Boreal forest fertilization leads to functional homogenization of ground beetle assemblages

1. Intensive fertilization of young spruce forest plantations (i.e. “nutrient optimization”) has the potential to meet increasing demands for carbon sequestration and biomass production from boreal forests. However, its effects on biodiversity, other than the homogenization of ground-layer plant communities, are widely unknown. 2. We sampled ground beetles (Coleoptera: Carabidae) in young spruce forest plantations of southern Sweden, within a large-scale, replicated ecological experiment initiated in 2012, where half of forest stands were fertilized every second year. We assessed multi-scale effects of forest fertilization on ground beetle diversity and community assembly, four years after commencement of the experiment. 3. We found that nutrient optimization had negative effects on ground beetle diversity at multiple spatial scales, despite having negligible effects on species richness. At the local scale, ground beetle species had lower variation in body size at fertilized sites...