Owing to very extensive reafforestation ef- human conditions affecting timberline are forts in the middle of the last century, high- classed according to their relative imporaltitude forests have been reestablished and tance. The main controlling factor is temtimberline has been reconstructed in the perature of the growing season. Precipitation, southern French Alps. The altitudes of the re- soils, human activity, land ownership, and constructed timberline and of the natural legal conditions are important secondary factimberline (where it is still preserved) are tors that influence local variations in timberfound to be comparable. The physical and line.