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International audience; Assembly processes shaping ecological communities can vary over time following variations of environmental conditions at different scales. Such temporal dynamism is exacerbated by climate change and increasing extreme events, and recent evidence suggests that, in turn, community composition and functions can vary substantially. However, empirical relationships between the spatio‐temporal dynamics of communities and that extreme events altering ecosystems are poorly investigated. We quantified the temporal dynamics of stream invertebrate communities over two years across 11 river basins prone to drying, covering a large geographical area of France. We tested predictions on the influence of the spatial arrangement and temporal dynamics of drying events across river networks. Combining a high temporal resolution of community description from taxonomic and functional perspectives, we quantified beta diversity over time and space and partitioned them into additive components: replacement of taxa and richness difference. Frequency and duration of drying events were precisely quantified and basins were classified based on the location of the drying events. We found a strong influence of the spatial drying pattern on the dissimilarities of community composition between sites. The high temporal variability of community structure was directly related to the frequency and duration of drying events. This temporal dynamism of communities was also strongly affected by the spatial drying pattern, indicating that fragmentation had a stronger effect on recolonisation processes for upstream‐drying basins. Finally, biological traits were unevenly distributed in space and time, suggesting a lack of functional redundancy that could have strong implications for ecosystem functions and services. The high temporal dynamics of communities highlighted in this study challenge the current definition of reference conditions in intermittent rivers, and the community sensitivity to frequency and duration of drying suggest that climate change might lead community dynamics to be increasingly driven by stochastic environmental variability.

International audience; Assembly processes shaping ecological communities can vary over time following variations of environmental conditions at different scales. Such temporal dynamism is exacerbated by climate change and increasing extreme events, and recent evidence suggests that, in turn, community composition and functions can vary substantially. However, empirical relationships between the spatio‐temporal dynamics of communities and that extreme events altering ecosystems are poorly investigated. We quantified the temporal dynamics of stream invertebrate communities over two years across 11 river basins prone to drying, covering a large geographical area of France. We tested predictions on the influence of the spatial arrangement and temporal dynamics of drying events across river networks. Combining a high temporal resolution of community description from taxonomic and functional perspectives, we quantified beta diversity over time and space and partitioned them into additive components: replacement of taxa and richness difference. Frequency and duration of drying events were precisely quantified and basins were classified based on the location of the drying events. We found a strong influence of the spatial drying pattern on the dissimilarities of community composition between sites. The high temporal variability of community structure was directly related to the frequency and duration of drying events. This temporal dynamism of communities was also strongly affected by the spatial drying pattern, indicating that fragmentation had a stronger effect on recolonisation processes for upstream‐drying basins. Finally, biological traits were unevenly distributed in space and time, suggesting a lack of functional redundancy that could have strong implications for ecosystem functions and services. The high temporal dynamics of communities highlighted in this study challenge the current definition of reference conditions in intermittent rivers, and the community sensitivity to frequency and duration of drying suggest that climate change might lead community dynamics to be increasingly driven by stochastic environmental variability.

Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has increased during the last 200 years, with 37% of all first records reported most recently (1970–2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization., Alien species of animals and plants can invade new regions of the earth. This study performs a global analysis of temporal dynamics and spatial patterns of alien species introductions over the past 200 years, and reports no saturation in the rate at which these invasion are increasing.

