Gaps are interruptions in the forest canopy, varying in size from a few m² to one hectare and even more. There are various causes for forest gaps, ranging from human activities like timber harvesting to clearings due to pathologies or animal impact. The size and shape of the gaps varies with the cause for the gap. Within the gaps the ecological factors change drastically, which in turn greatly affects the vegetation inside the gap. This causes the dynamic phenomena of regeneration and succession in a forest stand. Recolonisation dynamics are affected by the new micro climatic features like greater exposure to the sun, wider thermal range and water availability. Trees and grass species which can survive under the new ecological conditions establish themselves in the site. First heliophilic species develop (light loving species), then species with different preferences to shade slowly come into the gap. Overall the species composition becomes different from that of the neighbouring areas and not always does succession lead to the same climax vegetation. The recolonisation is hindered by grassy species and shrubs that hinder seedlings in germination, and by mammals that brows or trample the young vegetation or use branches to make nests in case of the Mountain Gorilla.

Data about causes of gap formation, gap persistence and taking over dynamics of the regeneration on the edges and within the gaps was collected from 24 areas which spread from 1870m to 2482m.

Both biotic and abiotic factors are agents of gap formation and persistence. Particularly human activity, fauna presence and a dense cover of herbaceous species. Regeneration is absent where trampling by elephants occurs more and where there is a higher bush pig activity. Seedlings and saplings spread from the edge of the gap.