Pacific Northwest Lichen Sensitivity Ratings by Species

Air quality sensitivity ratings are based on our own field studies and a world-wide literature review emphasizing references from western North America. Lichen sensitivy can vary with climate, the composition and proportion of airborne pollutants in the air, and topographic exposure. The ratings presented here are specific to the Northwest USA and may or may not be accurate for other regions. All literature cited here can be found in our annotated bibliography.

To learn about a particular species of lichen, click on the name. To browse through all of the listed species alphabetically, just scroll further down on this page.

All photos © S. Sharnoff except where indicated otherwise.

 

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Alectoria imshaugii

PNW Rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and wood of both conifers and hardwoods. Common in moist low to mid elevation forests east of the Cascade Range crest, but only occasional in the western Cascades. Ranges from southern British Columbia to California, east to western Montana and the Continental Divide.

Alectoria sarmentosa

PNW rating: Sensitive

Sulphur dioxide

Sensitive: 5-15 ppb (Peterson et al. 1992); (Kuusinen et al. 1990).

Intermediate: present at 12.6-19.2/ absent from 19.2-28.9 ppb (Wetmore 1983).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992); (Ryan 1990).

Habitat

On bark or wood, rarely on rock or mosses over rock. Common in low to mid elevation conifer forests, associated with old-growth forests; toward the eastern edge of its range increasingly restricted to moist, old-growth forest. Ranges from Alaska to California, east to Alberta and Montana; mainly west of the Continental Divide.

Alectoria vancouverensis

PNW rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and wood. Most common in the transition between valley forests and mountain forests (generally below about 700 m); often occurring in the same stands as A. sarmentosa, but usually dropping out below the elevation of highest dominance by Alectoria; more common on the immediate coast than A. sarmentosa. Coastal British Columbia south to California, in and west of the Cascade crest.

Bryoria capillaris

PNW rating: Sensitive

Sulphur dioxide

Sensitive: 5-15 ppb (Peterson et al. 1992); (Ryan 1990).

Intermediate: present between 20.8-31.2 ppb (Wetmore 1983).

Fluoride

Sensitive: ? (Peterson et al. 1992).

General

Sensitive: (McCune & Geiser 1997).

Sensitive to intermediate: 5.7-9 (Insarova et al. 1992).

Habitat

On bark or wood of both conifers and hardwoods but typically on conifers. Most common in understory of Abies, Picea, Pseudotsuga, and Thuja forests. Alaska to northern California, east to Newfoundland, with a disjunct in Colorado; most common in moist low elevation forests between the Cascade and Rocky Mountain crests.

Bryoria trichodes

PNW rating: Sensitive

Sulphur dioxide

Sensitive: present at 5.4.8-9.6/ absent at 9.6-19.2 ppb (Wetmore 1983); (Ryan 1990).

Sensitive to Intermediate: 5-35 ppb Peterson et al. 1992.

General

Sensitive: 9 (Insarova et al. 1992)

Habitat

On bark or wood of conifers. Wet coastal forests at low to high elevations. Alaska to Santa Cruz, mainly in the Coast Range, west of the Cascade crest in Oregon and Washington.

Candelaria concolor

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive to Intermediate: present 4.8-14.8/absent 18.5 ppb (Wetmore 1983).

Sensitive to Intermediate: 5-35 ppb (Peterson et al. 1992); (Crock et al. 1992).

Intermediate: zone 7, nitrophilous, tolerates 14.8 ppb (Hawksworth and Rose 1970).

Fluoride

Sensitive to Intermediate: 18 (LeBlanc et al. 1972).

General

Intermediate: (Johnson 1979); (Hoffman 1974); (LeBlanc & Sloover 1970).

Intermediate to Tolerant: (McCune 1988); 2-6.7 (Insarova et al. 1992).

Notes: very common, but fertile at 13% of the stations in zone 5 and sterile in all other zones (LeBlanc & Sloover 1970); affected by agricultural pollution (Purvis et al. 1992).

Habitat

On nutrient-rich bark or wood (mainly hardwoods), roofing; rarely on rock.Valleys and foothills, often in urban, suburban, and agricultural areas; occasional in the mountains. Widespread.

Cetraria chlorophylla

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive: present 3.7-11.1 ppb (Wetmore 1983); 5-15 ppb (Peterson et al. 1992); (Ryan 1990).

