The pristine ecological landscape has been changed over the centuries by the spreading of agricultural practices, which lead to the present agricultural landscape. The natural vegetation substituted by olive plantations (i.e., the potential vegetation; see Table 1) belongs in the evergreen (mainly Quercus ilex) Mediterranean forest (TER sites), the sub-Mediterranean (Quercus virgiliana) deciduous forest (REN sites) and the lowland mixed forest (Quercus robur, Fraxinus oxycarpa; MIR sites). The soil of all sampled sites was a mixture of sand and clay, while only MIR sites grow on finer, silt-rich alluvium.