Abstract:

By using the USCA (Unit Soil Carbon Amount) method, soil carbon storage in Northeast Plain of 230000 km2 was calculated based on the multipurpose regional geochemical survey. Results show that topsoil (020 cm) organic carbon storage is 76807 Mt with carbon density of 33278 t/km2, subsoil (0100 cm) organic carbon storage is 297841 Mt with carbon density of 129047 t/km2, and deep soil (0180 cm) organic carbon storage is 372916 Mt with carbon density of 161575 t/km2, which stay on the national average level. Soil carbon density increases from southern Northeast Plain (Liaoning Province) of warm temperate climate, to middle Plain of temperate climate and northern Plain of cold temperate climate. Topsoil carbon density increases from 22842, 34367 to 38615 t/km2. In comparison with that carbon data obtained by the Second National Soil Survey, topsoil organic carbon storage has decreased by 32059 Mt (294%) with an annual decrease of 1603 Mt and an annual decreasing rate of 173% Soil carbon density has reduced by 1060.6 t/km2, 1646.4 t/km2 and 1300.2 t/km2 in the south, the central part, and the north, respectively and by 1389.0 t/km2 averagely in the plain. There have also been different decreases in soil carbon density under various ecosystems and landuse types. Soil carbon density ratio has been introduced to study carbon dynamic balance between ecosystems. This research will provide basic knowledge to understand soil carbon distribution and to study the potential for soil carbon sequestration.

Key words:  Northeast Plain, multipurpose regional geochemical survey, the Second National Soil Survey, soil organic carbon storage, distribution rule, changing trend, soil carbon density ratio