Flowering apricot trees increase the abundance and modulate the distribution of wild bees within Korla fragrant pear (Pyrus sinkiangensis) orchards, but apricot trees in the surrounding landscape do not increase wild bee abundance

Pollinating insects rely on floral resources for survival and reproduction. Early flowering plants offer food resources for pollinating insects when floral resources are scarce, but they may also distract pollinating insects from pollination-dependent crops. Here we assessed how the abundance of bees and the pollination success of Korla fragrant pear (Pyrus sinkiangensis) is influenced by early flowering apricot trees within pear orchards or in the landscape at large, and how this influence is moderated by apricot flowering. The abundance of bees was measured using colored pan traps and pollination success was assessed by recording the initial fruit set and seed set. The density of apricot trees and land use types in radii of 0.5, 1.0, 1.5, and 2.0 km around focal pear orchards were assessed by landscape survey. The abundance of wild bees and honeybees was significantly higher in pear orchards with interspersed apricot trees than in mono-pear orchards. Pear trees next to an apricot tree row (5 m) had significantly higher wild bee abundance than pear trees at further distances (15 m, 30 m, 50 m, and 100 m). However, the positive effect of apricot trees on bee abundance in pear trees was only observed during apricot blooming, and the presence of apricot trees within or adjacent to pear orchards did not influence pear pollination success. The density of apricot trees in the surrounding landscape of pear orchards did not influence bee abundance and initial fruit set in pear orchards but it decreased seed set. Overall, our findings indicate that apricot trees in pear orchards can enhance bee abundance, but this effect only occurs at a relatively small spatial scale and during a short time span, and does not result in marked differences in pollination success. This indicates that flowering resources need to be close to or within the focal crop to have a positive effect on pollinating insect abundance.