Chestnut seedlings at Meadowview Farm in Meadowview, Va.
The Smokies are renown for their biological diversity and scenic beauty. But a short drive along either of two scenic byways—The Blue Ridge Parkway or the Cherohala Skyway—provides a window on forests under attack from invasive exotics. There are many places near the North Carolina end of the Cherohala Skyway where one can look to the north-northeast towards the Santeetlah Creek drainage and see acres of dead eastern hemlocks, testimony to the voracious appetite of the tiny hemlock woolly adelgid, an exotic invasive from Asia.
If one stops at Richland Balsam, the highest point on the Blue Ridge Parkway, and gets out of the vehicle, one will be standing in a mausoleum surrounded by the stone-grey skeletons of Fraser fir trees. Mature Fraser firs have been all but extirpated from the peaks of the Southern Appalachians by another adelgid—the balsam woolly adelgid.
Forests across the country are under siege from threats ranging from urban sprawl and fragmentation, to air and water pollution, to loss of native species and natural communities and to a seemingly unending barrage of invasive exotic plants, disease, and insects. The many and diverse forest ecosystems of the Southern Appalachians are no exception.
The U.S. Forest Service’s Southern Research Station based in Asheville recently issued a “report card” on forest health across the region that noted that of the 47 natural communities across the region five were critically imperiled and 13 were imperiled. The report stated that, “… regional experts believe communities are declining at a faster rate than seen in previous years—primarily due to impacts by invasive plants and pests.”
According to a December 2011 announcement by the U.S. Forest Service, invasive species (insects and diseases) cost the U.S. taxpayers about $138 billion dollars each year. The report called the invasion of nonnative plants and animals a “… catastrophic wildfire in slow motion,” and announced the first ever published national plan to combat the problem. The announcement calls for the Forest Service to be more proactive in addressing this invasion and to reach out to state and local agencies to work together to slow this onslaught. But this is no easy order.
Dr. Pete Bates, natural resources professor at Western North Carolina University, registered forester and president of the board of directors of Forest Stewards LLC notes, “…there is no panacea.” Bates said that as a forest steward, he appreciates all the efforts being put forth by different individuals, organizations and agencies but “it seems like every month there’s a new pest introduced and when you look, historically, at our efforts—we have a poor track record. Once these invasives are established they are difficult, if not impossible, to eradicate.”
No single natural event has altered the composition and ecology of Southern Appalachian forests like the loss of the American chestnut, Castanea dentata. The American chestnut was the dominant species in hardwood forests from Georgia to Maine. It accounted for anywhere from 25 to 40 percent of entire forest stands across more than 188 million acres. The American chestnut bloomed later in the spring than oaks and hickories, missing those late spring freezes and producing dependable mast year after year. It grew large and straight producing valuable timber and pioneers used it for everything from cribs to caskets.
The chestnut succumbed to an invasive Asian fungus, Cryphonectria parasitica, known commonly as chestnut blight. The blight is believed to have arrived in the U.S. on imported plant material. It was first documented in the early 20th century in New York City and by 1950 more than 400 million American chestnuts had been decimated. Sprouts still grow today but hardly make it past 10 to 15 years before the blight does them in. Occasionally a mature chestnut is discovered but they are so rare and widely dispersed that the American Chestnut Foundation (TACF) calls chestnut “functionally extinct.”
TACF founded in 1983 is at the forefront of efforts to restore the American chestnut to eastern forests. The organization has been working on developing a blight resistant chestnut by cross breeding American chestnut with the blight resistant Chinese chestnut.
Paul Franklin, communications director with TACF, said the organization recently initiated a joint project with the U.S. Forest Service and the University of Tennessee. In 2008, the partnership began planting TACF-bred hybrid chestnuts on national forest plots in the Smokies region. “This is the first time we’ve actually put trees back in a natural ecosystem,” Franklin said. The tree is a sixth generation hybrid and is 94 percent American chestnut and six percent blight-resistant Chinese chestnut.
Stacy Clark, research forester for the U.S. Forest Service, said that while there has been initial success, the project is a long-term project and it will be 10 or 15 years before any really meaningful insights regarding reestablishing the chestnut in the eastern forests are realized. “All of these trees are going to get the blight,” Clark said. “The question is, how are they going to deal with it—how resistant will they be—and the answer to that is probably 10 to 15 or more, years down the road.”
Sadly the blight is not the only obstacle to reestablishing the American chestnut. The tree is also susceptible to ink disease—a kind of mold (genus Phytopthora) that attacks the roots. “We don’t know a lot about Phytopthora—how to control it, so we look at ways to avoid it,” Clark said. Phytopthora doesn’t appear to be a problem from northern Kentucky northward or at altitudes above 3,000 to 3,500 feet, Clark said.
