Nitrogen Saturation: Mechanisms and Consequences of Altered Ecosystem Metabolism

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Nitrogen (N) saturation of terrestrial ecosystems is one of the most important contemporary ecological issues. Researchers at Michigan Technological University and the University of Michigan are conducting a long-term, field experiment in northern hardwood forests in order to understand the responses of forest carbon (C) and N cycling to chronic N deposition. Since the experiment began in 1994, simulated atmospheric N deposition has caused advanced stages of N saturation to occur in this very common Great Lakes ecosystem. Over the next three years, funds from the National Science Foundation will allow the research team to determine the mechanisms behind these responses and their potential long-term consequences. It is hypothesized that N saturation will decrease decomposition of soil organic matter, enhancing C storage in the soil, and that nitrate, dissolved organic C and dissolved organic N will continue to leach from these forests. The study is one of few long-term experiments world-wide where predictions regarding responses to N deposition, and the mechanisms controlling them, can be tested in the field.