Soil water condition for vegetative growth in Loess Plateau presents a gradient change from Southeast to Northwest. Quantitative analyses of spatial distribution and temporal change of fractional vegetative cover(Fc) can offer an important indication for evaluating the regional environmental changes after the implementation of returning farming land to forestry and grass land. The MODIS/NDVI images with 250 m×250 m spatial resolution were used as the data source to estimate Fc in the central precipitation gradient zone of Loess Plateau based on a dimidiate pixel method

and the spatial distribution and temporal change of Fc were obtained for the period from 2000 to 2010. The spatial characteristics and temporal trend of Fc were analyzed

while the relationships of Fc with climatic factors were discussed. Results showed that: (1) The Fc in the studied zone presented a decreasing trend from southeast to northwest. The maximum Fc value in southeastern region was 82.6% and the minimum Fc value in northwestern desert was only 38.6%; (2) The average Fc value in the studied zone appeared an increasing trend from 2000 to 2010 due to implementation of the project of returning farming land to forestry or grass land. The maximum average Fc value of 65.3% occurred in 2007 because of the maximum annual precipitation during the studied period; (3) The Fc value in the studied zone was affected by the precipitation and the temperature during the period of April to August in each year

the regression analyses of time series proved a significantly positive correlation between Fc and total precipitation and between Fc and average temperature.