Personal laser scanning reveals how canopy structure, topographic parameters and light regime influence natural regeneration in alpine protection forests

Natural forest regeneration is necessary to preserve forest stability, resilience, and long-term functionality. In Austria, where protective forests cover approximately 40 % of forested areas, regeneration deficits threaten the sustainability of ecosystem services, particularly in the face of increasing disturbance events. Natural regeneration does not only ensure a continuous forest cover, but itself increases the protective function of the entire stand by increasing water retention and slope stability, and preventing soil erosion and small rockfalls. Despite the importance of promoting regeneration, forest managers lack clear, data-based guidance on environmental and structural conditions that support it. We aimed to identify key site and stand variables that influence the density of natural regeneration in alpine protective forests and to provide actionable recommendations for improving forest management practices. Our analysis revealed that regeneration density is significantly influenced by topographic conditions and overstory structure, with varying preferences for light availability. Key factors included incident solar radiation, crown base height, and stand stratification. Results indicate that a one-size-fits-all approach to gap size or residual basal area is inadequate. Our findings advance the ecological understanding of alpine protection forest dynamics and deliver a practical framework for implementing site-adapted, sustainable forest management strategies. • Natural regeneration in alpine forests is shaped by stand and topographic variables. • LiDAR-based metrics improve modeling of regeneration density in protective forests. • Generalized additive models reveal nonlinear effects of canopy and site conditions. • One-size-fits-all silvicultural targets fail to meet species-specific light needs. • Findings support site-adapted, data-driven forest regeneration strategies.