Plants growing in the forest understory, including spring ephemerals, which are short-lived herbaceous plants, are important members of the forest plant community. A team of Appalachian Mountain Club scientists evaluated observations of leaf out and flowering in 11 understory plant and 14 tree species to help address the outstanding question of which plant group is shifting their springtime activity more. Overall, understory plants are advancing the timing of their activity twice as much as trees under warmer conditions. Interestingly, plants of the mid-Atlantic region – comprising the “middle” section of the Appalachian Trail – showed substantially more advancement than plants to the north or the south. And finally: when they looked at differences among the plant groups by region, they only saw evidence of greater advancement among understory plants in the north. The findings of this analysis are good news for the understory plants. Greater advancement in the springtime activity of these plants compared to leaf-out in the overstory canopy means more time for them to grow prior to being shaded out by the larger trees.

Understanding how climate change is affecting species is especially important for threatened or endangered species, which already exhibit perilously low species numbers. A research team led by Jeremy Yoder at California State University, Northridge sought to determine the environmental conditions that Joshua trees must experience to trigger flowering. Using over 10,000 images of Joshua tree contributed to iNaturalist, the team predicted whether and when Joshua trees flowered in years past, back to 1900, and tested the performance of the model in predicting the timing of flowering by comparing the predictions to observations contributed to Nature’s Notebook. They determined that over the past 120+ years, the trees have increased how frequently they flower, as a result of progressively warmer temperatures and more variable rainfall over the period.

In many deciduous forests, understory plants such as spring blooming wildflowers depend on a critical period of sunlight before overstory tree leaves block out the sun. Climate change has caused a shift to earlier leaf out in many plants, but not all taxa are shifting at the same rate. Two recent studies found conflicting results about whether wildflowers are advancing their springtime activity in step with overstory trees. The authors of the studies came together to investigate what might be behind the difference in results and found that difference in the types of data used, herbarium data in one and Nature’s Notebook data in the other, along with the geographic and temporal extent of the datasets evaluated, were likely the cause. The study demonstrates the importance of both types of data to explore these types of complex ecological questions. Once the methods of the two studies were adjusted to be more similar, the results indicated that wildflowers in the southern part of eastern North America are less sensitive to changes in temperature than overstory trees and that phenological activity was earlier in warmer years and in warmer locations.