SOIL SOURCE: Climate change may boost greenhouse gas emissions from soils, undercutting forests' impact on slowing global warming.
Image: Wkimedia Commons/Tigran Mitr am
As higher levels of carbon dioxide permeate the Earth's atmosphere, scientists have long counted on forests -- which, as individual trees, grow larger in carbon-rich environments -- to soak up some of the excess.
But after nearly a decade and a half of observing forest ecosystems in controlled settings, scientists now see evidence that elevating carbon levels may cause forests to release as much extra carbon as they absorb.
That's because trees, as they grow larger, need to absorb higher doses of nitrogen and other minerals, as well as the extra carbon dioxide. By feeding some of their excess carbon to microbes in the soil, they can accelerate the decomposition process, gaining access to those important minerals.
As a byproduct of that process, however, more carbon is released into the atmosphere.
"Under elevated CO2, everything is cycling much faster," said Richard Phillips, an assistant professor of biology at the Indiana University College of Arts and Sciences. "The net result is that plants get more nitrogen and store more carbon. But as those microbes cause matter in the soil to break down, carbon is released as a gas into the air."
In the end, more carbon is stored in the wood of the trees, which are growing larger -- but less is stored in the soil, where the decomposition process is taking place.
That finding could have significant implications for climate models, which attempt to factor in long-term carbon storage in forests as part of their overall picture of the global carbon balance.
"In soil, carbon gets worked over by microbes, back and forth, and ends up in these complex compound forms that are very stable," Phillips said. Carbon stored in soil can persist there for hundreds and even thousands of years, he said.
"When carbon is stored in a tree, it's only there for the tree's lifetime -- maybe 60 to 100 years," he added.
Hunting for missing carbon
Scientists had known for some time that elevating carbon dioxide levels in the air didn't necessarily result in more carbon stored in the soil. Free-Air Carbon Dioxide Enrichment (FACE) sites, such as the Duke Forest site where Phillips conducted his research, had for many years documented increased growth in trees without a corresponding rise in soil carbon. As Phillips explained, that indicated to researchers that another process was at work.
"The trees were growing larger, and ordinarily you'd think that bigger plants would mean more detritus, branches and leaves would be falling and adding their carbon to the soil," he said. "But we weren't seeing those levels rise as much as we thought. So somewhere, there was a loss."
It also appeared that the trees were continuing to grow larger, even after more than a decade of high-carbon exposure. Early models had predicted that growth due to higher carbon levels would peak and then plateau again, due to shortages of nitrogen and other minerals.
The fact that trees in the FACE studies have continued to grow at accelerated rates indicated that they were securing increased supplies of nitrogen in tandem with their higher doses of carbon dioxide.
Phillips was the first to propose that the trees, via their roots, might be dumping more sugars and other compounds at the soil, in order to fuel microbial activity and speed up the decomposition process. He termed this hypothesis Rhizo-Accelerated Mineralization and Priming (RAMP).
His findings were published this week in the early online edition of the journal Ecology Letters.
The net effects of this process are still unknown, Phillips said, adding that he hopes research in this vein will continue and factor into climate projections.
"Most of [the existing] models have limited representation of roots, and none of them include processes such as priming," he said. "Our results demonstrate that interactions between roots and soil microbes play an underappreciated role in determining how much carbon is stored and how fast nitrogen is cycled."
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
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9 Comments
Add CommentMore speculation and maybe this or maybe that with a good final conclusion, they dont know enough to really conclude anything. Not that I would expect warmists to do any real science. Always the flawed computer models and then they go out in the real world and determine somehow the model is right and what they observe is somehow misunderstood. This article is basically trying to make it seem as if nature could never deal with CO2 and of course only replacing nature with whatever the warmists think then can engineer for an atmosphere is the only way to "solve" global warming.
Reply | Report Abuse | Link to this@priddseren, There is more science in this article than you have ever posted in support of your own paranoid delusions, not that I would expect a denier to do any real science.
Reply | Report Abuse | Link to this"Always the flawed computer models and then they go out in the real world and determine somehow the model is right and what they observe is somehow misunderstood." yet another strawman argument. Do you really think your distortions convince anyone? You think we can't see you for the fossil fuel shill that you are? Why don't you convince us by publishing something, or is lying in the comments section the best you can do?