Tolerant: fairly tolerant (Kuusinen et al. 1990).

Fluoride

Intermediate: ? (Peterson et al. 1992).

General

Sensitive to tolerant: 2-10 (Insarova et al. 1992);

Intermediate: nitrophilous (McCune & Geiser 1997).

pH

Tolerant: favored by bark acidification (Nieboer & Richardson 1981)

Habitat

On bark and wood, fallen logs, fences, roofs, rarely on rock. Within the PNW, this is one of the most versatile foliose lichens, being found quite frequently in a range of habitats matched by few plants or lichens. Its habitats range from extreme oceanic sites to dry interior forests in continental climates. It tolerates both full sun and deep shade. Range is circumpolar, subarctic south through Cascades and Rocky Mountains to California and Colorado; common throughout the PNW.

Cetraria orbata

PNW rating: Intermediate

Sulphur dioxide

Intermediate: present at 19.2-28.9 ppb (Wetmore 1983).

General

Intermediate: (McCune & Geiser 1997).

Habitat

On bark and wood, mainly conifers but also on hardwoods. Mainly in low elevation moist forests, fairly shade tolerant but also in exposed microsites. British Columbia to California, inland to western Montana; rare east of the Continental Divide, common in areas of strongest Pacific coastal influence.

Collema furfuraceum

PNW rating: Sensitive

General

Intermediate: (McCune & Geiser 1997).

Habitat

On bark (especially broad-leaved trees), occasionally on rock. Found in moist habitats, in Oregon and Washington most common in moist low-elevation riparian forests. Widespread in North America, found throughout the forested part of the PNW, in both oceanic and continental climates.

Evernia prunastri

PNW rating: Tolerant

Sulphur dioxide

Sensitive: (Taylor & Bell 1983); 185 ppb/14 hr (Turk & Lange 1974).

Sensitive to Intermediate: (Ryan 1990); absent or rare at levels >22.2 ppb (Purvis et al. 1992); 5 (Nash & Wirth 1988); zone 5, tree bases,non- nitrophilous, 22 ppb (Hawksworth and Rose 1970); moderately sensitive (Kuusinen et al. 1990).

Intermediate: 18.5-24.1/- ppb (134); 8,NA,8 (Nash & Wirth 1988); grp 2 (Diamantopoulos et al. 1992).

Intermediate to Tolerant: 10->30 ppb (Peterson et al. 1992).

Notes: More sensitive to S deposition on conifers than on deciduous trees w/ less acidic bark (Kuusinen et al. 1990). High concentration and long exposure (fumigation) =>reduced photosynthesis and respiration, chlorophyll destruction (Sanz et al. 1992).

Fluoride

Sensitive: ? (Peterson et al. 1992); (Perkins & Millar 1987a).

Notes: Bleaching (Perkins & Millar 1987a).

Ozone/PAN

Sensitive: <20 ppm (Peterson et al. 1992); (Ryan 1990).

General

Sensitive: very sensitive (Sigal & Nash 1983); class 3, sensitive (Denison & Carpenter 1973).

Sensitive to intermediate: 4-10 (Insarova et al. 1992).

Tolerant: (McCune & Geiser 1997).

Notes: Inconclusive (Johnson 1979).

Metals

Notes: Slightly < C-fixation (photosynthesis) w/ Zn sol. (Brown & Beckett 1983).

Habitat

On wood or bark, especially hardwood trees and shrubs, occasionally on conifers. Ubiquitous in most habitats at low elevations west of the Cascade Range crest, especially hardwood forests, savannas, and in urban and agricultural areas; less abundant in lower mountain forests where it is best developed in pockets of hardwoods; east of the Cascade crest almost entirely restricted to riparian forests and shrubby areas. Most common west of the Cascade crest, sporadic east of the crest to Idaho, rarely inland to western Montana.

Hypogymnia physodes

PNW rating: Tolerant

Sulphur dioxide

Sensitive: <16-18 ppb (Vick & Bevan 1976); grp 3 (Diamantopoulos et al. 1992).

Intermediate: (Turk & Lange 1974); 19.2-26/29 ppb (Wetmore 1983); zone 4-5, base of tree, 5 extends up trunk: non-nitrophilous, 26-22 ppb (Hawksworth and Rose 1970).

