Profiling mechanism of Hippophae rhamnoides phytoremediation on microecosystem of rhizosphere soil surrounding a magnetite tailings pond in North China

Tailings pond poses a serious threat to the surrounding environment. This study aimed to explore the current status and mechanism of Hippophae rhamnoides (H. rhamnoides) restoration in the Zhoutaizi magnetite tailings pond in Chengde city by analyzing the physicochemical properties, heavy metal content, and microbial community characteristics of the rhizosphere soil of H. rhamnoides. Rhizosphere soil samples were collected from the planting areas (10 m, 50 m, and 80 m) at distances of 10, 50, and 80 m from the mountain, the dead plants areas (D) at a distance of 80 m from the mountain, and the unplanted areas (U) in the center of the Zhoutaizi magnetite tailings pond. The available manganese (Mn) content in groups 10 m, 50 m, 80 m, and D was higher than in group U (p< 0.05). Mn contributed to the relative abundances of Articulospora, Mortierella, Minimedusa, and Knufia, but negatively correlated with that of Fusarium and Cistella (p< 0.05). These results indicated that H. rhamnoides can improve soil quality and microbial community structure by increasing Mn content. The Chao and Ace indices in groups 10 m, 50 m, 80 m and D were higher than in group U (p< 0.05), implying that H. rhamnoides can increase the total number of soil microbial species. The electrical conductivity (EC) of groups D and U was higher than that of the other groups (p< 0.05). EC was positively correlated with Cistella, while negatively correlated with Minimedusa and Knufia (p< 0.05). Therefore, we speculated that the increase of harmful bacteria and the decrease of beneficial bacteria caused by high EC were one of the reasons for H. rhamnoides death. In short, H. rhamnoides can be used to some extent for restoring magnetite tailings pond, but high EC is the main obstacle to its restoration. This study provides a theoretical basis for the construction of green mines.