64 Emerging Voices in Soil and Paleosol Science (Posters)

This session promotes research from students at all levels that are investigating soils and paleosols. We invite submissions from field, laboratory, and modeling studies that leverage or examine pedogenic processes and archives, from deep-time through modern systems.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

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

Paper number: 64-8
Program: Technical Sessions
Time: 8:30 AM – 8:30 AM

Authors

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 Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413066

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.