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How to measure agroecology? A rapid appraisal approach based on focus group discussions
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Subsistance, attachements et attentions à l'épreuve des pollutions industrielles
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Microclimate modulation: An overlooked mechanism influencing the impact of plant diversity on ecosystem functioning
No full textInternational audienceAbstract Changes in climate and biodiversity are widely recognized as primary global change drivers of ecosystem structure and functioning, also affecting ecosystem services provided to human populations. Increasing plant diversity not only enhances ecosystem functioning and stability but also mitigates climate change effects and buffers extreme weather conditions, yet the underlying mechanisms remain largely unclear. Recent studies have shown that plant diversity can mitigate climate change (e.g. reduce temperature fluctuations or drought through microclimatic effects) in different compartments of the focal ecosystem, which as such may contribute to the effect of plant diversity on ecosystem properties and functioning. However, these potential plant diversity‐induced microclimate effects are not sufficiently understood. Here, we explored the consequences of climate modulation through microclimate modification by plant diversity for ecosystem functioning as a potential mechanism contributing to the widely documented biodiversity–ecosystem functioning (BEF) relationships, using a combination of theoretical and simulation approaches. We focused on a diverse set of response variables at various levels of integration ranging from ecosystem‐level carbon exchange to soil enzyme activity, including population dynamics and the activity of specific organisms. Here, we demonstrated that a vegetation layer composed of many plant species has the potential to influence ecosystem functioning and stability through the modification of microclimatic conditions, thus mitigating the negative impacts of climate extremes on ecosystem functioning. Integrating microclimatic processes (e.g. temperature, humidity and light modulation) as a mechanism contributing to the BEF relationships is a promising avenue to improve our understanding of the effects of climate change on ecosystem functioning and to better predict future ecosystem structure, functioning and services. In addition, microclimate management and monitoring should be seen as a potential tool by practitioners to adapt ecosystems to climate change
TROLL 4.0: representing water and carbon fluxes, leaf phenology, and intraspecific trait variation in a mixed-species individual-based forest dynamics model – Part 2: Model evaluation for two Amazonian sites
No full textTROLL 4.0 is an individual-based forest dynamics model that jointly simulates the structure, diversity and functioning of tropical forests, including their water balance, carbon fluxes and leaf phenology, while accounting for intraspecific trait variation for a large number of species. In a companion paper, we describe how the model represents the physiological and demographic processes that control the tree life cycle in a one-metre-resolution spatially-explicit scene and uses plant functional traits measurable in the field to parameterize such processes across species and individuals (Maréchaux et al., submitted companion paper). Here we evaluate the performance of TROLL 4.0 for two Amazonian sites with contrasting soil and climate properties. We assessed the model's ability to represent forest structure and composition using lidar-derived canopy height distributions and forest inventories combined with information on plant functional traits. We also evaluated the model's ability to represent carbon and water fluxes, as well as leaf area variation, at daily and fortnightly resolution over a decade, using detailed information from on-site eddy covariance towers, satellite data and ground-based or air-borne lidar data. We finally compared the responses of carbon and water fluxes to environmental drivers between simulated and observed data. Overall, TROLL 4.0 provided a realistic representation of forests at both sites. The simulated canopy height distribution showed a high correlation coefficient (CC) with observed aerial and satellite data (CC>0.92), while the species and functional composition were well represented (CC>0.75). TROLL 4.0 also realistically simulated the seasonal variability of carbon and water fluxes (CC>0.46) and their responses to environmental drivers, while capturing temporal variations in leaf area (CC>0.76) and its partitioning in leaf age cohorts. However, TROLL 4.0 overestimated annual gross primary productivity at both sites (mean RMSEP=0.94 kgC m-2 yr-1) and evapotranspiration at one site (mean RMSEP=0.75 mm day-1), likely due to an underestimation of the soil water depletion and stomatal control during the dry season. This evaluation highlights the potential of TROLL 4.0 to represent ecosystem fluxes and the structure and diversity of plant communities at a fine resolution, paving the way for model predictions of the effects of climate change, fragmentation and forest management on forest structure and dynamics
Modélisation mathématique et analyse de modèles spatio-temporels dédiés à la dynamique arbre-herbe dans les savanes humides
