近自然化改造提高松杉人工林土壤有机碳的作用机制

近自然化改造被视为针叶人工林多目标经营的主要措施之一，其间伐、补植为主的改造过程引起的林分结构及多样性变化，进而影响人工林土壤碳固持过程。项目组前期研究发现马尾松（Pinus massoniana）和杉木（Cunninghamia lanceolata）人工林近自然化改造后，显著增加了土壤有机碳，但近自然化改造增加土壤有机碳的机理仍不明确。本研究拟以广西友谊关森林生态系统定位观测研究站为平台，选取松杉近自然改造林和未改造纯林为研究对象，利用13C同位素示踪地上、地下凋落物分解过程，深入分析不同林分土壤有机碳的组成特征，揭示改造引起的凋落物、细根的组成和质量、土壤微生物群落组成及土壤呼吸的变化规律，阐明这些变化与土壤有机碳及其组成差异的内在联系。项目为理解近自然化改造对针叶人工林土壤有机碳影响规律提供一个系统研究案例，为南亚热带人工林生态系统碳管理及多目标经营提供理论依据。

Close-to-nature silviculture is regarded as one of the main measures for multi-objective management of coniferous plantations. The silviculture process should be affected in regard to stand structure and biodiversity, as well as soil carbon fixation process. Previous studies found that the close-to-nature silviculture enhanced soil organic carbon in plantations of both Pinus massoniana and Cunninghamia lanceolata in south subtropical region. However, the mechanism on the enhanced soil organic carbon is unclear. Therefore, this study is carried at Guangxi Youyiguan forest ecosystem research station, and selected close-to-nature managed forests of P. massoniana and C. lanceolata and their unmanaged plantations, using 13C-labeled tree litter to track the process of litter decomposition and analyze soil organic carbon composition in different stands. It aims to reveal the silviculture induced changes in composition and quality of litter and root, composition of soil microbial community, and soil respiration, and also to elucidate the internal relationship between these changes and soil organic carbon. The project will not only provide a systematic case study to understand the impact of close-to-nature silviculture on soil organic carbon in coniferous plantations, but slso provide scientific basis for carbon management and multi-objective management of plantations in south subtropical region.