关键词: 土壤, 生物炭, 镉污染土壤, 微生物群落, 土壤酶活性, 镉有效性

Abstract: A pot experiment was conducted with cadmium（Cd）‑contaminated cultivated soil as the test substrate to explore the effects of biochar at different application rates on soil microbial community structure and Cd availability. Four treatments were established：no biochar application（control，CK），biochar application at 2 g/kg （B1），4 g/kg （B2），and 8 g/kg（B3）.Soil physicochemical properties，available Cd concentration，soil enzyme activities，microbial biomass，and soil microbial community composition were determined. The results showed that soil pH value under B3 treatment increased by 0.25 compared with CK；the contents of soil organic matter，available phosphorus and available potassium increased by 35.90%，28.67% and 14.29%，respectively，while the concentration of soil available Cd decreased by 6.82%. Microbial biomass carbon under B1 and B2 treatments increased by 9.90% and 15.54% relative to CK，and microbial biomass nitrogen under B1，B2 and B3 treatments increased by 46.08%，21.77% and 62.05%，respectively.Compared with CK，soil catalase activity under B2 and B3 treatments increased by 19. 33% and 20. 72%，while soil acid phosphatase activity decreased by 43.25% and 42.25%. The dominant bacterial phyla in all treatments were Pseudomonadota，Bacillota，Bacteroidota and Acidobacteriota. Treatments B2 and B3 increased the relative abundances of Pseudomonadota and Acidobacteriota and reduced the relative abundance of Cyanobacteriota. The dominant fungal phyla across all treatments were Ascomycota and Unclassified_k_Fungi. Treatment B2 elevated the relative abundance of Ascomycota，and all biochar treatments reduced the relative abundance of Mortierellomycota. Soil catalase activity was positively correlated with the relative abundances of Pseudomonadota and Acidobacteriota，acting as a key factor affecting the bacterial community. Soil urease activity exhibited a significant negative correlation with the relative abundance of Rozellomycota，which was the key factor regulating the fungal community. In conclusion，biochar application could raise soil pH value and the contents of organic matter，available phosphorus and available potassium，enhance the activities of soil catalase，increase MBN，reshape the microbial community structure of Cd‑contaminated soil，improve the relative abundances of bacterial Pseudomonadota，Acidobacteriota and fungal Ascomycota，and reduce soil available Cd concentration；the optimal biochar application rate was 8 g/kg.

Key words: Soil, Biochar, Cadmium?contaminated soil, Microbial community, Soil enzyme activity, Cadmium availability