Colorful Nights: How LED Light Spectra Affect Tree Phenology and Tree-Herbivore Interactions

Artificial light at night (ALAN) is a major driver of global ecological change. In line with the WSL Strategy 2035, we study how ALAN's spectral composition ("light color") affects tree phenology, phytochemistry, and tree-insect interactions in European beech and pedunculate oak, two widespread species in Switzerland. Daylight studies show that shifts in LED light color impact plants and animals, suggesting that adjusting ALAN spectral composition could help mitigate ecological light pollution effects. Yet, such ALAN mitigation strategies have remained largely underexplored. The project will advance our understanding of how LED light color shapes tree phenology, phytochemistry, and insect herbivores at night. Our findings will help optimizing lighting parameters and contribute to more sustainable outdoor lighting solutions.