中文摘要：

土地利用变化对岩溶地下水溶解无机碳（DIC）的影响关系到岩溶作用强弱及其相关的全球碳循环的正确评价。对贵州茂兰原始森林内的板寨岩溶地下河流域和普定岩溶石漠化强烈的陈旗、灯盏河泉域三种不同的土地利用下的地下水的DIC及其稳定同位素进行了分析，结果表明，地下水的DIC表现形式主要为HCO3^-。对于缺少土壤覆盖的板寨和灯盏河岩溶地区，雨季主要因为稀释作用，HCO3^-含量出现年内最低值；而对于较多土壤覆盖的陈旗岩溶地区，雨季主要受土壤CO2效应控制。HCO3^-含量出现年内最高值，反映了土壤在岩溶作用及其碳循环中的特殊重要性。此外，夏季由于生物量的增加，δ^13DIC值较冬季偏轻1‰～2‰。而对于不同土地利用而言，石漠化影响下的地下水δ^13DIC较原始森林下的地下水偏重2．5‰-3．0‰，且随着石漠化的发展，土壤的进一步流失，地下水δ^13DIC进一步偏重，反映了石漠化后生物量比例减少和大气成因CO2比例增加对地下水δ^13DIC升高的影响。

英文摘要：

Influences of land use change on the dissolved inorganic carbon （DIC） of karst groundwater has implications for estimating the intensity of karstifieation and the karst-related global carbon cycle. In this paper, DIC and stable carbon isotopic compositions of ground waters under three different land use conditions, which are Banzhai karst groundwater in the virgin forest of Maolan, Chenqi and Dengzhanhe spring waters in Puding County, where karst rocky desertifieation developed severely, were analyzed. The results show that the DIC of groundwater was mainly in the form of HCO3^-. Because of the dilution effect, the HCO3^- concentration was lower in rainy season for the Banzhai and Dengzhanhe karst areas with little soil cover. However, because of the stronger soil CO2 effect compared to dilution effect, the HCO3^- concentration was higher in rainy season for the Chenqi karst area with greater soil cover. This difference shows that soil cover plays a very important role in the karstification. In addition, the values of δ^13DIC in summer were 1‰ - 2‰ lower than those in winter due to larger biomass effect in summer.With respect to the effect of different land use, the δ^13DIC values of groundwater under areas with karst rocky desertification were 2.5‰ - 3.0‰ higher than those under virgin forest. With the development of karst rocky desertification, soil losses became more serious, and the δ^13DIC values of groundwater were getting higher. This reflects the combined effect of biomass reduction and more atmospheric CO2 input under karst rocky desertification, both of which increased the δ^13DIC values of groundwater.