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Elevated CO2 Increases Douglas Fir Root-Tip Colonization by Ectomycorrhizas
Reference
Rygiewicz, P.T., Martin, K.J. and Tuininga, A.R.  2000.  Morphotype community structure of ectomycorrhizas on Douglas fir (Pseudotsuga menziesii Mirb. Franco) seedlings grown under elevated atmospheric CO2 and temperature.  Oecologia 124: 299-308.

What was done
Two-year old seedlings of Douglas fir (Pseudotsuga menziesii Mirb. Franco) were grown for four years in environmental chambers receiving atmospheric CO2 concentrations of either 350 or 550 ppm and ambient or elevated (ambient plus 4°C) air temperatures to study the impact of elevated CO2 and temperature on ectomycorrhizal fungal properties and community structure associated with this coniferous species.

What was learned
Over time, root tip colonization by ectomycorrhizal fungi increased from 31% at experimental initiation to 95% following four-years of treatment exposure.  Similarly, the diversity of ectomycorrhizal fungi also increased over time.  Elevated CO2 significantly increased root tip colonization during the spring and summer growing seasons, but had no apparent effects on ectomycorrhizal diversity.

What it means
As the atmospheric CO2 concentration increases, it is likely that Douglas fir seedlings will exhibit enhanced rates of photosynthesis and biomass production both above- and belowground.  With this increase of carbon input to the soil, as well as that resulting from increased root exudation, it is likely that fungal colonization of root tips will be enhanced without altering fungal diversity, thus increasing a host of symbiotic processes that can further increase seedling vigor and growth.