MOUNT ST. HELENS — Thirty years after Mount St. Helens disgorged an avalanche of ash-laden mud, rock and earth down the North Fork Toutle River, filling the valley to a depth of 150 feet, water and gravity are relentlessly reshaping the surreal landscape of the Hummocks Plain.
These forces of nature are setting the stage for a future forest that will replace the one swept away by the eruption.
Alders and cottonwoods colonized the jumbled ridges and peaks early, fixing nitrogen in the soil. Some of those trees are now 40 to 50 feet tall and create the feel of an open woodland. On uneven ground they grow at a slant.
In places, the alders are interspersed with young Douglas fir, western hemlock and lodgepole pine, gnawed by elk from base to browse height into twisted, fantastical shapes. The hummocks are painted yellow with mosses and white with crusted lichens.
Cold weather has hung on this spring; two weeks ago, eight inches of snow fell on the Hummocks Trail, and frogs and salamanders had not yet emerged from the pools that dot the landscape.
But life lurked nearby: In early May, the alder woods echoed with the territorial call of the redwing blackbird, and two black-and-white buffleheads glided on a secluded pond.
North of the volcano, on the fan-shaped, 3,750-acre pumice plain, plant succession has occurred in fits and starts. Lupine and fireweed were early colonizers, followed by willow and alder.
But conifers have been slow to establish themselves on the harsh plain, where all life above ground was obliterated by the volcano’s pyroclastic flows of hot pumice and ash and Spirit Lake became a steaming cauldron of bacteria, microbes and dead trees.
“Firs come up, but most die” on the pumice plain, said Roger del Moral, a University of Washington botanist. “There are very few that survive. The nutrient levels are so low, the rate of growth is slow.”
Del Moral has studied the return of life to the mountain continuously since 1980. At elevations of 3,000 to 5,000 feet on the Muddy River south of the mountain, “The conifers have been able to invade pretty quickly,” he said. In the eruption’s aftermath, the Muddy was inundated by lahars, rivers of gravelly sand and ash. “The lahar material is much more fertile than the pyroclastic flows,” he said.
Over 30 years, Mount St. Helens National Volcanic Monument has become “the most thoroughly studied large-forest disturbance in the world,” says Forest Service research ecologist Charlie Crisafulli, who has monitored the return of plants and animals to the pumice plain and to the seeps and ponds of the debris avalanche along the Toutle.
Hundreds of scientists from all over the world have come to study every aspect of ecological recovery on the mountain.
Much of that work has involved documenting natural succession on specific plots of ground. Crisafulli established plots on the pumice plain, where virtually all life had been eradicated by the blast. He and others have been able to chart precisely how plants and animals, from prairie lupines and beetles to hemlocks and Roosevelt elk, reassembled in new communities in the years and decades after the eruption.
The National Science Foundation has supported the ongoing work of a handful of scientists, including Crisafulli and John Bishop, a biologist at Washington State University Vancouver.
“The NSF has recognized the extraordinary value of collecting data over time,” Bishop said. “The first 10 years, the money was easier to come by because of the special nature of what happened.”
These days, “All the NSF funding is highly competitive,” he said. “At any given time there are only a couple of active grants. There are always more good ideas than we have funding for.”
One issue Bishop would like to investigate further is the role of catastrophic disturbances in maintaining biodiversity.
“There are negative effects but also positive roles from disturbance,” Bishop said. At Mount St. Helens, “the biodiversity is extremely high in the disturbed areas,” such as the blow-down zone north of the mountain where all trees were leveled by the blast, he said. “A lot more trees and shrubs came back in the blow-down area.”
Undisturbed forests nearby are much less biologically diverse.
30 years of research
Del Moral won his first NSF grant to study ecological recovery on Mount St. Helens soon after the 1980 eruption. His work of documenting the development of plant communities in carefully monitored plots across the monument — and beyond — has been funded continuously by NSF.
The information biologists have collected and the locations of their plots will be archived in a public database “so anyone with a GIS can find the plots,” del Moral said.
After May 18, 1980, del Moral recognized a once-in-a-lifetime opportunity.
“I could sense that an eruption like that was unique in the world,” he said. “Kamchatka is distant and inaccessible. People in Iceland have to take a helicopter or a boat” to reach their active volcanoes. “This one was close to sophisticated people and facilities.”
He has studied disturbed landscapes across the globe, not only on volcanoes but on glacial forelands, dunes and mine tailings. Each site has lessons to teach.
For example, del Moral studied the colonization of a new island called Surtsey, 20 miles off Iceland’s main island, which emerged from the sea in 1963.
“It has only 64 species of plants,” he said. “They managed to get there by wind and sea currents and plenty of birds. Seagulls were very important in bringing in nutrients, whereas wind brought in seeds on Mount St. Helens.”
On both sites, isolation and a stressful environment slowed the establishment of plant life for several years.
What are the questions science has not yet answered?
One has to do with the difficulty of predicting how well early life forms will succeed on hostile terrain. At Mount St. Helens, “in the early stages we couldn’t use standard statistical methods,” del Moral said. “Over time, predictability increases.”
Nature takes its course
Back on the Hummocks Trail, it’s obvious how water is reshaping the landscape.
A large pond has become even larger with the expansion of a beaver dam that is now 4 to 5 feet high and 450 feet across. Industrious beavers gnawed alder trunks and branches, stacked them high and sealed them with mud mortar, slowing the flow of water and creating a pond where a wetland had been.
Exposure to sunlight increases nutrients in the pond, encourages the growth of algae and attracts insects and pond-dwelling amphibians like frogs and salamanders.
In several places, the constantly shifting North Fork Toutle River and the unnamed rivulets that feed it have washed away sections of the Hummocks Trail. Trail sections have been rerouted and new footbridges built, mainly with volunteer labor.
Where the trail comes out onto the shore of the wide canyon of the Toutle, you can see how the river has eaten away at its banks, sending young alders tumbling downslope.
“The hummocks area is gradually being carried downstream,” monument scientist Peter Frenzen said. “Water and gravity reign.”
A sign near the end of the Hummocks Trail says it all:
“The hummocks will continue to change with every rainstorm slump and pond breakout. The appearance of life will soften this sharp, chaotic landscape with time.”
However, the regeneration of life around Mount St. Helens has not always followed a natural course. Human intervention has left its mark.
Someone, or some people, illegally planted trout in Spirit Lake early on, dramatically altering the lake’s ecology.
After the hummocks were reseeded in the early 1980s to reduce erosion, elk by the hundreds gravitated to the Toutle River Valley. In severe winters, dozens of the animals starved, prompting state wildlife officials to bring in hay and even to relocate some animals.
Recently, 3,800 acres owned by the Washington State Department of Transportation were added to the wildlife management area to increase the elk herd’s range.
But ecologically speaking, the abundance of elk has had its positive side, Frenzen said. It’s been a boon to predators, fattening coyotes and drawing black bears and even wolverines.
On the Hummocks Trail, exotic species like Scotch broom and knapweed have invaded, forcing the Forest Service to mount a battle to control them.
“We pick our battles with invasive species,” Frenzen said. “One three-year-old Scotch broom plant can produce 10,000 seeds per year and can remain viable in the soil for up to 60 years.”
Will the lush forests that carpeted the slopes of Mount St. Helens before the eruption return in some distant future?
Roger del Moral is not optimistic.
“Probably the cynical answer is that in 500 years the climate there will be like southern California,” he said. “People will be desperate for resources, parks will be overrun with people. What kind of vegetation will be available to recolonize the area?
“Whenever you rerun the tape, you get another answer.”