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Assessing the joint development of vegetation cover and soil properties is crucial to evaluate the efficiency of soil bioengineering techniques, especially during the most critical initial phase of vegetation colonization. We set up a laboratory experiment to quantify and disentangle the effect of Alnus incana roots on soil permeability and aggregate stability. Plants were grown in pots in a climate chamber for four different growing periods (1, 2, 4 and 8 months). Pots were filled with a soil coming from a moraine of a landslide area in Central Switzerland. After each growing period, surface permeability, soil volume permeability and soil aggregate stability were measured together with the development of the root systems. Our results show that alder roots significantly improve both surface and whole soil volume permeability already after 2 months of growth. Nevertheless, an increase in root length density does not necessarily correspond to an increase in permeability. We could set as a threshold a root length density of 0.1 cm/cm 3 until which an increase in root development corresponds to an increase in soil permeability, whereas after this threshold we observed a decrease in soil permeability. A significant increase in soil aggregate stability could be observed only with a root length density of 2 cm/cm 3 . No obvious correlation between soil permeability and aggregate stability could be found. Future work should validate these laboratory results with field data.

Root reinforcement is a key factor when dealing with slope stability problems and is an important quantitative criterion for the evaluation of the protective function of forests against shallow landslides, as well as for the adoption of appropriate practices in protection forest management.Although many models have been developed to estimate root reinforcement, a reliable quantification that considers both its spatial and temporal variability still remains a challenge. This work aims to extend the understanding of the long term spatial and temporal dynamics of root reinforcement after forest harvest in subalpine spruce forests by supplying new experimental data and applying a state-of-the-art model.We estimated root reinforcement decay 5, 10 and 15 years after timber had been harvested in spruce stands in a small catchment in the Swiss Alps. We collected root distribution data at different distances from the trees and calibrated and validated a root distribution model (RootDis). To

In European mountain regions, forests play an important role in the mitigation of risk due to natural hazards such as landslides, rockfalls, floods and avalanches.\ud \ud Conifer species usually provide a protective effect at higher altitude, while at lower altitudes broadleaf species are dominant. These forests are or were often managed as coppice systems.\ud \ud The high stem density of coppice stands, their rapid growth and the permanence of root systems in the soil can be considered as assets in terms of protective function. However, these considerations are poorly researched and there is generally a lack of studies investigating the suitability of coppice as protection forests. The issue is relevant, considering that many coppice stands in mountain regions have become uneconomic and are now abandoned and overaged. Whether and how to manage these forests stands is a key question for practitioners.\ud \ud In this contribution we analyze the implications of coppice management for slope stability and in particular to mitigate shallow landslides, focusing on root reinforcement, the main mechanism by which vegetation can reinforce slopes.\ud \ud We review available studies concerning root distribution and dynamics in coppice stands to formulate hypotheses about their contribution in terms of root reinforcement. Finally we highlight the lacks of knowledge and the further steps needed to properly evaluate the effectiveness of the coppices in protecting against shallow landslides