Inter-relações entre padrões de índice de vegetação e de pluviometria no Nordeste do Brasil.

Abstract

The objective of this study is to identify, analyse and interpret the main patterns of seasonal and interannual variability of the vegetation index NDVI and the precipitation in the Northeast region of Brazil. Monthly averages of NDVI used in this study were obtained from the AVHRR/ NOAA images, with a spatial resolution of 7.6 km and the mean monthly precipitation of the rain gauge stations distributed in the region, with data periods corresponding to those of the NDVI (1981-1990). The method of Factorial Analysis in Principal Components and hierarchical grouping of common factors were used to determine the seasonal and spatial variation patterns and homogeneous groups in the region being studied. Nine homogeneous regions were identified and characterized in relation to the seasonal and interannual variations of NDVI and precipitation, and eight homogenous regions in relation to the vegetation's response, represented by the NDVI, to the seasonal variation of the monthly precipitation. The results of the combined temporal analysis of NDVI and precipitation indicate that in the semi-arid regions with the lowest rainfall rates, located in the central region of the Northeast, with the predominant vegetation covering of seasonal forest (caatinga), the NDVI values increased after a significant precipitation with a time lag of one month. The other regions, located in the west and the east coast of the Northeast, with a predominant vegetation covering of "perenifolia" forest, savanna and elements of savanna, show a time lag of two months between the precipitation and the vegetation response. From the individual analysis of NDVI and the precipitation and the combined analysis of NDVFs and precipitation it is verified that the response of vegetation is very well associated to the rainfall regimes of the Northeast region of Brazil.