EVALUATION OF NITROUS OXIDE AND METHANE FLUXES IN URBAN LAWNS AND FORESTRY

Urban greenspaces are thought to be beneficial for the uptake and sequestration of greenhouse gases. This paper evaluates the efficiency at which managed urban lawns on the campus of the University of Cincinnati release and/or absorb the greenhouse gases methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O), compared to a local, unmanaged urban forest and lawn. N₂O has a greenhouse gas forcing of approximately 300 times CO₂, and methane of about 25 times that of CO₂. Samples were collected by following the USDA-ARS chamber-based trace gas flux measurement protocol using static, skirted flux chambers, and analyzed by FID and ECD methods. We hypothesized that the urban lawns’ ability to absorb the gases would be diminished compared to the forest and unmanaged grassland. Preliminary data show that CH₄ is being emitted from campus soils, but is being absorbed by the unmanaged lawn and urban forest. A similar trend was seen in N₂O emissions with higher emissions on campus lawns than those of unmanaged lawns, and no significant N₂O flux in the urban forest. These data will also be compared to soil carbon sequestration rates, also currently under investigation, for a full greenhouse gas balance. It appears that even if lawns are a strong sink for CO₂ stored in soils, this effect is counteracted by N₂O and CH₄ emissions, thus decreasing the ability of lawns to act as an overall greenhouse gas sink.