A CRITICAL ZONE OBSERVATORY IN KARST: WHAT PROBLEMS WOULD BENEFIT (Invited Presentation)

Critical zone observatories, 9 in the United States and 45 world-wide, were created to probe in great physical and chemical detail, and on many time scales, the dynamic living skin of the earth. The question posed is: what could a critical zone observatory in karst contribute to the overall network of observations? Karst drainage basins exist in a great variety of geologic, geomorphic, and climatic settings. In common, they have the dominance of chemical over physical weathering, a rapid response to precipitation events, and a serious problem of soil loss and soil instability. The critical zone in karst consists of the vegetative cover, the epikarst (soil and root zone, regolith, and irregular bedrock surface), a fractured vadose zone punctured by shafts and solutionally-widened fissures, a zone of abandoned conduits with active carbonate deposition, a zone of fluctuating groundwater heads and flow through active conduits, and a deep phreatic zone. Observing, sampling, and instrumenting an entire karst watershed would have multiple objectives. (1) Relative mass loss along the pathways of sinking streams, shafts, and vadose zone fractures as a function of rate and intensity of storm input. (2) The carbon cycle in karst probed by CO2 and 13C measurements. (3) Denudation rates and landscape evolution. (4) Chemical and isotope evolution through the epikarst, the vadose zone, and the zone of carbonate deposition with a view to improving paleoclimate interpretation of speleothems. (5) Rates of soil formation in karst and the balance between soil accumulation and soil transport.