Analisi fitosociologica dei fiumi della Toscana meridionale: il tratto medio-basso del Merse (Italia centrale)

After a brief introduction on the geological, hydrological and climatic characteristics, the authors describe the results of a phytosociological study concerning riparian and aquatic vegetation of the lower-middle Merse river (southern Tuscany, central Italy). Purpose of the contribution is to further knowledge on the syntaxonomy, ecology and dynamics of river vegetational communities in southern Tuscany. The paper outlines a rather complex syntaxonomy scheme pointing out the vegetation abundance of the section of the river studied. In fact, coenosis belonging to 12 different phytosociological classes were identified: Querco-Fagetea, Salicetea purpureae, Rhamno-Prunetea, Rosmarinetea officinalis, Molinio-Arrhenatheretea, Artemisietea vulgaris, Isoeto-Nanojuncetea, Bidentetea tripartitae, Agrostietea stoloniferae, Phragmito-Magnocaricetea, Potamogetonetea pectinati, Charetea fragilis. High environmental quality was evidenced by floristic and synecological analysis of the community. Due to the low presence of human activity, hydrophytic community indicating oligotrophic aquatic environment, high phytocoenotic diversity, floristically, structurally and ecologically well characterized tree/shrub population were found.