Citizen science projects are a powerful tool for monitoring long-term ecological trends. Great Smoky Mountains National Park has tracked ecosystem health throughout the park for decades. Staff, visiting students, and volunteers have monitored ozone-related damage to plants in a high-elevation biomonitoring garden at Purchase Knob since 2003. Yellow crownbeard (Verbesina occidentalis)-an ozone-sensitive species native to the southeastern United States-is the primary bioindicator species in the biomonitoring garden. Ozone-induced foliar injury on yellow crownbeard appears as purple stippling on the top surface of leaves. Ozone levels have been steadily decreasing at Purchase Knob since 2003, but foliar injury peaked in 2012 and has been improving since then. We also found that weather mediates the effect of ozone levels on yellow crownbeard; yellow crownbeard is more susceptible to ozone-related foliar injury in warm and humid weather, likely due to the increased stomatal conductance of ozone in these conditions. The marked reduction in ozone-related injury in the park over the last decade may highlight a success in recent air pollution regulatory efforts.

¹ University of Tennessee, Department of Ecology and Evolutionary Biology, Knoxville, TN

² National Park Service, Air Resources Division, Denver, CO

³ National Park Service, Great Smoky Mountains National Park, NC

* Corresponding Author: amy.luo.15@gmail.com