Minutes of the September 16, 2002 Meeting
Smoky Mountain AMS Chapter
Our bi-monthly meeting consisted of a tour of the Free-Air Carbon dioxide Enrichment site at Oak Ridge National Laboratory (ORNL). The tour was graciously conducted by Rich Norby, Principal Investigator on the project. We met at the site around 6:30 P.M. to begin the tour.
Rich talked about several subjects of interest to meteorologists. The site itself consists of 5 experimental plots. Two plots are fumigated to experience an ambient-air concentration of around 560 parts per million (ppm) of CO2 during daytime conditions when the leaves are out. Two control plots are equipped for CO2 fumigation, but are not fumigated. A third control plot has no equipment for CO2 fumigation, and controls for the effects of the fumigation apparatus simply being there, whether or not is it providing additional CO2. The experimental and control sites are replicative in the sense that all consist of evenly planted sweetgum, all of the same age. Instrumentation is present on all plots to measure meteorological conditions, as well as other variables such as soil respiration and fine root mass.
Because “pre-industrial” atmospheric CO2 concentrations were around 280 ppm, the concentrations on the experimental plots coincide with the “doubled-CO2“ climate-modeling experiments. However, caution was expressed about interpreting the results of these experiments because we have no idea about the structure and composition of forests in the future. Environmental conditions such as climate are not predictable, and insect populations could lead to the extinctions, at least regionally, of many common species today.
One result of interest was carbon storage in forests in the presence of increased CO2. During the first year of the FACE experiment, much additional carbon went into wood production, but in the second and third years the carbon-storage increase showed up more in leaves (systematically caught in small nets located on the plots) and fine roots, both of which are relatively rapid carbon-turnover pools relative to the woody stems.
A similar caution was expressed about simple interpretations of decreased leaf transpiration as stomata close. This response does not necessarily mean that water loss is decreased at the stand level and/or on an annual time scale. Experimental results have demonstrated the importance of these issues.
For more information about the ORNL FACE site, see their web site at http://www.esd.ornl.gov/facilities/ORNL-FACE/.
After thanking Rich Norby for an interesting and informative presentation, we adjourned to the Sagebrush restaurant in Oak Ridge around 7:45 P.M.
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