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Atmospheric CO2, Soil Nitrogen and Plant Phenolics
CO2Science.org ^ | Dr. Sherwood B. Idso & Dr. Keith E. Idso

Posted on 09/20/2002 12:03:10 PM PDT by Sabertooth

Atmospheric CO2, Soil Nitrogen and Plant Phenolics: How Their Interaction Influences Carbon Sequestration in Soils


Atmospheric CO2 enrichment stimulates photosynthesis in nearly all plants.  A major consequence of this phenomenon is that plants exposed to elevated levels of atmospheric CO2 typically produce more non-structural carbohydrates, which can subsequently be used to manufacture more carbon-based secondary compounds (CBSCs) or phenolics.  Why is this important?

For one thing, phenolic compounds inhibit the biodegradation of organic materials (Freeman et al., 2001).  Hence, if atmospheric CO2 enrichment results in the production of more of these decay-resistant substances, one would expect the ongoing rise in the air's CO2 content would ultimately lead to improved carbon sequestration in the world's soils, for the plant-produced organic matter supplied to the soils would be more resistant to decomposition.  What do experiments reveal about this hypothesis?

For a long time the picture was rather muddled.  Many studies reported the expected increases in CBSC concentrations with experimentally-created increases in the air's CO2 content.  Others, however, could find no significant plant phenolic content changes; while a few even detected CO2-induced decreases in CBSC concentrations.  Although chaos thus reigned in this area for some time, Penuelas et al. (1997) finally brought order to the issue when they identified the key role played by soil nitrogen concentration.

In analyzing the results of several different studies, Penuelas et al. noticed that when soil nitrogen supply was less than adequate, some of the CBSC responses to a doubling of the air's CO2 content were negative, i.e., a portion of the studies indicated that plant CBSC concentrations declined as the air's CO2 content rose.  When soil nutrient supply was more than adequate, however, the responses were almost all positive, with plant CBSC concentrations rising in response to a doubling of the air's CO2 concentration.  In addition, when the CO2 content of the air was tripled, all CBSC responses - under both low and high soil nitrogen conditions - were positive.  The bottom line was thus fairly simple.  With a tripling of the air's CO2 content, nearly all plants exhibited increases in their production of CBSCs; but with only a doubling of the air's CO2 concentration, adequate nitrogen nutrition was needed to ensure a positive CBSC response.

An example of the possible significance of this nitrogen dependency of CBSC production for ultimate real-world soil carbon sequestration is provided by the study of Kaye et al. (2000), who assessed the carbon sequestering abilities of pure stands of either Eucalyptus or Albizia trees - as well as four different percentage mixtures of them - after 17 years of growth on abandoned sugarcane fields in Hawaii.  It had previously been documented by Bashkin and Binkley (1998) that planting monocultures of Eucalyptus trees on these fields did not alter the quantity of carbon they contained by any appreciable amount.  As ever greater proportions of nitrogen-fixing Albizia trees were interspersed among the Eucalyptus trees, however, soil carbon content rose in direct proportion to the fraction of Albizia trees in the mixed-species stands.

What makes these observations especially exciting is that atmospheric CO2 enrichment, in addition to enhancing plant growth, often stimulates nitrogen fixation in both woody (Olesniewicz and Thomas, 1999) and non-woody (Niklaus et al., 1998; Dakora and Drake, 2000) legumes.  Hence, as the air's CO2 content continues to rise, we can expect earth's nitrogen-fixing plants to become ever more proficient in this important enterprise.

What makes this knowledge even more exciting is that some of the extra nitrogen thus introduced into earth's ecosystems will likely be shared with non-nitrogen-fixing plants (Uselman et al., 1999), as could well have happened in the mixed Albizia-Eucalyptus stands of Kaye et al.'s experiment.  In addition, since the microorganisms responsible for nitrogen fixation are virtually omnipresent in nearly all natural ecosystems (Gifford, 1992) - and since atmospheric CO2 enrichment can directly stimulate the nitrogen-fixing activities of these microbes (Lowe and Evans, 1962) - it can be appreciated that the ongoing rise in the air's CO2 content will likely provide more nitrogen for the production of more CBSCs in all of earth's plants.  And with more decay-resistant materials infused throughout plant tissues, the plant-derived organic matter that is incorporated into the soil should remain there for longer periods of time, which is the very essence of superlative carbon sequestration.

