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Trees on farms are a widespread feature of landscapes across a large part of Ethiopia with an important role in enhancing the resilience of smallholder livelihoods through the provision of ecosystem services. Despite their importance, little is known about what trees are planted or retained from natural regeneration by different types of farmers that results in the pattern of tree cover found in the region. We address this knowledge gap through analysis of household survey data from semi-arid and sub humid areas of Oromia regional state. A set of composite variables that represent distinctive patterns of tree cover on farms were derived from principal component analysis and Pearson correlation analysis. This revealed two major tree adoption strategies: farmer managed natural regeneration (FMNR) of trees to meet subsistence needs as well as contributing to other ecosystem services; and, high value agroforestry (HVAF) involving planted trees used largely to produce fruits, timber and fodder. Regression analysis further identified fine-scale variation in ecological and socio-economic factors that affect which of these two broad strategies are adopted by farmers. Favorable climatic conditions coupled with institutional arrangements to control free grazing were pre-conditions for HVAF, whereas poor biophysical potential and sloping land provided a positive incentive for farmers to adopt FMNR. Farmers with preferences for tree species with multiple utilities and locational flexibility favored FMNR while adoption of HVAF was more assetdriven. Our findings reveal that farmers integrate many native and exotic tree species on their farms to meet their variable farm conditions, needs and asset profiles in stark contrast to most tree promotion efforts that focus on a few, usually exotic, tree species. We recommend that future agroforestry promotion should embrace a diversity of tree species appropriate to matching the fine scale variation in ecological conditions and farmer circumstances encountered in the field.

Rethinking the logic of institutional environments aiming to facilitate agroforestry smallholders in economic development, this article compares smallholder input supply systems for crop and tree seeds in sub-Saharan Africa and reflects on two basic challenges: (1) how to develop a large number of relevant tree crops for different agroecologies, (2) how to reach smallholders in rural areas. Policy options for improving agroforestry input supply systems are discussed, whereby our article concludes with suggestions how sectoral approaches for crop seed systems can be modified to agroforestry seed-seedling systems. Biophysical differences have practical implications for how the logic of the 'African green revolution' would be translated into a corresponding revolution for agroforestry. K E Y W O R D SAGRA, agroforestry, institutions, productivity, seed systems | INTRODUCTIONGreat opportunities for producing value from agroforestry seeds are currently wasted.1 To allow smallholders to realize the full productive potential of quality agroforestry seeds, institutional environ-1 We use the term 'seed' to include seed and also vegetatively propagated planting stockThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Background: Indigenous tree and shrub species are critical feed resources for the pastoralist and agro-pastoralist areas in Ethiopia. Nutritional and mineral composition of seven high priority leguminous indigenous tree species, (Acacia nilotica, Acacia tortilis and Tamarindus indica) and non-leguminous species (Berchemia discolour, Cordia sinensis, Dobera glabra and Ziziphus spina-christi) were characterized to inform decisions on the species utilization and domestication. Method: Data on a total of 17 nutritional factors were generated on leaf samples from 10 to 12 trees per species following standard lab procedures. Descriptive statistics, one-way analysis of variance among species and types, and Spearman correlations between the nutritional factors were conducted. Results: Result showed that there were significant differences among the species for all chemical compositions and mineral contents except for iron. The leguminous species had significantly higher mean dry matter, organic matter, lignin and in vitro digestible organic matter in dry matter, whereas the non-leguminous species had significantly higher mean total ash, neutral detergent fibre, acid detergent fibre and hemi-cellulose. Similarly, the leguminous species had significantly higher mean iron, whereas the non-leguminous species had significantly higher mean macro-minerals, Mn and Zn. Across all the species and samples analysed, the majority (69%) of the paired comparisons revealed significant associations among the chemical compositions and digestibility, whereas nearly 54% of the comparisons were significant among the mineral contents. Conclusions: We conclude that the tree species investigated are important sources of protein, energy and minerals, and utilization and domestication should target both the leguminous and non-leguminous types.

Most tree nurseries in Ethiopia overemphasize mass seedling production to the expense of seedling quality. The study aimed at evaluating nursery characteristics and tree seed procurement approaches, and how these influenced seedling quality in eight purposively selected Woredas of Oromia region. A total of 169 respondents from government and non-government organizations, farmer nursery owners and development/extension agents and officers were interviewed. Seed quality was explored through assessing the seed supply sources, the type of seed source and mother tree selection, and the practices in seed physiological quality assessments. Our results revealed that over half (62.5%) of the nurseries were government owned, while 20% were NGO-run nurseries and the remaining 17.5% were owned by farmers. Nine challenges constraining tree seedling production and leading to underperformance were identified, with the two major problems shared by all nursery types being lack of sufficient material and germplasm input and using seeds of low or unknown quality. Informal seed dealers were the main source of seeds (87.6%) for all the nursery types. On the other hand, nursery operator's own seed collection was from any free-standing trees either planted or retained as these sources were easily accessible. Seeds were, on average, collected from few mother trees, implying a high probability of sourcing seeds of narrow genetic diversity. Analysis of variance revealed statistically significant differences in seedling germination among the different seed procurement approaches within the same seed type. The seeds obtained from formal seed dealers had the highest germination rates in both hard-coated (87.3%) and soft-coated (79.7%) seeds. Our findings suggest that there is need to improve the seed procurement and the seedling supply system through quality assurance of the seeds used in seedling production.