Responses of three Acacia species to simulated herbivory in a semi-arid southern African savanna

This study investigated responses of juvenile Acacia karroo , Acacia nilotica and Acacia rehmanniana to simulated herbivory in a semi-arid southern African savanna. For each species, we clipped twigs in the dry season and measured the removed twig biomass. Seven months after clipping, we counted the number of resprouts on clipped stems and measured their lengths, diameters and biomass. We also measured dieback length on clipped stems and dieback biomass (DB). Removed twigs of A. rehmanniana had the greatest biomass, followed by A. karroo and least was A. nilotica. However, A. nilotica had the greatest resprout biomass, followed by A. rehmanniana and least was A. karroo . Consideration of DB as lost biomass resulted in A. karroo fully compensating lost biomass, A. nilotica over-compensating and A. rehmanniana under-compensating. Acacia rehmanniana had the shortest resprouts while A. nilotica had the longest. The number and the diameter of resprouts did not vary among the species. We conclude by predicting that in semi-arid African savannas, under-compensation has the greatest probability of occurrence among woody species prone to severe shoot dieback following herbivory. [PUBLICATION ABSTRACT]