Phenology and distribution strategy of key plant species within the subalpine-alpine ecocline in the Valaisan Alps (Switzerland)

The phenology of seven important species of the subalpine and alpine vegeta tion belts (Larix decidua, Picea abies, Pinus cembra, Pinus mugo, Rhododend ron ferrugineum, Salix herbacea, Vaccinium myrtillus) has been studied in r elation to air temperature. The results show that each species possesses it s own strategy regarding the required number of degree-days to reach bud bu rst and the end of flowering. These temperature requirements are discussed and related to the general ecology of each species. Phenological strategy i s shown to be a good tool for understanding the distribution, according to climate, of the species studied, in particular at their higher elevation ra nge, and also for assessing the impact of climate change.