A Tale of Two Scales: Soils Across Coastal Terrestrial-Aquatic Interfaces
Authors
Kaizad F. Patel1, Avni Malhotra1* (avni.malhotra@pnnl.gov), Kenton Rod1, Ben Bond-Lamberty1, Xingyuan Chen1, Kennedy O. Doro2, J. Patrick Megonigal3, Teri O’Meara4, Allison N. Myers-Pigg1,2, Kenneth Kemner5, Nick Ward1, Michael N. Weintraub2, Vanessa L. Bailey1,2, COMPASS-FME team
Institutions
1Pacific Northwest National Laboratory, Richland, WA; 2University of Toledo, Toledo, OH; 3Smithsonian Environmental Research Center, Edgewater, MD; 4Oak Ridge National Laboratory, Oak Ridge, TN; 5Argonne National Laboratory, Lemont, IL
URLs
Abstract
Regional variability, local hydrological gradients, and complex interconnections make soils at the coastal terrestrial-aquatic interface (TAI) extremely difficult to characterize, simulate, and thus predict responses to future hydrological regimes. The team characterized soil biogeochemical parameters across the TAI in contrasting freshwater (western Lake Erie Basin) and estuarine (Chesapeake Bay) coastal systems. Researchers established transects at three sites in each region to capture: (1) upland forests, the terrestrial endmember; (2) transition forests with intermittent inundation; and (3) wetlands, with persistent inundation. Along each transect, soils were analyzed for physical and chemical parameters, including elemental composition, extractable nutrients and ions, water retention and particle size. At regional scales, freshwater and estuarine soils varied strongly in their biogeochemical controls and variance structures. The Lake Erie soils had elevated phosphate and nitrate concentrations and showed evidence of redox-driven sulfur cycling. The Chesapeake Bay soils, on the other hand, showed the impact of seawater encroaching into the uplands, with evidence of significant iron redox dynamics across the transects. At transect scales, uplands, transitions and wetlands differed in their soil biogeochemical drivers. Surprisingly, transitions were not the mid-point or average of adjacent uplands and wetlands. Transition soils in Lake Erie showed higher SOM and phosphate concentrations than upland and wetland, suggesting that the transition may be a hotspot for certain nutrients. Furthermore, researchers hypothesized that transition soils would have higher variance in soil biogeochemical variables but this was not supported across regions. While transition soils did have the highest variance in Western Lake Erie, wetlands had the highest variance in the Chesapeake Bay, likely due to tidal influences. This multi-scale characterization of TAI soils is a necessary first step for scaling and predictions, particularly as punctuated (storms, seiches) and gradual (lake level change and relative sea level rise) disturbances alter hydrological conditions across the TAI gradient.