This study investigated the effects of the program aimed at converting farmland into forest or grassland on the soil bacterial diversity in the Loess Hilly region. Corn land was selected as the experimental control, and Caragana intermedia land and Stipa bungeana land were selected as the experimental lands. Soil from three different land use types were selected as subjects. The soil bacterial communities were analyzed using a high throughput sequencing technique (MiSeq). The sequence region was 16S rRNA V3-V4 variable region. The α diversity, community composition, and relative abundances of the soil bacterial groups were analyzed, in order to explore the effects of soil physical and chemical properties on the bacterial community structure. The results showed that the structure and diversity of the microbial communities differed under the different land use types. At the phylum level, the dominant phyla were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, and Firmicutes. At the class level, α-Proteobacteria, Actinobacteria, Acidobacteria, β-Proteobacteria, Thermoleophilia, Gemmatimonadetes, Bacilli, and δ-Proteobacteria were predominant. Compared to the corn land, Proteobacteria and Actinobacteria were the dominant bacteria in the Caragana intermedia land, while Actinobacteria and Acidobacteria were the dominant bacteria in the Stipa bungeana land. Soil bacterial diversity was the highest in the shrub land. RDA analysis revealed that soil organic matters and total nitrogen were the most influential environmental factors. It was shown thus that the program of converting farmland into forest or grassland has significantly improved the soil fertility and environmental conditions, and the composition of the soil bacterial community has also been appreciably changed.
Keywords: Loess Hilly region; community structure; converting farmland into forest or grassland; high-throughput sequencing technology; soil bacteria.