MODIS EVI-based Variability in Amazon Phenology across the Rainforest-Cerrado Ecotone

摘要

The Amazon region contains one of the world's richest biodiversity and plays a major role in global dynamics of climate and global water and biogeochemical cycles. A better understanding of vegetation phenology and associated seasonal variations in carbon dynamics is necessary to develop reliable biosphere-climate models in the region. In this study, we investigated the interaction of climate and vegetation physiognomy on Amazon vegetation phenology through various eco-climatic transects traversing the Amazon transition ecotone. Our objective was to develop a better understanding of transitional ecotone vegetation dynamics and assess their relationship to rainforest and cerrado phenology patterns. The Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) time-series data were utilized for measuring seasonal variations in "greenness" across a series of eco-climatic transects. Overall, MODIS EVI derived phenology, showed pronounced, moisture induced dry-wet seasonal contrasts in the cerrado and intermediate seasonal contrast level in the light-limited rainforests. The transitional forests, representing a mixed response of light, water, and other factors, showed the least seasonality, however, the ecotone areas of converted forests depicted strong, moisture-limited, dry-wet seasonal contrasts due to the dominance of shallow rooted plants that cannot exploit water from deeper soil moisture layers in the dry season. The EVI seasonal profiles of tropical rainforests, transition ecotone forests, converted forests, and cerrado were unique. This yielded important phenology information useful in land cover characterization and for parameterization for biosphere-climate models.