The Plant Communities of the Class Isoëto-Nanojuncetea in Sardinia

A syntaxonomical revision of the plant communities of the Isoëto-Nanojuncetea class occurring in Sardinia is provided. Within this class, the ephemeral herbaceous hygrophilous associations linked to temporarily submerged surfaces occur, which are widespread in the European, Mediterranean, and Macaronesian countries. It groups plant communities floristically characterized by a rich set of annual hygrophytes or more rarely hemicryptophytes and geophytes, which are also physiognomically, ecologically, and structurally well differentiated. Within this class, two orders are recognized in Sardinia, such as Isoëtetalia and Nanocyperetalia, which are represented by several alliances. In particular, four alliances can be referred to as Isoëtetalia (Isoëtion, Menthion cervinae, Cicendio-Solenopsion laurentiae, and Agrostion pourretii), while a single alliance (Verbenion supinae) belonging to Nanocyperetalia has been identified. Within these alliances, several associations already described have been surveyed, while several other unpublished ones, are here proposed as new to science. Overall, 35 associations are recognized, 18 of which are described for the first time. Each higher-rank syntaxa and related associations are examined from a nomenclatural, floristic, ecological, and chorological point of view. In particular, the more significant phytosociological relevés regarding the examined associations were processed using cluster analysis, DCA ordination, optimclass diagram in order to highlight the correlations between them. As regards the floristic aspects, a checklist of the species occurring in the phytosociological relevés is provided.