Résumé
The species-richness of the flora in the European Alps results from complex interactions between geographical, climatic and environmental factors. In this study, we focus on a complex of closely related Alpine plants: Primula hirsuta, P. pedemontana and their relatives. Using a large DNA dataset of thousands of single-nucleotide polymorphisms sequenced across 149 individuals spanning all the western Alps, we refine phylogenetic relationships in this clade and explore the evolutionary origins of a mysterious lineage found in one valley of the Écrins range (France): the Valgaudemar. In particular, we demonstrate that this lineage did not originate from a simple allopatric divergence, but from an isolated lineage related to Primula pedemontana, which later got introgressed by P. hirsuta. This leads us to develop a phylogeographic scenario explaining the origins of the Valgaudemar lineage, and shed light on a potential glacial refugium in the south of the Écrins range. We believe this study takes part in the deep understanding of the origins of endemism in the European Alps and more generally of the maintaining of species diversity.
Auteurs, date et publication :
Auteurs Camille Voisin , Cédric Dentant , Delphine Rioux , Florian C. Boucher
Publication : Alpine Botany
Date : 2023
Volume : 133
Issue : 1
Pages : 21-33
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Aim Two core assumptions of species distribution models (SDMs) do not hold when modelling invasive species. Invasives are not in equilibrium with their environment and niche quantification and transferability in space and time are limited. Here, we test whether combining global- and regional-scale data in a novel framework can overcome these limitations. Beyond simply improving regional niche modelling of non-native species, the framework also makes use of the violation of regional equilibrium assumptions, and aims at estimating the stage of invasion, range filling and risk of spread in the near future for 27 invasive species in the French Alps. Innovation For each invader we built three sets of SDMs using a committee averaging method: one global model and two regional models (a conventional model and one using the global model output to weight pseudo-absences). Model performances were compared using the area under the receiver operating characteristic curve, the true skill statistic, sensitivity and specificity scores. Then, we extracted the predictions for observed presences and compared them to global and regional models. This comparison made it possible to identify whether invasive species were observed within or outside of their regional and global niches. Main conclusions This study provides a novel methodological framework for improving the regional modelling of invasive species, where the use of a global model output to weight pseudo-absences in a regional model significantly improved the predictive performance of regional SDMs. Additionally, the comparison of the global and regional model outputs revealed distinct patterns of niche estimates and range filling among the species. These differences allowed us to draw conclusions about the stage of invasion and the risk of spread in the near future, which both correspond to experts' expectations. This framework can be easily applied to a large number of species and is therefore useful for control of biological invasions and eradication planning.
Auteurs, date et publication :
Auteurs Laure Gallien , Rolland Douzet , Steve Pratte , Niklaus E. Zimmermann , Wilfried Thuiller
Publication : Global Ecology and Biogeography
Date : 2025
Volume : 21
Issue : 11
Pages : 1126-1136
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Rock glaciers are creeping bodies of ice and rock that account for an important part of the mountain cryosphere. In this study, we investigated long-term changes of the Laurichard rock glacier (French Alps), to understand how this rock glacier is responding to climate change. Using feature-tracking and photogrammetric measurements between 1952 and 2019, we quantified changes in thickness, flow velocities and from which we derived the ice/rock flux of the rock glacier at a decadal time scale. This is the first time that emergence velocity and surface mass balance changes have been reconstructed for a rock glacier. Our results reveal a very small surface mass balance ranging from −0.1 m a−1 to +0.05 m a−1, reflecting the role of debris in damping the melt rate of the underlying ice. Surprisingly, we found a more negative surface mass balance in the upper part than in the lower part of the rock glacier during the 1952–1971 cold period, likely due to a reduction in rock and snow mass accumulation. Our study shows that thickness changes are mainly driven by changes in surface mass balance except during the most recent period in the lower part of the rock glacier, which was also influenced by a compressive flow related to a protrusion that prevented the rock glacier from advancing. We conclude that the period 1994–2019 witnessed a marked acceleration in rock glacier flow, in agreement with the observations of other rock glaciers in the European Alps. This strong increase in surface speed is likely a consequence of changes in the basal conditions.
