SOIL CARBON TURNOVER IN A RECOVERING TEMPERATE FOREST

Soil radiocarbon measurements show that mineral soil carbon under a re covering temperate forest in South Carolina turns over twice as fast a s carbon in undisturbed soil. The observed 12-year turnover time influ ences the design and interpretation of CO2 fertilization experiments. Experiments conducted on formerly disturbed sites will show a soil car bon fertilization response considerably faster than experiments conduc ted on native sites. Calculating the soil carbon CO2 fertilization fac tor from observed increases in soil carbon requires values for the tur nover time and inventory of active soil carbon. We also use the observ ed turnover time to estimate the rate of atmospheric carbon dioxide se questration in soil following agricultural abandonment. Although using the observed turnover rate increases estimates of soil carbon uptake on abandoned land, the amount of carbon sequestered globally is minima l because the net area of land being abandoned is small.