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Diversity comes at a cost: multifaceted diversity reduces plant community stability in peatlands
No full text1. Understanding how ecological stability relates to diversity is of crucial importance under global change. Greater biodiversity is expected to stabilize aggregate community properties through compensatory dynamics, as species fluctuate asynchronously and offset one another. Yet, diversity-stability relationships are not straightforward and can vary across and within ecosystems, particularly in wetlands where strong abiotic filters shape community assembly and temporal dynamics.2. We examined how multiple facets of diversity (taxonomic, functional, and phylogenetic) and functional trait identity relate to temporal stability (invariability) and species asynchrony in peatland vegetation. We used a 17-year field experiment in a montane peatland complex spanning a bog and a transitional poor fen, combining open-top chamber (OTC) passive warming with natural hydrological contrasts.3. Water table depth was the dominant environmental filter of plant communities, explaining 46 % of total compositional variance, whereas OTC-induced warming had no detectable effect. Community temporal stability and species asynchrony were higher under drier conditions (deeper water table), consistent with moisture-driven constraints on peatland vegetation dynamics.4. Contrary to insurance hypothesis predictions, temporal stability decreased with multiple biodiversity facets, particularly phylogenetic diversity and species richness, but increased with deeper-rooted plant strategies, after controlling for experimental conditions. Species asynchrony was largely unrelated to biodiversity, except for functional redundancy, which was associated with lower asynchrony but showed no association with temporal stability. The stability-asynchrony association weakened substantially after controlling for hydrology.5. Synthesis. Our results reveal that in peatlands, hydrology simultaneously structures biodiversity patterns, temporal stability and species asynchrony, yielding negative diversity-stability relationships that contradict classical insurance hypothesis predictions. These findings suggest that in peatlands, stability arises primarily from hydrological constraints, with limited contribution from compensatory dynamics among plant species. In strongly constrained, species-poor ecosystems, conservation may therefore prioritize maintaining or restoring the key abiotic conditions that favor functionally adapted communities over increasing diversity to sustain stable ecosystem functioning under global change
Climate-growth relationships in the introduced dominant woody tree Neltuma juliflora in Santiago Island, Cabo Verde Archipelago (Eastern Atlantic)
No full textInternational audienceHighlights: • Provides the first dendroecological assessment of Neltuma juliflora in Cabo Verde. • Reveals strong variability in radial growth across four bioclimatic zones. • Shows negative effects of off-season rainfall and a modulatory role of temperature. • Highlights the ecological plasticity of N. juliflora under semi-arid conditions.Offers baseline knowledge to guide reforestation and climate adaptation in dry islands.Abstract: Neltuma juliflora (syn. Prosopis juliflora) is the dominant woody species in Cabo Verde, introduced through extensive reforestation efforts to combat land degradation. Despite its ecological and socio-economic relevance, little is known about its growth dynamics and climatic sensitivity in this region. This study investigates growth ring formation and climate-growth relationships of N. juliflora on Santiago Island. We sampled 165 trees across 11 blocks, grouped into four bioclimatic zones. Tree-ring widths were measured using standard dendrochronological techniques. Generalised Linear Models (GLMs) were applied to assess the influence of climatic variables, with multicollinearity controlled using the Variance Inflation Factor (VIF). Although false rings were present, distinct growth boundaries were observed. Mean radial growth varied from 1.53 to 2.11 mm/year across bioclimatic zones. The best GLMs suggest that higher precipitation outside of the usual rainy season could negatively affect growth, while mean annual temperature could have a marginally positive effect. Significant differences in tree-ring growth rate were observed between trees sampled at the four bioclimatic areas, likely reflecting the influence of climate and elevation, and of other factors such as soil and tree density. These results highlight the ecological plasticity of N. juliflora and support its potential use in dendroclimatic research in semiarid tropical regions. These findings have significant implications for ecosystem-based adaptation strategies and sustainable land management practices in Cabo Verde, particularly in the context of climate change and land degradation mitigation. The study underscores the need for longer chronologies and expanded geographic sampling across the archipelago in future work
