The effect of soil legacy on competition and invasion by Acacia dealbata Link
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Plant–soil feedbacks can exacerbate competition between invasive and native species, although the net effect of the interaction between soil biota and competition is likely to be species-specific. Very few studies have addressed the combined effect of soil and competition on plant performance and invasion by exotic woody species. This study explores plant growth and competition between Acacia dealbata and Pinus pinaster in three different soils—native, disturbed and invaded—in Portugal. The invasion of native P. pinaster forests by A. dealbata can be explained by the stronger competition ability of the exotic tree species. Competition is stronger in the native soil, allowing the establishment of A. dealbata in this soil and the displacement of P. pinaster. During invasion, A. dealbata changes soil conditions and establishes positive plant–soil feedbacks that promote its own germination and growth and increase P. pinaster mortality. Soil disturbance by the introduction of a different exotic species, Eucalyptus globulus, did not promote invasion by A. dealbata. We found a significant effect of soil legacy on both growth and competitive ability of the invasive A. dealbata. The ability of A. dealbata to outcompete the native P. pinaster in its own soil and the positive plant–soil feedbacks established after invasion are important mechanisms for A. dealbata invasion.
KeywordsAcacia Eucalypt Invasion Mediterranean climate Pine Plantation
This work was supported by the project MUTUALNET (PTDC/BIA-BEC/103507/2008), funded by the Portuguese Foundation for Science and Technology (FCT). SRR was supported by a grant from the Portuguese Foundation for Science and Technology (FCT) (Reference: SFRH/BPD/79599/2011) co-funded by the European Social Fund of the European Union. The authors would like to thank J. A. Crisóstomo for his help maintaining the plants during the experiment.
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