Pollinators in Blackcurrant Orchards: Complementary Roles of Sown and Spontaneous Flower Strips and Limited Spillover of Small Wild Bees Within Fields.

Agricultural intensification threatens pollinators and associated ecosystem services through pesticide use and the loss and fragmentation of natural habitats. Sowing flower strips and preserving spontaneous flowers are commonly recommended practices to support pollinators within fields. However, their effectiveness remains variable across studies and pollinator morphogroups, and their influence on pollinator activity is poorly studied in several crops, particularly in blackcurrant. Here, we studied flowering plant communities (sown and spontaneous) and four pollinator morphogroups (Bombus, large wild bee, small wild bee, and hoverfly) in nine blackcurrant orchards in Burgundy (France) during three sampling rounds in spring 2023. A seed mixture was previously sown by farmers in spring 2022 in four orchards, and in autumn 2022 or spring 2023 in the others. In each morphogroup, we investigated whether pollinator abundance in the blackcurrant inter-rows was influenced by the number of sown and spontaneous flowers and by position within the inter-rows (edge, inner, centre). We also examined whether pollinator abundance in blackcurrant bushes was related to floral abundance and pollinator activity in adjacent inter-rows. Flowering plant communities varied across sampling rounds, with sown species flowering only in inter-rows sown in spring 2022. The abundance of small and large bees increased with the number of spontaneous flowers, whereas hoverfly abundance increased with sown flowers. Small bee abundance, and to a lesser extent that of large bees, decreased in the inner and central transects of the inter-rows compared to the edge. Moreover, for all morphogroups, pollinator abundance in blackcurrant bushes was not influenced by flower abundance but increased with pollinator abundance in the adjacent inter-rows. These findings emphasise the complementary value of sown and spontaneous floral resources to support pollinators within orchards. The sharp decline in small bee abundance toward orchard interiors suggests potential dispersal limitations and highlights the importance of integrating suitable habitats to facilitate pollinator movement within crops.