PINE FORESTS: Pine plantations cause a 15 percent reduction in soil carbon and a 20 percent reduction in nitrogen, according to research by ecologist Sean Berthrong of Duke University.
Image: iStockphoto
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
ALBUQUERQUE—Because forests can lock away carbon in their woody trunks, planting vast swaths of trees on barren land could provide a means for countries to mitigate their carbon emissions. But a comprehensive new analysis warns that pine plantations can rapidly deplete the soil of its nutrients—and carbon—thereby reducing the benefits.
"It's a tough balancing act," says ecologist Sean Berthrong of Duke University. "Plantations are a usable but imperfect tool for carbon sequestration."
Since 2005 140 million hectares of land have been converted to forest globally, and an average of two million new hectares of forests are added each year. Such afforested areas account for only 4 percent of Earth's forests, but they already supply 35 percent of the world's wood products, according to the United Nations's Food and Agriculture Organization.
Berthrong's team analyzed data from 153 tree plantations—mostly eucalyptus and pine—to understand how they influenced soil nutrients and carbon. On average, new forests reduced soil carbon by 6.7 percent and nitrogen by 15 percent. Pine plantations, which are the most common, are the worst, causing a 15 percent reduction in soil carbon and a 20 percent reduction in nitrogen. Tree plantations can also cause other problems in soils, such as making them more acidic.
To minimize carbon and nutrient loss, Berthrong recommends foresters leave woody debris on the site after harvest as well as reduce plowing, which increases erosion and decomposition of buried organic matter. He also says that any program that provides carbon credits for afforestation projects take soil carbon into account.
Berthrong presented the research here at the Ecological Society of America Meeting, and it will be published in the journal Ecological Applications.
See what we're tweeting about
14 Comments
Add CommentI'm interested in this idea...would there be any way to mulch and compost the trees once mature and plant new ones in its wake? Would that help keep the soil fertilized?
Reply | Report Abuse | Link to thisIs the use of the forest product taken into account e.g. if the tree is used to make furniture perhaps the carbon is sequestered for longer than if it is used for paper.
Reply | Report Abuse | Link to thisI think there are a lot of pitfalls to carbon trading. Is the science exact enough that we know exactly how much a plot of land is capable of sequestering? Are we going to end up with on-going court battles with scientists lined up on each side debating over percentiles? What is it going to cost to evaluate each of these natural processes and how will it be monitored? I share people's concern that this is going to be about moving money around rather than fixing the problem. It would be much simpler if we stuck to man made processes. How much CO2 does the process create, how much does it sequester? Leave mother nature to do her thing, no one should get paid for it. After all she never gets paid for all the work she does for us. Just charge people if they get in her way.
Reforestation of our planet is absolutely necessary.
Reply | Report Abuse | Link to thisForests convert solar energy into basic food thus reducing the heating effect of energy reaching the surface of our planet. Forests moderate climate, store and recycle water draw up minerals from deep bellow the surface. Leaf litter and organic matter deposited by creatures living in forests are necessary for the processes that have evolved over millions of years to remain viable. Nothing is a weed in a forest.
For billions of years our planet has sustained itself and all its life forms without artificial fertilisers, tilling, dam building and all the rest of the tasks modern farming deems necessary to generate our needs.
Homo sapiens need to realise they are just another life form of no special significance. Knowledge is the only rewarding feature of existence once one has survived beyond childhood. If we hope to survive as a species we must understand our environment and respect the biodiversity that makes our planet sustain life.
When things go wrong, evolutionary pressures exterminate life forms that endanger the system. CO2 is not the cause of climate change, our population explosion is.
In the UK we now have successful use of heavy horses for forestry management which is proving to have other environmental benefits. Scientific Earthling is right though, we don't need any more people. Unfortunately capitalism is based on unending growth and so people are always encouraged to breed. To see the inevitable consequences just fill a petri dish with growth medium, add some bacteria and watch them successfully multiply to fill the plate until they run out of resources and all die to be replaced by something else.
Reply | Report Abuse | Link to thisWhy not thin the plantations periodically and turn the harvest into bio-char? This process could add much more carbon to the soil, while potentially generating electricity and heat.
Reply | Report Abuse | Link to thisCarbon sequestering must be rewarded if you expect people to do it. The lawyers will of course try to choke the process if allowed to. That is why laws must be made by congress instead of the courts. If judges did not try to make policy decisions it would not be a problem.
Reply | Report Abuse | Link to thisUsing horses for forestry management is used some in the U.S. as well. Capitalism's role in population growth seems twisted. Does your capitalist boss tell you to breed? Capitalism seems to do the opposite. The most successful capitalist countries have declining birthrates. The ones with the highest birthrates cannot support the people they already have. Primitive cultures are responsible for this. The modern societies feel guilty for their suffering and send them food to prevent starvation. They live to propogate even more without learning a thing. I agree with feeding them, but there must be change tied to this.
