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International audience; Theoretical advances and short-term experimental studies have furthered our understanding of how ecosystems respond to perturbation. However, there are few wellreplicated experimental studies that allow an assessment of long-term responses. Results from a controlled, large-scale field experiment in a subalpine grassland near Interlaken, Switzerland, show that 2–4 years of liming (Ca: 40 gm2yr1) still significantly affected the composition of the vegetation and the soil microbial community nearly 70 years after the treatments were imposed, whereas NPK fertilization (8 gm2yr1) only marginally affected vegetation composition. The exchangeable content of Ca ions and soil pH were higher in limed plots but were unaffected in fertilized plots. Plant species and PLFAs (phospholipid fatty acids) indicating low pH values were found in higher abundance in the unlimed plots, suggesting that the long-lasting effects of liming on the above- and belowground communities were mediated through changes in soil pH. The results of this long-term study indicate that the resilience of mountain ecosystems may be particularly low in response to perturbations that substantially alter soil pH or other key determinants of belowground processes.

International audience; Many mountain forests in the Alps protect residential areas and infrastructures from natural hazards. They are described as protection forests and their management aims to permanently provide a high protective effect. The maintenance and management of these forests are continuously improved and have reached a high standard. There is now a better understanding of the protective effects of the forest against natural hazards. In the Alps, there are currently several projects being conducted which aim to harmonize the assessment of natural hazards, damage potential and a resulting classification of protection forests. It is the objective to apply funding where needed in order to prevent damage from natural hazards. Currently, there is a need for improvement in the area of monitoring with advanced technology, such as Laser-Scanning (LIDAR), in linking inventory data from different sources, in simulation modeling to better estimate the long-term benefit of measures in the protection forest, and in transboundary collaboration.; Dans les Alpes, de nombreuses forêts protègent des localités et des infrastructures contre les dangers naturels. Elles sont désignées comme forêts protectrices. Elles sont soignées de façon à offrir durablement un effet protecteur aussi grand que possible. L'entretien et la gestion de ces forêts sont constammment améliorés et on atteint un niveau élevé. L'effet de la forêt contre les dangers naturels est de mieux en mieux connu. Plusieurs projets sont en cours dans l'arc alpin en vue d'harmoniser l'appréciation des dangers naturels et des dommages potentiels, et, à partir de là, la délimitation des forêts protectrices. L'objectif est d'utiliser les moyens disponibles pour la prévention des dangers de manière plus ciblée. Les possibilités d'amélioration se situent dans le suivi au moyen de techniques modernes (laser-scanning LIDAR), dans la liaison avec des données d'inventaire provenant de différentes sources, dans les modèles de simulation permettant de mieux évaluer l'efficacité à long terme des mesures en forêt protectrice, ainis que dans les collaborations transfontalières.