The vegetation of temporary ponds of Sardinia

The Mediterranean temporary ponds are considered priority habitat in the Directive 92/43/EEC (habitat n. 3170*) and detailed information on their floristic composition and susceptibility to invasive species seems a central issue for their preservation, because the development and maintenance of seasonal vegetation is merely the resultant of the development and maintenance of its component individuals. Sardinia presents fairly large extensions of land where such habitats are still well represented, thought not investigated in depth. Basing on literature and unpublished data, a survey on the current phytosociological knowledge of the temporary ponds of Sardinia is presented. Our field studies led to the first recognition in the island of 22 associations, of which 13 were new. Out of them, 16 have been ascribed to the Cicendio-Solenopsion laurentiae, grouping ephemeral acidophilous spring vegetation with Mediterranean-Atlantic distribution, one to the Isoetion, that differs from the previous one in having an earlier drying up, and further 6 to the Verbenion supinae, grouping summergreen subnitrophilous prostrate vegetation linked to long-submerged sediments of the Euro-Mediterranean area. Besides of the phytosociological characterization, for eachy syntaxon the susceptibility to invasive species has been indexed, basing on the following criteria: status of the non-native species according to the classification of Pysek et al. (2004), occurrence and frequency of the non-native species, dispersal strategy of the same, kind of preferred habitat (natural/artificial)