Effect of Mixed Forests on Soil Bacterial Community Structure and Functional Characteristics in the Yellow River Delta

To investigate the effects of mixed forests on soil bacterial characteristics in the Yellow River Delta, pure forests of Ailanthus altissima , Ulmus pumila , Robinia pseudoacacia , and Fraxinus velutina (hereafter Aa, Up, Rp, and Fv, respectively) and mixed forests of Aa-Rp, Up-Rp, Fv-Rp, and Ma ( Melia azedarach )-Fv were selected as the research objects. High-throughput sequencing technology was employed to analyze the structure, diversity, and function of bacterial communities in this region. The results showed that Acidobacteria , Proteobacteria , and Actinobacteria were the dominant microbial groups. The relative abundance of Acidobacteria was reduced by mixed patterns of Up-Rp, Fv-Rp and Ma-Fv, and the abundance of Proteobacteria was increased in Ma-Fv. The Chao1, ACE and Shannon indices of Aa-Rp and Fv-Rp were increased, while the Chao1 and ACE indices of Up-Rp and Ma-Fv were decreased. Functional prediction revealed that chemoheterotrophic and aerobic chemoheterotrophic bacteria had the highest abundance, with mixed forests exerting variable effects on different functional bacterial groups. In conclusion, mixed forest management exerts a significant influence on shaping bacterial community structure, regulating its diversity, and facilitating the directional enrichment of functional bacteria, which is conducive to enhancing the stability and sustainability of plantations.