Metro purchased the 1,200-acre Chehalem Ridge Natural Area in 2010, using funds from the region’s voter-approved bond measure to protect the forested land near Gaston.
Neighbors of Metro’s Chehalem Ridge Natural Area have seen a lot of change over the years. "I saw my first flying squirrel back in here," said one longtime farmer, leaning on a walking stick. He nodded to what was once an oak and fir woodland.
But on a rainy June Saturday, in an area densely planted in timber, the silence is conspicuous. No bird calls, no sudden scuttering of squirrels or snakes. Participants in a tour of Chehalem Ridge saw a forest floor unnaturally tidy and brown, littered only by fir needles. Trees are planted 8 to 10 feet apart in croplike rows. It’s an efficient landscape, profitable for the timber company that raised Douglas firs here for pulp.
For wildlife, not so much.
A work crew opened up this section of forest, which was planted with at least 500 Douglas fir trees per acre – roughly twice the density of a more natural, diverse forest.
Beginning this summer, Metro’s 1,200-acre Chehalem Ridge Natural Area will come back to noisy, dynamic life in a program of Douglas fir thinning, shrub and tree planting and removal of invasive species. Metro scientists and technicians are teaming with a Portland-based sustainable forestry firm, a father-son logging duo from Rainier, and students and researchers at nearby Pacific University to study the site, and plan and implement five to six years of restoration work.
This transformation has been in the making since early 2010, when Metro invested funds from a natural areas bond measure to buy this signature property near the small town of Gaston. Someday, when resources are available to develop visitor amenities, people are likely to explore trails and savor views of five Cascade peaks. For now Metro concentrates on creating a healthy landscape for wildlife and people, a commitment made at every voter-protected natural area.
Caring for the land is a big project in the Chehalem Mountains, south of the Tualatin Valley. Forming the valley’s southern boundary, they were uplifted by tectonic forces and blanketed with rich soils during the last ice age. Since the 1850s, people have planted orchard crops, wheat, wine grapes and timber on the mountains’ slopes. Nearly half of the Metro property is densely planted in fir — at least 500 trees to the acre. That’s roughly twice the density of a similar but more naturally evolved forest.
Metro’s long-term objective is to transform this industrial forest into what it had, for millennia: a diverse, wildlife-rich mosaic of old growth upland forest, nectar- and fruit-producing shrublands and shady, cool stream corridors.
Metro scientist Kate Holleran points out Chehalem Ridge Natural Area during a public tour of the property.
"The goal is land that has a high value to wildlife," said Metro natural resources scientist Kate Holleran, who is managing the restoration work at Chehalem Ridge.
That means a variety of tree species, tall trees with large-diameter limbs and natural cavities, and snags and down wood. In the work to create such habitats, Metro has a powerful ally: nature.
"The nice thing about this property is that the forest will change fast," said Scott Ferguson, lead forester with Portland’s Trout Mountain Forestry. His firm is working with Metro to thin and manage the land. "Only in Oregon and a few other places can you cut trees and, in two years, the land will look very different." Credit the rain and good soils.
Metro will monitor a mix of thinning styles
Work crews will thin trees to create openings of different sizes in the former timber plantation, with more trees coming down in larger openings. In 50-foot-wide openings, just one or a couple of "legacy" trees will remain. They exhibit what Ferguson calls "wolfy growth"— big branches and full crowns — that makes excellent habitat for wildlife. The varying opening sizes allow Metro to adapt its management plan once soils and plants begin to respond to the newly available light, water and nutrients. From 2013 through 2016, more thinning will take place.
"We’re thinning at multiple densities to learn how the forest will respond," Holleran said. "As time passes, we may realize, for example, that wide spacing is not going to work: that we’re having blow-downs or too many weeds. We may find, also, that tight spacing doesn’t provide enough growing space for forbs, grasses and shrubs to establish under the tree canopy. We are starting cautiously with a small area of thinning the first year."
Metro will also analyze how the understory, or lower-growing plants below the forest canopy, responds when competition is removed. "In the natural world, forest gaps occur in all different sizes," Holleran said. "Some are tiny: a big tree falls over, 20 feet of soil are exposed, and red alder comes in to colonize that." Some natural gaps are larger, caused by blow-downs or fires.
The 35 to 50 acres of timberland being thinned this year were once farmed for wheat, before being converted to timber production. These acres offer an excellent laboratory for forest managers as they observe results of different thinning strategies.
"It’s a really good situation," Ferguson said. "In fir plantations, timber companies manage the site and keep out invasives."
This relatively blank environmental slate offers Metro many options in its work to bring the land back to a more diverse state. In some of the newly formed gaps, shrubs, hardwoods and native perennials from Metro’s Native Plant Center will be planted. In others, the land will be left untouched, and scientists will watch what happens.
"In a natural forest, there is a native seed bank," Holleran said. "Since these lands were agricultural fields we don’t know if there is a native seed bank left, or if it was sprayed — or if it will respond."
A tour group explores the habitat at Chehalem Ridge, which will support more birds and other wildlife after this year’s forest thinning.
In addition creating a forest mosaic, thinning in the dense stands will create firebreaks that slow or stop wildfires. Other parts of Chehalem Ridge Natural Area were not planted in timber; they consist of a more open habitat of Oregon white oaks. There, limited thinning will remove firs and maples and provide the oaks with the light they need to thrive. These areas historically would have remained oak woodlands as fires — both human-set and natural — swept through and eliminated the oaks’ faster-growing competitors.
Timber removed will be sold as pulp, to help defray costs to restore the land. After the first thinning, firs grow rapidly; as remaining trees mature, those thinned over the next five years will be sold either as pulp or for lumber.
By 2016, when the thinning cycle ends, the land will have gotten a jumpstart in the natural habitat transitions created by centuries of fire, wind and other forces. As a group of interested neighbors stood in the rain, learning about the changes coming to Chehalem Ridge, one asked Ferguson, "What will you do when you’re finished?"
A natural area this large will always require monitoring and hands-on care. But, when it comes to forest thinning, Ferguson’s answer was succinct: "We’ll watch it grow."