Who comes first? Implications of the plant-microbiome-soil continuum feedback on plant performance

Abstract: Plants are sessile organisms that rely on their ability to explore the soil to access the nutrients and water they need to survive. Plants have co-evolved with certain groups of bacteria and fungi that provide nutrients and water and enhance tolerance to abiotic and biotic stressors in exchange for Carbon (C). This symbiotic interaction is central to plant establishment and survival in harsh environments, where edaphic properties exert selective pressures on plant growth and modulate the composition of the soil microbiome community, with potential detrimental effects on ecosystem composition. Globally, more than 50% of the biodiversity hotspots are in soils with particular characteristics, thus, edaphic properties are considered as second in importance after climatic variables. In this thesis, the aim was to study the impact of the soil properties on plant establishment and performance and how this affects the ability of the plant to recruit a microbial community to their roots, with a focus on the ectomycorrhizal fungi (EcM). The results presented in this thesis suggest that both edaphic properties and soil microbiome modulates plant establishment and growth. In addition, changing edaphic properties induce changes in plant metabolism that have direct impact on the root-associated community. These changes redefine plants’ C economy toward less demanding symbionts, having direct impact on the soil organic matter (SOM) dynamics. My results provide new insights on how anthropogenic-induced changes in the soil can have a strong impact on the soil ecology, which can in consequence, have a major impact in the forest biodiversity.