A new experimentation on circadian rhythms (July - September 2013)

Will test how impact on the daytime transpiration and carbon fluxes at the leaf level will scale up to affect whole ecosystem fluxes, and to disentangle the underlying mechanisms. This project is coordinated by Victor Resco de Dios (University of Western Sydney) and Arthur Gessler (Leibniz Institute Berlin) with participation of Juan Pedro Ferrio Díaz, University of Lleida, Ivan Prieto and Michael Staudt, CEFE-CNRS Montpellier, Edward Gerardeaux and Alain Renou, CIRAD Montpellier, Jörg-Peter Schnitzler, Helmholtz Zentrum München, Michael Bahn, Innsbrück University…

This study builds upon previous efforts (Resco de Dios et al., Ecology Letters, (2009) 12: 583–592; Resco de Dios et al., Global Change Biology, (2012) 18, 1956–1970; Resco de Dios et al, New Phytologist, in press), towards understanding the role of the circadian clock in ecosystem processes. This past work has provided circumstantial evidence of circadian regulation of net ecosystem exchange of CO2 and water, and also of BVOC emissions, by combining filtering and modeling techniques to minimize environmental variation in the datasets along with short (12 hours) manipulations during the night. However, we still lack an unequivocal and direct test of circadian regulation of gas exchange beyond the leaf level and in the field. The only direct test for ecosystem-level circadian regulation of NEE, ET and BVOC emissions is by continuous monitoring under a ~24/48-hour period with constant levels of light, temperature and other environmental drivers (“continuous environment” hereafter).

Treatments: 2 crops, cotton and bean, studied successively; 2 experimental phases: no water limitation, drought. Each phase lasts two weeks for one crop. Which crop will be first will depend on the development of the canopies. When the second crop starts to be studied, the first crop enters drought. Then it is 4 weeks of study under good water condition and then 4 weeks under drought conditions.

 Montpellier Ecotron

Each phase has 2 sub-phases: a first one for the study of circadian rhythm in constant light and a second one for the study of circadian rhythm in constant dark. The study of the circadian rhythm consists in the comparison between the physiology under variable diurnal conditions and under constant conditions. The variable conditions are controlled (done with artificial lamps to have similar conditions whatever the outside weather and to have a maximum light level equal at the constant light level that will be imposed by the lamps).

One phase lasts two weeks with the following succession of activities each day.

Montpellier Ecotron

JENA-BIODIVERSITY (German DFG funded project, 2012)


  • Sort out short terme components of long term biodiversity effect on productivity.
  • -Fill up knowledge gaps in diversity effects in biogeochemical cycles.
  • -Test complementaries in plant species reources uptake.
  • -Analyse role of plant diversity on below-ground food-webs.

Collaboration: with Jena University and Max Planck Institute + many other groups.

Montpellier Ecotron

The results of this second experiment will be presented at the Intecol Congress (London, 18-23 August 2013).

Abstract: Plant diversity and carbon fluxes: new insights from the CNRS Ecotron facility

Alexandru Milcu, Christianne Roscher, Dörte  Bachmann, Annette Gockele, Markus Guderle, Damien Landais, Clément Piel, Christophe Escape, Sebastien Devidal, Olivier Ravel, Nina Buchmann, Arthur Gessler, Gerd Gleixner, Anke Hildebrandt & Jacques Roy

The first experimental demonstration that biodiversity loss can impair ecosystem performance was performed in a controlled environment facility (The Ecotron at Silwood Park, UK) and the findings have had a profound impact on the direction of subsequent ecological research and conservation of natural systems [Naeem, et al. (1994), Nature 368: 734-737]. Two decades later, whilst there is unequivocal evidence that biodiversity loss reduces the efficiency by which ecological communities capture biologically essential resources, it is still challenging to assess the mechanisms through which species richness affects the carbon (C) fluxes in the field. We took advantage of the new CNRS Ecotron facility (Montpellier, France) to investigate the effects of plant species and functional diversity on the C fluxes of model grasslands sampled from a long term biodiversity experiment (The Jena Experiment). Among the unique features of the experimental setup is the use of a large lysimeter (2m2 and 2m depth) approach combined with online and continuous measurements of C fluxes. We found that higher plant species richness led to increased ecosystem C uptake and water use efficiency during the growing period. The mechanisms by which species richness affected the C fluxes are discussed.


