Global Warming May Affect the Capacity of Trees to Store Carbon, MBL Study Finds
WOODS HOLE, MA—One helpful action anyone can take in response to global warming is to plant trees and preserve forests. Trees and plants capture carbon dioxide during photosynthesis, thereby removing the most abundant greenhouse gas from the atmosphere and storing some of it in their woody tissue.
Yet global warming may affect the capacity of trees to store carbon by altering forest nitrogen cycling, concludes a study led by Jerry Melillo of the Marine Biological Laboratory (MBL), published this week in Proceedings of the National Academy of Sciences.
The paper summarizes the results of a 7-year study at Harvard Forest in central Massachusetts, in which a section of the forest (about one-quarter of an acre) was artificially warmed about 9oF above ambient, to simulate the amount of climate warming that might be observed by the end of the century without aggressive actions to control greenhouse gas emissions from fossil-fuel burning and deforestation.
The study confirmed, as others have, that a warmer climate causes more rapid decomposition of the organic matter in soil, leading to an increase in carbon dioxide being released to the atmosphere.
But the study also showed, for the first time in a field experiment, that warmer temperatures stimulate the gain of carbon stored in trees as woody tissue, partially offsetting the soil carbon loss to the atmosphere. The carbon gains in trees, the scientists found, is due to more nitrogen being made available to the trees with warmer soil.
“Tree growth in many of the forests in the United States is limited by the lack of nitrogen,” Melillo says. “We found that warming causes nitrogen compounds locked up in soil organic matter to be released as inorganic forms of nitrogen such as ammonium, a common form of nitrogen found in garden fertilizer. When trees take up this inorganic nitrogen, they grow faster and store more carbon.”
Melillo says that the biological processes that link soil warming, increased soil organic matter decay, increased nitrogen availability to trees, and increased tree growth will likely operate together in many temperate and boreal forests—forests found in North America, Europe, Eurasia and much of the developed world. Tree growth in tropical forests is often limited by factors other than nitrogen, so lessons from this new study are not widely relevant in the tropics.
While Melillo thinks that the carbon-nitrogen interactions he is studying at Harvard Forest will help us to make predictions of carbon storage in forest over the coming decades, he adds that “the carbon balance of forest ecosystems in a changing climate will also depend on other factors that will change over the century, such as water availability, the effects of increased temperature on both plant photosynthesis and aboveground plant respiration, and the atmospheric concentration of carbon dioxide.”
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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery and improving the human condition through research and education in biology, biomedicine, and environmental science. Founded in 1888 in Woods Hole, Massachusetts, the MBL is an independent, nonprofit corporation.
Citation:
Melillo, J., Butler, S., Johnson, J., Mohan, J., Steudler, P., Lux, H., Burrows, E., Bowles, F., Smith, R., Scott, L., Vario, C., Hill, T., Burton, A., Zhouj, Y, and Tang, J. (2011) Soil warming, carbon–nitrogen interactions, and forest carbon budgets. PNAS: Early Edition May 23, 2011, doi: 10.1073/pnas. 1018189108
“Warmer temperatures stimulate the gain of carbon stored in tree”
A small correction should be made in the title, Anthony. I suppose you mean to say “higher temperatures”. A temperature is neither warm nor cold.
DJ says:
May 28, 2011 at 7:17 am
I noticed that, also “buried by hand to minimize disturbance” and “Historical records, stone walls, and soil horizon characteristics indicate that the area was used for either pastureland or low-intensity agriculture before 1908.
Stone walls and pasture land are strong indicators that the grad students had no fun whatsover. Last week my wife and I planted 100 white pine “seedlings” (2-3 yr old) on our property on the side of Mt. Cardigan in New Hampshire. The flatter terrain wasn’t too bad as a lot of fines washed down there during the glacial retreat to mix in with the rocks, but on the steeper terrain where I couldn’t get the shovel between rocks it was negative fun.
I have a lot of respect for New England trees – thin soil, poor soil, 5-6 months of winter winds, and ice storms. Then we come along, cut them down and burn them for heat.
Great Dog Above! Is it negatory feedback? Hud’a thunk?
The heating source was probably the same one “discovered” by NOAA, after which they quietly began removing said heat source. These researchers probably used the collected overturned boats, upright burn barrels, and BB Q’s stashed behind the NOAA office building of climate change. Scatter a few of those around a little piece of forest and abracadabra, 9 degrees of heating.
I started to rip on this article but stopped myself – I realized at least these people are performing science – they didn’t just build a computer model and tweak it until they got the results they wanted.
