沉水植物的群落构建机制及其对环境变化的响应

Submerged macrophytes communities play a crucial role in maintaining clean water status in shallow lakes, while environmental changes (e.g. eutrophication, global warming) in recent decades have led to rapid succession or even declining of submerged macrophytes communities in shallow lakes. The theory of regime shift proposed in the classic limnological study focuses on the state of the lake, neglecting the succession of submerged macrophyte communities and the changes of their ecological functions along with the environmental changes. This study targets at the commonly-found submerged species in the Yangtze River Basin, via the mesocosm experiment system, the long-term monitoring on the permanent quadrat in shallow lakes and the field parameterized competition model, and uses contemporary species coexistence theory to analyze the mechanisms of community assembly of submerged macrophytes according to the niche differences and average fitness differences and their responses to environmental changes. We aim to investigate the succession of submerged macrophytes communities under environmental changes such as lake eutrophication and climate warming by linking plant functional traits with niche differences and average fitness differences and optimize the mathematical model for predicting the succession of submerged macrophyte communities in natural lakes. We also focus on assessing the role of propagules in community assembly and provide the reasonable solution for the restoration and reconstruction of submerged macrophyte communities in degraded lakes.

沉水植物群落对维持浅水湖泊的清水状态起着至关重要的作用，而近几十年来环境变化导致浅水湖泊沉水植物的群落迅速演替甚至衰退。经典湖沼学研究中提出的湖泊稳态转换理论聚焦于湖泊状态，而忽略了环境变化过程中沉水植物群落的演替及其生态功能变化。本项目以长江流域主要沉水植物为对象，通过受控实验体系、沉水植物群落固定样方的长期监测和基于野外参数校正的竞争模型，基于当代物种共存理论，从生态位和平均适合度差异两个方面分析沉水植物群落的构建机制及其对环境变化的响应，解析湖泊富营养化和气候变暖等环境变化过程中水生植物群落演替的规律，将植物功能性状及其集合与物种间的生态位和适合度差异进行关联分析，优化预测自然湖泊沉水植物群落演替的数学模型，着重评估繁殖体库在群落构建机制中的作用，为退化湖泊沉水植物群落的恢复重建提供合理的解决方案。

稳定性的水生植物群落对维持浅水湖泊的清水状态起着至关重要的作用，而近几十年来环境变化导致浅水湖泊水生植物的群落迅速演替甚至衰退。经典湖沼学研究中提出的湖泊稳态转换理论聚焦于湖泊状态，而忽略了环境变化过程中沉水植物群落的演替及其生态功能变化。本项目以水生植物为对象，通过基于人工模拟湖泊实验体系、水生植物地上群落和地下繁殖体库的长期样方监测，同时根据受控实验和野外调查的结果梳理水生植物的群落构建机制，预测自然水体中的水生植物群落演替规律。本研究基于伊乐藻-菹草的加温竞争实验以及多种沉水植物的竞争实验，发现与一年生植物相比，多年生水生植物的适合度计算较为复杂，特别是对于既有无性繁殖（特化的繁殖器官或克隆分株）又具备有性繁殖能力的水生植物，其适合度并不能直接应用经典研究中基于果实或者无性繁殖体的数量来计算。本研究还基于湖北荆州的洪湖、云南石屏的异龙湖、汉江王甫洲库区等自然水体，开展水生植物地下繁殖体库、地上植被的持续监测。结合竞争实验的结果发现，在清水系统中，沉水植物的演替与繁殖体库的特征较为一致，而在异龙湖和洪湖这类浊水系统中，繁殖体库中占优势的轮藻并未成为地上优势种群，繁殖体库中以无性繁殖体为主要繁殖方式的菹草（石芽）和蓖齿眼子菜（块茎） 成为地上植被的优势群落。我们的研究结果表明，沉水植物的繁殖性状在其群落构建中发挥重要作用，影响沉水植物在不同类型的环境变化(如富营养化、气候变暖等)过程中的优势种群演替。我们的研究结果提升了在环境变化背景下对水生植物群落演替的可预测性。

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