Indagine fitosociologica sulle praterie a Brachypodium retusum (Pers.) Beauv. della Sardegna.

The grasslands characterized by the dominance of Brachypodium retusum occurring in Sardinia are examined. These communities, belonging to the Thero-Brachypodion ramosi alliance (Lygeo-Stipetea class), are quite widespread in the Island, where they usually grow on carbonate substrata from the sea level up to 1300m of altitude. On the basis of several phytosociological relevés, it has been possible to recognize six associations well-differentiated from the floristic, ecological and syndynamic point of view. The autonomy of these associations is also supported by a numerical multivariate analysis based on quantitative data (dendrogram and P.C.A.). The associations surveyed are the following: Dorycnio suffruticosi-Stipetum offneri ass. nova, localized on summit plateaux at an altitude of 700-1200m (CE Sardinia), Stipo bromoidis-Astragaletum verrucosi ass. nova, very rare and circumscribed to the coastal hills (W Sardinia), Triseto splendentis-Brachypodietum retusi ass. nova, colonizing more or less stabilized screes at 200-900m of altitude (NE Sardinia), Asphodelo africani-Brachypodietum ramosi Biondi & Mossa 1992 corr., thermo-xerophilous community linked to coastal stands (S Sardinia), Ranunculo graminei-Brachypodietum retusi ass. nova, orophilous community growing on jointed rocky places at an altitude of 1100-1300m (CE Sardinia), Melico ciliatae-Brachypodietum retusi ass. nova, found on the coastal screes of Figarolo islet (NE Sardinia). Besides, a floristic comparison among the hitherto known associations belonging to this alliance is given.