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Assessment of satellite-derived vegetation indices across the Amazon forest

Humberto Alves Barbosa, Universidade Federal de Alagoas, (Presenting)
Marcos Daisuke Oyama, Instituto de Aeronáutica e Espaço,
Luis Gustavo Gonçalves, NASA Goddard Space Flight Center,

Different products derived from satellite remote sensing are available to study vegetation dynamics from several spatial, temporal and spectral resolution and algorithms have been developed to compute vegetation indices using blue, red and near-infrared imagery. The state of the art Enhanced Vegetation Index (EVI) product from the recently launched Terra Moderate Resolution Imaging Spectroradiometer (MODIS) has played a key role in detecting changes in the Amazonian vegetation phenology caused by drought stress. More recent investigations by Huete et al. (2006) and Xiao et al. (2006) built on this product over the Amazon region found an unexpected EVI peak in the late dry season, which was indicative of a more intense vegetation activity at the end of the dry season. In this study, we focus our investigations on the extent to which the Normalized Difference Vegetation Index (NDVI) has similar behavior to the EVI peak in the late dry season across the Amazon region using ten-day composites of NDVI and EVI data for the period 1998 and 1999 from the SPOT 4 satellite Végétation sensor. A simple comparison between the spatial and temporal patterns of the NDVI and EVI responses based on analyses of time series were determined in order to show agreement and discrepancies of the two indices in the late dry season. Our preliminary analysis confirmed the consistencies between this investigation and other investigations that spatial variations in the EVI across Amazon forests (i.e., the evergreen forests) exhibited the peak vegetation green up in the late dry season, whereas in areas converted to pasture the reverse was observed. In contrast, the NDVI differed significantly from the peak EVI in the late dry season for its minima in the late dry season. Although there was less NDVI variation observed in areas of evergreen forests relative to those in areas converted to pasture. But the later showed similar vegetation greenness minima in the late dry season and was much more impacted by drought stress. We believe the use of satellite-derived EVI observations as an index of canopy photosynthetic capacity holds great promise in evaluating changes in land vegetation at the tropical rainforest plant formations. Science Theme: LC (Land Use and Land Cover Change) Session: 2B: The Changing Amazon Landscape Presentation Type: Oral

Science Theme:  LC (Land Use and Land Cover Change)

Presentation Type:  Poster

Abstract ID: 145

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