No full textVegetation biome encompasses in wet ecosystems, self organized physiognomies that traduce complex dynamical processes leading to homogeneous distributions of forests, grasslands and savannas, to heterogeneous distributions of trees and grasses. Spatio-temporal patterns of vegetation, are characteristic feature of wetland ecosystems occurring in all continents. The development of a better understanding of their spatial dynamics, is an issue of considerable ecological and social economical importance, by regulating global climate and provides materials need for human. Mathematical modelling is a useful tool to describe dynamics of complex systems and, several mathematical models have been devoted to the study of tree-grass dynamics in savanna ecosystems, but with a scarcely attention, of spatial mechanism of tree and grass interactions that translated in space. This work dedicated to the modelling and the analyse via partial differential equations on tree and grass dynamics in humid savannas is divided in two main parts. In the first part, we propose and analyse a spatio-temporal model of tree-grass interactions in humid savanna. This first model, is based on two nonlocal reaction-diffusion equations with kernels of intra and inter specific competition and also a kernel indirectly acting as facilitation in term of reduction of fire effect on tree mortality; all off these in the reaction part of the model. The diffusion part is modelled via the Laplace operators considered in a one spatial domain. A qualitative analyse of this model reveals several ecological thresholds that shape the overall dynamics of the model. Thanks to linear stability analysis, the model account for the occurrence of space inhomogeneous solutions. All of these lead us to conclude that, the interplay between nonlocal competition and nonlocal facilitation, can explain the spatial periodic structuring sometimes observed in humid savannas. In the second part of this work, we consider nonlocal seed dispersal, as to describe the propagation in space of both tree and grass biomass. We therefore replaced, the Laplace operators by integral operators, and, we focus on the existence of travelling wave connecting the grassland homogeneous steady state to the forest homogeneous steady state of the model. A qualitative analyse of this reaction dispersion model, leads to the characterisation by a mathematical expression depending on several parameters of the model, of the minimal wave speed that controls the forest encroachment into the grassland. We therefore found that, the length of tree seed dispersal and the fire frequency can control the wave propagation.Dans les écosystèmes humides le biome de végétation englobe des physionomies autoorganisées qui décrivent des processus dynamiques complexes allant des distributions homogènes de forêts, de prairies et de savanes, à des distributions hétérogènes d’arbres et d’herbes. Ces physionomies de végétations sont des traits caractéristiques des écosystèmes en zones humides et sont observées sur tous les continents. Le développement d’une meilleure compréhension de leur évolution spatio-temporelle est un enjeu d’importance écologique et socio-économique considérable, pour la régulation du climat mondial et de l’approvisionnement en matériaux nécessaires à l’homme. La modélisation mathématique est un outil utile pour décrire la dynamique de systèmes complexes, et plusieurs modèles mathématiques ont été consacrés à l’étude des dynamiques arbres-herbes dans les écosystèmes de savanes, mais ceci, avec une attention limitée sur les mécanismes spatiaux entre arbres et herbes. Ce travail, qui consiste en la modélisation et l’analyse via des équations aux dérivées partielles des dynamiques arbres/herbes dans les savanes humides, est divisée en deux parties principales. Dans la première partie, nous analysons un modèle spatio-temporel d’interactions arbres-herbes en zones de savanes humides. Ce premier modèle est basé sur deux équations de réaction-diffusion intégro-différentielles avec, dans la partie réaction du modèle des noyaux de compétition intra et interspécifiques et un noyau agissant indirectement comme terme de facilitation en decrivant la réduction de la mortalité des arbres liée aux feux. La partie diffusion est modélisée via l’operateur de Laplace. Une analyse qualitative de ce modèle révèle plusieurs seuils écologiques qui régulent la dynamique globale du modèle. Grace à l’analyse de stabilité linéaire, le modèle rend compte de l’existence de solutions inhomogènes en espace. Ceci nous conduit à conclure que la présence conjointe de compétition non-locale et facilitation non-locale conduit à une structuration spatiale périodique dans les savanes humides. Dans la deuxième partie de ce travail, nous considérons la dispersion non-locale des graines pour décrire la propagation spatiale de la biomasse des arbres et des graminées. Nous remplaçons donc les opérateurs de Laplace par des opérateurs intégraux et nous nous focalisons sur l’existence d’une onde progressive reliant l’état stationnaire homogène de prairie à l’état stationnaire homogène de foret. Une analyse qualitative de ce modèle de réaction-dispersion nous permet de caractériser, par une expression mathématique dépendant de plusieurs paramètres du modèle, la vitesse minimale de l’onde progressive qui contrôle l’avancée de la forêt dans la prairie. Ainsi nous parvenons à la conclusion selon laquelle la longueur de dispersion des graines d’arbres et la fréquence des feux peuvent contrôler la vitesse de l’onde progressiv
Quantifying maternal investment in mammals using allometry
No full textInternational audienceAbstract Maternal investment influences the survival and reproduction of both mothers and their progeny and plays a crucial role in understanding individuals’ life-history and population ecology. To reveal the complex mechanisms associated with reproduction and investment, it is necessary to examine variations in maternal investment across species. Comparisons across species call for a standardised method to quantify maternal investment, which remained to be developed. This paper addresses this limitation by introducing the maternal investment metric – MI – for mammalian species, established through the allometric scaling of the litter mass at weaning age by the adult mass and investment duration (i.e. gestation + lactation duration) of a species. Using a database encompassing hundreds of mammalian species, we show that the metric is not highly sensitive to the regression method used to fit the allometric relationship or to the proxy used for adult body mass. The comparison of the maternal investment metric between mammalian subclasses and orders reveals strong differences across taxa. For example, our metric confirms that Eutheria have a higher maternal investment than Metatheria . We discuss how further research could use the maternal investment metric as a valuable tool to understand variation in reproductive strategies
Craniometric and Morphometric Characterization of Ouled Djellal Algerian White Arab Sheep
