Predatory arthropod diversity and community structure in maize-intercropped immature and mature monoculture oil palm plantations in East Aceh, Indonesia

Abstract

Monoculture oil palm reduces arthropod biodiversity, including predatory natural enemies of pests. This study compared diversity and community composition of predatory arthropods in two cropping systems in East Aceh, Indonesia: immature oil palm (TBM, 2–3 years) intercropped with maize (Zea mays L.) and mature oil palm (TM, ≥10 years) under monoculture. Pitfall traps, yellow pan traps, and sweep nets were deployed across five plots per system (March–May 2023). Specimens were identified to family level and analysed using the Shannon–Wiener index (H′), Pielou’s evenness (E), Simpson’s dominance (C), and Hutcheson’s t-test. Ten predatory arthropod families from five orders were recorded. The TBM system had higher abundance (1,767 individuals) but lower diversity (H′ = 1.57), driven by Coccinellidae dominance (52.63%) linked to aphid outbreaks on maize. The TM monoculture showed higher diversity (H′ = 1.98), evenness (E = 0.86), and lower dominance (C = 0.18). Diversity differed significantly between systems (p < 0.001). Understory vegetation density and litter depth were the main microenvironmental variables correlated with community composition. Maize intercropping enhances predator abundance, while mature monoculture supports greater diversity and stability. Integrating maize during the TBM phase is recommended as a natural enemy conservation strategy within integrated pest management in smallholder oil palm systems.