Dr. Sherwood B. Idso

Dr. Keith E. Idso

References

Bashkin, M.A. and Binkley, D.  1998.  Changes in soil carbon following afforestation in Hawaii.  Ecology 79: 828-833.

Dakora, F.D. and Drake, B.G.  2000.  Elevated CO2 stimulates associative N2 fixation in a C3 plant of the Chesapeake Bay wetland.  Plant, Cell and Environment 23: 943-953.

Freeman, C., Ostle, N. and Kang, H.  2001.  An enzymic 'latch' on a global carbon store.  Nature 409: 149.

Gifford, R.M.  1992.  Interaction of carbon dioxide with growth-limiting environmental factors in vegetative productivity: Implications for the global carbon cycle.  Advances in Bioclimatology 1: 24-58.

Kaye, J.P., Resh, S.C., Kaye, M.W. and Chimner, R.A.  2000.  Nutrient and carbon dynamics in a replacement series of Euclayptus and Albizia trees.  Ecology 81: 3267-3273.

Lowe, R.H. and Evans, H.J.  1962.  Carbon dioxide requirement for growth of legume nodule bacteria.  Soil Science 94: 351-356.

Niklaus, P.A., Leadley, P.W., Stocklin, J. and Korner, C.  1998.  Nutrient relations in calcareous grassland under elevated CO2Oecologia 116: 67-75.

Olesniewicz, K.S. and Thomas, R.B.  1999.  Effects of mycorrhizal colonization on biomass production and nitrogen fixation of black locust (Robinia pseudoacacia) seedlings grown under elevated atmospheric carbon dioxide.  New Phytologist 142: 133-140.

Penuelas, J., Estiarte, M. and Llusia, J.  1997.  Carbon-based secondary compounds at elevated CO2Photosynthetica 33: 313-316.

Uselman, S.M., Qualls, R.G. and Thomas, R.B.  1999.  A test of a potential short cut in the nitrogen cycle: The role of exudation of symbiotically fixed nitrogen from the roots of a N-fixing tree and the effects of increased atmospheric CO2 and temperature.  Plant and Soil 210: 21-32.


Last updated 18 September 2002
Copyright ©

2002.

Center for the Study of Carbon Dioxide and Global Change (www.co2science.org).


TOPICS: Culture/Society; News/Current Events
KEYWORDS: carbondioxide; globalwarming
Among other things, this article indicates that elevated levels of atmospheric CO2 will lead to more fertile soils.

SUVs will make the deserts bloom.




1 posted on 09/20/2002 12:03:10 PM PDT by Sabertooth
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To: PatrickHenry; Quila; Rudder; donh; VadeRetro; RadioAstronomer; Travis McGee; Physicist; ...
((((((growl)))))



2 posted on 09/20/2002 12:03:58 PM PDT by Sabertooth
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To: Sabertooth
SUVs will make the deserts bloom.

DESERT HABITATS DISAPPEARING!

Mongolian Gerbils threatened with extinction!

Man's influence suspected!

So vote Nader!

3 posted on 09/20/2002 12:15:17 PM PDT by VadeRetro
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To: VadeRetro
Do you suspect that Nader's interest in gerbil preservation is more than political?



4 posted on 09/20/2002 12:25:41 PM PDT by Sabertooth
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To: Sabertooth
SUVs will make oil

(someday)

5 posted on 09/20/2002 12:27:35 PM PDT by Rudder
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To: Sabertooth
Do you suspect that Nader's interest in gerbil preservation is more than political?

No, but "political" is a dirty enough word.

6 posted on 09/20/2002 12:29:06 PM PDT by VadeRetro
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To: Sabertooth
Not only should we consider this view on the benefits of CO2 enrichment, but also consider an old scientific dictum called Vant Hoff's Law that states that for every 20 degrees you raise the temperature, you increase the metabolic (respiration) rate and oxygen demand by 300 percent. So... global warming will increase the respiration rate and therefore the CO2 production rate AND volume, contributing to CO2 production. ALSO, photosynthetic and other carbon fixing organisms and organelles will FIX more CO2 if the temp goes up -- per vant Hoff's law.

