Carbon dioxide makes aspens grow faster

Aspen trees grow faster with increasing amounts of carbon dioxide in the atmosphere, say researchers from the University of Wisconsin-Madison and the University of Minnesota.

The scientist found that over the last 50 years, the rise in carbon dioxide increased aspen trees’ growth rates by 53%. The study, funded by the National Science Foundation, was published today in the journal Global Change Biology.
“We were quite surprised to see this large of a response,” says Rick Lindroth, an ecologist at the University of Wisconsin-Madison and an author of the study. “We wouldn’t have been surprised to see some effect, but a 53% increase is a whopping increase.”

The researchers studied aspen tree cores from the past 50 years to determine what factors were affecting their growth rate. They evaluated the trees’ age and sex, as well as water availability and carbon dioxide levels. Carbon dioxide had the most pronounced effect on growth rate, but only if the trees were receiving adequate water. In times of drought, carbon dioxide did not speed up the aspens' growth rate. Age also played a role, with juvenile trees around 10 years old growing the quickest.

Lindroth says the study could be used to better understand how forests will respond to increasing amounts of carbon dioxide over the next 50 years. “Forests are already responding to the increase in carbon dioxide,” he says. “And compared to what is expected over the next 50 years, this increase is relatively small.”

The study also highlights the importance of our forests as a carbon sink, and suggests that they could play an important role in mitigating the effects of climate change. However, says Lindroth, in dry, arid regions such as the U.S. southwest, the forests might play less of a role than previously thought, since water is an important factor.

How the faster-growing aspens are affecting the rest of the forest is still an unknown. The trees' accelerated growth rate could have negative effects on the smaller plants and shrubs growing beneath them. But, it will also depend on how other species are adapting to carbon dioxide, says Lindroth. If aspens are adapting more quickly compared to other species, they could become the dominant tree in many forests.

http://www.treesforlife.org.uk/tfl.aspen.html


http://www.treesforlife.org.uk/kingussie2001/aspen_action.html

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