*2.5.2 Classification system and evaluation criteria of vegetation and soil coupling type of* H. ammodendron *plantation*

According to the coupling coordination degree (D), combined with the comprehensive evaluation function of vegetation f(x) and soil environment g(y) calculated based on the classification method of Peng [29], the vegetation-soil coupling


*Characteristic on the Stability of* Haloxylon ammodendron *Plantation… DOI: http://dx.doi.org/10.5772/intechopen.99050*

> **Table 4.**

 *Life table of six* H. ammodendron *plantations at different chronosequence stage.*

**Figure 5.** *Standard survival and death curves of* H. ammodendron *plantations at different chronosequence stage.*

coordination type and evaluation criteria of *H. ammodendron* plantation were proposed, result shown in **Table 6**. If the ratio of f(x) to g(y) was bigger than 1, it indicated that the growth and development speed of vegetation was faster than that of soil. If the ratio was smaller than 1, it indicated that the growth and development speed of vegetation was slower than that of soil, and soil fertility resources were not fully utilized by the vegetation. If the ratio was closer to 1, it indicated that the succession state between them was more synchronous and coordinated. According to the D and the ratio between f(x) and g(y), the vegetation and soil coordinated development could be divided into 5 categories and 15 sub-categories. The coupling intensity and coupling coordination were not in one-to-one correspondence relationship, and both of them often appeared alternately, which was in line with the fluctuating development law between vegetation and soil subsystems.
