Graduate Exit Seminar - Thomas J. Doohan

Plan to join Thomas J. Doohan's graduate exit seminar on December 10, 2025, at 10:15 am at Kottman Hall Room 245 or via Zoom. Thomas will present, "Soil organic C stabilization dynamics across a continuum of disturbances and spatial scales"

Abstract: Monitoring changes in soil organic C (SOC) stocks over time is essential to ensure expected increases are occurring. However, our ability to monitor changes in bulk SOC stocks over time is limited by uncertainty in 1) how SOC and SOC fractions with contrasting stability and permanence are influenced by changing management, 2) how they vary with contrasting land use histories, and 3) how they are influenced by dynamic and inherent soil properties. My research aimed to reduce these uncertainties by quantifying change in SOC stock size and stability resulting from soil disturbance following changes in management or land use. Moreover, this work aims to elucidate factors which predict changes in SOC stocks and are linked with SOC stabilization and soil development, i.e., pedogenesis. To that end, we employed a resampling approach coupled with Bayesian inference to assess changes in SOC stocks (calculated using an equivalent soil mass approach) in 1) a large (ca. 4600 km²) agricultural river basin in northwest Ohio which has observed increased adoption of no-till practices over the last 50 years, and 2) a small (ca. 20 ha) reclaimed surface coal mine in southwest Ohio. Then we used mid-infrared spectroscopy to predict a theoretical maximum mineral-associated organic matter (MAOM) limit and MAOM saturation for a diverse set of Ohio soils. We found in our agricultural soils that only the particulate organic matter fraction stocks responded to decreased soil disturbance. However, we saw increases in all bulk SOC and SOC fraction after 25 years in our reclaimed minesoils. Furthermore, we observed morphological changes continued after 25 years in these reclaimed minesoils. Lastly, we estimated the theoretical maximum limit of MAOM content to be 66 (CI = [64,71]) g C kg^-1 silt + clay and demonstrated that saturation was significantly influenced by drainage class and cover class.

Advisor: Dr. M. Scott Demyan