Dead bamboo culms promote litter mass, carbon and nitrogen loss, but do not modulate the effect of soil fauna on litter decomposition

Abstract

Bamboos contribute significantly to carbon cycling in many (sub)tropical and temperate forests. In East Asia, unmanaged Moso bamboo stands accumulate large amounts of dead culms. However, very little is known about the indirect effects of dead culms on biogeochemical cycling through changes in soil conditions and decomposer communities. We evaluated the interactive effects of dead culms and soil fauna on litter decomposition in an unmanaged Moso bamboo stand. We placed leaf litter beneath the dead culms and on the forest floor (control) and used litterbags with different mesh sizes (1 mm and 42 μm) to control the access of soil mesofauna to the litter. We hypothesized that dead culms and soil fauna synergistically accelerate litter decomposition mainly because dead culms influence soil conditions and alter the litter fauna assemblage. We found that litter decomposing under the dead culms had greater litter mass, carbon and nitrogen loss, and microbial respiration rates than the control. The presence of soil mesofauna decreased litter mass, carbon and nitrogen loss but had no effect on the microbial respiration rate. Soil moisture was consistently higher under the dead culms, but their effect on soil temperature was dependent on the season. The litter decomposing below the dead culms had relatively higher mesofauna abundance and order richness. However, the contribution of the mesofauna to litter mass and nutrient loss was not modulated by the dead culms, suggesting that soil fauna had essentially the same effect on litter decomposition irrespective of the presence of dead culms. We showed that dead bamboo culms influence litter nutrient dynamics and promote habitat heterogeneity for soil microarthropods. Our results further highlight the ecological role played by dead culms and have implications for Moso bamboo management. The removal of dead culms from the forest floor could have substantial impact on the soil biota and ecosystem processes in managed stands.