Ozone injury on plants in Colorado wilderness

Ozone injury on plants in Colorado wilderness

This blog post was contributed by Kateryna Lapina, an atmospheric chemist working at the University of Colorado Boulder, Department of Mechanical Engineering. In her work she uses chemical transport models to estimate the negative impacts of ground-level ozone on vegetation, including the loss of major agricultural crops and ozone-sensitive tree species in the U.S.

In August 2014, a group of us visited Rocky Mountain National Park. Guided by a park biologist, we surveyed several locations for ozone damage on cutleaf coneflower, one of the ozone-sensitive plants growing in the park. We visited four sites where the cutleaf coneflowers have now been studied for years, and observed damage called stipple on many leaves. It was clear that, as in previous years, high ozone levels were common in the park that summer.

This year I made two visits to the study site – once in mid-June, and again two months later as the plants grew tall and had sufficient time to interact with the surrounding air. I didn’t observe any damaged leaves during my first visit. This was not surprising, as this was early in the growing season and ozone injury develops over time, plus ozone concentrations are relatively low earlier in the summer. Last week I went to see the same plants again, and the majority of the leaves had a well-pronounced ozone stipple on them, consistent with the fact that this summer we are having yet another high-ozone season in the Colorado Front Range.

Ozone injury on cutleaf coneflowers in the Rocky Mountain National Park.
Credit: Kateryna Lapina/University of Colorado Boulder

Cutleaf coneflowers in the Rocky Mountain National Park.
Credit: Kateryna Lapina/University of Colorado Boulder

A few days later I was visiting a beautiful mountain retreat located almost 30 miles straight North from the survey site, in the Red Feather Lakes area.  This place has minimal local sources of air pollution, and the nearest city of Fort Collins is a one-hour drive away. I spotted more coneflower plants growing in the area and upon examining their leaves I found the same pattern of ozone injury as I observed in the Rocky Mountain National park and at some of our ozone gardens. This serves as another reminder that ozone pollution is not a local problem, but it can threaten the health of humans, animals, and vegetation over a large area, many miles away from the emission sources.

Cutleaf coneflowers growing in the Red Feather Lakes area show signs of ozone damage (black dots on the enlarged photo).
Credit: Kateryna Lapina/University of Colorado Boulder