Ordination of Functional Groups and Organic Matter Parameters from the Middle Fork of the Salmon River, Idaho

Abstract

Classes of parameters (macroinvertebrate functional feeding groups, periphyton, transported and benthic organic matter) were examined by means of polar ordination techniques to determine distribution along a gradient from headwaters to large rivers. Functional group composition changed in a curvilinear fashion along the gradient. The largest portion of ecological change occurred within the headwater and small stream portion of the gradient and only slight changes occurred above a stream size of link magnitude 1000. The composition of stored and transported organic matter, together, changed in a linear fashion along the gradient in a manner similar to that found for macroinvertebrates. However, the difference in the form of the response suggests that environmental factors affect the combined composition of organic matter more evenly than functional feeding groups over the whole of a river system. All ordinations considered in this study sustain the conclusion that the ecological characterization of a study...