Contrasting effects of mass-flowering crops on bee pollination of hedge plants at different spatial and temporal scales

• Published in: Ecological applications Vol. 23; no. 8; pp. 1938 - 1946
• Main Authors: Kovács-Hostyánszki, Anikó, Haenke, Sebastian, Batáry, Péter, Jauker, Birgit, Báldi, András, Tscharntke, Teja, Holzschuh, Andrea
• Format: Journal Article
• Language: English
• Published: Washington, DC Ecological Society of America 01-12-2013; ECOLOGICAL SOCIETY OF AMERICA
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Bees - physiology; Biological and medical sciences; Bombus; Brassica napus; Brassica napus - physiology; bumble bee; bumble bee, Bombus spp; Bumblebees; canola; Crataegus; Crataegus - physiology; Crops, Agricultural - physiology; dog rose; dog rose, Rosa canina; ecosystem services; Edge effects; Flowers; Forest habitats; Forest insects; fruit set; Fruits; Fundamental and applied biological sciences. Psychology; Göttingen, Germany; hawthorn; hawthorn, Crataegus spp; Insect pollination; isolation; oilseed rape; oilseed rape, Brassica napus; Oilseeds; Pollinating insects; Pollination; Pollination - physiology; Population Density; Rosa; Rosa - physiology; Rosa canina; scale dependency; spp; Synecology; Terrestrial ecosystems; Time Factors; Central Europe; Europe; Germany; Lower Saxony; Göttingen; hawthorn; Brassica napus var. oleifera; Insecta; Rosaceae; Apidae; Rosa canina; Bombus; bumble bee; Cruciferae; Apoidea; Dicotyledones; Angiospermae; Flowering; Wild plant; Ecosystem services; Bombus spp; Cultivated plant; Aculeata; Hedge; isolation; Woody plant; Social insect; scale dependency; canola; Pollination; Crataegus spp; fruit set; Arthropoda; dog rose; oilseed rape; Brassica napus; Spermatophyta; Crataegus; Hymenoptera; Invertebrata; Oil plant (vegetal); Germany; Fructification
• ISSN: 1051-0761; 1939-5582
• DOI: 10.1890/12-2012.1

Landscape-wide mass-flowering of oilseed rape (canola
Brassica napus
) can considerably affect wild bee communities and pollination success of wild plants. We aimed to assess the impact of oilseed rape on the pollination of wild plants and bee abundance during and after oilseed-rape bloom, including effects on crop-noncrop spillover at landscape and adjacent-field scales. We focused on two shrub species (hawthorn
Crataegus
spp., dog rose
Rosa canina
) and adjacent herb flowering in forest edges, connected hedges, and isolated hedges in Lower Saxony, Germany. We selected 35 landscape circles of 1 km radius, differing in the amount of oilseed rape; 18 were adjacent to oilseed rape and 17 to cereal fields, and we quantified bee density via pan traps at all sites. Adjacent oilseed rape positively affected fruit mass and seed number per fruit of simultaneously flowering hawthorn (no effect on dog rose, which flowers after the oilseed rape bloom). At the landscape scale, oilseed rape had a negative effect on bumble bee density in the hedges during flowering due to dilution of pollinators per unit area and the consequently intensified competition between oilseed rape and wild shrubs, but a positive effect after flowering when bees moved to the hedges, which still provided resources. In contrast, positive landscape-scale effects of oilseed rape were found throughout the season in forest edges, suggesting that edges support nesting activity and enhanced food resources. Our results show that oilseed rape effects on bee abundances and pollination success in seminatural habitats depend on the spatial and temporal scale considered and on the habitat type, the wild plant species, and the time of crop flowering. These scale-dependent positive and negative effects should be considered in evaluations of landscape-scale configuration and composition of crops. Food resources provided by mass-flowering crops should be most beneficial for landscape-wide enhancement of wild bee populations if seminatural habitats are available, providing (1) nesting resources and (2) continuous flowering resources during the season.