Change in vegetation cover and its relationship with climate change in Jinghui Canal Irrigation Area of Shaanxi province

Using the Normalized Difference Vegetation Index(NDVI) from NOAA/NASA and the global temperature and precipitation data from Climatic Research Unit(CRU) of United Kingdom,this present study analyzed the trends of annual mean vegetation cover(NDVI),annual mean temperature and annual total precipitation of Jinghui Canal Irrigation Area in Shaanxi province of China from 1982 to 2006,and investigated the relationships among vegetation cover,temperature and precipitation.The results showed that the annual mean vegetation cover significantly increases by 0.1%/a(P0.05),and the annual mean temperature also markedly increases by 0.085℃/a(P0.05),but the precipitation decreases slightly.Furthermore,the annual mean NDVI was positively correlated with annual mean temperature(correlation coefficient R=0.49,P0.05),but was poorly correlated with annual total precipitation.The prolonged growing period resulted from increasing temperature and the reasonable water usages of vegetation cover provided by Jinghui Canal are two main factors which facilitate the increase in vegetation cover in Jinghui Canal Irrigation Area.At the monthly scale,the increase in monthly temperature can provide more temperate environment for vegetation growth.Also the increase in monthly precipitation will supply more water for vegetation growth,but the monthly NDVI does not show a significant increasing trend while the monthly precipitation is more than 100 mm.