The increase in atmospheric nitrogen (N) deposition from industrial pollution is of major concern in northern ecosystems, which are typically nutrient-limited. Previous studies have hypothesized that N deposition may increase the carbon dioxide (CO2) sink potential of northern ecosystems by stimulating plant productivity. Peatlands, in particular nutrient-limited bogs, have accumulated vast amounts of carbon (C) since deglaciation, yet the annual C balance is often a very small difference between plant production and soil decomposition. The main objective of this research is to improve our understanding of complex feedbacks between peatland ecosystems and the atmosphere in response to increasing atmospheric N deposition and climate change. Will N deposition enhance or diminish the CO2 sink potential of nutrient-limited bog ecosystems? What are the positive and negative feedbacks of N deposition to net ecosystem CO2 exchange and climate change? How do changes in vegetation function and structure, as well as corresponding changes in microclimate (moisture, temperature, light interception), contribute to changes in the carbon balance? How will changes in leaf chemistry, phenology, and plant function affect the seasonality of CO2 exchange? The overall framework for the research addresses 1) the impacts of N deposition on global atmosphere-biosphere interactions, and 2) the vulnerability of peatland ecosystems to become C sources rather than long-term C sinks. The project builds on 10 years of research and education at a long-term fertilization experiment with varying levels of nitrogen, phosphorus, and potassium at Mer Bleue Bog in Ottawa, Ontario, Canada. The measurements and experiments include several field and laboratory components: ecosystem and leaf-level CO2 gas exchange of mosses and vascular plants at a range of light levels, leaf biochemistry to test stress responses to potential N saturation, above and belowground plant production and decomposition, and microclimate within the plant canopy and soil profile. These data will contribute to a peatland ecosystem model that will improve our ability to predict thresholds of change in these globally important ecosystems.
The broader impacts of this project include training women undergraduates at Mount Holyoke College, to prepare them for graduate school and future careers in environmental science. The plan includes a cascade mentoring model, which trains students to become research collaborators by following the sequence of trainee during the first summer, mentor to new undergraduate research assistants in the second summer, and finally designers of scientific studies and authors of honors research theses, leading to presentations at international scientific meetings and publication in peer-reviewed journals. Strong collaborations with scientists from major research universities in Canada, Finland and the U.S. are essential for training undergraduates. By involving these students in vibrant research communities of graduate students, postdoctoral fellows and faculty, they will contribute to our understanding of the complexities of carbon and nitrogen cycling in northern peatlands through interdisciplinary research.
