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People, livestock, insects, diseases, snow, wind, fire, volcanic eruptions, earthquakes, and floods are constantly disrupting forests, slowing growth, and injuring or killing trees and other living components of the ecosystem. Disturbance is natural and necessary to forest ecosystems; without it, forests could not regrow, recycle, and pass through successive stages from seedlings to old growth. But, when disturbance causes more continuous, severe, or widespread effects than people consider acceptable or normal, the forest is described as "unhealthy."
Forest Health Defined Forest health is a human concept, and people have different views about what constitutes a healthy forest. As demands on forests change over time, so too will people's views of forest health. Currently, two ideas are included in most definitions of forest health.
What Is at Stake? More than 36% of the land area in Oregon and Washington is forested. Forest land in the two states includes more than 18 million acres of federal land (19 National Forests, 7 Indian Reservations, 4 National Parks, and almost 2.5 million acres managed by the Bureau of Land Management), more than 2.8 million acres of state land, and about 16 million acres of private industrial and nonindustrial forest land. The residents of Oregon and Washington depend on these forests for wood products, jobs, fisheries, recreation, scenery, school funding, clean water, and many other products and amenities. Much of what people value about the Pacific Northwest is tied to the forests.
Assessing Forest Health Forest health is assessed by monitoring the condition of various parts of the forest. Certain traits, such as tree growth, crown condition, mortality, and lichen communities, are good indicators of forest health. The condition of these indicators is used to characterize the forest as healthy, unhealthy, or something in between. Over time, monitoring shows changes in forest condition. Forest ecosystems age just as people do, so some yearly change is natural. Unexpected and large changes, though, would be cause for concern and lead to further investigations.
Detecting trends in forest condition and predicting long-term consequences of significant changes are the two cornerstones of monitoring activities. By knowing how and when forest conditions will change and what the ultimate consequence of these changes might be, scientists, managers, and citizens can work together to plan alternative solutions and actions.
Federal and state agencies and private organizations in Oregon and Washington monitor forest health by using a variety of surveys and inventories.
This Report This report was written to help people understand the disturbances at work in the forests of Oregon and Washington, their significance, the underlying causes, and possible actions to improve forest health. The disturbance agents we discuss in the following chapters are insects, diseases, weather, air pollutants, and fire. We also recognize that people are agents of forest disturbance, and the results of people's activities in the forest-such as fire suppression, tree harvest, tree planting, and restoration work-are woven into our discussions as well.
Chapter 1 is devoted to some forest health topics that people in both states are concerned about: vegetation change, mortality, weather trends, exotic pests, and air pollution. We also include a section on forest health monitoring methods.
The next two chapters contain information specific to each state (chapter 2, Oregon; chapter 3, Washington). Information in these chapters is arranged by ecological sections because disturbance agents and patterns are generally tied to the geography, climate, and vegetation that make up an ecological section. We also show which counties correspond to the ecological section being discussed.
Chapter 4 describes disturbance agents and their effects on the health of urban forests in Oregon and Washington. Chapter 5 describes a forest health monitoring research project carried out in the Pacific Northwest in 1994. And chapter 6 is a summary of the disturbances at work in Pacific Northwest forests, our expectations of future disturbances and forest condition, and some strategies for improving forest health in Oregon and Washington.
Sources of Information The primary sources of data for insects and diseases in this report are the cooperative (Forest Service and states) aerial survey, flown over all forested lands in Oregon and Washington each year; special aerial surveys for specific problems; various ground surveys; and forest insect and disease research. Information on fire, weather, and air quality came from specialists in the Forest Service and state agencies who, in turn, obtained their data from regional monitoring networks for those resources. Much of the information on ecological relations between trees and disturbance agents is based on the field experience of the pathologists, entomologists, ecologists, and fire and air specialists who contributed to this report.
References and Scientific Names To enhance readability, we have not cited references or included scientific names of trees, insects, and fungi in the text. Selected references are listed at the end of chapter 6. Scientific names are listed in appendix A, alphabetically by common name.
