Pine voles blamed for US oak declines

Scientists trying to understand why oaks are starting to disappear from North American forests may need to look just below the surface to find some answers, says a Purdue University press release.

Researcher Robert Swihart found that pine voles, small rodents that live underground, prefer oak roots to those of other common woodland seedlings.

The study identifies the rodents as a possible factor leading to high oak mortality rates that are threatening the resource base of the hardwood industry.

“You see a lot of mature oaks, but you don’t see a lot of oaks in the understory beneath the canopy,” observed Dr Swihart.

“If you don’t see them there, you won’t see mature oaks in 20 to 30 years.

“We are facing a period in our history that could lead to a great crash in oak availability.”

Dr Swihart offered pine voles a selection of tree roots to eat in the laboratory, and they overwhelmingly gravitated toward oak roots.

Voles caused more than twice as much damage to white oak roots than northern red oak and black cherry, and more than six times more damage to white oak than black walnuts.

The study showed that the voles snubbed yellow poplar roots altogether.

“Either the oak roots were much more nutritious and had higher energy content, or they contained fewer toxins, or some combination of those factors,” he explained.

“Those are the main reasons an animal will choose one food item over another.”

His findings have been published in the Canadian Journal of Zoology.

Source: Purdue University press release

Date: 03/03/2009

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