Soil organic carbon,
particulate organic carbon(POC),
light fraction organic carbon(LFOC),organic carbon contents in the different
particles fractions,contents of water-stable aggregates and soil organic matter contents in aggregates obtained with dry sieving method under different karst ecosystem such as natural forest,shrub and monoculture plantations were studied to elucidate their characteristics and correlations between each other quantitatively in this paper.The results showed that in 0~10 cm soil surface layers,the content of POC in shrub-grass soils was as much 1.40 times as that in natural forest,and the content of LFOC was as much 4.02 times as that in natural forest.With the depth increase of soil layers,the proportion of POC and LFOC in soil profile in natural forest was higher than that in shrub-grass,and only bigger soil aggregates from the shrubbery tendered to contained soil organic matter.The enrichment factors of soil organic carbon of particle fractions under 2 land use types,which size were below <0.05 mm,differentiated a little,but particle fractions(>0.1 mm and 0.1~0.05 mm)had a significant difference between natural forest and monoculture plantations,particularly in the soil surface layers.There were positive correlations among these indexes,particularly a significant positive correlation between LFOC and POC.