AMF and biochar reshape the bacterial network in rhizosphere soil of Ricinus communis under chromium (Cr) stress and improve soil quality

Arbuscular mycorrhizal fungi (AMF) and biochar synergistically mitigate Cr toxicity in plants. Ricinus communis roots are proficient in heavy metal accumulation. However, the role of AMF and biochar in reshaping bacterial networks during Cr remediation remains unclear. This study utilized pot experiments to investigate how the “AMF-biochar- Ricinus communis ” system influences bacterial networks in rhizosphere soil under Cr stress and enhances soil quality. Results indicated that under 150 mg/kg Cr stress, the AMF-biochar combination significantly increased castor plant fresh weight and soil quality index by 359.70 % and 121.25 %, respectively, compared to treatments without biochar or AMF (P < 0.05). Notably, under Cr stress, the combined treatment significantly increased the relative abundance of Arthrobacter while decreasing that of Streptomyces . Network analysis and community assembly results revealed that AMF and biochar together significantly enhanced soil bacterial network complexity and average niche width. In conclusion, the AMF-biochar combination effectively promoted Ricinus communis growth under Cr stress and regulated rhizosphere soil bacterial community stability and assembly processes, providing valuable insights into plant-microbe interactions under Cr(VI) stress. • AMF combined with biochar increased Ricinus communis . • Combined treatment alleviated the inhibition of Cr stress on plant root growth. • Combined treatment drives bacterial community composition and diversity. • Bacterial community changes from random process to deterministic process. • Combined treatments increased the niche breadth of bacterial communities.