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Effects of Elevated CO2 on Growth and Fungal Colonization of Three Tree Species
Reference
Godbold, D.L., Berntson, G.M. and Bazzaz, F.A.  1997.  Growth and mycorrhizal colonization of three North American tress species under elevated atmospheric CO2New Phytologist 137: 433-440.

What was done
The authors collected saplings of paper birch, Eastern hemlock, and Eastern white pine from Harvard Forest in Massachusetts, USA, and grew them for 25, 35, and 37 weeks, respectively, in climate-controlled glasshouses maintained at atmospheric CO2 concentrations of 375 and 700 ppm to determine the effects of elevated CO2 on growth and mycorrhizal colonization of these species.

What was learned
Although not many significant interactions of elevated CO2 on tree growth were found, elevated CO2 still increased whole plant and root biomass in all species studied from 19 to 56%, relative to control trees grown at ambient CO2.  In addition, atmospheric CO2 enrichment increased the number of root tips per plant by 56, 38, and 49% for birch, hemlock and pine saplings, respectively.  This phenomenon clearly presented fungal organisms with increased root areas to colonize.  CO2-enriched birch and pine saplings, for example, had 13 and 38% more root area colonized by ectomycorrhizal fungal species than their ambiently-grown counterparts, and CO2-enriched hemlock exhibited 47% more arbuscular mycorrhizal fungal colonization than its respective controls.

What it means
As the air's CO2 content rises, saplings of paper birch, Eastern hemlock, and Eastern white pine will likely increase rates of photosynthesis and carbohydrate production to increase whole plant and root biomass.  With increased root systems belowground, it is likely that greater fungal colonization of roots will occur, thus providing host plants with greater absorptive areas for obtaining water and mineral nutrients from the soil.  This phenomenon of enhanced belowground resource acquisition can positively feedback to increase plant growth and development to an even greater degree.  Thus, these three species will likely grow bigger and better as the CO2 content of the air steadily increases.


Reviewed 1 June 1999