An experiment that pumps carbon dioxide into groups of trees growing outdoors, designed to test how forests will respond to global warming may be ended by the US Department of Energy.
This is not a nefarious plot to squash the results of global warming research, but a genuine disagreement among two groups of scientists over how to proceed in climate change research.
The US Department of Energy has funded nearly 10 years of research at Duke Forest in Durham NC, Oak Ridge National Laboratory in Tennessee, and Harshaw Experimental Forest in Wisconsin. At each forest, rings of plastic pipes release carefully measured amounts of CO2 into the air around groups of trees. The experiment is known as FACE, for Free Air Carbon dioxide Enrichment.
Results so far indicate that forests respond to the extra carbon dioxide, an essential plant nutrient, by increasing growth. However, unless the forests are on fertile ground, growth is concentrated in short-lived plant parts like leaves or needles and fine roots. These parts die and decompose, releasing their carbon back into the atmosphere. When fertility is higher, trees may retain more of the carbon in wood. However, fertility experiments are not yet complete.
Project scientists believe that a few more years of data are needed to determine the effects of soil fertility on the ability of trees to sequester carbon. However, DOE scientists believe that the experiment has run its course and that it is time to sample the trees and soils as a final measure of the long-term impacts of the experiment.
Richard Norby, who oversees the experiment at Oak Ridge, said “"This comes up in all sorts of long-term experiments — when is the right time to say, `Enough,’ There’s no good answer to that."
Picture: Duke FACE Experiment, courtesy of Duke University
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