What was done
Beech (Fagus sylvatica L.) seedlings were grown for five years in open-top chambers fumigated with air containing 350 and 700 ppm CO2.  Subsequently, woody twigs were collected and incubated in native forest soils for 42 months to study the effects of growth CO2 concentration on the decomposition rates of woody litter produced by this deciduous species.

What was learned
After five years of treatment exposure, CO2-enriched seedlings attained an average wood biomass that was 29% greater than that of their ambiently-grown counterparts.  Fumigation with elevated CO2 reduced woody twig nitrogen and lignin concentrations by 38 and 12%, respectively.  However, these changes in chemical composition had no significant effect on woody twig decomposition rate, although the decomposition rate of the CO2-enriched twigs was 5% less than that of the ambient-treatment twigs.

What it means
As the air's CO2 content rises, it is likely that beech seedlings will respond by increasing their biomass.  In addition, woody twigs produced by this species will likely have lower nitrogen and lignin contents than they currently possess at the air's ambient CO2 concentration.  However, these changes in chemistry will have little effect on the decomposition rates of woody tree components.  Indeed, the authors concluded that "despite the initial differences in the chemical composition of ambient and elevated [CO2] wood, subsequent decomposition was unaffected and twigs derived from ambient and elevated [CO2] decomposed at similar rates."  Thus, the effects of elevated CO2 on decomposition rates appear to be negligible when compared with CO2-induced increases in litter production, which will likely significantly increase the amount of carbon that is sequestered within future forest soils beneath beech stands.