富营养化对沉水植物抗牧食能力的影响及其生态效应

富营养化可改变沉水植物群落结构和物种的物理特征、营养元素含量、化学防御物质含量等，从而改变其抗牧食能力。这种抗牧食能力的改变将如何影响沉水植被演替和衰退，仍缺乏研究，机理不明。本项目拟采集和培养长江中下游湖泊常见沉水植物，测定牧食动物对这些生长于不同营养条件下的沉水植物的牧食速率，明确沉水植物抗牧食能力随营养梯度的变化趋势；测定沉水植物的抗牧食性状，分析植物抗牧食性状、抗牧食能力与植物生长环境营养水平之间的关系，揭示湖泊富营养化影响沉水植物抗牧食能力的机理；利用中宇宙系统，构建适应于不同营养水平的典型沉水植物群落，监测其在牧食压力下群落生物量、多样性、系统稳态的变化，阐明富营养化改变沉水植物抗牧食能力的生态效应。本项目的开展，可以进一步完善我们对沉水植物群落演替和衰退机理的认识，更好地服务于我国湖泊管理和生态修复。

Nutrient enrichment affects community structure, the physical properties, nutritional content and content of defense chemicals of submerged macrophytes. Consequently, the nutrient enrichment may alter the defensive ability of submerged macrophyte against herbivores. However, the mechanism and consequences under the alteration of the defensive ability on the decline and succession of submerged macrophyte, remain unclear. In this project, we will conduct a series of field investigations and mesocosm experiments to examine the impacts of nutrient enrichment on defenses of submerged macrophyte against herbivores at population and community levels. Our aims are to understand: 1) the relationships between the defenses of submerged macrophyte against herbivores and the nutrient conditions where the plant grown; 2) the mechanisms of nutrient enrichment affecting the defensive ability of submerged macrophyte against herbivores; 3) the consequences of alteration of submerged macrophyte defensive ability on macrophyte community biomass，diversity and the ecosystem state. This project will tremendously improve our understanding of the processes and mechanisms driving community succession and decline of submerged macrophytes in lakes，as well as provide valuable knowledge and insights for lake restoration and management.