Dissertation Research: Effects of Plant Diversity on Community Invasibility in a California Riparian System

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9901984D'AntonioGreat concern over the impacts of invasive species has stimulated renewed interest in the hypothesis that diverse communities better resist invasion. Evaluating this hypothesis in natural communities has proven challenging because variation in diversity is controlled by, and therefore covaries with, disturbance, resources, consumers, etc.-the same factors directly impacting invasions. This research will isolate the independent effects of diversity and the effects of these covarying factors on the invasibility of sedge tussocks that dominate the Eel River. Each tussock houses a mini-community, varying naturally in native plant diversity, making an ideal system to explore the diversity-invasibility relationship. Exotic and native plants will be introduced on tussocks varying naturally in diversity and onto tussocks where diversity has been experimentally manipulated. This powerful combination will enable these investigators to determine how the number of species on a tussock influences its invasibility, evaluate the degree to which this relationship is driven by native diversity, and explore the underlying mechanisms. By additionally examining how diversity relates to invasibility at scales broader than the tussock, this research will also evaluate how the diversity-invasibility relationship changes with scale. This research will aid the conservation of threatened riparian communities, and enhance the predictability of invasion patterns across landscapes.