Reflections on the Nature of Soil and Its Biomantle


Department of Geography, University of Illinois, Urbana, IL 61801 (217: 356-7437, e-mail: (D. L. Johnson); Illinois State Geological Survey, 615 E. Peabody Dr., Champaign, IL 61820, e-mail: (Domier); Geosciences Consultants, 713 So. Lynn St., Champaign, IL 61820, e-mail: (D. N. Johnson).


Apart from the engineering approach to soil as movable regolith, most specialists who study soil view it as a plant-linked, land-only, and Earth-only entity whose character and properties are explained by a mix of four environmental factors—climate, organisms, relief, and parent material—that operate over time. These factors function to produce soil, where S=f (cl, o, r, p, t …). This relationship constitutes the five-factors, “clorpt,” explanatory model of soil formation that lends itself to the survey, classification, and mapping of soil for agricultural and environmental purposes and aids in soil valuations and soil conservation-management needs. In geomorphology and Quaternary research, it has met success in soil chronosequence and age-dating studies. But inasmuch as soil is the most complex and unparsimonious of all natural science entities, is any model so conceptually endowed that it allows a deep understanding of the full range and nuances of soil-forming processes? Can a conventional model provide new visions and different levels of knowledge beyond conventional levels? We present a multifaceted and biodynamic approach that views soil in different ways. One is that soil is the outer integument, or “skin” of all lithic-composed celestial bodies, planets, their satellites, and such. But Earth differs from others because water covers nearly three-fourths of its surface and life covers nearly all of its surface and produces a biodynamically mediated “epidermis”—a biomantle that other planets lack. The biomantle constitutes a subaerial-subaqueous continuum across the globe. Life imparts myriad biomechanical and biochemical processes—biodynamic processes—to the soil-biomantle continuum, and these coact with physical processes in producing soil landscapes. This multifaceted approach is embedded as a component of the dynamic denudation framework of landscape evolution, which carries useful and different explanatory and predictive powers for studying the global soil-biomantle that may be invisible, unacknowledged, or unstressed in other frameworks, including one where “organisms” essentially means plants. To appreciate how our approach differs from conventional views of soil formation, and to provide a historic context, we reflect on the nineteenth- and twentieth-century turning points in Earth sciences, mainly in geography, geology, and soils, which led to the five-factors (clorpt) model as the sine qua non way to explain soils. The details of our approach then follow.