Role of Acacia and Erythrina trees in forest regeneration by vertebrate seed dispersers in grasslands of Kibale National Park, Uganda

Abstract

The central question of this study was ‘Do fire-resistant savanna trees such as Acacia sieberiana and Erythrina abyssinica and frugivorous vertebrates influence forest regeneration in the fire-prone grasslands of Kibale National Park, Uganda?’ In order to address the above question, seed rain and species richness and abundance of seedlings/saplings of forest trees were estimated both below and ten meters away from the crowns of these savanna trees for a period of six months (August 2007- March 2008). In addition, the rate of seed removal by seed predators in both areas below and ten meters away from crowns was estimated. Both areas, below and ten meters away from crowns, received seed rain and contained seedlings/saplings similar to those of the trees in the nearby forest. Species richness and abundance were significantly higher below than ten meters away from the crowns. However this was not the case with regards to seed rain. Although distance from the forest edge had a negative influence on species richness and abundance of seedlings/saplings, crown sizes of savanna trees had a positive influence. It was also found that there was no significant correlation between seed rain and distance from the forest edge. Furthermore the rate of seed removal by seed predators below and ten meters away from the crowns of savanna trees was not significantly different. The results from this study therefore demonstrate that forest regeneration is possible below the crowns of Acacia sieberiana and Erythrina abyssinica trees in the grasslands of Kibale National park.

Key words: frugivorous vertebrates, seed rain, savanna trees, seed dispersal, seed predation, forest regeneration.