Abstract:

The earth critical zone (ECZ) is situated at the intersection of atmosphere, water, pedosphere, microsphere and lithosphere. Soil microbes play an important role in the carbon cycle processes of the ECZ. It is one of the current hotspots in key zone research to understand the structure and functions of the ECZ, and elucidate the carbon transformation process mediated by soil microorganisms in the key zone. On the basis of summarizing domestic and international progress, this review first introduces the structural connotation of the ECZ, and the characteristics of soil microbial structure and the research progress of the microbial-driven soil carbon cycle. Then it is pointed out that the current work is still limited to understanding the basic structure of the ECZ and describing the soil carbon storage characteristics. It is suggested to systematically explore the carbon cycling process from plant canopy to bedrock by the framework system of the ECZ. In the future, a variety of techniques and methods are integrated in the research, and the short-term and high-frequency observations and the long-term positioning observations are combined. An attention should be paid to the response and feedback mechanisms of soil organic carbon cycling to global changes and human activities at a long-term scale. Special attention should be paid to the microbial driving processes and the migration and transformation patterns of soil carbon within each sphere and at various interfaces of the ECZ. According to the background of time factors such as earth’s big data science project and global carbon emission pathways, we should carry out synchronous observation and systematic research on multi-interfaces, multi-processes and multi-time scales of atmosphere, vegetation, soil, microorganisms, bedrock, and groundwater, which would provide scientific basis for carbon cycle model optimization and climate change prediction, and also provide important theoretical reference for China’s terrestrial ecosystem to achieve the goal of carbon peaking and carbon neutrality.

Key words: earth critical zone, soil organic carbon, soil microbes, carbon cycle, carbon sink effect