入侵植物薇甘菊影响森林土壤碳吸存的微生物学机制研究

Exotic invasive plants are well known to change the coverage of terrestrial vegetations, which are likely to affect the assessing of ecosystem carbon stock. However, whether the invaded ecosystems are the "sink" or "source" of carbon stock is still unclear. No existing researches on possible reason, including climate differences in large scale and characters of specific invasive plants have supplied rational explanations to date. Soil microbes play a key role in determining the ecological outcomes in both plant invasions and soil carbon sequestration, while almost all the previous researches have neglected the bridge-functions of soil microbes between these two ecological processes. Based on our previous studies on the effects of invasive plants on soil microbial community, we hypothesized that differential extent of plant invasions would regulate soil microbes in biomass and construction as well as their respiration, etc., thus leading to the corresponding changes in soil carbon sequestration capacity of invaded forest ecosystems. Present project was designed to testify this hypothesis through field investigations and green-house experiments. The field investigations will be performed to examine the changes of soil carbon sequestrations and microbial characters, as well as their relationships, in Mikania micrantha invaded communities with different invasive extents in South China. The green-house experiments will be conducted to simulate different invasion extents and the key microbial groups that utilize 13C-marker and their PLFA-13C turnover rate will be detected using PLFA-SIP technology. Taken together, current research seeks to explore the effects of plant invasions on soil carbon sequestration from the view of bridge-functions of soil microbes. The results of this research may lead to increased understanding on the influence that plant invasions have on soil carbon sequestration and on how to more effectively manage existing and expanding invasive plants.

外来植物入侵改变地面植被覆盖，影响基于植被组成的碳储量估算。被入侵生态系统究竟是碳源还是碳汇至今仍未定论，有关气候因素和入侵植物个体特征的研究对此亦未能很好地作出解释。然而，以往的研究均忽视了土壤微生物在植物入侵和土壤碳吸存这两个生态过程中的桥梁作用。本项目结合申请者前期研究，提出不同入侵程度群落内土壤微生物的生物量、组成结构、呼吸等不同，因此植物入侵对土壤碳吸存的影响亦存在差异的新观点。通过野外研究华南地区受薇甘菊不同程度入侵群落内土壤微生物变化与土壤碳吸存变化之间的关系，结合温室栽培实验模拟不同入侵程度，利用磷脂脂肪酸谱图－稳定同位素示踪技术，分析吸收利用13C标记物的关键微生物类群及其PLFA-13C周转率，揭示植物入侵影响土壤碳吸存的微生物学机制。本项目紧密追踪生物入侵研究的发展动态，研究结果理论上有助于加深对植物入侵影响碳循环机理的认识，实践上可为有效防控植物入侵提供方法指导。

外来植物入侵改变地面植被覆盖，影响基于植被组成的碳储量估算。被入侵生态系统究竟是碳源还是碳汇至今仍无定论，有关气候因素和入侵植物个体特征的研究对此亦未能很好地作出解释。然而，以往的研究均忽视了土壤微生物在植物入侵和土壤碳吸存这两个生态过程中的桥梁作用。本项目在前期研究积累的基础上提出不同入侵程度群落内土壤微生物的生物量、组成结构、呼吸等不同，因此植物入侵对土壤碳吸存的影响存在差异的新观点。.本项目通过野外研究华南地区受薇甘菊入侵程度不同的群落内土壤微生物变化与土壤碳吸存变化之间的关系，结合温室栽培实验模拟不同入侵程度，利用磷脂脂肪酸谱图－稳定同位素示踪技术，跟踪13C标记物在植物、土壤和微生物之间的分配，并分析吸收利用13C的关键微生物类群，揭示植物入侵影响土壤碳吸存的微生物学机制。.野外研究结果表明，薇甘菊总体上增加土壤碳吸存，同时也受不同入侵程度群落内土壤其它参数和季节因素影响。在薇甘菊重度入侵的群落内，土壤有机质在表土最高，随土层加深逐渐降低；土壤的其它参数如铵态氮、酶类（过氧化氢酶、酸性磷酸酶和脲酶）等随深度变化明显，pH, 总氮、碱解氮和硝态氮等无明显变化。季节变化对表土有机质、pH影响显著，其中夏季和冬季的土壤有机质随入侵程度加深变化明显。温室内栽培实验表明薇甘菊光合吸收13C的能力强于本地植物，经光合吸收的13C在薇甘菊体内的转运速率，即从叶片到茎杆、从茎杆至根，从根至土壤均大于本地对照植物。随入侵程度加重，土壤微生物生物量增加，净13C％吸存速率随微生物量的增加而先增加后降低。光合吸收的13C主要被i15:0, 16:0, 10Me16:0, 18:1w9c和18:2w6,9五个PLFA组分所代表的微生物类群吸收；其中i15:0和10Me16:0所代表的微生物类群对短期（瞬时）的碳利用起主导作用，16:0，18:1w9c及18:2w6,9所代表的微生物类群对中长期碳利用起主导作用。.本项目首次将δ13C－PLFA技术用于研究入侵植物对生态系统碳循环的影响，探索了华南地区典型入侵植物薇甘菊影响土壤碳吸存的微生物机制，发现土壤微生物量与净13C吸存速率之间两个阶段的关系，合理地解释了为何目前植物入侵对土壤碳吸存的影响取得了不一致甚至相反的结论，我们的研究从理论上和实践上丰富和完善了入侵植物扩散对生态系统碳循环影响理论。