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D Smith

(Doug Miller) writes:

In article , D Smith wrote:
[trying to edit out some parts - hopefully without losing context]

(Doug Miller) writes:

In article , D Smith
wrote:
(Doug Miller) writes:

In article , D Smith
wrote:

[snip]

Clearly, any increase in plant growth in response to increased
atmospheric CO2 would not be an instantaneous response; IOW, plant growth,
and

the attendant removal of CO2 from the atmosphere, should be expected to lag
the increase in CO2 levels -- probably by many years:

Why? Chamber experiments with increased CO2 levels don't seem to need
to be run for years before showing results - the plants show increased
growth rates quite quickly. Where do you get the "many years" number from?

Bigger environment, obviously -- unless those tests have been conducted in
planet-sized test chambers.

What difference does this make? How do the trees know how big the box
of air is that they are taking CO2 from? IIRC, at least some of these
types of tests have been done on trees outdoors, with a clear membrane to
trap air and allow CO2 enrichment. As close to nature as possible.

I guess the concept of scale doesn't have any meaning to you.

Sure it does. Do you want to tell us all what it means to you, and why
you think it makes a difference in this case?

it takes a while to grow
a tree, you know.

...only when you are looking at the time it takes to reach full
growth. It's growing ALL of that time, and it's during the growth stages
that it acts as a carbon sink, not when it reaches maturity and growth
stagnates.

Which was, if you think about it a little more, precisely my point. Thank you
for emphasizing it.

No, your point was that you expect a time lag. Why do you think there
is a time lag between exposure-to-increased-CO2 and growth?

I didn't say there was a lag between exposure and growth. The point is that
there is a lag between exposure and significant ability of the plant to
sequester carbon from the atmosphere. It's quite simple, really: a sapling
can't sequester nearly as much carbon as a large tree; the lag is the time it
takes for the former to become the latter.

Wait a minute:

Are you saying that there is no lag between exposure and growth? (You
might just be saying that you didn't say there was, without asserting the
contrary.) And just what is the difference (to you) between "growth" and
"sequestering carbon". To me, it's pretty much the same - as trees get
bigger, they contain more carbon.

Your original statement (cut and paste from above) was:

the attendant removal of CO2 from the atmosphere, should be expected to lag
the increase in CO2 levels -- probably by many years:

Growth = carbon sequstration. so I STILL don't see how you come to the
conclusion that there is a time lag.

Large trees also lose branches, which is why mature trees (which
continue to photosynthesize and fix carbon) become carbon-stable (little
net change). Sure, they have lots of leaves and can do lots of
photosynthesizing, but much of that is used to replace carbon that is
being lost, so growth is negligible and carbon sequestration is
negligible.

And one more point: when looking at a landscape (i.e., carbon
sequestration over an area), it not only depends on how a single tree
behaves with age, but how many trees there are - we look at the forest,
not just the trees. In a newly forested area, often there are many small
trees, whereas at maturity a lot have died out and there are much fewer
large trees. Over an area, an intermiediate-age forest is the one with the
greatest rate of increase of mass (the most carbon sequestration).

[and this is leaving soil carbon out of the equation, which should be
included for completeness.]

What is it
about "more CO2 now" that helps the plant, but doesn't show up as growth
until later?

See above.

I'm not concerned that it hasn't happened yet; I would not
have expected it to.

How long do you think it will take? The biologists and foresters that
look at the details of plant and tree growth don't seem to share your
optimism. They worry that current sinks might reach a limit on how much
additional CO2 plants can take in. After all, there are other limiting
factors on plant growth - moisture, nutrients, etc.

That didn't seem to be a problem a few hundred million years ago when (or so
the geologists tell us) the planet was much warmer, and much more densely
foliated, than it is now...

Different environments. Different species of plants. Species adapted to
high CO2 levels (if we're talking about the same periods), whereas today's
vegetation has adapted to the current environment.

And if the environment changes, the vegetation will adapt.

So will we.

I hope so.