Ecologists clear firs to let ihn light for Washington's oaks

TACOMA, Wash. -- You don't have to visit Washington's old-growth rain forests to get a glimpse of the state's living history. It's in the lustrous leaves and rugged branches of surviving Oregon white oaks, which once dominated South Puget Sound prairies and still loom over some neighborhoods in Tacoma and the region.

"People don't realize how long-lived they are," said Connie Harrington, an Olympia-based forestry researcher who since 1999 has led a team of U.S. Forest Service scientists studying Washington's only native oaks.

Oregon white oaks can live 500 years or more, given the right circumstances. So it's possible that some of the South Sound's larger specimens sprouted before explorers such as Lt. Charles Wilkes entered Puget Sound in 1840.

Historically, Oregon white oak habitat ranged from British Columbia -- where they are commonly called Garry oaks -- to California. But the trees now occupy less than 1 percent of the area where they once were concentrated.

"It's incredible how much oak woodland has been lost," said Robin Dobson, a U.S. Forest Service botanist based in Hood River, Ore.

The reason? In urban areas, people have cut oaks to make way for roads, homes and businesses. On commercial timberlands, more valuable conifers have supplanted oaks. Elsewhere, oaks have died or are slowly dying because they can't compete with larger and more vigorous Douglas firs.

But as Harrington and her colleagues have found, oaks thrive if given a chance. All that's needed is to take them out of the dark.

"Oak trees love the sun," said David Anderson, a state Fish and Wildlife biologist based in Klickitat County, which at 195,000 acres has the state's largest concentration of Oregon white oaks. "They really don't like shade."

Biologists cite the oaks' importance to scores of species, perhaps most famously the vanishing Western gray squirrel. Its home on Fort Lewis includes 3,600 acres of oaks in areas that could be divided by a proposed cross-base highway.

The Army began trying to save oaks about 10 years ago by cutting firs that blocked the sun and selling the timber, said Jeff Foster, the post ecologist. Harrington's group has based much of its study on Fort Lewis, which provided several hundred thousand dollars in support, Foster said. The results have validated the post's oak conservation efforts.

"Even if these trees are pretty far gone, it looks like they can recover," Foster said.

Oregon white oaks are vital to wildlife as a source of food and a refuge for insects, birds and mammals.

Squirrels use oak woodlands like an aerial highway, a network of branches through which they race. They also rear their young in the trees. When oak limbs fall, cavity-nesting birds bore into the resulting hollows.

Oak acorns may be even more important to wildlife than any other food source, scientists have said. Of course, squirrels love the nuts. And in winter, deer paw the ground to find them.

"Everybody likes the acorns," Harrington said. "Woodpeckers, jays, band-tailed pigeons."

Even oak foliage is important. As browse for deer and elk, it provides as much protein as alfalfa, scientists say. Oaks also attract insects. For example, the larvae of the Propertius duskywing, a brown butterfly, hibernate in the leaves.

Before white settlement, American Indians periodically burned South Sound prairies and other valleys. The ground-level fires kept conifers at bay and encouraged the growth of comparatively fire-resistant oaks. This was important because tribes subsisted in part on the acorns and associated prairie vegetation, such as the bulbs of camas flowers.

Carri Marschner, Nature Conservancy land steward, has welcomed Harrington's help. She was happy to permit a Forest Service research crew to practice chain saw skills at the preserve by cutting down firs, which virtually imprisoned the oaks in shade.

"We definitely want to get all these mature oaks freed," she said as she watched crew members work.

E-mail Susan Gordon at susan.Gordon(at)thenewstribune.com

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