February 2006 0038-075X/06/17102-152-166 Vol. 171, No. 2 Soil Science Printed in U.S.A. Copyright 0 2006 by Lippincott Williams & Wilkins, Inc. AN APPLICATION OF THE RUNGE "ENERGY MODEL" OF SOIL DEVELOPMENT IN MICHIGAN'S UPPER PENINSULA Randall J. Schaetzl1 and Charles Schwenner2 This paper examines some soils in Michigan's upper peninsula that do not "fit" with the zonal soils of the region. The typical upland soils in this part of the Pictured Rocks National Lakeshore (PRNL), when not constrained by bedrock or high water tables, are strongly developed Spodosols (Haplorthods). We used the energy model (Runge, 1973) as a conceptual guide to help explain the genesis of nearby soils, whose chemistry and morphology are very different. The energy model presupposes that soils are affected mainly by water available for leaching and organic matter production, as conditioned by parent material. In our study area, where water available for leaching is limited (or even negative), as on steep slopes shallow to bedrock with multiple springs and seeps, and where erosional processes are strong, horizonation in the classical sense does not form. Instead, shallow Histosols (Saprists) form above bedrock, even on 45% slopes. Oxyaquic Haplorthods developed on flat uplands, on the same bedrock, are strongly horizonated, as most of the water that impacts them is available for leaching and pedogenesis. In another example, soils that have formed above calcareous bedrock maintain such high pH values that their faunal assemblages are rich and diverse, and base cycling is strong, leading to thick 0 + A horizon sequences. These soils (Lithic Udipsamments) resemble Mollisols and exhibit few marks of podzolization. Conversely, nearby Oxyaquic Haplorthods above acid sandstone bedrock have limited faunal assemb- lages, slow organic matter decomposition, and horizonation indicative of strong podzolization. These examples highlight how conceptual models can be used to guide our understanding of soil genesis and distribution. (Soil Science 2006;171:152-166) Key words: Pedogenesis, conceptual models, podzolization, base cycling, bedrock influence. OILS are extremely complex natural phe- ships, process linkages, and the nuances of pedo- Watson- nomena. Only by using conceptual models genesis (Dijkerman, 1974; Johnson and They take can we better understand and explain the Stegner, 1987; Smeck et al., 1983). complexity of the pedogenic system and distin- the complex and make it simple; they are sim- guish signal from noise. Rather than being plified descriptions of natural systems. precise mathematical formulations that can be History is full of examples by which the pedogenic models has solved, conceptual pedogenic models help application of certain soil genesis. It is put soils information into perspective and influenced perceptions of provide insight into the system interrelation- equally full of examples in which models have been largely ignored. In the latter situation, had these models been used, the way in which the Science Building, Michigan State 'Department of Geography, 314 Natural natural systems were perceived might have been University, East Lansing, M[ 48824-1115. Dr. Randall J. Schaet.l is corresponding author. E-mail;[email protected] very different. 2 USDA-Natural Resources Conservation Service, 201Rublein Street, Marquette, One pedogenic model that has perhaps MI 49855. received less than its due amount of distinction Received Apr1 19, 2005; accepted Aug. 29, 2005. is the "energy model", developed by Ed Runge, 37 3 3 the University of Illinois DO: 10.1097/01.ss.0000187 . 1026.04 a soil scientist then at 152 VOL. 171 -- No. 2 VAN APPLICATION OF THE ENERGY MODEL IN MICHIGAN 153 (Runge, 1973). Despite its potential as a hybrid locally but not universally, such as inputs of pedogenic model, the energy model has re- eolian dust, sulfate deposition in acid rain, or ceived little fanfare and has been applied only fire. The factors define the soil-environmental selectively. Although frequently included in theo- system in terms of the controls on pedogenesis retical reviews, for example, Barrett (1999), (Scull et al., 2003; Wilding, 1994). To precisely Dijkerman (1974), Hoosbeek and Bryant define the state of the soil system, as the model (1992), Huggett (1975), Johnson (2000), Phillips attempts to do, we need to address and define at (1989), Smeck et al. (1983), and Yaalon (1975), least five aspects of it-its five state factors. The given its status as a major pedogenic model, its factors were not meant to explain how these use/citation in empirical soils research has been particular conditions influenced soil properties, limited to a very few papers, all of which es- that is, if this was not a process model, only that a sentially mention the model but do not directly given set of environmental conditions would use it in their research design, for example, result in the formation of a particular soil Cremeens and Mokma (1986), Honeycutt et al. property. In the state factor model, climate and (1990), Rockwell and Loughman (1990), and organisms are considered to be "active" factors Singleton and Lavkulich (1987). Only Brye's whereas relief, parent material, and time are (2004) paper expressly uses the model to explain more "passive", that is, they are being "acted soil patterns and development. upon" by active factors and pedogenic pro- Our research in a complex. bedrock- cesses. The parent material factor reflects the controlled landscape in Pictured Rocks National initial state of the system. The functional- Lakeshore (PRNL), in Michigan's (USA) upper factorial model remains the standard against peninsula, uses the Runge model to help under- which all other pedogenic models are still stand the genesis of the soils therein. In applying judged-the main model used to explain soil the model, we not only provide an example of distributions at most scales. its utility but also test its applicability and On the other end, so to speak, of the model robustness outside of the range of conditions in continuum is the process-based model of Roy which it was developed. Our application of the Simonson, developed and presented in his 1959 energy model may actually heighten its appeal paper, and later refined (Simonson, 1978). and open up new avenues for its applicability Unlike the state factor model, which focused within the pedologic and soil geomorphic on factors that affected pedogenesis but said communities. nothing directly about pedogenic processes, Simonson's model was entirely process based. THEORETICAL BACKGROUND He observed that soils all have similarities and differences, and that their differences are due to Runge's energy model uses pieces of two the varying strengths of the same types of preexisting conceptual models: Jenny's (1941) pedogenicprocesses, operating on similar materials. functional-factorial model and Simonson's In the process systems model, pedogenesis is (1959) process systems model. Jenny's model viewed as consisting of two steps: (1) the formulates soil as being a function of five state accumulation of parent material and (2) the factors (Stephens, 1947). State factors resonate differentiation of that parent material into with many soils scholars and mappers, and like horizons; Simonson's model focuses on the many "successful" models, Jenny "sold" it well second step. He felt that soils differed because by writing about it clearly. Each state factor is the processes they shared varied in degree, not meant to define the state and history of the soil kind. The four major kinds, or bundles, of system (Wilding, 1994). They are not forces or processes were designed, by necessity, to be very causes but rather factors-independent variables general to cover the entire range of pedogenic that define the soil system. This functional- processes (Smeck et al., 1983). Although not factorial model is expressed as originally conceived as an equation, the model S = f(cl, o,r,p,t ... ), (1) can be written as where S is the soil or a soil property, cl is the S = f(a, r, t, t2), (2) climate factor, o is the organisms factor, r is the relief factor, p is the parent material factor, t is where S is the soil, a is additions, r is removals the time factor, and the string of dots represents or losses, t, is transfers/translocations, and t, is other, unspecified factors that may be important transformations. Simonson envisioned that losses 154 SCHAETZL AND SCHWENNERS SOIL SCIENCE and additions are to the soil (pedon) as a whole, near Runge's Illinois home are also exdellent the parent whereas translocatigns occur between horizons base cyclers, and thus the more fertile the within a single pedon. These four sets of pro- material, the better these grasses grow and main- cesses occur simultaneously in all soils; their more bases that can be cycled, thereby processes balance and character govern the nature of the taining a high soil pH and inhibiting soil (Simonson, 1978). like weathering and acidification. These exam- the more humus- The process systems model was not devel- ples illustrate the point thýt and the more oped for, and has not found strong usage in, the rich the pr6file, the less weathered it might be (Schaetzl, interpretation of soil spatial variability; for this isotropic (less developed) parent purliose, the functional-factorial model (Jenny, 1991). Consequently, Runge viewed in unison, as an 1941) is more appropriate. Users of Simonson's material and biota as worlýing tv factor. [Both intensity model have to haye some knowledge of o factor that offset the (t), as in Jenny's (1941) processes to effectively apply it to explain soil factors operate over time spatial variability. model. gravita- Runge's (1973) model merges the strong [Runge's model relies heavily on water and in process formulation of the Simonson model into tional energy that drives infiltrating well as (indirectly) Jenny's factorial framework. Runge emphasized turn causes horizonation, as two priorityfactors fiom Jenny's model, climate on radiant solar energy for organic matter to be known as and relief He combined them into a single production.