## 5 Conclusions and Outlook  
This study investigated the differences in the physicochemical properties, enzyme activities, microbial diversity, community structure, and functional gene diversity of soils in different ecological forest land restoration modes in the Loess Hilly Region. The focus was on discussing the impact and restoration mechanism of different restoration modes. Compared with abandoned land treatment, the soil water content and porosity of the three restoration modes of AR, AM, and AR&AM&MS increased significantly, while the bulk density decreased significantly. Further, the soil water content and porosity of the MS treatment decreased, but not significantly, and the bulk density increased, but also not significantly. The mechanical composition of the AR&AM&MS treatment had higher contents of silt and clay. Compared with the control treatment, the pH alkalinity and organic carbon content of the AR&AM&MS restoration mode were significantly reduced, the total salt content increased slightly, and the total carbon, total nitrogen, alkali-soluble nitrogen, ammonium nitrogen, nitrate nitrogen, total phosphorus, available phosphorus, total potassium, and available potassium contents all increased significantly. The results show that the restoration mode of mixed forest is better than that of pure forest grass. Compared with the abandoned land treatment, there is no significant change in the catalase content of the pure forest and mixed forest, but the urease, phosphatase, sucrase, BG enzyme, and NAG enzyme content in the mixed forest restoration mode all increased significantly, followed by the restoration mode of the pure forest of mountain peach. The species diversity index of different ecological forest restoration modes is similar, and the difference is not significant. The dominant bacteria in soil microorganisms include the phyla _Proteobacteria_, _Aciobacteria_, _Actinobacteria_, _Bacteroidetes_, and _Gemmatimonadetes_. Correlation analysis showed that the mixed forest restoration mode had the highest microbial abundance, mainly including the genera Rhodobacter, Actinomyces, and Sphingomonas; its composition was closest to that of the pure forest AR. The functional gene diversity of different ecological forest restoration modes was also similar, but there were differences in the direct functional genes, and the functional genes of the AR&AM&MS restoration mode were the most abundant. Finally, the relationships and differences between the physicochemical properties of soil, enzyme activity, microbial community diversity, and functional genes were discussed in depth, with a focus on revealing the restoration mechanism of the mixed forest mode. Therefore, promoting forest land restoration, improving species composition, and enhancing soil microbiology activity through appropriate management and management measures is an important way to restore and maintain soil productivity. The results of this study provide useful insights into the restoration of the ecosystem on the Loess Plateau. Based on the results of this work, it is further seen that the mixed forest restoration mode can improve soil structure, enhance soil physicochemical properties, retain moisture, optimize soil microbial community structure, and increase soil enzyme activity and microbial diversity. AR&AM&MS is especially suitable for application in the hilly areas of the Loess Plateau. It is hoped that these studies will arouse the interest of governmental decision-makers. While the restoration mode recommended in this paper may also be applied in forest restoration projects in ecologically fragile areas, this needs to be evaluatedcarefully. This requires enhanced and continued in-depth exploration of the importance of sustainable ecosystem management under this restoration mode.