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Carbon 'released, not stored' by soil
Tuesday, 20 March 2007
Wagdy Sawahel
SciDev.Net
Carbon 'released, not stored' by soil
Soils may not always act as carbon sinks, a new study suggests
Image: Derek Jensen

CAIRO: Rising levels of carbon dioxide in the air may turn soil from a potential carbon sink into an emission source by stimulating microbes to release carbon dioxide, according to a new study.

This article
Carbon 'released, not stored' by soil | COSMOS magazine
seems at odds with this one
Potential responses of soil organic carbon to global environmental change -- Trumbore 94 (16): 8284 -- Proceedings of the National Academy of Sciences

SOM is difficult to study because it is a complex mixture of substances having turnover rates that range from days to millennia.
The average global turnover time for soil organic carbon (to 1-m depth) was estimated as 32 years by Raich and Schlesinger (34), who divided the total C stock in soils by the average CO2 flux from soil (corrected for root respiration contribution).
Turnover times varied from 14 years to 400 years for different ecosystems in their study. Radiocarbon measurements of bulk soil C, however, often show that the average age of C in soils is several hundred to several thousand years (35-38).
Both results are explained if SOM contains components that turn over slower and faster than the several-decade average.