Soil organic carbon storage of paddy soils in China using the 1:1,000,000 soil database and their implications for C sequestration

Organic carbon storage in agricultural soils plays a key role in the terrestrial ecosystem carbon cycle. Paddy soils support important croplands in many parts of the world, especially in Asia. A thorough understanding of organic carbon storage in Chinese paddy soils would be helpful to both greenhouse gases emission and carbon sequestration studies. This paper examines soil organic carbon density (SOCD) and storage (SOCS) of paddy soils in China using the newly compiled 1:1,000,000 digital soil map of China as well as data from 1490 paddy soil profiles. Results show that paddy soils in China cover about 45.7 M ha, nearly 1.5 times more than the results of other studies. In China, the mean SOCD of paddy soils at a depth of 0-100 cm is 111.41C ha^-1, with a SOCS of 5.1 Pg. These results are 66-75% higher than studies from other scientists. However, the mean SOCD of paddy soils from 0 to 20 cm is 37.6 t C ha ^-1, with a SOCS of 1.7 Pg, which is 89% higher than studies from other scientists.