Aims We tested the dynamics of nine enzymes during leaf litter decomposition in Xishuangbanna tropical rainforest both in the field and laboratory to explore the response of enzyme dynamics to decomposition under different food-web structures.

Methods We used coarse and fine (1 mm and 100 μm mesh size, respectively) litterbags in the field to create different food-web structures during litter decomposition. Most soil macrofauna such as nematodes could access only the coarse mesh litterbags, leaving only microbiota such as mites in the fine mesh litterbags. In the laboratory, sterilization and inoculation were adopted to investigate different enzyme dynamics with nematodes or only microbiota participating in litter decomposition.

Important findings Invertase and amylase increased more for shorter food webs at early stages of decomposition, while activities of endocellulase, β-glucosidase, xylanase and polyphenoloxydase increased to their maxima at later stages, but greater increase occurred with extended food webs. Invertase and amylase had negative and endocellulase, β-glucosidase, xylanase and polyphenoloxydase had positive relationships with litter decomposition (mass loss). Activities of enzymes responded to the process of litter decomposition. Invertase and amylase played key roles for microbiota utilizing the substrates at early stages of decomposition, while endocellulase, β-glucosidase, xylanase and polyphenoloxydase worked on the further decay of recalcitrant compounds at later stages. All enzymes related to C decay acted as effective indicators of litter decomposition. The decomposition of plant organic matter was essentially an enzymatic process.