Soil Weathering Stage, Vegetation Succession, and Canopy Dieback

Abstract

A conceptual model that provides a means of viewing changes in vegetation as responses to weathering of soil mantles over thousands of years has been developed from investigations of vegetation communities on a soil chronosequence on sand dunes extending back in time to at least the last interglacial. Progressive and retrogressive phases in natural plant succession are indicated by this sequence. A similar model is used to postulate that the various canopy dieback symptoms and agents observed in the New England tablelands of New South Wales, Australia, represent the mechanisms by which changes are occurring in retrogressive ecosystems that have been disturbed by human land use. We suggest that investigations of the etiology of diebacks need to be made in the context of temporal changes in soil fertility associated with the degree of soil weathering.