Dynamic changes of vegetation's soil conservation value in Yuyang District of Northern Shaanxi in recent 30 years.

Based on the data of climate,topography,soil,and remote sensing images,and by usingthe universal soil loss equation(USLE)and geographic information system(GIS)techniques,the spatiotemporal dynamic changes of vegetation's soil conservation value in Yuyang District of Northern Shaanxi were analyzed.The results showed that in 1978-2005,the total mean annual vegetation's soil conservation value in the District increased by 280.37×106 yuan,with an increment about 67.6%,among which,36.5% increment was in 1978-1989and 22.8% increment was in 1989-2005.The increment of the total vegetation's soil conservation value in wind-blown sand region was about 1.7 times as that in loess hilly-gully region,while the mean per unit vegetation's soil conservation value in loess hilly-gully region was about 46 times as that in sand-blown region.In Yuyang District,its outer suburb had the highest mean per unit vegetation's soil conservation value,followed by suburb,and urban area,but its suburb had the highest increment of total vegetation's soil conservation value,followed by urban area,and outer suburb.