Elevated CO2 negates O3 impacts on terrestrial carbon and nitrogen cycles
Longlong Xia, Shu Kee Lam, Ralf Kiese, Deli Chen, Yiqi Luo, Kees Jan van Groenigen, Elizabeth A. Ainsworth, Ji Chen, Shuwei Liu, Lei Ma, Yuhao Zhu, Klaus Butterbach‐Bahl
Abstract
Increasing tropospheric concentrations of ozone (e[O$_{3}$]) and carbon dioxide (e[CO$_{2}$]) profoundly perturb terrestrial ecosystem functions through carbon and nitrogen cycles, affecting beneficial services such as their capacity to combat climate change and provide food. However, the interactive effects of e[O$_{3}$] and e[CO$_{2}$] on these functions and services remain unclear. Here, we synthesize the results of 810 studies (9,109 observations), spanning boreal to tropical regions around the world, and show that e[O$_{3}$] significantly decreases global net primary productivity and food production as well as the capacity of ecosystems to store carbon and nitrogen, which are stimulated by e[CO$_{2}$]. More importantly, simultaneous increases in [CO$_{2}$] and [O$_{3}$] negate or even overcompensate the negative effects of e[O$_{3}$3] on ecosystem functions and carbon and nitrogen cycles. Therefore, the negative effects of e[O$_{3}$] on terrestrial ecosystems would be overestimated if e[CO$_{2}$] impacts are not considered, stressing the need for evaluating terrestrial carbon and nitrogen feedbacks to concurrent changes in global atmospheric composition.