Résumé
Aim Plant–soil interactions can be major driving forces of community responses to environmental changes in terrestrial ecosystems. These interactions can leave signals in aboveground plant functional traits and belowground microbial activities and these signals can manifest in observed covariations. However, we know little about how these plant–soil linkages vary in response to environmental conditions at biogeographic scales for which experiments are impossible. Here, we investigate patterns of direct and indirect linkages between plant functional traits, soil microbial activities and environmental conditions in mountain grasslands along elevational gradients. Location The French Alps. Taxon Vascular plants and soil microbiota. Methods We analysed observational grassland data sampled along 14 elevational gradients across the entire French Alps (between 1500 and 2800 m of elevation). Using Graphical Lasso, we inferred a partial correlation network to tease apart direct and indirect plant–soil linkages without defining the direction of interactions a priori. Results We found tight spatial associations of plant traits with microbial activities, climate driving the former and soil properties the latter. In these plant–soil linkages, the dominance of specific plant traits was more important than their diversity. We then showed that in sites with conservative plant traits and reduced organic matter quality, soil microbes invested strongly in nutrient acquisition. Main conclusions By investigating plant–soil linkages along elevational gradients in the French Alps, we showed that plant functional traits and belowground microbial activity are tightly linked and how they depend on environmental conditions. Overall, we demonstrated how soil functioning can be integrated in studies of ecosystem shifts under environmental change at large spatial scales.
Auteurs, date et publication :
Auteurs Sarah-Sophie Weil , Camille Martinez-Almoyna , Gabin Piton , Julien Renaud , Louise Boulangeat , Arnaud Foulquier , Amélie Saillard , Philippe Choler , Jérôme Poulenard , Orchamp Consortium , Tamara Münkemüller , Wilfried Thuiller
Publication : Journal of Biogeography
Date : 2025
Volume : 48
Issue : 11
Pages : 2755-2770
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Tropical forests are generally considered to stand upon nutrient-poor soils, but soil nutrient concentrations and availabilities can vary greatly at local scale due to topographic effects on erosion and water drainage. In this study we physically and chemically characterised the soils of 12 study plots situated along a catena with a shallow slope in a tropical rainforest in French Guiana both during the wet and the dry season to evaluate seasonal differences. Soils along the catena were all Acrisols, but differed strongly in their water drainage flux. Over time, this differential drainage has led to differences in soil texture and mineral composition, affecting the adsorption of various nutrients, most importantly phosphorus. The more clayey soils situated on the slope of the catena had higher total concentrations of carbon, nitrogen, phosphorus and several micronutrients, while extractable nutrient concentrations were highest in the sandiest soils situated at the bottom of the catena. We found that carbon, nitrogen and extractable nutrients all varied seasonally, especially in the surface soil layer. These results are interesting because they show that, even at the local scale, small differences in topography can lead to large heterogeneity in nutrient concentrations, which can have large impacts on plant and microbial community organisation at the landscape level.
Auteurs, date et publication :
Auteurs Leandro Van Langenhove , Lore T. Verryckt , Clement Stahl , Elodie A. Courtois , Ifigenia Urbina , Oriol Grau , Dolores Asensio , Guille Peguero , Olga Margalef , Vincent Freycon , Josep Penuelas , Ivan A. Janssens
Publication : SOIL RESEARCH
Date : 2025
Volume : 59
Issue : 2
Pages : 130-145
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Fertilisation experiments have demonstrated that nutrient availability is a key determinant of biomass production and carbon sequestration in grasslands. However, the influence of nutrients in explaining spatial variation in grassland biomass production has rarely been assessed. Using a global dataset comprising 72 sites on six continents, we investigated which of 16 soil factors that shape nutrient availability associate most strongly with variation in grassland aboveground biomass. Climate and N deposition were also considered. Based on theory-driven structural equation modelling, we found that soil micronutrients (particularly Zn and Fe) were important predictors of biomass and, together with soil physicochemical properties and C:N, they explained more unique variation (32%) than climate and N deposition (24%). However, the association between micronutrients and biomass was absent in grasslands limited by NP. These results highlight soil properties as key predictors of global grassland biomass production and point to serial co-limitation by NP and micronutrients.
