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Modern pedology has developed from the emerging disciplines of seventeenth and eighteenth century chemistry, geography and geology, which in turn had roots in classical speculation about the nature of matter. It was during the nineteenth century that the idea slowly developed that soils are separate from other earth phenomena. They were thought by the geologists to form from the weathering of rocks and by the chemists to be the product of organic matter. The idea that several interrelated factors contribute to soil formation was possible only when soil was fully recognized as a unique natural body. This multifactor genesis of soils was most fully articulated in the nineteenth century by Vasilli Dokuchaev in Russia and Eugene Hilgard in the USA. While Hilgard developed his own ideas concerning the nature and formation of soils, it was not so clear how Dokuchaev thought of the idea of multiple factors of soil formation. Dokuchaev's inspiration may have come, at least in part, from the Russian chemist Dmitri Mendeleev. In 1876, Mendeleev suggested that the Imperial Free Economic Society of Saint Petersburg form a commission to study the black earth or chernoziom, and this commission consisted of representatives from agronomy, chemistry, geography, geology, physics and zoology. The commission chairman was Dokuchaev, and his thinking on the factors of soil formation must have crystallized using the interdisciplinary framework of the commission structure. While not quantified, the factors provided a basis for understanding soils which was carried to the West through Dokuchaev's student Konstantin Glinka in collaboration with the German pedologist Hermann Stremme to Curtis Marbut and Hans Jenny. Additionally, Jenny rediscovered and reintroduced Hilgard's independently conceived ideas of soil formation to the pedological community.
Factor's of Soil Formation” was a pedological classic that succinctly synthesized into a conceptual model soil concepts developed earlier by Dokuchaev and associates in Russia. It further articulated methods by which the system could be quantitatively studied in a more scientific approach to pedology. This forward-looking treatise focused mostly on uncultivated soils developed under short geologic time scales from relatively “uniform” glaciated parent materials. The functional relationships developed were constrained by geographical limits and analytical databases. Interdependence of state factors limited extension of models, especially to older landforms. Major contributions were: (i) a better appreciation of the Russian pedological works, (ii) a conceptual framework to comprehend soil distribution patterns, (iii) a methodology for pedological quantification, (iv) a stimulus to develop soil genesis models, (v) a basis for construction and quantification of soil taxonomy, and (vi) a synergistic ecosystem approach that rallied many diverse interests and approaches of pedology into one framework.
Paleosols ranging in geological age to 3 billion years are widely used as evidence for ancient surface environments—an enterprise dependent on the enormous literature on factors in soil formation, popularized by Hans Jenny. This kind of inference inverts the logic of Jenny in a manner common to geological sciences—deducing paleoenvironments from observed paleosol features, rather than deducing variation in soil features with observed environmental differences. A paleosol is a single product of many past influences, including alteration after burial, and because of this, some environmental relationships with soil color, clayeyness and organic matter are not useful for interpreting paleosols. One relationship that has proven useful for paleosols is that between depth to calcic horizon and mean annual rainfall. A new compilation of data presented here demonstrates that this relationship holds for aridland soils worldwide. The use of this relationship for interpreting paleoclimate from paleosols is illustrated with an example of the Eocene and Oligocene paleosols of Badlands National Park, South Dakota. Other approaches for the study of paleosols include identifying paleosols within a soil taxonomy, and simulating ancient soil development with mathematical process models. Identification of paleosols leads to broad areas on soil maps unless done with several paleosols. Process models often founder on assumptions, and those of the form δx/δt (where x is a measured soil property) are difficult to apply because time of formation (t) of a paleosol is estimable only to an order of magnitude. Thus the environmental factor approach to the interpretation of paleosols is likely to remain popular for some time to come.
The study of soils has long been an important component of geoarchaeology (the application of geosciences to archaeological problems). The widest applications of soil science have involved soil chemistry (for detecting the presence, nature, and intensity of human occupation) and the identification of soils as stratigraphic markers and their use as paleoenvironmental indicators. The “state factor” approach to pedology significantly increases the potential applications of soil studies in archaeological contexts. Chronosequences are useful in dating and correlating sites and for predicting the occurrence of sites of a given age. Consideration of the time factor also can profoundly influence interpretations of occupation zones in buried soils. Toposequences and lithosequences can be important in understanding and interpreting environmental change in an archaeological site and, along with biosequences, are useful in (i) reconstructing the relationship of human occupations to paleolandscapes and landscape evolution (ii) reconstructing paleoenvironments. Understanding and interpretation of soil stratigraphy in archaeological contexts also can be greatly enhanced by consideration of the state factors.