Auteurs, date et publication :
Auteurs Diego Cusicanqui , Antoine Rabatel , Christian Vincent , Xavier Bodin , Emmanuel Thibert , Bernard Francou
Publication : Journal of Geophysical Research: Earth Surface
Date : 2025
Volume : 126
Issue : 9
Pages : e2021JF006161
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Annual plants usually flower and set seed once before senescence results in the death of the whole plant (monocarpic senescence). Leaf senescence also occurs in polycarpic perennials; even in “evergreen” species individual leaves senesce. In the annual model Arabidopsis thaliana sugars accumulate in the senescent leaves and senescence is accelerated by high sugar availability. Similar to A. thaliana, sugar contents increased with leaf age in the perennial Arabis alpina grown under warm conditions (22 ◦C day/18 night). At 5 ◦C, sugar contents in non-senescent leaves were higher than at a warm temperature, but dependent on the accession, either sugars did not accumulate or their contents decreased in old leaves. In A. alpina plants grown in their natural habitat in the Alps, sugar contents declined with leaf age. Growth at a cold temperature slightly delayed senescence in A. alpina. In both warm and cold conditions, an external glucose supply accelerated senescence, but natural variation was found in this response. In conclusion, sugar accumulation under warm conditions could accelerate leaf senescence in A. alpina plants, but genotype-specific responses and interactions with growth temperature are likely to influence senescence under natural conditions.
Auteurs, date et publication :
Auteurs Astrid Wingler , Emma Josefine Stangberg , Triambak Saxena , Rupal Mistry
Publication : Journal of Integrative Plant Biology
Date : 2025
Volume : 54
Issue : 8
Pages : 595-605
Catégorie(s)
#CNRS #Lautaret #UGARésumé
A growing body of work examines the direct and indirect effects of climate change on ecosystems, typically by using manipulative experiments at a single site or performing meta-analyses across many independent experiments. However, results from single-site studies tend to have limited generality. Although meta-analytic approaches can help overcome this by exploring trends across sites, the inherent limitations in combining disparate datasets from independent approaches remain a major challenge. In this paper, we present a globally distributed experimental network that can be used to disentangle the direct and indirect effects of climate change. We discuss how natural gradients, experimental approaches, and statistical techniques can be combined to best inform predictions about responses to climate change, and we present a globally distributed experiment that utilizes natural environmental gradients to better understand long-term community and ecosystem responses to environmental change. The warming and (species) removal in mountains (WaRM) network employs experimental warming and plant species removals at high- and low-elevation sites in a factorial design to examine the combined and relative effects of climatic warming and the loss of dominant species on community structure and ecosystem function, both above- and belowground. The experimental design of the network allows for increasingly common statistical approaches to further elucidate the direct and indirect effects of warming. We argue that combining ecological observations and experiments along gradients is a powerful approach to make stronger predictions of how ecosystems will function in a warming world as species are lost, or gained, in local communities.
Auteurs, date et publication :
Auteurs Case M. Prager , Aimee T. Classen , Maja K. Sundqvist , Maria Noelia Barrios-Garcia , Erin K. Cameron , Litong Chen , Chelsea Chisholm , Thomas W. Crowther , Julie R. Deslippe , Karl Grigulis , Jin-Sheng He , Jeremiah A. Henning , Mark Hovenden , Toke T. Thomas Høye , Xin Jing , Sandra Lavorel , Jennie R. McLaren , Daniel B. Metcalfe , Gregory S. Newman , Marie Louise Nielsen
Publication : Ecology and Evolution
Date : 2025
Volume : 12
Issue : 10
Pages : e9396
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Over the centuries, specific farming practices shaped permanent grasslands in mountains. With socioeconomic change, farming practices have changed and with them the landscape. Over time, food production has been increasingly decoupled from the preservation of permanent grassland, endangering the delivery of crucial ecosystem services. This contribution looks into the role of institutions – including normative, regulative and cultural-cognitive elements – in preserving current bundles of ecosystem services provided by mountain grasslands. In particular, we investigate how such institutions affect farmers’ management choices. Based on a review of scientific literature and empirical data from three case studies, we compare institutions in Austria, France and Norway. The cases represent different modes of multi-level governance (EU and non-EU), different grassland management practices, linked to different farming systems (dairy, breeding, rearing of heifers, suckler cow and sheep production) and different socio-economic conditions. The results underpin that ecological insights into the impact of farming practices on the ecology of grassland need to be combined with an understanding of the complex institutional interactions that affect farming practices, to ensure the resilience of mountain grasslands. If the design of regulatory measures considers both changing dynamics, it may enable farms to adapt and transform while maintaining traditional grassland management practices © 2015 Elsevier Ltd. All rights reserved.
