Argonne, UIC researchers get the dirt on prairie soil
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ARGONNE, Ill. (Dec. 7, 2007) — Researchers from Argonne National Laboratory
and the University
of Illinois at Chicago have dug up some interesting dirt on prairie soil
and certain crops and grasses common to the central Midwest.
"Beyond growing crops like corn and soybeans, prairie soil is better
than soils found in other parts of the United States at retaining carbon dioxide," said
Roser Matamala, a terrestrial ecologist in Argonne's Biosciences
Division and
the principal investigator of two projects that measure the intake from and
release of carbon dioxide into the atmosphere. In addition, her research has
found that certain types of vegetation are better than others at absorbing
carbon dioxide.
The projects are located on an active farm site and a restored tallgrass prairie
at the National
Environmental Research Park on the grounds of the Fermi
National Accelerator Laboratory in Batavia, Ill.
The absorption and retention of CO2 by plants and soil, respectively,
is beneficial because it means less of the greenhouse gas lingers in the atmosphere,
absorbing the Sun's heat and contributing to the increase in Earth's average
temperature, Matamala said.
Data collected at the two research sites show that tall prairie grasses absorb
more CO2 per square meter in one year than corn and soy, she said,
adding that soybeans absorb the least amount of CO2. Tall prairie
grasses, which are common in Illinois and other parts of the central Midwest,
absorb up to 480 grams per square meter compared to 250 grams for corn.
Most absorbed CO2 is used by the plants as a fuel, Matamala
said, but it also becomes part of the plant, including the seed and grain.
Much of the absorbed CO2 in food crops like corn is harvested.
A substantial portion of a plant's absorbed CO2 is transported to the soil
regardless of the type of plant. The CO2 that is transported to the soil is
eventually converted into organic matter; that conversion process continues
for centuries before the soil becomes saturated, creating a sustained terrestrial
carbon sink, an accumulation of absorbed carbon. Carbon that gets to the soil
by this process does not accumulate in the atmosphere, thereby mitigating global
warming.
Prairie land's ability to retain high levels of CO2 is an important feature
of the vegetation and soils in the Midwest, Matamala said. Virgin prairie
land – land that has never been cultivated – is richer in organic matter compared
to restored prairie land. Organic matter makes soil dark in color.
Virgin prairie land has greater amounts of carbon than cultivated fields and
restored areas, such as found at the Fermilab site, because it is not disturbed
by cultivation, Matamala said. Plowed soil respires, releasing CO2.
The restoration of farmland leads to greater retention of CO2, she said. "The
soil in the prairie keeps more carbon dioxide in the winter compared to other
regions," Matamala said. Because the Midwest has longer periods of cooler
to cold temperatures, less CO2 is respired from the soil. And when the soil
freezes, less CO2 is respired. Conversely, warm to hot temperatures and humid
conditions activate microorganisms in soil and the microorganisms use the organic
matter to grow; that process respires CO2 back into the atmosphere. Cultivated
lands lose more soil carbon during spring and fall months compared to restored
prairie land because the microorganisms in the soil are activated by warm temperatures
and soil plowing.
The two projects are part of the AmeriFlux
Network, a coordinated collection
of long-term research sites in the Americas that are organized to quantify
and understand the role the terrestrial biosphere has in global climate change.
The goal of the AmeriFlux project is to collect data that computational scientists
use to refine the resolution of climate change models.
"Refining the resolution of climate models can provide a better picture
of what is happening in small geographical areas like cities, counties and
states versus large geographical regions," said Robert Jacob, an Argonne
climate modeler.
The project's research data is collected by two eddy covariance towers. One
tower is located on a farmland that rotates corn and soybean corps under tillage.
The other tower is located in a field that was restored with native grassland
species in 1989 and represents long-term Conservation
Reserve Program management.
AmeriFlux is sponsored by the U.S. Department of Energy's Office of Biological
and Environmental Research, the Department of Commerce's National
Oceanic and Atmospheric Administration, the
Department of Agriculture and the National
Aeronautic and Space Admininstration.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
The nation's first national laboratory, Argonne conducts leading-edge basic
and applied scientific research in virtually every scientific discipline. Argonne
researchers work closely with researchers from hundreds of companies, universities,
and federal, state and municipal agencies to help them solve their specific
problems, advance America 's scientific leadership and prepare the nation for
a better future. With employees from more than 60 nations, Argonne is managed
by UChicago
Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
For more information, please contact Angela Hardin (630/252-5501
or ahardin@anl.gov) at Argonne.
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