Clark said the Forest Service has plans to introduce more hybrid chestnuts through 2013, and Franklin said that while TACF feels good about its sixth generation hybrid, work is underway on the seventh and eight generation. “It’s our mission to see the American chestnut restored to the eastern forests,” Franklin said. “And we definitely intend to see it become a significant tree once again.” Franklin said that TACF is collaborating with partners in all 16 states that were once home to the American chestnut. “It’s been out of the woods for 50 years and a lot has changed,” Franklin said. “We are working to create a broad-based comprehensive plan for actually reintroducing the chestnut in the landscape.”
Researchers hope that knowledge gained from the efforts to breed blight-resistant chestnuts and reintroduce them into forest ecosystems will aid in the restoration of other species too. American elm and butternut or white walnut are two other important hardwoods of the eastern forests that have been plagued by non-native diseases. Dutch elm disease (DED), named because Dutch scientists first identified it in Holland in 1917, appeared in Cleveland, Ohio in 1930 and began laying waste to American elms. The American elm was common in eastern forests but it reached its glory in the yards and along the streets of almost every hometown in eastern America. There probably isn’t a city in the East that doesn’t have at least one “Elm Street.” Those streets are mostly devoid of their namesake now and the American elm has been relegated to an understory component in today’s forests.
Another prized hardwood disappearing from the Smokies region is butternut or white walnut, Juglans cinerea. The wood was valued for carving, cabinets and furniture. The roots and nuts were used for dyes for traditional Cherokee baskets. Butternut canker, another Asian fungal disease, arrived in the U.S. in the 1950s and scientists estimate that 70 to 80 percent of the butternuts across the Smokies have succumbed to the canker.
DED-resistant elms and canker-resistant butternuts have been found across their range and researchers are working on breeding disease resistant trees of both species. And while, at this point, there are no programs for reintroducing either species in forested landscapes there has been some success with American elms in urban settings.
The Southern Appalachian forests used to sparkle as the large white showy bracts of eastern flowering dogwood, Cornus florida, heralded spring and announced the awakening of the slumbering mountains. But in 1976 scientists in Washington State notice a disease attacking pacific dogwood, Cornus nuttallii. A couple of years later eastern flowering dogwoods in New York and Connecticut were exhibiting the same symptoms. The disease cascaded like an avalanche down the Southern Appalachians and by 1999 half of all the dogwoods in the 24 counties of Western North Carolina had disappeared.
The pathogen was described and named in 1991—Discula destructiva. The origin of this anthracnose fungus is unknown but its sudden appearance, fast spread and the lack of any resistance all lead researchers to believe it is introduced. Dogwood anthracnose is especially virulent above 3,000 feet in elevation and in moist, shady areas below 3,000 feet. Researchers have estimated that at least 90 percent of eastern flowering dogwoods in heavy shaded alluvial forests of the Great Smoky Mountains National Park have died. The aesthetic loss of those great white blooms in the spring, reddish-purple leaves in the autumn and bright red winter berries is surely one to lament, but the forests may miss the ecological functions of dogwood even more. The seeds, fruit, flowers, leaves, and bark of dogwood are all used as food by different forest animals.
Dogwoods also are vital to the calcium cycle of the forest. They are one of the few vascular plants that actually absorb calcium from the soil and rocks. The calcium is stored in the leaves and wood, and when the dogwood leaves fall to the ground each autumn that calcium becomes available to other plants and animals in the forest.
Researchers have linked the loss of this dogwood-calcium nutrient cycle to the decline of songbirds in the eastern forest. Land snails ingest the calcium from the dogwood leaf litter and are much more common under dogwood than any other trees in the forest. Songbirds, in turn, feed on the snails and accrue calcium, which is needed in eggshell production. The loss of the dogwood equals a reduction in the snail population, which in turn, leads to poorer eggshell production, limiting birds’ ability to nest successfully.
Studies in the Great Smoky Mountains National Park suggest that prescribed burns could help dogwoods. Research noted that areas within the park that had been subjected to wildfires over the past few decades showed more young dogwood stems than areas that had been fire free. According to the study, those areas that had burned twice had four times more dogwood stems than areas that had burned once and 20 times more stems than those areas that were fire-free.
Eastern hemlocks are not so numerous as American chestnuts used to be, but like the chestnut, they are a keystone species of eastern forests and there is a pitched battle to try and save them. Researchers, foresters, and biologists are apprehensive about what the loss of the hemlock could mean. The loss of the hemlock could mean the loss of food and shelter for numerous species of wildlife like owls, bats and the endangered northern flying squirrel. Because many hemlock communities are riparian, their loss could have deleterious effects on many aquatic species like native brook trout, which depend on the shade from hemlocks to keep water temperatures cool.
