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Energies renouvelables intermittentes et flexibilité du système électrique : le cas de la région Occitanie
No full textThis thesis addresses the integration of Variable and Renewable Energies (VRE) in the Occitanie region of France, a pertinent issue in the broader context of the global energy transition. The study revolves around the critical question of managing power system flexibility in the face of increased VRE integration.A hybrid deep-learning forecasting model is developed, combining time-series decomposition with Convolutional LSTM networks, to predict power system flexibility requirements. Subsequently, a cost-optimization model is introduced to explore flexibility sourcing from a spectrum of technologies. Last, a scenario analysis is conducted on future Occitanie power system flexibility. Using the cost-optimization model, we explore how can flexibility management can be performed under varying conditions.The findings provide valuable insights into power system flexibility, emphasizing the strategic importance of technologies like hydropower, grid, and storage. The thesis contributes significantly to the field of energy system management and flexibility, offering both theoretical frameworks and practical methodologies that are relevant to current challenges and future developments in renewable energy integration.Cette thèse aborde l'intégration des Energies Renouvelables Intermittentes (EnRI) dans le système électrique de la région française d'Occitanie, une question pertinente dans le contexte plus large de la transition énergétique. L'étude se concentre sur la question cruciale de la gestion de la flexibilité des systèmes énergétiques face à l'intégration croissante des EnRI. Un modèle hybride de prévision par apprentissage profond est développé, combinant la décomposition de séries temporelles et les réseaux LSTM convolutifs, afin de prédire les besoins de flexibilité d'un système électrique donné. Ensuite, un modèle d'optimisation des coûts est introduit pour explorer l'approvisionnement en flexibilité à partir d'un spectre de technologies. Enfin, une analyse de scénario est menée sur le futur de la flexibilité du système électrique Occitan. Les résultats fournissent des aperçus utiles sur la flexibilité du système électrique, soulignant l'importance stratégique de technologies telles que l'hydroélectricité, le réseau et le stockage La thèse contribue de manière significative au domaine de la gestion et de la flexibilité des systèmes électriques, offrant à la fois des cadres théoriques et des méthodologies pratiques qui sont pertinentes pour les défis actuels et les développements futurs liés à l'intégration des EnRI
A Theory of Intelligences
No full textIntelligence is a human construct to represent the ability to achieve goals. Given this wide berth, intelligence has been defined countless times, studied in a variety of ways and represented using numerous measures. Understanding intelligence ultimately requires theory and quantification, both of which have proved elusive. I develop a framework -- the Theory of Intelligences (TIS) -- that applies across all systems from physics, to biology, humans and AI. TIS likens intelligence to a calculus, differentiating, correlating and integrating information. Intelligence operates at many levels and scales and TIS distils these into a parsimonious macroscopic framework centered on solving, planning and their optimization to accomplish goals. Notably, intelligence can be expressed in informational units or in units relative to goal difficulty, the latter defined as goal complexity relative to system (individual or benchmarked) ability. I present general equations for intelligence and its components, and a simple expression for the evolution of intelligence traits. The measures developed here could be the basis for further refinements to gauge different facets of intelligence for any step-wise transformation of information. I argue that "proxies" such as environment, technology, society and collectives are essential to a general theory of intelligence and to possible evolutionary transitions in intelligence, particularly in humans. I conclude with testable predictions of TIS and offer several speculations
Comparative population genomics unveils congruent secondary suture zone in Southwest Pacific Hydrothermal Vents
