DETERMINISTIC UNCERTAINTY AND COMPLEX PEDOGENESIS IN SOME PLEISTOCENEDUNE SOILS

Deterministic uncertainty is a perspective on soil spatial variability that reconciles the traditional reductionist view (variability can be explained with more and better measurements) and the emerging nonline ar dynamics view (variability may be an irresolvable outcome of comple x system dynamics). In the podzolized soils of the 77 ka Newport Barri er, age, parent material, climate, and general vegetation cover are co nstant, and topographic and drainage variables explain only about 20% of the considerable spatial variation in soil morphology. The most lik ely explanations for the unexplained variations are the effects of pas t microtopography and individual plants on moisture flux. However, the variation in soil properties such as depth to the B-horizon is dispro portionately large compared to that of microtopography, and the soil l ifespan is two orders of magnitude longer than that of vegetation. Det erministic complexity (chaos) associated. with the unstable growth of minor perturbations could explain the observed soil landscape, A simpl e model of the interactions between moisture flux, soil moisture, and B-horizon formation is indeed unstable and chaotic. The Newport Barrie r soil landscape is thus characterized by deterministic uncertainty - pseudo-random variation associated with unstable growth cf known, but unobserved or unmeasured, pedogenic influences.