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Criterion 3 Indicator 16
Area and Percent of Forest Land Subject to Specific Levels of Air Pollutants (E.G., Sulfates, Nitrates, Ozone) or Ultraviolet B that May Cause Negative Impacts on the Forest Ecosystem
  Tree leaves and needles capture considerable amounts of solid, gaseous, and dissolved compounds from the atmosphere. Those air-borne gases and particles that are harmful to organisms in terrestrial and aquatic ecosystems are collectively called "pollutants." Air pollutants can have direct, visible, damaging effects on forest vegetation: foliage discoloration; partial death of foliage, branches, and crown; and stunted growth. The most visible effects from pollutants are commonly seen downwind from known pollution sources such as large cities, power plants, and mine smelters. Other effects on trees and plants are subtle and difficult to determine. These include modified physiological function such as reduced photosynthesis and diminished root growth, altered appearance and flowering, and changes in the historical distribution and abundance of vascular and nonvascular plants such as lichens.

Can This Indicator Be Quantified
Currently, it would be difficult to quantify the effects of air pollutants on forests in Oregon. In order to estimate or predict pollutant loadings and vegetation response to pollutants, it would be necessary to make detailed analyses of actual emissions; transport of emissions into and out of target areas; dispersion and transformation of chemicals that arrive in an area; and quantification of chemical exposure on forest vegetation and other organisms. Existing air quality monitoring stations in Oregon are few and scattered across the state. Local climate, meteorology, and the processes by which pollutants are deposited are different at low-elevation monitoring stations from conditions found at high-elevation stations. Similarly, deposition patterns around urban and industrial areas are different from patterns in rural areas and wilderness sites. Finally, Oregon has diverse forest ecosystems, ranging from moist to dry forests, and pollutant effects would vary among different forests.
Where pollution effects do seem to exist, it is very challenging to determine a direct causal relationship between diminished tree growth and a single pollutant or multiple pollutants. First, tree death and injury are caused by several factors that, although not related to pollution, are probably facilitated by it. Second, several pollutants can exist in the same air mass; this makes it difficult to tie specific problems to a single pollutant unless controlled exposure chambers are used. Common gaseous components of polluted air are: sulfur dioxide (SOx) from coal burning; nitrous oxides (NOx) from coal burning, automobiles, and agriculture; and ozone, which is formed when volatile organic compounds and nitrous oxides mix with sunlight. In addition, toxic metals like lead and copper, which are produced by smelters and coal burning, can be problems also. These metals can be deposited by rain, as well as carried in the air. When nitrogen (N) and sulfur (S) deposition rates exceed the rates at which soils can store these chemicals or plants can absorb them, the result can be conditions saturated by the two elements, which can be detrimental to terrestrial and aquatic organisms.
In general, air quality is always influenced by local and regional emissions and local meteorology. Also, the physical and chemical composition of an air mass dictates how the various components are dispersed, transported, transformed chemically, and deposited. The Pacific Northwest has good air quality compared to most areas of the United States for three reasons. First, incoming air masses originate over the Pacific Ocean where pollutant loadings are low. Second, air pollution emissions from industrial sources in the Pacific Northwest are still low compared to other regions, although a growing population and development could change this trend. Finally, no major point pollution source like a mine smelter exists in Oregon.

