Print PagePhenology, the timing of key life events in plants and animals, can be highly sensitive to climate change. Many plant species have responded to increasing temperature with significant shifts in phenology, including earlier spring flowering. However, differing phenologic plasticity among species in response to temperature increases have important implications for future state-wide biodiversity. For instance, earlier blossoming can result in greater risk of frost exposure and pollinator mismatch leading to species decline. Alternatively, nonresponsive species may lose benefits of greater early season productivity gained by phenologically plastic species allowing responsive species to increase in abundance. Despite the potentially significant impacts on biodiversity, few phenological studies include enough species to make predictions of future shifts in abundance based on phenologic responsiveness.
To improve our understanding of large-scale, state-wide responses to climate change, we used a novel, herbarium-based method for evaluating shifts in flowering phenology throughout Ohio. To evaluate phenological responses to temperature change across the state, we paired specimens from the Ohio State University Herbarium, dating from 1895, with temperature data from the U.S. Historical Climatology Network. By matching specimens with temperatures specific to their collection dates and locations, we normalized species’ phenologic response across time and location allowing analysis across a 116,000km2 region. The extensive herbarium records allow us to evaluate variation in phenologic responsiveness for a large number of species, facilitating prediction of phenological responsiveness across functional groups.
Results/Conclusions
Our analysis of spring temperature anomalies for 26 Ohio counties showed a significant rise from 1895 to the present, with some counties increasing by as much as 2oC. The flowering times of 66% of the 35 species examined to date responded significantly to higher spring temperatures with advancement of flowering phenology. Highly responsive species included Alliaria petiolata (garlic mustard) and Cornus alternifolia (alternate-leaved dogwood) with flowering advancement of 4.6 and 4.2 days per degree, respectively. Other species showed little or no shift in flowering time with higher temperatures, including Aesculus flava (yellow buckeye) and Viola conspersa (dog violet). With an average spring temperature increase of 3.5oC predicted for eastern North America in the next 90 years by the Intergovernmental Panel on Climate Change, flowering time may be advanced as much as two weeks for some species in Ohio forests. Clarifying species-specific responses is critical for assessing the threat of biodiversity loss in Ohio associated with climate change.
