Influence of plant communities and soil properties on trace gas fluxes in riparian northern hardwood forests

Wetlands contribute significant amounts of greenhouse gases to the atmosphere, yet little is known about what variables control gas emissions from these ecosystems. There is particular uncertainty about forested riparian wetlands, which have high variation in plant and soil properties due to their location at the interface between land and water. We investigated the fluxes of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) and associated understory vegetation and soil parameters at five northern hardwood riparian sites in the Adirondack Park, NY, USA. Gas fluxes were measured in field chambers 4 times throughout the summer of 2008. CO2 flux rates ranged from 0.01 to 0.10 g C m−2 h−1, N2O fluxes ranged from −0.27 to 0.65 ng N cm−2 h−1 and CH4 flux rates ranged from −1.44 to 3.64 mg CH4 m−2 d−1. Because we observed both production and consumption of N2O and CH4, it was difficult to discern relationships between flux and environmental parameters such as soil moisture and pH. However, there were strong relationships between ecosystem-scale variables and flux. For example, CO2 and N2O flux rates were most strongly related to percent plant cover, i.e., the site with the lowest vegetation cover had the lowest CO2 and highest N2O emissions. These ecosystem-scale predictive relationships suggest that there may be prospects for scaling information on trace gas fluxes up to landscape and regional scales using information on the distribution of ecosystem or soil types from remote sensing or geographic information system data.