Stipa breviflora
Grazing intensity, spatial scale and their interaction significantly affected the density of S. breviflora population (Table 1,P < 0.05). The F value of spatial scale factors on S. breviflora density was larger (F = 306.81), indicating that the response of S. breviflora density to spatial scale factors was more obvious than that of grazing intensity.
The changes of S. breviflora population density under different grazing intensities and spatial scales are shown in Fig. 2. The density of S. breviflora increased with the increase of grazing intensity (Fig. 2A), and we observed significant pairwise differences between CK and LG, CK and MG, CK and HG (P < 0.05), which also indicated that the density of S. breviflora was different in LG treatment , that is, the phenomenon of plant cluster fragmentation. Although there was no significant difference between the LG, MG and HG treatments we did observe a general trend of increasing density. The error extension lines between each treatment were long, indicating that the distribution of S. breviflora was highly variable within each treatment. The density of S. breviflora increased exponentially with the increase of spatial scale (Fig. 2B). Except for 5 cm×5 cm and 10 cm×10 cm, 20 cm×20 cm and 50 cm×50 cm, there were significant differences between the two spatial scales(P < 0.05). In fact, there is an exponential correlation between density and spatial scale of S. breviflora (density of S. breviflora = 0.5314+0.0112×exp (1.4160×spatial scale of S. breviflora ),r 2 = 0.9995).
Table1 Variance analysis results for the Stipa breviflora population