Influence of rainfall variability on the vegetation dynamics over Northeastern Brazil

摘要

The aim of this study is to examine the spatiotemporal patterns of vegetation dynamics and explores relationships between rainfall and normalized difference vegetation index (NDVI) over the heterogeneously vegetated region of Northeastern Brazil (NEB). The two datasets used in this study are composed of: (1) NOAA-AVHRR NDVI3g dataset processed by the Global Inventory Monitoring and Modeling Systems (GIMMS) group, and; (2) rain-gauge totals from a network of the 86 stations. This comparative analysis is based on correlation and rotated empirical orthogonal function (REOF) techniques of the standardized difference vegetation index (SDVI) and the standardized precipitation index (SPI) time series from January 1982 to December 2001 for the whole area of the NEB region. Results showed that highest correlations is achieved between SDVI and SPI with three-month lag (r=+0.60, significant at 95% level) for spatiotemporal analysis. A REOF analysis confirms this spatiotemporal relationship yielding three spatially separated modes in the southwestern, northwestern and central-eastern part of the NEB region. The study concluded that rainfall emerges as the dominant causative factor in the dynamics of vegetative drought (i.e. negative SDVI) in the region. Thus, these findings can provide some understanding of the links between NDVI and rainfall for monitoring the dynamics of vegetation in the region of NEB. (C) 2015 Elsevier Ltd. All rights reserved.