Drought affects the performance of native oak seedlings more strongly than competition with invasive crested wattle seedlings

Abstract

[EN] Two of the most important processes threatening vulnerable plant species are compet-itive displacement by invasive alien species and water stress due to global warming.Quercus lusitanica,an oak shrub species with remarkable conservation interest, couldbe threatened by the expansion of the invasive alien treeParaserianthes lophantha.However, it is unclear how competition would interact with predicted reductions inwater availability due to global climate change. We set up a full factorial experiment toexamine the direct interspecific competition betweenP. lophanthaandQ. lusitanicaseedlings under control and water-limited conditions.•We measured seed biomass, germination, seedling emergence, leaf relative growth rate,biomass, root/shoot ratio, predawn shoot water potential and mortality to assess theindividual and combined effects of water stress and interspecific competition on bothspecies.•Our results indicate that, at seedling stage, both species experience competitive effectsand responses. However, water stress exhibited a stronger overall effect than competi-tion. Although both species responded strongly to water stress, the invasiveP. lophan-thaexhibited significantly less drought stress than the nativeQ. lusitanicabased onpredawn shoot water potential measurements.•The findings of this study suggest that the competition with invasiveP. lophanthainthe short term must not be dismissed, but that the long-term conservation of thenative shrubQ. lusitanicacould be compromised by increased drought as a result ofglobal change. Our work sheds light on the combined effects of biological invasionsand climate change that can negatively affect vulnerable plant species