Boreal forest fertilization leads to functional homogenization of ground beetle assemblages

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 homogenization ground-layer plant communities, are widely unknown. We sampled ground beetles (Coleoptera: Carabidae) in southern Sweden, within a large-scale, replicated ecological experiment initiated 2012, where half stands were fertilized every second year. assessed multi-scale beetle diversity community assembly, 4 years after commencement experiment. found that nutrient optimization had negative at multiple spatial scales, despite having negligible species richness. At local scale, lower variation body size sites, resulting within-site functional homogenization. landscape with higher basal area bilberry cover, filtered carabid traits composition larger sizes, generalist predators summer breeding species. Synthesis applications. Fertilization is strong filter assemblages, leading functionally homogeneous communities short term, without changes The large-scale impoverishment because may have consequences system resilience ecosystem service provision by this diverse group. Large-scale establishment threatens conifer plantations, underlining risks introducing more intensive management schemes already heavily managed landscapes.