Differences in effects of non-crop habitat on the distribution of carabid beetles and spiders in adjacent farmlands

Conservation of species diversity is an important basis for sustainable agricultural development in agricultural landscapes, and non-crop habitats usually provide suitable habitats for epigeic arthropods. However, as common natural enemies of surface arthropods, carabid beetles and spiders respond differently to different types of non-crop habitats. Although previous studies have been comprehensive and detailed, most of them only focused on specific habitat types, neglecting the role of non-crop habitats on the edge of and inside adjacent cultivated land. Therefore, the present study examined whether non-crop habitats had a positive effect on carabid beetles and spiders and which habitat type had the most significant effect. In this study, Changtu County, Liaoning Province, China, was selected as the sampling area to investigate the abundance of carabid beetles and spiders in non-crop habitats, inner farmlands, and farmland margins. Using variance analysis, cluster analysis, redundancy analysis, and other methods, the distribution characteristics of carabid beetles and spider communities in different habitats and the impact mechanism of non-crop habitat types on diversity were assessed in detail. Different non-crop habitat types had clear spillover effects on farmland; however, these effects were different. Grasslands had significant effects on the diversity of carabid beetles in farmland, and other woodlands had significant effects on the diversity of spiders in farmland. The biodiversity of the farmland margin was significantly higher than that of the surrounding farmland and non-crop habitats. The diversity of carabid beetles at the farmland margin adjacent to native grassland was significantly higher than that at types of farmland margin, the diversity of spiders at the edge of the land adjacent to other woodlands was significantly higher. This study suggested that the rules of edge and spillover effects are consistent, enhancing the biodiversity of adjacent habitats. Among the herbaceous vegetation structural factors, vegetation coverage and diversity significantly affected the diversity of carabid beetles and spiders. This study verified that non-crop habitats could enhance biodiversity at the edge and inside farmlands. In general, non-crop habitats had a positive effect on improving the diversity of the natural enemies in farmlands, and the effects of forestland and grassland were distinct. The more complicated the vegetation community structure of non-crop habitats, the more conducive it is to maintaining a higher natural enemy diversity, thereby improving biological risk control. A detailed discussion of the response of epigeic arthropod diversity to environmental changes at multiple spatial scales is essential for the sustainable development of arable land systems in the context of global change and biodiversity crises.