The Foliar Area Index (IAF) is an important variable biophysical vegetation used in several models of primary production through scaling and global models of climate, hydrology, biogeochemistry and ecology. This article compares three IAF estimates in the Amazonian transition forest. The IAF is estimated by field observations of the light transmittance and Lambert-Beer equation, by remote sensing using the IAF monthly sub-product of the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensor and by hemispheric photographs. The IAF estimated by Lambert-Beer presented seasonality and an annual average ranging from 3.21 to 3.74 m2m-2 for the years 2001 to 2003. The average IAF estimated by the MODIS product ranged from 5.25 to 5.54 m2m-2 for the years 2001 to 2003. The mean LAI estimated by hemispheric photographs ranged from 3.05 ± 0.52 to 4.12 ± 0, 56 m2m-2 for the period from June 2004 to May 2005 (Silva, 2006). The IAF obtained by the MODIS product did not present significant correlations with the LAF estimated by the Lambert-Beer law and by hemispheric photographs. The IAIS product of the MODIS sensor for transitional forest and tropical forests may be important for canopy dynamics studies and needs to be validated to be used safely in biosphere-atmosphere coupling models. Keywords: transmittance of light in the canopy, leaf area, sensoramentoremoto , tropical forest.
