长江中下游浅水湖泊沉水植被演替过程中鱼类群落结构和功能多样性的响应机制

Structural and functional degradation of many shallow lake ecosystems in the middle and lower reaches of Yangtze River basin which due to improper development, and the revegetation of submerged macrophytes is the base for water ecosystem rehabilitation. But the characteristics variaion of submerged vegetation during the restoration process will affect the structure and function of fish community, vice versa, fish community will affect the succession direction and process of submerged macrophytes. We designed this research to investigate fish community and submerged macrophytes with hydroacoustics and traditional sampling method in the middle and lower Yangtze River Basin, and to study the relationship between fish community biodiversity, spatioal pattern, functional diversity and submerged vegetation with ArcGIS, Multivariate statistical analysis and Machine Learning. The goal is to find out vegetation characteristics which closely relate to fish community biodiversity and functional diversity, and explain mechanism of fish community response to submerged macrophytes succession in shallow lakes, then establish prediction model for fish community biodiversity and functional diversity which based on vegetation characteristics. Development of the project can not only provide scientific guidance for the ecological restoration of lakes, but can also promote the theoretical study of community construction and succession mechanism.

长江中下游大量浅水湖泊由于不当开发导致生态系统结构与功能退化，沉水植被修复和重建是这些湖泊生态修复的关键环节。沉水植被修复与重建过程中的特征变化会对鱼类群落的结构和功能产生影响，而鱼类群落反过来也会影响沉水植被演替的方向和进程。本项目拟以长江中下游浅水湖泊为研究对象，运用现代水声学与传统调查相结合的方法，对沉水植被和鱼类群落进行调查。分别运用多变量统计分析、ArcGIS空间分析、机器学习模型等方法定量研究鱼类群落多样性、空间分布格局、功能多样性同沉水植被的相互关系，厘清影响鱼类群落多样性及功能多样性的关键因子，揭示浅水湖泊沉水植被恢复和演替过程中鱼类群落的响应机制，据此建立以沉水植被特征为主要参数的鱼类群落结构和多样性预测模型，阐明鱼类群落多样性和功能多样性随沉水植被演替的变化趋势。项目的开展不仅可为湖泊生态修复提供科学指导，对促进群落构建与演替机制的理论研究也有重要意义。

本项目通过对藻型湖泊沉水植被恢复过程中不同生境鱼类丰富度、物种多样性和功能多样性特征的研究，分析了影响鱼类物种和功能多样性的沉水植被特征。首先，通过试验证明基于声学探测的沉水植物体积百分比（PVI）与植被生物量间具有很好的线性回归关系，验证了水声学在浅水湖泊沉水植被评估中的可靠性。其次，通过对比不同生境鱼类群落物种和功能多样性的差异，明确了影响鱼类群落物种和功能多样性的沉水植被特征包括覆盖率、种类组成、植株高度和生物量。总体上，沉水植被种类组成、覆盖率、植株高度和生物量与鱼类丰富度、物种多样性、功能离散度FDiv、功能分散度FDis呈正相关性，而功能丰富度FRic、功能均匀度FEve和RaoQ指数受沉水植被影响较小；此外，沉水植被对鱼类物种和功能多样性的影响因季节而异。第三，长江中下游浅水湖泊在由草型转变为藻型后，鱼类物种丰富度、物种多样性、功能丰富度FRic和功能离散度FDiv都有显著降低的趋势，但Pielou均匀度、功能均匀度FEve和RaoQ指数则变化较小。建议在藻型湖泊沉水植被修复的过程中，加强对鱼类功能丰富度FRic和功能离散度的调控。

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