中文摘要：

利用2003年西苕溪TM数据和DEM模型计算了55个样点上游3种空间尺度下（亚流域、河岸带和局部）的土地利用类型,通过冗余分析筛选出能够在显著水平上最大程度解释西苕溪流域底栖动物分布的最小变量组合——氨氮、荫蔽度、电导率、亚流域农田百分比以及栖境复杂度.方差分解结果表明氨氮是研究区域影响底栖动物分布的最重要环境变量,亚流域尺度农田百分比也是一个重要影响变量.在50%-100%适合度范围内最终筛选得到短脉纹石蛾Cheumato-psyche sp.1和Cheumatopsyche sp.2作为关键环境变量指示种.在一定范围内短脉纹石蛾的数量随着水体氨氮浓度和亚流域尺度农田百分比的上升而增加.短脉纹石蛾分布广泛、采集容易、具备一定的耐污能力和主动漂流能力、幼虫个体较大且在水中的生活史较长以及具有一定的生态可塑性等优点决定了短脉纹石蛾可以作为西苕溪流域的受干扰水体氨氮和亚流域尺度农田百分比的指示种.

英文摘要：

The land covering for 55 sampling sites in the Xitiao Stream were estimated as sub-basin,riparian-zone and local scales using 2003 satellite image and a Digital Elevation Model.Redundancy analysis indicated that the minimum combination including NH＋4,canopy,conductivity,percentage of sub-basin cropland and habitat complexity can significantly explain the variations of the macroinvertebrate communities were screened.The result of variance partitioning showed that NH＋4 was the most important variables affecting macroinvertebrate communities in the Xitiao Stream and sub-scale cropland% was also another important factor.Under a species fit range between 50% and 100%,Cheumatopsyche sp.1 and Cheumatopsyche sp.2 were finally selected as the indicator species.The abundance of Cheumatopsyche increased as the NH＋4 and the sub-scale cropland% increased.Cheumatopsyche has advantages as follows：wide distribution,easy to be collected,moderately tolerance,ability to drift,relative large body size with slower turnover rates and also ecological plasticity.Therefore,they exhibited to be very good indicators for the NH＋4 and the sub-basin scale cropland% of disturbed sites in the Xitiao Stream.