Exploring Ailanthus altissima as a bioindicator of ozone pollution

Background/Question/Methods

Ground-level ozone is one of the most significant air pollutants in the U.S.; it is harmful to human health, vegetation, and ecosystems.  Concurrently, Ailanthus altissima (tree-of-heaven, Ailanthus) is one of the most invasive plant species in the U.S.  Conservationists are highly concerned with Ailanthus due to its rapid range expansion and population growth; however, if found to be susceptible to ozone exposure in predictable ways, Ailanthus could be a useful bioindicator for ground-level ozone pollution.  A series of exposure experiments and field surveys were conducted during 2010 and 2011 to evaluate the utility of Ailanthus as a bioindicator of ozone pollution.  To explore the uniformity of Ailanthus’ reaction to ozone, Ailanthus seedlings from six locations across the country were exposed to ozone using continuously stirred tank reactor chambers within a greenhouse.  Seedlings from the same seed source were exposed to five different ozone concentrations to determine if a relationship exists between concentration of ozone exposure and total foliar damage of the plant.  Ailanthus seedlings were also planted in the field and monitored for ozone-induced foliar damage along with staghorn sumac, black cherry, common milkweed, and dogbane to evaluate how Ailanthus performed compared to other known ozone bioindicators. 

Results/Conclusions

Results revealed that plants originating from Corvallis, Oregon were significantly more susceptible to ozone pollution than the other seed sources (p < 0.05), and a positive, linear relationship was found between ozone exposure concentration, temperature, initial height, and foliar damage on Ailanthus plants (R²= 0.8543).  Results also showed that ambient ozone levels in Pennsylvania were sufficient to induce foliar symptoms on all surveyed flora species, including Ailanthus, in the field.  We conclude that Ailanthus is a suitable bioindicator for ozone pollution.