Abstract: To provide a basis for the eco-environment construction in karst mountain area, we examined the variation of soil labile organic carbon pool and carbon pool management index (CPMI) across different types of vegetation, including Cyclobalanopsis glauca secondary forest, shrub, Pinus massoniana forest, bamboo forest, grassland, cropland and bare land in the karst rocky mountain area of Northwest Guangxi. The results showed that: (1) Soil carbon storage and the contents of total nitrogen and available nitrogen in C. glauca secondary forest were significantly higher than that of the other plantations. Soil bulk density was lower than that of the other vegetation types except cropland. (2) The contents of soil organic carbon (SOC) and labile organic carbon (LOC) in all vegetation types decreased with increasing soil depth. The SOC content in 0-40 cm soil layer was 1.07-29.76 g·kg^-1, which decreased in the following order of C.glauca secondary forest > shrub >P.massoniana forest > bamboo forest > grassland > cropland > bare land. LOC content was 0.58-13.77 g·kg^-1, which decreased in the order of C. glauca secondary forest>shrub>P. massoniana forest>bamboo forest>cropland>grassland>bare land. The SOC/LOC was the lowest in the C. glauca secondary forest and highest in the cropland. (3) The CPMI decreased first and then increased, and decreased again with increasing soil depth. The mean value of CPMI in the 0-40 cm soil layer followed the order: C.glauca secondary forest>shrub>P. massonianaforest>cropland>bamboo forest>grassland>bare land. (4) Vegetation type, soil depth and their interaction had significant effects on CPMI and carbon pool characteristics. Our results indicate that soil organic carbon content and soil carbon pool stability could be improved efficiently by increasing vegetation cover and reducing disturbance from human activities in karst mountain area of North Guangxi.

Key words: coupled coordination., quality of population urbanization, quality of land urbanization