ABR: Experimental Comparison of Ecosystem Process Limitations Between Grasslands Dominated by Large Mammalian Ungulates

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9312435 McNaughton This project will consist of experimental studies of the control of ecosystem processes (emphasizing primary productivity, consumption by grazers and secondary productivity, plant mineral uptake as related to plant and herbivore nutrition, and soil mineralization rates) by nutrients, emphasizing, but not restricted to, nitrogen, in grazing ecosystems supporting abundant native ungulate populations. Study sites will be in Serengeti National Park, Tanzania, and Yellowstone N.P., USA. experiments will measure (1) the level of N required to saturate ecosystem processes, (2) the relative effect of small, multiple N applications (as might result from chronic air pollution) compared to a single, larger application equivalent to a urine dose (a natural recycling pathway), (3) the potential for N fertilization to induce deficiencies of other nutrients, as expressed in primary productivity, microbial activity, or properties of forages as an ungulate nutrient source, and (4) the effect of carbon enrichment, which will surely occur as atmospheric CO2 enrichment proceeds. These studies will contribute to a quantitative understanding of carrying capacity in native grazing ecosystems on two continents and in radically different climates, add to our understanding of the appropriate conservation strategies in ecosystems supporting abundant ungulate populations, and provide information about two components if global change (chronic nutrient enrichment from air pollution, and carbon enrichment) in ecosystems supporting large grazing mammals.