David Hare-Scott wrote:
songbird wrote:
FarmI wrote:
Billy wrote:

Well, in this case, it would be prairie grass (reflecting Salatin's
pasture),

What sort of species are you talking about when you say 'prairie
grass'? The reason why I ask is that the You-tube clips of Salatin's
place doesn't look like anything I'd call a 'prairie'. He looks
like he's got a farm on quite rich land in a well protected area.
'Prairies' to me suggest very open and exposed locations and the
grasses there would, TMWOT, be much tougher and less nutritious than
in good pasture land. I might be talking through my hat 'cos I
haven't got a clue about US farms, but that's what I'd expect here
in Oz if we were looking at farms of differing capacities.

right, anyone talking about grassland production in
the eastern seaboard of the USA being equivalent
to what happens on the prairies is full of it. the time
scale difference isn't minor and probably heavily
depends upon the average annual rainfall.

the soil of the prairies was probably produced over
the period of time after the last ice-age. it isn't that
thick. if it could accumulate at a rate of an inch a
year it would be much deeper...

ok, so let's return to the eastern seaboard and
wonder why the topsoil in unmolested places isn't
deeper? if it can be so productive why isn't it?
because it is woodland and not grassland and
unmanaged woodlands cycle carbon but do not
sequester once it's reached maturity. very little
is sequestered and that would be because of fires
that char and thus turn the carbon into a form not
easily consumed...

if trees and forests were so good for carbon
gathering and keeping the soils of the Amazon would
be deep and fertile, but they are not unless you
find the places that were altered by the natives in
prehistorical times.


Tropical rainforest is often on leached soil where most of the
nutrients are actually in the trees.

right, why is that though? you'd
figure that if it was truely good for
the ecosystem to have deep soil
that it would have figured that out
by now (millions of years of selective
pressure).


Saying that this environment
doesn't accumulated soil and therefore no forest will do so does not
necessarily follow. Particularly where temperate forests were cleared
for crop land you can certainly increase the amount of carbon stored
by converting them to pasture or back to forest.

again true, but only to a point and i think there
is a need now to go beyond what can be
accompished this way.


But your point
about reaching a maximum and then not storing any more is correct.
Evan so I don't think carbon sequestration is anything more than a
side show when it comes to managing climate change.

i'd change my statement to "not storing much more" because
i do think that periodic fires do store some more. just not
that much at a time.


so this says that reforestation is barking up the
wrong tree when it comes to CO2 sequestration
and rebuilding topsoil. (but i won't argue that
it's bad for species preservation and diversity
because that's needed too in many places -- so
there has to be the tradeoff there).



You are right that it is not a panacea but wrong in saying we cannot
build soil or sequester carbon by altering land use.

yeah, i mispoke somewhat there, but what i meant
was that the need for carbon storage is now more than
what is going to be achieved using either of those two
methods. building soil would help out all around, i won't
argue against that.

my wondering about topsoil is that if it is so good
for overall life then you'd think that by this time (after
millions of years) it would be selected for and there
would be much more of it than there is instead of
what we do find. so my curiousity is engaged on
the topic of the disappearing topsoil.

so much topsoil is lost to erosion and biological
processes that it ends up in the ocean and then
turned into coal and oil but the timescale for that
process is geological (not historical). the balance
needed is the use of the energy to match what the
ocean is capable of storing. we're way past that
(i'm not sure what that amount is), but we'd
know we've gotten there if the ppm of CO2 stablizes
and then starts falling and the ocean acidity does
the same.


songbird