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| ISBN-13: | 9781610912839 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 04/22/2013 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 217 |
| File size: | 17 MB |
| Note: | This product may take a few minutes to download. |
About the Author
Robert A. Mello is an attorney living in Vermont.
Read an Excerpt
Last Stand of the Red Spruce
By Robert A. Mello
ISLAND PRESS
Copyright © 1987 Robert A. MelloAll rights reserved.
ISBN: 978-1-61091-283-9
CHAPTER 1
Death in the Boreal Zone
The red spruce (Picea rubens Sarg.) brings beauty and grace to the most inhospitable climatic zone our eastern mountains have to offer, the montane boreal zone. In northern New England and New York this subarctic band extends from approximately 3,000 feet above sea level to the tree line; in the southern Appalachians it begins at about 5,000 feet and encompasses all the highest peaks. In this zone of fierce winds and severe cold, the growing season is short, and the soils are thin, rocky, and infertile. Yet the red spruce survives, often growing in pure stands and can live to be nearly 400 years old. Few other trees survive in the boreal zone. In the northern Appalachians only red spruce, balsam fir, and white birch can cope with such climatic conditions. Without these species, the upper third of the mountains would be mostly bare, eroded rock. These were the trees Thoreau saw jutting through the clouds over Vermont.
In the autumn of 1982, Dr. Hubert W. Vogelmann, Chairman of the Department of Botany at the University of Vermont, reported that the red spruces were dying in the virgin forests on the slopes of Camels Hump, a high peak of the northern Green Mountains of Vermont. Since 1965, when the forests there were inventoried, nearly half of the red spruces had died, some of which had been seedlings when Samuel de Champlain discovered Vermont in 1609. These young red spruces and their towering companions had dominated the vast expanses of high elevation and later had inspired the early settlers to give Vermont and her Green Mountains their names. Vogelmann described what he saw in an article entitled "Catastrophe on Camels Hump" published by Natural History in November 1982:
Gray skeletons of trees, their branches devoid of needles, are everywhere in the forest. Trees young and old are dead, and most of those still alive bear brown needles and have unhealthy looking crowns.... As more and more trees die and are blown down, the survivors have less protection from the wind, and even they are toppled over. The forest looks as if it has been struck by a hurricane.
Ordinarily, red spruces reseed quickly and heavily. As the great evergreens died and opened the canopy of the treetops, the bare forest floors became bathed in life-giving sunshine. Although an explosion of shrubs and other new vegetation followed, Vogelmann reported that there are no young spruces to be seen.
Vogelmann, a field botanist and ecologist for twenty years, has always preferred field work to library or laboratory study. His extensive investigations have earned him national recognition and awards from The Nature Conservancy, Syracuse University, the U.S. Environment Protection Agency, and others. Since earning his doctorate from the University of Michigan in 1955, Vogelmann has conducted several field studies in marshes, swamps, and high elevation cloud forests from Canada to South America. His first ecological investigations focused on the arctic and subarctic vegetation of the Knob Lake region of Quebec, Canada. In 1964, Vogelmann began a series of botanical explorations in the Andes Mountains, the Putumayo, and the upper Amazon basin of Colombia, South America. The following year the Botanical Museum of Harvard University sent him back to Colombia to collect specimens of medicinal plants. From 1966 to 1970, Vogelmann conducted another series of studies as a National Science Foundation Teaching Fellow in the tropical cloud forests on the Sierra Madre Oriental Mountains of eastern Mexico. The majority of Vogelmann's field work, however, has been in the high-elevation arctic and subarctic zones of the northern Appalachian Mountains; consequently, by 1979 he was very familiar with the red spruce.
The red spruce, one of North America's most beautiful, hardy and valuable trees, is a luxuriant evergreen with a thick, shiny coat of dark green needles. A dramatic conifer, it grows to be one hundred feet tall and stands in an open field like a pyramid, with regular whorls of branches rising along its straight mastlike trunk. The red spruce was named because of the cylindrical reddish-brown cones that hang from its branches.
The habitat of the red spruce is relatively small and in the U.S. is closely associated with the Appalachian Mountains, which offer the wet and cool climate that spruce trees like best. Its natural range extends from Nova Scotia and New Brunswick southwestward to North Carolina and Tennessee. The further south one goes to find red spruce, the higher up the mountains one must climb. In the northern extreme of its range, red spruce grow from near sea level up to an elevation of about 4,500 feet; in the Great Smoky Mountains at the southern end of its range, red spruces grow from elevations of about 4,500 to 6,500 feet. Of the eight spruce species that live in North America, only three (red spruce, white spruce, and black spruce) live in the East and, of these, the red spruce alone grows south of upper West Virginia.
