FIGURE 2 Biomass of A. trifoliata in different habitats
Note: RR: Root organs of A. trifoliata in rocky desertification habitat; NR: Root organs of A. trifoliata in a normal habitat; RS: Stem organs of A. trifoliata in a rocky desert habitat; NS: Stem organs of A. trifoliata in a normal habitat ; RL: leaf organs of A. trifoliata in rocky desertification habitats; NL: Leaf organs of A. trifoliata in normal habitats.
3.2  | Effect of rocky desertification habitat on the contents of basic secondary metabolites in A. trifoliata
Tannin and flavonoid belong to phenolic compounds, which are secondary metabolites of plants. They are good free radical scavengers and lipid peroxidation inhibitors in plants (Dicko et al., 2005). As shown in Figure 3, with the growth and development of A. trifoliata , the tannin content in roots, stems and leaves showed an upward trend, and the tannin content in leaves was the highest. At the same time, the tannin content in rocky desertification habitat increased faster than that in normal habitat, especially in leaves. In Guanling base, the difference of roots was the biggest in October, increased by1.35 times, stems was the biggest in October, increased by 1.17 times, leaves was the biggest in August, increased by 1.50 times; In Huaxi base, the difference of roots was the biggest in May, increased by 1.20 times, stems was the biggest in October, increased by 1.14 times, leaves was the biggest in August, increased by 1.63 times. The results showed that the content of tannin in roots, stems and leaves of A. trifoliatacould be increased in rocky desertification habitat, especially in leaves.