Abstract

The recent introduction of large geospatial databases and virtual measurement devices for streams of the United States have the potential to greatly improve stream classification systems as well as answer fundamental questions about river morphology. The physical condition of over 800 streams of the adjoining Upper Midwest and Temperate Plains ecoregions of the northcentral US were analyzed using principle components analysis of 10 selected site variables. Delineation was along three axes, with the first axis corresponding to differences in base flow, temperature, and soil permeability; the second corresponding to stream gradient, depth to bedrock and water table, and composite topographic index; and the third corresponding to stream sinuosity. Separation of streams into the two ecoregions was distinct, and primarily along axis 1. Adding a secondary matrix of 10 anthropogenic and geographic predictor variables produced a similar ecoregional separation, with latitude, percent of non-native plants, and overall intact habitat corresponding with axis 1. Natural and anthropogenic differences in streams of these two ecoregions appear inexorably linked, a situation probably common throughout the developed world.

摘要

最近引入的用于美国河流的大型地理空间数据库和虚拟测量设备具有极大地改善河流分类系统以及回答有关河流形态的基本问题的潜力。使用10个选定站点变量的主成分分析法，对美国中北部毗邻的中西部和温带平原生态区的800多个溪流的物理条件进行了分析。划定沿三个轴进行，第一个轴对应于基础流量，温度和土壤渗透率的差异。第二个对应于河流坡度，基岩和地下水位深度以及复合地形指数。第三个对应于流的弯曲度。进入两个生态区的水流截然不同，主要沿轴线1。