Pedogenic interpretation of a loess-covered, pleistocene-glaciated toposequence using the energy model

Runge’s energy model is one of several models of soil development that have been suggested in the last three-quarters of a century. This energy model includes three factors that affect the amount of energy input to a soil system (i.e., time, organic matter production/accumulation, and water available for leaching through the profile) and can be used to differentiate soil development among similarly classified soils in a defined landscape setting. In the context of the energy model, soil development was evaluated for four Typic Argiudolls along a toposequence in a loess-covered, glaciated landscape in south-central Wisconsin. Time was considered constant since loess was deposited at all sites during the last glaciation. Interpretations of pedogenic development along the toposequence were made in the context of the energy model based on soil surface organic matter and soil profile carbon (C) concentrations, measured water fluxes through undisturbed soil using tension lysimeters, a qualitative water-balance assessment, and clay content profiles. Pedogenic interpretations based on field observations and measurements were supported by estimates of relative kinetic energy input to the soil system from moving water and relative potential energy inputs stored in the existing soil C pool. Therefore, it was concluded that Runge’s energy model accurately indicated variations in the degree of soil development in similarly classified soils along a toposequence. The results of this study represent the first of its kind to quantify and interpret differential soil development based on units of energy input, as the energy model was originally intended. The results of this study also indicate that Runge’s energy model could be a useful tool in the prediction of soil morphological response to future land-use and/or hydrologic change in areas where the taxonomic classification of a soil mapping unit does not provided sufficiently specific information.