FLORISTIC, EDAPHIC AND STRUCTURAL DIFFERENCES AMONG MEDITERRANEAN GRASSLAND SYSTEMS DEVELOPED ON SLATES AND GRANITES

Twenty Mediterranean grassland systems located on slopes, half of them developed on granites and the other half on slates, were studied. Onl y the upper and lower plots of each slope were considered, thus establ ishing two basic comparisons: upper communities versus lower ones and communities on granites as compared with those developed on slates. Th e simple approach used here pursues the aim of establishing whether th ere are differences between grasslands developed on granites and those formed on slates. To do so, the following parameters were considered: floristic composition, edaphic variables, biomass, diversity and hete rogeneity. It is concluded that the grasslands developed on granites, distinguishing between high and low plots, are more oligotrophic than those developed on slates. Alpha diversity decreases from the most oli gotrophic communities to the most eutrophic communities, while heterog eneity increases. The decrease in alpha diversity is related to compet ition and grazing, which make the dominance of one or another species possible. The increase in heterogeneity indicates that the most eutrop hic grasslands are the most sensitive to spatial variations, since the oligotrophic ones are more mediated by edaphic poverty.