The amount, variety, age, and size mix of trees on a site
determine the extent and severity of damage by disturbance agents.
Changes
in forest vegetation affect forest health.
Thirteen thousand years ago, glaciers still covered much of North America. As the continent warmed, about 10,000 years ago, glaciers receded and coniferous forests expanded their range. Fossils from Mount Rainier suggest that the period from 6,000 to 3,400 years ago was actually warmer and drier than the current climate. Subalpine fir, Douglas-fir, ponderosa pine, noble fir, and lodgepole pine were common. California chaparral vegetation extended as far north as Vancouver Island. Fires were probably very frequent. The current cooler, wetter period began about 3,500 years ago, and fire frequency declined.
Forest Succession Forest succession is the change in species composition as plants grow, die, and are replaced over time. A tree that thrives in a sunny opening created by fire may not be able to reproduce in the shady environment of a mature forest. It will be replaced by a more shade-tolerant species. In the absence of disturbances that create openings, shade-tolerant climax species eventually dominate. Type, diversity, and frequency of disturbances interact with site factors such as soil type, topography, weather, climate, and surrounding vegetation to influence which plants invade a site after disturbance and how communities develop. People can affect plant succession by altering the type, severity, and frequency of disturbances.
American Indian and Pioneer Influences Native people modified the vegetation of the Pacific Northwest-both accidentally and deliberately. Fires set on sites such as Puget Sound's Whidbey Island, the Willamette Valley, and the eastern slopes of the Cascade Range enhanced the growing of bracken, camas, huckleberries, blueberries, and grouseberry and attracted browsing animals like deer and elk.
Early non-native visitors and settlers also modified the forest environment in Oregon and Washington. In many places, the virtual elimination of beaver by trapping for their pelts drastically altered riparian systems. Settlers copied the American Indians' technique of attracting grazing animals by setting many, sometimes devastating fires. Settlers also brought new species to the area: sheep, cattle, cheat grass, wheat, potatoes. Use of forests was initially limited to local demands for construction materials, firewood, and fencing. Some forest lands were converted to agriculture, town sites, and residential areas so, in some places, forest depletion became an issue.
Logging and Tree Farming Logging in the Pacific Northwest created many changes in forest vegetation both east and west of the Cascade crest. The forest industry gained momentum in Washington and Oregon in the late 1800s. The Puget Sound area had major shipping ports. Lumber was sent to San Francisco and helped build many West Coast cities. Logs were dragged out of the woods by oxen, horses, and mules and floated to steam-powered mills. By the turn of the century, narrow-gauge railways provided access to remote, rugged areas. Steam-donkey engines on skids and high-lead cables pulling logs above the forest floor made log removal easier and reduced soil compaction. Railroads allowed efficient transport of material to markets in the East, where ponderosa pine and western white pine from eastern Washington and Oregon were highly prized. Low shipping rates allowed Puget Sound producers to compete for interior markets, as well as continue to supply worldwide customers.
Beginning in the early 1900s, mechanized equipment was used extensively. From about 1910 to 1940, the lumber market was glutted. Land owners suffering major economic hardships during this period were forced to liquidate stumpage to pay for the land or other investments. They extracted only the most valuable logs as quickly as possible, leaving "weed" trees standing and high volumes of fuels lying on the ground. Sparks from steam engines and railroads started many fires, and burns through logging debris were hot and damaged the soil, seedlings, and remaining trees.
After World War II, the logging industry struggled to keep up with demand for wood products. Gas-powered chain saws and diesel and gasoline-powered trucks and tractors improved logging efficiency and reduced fire hazard. Removal of all wood within reach of cable settings (clearcutting) increased because of operational efficiency and ease of regenerating new forest in the Douglas-fir region. Slash burning was standard.