Factors of Soil Formation is a seminal book in terrestrial ecosystem ecology much as it is in pedology. The insights and syntheses therein remain a driving force in studies of natural and managed ecosystems. The influence of Factors of Soil Formation is illustrated by recent examples of ecological studies based explicitly on the climate, organism, relief, parent material, time, and human activity factors. Where single-factor studies are impractical, ecosystem studies treat the interactions of state factors (with each other and with processes internal to ecosystems) in process-based models whose development and validation are themselves dependent on state factor-based approaches. Finally, the legacy of Factors of Soil Formation, and the man who created it, is now being felt in the development of ecological research programs to analyze causes, consequences, and feedbacks of global environmental change.
The soil survey of the USA flourished under C.F. Marbut (1913-1934). His leadership transformed the ideas of Glinka, Hilgard, and others into a coherent U.S. pedological philosophy. There were two USDA soil inventory programs during the 1930s and 1940s—soil surveys under C.E. Kellogg and soil conservation surveys under E.A. Norton. The surveys were combined in 1951 and Dr. Kellogg continued to provide leadership from 1951 to 1974. According to Jenny (1941, p. 262) soil geographers were those scientists who developed maps, and soil functionalists were those scientists who developed curves and equations. Kellogg's philosophy for the soil survey embraced both geography and factor analysis. World War II delayed the impact of Jenny's book Factors of Soil Formation on U.S. pedological thought. In the decades since the 1940s field and laboratory investigations have repeatedly demonstrated the complexities and heterogeneity of soil patterns and soil genesis. Our understanding of the pedosphere benefited from the interaction of the methods of soil geography and those of soil factor functional analysis.
Soil formation theory and philosophy was born in eastern Europe during the late nineteenth century as the intellectual offspring of V.V. Dokuchaev and his students and colleagues. In the early twentieth century it diffused into western Europe and North America where it became fundamental theory for such practical applications as the USDA soil mapping program, and various intellectual efforts, such as Hans Jenny's eloquent and substantive treatise The Factors of Soil Formation. The framework also provided the philosophical foundation for such fundamental—albeit historically problematic—concepts as normal and zonal soils, monogenetic and polygenetic soils, and paleosols. It formed a major part of the philosophy behind chronosequence and paleopedological studies, and the concept of poly genetic landscapes, and was an important part of the philosophy behind climatic geomorphology as well as aspects of process geomorphology. In fact, the formational paradigm has been omnicient as the soil-theoretical foundation of the earth sciences during this century. A negative entry exists in this otherwise positive ledger in that the framework lacks visibility for two important theoretical and factual aspects of pedogenesis—soil evolution theory, and biomechanical processes. In these collective ways the framework has significantly impacted the disciplines of geography, geomorphology, soil geomorphology, Quaternary geology, and paleopedology, which includes undergraduate teaching and graduate training in these fields. Hans Jenny's role and image as the principal and eloquent advocate of the formational-factorial paradigm, among other accomplishments, has won him an honored and deserved place in twentieth century science.
This paper provides: (i) a brief historical review of soil-geomorphological approaches to investigations of soil-landscape formation, and (ii) an outline of a methodological and conceptual approach for three-dimensional (3-D) modeling of the soil-landscape continuum that utilizes geographic information systems (GIS), spatial analysis and field data. Four interrelated, iterative stages for developing 3-D models of the soil-landscape are outlined. The stages are designed to be explicit and applicable to the scale accuracy specified by the user. The first involves assembly and analysis of pertinent data to characterize a physiographic domain. The second stage is a geomorphometric characterization of the landscape from digital terrain models, which provides (i) a land surface representation to which other data are referenced and (ii) a division of the land surface into areas that correspond with soil patterns. The third stage uses georeferenced sampling as a basis for defining soil horizons, their attributes, and spatial arrangement in the landscape. The use of soil horizons rather than pedons as primary extrapolative units is a departure from traditional methods, but is central to developing a 3-D approximation of the soil diversity in the landscape. The fourth stage addresses the basic structure of the model to provide insight about (i) the range, variance, and correlation of soil and associated landform attributes and (ii) the pedogeomorphic processes that formed the landscape. The four stages may be viewed as an integrated procedure for defining explicitly decisions/assumptions, data analysis, visualization, and quantification of the scale and frequency of horizon patterns in three and four (time) dimensional landscapes.