as the results show that the addition of fiber-reinforced polymer led to an increase in the porosity rate. The experimental results of 3-point bending test were compared with those of finite element analysis. Printing rules aimed at minimizing errors and addressing limitations inherent in the printing process are defined in the current study
Metapopulation distribution shapes year‐round overlap with fisheries for a circumpolar seabird
No full textInternational audienceAlthough fisheries bycatch is the greatest threat to many migratory marine megafauna, it remains unclear how population exposure to bycatch varies across the global range of threatened species. Such assessments across multiple populations are crucial for understanding variation in impacts and for identifying the management bodies responsible for reducing bycatch. Here, we combine extensive biologging data from white-chinned petrel (Procellaria aequinoctialis) populations (representing >98% of their global breeding population) with pelagic and demersal longline and trawl fishing effort to map the global distribution and fisheries-overlap hotspots for the most bycaught seabird in the Southern Hemisphere. We tracked the year-round movements of Kalinka Rexer-Huber and Thomas A. Clay share joint first authorship