ABSTRACT
Contrasts in soil type in tropical regions are just as great as contrasts in vegetation. In between the red soils of tropical rain forest and the bare rock pavements and drifting sands of the tropical deserts, there is both complexity and diversity. Although it is most desirable to study vegetation and its underlying soil as an entity, unfortunately, in much of these areas, this is not yet possible. In the first place far too little is known about the processes of soil formation in tropical regions; the interactions between soil and vegetation are little understood. Secondly, on the evidence available there appears to be little correlation between the distribution of soil types on the one hand and of vegetation types on the other. Partly because of the vast extent of various grades of savanna and grassy woodland, the clear distinction between grassland soils and forest soils cannot be made as it can in higher latitudes. At the present state of knowledge one obtains the impression that parent-material is more important as a soil determinant than in the extra-tropical regions of North America and Eurasia. Vast areas of a single zonal type such as the chernozems of Russia and the Great Plains in the U.S.A. do not seem to occur, whereas a geological outcrop of a particular lithological type frequently seems to be co-extensive with a patch of a particular soil type. As knowledge grows and more realistic classifications are made, however, this impression may very well be dispelled.