They used a control plot with unheated buried wire – good. They didn’t control air temperature, or add CO2 – weaknesses to the study. OK, I can find a lot to critique but again – at least they measured something.
One little side note – I wonder if roots grow faster in the presence of alternating current (the electormagnetic waves caused by the current) and not just because they are warmer…That would be fun if true.
It looks like one or two of us actually read the study, including the methods.
What they did is bury soil heating wires 10 cm (~ 4 inches) deep and 20 cm (~8 inches) apart. The used a controller to keep the soil in the heated plot 5° C above the soil temp of the control plot, at one minute intervals – all year ’round. They did not alter the air temperature around the trees (other than what air layer may have been raised by the warmer soil, if any). They did not alter the CO2 levels of the air in either plot.
With this methodology, I can not see how they could possibly draw any conclusions about the nitrogen or carbon cycles in a CO2-driven temperature enhanced forest.
First, the idea that the soil temperature 4 inches down would be raised 5° C above ‘normal’, at every moment, year around is, I believe, fallacious, with any reasonably expected surface air temperature. I would have to see soil temperature graphs for soil temps against surface air temps at that depth. It seems incorrect to make the assumption that if average annual surface air temps rise 5° C that soil temps at 4 inches would also rise 5° C, every moment of the day, year around. Of course, no one expects that air temperatures will rise evenly by any X° C, 24 hours a day, year around, so the methodology does not represent any expected set of conditions to be measured.
Secondly, they assume that the expected temperature increase would have been caused by ‘doubling’ of atmospheric CO2 (or some set amount of increased CO2). Yet, the experiment raises soil temperature only — not CO2 levels and not surface air temperatures. So we have warmed roots, but not warmed the trunk, limbs, and leaves. Further, measuring CO2/N cycles without actually increasing the CO2 levels expected to have caused the warming must throw all their respiration and CO2 processing data out of whack with any real world result. I see no way they could have controlled for these missing elements.
The whole thing seems to be a bit like measuring the effects of fever on a human by warming just his feet, but not giving him any causative illness and its other symptoms. I will write to the lead author and ask him for a clarification.
Instead of growing trees and then letting them decay and release carbon back into the atmosphere, what if we cut them down and sequestered them underground and then grew new ones and repeated the process? AND we could pay for the carbon sequestering, by using the trees for something productive BEFORE they were sequestered.
I wonder if I could get a grant to study the economic feasability of this carbon sequestration project? Are there any WUWT readers that would like to particiapte? Think of all the new GREEN JOBS that this carbon sequestration project could support!!
oakgeo says:
May 28, 2011 at 10:05 am
“’… carbon dioxide … the most abundant greenhouse gas from the atmosphere …’”
“Okay, I couldn’t read past that first paragraph after seeing this example of CAGW propaganda and intellectual dishonesty.
Thank you, thank you, thank you, Oakgeo! That was my first reaction, too. I went (current venacular) , ” WHAT!!!???” WUWT over the years has again and again published data on water vapor, which actually ‘absorbs’ long-wave IR better than CO2, is present in the atmosphere at levels ranging from 1% to 4% vs CO2 of a measly ~0.039%— 25 t0 100 times as much!
Unbelievable!
Anthony,
The current Woods Hole study seems to answer the question of
where, if at all, the “carbon sink” and carbon-nitrogen fixing is in
forests with or without the increased CO2 levels as discussed in
Hoosbeek et al,. and a whole series of similar studies:
http://www.biogeosciences.net/8/353/2011/bg-8-353-2011.pdf
which determined the “carbon sink” effect, thought to be in the
sub-surface levels of a forests and most soil types was actually
significantly observable in only the top 1 – 5 cm of the forest floor’s
soil.
The answer coming from this Woods Hole study of a forest
that (1) hasn’t been previously used as farm land, (2) that’s being
experimentally warmed to mimic hypothetical future atmospheric
warming trends, (3) with the current real time rise and fall of New
England CO2 levels from ~2003 to ~2010 as a present but
uncontrolled (and unmentioned) variable:
The “carbon sink” is, for the most part, the above- and below
woody biomass of the trees themselves. The sub-surface nitrogen
seems to be more “available” under these slightly warmer conditions
for plant uptake, but not in a way that depletes the soil of it’s
nitrogen levels.
To many folks, this matches what they assume is just
common sense as to the way the world works. However, in this
area of environmental science, assumptions can’t be treated as
facts until they’ve been vetted through experimentation and
observation.
The “woody biomass” of a forest, a.k.a. the TREES, wasn’t under
consideration as an effective carbon sink in the Hoosbeek family
of studies.
