Featured Research

from universities, journals, and other organizations

Duke Open-air Experiment Results Could Deflate Hopes That Forests Can Alleviate Global Warming

Date:
February 16, 2004
Source:
Duke University
Summary:
A futuristic Duke University simulation of forest growth under the carbon dioxide-enriched atmosphere expected by 2050 does not reinforce the optimism of those who believe trees can absorb that extra CO2 by growing faster, said a spokesman for the experiment.

SEATTLE -- A futuristic Duke University simulation of forest growth under the carbon dioxide-enriched atmosphere expected by 2050 does not reinforce the optimism of those who believe trees can absorb that extra CO2 by growing faster, said a spokesman for the experiment.

During seven years of exposure to carbon dioxide concentrations 1 times higher than today's, test plots of loblolly pines have indeed boosted their annual growth rates by between 10 and 25 percent, found the researchers. But "the highest responses have been in the driest years, and the effect of CO2 has been much less in normal and wet years," said William Schlesinger, a professor of biogeochemistry and dean of Duke's Nicholas School of the Environment and Earth Sciences.

These counterintuitive findings suggest that nitrogen deficiencies common to forest soils in the Southeastern United States may limit the abilities of loblolly pine forests to use the extra CO2 to produce more tissues as they take in more of the gas, he said.

"In a dry year trees naturally grow less so the amount of nitrogen doesn't make any difference," he said. "In a wet year, when there's plenty of water, the amount of nitrogen does make a difference." Tree growth depends on the availability of nitrogen, which foresters routinely add to Southeastern soils in the form of fertilizer when they plant trees, he added.

Schlesinger will report on the first seven years of results from Duke's Free Air Carbon Dioxide Enrichment (FACE) experiment at a symposium on "CO2 Fertilization: Boon or Bust?" beginning at 8 a.m. PT on Monday February 16, 2004 during the American Association for the Advancement of Science's 2004 Annual Meeting in Seattle.

Funded by the U.S. Department of Energy, Duke's FACE experiment is set up as an open-air test of how higher CO2 outputs produced by fossil fuel emissions and other human activities could change a Southeastern forest ecosystem about 50 years from now.

Most scientists believe rising levels of carbon dioxide and other "greenhouse gases" are warming Earth's climate somewhat the way a greenhouse does when it traps the sun's heat. Policy makers who drafted the Kyoto Protocol to counteract global warming envision that planting more trees will help because that will remove some of the CO2. Under this scenario, trees may also grow faster in the higher CO2 atmospheres of the future.

To test that hypothesis, scientists at Duke's FACE site mounted pipes and valves on three separate rings of towers to release extra gas onto the forested test plots the towers surround. The computerized system maintains CO2 concentrations of 1 times today's levels, regardless of wind or weather conditions. Three additional tower rings surround similar test plots but emit no gas, thus serving as experimental "controls." Scientists measure effects of the extra carbon dioxide by comparing results from the active and control sites.

The FACE tower rings are located in Duke Forest, a research reserve created out of former agricultural land that was replanted with trees. "Essentially there's no topsoil on that site," Schlesinger said. "The land was probably exhausted by cotton and tobacco farming in the 1800s and early 1900s."

Scientists at FACE had an unanticipated opportunity to assess how drought affects trees growing in a CO2 enriched atmosphere when 2002 proved to be one of the driest years on record in North Carolina, Schlesinger said. By comparison, 2003 was one of the area's wettest years.

"As the experiment has continued, we realized just how hard it is to see what ultimately controls tree growth -- whether CO2, water or soil nutrients," he added.

Apart from the impact of nitrogen deficiency and drought, the scientists have found some indication that pine tree growth declined over the years at the high CO2 levels, he said. The trees bathed in high CO2 also added more fine roots, which Schlesinger suggests is just another indicator of low nitrogen. "If trees don't have a lot of nutrients they grow a lot of roots looking for them," he said.

Meanwhile, some other species in Duke's CO2-bathed forest plots have grown at faster rates than the loblolly pines, scientists report. Still-unpublished data shows 70 percent growth increases for poison ivy, according to Schlesinger.

There is also evidence that the extra carbon dioxide has induced more underlying rock to weather into soil through dissolution by CO2-produced carbonic acid. While that action would also remove carbon dioxide from the atmosphere and "store" the remnants in the added soil, the impact would be "trivial" compared to expectations from boosted tree growth, Schlesinger said.

Based on available evidence from the Duke experiment, "I'd be surprised if the forests of the world will take up more than one-third of the carbon dioxide from fossil fuel emissions in the year 2050, which is what our experiment simulates," he predicted.


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Cite This Page:

Duke University. "Duke Open-air Experiment Results Could Deflate Hopes That Forests Can Alleviate Global Warming." ScienceDaily. ScienceDaily, 16 February 2004. <www.sciencedaily.com/releases/2004/02/040216083140.htm>.
Duke University. (2004, February 16). Duke Open-air Experiment Results Could Deflate Hopes That Forests Can Alleviate Global Warming. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2004/02/040216083140.htm
Duke University. "Duke Open-air Experiment Results Could Deflate Hopes That Forests Can Alleviate Global Warming." ScienceDaily. www.sciencedaily.com/releases/2004/02/040216083140.htm (accessed September 20, 2014).

Share This



More Earth & Climate News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Music With Recycled Instruments at Colombia Fest

New Music With Recycled Instruments at Colombia Fest

AFP (Sep. 19, 2014) Jars, bottles, caps and even a pizza box, recovered from the trash, were the elements used by four musical groups at the "RSFEST2014 Sonorities Recycling Festival", in Colombian city of Cali. Duration: 00:49 Video provided by AFP
Powered by NewsLook.com
Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins