On the isotopic composition of carbon in soil carbon dioxide

In this study it is shown that the isotopic composition of carbon in soil CO ₂ differs from the isotopic composition of carbon in soil-respired CO ₂. Soil CO ₂ collected from a montane soil has an endmember δ¹³C value of -23.3%. whereas soil-respired CO ₂ in this system has a δ ¹³C value of -27.5%. This difference is very close to the theoretical difference of 4.4%. which is predicted by the difference in the diffusion coefficients for ¹²CO ₂ and ¹³CO ₂. Because of the measured and the theoretical difference between the isotopic composition of carbon in soil CO ₂ and soil-respired CO ₂ it is suggested that, in the future, a distinction should be made between them.