By the 1950s, the most productive portions of Pacific Northwest forests were being managed to maximize timber production. When cutover sites were replanted, Douglas-fir was usually the only species planted on the west side and ponderosa pine on the east side. Although the prevalence and distribution of species changed somewhat after logging and replanting, the planted seedlings did not always thrive, and native species often partly or completely revegetated harvested areas.
Fire Suppression Fire fighting gained momentum after huge fires at the turn of the century. For example, the Yacolt fire in 1902 burned nearly 239,000 acres in Clark and Skamania counties (Washington) and killed 38 people. Several fires, including the Columbia fire near Mount Hood, burned more than 170,000 acres in Oregon the same year.
Society demanded that the forests be protected. Laws regulating slash and slash-burning to protect forests were passed in 1911. Permits were required for burning slash in summer, and all snags over 25 feet had to be cut. A highly efficient and coordinated forest fire-fighting force was developed nationwide to aggressively attack and quickly control all wildfires. Fire-fighting efficiency increased dramatically after World War II when airplanes became available for detecting and suppressing fires. Campaigns such as "Smokey Bear" encouraged all citizens to help prevent forest fires.
Vegetation, Past and Present Today's forests are different in composition and structure from the presettlement period. Pacific Northwest forests have always been affected by disturbances (such as fires, wind storms, volcanic eruptions, and landslides). Disturbances west of the Cascades-predominantly wind storms and wildfire-rarely removed all large woody debris. Fires usually burned during periods of extremely dry weather, and generally several fires were required to consume the wood. Snags, large trees, and unburned patches survived. Wide age ranges in natural Douglas-fir forests suggest slow recolonization because seed sources were absent after large disturbances.
The activities of the increasingly intensified timber industry also disturbed the forests, but they did not mimic the natural disturbances. Today's commercial forests are younger, artificially dominated by even-aged Douglas-fir, have few snags and logs, and are more fragmented than less intensively managed forests or wilderness. Erosion and soil loss are chronic problems associated with roads and annual logging operations rather than periodic problems associated with natural fires.
East of the Cascades, disturbances ranged from frequent, mild, ground fires at low elevations to occasional, intense, stand-replacing fires at high elevations. The suppression of fire took away an important natural means for removing fuels and thinning stands, leaving sites dense with tree cover, particularly at low elevations. Fire suppression and the selective harvest of large pines transformed many open, parklike stands dominated by large pines, into dense, overcrowded stands of predominantly Douglas-fir and grand fir. Riparian areas were altered by grazing and loss of beaver and pool-stabilizing logs. Grazing also affected fire intensity and frequency and, as a result, understory species and stocking. High-elevation forests with longer natural fire frequencies have been less affected by fire suppression than were stands at low elevations.
The forested area in Oregon and Washington faces increasing pressure from human populations. Road building, urban development, agriculture, power lines, and reservoirs have all taken their toll on forested acres. At the same time as worldwide demand for forest products is increasing, demand for beautiful tree-covered recreation and home sites is also rising. Conflicting management objectives for wood products, attractive living spaces, and forested recreation sites will require resolution or compromise.
The ecological effects of these forest changes are reflected in changes in the disturbances that forests experience. Hemlock looper, a pest of old-growth hemlock stands that once killed trees on huge tracts of forest, now has much less host material available and is much less damaging. Injury to dense young trees caused by bear and bark beetles is increasingly common. On sites once dominated by pine, outbreaks of insects that consume Douglas-fir and true fir foliage, and damage by root diseases and dwarf mistletoes have increased in frequency and severity. In some areas, fires are much more devastating than before because of high fuel loads.
One obvious indicator of potential poor forest health is
conspicuous numbers of dead and dying trees.
Death of trees is normal, but the causes and patterns of mortality are complex. Insects, diseases, drought, wind storms, and fire have killed trees throughout millennia. More recently, other agents associated with people and their industry-air pollution, human-caused fire, and forest management activities-are contributing to tree mortality. Factors such as competition with other trees or plants or being eaten by grazing animals like deer and elk can also cause tree death. Often, death is the result of a combination of causes. For example, competition and drought may stress a tree to such an extent that insects can attack and kill it.
