The woody vegetation of the Cornicolani mountains (central Italy) and the coenological role of Styrax officinalis.

The Cornicolani Mountains are a low altitude group of limestone hills located in the Roman countryside in the central Italy. These mountains are characterized by a meso-mediterranean and sub-mediterranean bio-climates which allows a typical termophilous deciduous forest vegetation to be developed. The Cornicolani mountains are also known for showing the highest Italian concentration of Styrax officinalis, an E-mediterranean scrub which is widespread from the southern Balkans to the Turkey and Middle East and which exhibits two separated and relic populations in the Peninsular Italy. Although the membership of Styrax officinalis to the Italian flora is questioned by some botanists, in the Cornicolani mountains area this species exhibits very high frequency and cover values in the majority of the forest and shrubland communities. From a physiognomical viewpoint Quercus cerris is the most widespread wood species of the Cornicolani mountains and gives rise to three aspects of sub-mesophilous woods (all referable to the Melico uniflorae-Quercetum cerridis) and to termophilous woods which belong to the Rubio peregrinae-Quercetum cerridis, Sporadically can be abundant Quercus frainetto which forms mixed woods with Quercus cerris especially on the sandy and partially volcanic substates of the flat areas (Echinopo siculi-Quercetum frainetto). Mixed woods of Quercus pubescens and Quercus cerris (Pistacio terebinthi-Quercetum pubescentis carpinetosum orientalis) occurs on the shallow limestone soils of the N-Facing slopes and exhibit a very rich woody dominated layer composed of Carpinus orientalis, Styrax officinalis, Acer monspessulanum, Pistacia terebinthus, Fraxinus ornus, Phillyrea latifolia and Rhamnus alaternus. The distruction of this type of potential vegetation leads to the development of high-shrublands dominated by Carpinus orientalis, Styrax officinalis, Acer monspessulanum, and Pistacia terebinthus. The Quercus ilex woods are not very common and characterize the summits of the hills where high percentages of rocks and pebbles occur (Fraxino orni-Quercetum ilicis). Pistacia terebinthus and Styrax officinalis give rise to the most widespread shrubland type where these two dominant species are accompanied by Cercis siliquastrum, Rosa squarrosa, Phillyrea latifolia. In the moist sites, on deep soils, Rubus ulmifolius, Crataegus monogyna and Rosa sempervirens scrubs occur (Roso-Rubetum ulmifolii) whereas in the dry and rocky slopes a Mediterranean maquis dominated by Phillyrea latifolia, Pistacia terebinthus, Spartium junceum, Lonicera implexa and Euphorbia characias with abundant Ampelodesmos mauritanicus is found.