Auteurs, date et publication :
Auteurs Dajana Radujković , Erik Verbruggen , Eric W. Seabloom , Michael Bahn , Lori A. Biederman , Elizabeth T. Borer , Elizabeth H. Boughton , Jane A. Catford , Matteo Campioli , Ian Donohue , Anne Ebeling , Anu Eskelinen , Philip A. Fay , Amandine Hansart , Johannes M. H. Knops , Andrew S. MacDougall , Timothy Ohlert , Harry Olde Venterink , Xavier Raynaud , Anita C. Risch
Publication : Ecology Letters
Date : 2025
Volume : 24
Issue : 12
Pages : 2713-2725
Catégorie(s)
#CEREEP #CNRS #ENSRésumé
Data assimilation of snow observations significantly improves the accuracy of snow cover simulations. However, remotely-sensed snowpack observations made in areas of complex topography are typically subject to large error and biases, creating a challenge for data assimilation. To improve the reliability of ensemble snowpack simulations, this study investigated the appropriate conditions for assimilating MODIS-like synthetic surface reflectances. We used a simulation system that included the Particle Filter data assimilation technique. More than 270 ensemble simulations involving assimilation of synthetic observations were conducted in a twin experiment procedure for three snow seasons. These tests were aimed at establishing the spectral combination of MODIS-like reflectances that convey the more information in the assimilation system, rendering the most reliable snowpack simulation, and determining the maximum observation errors that the assimilation system could tolerate. The assimilation of the first seven MODIS-like bands, covering visible and near-infrared wavelengths, provided the best scores compared with any other band combination, and thus are highly recommended for use when possible. The simulation system tolerated a maximum deviation from ground truth of 5% without loss of performance. However, the assimilation of the first seven bands of true MODIS surface of reflectance fails on improving simulation results in rouged mountain areas.
Auteurs, date et publication :
Auteurs J. Revuelto , B. Cluzet , N. Duran , M. Fructus , M. Lafaysse , E. Cosme , M. Dumont
Publication : Journal of Hydrology
Date : 2025
Volume : 603
Pages : 126966
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Understanding how water use and drought stress in woody plants change in relation to compositional, structural and environmental variability of mixed forests is key to understand their functioning and dynamics. Observa tional and experimental studies have so far shown a complex array of water use and drought stress responses to species mixing, but progress is hampered by the costs of replicating measurements. A complementary approach consists in using in silico experiments with trait-based forest ecosystem models, which have the advantage of allowing the interpretation of the net mixing effect as the result of specific combinations of trait differences. We explore the potential of such an approach using a novel trait-based forest ecosystem model with a strong focus on plant hydraulics and data from 186 mixed forest inventory plots including holm oak (Quercus ilex L.) and eight co-occurring species. Sensitivity analyses focusing on the effect of differences in individual plant traits indicate that water use and summer drought stress of holm oak trees respond primarily to the variation in competitor’s height, root distribution and xylem hydraulic efficiency and safety. Simulations of pure and mixed stands across different combinations of climate aridity and stand leaf area index indicate that differences in traits may compensate for one another, so that the influence of a given trait (e.g. tree height) on water use or drought stress can be decreased or offset by the influence of another one (e.g. hydraulic efficiency). Importantly, we show that species mixing does not always have positive effects at the stand level. Overall, our simulation study shows that the complexity of species- and stand-level mixing effects on water use and drought stress arises primarily as the result of differences in key functional traits of the competitor, although stand structure and climate aridity may modulate mixing effects.
Auteurs, date et publication :
Auteurs Miquel De Cáceres , Maurizio Mencuccini , Nicolas Martin-StPaul , Jean-Marc Limousin , Lluís Coll , Rafael Poyatos , Antoine Cabon , Víctor Granda , Alicia Forner , Fernando Valladares , Jordi Martínez-Vilalta
Publication : Agricultural and Forest Meteorology
Date : 2025
Volume : 296
Pages : 108233
Catégorie(s)
#ANR-Citation #CNRS #FORET FontBlanche #FORET PuechabonRésumé
Radium-226, an alpha emitter with half-life 1600 years, is ubiquitous in natural environments. Present in rocks and soils, it is also absorbed by vegetation. The efficiency of 226Ra uptake by plants from the soil is important to assess for the study of heavy metals uptake by plants, monitoring of radioactive pollution, and the biogeochemical cycle of radium in the Critical Zone. Using a thoroughly validated measurement method of effective 226Ra concentration (ECRa) in the laboratory, we compare ECRa values of the plant to that of the closest soil, and we infer the 226Ra soil-to-plant transfer ratio, RSP, for a total of 108 plant samples collected in various locations in France. ECRa values of plants range over five orders of magnitude with mean (min–max) of 1.66 ± 0.03 (0.020–113) Bq kg−1. Inferred RSP values range over four orders of magnitude with mean (min–max) of 0.0188 ± 0.0004 (0.00069–0.37). The mean RSP value of plants in granitic and metamorphic context (0.073 ± 0.002; n = 50) is significantly higher (12 ± 1 times) than that of plants in calcareous and sedimentary context (0.0058 ± 0.0002; n = 58). This difference, which cannot be attributed to a systematic difference in emanation coefficient, is likely due to the competition between calcium and radium. In a given substratum context, the compartments of a given plant species show coherent and decreasing RSP values in the following order (acropetal gradient): roots > bark > branches and stems ≈ leaves. Oak trees (Quercus genus) concentrate 226Ra more than other trees and plants in this set. While this study clearly demonstrates the influence of substratum on the 226Ra uptake by plants in non-contaminated areas, our measurement method appears as a promising practical tool to use for (phyto)remediation and its monitoring in uranium- and radium-contaminated areas.