There is generally less air pollution in the Pacific Northwest than in the industrialized East. Based on National Acid Deposition Program monitoring data collected since the late 1970s, sulfate and nitrate deposition have stayed about the same in the Pacific Northwest. In Oregon, areas of major concern are the areas east and south of the Portland metropolitan area, east of the Interstate 5 highway corridor, and downwind from developed urban areas that produce ozone. The Columbia River Gorge National Scenic Area is of concern because ozone and heavy metal loadings seem to be increasing in the area, from levels recorded since 1993.
Limited data suggests that some macro-lichen species are adversely affected by atmospheric pollutants, as indicated by the species’ distribution, abundance, and tissue analyses. However, researchers have not yet established a direct link showing the susceptibility of macro-lichens and overstory species to atmospheric deposition of pollutants.
Although ozone damage has been seen on understory species such as blue elderberry and huckleberry in Oregon, there is little documented visible injury on tree species at field ozone concentrations. From exposure chamber studies that measured shoot and root growth response of two-year-old seedlings, evidence was gathered that ponderosa pine, alder, and aspen seedlings are sensitive to ozone; Douglas-fir is relatively insensitive; and hemlock and lodgepole pine are insensitive. It is not yet known if the pollution responses of seedlings can be extrapolated to trees. Limited data from forest stands suggests that damage by one pollutant like ozone could be offset by deposition of another pollutant like nitrogen. Ultraviolet-B radiation effects are not yet documented for western tree species.

Data Source and Availability
Atmospheric pollutant databases are extensive and have short-term information, but lack information about what areas are showing pollution effects on vegetation. Most air pollution databases are maintained by public agencies, and track compliance with air quality standards in the Clean Air Act. The table below shows gaseous or wet and dry deposition products, measurement duration, and web sites to access available data.
The AIRS (Aerometric Information Retrieval System) national network tracks pollutants that are detrimental to public health and welfare in the United States. In Oregon, most air monitors are in urban areas. Only 1 records nitrate and sulfate; 7 record ozone; and 35 measure fine particulates. Measurements are only available since 1993.
The IMPROVE interagency network protects the visibility of 156 Class 1 wilderness and national park areas in the United States from human-produced air pollution. In Oregon, dry deposition data is available only for the Three Sisters Wilderness since 1993 and Crater Lake National Park since 1988. Crater Lake also has a National Park Service gaseous pollutant monitoring site.
The NADP (National Acid Deposition Program) is also a national network. It collects wet deposition data and has six active and five inactive monitoring sites spread across Oregon.
The U.S. Forest Service has established a lichen biomonitoring program in its Pacific Northwest Region. Plots are established about 3.6 miles apart. The tissues of 10 lichen species are tested for concentrations of 27 elements, including heavy metals. Baseline samples exist for about 75 percent of the total national forest area in Oregon.
The National Forest Health Monitoring (FHM) Program is collecting baseline lichen data for about 170 field plots in Oregon. This program also assesses visible ozone damage on sensitive understory plants at nearby reference sites. No significant ozone damage was seen in 1998.
Table 16-1. Data sources 1 for gaseous and other air pollutants affecting forest ecosystems in Oregon
Data sources1 for gaseous and other air pollutants affecting forested ecosystems in Oregon       
DatabaseDurationCarbon MonoxideOzoneNitrogenSulfurLead MatterParticulate
IMPROVE1993+  X(dry)X(dry)  
NADP1979/84+  X(wet)X(wet)X 
Lichen biomonitoring21993+  XXXX
FHM monitoring1998+ X    

  1. Web sites for databases describing air pollutants affecting Oregon forests:
    AIRS — http://www.epa.gov/airsdata/
    IMPROVE — http://www.fs.fed.us/r6/aq/imprdata.htm
    NADP — http://nadp.sws.uiuc.edu/nadpdata/state.asp?state=OR
    Lichen biomonitoring http://www.fs.fed.us/r6/aq/lichen/
  2. Elemental concentrations of pollutants in lichen tissues.

Reliability of Data
The AIRS, IMPROVE, and NADP programs that monitor air pollutant concentrations have intensive national and state-level quality assurance audits and reviews, to ensure that programs are meeting regulatory standards set by the Clean Air Act. The U.S. Forest Service and FHM lichen and ozone biomonitoring programs in Oregon also follow national training, sampling, and audit protocols. However, the three air monitoring networks have major limitations, including a lack of data continuity for some sampling stations, and a limited number of stations located across the full range of forest ecosystems, from wet to dry and high to low elevation.

