Although flower nectar yield is well known to be temperature dependent, the effects of climate change on the availability of nectar to pollinators have rarely been studied.
Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs.
Mu et al. apply long-term artificial asymmetric warming to a perennial herb, Saussurea nigrescens, in a Tibetan alpine meadow and find that winter warming weakens vernalization and decreases floret and capitulum number, and that night-time warming reduces floret nectar volume. The overall effect is a reduction in nectar production per unit area of about 90 %, and the results suggest that decreases in floral quantity and quality as a result of global warming may have increasingly negative effects on plant–pollinator interactions.
This article appears in the special issue Plants and Climate Change.