This project belongs to the field of environmental science and technology, focusing on the natural ecological environment in environmental science. Biological invasion caused by human activities is one of the five most difficult environmental issues in the world and has attracted global attention. China is one of the countries hardest hit by biological invasion. The ecological and environmental impact of plant invasion is particularly prominent and has become a major challenge in my country's ecological protection. Among the many invasive alien plants invading our country, Spartina alterniflora from North America is the most typical. It has been introduced into our country for more than 40 years, but it has occupied almost half of my country's coastal salt marsh wetlands, resulting in a reduction of coastal wetland biodiversity and ecosystem degradation., loss of service function. This project mainly answers two important questions, namely, how Spartina alterniflora can quickly and successfully invade the Yangtze River Estuary salt marsh wetland, and what ecological and environmental impact it has on the local ecosystem, in order to provide scientific basis for the management of this invasive species and wetland protection and restoration. The research results have attracted widespread attention from colleagues at home and abroad. The main original results are as follows: 1. It was discovered for the first time that Spartina alterniflora invaded China's salt marsh wetlands and significantly increased the carbon and nitrogen pools of the ecosystem. It was further discovered for the first time on a global scale. There is positive feedback between plant invasion and nitrogen cycles. Plant invasion changes the carbon and nitrogen cycle in ecosystems, especially by increasing nitrogen pools (self-fertilization effect) to produce positive feedback from invasion. R.M., a famous American scholar. Callaway called this ldquo; invasive plant paradox rdquo; and used the data from this project to publish a paper in the journal Science to specifically elaborate it. The results of this project have led to a new direction in plant invasion research focusing on nitrogen cycle, and have been praised as one of the important advances in biological invasion research in the past 50 years. 2. It was the first to systematically clarify the impact of Spartina alterniflora invasion on the biodiversity of the Yangtze River Estuary salt marsh wetlands, providing decision-making basis for ecological control and wetland restoration of this species. This project comprehensively and deeply reveals the impact of Spartina alterniflora invasion on different biological functional groups (plants, microorganisms, benthos, insects and birds) of indigenous salt marsh biodiversity, especially destroying the uniqueness and integrity of indigenous ecosystems, resulting in the degradation of their functions and the reduction of the value of ecosystem services. This achievement has provided key scientific support for Shanghai's implementation of the ldquo; Spartina alterniflora ecological control and bird habitat optimization in Chongming East Beach rdquo; large-scale ecological project, and achieved good ecological results after the implementation of the restoration project. 3. A new mechanism for Spartina alterniflora to successfully invade the salt marshes of the Yangtze River Estuary was discovered, that is, the death of indigenous species was caused by the spillover of pathogenic endophytic fungi carried by Spartina alterniflora from its place of origin, replacing the indigenous species and successfully invading. The invasion of Spartina alterniflora was mainly caused by introduction to promote silting before reclamation. During the introduction, pathogenic endophytic Fusarium may be brought into China. This fungus overflowed, causing the indigenous species of reed to die due to an outbreak of top blight, thus forming a new pattern of widespread distribution of Spartina alterniflora in the intertidal zone. This project published 85 SCI papers, which were cited by him 2841 times in SCI papers, of which 8 representative papers were cited by him 870 times in SCI papers. The paper on the impact of plant invasion on the carbon and nitrogen cycle in ecosystems (Representative Paper 1) was recognized by ESI as ldquo; highly cited paper rdquo;. Since it was published in 2008, it has been cited 385 times by him in SCI journals such as Nature and Science. The project results provide key scientific evidence for the implementation of the 24 km2 extremely large invasive species control and wetland restoration project in Chongming Dongtan, Shanghai. Due to the important progress made, the project leader won two key projects of the National Natural Science Foundation of China with Spartina alterniflora as the research object in 2009 and 2016. The two won the Outstanding Doctoral and Master's Thesis Awards from Shanghai City respectively. The above achievements have effectively enhanced the influence of my country's research on plant invasion ecology in the international academic community.