Variação anual do EVI e NDVI de tipologias vegetais na APA de Ibirapuitã, Rio Grande do Sul, Brasil

This aimed to study the phenology of different vegetation typologies that cover the Ibirapuita environmental protection area (APA), located within the Pampa biome, Rio Grande do Sul. The objective was to verify the existence of seasonal patterns to allow discrimination of vegetation types through analysis of MODIS/vegetation indices time series. Also, we investigated the differences in the responses of the two vegetation indices - EVI and NDVI - of the main vegetation typologies of the APA for 2011. EVI and NDVI annual and intra-annual averaged data were collected and analyzed in the form of graphs and z statistics. The results showed that, during the summer and spring, there is a higher spatial heterogeneity and a greater productivity of the studied typologies, while in winter and autumn, during the period of senescence, there is less biological activity and increased spatial homogeneity of the spectral responses of plant types (with the exception cultivated pasture which is planted in autumn and winter). Among the herbaceous typologies, prostrate and cespitous grasslands, cultivated pasture and invasive-annoni showed varied mean values of EVI and NDVI, however, with similar seasonal trends. Despite the intra-annual differences found, typical patterns, which would allow the discrimination of vegetation types through temporal series analysis, were not observed here. NDVI values showed greater sensitivity to intra-annual phenological variations of the vegetation types considered. Palavras-chave: phenological variation, time series, vegetation indices, variacao fenologica, serie temporal, indices de vegetacao.