Turf Batttle: Invasive Plants Threaten St. Helens Ecosystems

Native Plants Magazine, Winter 2005/2006
By Roddy Scheer

As I stand atop Coldwater Ridge on this sunny summer afternoon, it's hard to believe that only 25 years have passed since the eruption of Mt. St. Helens turned the now verdant scene spread out before me into a barren moonscape. From my vantage point, a multi-colored wildflower carpet jockeys for space with abundant willow, alder and western hemlock trees in the foreground. Further out--seven miles away to be exact--the volcano itself, complete with its gaping crater and smoldering lava dome, stands defiantly, occasionally hinting at the fire down below by sending up puffs of white steam against a contrasting turquoise blue sky. Dressed up in Mother Nature's mid-summer finery, this teeming landscape hardly seems like it could be the same place described in accounts following the 1980 eruption as dark, desolate and lifeless.

But indeed, it is. Twenty-five years earlier, at 8:32 a.m. on the morning of May 18, 1980, the volcano exploded with the fury of 500 atomic bombs, launching ash 60,000 feet skyward while spewing pumice, rocks, and super-heated gases across 230 square miles of pristine Pacific Northwest forest. The unexpected lateral blast that day turned the whole north side of the mountain into the largest landslide in recorded history, burying nearby lands in hundreds of vertical feet of volcanic debris and, further out in the so-called "blast zone," knocking down millions of trees like so many toothpicks in the wind.

Even though they knew the blast was big, scientists were still amazed when the dust cleared by the sheer amount of destruction they saw. The massive eruption had literally sterilized thousands of acres of land left in its wake. Realizing they had a unique opportunity to watch the region restore itself from scratch, scientists urged elected officials to set aside the affected lands as off-limits to resource extraction and development. Congress obliged, creating the 110,000 acre Mt. St. Helens National Volcanic Monument in 1982 in order to facilitate research and education on the nature of volcanic eruptions and their effects on the surrounding landscape--in the absence of human intervention.

In the subsequent quarter century of monitoring and analysis at Mt. St. Helens, researchers have already gleaned secrets heretofore unknown to science not only regarding volcanic eruptions, but perhaps more importantly about the way Mother Nature handles ecosystem restoration, if left to her own devices. And while each individual discovery has proven significant in its own right, the biggest surprise overall has been the rapid rate of recovery on the lands surrounding the volcano.

Within two years of the eruption, for instance, researchers were amazed to see pretty little purple flowers sprouting up on the decimated pumice plain directly beneath the volcano's exposed crater. Scientists speculate that these hardy Prairie Lupine ( Lupinus lepidus ) plants, native to the Pacific Northwest, must have arrived in seed form via the wind and then taken root at some point following the eruption. Regardless of how they got there, though, the lupines were playing an important ecological role by improving soil quality for subsequent colonizing life forms.

  "Lupine has an association with a bacteria that takes nitrogen from the air and converts it into a form that other plants and animals can use," says Virginia Dale, a plant ecologist currently with the Oak Ridge National Laboratory who has devoted a significant portion of her career to research on ecosystem responses to the 1980 Mt. St. Helens eruption. "Since the volcanic material on the ground following the eruption had very low nutrient composition, the nitrogen provided by the lupines gave a tremendous pulse to the conditions so that when other plants came in, they had this critical element available to them."

Indeed, within just a few more years it became apparent how well the lupines--both the aforementioned Prairie variety as well as the stouter Broadleaf Lupine ( Lupinus latifolius ) --had done their job. By the mid-1980s, a panoply of color was running up and down the recently devastated ridges surrounding Mt. St. Helens during the summer flowering seasons. Fireweed ( Epilobium angustifolium ), Common Red Paintbrush ( Castilleja miniata ), Cardwell's Penstemon ( Penstemon cardwellii ) and other wildflowers--many of them more typical in higher elevation alpine meadows on the flanks of neighboring Cascade peaks like Mt. Rainier and Mt. Adams--were standing shoulder-to-shoulder with the ever-increasing lupine, dazzling researchers and weekend day trippers alike.

  "For vigorous colonizing early successional species, Mt. St. Helens was quite an opportunity," says forest ecologist Peter Frenzen, who came to work for the U.S. Forest Service at Mt. St. Helens soon after the 1980 eruption. Today, Frenzen serves as Monument Scientist, which means he is responsible for coordinating on-going research, transferring scientific findings to visitor information programs, and monitoring the recovery of plant and animal life at Mt. St. Helens.

Frenzen defines the concept of ecological succession as the pattern of one community of plants and animals gradually replacing another in response to changing environmental conditions in a given region. Many wildflowers are considered "early successional" species by ecologists, meaning that they colonize disturbed or otherwise open lands, where they can get lots of sunlight to produce lots of seeds while serving as an excellent food source for flying and crawling insects and other discriminating creatures. In contrast, old-growth Douglas fir trees--tens of thousands of which were blown down by hot gases during the 1980 eruption--fill in on terrain late in the successional cycle, and can live on as the dominant species in the forests of the Pacfic Northwest for thousands of years--barring any natural disasters killing them off early, that is.

"The forest had been stripped off and there were varying degrees of organics in the deposits," elaborates Frenzen. "So these [wildflowers] responded to a flush of available nutrients and also, most importantly, available sunlight."

