Seasonal dynamics of floral resources for pollinators and natural enemies

Abstract: There is public concern about declines of insect diversity and abundance in agricultural landscapes. These declines may be related to loss of habitats and resources for insects. Here, we assessed the availability of floral resources over the year in the agricultural area of Hoeksche Waard, The Netherlands, and explored scenarios to increase those resources. We collated data on plant communities from vegetation assessments, and linked these with functional traits of plant species, including flowering times and nectar accessibility for four insect groups important for pollination and pest control. Willow forest was found to be a key habitat for providing floral resources for bumblebees, solitary bees and syrphids since they flower early in the season when other habitats do not provide these resources yet. Willow forest and annual flower strips have a high flowering plant cover, but the area of these habitats at regional scale is small. Our data suggest that the conversion of grassland strips into flower strips may be an effective strategy to increase floral resources at landscape level.