漓江上游区河流生境异质性与鱼类多样性的维持机制

The relationship between habitat heterogeneity and aquatic biodiversity has become a hotspot in the area of river management and conservation ecology, and constructing/recovering habitat heterogeneity in rivers has become one of the main content of river restoration in the developed countries. However, basic understanding of the underlying mechanisms between habitat heterogeneity and aquatic biodiversity are poorly understood, which makes the bad effect of numerous ecological restoration cases in the world. The previous studies of the applicant found that the fish biodiversity was related to the river bank structure and aquatic vegetation significantly, and fish compositions in the upper streams of Lijiang River have been investigated, and the relationship between habitat heterogeneity and fish diversity in Lijiang River is poorly understood. Thus, taking a typical Karst stream, Li River, as an example in this project, field observation and sampling will be conducted in the upper streams of Lijiang River watershed, such as geomorphic feature, physical structure, hydrological characteristics, et al, which is to research in habitat classification of mountain streams in this area and the relationship between fish diversity and habitat heterogeneity in micro-scale(hydrology, water quality, characteristics of river bed and river bank et al.) and meso-scale(riffle, pool et al.), which is to clarify the maintenance mechanism of fish diversity in this area. Implementation of this project can provide theoretical basis and technical guidance for ecological restoration in mountain streams, and it has important value for conservation of aquatic biodiversity and the integrity of ecosystem in Lijiang River.

生境异质性与水生生物多样性的关系已经成为保护生态学和河流管理的研究热点，构建/恢复河流生境的异质性也已成为发达国家河流修复的主要内容之一，但由于对生境异质性维持水生生物多样性的机制尚未明确，导致世界各国众多河流在生态修复工程中的效果欠佳。申请者前期研究表明河流鱼类多样性与河岸结构及水生植物之间存在密切相关性，并且初步掌握了漓江上游的鱼类物种组成，但仍缺乏对漓江生境异质性与鱼类多样性的关系研究。本项目以典型的喀斯特地区河流--漓江为例，通过对漓江上游区河流的地貌形态、物理结构、水文特征等指标的现场测量，分析区域内河流生物栖息地分类情况；结合鱼类分布情况，从微观（水文、水质、河岸河床特征）和中观（浅滩/深潭）尺度上研究鱼类多样性与生境异质性的关系，阐明区域内鱼类多样性的维持机制。本项目对加强漓江流域水生生物多样性及河流生态系统完整性的保护具有重要意义，也将为山区河流的生态修复提供理论依据及技术指导。

生境异质性与水生生物多样性的关系已经成为保护生态学和河流管理的研究热点，而且构建/恢复河流生境的异质性也已成为发达国家河流修复的主要内容之一，但是生境异质性维持水生生物多样性的机制尚未明确，导致世界众多河流生态修复工程的效果欠佳。本研究结果显示漓江上游生境分为静水生境、缓流生境、急流生境三大类。细化各大类，共分为7种生境类型。其中静水生境包括水潭和瀑布潭，缓流生境包括浅流、深流和岸边缓流，急流生境包括浅滩和险滩。26个采样点共捕获鱼类2968尾，经鉴定共计淡水鱼类37种，隶属于4目11科28属。优势种分别为方氏品唇鳅、宽鳍鱲和侧条光唇鱼，其个体数分别占总个体数的25.64%、21.16%和12.84%。无度量多维排序分析（NMDS）和多变量变异系数分析（PERMANOVA)结果显示鱼类组成在不同生境间不存在显著差异。冗余分析（RDA）结果显示海拔、流速、电导率、浊度、水深和水面宽与鱼类群落有显著相关性，而与水温、溶解氧和底质颗粒大小的相关性较小。此外，因物种对环境的形态适应，不同物种偏喜不同的环境因子。. 方差分解结果显示鱼类群落组成受水文因子、空间因子和局部环境因子共同作用，而且ß 多样性主要由物种周转或替换(turnover)决定。Mantel检验结果显示物种周转（ßSIM and ßJTU）与水文因子、局部环境因子和空间因子成显著相关性，而嵌套（nestedness）与这些环境变量无显著相关性。另外，生境评价结果显示漓江上游区26个采样河段的生境综合指数得分介于82~155分之间。其中有3个河段的生境综合指数得分超过150分，属于“好”等级；12个河段的分值介于120~150分之间，属于“较好”等级；9个河段的分值介于90~120分之间，属于“一般”等级；2个河段的分值介于60~90分之间，属于“较差”等级。生物完整性指数和生境综合指数的相关性分析结果表明IBI分值与HI分值呈极显著正相关。生境综合指数HI值得分较高的河段，其IBI值也普遍较高。生境指标和生物参数的相关性分析结果表明，除河岸植被保护外，其余生境指标均与不同的生物参数具有显著或极显著相关性，进一步说明了河流生境质量状况的优劣会影响河流中水生生物的生物状态。