植物入侵是全球环境变化的重要驱动力之一，可通过改变多营养级生物间的互作关系而重塑生态系统结构与功能。特别是在受高强度人类活动干扰的海岸带湿地中，植物入侵常严重破坏大型捕食动物的觅食地，进而通过捕食作用的改变和营养级联效应由食物链上层至基层影响较低营养级的植食动物和植物，但以往相关研究常采用由食物链基层至上层的研究思路。本项目拟以长江口典型盐沼湿地为研究系统，采用由食物链上层至基层影响的新思路，应用野外调查和受控试验等方法，从捕食动物、植食动物、植物三个不同营养级生物的种群变化、三者之间相互作用、以及入侵植物-土著植物竞争关系等方面，系统研究互花米草入侵对盐沼湿地关键捕食过程的影响及其营养级联效应。本项目采用全新的研究途径，有望为认识植物入侵对盐沼湿地生物群落的影响提供新机制，为长江口等重要生态区植物入侵的管理提供科学依据。

Plant invasions are a key driver of global environmental change and can reshape the structure and functioning of ecosystems by changing species interactions among multiple trophic levels. In coastal saltmarsh wetlands with strong human disturbances, plant invasions often strongly impact the feeding habitats of large-bodied predators and affect herbivores and plants through altered predation intensity and trophic cascades from upper to basal trophic levels. Past studies, however, have often investigated the impacts of plant invasions using a bottom-up approach from basal to upper trophic levels. We propose to employ a top-down approach to investigate the impacts of Spartina alterniflora invasions on predation and trophic cascades in salt marshes in the Yangtze River Estuary. In field surveys and manipulative experiments, we will examine the impacts of plant invasions on 1) predator, herbivore, and plant populations, 2) interactions among those three trophic levels, and 3) competition between exotic and native plants. This project may thus reveal altered predation as a new mechanism underlying the impacts of plant invasions on biota in saltmarsh wetlands. The findings can inform management strategies of plant invasions in the Yangtze River Estuary and other ecologically important regions.