[Terrapreta] Interesting article

[folke Günther]

2008/5/5 David Wardle <David.Wardle at svek.slu.se>:

>  Not wanting to sound contrary, but I cannot agree with Gunther's comments
> *'**the conclusion that the addition of char to soil could be offset by
> the increased decomposition of litter, is* *wrong*' or '*After a century
> or* *two*, *all the litter would be expected to be metabolised,* *charcoal
> or not*.'
>
> Firstly, our litter bags contained humus and not 'litter'. Secondly, there
> is ample evidence (indeed you can find it in undergraduate textbooks on soil
> science) that there are significant pools of soil organic carbon (including
> in humus) that themselves are quite recalcitrant and take many centuries or
> millennia to break down. Therefore the claim about 'after a century or two'
> is not true.
>
> *FG: * OK I used a sloppy language. Humus, not litter. Several centuries,
> not one or two.
> But the the main conclusion that the humus, whose degadation was hastened
> by the charcoal, would have been degraded at a later time anyhow, remains.
> Therefore, the conclusion that the CO2 sequestration by charcoal is offset
> by the increased degradation of humus, is wrong. To realise thiat, a longer
> timescale has to be used.
>


>
>   ------------------------------
>
> *From:* folke Günther [mailto:folkeg at gmail.com]
> *Sent:* den 5 maj 2008 09:40
> *To:* Terra Preta; Richard Douthwaite; Exergigruppen; David Wardle
> *Subject:* Re: Interesting article
>
>
>
> Now, I have received the full article and a supplement describing the
> investigation method (attached). Actually, nothing changes my conclusions
> from yesterday; The inevitable decomposition of litter is hastened by the
> addition of charcoal, but since this would happen anyway, *the conclusion
> that the addition of char to soil could be offset by the increased
> decomposition of litter, is wrong.*
> FG
>
> 2008/5/4 folke Günther <folkeg at gmail.com>:
>
> I haven't received the pdf yet, but since there as been quite a
> discussion,I will go through the background. When I have got the pdf, I will
> go through it and give some more details.
> The basic is this:
>
>    1. *Burying charcoal in the soil always sequesters carbon (carbon
>    dioxide) from the atmosphere*
>
>
>     - This is true disregarding the route this charcoal may have taken
>       to the soil. I.e. even if the 'footprint' of this special  charcoal is
>       larger than its actual content of coal (say that it is flown around the
>       world), burying the charcoal mean that this certain amount is eliminated fro
>       the atmosphere.
>       -  I.e. If you burn it, it will return to the atmosphere, If
>       you bury it, it will stay in the soil for thousands of years
>
>
>    1. *Charcoal increase soil metabolism.*
>
>
>     - This may not come as a surprise to any of the members of this
>       list.The reasons for that, and its effects, have been discussed, and easily
>       observed, for a long time.
>
>
>    1. *If you mix litter and charcoal, the litter will decompose fasterthan if it is not mixed with charcoal.
>    *
>
>
>     - This was confirmed by the study. A large part (25% i the first
>       two years) of the litter was metabolised by the microorganisms. I do not
>       know if a simultaneous increase of the plants living in, on or near the bags
>       was observed. One could expect  that.
>
>
>    1. *In bags with only litter, some metabolism would be observed,
>    although smaller than in the litter mixed with charcoal.*
>
>
>     - This is perfectly normal.
>
>
>    1. *Thus, the presence of charcoal increase the rate of litter
>    decomposition.*
>
>
>     - Why am I not surprised?
>       - Jumping to the conclusion, however, that the presence of
>       charcoal in the soil would be offset by the increased metabolism of litter,
>       is wrong. After a century or two, *all the litter would be
>       expected to be metabolised,* *charcoal or not*.
>
>
>    1. Therefore, the sequestration effect of charcoal is *not *counteracted
>    by increased soil metabolism, since the SOM (Soil Organic Matter) is
>    ephemeral in comparison to the charcoal, and will decompose anyhow. However,
>    the in increased metabolism is reflected in a change in litter decomposition
>    rate.
>
> It would be very interesting to have the real figures, since that might
> allow a calculation of the metabolism increase. A friend observed a
> surprisingly high increase in the decomposition of a small compost heap when
> charcoal was added
>
>  2008/5/2 folke Günther <folkeg at gmail.com>:
>
> In the latest number of Sciene, (2 May), David Wardle, Marie-Charlotte
> Nilsson och Olle Zackrisson delivers an article: "Fire-Derived Charcoal
> Causes Loss of Forest Humus", where they claim that charcoal particles
> remaining after fire increase the microbial activity so they break down
> humic particles at a rate that counteracts the carbon sequestration effect
> of the carbon.
>
>
>
>
> ----------------------------------------
> Folke Günther
> Kollegievägen 19
> 224 73 Lund
> Sweden
> Phone: +46 (0)46 141429
> Cell: +46 (0)709 710306
> URL: http://www.holon.se/folke
> BLOG: http://folkegunther.blogspot.com/
>
>
>
>


-- 
----------------------------------------
Folke Günther
Kollegievägen 19
224 73 Lund
Sweden
Phone: +46 (0)46 141429
Cell: +46 (0)709 710306
URL: http://www.holon.se/folke
BLOG: http://folkegunther.blogspot.com/
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