This thesis is focused on the controllability of laser-induced refractive index changes at sub-micron level over long dimensions i.e., with high aspect ratios and sections on the nanoscale. To this end, we explore non-diffractive zerothorder ultrafast Bessel beams and factors contributing to energy confinement beyond the diffraction limit. Laser processing of transparent materials using non-diffracting beams offers a strong advantage for high aspect ratio submicron structures inside the bulk in view of nanophotonics and nanouidics applications. We present the role of various focusing conditions and laser parameters on material modification in bulk fused silica and explore the different interaction regimes. This thesis tackles mostly the moderate focusing conditions as they offer a stable interaction regime backed up dispersion engineering over a large range of laser parameters. The laser pulse duration was found to be key in defining the type of laser induced refractive index or structural modification. For instance, machining using femtosecond laser pulses results in increased refractive index structures whereas picosecond laser pulses result in uniform void i.e., low index structures. To acquire better control over the laser energy deposition and precision, a range of physical mechanisms responsible for the laser induced damage in non-diffractive excitation conditions have been observed experimentally and further interrogated by simulations indicating a critical role of light scattering on carriers. Time-resolved pump-probe microscopy measurements with a sub-picosecond temporal and sub-micron spatial resolution allow access to the instantaneous excitation and relaxation dynamics. Dynamic optical transmission and phase contrast o_er complementary information of either electronic and glass matrix response. Primarily, ultrafast dynamics of free carriers was studied as the electron mediated energy transfer to the lattice is key to the subsequent material transformation. Role of instantaneous excitation at different laser pulse durations and energies is outlined. Then complete carrier dynamics is presented at different laser parameters. Particularly dynamics in conditions of positive refractive index structures and uniform voids is indicating two different paths of electronic relaxation and energy deposition: a fast defect mediated relaxation for positive index structures and slow thermomechanical relaxation for nanosize void structures. Finally, by correlating the results of time resolved studies, simulations and post-irradiated photoluminescence results, we formulate potential formation scenarios for the positive refractive index and low index or uniform void structures, Cette thèse se concentre sur la contrôlabilité de l'indice de réfraction au niveau sub-micronique par changements d'indice induits par laser sur de longues dimensions i.e., avec des hauts rapports d'aspect élevés et des sections à l'échelle nanométrique. À cette fin, nous explorons les faisceaux ultracourts de Bessel non-diffractifs d'ordre zéro et les facteurs qui contribuent au confinement de l'énergie au-delà de la limite de diffraction. Le traitement par laser de matériaux transparents à l'aide de faisceaux non diffractifs offre un avantage important pour les structures sub-microniques en volume de haut rapport d'aspect à des fins applicatives en nanophotonique et en nanofluidique. Nous présentons l'effet de différentes conditions de focalisation et de paramètres laser sur la modification de la silice fondue, explorant ainsi les différents régimes d'interaction. Cette thèse aborde essentiellement des conditions modérées de focalisation car elles offrent un régime d'interaction stable sur une large gamme de paramètres laser, permettant l'ingénierie de la dispersion. La durée de l'impulsion laser s'est révélée être essentielle dans la définition du type de modification de l'indice de réfraction ou de modification structurale. Par exemple, l'usinage utilisant des impulsions laser femtosecondes entraîne une augmentation des structures d'indice de réfraction alors que les impulsions laser picosecondes engendrent une cavité uniforme i.e., des structures de faible indice. Pour acquérir un meilleur contrôle et une meilleure précision du dépôt d'énergie laser, un ensemble de mécanismes physiques responsables des dommages induits par laser dans des conditions d'excitation non-diffractives a été observé expérimentalement et examiné par des simulations indiquant le rôle essentiel de la diffusion de la lumière sur les électrons. Des mesures de microscopie pompe-sonde résolues en temps avec une résolution temporelle sub-picoseconde et spatiale sub-micronique donnent accès à l'excitation et à la relaxation dynamique instantanées. La transmission optique dynamique et le contraste de phase offrent des informations complémentaires sur la réponse électronique ou sur celle de la matrice vitreuse. La dynamique ultrarapide des porteurs libres a été particulièrement étudiée puisque le transfert d'énergie des électrons vers le réseau est la clé de transformation ultérieure du matériau. Le rôle de l'excitation instantanée pour différentes durées et énergie d'impulsion laser est exposé. Ainsi, la dynamique complète des porteurs de charge est présentée pour différents paramètres du laser. En particulier, la dynamique d'obtention de structures d'indice de réfraction positif et des cavités uniformes indique deux chemins différents de relaxation électronique et de dépôt de l'énergie: une relaxation rapide par l'intermédiaire de défauts pour les structures d'indice positif et une relaxation thermomécanique lente pour les cavités nanométriques. Enfin, en corrélant les résultats des études résolues en temps, les simulations et les résultats de photoluminescence après irradiation, nous formulons des scénarios potentiels de formation de l'indice de réfraction positif ainsi que des structures d'indice faible ou de vides uniformes

