INVESTIGATING ENVIRONMENTAL CONTROLS ON BEDROCK WEATHERING ON THE SOUTHERN CUMBERLAND PLATEAU

Mechanical weathering of bedrock in the near-surface is a crucially important process for soil production, sediment generation, and plumbing groundwater paths in the critical zone. However, our current understanding of the rates of and controls on the fracture generation and propagation processes that drive mechanical weathering in natural conditions is inadequate to address current problems in hydrogeology, geomorphology, and soil science. At the University of the South in Sewanee, Tennessee, we have established the Split Creek Observatory to study critical zone processes on the Southern Cumberland Plateau with undergraduates. On the Cumberland Plateau, forests are experiencing a trend of mesophication – the conversion of fire-tolerant, open-canopy forests to closed-canopy, fire-sensitive forests, with resultant tree mortality and species shifts. Because trees interact directly with bedrock via their roots, they have an important role in growing and opening bedrock fractures, both by expansion during root water uptake and by direct transmission of wind shear stress to the bedrock, which is exacerbated when trees die and become rigid. Here, we present preliminary evidence of relationships between tree distribution and behavior and bedrock fracturing, using seismic surveys, bedrock cores, and acoustic emission surveys.