Geostatistical theory and methods were used for describing spatial variability of community characteristic and above-ground biomass of functional group in sandy grasslands of the Horqin Sand.Results showed that vegetation richness and coverage had distinct degree and scale changes in spatial variability.Vegetation richness had the high spatial variability,while coverage had a high dependence in study area.The above-ground biomass of functional groups and community in sandy grasslands had a different spatial auto-relation range from 9.39 m to 252.69 m.This showed that factors,affecting ecological processes and patterns of above-ground biomass of different functional groups,played their ecological roles on different scales.The semi-variogram values of above-ground biomass of perennial herbs and Mesophytes,following the increase of spatial distances,showed decreasing trends when semi-variogram values exceeded the effective range.However,semi-variogram values of above-ground biomass of other functional groups,following the increase of spatial distances,showed a trend of increasing spatial variability,but semi-variogram values were no longer changed when exceeding the effective range.The above-ground biomass of perennial herb and intermediate xerad, owing to the effects of human disturbance and livestock activities and topographic condition,had no spatial difference in a range of five meters.It may be controlled by a process on larger scale.So,the above-ground biomass of different functional groups had the more complex mechanism and processes corresponding to disturbance and effects from human,livestock and nature.Moreover,changes on xerad not only influenced community's coverage,but also played an important role in maintaining ecological functions and the stability of grassland ecosystem