Sometimes a researcher must go out on a limb, scientifically speaking, to find the facts.

For Dr. Robert Teskey, though, the facts were 40 feet up a loblolly pine tree.

In his three-year study of the effects of ozone and carbon dioxide on the growth of Southern forests, the forest resources professor frequently found himself in the uppermost branches of loblolly pines.

"We found that existing ozone levels are reducing tree growth from three to five percent a year in the Southeast," Teskey said. "That is very significant because trees live so long. If you think of that loss in productivity as compound interest, it's like money in the bank that accrues in a negative way.

"There's still a lot of debate about these very small numbers. But there is absolutely no doubt in our study that, if concentrations of ozone increase by even 50 percent, there will be dramatic and obvious effects on trees -- lower leaf area and significant growth losses," he said.

Reaching those conclusions was no small feat. Added to the sheer logistical difficulty of studying branches at the tops of pine trees was the fact that the technology for such a project didn't exist.

So Teskey created it. Four years ago, Teskey designed a technology called the branch chamber. For the first time, entire branches of mature trees could be enclosed and monitored. Today branch chambers are used at numerous research sites in the United States and Europe.

"Before this work, 95 percent of air pollution research on trees was done on seedlings," Teskey said. "For the ozone project, we needed to look at mature trees; using seedling data to predict the effects of ozone on mature trees is like studying an infant and predicting the kind of adult it will become."

With the branch chambers in place on full-grown pines, Teskey pumped varying amounts of ozone into them and measured the effects. Some branches received less ozone than exists in the air, others received the same amount as present in the air and still others received increasing levels of ozone.

Rates of photosynthesis, respiration and water exchange for each branch were measured over a two-year period. This data was used to develop a model for an entire tree. Along with information on growth patterns and tree physiology, the model simulated the effects of ozone on an entire pine forest.

The results were ominous for the future.

"Slower growing forests," Teskey said flatly. "I think the effects will still be relatively subtle. But if air pollution continues to increase in this region -- which I think is a certainty -- then we'll see a loss of economic revenue from forest products.

"We'll probably also feel it in terms of the aesthetic beauty of the forests. We may enter a scenario similar to the Black Forest in Germany, where you see more dead and dying trees," he said.

Contrary to its reputation for pristine pines and clean air, the Southeast is a hotspot for ozone. In fact, ozone concentrations in the region are second highest in the country, second only to California.

"Here we have all the right conditions for making ozone in the summertime," Teskey said. "We have stagnant air, hot temperatures, sunlight and the burning of fossil fuels."

With the ozone project completed, Teskey has now turned his attention to the effects of carbon dioxide and temperature changes on Southern pines. Still using the branch chambers, from precarious perches in the treetops he is trying to identify the loblolly's role in the absorption of carbon dioxide and the forest's influence on the global climate cycle.

"Working at such heights is a problem that increases the difficulty and danger of the project," he said. "Falling 50 feet to the ground is different than tripping and falling in a cornfield. But to me the challenge of understanding such large and long-lived organisms overrides the difficulties involved."

As the main timber and pulpwood species in the Southeast, the loblolly pine plays a vital economic role. But economic use is only one aspect of the forest.

The effects of ozone and other pollutants not only reduce pine tree growth, but diminish the general quality of the environment, and cost money in lowered production and high clean-up costs. They also may contribute to the loss of plant diversity.

"There's the chance that sensitive species or some genetic variations will be lost," Teskey said. "We know that species in the Smoky Mountains such as yellow poplar and red maple are being significantly impacted by air pollution. While such species have little or no value for productivity, they have tremendous aesthetic value."

The role of the forest in terms of aesthetics and biodiversity is becoming a very important issue -- and one that relates to the special link between humans and trees.

All in all, the tall order of the day may be in learning how to assure a healthy environment for the forest and people of tomorrow.

"Forests obviously have a unique relationship with man because we depend on their products, but at the same time we feel a certain need to be in them -- to go in them and get spiritual renewal.

"That sounds very hug-a-tree, doesn't it? I guess the take-home message about increasing levels of ozone and carbon dioxide is that we can't ignore the significant effect we're having on plant communities," he said. "We need to consider that the effects of man-made stresses can be as important as the natural stresses on our forests."

Lauretta Hannon is the assistant director of public relations and publications at Wesleyan College. She earned a bachelor's degree in comparative literature from the University of Georgia and was assistant to the director of research communications.