Résumé

The impacts of climate change, particularly the increasing frequency and intensity of severe droughts, pose significant threats to terrestrial ecosystems. To ensure the maintenance of critical ecosystem functions under these conditions, it is essential to better understand the interactions between different soil communities. However, the extent to which drought-induced changes in microbial communities are influenced by soil biodiversity, especially the functional diversity of soil macrofauna, remains poorly understood. In this study, we investigated how microbial communities respond to contrasting levels of macrofauna functional diversity and to more severe and prolonged drought in a Mediterranean forest ecosystem, all under fully controlled conditions. We conducted a two-year mesocosm experiment using 16 large mesocosms at the Montpellier European Ecotron, employing 16S amplicon sequencing and inferred functional gene annotations to assess microbial responses. Our results revealed that the relative abundance of Gram-positive bacterial communities increased compared to Gram-negative ones in response to drought. Furthermore, higher levels of macrofauna functional diversity appeared to help stabilize microbial diversity and community composition during periods of severe and prolonged drought. The resilience of microbial communities to drought was further reflected by the enrichment of drought-tolerant genes in specific bacterial taxa. Overall, these findings highlight the importance of preserving soil biodiversity as a means to mitigate the effects of future droughts on soil functions and to enhance the resilience of terrestrial ecosystems in the face of ongoing climate change.

Auteurs, date et publication :

Auteurs Diana Morales-Fonseca , Sandra Barantal , François Buscot , Stephan Hättenschwiler , Alexandru Milcu , Johanne Nahmani , Emmanuel S. Gritti , Kezia Goldmann , Luis Daniel Prada-Salcedo

Publication : Frontiers in Microbiology

Date : 2025

Volume : 16

Pages : 1597272

Catégorie(s)

#CNRS #Ecotron de Montpellier

Résumé

Alpine and subalpine grasslands experience strong seasonal climatic variations, with snow cover for over six months maintaining steady soil temperature and moisture. This seasonal structure limits plant growth and strongly influences microbial activity, which together control key ecosystem functions like soil organic matter (SOM) inputs, mineralization, and greenhouse gas fluxes, ultimately influencing the composition and quantity of SOM. In our study, we monitored soil pedoclimate (temperature and moisture) and net ecosystem exchange (CO2 flux) at both plot and local footprint scales, using discrete measurements and flux tower, to characterize the seasonal context of alpine and subalpine grasslands. Meanwhile, we investigated the seasonal properties of topsoil organic matter (SOM) at six key times throughout the hydrological year: before snow cover, before snowmelt, after snowmelt, during the growing season, at vegetation peak, and during senescence. SOM properties were analyzed through the combination of methods including DRIFT spectroscopy, RockEval® thermal analysis, water-extractable organic carbon and permanganate-oxidizable carbon (POxC). Finally, soil incubations were conducted to assess microbial respiration sensitivity to temperature and moisture across these six periods, enhancing our understanding of seasonality’s impact on microbial features. Our study integrates in situ and in vitro measurements across multiple scales (soil sample, plot, and landscape), traditionally analyzed separately. This approach bridges microbial mechanisms with SOM quality and links them to ecosystem-scale carbon exchanges. Our findings highlighted a clear seasonality in SOM properties, offering valuable insights into the functioning of these grasslands. We identified a labile seasonal pool of SOM that persists through the winter due to low temperatures and low-carbon outputs, maintaining its availability for mineralization at the onset of the growing season—when primary producers have the highest nutrient demand. This labile pool decreases over the growing season, as microbial activity peaks and organic matter inputs decline. Additionally, seasonal shifts in microbial responses to temperature and humidity indicate functional acclimations: enhanced cold tolerance in winter, waterlogged tolerance during snowmelt, and increased capacity to degrade complex organic molecules during the growing season.

Auteurs, date et publication :

Auteurs Nicolas Bonfanti , Jérôme Poulenard , Pierre Barre , François Baudin , Didier Voisin , Jean-Christophe Clement

Publication : Ecosystems

Date : 2025

Volume : 28

Issue : 3

Pages : 29

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

We provide here the description of a 16-channel gas manifold that was designed to perform gas analysis in closed loops. We present the main components that are the solenoid valves, controlled by an ethernet relay. We show an example of its use in a biogeochemistry study and propose a method for post-processing the data. Lastly, we discuss its limitations. We attach an example of a CO2 dataset obtained with the manifold.

Auteurs, date et publication :

Auteurs Baptiste Hulin , Didier Jehanno , Simon CHOLLET , Samuel Abiven

Date : 2025

Catégorie(s)

#CNRS #Ecotron IleDeFrance

Résumé

Severe droughts affect vegetation through several processes, such as hydraulic failure, early leaf senescence, depletion of carbon reserves, and reduced growth. These, in turn, can delay drought recovery and influence ecosystem functioning beyond the drought duration.

