Soil organic carbon fluxes abd turnover rates estimated from radiocarbon enrichments

A simple method is described for analysing data on soil organic carbon and enriched ¹⁴C, to provide estimates of the carbon input rate, decomposition time and downward diffusivity in the soil column. Data on atmospheric ¹⁴C enrichment, needed for such calculations on soil cores sampled between 1960 and 1990, are provided. Five New Zealand pasture soils and a forest soil are analysed by this method. The results show the marked effect of earthworms on increasing the C input, reducing the decomposition time and increasing the downward diffusion rate of soil organic C. An undeveloped sandy soil had a small input rate and a rather low downward diffusion rate. The forest soil studied had an organic C input similar to that in good pasture soils but almost no downward diffusion, resulting in a very shallow layer of soil organic C.