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The Interactive Effects of Elevated CO2 and O3 on Chinese Tallow Tree

Paper Reviewed
Wang, H., Zhang, L., Ma, X., Zou, J. and Siemann, E. 2018. The effects of elevated ozone and CO2 on growth and defense of native, exotic and invader trees. Journal of Plant Ecology 11: 266-272.

Ozone (O3) is a primary air pollutant responsible for visible foliar injury and reduced growth in trees the world over. Carbon dioxide (CO2), in contrast, is an aerial fertilizer, responsible for boosting the photosynthesis and growth of trees. But are the positive effects of elevated levels of atmospheric CO2 strong enough to ameliorate the negative influence of O3 pollution?

A new study by Wang et al. (2018) that was published in the Journal of Plant Ecology provides insight into this important question. In their work, the team of five researchers examined the impact of elevated O3 (100 ppb) and CO2 (800 ppm) -- alone and in combination -- on two cultivars of Chinese tallow tree (Triadica sebifera) seedlings that were grown in controlled environment chambers for a period of 78 days.

Results of the study are presented in the figure below, where it is seen that the growth of both the Chinese and U.S. cultivars were negatively impacted by the elevated O3 treatment, suffering a reduction in total biomass of 8 and 18 percent, respectively. In contrast, elevated CO2 enhanced the total biomass of the Chinese cultivar by 17 percent and the U.S. cultivar by 6 percent.

In the combined elevated CO2 and elevated O3 treatment, the positive effects of CO2 enrichment were powerful enough to fully ameliorate the biomass reductions induced by elevated O3, as the Chinese and U.S. cultivars experienced growth enhancements of 20 and 22 percent, respectively, relative to the control.

Commenting on these findings, Wang et al. say that they "are consistent with previous findings ... which found that elevated CO2 limited the negative effect of elevated ozone."


Figure 1. The effects of ozone and CO2 on the total mass of US and China populations of T. sebifera. Adapted from Wang et al. (2018).

Posted 11 July 2018