Spatial-temporal dynamic features and tendency of the topsoil organic carbon in integrated rehabilitating karst rocky desert

Taking the Guizhou Province, a representative karst area, for example, three typical demonstration areas for integrated rehabilitation to karst rocky desertification is chosen in the study. Based on the field monitored data in April 2006 and repeated sampling data in April 2009, the spatial-temporal dynamic characteristics of the topsoil in fragile environment under integrated rehabilitating is analyzed. The result proves the following items. After 3 years rehabilitation, the increase in topsoil organic carbon density at different plots of different desertification grades is different with each other. The amount of the increase in topsoil organic carbon density at mild and moderate rocky desertification plots is the largest, inconspicuous or potential rocky desertification plots is the second, and the serious rocky desertification is the smallest. Organic carbon density of the topsoil under different engineering measures manifests as: closed treatment ＞ recovering farmland to forests and grassland ＞ the project of transforming slope to terrace. While the growth manifests as: recovering farmland to forests and grassland ＞ closed treatment ＞ the project of transforming slope to terrace. Along with the decreases in land area of mild rocky desertification grade or more seriously desertification grade, the carbon storage of the topsoil increases further, and the carbon storage of the topsoil mainly exists in potential rocky desertification plot or not deserted region. The growth trend of topsoil organic carbon density perhaps presents the “S” pattern along with the rehabilitation, but the organic carbon density of topsoil in inconspicuous and potential rocky desertification plots will keep steady state in a long time for those lands are the basic farmland generally. At the mild and moderate rocky desertification plots, the increase in topsoil organic carbon density is the largest in early rehabilitation stage. So take effective methods of land use and strengthen sustainable management is of extremely vital significance in improving the carbon sequestration.