Interannual climatic variability outweighs microhabitat effects on ground-active arthropod diversity in a semi-arid sandy ecosystem

• Arthropod trophic structure remained stable across interannual seasonal variation. • Arthropod abundance and richness peaked under moderate soil moisture conditions. • Caragana canopy microhabitats stabilize arthropod richness under climatic stress. • Caragana canopy facilitates arthropod diversity under drought via soil buffering. • Climate variability outweighed microhabitat effects on arthropod diversity. Understanding how interannual climatic variability shapes the trophic structure and diversity of ground-active arthropods across shrub microhabitats remains limited, particularly in desertified ecosystems. Here, we examine the abundance and taxa richness of phytophages and predators, and the diversity index of ground-active arthropods using pitfall traps in Caragana korshinskii and Artemisia ordosica shrub canopy microhabitats, with adjacent open spaces as control, in the Mu Us sandy land. These observations captured a seasonal moisture gradient from wet to exceptionally dry summers over three consecutive years. Our results revealed no significant differences at the microhabitat scale in trophic structure between interannual seasons, indicating a stable quantitative distribution of phytophagous and predatory arthropods between microhabitats. However, arthropod abundance and taxonomic richness exhibited pronounced unimodal seasonal patterns across all microhabitats, including phytophagous groups (except for taxa richness beneath the C. korshinskii canopy), with peaks occurring under moderately moist conditions following a previous wet year. Microhabitats beneath the C. korshinskii canopy consistently maintained stable soil arthropod richness across contrasting seasons, likely due to herbaceous height performances and stronger buffering of soil moisture-thermal conditions. On the contrary, A. ordosica shrubs provided comparatively weaker facilitative effects, highlighting the importance of species-specific functional traits, particularly during extremely dry summers. Overall, interannual climatic conditions exerted a stronger influence than the type of microhabitats on ground-active arthropod communities in this semi-arid sandy ecosystem. These findings underscore the necessity of integrating climatic context and shrub functional identity into revegetation strategies to enhance biodiversity conservation and ecosystem functioning in dryland restoration.