Manganese addition accelerates litter decomposition and alters litter mixing effects in the late stage in subtropical plantations of southern China

Background Manganese (Mn) is believed to be a key variable controlling litter decomposition, especially in the late stage. However, the direct effects of Mn on litter decomposition and litter mixing effects during decomposition have been rarely tested in subtropical forests. Methods We collected leaf litter of four common tree species (two broadleaf tree species, Liquidambar formosana and Schima superba; two coniferous tree species, Pinus massoniana and Pinus elliottii) from subtropical plantations of southern China, and used a field Mn addition experiment to assess the impact of Mn on single and mixed litter mass loss during 780-day decomposition. In addition, we measured soil nutrient availability and hydrolytic enzyme activities. Results Despite unchanged soil nutrient availability, Mn addition generally increased soil beta-1,4-glucosidase, cellobiohydrolase, leucine aminopeptidase, and acid phosphatase activities. Irrespective of litter types, Mn addition did not affect litter mass loss in the early stage (mass loss <40%) but enhanced litter mass loss in the late stage (mass loss >40%). During mixed litter decomposition, synergistic effects were more common for coniferous litter than for broadleaf litter. Moreover, Mn addition reduced the magnitudes of synergistic effects on litter decomposition and even changed synergistic effects to additive effects. Thus, the positive effect of Mn addition on litter decomposition was greater for single litter (18%) than for mixed litter (6%). Conclusions Mn availability is crucial for leaf litter decomposition in the late stage rather than in the early stage, and Mn addition influences mixed litter decomposition by reducing non-additive effects in subtropical plantations.

Automated summary

The study conducted in subtropical forests found that manganese has a greater impact on litter decomposition in the late stage rather than in the early stage, and influences mixed litter decomposition by reducing non-additive effects.