A
better method of measuring greenhouse gases
A few simple soybean plants may help solve a big question in the
debate over global warming and climate change. A team of professors
and graduate students at WSU is using soybean plants and a poplar
plantation to test a new method that will more accurately measure
the exchange of carbon between the earth's atmosphere and biosphere.
An ongoing problem in studying global climate change involves determining
just how much carbon dioxide is taken from the atmosphere and deposited
as carbon into world ecosystems. Scientists can estimate closely
how much carbon dioxide goes into the atmosphere from various sources,
but as yet know very little about how much is absorbed and stored
by carbon sinks such as oceans and forests. To solve this problem,
graduate student Maria Obiminda (Obie) Cambaliza and professors
George Mount, Brian Lamb, and Hal Westberg of the Laboratory for
Atmospheric Research are developing a new method of measuring vegetative
respiration quickly, flexibly, and accurately in the field.
The team used soybean plants to do their initial tests in the lab
because soybeans are fast growing and take in a lot of carbon dioxide.
They used a Fourier Transform Interferometer to detect the infrared
spectrum shift between carbon dioxide-13 and carbon dioxide-12;
since plants prefer carbon-12 to the more rare carbon-13 isotope,
changes in the ratio of isotopic concentrations between the two
can be used to measure plant respiration. The instrument can take
measurements every thirty seconds, thus providing an almost continuous
record of the levels of the carbon dioxide isotopes. Changes in
the soybean plants' respiration were recorded within seconds of
an artificial sunrise and sunset.
This summer Mount and Cambaliza tested their method in the field.
They set up a test site in a 100-square-kilometer stand of poplar
trees owned by Boise Cascade; with a large, homogenous concentration
of young, fast-growing trees that have a high respiration rate,
the area is ideal for taking measurements. Air was piped down from
various heights on a 25-meter-high tower to the instruments on the
ground, where measurements were taken continuously on site, twenty-four
hours a day. Previous methods required researchers to take sealed
samples from the field to be analyzed later at a lab-a cumbersome
process, especially considering that atmospheric samples usually
have to be taken at many points across a wide area, often in remote
locations. The combination of the tower and on-site instrumentation
allows researchers to take samples at any point, from the ground
to above the forest canopy.
Next summer Mount and Cambaliza will continue to test their instruments
at the National Science Foundation biological station near Pelston,
Michigan. The Washington State University researchers hope to make
their methods and instrumentation available for use by biological/atmospheric
researchers throughout the world. |
