Study on rainfall effect on vegetation change in the north piedmont of Yin moutain

The relationship between vegetation development and water condition is helpful for understanding the climate change impacts on terrestrial ecosystem, however, the relationship is so complex that it has not been studied adequately. In this paper, we choose the Normalized Difference Vegetation Index (NDVI), which is widely used for monitoring vegetation development and the Standard Precipitation Index (SPI), which is a multiple-time scale meteorological-drought index based on precipitation and took them as the proxy of vegetation vigor and moisture availability respectively. We conducted a correlation analysis on time series of monthly NDVI (1983-2002) during the growing season from May to October and the 1-month SPI of the corresponding month in the Yin mountain area of northern ectone in China. The result indicates that vegetation development is correlated with the moisture availability significantly. Moreover the correlation coefficient is seasonal changed, generally the highest correlation occurs at the beginning of the growing season. When comparing the Velocity of the NDVI change (VNDVI) and the correlations between NDVI and 1-month SPI, we found that VNDVI can impact the relationship between vegetation development and moisture availability.