Three main forest types,manmade forest,secondary forest,and primary forest,were chosen to study sites in karst calcareous soil of southwest of China.Eighteen sample plots of 20 m×20 m were established based on six representative communities.Soil aggregation samples were collected as different particle sizes and separated by dry sieving and wet sieving.Then,composition of machinery-stable aggregation and water-stable aggregation,distribution of total organic carbon,and organic carbon in aggregation were analyzed.The results showed that:(1)Soil machinery-stable aggregations and water-stable aggregations of three type forests were dominated by >2 mm particle size,and the proportion were 67.93%~81.24% and 30.49%~76.81%,respectively.The proportion of 1~10 mm size in machinery-stable aggregation and water-stable aggregation were 78.18%~88.67% and 43.41%~84.00% respectively.(2)The stability of all particle size aggregates were perfectly.The mean weight diameter (MWD) and the mean geometric diameter (GMD) of machinery-stable aggregations were 4.82~5.77 and 2.87~4.17,respectively;the MWD and GMD of water-stable aggregations were 0.75~2.13and 1.45~2.85.Percentage of aggregation destruction (PAD) of >0.25 mm and >2 mm particle size aggregations were 6.15~20.91 and 2.04~52.79,respectively.(3)There is high organic carbon content in the calcareous soil.The content of total organic carbon,organic carbon contents of machinery-stable aggregation and water-stable aggregation were 17.28~58.85 g/kg,19.12~91.47 g/kg and 17.16~78.86 g/kg,respectively.The content of organic carbon in machinery-stable aggregation were dominated by <2 mm particle size,while these of water-stable aggregates reverse.Organic carbon storage in >2 mm aggregations were the highest in all size fractions of machinery-stable and water-stable aggregation.Therefore,with soil disturbance decreasing along the manmade forest,secondary forest and primary forest,soil aggregation and stability and organic carbon content in calcareous soil showed an upward trend.