Ecological Role of Mortality Death of forest organisms is a necessary part of every forest ecosystem and part of the normal cycling of materials and processes. Tree death contributes woody material to the forest floor where it serves as moisture reservoirs and as habitat for a variety of plants, animals, and microorganisms. The wood and foliage eventually decompose, returning nutrients to the soil. Standing dead trees provide shelter, nesting, roosting, and hunting spots for birds and other animals. Trees that fall in or near streams give the stream the structure it needs to support fish and other aquatic organisms. Tree death creates an ever-changing mosaic of habitats within a forest, allowing light to reach the forest floor, seeds to germinate, and new vegetation to grow.
Patterns of Mortality Patterns of mortality are complex. The distribution of mortality from disturbances is determined by patterns of vegetation, the type of disturbance agent, and the physical environment. Where species and structure are similar over a large contiguous area, larger and more severe corresponding disturbances are more likely. Where the forest is less uniform, mortality is patchy and tends to correspond to groups of susceptible species, ages, and structures.
Some disturbances cause widespread mortality in stands of uniform species and age, such as mountain pine beetle in even-aged lodgepole pine. Other disturbance agents, like dwarf mistletoe and western spruce budworm, are favored by multistoried stands where seeds and larvae can drop from tall to short trees. Fire is more deadly in multistoried stands where the understory acts as a fuel ladder, allowing the fire to reach the tree tops.
Normal Mortality Many scientists and forest managers use historical conditions (from 1600 to 1850, before European settlement of the West) as the yardstick for determining "normal" conditions. Old journals, photographs, maps, and tree-ring analysis can be used to trace and compare historical forest composition, distribution, and disturbances with current conditions and disturbances. Such analyses have shown that disturbance patterns and mortality are outside the historical range of variability in some areas of Oregon and Washington.
For example, western spruce budworm outbreaks in northeastern Oregon are more frequent and severe now (some stands have more than 80% overstory mortality) than they were in the 1800s, largely as a result of the selective harvest of nonhost species (ponderosa pine and western larch) and fire suppression. These two practices have led to dense, multistoried stands of predominantly budworm-susceptible species (true fir and Douglas-fir).
Many places in eastern Oregon and Washington have dense second-growth ponderosa pine stands that replaced open, parklike stands of old-growth ponderosa because of fire suppression. These overstocked stands are extremely susceptible to attack by bark beetles. The number of stands in this condition and the resulting mortality is higher than in the past.
Fire frequency and severity have changed significantly over the past century as a result of fire suppression practices and increases in tree densities and flammable materials. When fires occur, they are much more severe and kill more trees on each burned acre.
Mortality Trends Recent trends in mortality can be tracked through forest inventories or surveys. Most survey and inventory data are relatively recent. The first aerial insect surveys began in the 1940s, and the first forest inventories began in the 1930s. Comparing data from year to year is useful and shows areas with potential problems.
Tree mortality in western Washington and northwestern Oregon has been, and probably will continue to be, relatively low with occasional local areas of high mortality from disturbances such as flooding, wind storms, fire, and insect outbreaks. The most significant mortality agent on the west side is root disease. Although not highly visible, root disease causes mortality on 10% of all lands in the Pacific Northwest and may kill more than 50% of a stand over a period of years.
In eastern Oregon and Washington, forest inventories show mortality has been above average over the past decade on both federal and nonfederal lands. Typical annual mortality in Oregon and Washington forests, based on 60 years of inventory data, is about 0.5% of the volume of wood present. The last inventories of eastern Oregon and Washington forests (excluding National Forests) show annual mortality at 0.84% for eastern Washington and 0.97% for eastern Oregon. National Forest inventory data show similar trends.
