Response of Spider and Epigaeic Beetle Assemblages to Overwinter Planting Regimes and Surrounding Landscape Compositions

Simple Summary Predatory spider and epigaeic beetle assemblages are major natural enemies (NEs) in agricultural ecosystems. The effects of non-crop natural habitats in supporting predatory NEs are well known for summer crop systems; however, limited attention has been given to summer–winter crop rotation transaction systems and during overwintering periods, especially in small-scale farmland systems. Here, we examine the effect of winter planting regimes and landscape composition on the species diversity and functional diversity of ground predators (spiders and carabids) in eight gradient landscape sites in southern China over two consecutive winters (2019/2020 and 2020/2021). Our work reveal that the spiders were more abundant and had a higher activity density in fallow rice fields (FRs) than oilseed rape fields (OSRs); however, the ground beetles were more abundant in OSRs than that in FRs. The composition of spider assemblages was impacted by semi-natural habitats (SNHs) during overwintering, while ground beetle assemblages were influenced mainly by overwintering planting patterns. The results suggest that different planting regimes and SNHs are a strategic way to enhance these ground predators. To conserve and improve predator diversity during overwintering, we suggest maintaining a diversity of planting regimes and conserving local semi-natural habitats. Abstract The rotation patterns of summer rice–winter oil seed rape and summer rice–winter fallow are the main planting regimes in the rice ecosystem in southern China. However, the impact of local rotation patterns and landscape factors on the overwintering conservation of predators in spider and epigaeic beetle assemblages remains poorly understood. Here, we investigate the diversity and density of spiders and beetles over two consecutive winters (2019/2020 and 2020/2021), focusing on the impact of two rotation patterns (rice–fallow and rice–oilseed rape) and surrounding landscape compositions on predator diversity. The main findings of our research were that spiders were more abundant and had a higher activity density in the fallow rice fields (FRs) compared to the oilseed rape fields (OSRs), whereas ground beetles exhibited the opposite pattern. Specifically, fallow rice fields supported small and ballooning spiders (e.g., dominant spider: Ummeliata insecticeps), while OSRs supported larger ground beetles (e.g., dominant beetles: Agonum chalcomus and Pterostichus liodactylus). Moreover, the composition of spider assemblages were impacted by semi-natural habitats (SNHs) during overwintering, while ground beetle assemblages were influenced by overwinter planting patterns. Overall, our results suggest that different planting regimes and preserving semi-natural habitats are a strategic way to enhance species diversity and functional diversity of ground predators. It is, therefore, recommended that to conserve and improve predator diversity during overwintering, land managers and farmers should aim to maintain diverse planting regimes and conserve local semi-natural habitats.