Quantifying river habitat structure in ecologically meaningful ways

摘要

Physical habitat structure (cf. water quality) is a poorly understood aspect of the relationships between river organisms and their environment. Habitat structure varies across a wide range of spatial and temporal scales, both naturally and in response to numerous human activities: usually control (e.g. channelisation) or exploitation (e.g. abstraction). Such changes have major biodiversity implications, making an understanding of the links between organisms and physical habitat structure vital for river management - as reflected in the Water Framework Directive (WFD). A fundamental challenge in making these links is finding an effective way of describing physical habitat structure and modification, given the variability and structural complexity ofriver habitats. We describe an approach to parameterising river habitats, identifying, then quantifying, gradients in both semi-natural habitat and in anthropogenic modification. The complexity/resolution of the resulting habitat indices can be varied according to the desired application - research or management. Case studies in the River Wye illustrate some of the benefits of such indices. Outputs from this work will support implementation of the WFD by capturing variation in river habitats that can be related to a wide range of organisms. More broadly, the methods we present have potential benefits for simplifying complex data, identifying environmental gradients, describing spatial patterns, quantifying organism habitat preferences and suggesting some rigorous approaches to the analysis of existing databases.