A new pioneer association of detrital substrata of the hilly and low-mountain belts in Central Apennines (Italy)

Plant communities dominated by Petrosedum ser. Rupestria in Italy have always been referred to the Sedo albi-Scleranthetea biennis Br.-Bl. 1955 class. Tis group of species was also ofen found more or less abundant in the garrigue and pasture vegetation. Some unusual plant communities dominated by Petrosedum rupestre (L.) P.V.Heath with a conspicuous presence of typical species of scree vegetation were found and sampled in the Abruzzo region, on more or less mobile debris. In order to classify such communities, syntaxonomic, structural, chorological and ecological analyses have been performed. All the Petrosedum ser. Rupestria dominated communities reported in Italy have been compared with the sampled vegetation. A new perennial pioneer association, linked to more or less mobile detrital substrata of the hilly and lower-mountane belts of the calcareous Central Apennines has been here described with the name Linario purpureae-Petrosedetum rupestris. Based on the syntaxonomic analysis, this association has been included in the Linarion purpureae alliance (Scrophulario bicoloris-Helichrysetalia italici order). Te Linario-Petrosedetum has been divided into two subassociations: a typical one named petrosedetosum rupestris and a thermophilous one of the lower altitudes named teucrietosum flavi. Te study revealed the originality of such communities and their appropriate classifcation in the Tlaspietea rotundifolii class. Tis is the frst record in Italy of a Petrosedum ser. Rupestria-rich community framed in the scree vegetation class.