Aggregate stability is a key property affecting the movement and storage of water, seedling emergence, and soil sensitivity to erosion. Many studies have shown that aggregate stability changes through time. Field monitor- ing studies performed with a relatively large (monthly) time step showed the seasonal trend of aggregate stability. However, shorter time step monitor- ing is required to explore dynamics of aggregate stability at short term. For now, biological activity was recognized to be the main factor of aggregate stability dynamics, but previous studies were currently based on the external stimulation of aggregate stability. The objectives of this study were to assess variations in aggregate stability at short time steps in the field and to identify the factors controlling these variations of stability. A 6-mo field monitoring was performed at short time step (2-5 d) on a bare field of Luvisol without organic amendment. Aggregate stability was measured for both on surface and subsurface materials by the ISO 10930 (2012) method. Rain amount and intensity, air temperature and humidity, soil temperature, water content and hydric history, and soil water repellency were measured as explanatory fac- tors. The results showed that aggregate stability varied greatly (up to 40%) over a few days for both surface and subsurface. Short term dynamics of aggregate stability were already shown by laboratory experiments, but such dynamics was never observed in the field for a bare soil without external stimulation of biological activity. For the surface, short time step variations of surface aggregate stability were primarily controlled by soil water content (WC0 and WC1/2), hydric history (DWC4 and API), and rain intensity. While large changes in aggregate stability were found for the subsurface, explanatory factors remain to be found.

One form of cruelty arises from ritually bounded social groups, where altruistic morality does not extend beyond the boundaries of one’s own enclave, and deliberate public cruelty to enemies is a ritual of group solidarity. Ritualized public displays of cruelty upon helpless victims are most strongly institutionalized in societies which combine hierarchic stratification with strongly ritualized group membership. Cruelty returns in its second form, bureaucratic callousness, through the impersonal structure of modern warfare and the exercise of organizational power. Uma forma de crueldade surge de grupos sociais unidos ritualmente, onde a moralidade altruísta não ultrapassa as fronteiras e limites de cada um, e a deliberada crueldade pública para com os inimigos é um ritual de solidariedade de grupo. Demonstrações públicas ritualizadas de crueldade sobre vítimas indefesas estão fortemente institucionalizadas em sociedades que combinam uma estratificação hierárquica com uma pertença de grupo fortemente ritualizada. A crueldade volta na sua segunda forma, a insensibilidade burocrática, através da estrutura impessoal da guerra moderna e do exercício do poder organizacional. Une forme de cruauté vient de groupes sociaux unis par des rites, où la moralité altruiste ne va pas au-delà des frontières et des limites de chacun et où la cruauté publique délibérée envers les ennemis est un rituel de solidarité du groupe. Les démonstrations publiques ritualisées de cruauté envers des victimes sans défense sont fortement institutionnalisées dans les sociétés qui allient une stratification hiérarchique à une appartenance de groupe fortement ritualisée. La cruauté revient sous sa seconde forme, l’insensibilité bureaucratique, à travers la structure impersonnelle de la guerre moderne et de l’exercice du pouvoir organisationnel. Una forma de crueldad surge de grupos sociales unidos ritualmente, donde la moralidad altruista no supera las fronteras y límites de cada uno, y la deliberada crueldad pública hacia los enemigos es un ritual de solidaridad de grupo. Demostraciones públicas ritualizadas de crueldad sobre víctimas indefensas están fuertemente institucionalizadas en sociedades que combinan una estratificación jerárquica con una pertenencia de grupo fuertemente ritualizada. La crueldad vuelve en su segunda forma, la insensibilidad burocrática, a través de la estructura impersonal de la guerra moderna y del ejercicio del poder organizacional.

