Plant-soil Feedback: A Mechanism to Explain the Spread of Invasive Species

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ABSTRACT: Positive feedback has been proposed as a mechanism that results in thestable persistence of alternative states of an ecosystem. Such feedbackmay operate through plant-induced alterations in soil microbialcommunities, which in turn alter plant communities through changes innutrient dynamics. The recent replacement of native understory plantcommunities in eastern deciduous forests by apparently stable communitiesof exotic species provides an excellent model system in which to test thepresence of soil-mediated positive feedbacks. Previous studies of thissystem have shown that the recent shift in community composition is relatedto changes in both nutrient cycling processes and microbial communitycomposition. I propose greenhouse microcosm and field plot experiments totest whether plants drive changes in soil-based ecosystem processes byaltering the soil microbiota, and whether these changes in turn promote thedominance of the exotics. The proposed studies will explicitly contrast alitter-driven above-ground mechanism with a root-driven below-groundmechanism. BROADER IMPACTS: If the hypothesis of plant-soil positive feedback created byaltered nutrient cycling is supported, it would both demonstrate aplausible mechanism for the persistence of alternative stable communitiesand help explain the establishment of dominance by some exotic plantspecies. In addition, this project will train at least 1 graduate student and 3 undergraduates.