Abstract: Soil organic matter (SOM), an important organic component in soils, plays a key role in maintaining soil fertility, food security and global change. Globally, soil scientists have made longterm and great efforts to improve our understanding of SOM cycling, particularly its formation and decomposition. There are much difficulty and challenge in the global environmental change context. Here, we reviewed the research advances in soil microbial residues, influence of plant litters on SOM cycling, priming effect and temperature sensitivity of SOM decomposition, deep SOM and responses of SOM cycling to environmental change in forest ecosystems. First, in laboratory and field-based long-term experiments, the simulated experiment conditions were different from the natural conditions, which may lead to deviation in the observations or results.Second, soil microbes, as the key driver of SOM cycling, control both SOM formation and decomposition. The microbial process and SOM cycling should be linked in further research, to ascertain the roles of microbes in SOM cycling. Third, multifactorial impacts of global environmental change on SOM should be addressed with an efficient, broadly applicable experimental design due to the coupling effects of multiple factors. Finally, the coupled linkages between above andbelow ground ecological processes from an ecosystem perspective should be strengthened by adopting the theories of multiple disciplines and advanced analytical techniques. Overall, this review would help improve our understanding of SOM cycling in terrestrial ecosystems, especially in forest ecosystems, and also has implications for researchers in grassland, agricultural and wetland ecosystems.

Key words: soil organic matter, litter, microbial necromass, temperature sensitivity, priming effect, deep soil, global environmental change.