Interesting Study on CO2 increase and plant growth

[Theorist]

Climate change surprise: High carbon dioxide levels can retard plant growth, study reveals : 12/02

To me it's common sense that if CO2 is the limiting growth factor for plants, adding CO2 is going to make them grow faster.

But, if one adds so much CO2, something else is going to become the limiting factor for plants (whether it's lack of phosphorous, or being out-competed by microbes, etc), and they will be restricted to that limit.

I find this study interesting, because they tested multiple variables associated with global warming, and found that plants will not be able to grow fast enough to use up all the excessive CO2 we produce, due to other limiting factors.

I mean it's common sense to me, but it's good it's been published in a credible way.

"The biggest surprise from the study was the discovery that elevated carbon dioxide only stimulated plant growth when nitrogen, water and temperature were kept at normal levels.

"Based on earlier single-treatment studies with elevated CO2, we initially hypothesized that, with the combination of all four treatments together, the response would be additional growth," said W. Rebecca Shaw, a researcher with the Nature Conservancy of California and lead author of the Science study.

But results from the third year of the experiment revealed a more complex scenario. While treatments involving increased temperature, nitrogen deposition or precipitation -- alone or in combination -- promoted plant growth, the addition of elevated CO2 consistently dampened those increases.

"The three-factor combination of increased temperature, precipitation and nitrogen deposition produced the largest stimulation [an 84 percent increase], but adding CO2 reduced this to 40 percent," Shaw and her colleagues wrote. "


"Why would elevated CO2 in combination with other factors have a suppressive effect on plant growth? The researchers aren't sure, but one possibility is that excess carbon in the soil is allowing microbes to outcompete plants for one or more limiting nutrients. "

"Perhaps we won't get as much help with the carbon problem as we thought we could, and we will need to put more emphasis on both managing vegetation and reducing emissions," said Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford and co-author of the Dec. 6 Science study."