Résumé
Our 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.
Auteurs, date et publication :
Auteurs Irene Calderon-Sanou , Marc Ohlmann , Tamara Munkemuller , Lucie Zinger , Mickael Hedde , Clement Lionnet , Camille Martinez-Almoyna , Amelie Saillard , Julien Renaud , Nicolas Le Guillarme , Ludovic Gielly , Wilfried Thuiller , Orchamp Consortium
Publication : SOIL BIOLOGY & BIOCHEMISTRY
Date : 2024
Volume : 190
Catégorie(s)
#ANR-Citation #CNRS #Lautaret #UGARésumé
Abstract. The surface temperature controls the temporal evolution of the snowpack, playing a key role in metamorphism and snowmelt. It shows large spatial variations in mountainous areas because the surface energy budget is affected by the topography, for instance because of the modulation of the short-wave irradiance by the local slope and the shadows and the short-wave and long-wave re-illumination of the surface from surrounding slopes. These topographic effects are often neglected in large-scale models considering the surface to be flat and smooth. Here we aim at estimating the surface temperature of snow-covered mountainous terrain in clear-sky conditions in order to evaluate the relative importance of the different processes that control the spatial variations. For this, a modelling chain is implemented to compute the surface temperature in a kilometre-wide area from local radiometric and meteorological measurements at a single station. The first component of this chain is the Rough Surface Ray-Tracing (RSRT) model. Based on a photon transport Monte Carlo algorithm, this model quantifies the incident and reflected short-wave radiation on every facet of the mesh describing the snow-covered terrain. The second component is a surface scheme that estimates the terms of the surface energy budget from which the surface temperature is eventually estimated. To assess the modelling chain performance, we use in situ measurements of surface temperature and satellite thermal observations (Landsat 8) in the Col du Lautaret area, in the French Alps. The results of the simulations show (i) an agreement between the simulated and measured surface temperature at the station for a diurnal cycle in winter within 0.2 ∘C; (ii) that the spatial variations in surface temperature are on the order of 5 to 10 ∘C in the domain and are well represented by the model; and (iii) that the topographic effects ranked by importance are the modulation of solar irradiance by the local slope, followed by the altitudinal variations in air temperature (lapse rate), the re-illumination by long-wave thermal emission from surrounding terrain, and the spectral dependence of snow albedo. The changes in the downward long-wave flux because of variations in altitude and the absorption enhancement due to multiple bounces of photons in steep terrain play a less significant role. These results show the necessity of considering the topography to correctly assess the energy budget and the surface temperature of snow-covered complex terrain.
Auteurs, date et publication :
Auteurs Alvaro Robledano , Ghislain Picard , Laurent Arnaud , Fanny Larue , Inès Ollivier
Publication : The Cryosphere
Date : 2022
Volume : 16
Issue : 2
Pages : 559-579
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs J. Pottier , Z. Malenovsky , A. Psomas , L. Homolova , M. E. Schaepman , P. Choler , W. Thuiller , A. Guisan , N. E. Zimmermann
Publication : Biology Letters
Date : 2014
Volume : 10
Issue : 7
Pages : 20140347-20140347
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Bradley Z. Carlson , Philippe Choler , Julien Renaud , Jean-Pierre Dedieu , Wilfried Thuiller
Publication : Annals of Botany
Date : 2025
Volume : 116
Issue : 6
Pages : 1023-1034
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Abstract. Among mountainous permafrost landforms, rock glaciers are mostly abundant in periglacial areas, as tongue-shaped heterogeneous bodies. Passive seismic monitoring systems have the potential to provide continuous recordings sensitive to hydro-mechanical parameters of the subsurface. Two active rock glaciers located in the Alps (Gugla, Switzerland, and Laurichard, France) have been instrumented with seismic networks. Here, we analyze the spectral content of ambient noise to study the modal sensitivity of rock glaciers, which is directly linked to the system's elastic properties. For both sites, we succeed in tracking and monitoring resonance frequencies of specific vibrating modes of the rock glaciers over several years. These frequencies show a seasonal pattern characterized by higher frequencies at the end of winters and lower frequencies in warm periods. We interpret these variations as the effect of the seasonal freeze–thawing cycle on elastic properties of the medium. To assess this assumption, we model both rock glaciers in summer, using seismic velocities constrained by active seismic acquisitions, while bedrock depth is constrained by ground-penetrating radar surveys. The variations in elastic properties occurring in winter due to freezing were taken into account thanks to a three-phase Biot–Gassmann poroelastic model, where the rock glacier is considered a mixture of a solid porous matrix and pores filled by water or ice. Assuming rock glaciers to be vibrating structures, we numerically compute the modal response of such mechanical models by a finite-element method. The resulting modeled resonance frequencies fit well the measured ones over seasons, reinforcing the validity of our poroelastic approach. This seismic monitoring allows then a better understanding of the location, intensity and timing of freeze–thawing cycles affecting rock glaciers.
