The diversity and functionality of tree‐dwelling arthropods are sustained in mixed‐species plantations compared with natural forest regeneration

Forestry plantations are increasingly expected to support biodiversity, yet the tree‐dwelling (arboreal) arthropod community of plantation saplings remains poorly characterised despite the important contribution of arthropods to forest biodiversity. Effectively managing mixed native species plantations can boost structural complexity, enhance microhabitat heterogeneity and improve biodiversity. We examined whether young white spruce ( Picea glauca (Moench) Voss) in mixed‐species plantations support tree‐dwelling arthropod diversity comparable to that of young trees in natural forest understory. Within the eastern boreal forest of Canada, 10 sites were selected in mixed‐species plantations and mature stands with naturally regenerated white spruce under a deciduous canopy. Sampling using beat sheeting and timed surveys was conducted during early and late summers of 2021 and 2022, with 2023 limited to early summer due to forest fires. We analysed γ , α and β diversity using rarefaction and extrapolation curves to estimate richness and abundance and investigated β diversity metrics, including LCBD (local contribution to β diversity) and SCBD (species contribution to β diversity). Across 5019 arthropods from 60 taxa, neither α nor γ diversity differed between forest types, and β diversity was consistently higher in natural forests. Natural (forest) understory regeneration contained more caterpillars and sawfly larvae, whereas plantation trees supported more aphids. Functional evenness was nearly identical across habitats, and LCBD was negatively correlated with species and functional richness as well as with canopy cover. SCBD highlighted key β diversity contributors such as the Eastern spruce budworm ( Choristoneura fumiferana Clemens) and ants. Findings suggest ecosystem‐based, mixed‐species plantations can sustain arthropod diversity and functionality comparable to natural regeneration, supporting biodiversity in boreal landscapes.