Intermediate to Tolerant: 10->30 ppm (Peterson et al. 1992); (Nash & Wirth 1988).

Tolerant: absent at levels >40 ppb (Purvis et al. 1992); semitolerant: 36-44 ppb (Johnsen & Søchting 1973); fairly tolerant (Kuusinen et al. 1990).

Notes: Reduction in total physiological activity (Ferry & Coppins 1979); 139-1204 ppm (Taylor & Bell 1983).

Fluoride

Sensitive: 17 (LeBlanc et al. 1971).

Sensitive to Intermediate: (Peterson et al. 1992); (Perkins & Millar 1987a).

Notes: Bleaching, turning red (Perkins & Millar 1987a).

General

Intermediate: (Skorepa & Vitt 1976).

Intermediate to Tolerant: 1.4-7 (Insarova et al. 1992).

Tolerant : (Johnson 1979); (McCune & Geiser 1997); one of the most pollution tolerant lichens, though studies using H. physodes at its southernmost limit may reflect rarity, or enhanced sensitivity (Wetmore 1987b).

Inconclusive: (LeBlanc & Sloover 1970).

Low pH

Intermediate to Tolerant: 14% K leakage (Farmer et al. 1992).

Habitat

On bark and wood, occasionally on rock or mossy. Ubiquitous in forests at low to mid elevations, often in nonforested habitats (steppe, shrub thickets, farmlands, etc.). Widespread, common throughout the PNW.

Hypogymnia tubulosa

PNW rating: Tolerant

Sulphur dioxide

Sensitive: present at 4-12 ppb (Wetmore 1983).

Fluoride

Sensitive: (Perkins & Millar 1987a); ? (Peterson et al. 1992).

General

Intermediate: (Johnson 1979); broadly intermediate, 2-8 (Insarova et al. 1992).

Tolerant: (McCune & Geiser 1997).

Habitat

On bark and wood. Mostly in open or semi-open habitats at low to mid elevations, including riparian areas, farm trees, urban areas, savannas, and wooded wetlands; sporadic in closed forest. Widespread, common throughout the forested parts of the PNW.

Lobaria oregana

PNW rating: Sensitive

Sulphur dioxide

Sensitive: <20 ppb (Peterson et al. 1992).

General

Sensitive: (McCune & Geiser 1997).

Volcanic ash

Notes: Specimens from the high impact sites showed reduction in photosynthetic capacity 40->50% (Moser et al. 1983).

Habitat

Usually on coniferous trees; sporadically on hardwoods including Alnus, Fraxinus, and shrubs. Oceanic forests, reaching maximum dominance in mid-elevation old-growth forests (Pseudotsuga - Tsuga heterophylla) on the western slope of the Cascades. Occasional in moist low-elevation forests in the foothills. Alaska to California, west of the Cascade crest; known east of the crest from only two sites (British Columbia and northern Idaho).

Lobaria pulmonaria

PNW rating: Sensitive

Sulphur dioxide

Sensitive: present at 10.4/absent between 10.4-13.6 ppb (Wetmore 1983); 5-15 ppb (Peterson et al. 1992); genus extremely sensitive: <9.25 ppb (Purvis et al. 1992); 7, zone 9, non-nitophilous, < 11.1 ppb (Hawksworth and Rose 1970).

Sensitive to Intermediate: (Nash & Wirth 1988) ; (Turk & Lange 1974).

Notes: 170 ppb/14hrs/ complete saturation (Nash 1976).

Ozone/PAN

Intermediate to Tolerant: 15->65 ppb (Peterson et al. 1992).

Tolerant: No signif effect on N fix. or Ps (Sigal & Johnston 1986).

General

Sensitive: class 4, very sensitive (Denison & Carpenter 1973); (McCune & Geiser 1997); 7-10: (Insarova et al. 1992).

Notes: Loss of mature parts and chlorosis (Wolsely & James 1992).

Low pH

Intermediate: 17.8% K leakage (Farmer et al. 1992); acid rain pH 2.6 caused 100% loss in N fix and 90% loss in Ps (Sigal & Johnston 1986).

Metals

Notes: Slightly < C-fixation (photosynthesis) w/ Zn sol. (Brown & Beckett 1983).

