There Was Once a Lot More CO2 In The air

[taniwha]

That's why I started googling: looking for numbers on CO2 and plant growth. I haven't found anything yet (been busy actually reading that last article I posted).

[MirariNefas]

Also, judging by the photos in the "bad for plants" article, it looks like their experimental method might leave a lot to be desired, possibly producing bogus results.

I looked at the article. It's fine. I'm sure they did a randomized block design and proper statistical analysis. If you find the paper they wrote on the subject we can analyze it further if you like.

Why would elevated carbon dioxide in combination with other factors have a suppressive effect on plant growth? The researchers aren't sure, but one possibility is that excess carbon in the soil is allowing microbes to outcompete plants for one or more limiting nutrients.

"By applying all four treatments, we may be repositioning the ecosystem so that another environmental factor becomes limiting to growth," Field observed. "For example, by increasing plant growth as a result of adding water or nitrogen, the ecosystem may become more sensitive to limitation by another mineral nutrient such as phosphorous, potassium or something else we hadn't been measuring."

Good quote. Illustrates my thinking. I'm not on the "CO2 is bad for plants" side. I think either position is incredibly naive. Keep things in an ecosystem context, and it all becomes a lot more complex.

[TallDave]

The text said that plants evolved when there was more CO2. But plants have continued to evolve as the levels of CO2 have gone down. The fact that plant species originated under high levels of CO2 doesn't seem to have anything to do with current plants because current plants have evolved to be ok with pre-industrial levels of CO2.

I did some semipro botany. CO2 can be a limiting factor. It's not that important in evolutionary terms because there are so many other limiting factors, at least one of which is likely to be limited for any given plant, but if you control all the factors you can increase growth by adding CO2.

http://wiki.answers.com/Q/How_do_increa ... ant_growth

[taniwha]

I will admit to having only skimmed that article. I can certainly agree that more CO2 in the soil can cause excessive microbial competition for soil based resources.

My point about their methods is that it appears everything was done in open air. This should severely limit their control over the amount of CO2 the plants can "breath". Thus my preference for the greenhouse results.

Now, redoing the experiment with definite control over both atmospheric and ground CO2 might be interesting.

Hmm, here's a thought: maybe that's why CO2 levels over 1000ppm don't make a lot of difference. At those levels, more CO2 gets into the soil, causing the microbes to gain on or even overtake the plants.

I would say that much more experimentation is necessary. I would do it myself if I had the facilities.

[MSimon]

Nature doesn't have a value system.

I do.

[MirariNefas]

And does that value system include supersizing everything?

[MSimon]

And does that value system include supersizing everything?

Yes.

My traditional New Years toast for at least the last 30 years has been:

More And Better.

[MirariNefas]

How nice for you. I'd still like a reference on that linear trend you were mentioning.

[MSimon]

The effects of an enriched CO2 atmosphere on crop productivity, in large measure, as positive, leaving little doubt as the benefits for global food security …. Now, after more than a century, and with the confirmation of thousands of scientific reports, CO2 gives the most remarkable response of all nutrients in plant bulk, is usually in short supply, and is nearly always limiting for photosynthesis … The rising level of atmospheric CO2 is a universally free premium, gaining in magnitude with time, on which we can all reckon for the foreseeable future.

The effect of enhanced CO2 is even greater for plants grown under low light conditions. The enhance growth is greater than 100 percent for a 100 percent increase in CO2. This compares to less than 50 percent for plants grown in normal light conditions.

The evidence that clinches the argument is that some greenhouse owner artificially elevate the CO2 level to triple what the level in the atmosphere is.

http://www.applet-magic.com/CO2plants.htm

[gregw]

That's why I started googling: looking for numbers on CO2 and plant growth. I haven't found anything yet (been busy actually reading that last article I posted).

Here you go.

http://www.co2science.org/data/plant_gr ... growth.php

[taniwha]

Thank you. Very interesting! (over 300% gain!?!)