Eastern US: Pine Voles prefer eating oak roots which causes high Oak mortality
Swihart’s study has been published in the current edition of the Canadian Journal of Zoology. “A lot of the focus has been on what’s occurring above ground. We decided to look at what’s going on below the ground. We know pine voles can do a lot of damage in apple orchards, but there is little, except for a few anecdotal accounts, of what they do in their natural environment.”
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Under a variety of growing conditions, oak seedlings have
comparatively high mortality rates, allowing other trees such as
shade-tolerant maples and sun-loving, fast-growing tulip poplars to
make up larger percentages of hardwood forests. Most of the studies on
why oaks have a hard time regenerating have focused on competition
from other seedlings, the use of acorns as food for small animals
above the ground and the use of oak seedlings as food for deer.
Swihart got the idea for his study from Ron Rathfon, a Purdue
Extension forestry specialist in southern Indiana who has studied oak
mortality issues.
Rathfon found in 2006 that animals, later determined
to be pine voles, had been responsible for killing at least 19 percent
of the dead oak seedlings observed in his study area. He said the
voles, which are common to eastern deciduous forests, were likely
responsible for the majority of oak seedling mortality because many
seedlings went missing, suggesting the voles had eaten or removed the
entire plants. There is little overall loss of oak forest to date, but
Rathfon said that might change if foresters, the timber industry and
landowners do not implement practices that better manage long-term oak
growth and development.
“We do see some data that more shade-tolerant
trees – particularly sugar maples – are becoming more prominent,”
Rathfon said. “It is a gradual, subtle shift that is taking place.”
Swihart said the loss of oaks would have other serious effects besides
losses to the hardwood industry. “Oak mortality could reduce the
capacity of hardwood forests to support wildlife populations that rely
on oaks for food – everything from deer and turkey down to mice and
songbirds,” Swihart said. Purdue undergraduate student Leslie
Schreiber worked with Swihart on the pine vole study. Funding for the
work came from Purdue Agriculture.
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