Links between soil texture and root architecture of Eucalyptus species may limit distribution ranges under future climates

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Root traits adapted to specific environmental conditions may impose a disadvantage to species when grown outside of their preferred habitat. Here we aim to identify whether Eucalyptus species typically considered as ‘less specialised’ may have root architectures that are adapted to either climate or soil texture, potentially limiting their current and future distribution. We compared the root architecture and biomass allocation of nine Eucalyptus species from a biodiversity hotspot. Plants were grown from seed in 60 cm deep, 40 cm wide rhizotrons filled with sandy soil, with roots observed over time and measured at harvest. Species that typically grow in coarse-textured soil tended to have more lateral roots exploring a greater soil volume compared to those typically found in fine-textured soils. Root distribution also varied with annual precipitation, with species typically found in dry climates – especially those preferring fine-textured soil – having fewer roots in the topsoil. Differences between root architecture and biomass allocation of juvenile Eucalyptus species were observed, suggesting adaptation to the environment that the species typically grow in. As these differences were expressed in a common substrate, phenotypic plasticity did not override genetic differences, making them vulnerable to a rapidly changing climate.