Long-term impacts of ski piste management on alpine vegetation and soils.
Downhill skiing, the machine-grading of slopes and the use of artificial snow induce major disturbances to the environment of alpine ski resorts. Our study aims to quantify the impacts of different ski piste management types (graded/ungraded; with/without artificial snow) on the environment and its development over time. We re-sampled study plots established 8 years earlier and compared vegetation and soil characteristics on different types of ski pistes to adjacent off-piste control plots, and analysed vegetation changes over time. Generally, machine-grading led to a decreased plant cover and plant productivity, and increased indicator values for nutrients, light and soil base content compared to control plots. Ungraded ski pistes and artificial snow led to increased vegetation indicator values for nutrients and soil humidity. Soil analyses conducted in 2008 generally confirmed the changes shown by the vegetation indicator values in 2000 and in 2008. Machine-grading had the greatest effects on soil characteristics by increasing soil density by more than 50%, by increasing pH and C/N ratio, and by decreasing total nitrogen concentrations. The differences between piste and off-piste plots were similar to those found 8years ago, but their proportions changed. The vegetation cover on machine-graded ski pistes decreased over the 8 years, showing no sign of recovery or succession. Ungraded ski pistes showed increased differences in indicator values for reactivity and humus between piste and control plots compared to the results obtained 8years earlier. Synthesis and applications. Machine-grading of ski runs and downhill skiing in general induced long-lasting impacts on vegetation and on both chemical and physical soil characteristics. Even though few impacts of artificial snow were significant, our results suggest that it may change moisture status of the vegetation, and thus caution is warranted when used in dry and nutrient-poor habitats. The vegetation cover on machine-graded pistes deteriorated over a period of 8years, illustrating that natural recovery did not occur in these alpine habitats. Consequently, the construction of new pistes by machine-grading in alpine habitats should be avoided, and existing pistes should be managed to avert further disturbances.