A revised classification system for British rivers based on their aquatic plant communities

Abstract

1. This paper describes a classification of British rivers based on their aquatic plant communities, and represents a revision of an earlier version published in the early 1980s. 2. Data on macrophytes from 459 riverine sites were added to the original database of 1055 sites, and analysed using TWINSPAN (Two-Way Indicator Species Analysis). 3. The overall structure of the new classification is the same as the first version. The highest level consists of four broad groups (A–D) representing an environmental gradient from lowland eutrophic rivers, to those that are essentially upland, torrential and oligotrophic. These four groups are divided into 10 River Community Types (RCTs) with further sub-divisions into 38 sub-types. For many sites, their allocation to a particular RCT has remained unchanged; other sites have been reassigned and this process has helped remove some of the minor anomalies in the previous system. 4. The results have confirmed that aquatic macrophytes are a valuable tool for classifying rivers, and suggest that in the absence of natural stress or human impact most communities are sufficiently robust to remain stable over time. 5. The original system has been used extensively over the past 15 years, particularly for nature conservation assessment. New applications include trophic ranking techniques for water quality monitoring, and the integration of the botanical classification within a broader system for conservation evaluation. It is intended that in future the classification will be extended to incorporate rivers in Northern Ireland, thus creating a system applicable to the whole of the UK. © 1998 John Wiley & Sons, Ltd.