The cause of carbon sequestration in forests- specifically forests that burn- has long thought that charcoal was a potential source of long-term C sequestration. We did a REALLY EXTENSIVE survey of post-fire environments, looking at all the charcoal we could find. On snags, on woody debris, in the soil. The results are about to be submitted for publication. The take home message is that we didn't really end up with any more black carbon (e.g. charcoal that is resistant to oxidation/degradation) than control plots (we digested the charcoal and the soils with a chemical oxidation procedure designed to isolate recalcitrant carbon stocks). Surprisingly, as it's only nine-years post fire.
We found that charcoal really didn't have as much carbon as expected, either. Although we can't say much about total black carbon formation because erosion is unknown (but likely minimal, given the sites we chose), at least at the plot level it appears that the fire consumed as much charcoal as it formed. These were quite severe fire sites (complete aboveground organic soil consumption and complete mortality, for instance) so perhaps lower severity sites would produce more due to a less intense fire. Hopefully a proposal will be submitted soon to fund exploration in less severely burned areas.