Coffee yield peaks at intermediate shade tree cover in the mid-hills of Nepal

Agroforestry systems help address global challenges by supporting biodiversity, rural livelihoods, and climate change adaptation. While Arabica coffee ( Coffea arabica L.) is traditionally grown in agroforestry systems, full-sun plantations have been promoted too, fueling the debate over optimal shade tree integration for coffee production. The present study assessed coffee yields in relation to canopy cover and carbon stocks at the plot level in the mid-hills of Nepal. We established monitoring plots and quantified coffee yields through cherry counting. The canopy cover was estimated from canopy photos. Shade trees were identified and their above-ground carbon stocks were measured using tree height and diameter at breast height. We found coffee yields ranging from 36 to 1081 kg ha⁻¹, with an overall mean of 364 kg ha⁻¹. Canopy cover varied from 0 to 90% across all plots. Shade trees stored an average of 43.5 Mg ha⁻¹ of carbon in their above-ground biomass. The total mean carbon stock—including above-ground, below-ground, and soil organic carbon to 30 cm depth—was 138.8 Mg ha⁻¹. A bell-shaped relationship (R ²  = 0.40) was observed between canopy cover and coffee yields. Medium canopy cover levels supported the highest yields. In contrast, both low (< 25%) and high (> 70%) canopy covers resulted in significant yield reductions. The agroforestry systems with the highest above-ground carbon stocks were associated with dense canopy covers (> 70%), indicating a trade-off between maximizing carbon sequestration and maximizing coffee yields.