Analysis of forest diversity in an area of high presence of Taxus baccata and Ilex aquifolium. The study case in the central Appennines (Italy).

This is a detailed study of the Taxus baccata coenosis and other related woods of the calcareous ridge of Cingoli, as part of the lower peaks of the Umbria-Marche Apennines. This entire calcareous ridge has already undergone phytosociological studies. The aim of this study is to highlight the vegetation diversity of the biotope, as correlated with the complex morphology of the valley, its different ecological conditions, and the human activity of coppicing. The study area is the ‘Macchia delle Tassinete’ Site of Community Importance, and it is the third lowest peak positioned between the Marche Apennines and the Adriatic Sea, with a NE-SW orientation. It is also characterised by the presence of populations of yew (T. baccata) and holly (Ilex aquifolium). The yew is found throughout the Italian regions, although in isolated and extremely limited areas, as relict forms of the Tertiary that have been preserved to date. These enclaves are present throughout the central-southern Apennines, but the object of the present study is certainly one of the largest and easternmost remaining areas for T. baccata in central Italy. The plant communities dominated by yew are in the first part of the valley of the river Fosso delle Scalette. Here, the exposure to humid winds coming from the sea and the northern quadrants creates microclimatic conditions that are suitable for the development of T. baccata, which grows best on calcareous substrates and in an oceanic climate. This coenosis is attributed to the new association Staphyleo pinnatae-Taxetum baccatae. Despite the low altitude, in the more shady and humid areas, there is a beech forest suited to low altitudes that includes yew, which has allowed the description of the new association Asparago acutifolii-Fagetum sylvaticae. This new association has been attributed to the new suballiance described here for the first time, named Lathyro veneti-Fagenion, included in the alliance Aremonio-Fagion. This new suballiance groups together the thermophilus beech forests of the mesotemperate bioclimatic belt of the central Apennines. Along the slopes, on a narrow but flat terrace where the soil is deep and fresh, there is an original wood dominated by Quercus cerris with abundant Ilex aquifolium and other mesophilus trees. This has been attributed to the new association Taxo baccatae-Quercetum cerris, which also occurs with the subassociation fagetosum sylvaticae, and is included in the endemic Italian alliance Physospermo-Quercion cerris. In the sunny and dry areas, species of the order Fagetalia decrease, and the beech forest gives way to forest dominated by Ostrya carpinifolia that has been attributed to the association Scutellario columnae-Ostryetum carpinifoliae. There are also more thermophilus woods that are dominated by white oak and are rich in Mediterranean species, and have thus been attributed to the association Roso sempervirentis-Quercetum virgilianae. In conclusion, the importance of the conservation of this rich diversity in forest typologies is highlighted by their inclusion in the different European Union Habitats, sensu Habitat Directive.