Effect of land use on organic carbon storage in soils in eastern China

The change of land from natural vegetation to agricultural use causes the loss of organic carbon stored in soils and is considered as an important contributor of CO2 to the atmosphere. Four types of land use were defined in the study as: 1) natural vegetation fields (NF); 2) fuel forest, fruit tree orchards and wasteland near residential areas (FF); 3) upland crop fields (UF) and 4) paddy fields (PF). For a large area in eastern China, 416 soil species cited in the book ''Soil Species of China-Volume One'' were placed in one of the four use categories. Statistical results showed that organic carbon density in soil profiles 0 to 62.3 cm ranged from 3.87 to 14.25 kg m(-2). Relative to NF, the loss of organic carbon in soils was correlated with human impact but varied with the type of human use. The total loss in the studied area was estimated to be 1.646 GtC. Although organic carbon in paddy soils was also significantly less than that in NE the mean carbon density in the profile 0 to 62.3 cm was 68.1% higher than that in UF and 23.6% higher than that in FF. Therefore, flooded rice is the preferred land use type with respect to the storage of organic carbon in heavily impacted soils. On the other hand, other ecological values, e.g., biodiversity, are also affected by land use type and any change in land use should be preceded by a comprehensive review of objectives and ecological impacts.