Unraveling microbial assembly and co-occurrence relationship at seasonal and vertical scales in an aged organic-contaminated site

Abstract

Organic-contaminated sites represent a global challenge in soil contamination, yet the spatiotemporal responses of microbial communities remain scarcely investigated. This study explored the landscape characteristics, environmental adaptations, assembly mechanisms, and species interactions of bacterial communities at seasonal and vertical scales in an aged organic-contaminated site. Results showed that seasonal variations (20.62 %) exerted a stronger influence on bacterial community composition and structure compared to soil depth (10.10 %), while organic contaminants and physicochemical factors contributed 8.77 % to the observed variations across both seasonal and vertical scales. Seasonally, summer bacterial communities exhibited lower diversity but better environmental adaptation, along with greater complexity and stability compared to spring and winter. Vertically, surface soil bacterial communities displayed higher diversity and stronger environmental adaptation but weaker complexity and stability than subsurface bacterial communities. Stochastic processes were less influential in shaping microbial community assembly during summer than in spring and winter, while their importance gradually increased with soil depth. Moreover, identified keystone species, such as Pseudomonas, Brevundimonas, and Acidovorax, were closely associated with the degradation of organic contaminants. These findings provide valuable insights into the comprehensive microbial responses to ongoing environmental disturbances in organic-contaminated sites, enhancing our understanding of soil pollution microecology.