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.
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.