Greenhouse Gas Fluxes in Floodplain Forests of Central-Illinois: Opportunities for Managing Denitrification?.

As diverse and productive systems, floodplain forests provide great ecological, social, and economic values. In central Illinois, they receive large inputs of nutrient rich sediments, high in organic matter, and floodwater with nitrate concentrations often > 15 mg N/L. Little is known about greenhouse gas fluxes from these floodplains in response to nutrient inputs, and whether expansion of these forests would effectively remove nitrate to N₂ rather than N₂O, given the high nitrate concentrations and limited flooding periods. The objective of this study was to determine the effects of nutrient rich sediments and floodwaters on greenhouse gas fluxes in floodplain forests. Gas fluxes (N₂O, CO₂, and CH₄) were determined in three floodplain forests (dominant species silver maple) along the Sangamon River in central Illinois during both flooded and dry periods. Static chambers were used during dry periods, and floating chambers during flood periods. Water quality was measured weekly in the Sangamon River and during sampling days. Soils were sampled for organic C and N pools. Floodplain forests had an increased release of greenhouse gases caused by the addition of nutrient rich topsoil and floodwaters due to agricultural runoff, with N₂O the most important flux. Expansion of floodplain forests would likely increase removal of nitrate by denitrification, but due to limited flood periods also greatly increase N₂O emissions.