Citation. Fargione, J. E. 2004. Biodiversity and community structure in a tallgrass prairie: Consequences of resource competition in space and time. Ph.D. Thesis. University of Minnesota. 

Abstract. Competition for resources is a major determinant of plant community structure, influencing species abundances and interactions. However, there is little empirical evidence addressing the traits conferring competitive ability, the mechanisms allowing species to coexist, and the consequences of these mechanisms for coexistence, invasion, and community productivity. Using a series of field experiments in a low nitrogen prairie communities at Cedar Creek Natural History Area, Minnesota, USA, I show that (1) species that have high root biomass, high root length, and low soil nitrate concentrations in monoculture are the best competitors for nitrogen. Bunchgrasses with the C4 photosynthetic pathway that possess these traits are the dominant competitors (Chapter 4);
(2) Species that grow at different times in the season, or have deeper roots, are more likely to coexist with one such dominant C4 bunchgrass, Schizachyrium scoparium (Chapter 2); (3) Diverse communities containing C4 bunchgrasses are more efficient at turning nitrogen into plant biomass, and interact with nitrogen fixing legumes to increase community productivity (Chapter 3); (4) Diverse communities inhibit invaders, with dominant competitors most strongly inhibiting invaders, and all species tending to most strongly inhibit invaders most similar to themselves (Chapter 5). I also review current knowledge of the mechanisms of competition and coexistence in plant communities, providing basis for the predictions tested in other chapters, and a context in which to interpret the results
(Chapter 1).