Seasonal dynamics of native and converted cerrado physiognomies with MODIS data

Abstract

The Cerrado or Brazilian savanna represents 23% of the land surface of the country. This important bid me, however, has been subjected to rapid rates of land conversion to agriculture and pasture. This has important environmental consequences to local and regional climate change and carbon fluxes. Therefore, a study of seasonal cerrado dynamics, including forest and converted areas, was conducted with four years of data (February 2000 to December 2003) from the Moderate Resolution Imaging Spectroradiometer (MODIS). The 16-day composite vegetation index (VI) data were used to analyze the seasonal patterns of photosynthetic vegetation activity and examine the separability of cerrado formations of varying physiognomies in Brasilia National Park and surrounding areas. The results showed that the cerrado formations exhibited a high seasonality contrast with a pronounced dry season from June through August and wet season from November to March. Discrimination within cerrado formations was difficult due to similarities in their seasonal dynamic behavior. Maximum contrast among all the cerrado formations occurred during dry season, suggesting this as the best time for cerrado physiognomy discrimination. The converted agricultural areas had a higher contrast than the native cerrado, and the forest formation had the lowest seasonal contrast. This enabled an operational method to discriminate the cerrado formation from the converted areas and adjoining forests. Thus, MODIS offers a useful tool to monitor the threatened cerrado biome