FUNCTIONAL BIODIVERSITY IN ETHIOPIAN AGROFORESTRY SYSTEMS: IMPLICATIONS ON SOIL FERTILITY AND LIVELIHOOD STRATEGY

Agroforestry is a human-managed habitat which is home of many and diversified plant species. Studies on various agroforestry systems developed in Ethiopia focused on system interactions, food production and spatial design. So far little attention has been given to the role of homegarden and parkland agroforestry systems and of functional plant diversity on plant species conservation and soil fertility improvement in the study area. The objectives of this study were to assess and evaluate plant species diversity and composition, characterize plant functional traits, examine effects of agroforestry on soil fertility improvement and assess women’s tree and shrub species preference in homegardens and their decision making process at five villages in the Amhara regional state of Ethiopia. Vegetation surveys were carried out on the two agroforestry systems common in the study area: homegarden (10 x 10 m sampling plot per household) and parkland (two transects 1000 m far from one another, including 50 x 100 m plots). Leaf functional trait characterization was carried out by choosing one healthy tree/shrub individual on which five leaves were collected, where leaf width, leaf length and petiole length were measured. Soil samples were taken in homegarden and parkland agroforestry systems and on adjacent agricultural land without trees (control) at 0-15 and 15-30 cm depths. A semi-structured questionnaire and focus group discussion were used as tools to collect information on lists of available wild fruits, and on women’s homegarden agroforestry tree and shrub species preference and their level of decision making. A total of 148 plant species, belonging to 51 families were recorded in the homegarden agroforestry system, whereas 24 plant species, belonging to 15 families were recorded in the parkland agroforestry system. Dominant tree/shrub species functional traits significantly varied across the villages in both agroforestry systems. Most functional traits like canopy cover, above-ground biomass, leaf length, leaf width, relative abundance of nitrogen fixing trees and tree diameter were positively correlated with key soil fertility parameters. Higher soil organic carbon, organic matter, available phosphorus and exchangeable potassium were found in the homegarden agroforestry system, while the lowest values were recorded on fields without trees (control). A comparatively similar wild fruit species composition was found in Kuyu, Mariamwuha and Addisalem villages. Wild edible fruits provide supplementary food, nutrition and generate income for households. Women and men have different livelihood alternatives, the former having more livelihood options than men. The level of women involvement in decision making in the choice of homegarden agroforestry tree/shrub species selection was not different among villages. The overall results suggest that homegarden and parkland agroforestry in the Amhara region should be given more attention for maintaining soil fertility and conserving plant agrobiodiversity. Future land use management would need to raise awareness on the importance of agroforestry systems for the provision of ecosystem functions and services and for improving food security.