[Geezer (OP)]

According to something I read or saw on the telly recently (can't remember where), trees continually live right on the edge of suffocation. They receive just enough CO2 to survive.

I was quite surprised. Is it true, and does it also apply to all plants?

[litespeed]

Geezer - You wrote: "... trees continually live right on the edge of suffocation. They receive just enough CO2 to survive."

This seems easy to me. The converse observation is they use just enough CO2 to live. Which, of course, is just about what you would expect an organizme to do.

[Geezer (OP)]

Let me re-phrase that!

There is just enough CO2 in the atmosphere to prevent them suffocating. If there was any less, they could not survive. I believe that was the thrust of the message.

[litespeed]

Geezer - You wrote: "Let me re-phrase that! There is just enough CO2 in the atmosphere to prevent them suffocating. If there was any less, they could not survive. I believe that was the thrust of the message."

THATS an interesting thought! JEEZE.  If that is true, we had better keep the coal fires burning!

[litespeed]

Geezer

You might just have discoverred The Next Great Appocolypse for the climatistas.  In the 1970's we were on the edge of destruction with another ice-age.  Then, in more recent times, we were on the edge of destrution from run-away-global warming.  NOW we may be on the edge of destruction because the plants have hardly enough CO2 to survive.

VIVA Fossil Fuels!

[frethack]

"climatistas"?

Come on man.  Its the wide spread use of pejoratives like these that hurt the credibility of those that have a genuine interest in quantifying natural climate variability (for instance...me).  We have to work twice as hard because people automatically lump us in with the so called "denialists" (another useless pejorative).  Stop politicizing science (these are words from the political realm).  Stand on the merits of your argument. 

[Geezer (OP)]

er, well, I don't think Litespeed really intended his comment to be taken too seriously (I think).

However, my post was quite serious. I actually did hear/read this somewhere. At the time, I got the impression that the author had a lot of credibility and that they were stating a simple, well known, fact.

I was really surprised when I heard it, and (as I know nothing about the subject) I just wondered if this is widely accepted by biologists.

[Geezer (OP)]

I recently had one guy try to jam an icepick-looking instrument through my cheekbone while pulling a tooth!  []

Did he, by any chance, keep asking "Is it safe?".

[Geezer (OP)]

Back on topic:

I'm not suggesting that this thing about trees would have any particular impact on climate change. Presumably, trees have become so good at "living on the edge" that they would not necessarily be able to consume much more CO2 even if they had access to it. They may even resist rapid evolution to take advantage of higher CO2 levels because they have been "fooled before".

I just think that it's a very interesting situation and I would like to know if it is true or not. Unlike my grandson's diaper, my question was not loaded.

[litespeed]

Fret - Point taken on 'climatistas'.

Geezer - I did some small googling on CO2 and photosynthesis, and did not see where CO2 is at such low levels plants are in any danger. After all, the current level of CO2 is not much changed in millions of years. However, I DID find this study of CO2 enrichment:
http://www.co2science.org/articles/V8/N10/B1.php

"... Lim et al. say that rising CO2 could "increase minimum greenness by stimulating photosynthesis at the beginning of the growing season," citing the work of Idso et al. (2000), who discovered that although new spring branch growth of sour orange trees began on exactly the same day of the year in both ambient (400 ppm) and CO2-enriched (700 ppm) open-top chambers, the rate of new-branch growth was initially vastly greater in the CO2-enriched trees. 

Three weeks after branch growth began in the spring, for example, new branches on the CO2-enriched trees were typically more than four times more massive than their counterparts on the ambient-treatment trees; while on a per-tree basis, over six times more new-branch biomass was produced on the CO2-enriched trees, before declining to an approximate 80% stimulation typical of the bulk of the growing season."

[Geezer (OP)]

Thanks Litespeed.

Yes, I believe plants do take advantage of increased CO2 levels to grow more quickly. But I'm not sure this would rapidly increase their "baseline" requirement as they evolve.

As you point out, the nominal CO2 level has been fairly constant for a long interval. Presumably, as plants have evolved, they have come to take that apparent constant as being close to a minimum, and optimized their systems on that "assumption", which might explain why they would be less successful if the CO2 level were to drop. If the CO2 level was to increase and stay elevated for a long time, I would assume plants would evolve to depend on that elevated level, but I have not the slightest idea how long that might take.

There may be some historical correlation between the evolution of plants and Earth's atmospheric constituents. Perhaps a study of that might reveal something we do not already know. Beats me.

[Nizzle]

Pff, let's all forget adaptation will we?
If there's less CO₂ in the atmosphere, we won't see the end of trees, we'd see the end of existing trees and the emergence of new ones.

[Geezer (OP)]

Pff, let's all forget adaptation will we?
If there's less CO₂ in the atmosphere, we won't see the end of trees, we'd see the end of existing trees and the emergence of new ones.

Well, yes. (Although I'm not really sure I fully understand the difference between adaptation and emergence.)

Anyway, you know all about this biological mumbo jumbo. Is it true that trees (some trees? all trees?) get only just enough CO2 to survive?

[Nizzle]

I don't know the CO₂ requirements for trees so I don't know whether there's just enough present in the atmosphere, but i highly doubt that this is true. In my opinion, if there would be less CO₂ available, the trees would just grow slower.

And whether trees will adapt or new trees will emerge will be linked to how fast the CO₂ concentration in the atmosphere will rise/fall.

[Geezer (OP)]

Rats! I suppose I'll just have to dig up the source for myself. As I remember, the quote came from someone who did understand this field quite well.

[Nizzle]

Trees have been around since before dinosaurs ruled the earth and have seen a lot of different levels of atmospheric CO₂ concentrations, much higher than now and much lower than now.
Please dig up that source. It would make an interesting read.

[Geezer (OP)]

Here's a link to an experiment that tends to confirm the observation.

http://www.co2science.org//articles/V10/N14/B2.php

The trees in the experiment could only survive at elevated temperatures when the CO2 level was increased above normal.

[Nizzle]

Hm, according to me after interpreting that article, the "LD 50 dose" of temperature for the sour orange tree at atmospheric CO₂ concentration would be an average of 46'C from the moment the tree can start photosynthesizing (dawn) until it stops (dusk).

I doubt there are many places on earth that have this average day temperature (except deserts but trees can't grow there anyway due to lack of water), so I'd say that trees are not close to suffocation at this time in history.

[Geezer (OP)]

You obviously never lived in Phoenix  [] (I did) Admittedly, those temperatures are higher than the daytime average.

What we really need is a study that shows the effect of reduced CO2 at normal temperatures. I'm sure somebody must have done some experiments.

[Nizzle]

Then you'll see that trees suffocate at normal temperatures with less than atmospheric CO₂ concentrations, which leads to the same conclusion that in this period of history, trees are not close to suffocation.