Soil and geomorphology in central Africa and C.G. Trapnell’s contribution to our understanding

The Zambian landscape is dominantly one of gently tilted plateaux at 1100 to 1600 m above sea level. It is mantled by soil in the final stages of weathering of the underlying Precambrian rocks, during 1 or more million years. This soil is devoid any further weatherable minerals and poor in cations and other plant nutrients. The plateaux are bevelled at their margins as stream have cut back from the down-faulted Luangwa and Zambesi valleys. This bevelled terrain, designated by C.G. Trapnell as Upper Valley, bears relatively young rich soil and a characteristic vegetation that contrast markedly from those of the plateaux. This physiographic contrast is fundamental. It is geographically and agriculturally significant, and both were recognized by Trapnell in 1930s against the prevailing view that climate was the over-riding factor in soil distribution. • The upper valley in Zambia is distinct geomorphologically and pedologically. • Colin Trapnell, surveying there in the 1930s, recognized its distinct ecology. • Contemporary surveys treat landform differently. • There is evidence that Trapnell’s original interpretation of landform is relevant.