March 3, 2009

Study: Oak wood might soon disappear

A U.S. researcher has discovered why oak trees are starting to disappear from North American forests -- the culprits are pine voles.

Purdue University Professor Robert Swihart said he found the small rodents that live underground have a strong preference for oak roots to those of other commonly growing seedlings.

You see a lot of mature oaks, but you don't see a lot of oaks in the understory beneath the canopy. If you don't see them there, you won't see mature oaks in 20 to 30 years, Swihart said. We are facing a period in our history that could lead to a great crash in oak availability.

Swihart and his colleagues offered pine voles a selection of tree roots to eat in the laboratory. He said the animals overwhelmingly gravitated toward oak roots.

Either the oak roots were much more nutritious and had higher energy content, or they contained fewer toxins, or some combination of those factors. Those are the main reasons an animal will choose one food item over another, Swihart said.

The study appears in the Canadian Journal of Zoology.