**5. Conclusions**

A human–land coupling system is a nonlinear system, which is a differential equation composed of several coupling factors. In this study, the coupling factors of forest and grass land, production and living land, unused land and population were considered to construct a fractional order dynamics model with a time delay based on a Holling-II transformation rate. The stability of the system and its regulation mechanisms are discussed based on the solution of the equilibrium point of the system. It is known that the coupling state of human–land systems includes a stable equilibrium state and periodic oscillation state, and the two states of the system can be determined according to the time delay. How to adjust from periodic change to a stable state, or how to adjust to a stable state when periodic change is presented, the time delay can be changed by changing the parameters of the model.

On the basis of constructing the human–land coupling evolution model of Yuxi City, the human–land coupling evolution and development models of mountainous areas and basin areas were respectively constructed based on the internal relationship between the mountainous area and the basin area. The parameters of the human–land coupling evolution and development models were obtained by simulation analysis, using the existing data. According to the analysis of the parameters, the mountainous area and the basin area playing different roles in the process of human–land evolution systems tend to a stable state, i.e., an equilibrium state, and there are significant differences in the transformation time among different land types. Therefore, different land-use regulation strategies should be selected in different regions. In mountainous areas, the average reclamation or development capacity should be reduced to lower the conversion of forest and grass land to production and living land, and at the same time, excessive interference of human beings should be reduced to speed up the natural recovery and succession of unused land to forest and grass land. In basin areas, in addition to reducing the average reclamation or the development capacity, the reclamation or development rate of the idle land and degraded land should be increased, and the conversion of idle land into productive and living land should be encouraged with the help of certain scientific and technological means.

**Author Contributions:** Conceptualization, L.W.; methodology, L.W.; software, L.W.; validation, L.W. and B.X.; formal analysis, L.W.; investigation, L.W.; resources, L.W.; data curation, L.W.; writing—original draft preparation, L.W.; writing—review and editing, L.W., Y.Y. and B.X.; supervision, B.X.; funding acquisition, L.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China, grant number 42161041.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **References**

