Managing for post-disturbance recovery. Lessons from active and passive restoration approaches in mountain forests.

When large and severe disturbances affect mountain forests, their ability to provide fundamental ecosystem services may be impaired for a long time. Indeed, in the Alps, forested slopes exert a crucial protective function and rapidly restoring the forest cover after a stand-replacing event is key to prevent the occurrence and mitigate the impact of subsequent natural hazards. Post-disturbance intervention can make or break forest recovery and should thus be tailored to meet management requirements and ecological needs. Widespread salvage logging removing all deadwood and other biological legacies in harsh environments where natural regeneration relies on facilitation mechanisms is a classical example of human intervention leading to undesired consequences. Quite often, when time is not a constraint, passive restoration can be the best option. Whenever active restoration is deemed necessary, particularly when large areas are affected, several challenges and limitations have to be addressed. Lack of saplings supply from tree nurseries, specialized workers and funding availability can hamper restoration activities. Some lessons learnt from mountain forests of the Italian Alps will be presented, considering restoration interventions after forest fires, windthrows and bark beetle outbreaks. Taking advantage of biological legacies, assisted regeneration and applied nucleation provided encouraging results, with nature-based solutions proving to be effective in promptly restoring the ecosystem services provided by forests, especially in protective stands. The reported results, considering ongoing climate change and its repercussion on disturbance regimes, highlight the urgent need to implement new methods in defining intervention priorities and new approaches in active and passive restoration.