Ecologists discover forests are growing faster

Feb 01, 2010

Speed is not a word typically associated with trees; they can take centuries to grow. However, a new study to be published the week of Feb. 1 in the Proceedings of the National Academy of Sciences has found evidence that forests in the Eastern United States are growing faster than they have in the past 225 years. The study offers a rare look at how an ecosystem is responding to climate change.

For more than 20 years ecologist Geoffrey Parker has tracked the growth of 55 stands of mixed hardwood forest plots in Maryland. The plots range in size, and some are as large as 2 acres. Parker's research is based at the Smithsonian Environmental Research Center, 26 miles east of the nation's capital.

Parker's tree censuses have revealed that the forest is packing on weight at a much faster rate than expected. He and Smithsonian Tropical Research Institute postdoctoral fellow Sean McMahon discovered that, on average, the forest is growing an additional 2 tons per acre annually. That is the equivalent of a tree with a diameter of 2 feet sprouting up over a year.

Forests and their soils store the majority of the Earth's terrestrial carbon stock. Small changes in their growth rate can have significant ramifications in weather patterns, nutrient cycles, climate change and biodiversity. Exactly how these systems will be affected remains to be studied.

Parker and McMahon's paper focuses on the drivers of the accelerated tree growth. The chief culprit appears to be climate change, more specifically, the rising levels of atmospheric CO2, higher temperatures and longer growing seasons.

Assessing how a forest is changing is no easy task. Forest ecologists know that the trees they study will most likely outlive them. One way they compensate for this is by creating a "chronosequence"—a series of forests plots of the same type that are at different developmental stages. At SERC, Parker meticulously tracks the growth of trees in stands that range from 5 to 225 years old. This allowed Parker and McMahon to verify that there was accelerated growth in forest stands young and old. More than 90% of the stands grew two to four times faster than predicted from the baseline chronosequence.

By grouping the forest stands by age, McMahon and Parker were also able to determine that the faster growth is a recent phenomenon. If the forest stands had been growing this quickly their entire lives, they would be much larger than they are.

Parker estimates that among himself, his colleague Dawn Miller and a cadre of citizen scientists, they have taken a quarter of a million measurements over the years. Parker began his tree census work Sept. 8, 1987—his first day on the job. He measures all trees that are 2 centimeters or more in diameter. He also identifies the species, marks the tree's coordinates and notes if it is dead or alive.

By knowing the species and diameter, McMahon is able to calculate the biomass of a tree. He specializes in the data-analysis side of forest ecology. "Walking in the woods helps, but so does looking at the numbers," said McMahon. He analyzed Parker's tree censuses but was hungry for more data.

It was not enough to document the faster growth rate; Parker and McMahon wanted to know why it might be happening. "We made a list of reasons these forests could be growing faster and then ruled half of them out," said Parker. The ones that remained included increased temperature, a longer growing season and increased levels of atmospheric CO2.

During the past 22 years CO2 levels at SERC have risen 12%, the mean temperature has increased by nearly three-tenths of a degree and the growing season has lengthened by 7.8 days. The trees now have more CO2 and an extra week to put on weight. Parker and McMahon suggest that a combination of these three factors has caused the forest's accelerated biomass gain.

Ecosystem responses are one of the major uncertainties in predicting the effects of . Parker thinks there is every reason to believe his study sites are representative of the Eastern deciduous forest, the regional ecosystem that surrounds many of the population centers on the East Coast. He and McMahon hope other forest ecologists will examine data from their own tree censuses to help determine how widespread the phenomenon is.

