The dynamics of soil redistribution and the implications for soil organic carbon accounting in agricultural south-eastern Australia

Anthropogenically induced change in soil redistribution plays an important role in the soil organic carbon (SOC) budget. Uncertainty of its impact is large because of the dearth of recent soil redistribution estimates concomitant with changing land use and management practices. An Australian national survey used the artificial radionuclide caesium-137 (137Cs) to estimate net (1950s1990) soil redistribution. South-eastern Australia showed a median net soil loss of 9.7tha-1yr-1. We resurveyed the region using the same 137Cs technique and found a median net (19902010) soil gain of 3.9tha-1yr-1 with an interquartile range from -1.6tha-1yr-1 to +10.7tha-1yr-1. Despite this variation, soil erosion across the region has declined as a likely consequence of the widespread adoption of soil conservation measures over the last ca 30years. The implication of omitted soil redistribution dynamics in SOC accounting is to increase uncertainty and diminish its accuracy.