Abstract: In order to study the dynamics of carbon density of typical forest communities in Xiangtoushan National Nature Reserve in Guangdong province (XTSNR), five 1-hm² forest ecosystem monitoring plots were constructed according to the vegetation type and age of the forest in XTSNR. The second censuses of the plots were conducted 5 years after the construction of the plots to analyze the changes of individual species, important values and carbon density within the plots. The results showed that: (1) With the natural restoration of the XTSNR forest, the individual density of the five plots increased significantly, and the individual density of the XTS-D plot increased the most (2356 plants·hm^–2), while that of the XTS-E plot of the coniferous and broad-leaved mixed forest increased the least (228 plants·hm^–2). (2) Compared with the initial census, the carbon density of XTS-A, XTS-B, XTS-C and XTS-D plots all increased, and the newly added carbon storage of mature forest XTS-D plots was the highest, with an increase of 22.41%. The carbon density of XTS-E mixed forest decreased by 9.23%. (3) The DBH class structures were different among the five plots; the middle DBH class (Ⅳ and V) contributed the most to the carbon storage of the mature forest XTS-A sample; large DBH class (Ⅸ) had the highest carbon storage in overmature forest XTS-B; the carbon storage of young and middle-aged trees (XTS-C and XTS-D) was mainly concentrated in trees of middle and small DBH classes (Ⅱ-Ⅳ). (5) The top 10 species of carbon density in the five plots were basically the same. Although Pinus massoniana in XTS-E plot was still a tree with high carbon density and important value, its individual number and important value decreased. Among the five plots, broad-leaved tree species showed the fastest increase in carbon density.

Key words: forest carbon density, plant community, important value, Xiangtoushan National Nature Reserve

摘要： 为研究广东象头山国家级自然保护区典型森林群落的碳密度变化特征，根据象头山森林的植被类型和林龄，建立5个1 hm²森林生态系统监测样地，并在样方建设后5年完成样地复查，分析样方内的物种组成、径级结构和碳密度变化。结果显示：(1) 随着象头山森林的自然恢复，5个样地的个体密度均有明显提升，XTS-D样地的个体密度增长量最大，为2356株·hm^–2，而针阔混交林XTS-E样地的个体密度增长量最低，为228株·hm^–2。(2) 与初次调查相比，样地XTS-A、XTS-B、XTS-C和XTS-D碳密度均有增加，其中成熟林XTS-D样地内新增碳储量最高，增幅达22.41%；针阔混交林XTS-E的碳密度有所下降，降幅达9.23%。(3) 不同林龄样地径级结构有所差异，中等径级(Ⅳ和V)对成熟林XTS-A样地的碳储量贡献最大；大径级(Ⅸ)在过熟林XTS-B中碳储量最高；而幼、中龄林(XTS-C和XTS-D)的碳储量主要集中在中、小径级树木中(Ⅱ～Ⅳ)。(4) 5个样地碳密度排行前10的树种基本一致，XTS-E样地的马尾松Pinus massoniana虽然仍是碳密度和重要值较高的树种，但其个体数和重要值都有所下降；5个样地中碳密度增长最快的均为阔叶树种。

关键词: 森林碳密度, 植物群落, 重要值, 象头山国家级自然保护区