河流鱼类群落构建机制及小水电开发的影响研究：以长江上游赤水河和南广河为例

The study of community assembly is integral for understanding species coexistence and biodiversity. The relevant studies in China focus on plant community. The upper Yangtze River is a hotspot of biodiversity for its rich endemic fish species, however, it is under serious threat by increasing construction of small hydropower stations. It can serve as a natural experimental laboratory to examine the mechanisms of fish community assembly in river ecosystems and effects from construction of small hydropower stations. In the proposed project, we will select two first order tributaries of the upper Yangtze River including Chishui River and Nanguang River, differently affected by the construction of small hydropower stations, to conduct a comparative study. We will examine fish community structure and diversity patterns at different spatial (local habitat, longitudinal pattern, and watershed) and temporal (seasonal and annual) scales, and explore the relationships among the taxonomic diversity, functional diversity and the traditional species diversity and their responses to environmental factors and the construction of small hydropower stations. We expect to reveal the coupling mechanisms between fish community and environmental and spatial factors at different scales, determine the relative importance of environmental filtering and dispersal limitation in the role of fish community assembly in the river ecosystems, and comprehensively demonstrate the mechanisms of fish community assembly and effects from construction of small hydropower stations. Our results are expected to help understand mechanisms of fish community assembly and species diversity preservation in river ecosystems, and provide theoretic references for ecological effect assessment of hydropower station construction, river restoration and management.

群落构建研究对解释物种共存和多样性维持至关重要，而我国这方面的研究主要集中在植物群落。长江上游特有鱼类丰富，是生物多样性研究和保护的热点地区，也是小水电开发比较集中的地区，为开展河流鱼类群落构建及小水电开发影响研究提供了试验场所。本项目以受小水电开发影响程度不同的赤水河和南广河流域为研究区域，从不同空间尺度（局域生境、河流纵向梯度、流域）和时间尺度（季节、年度）开展鱼类群落构建对比研究，分析鱼类群落结构和多样性分布格局，探讨分类学多样性、功能多样性和物种多样性之间的相关性及其对栖息地环境变化和小水电站建设的响应差异；分析鱼类群落与栖息地环境因子、空间扩散因子的耦合关系，揭示环境筛选与扩散限制在河流鱼类群落构建中的相对作用大小，阐明河流鱼类群落构建机制及小水电开发的影响。项目开展有助于加深理解河流鱼类群落构建和多样性维持机制，为水电工程生态影响评价、河流生态修复及管理等提供科学依据。

群落构建研究对解释物种共存和多样性维持至关重要，而我国这方面的研究主要集中在植物群落。长江上游特有鱼类丰富，是生物多样性研究和保护的热点地区，也是水电开发比较集中的地区。本项目以长江上游赤水河、南广河、香溪河、三峡库区、金沙江下游干流等为研究区域，从不同空间和时间尺度开展了鱼类群落构建研究。赤水河鱼类群落以流水性鱼类为主，南广河下游、香溪河、三峡库区、金沙江下游向家坝至溪洛渡江段等区域以广适性和静水性鱼类为主。长江上游鱼类群落结构具有明显的空间格局，沿河流纵向梯度，流水性鱼类比例下降，广适性和静水性鱼类比例增加。不同研究区域，鱼类物种多样性、分类学多样性、功能多样性之间的相关关系不同。同一研究区域，摄食、运动和繁殖等不同维度的功能多样性时空格局存在差异。赤水河河流纵向梯度鱼类物种丰富度空间格局主要受扩散因子（河流距离）影响，而在流域尺度，主要受河流环境因子（河宽、流速）影响。南广河流域鱼类物种和功能多样性空间格局主要受河流流量影响。香溪河河流纵向梯度鱼类功能多样性受扩散因子（到河口距离）与栖息地环境因子（流速、海拔、河宽）共同影响，但物种多样性和分类学多样性不受这些因子影响。三峡库区鱼类群落结构和多样性格局主要受库区蓄水导致的生境异质性影响。金沙江下游干流江段鱼类群落结构和多样性格局主要受水电梯级开发和库区鱼类网箱养殖活动等共同影响。综上所述，长江上游鱼类群落结构和多样性存在显著的时空格局，鱼类群落结构和多样性格局的影响因子与研究尺度和研究区域有关。分类学多样性和功能多样性比物种多样性更敏感，因此整合物种多样性、分类学多样性和功能多样性研究，可以更深入了解生态系统的生态过程和分布格局。研究结果助于加深理解河流鱼类群落构建和多样性维持机制，为水电工程生态影响评价、河流生态修复及管理等提供科学依据。研究成果也为长江“十年禁渔”效果评估提供了本底资料。