Spatial Variability of Ecosystem Function at Coastal Western Lake Erie


Roberta Peixoto1* (, Leticia Sandoval1, Fausto Machado-Silva1, Shan Pushpajom Thomas1, Katelyn Hopkins1,2, Chloe Cash1, Matthew Kovach1, Donnie Day1, Solomon Ehosioke1, Stephanie C. Pennington3, Kaizad F. Patel4, Kendalynn A Morris3, Peter Regier5, Lucie Stetten7, Nicholas Ward5, Ben Bond-Lamberty3, Inke Forbrich1, J. Patrick Megonigal6, Nate McDowell8, Kenton A. Rod4, Edward J. O’Loughlin7, Kenneth M. Kemner7, Kennedy Doro1, Trisha Spanbauer1, Thomas B. Bridgeman1, Roy Rich6, Teri O’Meara9, Michael N. Weintraub1,4, Vanessa Bailey4


1University of Toledo, Toledo, OH; 2Truman State University, Kirksville, MO; 3Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD; 4Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA; 5Coastal Sciences Division, Pacific Northwest National Laboratory, Sequim, WA; 6Smithsonian Environmental Research Center, Edgewater, MD; 7Argonne National Laboratory, Lemont, IL; 8Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA; 9Oak Ridge National Laboratory, Oak Ridge, TN



Recent intensification of the hydrological cycle leads to complex impacts on the functioning of coastal terrestrial-aquatic interfaces (TAIs). Predicting how more intense water level fluctuations alter coastal forest functioning, groundwater and soil redox potential, and greenhouse gas fluxes remains challenging due to the dynamic nature of soil saturation at the TAI. Researchers hypothesized that ecosystem structure of the TAI, defined by depth and duration of soil saturation, drives gradients of (1) groundwater and soil oxygen availability and redox potential; (2) greenhouse gas fluxes from soil and trees with carbon dioxide (CO2) increasing and methane (CH4) decreasing from the wetland to the upland; and (3) trees’ hydraulic function and photosynthetic capacity, all of which are inversely related to groundwater level below the surface. To measure those changes, researchers are monitoring upland forest-wetland transects at three sites on the southern shore of Lake Erie. The team measured (1) soil and groundwater redox potential; (2) CO2 and CH4 fluxes from soil and trees; and (3) tree sap flux. The research team found high variability of redox potential in soil across the TAI, and groundwater redox potential decreased as the groundwater level decreased below the surface, potentially due to decreasing influence of topsoil on inputs of electron acceptors in groundwater. Soil CO2 fluxes varied spatially, with higher fluxes in wetlands and transition zones than upland areas of Portage River, possibly due to dry conditions exposing wetland soils or higher organic matter input and root respiration from aquatic macrophytes or flood-stressed trees. Wetlands were the highest sources of soil CH4 at all sites. The upland zone was a higher sink for soil CH4 than transition and transitions were a higher source of tree stem CH4 compared to the upland at two of three sites. Furthermore, flooding of upland forests is associated with a loss of tree hydraulic function, which might reduce canopy, photosynthesis, and carbohydrate storage. This research is part of the Coastal Observations, Mechanisms, and Predictions Across Systems and Scales–Field, Measurements, and Experiments project, providing insights into the dynamic relationships between soil saturation and plant and biogeochemical functions regulating the high spatial-temporal variability of TAIs essential for improving the predictive responses to climate change.