Native cover crops enhance biodiversity and ecosystem services in hazelnut orchards

Abstract Agroecological restoration aims to restore biodiversity and ecosystem function in agricultural landscapes while sustaining crop production. Adopting native plants as cover crops may restore ecological value to cropping systems such as nut orchards. We focused on Oregon hazelnut orchards and compared how four seed mixes (native annuals, native perennials, conventional cover crops and unseeded controls) performed under three levels of orchard floor disturbance (flailing, flailing and scraping, and unmanaged/none) across three different orchard ages with corresponding differences in canopy shade over a 2‐year period. We evaluated cover crop performance by three criteria: the survival criteria (response to disturbance and shading), the production criteria (effects on weeds, erosion potential and soil moisture) and the ecological functioning criteria (abundance and diversity of native plants and pollinator visitations). We found that native species generally outperformed conventional cover crops and bare ground across these criteria. Plant survival was not affected by disturbance but shading reduced survival of most species. Native annuals had high cover in the first year, and native perennials had high cover across both years. Native perennial species provided the best weed reduction and erosion control while not reducing soil moisture, and hosted the highest pollinator abundances and diversity. Synthesis and applications . Our results suggest that agroecological restoration of orchards through native cover cropping is a viable strategy for improving ecological outcomes without compromising production needs.