PCA used to discriminate phenological variantions in Cerrado physiognomy, in Sao Paulo - Brazil

摘要

The Cerrado Biogeographic Province in Brazil, which occupies around 18percent of the national territory, is the ecosystem in more danger of disappearing as a result of agriculture frontiers. Their landscape structure is a gradient of density, height, woody and herbaceous species, resulting in at least five physiognomies, ranging from grassland to forest. The climate where the Cerrado occurs present two distinct periods: a dry one from June to September and a rainy one from October to May. Because of that seasonal variation and that physiognomic patchwork it is very difficult their identification and their quantification. During the dry period the herbaceous stratum become more and more dried. The woody species, on the other hand, tend to loose their greenness a little bit further, since it can get water from deeper supplies. The results are exactly what is noticeable through NDVI, i.e., a strong greenness response after the rain: from June/95 to July/95, the Cerrado s.s. physiognomy gained 31.5 hectares of greenness, lost 32.2 hectares, and 534.96 hectares remain the same (NDVI interval remain exactly the same - varying from zero to 0.46); from July/95 to August/95, gained 14.3 hectares of greenness, lost 23.4 hectares, and 560.97 hectares remain the same (NDVI interval change from 0 - 0.46 to 0 - 0.43); from August/95 to November/95, gained 63.09 hectares of greenness; lost 8.55 hectares and 527.04 hectares remain the same (NDVI interval change from 0 - 0.43 to 0.0252 - 0.43); and from November/95 to January/96, gained 184.5 hectares of greenness; lost 1.08 hectares and 413.1 hectares remain the same (NDVI interval change from 0 - 0.0252 to 0.01852 - 0.59).