Résumé
Abstract. Continental relative humidity (RH) is a key-climate parameter. However, there is a lack of quantitative RH proxies suitable for climate model-data comparisons. Recently, a combination of climate chamber and natural transect calibrations laid the groundwork for examining the robustness of the triple oxygen isotope composition (δ18O, δ17O) of phytoliths as a new proxy for past changes in RH. However, it was recommended that besides RH, additional factors that may impact δ18O and δ17O of plant water and phytoliths be examined. Here, the effects of leaf anatomy, leaf development stage and day/night alternations are addressed from the growth of the grass species F. arundinacea in climate chambers. Plant water and phytoliths are analyzed in δ18O and δ17O. Silicification patterns are examined using light and scanning electron observation of phytoliths. The isotope data show the increasing contribution of evaporated epidermal water to the bulk leaf water, from sheath to proximal and apical leaf blade. However, despite this isotope heterogeneity, δ18O and δ17O of the bulk leaf water can be predicted by the Craig and Gordon model, in the given experimental conditions (high RH). Regarding phytoliths, their forming water (mainly epidermal) is, as expected, more impacted by evaporation than the bulk leaf water. This discrepancy increases from sheath to proximal and apical blade and can be explained by the steepening of the radial concentration gradient of evaporated water along the leaf. However, we show that because most of silica polymerizes in epidermal long cells of the apical blade of the leaves, the δ18O and δ17O of bulk grass phytoliths should not be impacted by the diversity in grass anatomy. The data additionally show that most of silica polymerizes at the end of the leaf elongation stage and at the transition towards leaf senescence. Thus, climate conditions at that time should be considered when interpreting δ18O and δ17O of phytoliths from the natural environment. At least, no light/dark effect was detected on the δ18O and δ17O signature of plant water and phytoliths of F. arundinacea. However, when day/night alternations are characterized by significant changes in RH, the lowest RH conditions favoring evaporation and silica polymerization should be considered when calibrating the phytolith proxy. This study contributes to the identification of the parameters driving the δ18O and δ17O of bulk grass phytoliths. It additionally brings elements to further understand and model the δ18O and δ17O of grass leaf water, which influences the isotope signal of several processes at the soil/plant/atmosphere interface.
Auteurs, date et publication :
Auteurs Anne Alexandre , Elizabeth Webb , Amaelle Landais , Clément Piel , Sébastien Devidal , Corinne Sonzogni , Martine Couapel , Jean-Charles Mazur , Monique Pierre , Frédéric Prié , Christine Vallet-Coulomb , Jacques Roy
Publication : Biogeosciences Discussions
Date : 2019
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Jumping is an important form of locomotion, and animals employ a variety of mechanisms to increase jump performance. While jumping is common in insects generally, the ability to jump is rare among ants. An exception is the Neotropical ant Gigantiops destructor (Fabricius 1804) which is well known for jumping to capture prey or escape threats. Notably, this ant begins a jump by rotating its abdomen forward as it takes off from the ground. We tested the hypotheses that abdominal rotation is used to either provide thrust during takeoff or to stabilize rotational momentum during the initial airborne phase of the jump. We used high speed videography to characterize jumping performance of G. destructor workers jumping between two platforms. We then anesthetized the ants and used glue to prevent their abdomens from rotating during subsequent jumps, again characterizing jump performance after restraining the abdomen in this manner. Our results support the hypothesis that abdominal rotation provides additional thrust as the maximum distance, maximum height, and takeoff velocity of jumps were reduced by restricting the movement of the abdomen compared with the jumps of unmanipulated and control treatment ants. In contrast, the rotational stability of the ants while airborne did not appear to be affected. Changes in leg movements of restrained ants while airborne suggest that stability may be retained by using the legs to compensate for changes in the distribution of mass during jumps. This hypothesis warrants investigation in future studies on the jump kinematics of ants or other insects.
Auteurs, date et publication :
Auteurs Dajia Ye , Joshua C Gibson , Andrew V Suarez
Publication : Integrative Organismal Biology
Date : 2020
Volume : 2
Issue : obz033
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Plants play an important role in carbon and nitrogen fluxes in the
environment. Plants remove carbon from the atmosphere through
photosynthesis and deposit a fraction of this carbon into the soil as a
result of root exudation and senescence, contributing to soil formation.
Additionally, plants can facilitate sequestration of CO2 from the
atmosphere in inorganic form during the process of mineral weathering.