Auteurs, date et publication :

Auteurs S. Heinrich , X. Yu , J.‐M. Limousin , C. Werner , A. Bastos , A. Hoek Van Dijke , S. Walther , J. Kroll , R. Orth

Publication : Plant Biology

Date : 2025

Pages : plb.70082

Catégorie(s)

#CNRS #FORET Puechabon

Résumé

Belowground carbon (C), nitrogen (N) and phosphorus (P) inputs by plants via roots and rhizodeposition are key drivers of these elements cycling in soils. Tracing and quantification of rhizodeposition using isotope enrichment techniques is based on assumptions that have not simultaneously been tested for C, N and P. Our objectives were: (i) to compare the elemental and isotopic composition (IC) of roots and soluble rhizodeposits for C, N and P; and (ii) to compare the IC of root segments of different ages to assess the homogeneity of root system labeling.

Auteurs, date et publication :

Auteurs Pierre Stevenel , Samuel Abiven , Emmanuel Frossard , Idupulapati M. Rao , Federica Tamburini , Astrid Oberson

Publication : Plant and Soil

Date : 2025

Volume : 513

Issue : 1

Pages : 649-671

Catégorie(s)

#CNRS #Ecotron IleDeFrance

Résumé

Streambank erosion control and management are experiencing a significant paradigm shift, particularly in mountainous regions. There is an increasing demand for Nature-based Solutions such as soil and water bioengineering techniques (SWBE) with living plant material to protect both human assets and biodiversity from streambank erosion. The success of these techniques is highly dependent on vegetation growth and requires solid knowledge of the local species used. However, our knowledge of appropriate subalpine species is still limited, thus hindering the advancement of effective SWBE in these environments. To address this gap, we established an ex-situ experiment to study the biotechnical traits of subalpine species that contribute to streambank protection. Four species were cultivated in a growth chamber for four months: Salix caesia Vill., Salix foetida Schleich. ex DC. and Salix hastata Vill., restricted to the subalpine belt, and Salix purpurea L., a ubiquitous species. We then assessed both aerial and root traits (number, length and biomass) to evaluate the species’ potential for use in erosion control. The survival rate was excellent - up to 96%. S. hastata had high belowground biomass, promising for substrate stabilization, while S. purpurea produced numerous long shoots appropriate for surface protection. The two other willow species provided intermediate benefits, but their presence could promote biodiversity in SWBE structures. Our study reveals promising potential for the use of these species in high-elevation SWBE. Their morphological differences suggest that the four species should be used in accordance with specific streambank contexts.

Auteurs, date et publication :

Auteurs Juliette Rousset , Sarah Menoli , Adeline François , Stéphanie Gaucherand , André Evette

Publication : Environmental Management

Date : 2025

Volume : 75

Issue : 8

Pages : 1950-1962

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

Soil biogenic volatile organic compound (BVOC) emissions have been studied in different biomes, showing that their emissions are considerable. However, so far, previous studies have neglected the role of litter accumulation (considered here to be the amount of litter) in soil BVOC fluxes, and most of them refer to coniferous and evergreen forests, while litter emissions from Mediterranean deciduous forests remain poorly explored. To fill these gaps, the present work aimed to study BVOC fluxes in a Mediterranean deciduous forest, with particular attention being paid to the relationships between litter biomass accumulation in soil, microbial abundance, and soil BVOC fluxes. Measurements were performed in southern France in the downy oak (Quercus pubescens Willd.) forest of the Observatoire de Haute Provence (O3HP) during the late spring of 2023 using dynamic chambers coupled to an online proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). We investigated in situ daily BVOC fluxes from bare soil and different litter biomasses mimicking current, lower, or higher litter production as both decreases and increases in litter accumulation are expected in the Mediterranean region under the current context of climate change and greening management policies. The results showed a high BVOC diversity, with more than 135 emitted compounds. For a large majority of the measured compounds, fluxes were negative, suggesting that soil (bare soil covered by litter) takes up compounds through biochemical and/or physical processes. Some compounds, such as acetone, methanol, or sesquiterpenes, increased with increasing litter biomass, suggesting the importance of considering litter accumulation when assessing soil BVOC emissions from Mediterranean deciduous forests. Microbial abundance was highlighted as a potential driver of this relation between litter biomass and VOC fluxes.

