紫茎泽兰主效化感物质的微生物降解及其对入侵的影响机制

Allelopathy has been hypothesized to play a role in exotic plant invasions.The Novel Weapons Hypothesis argues that invaders may possess novel chemicals that are more phytotoxic to na?ve，native plants in the invaded range than to adapted species in the invader's native range. However, allelopathic effects can be highly conditional. For example allelopathic effects demonstrated in vivo can be difficult to demonstrate in field soils. Our previous research emphasized that soil biota can reduce the allelopathic effects of invaders on other plants. Meanwhile, allelopathic chemicals can change the composition and structure of soil microbial communities. With the methods of using microbial screening medium and high-throughput sequencing, this project aims to figure out and isolate the soil microbes which degrade allelochemials of Eupatorium adenophorum, and explore the regulation of soil biota on allelopathic effects of exotic plant species. Besides, with the method of high-throughput sequencing, we will test the influence of Eupatorium adenophrum allelopathic chemicals to the composition and diversity of soil microbial communities in the invaded area. This can help us assess how indirect plant interactions influence plant invasion process, and improve our understanding of the mechanism of biological invasions. The project can also increase our knowledge of invasive ecology theories, which will be helpful to the management and control of exotic plant invasions.

化感作用（Allelopathy）被认为在外来植物入侵过程中扮演了重要角色。"新武器假说"认为，相对于原产地植物，外来种释放的化学物质对入侵地植物更具毒性。然而，由于化感物质进入自然生境后受多种因素影响，实验室发现的化感作用在野外条件下的生态学效应备受争议。我们已有研究表明，土壤微生物可以削弱入侵植物的化感作用效果。同时，化感物质也可以改变土壤微生物群落。本项目拟通过微生物筛选培养基和第二代高通量测序相结合的方法，发现降解外来种紫茎泽兰（Eupatorium adenophorum）化感物质的微生物类群，探究土壤微生物对入侵植物化感作用的调控机制；同时，通过高通量测序检测化感物质对土壤微生物群落组成和多样性的影响，揭示化感物质对本地植物的间接作用，综合评价化感物质和土壤微生物对入侵进程的影响。本研究将有助于我们进一步理解生物入侵机制，丰富入侵生态学理论，为外来种的有效控制提供理论依据。

化感作用被认为在外来植物入侵过程中扮演了重要角色。然而，由于化感物质进入自然生境后受多种因素影响，实验室发现的化感作用在野外条件下的生态学效应备受争议。土壤微生物可以削弱入侵植物的化感作用，同时化感物质也可以改变微生物群落。为探明何种微生物在紫茎泽兰化感物质的分解转化过程中起主要作用，本研究利用紫茎泽兰的化感物质作为碳源，建立微生物筛选培养基，筛选出与化感物质降解密切相关的微生物种类15种，分别为Klebsiella pneumoniae、Klebsiella oxytoca 、Raonltella ornithinolytica、Klebsiella sp、Burkholderia、Enterobecter、Leclercia adecarboxylata、Cedecea neteri、Pseudomonas monteilii、Rhizobium sp、Enterobacter sp、Sphingobacterium multivorum、Cupriavidus sp、Stenotrophomonas sp、Novosphingobium sp。为了揭示紫茎泽兰入侵对土壤化学性质和细菌群落组成及多样性的影响，利用二代高通量测序的方法，比较了紫茎泽兰不同入侵程度的生境土壤中细菌群落的差异。土壤化学性质分析表明, 土壤pH值、有机质、全N和全K随紫茎泽兰的入侵而逐渐降低, 而土壤全P则在入侵程度最高的生境土壤中最高。紫茎泽兰入侵对土壤的细菌多样性影响较小, ACE和Chao指数在不同生境间的差异不显著。细菌在紫茎泽兰与本地植物混生群落的Shannon指数最低, 即细菌的多样性在中等入侵程度的生境最低。此外, 紫茎泽兰入侵改变了土壤细菌组成和结构, 酸杆菌门和疣微菌门的相对丰度, 从本地植物群落、混合群落到紫茎泽兰单优群落, 呈现出先增加后减少的趋势。通过分子手段检测了紫茎泽兰化感物质对土壤微生物群落组成和多样性的影响。紫茎泽兰叶浸提液的添加显著降低了土壤细菌群落的丰富度和多样性。冗余分析显示土壤细菌群落组成和结构的改变与土壤有机碳、总氮、pH有显著相关性。本项目的结果将有助于理解外来种入侵过程中释放的化感物质的环境行为，及其对外来种入侵进程的调控和影响机制，为将来研制适当的微生物制剂（菌肥）来消除入侵植物的化感作用奠定理论基础。此外，通过研究入侵种化感物质对本地生态