Annual aerial surveys for insect damage show that mortality visible from the air (mainly overstory trees; understory trees are difficult to see) has actually decreased in most of eastern Oregon and Washington over the past few years, after a period in the late 1980s when mortality from bark beetles was very high. Reduced mortality in the last few years may be due to increased summer rains which lessen tree stress and to the collapse of the current western spruce budworm outbreak.
Weather influences forest health by directly damaging trees
and by affecting the ability of trees to protect themselves against insects
and diseases.
The climate of the Oregon and Washington is generally mild with dry summers. Great variation in local areas is due to the influence of elevation, proximity to the ocean, the north-south mountain ranges, and prevailing storm paths. Differences in dominant vegetation reflect differences in climate across the region and the effects climate and weather have on plants.
The climate of western Oregon and Washington is strongly seasonal with less than 20% of the precipitation falling from May through July, the growing season for trees. The coastal areas have a maritime climate characterized by mild temperatures; prolonged cloudy periods; wet winters; cool, dry summers; and a long, frost-free season. Coastal mountains cause rain shadows that alter this maritime climate in the Puget Trough and Willamette Valley, making the summers warmer and the winters colder and reducing annual precipitation. With the rain shadows compounded by southerly latitudes, southwestern Oregon's valleys are still hotter and drier.
East of the Cascade Range, temperatures fluctuate more widely than in coastal areas, winters are colder, summers are hotter, and frost-free seasons are shorter. Although precipitation is considerably less than on the west side, it is much more uniform throughout the year. May and June are the months with the highest precipitation in some areas east of the Cascades.
Short-Term Weather Events Short-term weather events damage trees but are part of normal climate variation. Various kinds of weather kill trees outright or affect their susceptibility to injury, disease, or insect attack. Spring freezes shrivel tender foliage. Lightning damages portions of trees and temporarily reduces their defensive capacity. Although most trees can survive short-term flooding, complete submersion and silt buildup around trunks restrict oxygen intake and cause damage. Fungal spores enter tree wounds caused by wind or snow breakage. Many bark beetles take advantage of daily water stress, attacking host trees on warm summer afternoons when defenses are low.
The late 1980s and early 1990s in the Pacific Northwest were significantly drier than the long-term average. Many places-including southwest Oregon, the Blue Mountains, the Willamette Valley, and the Puget Sound area-experienced this drought. Outbreaks of some insects, related to increased moisture stress on trees particularly in overstocked stands, often follow dry years. Over the last century in the Pacific Northwest, the most recent drought appears to be part of a cycle of wet and dry periods each lasting 10 to 30 years. This climate pattern is within a currently accepted normal range of variability.
Long-Term Weather Changes Long-term climate changes have and will continue to produce changes in forests in Oregon and Washington. The environmental variable that limits forests most and defines forest community gradients is available moisture during the dry summers. Long-term changes in weather will also create changes in the intensity and frequency of natural disturbances, such as wildfire and wind storms, which influence forest composition and structure.
If the climate becomes significantly warmer and drier, forest communities may shift up slopes to higher, cooler, moister elevations; move to more northern latitudes; or move from southern to northern aspects. Because each plant species responds individually to the unique interactions of temperature, moisture, and site characteristics, some of the new communities are likely to be completely different assemblages from any community dominant today. Insects and diseases are likely to expand or contract their ranges along with their hosts, but they may also change their behavior or habitat in unexpected ways.
Because tree species are long lived relative to people, some of the forest changes caused by climatic fluctuations might not be obvious for decades or even centuries. Changes would be greatest in places where many species are already at their physiological limits (southwest Oregon, for example). An increase in insect and disease activity on relict populations, stressed by harsh site conditions, would be expected.
The Future A challenge facing climatologists, ecologists, and land managers is to improve understanding of how dominant weather patterns are likely to change-in both the short- and long-terms-and how these changes will affect forests. Although the climate has shifted in the past, determining if current trends in climate indicate a true climate shift or just a change within the normal range of variation is difficult. If a climate change is predicted, forest managers will need answers to many questions. How large will the change be? How soon is it expected to affect vegetation? How will plants, insects, and diseases respond? How will the industries and services that depend on forest communities be affected? Can forests be made more resilient to such changes?
