OXIDE AND CLAY MINERAL STABILIZATION OF SOIL ORGANIC CARBON ACROSS LAND-USES AND GEOMORPHIC POSITION IN THE PIEDMONT VIRGINIA, USA

Increasing soil organic carbon (SOC) sequestration through human land-use practices is imperative to mitigate climate change effects, but accumulation and storage rates are affected by geomorphic position and mineral weathering processes. The variability in SOC can be large, with terrestrial storage ranging from 10 to 200 Mg C ha-1 across the southeastern US. Morven Farm on the Piedmont in Virginia, USA, demonstrates historical intensive cropping from the late 1700s and more modern pastureland and afforestation from the early 1900s. Compared with other local farms further from the Blue Ridge, the meta-basalt parent material has created base cation rich soils. Our study examines Morven Farm in central Virginia to determine how SOC pools across land-uses (no-till cropping, secondary hardwood forests, pasture, loblolly pine plantation) and with geomorphic position (back, foot, and toeslopes). Moreover, we examine how Al and Fe as well as clay minerals relate to SOC accumulation in the soil. On the property, 96 sites were sampled by auger down to refusal along replicate topographic transects. Samples were analyzed for C and N using elemental combustion and inorganic elements via ICP-OES. Clay mineralogy was evaluated by X-Ray Diffraction and oxides by extractions. Secondary hardwood forests had significantly higher carbon pools with depth than pine plantation, but pasture, no-till cropping, and secondary hardwood forests did not vary significantly with depth or total profile pools per hectare. Our Fe oxide, Al oxide, and mineralogical show the impacts of land use and SOC sequestration with depth. These findings shed light on the importance of secondary minerals on SOC accumulation processes and help the University of Virginia and Commonwealth of Virginia reach their sustainability goals. Future experiments will investigate in-situ manipulations on expanding SOC accumulation for terrestrial storage.