Explore further: International donors pledge $3bn to save shrinking Aral Sea

More information: www.pnas.org/cgi/doi/10.1073/pnas.0912376107

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User comments : 19

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jester0000
5 / 5 (4) Feb 01, 2010
Don't tell me we're starting to worry about forests and trees growing TOO FAST!
Thrasymachus
5 / 5 (4) Feb 01, 2010
I don't think anybody's worried, but it does offer another data point in support of the reality of global climate change, and this information will help scientists estimate how much we can expect natural CO2 sequestration processes to offset accelerated human emissions.
TegiriNenashi
2.3 / 5 (6) Feb 01, 2010
That "climate change" cliche dispersed all over the article is ridiculous. Trees consume CO2 (duh!) and grow faster when its level raised. This happens independently of global warming bogeyman (which is yet to be proven).
Skeptic_Heretic
3 / 5 (2) Feb 01, 2010
Trees consume CO2 (duh!) and grow faster when its level raised. This happens independently of global warming bogeyman (which is yet to be proven).
Not in all cases.

In areas where the fertilizer provides everything in abundance carbon dioxide is the most needed compound and so it spurrs growth. The Eastern US is very fertile so it shows. Just about anywhere the ice sheet covered in the US is forresting more rapidly as the soil is quite rich.

In areas that aren't so rich, the CO2 uptake isn't as great nor is the plant growth. You are right that trees take it in, but it isn't an end all be all. Besides, longer growing season has jsut as great an affect, especially on hardwoods.
PPihkala
not rated yet Feb 01, 2010
the mean temperature has increased by nearly three-tenths of a degree

Degree of what? Fahrenheit or Celsius?
GrayMouser
2.6 / 5 (5) Feb 01, 2010
I don't think anybody's worried, but it does offer another data point in support of the reality of global climate change, and this information will help scientists estimate how much we can expect natural CO2 sequestration processes to offset accelerated human emissions.

The climate is ALWAYS changing. The last 10000 years has been extraordinarily stable compared to what historical proxies indicate it normally is.
As far as human generated CO2?
1) It's out of the atmosphere in 5 to 10 years so it remains a small percentage of the total CO2.
2) CO2 effects on planetary temperatures is unproven and, given that the original greenhouse theory was falsified a hundred years ago, there doesn't seem to be any reason to worry about it.
3) Historically, atmospheric CO2 levels have always risen AFTER an increase in the average temperature, not before it.
dachpyarvile
3.3 / 5 (4) Feb 02, 2010
Over the last several days I have been reading a number of studies that show that a number of volcanos studied are sending up 13C depleted CO2 gas. In a few of the studies they have shown similar depletion of 13C in the CO2 that is seen emanating from biomass and so-called fossil fuels.

Granted, the authors of these studies attribute the 13C-depleted CO2 to biomass and magma incursions into carbon-laden substances attached to the volcanos. But, if more studies reveal something similar in enough cases, it will require a reassessment of the actual percentage of man's involvement in sending the substance into the atmosphere. Time will tell.

As to the article, I do not find the information above in the Physorg article relative to biomass growth much of a surprise. I am glad that it has been reported. It, however, remains to be seen as to how that relates to atmospheric CO2 and similar effects on trees elsewhere. I for one look forward to more articles concerning such.
PinkElephant
5 / 5 (3) Feb 02, 2010
@GrayMouser,

Given the three major "points" you listed out, I wonder if you might benefit from reading AIP's synopsis of the matter:

http://www.aip.or.../co2.htm
Shootist
2.5 / 5 (2) Feb 02, 2010
Freeman Dyson, et. al. documented this back in the 1960s and 70s.
Clickster
1 / 5 (2) Feb 02, 2010
"Parker and McMahon's paper focuses on the drivers of the accelerated tree growth. The chief culprit appears to be climate change, more specifically, the rising levels of atmospheric CO2, higher temperatures and longer growing seasons."

