Investigating Hydrologic Connectivity as a Driver of Wetland Biogeochemical Response to Flood Disturbances
Authors
Corianne Tatariw1* (tatariw@rowan.edu), Ashleigh Kirker2, Lidia Molina Serpas2, Jasmine Morejon2, Elaine Rice2, Xingyuan Chen3, Behzad Mortazavi4, James Stegen3, C. Nathan Jones2
Institutions
1Rowan University, Glassboro, NJ; 2University of Alabama, Tuscaloosa, AL; 3Pacific Northwest National Laboratory, Richland, WA; 4Syracuse University, Syracuse, NY
URLs
Abstract
Wetlands serve as biogeochemical control points, regulating nitrogen (N) removal from local to watershed scales. Flood disturbances influence wetland biogeochemical activity by delivering dissolved organic matter (DOM) and nutrients to wetland soils. This delivery is regulated by the mode of hydrologic connectivity (i.e., hillslope-connected vs. floodplain-connected flowpaths) to the stream. However, researchers lack an understanding of how differences in flood-driven water and material delivery affect post-flood biogeochemical processing within wetlands. The objective of this study is to determine how hydrologic connectivity mediates wetland biogeochemical response to floods at a forested, headwater coastal-plain system. Researchers designed the project to adhere to Integrated, Coordinated, Open, and Networked (ICON) science principles.
Wetland water-level measurements show increasing inundation durations from hillslope-to-floodplain wetlands. Researchers have installed additional piezometers to empirically measure the surface water and groundwater water levels of the wetlands and the surrounding upland, which can be used to examine the solute dynamics from a hydraulic gradient. Potential denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in wetland soils varied between individual wetlands but were overall higher during the wet season. The team will use inundation duration and frequency of saturation events to further elucidate drivers of potential nitrate reduction pathways.
Researchers used the Advanced Terrestrial Simulator (ATS) to model subsurface, surface, and canopy water in a comparable small, forested wetland, and found that hydrogeomorphology drives reach-scale patterns of water availability and drying. The next goal is to use PFLOTRAN to model biogeochemical cycling in an individual wetland. To provide empirical measurements of watershed carbon and nitrogen export, a water quality sensor probe will be deployed at the watershed outflow. Overall, initial findings indicate that seasonal (i.e., wet vs. dry) drivers play an important role in regulating wetland and watershed nutrient processing across the gradient of hydrologic connectivity.