OLYMPIC NATIONAL PARK — Nature already has provided a few surprises for workers tasked with replanting the wastelands where lakes Aldwell and Mills once drowned the forest, Olympic National Park restoration biologist Joshua Chenoweth said.
The biggest surprise is thousands of big leaf maple and cottonwood seedlings that are colonizing parts of the newly exposed lake bed and silt terraces that line the Elwha River, Chenoweth told about 30 audience members at a forum last week at the Port Angeles Library.
Chenoweth said he doesn’t know yet how many of those tiny seedlings will last longer than a year or two, but their very presence is a welcome, hopeful sign.
The cool summer has been helpful, but Chenoweth said a survey of plants at the end of August will be telling.
“If even 10 percent make it, that’s awesome,” he said Wednesday.
Chenoweth is the head of a seven-year program to bring green life back to the drowned forest valley.
It is part of the $325 million Elwha River Restoration Project, which includes the removal of the Elwha and Glines Canyon dams.
The Elwha Dam, which once sat about 5 miles from the mouth of the Elwha River, was removed in March, leaving only the Elwha River in the valley that once cradled Lake Aldwell.
The Glines Canyon Dam, about 14 miles upriver, had been cut down from 210 feet to 90 feet at the end of July, and Lake Mills is now a small, shallow lake in the northern portion of the valley behind the dam.
Chenoweth explained that natural processes would revegetate the lake beds eventually.
“We’re talking about a bowl, and everything hanging over that bowl is healthy,” he said.
But not everything falling into the bowl is desirable.
The process needs to be hurried to avoid colonization of invasive species to allow native and desired plants to establish themselves before the weeds can take hold, Chenoweth said.
Yarrow is included in the seed mixes for many of the locations being restored, including the protected hillside where the Elwha Dam power plant once stood, Chenoweth said.
“Yarrow is both native and invasive,” he said.
In this case, it is useful because it can help crowd out the invasive exotic species, he said.
Of the 150 species classified as exotic species known to be in the area, the team has classified 33 as invasive and harmful in the revegetation zones.
The worst of those are Canada thistle and reed canarygrass, Chenoweth said.
An entire stand of reed canarygrass on a high terrace in the Lake Mills delta had to be sprayed with a National Park-approved herbicide, to keep it from taking over, he said.
Scotch broom and Bohemian and Japanese knotweed also are problematic, he said.
Other exotic species can be friendly to native plants, adding nitrogen and other beneficial elements to create a healthy soil, and can be crowded out by native plants as they mature.
The crews are working to establish dense stands of woody, deciduous bushes and trees that will fill the spaces and drop leaves to help create new soil, Chenoweth explained.
There are “safe sites” that encourage and protect young growth, retain moisture and hide them from herbivores, enabling them to live through the first, most vulnerable stage.
Those sites include the lee side of logs and cracks in the drying silt layers.
This summer, crews will redistribute logs, most of which snagged on the shore near the historic lake shore as the water receded, to areas that have little protection and are showing less-vibrant plant growth.
One of the biggest challenges to replanting is the sheer volume of silt in the exposed lake beds.
The silt-laden delta at the south end of Lake Mills is up to 70 feet thick in some areas, Chenoweth said.
Much of it is thinning out as the river water carries it downstream, but there are places where the soil underneath is inaccessible for plants, he said.
On the valley walls, the layer separating seedlings from the fertile soils underneath is between one and four feet thick — something that many plants can handle, he said.
Just over half of the build-up is “coarse sediments,” ranging from fine sand to cobbles.
Chenoweth began learning which plants do best in the sediment, which lacks the nutrients found in soil, even before dam removal began.
Crews brought up buckets of sediment from the lake bottom and tried to grow potted trees in it.
The survival rate of the plants in various soils determined where the plants would be put in the ground, Chenoweth said.
Grasses do fairly well in fine sediment, he explained.
The fine sediments are mostly clay and fine silt smaller than grains of sand, and grasses do well because they have thin roots.
But because of their shallow root systems, moisture may become a problem as lake levels continue to drop and the silt loses the remaining lake water.
Chenoweth said that cottonwoods are uniquely suited to lowering water levels, because their root systems will chase water as it recedes.
He said he wasn’t sure their roots could chase it as quickly as the water level drops, though.
One of the worst performers was an array of evergreens, which were planted in 2011 and didn’t survive long, Chenoweth said.
The Douglas fir simply died, and western red cedar seedlings were eaten.
“It was like candy for the deer and elk,” he said.
Planting crews are preparing for the second season of planting.
Those working on Lake Mills include park employees, Washington Conservation Corps members and volunteers, while the Lake Aldwell is being planted by crews working for the Lower Elwha Klallam tribe.
The planting season is October through March, during which time crews will plant tens of thousands of plants representing 49 native species, Chenoweth said.
They will average 1,200 plants per day, he said.
It will be harder to move seedlings into the lake bed this year because of the river that runs through it.
“We used the lake to boat the plants to the other side,” Chenoweth said.
With the lake gone, thousands of potted plants will need to be carried by hand or four-wheeler to the planting sites, but park officials have not yet figured out how they will get to the other side of the river.
The use of a helicopter is possible but not desired, he said.
Reporter Arwyn Rice can be reached at 360-452-2345, ext. 5070, or at arwyn.rice@peninsuladailynews.com.
