CHAOTIC EVOLUTION OF SOME COASTAL-PLAIN SOILS

Nonlinear dynamical systems (NDS) models of soil systems suggest that soil evolution may be potentially chaotic, and thus sensitive to initial conditions and to small perturbations. Chaos implies that the diversity of the soil cover should increase over time. This hypothesis was tested by comparing the diversity of soil types on either side of the Suffolk Scarp on the lower coastal plain of North Carolina. While parent material and other soil-forming factors at the two sites are similar, the Pamlico Terrace east of the scarp is late Pleistocene and the Talbot Terrace west of the scarp is middle to late Pleistocene and at least twice as old. A soil system model based on vertical clay distribution and textural differentiation is introduced to account for the major factors that lead to differentiation of soil series in the study area. The model is unstable and potentially chaotic and, like more general models, predicts that even where all other soil-forming factors are similar, the diversity and spatial variability of soils should be greater on older soil landscapes. Soil series were identified along 0.5 km transects on either side of the Suffolk Scarp in Craven County. Only one soil series was identified on the Pamlico site, while the Talbot transect included at least seven distinct soil series. The dramatically higher variability of the soil cover on the older landscape is predicted by the model and provides field evidence for chaotic pedogenesis