Agro-ecological implications of forest and agroforestry systems conversion to cereal-based farming systems in the White Nile Basin, Ethiopia

摘要

The Afromontane forests of southwest Ethiopia are high in endemism and biodiversity. However, the increasing human population and expansion of agricultural land have led to deforestation. We evaluated the effects of land use change on species composition, species diversity and soil fertility. Woody and herbaceous plant species were recorded in natural forest, agroforestry and cropland at different altitudes, using 15 plots with three replicates. A total of 90 soil samples were taken. In total, 77 woody and herbaceous species have been recorded. The selective felling of trees and shrubs in the agroforestry system to favor coffee growth through enhanced light penetration also favors grass and herb diversity. A Factor Analysis based on the soil characteristics shows a gradient in soil fertility from both forests and agroforestry to croplands. The bulk density, pH, organic C, total N, available P, cation exchange capacity and base cations saturation of the forest soil are equivalent with that of agroforestry. However, forests and agroforestry are significantly different from croplands regarding those soil characteristics. Therefore, this study suggests that the agroforestry practices are important for keeping biodiversity and soil fertility at levels which are similar to the natural forest.