Space-time variability in mediterranean pastures analyzed with diversity parameters

Different parameters of diversity and spatial niche amplitude (Pielou, 1975, Pineda et aL, 1981 b) have been used to describe the spatial organization of mediterranean grasslands in Central Spain. A slope sampled by 480 contiguous 8 X 8 cm quadrats proved to have a homogeneous floristic distribution when it was divided into 160 parts and maximum heterogeneity when divided into 4 sectors. These sectors corresponded to different geomorphological zones of the slope. The complexity of vegetation distribution on the slope was reflected by differences in organization - measured by diversity parameter A = H ( P / E ) / l o g a N (number of plots) between the parts obtained by division. The presence of low-entropy species - specialists - and high entropy species - generalists - was related to the different scales of slope organization. The spatial distribu- tion of plants was compared for different successional stages. Multivariate analysis of sampling plots confirmed previously identified organizational characteristics and clarified the nature of transitions between communities of different floristic composition or structure.