Les raisons de la mobilisation agricole en Europe expliquées par les agriculteurs eux‑mêmes
No full textInternational audienceDepuis l’hiver 2024, les mobilisations agricoles ont été largement interprétées, au plan médiatique, comme un rejet massif des normes environnementales. Mais est-ce vraiment le cas ? Qu’en disent eux-mêmes les agriculteurs mobilisés ? Une vaste étude a recensé leurs réponses en France, en Allemagne, en Belgique et aux Pays-Bas. Elle livre une image bien plus nuancée en fonction des États, où le poids des normes environnementales n’est finalement qu’un enjeu secondaire. Celui-ci a pourtant été au cœur de la réponse politique
Unlocking research on rhizodeposition: a step-by-step guide for producing, sampling and analyzing
No full textRhizodeposits, i.e. the organic materials released by living roots into the soil, play a major role in plant interactions with their biotic and abiotic environment. However, our understanding of rhizodeposition processes has remained limited due to the methodological challenges associated with the collection and analysis of rhizodeposits. Here, we aimed to synthesize knowledge from the various fields of expertise required for studying rhizodeposition, in order to support the scientific community in making informed methodological choices and to ensure the robustness and comparability of studies. In particular, we developed an open-access decision support tool (CARROT: Collecting and Analyzing Rhizodeposits: Reviewing and Optimizing Tool), using existing literature and practical expertise from the interdisciplinary network RhizosPHARE. This tool has been designed to help newcomers and specialists in the field i) to quickly identify the most appropriate methodological option(s) in terms of plant growth conditions, sample collection and sample analysis according to their scientific question and their experimental constraints, ii) to get practical recommendation about each method, and iii) to get a direct access to additional information and references. As part of these guidelines, we also suggest a standardized protocol for collecting root exudates from hydroponically grown plants to characterize their composition. Together with the CARROT tool, this protocol paves the way towards establishing consistent, standardized methods for characterizing rhizodeposition and its impact in the plant-soil system
Regularization of optimal control problems on stratified domains using additional controls
No full textInternational audienceIn this paper, we investigate a Mayer optimal control problem governed by a dynamics defined regionally. We consider that the state space is stratified into a family of disjoint regions with nonsmooth interfaces, and that in each region, the dynamics is given by a smooth expression. First, it is shown that this problem is equivalent to a new optimal control problem, with additional controls and a (smooth) dynamics defined as a convex combination of the smooth dynamics, along with a mixed control-state constraint. Next, we introduce a family of auxiliary optimal control problems. In these problems, we first regularize the nonsmooth interfaces. In addition, we consider the convex combination of smooth dynamics (only) within a boundary layer. Furthermore, we add a penalization term to the cost function to account for the mixed control-state constraint. Our main result is that solutions to these (smooth) problems converge (up to a subsequence) to a solution of the original one. It is obtained thanks to a new hypothesis related to solutions to the auxiliary problems, which is weaker than the transverse crossing condition of the literature. This technique is implemented numerically on two examples involving non-transverse crossings of interfaces showing its efficiency
Assessing liveweight dynamics and production responses to nutritional level in Sarda dairy ewes through walk-over-weighing technology
No full textInternational audienceIn Mediterranean dairy sheep systems, seasonal feed shortages often result in periods of undernutrition, negatively affect-ing animal performance and welfare [1], particularly during lactation. Liveweight (LW) is a practical indicator of nutri-tional status and body reserve dynamics; however, conventional weighing is labour-intensive and usually performed at low frequency. Walk-over-weighing (WoW) systems integrated with electronic identification (EID) allow frequent, low-labour monitoring of individual animals and may improve the detection of nutritionally driven LW changes [2].This study evaluated the sensitivity of a WoW system to detect moderate LW changes associated with contrasting nutri-tional levels in Sarda dairy ewes managed indoors or at pasture. Two experiments were conducted: (i) non-lactating ewes housed indoors and subjected to a short-term nutritional challenge; and (ii) lactating ewes managed on pasture with dif-ferent daily access times and supplemented with hay and concentrate. In both experiments, ewes exposed to the lower nutritional level showed reduced LW, and the WoW system consistently detected these differences over time. Under grazing conditions during lactation, nutritional differences were also reflected in milk production indicators.Overall, automated LW monitoring through WoW technology represents a feasible approach to track LW trajectories in dairy ewes under contrasting management conditions. Integrating LW data with routinely collected production traits (e.g. milk yield and composition) may support earlier identification of nutritional shortfalls and improve decision-making in welfare-oriented management.