Commercially, the red spruce was once one of the most valuable softwoods in America; today, it is still the most important of the spruces. Since red spruce at one time made up approximately 80 percent of the eastern spruce volume, the paper and construction industries have traditionally relied on it heavily for pulpwood and timber. The red spruce's long, straight trunk attains a diameter of three or four feet, making its logs a lumberman's prize. By the late 1930s, red spruces in both the northern and southern Appalachians had been so heavily and repeatedly logged that the tree had nearly disappeared from more than a million acres of forest land. Its exploitation prompted some ecologists even then to express concern about the tree's ability to recover its lost territory; forty years later, ecologists discovered a much more serious cause for concern.
In 1979, Vogelmann and his colleagues discovered that red spruces were dying inexplicably and prematurely. This evidence indicated that the decline of the trees was not only continuing, but accelerating. Three years later, when Vogelmann published his article in Natural History, the decline was still accelerating, and was not confined to Camels Hump. These trees were dying on the Appalachian Mountains from West Virginia to New England, on the Adirondack Mountains of New York, in the White Mountains of New Hampshire, in the Laurentian Mountains of Quebec, and throughout the Green Mountains of northern Vermont. Red spruces of various ages covering an enormous geographical area were dying simultaneously of unknown causes. Vogelmann observed that the greatest damage was occurring in the evergreen forests located at high elevations and on the slopes facing windward: "It is a disaster that, in a few short years, has dramatically changed the appearance of high mountains."
As a result of this sudden decline of the red spruce, scientists in the Northeast began trying to discover as quickly as possible the identity of the destructive forces at work. Forest environments are complex and require time to understand, but time was not on their side. Some prominent scientists viewed the dead evergreens as the omen of an impending environmental disaster, one that could eliminate the red spruce and possibly spread to other forest species. Yet, without a sound diagnosis, no reliable treatment could be offered to the remaining, embattled spruces.
CHAPTER 2Three Great Natural Enemies
The forest has three great natural enemies—fire, insects, and fungi. In North America, more mature timber has been destroyed by this formidable triumvirate than has been harvested by man. Since no fires of any known consequence had occurred on Camels Hump since 1965, the first of the three could be ruled out. This still left a variety of diseases and pests as potential villains. If a recognized insect or fungus could be found attacking the dead and dying red spruce trees, then the cause of the decline would be known quickly and with certainty. Therefore, Vogelmann and the others began their investigations here.
Although many insects are known to attack red spruce, only three are voracious enough to kill the trees in large numbers. The spruce budworm, considered one of the most dangerous of all the forest insects, has devastated more spruces and balsams in the Northeast than any other. Several serious outbreaks of budworm in Canada and New England killed a considerable part of the affected forests. The most catastrophic outbreak on record began in northern Quebec about 1909 and spread southward into New England. By the time the epidemic was over in 1923, more than 200,000,000 cords of balsam fir and many millions of cords of spruce timber had been destroyed. The budworm, a defoliator, eats the buds and new needles of the red spruces in the spring, causing the trees to weaken and often to die. Trees, weakened by the loss of foliage, then become targets of another enemy—the eastern spruce bark beetle—which burrows under the bark of the tree. The tree promptly dies from the attack of the beetles and by the penetration of lethal fungi through the openings made by insects.
The European spruce sawfly is another defoliator; it eats the old needles of the red spruce until the current year's new needles mature; then it eats them too. The sawfly has also caused an enormous loss of mature red spruce timber in the northeastern United States. The last outbreak of spruce sawfly in Vermont occurred in the late 1930s, leaving several thousands of acres of spruce forests in central and southern Vermont severely infested. Defoliated spruces were also found on Mt. Ellen, Mt. Abraham, and Mt. Battell near Lincoln, and on Green Peak in Dorset, Vermont.
Modern silvicultural management techniques combined with chemical spraying have helped control insect populations in recent years. The war against the spruce budworm and other enemies of the red spruce, however, was not yet won. In 1982 spruce-fir forests in Canada and Maine were blighted by another devastating epidemic of spruce budworm. More than 5 million acres of evergreen forests were infested in Maine, the nation's leading producer of paper products. Therefore, when Vogelmann searched Camels Hump for prime suspects to blame for the dying red spruces, he naturally put insects high on the list. This suspect had to be taken off the list, however, when the scientist reported that "we have not found any insects on Camels Hump that could cause the current mortality."
With insects ruled out as the cause of decline, scientists turned their attention to germs. The task of identifying a treekilling disease belongs to the plant pathologist. For the pathologist, the innumerable chemical, microscopic, physical, climatic and environmental components that can be gathered, examined, measured, tested, and analyzed from the ground up provide only half of the story. The other half remains underground.
The roots of many trees are measured in miles. For some, the area of the roots may exceed the area of the tree that towers above. The chemistry of the ground where the roots must live is more diverse and complex than the chemistry of air, and there is a greater variety of visible and invisible life in the ground than above it. There are more than one hundred thousand species of fungi alone; pick up a gram of dry soil and you will be holding in your hand up to one million fungal spores. That does not even count the myriad bacteria, viruses, and mycoplasma that are borne by the soil. This subterranean world of trees is, therefore, of great concern to the pathologist.
