Osmundo-Alnion woods in Tuscany (Italy): A phytogeographical analysis from a west European perspective

Riparian woods with Alnus glutinosa and Osmunda regalis in Tuscany (central Italy) were studied, whilst western European riparian alderwoods were analysed from a phytogeographical perspective, with particular reference to Osmundo–Alnion and its suballiances. Two associations were identified through the phytosociological analysis of the Tuscan coenoses: Carici pallescentis–Osmundetum regalis ass. nova for mainland Tuscany and Carici microcarpae–Alnetum glutinosae for the Tuscan islands. A phytogeographical analysis for western Europe (47 phytocoenoses, 567 relevés) was performed using floristic classification and chorology-based discriminant analysis. These allowed us to identify phytocoenoses: (1) attributed to Alnion incanae , correlated with the Eurasian and Boreal chorotypes; and (2) attributed to Osmundo–Alnion , correlated with the west Mediterranean, wide-distribution and Atlantic chorotypes. The floristic and ecological differences allowed us to divide Osmundo–Alnion into two suballiances: (1) phytocoenoses distributed on the Iberian peninsula, correlated with the Atlantic and endemic Iberian chorotypes, attributable to Osmundo–Alnenion ; and (2) phytocoenoses distributed in Algeria, Corsica, Sardinia, Sicily and Tyrrhenian Italy, correlated with the Mediterranean, endemic Sardinian–Corsican and endemic Italian chorotypes, attributable to Hyperico hircini–Alnenion glutinosae.