I’ve just had my first look at the Abebneh thesis. There’s some interesting stuff in there that seems to confirm some of my suspicions.

Dave wrote in #60:

“Please don’t post such silly statements! They detract from the serious science.
CO2 and O2 are going to be in about equal quantity during different times of the day.
O2 is present as 20% but CO2 is present at 340 ppm, several hundred times less.
There’s never going to be a deficiency of O2 for plants.”

I love sweeping generalizations.

Balloon meet needle:

http://jxb.oxfordjournals.org/cgi/content/full/54/388/1721

http://www.scielo.br/scielo.php?pid=S1677-04202002000200002&script=sci_arttext

plants under water, plants under snow or ice, plants without proper drainage
can all suffer from a lack of oxygen.

Dave will object to this as not his point.

Sorry if I seemed harsh. Perhaps it’s just that having been trained as a biochemist I’ve internalized the subject and can’t understand how someone can not realize what’s up with O2. Basically O2 is used when a livig thing wants to burn sugars, etc. for energy. Actually, oxygen isn’t used in the main cycle of respiration. It’s used by heme-like sorts of molecules to oxidize hydroquinone sorts of compounds and produce a couple or three ATP molecules. The net result is water and the oxidized quinone which then strips off more hydrogen from a molecule to oxidixe it and become the hydroquinone again. But the point is you need the same amount of oxygen to burn the sugar as was produced when the sugar was created from CO2 and H2). So the amounts of oxygen needed at night, say, is the same, at most, as the CO2 needed during the day to produce sugars. Actually the plant normally stores part of what it produces for growth and seeds, etc. And since there are hundreds of O2 molecules around for every molecule of CO2, It’s always going to be the CO2 which is ultimately in short supply.

I suppose it could be possible that just because a plant doesn’t have to be very efficient in O2 use, it could fail to evolve enzymes which bind O2 tightly like animal hemes do. But if a plant had to live in an area, like high altitude, where it needed more O2 than it usually absorbed, it’d be pretty easy to evolve better enzymes, whereas CO2 has been in short supply for most plants since at least the Carboniferous epoch and thus all the obvious improvements have already been made.

One way of judging things would be finding areas in oceans where there wasn’t much oxygen for one reason or another but still plenty of light. What sort of plants, if any, grow in such places?

Thank you D. Patterson for the thoughtful response.

In particular, the dendo reconstructions rely on a variety of 50 year to 100 year calibration periods from the natural streamflow gages as the basis of statistical calculations. These statistical calculations by even the most optomistic standards are estimates which are hugely reliant upon a calibration environment which may not have existed for major portions of the paleo periods under reconstruction.

Not only is there a calibration problem, but what is streamflow telling us to begin with? We know that it’s indicative of the depth of snowpack – that’s a given – but is it indicative of plant available moisture? In the beginning of the growing season it probably is, but because the medium in which the BCP grows is severely limited in it’s ability to hold water, this cannot be a reliable predictor across the full growing season.

So I’m back to my original question, How do you determine that moisture is not such a dominate influence on ring widths that it essentially swamps any other signal? Without a nearby rain gauge and temperature sensor, along with a suitable calibration period, I do not see a way to accurately account for moisture’s influence. Am I wrong in that assumption?

As far as CO2, I know plants can grow 50% faster at .1% carbon dioxide. I also know that 1% will knock a person unconsious and .5% is considered unhealthy. Which is basically why you can’t compare it to O2 any more than you can compare its percentages present to those of methane, sulphur, water vapor, nitrogen or silver.) (Silver? Yes, unless it weighs a few pounds, it can’t hurt you if it falls on you, but other forms of silver can cause death. What’s the LD50 of a thousandth of a gram travelling at the speed of light entering a person’s stomach?) Dihydrogen monoxide is one of the most dangerous substances on earth but without it we’d die. We need to know the circumstances to determine what it is the meaning of something is. The level of something depends upon the relative importance of it in the context we find ourselves. If something is “normally” 21% and something else “normally” .03% doesn’t increasing or decreasing them the same way sometimes (depending on the substance) result in the same effects and sometimes different ones? If you cut both 50%, what does A at 10.5% vis a vis what B does at .015%?

