Monthly Dynamics of Ground-Dwelling Beetle Assemblages in the Agro-Pastoral Ecotone of the Tacheng Basin, Xinjiang, China

Monthly dynamics of ground-dwelling beetles remain poorly resolved in agro-pastoral ecotones. From June to September 2025, beetles were sampled monthly with pitfall traps in 81 permanent 1 m × 1 m quadrats across nine plots representing temperate steppe, temperate desert steppe, and lowland meadow in the Tacheng Basin, Xinjiang, China. Specimens were identified to family, and analyses used family-level data. Assemblage composition varied significantly among months, whereas neither the overall habitat effect nor the habitat × month interaction was significant. Habitat × month interactions were significant for total beetle activity-density and for Tenebrionidae, Scarabaeidae, and Carabidae activity-density. Tenebrionidae dominated catches in July and August, whereas Scarabaeidae contributed the largest proportions in June and September. Significant within-month habitat contrasts in diversity metrics were detected only for Margalef richness in June. Neither distance class nor the distance class × month interaction was significantly associated with activity-density, diversity metrics, or assemblage composition. After conditioning on plot identity and month, measured vegetation and soil variables did not significantly explain residual assemblage variation. These findings highlight pronounced monthly turnover and the value of repeated sampling across months during the June–September period.