Regeneration Dynamics of an African Tropical Forest Canopy Dominant Tree Species

Abstract

The population structure and regeneration of Olea welwitschii in Kakamega differs in different forest blocks. There are differences in abundance between the forest blocks, that can be explained by past human-forest interactions – harvesting by mechanized loggers who clear-felled stands of desired merchantable species and the skilled pitsawers who selectively harvested desired tree species. There is a clear absence of seedlings/saplings pointing to a lack of regeneration inside the forest over the last 40 years. Intense seed predation by rodents and attack by fungal pathogens account for up to 99% mortality of fruits and seeds under the parent crowns. Olea welwitschii seedlings/saplings are evident in forest glades. These glades have been maintained by grazing and burning. Fires discourage the growth of trees, while grazing encourages the establishment of mound-building termite species upon which, grassland species such as Combretum molle colonize. Grazing appears to inhibit rodent predators while Combretum molle serves as perch and nesting sites for avian frugivores. Avian frugivores drop Olea seeds under Combretum’s crowns, which germinate and establish under reduced predation and fungal attacks germinate and establish. Patches inside the glades in which Olea regenerates become centres from which the forest continues to invade the glades.