Flower strips and remnant semi-natural vegetation have different impacts on pollination and productivity of sunflower crops

Abstract

Intensification of agricultural landscapes to fulfil increased global food demands has dramatically impacted biodiversity and ecosystem services. Several pollinator groups, which are vital for the maintenance of pollinator-dependent crops, have been severely affected by this intensification process. Management tools, such as the implementation of agri-environmental schemes, have been widely proposed to improve pollinator's communities and pollination services, although the effectiveness of wildflower strips in comparison to existing natural or semi-natural habitats and the impact on yield has not been fully demonstrated. Here, we aimed to assess the effect of flower strips implementation near sunflower fields in two intensive agricultural regions and to quantify their impact on visitation rates and sunflower productivity. Data were obtained in two regions in Spain (Burgos and Cuenca) in sunflower fields with associated semi-natural vegetation (SNVs), with implemented wildflower strips (WFSs) and without vegetation structures (NonVs). Visitation rates were monitored over 2 years by direct observations, and both sunflower seed production and weight were assessed in 52 fields per year. Our results revealed regional and inter-annual variation in visitation rates, likely driven by structural differences in the landscapes studied. In Cuenca, characterized by more heterogeneous and floral resources-richer landscapes, the effects of WFSs were significant in the second year of implementation, with higher visitation rates and productivity values in fields with implemented wildflower strips compared to those without. In contrast, in Burgos, no consistent effects among field treatments between years were observed. Synthesis and applications. The implementation of flower strips or maintenance of remnant semi-natural habitats adjacent to sunflower fields showed context-dependent effects on pollinator visitation rates and crop yield. In highly simplified agroecosystems, these interventions may be insufficient or may need longer times to produce significant effects. Yet, in regions where natural and semi-natural patches were already present, the implementation of flower strips was a successful strategy to promote pollinators and sunflower productivity