[1] Morgan-Davies, C., Tesnière, G., Gautier, J.M., Jørgensen, G.H.M., González-García, E., Patsios, S.I., Sossidou, E.N., Keady, T.W.J., McClearn, B., Kenyon, F., Caja, G., Grøva, L., Decandia, M., Cziszter, L., Halachmi, I., Dwyer, C.M., 2024. Review: Exploring the use of preci-sion livestock farming for small ruminant welfare management. Animal 18(S2), 101233. https://doi.org/10.1016/j.animal.2024.101233A[2] González-García, E., Alhamada, M., Nascimento, H., Portes, D., Bonnafe, G., Allain, C., Llach, I., Hassoun, P., Gautier, J.M., Parisot, S., 2021. Measuring liveweight changes in lactating dairy ewes by using an automated walk-over-weighing system. Journal of Dairy Science 104, 5675–5688. https://doi.org/10.3168/jds.2020-1907
Vvgai1 mutation impacts both organogenesis and functioning in Vitis labruscana microvines
No full textInternational audienceIn order to develop new genotypes to explore grapevine adaptation to climate, we introduced the Vvgai1 mutation in V. vinifera x V. labrusca hybrids. Vvgai1 mutation induced a strong miniaturisation of leaf and shoot length, as a result of a significant reduction of internodes size and an increase of the phyllochron. The lignification of the main shoots was delayed in the microvines in comparison to their macrovine counterparts while the leaf C assimilation rate was not impacted by the mutation. The shift from the alternate spiral (juvenile) to distichous (adult) phyllotaxis and the appearance of the first tendril occurred at lower node rank in macrovines. However, while macrovines did not produce any reproductive organs during the first vegetative cycle, microvines displayed the first perfect flowers on the main shoot from the internode 18, only a few months after embryo rescue and acclimation. The segregation of the sex type confirmed that the sex determining locus of the V. labrusca cv. Isabella is heterozygous. Conversely, the proportion of opposite-to-leaves organs following a labrusca-versus vinifera-type distribution suggested a more complex genetic determinism for this trait. These experiments provide a new set of microvine genotypes and phenotypic data for studying the response of V. labruscana to abiotic and biotic factors and open new questions about how phytohormones control the development of the grapevine liana.</div
Vaccination against H5 HP avian influenza virus leads to persistent immune response in wild king penguins
No full textInternational audienceAbstract Since 2021, the panzootic nature of high pathogenicity avian influenza (HPAI) represents an increasing threat to wild vertebrate populations. In this context, recent vaccines developed for poultry could provide tools for the conservation of wild endangered birds populations. The king penguin ( Aptenodytes patagonicus ), a long-lived seabird breeding in dense colonies with an extended chick-rearing period, has been identified as a possible surrogate species for a vaccination trial in a sub-Antarctic natural setting. Here we investigate the immune response of king penguin chicks to a self-amplifying mRNA vaccine against a H5 HPAI clade 2.3.4.4b protein. The cohort entails thirty vaccinated chicks (primo- and boost-injections), and 20 unvaccinated controls. Along 250 days of monitoring, the vaccinated chicks show a high and persistent immune response, granting a strong sero-neutralisation capacity against the virus, up to fledging. No adverse effects are observed. Screening for antibodies against unspecific avian influenza viruses suggests that no natural infection has occurred over the entire trial. The emergence of HPAI in the Southern Indian Ocean in October 2024 highlights the timeliness of such experimental tests. Our results thus show the vaccine could provide a potentially powerful tool for mitigation of avian flu outbreaks in the wild
Near-complete genome sequences of a rice necrosis mosaic virus isolate infecting rice in Argentina
No full textInternational audienceABSTRACT While rice necrosis mosaic virus (RNMV) has only been described in Asia, we identified this virus on a rice plant from Argentina using a viral metagenomic approach. We further confirmed this result by RT-PCR and small-RNA Illumina sequencing to obtain the near-complete genome and to confirm actual infection by RNMV