Floral resources are crucial to the survival of pollinators of all types. The phenology of these resources is especially important to native pollinators whose life histories have coevolved with their native partners. Climate change and urbanization are predicted to cause shifts in floral phenology, which may in turn negatively impact native pollinators. In this study, we ask how floral duration is affected by urbanization in small-scale prairie restorations in Louisville, KY. The Louisville urban heat island is one of the most pronounced in the country, with temperatures averaging ~3°C higher than in rural areas. We predicted that an increase in urbanization of the surrounding area would decrease floral duration due to warmer temperatures and consequently increased plant stress. We also hypothesized that plants would bloom earlier in more urban areas, especially spring flowering species. To get at this question, we sampled the floral community of 18 prairie restorations in 2018. Bi-weekly observations of floral abundance and species richness were recorded. We also characterized land use (e.g., % impervious surface, % lawn, % forest) within a 1.5km radius around each restoration using GIS tools.
Results/Conclusions
We found wide variation in floral duration across restoration sites. Some species, such as Symphyotrichum ericoides, varied in their floral duration by as much as six weeks, while other species, such as Oxalis acetosella, showed very little variation at all. However, we found no relationship between urbanization and floral duration or first flowering when averaged across all species. We did, however, see strong positive relationships between site species richness and phenology, indicating factors such as soil conditions may play a larger role than urbanization in influencing phenology. These results show that urban prairie restorations can maintain floral resources that may be important to native pollinators.