One reason for the lack of oak regeneration is the acidity of
the soil, according to at least one Penn State professor. But he
realizes he is alone in the state in his way of thinking.
“I am not alone globally in the way I think. In Europe,
scientists are on board with what I am saying, but here in
Pennsylvania I am the only one saying this,” said Bill Sharpe,
forest hydrology professor at Penn State.
“It is very frustrating sometimes but I have to be very
philosophical about it until everyone else figures it out
themselves … eventually,” he added.
He said he feels sorry for the deer hunters and the timber
industry.
“We all want the same thing – a very vibrant forest with clear
streams – we just have a disagreement on how we are going to get
there,” he continued, adding that he, too, is a deer hunter and
fisherman. “It would be good if we could get everyone together in
one study, but attempts to do that have been thwarted by political
interests.
“The way it is for me, if I am wrong, I am wrong. But let’s all
be honest. Let’s not weasel on the interpretations and just go on
ahead,” said Sharpe.
He adds that the soil in large areas of Pennsylvania are acidic
and always have been because the rocks they are made from are
acidic.
“Add on top of that the acid rain through the whole 20th century
we have had falling and it acidifies the soil further,” he said.
“This has resulted in altered growing conditions in any plant
growing in Pennsylvania today.”
He said that he has conducted some testing using liming of areas
to increase the ability of the soil to regenerate plant and tree
life such as oak.
“We have done some liming work and some chemistry replacing to
see what that does and we have had some great results, but we are
burdened by lack of funding – we don’t get help from the Department
of Conservation and Natural Resources (DCNR) or the forest
service,” said Sharpe. “They let us work on their property and
that’s about it.”
Sharpe added that there needs to be larger areas of testing with
liming, and he said it is not as expensive as some might
believe.
“At the state level we have proposed to use a large study area
to test – the forest agencies are reluctant,” he said, adding that
they may feel it too costly. “It (costs) is not as bad as fencing
and herbicide application.”
He suggests developing equipment to spread the lime rather than
aerial liming which could be costly.
While Stephen Horsley of the U.S. Forest Service’s Northeastern
Research Station (in Irvine) agrees with some of what Sharpe says,
he pointed to research which has indicated that deer overpopulation
is a significant factor in regeneration.
Horsley and Susan Stout, fellow silviculturist of the research
station, conducted a 10-year study which simulated the historic
range of deer density on the Allegheny Plateau in the 19th and 20th
centuries.
“We worked on a 10-year study where we had 10, 20, 38, or 64
deer per square mile in 32- or 64-acre fenced enclosures at about
160-acre sites,” he said.
“The study shows a dramatic impact on vegetation when you have a
large number of deer,” he added.
Sharpe, however, said without all of the acid in the soil,
plants and trees would grow enough that the number of deer browsing
would not make a difference.
He also adds that he does not feel that prescribed burning is
the answer.
“It is simply about replacing the nutrients in the soil – that
is what will regenerate these sensitive acid areas,” said
Sharpe.
“Acid deposition is a problem – I agree with (Sharpe.) It is a
problem that Pennsylvania receives some of the highest levels in
Western Pennsylvania in particular, despite the Clean Air Act of
1990,” he added. “And the numbers are still considerable for
sulfates and nitrates – they haven’t really come down.”
But again, he pointed out that even if those chemicals are not
good for the soil, tests conducted are not conclusive that oak
regeneration can be enhanced by liming.
Horsley described a study the research station is conducting
using four different amounts of lime, including none, two, four or
six tons per acre (of lime) used in a series.
“If the condition of the soil is a problem for oak, it should be
remediated by some of those (lime) rates – because we have used a
series of liming rates we should not miss the response. Since 1985
we have been conducting a liming study in sugar maple stands where
10 tons per acre of lime was applied,” said Horsley.
“Six tons per acre is a reasonably high rate of lime, so if
problems are caused by acid deposition effects – we should be able
to see an oak seedling response.”
He said they did not find any growth response in the oak
seedlings after two years, but they continue to look at six sites
they have around western Pennsylvania.
Horsley also said that while some species were not affected at
all with the liming tests at the sugar maple sites, others were;
sugar maple was greatly benefited by lime application.
One negative affect seen with the addition of lime in the sugar
maple study areas was a reduction in growth and increase in
mortality of black cherry.
“It seems to prefer more acid sites – it grows better in this
area of northwestern Pennsylvania than anywhere else in the world,”
said Horsley. “The finding that the addition of lime had a negative
impact (on one species) is an important one.”
Sharpe said that even though black cherry seems to be doing very
well in this part of the country (or world) he suggests that may
not always be the case.
“Every species has its tolerance, these things will drop out one
by one – who knows where we are headed? We can’t be too comforted
that the most valuable species is doing so well because that may
change in the future,” said Sharpe in closing.
