亚热带常绿阔叶林甲烷通量对植物多样性响应的生物学机制

Forest ecosystems act as atmospheric CH4 sink which is one of the most important forest ecosystem functions. In this project, we will select a long-term plant diversity experimental site (Biodiversity Ecosystem and Functioning – China, i.e. BEF-China) in a subtropical evergreen broadleaved forest in Jiangxi province, China. At the experiment site, we will conduct 2-year in situ CH4 flux measurements in soils and tree trunk, differentiate relative contributions of CH4 oxidation capacity by methanotroph and CH4 production by methanogen to CH4 flux using 13C- CH4 in soils of different plant diversities. We will seasonally collect soil and litter samples to measure activities of methanotroph and methanogen using incubation. In addition, we will also analyze community structure and diversity of methanotroph and methanogen using real-time PCR and high-throughput sequencing. More importantly, we will design a new ethylene-based fluorescent probe to detect dynamical changes in high-afffinity methanotrophic community in soils of different plant diversities in combination with flow cytometer and single-cell metagenomic sequencing. Based on these work, we will illustrate how CH4 efflux may respond to plant diversity via different pathways in this subtropical. We will establish plant diversity - methanotroph/methanogen activities - CH4 efflux model to quantify the relative contributions of different pathways to CH4 efflux. Our results will be useful for predicting how CH4 efflux may change to plant diversities in the scenario of plant diversity losses in this subtropical evergreen broadleaf forest in the future.

森林是大气甲烷汇，其大小是森林生态系统重要的功能指标。本项目拟以亚热带常绿阔叶林为研究对象，依托江西新岗山的中国亚热带森林生物多样性与生态系统功能实验研究(BEF-China)平台，通过为期2年的土壤、植物树干原位甲烷观测，以及原位13C-CH4示踪区分土壤甲烷氧化菌氧化大气甲烷量以及产甲烷菌产生的内源性甲烷量；并进行季节性土壤样品采集和室内培养实验，测定土壤甲烷氧化菌、产甲烷菌活性及其群落结构和多样性。此外，运用乙烯荧光标记分子结合流式细胞仪和单细胞基因组测序明确高亲和性甲烷氧化菌群落结构的动态变化；从机理上综合阐述亚热带常绿阔叶林甲烷通量对植物多样性的响应，构建植物多样性-甲烷氧化菌/产甲烷菌活性-甲烷通量模型，量化各途径对甲烷通量的相对贡献率，预测未来植物多样性丧失情景下亚热带常绿阔叶林甲烷通量的变化。

森林是大气甲烷汇，其大小是森林生态系统重要的功能指标。本项目以亚热带常绿阔叶林为研究对象，依托江西新岗山的中国亚热带森林生物多样性与生态系统功能实验研究(BEF-China)平台，通过为期3年的原位甲烷通量观测，结果表明植物多样性促进了森林甲烷汇，其机制在于：(1)植物多样性促进了甲烷氧化菌底物——可溶性碳氮含量，进而提高了甲烷氧化菌活性；(2)植物多样性对产甲烷菌活性没有显著影响；这与植物多样性下产甲烷菌、甲烷氧化菌群落结构和多样性变化相一致。基于13C-CH4同位素标记和高通量测序，我们发现甲烷氧化菌的优势类群是II甲烷氧化菌。此外，我们构建了植物多样性-土壤-甲烷通量新模型，量化了各因子对甲烷通量的相对贡献率，模型估算结果表明，在中国和全球尺度上，亚热带森林甲烷汇均随植物多样性增加而增加。这些研究结果为亚热带森林植物多样性保护和甲烷增汇提供了理论依据。