Auteurs, date et publication :
Auteurs Antoine Guillemot , Laurent Baillet , Stéphane Garambois , Xavier Bodin , Agnès Helmstetter , Raphaël Mayoraz , Eric Larose
Publication : The Cryosphere
Date : 2021
Volume : 15
Issue : 2
Pages : 501-529
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Increasing droughts threaten soil microbial communities and the multiple functions they control in agricultural soils. These soils are often fertilized with mineral nutrients, but it remains unclear how this fertilization may alter the capacity of soil multifunctionality (SMF) to be maintained under drought, and how plant-soil interactions shape these effects. In this study, we used a mountain grassland soil to test the interactive effect of mineral nutrient (Nitrogen and Phosphorous) addition and drought on SMF with and without plants (Lolium perenne) in a mesocosm experiment. We calculated SMF based on 8 microbial properties associated with the capacity of soil microbes to store carbon (C), nitrogen (N) and phosphorous (P) in their biomass, and to process these elements through organic matter depolymerization, mineralization, nitrification and denitrification processes. To investigate mechanisms underlying the SMF response we characterized the associated changes in soil stoichiometry and microbial community composition using 16S and 18S rRNA amplicon sequencing. Our results showed that fertilization decreased the SMF drought resistance when plants were present, but the opposite was observed in the unplanted mountain grassland soil. Our analysis suggested this was due to the interaction of plants, fertilization and drought in influencing four coupled properties related to high SMF: high soil moisture, low microbial C limitation, high bacterial diversity and low bacteria gram positive:gram negative ratio. Altogether, our results suggested that reducing the use of mineral fertilizer for plant production in mountain grassland could improve the ability of their soils to maintain their multifunctionality during drought period. Finally, our study clearly further demonstrated the importance of plant in the complex responses of SMF to global changes and showed that combining stoichiometric and microbial diversity assessment represents a powerful approach to disentangle the underlying mechanisms.
Auteurs, date et publication :
Auteurs Gabin Piton , Arnaud Foulquier , Lionel Bernard , Aurélie Bonin , Thomas Pommier , Sandra Lavorel , Roberto Geremia , Jean Christophe Clement
Date : 2025
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Plants affect the spatial distribution of soil microorganisms, but the influence of the local abiotic context is poorly documented. We investigated the effect of a single plant species, the cushion plant Silene acaulis, on habitat conditions and microbial community. We collected soil from inside (In) and outside (Out) of the cushions on calcareous and siliceous cliffs in the French Alps along an elevation gradient (2,000-3,000 m.a.s.l.). The composition of the microbial communities was assessed by Capillary-Electrophoresis Single Strand Conformation Polymorphism (CE-SSCP). Univariate and multivariate analyses were conducted to characterise the response of the microbial beta-diversity to soil parameters (total C, total N, soil water content, N-NH4+, N-NO3- and pH). Cushions affected the microbial communities, modifying soil properties. The fungal and bacterial communities did not respond to the same abiotic factors. Outside the cushions, the bacterial communities were strongly influenced by bedrock. Inside the cushions, the bacterial communities from both types of bedrock were highly similar, due to the smaller pH differences than in open areas. By contrast, the fungal communities were equally variable inside and outside of the cushions. Outside the cushions, the fungal communities responded weakly to soil pH. Inside the cushions, the fungal communities varied strongly with bedrock and elevation as well as increases in soil nutrients and water content. Furthermore, the dissimilarities in the microbial communities between the In and Out habitats increased with increasing habitat modification and environmental stress. Our results indicate that cushions act as a selective force that counteracts the influence of the bedrock and the resource limitations on the bacterial and fungal communities by buffering soil pH and enhancing soil nutrients. Cushion plants structure microbial communities, and this effect increases in stressful, acidic and nutrient-limited environments.
