Abstract: Quercus acutissima is a tree species widely planted in Jianghuai hilly lands. In this study, the Q. acutissima plantations after five years of different thinning [15% (T₁₅), 30% (T₃₀), 50% (T₅₀) and unthinning (CK)] were selected, and a sampling plot investigation was made to analyze the carbon density and its spatial distribution in these plantations. In treatments T₁₅, T₃₀ and T₅₀, the tree carbon density  increased by 9.1%, 29.6% and 28.4%, respectively, as compared with CK. The carbon density in tree organs was in the order of stem > root > branch > bark > leaf. With increasing thinning intensity, the carbon density in litters decreased while that in 0-50 cm soil layer had a slight increase, but no significant difference was observed between thinning and unthinning. The total carbon density of the Q. acutissima stands under different thinning intensities was in the order of T₃₀> T₅₀> T₁₅> CK, with an increase of 16.3, 14.5 and 3.6 t C·hm^-2 in treatments T₁₅, T₃₀ and T₅₀, respectively, as compared with CK, but there were no significant differences among the treatments. In treatments T₁₅, T₃₀ and T₅₀, soil respiration was also higher than that in CK, and the difference was significant between treatments T₃₀ and CK. Overall, thinning was helpful to the enhancement of carbon storage in theQ. acutissima plantations in Jianghuai hilly lands, and 30% thinning could be the best.

Key words: Quercus acutissima, thinning, carbon density, biomass.