Grassland invasibility varies with drought effects on soil functioning

Although it is known that ecosystems are more susceptible to invasion when disturbed, our knowledge of the mechanisms involved remains limited. Recent studies indicate that disturbance-induced changes in soil nutrient availability could influence community invasibility, but the importance of this mechanism in the real world is not known. We tested the hypotheses that (i) exotic plant species profit from drought effects on soil functioning more than do natives; and (ii) grassland invasibility depends on soil responses to drought disturbance, which are greater in soils that exhibit a larger nutrient pulse following drought. This was tested in a series of grassland sites of contrasting management intensity which we subjected to an extreme (40-day) drought, after which seeds from four different plant families of native species and related exotics were added to soils originating from the drought and control treatments under greenhouse conditions. We also examined the performance of seeded na...