Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Duke open-air experiment results could deflate hopes that forests can alleviate global warming

16.02.2004


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 1½ 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 1½ 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.

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu/

More articles from Ecology, The Environment and Conservation:

nachricht Robotic fish to replace animal testing
17.06.2019 | Otto-von-Guericke-Universität Magdeburg

nachricht Marine oil snow
12.06.2019 | University of Delaware

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

Im Focus: Tiny light box opens new doors into the nanoworld

Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.

Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Novel communications architecture for future ultra-high speed wireless networks

17.06.2019 | Information Technology

Climate Change in West Africa

17.06.2019 | Earth Sciences

Robotic fish to replace animal testing

17.06.2019 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>