Legacy effects of long-term CO2 enrichment on plant biomass recovery from fire seven years after return to ambient CO2 levels1

We sought to determine if elevated CO2 resulted in long-lasting changes to plant structure and function, particularly disturbance response patterns. Minimal legacy effects were observed 1 yr after the termination of a previous long-term experiment; however, those observations were based on 1 yr of data and only focused on fine root growth, herbivory, and arthropod diversity. We examined above- and belowground biomass inside the footprints of chambers from a former long-term elevated CO2 experiment in a scrub-oak community 7 yr after CO2 enrichment ceased and 2 yr after fire. Aboveground biomass was 40.6% higher in the previously elevated plots compared with ambient plots, suggesting that there are legacy effects in the form of more rapid aboveground recovery from fire on previously elevated CO2 plots. Belowground biomass exhibited minimal change since the historic CO2 enrichment, suggesting that differences were a result of the original treatment. After disturbance, regrowth occurs via sprouting from large belowground structures; thus changes in aboveground recovery are likely due to changes to belowground biomass caused by altered atmospheric CO2. Elevated CO2 has significantly affected disturbance recovery patterns in this community. These changes have the potential to alter plant carbon allocation patterns in frequently disturbed systems.