We investigated the dependence of emissions of elemental carbon and organic carbon and formation of secondary organic carbon in wildland fires on combustion conditions using fire radiative energy normalized by fuel-bed mass (FREnorm). We performed combustion experiments using fuel beds from three ecoregions in Georgia and varied moisture content to simulate prescribed fires (Rx) or wildfires (Wild). For fuel beds that contained surface fuels only, the higher moisture content in Rx led to less efficient combustion, which had lower EC and higher OC emissions and SOC formation. For fuel beds that contained duff and surface fuels, duff ignition led to smoldering with OC emissions and SOC formation being an order of magnitude higher in Wild compared to Rx for the duff-containing beds. These findings indicate that variable combustion conditions emerge from variability in fuel-bed composition and environmental conditions and are crucial for determining EC and OC emissions and SOC formation.