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Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopesAuthor(s): A. C. Miranda; H. S. Miranda; J. Lloyd; J. Grace; R. J. Francey; J. A. Mcintyre; P. Meir; P. Riggan; R. Lockwood; J. Brass
Source: Plant, Cell and Environment 20(3): 315-328
Publication Series: Scientific Journal (JRNL)
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DescriptionWe present the energy and mass balance of cerrado sensu stricto (a Brazilian form of savanna), in which a mixture of shrubs, trees and grasses forms a vegetation with a leaf area index of 1·0 in the wet season and 0·4 in the dry season. In the wet season the available energy was equally dissipated between sensible heat and evaporation, but in the dry season at high irradiance the sensible heat greatly exceeded evaporation. Ecosystem surface conductance g
sin the wet season rose abruptly to 0·3 mol m −2s −1and fell gradually as the day progressed. Much of the total variation in g swas associated with variation in the leaf-to-air vapour pressure deficit of water and the solar irradiance. In the dry season the maximal g svalues were only 0·1 mol m −2s −1. Maximal net ecosystem fluxes of CO 2in the wet and dry season were –10 and –15 μmol CO 2m −2s −1, respectively (sign convention: negative denotes fluxes from atmosphere to vegetation). The canopy was well coupled to the atmosphere, and there was rarely a significant build-up of respiratory CO 2during the night. For observations in the wet season, the vegetation was a carbon dioxide sink, of maximal strength 0·15 mol m −2d −1. However, it was a source of carbon dioxide for a brief period at the height of the dry season. Leaf carbon isotopic composition showed all the grasses except for one species to be C 4, and all the palms and woody plants to be C 3. The CO 2coming from the soil had an isotopic composition that suggested 40% of it was of C 4origin.
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CitationMiranda, A. C.; Miranda, H. S.; Lloyd, J.; Grace, J. ; Francey, R. J.; Mcintyre, J. A. ; Meir, P.; Riggan, P. ; Lockwood, R. ; Brass, J. 1997. Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopes. Plant, Cell and Environment 20(3): 315-328
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