Priority effects in European grassland plants : the role of plant origin and phylogeny in shaping competition and plant-soil feedback

Abstract

The timing and order of species arrival are key drivers of plant community assembly, yet the mechanisms underlying priority effects remain poorly understood. This thesis examines how direct competition and plant–soil feedback shape priority effects in grassland plant communities and how these processes are influenced by biogeographic origin and phylogenetic relatedness. Using a multi-year field experiment and complementary greenhouse experiments, competition and soil fungal effects were experimentally disentangled. Results show that both mechanisms generate predominantly negative priority effects and interact in a non-additive manner. Competitive effects were strongly linked to the biomass of early-arriving species. Priority effects were stronger among closely related species, mainly at the adult stage, indicating ontogenetic niche shifts. Overall, this thesis provides a mechanistic understanding of historical contingency in plant communities and informs ecosystem restoration and invasive species management.