Résumé
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
Catégorie(s)
#CNRS #FORET PuechabonRésumé
A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-20997-9.
Auteurs, date et publication :
Auteurs Yann Hautier , Pengfei Zhang , Michel Loreau , Kevin R. Wilcox , Eric W. Seabloom , Elizabeth T. Borer , Jarrett E. K. Byrnes , Sally E. Koerner , Kimberly J. Komatsu , Jonathan S. Lefcheck , Andy Hector , Peter B. Adler , Juan Alberti , Carlos A. Arnillas , Jonathan D. Bakker , Lars A. Brudvig , Miguel N. Bugalho , Marc Cadotte , Maria C. Caldeira , Oliver Carroll
Publication : Nature Communications
Date : 2021
Volume : 12
Issue : 1
Pages : 630
Catégorie(s)
#CEREEP #CNRS #ENSRésumé
Initial Cadmium (Cd) isotope fractionation studies in cereals ascribed the retention of Cd and its light isotopes to the binding of Cd to sulfur (S). To better understand the relation of Cd binding to S and Cd isotope fractionation in soils and plants, we combined isotope and XAS speciation analyses in soil-rice systems that were rich in Cd and S. The systems included distinct water management (flooded vs. non-flooded) and rice accessions with (excluder) and without (non-excluder) functional membrane transporter OsHMA3 that transports Cd into root vacuoles. Initially, 13% of Cd in the soil was bound to S. Through soil flooding, the proportion of Cd bound to S increased to 100%. Soil flooding enriched the rice plants towards heavy isotopes (delta Cd-114/110 = -0.37 to -0.39%) compared to the plants that grew on non-flooded soils (delta Cd-114/110 = -0.45 to -0.56%) suggesting that preferentially light Cd isotopes precipitated into Cd sulfides. Isotope compositions in CaCl2 root extracts indicated that the root surface contributed to the isotope shift between soil and plant during soil flooding. In rice roots, Cd was fully bound to S in all treatments. The roots in the excluder rice strongly retained Cd and its lights isotopes while heavy isotopes were transported to the shoots (Delta Cd-114/110(shoot-root) 0.16-0.19 parts per thousand). The non-excluder rice accumulated Cd in shoots and the apparent difference in isotope composition between roots and shoots was smaller than that of the excluder rice (Delta Cd-114/110(shoot-root) -0.02 to 0.08 parts per thousand). We ascribe the retention of light Cd isotopes in the roots of the excluder rice to the membrane transport of Cd by OsHMA3 and/or chelating Cd-S complexes in the vacuole. Cd-S was the major binding form in flooded soils and rice roots and partly contributed to the immobilization of Cd and its light isotopes in soil-rice systems. (C) 2020 The Author(s). Published by Elsevier Ltd.
Auteurs, date et publication :
Auteurs Matthias Wiggenhauser , Anne-Marie Aucour , Sarah Bureau , Sylvain Campillo , Philippe Telouk , Marco Romani , Jian Feng Ma , Gautier Landrot , Geraldine Sarret
Publication : ENVIRONMENTAL POLLUTION
Date : 2021
Volume : 269
Catégorie(s)
#ANR-Citation #CNRS #LautaretRésumé
All termites have established a wide range of associations with symbiotic microbes in their guts. Some termite species are also associated with microbes that grow in their nests, but the prevalence of these associations remains largely unknown. Here, we studied the bacterial communities associated with the termites and galleries of three wood-feeding termite species by using 16S rRNA gene amplicon sequencing. We found that the compositions of bacterial communities among termite bodies, termite galleries, and control wood fragments devoid of termite activities differ in a species-specific manner. Termite galleries were enriched in bacterial operational taxonomic units (OTUs) belonging to Rhizobiales and Actinobacteria, which were often shared by several termite species. The abundance of several bacterial OTUs, such as Bacillus, Clostridium, Corynebacterium, and Staphylococcus, was reduced in termite galleries. Our results demonstrate that both termite guts and termite galleries harbor unique bacterial communities.IMPORTANCE As is the case for all ecosystem engineers, termites impact their habitat by their activities, potentially affecting bacterial communities. Here, we studied three wood-feeding termite species and found that they influence the composition of the bacterial communities in their surrounding environment. Termite activities have positive effects on Rhizobiales and Actinobacteria abundance and negative effects on the abundance of several ubiquitous genera, such as Bacillus, Clostridium, Corynebacterium, and Staphylococcus. Our results demonstrate that termite galleries harbor unique bacterial communities.
Auteurs, date et publication :
Auteurs Patrik Soukup , Tomáš Větrovský , Petr Stiblik , Kateřina Votýpková , Amrita Chakraborty , David Sillam-Dussès , Miroslav Kolařík , Iñaki Odriozola , Nathan Lo , Petr Baldrian , Jan Šobotník , Thomas Bourguignon , Gladys Alexandre
Publication : Applied and Environmental Microbiology
Date : 2021
Volume : 87
Issue : 2
Pages : e02042-20
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Simple Summary Urbanization modifies the composition of all biological communities, including insect pollinator communities, but what is filtered out? To answer this question, we compared the pollinators and their morphological and behavioral characteristics between Paris green spaces and nearby rural grasslands. We monitored the pollinators foraging on identical plant plots in these two environments for two years, and from spring to fall. Pollinators in the city were relatively less diverse than their rural counterparts. They comprised fewer bees belonging to solitary or ground-nesting species, but the bees had a larger body size overall. These data add to the body of evidence of a filtering of pollinator communities by the urban environment, partly because the abundance and distribution of nesting and feeding resources are modified. Since the diversity of pollinators is important for plant pollination, such effects must be considered in order to preserve the insect pollinator community and maintain the pollination function despite the increasing urbanization of our landscapes. Even though urban green spaces may host a relatively high diversity of wild bees, urban environments impact the pollinator taxonomic and functional diversity in a way that is still misunderstood. Here, we provide an assessment of the taxonomic and functional composition of pollinator assemblages and their response to urbanization in the Paris region (France). We performed a spring-to-fall survey of insect pollinators in green spaces embedded in a dense urban matrix and in rural grasslands, using a plant setup standardized across sites and throughout the seasons. We compared pollinator species composition and the occurrence of bee functional traits over the two habitats. There was no difference in species richness between habitats, though urban assemblages were dominated by very abundant generalist species and displayed a lower evenness. They also included fewer brood parasitic, solitary or ground-nesting bees. Overall, bees tended to be larger in the city than in the semi-natural grasslands, and this trait exhibited seasonal variations. The urban environment filters out some life history traits of insect pollinators and alters their seasonal patterns, likely as a result of the fragmentation and scarcity of feeding and nesting resources. This could have repercussions on pollination networks and the efficiency of the pollination function.
Auteurs, date et publication :
Auteurs Vincent Zaninotto , Adrien Perrard , Olivier Babiar , Amandine Hansart , Cecile Hignard , Isabelle Dajoz
Publication : INSECTS
Date : 2021
Volume : 12
Issue : 3