Mid and long-term ecological impacts of ski run construction on alpine ecosystems

The increasing extension of ski areas is a worldwide trend. The machine-grading of slopes involved during ski run construction changes the physical, chemical and biological properties of the soil, with significant, long term ecological impact on the environment. Establishing and developing plant communities in these areas is crucial to rehabilitate the biotic and abiotic soil environment, to improve slope stability and reduce the risk of natural hazards, such as water erosion and shallow landslides. This study was funded by the European Regional Development Fund - Interreg Alpine Space project, and developed by the Link4Soils Project team (https://www.alpine-space.eu/projects/links4soils/en/home). The research evaluated the long-term effects of machine-grading and restoration on plant-soil properties of ski runs, in order to contribute to formulating the best practices in ski run constructions. Study plots were established in 2000 and re-surveyed in 2017 on ski runs, which had been machine-graded and hydro-seeded in the 1990s. Vegetation, root trait and soil surveys were carried out on ski run plots and compared to paired, undisturbed control sites off the ski runs. Plant cover remained unchanged on the ski-runs over time but plant richness and diversity considerably increased, reaching similar levels to undisturbed vegetation. Plant composition moved towards more semi-natural stages, showing a reduction in seeded plants with a comparable increase in the cover of colonizing native species. Root trait results were site-specific, showing great variations between the mid and long-term effects of machine-grading and revegetation when compared to undisturbed sites. Under long-term management, the soil pH was still higher and the organic C content still lower in the ski runs than in the undisturbed sites, as the aggregate stability. The application of appropriate restoration techniques (e.g. soil profile reconstruction, saving and reusing native topsoil; revegetation, using seed mixture of adapted species) can produce significant and sustainable recovery in vegetation even above the timberline. Evaluating the rate and nature of any recovery observed, provides extra insight to the companies working in preparing and managing these areas, though it has been found that bringing about significant changes in root properties can take several decades. The potential benefits of an efficient maintenance of ski runs in the mid-long term are not only aimed for commercial purposes but also to potentially reduce natural hazards and increase the off-season attractiveness of the area, by preserving the whole ecosystem properties.