Since the Woods Hole study wasn’t trying to demonstrate or
“prove” anything about the effect of atmospheric CO2,
most atmospheric CO2 level observations and discussion would
be extraneous material.
There’s absolutely no good evidence, at this time, that
increased atmospheric temperatures of ~1 to ~2 or even ~5
degree Celsius OR Fahrenheit would effect the forest soil
temperature or composition to a depth or more than a couple
of inches. Any discussion of deeper atmospheric temperature
penetration of the soil would be both speculative and non-relevant
to this particular Woods Hole study.
The study brings existing environment science one baby step
closer to reality.
And there’s a side-effect as well: more trees for paper grocery bags! Since we’re not allowed to use plastic (evil Big Oil sourced) bags any more, and must use paper instead, this is great.
Oh wait – moving to paper bags means less Evil Big Oil used, means less global warming, means slower growing trees… Well, crap!
They would have done better with our money and their time, if they had spent seven years studying the avoidance of non sequiturs. They warmed 10cm of top soil by 5C with electricity from their nearest power station. Where, I wonder, do they think the business end of a hardwood tree is located? How far down do they think that additional heat extended? As an experiment to test the effects of warming arising from additional carbon dioxide they might just have well used their power grid to run an electric train set.
“Jim G says:
May 28, 2011 at 8:50 am
So, with all the extra CO2 and additional photosynthesis we will, no doubt, end up with more O2. What does that cause at the other end other than more forest fires?”
This will not be a concern. Suppose that the oxygen content is now 20.950% of the atmosphere. If enough carbohydrates are then burned to cause CO2 to go up by 0.010% then the oxygen would drop to 20.940% in the absence of any change in photosynthesis. But if we assume that 10% of the extra CO2 that we put into the air goes into increased photosynthesis, then the O2 drops to 20.941% instead of 20.940%.
So the bottom line is that any extra photosynthesis just causes O2 to go down very slightly slower.
@Interstellar Bill May 28, 2011 at 12:43 am:
Bill, that was my first reaction, too. And I thought that maybe the experiment (an actual real world experiment in climatology – what a novel idea!) was missing the CO2 factor. But in reading more, I realized that this is the way you do science – by isolating factors (as much as you can) so that you can change one factor and observe/measure the results. This they seem to have done. And they did it while the CO2 was at a constant level (yes, the CO2 is essentially constant.). Doing this “changing one factor at a time” science is the best way – the only real way – to begin compiling a matrix of the factors (and determining which ones are not factors, too).
@andic May 28, 2011 at 12:30 am:
AndiC, this is actually a really good way to do this. By introducing an exaggerated increase (or decrease, in some cases), an experimenter can get a clearer signal from the results. It doesn’t mean the experimenter thinks that amount of increase is likely. As I understand it , this is the way carcinogen tests are done. No, nobody is going to ingest cyclamates at the rate those tests in the 1960s and 1970s were done – but with extremes comes more clarity of the results. Now they’ve got ONE piece of solid science. When perhaps another 15 to 20 such experiments are done, we will have enough pieces to put together. It would actually help, now that they’ve gotten this exaggerated test done – to clarify that there is a signal there – it would behoove them to now do gradations testing, to determine how lesser amounts affect trees, to come up with a quantified curve (exactly because of your point), so they will be able to begin to identify the effects of this/i> factor, when looked at in a matrix of other factors.
Gary: “Did they also raise the CO₂by two doublings to simulate the “cause” of the temperature rise? I calculate 380*2^2, or 1520ppm. If not, their experiment is a massive fail.”
Exactly. If they simulated the temperature rise (a very large temperatures rise beyond all reasonable expectation) and did not include the large increase in CO2 that they propose will be the cause (with no evidence to date that such an amount of carbon is available on Earth) then it is not a particularly useful simulation.
If the air had much more CO2 then the production of CO2 by the ground might be very different. Who knows?
As CO2 fertilisation is well known to happen, then the trees might have put on far more mass than they did from just having a longer growing season.
Also, if the Earth warms, then Northern forests will look a lot more like Temperate forests, growing much more as the season extends from say, 90 days to 130. For every degree of warmth and every 5 ppm CO2 increase there are tangible, measurable biospheric benefits only a portion of which were indicated by the experiment.
It is not necesary to use a portion of a forest – any greenhouse with augmented CO2 (lots of them have it) can give accurate demonstrations of the benefits of heat and CO2 fertilisation.