Auteurs, date et publication :
Auteurs Markus Schermer , Ika Darnhofer , Karoline Daugstad , Marine Gabillet , Sandra Lavorel , Melanie Steinbacher
Publication : Land Use Policy
Date : 2025
Volume : 52
Pages : 382-391
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Abstract. Light-absorbing particles (LAPs) such as black carbon or mineral dust are some of the main drivers of snow radiative transfer. Small amounts of LAPs significantly increase snowpack absorption in the visible wavelengths where ice absorption is particularly weak, impacting the surface energy budget of snow-covered areas. However, linking measurements of LAP concentration in snow to their actual radiative impact is a challenging issue which is not fully resolved. In the present paper, we point out a new method based on spectral irradiance profile (SIP) measurements which makes it possible to identify the radiative impact of LAPs on visible light extinction in homogeneous layers of the snowpack. From this impact on light extinction it is possible to infer LAP concentrations present in each layer using radiative transfer theory. This study relies on a unique dataset composed of 26 spectral irradiance profile measurements in the wavelength range 350–950 nm with concomitant profile measurements of snow physical properties and LAP concentrations, collected in the Alps over two snow seasons in winter and spring conditions. For 55 homogeneous snow layers identified in our dataset, the concentrations retrieved from SIP measurements are compared to chemical measurements of LAP concentrations. A good correlation is observed for measured concentrations higher than 5 ng g−1 (r2=0.81) despite a clear positive bias. The potential causes of this bias are discussed, underlining a strong sensitivity of our method to LAP optical properties and to the relationship between snow microstructure and snow optical properties used in the theory. Additional uncertainties such as artefacts in the measurement technique for SIP and chemical contents along with LAP absorption efficiency may explain part of this bias. In addition, spectral information on LAP absorption can be retrieved from SIP measurements. We show that for layers containing a unique absorber, this absorber can be identified in some cases (e.g. mineral dust vs. black carbon). We also observe an enhancement of light absorption between 350 and 650 nm in the presence of liquid water in the snowpack, which is discussed but not fully elucidated. A single SIP acquisition lasts approximately 1 min and is hence much faster than collecting a profile of chemical measurements. With the recent advances in modelling LAP–snow interactions, our method could become an attractive alternative to estimate vertical profiles of LAP concentrations in snow.
Auteurs, date et publication :
Auteurs Francois Tuzet , Marie Dumont , Laurent Arnaud , Didier Voisin , Maxim Lamare , Fanny Larue , Jesus Revuelto , Ghislain Picard
Publication : The Cryosphere
Date : 2019
Volume : 13
Issue : 8
Pages : 2169-2187
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Although it is known that multiple interactions among plant functional traits, microbial properties, and abiotic soil parameters influence the nutrient turnover, the relative contribution of each of these groups of variables is poorly understood. We manipulated grassland plant functional composition and soil nitrogen (N) availability in a multisite mesocosm experiment to quantify their relative effects on soil N turnover. Overall, root traits, arbuscular mycorrhizal colonization, denitrification potential, as well as N availability and water availability, best explained the variation in measured ecosystem properties, especially the trade-off between nutrient sequestration and plant biomass production. Their relative contributions varied with soil N availability. In relatively N-p oor soils (10–20 μg·N·g−1 soil), N turnover was mainly controlled by microbial properties and abiotic soil parameters, whereas in the relatively N-rich soils (110–120 μg·N·g−1 soil), N turnover was mainly controlled by plant traits and microbial properties. This experiment is a strong demonstration of the importance of functional characteristics of both plants and soil microbes, and their interplay with soil N availability, for N turnover in grassland soils.
