Soil's large carbon stores could be freed by increased CO2, plant growth

January 5, 2015 by Morgan Kelly
Researchers based at Princeton University report that an increase in human-made carbon dioxide in the atmosphere could initiate a chain reaction between plants and microorganisms that would unsettle one of the largest carbon reservoirs on the planet — soil. The researchers developed the first computer model to show at a global scale the complex interaction between carbon, plants and soil. The model projected changes (above) in global soil carbon as a result of root-soil interactions, with blue indicating a greater loss of soil carbon to the atmosphere. Credit: Benjamin Sulman, Princeton Environmental Institute

An increase in human-made carbon dioxide in the atmosphere could initiate a chain reaction between plants and microorganisms that would unsettle one of the largest carbon reservoirs on the planet—soil.

Researchers based at Princeton University report in the journal Nature Climate Change that the in soil—which contains twice the amount of carbon in all plants and Earth's atmosphere combined—could become increasingly volatile as people add more to the atmosphere, largely because of increased . The researchers developed the first computer model to show at a global scale the complex interaction between carbon, plants and soil, which includes numerous bacteria, fungi, minerals and carbon compounds that respond in complex ways to temperature, moisture and the carbon that plants contribute to soil.

Although a greenhouse gas and pollutant, carbon dioxide also supports plant growth. As trees and other vegetation flourish in a carbon dioxide-rich future, their roots could stimulate microbial activity in soil that in turn accelerates the decomposition of and its release into the atmosphere as carbon dioxide, the researchers found.

This effect counters current key projections regarding Earth's future carbon cycle, particularly that greater plant growth could offset as flora take up more of the gas, said first author Benjamin Sulman, who conducted the modeling work as a postdoctoral researcher at the Princeton Environmental Institute.

"You should not count on getting more carbon storage in the soil just because tree growth is increasing," said Sulman, who is now a at Indiana University.

On the other hand, initiated by root growth could lock carbon onto mineral particles and protect it from decomposition, which would increase long-term storage of carbon in soils, the researchers report.

Whether carbon emissions from soil rise or fall, the researchers' model depicts an intricate soil-carbon system that contrasts starkly with existing models that portray soil as a simple carbon repository, Sulman said. An oversimplified perception of the soil carbon cycle has left scientists with a glaring uncertainty as to whether soil would help mitigate future carbon dioxide levels—or make them worse, Sulman said.

"The goal was to take that very simple model and add some of the most important missing processes," Sulman said. "The main interactions between roots and soil are important and shouldn't be ignored. Root growth and activity are such important drivers of what goes on in the soil, and knowing what the roots are doing could be an important part of understanding what the soil will be doing."

The researchers' soil- model has been integrated into the global land model used for climate simulations by the National Oceanic and Atmospheric Administration's (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL) located on Princeton's Forrestal Campus.

Explore further: Dirty pool: Soil's large carbon stores could be freed by increased CO2, plant growth

More information: "Microbe-driven turnover offsets mineral-mediated storage of soil carbon under elevated CO2." Nature Climate Change 4, 1099–1102 (2014) DOI: 10.1038/nclimate2436

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15 comments

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gkam
2.6 / 5 (10) Jan 05, 2015
So much for the hope of the Deniers.

We have to stop this carbon release now. We must rid ourselves of Dirty Fuels.
gkam
2.5 / 5 (10) Jan 05, 2015
I am more concerned about the methane locked in the permafrost and in hydrates/clathrates in the oceans.
rho1953
2.3 / 5 (9) Jan 05, 2015
Oh no! Those heretics! We cannot have climate deniers! They must be eliminated! Can't any of you see where we are headed? The inevitable conclusion must be that the herd of men must be culled. There is no free lunch, there are no fuels that can replace fossil fuels and keep us warmed in the winter, cool in the summer, transport us, build our products. There is an innate insanity from the AGW pushers. They are totalitarians who will dismantle society and development. They are as insane as the fundamentalist religions.
Science Officer
2.9 / 5 (10) Jan 05, 2015
So wiping out the Rain Forests would be a good thing then? Please, make up your minds.
psychosalmon
2 / 5 (8) Jan 05, 2015
So now the models have even more positive feedback. Pretty soon one child in Des Moines breathing out will threaten the immediate extinction of the human race. To believe this nonsense, increasing 3.5/10000 molecules of CO2 to 4.0 or 4.5 tips some balance in the soil. Tell you what, when you and I breathe out, we exhale 400/10000. So if you breathe on a pile of dirt, literally the stuff should explode with outgassing CO2. 100 times more powerful than the ambient, doing pushups over soil should be banned immediately. Any large sporting gathering around soil like a soccer match should be banned because the field may erupt. To be clear, burning Cannabis is ok though, especially if you are updating climate models.
Mike_Massen
2.6 / 5 (10) Jan 05, 2015
rho1953 muttered sardonically
Oh no! Those heretics! We cannot have climate deniers! They must be eliminated! Can't any of you see where we are headed? The inevitable conclusion must be that the herd of men must be culled
The problem is arbitrary deniers DONT have an education in Physics sufficient for them to understand the combinatorial complexity. Its all based on Heat transfer but, the arrangements/permutations are vast, not one denier I've seen in my years here has EVER refuted CO2's issue absorbance/of re-radiation

http://www.chem.a.../sim/gh/

rho1953 claimed
There is no free lunch, there are no fuels that can replace fossil fuels and keep us warmed in the winter, cool in the summer, transport us, build our products
Renewables work, more needed :-)

rho1953 claimed
They are as insane as the fundamentalist religions
They have an education in Science & especially:-
https://en.wikipe...c_method

