PROGRESSIVE AND REGRESSIVE PEDOGENESIS AND COMPLEX SOIL EVOLUTION

The simultaneous operation of regressive and progressive pedogenetic pathways raises the possibility that soil evolution may exhibit patterns far richer and more complex than increasing development over time. This possibility is explored via a numerical model incorporating the relative rates of progressive and regressive pedogenesis and feedbacks between these rates and the degree of soil development. This model may exhibit deterministic chaos and sensitive dependence on initial conditions with realistic parameter values. Variations in profile development in a region of the North Carolina Coastal Plain where soil-forming factors are relatively constant is consistent with deterministic chaos. Chaotic soil evolution suggests that soil development may reflect the interplay between progressive and regressive soil-forming processes in addition to-or instead of-the age of a surface or deposit. The former may produce a state of development which is unique to a particular time, sensitively dependent on the (unknown) initial conditions, and not simply related to age. Soils and their genetic signatures as indicators of relative ages and Quaternary environments may need to be reinterpreted in this light. © 1993 by Academic Press, Inc.