A STUDY OF AN EAST AFRICAN CATENA

Abstract

SummaryThe Buwekula catena occupies a tor landscape which was formed in two stages, as in Linton's two‐cycle theory. Weathering under present conditions has been traced from the proportions of minerals. Feldspar and magnetite show weathering trends and among non‐opaque heavy minerals there is an order of weatherability in the series biotite, muscovite, and epidote.The soil sequence from summit to valley is as follows. Buwekula Shallow occurs on the upper slopes and is a comparatively youthful soil. Buwekula Red occurs on the upper and middle sections of pediments and is a deeply and thoroughly weathered soil the parent material of which has sustained more than one cycle of weathering. Buwekula Brown is a topohydric variant of Buwekula Red and occurs in the lower sections of the pediments. Two alluvial series (Buwekula Yellow‐Brown and Buwekula Grey) are derived from weathering and erosion products of the deeply weathered upland associates.Mineralogical and geomorphic evidence indicates that much weathering took place before the present land surface evolved and that the upland soils are being formed to a large extent on pre‐weathered material. Since the formation of the present land surface further weathering has given rise to the present soil profiles which appear to be in equilibrium with their environment, so that the development of soil horizons is keeping pace with all the processes responsible for their removal.The distribution of individual soil series of this catena has a considerable influence on the land‐use pattern of the area. Despite the ample and favourably distributed rainfall the Buwekula soils are not as productive agriculturally as some other soils in Uganda under similar climate. The main reasons for this are their high acidity associated with extremely low percentages of base saturation and their liability to accelerated erosion.