Paul and Ecolog:
Paul, would you also say that "phytolith sequestration" might not be a cheap
way to sequester C?
With respect to the "whole pie," I would like to understand what the net
effects would be of the program suggested and how such a conclusion is
reached. Especially with regard to policy and the allocation of scarce
(grant, etc.) resources, it would seem prudent to both demonstrate and test
the theoretical foundations before doing anything else, and I don't know
just how, beyond blind faith, just how this would be done.
I would also like to gain a greater understanding of the predictive ability
of the models, particularly with regard to the null hypothesis. Right now,
my gut tells me (it has been wrong many times) that the fraction of the pie
attributable to phytoliths would be, while perhaps impressive in pure
quantitative terms, insignificant in terms of the actual percentage slice of
the whole pie. I would be interested in Ryerson's gut feeling on this, and
those of similarly-qualified researchers.
WT
----- Original Message -----
From: "Paul E. Reyerson" <[email protected]>
To: <[email protected]>
Sent: Friday, February 12, 2010 5:44 AM
Subject: Re: [ECOLOG-L] CLIMATE Change Warming CO2 reduction phytoliths? Re:
[ECOLOG-L] Plantstones - a solution for increaseing CO2 in atmosphere?
Perhaps I should rephrase my original statement regarding phytolith C
sequestration: This MAY be a cheap way to sequester C, but it should be
considered as just one piece, not the whole pie.
It is true that a small amount of organic C is occluded in phytoliths, and
this can be sequestered for long periods of time. (As an aside, the occluded
C can be used for radiocarbon dating and stable isotope research.). Many
plants produce phytoliths, but grasses tend to produce more than trees.
Crops such as maize, wheat, sorghum, sugarcane, etc. all produce sizeable
amounts of phytoliths, so it seems to me that modern agriculture is already
practicing the phytolith sequestration technique.
The fundamental issue here centers on the biogeochemical cycle of silica, of
which phytoliths are largely composed. Plants remove dissolved silica
through their roots, make phytoliths, and release them back into the soil
upon death or litterfall. If a soil is in stasis, then one would expect to
see annual phytolith inputs offset by outputs (dissolution). From this one
can determine the average residence time of phytoliths in the soil. As
stated above, forests produce less phytoliths. Coupled with a more humid
climate, phytolith residence times in forest soils is quite short. On the
other hand, phytoliths can persist much longer in grassland ecosystems due
to large production and drier climate. Long story short, one would expect to
find much larger soil phytolith pools (and hence more occluded C) in
grassland ecosystams than forests. With that said, I find it difficult to
imagine that the conversion of native grassland to crop monoculture (maize,
say) would ultimately sequester more C. To my knowledge, no one has studied
this. Conversely, conversion of forests to crops may indeed increase
phytolith C sequestration by increasing the soil phytolith pool. But does
anyone really expect this to replace the C lost from the forest biomass? No.
In my opinion, phytolith C sequestration in agriculture must be considered
with all other forms of C sequestration/release. Responsible farming
practices will reduce soil erosion and increase soil organic matter and
phytolith content. On the other hand, application of petrochemical
fertilizers, burning of fossil fuels, and removal of native vegetation can
all release large amounts of C into the atmosphere.
Besides climate and vegetation I (and other researchers) have found that
localized soil properties may influence soil phytolith concentrations. A
recent paper demonstrated that a direct relation exists between soil
phytolith concentration and volcanic glass content (Henriet et al 2008,
Biogeochemistry). Both are forms of highly soluble, amorphous silica. Thus
it appears that volcanic glass can act as a buffer for soil phytoliths,
independent of climate. I have found similar results when working with North
American Mollisols which contain a sizeable amount of glass.
Paul Reyerson
PhD candidate
University of Wisconsin-Madison
-----Original Message-----
From: Ecological Society of America: grants, jobs, news
[mailto:[email protected]] On Behalf Of Wayne Tyson
Sent: Thursday, February 11, 2010 4:33 PM
To: [email protected]
Subject: [ECOLOG-L] CLIMATE Change Warming CO2 reduction phytoliths? Re:
[ECOLOG-L] Plantstones - a solution for increaseing CO2 in atmosphere?