Trees have coevolved with their native pests for thousands
of years.
Forest health can be greatly affected when exotic pests are
introduced and upset the balance.
Exotic plants and animals-those introduced from places outside of their native range-can be harmful to native species. Many introduced organisms are beneficial, such as crop plants, ornamentals, game animals, and livestock; these organisms were deliberately introduced and are essential to United States commerce and society. In the Pacific Northwest, the exotics that cause the most damage to forest trees are accidentally introduced insects and fungi. Introduced weeds are also destructive, competing with native forest vegetation for space, nutrients, and water.
Problems With Exotics Without natural checks, the population of an introduced pest can grow rapidly and wreak havoc on the host organism. After a fungus disease-white pine blister rust-was introduced 86 years ago, western white pine has been significantly reduced in many Oregon and Washington forests where it once was common. The balsam woolly adelgid, an insect that was introduced to the Pacific Northwest in the 1930s, has damaged grand fir at low elevations in the Willamette Valley to such an extent that most are unable to reproduce.
Exotic pests seriously affect Northwest forests. Damaged trees diminish the value of property and recreation experiences. Revenue is lost from recreation, forest products, and real estate. Quarantines to prevent pest spread disrupt and affect the costs of transporting local forest products. Control efforts (such as pesticide treatments or resistance breeding programs) are expensive, and additional money must be spent to replace killed or damaged trees. In Oregon and Washington, the cost of trapping, analysis, and eradication of gypsy moth from 1985 to 1995 exceeded $50 million.
Most important, undesirable exotics change forest ecosystems. Potential effects range from slight decreases in native populations to permanent alteration of biological communities. Although much attention is directed at introduced insects and diseases, the current and potential effect of introduced plant species on forests is huge. Not only do exotic plants compete with native vegetation but they can also change the physical and biological environment. Changes have been noted in moisture and nutrient status, microbial populations, and soil characteristics where exotic plants have become established. Organisms dependent on native plants and adapted to a particular environment are also affected.
Introduction of Exotic Pests Exotic pests usually travel to new areas as hitchhikers. Weed seeds, fungus spores, insect eggs, cocoons, or larvae arrive on plants, furniture, lawn mowers, logs, ships, cars, trailers, trains, and planes. Less frequently, they are blown or washed in by storms or other anomalous weather. Port-Orford-cedar root disease is thought to have arrived in the Pacific Northwest on infected ornamental plants in the 1920s; it then spread to both native Port-Orford-cedar in southwest Oregon and ornamental Port-Orford-cedar throughout western Washington and Oregon.
Increased travel, population expansion, and new trade with South America, Japan, China, and the former Soviet Union will contribute to increased introductions of plants and animals and increased chances that they will become established once they arrive. The benefits of economic growth for states such as Oregon and Washington resulting from trade with other countries has to be weighed against the risk of introducing new pests and the potential damage to forests. New regulations for imports of logs and lumber (and other unmanufactured wood items) have recently been implemented by the states and the Animal and Plant Health Inspection Service (APHIS), a branch of the U.S. Department of Agriculture, to reduce the risk of introducing forest pests into the United States.
Reducing Introductions Experts have suggested the following measures to slow introductions and prevent establishment of exotic pests.
Control and Eradication A pest becomes established once it is able to reproduce and maintain a population that survives from year to year. For exotic pests already established in Pacific Northwest forests, management strategies already in place are minimizing their effects: natural enemies such as predators and parasites are being released to control populations of some exotic pests; resistance breeding programs are in place for white pine blister rust and Port-Orford-cedar root disease; and appropriate silviculture and pest management practices are applied in many areas to minimize exposure and spread. Unlike white pine blister rust or Port-Orford-cedar root disease, the European and Asian gypsy moths are not yet "established" in the Pacific Northwest. The moth populations are still too low to breed effectively and establish permanent populations. Eradication efforts, such as pesticide treatments, are the most practical and effective at this preestablishment stage. In 1996, ten urban areas in the Northwest were treated for gypsy moth to prevent their establishment.
