Dual-chamber measurements of δ13C of soil-respired CO2 partitioned using a field-based three end-member model

► Natural variations in carbon isotope composition (δ13C) of soil respiration. ► Dual-chamber technique to ensure that δ13CRs is subjected to minimal artefacts during measurement. ► Three end-member mixing model for partitioning the soil surface CO2 flux. ► Fractional contribution of the long-term SOM-derived flux from younger and more labile sources.