Background and aims <p>Alley cropping agroforestry, which is the integration of tree strips into arable land, is known to enhance soil biodiversity as compared to open cropland. Earthworms, a key group of soil fauna, are strongly promoted through trees in agroforestry. Although tree leaf litter is often assumed to play an integral role in the promotion of earthworms, experimental data is lacking. This study aims to shed light on the effect of tree leaf litter on earthworm communities in agroforestry.</p> Methods <p>Our study was conducted in a 17-year-old poplar alley cropping system in Germany. Earthworms were collected using chemical extraction along point transects at multiple distances from the tree strip into the windward and leeward section of its adjacent crop alleys. Additionally, leaf litter was manually collected from the soil surface and soil samples for general soil properties were taken at 0—30 cm soil depth.</p> Results <p>Overall distribution of earthworms mirrored the spatially heterogeneous distribution of tree leaf litter with greater population density and biomass in the tree strip and in the leeward crop alley as compared to the windward crop alley. However, earthworm distribution patterns were species-specific. While anecic and epigeic earthworms were positively associated with tree leaf litter, endogeic earthworms showed no observable response.</p> Conclusion <p>Our results confirm tree leaf litter inputs as a major driver of earthworm communities in mature agroforestry systems. Furthermore, species-specific responses of earthworms to tree leaf litter are likely attributed to distinct feeding behavior and habitat requirements.</p>