Ordination showed that at least three factors affected the species distribution among the sampled sites, namely (in an apparent order of importance), potential vegetation, soil type and soil management, so that the outlining of a clear ecological gradient is probably hindered by the interaction among such factors. On the basis of the explained variability by the first three PCA axes (i.e., 50%), and the indirect gradient analysis arguable by the site distribution along the axes, it is indeed possible to hypothesize that, in our sites, each factor was slightly prevailing on the others at the local scale in an apparent random manner. Similar results have been found by  where soil management was one among several factors affecting arthropods distribution in olive agroecosystem, and by , where groundcover vegetation played different roles at different geographical scales. It is not to be excluded that even in the studied sites the interaction of several factors, e.g. soil tillage, residue management and N fertilization rate, could affect soil biota diversity as found by .