Objective  Vegetation restoration is crucial to improve the ecological environment of mining areas, which can promote the reconstruction of soil development, thereby regulating biogeochemical cycles and exerting ecosystem functions. However, previous studies mainly focused on the nitrogen cycle and driving mechanism of grassland, wetland, farmland and other ecosystems, and lack of in-depth research on how plant restoration in mining areas affects nitrogen cycle microbial taxa and functional gene abundance.

  Method  A total of 25 topsoil samples were collected in the east reclamation areas including Medicago sativa (GL), Hippophae rhamnoides (BL), Pinus tabulaeformis (CF), Robini pseucdoacacia (BF) reclamation lands, and control (CK) area of Heidaigou open-pit mine, Junger Banner, Inner Mongolia. SmartChip Real-Time PCR System was used to determine the abundance of nitrogen cycle functional genes.

  Result  ① The effects of different vegetation on soil physical and chemical properties, enzyme activities and gene abundance of nitrogen cycle function were significantly different (P < 0.05). BL is superior to other vegetation in the accumulation of organic carbon and available phosphorus, and BF is superior to ammonium nitrogen, but total nitrogen and organic carbon are lower than CK. Greening significantly increased catalase activity and decreased β- Glucosidase, urease and leucine aminopeptidase activities. However, the effect of reforestation on gene abundance of nitrogen cycle function was consistent: BF > CF > BL > GL > CK. ② The gene abundance of nitrogen cycle function was positively correlated with pH (P < 0.01), and negatively correlated with nitrate nitrogen, total nitrogen, urease, leucine aminopeptidase and alkaline phosphatase (P < 0.05). ③ Different vegetation could directly affect the abundance of soil catalase or nitrification functional genes, thereby manipulating the abundance of soil nitrogen cycle functional genes, or affecting soil catalase through the abundance of denitrification functional genes, which might indirectly affect the nitrogen cycle process.

  Conclusion  Plant restoration in open pit mines affects enzyme activity and gene abundance of nitrogen cycle function, which affects nitrogen cycle process. In addition, according to the analysis of soil physical and chemical properties and enzyme activities in various fields, shrubs (Hippophae rhamnoides) have a better effect on the improvement of soil quality in this area. This study is helpful to further understand the influence of plant restoration on soil nitrogen cycle in mining areas, and provides a theoretical basis for fragile ecological restoration in the Loess Plateau.