title: Nocturnal stomatal conductance responses to rising [CO2], temperature and drought.
abstract: The response of nocturnal stomatal conductance (g(s,n)) to rising atmospheric CO(2) concentration ([CO(2)]) is currently unknown, and may differ from responses of daytime stomatal conductance (g(s,d)). Because night-time water fluxes can have a significant impact on landscape water budgets, an understanding of the effects of [CO(2)] and temperature on g(s,n) is crucial for predicting water fluxes under future climates. Here, we examined the effects of [CO(2)] (280, 400 and 640 μmol mol(-1)), temperature (ambient and ambient + 4°C) and drought on g(s,n,) and g(s,d) in Eucalyptus sideroxylon saplings. g(s,n) was substantially higher than zero, averaging 34% of g(s,d). Before the onset of drought, g(s,n) increased by 85% when [CO(2)] increased from 280 to 640 μmol mol(-1), averaged across both temperature treatments. g(s,n) declined with drought, but an increase in [CO(2)] slowed this decline. Consequently, the soil water potential at which g(s,n) was zero (Ψ(0)) was significantly more negative in elevated [CO(2)] and temperature treatments. g(s,d) showed inconsistent responses to [CO(2)] and temperature. g (s,n) may be higher in future climates, potentially increasing nocturnal water loss and susceptibility to drought, but cannot be predicted easily from g(s,d). Therefore, predictive models using stomatal conductance must account for both g(s,n) and g(s,d) when estimating ecosystem water fluxes.
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
authors.forename: Melanie J B
authors.initials: MJB
authors.lastname: Zeppel
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW 2753, Australia.|Louis Calder Center - Biological Field Station and Department of Biological Sciences, Fordham University, Armonk, NY 10504, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Lewis
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Chaszar
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW 2753, Australia.
authors.forename: Renee A
authors.initials: RA
authors.lastname: Smith
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
authors.forename: Belinda E
authors.initials: BE
authors.lastname: Medlyn
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA.|Biosphere 2, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Travis E
authors.initials: TE
authors.lastname: Huxman
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Richmond, NSW 2753, Australia.
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
mesh_terms: D002245:Carbon Dioxide; D002980:Climate; D055864:Droughts; D017753:Ecosystem; D004777:Environment; D005052:Eucalyptus / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology*; D012987:Soil; D013696:Temperature
chemical_list: D012987:Soil; D002245:Carbon Dioxide