Résumé
Abstract. Saharan dust outbreaks have profound effects on ecosystems, climate, human health, and the cryosphere in Europe. However, the spatial deposition pattern of Saharan dust is poorly known due to a sparse network of ground measurements. Following the extreme dust deposition event of February 2021 across Europe, a citizen science campaign was launched to sample dust on snow over the Pyrenees and the European Alps. This somewhat improvised campaign triggered wide interest since 152 samples were collected from the snow in the Pyrenees, the French Alps, and the Swiss Alps in less than 4 weeks. Among the 152 samples, 113 in total could be analysed, corresponding to 70 different locations. The analysis of the samples showed a large variability in the dust properties and amount. We found a decrease in the deposited mass and particle sizes with distance from the source along the transport path. This spatial trend was also evident in the elemental composition of the dust as the iron mass fraction decreased from 11 % in the Pyrenees to 2 % in the Swiss Alps. At the local scale, we found a higher dust mass on south-facing slopes, in agreement with estimates from high-resolution remote sensing data. This unique dataset, which resulted from the collaboration of several research laboratories and citizens, is provided as an open dataset to benefit a large community and to enable further scientific investigations. Data presented in this study are available at https://doi.org/10.5281/zenodo.7969515 (Dumont et al., 2022a).
Auteurs, date et publication :
Auteurs Marie Dumont , Simon Gascoin , Marion Réveillet , Didier Voisin , François Tuzet , Laurent Arnaud , Mylène Bonnefoy , Montse Bacardit Peñarroya , Carlo Carmagnola , Alexandre Deguine , Aurélie Diacre , Lukas Dürr , Olivier Evrard , Firmin Fontaine , Amaury Frankl , Mathieu Fructus , Laure Gandois , Isabelle Gouttevin , Abdelfateh Gherab , Pascal Hagenmuller
Publication : Earth System Science Data
Date : 2023
Volume : 15
Issue : 7
Pages : 3075-3094
Catégorie(s)
#CNRS #Lautaret #UGARésumé
In the high Arctic, thermal bridging through frozen shrub branches has been demonstrated to cool the ground by up to 4°C during cold spells, affecting snow metamorphism and soil carbon and nutrients. In alpine conditions, the thermal conductivity contrast between shrub branches and snow is much less than in the Arctic, so that the importance of thermal bridging is uncertain. We explore this effect by monitoring ground temperature and liquid water content under green alders and under nearby alpine tundra in the Alps. During a January 2022 cold spell, the ground temperature at 5 cm depth under alders is 1.3°C colder than under alpine tundra. Ground water freezing under alders is complete, while water remains liquid under tundra. Finite element simulations reproduce the observed temperature difference between both sites, showing that thermal bridging does affect ground temperature also under Alpine conditions.
Auteurs, date et publication :
Auteurs Florent Domine , Kevin Fourteau , Philippe Choler
Publication : Geophysical Research Letters
Date : 2023
Volume : 50
Issue : 24
Pages : e2023GL105100
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Mountain shrublands are widespread habitats of the European Alps. Shrub encroachment into above treeline grazed lands profoundly modifies biodiversity and ecosystem functioning. Yet, mountain shrublands remain overlooked in vegetation distribution modeling because it is difficult to distinguish them from productive grasslands. Here, we used the pigment-sensitive spectral indices based on Sentinel-2 bands within a specific phenological window, to produce a high-resolution distribution map of mountain shrublands in the French Alps. We evaluated the performance of our classification using a large dataset of vegetation plots and found that our model is highly sensitive to Ericaceous species which constitute most of the dense alpine shrublands in the French Alps. Our analysis of topoclimatic and land use factors limiting the shrubland distribution at regional scale found that, consistent with the ecophysiology of shrubs, expansion is limited by a combination of water deficit and temperature. We discussed the past and current land-use implications in the observed distribution and put forward hypotheses combining climate and land-use trajectories. Our work provides a baseline for monitoring mountain shrub dynamics and exploring the response of shrublands to past and ongoing climate and land use changes.
