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Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest
Author(s) -
Doughty Christopher E.,
Goulden Michael L.,
Miller Scott D.,
da Rocha Humberto R.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl026750
Subject(s) - eddy covariance , canopy , circadian rhythm , irradiance , nocturnal , morning , environmental science , rhythm , atmospheric sciences , amazonian , photosynthesis , atmosphere (unit) , period (music) , biology , ecology , botany , ecosystem , meteorology , geography , geology , physics , amazon rainforest , neuroscience , quantum mechanics , acoustics
We used a controlled‐environment leaf gas‐exchange system and the micrometeorological technique eddy covariance to determine whether circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day. When exposed to continuous and constant light for 20 to 48 hours leaves of eleven of seventeen species reduced their photosynthetic rates and closed their stomata during the normally dark period and resumed active gas exchange during the normally light period. Similarly, the rate of whole‐forest CO 2 uptake at a predetermined irradiance declined during the late afternoon and early morning and increased during the middle of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported for herbaceous plants in the laboratory. The importance of endogenous gas exchange rhythms presents a previously unrecognized challenge for efforts to both interpret and model land‐atmosphere energy and mass exchange.