Collaborative Research: Testing the Role of Resource Heterogeneity and Clonal Plant Integration on Plant Diversity in Grasslands

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Non Technical Summary (200 words) "Collaborative Research: Testing the Role of Resource Heterogeneity and Clonal Integration on Plant Diversity in Grasslands"PIs: KL Gross, GG Mittelbach, HL Reynolds (NSF proposal #0235699)What determines the number of coexisting species in a local area is a long-standing question for ecologists. This is particularly challenging for plant communities because plants require similar resources and so we would expect the number of coexisting species to be strongly limited by competition. One important, but rarely tested, hypothesis to explain the high diversity of plant communities is that variation in resource levels across different patches (i.e., spatial resource heterogeneity) may regulate species diversity. We are currently testing this hypothesis in a large-scale field experiment in Michigan grassland by experimentally increasing soil resource levels through fertilization in either a homogeneous or heterogeneous fashion. This manipulation is combined with a species (seed) addition treatment to test if the ability of species to invade these grassland communities changes under different nutrient regimes. In this renewal, we will continue to follow changes in plant species diversity in response to our treatments of nutrient patchiness and potential species invasion. We also will establish a new experiment in which we will determine whether the presence of clonal plants - species that grow by producing vegetative shoots - influences the ability of non-clonal species to respond to heterogeneity in soil resources.