1. Context Mountain ecosystems provide important regulation ecosystem services such as erosion mitigation. These processes are largely determined by the type of plant community, that is modified with elevation. The influence of plant community changes on soil processes with elevation is still poorly known. 2. Methods In June 2018, a study was carried out along an elevational gradient (1400 – 2400m) in the Massif de Belledonne (French Alps). At six altitudinal levels and under three keystone species (Picea abies, Juniperus communis and Vaccinium myrtillus), we measured root biomass and fine-root traits at the community level and two soil processes linked to erosion mitigation: erodibility and infiltration. We aimed to test environment-trait and trait-processes relationships considering vegetation, climate and soil. 3. Results At high elevation, where temperature and fertility are lower, we observed an increased production of roots with high absorptive capacity (small diameters and high specific root length), a strategy favouring belowground resource acquisition in the short growing season. Roots also demonstrated increasing persistence through the production of greater tissue density. Erosion mitigation decreased along elevation, and were explained by both soil properties and – to a lesser extent – root characteristics. 4.Perspectives The understanding of theses processes would be improved by the study of soil animal and micro-organisms diversity and activity.