Abstract:

Background & Aims: Global warming caused by sharp increase in atmospheric greenhouse gas (CO₂, CH₄, and N₂O) emissions has become a major concern for both international and scientific communities. Understanding how soil fauna mediate the carbon and nitrogen processes to drive greenhouse gas emissions is a frontier scientific issue in global climate change research. As a key arthropod group with extremely high species diversity globally (over 12,000 species), millipedes can directly or indirectly regulate soil carbon and nitrogen cycle processes and the associated emissions of greenhouse gases (i.e., CO₂, CH₄, and N₂O) through their multiple roles as consumers, decomposers, predators, and soil engineers. At present, research on the mechanism by which soil fauna affect greenhouse gas emissions mainly focuses on groups such as earthworms and termites, while studies on millipedes regulating soil greenhouse gas emissions are extremely scarce. Most of them are microscopic or control experiments conducted in the past 20 years on dozens of model species from 25 families and 34 genera under 5 orders. This paper systematically reviews relevant domestic and international research findings about the effects of millipedes on soil carbon and nitrogen cycling as well as the emissions of greenhouse gases such as CO₂, CH₄, and N₂O. We also preliminarily summarize the underlying processes and mechanisms. 

Review Results: (1) Millipedes directly promoted CO₂, CH₄, and N₂O emissions by stimulating their own respiration, gut enzyme activities, and functional microbial activities during litter feeding and decomposition; simultaneously, they indirectly affected greenhouse gas emissions through litter fragmentation and the mediation of microbial and soil faunal activities via fecal pellets. (2) Millipedes regulated soil greenhouse gas production by affecting soil carbon and nitrogen mineralization and microbial respiration processes through secretion, digestion, and excretion. (3) By mediating changes in soil functional microorganisms, functional enzymes, and aerobic-anaerobic conditions, millipedes influenced soil nitrification, denitrification, oxidation, and reduction processes, thereby regulating CO₂, CH₄, and N₂O emissions. (4) Through interactions with plant roots, soil, microorganisms, and other arthropods, millipede activities mediated changes in plants and soil environment, thereby indirectly driving soil greenhouse gas emissions by influencing key processes such as carbon and nitrogen mineralization, nitrification, denitrification, methane production and oxidation. 

Conclusion: Future research should focus on the mechanism analysis based on in situ field control and microcosmic experiments, exploring the mechanisms by which different feeding-habit millipedes affect key processes in soil carbon and nitrogen, as well as carbon and nitrogen fixation and greenhouse gas emissions. It is also essential to scientifically evaluate the promoting or inhibiting effects of millipede activities on the releases of CO₂, CH₄, and N₂O.

Key words: millipedes, greenhouse gas, litter decomposition, carbon and nitrogen mineralization, nitrification, denitrification, methane oxidation, methane production