The net fluxes of carbon dioxide (CO<sub>2</sub>) between the atmosphere and agricultural systems are mainly characterized by the changes in soil carbon stock, which is determined by the balance between carbon input from organic materials and output through soil C decomposition. The spatiotemporal changes of cropland soil organic carbon (SOC) in response to different carbon (C) input management and environmental conditions across the global main cereal systems were studied using a modeling approach. We also identified the key variables driving SOC changes at a high spatial resolution (0.1&deg;&thinsp;&times;&thinsp;0.1&deg;) and long time scale (54 years from 1961 to 2014). The widely used soil C turnover model (RothC) and the state-of-the-art databases of soil and climate were used in the present study. The model simulations suggested that, on a global average, the cropland SOC density increased at an annual rate of 0.22, 0.45 and 0.69&thinsp;MgC&thinsp;ha<sup>&minus;1</sup>&thinsp;yr<sup>&minus;1</sup> under a crop residue retention rate of 30&thinsp;%, 60&thinsp;% and 90&thinsp;%, respectively. Increased quantity of C input could enhance the soil C sequestration or reduce the soil C loss rate, depending largely on the local soil and climate conditions. Spatially, under a certain crop residue retention rate, a relatively higher soil C sink were generally found across the central parts of the United States, western Europe, northern regions of China, while a relatively smaller soil C sink generally occurred in regions at high latitudes of both northern and southern hemisphere, and SOC decreased across the equatorial zones of Asia, Africa and America. We found that SOC change was significantly influenced by the crop residue retention rate (linearly positive), and the edaphic variable of initial SOC content (linearly negative). Temperature had weakly negative effects, and precipitation had significantly negative impacts on SOC changes. The results can help target carbon input management for effectively mitigating climate change through cropland soil C sequestration on a global scale.
Wang, G., Zhang, W., Sun, W., Li, T., & Han, P. (2017). Modeling soil organic carbon dynamics and their driving factors in the main global cereal cropping systems. Atmospheric Chemistry and Physics, 17(19), 11849–11859. https://doi.org/10.5194/acp-17-11849-2017