Let’s look at it this way. A hypothetical.

Plant A “likes best” 15% oxygen and .1% carbon dioxide and a temperature of about 60 F and 200 inches of rain and starts growing in such an environment. Over time as climate changes, conditions change and we are now at 10% oxygen, .05% carbon dioxide, 50 F and 100 inches of rain. Will the plant die? Probably not. Is it deficient on such matters? Yes. How well can it handle it? Depends on the plant. Might make little difference. Might kill it.

On the flip side, how about if it’s 20% .2% 70 F and 200 inches. It’s now “enhanced”. Could that kill it, will it handle it, who knows. More doesn’t mean better any more than less means worse.

But in neither case is it “where it wants to be” when conditions change.

That’s just sidetracking everything. The point is, do these things and the other variables have to be taken into account? Maybe. Which ones? I don’t know. Can the signals of “such things” (those and things like amount of sunlight, direct or difused. Normal air humidity and barometric pressure. Length of growing seasons. Amount of snowfall and speed with which it turns to water.) be removed from any study we do of the plant itself, to try and use it as a proxy for any of the variables or any other ones?

Are you categorically denying that O2 could be a factor in “some way”?

This (treeometers) is a microcosm for the climate change debate; how do the factors overlap and what effects do they have. The fact is, there are a lot of factors involved, you look at them, and you determing which ones are important, what’s not, and how everything interrelates.

I am thinking you are aware that there is less oxygen the higher you get.

Sure, and that means there will be 50% as much O2 at 6000m (18000+ft) as a sea-level, but that’s a trivial reduction compared to the absolute difference in CO2 vs O2 levels. I’m thinking you’re able to run order of magnitude calculations in your head and shouldn’t need to make speculations which can’t possibly work.

Now if plants were like people and had to take the O2 in via a blood stream it’d be another story, but they simply use stomata so you can compare concentration to concentration.

Third thing to rescue something from this pointless discussion. The fact is that the concentration of CO2 at the earth’s surface is about as low as it can get and maintain our present ecosystems. Plants will draw down the CO2 concentration over time so that it’s basically the limiting factor. That CO2 is now rising to “unpresadented levels” for some time isn’t particularly worrisome, just a temporary blip which plants worldwide would be thanking us for if they had or needed lungs.

Do you have anything showing such a thing? That would be more helpful.

I wouldn’t categorize that as “silly” any more than it’s nonsense to ask a climate modeller, that a model correctly hindcasting the last 10 years give me a run forecasting the next 10 years to both get an unchangable result and make them show they have faith in it.

I assume you’ve never run 5 miles in the high desert compared to at sea level? I wouldn’t want to run 5 miles at 11,000 feet. 4,600 was bad enough.

Although of course, logically, if the tree is growing there, there must be enough oxygen for it to live, but it may not be living as well as it could (the same can be said for any factor I guess).

Dave Dardinger,

Science need never be pompous! Asking the wild what-if questions is fine, they show a mind probing at the limits of our ignorance/understanding. Granted sometimes those random walks of thought experiments take you to a place where, given a moment’s pause, you realise the obvious contradiction and are left with ‘Doh!’ as the answer. Still, those questions should be encouraged. Please in the future don’t be so quick to slap down the wandering mind. A gentle nudge in the right direction will suffice.

Regards,
Earle

We know plants take in oxygen during part of the growing cycle, so why not ask about oxygen deficiency if you’re going to ask about carbon dioxide deficiency?

Please don’t post such silly statements! They detract from the serious science. CO2 and O2 are going to be in about equal quantity during different times of the day. O2 is present as 20% but CO2 is present at 340 ppm, several hundred times less. There’s never going to be a deficiency of O2 for plants.