Study site
We selected five grassland pastures located in northwest China, namely Duo lun (DL), Er er duo si (EE), Hai La er (HL), Sha po tou (SP), Wu lan aodu (WA). The pastures chosen were far from urban industrial areas and had little human activity other than grazing. Climatic conditions are reflected by four indicators: dry season temperature (DT), dry season precipitation (DP), rainy season temperature (RT) and rainy season precipitation (RP). DL (DT=0.1 ℃, RT=4.69 ℃, DP=118.8 mm, RP=306.7 mm), EE (DT= 4.78 ℃, RT=8.88 ℃, DP=98.3 mm, RP=280.1 mm), HL (DT= 5.77 ℃, RT=9.94 ℃, DP=40.1 mm, RP=104.5 mm), SP (DT= 7.37 ℃, RT=11.01 ℃, DP=62.5 mm, RP=139.8 mm), WA (DT=5.77 ℃, RT=9.94 ℃, DP=40.1 mm, RP=104.5 mm). In the pasture, different grazing intensity locations were selected to set the quadrat. Grazing intensity was divided according to dry season vegetation cover (DVC) and rainy season vegetation cover (RVC). The control group (grazing intensity 0, DVC> 60%, RVC> 70%) and four gradients of different grazing intensities, namely 1 (45%<DVC<60%、55%<RVC<70%), 2 (30%<DVC<45%、40%<RVC<55%), 3 (15%<DVC<30%、20%<RVC<40%), and 4 (DVC<15%、RVC<20%). Plant species were identified and counted in five replicate quadrats for each grazing intensity at each site.