The interactions between soil invertebrates and microbes mediate litter decomposition in the rainy zone of western China

Background and aims: Knowledge regarding the interactive effects of soil invertebrates and microbes on litter decomposition is limited. We aimed to reveal the interaction between soil invertebrates and microbes, and the mechanism underlying the effects of them on litter decomposition. Methods: Foliar litter of German oak (Quercus acutissima Carruth.) and China cedar (Cryptomeria sinensis Miquel.) were enclosed in the nylon bags with two different mesh sizes and incubated on the floor in a rainy zone of western China, respectively. Then retrieved at four critical periods each year in two years. The mass loss, invertebrates, and microbial community in the litterbags were measured. Results: The invertebrate abundances in both litter species were higher in the first year than in the second year, and that in German oak litter was higher than that in China cedar litter at most periods. Meanwhile, German oak litter decomposed faster than China cedar litter, and significantly higher decomposition rates occurred in the micro and early rainy seasons. Furthermore, soil invertebrate exclusion made the decomposition rates of German oak and China cedar litter decrease by 14.45% and 26.45%, respectively. Additionally, the interactive effects between invertebrates and microbes on litter decomposition varied greatly with litter quality and critical periods. The interactive effects between soil invertebrates and microbial communities dominated litter mass loss in the first decomposition year, but the gram-positive bacteria became the dominant decomposers in the second decomposition year. Conclusion: These results provided a holistic decomposition view, highlighting how invertebrates and microbes act in synergy to degrade litter.