"This article is basically trying to make it seem as if nature could never deal with CO2 and of course only replacing nature with whatever the warmists think then can engineer for an atmosphere is the only way to "solve" global warming." please show me in the article where it says that. Sorry, I forgot, the only things you have to support your arguments are strawmen and delusions. Facts never enter into it. But thanks for again reminding us of how desperate the deniers have become in their lame attempt to change reality to suit their politics.
"When carbon is stored in a tree, it's only there for the tree's lifetime -- maybe 60 to 100 years," he added.
Reply | Report Abuse | Link to thisNot true, IF the tree is harvested into lumber and used to construct a new home. Until that home burns... the carbon is sequestered. That could be centuries more. Meanwhile it's replacement tree will continue to pull tons of CO2... to build more homes. Well... you get the idea. GK
"...Not true, IF the tree is harvested into lumber and used to construct a new home. Until that home burns... the carbon is sequestered. That could be centuries more."
Reply | Report Abuse | Link to thisNot the way they build homes in America. Wishful thinking isn't going to save the planet.
"Not that I would expect warmists to do any real science."
Reply | Report Abuse | Link to thisWhat is your definition of a warmist? It is not in the dictionary. Creating a straw man is not going to get you very far in the real world of peer reviewed science. First you have to learn the language before you will ever be taken seriously in any academy of learned men.
singing flea says: "Wishful thinking isn't going to save the planet."
Reply | Report Abuse | Link to thisIn what alternate universe, does planet Earth require "saving"??
You have revealed the true "cause" of CAGW movement. The narcissist delusion creating the "Noble Cause" exaggeration of so called "consensus climate science". Your messiah complex is interfering with the scientific method, making proper science near impossible.
Even though CO2 has increased significantly for the past 15 years, no correlating global temperature increase can be found. There are warm periods and then cool periods, as there always has been. The LIA was a cool period, followed by our present warm period, similar to the previous warm period (medieval warm period MWP) that preceded the LIA.
Since the historical record shows civilization and our food supply flourish during the warm periods and suffer unspeakably during the cool periods - I must ask... Save us from WHAT... again. GK
You may want to get your facts straight. Until then it'll be valid to call you a liar.
Reply | Report Abuse | Link to thisI have stopped assuming that there can be un- or misinformed people after decades of discussion about AGW. Hence you must be malicious.
Ralf123 in reply to G. Karst says: "You may want to get your facts straight. Until then it'll be valid to call you a liar."
Reply | Report Abuse | Link to thisNow there is an intelligent, fact filled, rebuttal... NOT!
Typical of responses delivered by ideology advocates who do not even know enough details to state what they disagree with.
Could it be Ralf123 is a historical revisionist, who denies the Medieval Warm Period (MWP) or perhaps he denies the Little Ice Age (LIA). There is much written of both so I doubt that is the problem. I'm fairly certain he agrees about the current warm period.
That just leaves the statement that all life thrives during warm periods and suffers during cold. Seems self evident to most and is certainly part of the historic record. Plants certainly need warmth and CO2 to thrive. Warming increases bio-available moisture (increased precipitation) so the arid areas bloom more often.
So I am left with the conclusion that you disagree because the contrast highlights your purely ideological stance and agenda. Ideology, should always be well tempered, by reality... otherwise it is brittle, fragile, and unable to persist.
Ralf says: "after decades of discussion about AGW"
You have wasted decades of discussion, when you decided to exclusively listen to fellow ideologist, who believed they had an vehicle for social engineering. Broaden your inquiries and discussions. You might learn some small part of reality. We can always hope that conformity will give way to realism... eventually, but being a skeptic... I have my doubts. GK
Here is the latest paper quantifying the Medieval Warm Period (MWP).
Reply | Report Abuse | Link to thisDonna Surge, University of North Carolina,
Department of Geological Sciences
and...
James H. Barrett, McDonald Institute for Archaeological Research, University of Cambridge
presented their findings that the MWP was aprox 1 degree C warmer than present.
http://www.sciencedirect.com/science/article/pii/S0031018212003926
What isn't explained is Mann's hockeysticks and how CO2 can possibly be blamed. GK