Environmental factors acting at multiple scales determine assemblages of insects and plants in agricultural mountain landscapes of northern China

Mountainous regions harbor high levels of biodiversity, while often experiencing substantial pressure from agricultural production. Our current understanding of factors driving changes in the highly diverse species assemblages of these regions is generally limited. We used variance partitioning based on redundancy analysis to establish the effects of environmental variables on the species composition of vascular plants and three insect taxa (Geometridae, Arctiinae and Carabidae). These environmental determinants are linked to three distinct spatial levels: the regional level - the four study regions positioned at similar to 400 m altitudinal intervals, the landscape level - the landscape structure in the vicinity of each study plot, and the plot level the environmental conditions. at individual sampling locations. Our results showed that variations in the species composition of vascular plants and carabids were more closely linked to plot-level characteristics than to regional-level factors, while the opposite trend was observed for the two moth taxa. When effects explicitly linked to the four study regions were controlled, plant and carabid assemblages showed strong links to the percentage of semi-natural habitat at the landscape level, while geometrid and arctiinid assemblages were affected primarily by the overall plant species richness and plant coverage at the plot level. Overall, the variations in the species composition of different taxa can be explained by varying sets of environmental variables acting at different spatial scales, and the relative role of these variables is highly taxon-specific. Regional-scale approaches are crucial for biodiversity conservation in mountainous agricultural landscapes, as exemplified by the responses in the two moths taxa, while a high proportion of semi-natural habitats in the agricultural landscape is not only linked to a diverse vegetation, but also to species-rich carabid assemblages. (C) 2016 Elsevier B.V. All rights reserved