Fig. 3

Alpha diversity index of bacterial (A) and fungal (B) communities affected by SPSB concentrations. CK (no biochar), S1 (2.5% w/w biochar + soil), S2 (5% w/w biochar + soil), S3 (7.5% w/w biochar + soil). The significant differences are determined by the Tukey test, with different lowercase letters indicating significant differences between groups (P < 0.05)00