Dinâmica de vegetação e regime de precipitação em bacia hidrográfica da região semiárida de Pernambuco

Abstract

The work aimed to evaluate the relationship between the rainfall regime and dynamics of vegetation cover in the Upper Basin Ipanema. The study area is the basin of the Upper Ipanema, Ipanema inserted in the river basin, which is limited between Pesqueira and Arcoverde, located in the semiarid region of Pernambuco. We used remote sensing techniques to determine vegetation indices and evaluate the dynamics of vegetation cover; correlated behavior of vegetation indices with rainfall in the basin during the study period; sought to identify the classes of land cover and rainfall classes. The predominant vegetation in the region correspond to the savanna, especially coverage of different densities and grazing. Were used 11 images Sensor TM Landsat -5 and an image of Landsat - 8, orbit 215, paragraph 66 months from September to December in the years 1985 to 2013. Two vegetation indices, NDVI and SAVI were evaluated, the latter three adjustment factors for the substrate canopy (U = 0.1, 0.5 and 1). In order to assist in the interpretation of vegetation indices, we performed a supervised image classification, determining five classes of use and vegetation cover in the basin. We checked for correlations between use map and land cover with different indices computed, and these latter with the annual accumulated rainfall and days prior to the date of the images used. We used the technique of quantile classification of rains in the basin between 1984 and 2013. Among the years of study of images with higher rainfall occurrence were classified as Standard, ranging between 640.4 mm and 838.4 mm per year. The NDVI vegetation index was the best represented the dynamics of vegetation in the basin with r = 0.93, followed by SAVI (L = 0.5 ) with r = 0.69. The vegetation dynamics in the Upper Basin Ipanema is a function not only of the annual rainfall regime in the region, but especially the intra - annual variations, particularly for rainfall record of 90 days.