[Regulation of soil carbon and nitrogen by lignin-degrading microbial consortia in Moso bamboo forest]

During the management of Moso bamboo forests, a large number of stumps and underground rhizomes are left behind, which degrade slowly due to high lignin content, hindering nutrient recycling and soil organic carbon sequestration in Moso bamboo forests. In this study, three bacteria strains with strong lignin-degrading capabilities from different genera were isolated from the rhizosphere of Moso bamboo: Serratia marcescens (a26), Ochrobactrum anthropi (b1) and Pseudomonas asuensis (b6). We inoculated these strains individually, in pairs, or as a three-strain combination into aniline blue medium to compare their lignin-degrading abilities. Simultaneously, they were inoculated into soil containing Moso bamboo leaf and root litter to investigate the effects of leaf and root litter degradation by bacterial communities on soil nitrogen and organic carbon pools. The results showed that: 1) Under aniline blue medium conditions, the three-strain combination (a26×b1×b6) exhibited the highest lignin-degrading ability. 2) In soil with leaf litter, inoculation of single strains and the a26×b1, a26×b6 double-strain combinations promoted nitrogen return from bamboo leaves by increasing the abundance of bacterial cellulose-degrading functional gene (GH48) and chitin-degrading functional gene, significantly raising ammonium and nitrate content in the soil (rising by 10.4%-20.9% and 11.4%-17.1%, respectively), but had minimal impact on soil active organic carbon pool. Inoculation with the a26×b1×b6 three-strain combination showed no effect on soil inorganic nitrogen and active organic carbon pool. 3) In soil with root litter, inoculation with single strains had little effect on soil inorganic nitrogen and active organic carbon pools. Inoculation with the b1×b6 and a26×b1×b6 bacterial communities significantly increased the proportion of GH48 (increases of 40.9% and 56.9%), maintained soil inorganic nitrogen content, and significantly increased soil microbial biomass carbon (by 46.5% and 81.1%) and dissolved organic carbon content (by 17.8% and 25.2%), benefiting soil carbon sequestration. These findings could provide effective pathways for rapid degradation of Moso bamboo litter and offer scientific references for carbon and nitrogen cycling of the "litter-soil-microorganism" continuum.