EFFECTS OF FIRE FREQUENCY ON PLANT-COMMUNITIES AND LANDSCAPE PATTERN IN THE MASSIF DES ASPRES (SOUTHERN FRANCE)

Fire frequency can affect pattern and diversity in plant communities a nd landscapes. We had the opportunity to study changes due to recurrin g wildfires on the same sites over a period of 50 years in the ''Massi f des Aspres'' (southern France). The study was carried out in areas o ccupied by Quercus suber and Q. ilex series. A comparison of historica l and cartographical documents (vegetation maps covering a 50 year int erval and an accurate map of major wildfires during this period) allow ed us to determine the changes occurring over time with or without fir e action. Plant communities were grouped into three main vegetation ty pes: forests, treed shrublands and shrublands. The passage of three su ccessive wildfires on the same site led to a decrease in forest areas and an increase in shrublands; however, shrublands were already presen t before the first fire of the period under consideration. Less freque nt fire occurrence induced more complex heterogeneity and greater land scape diversity. In the study region as a whole, with or without fire action, a significant decrease in forest surfaces was recorded, wherea s there was an increase of unforested communities such as treed shrubl ands and shrublands. In some parts of the Massif fires increased the h omogeneity of the landscape, in other parts they created a greater het erogeneity and diversity of plant communities.