But along with the rush of native colonizing plants that scientists expected to show up on the devastated lands came some uninvited guests as well. And while some of these non-native plants found their way into the national monument on the bumpers of cars and the heels of hikers, land managers have only themselves to blame for dispersal of some of the so-called invasives. Indeed, just a few months after the 1980 eruption, the U.S. Forest Service made an ill-fated attempt to stabilize fragile terrain throughout the decimated "blast zone" via aerial seeding with non-native grasses and legumes. Most of the seeds failed to take root in the nutrient-deprived volcanic deposits, though, so the effort was declared a bust and quickly abandoned.

But unfortunately one of the non-native legumes, Birdsfoot Trefoil ( Lotus corniculatus ), took root gradually and began spreading from the flanks of the volcano throughout the subsequently designated national monument. Today, researchers worry that the plant, which sports pea-like yellow flowers in the summer and was originally brought to the U.S. as a garden ornamental from Europe--could crowd out native plants vying for survival in the post-eruption landscape.

Plant ecologist Dale, who has been monitoring succession patterns in research plots along Mt. St. Helens' debris avalanche, is disheartened by the profusion of Birdsfoot Trefoil there.   "What we find is that even though there is greater plant cover in those plots that have the Birdsfoot Trefoil, there are less native plant species and lower diversity in general, so it is having an effect," she says.

While Dale laments the fact that aggressive non-native species were used for the aerial seeding efforts, she acknowledges that back in those days, regional native plant nurseries did not exist, so land managers had few if any choices regarding which types of stabilizing plant species to use. She finds the fact that the seeding didn't even work to achieve its desired effect yet still caused major environmental problems particularly irksome, though.

Meanwhile, Frenzen is focused on his own non-native plant bugaboo, Scotch Broom   ( Cytisus scoparius ), another European ornamental garden import run amok. With limited resources and seemingly inexhaustible sweat equity, the soft-spoken scientist is deeply invested in a Herculean--and some would say Sisyphean--effort to rid the national monument of the tall and stalky green plant with the handsome yellow blooms, which is prevalent on adjacent private lands and thrives in open clearings. Frenzen is particularly concerned about Scotch Broom not so much because it doesn't belong there in the first place, but because it has the potential to interrupt the natural expected pattern of ecological succession on the land.

"Most early colonizers will be around in the early succesional stages, but when the shrub layer and forest vegetation come in and start shading things, these plants tend to drop out," he says. "But Scotch Broom is one that has the potential to colonize and then hold a site, to the exclusion of other species."

For the last several summers Frenzen has assigned graduate student interns to detect and remove Scotch Broom on acre-by-acre sweeps of the national monument. The students mark the "infested" areas with GPS coordinates, and then Frenzen and other staffers can monitor recurrence following initial removal efforts.

Frenzen has also pressed inmate work crews from Cowlitz County, which holds jurisdiction over the north side of the national monument, into service in keeping Scotch Broom in check. These supervised crews from the county jail travel up to the flanks of Mt. St. Helens as much as three times a week for 10-12 hours to manually remove Scotch Broom where staffers and students have identified it taking hold.

Carol Chandler, a wildlife biologist with the U.S. Forest Service, concedes that trying to manually extract Scotch Broom--infamous for its prolific seed generation and dispersal abilities, not to mention its adaptability to new environments--is an uphill battle at best. "Unless you totally remove every root, Scotch Broom is not gone," she says. "So it's a difficult one to just try and weed-wrench or hand-pull."

Chandler is overseeing completion of an Environmental Impact Statement (EIS) regarding implementation of various techniques to control and/or eradicate 33 aggressive non-native plant species, including Scotch Broom, within the national monument and beyond in the surrounding Gifford Pinchot National Forest.

One contentious part of the EIS is its recommendation to utilize chemical herbicides to keep various aggressive non-natives in check. After reviewing scientific literature and field reports from other Forest Service scientists, Chandler believes that using herbicides may be the only way to prevent the monument from being overrun by noxious weeds to the exclusion of native plant and wildlife species.

For his part, Frenzen would welcome the opportunity to use herbicides to complement on-going manual eradication efforts, despite his commitment to restrict human manipulation of lands within the monument. "Having the area covered in Scotch Broom is not consistent with the purposes of the monument, because it's an introduced exotic," he says. "People want to come to see the natural succession, not Scotch Broom fields."

Despite lingering debate about whether applying synthetic chemicals around Mt. St. Helens qualifies as "letting nature run its course," Chandler is optimistic that monument land managers will be able to use herbicides by the end of 2006. While Scotch Broom and Birdsfoot Trefoil will remain top priorities, Chandler says that burgeoning populations of other aggressive non-natives already identified on monument lands will be targeted as well in the round-up. Some of the usual suspects include Japanese Knotweed ( Polygonum cuspidatum ), Purple Loosestrife ( Lythrum salicaria ), Tansey Ragwort ( Senecio jacobaea ), Spotted Cat's Ear ( Hypochaeris radicata ), Oxeye Daisy ( Chrysanthemum leucanthemum ), Canada Thistle ( Cirsium arvense ), Hound's Tongue ( Cynoglossum officinale ), Butter and Eggs ( Linaria vulgaris ), and Dalmatian Toadflax ( Linaria dalmatica ).

With the sun setting behind me, I take one last look at the wildflowers reveling in golden light from my perch at Coldwater Ridge. It dawns on me that without several of the plants listed by Chandler, the view I am beholding could be significantly less colorful. But I reassure myself that the plants native to the region--no slouches in regard to color in their own right--will be better off without these interlopers competing for space and nutrients, and will be able to tell researchers new things about how Mother Nature runs ecological recovery efforts, unimpeded by humans or the non-native plant that tag along with them. That said, I can't wait to scrape off my boots and come back next summer, to watch it unfold all over again.