CO2 and Trees
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After you've been exercising for an hour or two, you really know how to appreciate oxygen. Hi, I'm Bryan Yeaton and this is The Weather Notebook. Humans couldn't live without oxygen. And plants couldn't live without the gas humans exhale--carbon dioxide or CO2. That's why some scientists and politicians are studying trees to mitigate global warming which is caused in part by CO2.

They hope that if we plant enough trees, maybe the forests will soak up all the CO2 that cars and factories spew out each day.

It's been an idea with promise. Research has shown that when plants are raised in a greenhouse with extra carbon dioxide, they grow more quickly. But results from a newly completed study by Duke University researchers may have thrown a wrench in the works.

These scientists gave locally-grown pine trees twice the usual amount of CO2. In the first two years they grew up to 25 percent faster. But the extra growth came at a cost because the trees used more of the nutrients in the soil, particularly nitrogen. This depleted the soil more quickly than usual, and in the next two years, the trees went back to growing at an average level.

It appears that trees are and like us, they need good nutrition if they're going to stay pumped up. So while the research hasn't yet been extended to other types of trees, if the results hold up with other species, it could mean that forests will only play a limited role in helping us avoid global warming.

Today, we thank writer Bob Henson of Boulder, Colorado. The Weather Notebook is a production of the Mount Washington Observatory with support from the Subaru.