Fungi are the most common, significant cause of tree diseases. Nearly two thousand species of fungi have been found to infect trees. The most serious fungal infections are those that attack and rot the roots of forest trees and other plants.a The red spruce, however, suffers from few serious diseases. The tree is naturally resistant to many common pathogens. If a red spruce is injured or stressed by an external cause, it may then be susceptible to invasion by a host of deadly soilborne and airborne fungi that cause severe rotting of its roots and heartwood, cankers, defoliation, rusts, and death. But as long as the red spruce is healthy and exhibiting good growth, it has the inherent ability to resist the entrance or subsequent development of fungi even when environmental conditions are suitable for their growth.
Dr. Philip M. Wargo, a plant pathologist with the U.S. Forest Service, along with several scientists from the Yale School of Forestry and Environmental Studies, extensively surveyed red spruces on Camels Hump and eight other mountains in Vermont, New Hampshire, Massachusetts, and New York to see whether a disease organism was responsible for the mortality. They examined 288 healthy, sick, dead, and dying red spruce trees. They found a fungus, Armillaria mellea, on the roots of dead and declining red spruces at all elevations. The more advanced the infection, the sicker the tree.
Responsible for one of the most severe tree root diseases of all the fungi, Armillaria mellea is native to most forest soils worldwide, including the northeastern United States. It attacks and kills the roots of many kinds of hardwood and softwood trees. Trees infected by it usually die. At first, the needles of a victim may turn a pale, yellowish-green and fall prematurely or remain undersized or scanty. As the tree's overall growth rate slows down, the growth and foliage at the crown begin to deteriorate. In the advanced stages, as its needles turn brown and fall, the tree looks like it is dying from the top down and from the outside in. As the disease progressively kills and rots away the roots, the tree loses its support and becomes easily broken or uprooted by the wind. When the tree is dead or nearly so, honey-colored toadstools may appear at the base of the tree, producing billions of spores that will be carried by the winds to infect other susceptible trees in the forest.
These were the very symptoms that Vogelmann saw on the dead and dying red spruces on Camels Hump and elsewhere. Nevertheless, the pathologists determined that Armillaria mellea was not the cause of the disaster. Like nearly all fungi it is a passive opportunist, almost never attacking or seriously harming a healthy tree. Armillaria mellea becomes dangerous to a red spruce only when some other primary force, such as unfavorable environmental conditions, poor soil, moisture imbalance, or insect defoliation weakens the tree and predisposes it to infection. Furthermore, the pathologists observed that the number of trees infected by Armillaria mellea was least in the very regions where the most trees were dead and dying. The intensity of the red spruce decline got worse the higher up the mountains the scientists ascended, and it was most prominent above elevations of 3,000 feet, where red spruce was most dominant; the opposite was true of the fungus. Above 3,000 feet 61 percent of the recently dead red spruces had no infection at all, and 91 percent of the severely declining trees were also free of infection. More red spruces were dying there in the absence of Armillaria mellea than in its presence.
In a research paper published in the Plant Disease Journal, the pathologists concluded that Armillaria mellea, the only disease organism found on the red spruces, was not the primary cause of the red spruce mortality:
The association of A. mellea with declining trees indicated that the trees are being predisposed to damage by some undetermined biotic or abiotic stress. The fact that trees are dying in the absence of A. mellea indicates that the stress is sufficient by itself to cause mortality or that other secondary organisms are interacting with the stress to kill the trees.
Detailed scientific investigations conducted by knowledgeable specialists had ruled out the forest's three great natural enemies—fire, insects, and fungi—as primary causes of the red spruce decline. When events cannot be explained with certainty by the application of known scientific facts, the scientist must turn to the uncertain world of theory.
Thus Vogelmann, Dr. Richard M. Klein of the University of Vermont, and concerned scientists from Europe, Canada, and the United States set out to identify the forces responsible for the widespread decline of these great trees. Their work would produce a thicket of related but opposing theories and hundreds of scientific reports published in dozens of journals in Europe and the United States. The competing theories they developed would divide the community of American botanists into several vocal factions, sometimes sending long-term colleagues on separate paths. In the process, Camels Hump came to be one of the most closely studied mountains in the world.
(Continues...)
Excerpted from Last Stand of the Red Spruce by Robert A. Mello. Copyright © 1987 Robert A. Mello. Excerpted by permission of ISLAND PRESS.
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Table of Contents
About the Natural Resources Defense CouncilTable of Figures
Introduction
Foreword
Acknowledgments
Atop Mt. Greylock, 1844
Introduction
Chapter 1. Death in the Boreal Zone
Chapter 2. Three Great Natural Enemies
Chapter 3. A Close Correlation
Chapter 4. Discovering Inuisible Pathways
Chapter 5. The Search for Natural Causes
Chapter 6. Treatment Withheld
Chapter 7. Twilight
Appendix 1: Historical Progress toward Understanding Acid Precipitation
Appendix 2: More Recent Developments on Acid Rain Recognized by National and International Agencies
Endnotes
Selected Bibliography
Index