http://www.duluthsuperior.com/mld/du...or/9463233.htm

Scientists study trees to get to root of pollution debate

ENVIRONMENT:Researchers in northern Wisconsin examine the effects of
high levels of carbon dioxide and ozone on forests.

BY JOHN MYERS

NEWS TRIBUNE STAFF WRITER

RHINELANDER, Wis. - Inside what conspiracy buffs might guess is a
communications center for UFOs, scientists instead are asking a very
down to earth question.

What are we doing to our trees?

About 60 researchers from seven countries are trying to find the
answer in northern Wisconsin, studying the impacts that elevated
carbon dioxide and ozone pollution have on aspen, birch and maple
trees.

Scientists are probing the soil for bugs and nutrients, electronically
monitoring how individual leaves and tree trunks "breathe," checking
how much water roots take up and conducting a dozen other major
experiments. So many scientists come here that they must be careful
not to bump into each other's work.

It's called FACE -- Free Air Carbon Enrichment -- and the effort is
revealing human impacts on forests never before documented.

In an abandoned farm field northwest of Rhinelander, researchers have
built 12 giant rings of PVC pipe around meticulously planted
experimental forests.

Each open-air ring, 100 feet in diameter with pipes 30 feet high,
contains 650 aspen, maple and birch trees planted in 1997.

For the past seven growing seasons, some of the trees have been
getting a dose of carbon dioxide equivalent to the level all forests
are expected to see later this century. Carbon dioxide, or CO2, is the
primary pollution created when coal, oil and gas are burned.

Some of the trees also are getting a daily blast of ozone, another
fossil fuel pollutant. Ozone, O3, is the kind of pollution once
associated with big city smog. Now, it's spreading across the globe to
inundate rural areas as well.

It's the only large-scale experiment in the world measuring the
effects of carbon and ozone on trees.

"We're trying to be a window into the future of what our forests will
look like under the elevated carbon dioxide and ozone levels that
we'll see a few years from now," said David Karnosky, director of the
FACE project and a Michigan Technological University scientist.

MORE CARBON, MORE OZONE

That carbon levels are way up isn't in question. Background carbon
dioxide levels in our air were stable at about 280 parts per million
for 100,000 years, according to data published by NASA. But during the
past 100 years, that's increased to 360 parts per million and
continues to rise at least 1.5 parts per million each year.

Carbon levels are expected to hit 560 parts per million by the end of
this century.

Ozone also is increasing rapidly, from about 10 parts per billion 100
years ago to more than 40 parts per billion today and higher than 80
parts per billion in urban areas during smoggy days. That's more than
enough to cause major damage to trees, the FACE experiment is showing.

What those levels of ozone and carbon dioxide, called greenhouse
gases, might do to global climate in coming decades is the subject of
heated debate. A majority of scientists say they probably will create
a warmer world. But the researchers in Rhinelander don't have a dog in
that fight.

"Our experiment has nothing to do with global warming. Whether or not
global warming is happening, the amount of carbon and ozone is
increasing. That's not in dispute," Karnosky said. "We want to know
the impact on trees, not on the weather."

THE DANGER OF OZONE

The findings are drawing interest on many fronts.

High doses of carbon dioxide make trees grow fast. That's exactly what
most scientists thought would happen, since carbon dioxide is the most
basic element trees need to survive. Trees inside of the carbon-only
rings are noticeably thicker, leafier and much taller than those in
nearby rings exposed only to natural air.

Ozone's impact is even more stark, but in the negative. Many trees
near the ozone-spewing pipes already have died. Those farther inside
the rings are stunted and prone to diseases.

Trees exposed to elevated levels of both carbon and ozone grow about
normally. The combined effects of increased carbon and ozone appear to
cancel each other out, although scientists aren't sure why.

Broader, long-term impacts of the experiment still are developing
along with the trees inside the rings.

"What does this mean on a landscape level, over a long period? The
answers to the most intriguing questions are still out there a few
years away," Karnosky said while examining an aspen branch inside one
of the rings.

While carbon-enhanced trees are bigger and grow faster, for example,
the entire ecosystem around them appears to be thrown off-kilter. The
same thing is happening around trees that get both carbon and ozone.

"Ozone at relatively moderate levels, not even high levels, negates
the productive effects of elevated CO2," said Kevin Percy, a scientist
with the Canadian Forest Service participating in the FACE project.
"We're talking levels that we already see in southern Wisconsin right
now, and levels that are expected to affect 50 percent of all forests
globally in a few years."

