Abstract:
Climate smart Coffee enset-based agroforestry is widely promoted as a nature-based climate mitigation strategy, yet its effectiveness hinges on how system structure governs carbon allocation across biomass and soil pools. Although it dominates humid smallholder landscapes in southern Ethiopia, quantitative evidence linking management intensity to ecosystem-level carbon storage remains scarce. This study evaluated how structural complexity influences carbon partitioning across four land-use types: home garden agroforestry (HGAF), coffee agroforestry (CAF), monocrop coffee (MC), and annual cropland (CL). A total of 64 field plots were surveyed, where all trees were measured for diameter at breast height and 248 soil samples were collected from 0–60 cm depth. Biomass carbon was estimated using allometric equations, while soil organic carbon (SOC) was determined using the Walkley–Black method. Biomass carbon stocks differed significantly among land-use systems (p < 0.05), increasing with vegetation structural complexity Structurally complex coffee–enset agroforestry systems achieved the highest biomass carbon storage (150.21 ± 18.6 Mg C ha⁻¹), while monocrop coffee systems exhibited markedly lower stocks (43.42 ± 7.01 Mg C ha⁻¹). Aboveground biomass represented 86–87% of biomass carbon across systems, indicating consistent vertical carbon allocation despite differences in management intensity. Tree biomass contributed 78.4% of total biomass carbon in CAF but only 49.4% in HGAF, reflecting contrasting canopy architectures. Soil organic carbon also varied significantly (p < 0.05), with highest stocks in HGAF (147.48 Mg C ha⁻¹) and lowest in cropland (100.28 Mg C ha⁻¹). When combined, total carbon was greatest in CAF (280.08 Mg C ha⁻¹). These results demonstrate that agroforestry carbon storage is governed not only by tree presence but by vegetation stratification and management intensity, which regulate biomass-soil carbon trade-offs. These findings show that structurally complex Coffee–enset-based agroforestry systems function as effective climate smart land uses in the humid tropical highlands of Ethiopia. Embedding these systems in climate mitigation and landscape restoration strategies can simultaneously strengthen carbon sequestration and ecological resilience.
Key Words: Carbon Sequestration, Soil Organic Carbon, Climate Resilience, Vegetation Structural Complexity, Species Diversity.