Page 143 - Environment: The Science Behind the Stories

ThE SCIENCE BEhIND ThE STOry

FaCE-ing a high-CO change in the carbon dioxide–soaked

Future 2 world that awaits us.
Dozens of organizations have
sponsored FACE facilities—36 sites in
Can fumigating trees with carbon
dioxide tell us what to expect from 17 nations so far, including U.S. sites in
global climate change? Hundreds of Arizona, California, Illinois, Minnesota,
scientists think so, and they are test- Nevada, North Carolina, Tennessee,
ing plants’ responses to atmospheric Wisconsin, and Wyoming. The sites
change at unique outdoor Free-Air CO cover a variety of ecosystems, from
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Enrichment (FACE) facilities. aspen Face site researcher dr. Mark forests to grasslands to rice paddies,
Our civilization is radically alter- Kubiske of the u.S. Forest Service and the plots range in size from 1 m to
ing Earth’s carbon cycle by burning 30 m (3–98 ft) in diameter.
fossil fuels and deforesting landscapes. open-air conditions, FACE experiments To understand how a typical FACE
Today the atmosphere contains over include most factors that influence a study works, let’s visit the Aspen FACE
40% more carbon dioxide (CO ) than plant community in the wild, such as Experiment at the Harshaw Experi-
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it did just two centuries ago, and the variation in temperature, sunlight, pre- mental Forest (where aspen trees are
amount is rapidly increasing. Rising cipitation, herbivorous insects, disease common) near Rhinelander, Wisconsin.
CO concentrations are warming our pathogens, and competition among Here, tall steel and plastic towers and
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planet, and global climate change plants. By measuring how plants pipes ring 12 circular plots of forest
brings many unwelcome consequences respond to changing gas composi- 30 m (98 ft) in diameter (Figure 1).
(Chapter 18). tions in such real-world conditions, we The pipes release CO , bathing the
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Plants and other autotrophs can better learn how ecosystems may plants in an atmosphere 50% richer
remove carbon dioxide from the atmos-
phere to use in photosynthesis, and all
organisms add CO to the atmosphere
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by cellular respiration (p. 50). Will more
CO mean more plant growth, and will
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more plants be able to absorb and
store much of the extra CO ? Perhaps,
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but before we rely on forests and
phytoplankton to save us from our own
emissions, we’d better be sure they
can do so.
Historically, if a researcher wanted
to measure how plants respond
to increased carbon dioxide, he or
she would alter gas levels in a small
enclosure such as a lab or a green-
house. But can we really scale up
results from such small indoor experi-
ments and trust that they will show
how entire forests will behave? Many
scientists thought not, so they pio-
neered Free-Air CO Enrichment. In
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FACE experiments, ambient levels of
CO encompassing areas of forest (or
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other vegetation) outdoors are precisely Figure 1 at the aspen Face facility in Wisconsin, tall towers and pipes control the
controlled. With their large scale and atmospheric composition around selected patches of trees.

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