title: On the persistence of memory: soft clocks and terrestrial biosphere-atmosphere interactions.
abstract: The circadian clock is considered a central "orchestrator" of gene expression and metabolism. Concomitantly, the circadian clock is considered of negligible influence in the field and beyond leaf levels, where direct physiological responses to environmental cues are considered the main drivers of diel fluctuations. I propose to bridge the gap across scales by examining current evidence on whether circadian rhythmicity in gas exchange is relevant for field settings and at the ecosystem scale. Nocturnal stomatal conductance and water fluxes appear to be influenced by a "hard" clock that may override the direct physiological responses to the environment. Tests on potential clock controls over photosynthetic carbon assimilation and daytime transpiration are scant yet, if present, could have a large impact on our current understanding and modeling of the exchanges of carbon dioxide and water between terrestrial ecosystems and the atmosphere.
authors.affiliation: Hawkesbury Institute for the Environment; University of Western Sydney; Richmond, NSW Australia.
authors.forename: Víctor
authors.initials: V
authors.lastname: Resco de Dios
mesh_terms: D001272:Atmosphere; D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D017753:Ecosystem; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology
keywords: biosphere-atmosphere interactions; circadian clock; diel cycles; endogenous regulation; evapotranspiration; gas exchange; gross ecosystem exchange; hysteresis; up-scaling