Extensive mining of rare earth deposits has caused severe soil erosion, resulting in the degradation of plant–soil systems and the reduction in microbial diversity. Combined ecological remediation technology is the key method of vegetation reconstruction and ecological restoration in abandoned tailings. In this study, the effects of different cover crops–biochar–organic fertilizer and biochar–organic fertilizer treatments on soil fungal communities in rare earth tailings soil were analysed using high-throughput sequencing technology. Linear discriminant analysis effect size (LEfSe) was used to analyse saprophytic, mycorrhizal, and potential pathogenic fungi in soils after different combined remediations. Moreover, the effects of soil environmental factors on fungal community species’ composition were analysed by redundancy analysis (RDA) and variance partitioning analysis (VPA) after different combined remediations. LEfSe indicated a risk of citrus pathogenicity by Diaporthaceae indicator fungi after biochar–organic fertilizer combined treatment. RDA and VPA revealed that pH was the main environmental factor affecting the fungal community in the different combined remediation treatments. Additionally, the Paspalum wettsteinii cover crops–biochar–organic fertilizer and biochar–livestock manure treatments were more conducive to arbuscular mycorrhizal fungi recruitment. We also clarified the fungal community composition structure, soil environmental factors, and fungal community relationships in rare earth tailings soil after different combined remediation treatments.

Rapid urbanization has exerted immense pressure on urban environments, severely constraining the growth of ancient trees. The growth of ancient trees is closely linked to the microbial communities in their rhizospheres, and studying their community characteristics may provide new insights into promoting the growth and rejuvenation of ancient trees. In this study, the rhizosphere soil and root systems of ancient Ginkgo biloba trees (approximately 200 years old) and adult G. biloba trees (approximately 50 years old) in Shanghai were selected as research subjects. Phospholipid fatty acid (PLFA) analysis and high-throughput sequencing were employed to investigate the diversity of microbial communities in the G. biloba rhizosphere. The results indicated that the 19 PLFA species selected to characterize the soil microbial community structure and biomass were present in the rhizosphere soil of both ancient and adult G. biloba trees. However, the total microbial biomass and the microbial biomass in the rhizosphere soil of ancient G. biloba were lower than the microbial biomass in the rhizosphere soil of adult G. biloba. The biomasses of Gram-negative bacteria (G⁻), arbuscular mycorrhizal fungi (AMF), and protozoans (P) were significantly different. Total phosphorus, organic matter, and pH may be the key factors influencing the soil microbial community in the rhizosphere zone of ancient G. biloba. An in-depth study of AMF showed that the roots and rhizosphere soil of G. biloba contained abundant AMF resources, which were assigned to 224 virtual taxa using the MaarjAM reference database, belonging to four orders, ten families, and nineteen genera. The first and second most dominant genera were Glomus and Paraglomus, respectively. Archaeospora and Ambispora were more dominant in the rhizosphere than the roots. Furthermore, the abundance of live AMF was significantly higher in ancient G. biloba than in adult G. biloba. Therefore, future research should focus on the improvement of soil environmental characteristics and the identification and cultivation of indigenous dominant AMF in the rhizosphere of ancient G. biloba, aiming for their effective application in the rejuvenation of ancient trees.