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Mima mound microtopography and vegetation pattern in Kenyan savannas

Published online by Cambridge University Press:  10 July 2009

George W. Cox  and
Christopher G. Gakahu
George W. Cox
Affiliation:
Department of Biology, San Diego State University, San Diego, CA 92182-0057, USA
Christopher G. Gakahu
Affiliation:
Department of Zoology, University of Nairobi, PO Box 30197, Nairobi, Kenya
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Abstract

Earth mounds are important determinants of vegetation pattern in savannas, acting as foci for establishment of woody plants. In the Kenya highlands, mounds formerly attributed to termites have recently been found to be Mima mounds produced by rhizomyid mole rats. We investigated Mima mounds on black cotton soils near Kenyatta International Airport and on brown clay soils between Nairobi and Thika. At Kenyatta Airport, mounds had loamier, more granular soils than intermounds, and contained small rocks that mole rats can move. At the site between Nairobi and Thika, mound soils were more friable, higher in pH, and lower in carbon than intermound soils. Data from this and other studies indicate that Mima mound soils are more favourable for plant growth than those of true termite mounds. Mound vegetation exhibited lower coverage of grasses and greater coverage by forbs, shrubs, and bare ground, a pattern indicative of intense grazing and soil disturbance. Acacias, absent from most mounds, were abundant in the zone bordering the mound. This pattern may reflect the favourability of mound soils, combined with the effects of high grazing pressure. Future studies of savanna vegetation should distinguish between termite mounds and Mima mounds.

Keywords

Acacia drepanolobiumAcacia tortilisKenyaMima moundsrhizomyid mole ratssavannastermitaria
Type
Research Article
Information
Journal of Tropical Ecology , Volume 1 , Issue 1 , February 1985 , pp. 23 - 36
Copyright
Copyright © Cambridge University Press 1985

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