Auteurs, date et publication :
Auteurs Frédéric Girault , Frédéric Perrier , Jean-Marc Ourcival , Roxane Ferry , Yves Gaudemer , François Bourges , Jean-François Didon-Lescot
Publication : Science of The Total Environment
Date : 2025
Volume : 766
Pages : 142655
Catégorie(s)
#CNRS #FORET PuechabonRésumé
Soil organisms play a major role on litter decomposition process and nutrient cycling in forest ecosystems. These organisms are extremely sensitive to environmental conditions such as soil temperature and moisture conditions which control their demographic parameters and activity. The ongoing climate change can therefore directly affect soil biota communities and the processes they drive. Besides, climate change can also indirectly affect soil biota by altering tree functional traits (e.g., N, Ca, Mg, water holding capacity) with cascading effects on the litter quality. The aim of this study was to determine the relative effects of increased drought and litter type on mi crobial biomass (bacteria and fungi) and mesofauna abundance (Collembola and Acari) in three experimental sites representative of the three main forests encountered in the northern part of the Mediterranean Basin (dominated by either Quercus pubescens, Quercus ilex or Pinus halepensis) where rainfall exclusion experiments were taking place. At each site, and in each precipitation treatment (natural and amplified drought plots), we collected and transplanted foliage litters (i.e., species × drought level). After two years, we reported a litter species effect: Q. pubescens litter presented consistently the higher abundance of all soil biota groups compared to Q. ilex and P. halepensis litters in each forest. Surprisingly, despite that the amplified drought treatment induced a modification of the litter quality, we did not reported an indirect reduced precipitation effect on soil biota pa rameters. While Oribatid Acari abundance decreased with amplified drought in all three forest types, the direct effects on the other soil biota groups were forest-dependent. In P. halepensis forest, amplified drought resulted in higher bacterial and fungal biomasses but lower Collembola abundance. In Q. ilex forest both Collembola and predatory Acari abundances decreased with amplified drought. In addition, the positive relationships between Collembola and Oribatida abundances and litter mass loss disappeared under amplified drought conditions in both Q. ilex and P. halepensis forests. These results suggest a key role played by Ca, Mg, specific leaf area (SLA) and water holding capacity (WHC) as drivers of soil biota parameters. Finally, the study highlights that within the same Mediterranean region, climate change could differently alter the soil organisms inhabiting the litter layer and their contributions to the decomposition process depending on the tree species and soil biota group considered.
Auteurs, date et publication :
Auteurs Adriane Aupic-Samain , Mathieu Santonja , Mathilde Chomel , Susana Pereira , Elodie Quer , Caroline Lecareux , Jean-Marc Limousin , Jean-Marc Ourcival , Guillaume Simioni , Thierry Gauquelin , Catherine Fernandez , Virginie Baldy
Publication : Soil Biology and Biochemistry
Date : 2025
Volume : 154
Pages : 108122
Catégorie(s)
#CNRS #FORET Nouragues #FORET O3HP #FORET PuechabonRésumé
Across the globe, ecological communities are confronted with multiple global environmental change drivers, and they are responding in complex ways ranging from behavioral, physiological, and morphological changes within populations to changes in community composition and food web structure with consequences for ecosystem functioning. A better understanding of global change-induced alterations of multitrophic biodiversity and the ecosystem-level responses in terrestrial ecosystems requires holistic and integrative experimental approaches to manipulate and study complex communities and processes above and below the ground. We argue that mesocosm experiments fill a critical gap in this context, especially when based on ecological theory and coupled with microcosm experiments, field experiments, and observational studies of macroecological patterns. We describe the design and specifications of a novel terrestrial mesocosm facility, the iDiv Ecotron. It was developed to allow the setup and maintenance of complex communities and the manipulation of several abiotic factors in a near-natural way, while simultaneously measuring multiple ecosystem functions. To demonstrate the capabilities of the facility, we provide a case study. This study shows that changes in aboveground multitrophic interactions caused by decreased predator densities can have cascading effects on the composition of belowground communities. The iDiv Ecotrons technical features, which allow for the assembly of an endless spectrum of ecosystem components, create the opportunity for collaboration among researchers with an equally broad spectrum of expertise. In the last part, we outline some of such components that will be implemented in future ecological experiments to be realized in the iDiv Ecotron.
