Abstract: In the present study, we investigated the decomposition dynamics of the fine roots of Castanopsis carlesii and Cunninghamia lanceolata in both a Ca. carlesii forest and a Cu. lanceolata plantation. From a 2-year experiment, we found the following: (1) Fine roots of Ca. carlesii decomposed faster in its own forest than in a Cu. lanceolata plantation. The decomposition rate of fine roots of 0-1 and 1-2 mm-diameter classes of Ca. carlesii in its own forest was 2.0 and 4.7 times faster, respectively, than that in the Cu. lanceolata plantation. (2) The decomposition dynamics of fine roots of both diameter classes of Cu. lanceolata varied greatly between its own plantation and a Ca. carlesii forest. The decomposition rate of 0-1 mm fine roots of Cu. lanceolata in its own plantation was 1.5 times faster but for 1-2 mm roots only 0.48 times faster than that in a Ca. carlesii forest. These findings suggest that specific forest soil may have a strong effect on fine-root decomposition.