Impacts of dibutyl phthalate on the microbial community assembly process in black soil of Northeast China

Dibutyl phthalate (DBP) accumulation threatens soil microbial communities, yet its effects on microbial assembly mechanisms remain unclear. This study investigated the impacts of DBP with a wide range of level (i.e., 0–40 mg kg −1 , DBP0, DBP10, DBP20, and DBP40) on microbial community assembly processes in black soil of Northeast China through 90-day controlled laboratory incubations. A framework of infer community assembly mechanisms by phylogenetic bin-based null model analysis (iCAMP) was used to qualify the soil community assembly processes. The findings demonstrated significant reductions in soil enzyme activities (urease, β-glucosidase) and respiration intensity with elevated DBP concentrations. Microbial α-diversity declined significantly, with Shannon and Chao1 indices decreased by 1.79 % and 4.78 % for DBP10, 5.29 % and 9.70 % for DBP20, 14.66 % and 10.22 % for DBP40, respectively. The abundance of bacteria linked to soil carbon and nitrogen cycling exhibited reduction, such as Nocardioides (decreased from 1.24 % to 0.52 %) and Gp6 (decreased from 5.65 % to 3.67 %). Conversely, the relative abundances of bacteria which are associated with DBP degradation increased, such as Streptomyces (Increased from 20.21 % to 34.01 %) and Bacillus (Increased from 2.49 % to 5.21 %). DBP significantly altered microbial community assembly processes. As DBP concentration increased, the relative importance of homogeneous selection rose from 45.41 % to 55.63 %, while dispersal limitation declined from 48.89 % to 35.09 %. DBP homogenizes environmental conditions and a transition from neutral diffusion dynamics to pressure-driven selection, favoring taxa adapted to DBP degradation. This study advances understanding of DBP’s ecological impacts on soil microbial communities and their assembly dynamics.