Roadside vegetation in mediterranean France
Heindl, B.; Ullmann, I.
In southern France, roadside vegetation along roads of different categories was studied in the western mediterranean lowlands and the adjacent foothills of the Cevennes and in the southeastern part of the Bassin de l'Aquitaine, according to the method of Braun-Blanquet. Our studies show in general that roadside vegetation in both the region with mediterranean climate and the area influenced by subatlantic climate is structured in a similar manner to roadside vegetation in temperate Europe. The most prominent feature of the roadside coenoses is the dominance of one species or the co-dominance of a few species associated with a limited overall floristic spectrum. However, regarding the spectra of plant communities, there is a strict division between the two climatic sub-regions of the study area. The plant communities of the road verges (apart from those bordering the road surface) in the mediterranean region are easily classified as communities of the Brachypodion phoenicoidis Br.-Bl. 1931. In the agricultural landscapes of the Bassin de l'Aquitaine the roadside phytocoenoses are characterized by a basic floristic inventory of widespread species without distinct phytogeographical and syntaxonomic affinities, whereas the dominant species are either mediterranean or subatlantic-submediterranean floristic elements. Whereas phytogeographical affinities are quite definite in both the floristic and the phytocoenological spectra of roadside vegetation, they are less clear in zonation patterns. In mediterranean France a high amount of the variation within zonation patterns is obviously due to differences in disturbance. For a better understanding of the influence of aridity on the diversity of vegetation zones on road verges, further studies are necessary in areas with a more pronounced aridity and a lower human impact than the Mediterranean.