全球变暖下入侵植物与土壤微生物群落共演化对氮沉降的响应与机制

The plant-soil feedback (PSFs) hypothesis is often invoked to explain successful invasion of exotic plants. However, existing studies on PSFs mainly regard the invaded soil microbial community as a grey box, or even a black box. Thus, the increased global warming and nitrogen deposition might make it more complex in the soil micro-ecological mechanisms of exotic plant invasion. The present project will be carried out using the new-generation metagenomics methods and technology (i.e., combination of metagenomics and new-generation high throughput sequencing technology) to gain insights into the community structure and metabolic characteristics of soil microorganisms under different degrees of invasion mediated by the notorious invasive plants (i.e., Conyza canadensis), and different coverage of exotic non-invasive (i.e., Cosmos bipinnata) and native species (i.e., Pterocypsela laciniata) in China. This project aims to validate the following co-succession hypothesis: (1) exotic invasive plants could drive the succession of community structure and metabolic characteristics of soil microorganisms during their invasion process; (2) the re-construction of community structure and metabolic characteristics of soil microorganisms mediated by exotic invasive plants is beneficial for their own growth and expansion; (3) the succession of community structure and metabolic characteristics of soil microorganisms increased obviously with the enhanced invasion degree of exotic invasive plants, which is more conducive to the growth and expansion of exotic invasive plants, finally, it will reach a stable state in which soil microbial community can make the best of facilitating the further invasion of exotic plants; and (4) global warming and nitrogen deposition could accelerate the co-succession process between exotic plant invasion and soil microbial community, and both they have synergistic effects on the co-succession process between exotic plant invasion and soil microbial community. These studies will not only theoretically provide evidence for the PSFs hypothesis, and enrich the system of invasion ecology, especially the soil micro-ecological mechanisms of exotic plant invasion, but also in practice lay an important theoretical foundation for effective invasion prevention and control under global warming and nitrogen deposition.

目前植物-土壤微生物反馈假说阐释外来植物成功入侵的研究多将土壤微生物群落作为灰箱甚至黑箱；且随着全球变暖和氮沉降加剧，外来植物成功入侵的土壤微生态学机制愈加复杂。本项目基于新一代宏基因组学理论和技术对入侵植物不同入侵程度、外来非入侵近缘植物和本地近缘种不同盖度的土壤微生物群落结构进行全景式对比分析，以验证我们提出的外来植物成功入侵-土壤微生物群落共演化假说：外来植物在成功入侵进程中改变了原有土壤微生物群落结构和功能；土壤微生物群落重构更利于入侵植物的生长扩张；土壤微生物群落的持续演替将越利于该入侵植物，进而达到最利于有该入侵植物生长的某种稳态；全球变暖和氮沉降均促进该共演化，且两者具有叠加效应。研究结果不仅在理论上进一步佐证外来植物成功入侵的土壤-微生物反馈假说，阐明全球变暖和氮沉降下外来植物成功入侵的土壤微生态学机制，丰富入侵生态理论体系；且在实践上也为入侵植物的防控提供切实的理论指导。

目前植物-土壤反馈假说阐释外来植物成功入侵的研究多将土壤微生物群落作为灰箱甚至黑箱；且随着全球变暖和氮沉降加剧，外来植物成功入侵的土壤微生态学机制愈加复杂。本项目以全球变暖及氮沉降为研究背景，以入侵植物-环境(增温与施氮)-土壤(微生物)为中心，对其生态影响、快速入侵的机制、资源利用策略、与微生物的关系及其防控利用等进行了全景式对比分析研究。. 结果表明，外来植物在不同土壤营养条件下往往能采取不同的资源利用、生物量分配策略使其成功入侵，同时借助自身的化感物质排挤本地物种，促进自身生长，这将进一步增加外来植物成功入侵的可能性。随着入侵程度的提高，土壤酶活、pH、微生物（真菌、细菌（特别是固氮菌））亦随之变化，这种演化往往有利于外来植物的成功入侵。这种入侵机制与进程在全球变暖与氮沉降增加的背景下往往会进一步加剧，从而形成了“环境变化-植物入侵-土壤特征改变-植物入侵-环境变化”循环演进的开源系统。基于此，本项目亦提出了利用生物替代、动植物协同等方法来防控外来入侵植物的方法，同时验证了外来入侵植物在生态修复中的作用机制。..因此，本研究成功揭示了以全球变暖和大气氮沉降及其复合效应为典型代表的全球变化在外来植物成功入侵进程中所起的作用及其生物生态学机制。同步验证了外来植物成功入侵对本地植物及其土壤动态的影响机理，特别是土壤微生物群落演化进程的影响机制。基本阐明了全球变暖和大气氮沉降及其复合效应对入侵植物与土壤微生物群落间共演化进程、机制及其在外来植物成功入侵进程中的作用。这些发现不仅丰富了环境变化与植物入侵、植物入侵与土壤菌群之间的作用机制研究，也从一定程度上比较系统地阐明了环境变化、微生物对外来植物成功入侵的作用机理，特别是全球变暖及氮沉降背景下入侵植物与微生物共演化的进程与机理。