2.2 | Experimental design
A long-term grazing intensity experiment was established in 2004. We had four grazing intensities: control (zero sheep-unit ha-1 month-1, G0), light (0.15 sheep-unit ha-1 month-1, G0.15), moderate (0.30 sheep-unit ha-1month-1, G0.30), and heavy grazing (0.45 sheep-unit ha-1 month-1, G0.45) (Zhang et al., 2021). Each treatment had three replicates. Under a complete randomized block design, 12 plots, each with an area of 4.4 ha, were separated by fences. Sheep with similar size were selected in advance and the grazing period lasted from June 1 to November 30 every year.