No full textHow the interplay of biotic and abiotic factors shapes current genetic diversity at the community level remains an open question, particularly in the deep sea. Comparative phylogeography of multiple species can reveal the influence of past climatic events, geographic barriers, and species life history traits on spatial patterns of genetic structure across lineages. Here, we conducted a comparative population genomic study on seven hydrothermal vent species co-distributed in the Back-arc Basins of the Southwest Pacific region. Using ddRAD-seq, we compared distribution range-wide genomic diversity patterns across species and discovered a shared zone of phylogeographic break. Although species exhibit congruent patterns of spatial structure, they also show variation in the degree of divergence among lineages across the suture zone. Additionally, two species have a sympatric contact zone in the Woodlark Basin. Demogenetic inference revealed shared histories of lineage divergence and secondary contact. Low levels of asymmetric gene flow probably occurred in most species between the Woodlark and North Fiji basins, but the exact location of contact zones varied from species to species. Results show that gene flow is heterogeneous across the genome, indicating possible partial reproductive isolation between lineages and early speciation.Our comparative study sheds light on the factors that shape genetic variation at the community level, and our findings enrich our understanding of deep-sea biogeography patterns. Emphasizing the pivotal role of historical and contemporary factors, our research underscores the necessity for a holistic approach, and in particular filling in the gaps regarding life history traits of deep-sea species (generation time, development type, duration of the larval phase)
prospect: an R package to link leaf optical properties with their chemical and structural properties with the leaf model PROSPECT
No full textInternational audienc
Résistons ! Le parcours des bactéries pathogènes dans les fermes aquacoles
No full textAffiche de vulgarisation scientifique à destination du jeune publicPlongez au cœur des écosystèmes aquatiques et découvrez comment les pratiques d'aquaculture peuvent impacter la santé des espèces ! Ces affiches diffusées dans le cadre d'une animation pour la Fête de la Science 2024 présentent les enjeux sanitaires liés au développement de l'aquaculture dans la baie de Nha Trang au Vietnam, en s'appuyant sur les résultats du projet de recherche NEMESIS
Impact of climate change on maize productivity and nitrogen cycling in the subhumid tropics: a field case study under rainfall extremes in Zimbabwe
No full textInternational audienceChanges in rainfall patterns and extreme wet and dry events are more frequent and will intensify globally because of global warming disrupting the water cycle (Rohde, 2023). This is particularly the case in Southern Africa with an increasing intensity and frequency of rainfall extremes. These events often lead to water stresses ranging from droughts to waterlogging, which may adversely impact the soil-crop processes (Kim et al., 2024) and reduce crop productivity and nutrient use efficiency. However, studies using rainfall manipulation experiments remain scarce. Most of such existing experiments have been conducted on natural ecosystems such as grasslands and woodlands in the northern temperate regions, with a clear gap on croplands in the tropics and poor focus on interactions with nutrient cycling (Beier et al., 2012).To better understand the soil-crop nitrogen (N) dynamics under rainfall extremes, a fieldscale rainfall manipulation experiment has been carried out in 2022-2023 and 2023-2024 cropping seasons in Harare, Zimbabwe (17°42'13.5"S 31°00'29.4"E) under sub-humid conditions. This is a part of a large 1.5 ha new long-term experiment established since November 2022 and registered within the Global Long-Term Agricultural Experiment Network (https://glten.org/experiments/368). Three main rainfall treatments replicated three times were established: reduced rainfall (-30%), normal rainfall and heavy rainfall (events of 100 mm/24h). The reduced rainfall treatment is achieved with an exclusion system above the maize canopy using transparent shelters covering about 30% of the plots surface. The heavy rainfall events are simulated with an irrigation system, and two events are applied per cropping season. Within these rainfall treatments, the study focused on four cropping systems treatments, resulting from the combination of two N fertilization levels (0 and 80 kg N ha-1 yr-1), with or without mulching (0 and 6 t DM ha-1 yr-1). A bare soil treatment was also set up and monitored to study the soil functioning without crop. Key variables related to biomass production and N dynamics such as leaf area index, crop biomass and N uptake, yield, soil temperature, soil water and mineral N, mulch decomposition, and emissions of nitrous oxide (N2O) were monitored from the first cropping season. An in-situ experiment using 15N labelled fertilizer was conducted during the