Dinâmica da cobertura vegetal no nordeste paraense, à partir das técnicas de geoprocessamento

Abstract

Since the end of the 19th century the Northeast Paraense has suffered drastic alterations in its original vegetation cover, generating an incalculable genetic loss in this ecosystem Vieira (1996). The work of Alencar & Vieira (1996) shows that the dynamics of land use in the Bragantine region between 1984 and 1991, presents a tendency for regeneration of primary and secondary forests in a former agricultural frontier region of the Amazon. Due to the lack of more recent studies, it is necessary to update these data. The objective is to update the data on land use and vegetation cover with emphasis on the stages of secondary succession in this region. The analysis was carried out in the municipalities of Peixe-Boi, Capanema and Nova Timboteua, based on orbital data from the satellite images Lansat 5TM and Landsat 7ETM5 from the years 1984, 1991 and 1999. The '99 image was geocorrected to the classification developed on the 1991 image to facilitate the location of training sites. The Non-Supervised classification represented the first attempt to group the classes found in the image. Supervised classification of the '99 image was based on the Maximum Linkage Algorithm. The preliminary results of the supervised classification showed that approximately 45% of this landscape is scrubland in various successional stages, 12% is primary vegetation distributed mainly along rivers and streams and 43% is agriculture and cattle ranching. However, this data needs to be confirmed in loco. By cross-referencing these images, it will be possible to verify the dynamics occurring over a period of approximately 15 years. Comparing the preliminary results of the 1991 image with the 1999 image, it can be said that the fragments of primary vegetation are in a good state of conservation, although showing signs of shrinking. On the other hand, the old stands show signs of expansion, which can be a very significant factor in the regeneration of secondary ecosystems in this region.