Intercropping of insect-pollinated crops supports a characteristic pollinator assemblage

Abstract

Intensive agriculture is one of the key drivers of global –pollinator decline. More ecologically sustainable cropping methods are urgently needed to preserve pollinators and to maintain future crop yields. This study examined the impact of strip intercropping on pollinators of spring turnip rape and faba bean. The pollinator abundance, species diversity, and species assemblages in monoculture and intercropping treatments were compared in a two-year field experiment in 2019—2020. Pan traps and transect counts were used to sample pollinators.Transect counts showed the highest pollinator abundance in turnip rape monoculture, medium in intercropping, and the lowest in faba bean monoculture. Pan traps indicated no difference in pollinator abundance among treatments but revealed increasing abundance and species diversity during the flowering season. Temporal change in species assemblage was also detected. Each treatment had distinct pollinator assemblage despite explicit honeybee dominance. All the most common pollinator species were present in the intercropping treatment, but there was no treatment impact on rare species. The rarefied species pool in the intercropping treatment exceeded that of monocultures but pollinator species richness did not differ among the treatments. Pollinator species diversity and evenness were higher in faba bean monoculture than in turnip rape monoculture, but neither had a pairwise difference with the intercropping treatment. Intercropping partially succeeded in substituting abundant turnip rape pollinators with more specialized faba bean pollinators. This resulted in a pollinator species assemblage with a broader range of foraging traits and more even abundance distribution compared with that in pure stands. At the landscape scale, such a shift would potentially improve ecological sustainability by reducing pollinator shortages, preventing pollinator dilution, and interfering less with natural plant pollination. However, rare pollinator species and landscape-level species diversity of pollinators must be supported with additional complementary methods.