Growth stage, management and habitat influence the taxonomic and functional composition of arthropod communities in apple orchards

Apples are the most cultivated fruits in temperate regions, and their production relies on heavy use of synthetic pesticides, causing major environmental problems and the loss of biodiversity. Pests in tree canopies are commonly controlled by the use of synthetic pesticides, but habitat manipulations in orchard alleys are an alternative practice to promote natural pest control services. Integrated pest management (IPM) and organic production methods are considered to be more sustainable and environmentally friendly than conventional production, but the knowledge of the differences between arthropod communities in IPM and organic apple orchards differ from each other is limited. Therefore, we sampled alley and canopy arthropod communities in eight orchards under IPM and eight organic apple orchards, respectively, during three sampling dates in the apple growing season. Our results show that seasonal effects predominantly shape the taxonomic composition and abundance of arthropod community, especially within canopy habitats, while management effects are context-dependent for several taxonomic groups. The species composition of spider communities in canopy habitats differed significantly between management systems depending on dates, with some common species being more abundant in IPM than in organic orchards later in the season. The functional diversity of spider communities was significantly lower in the orchard alleys than in tree canopies, and increased in alley, but decreased in canopy habitats over time. Communities in IPM orchards had a higher proportion of spiders with ballooning ability, indicating that aerial dispersal is more common for spiders in IPM compared to organic orchards. The results of this study highlight the context dependency of management effects on the taxonomic and functional composition of arthropod communities, as these are likely to be most pronounced at certain times of the growing season and in certain habitats. Functional diversity and trait composition were more sensitive to management differences than taxonomic composition. Our results therefore emphasise the need to consider both taxonomic and functional metrics, and to incorporate seasonal and habitat considerations, when assessing the effects of sustainable management practices on arthropod communities in the future. • Interactions among seasons, habitats, and management in apple orchards impact arthropod community composition and diversity. • Seasonal changes have significant effects on taxonomic composition at specific times of the growing season. • Organic and conventional orchards show differences in arthropod communities, but these are seasonal-dependent. • Functional diversity of spiders is more affected by management than taxonomic diversity. • Both taxonomic and functional metrics must be considered for orchard management.