Progressive Nitrogen Limitation in Terrestrial Ecosystems: Empirical Test of a Biogeochemical Paradigm

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Carbon dioxide is released to the atmosphere when humans burn oil, coal, and gasoline, and is the major cause of global warming. Increasing carbon dioxide in the atmosphere may help plants take it up faster through the process of photosynthesis. Will carbon uptake by forests help counteract human emissions of carbon dioxide over the next century, and thereby help mitigate climate change? Some models suggest that it might, but these models assume that plants will be able to acquire enough nutrients from the soil, an assumption that may well be faulty. This research project will determine how rising carbon dioxide affects the cycling of nitrogen, the nutrient whose short supply most frequently restricts plant growth. Specifically, this research will determine whether the initial positive responses of plants to increasing carbon dioxide eventually fade away because the availability of nitrogen declines. This project will also examine how increased atmospheric carbon dioxide may alter the cycles of other elements, including the element molybdenum, which is known to be key to the ability of ecosystems to accumulate limiting nitrogen. The findings will be important for understanding how nitrogen cycling influences how much carbon ecosystems might accumulate as carbon dioxide continues to rise. The project will contribute to education and will specifically target minority students for involvement in research. The project will develop critical thinking exercises that build on the research results, designed for use in undergraduate courses. Integration of research and education is particularly important in ecosystem ecology and biogeochemistry, because these fields of ecology are traditionally underrepresented in undergraduate ecology courses, and because these fields have key implications for policy decisions surrounding global climate change and carbon management.