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

Abstract

The proliferation of ski run construction is a worldwide trend. The machine-grading of slopes involved during ski run construction changes the physical, chemical and biological properties of the soil, having significant long-term ecological impact on the environment. Establishing and developing plant communities in these affected areas is crucial in rehabilitating the biotic and abiotic soil environment, while also improving slope stability and reducing the risk of natural hazards. This study evaluates changes in plant-soil properties and the long-term effects of machine-grading and subsequent restoration of ski runs so as to contribute to formulating the best practices in future ski run constructions. Study plots were established in 2000 and re-surveyed in 2017 on ski runs, which had been machine-graded and hydroseeded 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 after-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 standard actions applied (machine-grading, storage and re-use of topsoil, hydroseeding of commercial seed mixtures, application of manure soon after seeding and low-intensity grazing) allowed the ecosystem to partially recover in three decades, and even if the soil has still a lower chemical and physical fertility than the undisturbed sites, the plant species composition reveals a satisfactory degree of renaturalization.

Grassland Restoration at a Graded Ski Slope: Effects of Propagation Material and Fertilisation on Plant Cover and Vegetation

“…The average species number was 21, but 28 in the last surveyed year, i.e., only one less than the species richness of the surrounding vegetation. This richness is similar to that found 4-40 years after revegetation on graded slopes in the Alps subalpine-alpine zone (34 species in Klug-Pümpel and Krampitz [45]; 29 species in Roux-Fouillet et al [14]; 25 species in Hudek et al [17].…”

“…This difference was due to the fact that species from the donor grassland were introduced only once at the sowing time, while the receptor site vegetation represented a continuous seed source of potential plant colonisers. Similar trends of restored vegetation progressively approaching the receptor site vegetation were found by Klug-Pümpel and Krampitz [45] and Hudek et al [17] at graded slopes where the surrounding grasslands were close to the restored area.…”

“…Topsoil storage and re-use was found to be an effective method to facilitate the ecosystem recovery after grading [17]. Before grading, the fertile topsoil is removed with an excavator and piled close to the ski run.…”

Recent thermokarst evolution in the Italian Central Alps

“…Given the very slow renaturalization, partial ecosystem recovery is often achieved in two to three decades through specific actions (such as machine-grading, storage and re-use of topsoil, hydroseeding of commercial seed mixtures, application of manure soon after seeding, and low-intensity grazing). [60][61][62] However, at high altitudes ski-run recovery and revegetation becomes increasingly difficult. 60 Our data confirm that the spontaneous revegetation of a ski run at high elevations is difficult, with the vegetation colonization taking 17 years to start and following the primary succession dynamics.…”

“…This initial delay confirms the harshness of the ski-run environment. This could be due to the particular conditions of the ski run, characterized by substantial alterations of soils with a relatively hard surface of compacted material (not allowing the permanence of seeds and the fixing of the new plantulae to the terrain), the lack of nutrients, and high pH (e.g., [60][61][62] ). Moreover, the ski run is characterized by the lack of a soil with a seed bank, which may increase substantially the speed of vegetation colonization, as observed in the colonization of landslides in periglacial environments (e.g., 72 ).…”