Forest Restoration in Abandoned Agricultural Land: a Case Study from East Africa

background

This study quantifies the pattern of forest recovery following clearing and 3 years of cultivation of an abandoned agricultural land adjacent to a 300ha relatively undisturbed natural forest in a moist-evergreen forest in Kibale National Park, Uganda.

Research Goals & Methods

Seedling growth and mortality, dominant cover, aboveground biomass, frugivore visitors and rodent abundance for forest regeneration in study plots were assessed. Two management treatments were followed: cuttings of Erythrina abyssinica, Ficus brachylepis, Ficus natalensis and Ficus dawei were taken to act as foci for seed dispersal; and sowing seeds of Albizia grandibracteata, Cordia abyssinicaa, Maesa lanceolata and Trema orientalis was conducted.  The researchers quantified seedling growth and mortality, dominant cover, frugivore visitors, and rodent abundance.

Conclusions & Takeaways

The results show the rate of seedling establishment and mortality was slow for the first 2 years but increased rapidly in years 3 and 4, with a higher pattern of mortality in the dry season. The following tree species, Milletia dura, Diospyros abyssinica, Maesa lanceolata, and Bridelia micrantha constituted 76.2% of the recruiting tree community. Most of the seeds established on the plots had fleshy fruits or dry dehiscent pods only few were wind dispersed. In the management plots the only species for which recruitment increased as a result of seeding was Albizia grandibractea. Although the site in Kibale was lightly disturbed, tree recovery was slow. Suggesting that the rate of recovery seems to be strongly determined by interactions between tree seedlings and two dominant grasses, Pennisetum purpureum and Anthephora pubescens. Both of the management programs instituted to increase seedling recruitment were unsuccessful due to high rodent densities. The authors conclude that tree plantations should be encouraged as they act as shelter trees fostering indigenous trees to grow in the understory. This might be a profitable mechanism to regenerate abandoned agricultural lands in East Africa.