There are effective chemical treatments that kill the hemlock adelgid but there is no way to treat all hemlocks across the landscape. The Great Smoky Mountains National Park (GSMNP) has treated more than 100,000 hemlocks, but that is only a small percentage of the 1,400 acres of old growth hemlocks that have been mapped, and for some areas it is already too late. When one adds the hemlocks throughout the millions of acres of national forests across the region, it’s easy to see what kind of daunting task is at hand. Land managers have tried introducing exotic beetles that feed on the hemlock adelgid in its native landscape but that has, so far, failed to stem the tide.
Frank Varvoutis, owner of Hemlock Healers in Waynesville, N.C., began battling the adelgid as one of the first members of the Great Smoky Mountains National Park’s hemlock treatment crew. “The park actively treats pockets of hemlocks in highly visited areas and is maintaining some old growth stands,” Varvoutis said. He said that soil injections are highly effective and that he has seen treatments last for years. Varvoutis noted that while saving large expanses of hemlocks in the wilderness was probably not feasible, saving hemlocks on private property and in urban settings was quite doable. And he noted that the advent of generic chemicals made the treatment much more affordable. He said that it cost about $70 to treat one 24-inch diameter hemlock and that the treatment would last four to six years.
There are invasive insects and invasive fungi and in at least one case they have joined to produce a deadly one-two punch. According to Kristine Johnson, forester in the GSMNP, in the early 1990s the park had a healthy beech forest. Now, according to Johnson, most of the beech gaps at higher elevations in the park have succumbed to beech bark disease.
The first punch is a body shot. The beech scale, an introduced insect, bores holes into the beech bark. The knockout punch then comes when a fungus invades the tree through the holes provided by the scale. The original invading fungus was Neonectria faginata, introduced from Europe. But recently researchers are also finding a native Neonectria-ditissima that is following the beech scale.
Beech bark is rather new on the scene and GSMNP has enlisted the help of Discover Life in America’s (DLIA) “Tree Teams.” Todd Witcher, executive director of DLIA, said the park asked for help because the disease was complex and so little was known about the various arthropods inhabiting or utilizing the beech trees. Witcher said that DLIA utilizes citizen-scientists (volunteers) to capture arthropods in the beech gaps. Witcher said the project had two major components. One, of course, was to try and shed light on the beech bark disease complex. But just as important was to see what critters were present and what their relationship to the rest of the forest ecosystem might be and what kind of ripple effects might occur should the beech gaps be lost.
Let the healing begin
It’s easy to see that the challenges facing today’s forests are myriad, various, and complex—without even broaching the subject of climate change or talked about other native pests like the emerald ash-borer and gypsy moth that are marching towards our region.
Suffice it to say the forests of the Southern Appalachians can’t be “cured.” As Bates at Western Carolina Univeristy and Clark with the U.S. Forest Service have noted, there are no known cures for these introduced pathogens. And as the hemlock dilemma has shown, even where there are ways to deal with individual pests on individual trees, there have been, to date, no effective ways of dealing with a species across its entire range. So what are land managers to do?
Bates believes the most practical course for land managers is to adhere to what he calls, “the ecological axiom—stability in diversity.” The key he said is to, “preserve ecosystem integrity.” He said land managers need to be innovative and knowledgeable about the many mechanical and sivicultural treatments available like shelterwood, crop tree release, prescribed burns and removal of invasive exotics where possible.
While it is romantic to think about pre-Colombian forests, Bates said land stewards must look to the future. There was no chestnut blight, dogwood anthracnose, hemlock woolly adelgid, etc. present in North American pre-Colombian forests. But those and many more pests are likely forever more present. And today’s healthy forest will have to be a forest diverse enough to handle these pests while retaining enough integrity to support a balanced and adaptive ecosystem while providing those things like clean water, carbon sequestration, wildlife habitat and recreational opportunities that we have come to depend on forests to provide.
Some of the most aggressive include:
- Kudzu – that fast growing vine that covers anything that gets in its way. Park rangers battle kudzu at 116 sites.
- Privet - forms dense thickets and out-competes native plants. Rangers spend up to 500 hours or more each year trying to eradicate privet.
- Japanese grass – prevalent in Cades Cove and Sugarlands.
- Multiflora rose – introduced for wildlife cover and food back in the 1940s is a bane throughout the park at mid to lower elevations.
- Mimosa – introduced from Asia in 1745 mimosa is really hard to control because it sprouts readily and seeds can remain viable for 50 years.
- Musk thistle – one plant can produce more than 100,000 seeds. It is especially pernicious in open balds.
- Garlic mustard – grows well in the shade and can dominate native ground cover in the span of a few years.
- Oriental bittersweet – this climbing vine from Asia grows almost as rapidly as kudzu and smothers almost anything and everything in its path. It also hybridizes with American bittersweet destroying the native’s genetic integrity.
- Japanese honeysuckle - also introduced as wildlife cover and to control erosion. Because it is an evergreen it can grow all winter giving it a leg up when it comes to competing with native deciduous plants.