Abstract:

The alteration of terrestrial carbon cycling under climate warming is regulated by soil organic carbon (SOC) dynamics. Previous studies have developed multiple warming methods, mainly including laboratory incubation experiment, field in-situ manipulative experiment, and temperature gradient sampling, to investigate the responses and mechanisms of SOC dynamics to climate warming. However, due to the methodological limitations, the studies on the effect of warming on SOC dynamics cannot lead to consistent conclusions. SOC dynamics mainly include two processes: carbon input and carbon decomposition, and are also regulated by carbon persistence. The changes of carbon input, carbon decomposition, and carbon persistence together determine the response of SOC dynamics to warming. Previous studies showed that both carbon input and decomposition may positively respond to warming, which is related to the enhanced activities of plants and soil microbes. However, some studies pointed out that warming-induced alterations of soil physical and chemical properties (e.g., the decrease of soil water content) and biological processes (e.g., microbial community thermal adaptation) may affect the responses of carbon input and decomposition to warming. Moreover, inconsistent responses may arise when focusing on the SOC responses to warming in top (0-30 cm) or deep (>30 cm) soils due to the limitations of environmental factors on carbon input and decomposition in deep soils, as well as the different persistence of SOC in deep soils compared to top soils. Future research should focus on developing new warming methods, increasing research on deep soils and climate-sensitive ecosystems, introducing new technologies to study the source, structure, and protection of soil organic matter, paying attention to the response of plant-soil animal-soil microbe system to warming and its regulation on SOC dynamics, to improve uncertainties in carbon cycle models and more accurately predict the feedback of the global carbon cycle to climate warming.

Key words: climate warming, soil organic carbon input, soil organic carbon decomposition, soil organic carbon persistence, deep soil