You ?
Mike_Massen
2.7 / 5 (12) Jan 05, 2015
psychosalmon desperately made an idiot idea
So now the models have even more positive feedback. Pretty soon one child in Des Moines breathing out will threaten the immediate extinction of the human race
Then psychosalmon goes & superficially explores his bad idea
To believe this nonsense, increasing 3.5/10000 molecules of CO2 to 4.0 or 4.5 tips some balance in the soil. Tell you what, when you and I breathe out, we exhale 400/10000. So if you breathe on a pile of dirt, literally the stuff should explode with outgassing CO2. 100 times more powerful than the ambient, doing pushups over soil should be banned immediately
Where is the evidence for your crazy notion, hwo did U work it out OR just having a bitch session, do U do this often when U gals mutter around a coffee ?

psychosalmon continued
To be clear, burning Cannabis is ok though, especially if you are updating climate models
To be REALLY clear, you need an education and get off the weed !
bradalb0
2.1 / 5 (7) Jan 06, 2015
The article admits to many assumptions and states:

"An oversimplified perception of the soil carbon cycle has left scientists with a glaring uncertainty as to whether soil would help mitigate future carbon dioxide levels—or make them worse"

So based on what assumptions you make, how good or bad your data is and how many control loops you've missed or miscalculated, the end result could be anyone's guess.

However, any mechanism that doesn't end in an equilibrium is not realistic. A runaway loop that either sequesters all carbon to completion or releases all carbon until exhaustion would have already made its existence known over the millions of years that plants have been growing and the wide range of CO2 levels we've already experienced.
MrLuigiVercotti
1.7 / 5 (6) Jan 06, 2015
Oh, Dear - this is just another MODEL... makes me think of the Dead Parrot sketch

gkam
3 / 5 (8) Jan 06, 2015
Perhaps you should have been watching Nova.
Mike_Massen
3 / 5 (10) Jan 06, 2015
bradalb0 claimed
So based on what assumptions you make, how good or bad your data is and how many control loops you've missed or miscalculated, the end result could be anyone's guess
This may be true in a purely numerical control without foundations. IThis situation however we have knowledge of the foundations ie Mass of Carbon & good estimates that move through the biosphere & the key driver; Heat.

bradalb0 claimed
However, any mechanism that doesn't end in an equilibrium is not realistic
Keh ? there are relative equilibrium states. bear in mind any system in full equilibrium has a high degree of homogeneity.

bradalb0 made a straw man
A runaway loop that either sequesters all carbon to completion or releases all carbon until exhaustion would have already made its existence known over the millions of years that plants have been growing and the wide range of CO2 levels we've already experienced
Immense feedbacks natural & other, so won't happen.
bradalb0
2.3 / 5 (3) Jan 07, 2015
Mike_Massen
You seem to be having difficulty with some pretty basic concepts in chemistry. Your first comment saying that we have good knowledge of how carbon moves through the biosphere is actually the basis of the author's uncertainty. Decompositional release or mineral sequestration are just two of many paths that carbon may take and the author has no definitive answer as to whether one or the other might dominate or whether they might just cancel each other out. And your non-sequitur about heat being the "key driver" has nothing to do with chemical equilibrium. Heat only comes into play WRT the kinetics of the various reaction paths.
Next, I have no clue what equilibrium and homogeneity have to do with each other. You reach equilibrium when the amount of reactants and products are at steady state. The forward and reverse reactions are in balance. My definition of homogeneity is that every thing is the same. A totally different concept and outcome.
I'd go on but space for limits
Mike_Massen
2.1 / 5 (7) Jan 07, 2015
bradalb0 claimed
You seem to be having difficulty with some pretty basic concepts in chemistry. Your first comment saying that we have good knowledge of how carbon moves through the biosphere is actually the basis of the author's uncertainty
Please don't be so narrow assuming simplistic aspects of my post & No, NOTE: I mentioned Mass of Carbon & didn't focus on chemistry.

bradalb0 muttered
And your non-sequitur about heat being the "key driver" has nothing to do with chemical equilibrium
NO, in the overall context U are narrow, heat affects many industrial (Eg Haber process) & biological chemical equilibria (Eg thermophile metabolic rate). ie Would you claim there is no change to CO2 release if you add/remove heat - doh !

bradalb0 claimed
Heat only comes into play WRT the kinetics of the various reaction paths
No, heat flow translates to temperature differential re thermal resistivity, that clearly influences equilibria it MUST be factored.

cont
Mike_Massen
2.1 / 5 (7) Jan 07, 2015
bradalb0 with a fair question
Next, I have no clue what equilibrium and homogeneity have to do with each other
Eg Take water re pK & pH, at neutral & equilibrium the fluid is essentially homogenous, if U change pH re acid/base the system is not at equilibrium until its well mixed & only then homogeneous ie It has no chemical vector driving its reaction rate one way or the other.

bradalb0 almost got there
You reach equilibrium when the amount of reactants and products are at steady state
Sure AND depending on heat flow which is accounted for by temperature differential.

bradalb0 again almost
The forward and reverse reactions are in balance
Sure but, only at those particular conditions which equate to homogeneity.

bradalb0 claimed
My definition of homogeneity is that every thing is the same
Nonscientific but fine, it excludes a wider understanding. We were talking climate iirc. If there were equilibrium there would be (thermal) homogeneity.
bigterguy
3 / 5 (1) Feb 07, 2015
"On the other hand, microbial activity initiated by root growth could lock carbon onto mineral particles and protect it from decomposition, which would increase long-term storage of carbon in soils, the researchers report."

So these folks don't know whether increased CO2 would increase or decrease carbon in soil. At least they are being honest.

Nice work, but the headline is grossly misleading.

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