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Eleven Years of CO2 Enrichment of a Scrub Oak Ecosystem
Seiler, T.J., Rasse, D.P., Li, J., Dijkstra, P., Anderson, H.P., Johnson, D.P., Powell, T.L., Hungate, B.A., Hinkle, C.R. and Drake, B.G. 2009. Disturbance, rainfall and contrasting species responses mediated aboveground biomass response to 11 years of CO2 enrichment in a Florida scrub-oak ecosystem. Global Change Biology 15: 356-367.

What was done
For a full eleven years, the authors enriched the air with an extra 350 ppm of CO2 within half of a set of sixteen open-top chambers that enclosed portions of a fire-regenerated Florida (USA) scrub-oak ecosystem, which was comprised of a mix of three oak species (Quercus myrtifolia, Q. geminata and Q. chapmanii) that accounted for about 90% of the total aboveground ecosystem biomass, plus several other plant species that accounted for the remaining 10% of the ecosystem biomass.

What was learned
Seiler et al. report that the relative growth-enhancing effect of the elevated atmospheric CO2 concentration on community biomass increased steeply during the first three years of their study, reaching 67.3% in 1999, and that this overall community biomass stimulation remained stable for the duration of the experiment, such that at the time of final harvest, the overall CO2-induced biomass stimulation was 67.5%. Breaking this result down just a bit, their data also indicated that the species specific CO2-induced biomass stimulation at the end of their study was a huge 128% for Q. myrtifolia, a minor 6% for Q. geminata, and a whopping 217% for Q. chapmanii, although the latter species was only responsible for about 3% and 6% of the total aboveground biomass in the ambient and CO2-enriched chambers, respectively.

What it means
The ten researchers say the results of their long-term study show that "atmospheric CO2 concentration had a consistent stimulating effect on aboveground biomass production." This is a typical finding of studies of long-lived woody plants that have been maintained for periods of several years, as is demonstrated by the results of several of them that are described and archived under Long-Term Studies (Woody Plants) in our Subject Index.

Kimball, B.A., Idso, S.B., Johnson, S. and Rillig, M.C. 2007. Seventeen years of carbon dioxide enrichment of sour orange trees: final results. Global Change Biology 13: 2171-2183.

Reviewed 29 April 2009