RAPID: Collaborative Research: Do negative plant-soil feedbacks outweigh positive ectomycorrhizal mutualisms in dipterocarp rainforest?

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High tree species diversity is a characteristic feature of rainforests in South America, Africa and Southeast Asia. However, it continues to be difficult for ecologists to explain how such a large number of species can be different enough to coexist when they all use the same small set of resources (light, water, nutrients). Theoretically, only a few dominant competitors should persist. One hypothesis explaining this conundrum is that soil fungi cause seedlings to die as tree populations grow, thus preventing any one species from becoming much more common than any other species. Current research on this topic is promising but has two primary shortcomings. First, it has largely been limited to Central and South American rainforests, despite fundamental differences in soil fungi around the world. Second, it has not considered that some soil fungi benefit, not harm, seedlings. In this project, investigators will take advantage of a rare mass seeding event in Malaysian Borneo to establish experiments that will test hypotheses about positive plant-fungal interactions in this ecologically under-explored part of the world. The work has great potential to lead to new insights into the ecological processes that shape the astounding diversity of tropical rain forests. In addition to improving our ecological understanding of the maintenance of tropical biodiversity, the insights gained through this research will help conserve the critically endangered rainforest ecosystems of Southeast Asia. Although these rainforests harbor a major share of global biodiversity and play a critical role in the function of the global biosphere, the region is experiencing alarming rates of deforestation. By studying the factors that impact seedling recruitment, this research will provide important knowledge required for successful reforestation and restoration of degraded forests. In addition, the study will shed light on the little known and potentially at risk microbial dimensions of biodiversity in these rainforests. Finally, this work will provide invaluable training for graduate students at US universities to work in a very complex ecosystem and increase US capacity to engage in these ecosystems.