Spatial and Temporal Trends in Greenhouse Gas Fluxes from a Temperate Floodplain Along a Stream-Riparian-Upland Gradient

Abstract:

Increasing floodplain and wetland restoration activity has raised concerns about potential impacts on the release of greenhouse gases (GHG) to the atmosphere due to restored connectivity between aquatic and terrestrial ecosystems. Research has shown GHG fluxes from hydrologically active landscapes such as floodplains and wetlands vary spatially and temporally in response to primary controls including soil moisture, soil temperature, and available nutrients. In this ongoing study, we are measuring GHG fluxes at six locations 24 times over a year within an Appalachian floodplain. Site locations are based on dominant landscape positions and hydrologic activity along a topographic gradient including the stream margin, an active slough, and the upland area. GHG fluxes are measured using a Picarro G2508 Cavity Ring Down Spectrometry GHG Analyzer employing the static chamber method. We are also conducting large synoptic sampling of GHG fluxes across the floodplain surface during the wet and dry seasons to explore spatial heterogeneity trends between extreme soil moisture conditions. Data collected thus far has shown correlations between CO₂ and soil temperature and soil moisture. CH₄ and N₂O fluxes have shown to largely depend on degree of saturation in the soil. By the conclusion of our project, we predict temporal patterns in GHG fluxes and soil nutrient content that reflect an increase in microbial function and the release of CO₂, CH₄, and N₂O during warmer and wetter seasons. Spatially, we hypothesize differences in GHG fluxes based on the frequency and duration of the floodpulse at the various locations similar to patterns we have seen thus far of increased production in CH₄ and N₂O at the intermittently flooded versus dry locations.