Résumé

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 #UGA

Résumé

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 #UGA

Résumé

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 #UGA

Résumé

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 #UGA

Résumé

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

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

Important biochemical reactions in soils are catalyzed by extracellular enzymes, which are synthesized by microbes and plant roots. Although enzyme activities can significantly affect the decomposition of soil organic matter and thus influence the storage and cycling of carbon (C) and nitrogen (N), it is not clear how enzyme activities relate to changes in the C and N content of different grassland soils. Here we address whether the activity of C-acquiring (b-1,4-glucosidase, BG) and N-acquiring (L-leucine aminopeptidase (LAP) and b-1,4-N-acetyl-glucosaminidase (NAG)) enzymes is linked to changes in the C and N content of a variety of human-managed grassland soils. We selected soils which have a well-documented management history going back at least 19 years in relation to changes in land use (grazing, mowing, ploughing), nutrient fertilization and lime (CaCO3) applications. Overall we found a positive relationship between BG activity and soil C content as well as between LAP þ NAG activity and soil N. These positive relationships occurred across grasslands with very different soil pH and management history but not in intensively managed grasslands where increases in soil bulk density (i.e. high soil compaction) negatively affected enzyme activity. We also found evidence that chronic nutrient fertilization contributed to increases in soil C content and this was associated with a significant increase in BG activity when compared to unfertilized soils. Our study suggests that while the activities of C- and N-acquiring soil enzymes are positively related to soil C and N content, these activities respond significantly to changes in management (i.e. soil compaction and nutrient fertilization). In particular, the link between BG activity and the C content of long-term fertilized soils deserves further investigation if we wish to improve our understanding of the C sequestration potential of human-managed grassland soils.

Auteurs, date et publication :

Auteurs Valeria L. Cenini , Dario A. Fornara , Geoffrey McMullan , Nigel Ternan , Rachael Carolan , Michael J. Crawley , Jean-Christophe Clément , Sandra Lavorel

Publication : Soil Biology and Biochemistry

Date : 2025

Volume : 96

Pages : 198-206

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

Abstract
Asteraceae, the daisy family, are one of the most diverse families of angiosperms and are predominant in many ecosystems, including grasslands, deserts, savannas and high-elevation mountains. They are characterized by a peculiar inflorescence, the capitulum, which mimics a flower, but is actually made up of many tightly grouped florets. The capitulum is considered a key character underpinning the impressive evolutionary success of the family, and it plays a pivotal role in the economic importance of the family, given that many species are cultivated for their capitulum for agricultural and horticultural purposes. However, to date, there is still no comprehensive understanding of the extent of the morphological diversity of capitula across lineages of Asteraceae. This is mainly due to a lack of appropriate tools for describing such a complex and condensed structure. To address the problem, we present a protocol for characterizing the full diversity of capitula from any lineage of Asteraceae. This involves making a whole dissection of a capitulum from fresh material; it is simple and cost-effective and requires relatively easy-to-transport equipment meaning that it can be done during fieldwork.

Auteurs, date et publication :

Auteurs Lin Fu , Luis Palazzesi , Jaume Pellicer , Manica Balant , Maarten J M Christenhusz , Luca Pegoraro , Iván Pérez-Lorenzo , Ilia J Leitch , Oriane Hidalgo

Publication : Botanical Journal of the Linnean Society

Date : 2023

Volume : 201

Issue : 4

Pages : 391-399

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

The lichen collection of the alpine station of Lautaret developed by Georges Clauzade and Yves Rondon is a testimony to the early lichenological researches conducted in the region. Rich of 450 samples, with about 300 species, it includes nearly 60 of rare to very rare species which some have been observed for the first time in the area of the Lautaret.

Auteurs, date et publication :

Auteurs Juliette Asta , Christophe Perrier , Natacha Clairet

Publication : Bulletin de la Société Linnéenne de Lyon

Date : 2025

Volume : 88

Pages : 48

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

High-throughput sequencing of amplicons from environmental DNA samples permits rapid, standardized and comprehensive biodiversity assessments. However, retrieving and interpreting the structure of such data sets requires efficient methods for dimensionality reduction. Latent Dirichlet Allocation (LDA) can be used to decompose environmental DNA samples into overlapping assemblages of co-occurring taxa. It is a flexible model-based method adapted to uneven sample sizes and to large and sparse data sets. Here, we compare LDA performance on abundance and occurrence data, and we quantify the robustness of the LDA decomposition by measuring its stability with respect to the algorithm's initialization. We then apply LDA to a survey of 1,131 soil DNA samples that were collected in a 12-ha plot of primary tropical forest and amplified using standard primers for bacteria, protists, fungi and metazoans. The analysis reveals that bacteria, protists and fungi exhibit a strong spatial structure, which matches the topographical features of the plot, while metazoans do not, confirming that microbial diversity is primarily controlled by environmental variation at the studied scale. We conclude that LDA is a sensitive, robust and computationally efficient method to detect and interpret the structure of large DNA-based biodiversity data sets. We finally discuss the possible future applications of this approach for the study of biodiversity.

Auteurs, date et publication :

Auteurs Guilhem Sommeria‐Klein , Lucie Zinger , Eric Coissac , Amaia Iribar , Heidy Schimann , Pierre Taberlet , Jérôme Chave

Publication : Molecular Ecology Resources

Date : 2025

Volume : 20

Issue : 2

Pages : 371-386

Catégorie(s)

#ANR-Citation #CNRS #FORET Nouragues #UGA

Résumé

Remote sensing is an invaluable tool for tracking decadal-scale changes in vegetation greenness in response to climate and land use changes. While the Landsat archive has been widely used to explore these trends and their spatial and temporal complexity, its inconsistent sampling frequency over time and space raises concerns about its ability to provide reliable estimates of annual vegetation indices such as the annual maximum normalised difference vegetation index (NDVI), commonly used as a proxy of plant productivity. Here we demonstrate for seasonally snow-covered ecosystems, that greening trends derived from annual maximum NDVI can be significantly overestimated because the number of available Landsat observations increases over time, and mostly that the magnitude of the overestimation varies along environmental gradients. Typically, areas with a short growing season and few available observations experience the largest bias in greening trend estimation. We show these conditions are met in late snowmelting habitats in the European Alps, which are known to be particularly sensitive to temperature increases and present conservation challenges. In this critical context, almost 50% of the magnitude of estimated greening can be explained by this bias. Our study calls for greater caution when comparing greening trends magnitudes between habitats with different snow conditions and observations. At a minimum we recommend reporting information on the temporal sampling of the observations, including the number of observations per year, when long-term studies with Landsat observations are undertaken.

Auteurs, date et publication :

Auteurs Arthur Bayle , Simon Gascoin , Logan T. Berner , Philippe Choler

Publication : Ecography

Date : 2025

Volume : 2024

Issue : 12

Pages : e07394

Catégorie(s)

#CNRS #Lautaret #UGA