Abstract
The aquatic and hygrophilous vegetation of Lakes Chiusi and Montepulciano (Siena, central Italy) was studied according to the phytosociological method. The survey led to the identification of 44 community types belonging to 10 syntaxonomic classes. A comparison between the current and past situation is also shown, taking into account the main floristic and phytosociological literature sources for the study areas. Some coenoses dominated by rare species at the national or regional scale were detected, such as Najadetum minoris, Potamo perfoliati-Vallisnerietum spiralis, Eleocharis acicularis community, Mentho aquaticae-Caricetum pseudocyperi, Thelypterido palustris-Phragmitetum australis and Eleocharito palustris-Hippuridetum vulgaris. Seven habitats are important for nature conservation according to the European Directive 92/43/EEC. Two other habitats are considered of regional interest according to Tuscan legislation. Moreover, this study emphasises the presence of several communities of great naturalistic and phytogeographic importance which are currently not included in any habitat of conservation interest. Similar to many other wetland systems across the Italian peninsula, the survey showed that the study areas still host a remarkable floristic and vegetation biodiversity, in spite of strong anthropogenic pressures putting at risk their conservation in the long term.