Effects of soil fauna on leaf litter decomposition and nutrient release during a two-year field experiment in a poplar plantation

AimsSoil fauna play a key role in the litter decomposition process in two ways; directly via fragmentation and consumption of the litter, and indirectly through changes in soil structure and the activity of microorganisms. The study aimed at better understanding how soil fauna affects the release of nutrients from litter.MethodsWe conducted a litter decomposition experiment using litterbags of three mesh sizes (0.01 mm, 1 mm, and 4 mm), and chemical treatments (no naphthalene; naphthalene application) to assess soil fauna effect on nutrient release in a poplar plantation in eastern China over a two-year period from Jan 2019 to Dec 2020.ResultsWe found that the contribution of soil fauna to the mass loss of poplar leaf litter was 29% over the two-year period, and the contribution was more pronounced within the first four months. Soil macrofauna and meso-/micro- fauna contributed similarly to leaf litter mass loss, while microbial decomposition contributed the most to the decomposition process. The presence of soil fauna significantly promoted the degradation of cellulose and lignin, and accelerated the release of nitrogen at later stages of decomposition. A structural equation model revealed that higher soil fauna abundance not only promoted the litter decay rate directly, but also indirectly through modifying nitrogen and lignin contents.ConclusionsOur results highlight the importance of soil fauna on cellulose and lignin degradation, and the importance of including this when simulating decomposition models for obtaining a better mechanistic understanding of forest litter decomposition.

Automated summary

Soil fauna play a crucial role in the decomposition of litter through both direct fragmentation and consumption of the litter, and indirect changes in soil structure and microbial activity. This study aimed to investigate the impact of soil fauna on nutrient release from litter. A two-year litter decomposition experiment was conducted in a poplar plantation in eastern China, using different mesh sizes of litterbags and chemical treatments. The results showed that soil fauna contributed to 29% of the mass loss of poplar leaf litter over the two-year period, with a more pronounced effect in the first four months. Soil macrofauna and meso-/micro- fauna had similar contributions to litter mass loss, while microbial decomposition had the highest contribution. The presence of soil fauna promoted the degradation of cellulose and lignin, and accelerated the release of nitrogen. The findings suggest that including soil fauna in decomposition models is essential for a better understanding of forest litter decomposition mechanisms.