The Analysis Of Vegetation Index Change In Jiangxi Province Based On Spot Vegetation Data

Changes in vegetation cover has been hot global research, the traditional multispectral images have low time resolution,they can only be used in study in some time point,it is difficult to recover vegetation cover dynamics in the time series. NDVI time-series product can make up for this shortfall, many scholars use time-series NDVI products to do a lot of researches in regional, continental and global expansion.In this study, we take Jiangxi Province as the study area to study the change law on vegetation cover using Spot Vegetation data between 1999-2013.The first step is using Savitzky-Golay filtering to reconstruct the time-series NDVI data; then we use the average method, difference method to analyse the NDVI variation in time and space, and we use a linear regression analysis-by-pixel to analyse its trends. Using partial correlation analysis, we analyse the dependencies of NDVI with precipitation and temperature, and we take qualitative analysis of the impact of human factors on NDVI change. Studies have shown that:1. Savitzky-Golay filter can be a good reconstruction method on the time-series NDVI data and high quality time series NDVI data can be obtained.2. From the spatial distribution terms, NDVI distribution in Jiangxi Province have a great relationship with the topography of Jiangxi Province, Jiangxi Province is surrounded by mountains in the south、east and west, its middle ereas are plain,the area between plain and mountains are hilly areas, NDVI becomes smaller with the decreasing altitude.3. From the time distribution terms, NDVI of Jiangxi Province showed growth trend in 1999 to2013, its growth rate was 0.04 / 10 a, where the increase in spring、summer and autumn were greater than the annual increase, only the increase in winter slightly was less than annual growth. From month terms, from March to August, it rose significantly, which gained the highest from the April to May with the increase amplitude to 0.082, it had different amplitude decreased from September to February in the next year, which gained the most significant decline in October to November with amplitude reduction to 0.074.4. From the trends terms, Jiangxi Province has a good direction to increase in vegetation cover in the past 15 years with whose has the increase area with the percentage of 83.62%, the reduction areas of vegetation cover were mostly distributed in the rapid development of the city and county.5. the annual precipitation and annual mean temperature in Jiangxi Province have no significant variation in the past 15 years,NDVI has a better correlation with temperature than the precipitation,and the impact of precipitation and temperature has hysteretic nature on NDVI.