Soil arthropods promote litter enzyme activity by regulating microbial carbon limitation and ecoenzymatic stoichiometry in a subalpine forest

Soil arthropods are crucial decomposers of litter at both global and local scales, yet their functional roles in mediating microbial activity during litter decomposition remain poorly understood. Here, we conducted a two-year field exper-iment using litterbags to assess the effects of soil arthropods on the extracellular enzyme activities (EEAs) in two litter substrates (Abies faxoniana and Betula albosinensis) in a subalpine forest. A biocide (naphthalene) was used to permit (nonnaphthalene) or exclude (naphthalene application) the presence of soil arthropods in litterbags during decompo-sition. Our results showed that biocide application was effective in reducing the abundance of soil arthropods in litterbags, with the density and species richness of soil arthropods decreasing by 64.18-75.45 % and 39.19-63.30 %, respectively. Litter with soil arthropods had a greater activity of C-degrading (beta-glucosidase, cellobiohydrolase, polyphenol oxidase, peroxidase), N-degrading (N-acetyl-beta-D-glucosaminidase, leucine arylamidase) and P-degrading (phosphatase) enzymes than litter from which soil arthropods were excluded. The con-tributions of soil arthropods to C-, N-and P-degrading EEAs in the fir litter were 38.09 %, 15.62 % and 61.69 %, and those for the birch litter were 27.97 %, 29.18 % and 30.40 %, respectively. Furthermore, the stoichiometric analyses of enzyme activity indicated that there was potential C and P colimitation in both the soil arthropod inclusion and exclu-sion litterbags, and the presence of soil arthropods decreased C limitation in the two litter species. Our structural equa-tion models suggested that soil arthropods indirectly promoted C-, N-and P-degrading EEAs by regulating the litter C content and litter stoichiometry (e.g., N/P, LN/N and C/P) during litter decomposition. These results demonstrate that soil arthropods play an important functional role in modulating EEAs during litter decomposition.

Automated summary

Soil arthropods play a crucial role in mediating microbial activity during litter decomposition. In a field experiment, the presence of soil arthropods significantly increased the activity of C-, N- and P-degrading enzymes in litter. The presence of soil arthropods indirectly regulated the enzyme activity by influencing the litter C content and stoichiometry during decomposition.