Profile distribution characteristics of soil organic carbon in secondary forests in depressions between Karst hills

The profile distribution characteristics of soil organic carbon (SOC) content and density in three secondary forests communities (Alangium chinensis, Rhus chinensis and Vitex negund) in depressions between Karst hills in southwest China were in vestigated. The results show that there are significant correlations (p0.01) between soil organic carbon contents and root contents in the three communities. The average soil organic carbon contents and densities are different in the layers from 010 cm to 5060 cm of the three communities, and both of them are in the order of Vitex negundo Alangium chinensis Rhus chinensis. Soil organic carbon contents and densities in the three forest types are decreased with the increase of soil depth, and there is a good liner relationship between them. The maxima of soil organic carbon and density are likely in 010 cm soil surface layer. The significant or highly significant differences are found in both soil organic carbon contents and densities between 010 cm soil layer and other layers in the same forest community, while no significant differences are found among other layers. Soil organic carbon contents and densities are in the order of Vitex negundo Alangium chinensis Rhus chinensis communities in the same soil layers of different forest communities. The soil organic contents of 1040cm soil layers and soil organic carbon densities of 2030cm soil layers of Rhus chinensis community are significantly lower than those of the other two communities. Therefore, reasonable vegetation restoration plays a key role in improving regional ecological reconstruction and carbon storage in degraded ecosystems in depressions between Karst hills in southwest China.