[Carbon density and its spatial distribution in Quercus acutissima plantations under different thinning intensities]

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 x 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.