Landscape composition, configuration, and trophic interactions shape arthropod communities in rice agroecosystems.
Increasing landscape heterogeneity of agroecosystems can enhance natural enemy populations and promote biological control. However, little is known about the multiscale effects of landscape heterogeneity on arthropod communities in rice agroecosystems, especially in combination with trophic interactions. We examined for the first time how landscape heterogeneity, measured by four independent metrics of landscape composition and configuration at three spatial scales, affected species abundance and species richness of rice arthropods within four functional groups and the abundance of the most common species at 28 sites in the Philippines. We additionally examined the influence of trophic interactions among these functional groups. We found that both the compositional and configurational landscape heterogeneity in combination with trophic interactions determined the structure of rice-arthropod communities. Herbivore abundance decreased with increasing landscape diversity. The abundance of parasitoids and species richness of both parasitoids and predators increased with the structural connectivity of rice bunds. Fragmentation of the rice landscape had a clear negative effect on most arthropod groups, except for highly mobile predatory arthropods. Abundance of common predators and detritivore species decreased with increasing complexity in the shape of rice patches. Trophic interactions, measured as the abundance of prey, outweighed the importance of landscape heterogeneity for predators. In contrast, parasitoids responded positively to configurational landscape heterogeneity but were unaffected by prey abundance. Synthesis and applications. Our research shows how landscape heterogeneity and trophic interactions have different effects on different functional groups. While predator abundance was solely driven by the availability of prey, all other functional groups in the rice-arthropod community were significantly affected by the composition and configuration of surrounding landscape features. Landscape management aiming to improve biodiversity and biological control in rice agroecosystems should promote a diversity of land uses and habitat types within 100-300 m radii to reduce the presence of pests. Management practices should also focus on maintaining smaller rice patches and the structural connectivity of rice bunds to enhance populations of the natural enemies of rice pests. Future research should focus on the temporal and spatial manipulation of rice fields to maximize the effects of biological control.