GEISER, LINDA H. USDA-Forest Service, Siuslaw National Forest, PO Box 1148, Corvallis, OR 97339. - Establishing background ranges and mapping of lichen sulfur, nitrogen and metal concentrations in Pacific Northwest forests.
Lichen data are being collected in western Oregon, Washington and
southeastern Alaska to aid decision-making processes that affect air
quality on national forests. Common lichens are analyzed for tissue
concentrations of pollutants such as sulfur, nitrogen, lead, and
metals. To identify geographic areas of concern and assess the
significance of trends over time, forest managers must be able to
distinguish elevated values from values typical of background sites.
To determine background ranges, tissue data from 8 national forests
were compared after removing sites close to urban areas, roads and
high human activity. Ranges of anthropogenic elements in southeastern
Alaska were similar to OR and WA Forests. The 97.5% quantiles of the
combined “clean sites” database were used as cut-offs for elevated
values. All values were then mapped. Elevated values for sulfur and
nitrogen were observed along the Columbia River Gorge National Scenic
area (CRGNSA), the northern half of the Mt. Hood National Forest, the
I-5 corridor, urban areas and near national forest boundaries. Lead
was highest in urban areas, the CRGNSA and along the crest of the
Cascade Range. Other metals were elevated in the CRGNSA, in urban
areas, in areas with serpentine soils on the Umpqua National Forest,
and in the north half of the Gifford Pinchot National Forest
corresponding to areas of greatest ash deposits from Mt. St. Helens
eruptions. A next step is to determine whether adverse effects on
forest health, community composition or ecological function can be
detected in areas where natural events or conditions cannot explain
elevated values.
Key words: air pollution, lichens, metals, nitrogen, Pacific Northwest, sulfur