Seedling populations and regeneration of woody species in dry Afromontane forests of Ethiopia

Abstract

The composition and density of seedlings, as well as height class distribution of woody species, were studied at two dry Afromontane forests in Ethiopia. A total of 40 species were recorded at Gara Ades and 41 at Menagesha forests. The density was 16 290 and 32 650 seedlings/ha at Gara Ades and Menagesha, respectively. A few species were not represented in the seedling bank, although mature trees were present. This may suggest that the species are under threat of local extinction or ‘that they recruit after major disturbances’. The trend in the height class distribution varied from species to species. However, about 50% of the species showed a negative exponential distribution at both sites, while there were indications of intermittent regeneration in the others. Seedling survival and growth of four species were also investigated, both under shade and in the open, at Gara Ades. The number of surviving seedlings declined progressively during the study period in all the species. Damage and uprooting by animals and people, drought, defoliation by insects and burial by siltation are among the apparent causes of seedling mortality. Mean annual height increment was generally low (< 15 cm) in the four species. Only one of the species showed more rapid height growth in gaps than under shade while the other three species had almost similar growth rates under shade and in gaps. The seedling growth analysis does not support the view that climax species quickly commence rapid height growth after canopy gap develops above them. The results show that in dry Afromontane forests, formation of seedling banks under the forest canopy is the major regeneration route of woody plants, especially climax species.