长江口盐沼湿地生态系统稳态转换过程与机制研究

Under the intensive impacts of human activities and global changes, regime shifts in the saltmarsh wetland ecosystem are taking place frequently. It could result in dramatic changes in the structure and function of saltmarsh wetland ecosystem and bring big challenges to coastal conservation and management. Studies on regime shift process and mechanism in the saltmarsh wetland ecosystem are essential to provide a powerful tool to probe the resilience of saltmarsh wetland ecosystem. However, quantitative researches on the regime shift process and mechanisms induced by multiple perturbations in the saltmarsh wetland ecosystem are still far from complete. Early warnings of regime shift are still lack of an effective methodology. This study will conduct a comprehensive methodology (field observation, controlled experiments, remote sensing image analysis and mathematics modeling) on the natural saltmarsh wetlands in the Yangtze estuary to: 1) analyze the process and impacts of regime shifts in the saltmarsh wetland ecosystems caused by Spartina alterniflora invasion and environmental changes, and 2) probe the regime shift mechanisms by analyzing feedbacks (interactions between species and positive feedbacks between species and environments), and identifying the critical thresholds and early warning signature. It is expected that this study could enrich the theory and methodology on regime shift and provide the scientific and technology supports for coastal zone protection, ecological restoration, risk warning and ecosystem based management.

在人类活动和全球变化影响下，滨海盐沼湿地生态系统稳态转换现象频发，导致其结构和功能发生突然转变，给海岸带保护和管理带来极大挑战。深入研究盐沼湿地生态系统稳态转换过程和机制是解决这一问题的关键。但迄今为止，对多重扰动下，盐沼湿地稳态转换过程和机制还缺乏充分理解，尚缺乏对稳态转换进行早期预警的有效方法。本项目将以长江口盐沼湿地生态系统为研究对象，通过野外监测、控制实验、遥感分析和数学模型等手段，分析外来物种互花米草入侵和潮滩环境变化共同扰动下，盐沼湿地生态系统的稳态转换过程和影响；并通过研究稳态转换驱动因子、盐沼植物间相互作用及盐沼植物与环境间的正反馈作用、稳态转换阈值和早期预警信号，揭示盐沼湿地生态系统稳态转换机制。以期在理论和方法上丰富生态系统稳态转换机理的研究，并为我国开展海岸带保护、生态修复、风险预警和生态化管理提供科学依据和技术支撑。

盐沼湿地生态系统的稳态转换导致其结构和功能发生突然转变，给海岸带保护和管理带来极大挑战。深入研究盐沼湿地生态系统稳态转换过程和机制是解决这一问题的关键。本项目以长江口盐沼湿地生态系统为研究对象，通过野外监测、控制实验、遥感分析和数学模型等手段，分析了外来物种入侵和潮滩环境变化扰动下，盐沼湿地生态系统的稳态转换过程和影响；并通过研究稳态转换驱动因子、盐沼植物间相互作用及盐沼植物与环境间的反馈作用和稳态转换阈值，揭示了盐沼湿地生态系统稳态转换机制。研究结果表明：（1）互花米草入侵引起盐沼湿地群落构建由几种本地盐沼植物组成的结构转换成以外来物种互花米草为主要优势物种的结构；潮滩环境变化则通过影响盐沼植物的存活、传播和定植引起盐沼湿地发生低生物量的“光滩”和高生物量的“盐沼”两个相对稳态间的转换；盐沼湿地稳态转换过程具有明显的“扰动下跃迁”和“滞后效应”特征，结构的转换进一步影响了盐沼生态系统的总初级生产力（GPP）、生物多样性维持、保滩护岸等生态功能。（2）盐沼湿地生态系统的稳态转换是株源密度、潮滩高程、流速、盐度等多个驱动因子共同作用的结果，盐沼植物的生物特性和潮滩物理环境间的反馈作用是驱动盐沼湿地生态系统发生稳态转换的主要作用机制。（3）长江口典型的盐沼植物芦苇（Phragmites australis）、互花米草（Spartina alterniflora）和海三棱藨草（Scirpus mariqueter）存活的高程阈值和盐度阈值分别为2.79m、2.51m、2.36m和13.35ppt、43.58ppt和21.30ppt；水动力和冲淤变化的耐受阈值则受盐沼植物生活史的变化而改变；只有在生物和物理阈值同时满足时，盐沼湿地生态系统才可能发生“光滩”和“盐沼”间的转换。研究在理论和方法上丰富了生态系统稳态转换机理的研究，在此基础上研发的盐沼植被修复技术已成功应用于长江口的海岸带生态修复工程，为我国开展海岸带生态修复、风险预警和生态化管理提供了重要的科学依据、技术支撑和成功案例。