Old forests of the Massif Central. Auvergne-Rhônes-Alpes region.2020

Old forests are those that have not undergone a period of non-forest use (e.g. deforestation and agricultural use) since at least the mid-19th century, a period of the minimum forest for which the distribution of the remaining forests is fairly well known through the maps of the staff. This continuity of forest use can go back to a much older period (several centuries up to several millennia sometimes), hence the irreplaceable heritage character of these forests. Old forests are home to species that rarely occur elsewhere, especially among the vascular flora but also among mycorhyzial fungi. These species have limited dispersal capacities and/or are related to forest soil characteristics. The first threat to old forests is clearing, as a result of a change in use (cropping or grassland, roads, buildings, wind farms or photovoltaics, etc.) but also due to forest-related developments (e.g. desert, deposition). The other major risk is the significant change in the characteristics of forest soil that may result from some work, either directly (soiling or tillage, amendments, etc.) or indirectly (substitutions of species that lead to a profound change in litter).