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Agroforestry represents a potentially multi-beneficial approach to land management as it may enhance a farming household's income and income stability simultaneously with nutrition security and climate change mitigation. However, our comprehension of the specific characteristics within agroforestry systems that bolster economic productivity remains limited, exacerbating the challenges of land management for smallholder livelihoods. This complexity is compounded by the potential influence of carbon revenue, adding an additional layer of intricacy to the equation. This paper aimed to identify the key economic determinants of multistrata agroforestry in sub-Saharan Africa with and without potential carbon revenue. A quantitative survey of 135 farmers was performed regarding their multistrata agroforestry systems with contrasting histories in three regions of Ethiopia. The carbon sequestration rate and carbon stocks in agroforestry were assessed on one-fifth (27) of the farms. The relative importance of hypothetical determinants of agroforestry systems' economic performance was modeled using descriptive statistics and generalized linear models. Farm size and fertilizer usage were the primary drivers of the farm economy, but farm net income was also highly influenced by the richness and diversity of the income sources. In addition, tree diversity had a positive impact on the net income, whereas the proportion of legume trees and trees with a large diameter correlated negatively with the income. Potential carbon revenue at prices of US$40 tCO 2 −1 and US$100 tCO 2 −1 increased income for multistrata agroforestry farms without significantly changing the magnitude of the identified key determinants. This suggests that the most economically viable agroforestry systems inherently possess a strong capacity for carbon sequestration, effectively serving as carbon sinks. Consequently, carbon revenue serves as a compelling financial incentive for the adoption of these agroforestry systems. Ultimately, this research underscores the pivotal role of biological and product diversity in shaping economic productivity within multistrata agroforestry systems. Moreover, it highlights the accessibility of diversity management for smallholder farmers, even under conditions of resource constraints. [Display omitted] • The economic determinants of agroforestry systems remain not well understood. • The determinants with and without potential access to carbon market were identified. • The farm income was mainly affected by farm size and fertilizer use. • Diversity of the income sources was key determinant regardless of carbon revenue. • Diversity is manageable for all smallholder farmers. [ABSTRACT FROM AUTHOR]

Soil carbon (C) represents the largest terrestrial carbon stock and is key for soil productivity. Major fractions of soil C consist of organic C, carbonates and black C. The turnover rate of black C is lower than that of organic C, and black C abundance decreases the vulnerablility of soil C stock to decomposition under climate change. The aim of this study was to determine the distribution of soil C in different pools and impact of agricultural management on the abundance of different species. Soil C fractions were quantified in the topsoils (0–15 cm) of 23 sites in the tropical highlands of Ethiopia. The sites in central Ethiopia represented paired plots of agroforestry and adjacent control plots where cereal crops were traditionally grown in clayey soils. In the sandy loam and loam soils of northern Ethiopia, the pairs represented restrained grazing with adjacent control plots with free grazing, and terracing with cereal-based cropping with adjacent control plots without terracing. Soil C contained in carbonates, organic matter and black C along with total C was determined. The total C median was 1.5% (range 0.3–3.6%). The median proportion of organic C was 85% (range 53–94%), 6% (0–41%) for carbonate C and 6% (4–21%) for black C. An increase was observed in the organic C and black C fractions attributable to agroforestry and restrained grazing. The very low concentration of the relatively stable black C fraction and the dominance of organic C in these Ethiopian soils suggest vulnerability to degradation and the necessity for cultivation practices maintaining the C stock. [ABSTRACT FROM AUTHOR]

The rapid conversion of native forests to farmland in Ethiopia, the cradle of biodiversity, threatens the diversity of the arbuscular mycorrhizal fungi (AMF) pivotal to plant nutrition and carbon sequestration. This study aimed to investigate the impact of this land-use change on the AMF species composition and diversity in southern Ethiopia. Soil samples were collected from nine plots in each of three land-use types: native forest, agroforestry, and khat monocropping. The plots of the three land-use types were located adjacent to each other for each of the nine replicates. Three 10 × 10m subplots per plot were sampled. AMF spores were extracted from the soil samples, spore densities were determined, and species composition and diversity were evaluated through morphological analysis. Both spore density and species richness were statistically significantly higher in the native forest than in the agroforestry plots with no clear difference to khat, whereas the true diversity (exponential of Shannon-Wiener diversity index) did not differ among the three land-use types due to high evenness among the species in agroforestry. In total, 37 AMF morphotypes belonging to 12 genera in Glomeromycota were found, dominated by members of the genera Acaulospora and Glomus. The highest isolation frequency index (78%) was recorded for Acaulospora koskei from native forest. Consequently, the agroforestry system did not appear to aid in preserving the AMF species richness of native forests relative to perennial monocropping, such as khat cultivation. In contrast, the native forest areas can serve as in situ genetic reserves of mycorrhizal symbionts adapted to the local vegetative, edaphic, and microbial conditions.