What was done
Loblolly pine (Pinus taeda) seedlings were grown for four years in the field within open-top chambers receiving atmospheric CO2 concentrations of 350 and 650 ppm to study the effects of elevated CO2 on wood properties and stem growth rings in this economically important timber species.

What was learned
Elevated CO2 did not significantly affect anatomical features of xylem (wood) cells, including their cell wall to cell interior ratio, resin canal area, and resin canal density.  Elevated CO2 did, however, significantly increase annual growth-ring widths by 93, 29, 15, and 37% during each of the four consecutive years comprising this study.  Similarly, although not significant in this case, atmospheric CO2 enrichment also increased the average ring density for each of the study years by 60, 4, 3, and 5%.  Thus, elevated CO2 significantly increased ring width and tended to increase ring density throughout this study, with the greatest responses occurring in the earlier years of the study.

What it means
As the CO2 content of the air rises, it is likely that loblolly pine, which is an economically important timber species, will respond by increasing its photosynthesis and growth.  The consequences of these phenomena are far-reaching, as indicated by the authors statement that "projected increases in the atmospheric content of CO2 may result in increased wood production without a loss in structural strength in loblolly pine."  Furthermore, it is conceivable that loblolly pine can even increase its structural integrity by increasing its wood density, if the observed trends for this parameter persist through its juvenile growth phase.