Abstract: An investigation was made on the soil total organic carbon (TOC), water-soluble organic carbon (WSOC), readily oxidizable carbon (ROC), and their correlations with soil basic physicochemical properties in different age Chinese fir plantations in south Jiangsu. With the increasing age of the plantations, soil TOC content increased after an initial decrease, being the highest in over-mature stand and the lowest in middle-age stand. Soil WSOC and ROC contents had the same variation trend as soil TOC, and the WSOC/TOC and ROC/TOC ratios had no stable variation. There existed significant correlations between WSOC and ROC and among these two labile organic carbons and TOC, TN, and C/N, but no significant correlations between the labile organic carbons and soil total S, moisture content, pH, and bulk density. However, the correlations were not identical in the different age plantations. The soil organic carbon in different age Chinese fir plantations might play different roles in the carbon cycling of the forest ecosystem.

Key words: Patch, Boundary, Sandy landscape, Mu Us sandy land