Honey bees enhance pollination network stability and function

To investigate the richness and abundance of flower visitors, flower visitors were observed along three transects in 28 sites in 2021 and 20 sites in 2022. Each transect in each plot was surveyed for 60 min per day on four clear days without strong winds (9:00-19:00), for a total of 720 min per plot (60 min × four different days × three transects). The area of mass-flowering plants of B. rapa var. oleifera within 1 km of each plot was also recorded. Of the 48 sample plots, we defined the 24 plots with the larger area of rapeseed area as high mass-flowering crop plots (high MFC) and the other half as low mass-flowering crop plots (low MFC). If an insect came into contact with anthers or stigmas of flowers, we recorded a pollination visit without considering the pollination's effectiveness. We did not observe pollinator visits at night, because few pollinators visited flowers at low temperatures. We summed the number of pollinators observed visiting flowers over 12 hours for each network, as mentioned above. Each pollination network is composed of a quantitative adjacency matrix, which indicates the total number of visits of each pollinator to each plant species.

为探究访花昆虫（flower visitors）的类群丰富度与种群丰度，本研究于2021年在28个样地、2022年在20个样地中，沿三条样带开展访花昆虫观测。每个样地内的每条样带，均在4个无强风的晴朗日间开展每日60分钟的调查，观测时段为9:00-19:00，单样地总调查时长为720分钟（即60分钟/天 × 4个不同观测日 × 3条样带）。同时记录每个样地1公里范围内的油用油菜（Brassica rapa var. oleifera）盛花植株的种植面积。本研究共纳入48个样地，将其中24个油用油菜种植面积较大的样地划分为高盛花作物样地（high MFC），剩余24个样地划分为低盛花作物样地（low MFC）。若昆虫接触到花卉的花药或柱头，则记录为一次授粉访花，不考量该访花的授粉有效性。由于低温环境下访花昆虫极少活动，本研究未开展夜间授粉访花观测。如前文所述，本研究对每个授粉网络（pollination network）统计12小时内观测到的访花昆虫总数。每个授粉网络均由定量邻接矩阵（quantitative adjacency matrix）构成，该矩阵可反映每种访花昆虫对每种植物的访花总次数。