Patterns and Drivers of Woodland Understory Flower Phenology and Canopy Closure

Uploaded by vmc on 02/12/2023

Tags: Climate Change  

Attachments: Slide15.jpeg (245KB) Tourville.srt (34KB)

This was presented by Jordon Tourville as a part of a series of contributed talks from the 2022 FEMC Annual Conference. To learn more about the conference, visit: https://www.uvm.edu/femc/cooperative/conference/2022. Warming and changes in precipitation associated with climate change will likely impact the onset of spring flowering and other phenological stages for forest plants across the northeastern United States. Understory forbs of northern hardwood and montane spruce-fir forests may be sensitive to spring warming before canopy closure, however, detailed information on the spatial patterns and drivers of phenological change for these taxa is still lacking. Here, we discuss the results of a preliminary effort to summarize spring leaf out and first flower onset for several canopy tree, understory forb, and spring ephemeral species across elevational gradients in New England. We also compare woodland and alpine plant phenological sensitivity to regional warming. Phenological observations from the Appalachian Mountain Club’s (AMC) Mountain Watch (MW) project, the National Phenology Network (NPN), and iNaturalist were collated and synthesized between 2004 and present (~800,000 observations). Phenological observations were paired with environmental variables and separated by year to uncover (1) spatial patterns of spring understory phenology (and how it relates to canopy closure timing), (2) critical climatic drivers of spring phenology, and (3) phenological responses of understory plants to warmer years. Median flowering time for each year of observation for 14 understory forb species and 10 alpine species, and median leaf out time for 4 canopy tree species were also calculated. Overall, we find strong negative relationships between elevation, spring mean temperatures, accumulated growing degree days (AGDD), and open flower timing for our understory forb species. Additionally, understory flowering times have been shifting earlier than canopy leaf out times, and alpine plant flowering does not appear to be as responsive to warming as lower elevation woodland plants. Our preliminary analyses provide much needed baseline information on woodland phenology across the region. Moving forward, these data will allow us to explore temporal trends in flower and leaf out timing in relation to patterns of warming and help us to better anticipate threats to understory plants.