Syntaxonomic revision of the Apennine grasslands belonging to Brometalia erecti, and an analysis of their relationships with the xerophilous vegetation of Rosmarinetea officinalis (Italy)

This study provides an update of our phytosociological knowledge of the vegetation of the Apennine grasslands that belong to Brometalia erecti, and it includes a new syntaxonomic revision. The statistical analyses were carried out through cluster analysis methods on the associations described for the Apennine grasslands, to which the garrigue associations of Rosmarinetea officinalis described for the same areas have been added. This has allowed a better definition of the interconnecting relationships between the xerophilous grasslands of Brometalia erecti and the chamaephytic vegetation of Rosmarinetalia officinalls. In the Apennine territories, these structural typologies are often found in a mosaic because they are linked to gradients that are closely connected to the erosion of the soils. The analysis of the interconnecting relationships between the associations of Rosmarinetea officinalis with the xerophilous grassland of the Phleo ambigui-Bromion erecti and Xerobromion has allowed a critical evaluation of the syntaxonomic attributes detailed by previous contributions, the demonstration of the absence of the Xerobromion alliance in the Apennines, and the attribution of the associations of the said alliance to the Artemisio albae-Saturcion montanae alliance (of the Rosmarinetea officinalis class) instead. This group of associations within this alliance has allowed the new Astragalenion monspessulani suballiance to be described, which is differentiated by a consistent group of species, among which many are of the Festucetalia valesiacae order. Within the Brometalia erecti order, the Phleo ambigui-Bromion erecti and Bromion erecti alliances are described. The following suballiances are included in the first of these: the typicum Phleo ambigul-Bromenion erecti (suball. nova), specific to the mesotemperate belt of the central Apennines; Sideridenion italicae nom. corr. (= Sideridenion syriacae Biondi et al. 1995); and Brachypodenion genuensis. The last of two of these are diffuse in the central- southern Apennines and the central-northern Apennines, respectively, with the last one found in the higher sectors. Finally, the new submediterranean suballiance Polygalo mediterraneae-Bromenion has been added to the Bromion erecti alliance, which includes the associations erecti I on substrata with clay components, where the erosion of the soils promotes the penetration of Mediterranean pioneer species.