SciELO - Scientific Electronic Library Online

 
vol.35 issue2Clouds, rain and biosphere interactions in AmazonThe drought of the century in the Amazon Basin: an analysis of the regional variation of rainfall in South America in 1926 author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Acta Amazonica

Print version ISSN 0044-5967

Abstract

SOUZA FILHO, José Danilo da Costa; RIBEIRO, Aristides; COSTA, Marcos Heil  and  COHEN, Julia Clarinda Paiva. Control mechanisms of the seasonal variation of transpiration in a northeast amazonian tropical rainforest. Acta Amaz. [online]. 2005, vol.35, n.2, pp. 223-229. ISSN 0044-5967.  http://dx.doi.org/10.1590/S0044-59672005000200012.

In the present work we study the seasonal variation of the transpiration of a tropical forest, and its dependence on biotic and abiótic factors. We used data of the project CARBOPARÁ, part of The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), collected in the National Forest of Caxiuanã, northeastern Amazonia. The average transpiration in a 39-day period during the rainy season was 2.9 mm day-1. In a 29-day period during dry season, the average transpiration was 4.3 mm day-1. The maximum values of the surface conductivity (Cs) are 0.060 m s-1 and 0.045 m s-1 for the rainy and dry period, respectively, observed at 08:00 h local time. The aerodynamic conductance averages (Ca) 0.164 m s-1 and 0.210 m s-1, for the rainy and dry periods, respectively, while the maximum values of Ca are 0.220 and 0.375 m s-1, for the same periods, respectively. It was verified that Cs presents an inverse exponential relationship with the deficit of atmospheric water vapor, for different intervals of global solar irradiance. The hourly analysis of the decoupling factor suggests that the morning transpiration is mainly controlled by the availability of energy. During the afternoon, on the other hand, for both periods studied, the forest becomes progressively coupled to the atmosphere, denoting larger superficial control on the transpiration process.

Keywords : Transpiration; Aerodynamic and Surface Conductances; Decouple Factor.

        · abstract in Portuguese     · text in Portuguese     · pdf in Portuguese