Classifying Mediterranean Ecosystems in the Mediterranean Rim Countries and in Southwestern U.S.A.1

Université d'Aix-Marseille III, Centre de Saint-Jérôme, Laboratoire de Botanique et d'Ecologie Méditerranéenne, 13397 MARSEILLE/CEDEX 4. Abstract: Methods of classifying ecosystems have developed differently in Europe and America. Individualization of bioclimatic zones and of altitudinal levels proved most valuable, particularly the role of edaphic factors. This methodology can be associated with the vegetation series concept, that is, a succession of community types which, within a given altitudinal level and bioclimatic zone, and for specific edaphic conditions, leads to establishment of the climax community. Man's impact in these theoretical schemas can be directly considered. The methodology is open to numerous applications. Methods of classifying ecosystems, in particular forest ecosystems, which represent the most evident vegetation structures, have developed in a very different manner in European and Anglosaxon countries. It is of interest to compare the methods used in the countries bordering the Mediterranean Sea and in Mediterranean California. We shall not discuss again the physiognomic and climatic analogies existing between both regions (cf. Di Castri and H. Mooney 1973), and shall only try to retrace the development of the methods of classifying ecosystems in both regions.