Tree-crop combinations and their variable effects on agroecosystem services: A systematic review and meta-analysis of temperate silvoarable agroforestry in the Northern Hemisphere

Silvoarable agroforestry can increase yields and enhance agroecosystem services while enabling efficient field operations through adjustable alley widths. Although several meta-analyses reviewed agricultural diversification and agroforestry, most focused on general systems or individual services at a global scale or within Europe. To date, there has been no study that combines systematic review and meta-analysis to synthesize the effects of temperate silvoarable agroforestry across multiple agroecosystem services. This study analysed 37 empirical studies, covering 87 experiments and 1127 data records. Poplar–cereal combinations were most studied (35 %), followed by walnut–cereal (13 %) and mixed tree–cereal systems (10 %). Results show that temperate silvoarable agroforestry increased biodiversity by 20 % compared to monocropping, with greater gains in systems less than six years old, during spring to early summer, and where leguminous crops were included. For crop yield and soil quality, results were not significant and showed high variability depending on context. Yield declined by 15 % in systems with tree heights over 10 m and alley widths up to 96 m, likely due to shading and belowground competition. Results on carbon sequestration, pest and disease regulation, product quality, and water quality remain inconclusive due to limited data. The findings suggest that silvoarable agroforestry can enhance agroecosystem services. To realize this, genetic diversity (through suitable species selection), spatial design (matching tree height with alley width), and temporal diversity need to be carefully integrated and tailored to farmer's goals, site conditions, and management. More long-term, geographically diverse studies are needed to better guide system design and policy.