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
Ok, they changed one variable and measured the effects. Sounds like science.
Now as to the comments about testing the extremes. I have done many experiments, and linear regression fits almost never work except in the extreme cases. There is almost always some sort of logarithmic or exponential zone followed by a more linear fit zone. A lot of data doesn’t even really seem to fit that pattern with slopes going the “wrong” direction for a bit then going back in the expected way. This seems especially true in biological systems for some reason. It is one of the reasons I wince at most of the graphs that show some sort of “almost sinusoid” with a local trend line that can change quite extensively depending on where on the “almost sinusoid” one chooses to look. By “almost sinusoid”, I mean a signal that looks like a sine wave, but when measured carefully has no consistent period and may even be somewhat chaotic (in the mathematical definition sense).
Many chemical studies looking for carcinogenic effects were done in such a manner that dihydrogen oxide would have been banned as a hazard. Biological systems have a problem when one introduces extremely large quantities of almost any substance, especially if the introduction is sudden. I would hazard a guess that more careful studies of many of the banned chemicals would have found them safe or even beneficial at low dosages, but the extrema methodology eliminated that discovery. So I am not a fan of the extrema technique except as a way to explore extrema effects in conjunction with other experiments looking at the lower trends.
The problem is the politics of science and this inane idea in society that we must eliminate all risk from the world. With this in place, we never do the finer grained studies because we are afraid that someone will read that “material X is beneficial” and not hear the part after that says “below Y milligrams per day.” No one wants to argue the science to a jury of people who likely won’t understand the data and will be swayed by the purely emotional appeal of the plaintiff’s attorney.
Ok, I am now going to expose my ignorance, something I have been averse to doing for fear of ridicule…….
What role does oxygen play, if any, in warming/cooling the atmosphere? Presumably, if all this extra CO2 allows more photosynthesis, more oxygen is released into the atmosphere. Then what? Nothing? Just more oxygen for us to breathe?
My other question is about measurement of CO2 in the atmosphere. I seem to recall reading somewhere, here probably, that there is little exchange of air between the northern and southern hemispheres. In the northern hemisphere winter, deciduous trees lose their leaves and photosynthesis is reduced, so less carbon dioxide is taken out of the atmosphere than in the summer. The same applies in the southern hemisphere winter and summer. Presumably, then, carbon dioxide levels fluctuate between the seasons. When is it measured? All year round? Is a global average produced? A global average would, theoretically, produce a balance between northern and southern hemispheres, i.e. a northern winter reduction in CO2 absorbtion would be offset by the southern summer increase – or would it? There is a larger land mass in the northern hemisphere and a greater coverage of trees, so a northern hemisphere summer would give a global average reduction in CO2?
Or am I just talking bo**ocks?
Any answers (in simple terms, please – as you can tell, I am not a scientist) putting me straight would be more than welcome as I spend sleepless nights pondering this conundrum. (Well, not really.)
strange surfacing to deal with when dealing with mother nature when releases or destroys”instruct best solution of balances which occuring for living/to be animals for dwelling dealing with the trees odors when in the atmosphere to communicate or move apart. side effects exists from some trees many shouldn’t be contended with/for others deadly if mind functioning wrong with the chemical its releasing from what isn’t yet is.
p238;
Truly psychotic. Get help.