In the dry calcareous Prealps area, a sylvo-pastoral management experiment started at Laborel, a mountain village of the department of Drôme, in the South-East of France. This little agricultural country, the Baronnies, was transformed in its landscape by a great increase of brushes and Scots pine (Pinus sylvestris L.) pine-wood. In the plots which were heavily grazed by a sheep-flock, the natural colonisation by Scots pine is very difficult; so, it appeared that a new dense area overgrown with grass (by seeding) does not help the young Scot pine implantation. The aerial photographs' interpretation, which helped to reconstitute the vegetation dynamism between 1948 and 1989, showed that, for forty years, a more or less compact pine-wood, colonized the area when there was no any agricultural activity; this constitutes a favourable element, above the altitude of 1,000 meters, for the installation of mixed pine-wood and beech-grove, and then a pure beech-grove when edaphic and climatic conditions are favourable.