The AIRS, IMPROVE, and NADP sites are part of national monitoring networks. But most of the collected information is site-specific because there are few network stations, and local conditions such as weather and elevation are very variable. The U.S. Forest Service’s lichen biomonitoring program is limited to plots on a 3.6-mile grid across national forest lands. Lichen and ozone biomonitoring for the Forest Health Monitoring Program extends across all ownerships but is limited to forested plots on a 17-mile grid across the state. Given the present limited data, it is difficult to make broad quantitative statements about air pollution impacts on forests in a large state like Oregon.

Recommended Action for Data Collection
Regional air quality experts must determine if a sparse network of permanent and/or passive analyzers is sufficient to monitor ozone and other air pollutants, from urban to wilderness areas and across flat to very mountainous terrain. They can also recommend which existing monitoring sites should not be deactivated because of their critical location in wilderness or other special areas. The Columbia River Gorge National Scenic Area needs particular attention and perhaps more monitoring because of increasing pollution from the Portland and Vancouver metropolitan areas.
Lichen collection and tissue analysis should be completed for all national forests. New sampling and interpretations with overstory vegetation could be done on BLM, National Park Service, and state forest and range lands. Interagency programs could study multiple pollution effects on young and old trees compared to seedlings, establish transects through the Columbia River Gorge to quantify air quality change and tree growth response, and develop distribution maps showing the sensitivity of major forest species to ozone and other pollutants.


Selected References
Grulke, N. E., and L. Balduman. In press. Deciduous conifers: high N deposition and O3 exposure effects on growth and biomass accumulation in ponderosa pine. Water, Air and Soil Pollution.
Hogsett, W. E., and D. T. Tingey, C. Hendricks, D. Rossi. 1989. Sensitivity of western conifers to SO2 and seasonal interaction of acid fog and ozone. In: Olson, R. K., and A. S. Lefohn, editors; Effects of air pollution on western forests, pp. 469-491. In: APCA
Transactions Series ISSN 1040-8177; No. 16. Air and Waste Management Association, Anaheim, CA. 577 pp.
Peterson, D. L. In press. Monitoring air quality in mountains: Designing an effective network. In: Proceedings of EMAP Symposium: Western ecological systems: status, issues and new approaches, mountains and forest ecological systems, April 6-8, 1999, San Francisco, CA. Environmental Monitoring and Assessment J.
Peterson, J., and D. Schmoldt, D. Peterson, J. Eilers, R. Fisher, R. Bachman. 1992. Guidelines for evaluating air pollution impacts on Class 1 wilderness areas in the Pacific Northwest. USDA Forest Service Pacific Northwest Research Station, Portland, OR. General Technical Report PNW-GTR-299. 83 pp.
USDA Forest Service. 1997. First approximation report for sustainable forest management. Washington, D.C.
Waring, R. H., and S. W. Running. 1998. Forest ecosystems — Analysis at multiple scales (2nd edition). Academic Press, San Diego, CA. 370 pp.

People Interviewed
  Chris Anderson, Environmental Protection Agency, Corvallis, OR.
Robert Bachman, USDA Forest Service, Pacific Northwest Region, Portland, OR.
Steve Boutcher, USDA Forest Service, Pacific Northwest Region, Portland, OR.
Sally Campbell 1, USDA Forest Service, Pacific Northwest Region, Portland, OR.
Linda Geiser, USDA Forest Service, Siuslaw National Forest, Corvallis, OR.
Nancy Grulke, USDA Forest Service, Pacific Southwest Region, Riverside, CA.
Bill Hogsett 1, Environmental Protection Agency, Corvallis, OR.
Bruce McCune, Dept. of Botany and Plant Pathology, Oregon State University, Corvallis, OR.
Anne Mebane, NRIS, USDA Forest Service, Pinedale, WY.
Paul Miller, USDA Forest Service (retired), Pacific Southwest Research Station., Riverside, CA.
Peter Neitlich, National Park Service, Nome, AK.
David Peterson 1, USGS Biological Resources Division, Seattle, WA.
  1. Completed technical review of draft before its submission to Oregon Department of Forestry.