Landscape and agrochemical use effects on abundance and diversity of pollinators in the North China Plain

Changes in human diets and cropping systems have led to a growing global dependence of agriculture on pollination, but pollinators are experiencing decline worldwide. Key stressors contributing to pollinator decline include natural habitat loss, a reduction in flower resources, and exposure to pesticides. In this study, we investigated effects of land use and estimated agrochemical use (fertilizer, biocides and plant growth regulators) on the abundance and diversity of pollinators across 24 landscape sites in the North China Plain using data from pan trapping across three seasons. We quantified agrochemical use as the average use intensity in agricultural production land (comprising arable land, orchards, agroforestry, and planted trees) and the landscape-wide exposure. The most abundant potential pollinators were bees (mainly Halictidae) and flies (mainly Muscidae and Syrphidae). Pollinator abundance, diversity and species composition were significantly affected by sampling season, with higher abundance and species diversity in autumn than in spring and summer. Pollinator abundance was positively associated with the proportion of arable land but negatively related with the proportion of orchard land and the agrochemical use intensity in agricultural production land and to the landscape-wide agrochemicals use. Overall, this study uncovered a weak signal of agrochemical use but a strong effect of season on pollinator diversity in the landscape setting of the North China Plain. Lower agrochemical use and a greater proportion of arable land were associated with higher abundance of some pollinator species in this intensive cereal production region. Results suggest that in the context of the North China Plain, pollinator abundance might be shaped more by aphid populations that support dominant species of hoverflies and by bare soil that favours nesting of wild bees, rather than by floral resources. Findings suggest that reducing agrochemical use intensity in agricultural production land, especially in orchards and other systems with trees, might facilitate pollinator conservation.