Therophytic halophilous vegetation classification in south-eastern Italy

Aims: Halophilous, sub-halophilous, and halo-nitrophilous annual plant communities belonging to the Thero-Salicornietea and Saginetea maritimae classes have been analyzed in South-Eastern Italy. Even if numerous contributions have been provided on these vegetation types, at diverse scales of observation, the different and sometimes contrasting syntaxonomic treatments adopted by different authors, as well as the phytogeographical interpretations, have led to uncertainty about their proper classification and nomenclature. Methods: In the present contribution a data-set of 391 relevés (230 from literature and 161 original data) was first subjected to some basic statistics and then analyzed through flexible beta clustering. CH index was used to determine the best partition, and the phi coefficient for the identification of diagnostic species. Indirect gradient analysis was performed by DCA ordination. Results: Results were interpreted from a syntaxonomic point of view. As regards Thero-Salicornietea, halophilous communities are well separated from the halo-nitrophilous ones in the two orders Thero-Salicornietalia and Thero-Suaedetalia splendentis. Within Thero-Salicornietalia, a new alliance, Salicornion venetae, including the tetraploid Salicornia vegetation typically growing in long flooded sites of the Adriatic region, is here proposed. As for Saginetea maritimae, two main groups well separate: rocky coasts, sandy soils (Saginetalia maritimae, with the E-Mediterranean alliance Sileno sedoidis-Catapodion balea-rici) and salt marshes, clayey-silty soils (Frankenietalia pulverulentae, here with the two alliances Frankenion pulverulentae and Limonion avei).