Effects of land use in alpine grasslands on the probability of landslides

Landslides in topsoils, locally known as 'Blaiken', are caused by a set of factors which determine the probability of such slides. Apart from bedrock, relief and climate, the geomorphological changes in connection with land use, as well as vegetation and soil changes may influence landslides in alpine cultural landscapes. Within the framework of the EU project INTEGRALP (INTERREG II), the risk of erosion due to changes in land use within subalpine-alpine study sites was investigated (Passeier Valley, South Tyrol, Italy; Stubai Valley, North Tyrol, Austria). 42 potential factors were analysed in eroded and also in non-eroded areas. The factors included geomorphological, pedological, phytosociological and land-use characters. The statistical evaluation of the data was carried out via step-wise logistical regression. Twelve factors made a statistically significant contribution to the probability of landslides, and about 97% of the samples could be correctly categorised by using these factors. Apart from exposition, inclination and soil depth, land use was an important factor to landslides in topsoils. Managed meadows and pastures were significantly less erodible than abandoned grasslands. However, not the land-use activities themselves lead to changes in erosion risks, but rather the direct or indirect effects on vegetation and soil properties. They include relative cover of grasses, herbs and dwarf shrubs as well as the total root length and the rooting density in main fracture depth.