Impact of different chestnut coppice managements on root reinforcement and shallow landslide susceptibility

The abandonment of chestnut coppice management since the end of WWII has caused a general overaging of coppice stands leading to their inability to meet stand and soil stability standards. In view of the important role played by roots against the triggering of shallow landslides, we investigated root systems and their contribution to slope stability in chestnut coppices. In particular, we looked at possible different root regrowth dynamics and their effects on root reinforcement as function of different sylvicultural treatments. To this purpose we selected young (managed and unmanaged) and an old unmanaged coppice stands in two sites (Gerra and Bedano) in the southern Swiss Alps. We collected data on root distribution and root tensile force in the field and then applied the RBMw (Root Bundle Model Weibull) to estimate the degree of root reinforcement provided by the different silvicultural options. Results highlight the chestnut tree's ability to renew the root system each time a stool is subject to a coppicing again. This implies there are important differences in terms of root regeneration, distribution and contribution to soil stability between young and overaged coppices. No significant differences in terms of root distribution and related soil reinforcement could be detected as a function of the different management options in young trees. Whenever possible, long-term silvicultural strategies in areas prone to shallow landslides should aim to convert pure chestnut coppices into mixed high forest stands.