The characterization of steady state in Earth surface systems: findings from the gradient modelling of an Indian climosequence

Gradient modelling of a steep ecocline in South India has highlighted a suite of landscape units, which appear to be entirely ordained by a simple water balance index. This univariate climofunction is reflected in vegetation, landform, weathering and soil patterns. Although the vegetation successions are the most spectacular, consistent pedogeomorphological trends were identified at several embedded scales of reality: at the microscopic scale, the existence of illite-rich saprolite situated between the kaolinite-dominated and smectite-dominated core areas of the climosequence, so far, a ‘missing mineralogical link’ — only predicted by geochemical theory — was effectively verified by field evidence. At the megascopic scale, the variation in ‘topographic texture’ from polyconvex to polyconcave land systems via a convexo–concave transition zone also suggests a strong relationship between hydroclimatic budgets and landforms. Such an exceptional environmental cabinet is well-suited to reexamining other benchmark climosequences of the Tropics and to readdressing the debated theories of climatic geomorphology by a discussion on the applicability of ‘climax’ and ‘steady state’ to tropical landforms.