With increasing temperatures and levels of CO2 in the atmosphere, it is
unknown what effect these changes will have on plant growth and
weathering of silicate rocks, and by extension on carbon accumulation in
the soils. To identify climate change effects on C and N fluxes, a
controlled study was conducted at Ecotron Ile-de-France utilizing
mesocosms maintained at elevated and ambient CO2 concentration and
temperature with four different vegetation treatments: control, alfalfa,
velvet mesquite, and green sprangletop. Each experiment lasted for 4
months with monthly rainfall events using deionized water. After each
rain, soil solution and drainage were collected and analyzed for major
and trace elements, as well as anions, nitrogen, and organic and
inorganic carbon. CO2 concentrations in the soil air were monitored as
well. At the end of this study, soil samples were collected from each
mesocosm at four different depths and then analyzed for organic carbon,
inorganic carbon, and total nitrogen. Accumulation of organic and
inorganic carbon and nitrogen with clear differences with depth was
observed in all mesocosms. Elevated CO2 in the atmosphere influenced C
accumulation in the soils, while the type of vegetation significantly
affected concentrations of nitrogen and organic carbon in soil and
solution. This indicates that climate change would affect carbon and
nitrogen fluxes in the soils causing feedbacks to the atmospheric CO2.
Auteurs, date et publication :
Auteurs R. Hingley , S. Juarez , K. Dontsova , E. Hunt , J. F. Le Galliard , S. Chollet , A. Cros , M. Llavata , F. Massol , P. Barré , A. Gelabert , D. Daval , P. A. A. Troch , G. Barron-Gafford , J. L. M. Van Haren , R. Ferrière
Date : 2016
Volume : 53
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSAuteurs, date et publication :
Auteurs Amélie Saunier , Elena Ormeño , Christophe Boissard , Henri Wortham , Brice Temime-Roussel , Caroline Lecareux , Alexandre Armengaud , Catherine Fernandez
Publication : Atmospheric Chemistry and Physics
Date : 2017
Volume : 17
Issue : 12
Pages : 7555-7566
Catégorie(s)
#CNRS #FORET O3HPAuteurs, date et publication :
Auteurs Luc Allard , Manon Popée , Régis Vigouroux , Sébastien Brosse
Publication : Aquatic sciences
Date : 2025
Volume : 78
Issue : 2
Pages : 315-325
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Fungal communities in the root endosphere are heterogeneous at fine scale. The passenger hypothesis assumes that this heterogeneity is driven by host plant distribution. Plant composition and host plant configuration should then influence root fungal assemblages. We used a large-scale experimental design of 25 mixtures of grassland plants. We sampled Brachypodium pinnatum in each mesocosm, and used amplicon mass-sequencing to analyze the endospheric mycobiota. We used plant distribution maps to assess plant species richness and evenness (heterogeneity of composition), and patch size and the degree of isolation of B. pinnatum (heterogeneity of configuration) on fungal community assembly. The Glomeromycotina community in B. pinnatum roots was not related to either floristic heterogeneity or productivity. For Ascomycota, the composition of operational taxonomic units (OTUs) was driven by plant evenness while OTU richness decreased with plant richness. For Basidiomycota, richness increased with host plant aggregation and connectivity. Plant productivity influenced Ascomycota, inducing a shift in OTU composition and decreasing evenness. Plant heterogeneity modified root mycobiota, with potential direct (i.e. host preference) and indirect (i.e. adaptations to abiotic conditions driven by plant occurrence over time) effects. Plant communities can be envisioned as microlandscapes consisting of a variety of fungal niches.
Auteurs, date et publication :
Auteurs Cendrine Mony , Philomène Brunellière , Nathan Vannier , Anne-Kristel Bittebiere , Philippe Vandenkoornhuyse
Publication : New Phytologist
Date : 2025
Volume : 225
Issue : 4
Pages : 1777-1787
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
• Introduction Millions of hectares of Quercus ilex forests dominate disturbed landscapes in the western part of the Mediterranean basin. Although these forests are very widespread, little is known about the composition and structure of their associated ectomycorrhizal fungal communities.• Results and discussion We examined seasonal patterns in ectomycorrhizal communities and their response to increased drought using a rainfall exclusion experiment established in a Q. ilex coppice since 2003. Ectomycorrhizae were sampled four times in 2007–2009. By sequencing fungal ITS, we identified 129 species in 1,147 sequenced ectomycorrhizal root tips. The fungal community in the surface organic horizon was well described by the logseries theoretical model, with 47.9% of singleton species. The composition of the community was strongly dominated by Basidiomycetes, with three families (Thelephoraceae, Russulaceae and Cortinariaceae) accounting for 72.9% of the root tips. Relative abundance of Russulaceae and Thelephoraceae showed pronounced seasonal shifts. Experimental reduction of rainfall resulted in significant shifts in community composition and seasonal fluctuations but had no effect on global richness of the community.• Conclusions Together, these results suggest that the predicted rainfall reduction in this region due to climate change will lead to shifts in species composition in ectomycorrhizal communities.
