Influence of the termite Macrotermes michaelseni (Sjöst) on soil fertility and vegetation in a semi-arid savannah ecosystem

The growth and species structure of vegetation in relation to the proximity of termite (M. michaelseni) mounds was studied in a semi-arid savannah ecosystem during 1978–1980. The dry matter yield in the termite-modified area at 1–10 m distance from mounds was significantly greater (P < 0.01) than that in the area beyond 22 m which is relatively unaffected by the termites. Themeda triandra and Digitaria scalarum, dominant grass species of the area, were totally absent in the 1–10 m zone around the mound. The major species in the immediate vicinity of the mound were Pennisetum stramineum and Cynodon dactylon, the latter was a dominant species (over 90%) within the 0–10 m zone and entirely absent beyond 15 m from the mound. The number of grass species increased from 2–3 species around the mound to 6–7 species in the area apparently beyond the influence of the mound. High concentration of nutrients and favourable water availability, together with good drainage, appeared to be the major causes of increased biomass and different species composition of vegetation around the mound.