氮沉降下入侵克隆植物繁殖分配策略及与其入侵力的耦合和机制

Clonal plants in various habitats can exhibit different strategy of reproductive allocation to improve their competitiveness and invasiveness. In recent years, the increased in the levels and the diversificated in the form of anthropogenic N (nitrogen) deposition make more complex in the invasion mechanisms of exotic clonal plants. Thus, this study was carried out with invasive plant species (Solidago Canadensis and Wedelia trilobata) and their native relatives (S. decurrens and W. chinensis) seleseted as research target in order to (1) insights into the relationship between reproductive allocation strategy and invasiveness of invasive clonal plants with soil N concentration through field investigation, and (2) determines the characteristics of reproductive allocation strategy and invasiveness of invasive clonal plants and then analyzes their coupling relationship through laboratory experiment treated with different levels and forms of artificial N to simulate atmospheric N deposition. Meanwhile, the invasive mechanism of microbial ecology for invasive clonal plants under atmospheric N deposition were identified through the determination of N use efficiency, the community structure and function of endogenic N-fixing bacteria and exogenous N-fixing bacteria of invasive clonal plants from the perspective of the obtain and use of N. The results of this project can give a platform to better understand the mechanism of successful invasion of exotic clonal plants under global change exemplified by anthropogenic N deposition and then lay an important theoretical foundation and practical significance for effective invasion prevention and control.

在不同外界环境下克隆植物会表现出不同的繁殖分配策略以提高其竞争入侵力。近年来大气氮沉降水平的增加及类型的多样化使得外来克隆植物的入侵机制更趋复杂。所以，本项目拟选取成功入侵的克隆植物加拿大一枝黄花和南美蟛蜞菊及其本土近缘种一枝黄花和蟛蜞菊为研究对象，通过野外调查入侵克隆植物繁殖分配策略和其入侵力及与土壤氮含量的相关性，并结合室内控制实验通过人工增施不同水平及类型的氮素来模拟大气氮沉降以研究氮沉降背景下入侵克隆植物的繁殖分配策略及入侵力特征，进而分析两者的耦合关系。同时，通过测定入侵克隆植物的氮素利用率，并结合分子生物学手段来分析其内生固氮菌和外生固氮菌的群落结构及其功能，从氮素获取和利用的角度来阐明氮沉降背景下入侵克隆植物繁殖分配策略及其入侵力的微生物生态学机制。该研究结果将对更清楚地认识以氮沉降为代表的全球变化背景下外来克隆植物成功入侵的机理及其防控均具有重要的理论和实际意义。

一些外来植物成功入侵主因之一就是可与土壤微生物群落形成反馈作用，即外来植物的成功入侵与其根际土壤微生物关系密切。随着全球环境变化特别是氮沉降日益增加和多样化，会改变土壤及土壤微生物生态特性，使外来植物入侵的微生物生态学机理趋于复杂。因此，本研究基于土壤微生物群落结构和功能特征(固氮菌)视阈下，采用基于新一代高通量测序技术的宏基因组学技术进行全景式分析氮沉降背景下外来植物入侵对土壤固氮菌群落结构和功能特征的重构作用，从而阐释以氮沉降等为典型代表的全球环境变化背景下外来植物入侵成功的微生物生态学机理。.研究结果表明：(1)不同水平氮沉降背景下反枝苋(Amaranthus retroflexus)入侵明显改变了土壤固氮菌群落结构。此外，土壤pH显著影响土壤固氮菌群落的OTU。因此，不同水平氮沉降背景下反枝苋(A. retroflexus)入侵可能通过改变土壤pH值来间接影响其根际土壤固氮菌群落结构，从而创造一个利于其入侵的土壤微环境。(2)在所有类型氮沉降背景下反枝苋(A. retroflexus)入侵增加了土壤固氮菌群落的sequence number，且在CO(NH2)2-N和混合氮增施背景下反枝苋(A. retroflexus)根际土壤固氮菌群落的sequence number大于在NH4+-N和NO3–-N增施背景下。因此，在氮沉降日益增加和多样化的背景下，反枝苋(A. retroflexus)可通过植物-土壤固氮菌群落互作创造一个利于其入侵的土壤微环境，从而可提升其入侵竞争力，尤其是通过提升土壤固氮菌的种类数量从而增加土壤氮素可利用水平，进而促进其进一步的入侵进程。.该研究结果将对更清楚认识以氮沉降为代表的全球变化背景下外来植物成功入侵的机理、生态安全性及其防控具有重要的理论和实际意义。