DON JOHNSON’S CONCEPTUAL AND THEORETICAL CONTRIBUTIONS TO SOIL GEOMORPHOLOGY

During his long career, Don Johnson, a soil geographer and geomorphologist at the University of Illinois, made many profound and sweeping contributions to the theory behind soil geomorphology and pedology. In this presentation, I will summarize some of the many contributions made by Don, his co-workers and his students, and set them within a broader context. Chief among Don’s contributions was the notion of soil evolution – that soils evolve and can regress, rather than following a purely developmental and progressive pathway toward some “normal soil” endpoint. This work culminated in the award-winning, 1987 paper, Evolution Model of Pedogenesis. Don also was a strong proponent of the importance of biomechanical processes in the soil system. His work popularized the notion of the biomantle, formed by such processes. Throughout his career, Don continued to stress that most stone lines are formed by biomechanical processes, e.g., the burrowing and mixing of soils by infauna. This work was truly insightful to many, particularly among the archeological community. Indeed, much of his work centered on the pedoturbative effects of soil fauna, which he categorized into three types: mixmasters, crater-makers, and mounders. All of this work culminated in the development of the dynamic denudation model of soil and landscape formation. This holistic model has wide utility for explaining the joined nature of soil and slope development, by incorporating three pedogeomorphic agents (gravity, water and biota). It is especially useful for the explanation of three tiered soils with stone lines, and it is globally applicable. The academic community will surely miss Don’s enthusiasm, insight, positive attitude and the fresh way in which he looked at the world. It is my hope that, though this presentation, his work can be more fully brought to light.