Quantification of Soil Carbon Stocks in the Field – Some Anthropedogeomorphic Issues From the Corn Belt.

Soil spatial variability in low relief glacial landscapes is often overlooked, poorly documented, casually explained as random, and rarely communicated in soil surveys.  Modern soil spatial variability is the cumulative result of a complex interaction between geologic, biologic, hydrologic, anthropogenic, and pedologic processes acting over time.  A great deal of modern soil spatial variation is systematic and can be explained through an integrated understanding of glacial and eolian sedimentation systems and post-glacial landscape evolution.  The processes involved and the resulting variability occur across multiple scales on the landscape.  Soil landscapes in the glacial mid-continent have systematic pedologic properties both along hillslopes and within landscape positions.  This pedologic variability often leads to similar variability in properties like crop yield, water movement, organic carbon content, and aggregate stability.  An understanding of pedologic variability can aid in the applied aspects of soil resource decision making scenarios and aid in understanding soil carbon stocks.  The purpose of this presentation will be to discuss the complex integration of glacial and post-glacial processes across the mid-continent and to highlight quantitative examples leading to a systematic understanding of modern soil-landscape relationships.  Examples from Iowa, Illinois, and Ohio landscapes with < 3 meters modern relief will be the focus of the presentation.  The cumulative contribution of glacial depositional systems, sediment facies relationships, periglacial processes, Holocene hillslope erosion-sedimentation, bioturbation, and post-settlement agricultural practices on modern soil spatial variability and ultimately on soil organic carbon stocks will be discussed.  Scientists monitoring soil carbon stocks in the field should be very aware of in-field variability associated with past agricultural practices and pedogeomorphic landscape evolution.