Pollination services in the North China Plain measured using buckwheat sentinel plants; is there a deficit?

The transition of food systems for healthy diets and sustainable food systems calls for greater production of fruit and nuts, i.e. pollinated crops. The North China Plain (NCP) is a cereal dominated area that needs to transition to a more sustainable food system with a nutritionally more diverse output. Buckwheat pairs high nutritional quality with low input requirement, but it is pollination dependent. There is little knowledge on the pollinator communities and pollination service in the NCP. We selected Quzhou county as a study region on the NCP, and used potted plants of buckwheat (Fagopyrum esculentum M.) to measure pollination in three treatments: insect exclusion, open pollination, and honeybee supplementation. Measurements were made at 24 sites across the county in 2021 and 2022. At each site, we directly observed the activity of flower-visiting insects and measured the pollination rate, seed set, seed abortion rate and yield-related indicators. Most flower visits were made by hoverflies (Syrphidae) and flies from the families Muscidae, Sarcophagidae, and Calliphoridae. Compared with open pollination, insect exclusion reduced buckwheat pollination rate and seed set by more than 90 %. Without honeybee supplementation, the pollination rate in different experimental sessions was reduced by 12–21 %, and the seed set was reduced by 22–33 %. Honeybee supplementation increased harvest index and seed weight per plant with factors of 1.6 and 2.0, respectively. Hence, a pollination deficit would exist if only natural pollinators were relied upon. Managed honeybees provide an efficient means for enhancing pollination of buckwheat in the North China Plain.