Abstract:

The soil carbon pool plays a key role in terrestrial ecosystem carbon
cycle. A toal of 217 soil profiles has been collected, a total of 2 170 soil samples were obtained for measuring the average bulk density, moisture content and organic carbon content based on the six-year（2004-2009） environmental investigation implemented in western Jilin Province. The vertical distribution characteristics, reasons and mechanism of soil organic carbon（SOC） under different land use/cover types were analized. The result shows that the vertical distribution of SOC under different land use types has sharply different characteristics, and they can be divided into three types. The decreasing type including grassland, farmland and wetland, SOC of them mostly enriched in the planting layer (0-30 cm), and decreases with depth. Bottomland is under the increasing type, according to the appropriate hydrological conditions and lush vegetation. Meanwhile, SOC of saline and sandy land belongs to the stable type, stay at the lowest standard. The soil organic carbon density of different land use types varies a lot, the general trend from high to low is paddy field, grassland, upland field, wetland, degraded grassland, bottomland, woodland, sandy land and saline land. The soil organic carbon density of paddy field is (169.25±17.70) t/hm²; while, saline land is (26.50±10.00) t/hm². Therefore, the main factors that influence soil organic carbon contents are vegetation biomass, and soil physical and chemical properties.

Key words: soil organic carbon, land use, vertical distribution, soil carbon density, western Jilin Province