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Title: Patterns of water and heat flux across a biome gradient from tropical forest to savanna in brazil
Authors: Rocha, Humberto Ribeiro da
Manzi, Antônio Ocimar
Cabral, Osvaldo M.R.
Miller, Scott Dennis
Goulden, Michael L.
Saleska, Scott Reid
Restrepo-Coupé, Natalia
Wofsy, Steven C.
Borma, Laura de Simone
Artaxo, Paulo
Vourlitis, George Louis
Nogueira, J. S.
Cardoso, Fernando Luiz
Nobre, Antônio Donato
Kruijt, Bart J.
Freitas, Helber Custódio de
Randow, Celso Von
Aguiar, Renata Gonçalves
Maia, Jair Max Furtunato
Keywords: Atmosphere-biosphere Interaction
Humid Environment
Net Radiation
Precipitation Intensity
Seasonal Variation
Sensible Heat Flux
Soil Moisture
Tropical Forest
Water Vapor
South America
Issue Date: 2009
metadata.dc.publisher.journal: Journal of Geophysical Research: Biogeosciences
metadata.dc.relation.ispartof: Volume 114, Número 1
Abstract: 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, Santarém 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. Copyright 2009 by the American Geophysical Union.
metadata.dc.identifier.doi: 10.1029/2007JG000640
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