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Inter-species variability of root-knot nematode infection dynamics through the simultaneous monitoring of both pathogen and host development
No full textRoot-knot nematodes (RKN) cause significant crop yield losses worldwide. However, significant variations in the extent of damage are observed both within and among species. In this study, three economically important plant species in Mediterranean agriculture were selected based on their contrasting susceptibility to RKN infection. Infection dynamics were compared by simultaneously monitoring the development of both the pathogen and the host over two consecutive nematode generations. The resulting data confirmed pronounced differences in symptom expression, particularly during the second cycle. To identify potential sources of the observed variations in host susceptibility, a broad range of functional and architectural plant traits were studied through an integrated experimental-modelling approach. The results suggest that the higher susceptibility of tomato plants may result from the combined effects of reduced photosynthetic capacity and increased hydraulic sensitivity associated with small root diameter. Our results provide new insights into the mechanisms underlying plant tolerance to RKN, offering valuable guidance for plant breeding programs and for designing management strategies that sustain crop productivity while limiting prevent long-term soil infestation
Revisiter les modèles socioéconomiques associatifs - Historicité, Réciprocité, Territorialité, Activité
No full textInternational audienc
Local knowledge : the domestication of tropical fruit trees
No full textFruit trees provide food, drive economies and often holdsignificant sociocultural value, factors that have histori-cally driven the domestication of many species. The evo-lutionary journey shaped by gathering, eating and tradinghabits is largely overlooked. In Cameroon, a countryundergoing a food transition, the Agropolis Foundation's?Arbopolis' project used a participatory approach thatbrought together growers, consumers and researchers todemonstrate the importance of safou (the fruit of Dacry-odes edulis) in diet and cultural practices. These findingswill bolster the resilience of local food systems and sup-port the sustainable management of this species' geneticresources
Drivers and impacts of sediment deposition in Amazonian floodplains
No full textInternational audienceThe Amazon River carries enormous amounts of sediment from the Andes mountains, much of which is deposited in its floodplains. However, accurate quantification of the sediment sink at fine spatiotemporal scales is still challenging. Here, we present a high-resolution hydrodynamic-sediment model to simulate sediment deposition in a representative Amazon/Solimões floodplain. The process is found to be jointly driven by inundation, suspended sediment concentration in the Amazon River, and floodplain hydrodynamics and only weakly correlated with inundation level. By upscaling the sediment deposition rate (1.33 ± 0.24 kg m −2 yr −1 ), we estimate the trapping of 77.3 ± 13.9 Mt (or 6.1 ± 1%) of the Amazon River sediment by the Amazon/Solimões floodplains every year. Widespread deforestation would reduce the trapping efficiency of the floodplains over time, exacerbating downstream river aggradation. Additionally, we show that the deposition of sediment-associated organic carbon plays a minor role in fueling carbon dioxide and methane emissions in the Amazon
Ground‐Dwelling Spider Community Responses to Forest Management in a Mediterranean Oak Forest
No full textInternational audienceTimber production is one of the most important ecosystem services provided by hardwood forests, but clear‐cutting causes severe soil disturbance. There is a current need to develop alternative forest management practices to clear‐cutting in order to simultaneously promote timber production, preserve biodiversity and enhance forest health and economic value. Here, we experimentally manipulated a Quercus pubescens forest to evaluate the effects of a thinning gradient (i.e., partial tree removal) ranging from 25% to 75% basal area reduction and a logging residue retention (i.e., slash management) on ground‐dwelling spider abundance and species richness. These two alternative management practices were compared with clear‐cutting (100% basal area reduction) and logging residue exportation methods. In each treatment, we recorded soil temperature and moisture, understorey vegetation cover, richness and functional traits and mesologic factors describing habitat characteristics. We found clear‐cutting had a stronger effect than thinning on the microclimatic conditions, i.e., higher temperatures, drier soils and reduced forest buffering capacity. The 25% thinning intensity was sufficient to drastically reduce both spider abundance and richness, but we did not find a more significant reduction when more intensive cutting was applied. This result suggests a threshold effect in the response of spiders to cutting. Significant changes in the functional diversity of understory plant communities in response to basal area were observed, along with strong effects on spider communities. Unexpectedly, slash retention appeared to have little or no effect on the forest microclimate, spider abundance and species richness. This work is intended for forest managers and policymakers and aims to contribute to the development of relevant practices that address current environmental and economic challenges. While our findings provide valuable insights into understudied forest management practices in Mediterranean climates, additional research is required, particularly through multi‐seasonal and long‐term spider sampling
Learning to Bid in Proportional Allocation Auctions with Budget Constraints
No full textInternational audienceThe Kelly or proportional allocation mechanism is a simple and efficient auction-based decentralized resource allocation scheme that distributes an infinitely divisible resource proportionally to the agents' bids. When agents are aware of the allocation mechanism, their interactions form a game. The properties of its Nash equilibria are well understood under the simplifying assumption of unbounded budgets. In this paper, we analyze the game in a more realistic budget-constrained setting, motivated by its optimality in terms of the liquid price of anarchy (LPoA). Specifically, we establish a sufficient condition for the uniqueness of the Nash equilibrium and design a distributed sequential learning procedure that provably converges to the equilibrium. In particular, our sufficient condition holds when the payoff functions of the agents are of the proportional fair type in the allocated fraction. Finally, extensive numerical experiments shed light on the interplay between the heterogeneity of the payoff functions and the agents' budgets
