MODELING SOIL PRODUCTION RATES FOR GLACIATED AND UNGLACIATED HILLSLOPES OF THE APPALACHIAN PLATEAU

The balance between regolith production and erosion determines whether a landscape is soil-mantled and how much agricultural soil loss is sustainable. Many studies consider climate and uplift extremes when determining soil production rates. Here we explore controls on rates of soil production on glaciated and unglaciated hillslopes of the Appalachian Plateau.

The Appalachian Plateau is located west of the spine of the Appalachian Mountains and is mostly underlain by Paleozoic strata; the northern parts have been glaciated. There is no present-day, tectonic uplift.

Our focus is two sites in Central Ohio which allows us to compare soil development in differing landscapes. The first is Denison’s University’s Biological Reserve (DUBR), which is a temperate deciduous forest, with some conifer plantation that was clear-cut in the last 100 years. It is mostly inceptisol soils, is underlain by siltstone, and was glaciated. Our second site is Neotoma Valley (NV), just south of Lancaster, Ohio. NV is a deciduous forest with inceptisols underlain by the Blackhand Sandstone. NV was not glaciated recently, as it was ~10 km southeast of the LGM.

At DUBR, we surveyed >200 tree throw events, describing them in terms of spatial and temporal frequency, aspect, and root wad dimensions. Using those numbers, we infer an average soil flux rate of 0.57 m³ m^-1 yr^-1. Using the rate of soil creep from Kaye Everett's previous work in NV, and the calculated DUBR soil flux, we computed a diffusivity coefficient for each. The DUBR and NV had K values of 0.0021 m² yr^-1 and 0.00078 m² yr^-1, respectively. Next, we calculated zonally averaged negative curvature at surveyed tree-throw events in the DUBR and soil pits in NV with radii of 2-20 m. With curvature, K, and soil density, we modeled soil production. For the DUBR, we found a range of 10 m/Ma to 100 m/Ma. In NV the range was 1 m/Ma to 40 m/Ma.

These rates are in the range of Be-10-derived rates from other tectonically quiescent sites and agree with catchment-averaged erosion rates from higher relief areas of the Appalachians. We are currently measuring Be-10-derived soil production rates for the hillslopes of NV. We hope to provide some of the first millennial-scale soil production rates for forested hillslopes of the Appalachian Plateau to provide context for nearby, agriculturally-driven rates of soil loss.