Nomenclature: Troupin (1978, 1983, 1985, 1988) for grasses and forbs; Beentje (1994) for woody plants; Pearce (1997) for termites.
Thicket clumps: A characteristic feature of the Kagera savanna landscape, East Africa
Article first published online: 29 JAN 2009
2008 IAVS - the International Association of Vegetation Science
Journal of Vegetation Science
Volume 19, Issue 1, pages 31–44, February 2008
How to Cite
Bloesch, U. (2008), Thicket clumps: A characteristic feature of the Kagera savanna landscape, East Africa. Journal of Vegetation Science, 19: 31–44. doi: 10.3170/2007-8-18315
- Issue published online: 29 JAN 2009
- Article first published online: 29 JAN 2009
- Received 15 March 2006; Accepted 11 May 2007
- Dry evergreen forest;
- Ecosystem dynamics;
- Vegetation mosaic
Question: What are the genesis and development of thicket clumps within a savanna landscape at geomorphically different locations and what are the driving forces?
Location: The Kagera Region, in the border area of Rwanda, Uganda and Tanzania.
Methods: The vegetation of 32 dry evergreen thicket clumps and their surrounding savannas have been analysed at different geomorphic locations. At each vegetation plot Na+, K+, Mg2+, Ca2+, Al3+, Fe2+/3+, H+, P, C, N, bulk density and particle size were determined for each soil horizon. The impact of soil and termite mounds on thicket clump dynamics on seasonally waterlogged plains, gentle slopes and stony hillsides were assessed.
Results: Thicket clumps and their surrounding savannas have a distinct structure and floristic composition. They also have distinct soil properties although parent materials are the same. On seasonally waterlogged plains, new thicket clumps can develop on Macrotermitinae mounds; on stony hillsides, Trinervitermes and Macrotermes show a uniform distribution pattern and may initiate the genesis of thicket clumps.
Conclusions: Geomorphology broadly determines the significance and interactions of the main factors affecting site-specific vegetation dynamics. On seasonally waterlogged plains, thicket clumps are restricted to termite mounds. Since intra-species competition dictates a minimal distance between neighbouring Macrotermitinae colonies, thicket clumps do not coalescence. By contrast, on stony hillsides, the vegetation mosaic is highly dynamic and determined by the interplay of several factors. The growth of thicket clumps is mainly a function of the fire regime and the browsing intensity. At the present time, frequent cool, early dry season fires and the near absence of large browsers have favoured the advance and coalescence of thicket clumps and forest patches on stony hillsides.