Polarization spectroscopy as an innovative method for the early detection of biofouling in drip irrigation with reclaimed water
No full textInternational audienceBiofilms are a health and operating issue in various fields, particularly in drip irrigation systems based on reclaimed water. To ensure the proper functioning of drip irrigation systems and save water, biofouling needs to be detected and quantified in drippers. Few studies have investigated the use of near infrared (NIR) spectroscopy for biofilm monitoring, particularly in the context of drip irrigation systems. A major challenge lies in the strong influence of water on NIR spectra, which complicates biofilm detection and analysis. This study assessed polarization spectroscopy as a new approach to detect biofilms in the presence of water and to discriminate between biofilms and the embedded insoluble elements. Samples were probed with near infrared polarized light to collect single and multi-scattered light separately. Principal component analysis of the spectra in the 1100-1300 nm region was used to distinguish spectra associated with water alone and with biofilm samples in water. Biofilms of a thickness of less than 100 µm could be detected in the presence of water. Partial least squares with discriminant analysis (PLS-DA) was used to discriminate biofilms, biofilms with kaolinite, and biofilms with calcium carbonate (all in the presence of water). The method achieved a discrimination accuracy of 96.4%, demonstrating strong potential for application in cases of biofilm-induced composite clogging. Thus, polarized light spectroscopy in the near infrared region proves effective overcoming the presence of water for detecting and discriminating biofilms. This approach holds promise for application across various fields where biofilm formation presents a challenge
Very-high resolution coral reef mapping in Mayotte using Satellite Imagery
No full textInternational audienceTropical coral reefs are the most biodiverse ecosystems on the planet, but increasing human pressures are rapidly degrading those sensitive ecosystems. Marine habitat maps, often used to manage coastal environments, tend to be available at spatial resolutions too coarse for the needs of management, impacting management strategies and monitoring efforts. Here, we developed an innovative approach forconducting very high-resolution (sub-meter) mapping of benthic habitats semi-automatically and applied it across the 195 km of Mayotte's reef flat. The mapping was performed using 50-cm resolution Pleiades satellite imagery and LiDAR-derived bathymetry. Satellite images were supplemented by underwater images acquired along 193 transects using a GoPro camera fixed to a diver propulsion vehicle. To achieve a very high spatial accuracy, underwater images were positioned with a few centimeters accuracy using a Global Navigation Satellite System (GNSS) system and post-processed kinematic (PPK) corrections. Geo-referenced image frames were extracted from the videos and integrated for annotations into CoralNet, a free online benthic image analysis software using semi-automatic deep learning analysis. About 10% of the video frames (3323 images) were annotated, allowing the analysis of over 31,500 images and calculate habitats' covers on the reef. Satellite images were segmented using an Object-Based Image Analysis (OBIA) approach and segments properties were used with other variables in a Random Forest pixel-based classification. To ensure replicability, data processing and analyseswere conducted using free and open source software Orfeo ToolBox, QGIS, and R Stats. Thirteen benthic habitats, extending from coastal mangroves to the outer reef slope, were mapped at the pixel level. CoralNet classifiers achieved 65% accuracy, while the Random Forest models reached an accuracy of 76%. The composition of benthic assemblages varied significantly around the island, with changes inlive corals accompanied by a rise in muddy habitats, turf, and dead corals as anthropogenic pressures intensify. The detailed habitat maps produced through this project will serve as an essential management tool to inform the management of Mayotte's coastal waters and the approach developed could help produce more regular and systematic habitat maps in support of coastal zone management
Bathymetry mapping using the high resolution VENμS satellite: an easy-to-transfer estimation over Glorioso Islands
No full textInternational audienceAccurate global bathymetry mapping underpins natural hazard prediction or marine habitat management. However approximately 80% of the seafloor remains unmapped. Traditional waterborne (multi-/single-beam sonar) and airborne (lidar, spectral inversion) methods provide high precision and complementary coverage but are constrained in cost, accessibility, and temporal resolution. Spaceborne approaches, leveraging high- to very high-resolution multispectral and lidar sensors, increasingly enable shallow-water bathymetry retrieval at regional to global scales. This study investigates the potential of the VENμS mission for deriving shallow bathymetry over Glorioso Archipelago (Indian Ocean). VENμS superspectral imagery (12 bands, 4 m resolution, daily revisit) was collected in 2022 and attempted to predict ~83,000 lidar illuminations acquired in 2009. Three predictor series were investigated: surface reflectance, ln-transformed surface reflectance, and band ratios of ln-transformed surface reflectance. Nine depth ranges, from 0 to -45 m, were modeled using stepwise three-factor linear regressions, with performance assessed across calibration, validation, and test subsets. Results indicate excellent performance with ln-transformed surface reflectance achieving the highest predictive skill. The [0; -10 m] interval was optimal, with R2test reaching 0.93 using blue, green, and yellow-2 bands, even if the [0; -30 m] range was satisfactorily modelled (R2test = 0.78). VENμS-derived bathymetry maps show strong concordance with lidar to ~5 m depth, though increasing divergence suggests potential sediment redistribution over the 13-year period. These findings demonstrate that simple, transferable linear models applied to VENμS imagery can yield accurate, scalable shallow-water bathymetry, highlighting the mission’s value for cost-effective coastal mapping and supporting global seabed initiatives such as Seabed 2030
