Interactions between vegetation, roots and soil stability in restored high-altitude ski runs in the Alps

Construction of ski runs has a very heavy impact on alpine ecosystems since it results in total destruction of the existing vegetation and profound alteration of the soil. Restoration work must thus set out to develop a protective plant cover immediately and promote re-establishment of a functional plant-soil system in the long term. The aims of the present study, conducted at the Monterosa ski resort (Val d'Ayas, Aosta, Italy) were to evaluate (1) how disturbance related to ski run construction at high altitude (2200-2600 m a.s.l.) has affected vegetation and soil properties compared to undisturbed sites, and (2) how vegetation and soil properties change in machine-graded ski runs with increasing time after hydroseeding. Herbaceous cover and specific composition, root density, physico-chemical soil properties, and aggregate stability were evaluated to determine the vegetation and soil dynamics of four runs constructed above timberline and hydroseeded 4, 6, 10, and 12 years ago, respectively, and of the adjacent undisturbed alpine pasture as control. The seeded species had quickly formed a cover that was still high even after 10 years. However, cover values were always extremely low for wild species, and this could be related to their strategies and to altered soil properties (higher pH, organic matter impoverishment, and loss of both fine particles and aggregates). The study indicated that more has to be done to conserve or restore physico-chemical soil properties as a decisive factor in establishing a self-sustaining native plant community.