Past projects in the Macrocosms:

  1. Impact of extreme events and increase CO2 on a mid-altitude grassland (VALIDATE) (PI: J.-F. Soussana, ANR funded, 2011-2012)
  2. Mechanisms behind the biodiversity- ecosystem function relationship (JENA-BIODIVERSITY) (PI: G. Gleixner, DFG funded, 2012)
  3. Circadian rhythms at the canopy level (CIRCAFLUX) (PIs:  V. Resco de Dios and A.Gessler, multiple funding inlcuding ExpeER, 2013 )
  4. Microclimate vs. plant effects on soil respiration (PI: M. Bahn, ExpeER funded Innsbruck University – Ecotron collaboration, 2013)
  5. Oxygen as missing link to soil respiratory quotient (RESP_O2) (PI: M. Kazda, ExpeER funded, 2014-2015)


Past projects in the Microcosms:

  1. Climate change effects on Mediterranean biodiversity and consequences for ecosystem functioning (CLIMED) (PI S. Hättenschwiler, ANR funded, 2011-2012)
  2. Végétalisation des talus des voies ferrées (TALVEG) (PI Valorhiz, H. Boukcim, Oseo funded, 2013-2015)
  3. Tradeoffs between replicability and reproducibility in microcosm model systems (REPRO) (PI A. Milcu, J. Roy, ExpeER funded, 2014-2015)
  4. Drosophila epigenetics and environment (EPIGEN) (PI: G. Cavalli,own funding, 2014-2015)
  5. Impact of CO2 fixation by PEPc on carbon isotope composition of root-respired CO2 in a C3 plant (ISOPEPS) (PI F. Badeck, ExpeER funded, 2015)
  6. Genetic variability in tillering response of durum wheat to assimilate availability modulated by PPFD (TILLER) (PI F. Rizza, ExpeER funded, 2015)
  7. Microbial resilience and resistance to climatic stress as a function of N and P availabiliy: functional and stoichiometic approaches (RESIL-MICROBES) (PI I Bertrand & P Hisinger, EC2CO flunded, 2016) 



VALIDATE (ANR funded project, 2011-2012)

Impact of extreme climate events (drought and heat wave) on grasslands interaction with CO2 increase.
Coordination INRA at Clermont-Ferrand (with CEFE-CNRS, Austria, Germany).
Consequences on:

  • biogeochemical cycles (carbon storage, water and nitrogen balance...);
  • biodiversity (soil and vegetation);
  • quantity and quality of green biomass.

Montpellier Ecotron

The results of this first experiment have been presented at the Climate Extremes and Biogeochemical Cycles Conference (Innsbrück, 2-5 April 2013) and at the European Geosciences Union General Assembly (Vienna, 7-12 April 2013)

Abstract: Summer extreme climatic event in the future: impact on the net CO2 and water fluxes of an upland grassland and buffering impact of elevated atmospheric CO2.

Jacques Roy1, Damien Landais1, Clément Piel1, Marc Defossez1, Christophe Escape1, Sébastien Devidal1, Philippe Didier1, Olivier Ravel1, Michael Bahn2, Florence Volaire3, Angela Augusti4  Jean-François Soussana4, Catherine Picon-Cochard4

1) European Ecotron of Montpellier CNRS France, 2) Institute of Ecology University of Innsbruck Austria, 3) CEFE CNRS, INRA  Montpellier France, 4) UREP INRA Clermont-Ferrand France

Extreme climatic events are expected to be more frequent and intense in a few decades, but they will also occur in a climatic context different from the current one.  In the Montpellier Ecotron, we studied the response of intact grassland monoliths (1m², 60 cm deep) sampled in an upland grassland of the French Massif Central. The first year the grasslands were acclimated to the average climatic conditions of the years around 2050 (+ 4 °C and – 56 mm for summer precipitations). The second year, the same climate was maintained but in half of the experimental units we imposed a summer drought and heat wave (50 % reduction of precipitations for a month and then 100 % precipitation reduction combined with a 3,4 °C increase in temperature for two weeks). A CO2 treatment (520 vs. 380 µmol/mol) was crossed with the climatic treatment.
Net CO2 fluxes were measured continuously during the second year of the experiment. The extreme climatic event induced a total senescence of the canopy whatever the CO2 treatment. The interactive effect of elevated CO2 with the drought treatment was significant at the onset of the drought and particularly large in the fall after the recovery period, with a net photosynthesis twice as high in the (extreme climate+ CO2) treatment compared to the control. Integrated over the year, elevated CO2 totally buffered the impact of the extreme climatic event on net CO2 exchanges. These results are discussed together with the evapotranspiration and soil humidity data.