Ecology of Bison, Elk, and Vegetation in an Arid Ecosystem

Schoenecker, Kathryn

Herbivory has profound effects on vegetation production and structure in many different plant communities. The influence of herbivory on plants and ultimately ecosystem processes is shaped by the types of plants consumed, the intensity of herbivory, the evolutionary history of grazing, and the availability of water and nutrients to plants. The effect of ungulate herbivores on vegetation is of great interest to ecologists, land managers and agriculturalists. In addition, the Department of Interior recently established a Bison Conservation Initiative to provide for the conservation and restoration of North American plains- and wood bison, which includes establishing new populations and expanding existing populations. The San Luis Valley, Colorado, is being considered as a potential location for a bison conservation herd. Resource managers need to know the vegetation impacts of adding a second large ungulate to a system that already has elk. In Chapter 1 I conducted a landscape-scale observational study comparing areas with bison and elk grazing to areas with just elk grazing. In Chapter 2 I focused on plant responses to herbivory, using an ungrazed (exclosed) treatment to test theory on grazing optimization and plant compensation. In Chapter 3 I focused entirely on bison to evaluate their population dynamics using hierarchical Bayesian modeling.