中文摘要：

选择中国南方亚热带地区具有不同地质背景和生态状况的广西柳州市官村地下河（灌木林生态环境、人类活动影响显著）、云南省广南县木美地下河（石漠化严重）和贵州茂兰板寨地下河（原始森林生态）3个岩溶水系统为例,对比研究岩溶水中溶解无机碳浓度和碳汇效应的差异。结果表现,（1）流域管道水的溶解无机碳平均浓度排列顺序为：官村〉木美〉板寨,表层岩溶带泉水的排列顺序为：木美〉官村〉板寨。（2）水的PCO2分压计算结果显示：3个流域岩溶水的方解石溶解度基本达到饱和,PCO2的大小顺序为：官村地下河〉木美地下河〉板寨地下河。（3）根据一个水文年的流量监测计算官村地下河流域的岩溶碳汇强度为12.34tC/（km2.a）,板寨地下河流域的为11.8tC/（km2.a）,木美地下河流域为34.11tC/（km2.a）。木美地下河流域的石漠化现状相当严重,石漠化面积高达90%,而板寨地下河为原始森林区,但木美地下河流域的岩溶碳汇强度却最大,这与其流域面积大、调蓄功能强,且有外源水补给有关。这也同时表明,单从生态环境的角度去研究岩溶作用碳汇潜力是不够的。

英文摘要：

Testing the CO2-C content released from the soil is the way to study the mineralization rate of the soil organic carbon（SOC）.Thus,we collected soil samples from farmland,shrub land and forest in Maocun karst area in Guilin,and incubated in the laboratory in the dark at 25 ℃ with a constant moisture of 75 % during 90 days,then analyzed the amount of cumulative CO2-C released over 90 days to study the difference of SOC mineralization rate under different land use types.It was found that the mean concentration of CO2-C（gCO2-C·kg-1soil·90d-1） from SOC mineralization in farmland was 62.9% and 56.6 % lower than those in the shrub land and forestland respectively.Meanwhile,the chemical structure of soil organic carbon pool in above-mention land use types is studied.The SOC pool are divided into three pools,that is passive-,slow-,and ative-organic carbon pool.Firstly,using acid hydrolysis（6M HCl） to fractionate passive organic carbon,then separate active and slow carbon pools and calculates their decomposition rate and residence time with the ＂three-pool first-order model＂.The results showed that active carbon pool（Ca） comprised 1.82 % to 2.71 % of the SOC,with an average mean residence time（MRT） of 8.4 to 16.3 days,while slow carbon pool comprised 33.91 % to 45.47 % of the SOC,with an MRT of 4.8 to 7.7 years,and passive carbon pool comprised 51.82 % to 64.01 %,with an assumed MRT of 1 000 years.Finally,the chemical structure of the organic carbon was analyzed by solid state 13C via polarization magic angle spinning nuclear magnetic resonance（13C CPMAS NMR）.The results showed that,in comparison to the shrub and forest lands,the proportion of alkyl C and aromatic C in farmland which suffered more human disturbance increased,while the proportion of O-alkyl C and O-alkyl C decreased.Both the order of alkyl C/ O-alkyl C and hydrophobic C / hydrophilic C are farmland 〉 forestland 〉 shrub land,while the order of aliphatic C/aromatic C was the opposite.This shows that SOC in farmland has high