Abstract: The ecosystem in the upper reaches of the Yellow River is fragile, and it is affected by the unique ecological environment and relatively simple vegetation types. The distribution of fractional vegetation cover (FVC) and its driving factors provide a reference for local vegetation protection. In this paper, the monthly data of MODIS1M NDVI (2000-2015) were used to calculate the maximum FVC in the upper reaches of the Yellow River and analyze its distribution and characteristics. Moreover, the corresponding proxy variables were used to quantitatively study the affecting factors of FVC by using the geographical detector (Geodetector) model based on the statistics theory and considering the topographical, geological and climatic factors as well as human activities. The study showed that:  ① The FVC in the upper reaches of the Yellow River was improved. The spatial distribution of FVC was stable even if there was a slight fluctuation;  ② The distribution of FVC was mainly affected by annual precipitation. There were some regional differences in the effects of other factors, for example, the distribution of FVC in the southwest of the study area was subject to the joint effect of topography and pressure, the effects of topographic factors in the central and northeast regions were relatively low, and the FVC was mainly subject to precipitation, humidity, land use types, soil types and underlying surface;  ③ The interaction between the annual precipitation and the soil types and land use types was dominant to affect the spatial distribution of FVC;  ④ Holistically, the factors affecting the spatial distribution of FVC were in an order of climatic environment factors > non-climatic environmental factors > human activities. The interaction of human activities with environmental factors (such as precipitation) could be used to fully explain the spatial distribution of FVC;  ⑤ In the ecological restoration in this area, the full utilization of precipitation and the improvement of land use ways should be focused on.

Key words: fractional vegetation cover (FVC), spatial stratified heterogeneity, affecting factor, Geodetector, upper reaches of the Yellow Rive