Soil organic carbon and its distribution characteristics in the soil profile for four forest types in west Guizhou

The carbon bank of the forest soil has become one of the key research subjects concerning global carbon cycle in the context of global climate change.Taking the 4 major forest types in West Guizhou composed of Betula luminifera,Cryptomeria fortunei,Pinus armandii and Cunninghamia lanceolata as the research subjects,this paper studied the organic carbon contents of the soil,the density and the vertical distribution characteristics of the organic carbon.The results indicated that the organic carbon contents in the forests of Pinus armandii,Cunninghamia lanceolata,Cryptomeria fortunei and Betula luminifera were respectively 51.09 g.kg-1,39.47 g.kg-1,37.49 g.kg-1,36.31 g.kg-1 and the carbon density was respectively 30.56 kg.m-2,22.97 kg.m-2,21.00 kg.m-2 and 20.13 kg.m-2,uniformly showing the descending order that Pinus arma ndii Cunninghamia lanceolata Cryptomeria fortune Betula luminifera,and the organic carbon contents as well as the carbon density of the soil in the forest of Pinus armandii were strikingly greater than those of the other 3 forests,among which the difference was not so distinct.Both the organic carbon contents and carbon density of the soil decreased gradually with the deepening of the soil in all the 4 forests and the organic carbon contents were the highest in the 0~10 cm-deep soil,as 1.45~1.61 times high as the average values of the whole soil profile,while the carbon densities in the 0~20 cm-deep soil accounted for 32.69%～38.08% of the whole soil profile,prominently higher than those of the other soil depths.The carbon densities between different soil depths from below 20 cm-deep soil did not differ so much,and such characteristics indicated the soil carbon was more or less concentrating on the surface of the soil.For all the 4 forest types,there were strong negative correlations between the soil carbon contents and the pH values of the soil,and strong positive correlations between the soil carbon contents and total N as well as alkaline hydrolysis N,and various correlations between the soil carbon contents and total P,quick-acting P,total K,quick-acting K and base exchange capacity.There was high accuracy concerning the established regression equations,and the contents of N and P in the soil had great impact on the carbon contents of all the 4 forest soil.