Estimation And Dynamic Variations For Vegetation Fractional Cover In The Three-north Region Of China And The Hai River Basin Based On RS And GIS

Vegetation fractional cover(FC) is an important indicator of vegetation and ecological environment, and is also the basic data of hydrology, meteorology and water-soil protecting in region or global study. Three-North region of China and the Haihe River Basin FC estimated correctly by remote sensing is the basis for integrated assessment of environmental effects of the Three-North Shelter Forest Programme(TNSFP) and the Haihe River Basin.Based on Landsat-TM and HJ-1 data, using the improved model of dimidiate pixel method, the FC of the typical study area is estimated. By on the spot review of the typical study area, the result of estimation of FC is proved to be valid with a correlation coefficient of the real value and the estimated value of 0.96 and R2 of 0.92. The result shows that it is feasible to use this improved model for estimating the regional FC. Then we spreaded this improved model to etimate the FC of the Three-North region of China and the Hai River Basin based on MODIS-NDVI products.This paper analyzed the spatiotemporal changes of the FC in the Three-North region of China using the difference method. The result shows that the FC in this region had an obvious change in 2001-2007. The mean FC increased by 2.07% for the whole region, and the increment in Jilin, Shanxi, Shaanxi, and Ningxia provinces reached to 27.37%, 14.12%, 9.29%, and 9.22%, respectively. The increase of FC was mainly caused by the increasing precipitation and the enhancement of peoples'environmental awareness, as well as the implementation of closing hillsides to facilitate afforestation, returning farmland to forest/grassland, and especially, the Three-North Shelter Forest System Program.This paper analyzed the spatiotemporal changes of the FC in the Hai River Basin using the slope method for the period of 2000 to 2007. The results show that the FC of the study area is high in cropland of the plain, the value changes from 0.6 to 0.8. While it is lower in the upper basin of Yongding River, FC is less than 0.3. In recent eight years, the FC of Hai River Basin shown a trend of increase, only decreased in some cropland regions located in the Eastsouth of the study area and the urban expand area.For better understanding the effects of precipitation on FC in the Hai River Basin, we also investigate the relationship between FC and precipitation. Their correlation coefficient has been calculated in different temporal duration and the results show that the annual maximum of FC is significantly related to the accumulated precipitation from Mar. to Aug. in the same year with a correlation coefficient of 0.687. The change of FC is consistent with that of precipitation for the years we analyzed.