[Estimation of China soil organic carbon storage and density based on 1:1,000,000 soil database]

Based on 1:1,000,000 soil database, and employing the methods of spatial expression, this paper estimated the soil organic carbon storage (SOCS) and density (SOCD) of China. The database consists of 1:1,000,000 digital soil map, soil profile attribution database, and soil reference system. The digital soil map contained 926 soil mapping units, 690 soil families, and 94 000 or more polygons, while the soil profile attribution database collected 7292 soil profiles, including 81 attribution fields. The SOCDs of soil profiles were calculated and linked to the soil polygons in the digital soil map by the method of "GIS linkage based on soil type", resulting in a vector map of 1:1,000,000 China SOCD. The SOCS of the country or of a soil could be estimated by summing up the SOCS of all polygons or the polygons of a soil, and their SOCD were the SOCS of them derived by their areas. The estimated SOCS and SOCD of the country was 89. 14 Pg (1 Pg = 10(15) g) and 9.60 kg m(-2), respectively, covered all the soils with a total area of 928.10 x 10(4) km2, which might be considered closest to the real value.