Objective Litter in mixture may exhibit ‘non-additive effects’ on decomposition, potentially accelerating or inhibiting the process, yet the underlying mechanisms remain unclear.

Method This study focuses on a subtropical Moso bamboo (Phyllostachys edulis) forest ecosystem, utilizing leaves of Phyllostachys edulis (MZ), Rubus buergeri (HM) and Parathelypteris glanduligera (JXJ) as expermental materials. Both single litter and various mixed combinations were incubated with soil over a 60-day period, and the changes of litter mass loss, chemical properties and soil bacterial community structure were measured.

Result A synergistic effect was observed in the mass loss of litter when MZ and HM leaves were mixed, significantly enhancing decomposition, whereas the presence of JXJ leaves exhibited an antagonistic effect on decomposition with other litter combinations. Significant variations in soil bacterial diversity and community structure were found across different litter treatments (P < 0.05). Multiple regression results showed that higher carbon/nitrogen (C/N) ratios in mixed litter correlate with increased soil bacterial diversity and relative abundance of Actinobacteriota, leading to a stronger antagonistic effect of mixed litter.

Conclusion This study demonstrates that significant interactions exist among different species of litter in the natural Moso bamboo forest ecosystem, which results in non-additive effects on litter decomposition. And the soil bacterial communities are the key to deciphering these effects.