Trees benefit from excess carbon dioxide

Studies show carbon dioxide causes more than climate change.
December 06, 2009

Long considered a major driver of global climate change, a pair of studies by University of Minnesota researchers have revealed positive aspects of excess carbon dioxide in the atmosphere.
A study by researchers at the University of Minnesota-Morris and the University of Wisconsin found aspen trees, a Minnesota paper industry staple, are responding well to excess carbon dioxide.
The study, published Friday in Global Change Biology found that an increase in carbon dioxide has caused a 53-percent increase in the trees’ growth rate over the past 50 years.
University of Minnesota professor Peter Reich published a related study in Science magazine showing that an increase in carbon dioxide may limit the damaging effects nitrogen pollution has on plant diversity.
Chris Cole, a professor at Morris who co-authored the study on aspen trees, said the results are especially important in Minnesota and Wisconsin, where aspen span more than 7 million acres oftimberland.
“Aspen are commercially, ecologically and emotionally important trees,” he said.
About 920 trees were studied throughout three regions of Wisconsin over a period of more than five years, but Cole said the results do not necessarily mean that aspen will continue to grow.
“They’re growing in large part because of the effects of carbon dioxide,” he said. “That doesn’t mean growth rates will last down the line.”
Rick Lindroth, a professor at the University of Wisconsin and co-author of the aspen tree study, said researchers were surprised with the results. Oak and pine trees have not observed faster growth rates, making the study unique to previous research.
“What this means is our beloved forests are recognizing change,” he said. “There was a ‘what if’ question that frequented the study … Its results concluded that aspen responded well to carbon dioxide, which is fascinating.”
Lindroth said global climate change affects more than just temperature. Climate change, he said, played a large role in the study’s results.
Wisconsin’s climate has stayed relatively consistent compared to other parts of the United States, Cole said.
The study is the first to determine that growth rates in the region are directly linked to rising levels of atmospheric carbon dioxide.
Lindroth called carbon dioxide a “superfood” for the trees and said it is the driving force for aspen growth.
Aspen trees were chosen for the study because of their ubiquity and because the trees are particularly responsive to changes in environment.
“Aspen are unique … The trees are sort of the white rat of the forestry world,” he said.

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