Lags in phenological acclimation of mountain grasslands after recent warming

1. In the current biodiversity crisis, one of the crucial questions is how quickly plant communities can acclimate to climate warming and longer growing seasons to buffer the impairment of community functioning. Answering this question is pivotal especially for mountain grasslands that experience harsh conditions but provide important ecosystem services to people. 2. We conducted a reciprocal transplant experiment along an elevation gradient (1920 m vs. 2450 m) in the French Alps to test the ability of plant species and communities to acclimate to warming and cooling. For three years, we measured weekly the timing of phenological events (e.g. start of flowering or greening) and the length of phenological stages linked to demographic performance (e.g. lengths of flowering or greening periods). 3. We found that warming (and cooling) changed the timing of phenological events strongly enough to result in complete acclimation for graminoids, for communities in early and mid-season, but not at all for forbs. For example, warming resulted in later greening of communities and delayed all phenophases of graminoids. Lengths of phenological stages did not respond strongly enough to climate change to acclimate completely, except for graminoids. For example, warming led to an acclimation lag in the community's yearly productivity and had a strong negative impact on flowering of forbs. Overall, when there was an acclimation failure, responses to cooling were mostly symmetric and confirmed slow acclimation in mountain grasslands. 4. Synthesis. Our study highlights that phenological plasticity cannot prevent impairment of community functioning under climate warming in the short-term. The failures to acclimate after three years of warming signals that species and communities underperform and are probably at high risk of being replaced by locally better-adapted plants.dataFocals_030621.RData or dataFocals_030621.csv Plot: Treatment groups LC: SubalpineControl LT: AlpineWarmed GC: AlpineControl GT: SubalpineCooled Repetition: Number of plot repetitions Observation_Date: Species: Focal species names Phenophase: Phenological phases as described in the main manuscript Number_of_individuals: Number of individuals present in the phenophase. For details, please refer to the main manuscript. dataNDVI_030621.RData or dataNDVI_030621.csv Plot: Treatment groups LC: SubalpineControl LT: AlpineWarmed GC: AlpineControl GT: SubalpineCooled Subplot: Coding for 1mx1m subplots X: Only for Controls A,B,C,D: Only for Treatments Plot_Repetition: Number of 4mx4m plot repetitions Measurement_Repetition: 3 times measurement repetitions Measurement_Date: Measurement_Sm: Gap-filled NDVI measurements. For the methodology, please refer to the main manuscript. Funding provided by: Agence Nationale de la RechercheCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001665Award Number: TransAlp ANR‐20‐CE02‐0021For the dataset collection and the processing, please refer to the methods section of the manuscript

Differential effects of soil trophic networks on microbial decomposition activity in mountain ecosystems

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Altitudinal Zonation of Green Algae Biodiversity in the French Alps

International audienceMountain environments are marked by an altitudinal zonation of habitat types. They are home to a multitude of terrestrial green algae, who have to cope with abiotic conditions specific to high elevation, e.g., high UV irradiance, alternating desiccation, rain and snow precipitations, extreme diurnal variations in temperature and chronic scarceness of nutrients. Even though photosynthetic green algae are primary producers colonizing open areas and potential markers of climate change, their overall biodiversity in the Alps has been poorly studied so far, in particular in soil, where algae have been shown to be key components of microbial communities. Here, we investigated whether the spatial distribution of green algae followed the altitudinal zonation of the Alps, based on the assumption that algae settle in their preferred habitats under the pressure of parameters correlated with elevation. We did so by focusing on selected representative elevational gradients at distant locations in the French Alps, where soil samples were collected at different depths. Soil was considered as either a potential natural habitat or temporary reservoir of algae. We showed that algal DNA represented a relatively low proportion of the overall eukaryotic diversity as measured by a universal Eukaryote marker. We designed two novel green algae metabarcoding markers to amplify the Chlorophyta phylum and its Chlorophyceae class, respectively. Using our newly developed markers, we showed that elevation was a strong correlate of species and genus level distribution. Altitudinal zonation was thus determined for about fifty species, with proposed accessions in reference databases. In particular, Planophila laetevirens and Bracteococcus ruber related species as well as the snow alga Sanguina genus were only found in soil starting at 2,000 m above sea level. Analysis of environmental and bioclimatic factors highlighted the importance of pH and nitrogen/carbon ratios in the vertical distribution in soil. Capacity to grow heterotrophically may determine the Trebouxiophyceae over Chlorophyceae ratio. The intensity of freezing events (freezing degree days), proved also determinant in Chlorophyceae distribution. Guidelines are discussed for future, more robust and precise analyses of environmental algal DNA in mountain ecosystems and address green algae species distribution and dynamics in response to environmental changes

Soil organic matter changes under experimental pedoclimatic modifications in mountain grasslands of the French Alps

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Optimized combinatorial pMHC class II multimer labeling for precision immune monitoring of tumor-specific CD4 T cells in patients