Air pollution alters the chemical environment in which plants
grow
and affects the health of the forest.
The population in Oregon and Washington is projected to increase into the future, and with more people come more cars and other services that cause air pollution. Washington Environment 2010, a recent study by the State of Washington and the Environmental Protection Agency, projects that over the next 15 years, concentrations of the pollutants of greatest concern to natural resource managers-sulfur compounds, nitrogen compounds, and ozone-will not improve. In fact, ozone is expected to increase by 30% in the Puget Sound area unless additional actions are taken.
Air-quality work in Oregon and Washington forests has focused on the effects of ozone on vegetation, using lichens as air-quality bioindicators, evaluating the sensitivity of alpine lakes to acid deposition, and determining the acidity of cloud water.
Ozone Ozone is formed on warm sunny days from hydrocarbons and nitrogen dioxide emitted by cars and trucks. Unlike stratospheric ozone, which protects life on Earth from the Sun's ultraviolet rays, ozone in the troposphere-created from nitrogen oxides and volatile organic compounds by sunlight-is known to be unhealthy for people as well as plant life.
Ozone is generally a problem to forest vegetation only in the summer when plumes of pollutants flow downwind from major urban centers. Possible effects to vegetation include visible leaf injury, reduced photosynthetic capacity, increased respiration, premature leaf death, reduced growth, and mortality.
Ozone damages the most sensitive plants at concentrations lower than those that are harmful to people. The federal human-health standard is 120 parts per billion (ppb). Lichens, a group of ozone-sensitive organisms, can be adversely affected at concentrations between 15 and 70 ppb. Effects on lichens are subtle but can ultimately be fatal. Entire lichen species can disappear from the landscape before anyone notices. Recent studies of native herbaceous seedlings and ozone profiles commonly found in the Pacific Northwest showed that typical ozone concentrations could cause damage and increase mortality of certain common species.
The Forest Service air program in Oregon and Washington and the Washington Department of Ecology currently measure ozone electronically at Darrington, for the Glacier Peak Wilderness; Packwood Lake, for the Goat Rocks Wilderness; and Wishram in the Columbia River Gorge. Ozone is also being measured in wilderness areas by passive sampling, which uses inexpensive coated filters that chemically react at a known rate when exposed to different ozone concentrations. The next step is to establish plots of ozone-sensitive species in the highest ozone-exposure areas downwind of the Puget Sound and Portland urban areas as another monitoring method.
Lichens As Bioindicators Lichens (plants made up of a symbiotic association of alga and fungus) are sensitive to common pollutants in the Pacific Northwest: sulfur dioxide; oxidants such as ozone, acid rain, and fluorine; and some metals. Lichen species vary in their sensitivity to different pollutants. The presence or absence of different lichen species and the symptoms of pollution injury can help locate places with relatively high amounts of air pollution.
Lichens are being inventoried and monitored extensively west of the Cascades. Initial analysis of monitoring results showed a curious absence of leafy, nitrogen-fixing (air-pollution sensitive) lichens and an unexpected abundance of nitrogen-loving (pollution tolerant) lichens in the Willamette Valley and the Columbia River gorge.
Acidity of Cloud Water Water in clouds and fog can become acidic through interaction with atmospheric pollutants. Plants can absorb this acidic moisture through aboveground parts or through their roots after the moisture condenses and drips to the ground. Acidic cloud water can inhibit growth of sensitive species. Cloud water was monitored during the summer of 1991 at Stampede Pass and Granite Peak in the Alpine Lakes Wilderness, and during the summer of 1994 at Green Mountain in the Glacier Peak Wilderness. The minimum acidity of cloud water (pH 3.6) collected in 1991 for both sites was far more acidic than is necessary to inhibit growth of some species. Unfortunately, the only information currently available about effects on local species is for conifer seedlings exposed to acidic fog under controlled conditions. More information is needed about the effects of acidic cloud water, as well as injury thresholds to local species, before cause for concern is verified.