The article at the link apparently has zero references and zero theoretical
or evidentiary foundation that can be independently verified (unless one
counts the following: "We have developed and hold IP on proceedures [sic]
for quantification and for the practical application of this process as well
as both a granted and pending international patent applications on the use
of these proceedures [sic] for the purpose of carbon sequestration (Parr and
Sullivan, 2004"). This seems more in the nature of promotion than science,
not to say that science is not involved, only that it is apparently secret
and proprietary. If that is correct (and I am eager to have my
misapprehensions corrected), it would seem questionable whether this
particular item belongs on an avowedly science-based listserv. (I am not
suggesting that the communication or any others in this vein be removed;
only that subscribers be vigilant and challenge such posts, for the benefit
of subscribers who might become converts to such a pitch--if "pitch" is the
right word. The site does seem to be "encouraging" that grants be directed
to "research," but that makes me wonder how the customary aspects of science
such as peer review and replication of research figure into this issue, and
when.
Reyerson's agreement "that phytoliths (plantstones) offer a cheap way to
sequester carbon" doesn't seem to square with his doubts, which seem
reasonable to me. It would be nice for Reyerson to supply links or copies of
his references and/or to expand on/link/reference "his own research." At the
moment, I don't share Reyerson's optimism, but am subject to being
converted.
I haven't looked into phytoliths in years, but if I recall correctly, they
are silicaceous remains, primarily of grasses and cactus (calcium oxalate) .
It would seem that a fundamental bit of arithmetic based on some fairly
simple-to-acquire data (content in standing vegetation, content in soils,
rate of sequestration, term of sequestration compared to other forms, etc.)
might bring the facts into focus. References to sources of such data and
discussion of the plus-or-minus fudge factor involved in the estimates might
be useful in understanding the true impact of any proposed "program" for
said sequestration. For example, what percent of the sequestered carbon in
present-day standing vegetation is represented by phytolith-sequestered
carbon, and how much longer, considering the net effects of their rate and
volume of re-absorption of carbon by non-phytolith-bearing plants,
represents an actual net increase over present-day conditions? Also, what
will be the effects of displacing functioning ecosystems with anthropogenic
applications ("As an indication of the importance of this research, the
Australian Research Council Discovery Grant Program has funded further
development during 2007-2009. We firmly expect that as a result of this
work, plantstone carbon research will reach industries such as forestry,
horticulture, mining and the rehabilitation of salt affected land, as well
as crops such as wheat, barley, sugarcane and maize, as well as pastures.").
Until there is something the authors or promoters care to share with the
scientific community, endorsement of their conclusions would seem a bit
premature. I hope that they will clarify such issues soon. I likewise hope
that other Ecolog subscribers will add clarity and any necessary
corrections. I sincerely hope that I am wrong in my impressions, and stand
ready to be corrected by specific evidence and logic.
WT
----- Original Message -----
From: "Paul E. Reyerson" <[email protected]>
To: <[email protected]>
Sent: Thursday, February 11, 2010 11:17 AM
Subject: Re: [ECOLOG-L] Plantstones - a solution for increaseing CO2 in
atmosphere?
I agree that phytoliths (plantstones) offer a cheap way to sequester carbon.
However it is not at all clear that phytoliths are retained in soils for
millenia on a large scale. Recent studies (I'm thinking of Alexandre et al
1997) showed that, in humid tropical regions at least, that soil phytoliths
undergo an annual turnover rate of 92%. Turnover rates in drier regions will
undoubtedly be lower, but there is very little research out there which
documents this. For example, Blecker et al (2006) documented higher
concentrations of soil phytoliths in shortgrass and mixed grass steppes when
compared to tall grass, which they attributed to drier climate. My own
research has suggested that higher retention rates in these regions may not
be as simple as climate. Localized soil properties may also have an impact.
Paul Reyerson
PhD candidate
University of Wisconsin-Madison
-----Original Message-----
From: Ecological Society of America: grants, jobs, news
[mailto:[email protected]] On Behalf Of Matheus Carvalho
Sent: Thursday, February 11, 2010 12:41 PM
To: [email protected]
Subject: [ECOLOG-L] Plantstones - a solution for increaseing CO2 in
atmosphere?
Dear list:
I watched a very interesting talk yesterday about this. They are the
"plantstones":
http://www.plantstone.com.au/
Matheus C. Carvalho
Senior Research Associate
Centre for Coastal Biogeochemistry
Southern Cross University
Lismore - Australia
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