Warmer temperatures are linked to mismatch among forest plants

 By Tara K. Miller and Richard B. Primack

“To say that a man is your Friend, means commonly no more than this, that he is not your enemy.”  

- Henry David Thoreau in A Week on the Concord and Merrimack Rivers 

Many plants are responding to a warming climate by leafing out and flowering earlier in the spring. However, mismatches may occur when species respond at different rates. 

In a new study in Journal of Ecology, we showed that trees are shading out spring wildflowers across eastern North America by leafing out earlier in the spring in response to climate change. This might contribute to the loss of wildflower populations in coming decades as the climate continues to warm.

Native wildflowers, such as these Dutchman’s breeches,
are not keeping pace with trees as they advance
their leaf-out with warming temperatures
(© Andrew Cannizzaro CC-BY-2.0)

Many spring-blooming native wildflowers conduct most of their photosynthesis before the canopy trees above them leaf out and shade them over. As temperatures warm, trees and shrubs may block sunlight from reaching the forest floor earlier in the year, leading to a shrinking time period for native wildflowers to photosynthesize with full sunlight. Just a few days loss of sunlight access can mean a sizeable decrease in a wildflower’s carbon energy supply.

Our study confirms the results of an earlier study from Concord, MA that used the observations of Henry David Thoreau from the 1850s as a baseline, and extends the scope across eastern North America using data from herbarium specimens, which are pressed plants in museums.

Map of herbarium specimen collection
locations in eastern North America
(© Miller et al. 2022, Journal of Ecology)

Publication: Tara K. Miller, J. Mason Heberling, Sara E. Kuebbing, and Richard B. Primack. (2022). Warmer temperatures are linked to widespread phenological mismatch among native and non-native forest plants. Journal of Ecology.