Ozone sensitive plant species on National Park Service lands

Bell, Michael; Felker-Quinn, Emmi; Kohut, Robert

Tropospheric ozone is formed by atmospheric reactions between sunlight and atmospheric pollutants including NOx and volatile organic compounds. Ozone is a significant phytotoxic pollutant that damages vegetation by entering leaves through the stomata and altering cellular function, resulting in visible leaf damage, decreased growth and reproduction, or early leaf senescence. While peak ozone concentrations are decreasing nationally, total ozone exposure in some regions is still above the threshold to cause damage to vegetation. Each plant species has a varying level of tolerance to ozone based on leaf chemistry, timing and rate of gas exchange, and environmental conditions. Community effects can lead to shifts in dominant species, change in light dynamics in the understory, or slowing succession rates post-disturbance. The National Park Service is responsible for identifying Air Quality Related Values that are impacted by ozone. The National Park Service (NPS) convened a workshop in June 2003 to review and update lists used by the NPS and the U.S. Fish and Wildlife Service (FWS) to identify ozone sensitive plant species. At the workshop, ozone effects scientists made recommendations for the lists; subsequent to the workshop, an additional group of scientists provided review and comments to the lists. Since the workshop, many scientific studies have been completed to measure the ozone sensitivity of additional plant species. This document is an update to the report Ozone Sensitive Plant Species on National Park Service and U.S. Fish and Wildlife Service Lands: Results of a June 24-25 2003 Workshop (Porter 2003). Peer reviewed documents published after June 2003 were reviewed to determine if vegetation showed negative growth affects or visible damage under expected levels of ozone exposure. Additionally, this list updates the taxonomic nomenclature of the original list based on the Integrated Taxonomic Information System (www.ITIS.gov). The species within this report are those that have a visible physical response (e.g., chlorotic mottle, leaf stipple) to ozone exposure. While additional physiological responses have been measured in other species, the listed species allow managers and scientists to visually evaluate where ozone impacts are occurring.

Ozone sensitive plant species on National Park Service lands

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