Abstract:

Landuse change is one of the most important factors that influence the variation of the soil organic carbon pool. Soil organic carbon density (SOCD) under different landuses and the effect of soil carbon source/sink caused by landuse change in Northeast China was investigated using soil data from the regional multipurpose geochemical survey and landuse data of two temporal points: 1980s and the year of 2000. The following conclusions were drawn: (1) SOCD varied significantly with different landuses; bog and thick forest have the highest SOCD, and sand land, saline land and thin grass land are the landuse types with low SOCD; (2) the reserve of surface soil (020 cm) organic carbon in the study area is 482.1×1010 kg, and the two most large soil carbon pools are the thick forest and the dry farm land, which account for, respectively, 43.8% and 21.4% of the total organic carbon pool of the study area；(3） the carbon source caused by landuse change is 5.73×1010 kg, and the carbon sink is 3.56×1010 kg, so the aggregate effect of the landuse changes results in an effect of soil carbon source of 2.17×1010 kg (21.7 Tg) in the study area; (4) the typical landuse change types that caused soil carbon sinks are the change of dry farm land to paddy field, and the change of thin forest and other forest to thick forest; and the typical landuse change types that caused soil carbon sources are the changes of thick forest and thick grass land to dry farm land, and the change of bog to dry farm land, paddy field, etc.

Key words: soil organic carbon density (SOCD), soil carbon source/sink, northeast China, landuse change