Auteurs, date et publication :

Auteurs Manon Rocco , Julien Kammer , Mathieu Santonja , Brice Temime-Roussel , Cassandra Saignol , Caroline Lecareux , Etienne Quivet , Henri Wortham , Elena Ormeño

Publication : Biogeosciences

Date : 2025

Volume : 22

Issue : 14

Pages : 3661-3680

Catégorie(s)

#CNRS #FORET O3HP

Résumé

Climate change impacts forest functioning and dynamics, but large uncertainties remain regarding the interactions between species composition, demographic processes and environmental drivers. While the effects of changing climates on individual plant processes are well studied, few tools dynamically integrate them, which precludes accurate projections and recommendations for long-term sustainable forest management. Forest gap models present a balance between complexity and generality and are widely used in predictive forest ecology, but their lack of explicit representation of some of the processes most sensitive to climate changes, like plant phenology and water use, puts into question the relevance of their predictions. Therefore, integrating trait- and process-based representations of climate-sensitive processes is key to improving predictions of forest dynamics under climate change.

Auteurs, date et publication :

Auteurs Tanguy Postic , François De Coligny , Isabelle Chuine , Louis Devresse , Daniel Berveiller , Hervé Cochard , Matthias Cuntz , Nicolas Delpierre , Émilie Joetzjer , Jean-Marc Limousin , Jean-Marc Ourcival , François Pimont , Julien Ruffault , Guillaume Simioni , Nicolas K. Martin-StPaul , Xavier Morin

Publication : Geoscientific Model Development

Date : 2025

Volume : 18

Issue : 20

Pages : 7603-7679

Catégorie(s)

#CNRS #FORET Puechabon

Résumé

Abstract. Studying the Critical Zone (CZ), i.e. the outermost envelope of Earth, and its bio-geochemical processes requires an interdisciplinary approach. The deployment of critical zone observatories has led to significant scientific advances but does not offer the possibility of comparing treatments or apprehending different climatic scenarios. Conversely, mesocosm studies are often discipline-specific and can be limited in scope. Here, we propose a complementary approach that relies on the combination of 15 lysimeters and a climate chamber. The lysimeters have been equipped to allow for a detailed monitoring of the water flow, which connects most biogeochemical processes in the critical zone. This monitoring relies on scales, tipping buckets, soil moisture sensors and a facilitated high frequency sampling of discharge water. Besides, in-situ continuous gas analysis is enabled by a 45-channel manifold. The climate simulator is a 81 m³ isolated chamber that enables regulation of temperature; atmospheric CO₂; relative humidity; quantity and quality of irrigation water and quantity and quality of light. We evaluate the design in terms of its ability to assess the interactions between CZ processes. The main advantages of this set-up are as follows: it allows for the simulation of future climates or extreme events; it enables replication and the application of different treatments, facilitating the isolation of processes and the assessment of anthropogenic impacts; and it provides automated data acquisition.

Auteurs, date et publication :

Auteurs Baptiste Hulin , Scott Saleska , Didier Jehanno , Simon Chollet , Katerina Dontsova , Hannes Bauser , Valerie Milici , Samuel Abiven

Publication : EGUsphere

Date : 2025

Pages : 1-20

Catégorie(s)

#CNRS #Ecotron IleDeFrance

Résumé

The process of species delimitation, defined as the act of recognising biologically meaningful taxonomic units, enables the detection of overall biodiversity and the exploration of speciation processes. Given the complex nature of the origin of biodiversity, a significant number of cryptic Alpine plant groups exhibit ambiguity regarding their phylogenetic relationships and species circumscription. In this study, we attempt to apply the principles of integrative taxonomy to a complex of cryptic alpine plants from the genus Noccaea, which are often described as substrate specialists. We benefited from an extensive sampling across the Alps combined with high-throughput genotyping to apply a modern and standardised method of species delimitation. We find that the Noccaea rotundifolia complex is represented by five species within the Alps, which exhibit a restricted geographic distribution. Four of these species diverged approximately 350 ka ago (259–429), indicating a recent diversification. Instead of recognizing species with different substrate affinities, as done by current taxonomy, we rather find that the most widespread species are substrate generalists but with allopatric distributions. Our findings indicate that N. rotundifolia is growing exclusively in the west of the well-known biogeographic barrier of the Aosta Valley. N. corymbosa is found to grow between the Aosta Valley barrier and the Lake Como one. N. cepaeifolia, in turn, is observed in the eastern Alps, separated by the Brenner valley. Overall, this study provides a detailed systematic review, supporting the pivotal role of the recognized Alpine biogeographic barriers, in shaping species distribution and speciation.

Auteurs, date et publication :

Auteurs Camille Voisin , Philippe Choler , Camille Vacher , Christophe Perrier , Julien Renaud , Delphine Rioux , Florian C. Boucher

Publication : Molecular Phylogenetics and Evolution

Date : 2025

Volume : 211

Pages : 108381

Catégorie(s)

#CNRS #Lautaret #UGA