中文摘要：

为探明喀斯特生态脆弱区土地利用方式转变对土壤有机碳的影响,以贵州省不同海拔梯度下的草地及其相应开垦的农田为研究对象,采用成对设计的方法研究了不同海拔梯度下草地、农田的有机碳特征及草地生态系统类型转变对土壤有机碳的影响。结果表明：研究区草地、农田土壤体积质量随土层深度增加显著升高（P〈0.05）,增幅为17.85%～45.74%,草地转变为农田后土壤体积质量均显著增加,增幅为5.09%～10.88%。研究区草地、农田土壤有机碳含量随土层深度的增加而显著降低,表层（0～10cm）土壤有机碳含量占整个研究区（0～50 cm）的54.93%,呈表层富集现象.草地生态系统类型转变导致整个研究区土壤有机碳含量显著下降,降幅为19.64%～57.12%,且降幅随着海拔高度的增加而增大;草地转变为农田使土壤有机碳密度下降,降幅12.22%～50。73%。

英文摘要：

The influence of land use shift on soil organic carbon was investigated in karst ecological fragile using paired design method with the grassland and their corresponding reclaimed farmland under different altitudes in Guizhou Province as the research object.The results showed that soil volume mass in studied area was significantly raised with the soil depth increasing（P〈0.05）,the amplification was 17.85%～45.74%.The soil volume and mass increased significantly after the grassland was transferred into farmland,and the amplification was 5.09%～10.88%.The soil organic carbon content significantly decreased with the soil depth increasing,and the soil surface（0～10 cm） organic carbon content was 54.93%in studied area（0～50 cm）,which appeared enrichment in surface soil.The shift on grassland ecosystem resulted in organic carbon content in the studied area decreased significantly,the decline was 19.64%～57.12%,and increased with altitude increasing.The grassland was transferred into farmland,which caused the density of soil organic carbon decreased,and the decline was 12.22%～50.73%.The study results provided references for a further understanding of ecosystem shift to global carbon cycle and regional land use.