C-14 measurements of soil organic matter, soil CO2 and dissolved organic carbon (1987-1992)

For several undisturbed sites in Germany, C-14 data are reported for soil organic matter (SOM) (4 sites), soil CO2 (10 sites) and dissolved organic carbon (DOC) (1 site). With the assumption of a fast degradable component (lifetime ca. 1 yr) and a slow degradable component (lifetime ca. 100 yr), a range between 0.6 and 1.6 mm yr(-1) has been determined for the downward migration rates of soil organic carbon at the sampling sites from the soil C-14 data. The soil CO2 measurements show that in deciduous forests the fast degradable component is ca. 60% and the slow degradable component is cn. 40% of the SOM. In coniferous forests this ratio is reversed. The C-14 results for DOC could not be explained with the assumption of a first-order decay process. The removal of soil organic carbon by DOC is of minor importance for the estimation of carbon budgets for the investigated site.