Auteurs, date et publication :
Auteurs Nicolas Legay , Sandra Lavorel , Catherine Baxendale , Ute Krainer , Michael Bahn , Marie-Noëlle Binet , Amélie A. M. Cantarel , Marie-Pascale Colace , Arnaud Foulquier , Eva-Maria Kastl , Karl Grigulis , Bello Mouhamadou , Franck Poly , Thomas Pommier , Michael Schloter , Jean-Christophe Clément , Richard D. Bardgett
Publication : Ecosphere
Date : 2025
Volume : 7
Issue : 11
Pages : e01448
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Alpine plants like Soldanella alpina L. are subjected to high PAR and high UV radiation. Among the important photoprotective mechanisms that prevent photoinhibition under such conditions, passive optical barriers such as UV-absorbing compounds were investigated. In this study, temporal and spatial patterns of epidermal UV-A absorbance for S. alpina leaves were investigated with a combination of absorbance measurements at 375 nm and imaging methods. UV-A absorbance was highest in plants acclimated to full sunlight and was markedly stable during the leaves’ lifetime. UV-A absorbance was correlated with leaf structure (leaf mass per area ratio, density of epidermal cells and stomata) and biochemical features such as chlorophyll and carotenoid content and ratio, which are characteristics of light acclimation. UV-A-absorbing compounds were mainly localised in the epidermal vacuoles and trichomes. Leaves with low UV-A absorbance were significantly more photosensitive than leaves with high UV-A absorbance. However, the epidermal UV-A absorbance increased in low-absorbance leaves under full sunlight even in the absence of UV radiation. Results suggest that high epidermal UV-A absorbance protects S. alpina leaves from photoinactivation, which is especially important after snowmelt, when plants are suddenly exposed to full sunlight.
Auteurs, date et publication :
Auteurs Constance Laureau , Sylvie Meyer , Xavier Baudin , Christophe Huignard , Peter Streb
Publication : Functional Plant Biology
Date : 2025
Volume : 42
Issue : 7
Pages : 599
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Abstract. From the micro- to the mesoscale, water and energy budgets of mountainous catchments are largely driven by topographic features such as terrain orientation, slope, steepness, and elevation, together with associated meteorological forcings such as precipitation, solar radiation, and wind speed. Those topographic features govern the snow deposition, melting, and transport, which further impacts the overall water cycle. However, this microscale variability is not well represented in Earth system models due to coarse resolutions. This study explores the impact of precipitation, shortwave radiation, and wind speed on the water budget distribution over a 15.28 ha small, mid-elevation (2000–2200 m) alpine catchment at Col du Lautaret (France). The grass-dominated catchment remains covered with snow for 5 to 6 months per year. The surface–subsurface coupled distributed hydrological model ParFlow-CLM is used at a very high resolution (10 m) to simulate the impacts on the water cycle of meteorological variability at very small spatial and temporal scales. These include 3D simulations of hydrological fluxes with spatially distributed forcing of precipitation, shortwave radiation, and wind speed compared to 3D simulations of hydrological fluxes with non-distributed forcing. Our precipitation distribution method encapsulates the spatial snow distribution along with snow transport. The model simulates the dynamics and spatial variability of snow cover using the Common Land Model (CLM) energy balance module and under different combinations of distributed forcing. The resulting subsurface and surface water transfers are computed by the ParFlow module. Distributed forcing leads to spatially heterogeneous snow cover simulation, which becomes patchy at the end of the melt season and shows a good agreement with the remote sensing images (mean bias error (MBE) = 0.22). This asynchronous melting results in a longer melting period compared to the non-distributed forcing, which does not generate any patchiness. Among the distributed meteorological forcings tested, precipitation distribution, including snow transport, has the greatest impact on spatial snow cover (MBE = 0.06) and runoff. Shortwave radiation distribution has an important impact, reducing evapotranspiration as a function of the slope orientation (decreasing the slope between observed and simulated evapotranspiration from 1.55 to 1.18). For the primarily east-facing catchment studied here, distributing shortwave radiation helps generate realistic timing and spatial heterogeneity in the snowmelt at the expense of an increase in the mean bias error (from 0.06 to 0.22) for all distributed forcing simulations compared to the simulation with only distributed precipitation. Distributing wind speed in the energy balance calculation has a more complex impact on our catchment, as it accelerates snowmelt when meteorological conditions are favorable but does not generate snow patches at the end of our test case. This shows that slope- and aspect-based meteorological distribution can improve the spatio-temporal representation of snow cover and evapotranspiration in complex mountain terrain.
Auteurs, date et publication :
Auteurs Aniket Gupta , Alix Reverdy , Jean-Martial Cohard , Basile Hector , Marc Descloitres , Jean-Pierre Vandervaere , Catherine Coulaud , Romain Biron , Lucie Liger , Reed Maxwell , Jean-Gabriel Valay , Didier Voisin
Publication : Hydrology and Earth System Sciences
Date : 2023
Volume : 27
Issue : 1
Pages : 191-212