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How is the carbon use efficiency of microbial communities distributed within the soil pore network
No full textInternational audienceSoils play a key role in mitigating global warming due to their capacity to sequester CO₂, a process likely impacted by the efficiency with which microbial communities transform organic matter into biomass. The activity of microbes is affected by the conditions they find themselves in (moisture, oxygen, etc.). Soils are characterized by a network of pores of different sizes, which create a variety of microenvironments that can influence resource availability, microbial activity and soil C dynamics. However, the influence of conditions at the porescale on microbial carbon use efficiency remains poorly quantified. In this study, we conducted short-term incubations using a mixture of 13 C-labelled compounds to assess the carbon use efficiency of microbial communities residing in pores with maximum neck diameters between 15 and 30 μm and between 75 and 200 μm. The study was carried out in an agricultural soil (Eutric Cambisol) under three different management practices and a grassland (Sandy Cambisol) in order to have a range of pore structures, C contents, pH and different microbial communities. Our findings show that microbial mineralization of added substrate was higher in the large pores but that the carbon utilization efficiency was lower. The differences across pore sizes were likely due to the different constraints at the microenvironment scale (moisture, predation, available space, substrate abundance, etc.). These results suggest that microbes adopt distinct carbon processing strategies and functional roles, depending on pore size
Protected areas influence fire regimes globally
No full textInternational audienceProtected areas (PAs) aim to support global conservation efforts including the maintenance of fire regimes and mitigation of negative fire impacts. Analyzing data from over 20 million fires worldwide, we found that PAs, along with the various protection levels defined by the International Union for Conservation of Nature (IUCN), significantly influenced burned area (BA) and fire regime attributes across continents and biomes in distinct ways, with varying impacts on fire size, spread, intensity, and duration. In most biomes, the proportion of BA within PAs was smaller than the proportion of PA itself, indicating that PAs were generally less impacted by wildfires. However, in tropical grasslands, tropical dry broadleaf forests and temperate conifer forests, the BA fraction inside PAs was larger. The strictest IUCN protection categories (Ia and Ib) were associated with the lowest BA, compared to National Parks (IUCN II) and other less restrictive protection categories. However, this pattern varied by biome, with mediterranean forests, temperate broadleaf and mixed forests, temperate grasslands and tropical coniferous forests showing increased fire proneness in the strictest IUCN categories and more intense fires. Insights from this research can guide targeted environmental policies to strengthen PA networks to maintain fire regimes
Changes in phenology mediate vertebrate population responses to temperature globally
No full textInternational audiencePhenotypic responses to climate affect individual fitness, but the extent to which this translates into effects on population dynamics remains poorly understood. We assemble 213 time series on phenotypes and population sizes of wild vertebrates globally and match them with local climate data. Our meta-analysis shows that morphological traits are mostly climate insensitive. However, phenology is earlier in warmer-than-average years, which contributes positively to population growth in most species. At lower latitudes, temperature has weaker effects on phenology but stronger direct negative effects on population growth, likely because these populations are less capable of tracking climate via plasticity. Variation in the phenology-mediated effect of temperature on population growth cannot be explained by latitude, generation time, migratory mode, or diet. This suggests that simple relationships between species characteristics and population responses to warming may not occur in nature. Instead, we may need to embrace ecological complexity by considering local-scale predictors that capture intra-specific variation
Observation of a cross-section enhancement near the production threshold in TeV collisions with the ATLAS detector
No full textInternational audienceA measurement of production is presented in the invariant-mass region near the pair production threshold, GeV, in final states with two charged leptons and multiple jets. The measurement is based on of proton-proton collision data collected at TeV with the ATLAS detector at the Large Hadron Collider. The data are compared to two models of production: a baseline model including only perturbative QCD predictions for the hard process, and an extended model that, in addition, incorporates non-relativistic QCD simulations of colour-singlet quasi-bound-state formation near the threshold. The agreement between the data and the models is quantified via a profile-likelihood fit to the reconstructed distributions, in bins of two angular observables sensitive to spin-correlations in the system. An excess of events is observed over the baseline perturbative QCD prediction, with an observed significance over standard deviations. This excess is consistent with the formation of colour-singlet and spin-singlet -wave quasi-bound states, as predicted by non-relativistic QCD, and corresponds to an observed cross-section of pb
Histoire intellectuelle de la Chine: [résumé des cours et travaux : 2021-2022]
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Techniques et économies de la Méditerranée antique: [résumé des cours et travaux : 2021-2022]
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Philosophie du langage et de l’esprit: [résumé des cours et travaux : 2021-2022]
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