Dimensions US-China: Collaborative Research: Microbe eco-evolutionary feedbacks as drivers of plant coexistence and diversity gradients

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Grasslands comprise 26% of global land area and 80% of agriculturally productive land. In addition to their agricultural importance, grasslands also play key roles in diverse ecosystem services, including the production of clean water and the prevention of flooding. Native grasslands are often very species-rich, with richness increasing with increasing annual precipitation and declining following disturbance. These patterns of diversity can have important consequences because species-rich grasslands have been shown to be more productive and more resilient to unpredictable events like drought, flooding, or tornado damage. It is essential to understand the processes that govern both the patterns of plant diversity and the benefits of plant diversity to better manage grassland areas. The different processes that create and maintain the rich diversity of plant species coexisting in grasslands are unknown, but recent research suggests that plant pathogens may play a role. This project examines the extent plant disease determines natural patterns of plant diversity within grasslands by conducting parallel experiments at multiple field sites within the United States and China. Undergraduates, graduate students and post-doctoral researchers will be trained in diverse field and laboratory methods, including students and faculty from colleges and community colleges adjacent to study sites in Illinois, Missouri and Kansas. Data from this project will generate new directions for the management of rangelands and also lead to improvements in the yield and resilience of agricultural and native ecosystems.Pathogens are predicted to accumulate and limit plant productivity most strongly in grasslands with low plant phylogenetic diversity, low plant genetic diversity and high precipitation. These predictions will be tested through a coordinated set of field observations, field manipulations, and greenhouse assays, performed on parallel diversity and rainfall gradients in North American and Asian grasslands. Specifically, patterns of plant and pathogen phylogenetic diversity, patterns of plant resistance due to genetic diversity, and patterns of ecological and evolutionary feedback will be tested across rainfall gradients in central United States and China. Rainfall manipulations of experimental plant communities will test environmental dependence of plant species coexistence, productivity benefits of plant diversity, and the role of pathogens as drivers of these processes. These empirical studies will be integrated with mathematical models to generate predictions of patterns and benefits of plant biodiversity, as well as predictions of vulnerabilities of grasslands to environmental perturbations.