second cropping season to study the fate of fertilizer under the three rainfall treatments with and without mulch. Labelled N fertilizer was applied on microplots as basal application, first and second topdressing using non-cumulative split application approach with both soil and plant N and 15N monitoring at different stages of plant growth. The first-year results indicate that N dynamics in the soil were slightly affected by rainfall treatments and the presence of mulch. Total aboveground biomass and grain yield were negatively affected by reduced rainfall and absence of N fertilization. Mulch exhibited a buffering effect in topsoil layers, reducing soil temperature variations and maintaining moisture for a longer period during dry spells. The decomposition kinetics of the mulch were little affected by rainfall treatments but was quick, with 50% of initial dry mass decomposed in about 70 days. These results suggest a highly variable impact of rainfall extremes on biomass production, maize residue decomposition and N cycle depending on their timing, intensity and frequency of occurrence. Results from plant N uptake and from the ongoing analysis of the 15N labelling experiment, along with the planned modelling work with the STICS soil-crop model should provide further clarification on the interaction between rainfall patterns and N cycle, as well as the short and long term consequences on plant biomass production and recycling
Tree growth‐forms reveal dominant browsers shaping the vegetation
No full textInternational audiencePlants adopt particular growth‐forms when they are exposed to extreme environmental conditions. In this study, we describe a unique woody plant growth‐form induced by large mammalian herbivores and discuss that this growth‐form could have evolved as a strategy for escaping the browser zone in herbivore driven ecosystems. We analysed responses of key architectural and morphological attributes (branching and thorn density, tree dimensions, presence of flowers and fruits) of three Eurasian spiny tree species ( Malus sylvestris , Prunus cerasifera and Pyrus communis ) to different levels of browsing by large herbivores in the temperate Białowieża Forest, Poland. Under high browsing pressure, studied trees displayed two distinct forms of the crown: a bottom sterile part developing into a densely branched structure with high density of thorns (‘cage‐form’), and an upper reproductive part that escaped from herbivore control (‘escaped‐form’). The size of cage‐form influenced the feeding behaviour of red deer ( Cervus elaphus ) by increasing the time deer spend foraging and increasing the bite rate. The height at which cages started to escape and their diameter matched with foraging reach of red deer. Synthesis . We argue that the frequency and cage dimensions of this woody growth‐form in the landscape could inform on the type and intensity of recent herbivory. Moreover, its distinctive inducibility suggests that this growth‐form did not emerge recently under anthropogenic pressure but could be the legacy of ancient herbivory effects. Observational evidence suggests that this growth‐form emerged in several herbivore‐driven systems around the globe and may be used to identify the dominant herbivores that control vegetation structure in these ecosystems. Read the free Plain Language Summary for this article on the Journal blog
Projet BioEOS – Estimation et suivi de la biodiversité côtière à large échelle à partir de l’imagerie multi et hyperspectrale
No full textInternational audienceLa biodiversité est un capital naturel agissant sur les fonctions des écosystèmes et qui fournit des services et des avantages importants, allant des besoins alimentaires au patrimoine culturel. Cependant, les espèces disparaissent actuellement à un rythme 100 à 1000 fois supérieur au rythme naturel.Bénéficiant du label SCO (Space Climate Observatory), le projet BioEOS propose de développer un outil d’observation permettant de fournir des données (i) d’une part pour caractériser, via des proxys, la dynamique spatio-temporelle de la biodiversité côtière en analysant les séries temporelles d’images satellitaires multi-capteurs (multi et hyperspectraux) et (ii) d’autre part, pour cartographier les changements et produire des indicateurs pour rendre compte de l’impact des changements globaux sur l’état de la biodiversité côtière.Une stratégie de développement pour optimiser l’extraction de l’information recherchée a été mise en place pour l’élaboration d’un démonstrateur sur les territoires du sud-ouest de l’Océan Indien. Nous présenterons les premiers résultats qui concernent les volets suivants :- Fusion de données satellitaires issues des différents systèmes exploités pour augmenter le potentiel de discrimination spectrale en utilisant des approches basées sur les algorithmes de pansharpening (Gram-Schmidt, Gram-Schmidt Adaptatif, PCA et Brovey).- Traitements réalisés sur la base des algorithmes déjà éprouvés par la communauté scientifique (inversion d’un modèle de transfert radiatif, segmentation par apprentissage profond, démélange et indices spectraux) permettant de générer des informations sur la bathymétrie, les types de fond et la qualité des masses d’eau
