Abstract: We investigated the responses of different forest plantations to inoculation of arbuscular mycorrhizal fungi (AMF) in a newly compacted spoil heap at the Heidaigou coal mine in Zhungeer Banner, Ordos City, Inner Mongolia. We examined the effects of AMF inoculation on understory vegetation diversity, soil physicochemical properties, and enzyme activity in three types of plantations, including Hippophae rhamnoides, Amorpha fruticosa, and Caragana korshinskii. The results showed that AMF inoculation significantly increased species richness and diversity in the Hippophae rhamnoides and Amorpha fruticosa plantations. The inoculated Hippophae rhamnoides plantation exhibited the highest species richness index (2.3215), while the Amorpha fruticosa plantation showed the highest Shannon diversity index (1.9079) and evenness index (0.7438). Furthermore, AMF inoculation significantly increased soil available phosphorus content (from 7.2 to 12.8 mg·kg^-1) and enzyme activities, with phosphatase activity being increased by 25.4% and urease activity by 18.7%, and thus had positive consequences on soil quality. The findings suggest that Hippophae rhamnoides and Amorpha fruticosa are pioneer species suitable for vegetation restoration in newly compacted spoil heaps, and that AMF inoculation plays a significant role in promoting vegetation recovery and enhancing community diversity.

Key words: open-pit mineral dump, plantation community, AMF inoculation, ecological restoration, diversity index