Organic Carbon Contents and Vertical Distribution Characteristics of the Soil in Three Forest Types of the Karst Regions in Central Guizhou Province

Under the global climate change context,the organic carbon bank of forest soil has become one of the main research topics concerning the global carbon cycle.Taking the mixed broadleaves,mixed conifers and broadleaves,and shrubs of the Karst regions in the middle of Guizhou as the research objects,this paper analyzed the organic carbon contents in the soil and litter.The research results showed that the average organic carbon contents and carbon density of the soil in the soil profile at 0-80 cm depth were separately 19.10 g/kg and 18.62 kg/m2 for mixed broadleaves,9.21 g/kg and 9.67 kg/m2 for shrubs,and 8.38 g/kg and 8.60 kg/m2 for mixed conifers and broadleaves,with significant differences(P0.05) between the differents forest types,which indicated the accumulation and storage of organic carbon in the soil differed between the different forest types in the same region.The organic carbon contents and carbon density of the soil were the greatest in the 0-20 cm soil depths for all the three forest types,there was significant differences between the different soil layers(P0.05) and the difference decreased with the increase of soil depths,which showed the organic carbon contents intensely tended to distribute in the surface of the forest soil.Therefore,intervention should be avoided and vegetation cover should be increased to lower soil and water loss.For all the three forest types,there was negative correlation between the organic carbon contents and the soil bulk weight and the fitting degree(R2) in the regression equations was considerably high showing comparatively good qualities of the fitting equations.The three forest types differed significantly from each other in both the present litter quantity and the organic carbon quantity(P0.05),which proved the different forest types in the same region had different capacities in litter accumulation and decomposition.