Let me see if I understand: trees are growing faster and CO2 is the CULPRIT?!!? Really nice to see totally objective, non-agenda driven journalism for a change.
3432682
2 / 5 (3) Feb 02, 2010
CULPRIT. Yeah, that additional PLANT FOOD (CO2) is a real terror. It's about time "science" and the media noticed the huge increase in plant growth, especially in agriculture. Oh, wait. That's good news. Never mind.
Skeptic_Heretic
1 / 5 (3) Feb 02, 2010
@GrayMouser,

Given the three major "points" you listed out, I wonder if you might benefit from reading AIP's synopsis of the matter:

http://www.aip.or.../co2.htm

It's lacking in it's coverage. No mention of Niels Bohr disproving the claim that the atmosphere was heated by absorbing infrared radiation (IR) with research that indicated the process of absorbing specific wavelengths of light changed the energy state of the electrons in gas molecules instead of increasing their temperature.
PinkElephant
5 / 5 (2) Feb 03, 2010
...the process of absorbing specific wavelengths of light changed the energy state of the electrons in gas molecules instead of increasing their temperature.

Um, yeah. Except it's not very relevant to the effect in question. The effect in question is that once so perturbed, those electrons eventually settle back down by re-emitting the extra energy as yet more infrared photons. And those photons are emitted in all directions equally (randomly), meaning that about half are aimed upward into space, while the other half are aimed downward back toward the ground: which raises the total amount of radiation directed at the ground, which raises ground temperature.

Granted, it IS kind of a long synopsis, but if one ACTUALLY reads it from start to finish, I don't think one would really walk away concluding that it "lacks in coverage." And at the very least, all of GrayMouser's points are actually addressed in some detail...
Skeptic_Heretic
1 / 5 (3) Feb 03, 2010
which raises the total amount of radiation directed at the ground, which raises ground temperature.


Well that brings you to Wood's experiment in which he found that delay of escaping energy does not increase temperature without an increase in environmental energy.

After that one needs to look at Dr. Gerhard Gerlich and Ralf D. Tscheuschner's work on GH Theory. http://arxiv.org/...61v2.pdf

Warning: long read

However, it's a deconstruction of the GHT through Thermodynamics and other known physical laws.
PinkElephant
5 / 5 (1) Feb 03, 2010
What's "environmental energy"? Is that like something that powers Green Peace? =P

As for arxiv paper you linked, I've read it. There are two observations I can make regarding it: 1) about 50% of it is polemic going after strawmen, and 2) it deliberately over-analyzes in order to obfuscate.

For example, compare its "treatment" of radiation budget (claiming intractability) and atmospheric greenhouse effect, with this:

http://eesc.colum...nir.html

Is the above a perfect model? No. But, for instance, one doesn't need to model the behavior of every constituent atom, in order to derive the first approximation for the energetics of a heat engine.

Lastly, I assume you understand that frequently in science, models exist that reproduce observations well even though such models were not derived analytically from any first principles. E.g.

http://www.aip.or...mary.htm

(see chart at the bottom, and the text right above it.)
vanderMerwe
1 / 5 (1) Feb 07, 2010
Well, it's obvious to me that we need to start a gov't funded programme to put these obese trees on a healthy diet of low CO2 air. :-)
Quantum_Conundrum
1 / 5 (2) Feb 07, 2010
I should get a MEDAL.

Trees > CO2 emmissions.

All we need to do is plant some trees and keep the Haitians from cutting them down...
ArtflDgr
1 / 5 (1) Feb 08, 2010
I don't think anybody's worried, but it does offer another data point in support of the reality of global climate change

hey! its a dingbat idea that everything leads to one conclusion... a large negative feedback thing actually does the OPPOSITE of what you just said.

but today we have replaced the god of the gaps with the equivalent of bill and ted of the gaps making crap up and pretending to make a principaled conclusion (but yet, cant explain the principals, and so its always one conclusion).

Skeptic_Heretic
not rated yet Feb 08, 2010
Lastly, I assume you understand that frequently in science, models exist that reproduce observations well even though such models were not derived analytically from any first principles. E.g.

And that serves to show us that we're missing something in the behavior of the observed. That would be the claim of all who think the science is not settled. Something has been missed.

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