Drought reduces floral resources for pollinators

• Published in: Global change biology Vol. 24; no. 7; pp. 3226 - 3235
• Main Authors: Phillips, Benjamin B., Shaw, Rosalind F., Holland, Matthew J., Fry, Ellen L., Bardgett, Richard D., Bullock, James M., Osborne, Juliet L.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-07-2018
• Subjects: Abundance; Animals; Biodiversity; calcareous grassland; Climate change; Composition; Drought; drought stress; Droughts; Environmental impact; Flowers; Flowers - classification; Flowers - physiology; functional traits; Grassland; Grasslands; Herbivores; Lathyrus pratensis; Nectar; Onobrychis viciifolia; Plant communities; Plant Nectar - analysis; Plant populations; Pollen; pollination; Pollination - physiology; Pollinators; Prunella vulgaris; Resources; Species diversity; Species richness; Stress (physiology); Stress, Physiological - physiology; water availability; drought stress; pollination; functional traits; Lathyrus pratensis; Prunella vulgaris; calcareous grassland; nectar; Onobrychis viciifolia; climate change; water availability
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.14130

Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. By increasing plant physiological stress, drought is likely to affect the floral resources (flowers, nectar and pollen) that are available to pollinators. However, little is known about impacts of drought at the community level, nor whether plant community functional composition influences these impacts. To address these knowledge gaps, we investigated the impacts of drought on floral resources in calcareous grassland. Drought was simulated using rain shelters and the impacts were explored at multiple scales and on four different experimental plant communities varying in functional trait composition. First, we investigated the effects of drought on nectar production of three common wildflower species (Lathyrus pratensis, Onobrychis viciifolia and Prunella vulgaris). In the drought treatment, L. pratensis and P. vulgaris had a lower proportion of flowers containing nectar and O. viciifolia had fewer flowers per raceme. Second, we measured the effects of drought on the diversity and abundance of floral resources across plant communities. Drought reduced the abundance of floral units for all plant communities, irrespective of functional composition, and reduced floral species richness for two of the communities. Functional diversity did not confer greater resistance to drought in terms of maintaining floral resources, probably because the effects of drought were ubiquitous across component plant communities. The findings indicate that drought has a substantial impact on the availability of floral resources in calcareous grassland, which will have consequences for pollinator behaviour and populations.
Climate change is predicted to result in increased occurrence and intensity of drought in many regions worldwide. We simulated drought using a field experiment and measured the impacts on the availability of flowers and nectar for different plant species and plant communities. Drought consistently reduced the number of flowers available which will have consequences for pollinator behaviour and populations.