Análise das modifica es da cobertura vegetal da planície fluvial do alto rio Paraná no período entre 1976 e 2007 = Analysis of vegetation changes in the Paraná river floodplain between 1976 and 2007

A vegeta o da planície fluvial do rio Paraná sofre a press o da ocupa o antrópica desde a década de 1950. A área próxima a Porto Rico (Paraná) tem sido estudada desde os anos 1980, mas n o há estudos dirigidos à distribui o espacial da vegeta o. Os objetivos deste trabalho s o cartografar as unidades vegetais e verificar a evolu o temporal de sua distribui o entre 1976 e 2007. Para isso foram utilizadas imagens orbitais de 1976 (LANDSAT MSS-1), 1987 (LANDSAT TM-5), 2000 (LANDSAT ETM+7) e de 2007 (CBERS-2 CCD). Asimagens foram georreferenciadas e classificadas pelo algoritmo Bhattacharya. Foram identificadas três classes de vegeta o, corpos de água e áreas de solo exposto. A análise multitemporal demonstrou aumento contínuo da área de solo exposto, aumento da área dos corpos de água, mudan a de posi o das áreas úmidas no período entre 1976 e 1987 e modifica es mais sutis de ambas as classes no período entre 1987 e 2007. As áreas de vegeta o arbórea diminuíram em quase todos os anos. Tais dados permitem afirmar que a atua o antrópica sobre a planície vem se ampliando e que as principais cheias modificaram sua morfologia. The removal of vegetation from the Paraná river floodplain has been increasing since the 1950s the until present time, but no study has been made about its spatial distribution. The purpose of this paper is to map and analyze the temporal evolution of vegetation distribution over the Parana river floodplain between 1976 and 2007. Orbital images from 1976 (LANDSAT MSS-1), 1987 (LANDSAT TM-5), 2000 (LANDSAT ETM+7) and 2007 (CBERS-2 CCD) were utilized to compare the evolution of the vegetation distribution over that time period. Theimages were georeferenced using SPRING 4.3.3 software and classified by the Bhattacharya algorithm; the maps were produced using the Global Mapper 7.4 software. Three different classes of vegetation, water bodies and exposed soil areas were distinguished for each studied year. The comparison of the generated vegetation maps showed a significant enlargement of the water bodies and a position change of the humid vegetation areas between 1976 and 1987, among other small modifications in the referred classes between 1987 and 2007. This indicates that the major river floods modified the morphology of the floodplain, and that the continuous enlargement of the exposed soil areas, along with the reduction of the vegetation areas, showedthat anthropic action over the floodplain has increased over the years.