The long-term monitoring of vegetation cover in the Amazonian region of northern Brazil using NOAA-AVHRR data

Abstract

We have analysed monthly composites of normalized diVerence vegetation index (NDVI ) calculated from NOAA's Advanced Very High Resolution Radiometer (AVHRR) for the Amazonian region of northern Brazil across a decade (August 1981 to June 1991 to ascertain if the dominant vegetation types could be diVerentiated, and to seek inter-annual climatic variation due to changing environmental conditions. The vegetation types observed included dense forest (submontana and terras baixas), open forest (submontana and terras baixas), transitional forest, seasonal forest (caatinga), and two types of savanna (cerrado). We found that monthly NDVI composites revealed seasonality in cerrado and especially in caatinga cover types, which can be used in their identi® cation, whilst the phenology of other forest cover types varies little throughout the year. Additionally, yearly composite NDVI values showed a clear and signi® cant reduction ( p>0´95) in dry years, such as those with El Nin Ä o Southern Oscillation events. These results indicate the potential use of multi-temporal NDVI data for the environmental characterization and identi® cation of forest ecosystems. Our research found NDVI images from NOAA AVHRR oVer a long-term data set that is unequalled for monitoring terrestrial land cover. However, these data have to be used with a degree of caution, especially in regards to atmospheric interference, such as cloud contamination and volcanic eruptions, and post-launch changes in calibration.

Estudo da variabilidade do NDVI sobre o Brasil, utilizando-se a análise de agrupamentos

“…Esses índices têm sido amplamente usados para o monitoramento regional ou global da cobertura vegetal (e.g. Eastman & Fulk 1993, Anyamba & Eastman 1996Potter & Brooks 1998;Richard & Poccard 1998 Batista et al (1997) analisaram a composição mensal do NDVI (AVHRR/ NOAA) da região amazônica, para o período de agosto de 1981 a junho de 1991. Eles averiguaram que os tipos de vegetação dominantes podem ser diferenciados e que é possível identificar-se variações da cobertura vegetal associadas a mudanças climáticas.…”

Tropical forest structure: a missing dimension to Pleistocene landscapes

“…JOURNAL OF QUATERNARY SCIENCE northern Brazil indicate that forest density is significantly reduced during ENSO years (Batista et al, 1997;Asner et al, 2000) because of heightened occurrence of drought (C. and concomitant increased frequency of forest fires (Barlow and Peres, 2004). Field research indicates that tree mortality in ENSO-induced drought events is much higher relative to other years (Williamson et al, 2000;.…”

Moisture Content (NDWI) and Spatial-Temporal Analysis of the Surface Albedo of the Moxoto-PE Basin River

“…Diversos autores explicam, através da utilização de séries temporais de vegetação, a relação entre os dados espectrais da vegetação com dados de precipitação (Batista et al, 1997;Fensholt & Sandholt, 2003;Gurgel et al, 2003).…”