Coarse woody debris can influence soil biotic activity mainly through changes in soil environmental conditions. Unmanaged Moso bamboo stands are characterized by a high density of dead culms on the forest floor. However, it is unknown whether culm debris would influence the soil environment and soil biota affecting indirectly leaf litter decomposition underneath the debris. In this study, we controlled the accumulation of culm debris and the presence of soil fauna to test their effect on leaf litter decomposition and microbial activity. In addition, we measured soil environmental conditions and surveyed the mesofauna community in the litter. After one year of decomposition, we found that: (1) mass loss and microbial respiration rates of litter were higher under the culm debris; (2) soil fauna decreased litter mass loss but had no effect on microbial respiration; (3) soil moisture was significantly higher under the debris throughout the experiment and (4) greater mesofauna abundance and order richness were associated with the litter under the debris. Our results emphasize the importance of accumulated debris, especially in the context of managed stands, since the alteration or removal of culm debris from the forest floor may affect soil biota and nutrient cycling in Moso bamboo stands.