Atmospheric fluxes of reactive nitrogen to a northern mixed hardwood forest ecosystem NOx (NO + NO2), and NOy species (NOx + oxidation products) are important parts of the nitrogen cycle that affects the location and magnitude of carbon storage. Characterizing the fluxes of these reactive nitrogen oxides is important for our understanding of how the biosphere is affected by the deposition and transport of atmospheric nitrogen species produced by fossil-fuel combustion, both at present, and in a future with even greater anthropogenic nitrogen emissions. To understand the extent to which the atmosphere provides nutrient nitrogen to the forest ecosystem at the University of Michigan Biological Station (UMBS), the fraction of the net deposited nitrogen incorporated into the biosystem must be determined. My research project contributes to this effort by making simultaneous above-canopy flux measurements of NO, NO2, and NOy (total reactive nitrogen) so we will be able to determine the relative and absolute contributions of NO and NO2 to total NOy deposition over the UMBS forest ecosystem, collecting data from a range of seasonal, meteorological, and transport conditions. This data will be incorporated into a larger data set, including collaborative measurements of the fluxes of other NOy component species, isoprene, ozone, hydrocarbons, CO2, and water, as well plant physiological and ecological data reflecting the health and metabolism of the forest, foliar uptake, isotope studies, and the contribution of soil fluxes. This set of data, along with knowledge of leaf-level biochemistry (both in terms of reactive nitrogen production and the understanding of NO signaling in the plant) will help us understand forest canopy uptake and emission and how forest canopies affect the atmosphere above them as well as how they are affected by that same atmosphere.