Auteurs, date et publication :
Auteurs Julien Roy , Cécile Hélène Albert , Philippe Choler , Jean-Christophe Clément , Sébastien Ibanez , Sébastien Lavergne , Patrick Saccone , Lucie Zinger , Roberto Alejandro Geremia
Publication : Frontiers in Microbiology
Date : 2025
Volume : 4
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Dynamic avalanche modeling requires as input the volumes and areas of the snow released, and consequently the fracture heights. Determining these parameters requires high-resolution spatial snow surface data from before and after an avalanche. In snow and avalanche research, terrestrial laser scanners are used increasingly to efficiently and accurately map snow surfaces and depths over an area of several km2. In practice however, several problems may occur, which must be recognized and accounted for during post-processing and interpretation. Thus, we combine terrestrial laser scanning with photogrammetry, total station measurements and field snow observations to document and accurately survey an artificially triggered avalanche at the Col du Lautaret test site (2058 m) in the French Alps. The ability of TLS to determine avalanche modeling input parameters efficiently and accurately is shown, and we demonstrate how, merging TLS with the other methods facilitates and improves data post-processing and interpretation. Finally, we present for this avalanche the data required for the parameterization and validation of dynamic avalanche models.
Auteurs, date et publication :
Auteurs Alexander Prokop , Peter Schön , Florian Singer , Gaëtan Pulfer , Mohamed Naaim , Emmanuel Thibert , Alvaro Soruco
Publication : Cold Regions Science and Technology
Date : 2025
Volume : 110
Pages : 223-230
Catégorie(s)
#CNRS #Lautaret #UGARésumé
It is well established that the abundances of nitrogen (N) transforming microbes are strongly influenced by land-use intensity in lowland grasslands. However, their responses to management change in less productive and less fertilized mountain grasslands are largely unknown. We studied eight mountain grasslands, positioned along gradients of management intensity in Austria, the UK, and France, which differed in their historical management trajectories. We measured the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) as well as nitrite-reducing bacteria using specific marker genes. We found that management affected the abundance of these microbial groups along each transect, though the specific responses differed between sites, due to different management histories and resulting variations in environmental parameters. In Austria, cessation of management caused an increase in nirK and nirS gene abundances. In the UK, intensification of grassland management led to 10-fold increases in the abundances of AOA and AOB and doubling of nirK gene abundance. In France, ploughing of previously mown grassland caused a 20-fold increase in AOA abundance. Across sites the abundance of AOB was most strongly related to soil NO3--N availability, and AOA were favoured by higher soil pH. Among the nitrite reducers, nirS abundance correlated most strongly with N parameters, such as soil NO3--N, microbial N, leachate NH4+-N, while the abundance of nirK-denitrifiers was affected by soil total N, organic matter (SOM) and water content. We conclude that alteration of soil environmental conditions is the dominant mechanism by which land management practices influence the abundance of each group of ammonia oxidizers and nitrite reducers.
Auteurs, date et publication :
Auteurs Ute Szukics , Karl Grigulis , Nicolas Legay , Eva-Maria Kastl , Catherine Baxendale , Richard D. Bardgett , Jean-Christophe Clément , Sandra Lavorel , Michael Schloter , Michael Bahn
Publication : Science of The Total Environment
Date : 2025
Volume : 648
Pages : 745-753
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Methods: We studied the functional relationships between plants and grasshoppers in sub-alpine grasslands under different management regimes in the Central French Alps. We applied the theoretical multitrophic response–effect framework described by (Journal of Vegetation Science, 24, this issue) to identify key traits linking plants and grasshoppers to biomass production. The linkages between selected plant and grasshopper traits were analysed using community-weighted mean traits (CWM) and functional diversity (FD; Rao’s quadratic diversity).
Results: Uni- and multivariate models provided evidence about the relative importance of trait linkages within and across trophic levels. We showed that management affected both plant and grasshopper traits and that the interaction between them was linked to biomass production. While a number of CWM traits and FD were involved in the interaction, CWM of leaf dry matter content (LDMC) and grasshopper dry body mass (GMass) chiefly mediated the impact of management change on biomass production.
Conclusions: Our study suggests that both trait values of the most abundant species and functional trait variation within and across trophic levels in combination may best explain the impact of land-use changes on ecosystem function. To improve our mechanistic understanding across trophic levels, a better knowledge of response and effect traits remains a major goal, especially for animal ecologists, while a strong collaboration among disciplines is needed to bridge the existing gaps.
Auteurs, date et publication :
Auteurs Marco Moretti , Francesco de Bello , Sébastien Ibanez , Simone Fontana , Gianni B. Pezzatti , Frank Dziock , Christian Rixen , Sandra Lavorel , Robin Pakeman
Publication : Journal of Vegetation Science
Date : 2025
Volume : 24
Issue : 5
Pages : 949-962