1. 1.广州大学地理科学学院,广东 广州 510006
2.中国科学院华南植物园,广东 广州510650
• 出版日期:2016-01-20
• 通讯作者: 张德强 E-mail:xmchen@scib.ac.cn;zhangdeq@scib.ac.cn

### Variations in the Fractions and Stabilization of Soil Organic Carbon with Forest Succession in Southern China

Xiaomei Chen 1( ), Junhua Yan 2, Meizhen Lin 1, Guowei Chu 2, Jianping Wu 2, Deqiang Zhang 2( )

1. 1.School of Geographical Sciences, Guangzhou University, Guangzhou 510006, China
2.South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
• Online:2016-01-20 Published:2016-01-10
• About author:

First author: Chen Xiaomei(1985-), female, Nan'an City, Fujian Province, Lecture. Research areas include responses of forest ecosystems to global changes. E-mail: xmchen@scib.ac.cn

Corresponding author: Zhang Deqiang (1963-), male, Huizhou City, Guangdong Province, Professor. Research areas include the relationship between global change and ecosystems. E-mail: zhangdeq@scib.ac.cn

• Supported by:
Project supported by the National Natural Science Foundation of China "Responses of soil organic carbon fractions to precipitation patterns change in a subtropical zonal forest in southern China" (No.31400415);Education Department of Guangdong Province "Mechanism of soil carbon accumulation in subtropical forests along an urban-to-rural gradient in Southern China"(No.2014KQNCX110)

Soil Organic Carbon (SOC) fractions play a critical role in the stabilization of SOC. It is essential to clarify the variations in SOC fractions along forest succession for predicting soil carbon (C) source/sink capacity as forest develops. In the present study, we collected and analyzed soil samples in Total Organic Carbon (TOC) content and the concentration of its Readily Oxidizable Organic Carbon (ROC) and Non-Readily Oxidizable Organic Carbon (NROC) fractions in a Pine Forest (PF), a pine and broadleaf Mixed Forest (MF), and an old-growth monsoon evergreen Broadleaf Forest (BF) in the subtropical China. The three forests represent different successional stages of forest in southern China, with the PF being at the early, the MF at the middle and the BF at the climax stages, respectively. To clarify the reasons for why SOC fractions changed with forest succession, litterfalls in these forests were also collected to assay C functions by means of 13C Nuclear Magnetic Resonance (NMR) analysis. Results showed that although there was no significant difference in the content of ROC among the three forests, the ratio of ROC to TOC in the PF was significantly higher than that in both of the BF and MF. This was likely due to the higher content of O-alkyl C in fresh litter in the PF than in the other two forests. Unlike ROC, however, NROC content was the highest in the BF, followed by the MF and then PF, which could be attributed to the lower recalcitrance index in the partly-decomposed and decomposed litterfall layers in the PF than in the MF and PF. Finally, TOC concentration was significantly the highest in the climax BF, the lowest in the youngest PF, and in between in the MF. Our results suggest that the accumulation of NROC, which is the recalcitrant fraction of SOC, may be the major reason for why forests at the middle and late stages (i.e., the MF and BF, respectively) maintain higher TOC content and Organic Carbon (OC) stabilization in soils.

Table 1 Vegetation characteristics and soil properties of three forests at Dinghushan

Fig. 1 The soil TOC,ROC and NROC in three forests
Bars are means and error bars are standard deviations. Means with different letters are significantly different among the forest types in each soil layer in each panel

Table 2 The percentages of ROC to TOC at three forest types (unit:%)

L: 未分解层, Fresh litter layer;F:半分解层, Fermentation layer;H:已分解层, Humus layer
Fig. 2 Distribution of C functional groups in the forest floor layers among the three forests(unit:%)

Table 3 The recalcitrance index in the forest floor of three forests(unit:%)