Wildflower strips enhance pollination in adjacent strawberry crops at the small scale.

Dominik Ganser,Eva Knop,Matthias Albrecht,Barbara Mayr

doi:10.1002/ece3.4631

Abstract

Wildflower strips (WFS) are increasingly used to counteract the negative consequences of agricultural intensification. To date, it is poorly understood how WFS promote flower visitation and pollination services in nearby insect‐pollinated crops. We therefore ask whether WFS enhance pollination service in adjacent strawberry crops, and how such an effect depends on the distance from WFS. Over 2 years, we examined the effects of experimentally sown WFS compared to grassy strips on pollination services in adjacent strawberry (Fragaria ananassa) crops across a total of 19 study sites. Moreover, we examined flower visitation, species richness and community composition of the most important insect pollinator taxa at different within‐field locations varying in distance to WFS. We found increased pollination services at the edge of WFS compared to locally reduced pollination services at the center, which resulted in no significant difference in seed set between WFS and control fields. Total flower visits and species richness of pollinators were higher in WFS than in adjacent strawberry fields. Moreover, wild bee visitation was enhanced in adjacent strawberry crops near WFS compared to field centers, and intermediate at field edges near grassy strips. Our study demonstrates that diverse WFS can increase wild bee visitation and pollination services in the field edges of adjacent strawberry crops, but that overall visitation and pollination services do not increase. Moreover, our findings show that major pollinator taxa exhibit distinct responses, resulting in a shift of pollinator community composition as a function of distance to WFS with direct effects on crop pollination. Our results that WFS enhance rather than reduce crop pollination services near WFS should distract possible concerns by farmers that WFS may locally absorb rather than export crop pollinators. Considering the spatial restricted enhancement of wild bees and associated pollination services we suggest to establish WFS in the center of crop fields.

Highlights

Managed and wild pollinators provide important crop pollination services and can thereby improve the yield of many animal‐pollinated crops (IPBES, 2016)
Managed honey bees (Apis mellifera L.) are used widely as crop pollinators, but recent global meta‐analyses have highlighted the importance of wild pollinators for crop pollination (e.g. Garibaldi et al, 2014; Holzschuh, Dudenhöffer, & Tscharntke, 2012; Mallinger & Gratton, 2015; Winfree, Williams, Dushoff, & Kremen, 2007), which account for roughly half of the economic value of pollination services worldwide (Kleijn et al, 2015)
The loss and degradation of semi‐natural habitats has reduced the amount of floral resources (Goulson, Lye, & Darvill, 2008; Williams & Osborne, 2009) and the availability of nesting sites for pollinators (Steffan‐Dewenter & Schiele, 2008), which are considered the underlying mechanism of wild pollinator decline in agroecosystems (e.g. IPBES, 2016)

Summary

Introduction

Managed and wild pollinators provide important crop pollination services and can thereby improve the yield of many animal‐pollinated crops (IPBES, 2016). Managed honey bees (Apis mellifera L.) are used widely as crop pollinators, but recent global meta‐analyses have highlighted the importance of wild pollinators for crop pollination (e.g. Garibaldi et al, 2014; Holzschuh, Dudenhöffer, & Tscharntke, 2012; Mallinger & Gratton, 2015; Winfree, Williams, Dushoff, & Kremen, 2007), which account for roughly half of the economic value of pollination services worldwide (Kleijn et al, 2015). The loss and degradation of semi‐natural habitats has reduced the amount of floral resources (Goulson, Lye, & Darvill, 2008; Williams & Osborne, 2009) and the availability of nesting sites for pollinators (Steffan‐Dewenter & Schiele, 2008), which are considered the underlying mechanism of wild pollinator decline in agroecosystems (e.g. IPBES, 2016). Pollinators with long lifecycles, such as bumble bees or honey bees, are critically affected in their health (Alaux et al, 2017), reproduction success (Williams, Regetz, & Kremen, 2015; Williams, Ward, et al, 2015) and the survival between lifecycle stages (Carvell et al, 2017) without enough food resources throughout the entire activity periods

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