Vegetation change and its relations with climate variables in Wuqi of Shaanxi

By using the monthly GIMMS normalized difference vegetation index(NDVI)data and local meteorological records,the inter-annual vegetation change and its relations with the climate variables in Wuqi County of Shaanxi Province in 1982-2003 were examined.The results showed that in the past 22 years,the vegetation coverage in the County had an overall improvement though undulation was observed.The areas with lower vegetation coverage decreased,while those with higher vegetation coverage increased.The annual NDVI had a positive correlation with precipitation,and the improved vegetation coverage benefited the decrease of wind speed.There was a significant positive correlation between the precipitation in spring and the NDVI in summer,and the precipitation in summer and the NDVI in autumn.In the meanwhile,the correlation of annual mean NDVI with the precipitation both in summer and in autumn was also significantly positive,indicating that precipitation was the key factor determining the distribution of vegetation in Wuqi.The NDVI in summer had a significant negative correlation with the evaporation in spring and summer but a positive correlation with the relative humidity in these seasons,while the NDVI in winter had a significant negative correlation with the relative humidity in this season.