Impact on soil CO2 concentration by the changes of land use and vegetation cover in karst area

Three watersheds, the Mapao-Guozhuang Spring Catchment in Fenyang, Shanxi Province, the Dalongdong Underground River Watershed in Xiangxi, Hunan Province and the Guijiang Watershed in Guangxi Province, with different geologic and climatic conditions are selected as the study areas. Those three watersheds represents different typical land use type and vegetation cover. Their soil CO2 concentrations at 20～50cm depth under the ground are tested. The results prove that the change of land use and vegetation cover affects intensely on soil CO2 concentration from 20 to 50cm depth. Many plots in the Dalongdong Underground River Watershed show the character of Bidirectional gradient, which means that along with depth, CO2 concentration rises at first, but begins to reduce from 40cm deep downwards. In the Mapao-guozhuang Spring Catchment, soil CO2 concentration in the corn fields is higher than that in the potato fields. With vegetation condition improving from grass to shrub and to forest, soil disturbance gets less, the distinctions of CO2 concentration become smaller and the variation scope tends to stable. In every study watersheds, between the same vegetation cover patterns, the less the change in community structure and dominant species, the less variation scope of soil CO2 concentration.