International audience; Epidemiololgical investigations were performed in a 3-ha maritime pine (Pinus pinaster) plantation established on a site heavily infested by Armillaria ostoyae. Geostatistics were used to examine the density and the distribution of the initial inoculum. Disease dynamics were monitored for 17 years after planting. On the whole site, the cumulative mortality rate reached 35% over this period, plateauing at 12 years. Disease progress curves differed according to the density of the initial inoculum, although in all the cases, the Gompertz model described the epidemics, well. The epidemiological contributions of both primary (initially colonized Stumps) and secondary inoculum (newly dead pines) were evaluated by analyzing their spatial relation to annual mortality. Newly dead pines inoculum from year 3 and their role increased with acted as secondary time. When the initial inculum density was low, the contribution of secondary inoculum to epidemic development increased faster and halted sooner than when the density of primary inoculum was high. Regardless of its density, the primary inoculum acted throughout the dynamic phase of the epidemic. When the inoculum density was low, the probability of mortality during the first 6 years of the epidemic depended on the tree distance from the nearest stumps colonized by Armillaria sp. When the inculum density was high, the probability of mortality was higher and not related to the distance between trees and colonized stumps

We present extensions of mathematical results about discrete time and discrete state Markovian demographic models, to biologically more realistic conditions. Under certain conditions, they allow to know the asymptotic behaviour of these models, especially their different kinds of temporal stability. In practice, these results imply the reference to a canonical theoretical framework, which should render these models' analyses more comparable. We insist that these results are qualitative and mathematical, and do not replace a quantification as well as biological questioning and interpretation., Nous présentons une généralisation à des conditions biologiquement plus réalistes de résultats mathématiques déjà connus à propos de modèles démographiques Markoviens discrets. Pourvu que certaines conditions soient vérifiées, ils permettent de connaître à priori le comportement asymptotique de tels modèles, notamment leurs différentes formes de stabilité. Il s'ensuit surtout une manière canonique d'analyser les résultats de tels modèles, qui rend l'analyse de ces modèles davantage comparable. Nous insistons sur le fait que ces résultats sont qualitatifs et mathématiques, et ne remplacent en rien une phase de quantification, ainsi qu'un questionnement plus biologique.

We present extensions of mathematical results about discrete time and discrete state Markovian demographic models, to biologically more realistic conditions. Under certain conditions, they allow to know the asymptotic behaviour of these models, especially their different kinds of temporal stability. In practice, these results imply the reference to a canonical theoretical framework, which should render these models' analyses more comparable. We insist that these results are qualitative and mathematical, and do not replace a quantification as well as biological questioning and interpretation., Nous présentons une généralisation à des conditions biologiquement plus réalistes de résultats mathématiques déjà connus à propos de modèles démographiques Markoviens discrets. Pourvu que certaines conditions soient vérifiées, ils permettent de connaître à priori le comportement asymptotique de tels modèles, notamment leurs différentes formes de stabilité. Il s'ensuit surtout une manière canonique d'analyser les résultats de tels modèles, qui rend l'analyse de ces modèles davantage comparable. Nous insistons sur le fait que ces résultats sont qualitatifs et mathématiques, et ne remplacent en rien une phase de quantification, ainsi qu'un questionnement plus biologique.

