Abstract
The objective of the study is to create a typology of macrophytes for the reference watercourses of the Meuse River catchment basin in Wallonia as a step towards the implementation of the European Water Framework Directive. The 50 sites studied are the object of a physicochemical and environmental characterization followed by a floristic survey (phanerogams, mosses, liverworts, and macroalgae). Six clusters of watercourses with their characteristic species are highlighted by two-way clustering and indicator species. The abundance of phanerogams in some watercourses of the Arden region is not only linked to light intensity but also depends on the degree of slope and the nature of the geological substrate.
Highlights
The objective of the study is to create a typology of macrophytes for the reference watercourses of the Meuse River catchment basin in Wallonia as a step towards the implementation of the European Water Framework Directive
Our work focuses on phanerogams, bryophytes, and macroalgae, and environmental factors such as slope, shading, the spring and site altitude, the land cover of the banks, their width, and geological stages and substrates
The multiple factorial analysis (Figure 2), corroborated by the result of a k-means classification applied to the coordinates of the sites in the first factorial plan of the Multiple factorial analysis (MFA), separates the watercourses of the Arden, those of Lorraine and those of Condroz and Famenne
Summary
The interest in using macrophytes to assess the ecological quality of aquatic environments is underlined by many European authors, including Kohler [1, 2], Newbold and Holmes [3], Haslam [4], and Haury and Peltre [5].Research regarding indicative species (auto-ecological method) and indicative plant communities (synecological method) has been carried out in detail during the last 40 years and several macrophytic indexes (Holmes et al [6], Haury et al [7], and Schneider and Melzer [8]) have been proposed to assess the quality of watercourses.In Western Europe, macrophytic typologies were established by Butcher for Britain [9], by Holmes et al for England, Wales, and Scotland [10], by Grasmuck et al for French Lorraine [11], by Chatenet et al for French Limousin [12], and by Sossey-Alaoui for Luxemburg [13]. The recent work of Sossey-Alaoui and Rosillon [14] analysed a set of plant data coming for the entire watercourses monitoring network of the Wallonia Region. All these works included impacted and nonimpacted watercourses. The Water Framework Directive 2000/60/CE [15] requires the assessment of the observed state of watercourses compared to nonimpacted, pristine, or almost pristine corresponding reference conditions This implies an environment with very low pressures, without the effects of major industrialization, urbanization, or intensification of agriculture and with only very minor modifications of physicochemistry, hydromorphology, and biology. It requires the drawing up of selection criteria related to all the pressures affecting the watercourses
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