中文摘要：

分析不同土地覆被方式土壤有机碳的差异和特点有助于深入研究岩溶区碳循环的特点和规律。以西南岩溶地区森林、灌丛和果园3种土地覆被方式为研究对象，对0~100cm各层土壤总有机碳及团聚体有机碳的差异和特征进行研究，结果表明：（1）3种土地覆被方式以森林土壤总有机碳含量最高（12.53~39.33g·kg-1），灌丛次之（8.48~27.99g·kg-1），果园最低（8.40~18.61g·kg-1），不同土地覆被方式土壤总有机碳不仅在0~20cm差异显著，而且在40~70cm土层也有明显差异（P<0.05）；各土地覆被方式0~100cm各层土壤均以>0.25mm水稳性大团聚体为主，果园土壤>2mm团聚体质量分数在0~90cm土层显著低于森林和灌丛（P<0.05）。（2）土地覆被方式对土壤>2mm大团聚体内有机碳含量的影响最为显著，森林土壤>2mm团聚体有机碳的含量为12.32~39.88g·kg-1，在0~100cm各层均显著高于灌丛和果园，并且灌丛土壤>2mm团聚体有机碳的含量在0~30cm和40~90cm土层也显著高于果园（P<0.05）。另外，果园土壤<0.25mm微团聚体内有机碳的含量明显高于>0.25mm大团聚体，然而森林0~100cm土层和灌丛0~30cm土层各粒级团聚体有机碳含量没有显著差异（P<0.05）。（3）3种土地覆被方式，>0.25mm大团聚体对土壤有机碳的贡献均高于<0.25mm微团聚体；森林、灌丛和果园0.25~2mm团聚体对有机碳的贡献率分别为40.31%~67.76%，41.99%~59.38%和48.72%~68.18%，是贡献率最高的团聚体；不同土地覆被方式之间>2mm团聚体对有机碳的贡献差异最为显著，森林土壤明显高于灌丛和果园；3种土地覆被方式中果园土壤<0.25mm微团聚体对有机碳贡献率相对较高，其0.053~0.25mm微团聚体对有机碳的贡献率为13.08%~26.98%，仅次于0.25~2mm大团聚体。

英文摘要：

Under the global climate change,land cover types,as one of the most important indicators that influencing thesequestration of soil organic carbon and the distribution of soil organic carbon in aggregates,have been increasingly focused on.Therefore,analysis of the effects of land cover on soil organic carbon is useful to study characteristics of the carbon cycle in Karst area.In this paper,content of soil organic carbon and the distribution of soil organic carbon in aggregates under the three land cover types(forest,shrub,and orchard field)were studied.Results showed that:(1)soil organic carbon content was obviously influenced by land cover types.The content of soil organic carbon was highest in forest(12.53~39.33g·kg-1),second in shrub(8.48~27.99g·kg-1),and the lowest in orchard field(8.40~18.61g·kg-1),with the significant difference in the0~20cm layers and40~70cm layers among the three land cover types(P<0.05).The content of macro-aggregate(>0.25mm)was higher than micro-aggregate(<0.25mm)in every layer of the whole soil profile(0~100cm).Stability of soil aggregates in forest and shrub was greater than that in orchard field.The content of macro-aggregate(>2mm)in0~90cm layers of orchard field soil was obviously lower than that of forest and shrub soil(P<0.05).(2)Soil organic carbon associated with aggregate also influenced by land cover types.The content of organic carbon associated with macro-aggregate(>2mm)under forest(12.32~39.88g·kg-1)was obviously higher than that of shrub and orchard field in every soil layer(P<0.05).And the content of organic carbon associated with macro-aggregate(>2mm)under shrub soil in0~30cm and40~90cm layers was significantly higher than that of orchard field.In addition,organic carbon content associated with macro-aggregate(>0.25mm)was lower than that of micro-aggregate(<0.25mm)under orchard field.However,there was no significant difference of the organic carbon content associated with aggregate among the different aggregate fractions of forest(0~100cm layer)and shrub soil(0~30cm l