title: Processes driving nocturnal transpiration and implications for estimating land evapotranspiration.
abstract: Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12-23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51-98 vs. 7-8 mm yr(-1)). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake.
authors.affiliation: 1] Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, 25198 Lleida, Spain [2] Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW 2753, Australia.
authors.forename: Víctor Resco
authors.initials: VR
authors.lastname: de Dios
authors.affiliation: Ecotron Européen de Montpellier, UPS 3248, CNRS, Campus Baillarguet, 34980, Montferrier-sur-Lez, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Roy
authors.affiliation: Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, 25198 Lleida, Spain.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Ferrio
authors.affiliation: School of Environmental Sciences, University of Liverpool, Liverpool, L69 3GP, UK.
authors.forename: Josu G
authors.initials: JG
authors.lastname: Alday
authors.affiliation: Ecotron Européen de Montpellier, UPS 3248, CNRS, Campus Baillarguet, 34980, Montferrier-sur-Lez, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Landais
authors.affiliation: 1] Ecotron Européen de Montpellier, UPS 3248, CNRS, Campus Baillarguet, 34980, Montferrier-sur-Lez, France [2] CNRS, Centre d'Ecologie Fonctionnelle et Evolutive (CEFE, UMR-5175), 1919, route de Mende, 34293, Montpellier, France.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Milcu
authors.affiliation: 1] Swiss Federal Institute for Forest, Snow and Landscape Research WSL Long-term Forest Ecosystem Research (LWF), 8903 Birmensdorf, Switzerland [2] Institute for Landscape Biogeochemistry, Leibniz-Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
mesh_terms: D001272:Atmosphere; D002245:Carbon Dioxide / Q000737:chemistry; D017753:Ecosystem; D003368:Gossypium / Q000502:physiology*; D015233:Models, Statistical; D027805:Phaseolus / Q000502:physiology*; D017440:Photoperiod; D018515:Plant Leaves / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology*; D012987:Soil / Q000737:chemistry; D013696:Temperature; D014835:Volatilization; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide