Air Flow, Evaporation and Mineral Accumulation in Mounds of Macrotermes subhyalinus (Rambur)

Abstract

Accumulations of mineral salts such as calcium carbonate in certain African termite mounds (Hesse 1955; Milne 1947; Watson 1962,1967; Weir 1969,1972; Wild 1952) are of considerable ecological and agricultural importance in savanna grasslands and other areas, though the mechanisms which lead to them remain uncertain. In some cases the mound is a mass of subsoil raised above ground level by the termites (Hesse 1955), and if the subsoil is mineral-rich the mounds will be also. The chemical composition of termites and of fungus gardens has been analysed and discounted as a source of minerals (Hesse 1955), though it has since been shown that fungus comb may be consumed and replaced by termites very rapidly (Grasse & Noirot 1958a; Sands 1969). The upward movement of water through the soil (Milne 1947) was shown not to be primarily responsible for mineral accumulation in two mounds in Rhodesia (Watson 1969). Measurements and experiments on air flow through mounds of Macrotermes subhyalinus (Rambur) (formerly known as M. bellicosus), were done on the Serengeti Plains, Tanzania, during the months of September and October 1969, and the effect of this air flow on the thermal, mineral and water budgets of the mounds is assessed.