R.S.Brown says:
May 28, 2011 at 12:07 pm
> The current Woods Hole study …
Pedantry alert – Woods Hole has offices for:
Woods Hole Oceanographic Institute (WHOI – pronounced who-ee, not huey)
Marine Biological Labratory
National Fisheries
US Geologic Survey (ocean floor core studies, I believe)
Woods Hole Research Center (addresses the great issues for a healthy planet through science, education, and policy)
J. Erik Jonsson Center of the National Academy of Sciences (conference center, not research).
I’m surprised no one has pointed out MBL is a bit of an odd organization to be studying an inland forest, but I think it’s a continuation of the studies they’ve done in the coastal zone.
At any rate – referring to a “Woods Hole” study is terribly ambiguous.
Well, there are decent charts showing the “mean ground temperature,” which should increase with warmer surface temps (and air temp after accounting for evaporation). http://www.geo4va.vt.edu/A1/A1.htm , after the hot springs sections.
However, for this experiment, roots are mainly in the top foot or two of soil and seven years of heating should get raise the soil temperature, at least to the water table.
Trees grow 3 times faster next to a coal fired power station.
Trees like warmth and extra CO2.
PARTIALLY offsetting the soil carbon loss to the atmosphere. We lose on net
Trees and plants in general seem like a crazy idea for stashing CO2. Just like glaciers are a nutty way to provide fresh water. Assuming trees and plants die at the same rate they are created, the CO2 found in them is in a constant pass-thru state. Rotting plants put back into the system what they took from it while alive.
@Steve Garcia: After skimming through all the responses here, yours is the only one I can really concur with. All those complaining that they did not ALSO change this and ALSO change that, and that the experiment is therefore meaningless, seem to understand nothing of how you isolate factors by changing one thing at a time. I know that from years of debugging computer code. The surest way of getting your t**s in a tangle is to change more than one thing at a time. This is fundamental to experimental technique. Thanks for the sane contribution.
Ric Werme says: May 28, 2011 at 2:35 pm
Ric,
There’s no pedantry involved here at my end. The “current”
study is the one under discussion, posted at the top of the thread.
You said:
What unmitigated whale drek. I didn’t refer to just “a” Woods Hole
study, I referred to the one cited at the top of the thread. Also,
above, at R.S.Brown says: May 28, 2011 at 1:51 am, I posted a
clear link to the Woods Hole study at:
http://www.mbl.edu/news/press_releases/pdf/pnas11_melillo_soilwarm.pdf
You hadn’t entered into the commentary on the thread until about 4
hours after that was posted. It was there for you to see. It should have
given you some clue as to the Woods Hole study I was referring to then
and later.
Indeed, Anthony provided a link to the PDF of ” the current Woods Hole
study” on the line just after the citation above. It’s the short line that
says, “PDF of paper”.
Clicking on that link also takes you to
http://www.mbl.edu/news/press_releases/pdf/pnas11_melillo_soilwarm.pdf
I figured most folks who would discuss the study and its results would
actually read the PDF, which includes all the notations anyone
would need to identify what division of Woods Hole was doing the work,
and where the several authors were based.
Your link:
http://www.geo4va.vt.edu/A1/A1.htm
is rather curious.
Since the map used there in figure 2. shows “mean earth temperatures”
as measured “in groundwater wells 30 to 50 feet deep”. It’s interesting, but
seems to be little more that a digression or, more likely, a distraction from the
thread’s topic.
It’s meaningless to the study at hand.
First, I will make a full disclosure- I did not read the study. But to those who did, did these researchers take into consideration and remove the effect of disturbing the compacted soil thus allowing more air into the ground, Kinda like aerating the soil, or oops tilling the soil to make plants grow better? I would like to know the grid spacing and how even the heat was dissapated, surely thay had lots of thermometers inserted thruout the experimental aera. Maybe the extra electromagnetic rediation thru the wires cause a new unknow CO2 and nitrogen magnet. Who knows the possibilities are boundless and endless
I’ll bet commercial greenhouses around the world are so thankful for this discovery and are right now putting heating tape in the grow beds. And those of us who put in a garden every year are now retooling what we usually do in order to warm up the soil and keep it warm. In addition, the editors of Sunset Magazine are probably right now meeting in executive session to pore over the study results so they can write new articles on how to warm up soil. Thank God for climate change scientists.
…pore… Sheesh. I could have sworn I typed “pour”. Too much Irish Cream in me mornin coffee.
[I’d fixed it for you: pore n. be absorbed in the reading or study of : Heather spent hours poring over cookbooks. Next job: affect vs effect. Don’t know if I’m up to that one. ~dbs, mod.]
Bigger bugs?
But do they have a model that proves that?