Distribution of Organic Carbon in Soil Aggregates from Four Kinds of Forest Vegetation on Jinyun Mountain

: This study was intended to explore the distribution and stability of soil aggregates and the organic carbon for different forest types and to provide a scientific basis for the efficient management of soil carbon pools in subtropical forest ecosystems. Four subtropical forest types, including bamboo forest, broad-leaf forest, coniferous forest, and a mixed coniferous and broad-leaf forest on Jinyun Mountain (Chongqing Municipality), were selected as research subjects to explore the distribution of soil aggregates and organic carbon in different layers (depths of 0-20, 20-40, 40-60, and 60-100 cm). The results showed:The content of >2 mm aggregates and mean weight diameter (MWD), geometric mean diameter (GMD), and >0.25 mm aggregate content (R0.25) in broad-leaf forests decreased with soil depth, while other forests did not have a similar distribution pattern. In each soil layer, bamboo forest soils were mainly composed of >2 mm fractions of aggregates, which made up 30.73%-53.08% of the total content; The content of 2-0.25 mm particle size aggregates of broad-leaf and mixed forest soils was higher than that for other sizes, and its content ranged from 36.27% to 44.67% and 48.69% to 52.44%, respectively. The 2-0.25 mm and 2 mm fraction of bamboo forest aggregates was as high as 27.44%-53.47%. Broad-leaf forests and mixed forests had the highest contribution to the organic carbon of the 2-0.25 mm fractions of soil aggregates. Among the four forest types on Jinyun Mountain, the soil aggregates in bamboo forest have better stability, but the stability of aggregates in coniferous forests is poor. In each soil layer, the content of bamboo forest organic carbon in the various aggregates was the highest, and that of coniferous forest was the lowest.