Title
Forest restoration in abandoned agricultural land: A case study from East Africa
Author(s)
Chapman C.A., Chapman L.J.
Published
1999
Publisher
Conservation Biology
Abstract
Millions of hectares of tropical forests have been converted to agricultural land and abandoned, so it is important that we understand the process of forest recovery and comprehend how pathways are modified by different types of disturbance in different geographic regions. In a 4-year case study, we quantified the pattern of forest recovery following clearing and 3 years of cultivation of a moist-evergreen forest in Uganda. Long-term observation (746 hours) of frugivore visitation to the regenerating area demonstrated that birds were frequent visitors (5.8 birds/hour), whereas large mammalian frugivores rarely used the area. Frugivore visitation rates facilitated seedling recruitment that averaged 0.51 seedlings/m2 from 22 tree species by the end of the study. Recruitment included species with large seed, despite the fact that seed-eating rodents were a almost twice as abundant in the regenerating area than in mature forest. By the end of the study, however, only 20 trees were =0.5 m tall, and no trees were =2 m tall. This slow recruitment reflected high seedling mortality and dominance of the area by elephant grass (Pennisetum purpureum) and the herb Acanthus pubescens. After 4 years, trees =0.5 m tall attained a biomass of only 8.92 kg/ha, whereas the biomass of P. purpureum and A. pubescens had reached 35,500 kg/ha and 18,100 kg/ha respectively. We provide an initial assessment of two programs designed to enhance restoration of abandoned agricultural lands: planting of cuttings to act as dispersal foci and sowing of seeds. Our results showed that density of seedlings growing in the management plot where we sowed seeds (0.35 seedlings/m2) and in the plot where we established cuttings (0.30 seedling/m2) was lower than in the control plot (0.51 seedlings/m2). This East African site was only lightly disturbed, yet tree recovery was occurring slower than in heavily degraded sites described from South America. The rate of recovery seemed to be strongly determined by interactions between tree seedlings and P. purpureum and A. pubescens.
Keywords
abandoned land; frugivory; habitat restoration; recruitment; regeneration; seedling establishment; tropical forest; Uganda; Acanthus pubescens; Pennisetum purpureum

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PUB12765