Abstract:Soil organic carbon (SOC) is an important pool of global carbon, and SOC transformation controls the global biogeochemical cycle of carbon. Soil macrofauna, due to their large biomass and abundant biodiversity, play an important role in regulating stability of SOC through their feeding activity in soil. Because of its facility in determination of transformation rate and localization of transformation products, 14C isotope tracer technique has been proved to be an effective approach for studies on the stability of SOC. This review focused on the transformation of SOC by three typical soil-feeding macrofauna, termite (Isoptera: Termitidae), rose beetle larva (Coleoptera: Scarabaeidae) and earthworm (Oligochaeta: Lumbricidae), using 14C isotope tracer technique. The microbial activities related to the transformation processes are also discussed. Soil-feeding termites and humus-feeding scarabaeid beetle larvae can selectively mineralize and degrade the peptidic component of humic acids in soil through combined functions of special proteolytic activities and extreme alkalinity (pH 10-12.5) of gut compartments in their intestinal tracts, and, as a result, enhance the humification of the humic acids. High cellulase activities present in the guts of geophagic earthworm make earthworms able to degrade cellulose. Lignin degradation occurs in worm cast and earthworms also feed on litter and leaves, however, little is known about whether earthworms can mineralize or selectively degrade the recalcitrant pool of SOC. Significantly high microbial and enzymatic activities are present in the guts of macrofauna, however, it is yet unclear to which extent the gut microorganisms contribute to the degradation and humification of SOC by the soil animals and from where the enzymes originate. Several gaps in knowledge about the impact of soil-feeding macrofauna on the biogeochemical processes of SOC have been identified and a number of research priorities have been suggested.