Mark Kubiske, a research plant physiologist for the U.S. Forest
Service and a FACE researcher, said ozone pollution probably already
has cut forest productivity in the Northland. One research paper
estimates aspen productivity has been cut 30 percent.

"Ozone is the most severe pollutant we have in the Lakes states. We
like to think of our air up here as clean. And it is, relatively,"
Kubiske said. "But, already, three or four days each month, we're
seeing ozone plumes that reach (the Northland) at levels enough to
cause harm to plants and trees."

CHANGING ECOSYSTEMS

Scientists also are finding abnormalities in the soil when trees are
exposed to higher ozone and carbon. Leaves die earlier each year, and
root systems are smaller, probably making the trees more susceptible
to drought.

Inside the high carbon rings, forest tent caterpillars increase in
numbers during their outbreaks. Leaf rust and aphids increase along
with carbon and ozone, and wood-boring insects do more damage.

But each type of tree reacts a little differently.

"There is a pretty big range of variation," Karnosky said, noting one
variation of aspen is doing better under higher ozone levels, probably
because its competition is dying off.

When carbon and ozone are increased, even forest composition -- the
types of trees that make up a forest -- may be changing. Birch trees
tolerate more ozone than aspen. If birch come to dominate over aspen,
as the experiment seems to indicate might happen, there could be major
changes in the type of trees available for paper and board mills and
for wildlife in our forests.

Grouse, deer and moose thrive off young aspen, for example, but not as
much off birch.

"We could have a substantive change in forest dynamics in just a few
years," Percy said. "Birch might be the winner in the northern forest
of 2050."

The future of our forests is a critical issue for the Northland -- for
quality of life, the timber harvest industry and tourism. Dense
forests define the Northland, provide habitat for its wildlife, filter
water for streams and lakes, and provide a living for many residents.

Any efforts to deal with carbon and ozone pollution worldwide, or a
lack of effort, will affect trees here at home. A similar experiment
in Illinois is looking at the pollutants' impact on crops.

"To the public in the Lake states, this is pretty important stuff,"
Kubiske said. The increasing levels of carbon dioxide and ozone
pollution "have the potential to affect just about everyone's lives up
here. You're talking about altering entire forest ecosystems and
possibly agriculture systems. People should pay attention."

CARBON SINK CLOGGED?

It's not just local impacts of a changing forest, however, but what
value our trees might have in helping to solve the global climate
change problem. Scientists want to know how trees react to carbon and
ozone to test a theory that northern forests may act as a carbon
"sink" that will help diminish the global carbon problem.

The increase in carbon, from burning fossil fuels that release carbon,
is being blamed by many scientists for raising global temperatures
enough to affect our climate. All that carbon dioxide is keeping heat
in like a greenhouse, the theory goes. It's already credited with
melting polar ice fields and glaciers, making plants bloom earlier
each spring and lakes freeze later each fall.

The carbon sink theory is that trees will absorb much of the excess
carbon now being spewed by power plants, cars and factories from
Connecticut to Chile to China. In some countries, tree planting
efforts already have begun to act as carbon "credits" so nations can
meet global agreements to reduce carbon.

But the Rhinelander scientists are exposing a pesky fly in the carbon
sink theory. When exposed to elevated levels of carbon and ozone in
the atmosphere, trees are taking in and storing less carbon in their
trunks and in the nearby soil.

Some of the young trees may even be giving off more carbon than they
absorb, contributing to the problem rather than helping it.

Increased exposure to the pollutants is causing increased respiration
of carbon.

"The potential of forests to have major impacts at reducing carbon
dioxide in the atmosphere isn't what some people predicted," Percy
said. "When you add in ozone to the equation, in many trees,
respiration of CO2 goes up."

The results could have a staggering impact on international carbon
reduction efforts as political discussions continue on how to solve a
growing global pollution problem. And if trees can't take more carbon
in, experts trying to solve the carbon problem will have to look
elsewhere -- probably at cutting carbon emissions instead.

"The results, hopefully, will speak for themselves," said Neil Nelson,
U.S. Forest Service liaison to the FACE experiment.

Kubiske agreed, noting he hopes policy-makers are listening.

"There's a lot we still need to tease out as we go forward," he said.
"But the preliminary results indicate that forests may not be as
important for carbon storage as was hoped. That's going to get a lot
of attention in the next few years all over the world."