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CO2 Effects on Wood Density of Norway Spruce Trees
Kostiainen, K., Kaakinen, S., Saranpaa, P., Sigurdsson, B.D., Linder, S. and Vapaavuori, E.  2004.  Effect of elevated [CO2] on stem wood properties of mature Norway spruce grown at different soil nutrient availability.  Global Change Biology 10: 1526-1538.

What was done
The authors investigated the effects of elevated CO2 (doubled concentration: 720 ppm vs. 360 ppm) and elevated nutrient input to soil (described as "heavy fertilization," i.e., "higher than used in forestry in practice") on a number of wood properties of 40-year-old Norway spruce (Picea abies L. Karst.) trees that were enclosed by open-top chambers for a period of three years.

What was learned
Kostiainen et al. report that previous data from this long-term study "showed that fertilization decreased wood density (Makinen et al., 2002)," and in the presence of elevated CO2, such was still found to be the case in the new study, but only for earlywood density (a mean decrease of 3.8% over the three years of the study).  In the case of latewood density, the extra CO2 supplied to the trees overrode the negative effect of heavy fertilization and increased mean wood density by 4.6%.  Moreover, in the treatment where no extra nutrients were supplied to the trees, both earlywood and latewood density were increased by the doubling of the air's CO2 concentration: by 4.8% in the case of earlywood density and by 2.0% in the case of latewood density.

What it means
Under normal growing conditions, it would appear that a doubling of the air's CO2 concentration would increase the wood density of Norway spruce trees by something on the order of 2-5%.

Makinen, H., Saranpaa, P. and Linder, S.  2002.  Wood-density variation of Norway spruce in relation to nutrient optimization and fiber dimensions.  Canadian Journal of Forest Research 32: 185-194.

Reviewed 17 November 2004