So, where's the bad news?

By the way, research at the University of SW Louisiana in the 70s demonstrated that the limiting factor of growth in a US cornfield (presumes adequate bio-available nitrogen) was CO2 concentration -- in other words there was insufficient CO2. Temperature was the second most important (presuming adequate rain or irrigation.)

p.s. Geneticists are looking at creating CO2-fixing bacteria to 'pour' into the ocean to fix more CO2 and reduce atmospheric CO2

7 posted on 09/20/2002 12:35:49 PM PDT by Blueflag
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To: Blueflag
Geneticists are looking at creating CO2-fixing bacteria to 'pour' into the ocean to fix more CO2 and reduce atmospheric CO2

Thank God the geneticists evolved just in time to save the planet from us.




8 posted on 09/20/2002 12:39:47 PM PDT by Sabertooth
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To: Sabertooth
In a broader sense this article is pointing out that the earth has an incredible capability to adapt and purify itself. The environmental extremists never seem to embrace this concept. But, rather would like to scare everyone into thinking that the end in near. If the environment is so bad, then why does life expectancy keep increasing?
9 posted on 09/20/2002 12:42:11 PM PDT by HoosierFather
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To: Sabertooth
This idea is almost as good as introducing starlings to kill the house sparrows ...
10 posted on 09/20/2002 12:57:28 PM PDT by Blueflag
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To: HoosierFather
In a broader sense this article is pointing out that the earth has an incredible capability to adapt and purify itself. The environmental extremists never seem to embrace this concept.

In their minds, they worship a powerless Gaia.

On the other hand, I don't believe in Gaia as an entity, but the global ecosystym is quite gaia-like in its resilience.

Go figure.




11 posted on 09/20/2002 1:10:46 PM PDT by Sabertooth
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To: VadeRetro
Mongolian Gerbils threatened with extinction!

Does that make SUV drivers homophobic, perhaps even guilty of a hate crime?

12 posted on 09/20/2002 1:28:48 PM PDT by Always Right
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To: Sabertooth
Do you suspect that Nader's interest in gerbil preservation is more than political?

Ralph's long admired gerbils from afar, but so far he's never had the nerve to ask one out.

13 posted on 09/20/2002 1:48:06 PM PDT by Right Wing Professor
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To: HoosierFather
Earth adapting itself is the big Gaia Hypothesis of Dr James Lovelock. It seems the Gaia Hypothesis is moving from the Greens to the Conservatives of late.
14 posted on 09/20/2002 1:55:55 PM PDT by Doctor Stochastic
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To: Sabertooth
100% ALL of the carbon contained in fossil fuels was once a normal part of the biosphere. So what is the problem with releasing it back into the biosphere where it belongs?

The sooner the better!
15 posted on 09/20/2002 1:58:46 PM PDT by mcsparkie
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To: Right Wing Professor
Ralph's long admired gerbils from afar, but so far he's never had the nerve to ask one out.

The only proveable connection so far is that he seems to be hung like one.

16 posted on 09/20/2002 2:53:21 PM PDT by VadeRetro
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To: Sabertooth
Cool! Thanks for the ping :-)))
17 posted on 09/20/2002 8:36:31 PM PDT by RadioAstronomer
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To: Sabertooth
When I drive my SUV into the forest I constantly stop by the side of the road and participate in nitrogen fixing. Of course, it could be the diuretics.
18 posted on 09/20/2002 9:47:36 PM PDT by capitan_refugio
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To: Sabertooth
And with more decay-resistant materials infused throughout plant tissues, the plant-derived organic matter that is incorporated into the soil should remain there for longer periods of time, which is the very essence of superlative carbon sequestration.

Let's not forget that the oceans themselves are a vast CO2 sink...

19 posted on 09/20/2002 9:53:01 PM PDT by Aracelis
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To: Sabertooth
..."That is not logical. Carbon-units are not true lifeforms"
20 posted on 09/20/2002 10:03:39 PM PDT by Consort
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