No full textInternational audienceBackground: In zooarchaeology, reference collections are essential for identifying skeletal remains and for predicting measurements of living animals. To date, the archaeozoological studies in Algeria are still limited and morphometric reference datasets of local breeds are yet to be established. This study aimed to reveal the correlations between measurements of living animals and their skulls.Methods: A total of 30 females of the Ouled Djellal Algerian White Arab breed were analyzed: 15 adults and 15 young adults. Eight external body measurements were taken before slaughter and the live weight was estimated. After slaughter, the heads were collected, meticulously cleaned, weighed and measured. Sixteen craniometric measurements were taken and two indices were calculated.Result: The differences between the mean values of young adults and adults were not statistically significant (p>0.05), except for wither height, naso-dental oblique length (CL31), greatest palatal breadth (CB14), greatest breadth across the premaxillae (CB18) and least height of the occipital (CH5). Young adults have a higher neurocranium and are more massive, whereas adults have a wider viscerocranium. Correlations between cranial and external measurements were partially significant, predominantly in adults. The strongest correlation was observed between the thoracic perimeter and condylobasal length (p<0.0001). These results provide a new reference dataset for archaeozoology
FCAvizIR
No full textImplication is a core notion of Formal Concept Analysis and its extensions. It provides information about the regularities present in the data. When one considers a relational data set of real-size, implications are numerous and their formulation, which combines primitive and relational attributes computed using Relational Concept Analysis framework, is complex. For an expert wishing to answer a question based on such a corpus of implications, having a smart exploration strategy is crucial. FCAvizIR is a web platform which implements a visual approach for such exploration. Comprised of three interactive and coordinated views and a toolbox, FCAvizIR has been designed to explore corpora of implication rules following Schneiderman's famous mantra ``overview first, zoom and filter, then details on demand''. It enables metrics filtering, e.g. fixing a minimum and a maximum support value, and the multiple selection of relations and attributes in the premise and in the conclusion to identify the corresponding subset of implications presented as a list and Euler diagrams
Phylogenetic relationships of Neogene hamsters (Mammalia, Rodentia, Cricetinae) revealed under Bayesian inference and maximum parsimony
No full textInternational audienceThere is an ongoing debate about the internal systematics of today’s group of hamsters (Cricetinae), following new insights that are gained based on molecular data. Regarding the closely related fossil cricetids, however, most studies deal with only a limited number of genera and statements about their possible relationships are rare. In this study, 41 fossil species from the Late Miocene to the Pliocene, belonging to seven extinct cricetine genera, Collimys , Rotundomys , Neocricetodon , Pseudocricetus , Cricetulodon , Apocricetus and Hattomys are analysed in a phylogenetic framework using traditional maximum parsimony and Bayesian inference approaches. Following thorough model testing, a relaxed-clock Bayesian inference analysis is performed under tip-dating to estimate divergence times simultaneously. Furthermore, so-called ‘rogue’ taxa are identified and excluded from the final trees to improve the informative value of the shown relationships. Based on these resulting trees, the fit of the topologies to the stratigraphy is assessed and the ancestral states of the characters are reconstructed under a parsimonious approach and stochastic character mapping. The overall topologies resulting from Bayesian and parsimonious approaches are largely congruent to each other and confirm the monophyly of most of the genera. Additionally, synapomorphies can be identified for each of these genera based on the ancestral state reconstructions. Only Cricetulodon turns out to be paraphyletic, while ‘ Cricetulodon ’ complicidens is a member of Neocricetodon . Lastly, this work makes a contribution to a debate that went on for decades, as the genus Kowalskia can be confirmed as junior synonym of Neocricetodon
Capturing the diversity of population recombination landscapes in fish and insects
No full textInternational audienceIn most mammals and snakes, recombination hotspots are regulated by the PRDM9 protein and evolve rapidly. Loss of a functional Prdm9 gene in other taxa, such as birds, some teleost fish or invertebrates, is associated with a different map of hotspot localisation and more stable recombination landscape dynamics. However, recombination landscapes are well described in only a handful of species, and the determinants of recombination rate variation in non-mammalian species are still poorly understood. We reconstructed fine-scale linkage disequilibrium recombination maps in wild populations of several teleost and insect species, including salmonids, thysanopterans, stick insects and termites, which have a full-length PRDM9. In contrast to European sea bass, salmonids show that hotspots are localised independently of transcription start sites and CpG islands, and evolve rapidly between populations, suggesting that PRDM9 is the main driver of hotspot regulation in this group. Insects show a high diversity of recombination landscapes, with some groups totally lacking hotspots. Recombination is strongly correlated with methylation landscapes, as previously described in some social insects. Since methylation inhibits recombination, recombination rates are higher outside gene regions, explaining the differences observed with vertebrates, where methylation is elevated along the entire genome. Preliminary evidence suggests that the function of PRDM9 in regulating recombination was also ancestral to insects. Taken together, these results provide a more comprehensive view of the diversity of recombination landscapes in animals and their main drivers