The colonization of Pteridium aquilinum reduces the heavy metal content in waste slag and changes the composition of soil abundance bacteria and rare bacteria

Ferns are pioneer plants that can grow on waste slag in antimony mining areas. They can influence the abundance of soil microorganisms, but the mechanism by which they do so remains unclear. This study investigated the differential effects of Pteridium aquilinum on abundant (relative abundance >0.5 %) and rare (relative abundance <0.01 %) microbial taxa in waste slag. Our results showed that P. aquilinum colonization significantly reduced soil heavy metal concentrations (Sb: 66.08 %; Pb: 22.99 %; Hg: 15.15 %; Zn: 14.83 %; As: 7.39 %) and induced distinct restructuring of the microbial community. Among abundant bacterial taxa, P. aquilinum colonization significantly increased the relative abundances of Roseiarcus and Acidipila, while decreasing those of Aquabacterium, Conexibacter, Ferrithrix, Roseiarcus, Acidipila and Sulfobacillus. Notably, colonization by the fern resulted in the disappearance of rare phyla (Rokubacteria, Synergistetes, Euryarchaeota, and Spirochaetes), while promoting the emergence of rare genera (Fimbriimonadaceae, Babeliaceae, Acidisoma, Anaeromyxobacter, and Amycolatopsis). Redundancy analysis revealed strong correlations between these microbial community shifts and changes in heavy metal concentrations. These findings suggest that P. aquilinum colonization mediates both heavy metal remediation and microbial community succession in waste slag, particularly through the turnover of rare bacterial taxa. This work provides new insights into screening for functional rare bacteria through plant-soil-microbe interactions to improve waste slag management.