[IMAGE: Pacific Lutheran Scene] 
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A c a d e m i c D i s t i n c t i o n


  Researchers get to the root
of a problem by heading
for the top

B Y  K A T I E  M O N S E N  ' 9 6

Student Tara Hudiburg '98, high above a branch of maple leaves, guides a rope on a pulley to bring supplies to her station on a 30-foot-high research platform in Pack Forest, Wash.

S ometimes the key to understanding a tree is to go straight to the top.

At the top is where you'll find Tara Hudiburg '98 on a sunny June morning. A mile or so into Pack Forest at the base of Mt. Rainier, she sits suspended in the trees on a 30-foot-high aluminum scaffolding.

There, high above the skinny gray trunks of the undergrowth, Hudiburg clips a leaf from a nearby big leaf maple, catches it as it falls and clamps it into the heavy pressure "bomb" she and biology Professor David Hansen hoisted up to the platform with a pulley.

On her five-foot-wide wooden perch a couple of stories above the bracken and sword ferns, Hudiburg uses gas from a nitrogen tank to slowly increase pressure on the leaf as it hangs upside down in a dense metal chamber, with just its stem exposed. She watches carefully until a drop of water appears at the stem, and records how much pressure it took to push that drop out.

Hudiburg works with confidence - she's done such experiments before, but never in the air. Up there, at the top of the tree, she has access to the leaves receiving the most sunlight. Since she's particularly interested in how the leaves lose water in the sun, this step up really is just that, a gain in altitude as well as the quality of her outdoor lab.

This is Hudiburg's second summer as an undergraduate researcher, thanks to a $339,000 grant from the M.J. Murdock Charitable Trust. This summer, 10 natural sciences students and five professors probed the realms of geosciences, chemistry, math and biology, supported by the grant. The students worked at the crossroads of theory and application, a crux known as active learning.

Such active learning has found quite a home in the natural sciences. Seven students supported by means other than the Murdock grant were also involved with summer research projects this year, part of the research community in Rieke Science Center. The whole group gathered weekly for lunch and student and faculty research presentations.

Hudiburg and Hansen's project picked up where it left off last summer, comparing the ways alder and maple trees manage water. Through observations and calculations, they determined that although maple leaves gave off more water during the day (through a process called transpiration), they still maintained a higher amount of water in them than alder leaves. So, despite a higher water loss, the maple leaves didn't tend to wilt as much as the alder leaves.

While wilted leaves may sound uninteresting, they open up a posse of questions for scientists to explore. Why don't the leaves of the two species behave the same? Do the differences have something to do with how and where the trees grow?

Not just scientists are interested in such research, however. While Hansen isn't working toward a particular practical application, he can quickly describe one. The alder and maple species that grow in this area are considered weeds. Their wood isn't of sufficient quality for furniture, Hansen said, and the trees can be used for little more than firewood. But when alder and maple come in to an area, they suppress conifer growth. And since conifers (particularly Douglas firs) are a key timber crop, the behavior of those "weed" trees may be of interest to forestry.

This summer, with the help of Megan Turnock '98, a biology major working on an independent study project, Hudiburg and Hansen are trying to provide answers to some of the newly-found questions. These answers are sought for themselves and other scientists, as well as for others (such as those in the forestry industry) who may make use of the results.

The project falls within the branch of biology known as ecophysiology, the study of how plants' physical nature and physiological functions determine how they fit into their environment, and why plants in similar conditions behave differently.

For example, red alder and big leaf maple are found in land that was clear cut or burned in a fire. They are pioneer species in secondary forests, as opposed to residents of virgin forests. Both trees tolerate large amounts of water and can grow well in shade and nutrient-depleted soil.

How the two trees spring up in a cleared-out area is a different matter. Alder comes into and spreads out in cleared areas quickly, while maple takes a little while to establish itself, but then takes over. The difference in their behavior may lie in their relative water uses.

To explore that hypothesis, Hudiburg and Hansen measure leaf temperature, the amount of sunlight striking the leaves, the rate at which the sap flows through the trees, the structure of the water-carrying cells in the tree, and many other bits of the trees' structure and activity. They attempt to "try to get a good feel for what these trees are doing," Hansen said.

With the numbers they get and comparisons they make, they will try to answer what causes the difference in the trees' relationship to water, and to determine if those characteristics are related to the trees' pioneering behavior.

"That's the fun part," Hansen said, "Trying to figure out what it all means."

The team is also comparing black cottonwood, another secondary forest species, to the alder and maple. At the Pack Forest site (owned by the University of Washington School of Forestry), the group monitors 12 trees, four of each kind.

Hudiburg and Hansen hope to run the project through September, until deciduous trees do what they do, and the leaves are gone.

After that, Hansen hopes to publish the research, putting the information out into the scientific community, where it can be questioned, used and researched further by others.

"It's not science until you share it with other people," he said. "Otherwise, it's just tinkering."

Students Tara Hudiburg '98 (left), Megan Turnock '98 and biology Professor David Hansen transfer information on leaf temperature from a datalogger to a portable computer to take back to PLU to analyze.

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Source: Pacific Lutheran Scene, Fall 1997
Edited by: Linda Elliott, Summer Senior Editor (elliotlm@plu.edu)
Maintained by: Webmaster (webmaster@plu.edu).
Last Update: 12/09/97