Post-dispersal fate of Acacia seeds in an African savanna
Date
2005-10
Authors
Walters, Michele
Milton, Suzanne J.
Somers, Michael J.
Midgley, Jeremy J.
Journal Title
Journal ISSN
Volume Title
Publisher
Southern African Wildlife Management Association (SAWMA)
Abstract
African Acacia species are often major contributors to the progressive increase in the woody component of savannas, a phenomenon commonly referred to as bush encroachment. In Hluhluwe-iMfolozi Park, the numbers of adult Acacia nilotica (L.) Willd. Ex Del. subsp. kraussiana(Benth.) Brenan trees per hectare far exceed those of A. karroo Hayne adults. The relative dominance is reversed in the juvenile stage with A. karroo outnumbering A. nilotica threefold outside closed woodlands. We experimentally investigated the effects of location, structural habitat type, species, predator type and rodent presence on the level of post-dispersal seed predation in an attempt to explain species dominance in Hluhluwe-iMfolozi Park. Post-dispersal predation of A. karroo seeds (21.8%) was higher than that of A. nilotica (12.7%). Predation levels depended on site, structural habitat type, level of protection from different predator types and rodent presence/absence. There was more rodent predation in tall grass areas (26.0%) than grazing lawn (10.7%) or canopy areas (15.2%), and most seeds (19.7%) were lost from unprotected control groups. Rodent presence was a significant factor in a model aiming to determine reasons for unexplained seed disappearance. Post-dispersal predation of seeds could not account for the differences in success between A. karroo and A. nilotica in Hluhluwe-iMfolozi Park.
Description
The original publication is available at http://content.ajarchive.org
Keywords
Acacia -- Africa -- Seeds, Hluhluwe-Umfolozi Park, Seeds -- Dispersal -- South Africa -- KwaZulu-Natal, Bush encroachment -- South Africa - -KwaZulu-Natal
Citation
Walters, M., Milton, S. J., Somers, M. J. & Midgley, J. J. 2005. Post-dispersal fate of Acacia seeds in an African savanna. South African Journal of Wildlife Research, 35(2):191–199.