Auteurs, date et publication :
Auteurs Arthur Bayle , Bradley Z. Carlson , Baptiste Nicoud , Loïc Francon , Christophe Corona , Sandra Lavorel , Philippe Choler
Publication : Frontiers of Biogeography
Date : 2025
Volume : 16
Issue : 1
Catégorie(s)
#CNRS #Lautaret #UGARésumé
The European Alps are experiencing more than twice the increase in air temperature observed in the rest of the world. Thus, the treeline ecotone, and the unique habitats above it, offer a preview of drastic changes in plant and animal communities. However, our knowledge about climate change impacts on microbial diversity belowground is scarce. Here we investigate how upslope shift of the treeline ecotone, associated with changes in soil nutrient content, temperature and precipitation, will influence alpine ectomycorrhizal (EM) communities of Dryas octopetala, Bistorta vivipara and Salix herbacea across different habitat types in the Alps. We also assessed the degree of EM community taxonomic composition turnover in these habitats across three different climatic projections for 2040 and 2070. Our results indicate that the specialized EM fungal communities from snowbed habitats will be mostly negatively influenced under the current trajectory of environmental shifting predicted for the region. In contrast, fungi from the treeline ecotone, having wider niches, will be positively influenced by future climate and extend upwards. In addition, our predictions of EM community turnover for putative future climatic scenarios revealed high rates of turnover across the entire alpine region. This, together with glacier retreats, will aid colonization of alpine snowbed habitats by new EM plants and associated fungi, bringing additional pressures on local mycorrhizas and likely leading to fungal species extinctions.
Auteurs, date et publication :
Auteurs R. Arraiano-Castilho , M. I. Bidartondo , T. Niskanen , I. Brunner , S. Zimmermann , B. Senn-Irlet , B. Frey , U. Peintner , T. Mrak , L. M. Suz
Publication : Fungal Ecology
Date : 2024
Volume : 67
Pages : 101300
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Lucía Laorden-Camacho , Elena Tello-García , Karl Grigulis , Marie-Pascale Colace , Christiane Gallet , Ursula Peintner , Ulrike Tappeiner , Georg Leitinger , Sandra Lavorel
Date : 2024
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Frost stress is the main factor determining the distribution of plants at high latitude and elevation. Although species are currently adapted to their highest location, climate change is likely to modify their adaptation strategies in the face of climatic stress. This is particularly true for trees at their altitudinal limit, where the number of freeze-thaw episodes is likely to increase.
To monitor the exposure to frost stress and its impact on tree growth, we monitored five contrasted species (Acer pseudoplatanus, Betula pendula, Larix decidua, Picea abies and Sorbus aucuparia) over a 3-year period in the Lautaret alpine garden (2100 m asl) by using an automatic, autonomous, connected micro-dendrometer. These systems continuously measured (every 30 minutes or 1 hour) both variations in trunk diameter and air temperature in the vicinity of the measurement, making it possible to determine the number and duration of frost cycles, growth periods and ecophysiological functioning of the species monitored in these extreme conditions. We observed specific responses of the trees, in relation to their wood anatomy and leaf phenology
Auteurs, date et publication :
Auteurs Thierry Ameglio , Katline Charra-Vaskou , Loïc Francon , Lucie Liger , Laurent Barroux , Christophe Serre , Christophe Corona , Guillaume Charrier
Date : 2024
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Mountains are particularly vulnerable to climate change, as they are warming at a rate that exceeds the global average, significantly impacting cold-adapted ecosystems. In these environments, soil organic matter (SOM) stocks are often considerably larger than at lower elevations. These stocks are therefore highly susceptible to global warming and the associated risk of greenhouse gas (GHG) (CO₂, CH₄, N₂O) emissions driven by temperature-induced increases in SOM mineralisation. In order to quantify these emissions and the change of mineralisation rates under warming, it is necessary to gain an understanding of the annual mineralisation balance. We investigated how warming impacts the duration and intensity of mineralisation in different seasons. The main aim of this study is to quantify alpine SOM mineralisation rates and GHG production under a range of seasonal conditions, including those associated with warming. An in vitro approach was employed to expose alpine topsoils (0–10 cm) to the conditions of key seasonal periods: snow cover, growing season and rainfall/snowmelt. This was achieved by experimentally varying temperature and inflow of precipitation water. Additionally, the soil samples were subjected to a temperature increase of 4°C. The short-term responses of carbon (C), nitrogen (N) and phosphorus (P) mineralisation and GHG production were monitored. The results demonstrated that alpine soil respiration rates exhibited a twofold increase with a 4°C warming, while the relative proportion of labile SOM demonstrated a decline with rising temperatures. Water saturation from simulated rain and snowmelt played a crucial role in organic matter mineralisation and increased the mineralisation of carbon (+12% to +53%), nitrogen (+20% to +80% of net ammonification) and phosphorus (+50% of net phosphate production). This suggests that nutrients present in the snowpack or the rain were added to the soil. In contrast, soil–water saturation decreased net nitrate production by between 10% and 90%. The results of this study highlight the potential for alpine soil warming to release labile SOM and demonstrate the influence of the snow regime on nutrient and carbon fluxes.
