List, cc Andrew
I would like to advance an opposite view - that this article is giving
soil CDR (through biochar) a boost. Biochar is not the only form of “soil
CDR”, but it is the only one with claims to recalcitrance (older soil carbon).
My guess is that of the 157 sites which the authors looked at with age
distributions, a high percentage of those with older carbon were so blessed
because of wildfires and charcoal.
The paper itself seems (to a non-expert) well done - but I found the
supplemental even more interesting. I was surprised especially that the CESM
model (C for Community - the first of five) shows such a small amount of
existing soil carbon (at least in the main soil carbon category being analyzed)
- much less than the other four. I have been in contact with the developers
of the CESM model - but not yet convinced them of the difference in biochar
from other means of accomplishing the French goal from COP21: “4p1000”. The
supplemental (probably free) is at:
http://science.sciencemag.org/content/suppl/2016/09/21/353.6306.1416.DC1
<http://science.sciencemag.org/content/suppl/2016/09/21/353.6306.1416.DC1>
There are a wonderful set of papers given in the cites. The one that
looked most pertinent to this article was supposed (via Google Scholar) to be
at this site - but wasn’t: http://escholarship.org/uc/item/1pw7g2r2#page-1
<http://escholarship.org/uc/item/1pw7g2r2#page-1>. It leads instead to a
non-fee paper with this title: Explicitly representing soil microbial processes
in Earth system models” . That is pertinent, but is anyone able to get the
desired paper in non-fee form?
The Science paper (and all the cites I investigated) ignored biochar.
It would be most interesting to have these ESM (= Earth System Models) authors
investigate biochar in a similar age-of-carbon manner. Starting with the age,
composition, and high NPP of the Amazon’s extensive Terra Preta soils should be
worthwhile in answering questions about the validity of biochar as a soil-CDR
approach.
Ron
> On Sep 22, 2016, at 5:58 PM, Andrew Lockley <[email protected]> wrote:
>
> Poster's note : appears to imply that rather more care needs to be taken with
> soil, and that soil CDR will be significantly more challenging than is
> sometimes argued.
>
> http://science.sciencemag.org/lookup/doi/10.1126/science.aad4273
> <http://science.sciencemag.org/lookup/doi/10.1126/science.aad4273>
> Radiocarbon constraints imply reduced carbon uptake by soils during the 21st
> century
>
> Yujie He1,*, Susan E. Trumbore2, Margaret S. Torn3,Jennifer W. Harden4,5,
> Lydia J. S. Vaughn3, Steven D. Allison1,6, James T. Randerson1
>
> Email: [email protected] <mailto:[email protected]>
> Science 23 Sep 2016:
> Vol. 353, Issue 6306, pp. 1419-1424
> DOI: 10.1126/science.aad4273
>
> Abstract
>
> Soil is the largest terrestrial carbon reservoir and may influence the sign
> and magnitude of carbon cycle–climate feedbacks. Many Earth system models
> (ESMs) estimate a significant soil carbon sink by 2100, yet the underlying
> carbon dynamics determining this response have not been systematically tested
> against observations. We used14C data from 157 globally distributed soil
> profiles sampled to 1-meter depth to show that ESMs underestimated the mean
> age of soil carbon by a factor of more than six (430 ± 50 years versus 3100 ±
> 1800 years). Consequently, ESMs overestimated the carbon sequestration
> potential of soils by a factor of nearly two (40 ± 27%). These
> inconsistencies suggest that ESMs must better represent carbon stabilization
> processes and the turnover time of slow and passive reservoirs when
> simulating future atmospheric carbon dioxide dynamics
>
>
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