PARENT SESSION
Contributed Oral Session 164: Wetland Chemistry
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Short-term effect of hydrologic pulses on nitrogen biogeochemistry in created riparian wetlands in the Midwestern USA.

Hernandez, Maria^*,1, Mitsch, William¹, ¹ Olentangy River Wetland Research Park, Columbus, Ohio, USA

ABSTRACT- Gaseous nitrogen (N₂O and N₂) fluxes and nitrogen accumulation in plants were investigated in two 1-ha flow-throw created wetlands receiving controlled flood pulses in Columbus Ohio USA. Seasonal pulses were simulated by pumping river water at a high rate during the first week of each month; in the remaining three weeks the wetlands receive low flow. The pulse regime operated from January to June; from July to December the wetlands receive steady flow. Nitrogen gas fluxes were quantified in plots at different elevations (upland plots only affected by groundwater pulses, plots in the edges with alternate wet and dry conditions, and plots which are permanently flooded). Vegetation enhanced N₂O fluxes when plots were inundated but when no surface was present water nitrous oxide fluxes were similar in plots with and without vegetation. The average of denitrification rates were higher in flooded plots (924 ± 177 gN m^-2 h ^-1 ) than in edges (580 ± 86 g N m^-2 h^-1) and transitional upland plots ( 482 ± 131 g N m^-2 h ^-1).In permanent flooded plots N₂O/N₂ ratios were similar before and after the pulse ( 0.02 ± 0.01 and 0.03 ± 0.01), in edge and upland plots, ratios were lower during the pulse (0.03 ± 0.01 and 0.02 ± 0.01) than after pulse (0.17 ± 0.08 and 0.17± 0.05). Average nitrogen accumulations were 16.54 ± 2.6 and 5.90 ± 1.0 g-N m^-2 in belowground and aboveground biomass respectively.

Key words: Pulses, Denitrification, Nitrogen, Riparian