How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Elevated CO2 Enhances Growth in a Mature Sweetgum Stand
Reference
Norby, R.J., Todd, D.E., Fults, J. and Johnson, D.W.  2001.  Allometric determination of tree growth in a CO2-enriched sweetgum stand.  New Phytologist 150: 477-487.

What was done
A FACE study was established within a ten-year-old stand of sweetgum (Liquidambar styraciflua L.) trees growing in a forest plantation on nutrient-rich soils in Tennessee, USA.  The trees, which were in a linear growth phase at the onset of the experiment, were exposed to atmospheric CO2 concentrations of 390 and 530 ppm.  This paper reports the initial growth responses observed during the first two years of atmospheric CO2 enrichment.

What was learned
The 36% increase in the CO2 content of the air in this experiment enhanced aboveground tree biomass by 33 and 15%, respectively, during the first and second years of the study.  Thus, the 24% average increase in growth could have been as high as 67% if the experimental CO2 concentration had been doubled.  These data demonstrate that mature trees existing in a closed-canopy can respond positively to atmospheric CO2 enrichment.

What it means
As the CO2 content of the air continues to rise, it is likely that mature deciduous forest trees -- like sweetgum -- will respond positively by increasing their biomass, regardless of whether they are in an exponential (juvenile) or linear (mature) growth phase.  Thus, even mature forest trees, which have been thought by some to be unresponsive to elevated CO2, may continue to remove carbon from the air in an enhanced manner long into their "golden years."