Habitat

On trees (both conifers and hardwoods), shrubs, and mossy rock Moist lowland to mid elevation forests in areas of strong coastal influence; frequent west of the Cascade crest, occasional in n Idaho, uncommon to rare elsewhere east of the Cascades. Alaska to central California, inland to western Montana.

Lobaria scrobiculata

PNW rating: Sensitive

Sulphur dioxide

Sensitive: 5-15 ppb (Peterson et al. 1992); genus extremely sensitive, <9.25 ppb (Purvis et al. 1992); one of the most air-poll.-sensitive lichens (Hallingback 1989); 14.5 (Nash & Wirth 1988); zone 10, non-nitrophilous, 'pure air' (Hawksworth and Rose 1970).

General

Sensitive: 10 (Insarova et al. 1992); (McCune & Geiser 1997).

Low pH

Sensitive: 56.7% K leakage (Farmer et al. 1992); symptoms of acid rain damage are chlorosis, loss of mature lobes, negative growth rate (Wolsely & James 1992).

Metals

Notes: reduced C-fixation (photosynthesis) w/ Zn soln. (Brown & Beckett 1983).

Habitat

On trees, shrubs, and mossy rocks, rarely on the ground. Most frequent in low-elevation hardwood forests, swamps, and savannas west of the Cascade crest; also in low- to mid-elevation old-growth conifer forests; east of the Cascade crest restricted to sheltered mossy outcrop areas, often near lakes or streams. Circumpolar boreal south to Montana and northern California; rare east of the Cascades where it is known only along Salmon River and in western Montana.

Melanelia exasperatula

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive: S (Diamantopoulos et al. 1992).

Intermediate: present at 12-32/absent at 24 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); tolerant to 28 ppb (Purvis et al. 1992); (Ryan 1990); grp 3, zone 6-7, 7 up trunk, non-nitrophilous, 18.5-14.8 ppb (Hawksworth and Rose 1970).

General

Intermediate: broadly intermediate2.9-8 (Insarova et al. 1992); often in relatively polluted areas and increasing (Purvis et al. 1992); nitrophilous (McCune & Geiser 1997).

Habitat

On bark or wood (both conifers and hardwoods), rarely on rock. Frequent in a very broad range of habitats, from low to high elevations, in both continental and oceanic climates, and in deep shade to exposed habitats. Widespread, throughout western North America, common on both sides of the Cascades.

Nephroma bellum

PNW rating: Sensitive

Sulphur dioxide

Sensitive: genus is sensitive (Purvis et al. 1992).

General

Sensitive: (McCune & Geiser 1997).

Sensitive to Intermediate: 6-9 (Insarova et al. 1992).

Habitat

On trees, shrubs, and mossy rocks. Moist forests with strong coastal influence; often on riparian hardwoods. Widespread; throughout the PNW, but infrequent to rare east of the Cascade crest.

Nephroma helveticum

PNW rating: Sensitive

Sulphur dioxide

Sensitive: genus is sensitive (Purvis et al. 1992).

General

Sensitive: 8 (Insarova et al. 1992); (McCune & Geiser 1997).

Habitat

On mossy rocks and woody plants. Generally in moist shady habitats; primarily moist low-elevation (often riparian) forests. Widespread, throughout the PNW, but most common in forests with a strong coastal influence.

Nephroma laevigatum

PNW rating: Sensitive

Sulphur dioxide

Sensitive: genus is sensitive (Purvis et al. 1992).

General

Sensitive: (Insarova et al. 1992); (McCune & Geiser 1997).

Intermediate: present at 26 ppb (Wetmore 1983).

Metals

Notes: reduced C-fixation (photosynthesis) w/ Zn sol. (Brown & Beckett 1983).

Habitat

On trees (mainly hardwoods) and shrubs, less often on rock. Moist low to mid elevation forests, often in riparian areas and on understory shrubs. Common from Alaska to California, west of the Cascade Range crest.

Nephroma parile

Nephroma resupinatum

PNW rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and rock. Shady to somewhat open, moist riparian forests, occasionally in upland forests west of the Cascade Range crest. Widespread in boreal, Montana, and oceanic forests, in the PNW most common in areas of strongest oceanic influence.

