64-10 Topographic Influence on the Microchemical Variations in Redoximorphic Features in a Bottomland Hardwood Forest

Session: Emerging Voices in Soil and Paleosol Science (Posters)

Poster Booth No.: 132

Presenting Author:

Jaslyn Herold

Authors:

Herold, Jaslyn Ilene¹, Richards, Devin M.², Balogh-Brunstad, Zsuzsanna³, Moon, Jessica B.⁴, El Masri, Bassil⁵, Runkle, Benjamin R.⁶, Stinchcomb, Gary E.⁷

(1) Department of Earth Sciences, University of Memphis, Memphis, TN, USA, (2) Department of Earth Sciences, University of Memphis, Memphis, TN, USA, (3) Department of Geology and Environmental Sciences, Hartwick College, Oneonta, NY, USA, (4) Biological Sciences Department, Murray State University, Murray, KY, USA, (5) Earth and Environmental Science Department, Murray State University, Murray, KY, USA, (6) Biological & Agricultural Engineering, University of Arkansas, Fayetteville, AR, USA, (7) Department of Earth Sciences, University of Memphis, Memphis, TN, USA,

Abstract:

Aquic soils and wetlands in general are critical components to terrestrial ecosystems because of their ability to sequester contaminants, cycle nutrients and greenhouse gases, and store carbon. The reduction and oxidation (redox) of chemicals in these soils is a key feature that enables many of these services. Secondary soil iron-manganese nodules (FMN) form due to these redox conditions and influence the cycling and availability of key nutrients and toxicants in wetland ecosystems. This study seeks to identify micron-scale spatial differences in the geochemistry of FMN as a function of topography, hydrology, and soil carbon age.

 

The soil pore water levels from a bottomland hardwood forest in Kentucky were monitored for 10 months to track seasonal inundation. Co-located soil profiles from terrace, floodplain, and channel sites were sampled for thin sections and analyzed using a micro-XRF spectrometer to make elemental maps of FMN at 25 μm resolution. Image analysis software was used to measure the spatial properties of FMN. These data are compared to previously collected hydrology and soil radiocarbon data.

 

Hydrology data show that the upper 40 cm of terrace and floodplain soil remain saturated for ~42% of the time, while channel soil remains saturated for ~70% of the time. Micro-XRF results show that the spatial distribution of manganese (Mn) in the FMN reflects this trend in soil hydrology. FMN are larger at depth, regardless of landform, which is consistent with greater soil moisture deeper in the profile. The largest FMN occur in the wetter channel site where the inner area of the nodule is dominated by Mn. This nodule morphology is likely driven by (1) the relative ease of Mn reduction vs. Fe reduction and (2) the duration of inundation with water. Some elements show greater adsorption to FMN including phosphorus, cerium, and barium, indicating their role as nutrient and contaminant stores. The results of this study will complement conservation work being done to protect these vulnerable ecosystems by providing a deeper understanding of the complex relationship between soil microorganisms, nutrient cycling, and gas flux. Additionally, this study is providing further insight for the use of these soil features as a tool for environmental reconstruction and prediction.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8159

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