3.2 Community phylogenetic diversity and structure
Fencing duration significantly increased phylogenetic diversity (PD), and PD in the sites of fencing since 1979 was the highest (Figure 3). There was no significant difference in PD among different shrub cover treatments. There was a significantly positive relationship between phylogenetic diversity and species richness (R2 = 0.824, p < 0.001) (Figure. 4).
SESMPD (TL) was significantly affected by fencing duration, shrub cover and their interaction. SESMPD (TL) was significantly lower in the plots of high shrub cover (around -1.96, phylogenetic clustering) than in the plots of low or medium shrub cover under fencing since 2003 and 1983 (higher than -1.96 and lower than 1.96, phylogenetic random); and significantly lower in the plots of low shrub cover under fencing since 1979 (around -1.96, phylogenetic clustering) than in the plots of low shrub cover under fencing since 1983 or 2003 (around zero, phylogenetic random). There was no significant difference in SESMPD (IS) among different fencing duration or shrub cover treatments (Figure. 5B).
The values of SESMNTD (IS or TL) were between -1.5 and 1, which were significantly affected by shrub cover (Table 2), and SESMNTD in the high shrub cover plots was obviously lower than that in the low or medium shrub cover plots.