Doctoral Dissertation Improvement: Mycorrhizal legacy effects of a plant invasion may limit forest restoration

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Invasive plants have large direct impacts on native plant populations and communities. However, an invasive species may also change the environment in ways that persist long after the species itself is gone, through a legacy effect. Legacy effects may be caused by the disruption of mycorrhizal mutualisms, in which plants rely on certain soil fungi for nutrient acquisition. We do not understand the degree to which plant invasions affect plant-fungal interactions, and no one has yet described how long these impacts persist after invasion as a legacy effect. Scotch broom is an aggressive, introduced shrub with important ecological and economic impacts. This project aims to understand how invasion by Scotch broom affects mycorrhizae and the consequences this may have for restoration of local, native forests of Douglas fir, which partly depend on mycorrhizal fungi. Research will quantify the temporal aspects of both the development and persistence of this potential legacy of biological invasion, using a combination of large-scale field experiments and observational studies, greenhouse experiments, soil nutrient analyses, and a state-of-the-art molecular approach to characterize fungal communities. Beyond its intellectual merits, this research will have broader impacts in resource management. A major aim is to inform the management of an aggressive, introduced shrub in the context of reforestation. Scotch broom invasion has significant economic impacts on the regional economy of the Pacific Northwest due to losses of timber, agriculture and range production, and wildlife. Through close collaborations with private and public foresters, the information gained from this research will be available immediately for management. Findings will be disseminated in both formal and informal settings. Several undergraduates from diverse backgrounds will gain valuable lab and field research skills and conduct independent research on different aspects of the project.