Bacterial functional traits: a key driver of soil organic carbon dynamics during reductive soil disinfestation

Reductive soil disinfestation (RSD) significantly enhanced SOC content. However, its microbial mechanisms mediated through changes in microbial necromass carbon, particularly under different organic amendments, remain poorly understood. Here, we evaluated the effects of RSD combined with two types of organic amendments (wheat vs. soybean straw) on soil chemical properties, SOC fractions, microbial community composition and diversity, 16S rRNA gene operon (rrn) copy number, co-occurrence networks, and functional profiles. The results showed that microbial necromass carbon increased markedly after RSD treatment and accounted for up to 75% of the total SOC. Compared to wheat straw, soybean straw amendment resulted in higher relative abundances of Firmicutes (47.70%), Halobacterota (506.99%), and Euryarchaeota (1671.36%), intensified anaerobic conditions during RSD, improved suppression of aerobic fungi, and preferentially promoted the accumulation of fungal necromass carbon (33.25%). Conversely, the wheat straw treatment induced moderate anaerobic conditions, less pronounced than with soybean straw but stronger than the control, while sustaining higher bacterial abundance and promoting more robust bacterial succession, thereby preferentially leading to accumulation of bacterial necromass carbon (141.74%). These findings underscore the important role of bacteria functional traits in mediating carbon sequestration under anaerobic straw incorporation and provide new insights for optimizing organic amendment strategies in RSD practices to enhance soil carbon sequestration efficiently.