WHAT DO VEGETATION INDICES TELL US ABOUT THE DYNAMICS OF THE AMAZON EVERGREEN FORESTS?

Humberto Allves Barbosa, T. V. Lakshmi Kumar

Resumo


Our understanding of the response of satellite–based vegetation indices to the meteorological conditions in terms of temperature and precipitation conditions of the Amazon evergreen forest is arguably weaker than that of any other tropical continental region, despite the obvious connection. To assess such response, we have used different dataset of vegetation indices – the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Fraction of Vegetation Cover (FVC) derived from SPOT 4 Satellite VEGETATION data and Meteosat Second Generation (MSG) satellite products. Based on the covers time scales from daily to dekadal, at spatial resolutions from 1 to 3 km, and provides temporal coverage for the period of extremely El Niño event (between 1998-2000). And the weather data were compiled from the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) – HydroNet collection. The obtained results suggest that the combined effects of precipitation decrease and air temperature increase in the healthy Amazon evergreen forest is a possible explanation of the higher EVI values and the lower NDVI values during the dry season. On the other hand, FVC reflects the combined effects of precipitation and air temperature changes, shows the higher values for pasture and lower values during the wet season consistent with an increase in precipitation and a decrease in air temperature. Such distinct vegetation responses may be viewed as a function of the spatial scale.
Key words:.Vegetation indices, meteorological conditions, green-up, El Niño.

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