Invasive species are nowadays considered as one of the most important threat to biodiversity. By displacing native species, modifying ecosystem functioning and causing substantial losses to agricultural production, they represent a menace to natural and managed ecosystems. Although ecology of invasions has become an important research topic since the last decades, the mechanisms that determine why a given species may invade a given ecosystem and why some biomes are less resistant to invasion are still not clarified. Ecology of invasions is divided into 2 main topics: invasiveness and invasibility. While invasiveness refers to species ability to invade a community, invasibility focuses on the resistance of a community to invasion. Invasiveness may be the result of ecological processes, such as release from biotic constraints or human alteration of the environment (disturbance, stress…) or the consequence of evolutionary processes, such as hybridization or polyploidization that may increase genetic variation and therefore, enhance niche breadth. Invasibility has been said to be influenced by disturbance and biotic factors such as community diversity, dominant species identity, biotic interactions or community compositional stability. The invasion success is the consequence of the interaction between species invasiveness and community invasibility. Most studies in ecological invasions have focused on either invasiveness or invasibility, but hardly both together. By working at the same time and in the same conditions with native and introduced genotypes and by comparing their ecological performances, this thesis aims at a better understanding of both invasiveness and invasibility mechanisms. Two worldwide invasive species, Centaurea maculosa and Senecio inaequidens, were used in several experiments (pot, microcosm, field) to disentangle the importance of invasiveness and community invasibility in their invasion success. Both species encountered polyploidisation in their native range, leading to the presence of diploid and tetraploid populations, whereas only tetraploid populations have been found in the introduced range. Using native diploid, native tetraploid and introduced tetraploid genotypes of the two model-species, allows assessing the effects of genetic variation (diploid vs. tetraploid genotypes) and environmental variation (genotype from native vs. introduced range) on species phenotypic traits variations and consequently on fitness variation and invasiveness. In the community context, studying response of different genotypes to experimental factors and community change gives information on the interaction between invasiveness and invasibility. Plants were grown in pot, in field or in artificially built communities where (i) the management treatment, (ii) the community diversity and (iii) the spatial organisation of resident species were manipulated. In addition, (iv) community species composition, (v) community competitive ability and (vi) compositional and functional stability of the community were monitored. According to the experiments, data were gathered on survival, morphological traits (vegetative height, lateral spread, shoot and root biomass), leaf traits (specific leaf area, leaf dry matter content) and reproductive traits (probability of flowering, capitulum production) of the genotypes (native diploid, native tetraploid and introduced tetraploid) of both model species. Through the use of statistical models and multivariate approaches, the effects of management and biotic factors on survival, growth and reproduction of native and introduced genotypes of these two worldwide invasive species were assessed. Invasion strategy of the two model species was investigated through a growth experiment in optimal conditions in a pot experiment. High investment in seed production could explain invasive success of S. inaequidens through high propagule pressure, whereas C. maculosa's strategy seemed to be oriented towards interactions with belowground communities, as shown by the shift in rhizosphere bacterial communities between genotypes. For both species, polyploidisation in the native range could be linked to a specialisation towards higher competitive ability, which could have allowed the first step of invasion. Introduction in the new range could be related to a loss of specialisation through selection of traits allowing coping with various or changing environments, improving successful spread. Survival of both model species was highly affected by community spatial pattern, management and neighbouring competition. Responses of growth and reproductive output of native and introduced genotypes to management, community spatial pattern and community diversity were species-specific. Growth and reproductive output of both genotypes of S. inaequidens were affected by experimental factors whereas introduced genotypes of C. maculosa were less affected than native ones. Comparison of response of native and introduced genotypes to experimental factors allowed defining two strategies of invasion based on phenotypic plasticity. Centaurea maculosa was able to maintain fitness in all kinds of environments, either favourable or stressful ("Jack-of-all-trades" invader). Senecio inaequidens was able to deal with all kinds of environments and was also able to increase its fitness in favourable conditions ("Jack-and-Master" invader). The combination of the effects of management, community spatial pattern and community diversity on species genotypes allowed defining, for both invasive species, two invasion phases which were impacted by different factors. The introduction phase corresponds to the survival of seedlings and their ability to deal with neighbouring competition. If seedlings manage to survive despite neighbouring competition, they grow and reproduced in order to spread, which corresponds to the establishment phase. In terms of management perspectives, regular mowing or use of highly covering species could limit invasive success of S. inaequidens and C. maculosa respectively. The synthesis of all the experiments conducted in this thesis with C. maculosa and S. inaequidens highlights (1) the importance of polyploidisation in the invasion process as well as (2) the species-specific invasion strategies and consequently (3) the species-specific response of invasive species to abiotic and biotic factors. It also emphasizes on (4) the temporal evolution of the interaction between invasiveness and invasibility since the community factors that affected invasive species fitness changed according to the invasion stage (introduction vs. establishment phase) of the invader. The provided insights into the importance of the interaction between species invasiveness and community invasibility will contribute to improve knowledge in ecology of invasions, in addition to supply some clues for management efficiency.