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Effects of CO2 on Temperate Forest Regeneration
Reference
Berntson, G.M. and Bazzaz, F.A.  1998.  Regenerating temperate forest mesocosms in elevated CO2: belowground growth and nitrogen cycling.  Oecologia 113: 115-125.

What was done
The authors removed intact chunks of soil from a research site located in the Transition Hardwood-White Pine-Hemlock forest region of New England measuring 25 x 40 x 7 cm and placed them in plastic containers within controlled environment glasshouses receiving either 375 or 700 ppm CO2 to study the effects of CO2 on the regeneration of plants from seeds and rhizomes present in the soil.  Treatment CO2 concentrations were maintained for nearly two years, but only during the normal growing season.  When growth abated in November, the mesocosms were placed outside in ambient air until spring growth resumed in mid-March.

What was learned
At the conclusion of the experiment, total mesocosm plant biomass --more than 95% of which was supplied by yellow and white birch tree seedlings-- was 31% higher in elevated CO2 than it was in ambient CO2, with a mean enhancement of 23% aboveground and 62% belowground.  In addition, elevated CO2 significantly increased the percentage mycorrhizal colonization of root tips, boosting this parameter by 71% in yellow birch and 45% in white birch.  Furthermore, yellow birch seedlings exhibited 322% greater root length and 305% more root surface area in the CO2-enriched mesocosms.

What it means
As forests regenerate in future atmospheres of greater CO2 concentration, the increases in root growth and mycorrhizal root colonization that result from elevated CO2 will likely enable seedlings and juvenile trees to acquire greater amounts of soil nutrients more effectively than they presently do.  This enhanced acquisition of nutrients should allow regenerating forest trees to support the increased tree biomass that typically results from atmospheric CO2 enrichment.


Reviewed 1 February 1999