Can β-diversity drive dry pastures conservation priorities?

β-diversity is a major determinant of species diversity at the regional scale. Biological, spatial and environmental determinants have been suggested as drivers of composition variation in semi-natural grasslands. The relative importance of such factors is inconsistent among studies also in relation to scale differences. Our aim is to discuss the influence of the scale in determining the relative contribution of spatial and environmental factors to the variation inβ-diversity. We used data on central Italian dry grassland (Habitat 6210) and considered two different extents. We built dissimilarity matrices based on species abundances, metric coordinates and environmental factors. We used the former as response in a Multiple Regression on distance matrices to obtain a partition of the variance between the other factors. Furthermore, we used Multivariate Regression Trees to identify the major environmental determinants of grassland composition. Our results strongly suggest that, to conserve most of the diversity in dry grasslands of the habitat, we should take into account differences in rainfall at the broadest scale, and in soil development at a local scale.