With immunotherapy gaining increasing approval for treatment of different tumor types, scientists rely on cutting edge methods for the monitoring of immune responses and biomarker development in patients. Due to the lack of tools to efficiently detect rare circulating human tumor-specific CD4 T cells, their characterization in patients still remains very limited

Strong links between plant traits and microbial activities but different abiotic drivers in mountain grasslands

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Mountain soil multitrophic networks shaped by the interplay between habitat and pedoclimatic conditions

International audienceOur knowledge of the factors influencing the distribution of soil organisms is limited to specific taxonomic groups. Consequently, our understanding of the drivers shaping the entire soil multitrophic network is constrained. To address this gap, we conducted an extensive soil biodiversity monitoring program in the French Alps, using environmental DNA to obtain multi-taxon data from 418 soil samples. The spatial structure of resulting soil multitrophic networks varied significantly between and within habitats. From forests to grasslands, we observed a shift in the abundance of trophic groups from fungal to bacterial feeding channels, reflecting different ecosystem functioning. Furthermore, forest soil networks were more strongly spatially structured which could only partly be explained by abiotic conditions. Grassland soil networks were more strongly driven by plant community composition and soil characteristics. Our findings provide valuable insights into how climate and land-use changes may differentially affect soil multitrophic networks in mountains

Data from: Spatial scale and intraspecific trait variability mediate assembly rules in alpine grasslands

Assembly of grassland communities has long been scrutinized through the lens of functional diversity. Studies generally point to an overwhelming influence of climate on observed patterns of functional diversity, despite experimental evidence demonstrating the importance of biotic interactions. We postulate that this is because most observational studies neglect both scale dependencies of assembly processes and phenotypic variation between individuals. Here, we test for changes in the importance of abiotic filtering and biotic interactions along a stress gradient by explicitly accounting for different scales. In addition to quantifying intraspecific trait variability (ITV), we also vary the two components of spatial scale, including grain (i.e. community size) and extent (i.e. the geographical area that defines the species pool). We sampled 20 grassland communities in ten sites distributed along a 975-m elevation gradient. At each site, we measured seven functional traits for a total of 2020 individuals at different spatial grains. We related community functional diversity metrics to the main environmental gradient of our study area, growing season length (GSL), and assessed the dependence of these relationships on spatial grain, spatial extent and ITV. At large spatial grain and extent, the imprint of environmental filtering on functional diversity became more important with increasing stress (i.e. functional diversity decreased with shorter GSL). At small spatial grain and extent, we found a convex relationship between functional diversity and GSL congruent with the hypothesis that competition is dominant at low-stress levels while facilitative interactions are dominant at high-stress levels (i.e. high functional diversity at both extremes of the stress gradient). Importantly, the effect of intraspecific variability on assembly rules was noticeable only at small spatial grain and extent. Synthesis. Our study reveals how the combination of abiotic stress and biotic interactions shapes the functional diversity of alpine grasslands at different spatial scales, and highlights the importance of phenotype variation between individuals for community assembly processes at fine spatial scale. Our results suggest that studies analysing trait-based assembly rules but ignoring ITV and focusing on a single spatial scale are likely to miss essential features of community diversity patterns

Climate, soil resources and microbial activity shape the distributions of mountain plants based on their functional traits

International audienceWhile soil ecosystems undergo important modifications due to global change, the effect of soil properties on plant distributions is still poorly understood. Plant growth is not only controlled by soil physico-chemistry but also by microbial activities through the decomposition of organic matter and the recycling of nutrients essential for plants. A growing body of evidence also suggests that plant functional traits modulate spe-cies' response to environmental gradients. However, no study has yet contrasted the importance of soil physico-chemistry, microbial activities and climate on plant species distributions, while accounting for how plant functional traits can influence species-specific responses. Using hierarchical effects in a multi-species distribution model, we investigate how four functional traits related to resource acquisition (plant height, leaf carbon to nitrogen ratio, leaf dry matter content and specific leaf area) modulate the response of 44 plant species to climatic variables, soil physico-chemical properties and microbial decomposition activity (i.e. exoenzymatic activities) in the French Alps. Our hierarchical trait-based model allowed to predict well 41 species according to the TSS statistic. In addition to climate, the combination of soil C/N, as a measure of organic matter quality, and exoenzymatic activity, as a measure of microbial decomposition activity, strongly improved predictions of plant distributions. Plant traits played an important role. In particular, species with conservative traits performed better under limiting nutrient conditions but were outcompeted by exploitative plants in more favorable environments. We demonstrate tight associations between microbial decomposition activity, plant functional traits associated to different resource acquisition strategies and plant distributions. This highlights the importance of plant-soil linkages for mountain plant distributions. These results are crucial for biodiversity modelling in a world where both climatic and soil systems are undergoing profound and rapid transformations