Pannaria leucostictoides

PNW rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and wood of both hardwoods and conifers. Edges of coastal forests, oak savannas, and other valley and foothills woodlands, rarely inland on edges of old oceanic forests. British Columbia to California, occuring west of the Cascade Range crest but with rare disjuncts in Idaho.

Pannaria mediterranea

PNW rating: Sensitive

General

Sensitive: 8 (Insarova et al. 1992); (McCune & Geiser 1997).

Habitat

Mainly on bark, sometimes on mossy rock or soil. Occasional in the western Cascades at low elevations but rare east of the Cascade crest.

Pannaria rubiginosa

PNW rating: Sensitive

General

Sensitive: 10 (Insarova et al. 1992); (McCune & Geiser 1997).

Habitat

On bark and wood of both conifers and hardwoods. In a wide variety of moist lowland habitats; the largest populations in Oregon and Washington are in coastal thickets of old shrubs on wet deflation plains. Widespread, rare and scattered west of the Cascade Range crest; British Columbia to New Mexico and California.

Parmelia hygrophila

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Intermediate to Tolerant: 10->30 ppb (Peterson et al. 1992).

Ozone/PAN

Sensitive to Intermediate: <20-70 ppb (Peterson et al. 1992).

General

Intermediate: nitrophilous (McCune & Geiser 1997).

Habitat

On bark and wood, rarely rock. Common in moist low to mid-elevation forests, also in urban and agricultural habitats west of the Cascade Range crest. Alaska to Oregon, from the coast inland to western Montana.

Parmelia sulcata

PNW rating: Tolerant, Nitrophilous

Sulphur dioxide

Sensitive: (Skorepa & Vitt 1976); moderately sensitive (Kuusinen et al. 1990).

Sensitive to Intermediate: grp 2: (Diamantopoulos et al. 1992).

Intermediate: present at 19.24-37/ absent at 35.15 ppb (Wetmore 1983); to 25.9ppb (Taylor & Bell 1983); ? (Ryan 1990); zone 4, base of trunk, non- nitrophilous, 25.9 ppb (Hawksworth and Rose 1970).

Intermediate to Tolerant: 10->30 ppb (Peterson et al. 1992); 3 (Nash & Wirth 1988).

Tolerant: 36-44 ppb (Johnsen & Søchting 1973).

Notes: see (LeBlanc & Rao 1973a).

Fluoride

Sensitive: (Ryan 1990); (Perkins & Millar 1987a); (Perkins & Millar 1987b).

Sensitive to Intermediate: ? (Peterson et al. 1992).

Tolerant: 14 (LeBlanc et al. 1972)

Notes: bleaching/red coloration (Perkins & Millar 1987a); (Perkins & Millar 1987b), (LeBlanc et al. 1971); 14 (LeBlanc et al. 1972).

Ozone/PAN

Sensitive: (Ross & Nash 1983); (Ryan 1990).

Sensitive to Intermediate: <20-70 ppb (Peterson et al. 1992); 50 ppb PAN: photosynth < 50%/ 3 days (Sigal & Taylor 1979).

Notes: Bleaching, algal layer damaged (Sigal & Taylor 1979) increased starch in chloroplast (Eversman & Sigal 1984).

General

Sensitive to Tolerant: (Insarova et al. 1992).

Tolerant: (McCune & Geiser 1997); most resistant, class 1 (Denison & Carpenter 1973); (Johnson 1979);(LeBlanc & Sloover 1970); 6(McCune 1988).

Notes: see (LeBlanc & Sloover 1970) reduced sulphate uptake & protein synthesis/increased chlorophyll content (Tyler 1989)

Habitat

On bark and wood, less often on rock or mossy rock. Occurring in a wide range of habitats, in both continental and oceanic climates, ranging from urban areas to the mountains but dropping out at the highest elevations. Widespread, common throughout the PNW.

Phaeophyscia orbicularis

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Intermediate: present at 22.2-29.6/absent at 33.3 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); (Ryan 1990); 29.6-33.3 ppb (Johnsen & Søchting 1973); zone 5-6, nitophilous, 22.2-18.5 ppb (Hawksworth and Rose 1970).

Fluoride

Sensitive: ? (Peterson et al. 1992).

Intermediate: 16 (LeBlanc et al. 1972).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992); (Ryan 1990).

