Recovery of the forest’s protective effect after stand-replacing wind disturbances

The protection of people and infrastructure from natural hazards, such as rockfall, snow avalanches or landslides, is an indispensable ecosystem service of forests in mountain areas. However, open questions remain regarding its long-term and reliable provision, which will amplify with climate change. Natural disturbances, such as wind storms, can cause temporary losses of the forest's protective effect against natural hazards potentially leading to higher risks for settlements and infrastructures. In this study, we analyzed the recovery of the protective effect of more than 1700 windthrow areas in the Swiss Alps. We quantified recovery 13 and 31 years after the storm Vivian in 1990 based on forest structural variables derived from highresolution canopy height models and single tree detection. We observed a considerable recovery of tree height (67 % on average), forest cover (90 %) and stem density (46 %) 31 years after the storm. Basal area showed a lower recovery of 16 % on average with 25 % of the studied areas showing a retarded recovery of ≤ 6 %. This highlights the extended timescales required for full recovery of the protective effect against certain hazard types, such as rockfall or landslides. Recovery rates were most importantly influenced by temperature, precipitation, local topography, gap size and lithological substrate, underlining the importance of local environmental conditions when predicting forest recovery. The study highlights future research gaps, including the role of deadwood as well as species mixture in the recovery of the forest's protective effect after disturbances.