Auteurs, date et publication :
Auteurs Franck Richard , Melanie Roy , Oula Shahin , Christopher Sthultz , Myriam Duchemin , Richard Joffre , Marc-André Selosse
Publication : Annals of Forest Science
Date : 2011
Volume : 68
Issue : 1
Pages : 57-68
Catégorie(s)
#CNRS #FORET PuechabonRésumé
Understanding the factors underlying the distribution of biodiversity is a challenging issue in ecology. Here, we examined the distribution patterns of ectomycorrhizal fungal diversity across the soil profile in three Quercus ilex forests. Contact exploration type strongly dominated at all sites, but was most prevalent in the upper, organic-rich soil layers. At each site, three quarters of the ectomycorrhizal tips and 59 % of taxa were restricted to the ten first centimeters of the soil profile. The relative abundance of the dominant family Russulaceae increased with increasing soil depth. Species composition varied significantly among sites, with most species being rare. Species that occurred in only one of the three sites accounted for 78.9 % of all species, and 57.3 % of species were represented by a single ECM root tip. Our results suggest that (i) rare species at both local and regional scales contribute to the highly diverse fungal assemblages in Mediterranean forests and (ii) multi-sites studies including the whole soil profile are needed to provide comprehensive overviews of the taxonomic and functional diversities of ectomycorrhizal communities.
Auteurs, date et publication :
Auteurs Oula Shahin , Nicolas Martin-St Paul , Serge Rambal , Richard Joffre , Franck Richard
Publication : Symbiosis
Date : 2013
Volume : 61
Issue : 1
Pages : 1-12
Catégorie(s)
#CNRS #FORET PuechabonRésumé
Abstract. Intraspecific trait variation has large effects on the ecosystem and is greatly affected by human activities. To date, most studies focused on single
Auteurs, date et publication :
Auteurs Beatriz Diaz Pauli , Eric Edeline , Charlotte Evangelista
Publication : Conservation Physiology
Date : 2020
Volume : 8
Issue : 1
Catégorie(s)
#ANR-Citation #CNRS #Ecotron IleDeFrance #ENSRésumé
Ecosystems integrity and services are threatened by anthropogenic global changes. Mitigating and adapting to these changes requires knowledge of ecosystem functioning in the expected novel environments, informed in large part through experimentation and modelling. This paper describes 13 advanced controlled environment facilities for experimental ecosystem studies, herein termed ecotrons, open to the international community. Ecotrons enable simulation of a wide range of natural environmental conditions in replicated and independent experimental units whilst simultaneously measuring various ecosystem processes. This capacity to realistically control ecosystem environments is used to emulate a variety of climatic scenarios and soil conditions, in natural sunlight or through broad spectrum lighting. The use of large ecosystem samples, intact or reconstructed, minimises border effects and increases biological and physical complexity. Measurements of concentrations of greenhouse trace gases as well as their net exchange between the ecosystem and the atmosphere are performed in most ecotrons, often quasi continuously. The flow of matter is often tracked with the use of stable isotope tracers of carbon and other elements. Equipment is available for measurements of soil water status as well as root and canopy growth. The experiments run so far emphasize the diversity of the hosted research. Half of them concern global changes, often with a manipulation of more than one driver. About a quarter deal with the impact of biodiversity loss on ecosystem functioning and one quarter with ecosystem or plant physiology. We discuss how the methodology for environmental simulation and process measurements, especially in soil, can be improved and stress the need to establish stronger links with modelling in future projects. These developments will enable further improvements in mechanistic understanding and predictive capacity of ecotron research which will play, in complementarity with field experimentation and monitoring, a crucial role in exploring the ecosystem consequences of environmental changes.
Auteurs, date et publication :
Auteurs Jacques Roy , François Rineau , Hans J. De Boeck , Ivan Nijs , Thomas Pütz , Samuel Abiven , John A. Arnone , Craig V. M. Barton , Natalie Beenaerts , Nicolas Brüggemann , Matteo Dainese , Timo Domisch , Nico Eisenhauer , Sarah Garré , Alban Gebler , Andrea Ghirardo , Richard L. Jasoni , George Kowalchuk , Damien Landais , Stuart H. Larsen
Publication : Global Change Biology
Date : 2025
Volume : 27
Issue : 7
Pages : 1387-1407