雅砻江(锦屏段)及其主要支流的大型底栖动物

分别于2004年5月和11月对雅砻江锦屏段及其主要支流25个采样点的大型底栖动物进行了采样.研究发现, 5月和11月整个采样区域的最优势类群为四节蜉稚虫1种(Baetis sp.)(Baetidae, Ephemeroptera)，相对百分比分别达到14.9%和27.0%.利用大型底栖动物的物种组成和物种相对丰度，应用双向指示种分析和无偏对应分析，对11月份的25个样点的分组研究表明，底栖动物类群按照所处的生境类型分为4个主要类群.典范对应分析表明，5月影响底栖动物群落结构的主要环境因子为海拔高度、氨氮和硬度，11月影响底栖动物分布的主要环境因子为海拔高度、二氧化硅、硬度和氨氮.

Macrobenthos in Jinping reach of Yalongjiang River and its main tributaries

In this paper,an investigation was made on the macrobenthos at 25 sites in the Jinping reach of Yalongjiang River and its main tributaries in May and November 2004,aimed to study the relationships between macrobenthos distribution and environmental factors.The results showed that the dominant species of macrobenthos was Baetis sp.(Baetidae,Ephemeroptera),with a relative abundance being 14.9% and 27.0% in May and November,respectively.Based on the species composition and their relative abundance,and by using two-way indictor species analysis(TWINSPAN)and detrended correspondence analysis(DCA),the macrobenthods was divided into four groups,according to the habitat types of the sites.Canonical correspondence analysis(CCA)on the relationships between macrobenthods community structure and environmental factors indicated that in May,elevation and water hardness and NH_4 -N content were the main environmental factors affecting macrobenthods distribution,while in November,elevation,water hardness,NH_4 -N and SiO_2 contents were the main ones.