The earth can support more people when global warming increases rainfall and lengthens the growing season. The earth is in an interglacial period of an ice age. The interglacial period usually lasts 10-12k years and is already that old.
The earth has been warmer than this fairly recently. Take note that Greenland is now white and has been ever since the Vikings froze out after living there for 250 years. They practiced agriculture on land that is unusable for farming due to climate. Hannibal crossed the Alps with an army and elephants. Can anyone ride an elephant over the Alps today?
It has also been cold recently. It was possible to ice skate from Poland to Sweden and the Thames froze solid during winter during the 1600-1800 A.D. period.
Need to close that carbon loop on the tree plantations? Biochar the debris.
Reply | Report Abuse | Link to thisI followed the trail of this research and while I am still learning more it is already clear that the provocative title of this article is just hyperbole meant to attract readers. It worked. You got me, but I feel misled. It is more than a little disappointing that SciAm would stoop to the scary title just to grab our attention. I am assuming that the headline writer was indeed enough of a scientist to understand his manipulation. If not, it is even worse.
Reply | Report Abuse | Link to thisIt seems to me that the studies are very preliminary and concern forestation on sites that were previously grassland in Argentina and not reforestation or sites that have been in plantation for a long time. It would not be surprising if the first generation of growing trees would take-up nutrients previously stored in grassland soils and turf, much the way crops did/do when we plowed up prairie soils. Most plantations are NOT on these kinds of land. In fact, in the U.S. they tend to be on depleted soils already acid and already deficient in such things as P & N. These can be added using biosolids, which helps the trees sequester carbon and completes the ecological loop from flush to field.
BTW - carbon trading programs do indeed take into account carbon stored in soil, trees, roots and deadwood. Forests, however, are essentially carbon neutral once established, but that is another story.
This is an extremely important issue, popping out in Scientific American now and then.
Reply | Report Abuse | Link to thisAre the percentages portrayed the concrete numerical evidence that pine trees reduce the carbon-mitigating benefits? Moreover, was there any comparison made as to the amount of carbon dioxide absorbed by the living pine trees?
(btt1943)
We need the facts badly before drawing any conclusion.
That's good idea, though most of the trees we studied were used for commercial purposes. Since the lumber goes largely to paper pulp or saw timber, it would be hard to mulch it.
Reply | Report Abuse | Link to thisHowever, my co-authors and I suggest that leaving behind things like bark, leaves, and twigs (which contain high concentrations of several nutrients, but low commercial value) could help slow changes in soil nutrient status.
You are very right-reforestation is a vital process that has many benefits. However, there is a slight distinction here that we need to draw between reforestation and afforestation. Reforestation is the replanting of trees on areas that have been cleared by humans. This process has many benefits to people and the ecosystem. Afforestation is the conversion of land that was not historically forested into a forest. Our work focuses on the later process, afforestation.
Reply | Report Abuse | Link to thisAfforestation does indeed sequester a lot of carbon, but our point is that there is a price to be paid for this carbon sequestration. Afforesting lands that historically did not support trees is problematic since trees often have higher nutrient and water demands than the native ecosystems they replace. Native ecosystems develop based upon what the climate and soil will suport, planting trees is not necessarily always better than what previously existed there.
Thanks for the explanation. I think the SciAm staff did you a serious disservice by writing a silly overblown headline. It annoyed the heck out of me and I thought you were some kind of nut. It wasn't until I check out your reserach that I understood what you were really talking about.
Reply | Report Abuse | Link to thisIf I were you, I would complain about the title. This is the kind of thing that discredits real science and honest efforts to understand, and perhaps mitigate, climate change.
Thanks for the explanation. I think the SciAm staff did you a serious disservice by writing a silly overblown headline. It annoyed the heck out of me and I thought you were some kind of nut. It wasn't until I check out your research that I understood what you were really talking about.
Reply | Report Abuse | Link to thisIf I were you, I would complain about the title. This is the kind of thing that discredits real science and honest efforts to understand, and perhaps mitigate, climate change.
Re leaving the branches, bark etc, that is what we usually do in the U.S. We do lots of other things to maintain the fertility and do things like apply biosolids. You know that you are writing from Duke University right in the middle of America’s “wood basket”. It might be a good idea to take a better look at the forestry practices right outside town. I frankly don’t know what they do in Argentina on land that was naturally grassland, but in the U.S. we have come to practice pretty good forestry. A young loblolly pine plantations sequesters carbon faster than almost any other forest type.
How does New Zealand with its radiata pine plantations fare?
Reply | Report Abuse | Link to this