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sur le développement des zones arides et semi-arides

Titre : Plant-soil feedback and invasion by Australian acacias

Auteur : Afonso, Catarina

Université de soutenance : Universidade de Coimbra

Grade : Mestrado em Ecologia (Ecologia Aplicada), 2012

Résumé
Two Australian acacias considered invasive in Portugal, Acacia dealbata and Acacia melanoxylon, were examined for plant-soil feedbacks in parallel greenhouse experiments. Feedback was evaluated by examining biomass variation in plants grown in unsterilized and sterilized soils from different areas. Soils were collected from areas of native vegetation, areas invaded by A.dealbata and areas disturbed by wildfire. To explore the causes of feedback, several soil-related factors were measured : pH, nutrients, arbuscular mycorrhizal root colonization and nodulation by rhizobes. Results indicate the occurrence of biotic resistance of some native communities and facilitation of acacia invasion by disturbance by wildfire. Invasion and disturbance also enhanced acacia nodulation and mycorrhization. The most important predictors of plant growth were high soil ammonium content, and low organic matter content. Mycorrhization and nodulation were important for A.dealbata and A. melanoxylon, respectively. The importance of belowground mutualists on acacia growth was confirmed by lower plant growth in sterilized soils.

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