Use of MODIS enhanced vegetation index to detect seasonal patterns of leaf phenology in central Amazon várzea forest

MODIS 16-day composite EVI, NDVI, and VI Quality Analysis values for 2000-2005 were extracted for 21 varzea forest sites along the Solimoes-Amazon floodplain west of Manaus, Brazil. VI values were filtered to exclude dates with VI-QA values greater than 3, and time series of median values of the remaining pixels were examined in conjunction with river stage levels recorded at the Manacapuru gauge. All sites showed a regular seasonal variation in EVI, ranging from a mean low for all sites of 0.41 to a mean high of 0.61. The amplitude of variability in NDVI was about 50% that of EVI. Minimum EVI, corresponding to minimum leaf area, occurred in late May, about 40 days preceding maximum river stage; EVI peaked in mid-October, about 30 days before lowest river levels. These temporal patterns are in general agreement with field observations of leaf phenology at va¿rzea stands near Manaus.