FLUVIOKARST DEFORESTATION: CHANGES IN VADOSE PROPERTIES RELATED TO PREFERENTIAL FLOW LOSS

The inner Bluegrass region of Kentucky is underlain by the interbedded limestones and shales of the Lexington Limestones, creating shallow karst development on the rolling plateau. Steeper (8-15°) slopes have developed along the escarpment of the Kentucky River, where recent erosion is now exhuming epikarstal conduits in the downhill forests. Upland areas have been used primarily for agricultural or fescue pasture since the early 1800's. Changes in soil properties revealed in soil horizon examination, datalogging of soil water content, and measurement of infiltration rates show clear changes of soil properties between forest and grass. Soil texture and soil depth measurement of matching forest and grass transects indicate that tree roots perform a critical system process in the thin residual soils by entering the bedrock along weakened pathways, permitting preferential flow of water and accompanying silts to deep layers and bedrock that is restricted to higher layers under long-term grass cover. Clay translocation seals lower grass horizons and increases the tendency for water to emerge as return flow or to enter preferentially selected deeper pre-existing conduits. As the capacities of matrix storage and the epikarstal conduits are exceeded, seepage opens gullies at the top of the forests below the grassed slopes.