Auteurs, date et publication :
Auteurs Nicolas Bonfanti , Jean-Christophe Clement , Annie Millery-Vigues , Tamara Münkemüller , Yves Perrette , Jérôme Poulenard
Publication : European Journal of Soil Science
Date : 2025
Volume : 76
Issue : 1
Pages : e70050
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Aim Land surface models (LSMs) currently represent each plant functional type (PFT) as an average phenotype, characterised by a set of fixed parameters. This rigid and constant representation is a limit in understanding the dynamics of highly diverse ecosystems, such as permanent grasslands, and their response to global change. Location France. Time Period 2001–2019. Major Taxa Grassland plant species. Methods We incorporated spatially explicit trait variability at the France scale in the ORCHIDEE land surface model to assess how the net primary productivity (NPP) will spatially vary over the years. More precisely, we focused on three key functional traits that govern the NPP of grassland ecosystems: specific leaf area (SLA) and leaf nitrogen content (LNC), as measured traits, and leaf lifespan (LLS) as an estimated trait. Community-weighted means (CWM) were implemented in various combinations with prescribed and spatially varying traits. We compared the outcomes of each NPP simulation to remotely sensed proxies of productivity by using the MODIS satellite-driven NPP products. Results The sensitivity of NPP to traits depends on climate conditions, such as temperature and water limitation. Considering trait variability decreases the NPP in the most productive regions (plains) and increases the NPP in the less productive regions (mountains) compared to the case with constant trait values. This leads to a more homogenous NPP across France. Compared to the observed MODIS NPP and FLUXCOM GPP, the simulation using varying traits improves the spatial NPP and GPP variations in several regions and most climate conditions. Main Conclusions Based on the existing trait data, we revealed that incorporating the CWM of traits in an LSM such as ORCHIDEE can be effectively performed. Improving the modelling and predictions by considering the relationships between biodiversity, functional biogeography, and ecosystem functioning is essential in current and future ecological research.
Auteurs, date et publication :
Auteurs Sara Chebbo , Cyrille Violle , Lucie Mahaut , Jens Kattge , Marc Peaucelle , Philippe Choler , Nicolas Viovy
Publication : Journal of Biogeography
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Photosynthesis, electron transport to carbon assimilation, photorespiration and alternative electron transport, light absorption of the two photosystems, antioxidative protection and pigment contents were investigated in S. alpina leaves. S. alpina is an alpine snow-bed plant which can be found with green leaves after snowmelt. At least 24% of the leaves were formed at the beginning of the vegetation period in the previous year and survived two consecutive vegetation periods under contrasting environmental conditions. In leaves still covered by snow (SNOW), the parameters of antioxidative protection and carbon assimilation were lower than in leaves from the previous vegetation period (NEW) or several weeks after snowmelt (OLD). Directly after snowmelt, antioxidative protection was strongly but transitionally increased. The senescence of leaves did not depend on antioxidative scavenging capacity. Lower carbon assimilation was not related to increases in alternative electron flow (ETRalt) in SNOW leaves. In the second vegetation period, light absorption by PSII decreases in favour of PSI in OLD leaves. This allows OLD leaves to keep the electron transport chain more oxidised and to support photorespiration with increased ATP synthesis by cyclic electron transport around PSI. This study describes how the leaves of a unique plant can cope with contrasting environmental conditions.
Auteurs, date et publication :
Auteurs Peter Streb , Philippine Dubertrand , Gabriel Cornic , Kamel Soudani , Giovanni Finazzi
Publication : Physiologia Plantarum
Date : 2025
Volume : 177
Issue : 1
Pages : e70045
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Mountain regions face substantial challenges and opportunities arising from global change. The capacity of mountain regions for (systemic) innovation will be determinant to the success of system transformations envisioned by social actors of mountain communities. By analysing the social networks of two regions in the Alps and relating them to desired future visions of sustainable regional development, we provide insights about innovative capacities in mountain regions and propose how to strengthen these capacities in order to support regional transformations. In particular, we analyse innovation systems’ collaboration networks to evaluate the innovative capacity of communities, co-construct visions with mountain stakeholders, and assess innovation requirements to meet these visions. Accordingly, we propose changes to the collaboration networks for addressing regional innovation system (RIS) capacities to help achieve visions through systemic innovation. Our analysis furthers the understanding on the type and magnitude of regional innovation system changes required to more effectively address desired transformative visions in mountain regions. We close by discussing implications of our approach for the assessment of innovative capacity and the transformation of mountain regions.
Auteurs, date et publication :
Auteurs Victor Blanco , Tobias Luthe , Enora Bruley , Adrienne Grêt-Regamey
Publication : Regional Environmental Change
Date : 2025
Volume : 23
Issue : 3
Pages : 102