Changes in forest health can be detected
by monitoring the
condition of the forest.
Several monitoring tools and methods are available for measuring the forest. Some have been used for years; others are new and have had only limited use. Many forest monitoring programs, such as forest inventories, focus primarily on vegetation condition and change. Other parts of the environment-like weather, air quality, riparian habitat, fisheries, and wildlife-are measured in separate surveys or, more recently, in multiresource surveys.
Aerial Survey The Forest Service and the States of Oregon and Washington began a cooperative aerial survey for insect damage in 1947; only National Forests and some state lands were surveyed. From the 1960s and continuing to the present, all forested lands in the two states, regardless of ownership, are surveyed by air. The states also fly special aerial surveys to track specific problems, such as bear damage in coastal Oregon forests.
Survey results are used by Forest Service and state resource managers to track the approximate location and acreage of dying or damaged trees, to follow cycles of insect outbreaks, and to predict future damage. Land owners and managers use survey results to locate areas of insect or disease damage on their lands and to aid them in management decisions.
Forest Inventory The Forest Service began to inventory the timber resource on federal, state, and private lands in the 1930s. In 1993, the National Forest inventory in Oregon and Washington was changed to a multiresource survey, in which understory vegetation, forest floor woody material, wildlife habitat, and damage agents are also recorded.
Forest inventories are ground-based (rather than aerial); they now consist of a series of systematically located plots that are remeasured periodically, at 8- to 10-year intervals. Data from the plots are pooled to provide an estimate of forest condition across any grouping, geographic or biological.
Forest Heath Monitoring Plot Network A network of forest health monitoring plots has been established on forested land of all ownerships across the United States. It consists of a series of ground plots on which variables, selected because scientists thought they would be good indicators of forest health, are measured. Although some variables are the same as inventory measurements, others are quite different, such as tallying the number and diversity of lichens as indicators of air quality.
Forest Health Monitoring is a national program, a partnership between several federal and state agencies. The program was started in the Northeast in response to concerns about acid rain and now includes 19 states. Oregon and Washington established and measured 25 plots in 1994 as a pilot project (see chapter 5 for results of the pilot project). The two states are scheduled to fully implement the program in 1997. The purpose of the Forest Health Monitoring program is to determine the condition of forests over large areas, such as the West or the entire United States, and to detect changes in forest health at a broad scale.
New Monitoring Technology The launching of satellites and the explosive growth in computer technology have created many possible applications of new technologies to forest monitoring. Commercially available satellite imagery of forested land can be sorted and classified to identify species composition, tree size, and canopy density for any given area of forest. Changes in vegetation can be detected by periodic comparisons of satellite images. In Oregon and Washington, satellite imagery of the National Forests is being purchased, classified, and used by the Forests.
Geographic information systems (GIS) are used extensively to store and retrieve aerial survey and other monitoring data. These systems geographically reference each piece of information and allow maps to be made that include many layers of data. Another new technology is the global positioning system (GPS). Using signals from several satellites, a portable GPS unit can calculate the precise location of a field plot. Currently, GPS units are taken to each forest inventory plot to record plot location. The location can then be entered on a GIS, and the inventory data for that plot can be related to other data for that particular location.
Risk Rating Monitoring susceptibility, or risk to disturbance agents, is another way of monitoring forest health. Using stand examination data from site visits, inventory data, aerial photography, and knowledge of forest conditions conducive to insects, disease, and fire, forested areas can be assigned a rating of current risk to a particular disturbance agent. Over time, risk can change through "natural" maturing of the forest, removal of some trees by a disturbance, or management activities such as thinning, prescribed fire, or harvest. Subsequent risk ratings using updated information can show these changes in risk. Several computer programs for risk rating stands and watersheds are being used by National Forests to assist them in watershed analysis.
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