Characteristics of Temporal-Spatial Evolution of Vegetation Cover in Shaanxi Province and Its Response to Climate Change

The paper analyzes the temporal and spatial evolution of vegetation cover and its response to climate change of Shaanxi Province during 1982 to 2006 by using GIMMS/NDVI data.The outcomes show that temporal and spatial distribution of NDVI of Shaanxi Province has the characteristics of reduction from south to north,and the NDVI of the north,south and central areas is the maximum in summer,comparative in spring and autumn and the minimum in winter.In 25 years,the NDVI of the three areas is notably increased,and the growing rate is the maximum in spring and the reduction tendency in summer.The trend of temperature increase is clear,resulting in extension of growing period.This is one of the main reasons of NDVI increase.The total annual precipitation of the three areas shows the trend of reduction,while the reduction of precipitation has not caused the reduction of NDVI which shows that the local precipitation can meet the basic requirements of vegetation growth.The reduction of NDVI in summer may relate to the increase of human activities.In inter-annual scales,the increase of temperature of the three areas is advantageous to the growth of vegetation and more precipitation can supply more water to benefit the growth of vegetation.When the monthly precipitation is less than 100 mm,NDVI increases significantly.however,when the precipitation is greater than 100 mm,the clear growth trend does not exist any more.