Rising Atmospheric Carbon Dioxide and Potential Impacts on the Growth and Toxicity of Poison Ivy (<i>Toxicodendron radicans</i>)

Abstract

Because of its ability to induce contact dermatitis, the establishment and spread of poison ivy is recognized as a significant public health concern. In the current study, we quantified potential changes in the biomass and urushiol content of poison ivy as a function of incremental changes in global atmospheric carbon dioxide concentration (CO 2 ). We also examined the rate of new leaf development following leaf removal to simulate responses to herbivory as functions of both CO 2 and plant size. The experimental CO 2 values (300, 400, 500. and 600 µmol mol −1 ) corresponded approximately to the concentration that existed during the middle of the 20th century, the current concentration and near and long-term projections for this century (2050 and 2090), respectively. Over 250 d, increasing CO 2 resulted in significant increases in leaf area, leaf and stem weight, and rhizome length relative to the 300 µmol mol −1 baseline with the greatest relative increase occurring from 300 to 400 µmol mol −1 . There was a nonsignificant (P = 0.18) increase in urushiol concentration in response to CO 2 ; however, because of the stimulatory effect of CO 2 on leaf biomass, the amount of urushiol produced per plant increased significantly for all CO 2 above the 300 µmol mol −1 baseline. Significant increases in the rate of leaf development following leaf removal were also observed with increasing CO 2 . Overall, these data confirm earlier, field-based reports on the CO 2 sensitivity of poison ivy but emphasize its ability to respond to even small (∼ 100 µmol mol −1 ) changes in CO 2 above the mid-20th century carbon dioxide baseline and suggest that its rate of spread, its ability to recover from herbivory, and its production of urushiol, may be enhanced in a future, higher CO 2 environment.