Auteurs, date et publication :
Auteurs Anja Schmidt , Jes Hines , Manfred Türke , François Buscot , Martin Schädler , Alexandra Weigelt , Alban Gebler , Stefan Klotz , Tao Liu , Sascha Reth , Stefan Trogisch , Jacques Roy , Christian Wirth , Nico Eisenhauer
Publication : Ecology and Evolution
Date : 2025
Volume : 11
Issue : 21
Pages : 15174-15190
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Thermoregulation is critical for ectotherms as it allows them to maintain their body temperature close to an optimum for ecological performance. Thermoregulation includes a range of behaviors that aim at regulating body temperature within a range centered around the thermal preference. Thermal preference is typically measured in a thermal gradient in fully-hydrated and post-absorptive animals. Short-term effects of the hydric environment on thermal preferences in such set-ups have been rarely quantified in dry-skinned ectotherms, despite accumulating evidence that dehydration might trade-off with behavioral thermoregulation. Using experiments performed under controlled conditions in climatic chambers, we demonstrate that thermal preferences of a ground-dwelling, actively foraging lizard (Zootoca vivipara) are weakly decreased by a daily restriction in free-standing water availability (less than 0.5°C contrast). The influence of air humidity during the day on thermal preferences depends on time of the day and sex of the lizard, and is generally weaker than those of of free-standing water (less than 1°C contrast). This shows that short-term dehydration can influence, albeit weakly, thermal preferences under some circumstances in this species. Environmental humidity conditions are important methodological factors to consider in the analysis of thermal preferences.
Auteurs, date et publication :
Auteurs Jean-François Le Le Galliard , David Rozen-Rechels , Anjélica Lecomte , Clémence Demay , Andréaz Dupoué , Sandrine Meylan
Publication : PLOS ONE
Date : 2025
Volume : 16
Issue : 2
Pages : e0247514
Catégorie(s)
#ANR-Citation #CEREEP #CNRS #ENSRésumé
Abstract. Information about forest background reflectance is needed for accurate biophysical parameter retrieval from forest canopies (overstory) with remote sensing. Separating under- and overstory signals would enable more accurate modeling of forest carbon and energy fluxes. We retrieved values of the normalized difference vegetation index (NDVI) of the forest understory with the multi-angular Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo data (gridded 500 m daily Collection 6 product), using a method originally developed for boreal forests. The forest floor background reflectance estimates from the MODIS data were compared with in situ understory reflectance measurements carried out at an extensive set of forest ecosystem experimental sites across Europe. The reflectance estimates from MODIS data were, hence, tested across diverse forest conditions and phenological phases during the growing season to examine their applicability for ecosystems other than boreal forests. Here we report that the method can deliver good retrievals, especially over different forest types with open canopies (low foliage cover). The performance of the method was found to be limited over forests with closed canopies (high foliage cover), where the signal from understory becomes too attenuated. The spatial heterogeneity of individual field sites and the limitations and documented quality of the MODIS BRDF product are shown to be important for the correct assessment and validation of the retrievals obtained with remote sensing.
Auteurs, date et publication :
Auteurs Jan Pisek , Angela Erb , Lauri Korhonen , Tobias Biermann , Arnaud Carrara , Edoardo Cremonese , Matthias Cuntz , Silvano Fares , Giacomo Gerosa , Thomas Grünwald , Niklas Hase , Michal Heliasz , Andreas Ibrom , Alexander Knohl , Johannes Kobler , Bart Kruijt , Holger Lange , Leena Leppänen , Jean-Marc Limousin , Francisco Ramon Lopez Serrano
Publication : Biogeosciences
Date : 2021
Volume : 18
Issue : 2
Pages : 621-635