Richard Thomas, professor of biology at West Virginia University, has been published in the Proceedings of the National Academy of Sciences of the United States of America for his research on the effects of pollution on eastern red cedar trees in the Central Appalachian Mountains.

The journal highlights cutting-edge research and is one of the world’s most-cited multidisciplinary scientific publications.

In 2008, Thomas began examining the growth of red cedar trees in Grant County, W.Va. His findings, however, quickly set the research on a path surveying the efficacy of the U.S. Clean Air Act’s 1970 amended legislation.

Using the carbon isotope ratios of 13C and 12C that were found in the wood of tree rings, Thomas and his team were able to explore the physiological functioning of the trees over the past 100 years.

The isotope ratios provided evidence that the stomata, the tiny pores in the leaves that regulate the gas exchange of CO2 and water, were slowly closing over decades of acidic pollution.

There was a change in the isotope ratio around 1982 that indicates that the stomata began to reopen around that time.

“Our study shows that about 10 years after this landmark environmental legislation, as acidic pollution decreased, the stomata of these trees began to reopen and they continued to open slowly over the next 35 years,” he said.

“Photosynthesis and tree growth increased at the same time.”

The research team examined many possibilities that might cause changes in the isotope ratios. “The only thing we could conclude that was causing this was that there was a reduction in pollution,” Thomas said.

His study findings, he added, support the assertion that the often-times controversial Clean Air Act legislation has benefitted West Virginia forests.

Thomas found a similar isotopic signal from the tree rings produced during the 1930s.

“It is fascinating because if you think about trees, you don’t think about them recording history—but here, these trees have recorded The Great Depression and they’ve recorded the environmental legislation of the Clean Air Act,” he said.

Thomas said the project is one of the most interesting ones he has worked on in his academic career. Although it has concluded, there are plans for expansion of the research.

Other researchers on this study include Scott Spal, a master’s graduate from WVU; Kenneth Smith, an undergraduate student at WVU; and Jesse Nippert, an associate professor at Kansas State University.

For more information, contact Richard Thomas, at 304-293-6673 or



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