Bamboo-sourced microbial fertilizers impact soil carbon cycling: Metagenomic insights from Moso bamboo plantations

Effective management of soil organic carbon (SOC) in bamboo forest provides a potential opportunity to address climate change. However, the microbial mechanisms by which bamboo-sourced microbial fertilizer (BSMF) regulate C cycling gene to alleviate C decline remain unclear. In this study, we employed metagenomics to assess microbial C cycling in Moso bamboo plantations subjected to no fertilizer (CK) and three BSMFs: Bacillus subtilis ACP81 (ACP81), Terribacillus goriness CS3 (CS3), and ACP81+CS3 (A+C). Results showed that, compared to CK, A+C significantly increased the contents of SOC, highly labile organic carbon (HLOC), moderately labile organic carbon (MLOC), and mineral-associated organic carbon (MAOC), whereas ACP81 and CS3 resulted in opposite trends (P < 0.05). Moreover, Chloroflexi, Mucoromycota, Bifiguratus , and Acidothermus were represented in A+C; Firmicutes and Metarhizium in ACP81; Dactylella in CS3; and Clavulinopsis in CK. Metagenomic analysis revealed that the CS3 significantly enriched the abundance of genes uidA , rfbB , katG , bgaA, glcD , and mttB , whereas A+C enhanced the genes coxM and MAN , and FUCA was abundant in ACP81 (P < 0.05). RDA and Mantel analysis revealed soil C fractions were shaped by available nitrogen (AN) and potassium (AK), microbial communities, and C cycle genes, with AK was the most crucial factor for C fractions identified by random forest model. The partial least–squares path model indicated that soil AK and C cycle genes directly affect the C fractions. These findings provide novel insights into the linkages between BSMF and C cycling, suggesting a management practice to enhance soil C sequestration in bamboo plantations. • This method reduces wastewater waste and treatment costs. • A+C fertilizers accumulate SOC content more easily than ACP81 and CS3. • A+C fertilizers enriched coxM and MAN genes, promoting C fixation. • CS3 treatment promoted C loss by enriching genes involved in C degradation and methane metabolism. • C cycle genes and AK directly affected the soil C fractions.