Essai de synthèse sur la dynamique actuelle des châtaigneraies cévenoles et ses conséquences sur la diversité végétale

Abstract

The present vegetation of the Cévennes mountains (southern France) dominated by sweet chestnut (Castanea sativa) is an outcome of an uninterrupted and frequently intense human influence existing since millennia. It is very different from the deciduous Downy oak (Quercus pubescens) forest which occupied the area at the end of the last glaciation, during a period when climate was quite similar to present day conditions in this subhumid, mid-altitude Mediterranean climate bioregion. Since human impact has been drastically decreasing for the last half century, but especially in recent years, possible vegetation trends can be envisioned for this formerly chestnut-dominated vegetation built on steep slopes and terraces. Based on experimental results in seed germination studies as well as on analysis of plant species diversity trends, we propose some possible trajectories and eventual ‘threshold crossings’ for the vegetation and landscapes of a region suffering rural exodus and agricultural abandonment. All new changes and trajectories have to be modelled taking into account a series of new constraints. © 2005, Taylor & Francis Group, LLC.