Elucidating the controls of hillslope hydrologic connectivity and the degree of chemical weathering on soil development in vertisols: Using electromagnetic induction (EMI) to illuminate spatial and temporal patterns in soil moisture and total dissolved solids

Thursday, 27 July 2017: 10:30 AM
Paul Brest West (Munger Conference Center)
Okeson Rae Morgan, University of Kansas, Lawrence, KS, United States
Vertisols, common in the Great Plains and Midwest United States, possess shrink-swell properties and have the ability to seasonally alter the state of hillslope hydrologic connectivity (HHC) and the degree of chemical weathering in these soils. HHC describes how a continuous connection of saturated units manifests from the top to the bottom of a slope. The development and evolution of interconnected pore spaces, or macropores, is seasonally transient in vertisols due to the shrink-swell nature of these soils. HHC is inherent in the soil development of vertisols as macropore occurrence is closely related to antecedent moisture conditions and can drastically alter infiltration rates. However, quantitative relationships between HHC and chemical weathering in hillslopes mantled by vertisols is lacking. The purpose of this research is to elucidate the interactions between HHC and chemical weathering in order to better quantify soil development in vertisols. Here, we use geophysics to explore the spatial variability in soil moisture over differing saturation conditions (e.g., wet vs. dry). Currently, my research relies on 1-D measurements of soil hydrology (water levels from piezometers and soil moisture), water chemistry (lysimeters and piezometers) and bulk soil geochemistry (10 cm intervals) to explore HHC in a forested hillslope (summit, backslope, footslope, and toeslope) mantled by vertic soils in eastern Kansas therefor EMI will provide us with the means to study groundwater flow in the heterogeneous subsurface. We expect that the water table will maintain a connection in the spring and early summer due to increased precipitation resulting in bulk soil-water geochemistry results more closely reflecting bulk soil geochemistry at depth when periods of elevated moisture conditions persist. In addition, we expect EMI data to correlate to areas of high ion concentrations within the transect thus providing a useful tool to compare with soil moisture and total dissolved solids for the purpose of laterally inferring soil moisture conditions.