Soil–vegetation interaction on slopes with bush encroachment in the central Alps – adapting slope stability measurements to shifting process domains

In the European Alps many high mountain grasslands which were traditionally used for summer pasturing and hayinghave been abandoned during recent decades. Abandonment of mown or grazed grasslands causes a shift in vegetation compositionand thus a change in landscape ecology and geomorphology. Alpine areas are very fragile ecosystems and are highly sensitive tochanging environmental conditions, which can affect the geomorphic regime of these high energy environments. The effect of landuse intensification on erosion rates is well documented, whereas the effect of land abandonment on erosion rates is still discussedcontroversially, particularly in relation to its short-term and long-term consequences. Generally, an established perennial vegetationcover improves the mechanical anchoring of the soil and the regulation of the soil water budget, including run-off generation anderosion. However, changing vegetation composition affects many other above- and below-ground properties like root density,diversity and geometry, soil structure, pore volume and acidity. Each combination of these properties can lead to a distinct scenarioof dominating surface processes. The study of soil properties along a chronosequence of green alder (alnus viridis) encroachment onthe Unteralptal in central Switzerland revealed that shrub encroachment changes soil and vegetation properties towards an increaseof resistance to run-off related erosion processes, but a decrease of slope stability against shallow landslides. Copyright © 2014 JohnWiley & Sons, Ltd.