[Terrapreta] Interesting article

[Richard Haard]

It would be interesting to see a chart that shows SOM duration against  
soil temperature and soil moisture. Lastly SOM duration against  
cultivation.

rich


On May 8, 2008, at 10:24 PM, Michael Bailes wrote:

> Some say SOM is said to break down within 400 years. With the global  
> average being 32 years. I do get abit confused in this paer  
> identifing just what C is being talked about
>
> The average global turnover time for soil organic carbon (to 1-m  
> depth) was estimated as 32 years by Raich and Schlesinger (34),
> 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
> There is general agreement that SOM contains at least three  
> identifiable C pools: root exudates and rapidly decomposed  
> components of fresh plant litter ("active" pool); stabilized organic  
> matter that persists in soils over several thousands of years  
> ("passive" pool); and a poorly defined "intermediate" or "slow" C  
> pool that has turnover times in the range of years to centuries  
> (Fig. 1). I will use these terms in this paper, and in addition will  
> refer to fast-cycling C as the combined active and intermediate  
> pools (all nonpassive C).
> http://www.pnas.org/cgi/content/full/94/16/8284?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&searchid=1&FIRSTINDEX=0&minscore=5000&resourcetype=HWCIT
>

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