Dissertation Research The Role of Ectomycorrhizal Associations in Tropical Monodominance

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Although tropical rain forests are characterized by a high diversity of tree species, the tree Dicymbe corymbosa forms pure stands that exclude a wide array of other rainforest trees. The proposed research explores the possibility that particular root-inhabiting fungi enable Dicymbe corymbosa to exclude other trees, which leads to the formation of pure stands by this rainforest tree. In these tree-fungal partnerships, trees give fungi carbon they produce from photosynthesis, and in exchange the fungi give the trees limiting nutrients from the soil. We propose that positive interactions mediated through these plant-fungal partnerships, with concurrent negative interactions between the partner fungi and the microorganisms that decompose leaf litter, maintain monodominance of a tree that exists within a larger community of high tree diversity. To test this hypothesis, we will integrate both field and experimental studies in a naturally occurring monodominant forest in the Guiana Shield. This research will significantly enhance our limited understanding of plant-fungal interactions in tropical rainforests, integrating processes from molecules to ecosystems in a conceptual framework that has not yet been tested for dominant, tropical tree species. This research will also contribute to the training of undergraduate students from the University of Guyana, and will employ field assistants from the indigenous Patamona tribe, an Amerindian group in the interior of Guyana, where job opportunities are scarce.