Biological Legacies and Rockfall: The Protective Effect of a Windthrown Forest

Windstorms represent one of the main large-scale disturbances that shape the European landscape and influence its forest structure, so post-event restoration activities start to gain a major role in mountainous forest management. After a disturbance event, biological legacies may enhance or maintain multiple ecosystem services of mountain forests such as protection against natural hazards, biodiversity conservation, or erosion mitigation. However, the conservation of all these ecosystem services after stand-replacing events could go against traditional management practices, such as salvage logging. Thus far, the impact of salvage logging and removal of biological legacies on the protective function of mountain stands has been poorly studied. Structural biological legacies may provide protection for natural regeneration and may also increase the terrain roughness providing a shielding effect against gravitational hazards like rockfall. The aim of this project is to understand the dynamics of post-windthrow recovery processes and to investigate how biological legacies affect the multifunctionality of mountain forests, in particular the protective function. To observe the role of biological legacies we performed 3000 simulations of rockfall activity on windthrown areas. Results show the active role of biological legacies in preventing gravitational hazards, providing a barrier effect and an energy reduction effect on rockfall activity. To conclude, we underline how forest management should take into consideration the protective function of structural legacies. A suggestion is to avoid salvage logging in order to maintain the multifunctionality of damaged stands during the recovery process.