The arthropod communities are influenced by both local conditions and features of the surrounding landscape. Landscape complexity and stand factors may both influence arthropod communities in poplar forests, but the multiscale effects of these factors on poplar defoliators and natural enemies are still poorly understood. We collected poplar arthropods at 30 sampling sites within five forest landscapes in Xinjiang, China, and assessed whether landscape complexity and stand factors influence species abundance and diversity of poplar arthropods. Landscape complexity was quantified by several independent metrics of landscape composition, configuration, and connectivity at three spatial scales. We also determined the most powerful explanatory variables and the scale effect of each arthropod. Results found that landscape complexity and stand factors had different effects on different poplar arthropod communities. Landscape complexity promoted natural enemies at different spatial scales, but it inhibited the population of poplar defoliators at the scale of 200 m. Specifically, the abundance and diversity of all defoliators decreased with increasing proportion of nonhost plants. Landscape diversity only had a negative effect on defoliator abundance. The shape complexity of habitat patches increased the abundance of carabid beetles but reduced the abundance of green leafhoppers and migratory locusts. The abundance and diversity of predators increased with increasing structural connectivity of forest landscape. Additionally, both the abundance and diversity of all defoliators were positively correlated with the average height of herbaceous plants. Diversity of all defoliators increased with increasing size of host trees. The distance from sampling site to the nearest village positively influenced the abundance and diversity of all predators. Arthropod abundance and diversity in poplar forests were driven by stand factors and landscape complexity. Therefore, maintaining complex shape and structural connectivity of habitat patches and keeping poplar stands away from the village are crucial for management of forest landscape to enhance natural enemies. And in order to reduce the abundance of defoliators in poplar forest, the diversity of surrounding habitat types should be promoted within 200 m radii.

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1. Many carabid beetles are among the most important biocontrol agents and are biological indicators of environmental change, although relatively little is known about how local and landscape factors affect forest ground beetle assemblages. Understanding such effects of multi-scale environmental drivers on ground beetles can promote carabid diversity and conservation.2. Ground beetles were sampled by pitfall trapping in 40 poplar forest stands (sampling plots) along the Irtysh River in Northwestern China. We investigated responses of carabid activity density, species diversity and functional diversity (FD) to stand characteristics and surrounding landscape structure (the overall diversity and percentage cover of vegetation productivity classes in the surrounding area of each sampling plot based on normalised difference vegetation index).3. While carabid activity density only responded positively to the overall diversity of vegetation productivity classes, carabid species diversity was positively associated with this landscape factor as well as vegetation cover but negatively associated with the nearest distance from sampling plot to the river. Only carabid FD responded significantly to percentage cover of vegetation productivity classes, showing a positive correlation with the proportion of medium vegetation productivity. Furthermore, overall carabid FD declined with increasing tree canopy cover. 4. Our results can help predicting spatial patterns of ground beetles according to landscape diversity and proportions of surrounding vegetation types and improve the design of conservation strategies (such as altering canopy cover) of carabids, especially forest specialist species. Any forest management strategies for promoting carabid diversity should consider the pervasive effects of landscape composition and configuration besides local stand characteristics.

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