by Matt of Carbon Neutral Digest

Heather McCarthy was a doctoral researcher at Duke University and examined how trees store carbon in a higher carbon environment. Her research was published in the Ecological Society of America’s journal and there has been a windfall of articles published about her work; you can click here, here, here, and you can try Google.

CND has a chance to speak with Heather McCarthy about her research

Were there different levels of increased carbon in the air studied?

Heather McCarthy: There are just two different levels of carbon dioxide studied: current (”ambient”, approximately 380 ppm, but obviously changing slightly through the study since it has been underway for 11 years), and current plus 200 ppm (”elevated”, approximately 580 ppm).

How did you increase the carbon of the air in a forest?

Heather McCarthy: The extra CO2 is delivered through PVC pipes, which are arranged to form circular plots of 30 meter diameter. These plots are entirely open to the atmosphere, so CO2 is constantly being pumped in to replace CO2 that leaves the plots. The PVC pipes are taller than the trees in the plots, and have holes that release CO2 at different heights, so that the entire tree canopy is exposed to elevated CO2 levels. The release of CO2 from each pipe can be controlled separately, so compensations can be made for wind speed and wind direction. CO2 concentrations are monitored at different horizontal and vertical locations in the plot to ensure that the entire plot stays near the target concentration of CO2, and relatively good control can be achieved. Both “ambient” and “elevated” CO2 plots have this same infrastructure with the PVC pipes that release air into the plot. But in the case of ambient CO2 plots, the air that is released into the plot is just normal background air, without extra CO2 added. I think this description will make more sense if you look at the link with some pictures, that I have included below.

More detailed information on the protocol is here:
http://face.env.duke.edu/enrichment.cfm

and the first couple of images on this page show the setup:
http://c-h2oecology.env.duke.edu/site/images.html

From what I have read in reports about your work, trees are not the best way to store carbon?

Heather McCarthy: The news reports have conflated several points. The forests we studied (along with nearly all forests) store carbon. Storage of carbon in vegetation and in the oceans is the main reason why atmospheric CO2 concentrations are not increasing even more rapidly, based on CO2 emissions. We just didn’t find that (existing) forests stored dramatically more carbon (than they do in the current atmosphere) when they were exposed to increased CO2 levels (as will be in the future atmosphere).

What are the implications of your research on the use of trees as a carbon offsetting program?

Heather McCarthy: It means that trees will probably offset less carbon than some people had previously expected, if these people were assuming that large enhancements of growth would occur when trees are growing in a higher CO2 atmosphere. Our research also quantified how much carbon is currently being stored in a particular forest of a particular age (25 years) and species (loblolly pine). On larger scales how much carbon can be offset by planting new forests depends on a lot of things (which our research doesn’t cover): what kind of trees are being used, what happens to the wood products when the trees are harvested (decomposition of the wood will release the stored CO2 back to the atmosphere), whether older forests which contain a lot of carbon will be removed and replanted with young trees which grow quickly (thus bring in more new carbon) but contain less standing carbon, and how much of the area that could be planted with forests doesn’t already have forests.

Have you ever purchased a carbon offset or become carbon neutral?

Heather McCarthy:  I have not.

What is the next step in your research?

Heather McCarthy: I finished my PhD work in February and currently have a post-doctoral research position at the University of California, Irvine. I do hope to remain involved in the Duke FACE project in some capacity.

I am sure that we will be reading more about Heather’s research in the future.

Click here to read more information about trees as an offset project.

This interview has been reprinted from Carbon Neutral Digest.

We thought it was so good, it should be published again.  Thanks for sharing Matt!