UNIVERSITY PARK, Pa. -- Applying lime and fertilizer to areas where timber was harvested can dramatically improve the regeneration of trees, according to a researcher in Penn State's College of Agricultural Sciences, who just completed a three-year study of new forest growth in Somerset County.

In a paper published March 5 in the journal Forest Ecology and Management, Bill Sharpe -- a professor of forest hydrology who has chronicled the effects of acid rain in Pennsylvania for more than two decades -- maintains that soils in many places have become too acidic to support adequate new growth of some economically important species. "The addition of lime and fertilizer in combination with herbicide appeared to significantly improve growing conditions and resulted in taller and more diverse regeneration," he says.

The study was conducted in cooperation with the Pennsylvania Department of Conservation and Natural Resources' Bureau of Forestry. But in a finding sure to prove an eye-opener for that agency, Sharpe's research indicated that an herbicide commonly sprayed in the state to kill hay-scented ferns to promote tree growth actually made soils more acidic and elevated levels of aluminum, which is toxic to trees and other plants.

"Use of the herbicide may actually be making things worse," says Sharpe, who teamed with former graduate student Angela Schreffler on the study. "Chemical measurements of soil water revealed that the standard practice of herbicide application alone actually made soil water more acidic and increased aluminum concentrations."

The research was done on three sites where timber was removed in a "shelterwood cut," which Sharpe describes as "standard Bureau of Forestry practice, leaving quite a few trees behind to provide seeds for regeneration." The land then was fenced to keep deer out, and each site was divided into several research plots. Some plots received lime and fertilizer only, others received herbicide only, and others got lime, fertilizer and herbicide. Control plots were established where no materials were applied.

"Study data revealed that the benefits of liming were reduced by the relatively large amounts of sulfur deposited in forest soils as a result of many decades of acid rain," says Sharpe. "When herbicides were combined with lime and fertilizer treatments, woody seedling numbers, diversity and height growth improved significantly. Results were not as good for limed plots without herbicide treatment due to competition for growing space. But where ferns were damaged and partially eliminated by logging equipment, woody seedling growth was very good."

An increase of red maple trees in Pennsylvania forests has been noted in the last decade, occurring at the same time that northern red oaks have been decreasing in prominence, a trend that concerns many foresters. Sharpe believes his research has shown one reason why. "The red maple is a more acid-tolerant species," he says. "Residual red maple tended to grow better on the more acidic herbicide-only plots. In fact, it could be argued that the standard red oak shelterwood cut with herbicide treatment favored red maple growth."

Pennsylvania is downwind from the greatest industrial complex in the world -- the Ohio Valley -- and the state's forest soils have been polluted by acid precipitation originating from there for many decades. The acid comes primarily from sulfur dioxide in the emissions from coal-fired power plants in Ohio, Indiana, Illinois, West Virginia and western Pennsylvania.

"Pennsylvania long has been the victim of the most acidic precipitation in North America," Sharpe says. "Acid deposition increases soil water aluminum, which is toxic to plants and also lowers the availability of calcium and magnesium, which are essential elements for plant growth. We have a forest regeneration problem and a forest health problem in Pennsylvania.

"Our research group has been studying the relationships between these problems and acid deposition for the past dozen or so years. If you argue that the problem is poor growth due to acid rain-caused soil acidity and loss of calcium and magnesium, putting these nutrients back into the soil should fix the problem and indicate that your argument is correct. In this case, it appeared as though soil acidity was indeed a large part of the problem.

"The good news is that this study showed that with appropriate use of herbicide, lime and fertilizer, forests can regenerate very nicely in as little as two or three growing seasons."

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EDITORS: Contact Bill Sharpe at 814-863-8564 or e-mail at wes@psu.edu.

Contact:

Jeff Mulhollem jjm29@psu.edu 814-863-2719 814-863-9877 fax #126