Article

The role of similarity-dissimilarity matrices is discussed within a conceptual framework that shows the strict connections between similarity, classification and diversity in vegetation studies. Examples of application of the evenness of the eigenvalues of similarity matrices (E()) to define classes, to measure correlation between biological communities and environmental factors and to measure diversity of vegetation systems as a parameter , by the formula k, where k is the number of classes and   E(), are given by considering two data sets regarding beech forests of the Italian peninsula.