Variation in a satellite-based vegetation index in relation to climate in China

Abstract

Climate-related increases in terrestrial vegetation activity in the northern regions of the Northern Hemisphere have been identified by recent satellite based studies. How- ever, evidence for this increase from ground observations is very limited. In the current study, we used a time series data set for the Normalized Difference Vegetation Index (NDVI) for the growing season (April to October) from 1982 to 1999, along with historical climate data, to analyse year to year variations in vegetation activity and to explore the relationship between the growing season NDVI and climatic variables in China. Vegetation activity, as measured by NDVI, increased in 81% of the study area, with significant gains in 27% of the region. The magnitude of the mean growing season NDVI for the 1980s and the 1990s was not significantly different. The increase in NDVI corresponded to an increase in temperature on the national scale, while regional variations in NDVI appeared to be related to precipitation. The NDVI trend showed a large spatial heterogeneity, possibly associated with changes in regional climate, land use and vegetation type. Our study suggests that agricultural practices caused an increase in NDVI in some regions, and rapid urbanization on the east coast resulted in a sharp decrease in NDVI since the 1980s.