Effect of elevated CO2 on net ecosystem carbon production in Florida scrub oak during a nine year study

The effect of elevated atmospheric CO₂ on net ecosystem carbon production (NEP) of forests has seldom been determined using gas exchange. We used open top chambers to periodically measure NEP of a Florida scrub oak ecosystem exposed to elevated atmospheric CO₂. At the same time, we continuously measured NEP of the ecosystem using a nearby eddy covariance system. A comparison between simultaneous measurements from the eddy covariance system and chambers at normal ambient CO₂ concentrations confirmed that the chambers produced less than a +/-10% difference on gas exchange. We used the chamber data to scale the eddy covariance measurements and compared the results of NEP with the CO₂ effect to the sum of biomass estimates for shoots, roots, and soil carbon measured in the elevated CO₂ chambers. After nine years of CO₂ fumigation, the estimated stimulation of elevated atmospheric CO₂ on NEP was 10.72 tCha^-1 compared to biomass stimulation of 6.36 tCha^-1.