a1 School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Wits 2050, South Africa
Elephants (Loxodonta africana (Blumenbach 1797)) can have a major transforming effect on savanna structure through felling, debarking or uprooting trees (Dublin et al. 1990, Laws 1970, Mapaure & Campbell 2002). However, it is difficult to separate their influence from that of other causes of tree mortality, including wind storms (Spinage & Guinness 1971), drought (Lewis 1991, van de Vijver et al. 1999), fire (Higgins et al. 2000), and in some situations frost (Childes & Walker 1987, Holdo 2006), especially when interactions among them may occur (de Beer et al. 2006, Laws et al. 1975, Pienaar et al. 1966). Furthermore, the consequences for woodland dynamics depend on the size classes of the trees affected, as well as on how the disturbance is concentrated in time and space. Mortality of canopy trees has a much greater and longer-lasting impact than losses among the regenerating stages of these trees. However, the consequences may be less adverse for ecosystem function and biodiversity if the disturbing effects are locally concentrated, generating a patch mosaic of stands at different stages of regeneration (Remmert 1991).
(Accepted February 28 2009)
p1 Present address: Songwe River Transboundary Catchment Management Project, c/o Fishery Department, P.O. Box 111, Karonga, Malawi.