Understory floristic diversity and soil seed bank status of planted and unplanted portions of South Busoga Forest Reserve, Eastern Uganda

Abstract

South Busoga Central Forest Reserve, an isolated reserve in Uganda has been degraded for over forty years. To restore the reserve, the National Forestry Authority established plantations in some parts of the reserve and plans to reserve 40% under native vegetation. Until now, no study exists to inform management of the availability of native species in the degraded area to support natural forest regeneration. The objectives of this study were to: (i) establish if there are seeds of native forest species in the soil seed bank of plantations and unplanted areas (ii) assess the potential of the understory of plantations to serve as ‘seed sources’. A seed bank assay of soils from plantations; Eucalyptus grandis, Maesopsis eminii and Pinus caribaea and unplanted areas was performed. Understory vegetation was sampled in 125 subplots of 5 × 5 m, randomly distributed in the plantations. In the seed bank, we recorded a total of 56 species in plantations and 22 in unplanted. There were more species in soils under E. grandis (12) > M. eminii (10) > P. caribaea (9) > unplanted area (3). Apart from Ficus sp. and Drypetes sp. that are woody, the rest of the species were non-woody. In the understory, we encountered a total of 56 species but only fifteen were native tree species with occurrence of less than five individuals each. These results show that sustained forest degradation depletes soil seed banks of native forest species and that plantations of exotic species can also nurse native species in their understory.