Das Melico ciliatae-Robinietum pseudacaciae, eine neue Robinienwald-Assoziation in der inneralpinen Trockenvegetation des Vinschgaues (Südtirol, Italien).

The Melico ciliatae-Robinietum pseudacaciae, a hitherto unknown community of black locust forest, is described on the basis of phytosociological relevés. The association is developed in the inneralpine, precipitation-poor Vinschgau Valley (South Tyrol, Italy), where it is found in the colline and submontane belt on the south-exposed valley slope. The low forests are dominated by Robinia pseudacacia with species of dry grasslands prevailing in the understorey. Melica ciliata dominates throughout almost all stands. Furthermore, black locust communities on deeper, less dry soils were recorded in the study area, i.e. the Balloto-Robinietum and the Chelidonio-Robinietum. The Melico ciliatae-Robinietum is clearly differentiated from these units and from the other Central European Robinia pseudacacia-communities described so far. It has many good differential species, mainly species of dry grasslands and rock ledge communities. It is also differentiated negatively by the almost complete absence of nitrophilous species of the Galio-Urticetea class. The stands of Melico ciliatae-Robinietum may result from plantations of Robinia pseudacacia and/or from spontaneous spreading of the species. The dominance of Melica ciliata in the Melico ciliatae-Robinietum is remarkable. Outside this community, this species occurs in the study area only in small-sized stands on stony, sunny sites; it is possibly facilitated on the very dry sites by the allelopathic effect of black locust.