New, Surprising Insights into Potential Effects of Ozone Pollution on Forest Growth


Fossil fuel use is causing an increase in the concentrations of both carbon dioxide and ozone in the atmosphere. The increasing carbon dioxide concentration is expected to stimulate tree growth, while available data indicate that increasing ozone can counteract the beneficial effects of increasing carbon dioxide on tree growth. Recently published measurements from the longest running field experiment exposing trees to elevated carbon dioxide and ozone, research sponsored by DOE, surprisingly indicate that the combination of elevated carbon dioxide and ozone stimulated root growth in some tree communities. The scientists conducting the research suggested that the death of ozone-sensitive trees followed by increased growth of ozone-tolerant trees made possible by access to space and soil nutrients that would have been used by ozone-sensitive trees might be the explanation for the increased root growth. But whatever the mechanism might be, these new results indicate a possible long term response to increasing concentrations of carbon dioxide and ozone that is not generally considered in assessments of potential effects of the changing composition of the atmosphere on forest tree growth.