中文摘要：

研究岩溶区与非岩溶区土壤有机碳及其与养分之间的关系异同,有利于揭示岩溶区土壤有机碳的积累机制。以广西桂林毛村岩溶试验场为采样点,采集岩溶区、混合区和非岩溶区典型水稻田、柑橘园和玉米地的表层土壤,采用常规方法测定土壤有机碳、养分和特征元素含量并分析它们之间的相关性。结果显示,3种土地利用方式下,岩溶区土壤有机碳、全氮、pH和交换性Ca^2＋均显著高于非岩溶区。岩溶区水稻田中土壤溶解性有机碳和碱解氮含量显著低于非岩溶区,而土壤阳离子交换量和交换性Mg^2＋却显著较高。但是,这4个指标在柑橘园和玉米地中无显著差异。统计结果显示,3种土地利用方式下,土壤全氮含量与土壤有机碳含量呈极其显著正相关（p〈0.01）;就水稻田土壤而言,土壤有机碳与阳离子交换量和交换性Ca^2＋分别呈极其显著正相关（p〈0.01）和显著正相关（p〈0.05）。以上研究结果表明：较高pH、全氮和交换性Ca^2＋含量是维持岩溶区较高土壤有机碳含量的重要因素,而3种土地利用方式中水稻田土壤有机碳积累量最高。

英文摘要：

The study reveals the accumulation mechanism of soil organic carbon （ SOC ） in karst region through comparing SOC and its relationship with nutrients between karst area and non-karst area. Soil samples in paddy field, citrus orchard and maize fields were collected from karst area, mixed zone and non-karst area in Maocun karst experimental site in Guilin. Contents of SOC and nutrients were detected using conventional methods and their correlations were also analyzed. The results show that contents of SOC, TN, pH and exchangeable Ca^2 ＋ in karst area were significant higher than that in non-karst area under three land-use types. There were significant lower contents of dissolved SOC and alkali-hydrolyzale nitrogen, but higher contents of cation exchange capacity （CEC） and exchangeable Mg^2＋in paddy fields in karst area than that in non-karst area. However, the above four indicators in citrus orchard and maize fields show no significant differences among the three areas. Statistics show that a significant positive correlation （p 〈 0. 01 ） was found between SOC and TN under three land-use types. There was also a significant positive correlation among SOC and CEC （p 〈0. 01） and exchangeable Ca^2 ＋ （p 〈0. 05） respectively in paddy fields. These results indicate that higher contents of pH, TN and Ca^2 ＋ were important factors in maintaining higher SOC content, and the amount of SOC accumulation in paddy field was highest under three land-use types in karst area.