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Atmospheric CO2 Enrichment Stimulates Expansion Rates of Poplar Leaves
Taylor, G., Ceulemans, R., Ferris, R., Gardner, S.D.L. and Shao, B.Y.  2001.  Increased leaf area expansion of hybrid poplar in elevated CO2.  From controlled environments to open-top chambers and to FACE.  Environmental Pollution 115: 463-472.

What was done
The authors compared the results of atmospheric CO2 enrichment studies performed on different poplar species grown in controlled environment chambers, open-top chambers, and FACE plots to identify any conserved responses to elevated CO2 across these various experimental designs.  Specifically, they were looking for leaf responses to atmospheric CO2 enrichment, since leaf growth is a strong determinant of stemwood production in the Populus genus.

What was learned
Regardless of experimental design, elevated CO2 consistently enhanced leaf extension rates in nearly every poplar genotype studied.  For all genotypes, atmospheric CO2 enrichment also increased total leaf area per tree.  Thus, although not reported directly in this paper, the strong positive relationship that exists between leaf growth and wood production for this genus suggests that elevated CO2 also stimulated wood production in these genotypes.

What it means
As the CO2 content of the air increases, it will likely stimulate leaf extension rates in poplar trees, thus increasing leaf growth and subsequent stemwood production.  Hence, this genus, which is often grown on a rotational basis on managed tree plantations, will likely reach harvestable size more rapidly, which also suggests that the long-term sequestration of carbon by managed plantations of this genus will likely increase with future increases in the air's CO2 concentration.