Mise en évidence de la dynamique de quelques écosystèmes forestiers et préforestiers provençaux aux étages méditerranéens SL à l'aide des taxons indicateurs

Evidence is presented for dynamic successions in the Provence on the basis of a multivariate analysis, of a very large sample. Different phases in the Quercus suber series on silicious substrate are shown. Also the evolution of the vegetation groupings on Ventoux and Sainte-Baume mountains on calcareous substrate and at different levels in the zonation is specified. The succession of the grasslands is as follows: Isoetes and Nasturtium groupings, Serapias, Lotus and Trifolium, then Vulpia and Aira groupings, and finally Helianthemum guttatum grasslands, preceding the shrub groupings: Cistus ladaniferus, then Cistus albidus and Cistus monspeliensis. Then follow either Erica and Calluna maquis or Quercus suber formations. On Mont Ventoux, the stages of degradation of the Quercus pubescens forests are Aphyllantes and Thymus vulgaris grasslands, and Buxus sempervirens and Genista scorpius scrubs. On the oromediterranean level, the transition from Avena setacea and Galium villarsii grasslands, then Ononis caenisia grasslands to Pinus uncinata forests is demonstrated. The development of reforestation is predicted on the basis of the floristic composition of the previous stages. On Sainte-Baume Mountain, the Quercuspubescens supramediterranean series is formed by the following stages: low scrubs of the Lavandulo-Astragaletum, and Prunus mahaleb and Phillyrea media, Acer monspes- sulanum groves, and forests with prevailing Quercuspubescens. The succession on rocky traverses and crests is slightly different. The first stages are Sesleria grasslands and the later ones are woodland groupings of Tilia platyphyllos, Acer opalus and llex aquifolium.