Although invasive tree species pose a significant threat to biodiversity, their impact on terricolous bryophytes has been insufficiently recognized. In addition, almost all previous studies focused on differences between invaded and uninvaded stands, not accounting for the effect of invader abundance. Here we aimed to assess the impact of Prunus serotina and Robinia pseudoacacia on terricolous bryophytes on nutrient-poor (Pinus sylvestris stands) and nutrient-rich (Quercus spp. stands) sites, along a gradient of invader biomass. We assessed the cover and species richness of bryophytes by vegetation surveys in 160 study plots (100 m