University scientists in plant pathology and forestry hope to move to the front of air pollution research with the recent addition of a new high-tech greenhouse.

The 4,000-square-foot greenhouse, located behind the Forest Resources Lab, is equipped with the most modern facilities for researchers to study the impacts of acid rain, ozone and sulfur dioxide on vegetation, said John M.Skelly, professor of plant pathology.

Acid rain, one of the top environmental issues of the '80s, results when sulfur dioxide and nitrogen oxide are oxidized in the atmosphere, forming sulfuric acid and nitric acid. Large quantities of these two oxides are produced from the burning of fossil fuels.

Ozone, another critical pollutant, forms when sunlight reacts with nitrogen oxides and hydrocarbons in the air. A majority of these chemicals come from such sources as automobile emmissions and power-generating stations.

Experiments in the new greenhouse will be designed to develop a better understanding of the role of these two pollutants in forest tree disease and dieback.

William Merrill, professor of plant pathology, explained that the role of air pollutants in forest tree disease and dieback is poorly understood.

"Although scientists have frequently correlated forest decline with high levels of acid rain and ozone, there is still no complete evidence that these pollutants have a direct effect on forest trees," he said.

Acid rain and ozone are not the only factors that may injure trees, he said. Merrill explained it is crucial to consider all factors that may affect the health of a tree before making conclusions about possible causes for decline.

In addition to acid rain and ozone, droughts, insects and disease attacks may also put enough stress on trees to cause diebacks, he said.

"One theory of forest decline is that acid rain and ozone combine to cause nutrient leaching from foliage and forest soils," Merrill said. "This weakens trees and leaves them more susceptible to damage from such factors as insect or disease attacks."

The new greenhouse will enable researchers to create precisely controlled growing conditions for experimental plants. With this control, the impact of a single factor, such as acid rain, may be better understood.

By growing all plants under similar conditions, while varying only the concentration of acid rain, the true effects of the pollutant may be revealed.

"The growth chambers containing experimental plants will be computer controlled to deliver and monitor precise amounts of acid precipitaition, ozone and other gaseous air pollutants," he said.

Another unique feature of the greenhouse experiments will be the use of pollutant-free air, Skelly said. A charcoal filtering system will remove all air pollutants that otherwise might affect test plants.

"Here in central Pennsylvania, as in most of the East, the air is of such quality that it would have an effect on (experimental) plants. The filter system helps us to avoid this problem," he said.

In addition to pollutant delivery, the chambers will also be controlled to regulate other plant growth parameters, such as temperature, soil moisture, relative humidity, and light quality.

"Essentially, we can grow a plant in here and the plant will think that it is actually growing outside," he said.

Skelly, Merrill and two graduate students in plant pathology, Tina Dreisbach and Reante Hellman, will begin using the greenhouse this summer to study a widespread disease of Eastern White Pine, the most widely distibuted pine species in North America.

"The disease, (needle blight), has been recognized in the East since the early 1900s," Merrill said. "To this date, no one knows what the cause is."

Studies so far have only focused on one of the factors that may have caused the disease, such as a drought or an insect attack, explained Merrill.

The new greenhouse will be used to study the interaction among several disease factors -- acid rain, ozone and fungi -- in all possible combinations .

This will give researchers a more realistic picture of the actual disease conditions in nature, Merrill said.

In another project, Skelly and Donald Davis, professor of plant pathology, will use the gas-controlled chambers to screen 12 different hardwood species common to Pennsylvania forests for sensitivities to ozone, sulfur dioxide and acid rain.

Symptoms of damage due to varying exposures to acid rain, sulfur dioxide and ozone will be evaluated over the entire project, which is expected to last three years.

Skelly and others will also use the greenhouse to search for similarities between Norway Spruce tree decline in the Northeast to the well known forest declines in the Black Forest of West Germany.

Preliminary field studies have found that some extensive Norway Spruce plantations planted in the '30s are showing similar symptoms of decline as those in Germany, said Skelly.