Open AccessPatterns of water and heat flux across a biome gradient from tropical forest to savanna in Brazil
Author(s) -
da Rocha Humberto R.,
Manzi Antonio O.,
Cabral Osvaldo M.,
Miller Scott D.,
Goulden Michael L.,
Saleska Scott R.,
R.Coupe Natalia,
Wofsy Steven C.,
Borma Laura S.,
Artaxo P.,
Vourlitis George,
Nogueira José S.,
Cardoso Fernando L.,
Nobre Antonio D.,
Kruijt Bart,
Freitas Helber C.,
von Randow Celso,
Aguiar Renata G.,
Maia Jair F.
Publication year - 2009
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jg000640
Subject(s) - dry season , evapotranspiration , biome , eddy covariance , wet season , environmental science , tropical and subtropical dry broadleaf forests , bowen ratio , sensible heat , tropics , atmospheric sciences , precipitation , flux (metallurgy) , seasonality , hydrology (agriculture) , ecology , geography , ecosystem , agroforestry , biology , geology , chemistry , geotechnical engineering , organic chemistry , meteorology
We investigated the seasonal patterns of water vapor and sensible heat flux along a tropical biome gradient from forest to savanna. We analyzed data from a network of flux towers in Brazil that were operated within the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA). These tower sites included tropical humid and semideciduous forest, transitional forest, floodplain (with physiognomies of cerrado), and cerrado sensu stricto. The mean annual sensible heat flux at all sites ranged from 20 to 38 Wm −2 , and was generally reduced in the wet season and increased in the late dry season, coincident with seasonal variations of net radiation and soil moisture. The sites were easily divisible into two functional groups based on the seasonality of evaporation: tropical forest and savanna. At sites with an annual precipitation above 1900 mm and a dry season length less than 4 months (Manaus, Santarem and Rondonia), evaporation rates increased in the dry season, coincident with increased radiation. Evaporation rates were as high as 4.0 mm d −1 in these evergreen or semidecidous forests. In contrast, ecosystems with precipitation less than 1700 mm and a longer dry season (Mato Grosso, Tocantins and São Paulo) showed clear evidence of reduced evaporation in the dry season. Evaporation rates were as low as 2.5 mm d −1 in the transitional forests and 1 mm d −1 in the cerrado. The controls on evapotranspiration seasonality changed along the biome gradient, with evaporative demand (especially net radiation) playing a more important role in the wetter forests, and soil moisture playing a more important role in the drier savannah sites.