Abstract: The grasslands of Northern China are an important ecological barrier preventing and controlling desertification; there has been a long history of large ecological restoration projects in this area. In order to understand the impacts of various restoration projects on species composition, productivity and species diversity of grassland communities, this study focused on the grasslands of the Beijing-Tianjin Sand Source Control Project, evaluating the effects of four typical restoration practices and their combinations: Fencing to exclude grazing animals, over sowing, small watershed conservation and basic ranch by comparing areas in and out of the Project area and discusses the driving mechanism of any differences. All of the engineering based restoration measures tended to increase the height and cover of communities; the restoration of grazing excluded steppe provided the best example of this. The prevalence of species from Gramineae and Cyperaceae increased while weeds decreased. The constructive species of communities changed from shorter species such as Stipa sareptana var. krylovii, Cleistogenes squarrosa and Thymus serpyllum to taller perennial Poaceae species such as Stipa grandis, Leymus chinensis and Achnatherum sibiricum. All of the engineered restoration measures tended to increase the above-ground biomass but below-ground biomass in typically management areas planted with artificial fodder decreased significantly, which led to a significant drop in overall community biomass; the overall biomass, above-ground biomass and below-ground biomass increased significantly where grazing was excluded. The ratio of the biomass of C₃ plants and perennial plants tended to increase. None of the engineered restoration measures increased the abundance of species in communities but all tended to decrease the evenness of species; the Shannon-Wiener index in supplementary grass planted and typical grazed areas decreased significantly. The results showed that long-term engineering measures restored the vegetation cover and productivity of grassland and increased fodder quality which helped stabilize sand, increased carbon sequestration fodder availability. However, engineering intervention may result in reduced species diversity of vegetation communities in a long term.

Key words: the Beijing-Tianjin Sand Source region, restoration practice, grassland restoration, species diversity, productivity composition