Artificial light at night (ALAN) decreases plant diversity and performance in experimental grassland communities – Data on species biomass and traits

Artificial light at night (ALAN) affects many areas of the world and is increasing globally. To date, there has been limited and inconsistent evidence regarding the consequences of ALAN on plant communities as well as the fitness of their constituent species. ALAN could be beneficial for plants as they need light as an energy source, but they also need darkness for regeneration and growth. We created model communities composed of 16 plant species sown, exposed to a gradient of ALAN ranging from ‘moonlight only’ to conditions like situations typically found directly underneath a streetlamp. We measured plant community composition and its production (biomass), as well as functional traits of three plant species from different functional groups (grasses, herbs, legumes) in two separate harvests. We found that biomass was reduced by 33% in the highest ALAN treatment compared to the control, Shannon diversity decreased by 43% and Evenness by 34% in the first harvest. Some species failed to e...