CAS Workshop on Ecosystem Succession Theory and Practice of Ecological Restoration

（中国科学院华南植物研究所，广东肇庆鼎湖山树木园 526070）

摘要：本文研究了鼎湖山南亚热带森林同一演替系列中三个不同演替阶段（马尾松针叶林、马尾松荷木混交林和季风常绿阔叶林）生态系统碳贮量和分配格局特征，并探讨了该地区森林生态系统碳吸存在其演替过程中的潜力和速度。结果表明：1）马尾松林各组分碳素含量高于季风常绿阔叶林对应组分的碳素含量（后者是前者的72.0~94.5%）；两林分，不同层次比较，植物碳素含量均为：乔木层 > 灌木层 > 草本层，不同器官比较，碳素含量以根或干最高。2）乔木层生物量随森林演替进展而增加。马尾松针叶林、马尾松荷木混交林和季风常绿阔叶林乔木层生物量分别为：143.5、270.1和407.82 t.hm^-2，其中大部分由干和皮组成，各器官占乔木层生物量的平均比例为：叶2.8％、枝19.3％、干和皮混合57.0％、根20.9％。林下层生物量为4.23~14.10 t.hm^-2，是乔木层的1.0~9.8%，但随森林演替进展而减少。3）土壤容重随深度增加而增加，但随森林演替进展而减少。与土壤容重相反，土壤有机碳含量随深度增加而明显减少，但随森林演替进展而增加。4）3个森林生态系统碳总贮量分别为135.76、213.99和261.20t.hm^-2。生态系统碳贮量在各组分的格局十分相似，植被、土壤和凋落物层所占比例均分别约为67.6％、30.2％和2.2％。与其它地带森林比较，鼎湖山保护区森林植被与土壤碳贮量之比和表层（0~20cm土层）的土壤碳占整个土层的比例都较高。5）南亚热带生态系统碳吸存潜力随森林演替进展增长巨大。马尾松林发展到混交林，生态系统吸存碳量为78.23 t.hm^-2，演替到阔叶林则为125.44 t.hm^-2，其中大部分分配在植被层（69.0~72.1%）。马尾松林演替到混交林过程中，植被碳积累速度为0.83~7.37 t.hm^-2.a^-1，平均2.48 t.hm^-2.a^-1。

关键词：森林演替；碳贮量；碳吸存；南亚热带；鼎湖山保护区

Role of forest succession on carbon sequestration of forest ecosystems in lower subtropical China

(South China Institute of Botany, Chinese Academy of Science, Dinghushan, Zhaoqing, Guangdong 526070, China)

Abstract：There is the potential to reduce carbon sources and increase carbon sinks from management of the world�s forests. Carbon emissions from forests can be reduced by protecting and conserving the carbon pools in existing forests. Carbon sinks can be created by expanding carbon storage capacities through increasing the area and/or carbon density of native forests, plantations and agroforests. With the implement of Natural Forest Protection Program and Forest Reservation Project in the near future, it can be predicted that Chinese forest ecosystems will act as a huge carbon sink. However, there is little information available about carbon sequestration on forest ecosystems, especially on forest ecosystems of subtropical China.

This research was conducted in Dinghushan Biosphere Reserve (DHSBR), which is located in lower subtropical China. There are mainly three types of forest, including pine forest (PF), pine and broadleaf mixed forest (PBMF), and monsoon evergreen broadleaf forest (MEBF), which represent three stages of a series of forest succession. The carbon storage and its distribution pattern in these forest ecosystems were studied, and the potential, rate and allocation of carbon sequestrated by forest ecosystems in Dinghushan based on this study were also discussed in this paper. Results showed as follows:

1) The mean carbon concentrations of vegetation decreased with the development of Pine Forest ecosystems. Carbon concentrations for plant organs except for leaves were generally 20 percent higher in pine forest than those in monsoon evergreen broadleaf forest. Both pine forest and monsoon evergreen broad-leaves forest, carbon concentrations were significantly higher in tree layer than those in other layers comparing with different layers, and generally highest in root or branches comparing with different organs.

2) Biomass of tree in the studied forests increased with development of forest succession, and was estimated to be (t.hm^-2): 143.5 (PF), 270.1 (PBMF) and 407.82 (MEBF). This biomass was mainly distributed in the component of stem and bark. The percentages of different organs accounted for tree biomass were: 57.0% stem and bark, 20.9% root, 19.3% branch, 2.8% leaves, respectively. Biomass of understory plant was 4.23~14.10t.hm^-2, decreasing with development of forest succession. Similar to biomass of understory, standing stock of litters on the forest floor decreased with development of forest succession, ranging from 3.92 to 10.91t.hm^-2.

3) Soil bulk density was 0.86~1.54g.cm^-3, and increased generally with depths (1.07, 1.25, 1.30 and 1.30 g.cm^-3 for 0~10, 10~20, 20~40 and 40~60 cm soil depth, respectively) in all forests. Soil bulk density in all levels of soil depths in pine forest were similar to those in pine and broadleaf mixed forest, however, in both forests they were higher than those in monsoon evergreen broadleaf forest. Soil carbon concentrations in all forests decreased with soil depths (2.23, 1.13, 0.71 and 0.49% for 0~10, 10~20, 20~40 and 40~60 cm soil depth, respectively) and exhibited the order of monsoon evergreen broadleaf forest > pine and broadleaf mixed forest > pine forest.

4) The total carbon storage of three forest ecosystems was estimated to be (t.hm^-2): 135.76 (PF), 213.99 (PBMF) and 261.20 (MEBF), of which 67.6 percent was contributed by vegetation, 30.2 percent by soil, and only 2.2 percent by standing litters on the floor. Comparing with other similar forests, the carbon storage in vegetation was relative higher in the studied forest, the carbon storage in soils, however, was relatively lower in the studied forest. The ratio of vegetation carbon to soil carbon in these forests was very high (2.2), comparing with the average value for Global forest and Chinese forest (0.46 and 0.36, respectively). In addition, the proportion of carbon storage in the upper soil (0~20cm) to that in the whole soil in the studied forests was also higher, comparing with comparing with the average value for Global forest and Chinese forest.

5) The carbon sequestration increased significantly with development of forest succession in lower subtropical China. Carbon storage would increase by 58 percent (from 135.76t.hm^-2 to 213.99t.hm^-2), if pine forest developed to pine and broadleaf mixed forest by succeeding, and would increase by 92 percent (from 135.76t.hm^-2to 261.20t.hm^-2). In Dinghushan forests, the rates of carbon sequestration increment was estimated ranging from 0.83 to 7.37 t.hm^-2.a^-1, with a mean value of 2.48 t.hm^-2.a^-1, during the period from pine forest to pine and broadleaf mixed forest by succeeding.

Key words：forest succession; carbon storage; carbon sequestration; lower subtropical China; Dinghushan Biosphere Reserve

基金项目：国家自然科学基金项目（30270283）、中国科学院知识创新工程领域前沿项目、中国科学院华南植物研究所所长基金项目和广东省自然科学基金项目（021524）资助。

张佑昌、莫定升等同志参加部分野外工作，在此一并致谢。