Recent progress in the inference of dispersal and density from genetic data
No full textInternational audienceModel-based analysis of neutral genetic data allows to indirectly estimate demographic and historical parameters such as population sizes, migration rates or divergence times because those parameters shape the repartition of genetic variability within and between populations over time. In numerous species, dispersal is spatially-limited (individuals preferentially find geographically close mates) and individuals may be spread over a continuous habitat rather than aggregated into discrete panmictic populations. However, inference methods accounting for localized dispersal still bear a number of limitations in terms of biological complexity of the underlying spatial models and of type of information brought by the analyses (e.g. which parameters can be estimated, as well as their biological interpretation). In this study, we used a new recent simulation-based inference method coupled with a spatial genetic data simulator to infer local demographic parameters of population in a continuous habitat. Our results show that we can estimate with good precision more parameters than with previously available methods, notably by independently inferring population density, dispersal rate and the shape of the dispersal distribution. In contrast to competing studies, we reach these results without assuming that the total population size or the habitat size is known. Instead, these results are possible because the simulations do not require coalescent approximations (such as assuming large population size and small migration rate), and because simulation-based methods can exploit summary statistics for which no simple analytical expectation is known. These results highlight the power of simulation-based inference in population genetics and pave the way for new demogenetic inferences under more realistic spatial population genetic models
Optimisation du protocole de séchage des graines d’agrumes en vue de leur cryoconservation et évaluation de l’effet sur la multiplication clonale
No full textMasterAfin de sécuriser à long terme la conservation des agrumes l’équipe SEAPAG à la station INRAE de San Giuliano développe la congélation des graines dans l’azote liquide (Cryoconservation). La réussite de cette technique repose sur la diminution de la teneur en eau intracellulaire. Malheureusement la majorité des agrumes de la collection est sensible à cette étape, c’est-à-dire qu’elle perd la capacité germinative en dessous d’un certain seuil de teneur en eau (WC). Comme les mandariniers constituent le groupe ayant le plus gros effectif variétal (> 300 accessions) de la collection, nous avons évalué deux méthodes de séchage des graines pour accélérer le processus, sur 13 variétés de mandarine, ainsi que 2 oranges et 2 citranges, ainsi que le rôle des téguments dans ces flux d’eau. Nous avons observé que les téguments n’avaient pas d’influence sur la sortie d’eau au moment du séchage mais qu’en revanche qu’ils étaient une barrière pour la réhydratation lors de la germination. La vitesse de perte d’eau lors du séchage des graines est très variable selon la variété. Nous avons mesuré le temps nécessaire pour que les graines atteignent un WC compris entre 10 et 15 % (conditions optimales pour la congélation des graines d’agrumes). Si Tachibana ne nécessite que 48 h sous hotte à flux pour que son WC soit inférieur à 15%, plusieurs variétés n’arrivent jamais à ce seuil quelle que soit la durée de séchage. Les taux de germination diminuent fortement avec le séchage et à l’exception de Willow leaf (32%) aucune mandarine ne germe après congélation dans l’azote liquide. Bien que plus rapide la méthode de séchage sous hotte est beaucoup trop aléatoire pour contrôler le WC néanmoins associée en amont avec la méthode d’incubation en atmosphère contrôlée à 75% d’humidité relative, elle peut accélérer le processus. Ayant à faire à des variétés avec des graines polyembryonnées, nous avons évaluée les effets du séchage sur la proportion de germinations issues d’embryons zygotiques et nucellaires. Le séchage augmente la proportion de zygotiques mais ces derniers restent néanmoins minoritaires (environ 25 % chez la mandrine Willow leaf)