Sensitve: (Sigal & Nash 1983).

Sensitive to Tolerant: 1.4-8.6 (Insarova et al. 1992).

Intermediate to Tolerant: (LeBlanc & Sloover 1970).

Tolerant: see notes (Hoffman 1974).

Habitat

On bark, occasionally on rock (including concrete). Found in a wide variety of lowland habitats, often in agricultural, urban, or riparian settings. Widespread in western North America.

Physcia adscendens

PNW rating: Tolerant, Nitrophilous

Sulphur dioxide

Intermediate: present at 18.5-29.6/absent at 33.3 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); (Ryan 1990); 29.6-33.3 ppb (Johnsen & Søchting 1973) ; zone 4, nitophilous, 25.9 ppb (Hawksworth and Rose 1970).

Tolerant: grp 1 (Diamantopoulos et al. 1992).

Fluoride

Sensitive: (Peterson et al. 1992); (Perkins & Millar 1987a).

Sensitive to Intermediate: 17 (LeBlanc et al. 1971).

General

Intermediate: see notes (LeBlanc & Sloover 1970).

Intermediate to Tolerant: 2-7.1 (Insarova et al. 1992).

Tolerant: 8.1 (Hoffman 1974); (McCune & Geiser 1997).

Notes: very common, but fertile only 3 times in zone 4 & 5 times in Zone 5 (LeBlanc & Sloover 1970).

Habitat

On bark (especially angiosperms but also occasionally on conifers), rarely on rock.Low to mid elevation forests and open shrubby areas, common in agricultural, urban, and suburban areas; partial shade to full sun. Widespread; common throughout the PNW.

Physcia aipolia

Photo courtesy of Jim Riley

PNW rating: Sensitive, Nitrophilous

Sulphur dioxide

Sensitive: grp 3 (Diamantopoulos et al. 1992); zone 7-8, nitophilous, 14.8-13 ppb (Hawksworth and Rose 1970).

Intermediate: 9.6-18.5/24.1 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); (Ryan 1990).

Fluoride

Sensitive: ? (Peterson et al. 1992); (Perkins & Millar 1987a).

Sensitive to Intermediate: 20 (LeBlanc et al. 1972).

General

Sensitive: Class 4, very sensitive (Denison & Carpenter 1973); (LeBlanc & Sloover 1970); (McCune & Geiser 1997).

Sensitive to Intermediate: 4-10: T-I to S (Insarova et al. 1992).

Notes: common in unpolluted districts (Purvis et al. 1992).

Habitat

On bark and wood, usually on hardwoods.Very common west of the Cascade Range crest, occasional east of the Cascade crest; often in urban and agricultural settings, but also common on hardwoods in the mountains. Widespread; throughout the PNW.

Physcia caesia

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive to Intermediate: (Ryan 1990).

Intermediate: 10-35 ppb (Peterson et al. 1992).

Fluoride

Sensitive: ? (Peterson et al. 1992).

General

Sensitive to Intermediate: 5.6-8.6 (Insarova et al. 1992).

Tolerant: pollution tolerant (Purvis et al. 1992).

Habitat

On rock, rarely on bark or wood.Exposed to sheltered rocks in a wide variety of habitats; alpine to sea level, including on rocks in the ocean spray zone. Widespread; fairly common throughout the PNW.

Physcia tenella

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Intermediate: present at 22.2/absent at 25.9 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); (Ryan 1990); zone 5, nitophilous, 22.2 ppb (Hawksworth and Rose 1970).

Fluoride

Sensitive: ? (Peterson et al. 1992); (Perkins & Millar 1987a).

Ozone/PAN

Tolerant: >65 (Peterson et al. 1992); (Ryan 1990).

General

Intermediate to Tolerant: 1.7-7.1 (Insarova et al. 1992).

Tolerant: (Sigal & Nash 1983).

Habitat

On bark or wood, occasionally on rock. Occasional at low to mid elevations, most often on hardwoods and shrubs in open to semi-open habitats. Widespread, throughout the PNW.

Physconia enteroxantha

PNW rating: Sensitive, Nitrophilous

Sulphur dioxide

Sensitive: (Ryan 1990).

General

Sensitive: (McCune & Geiser 1997).

Intermediate: 3-5 (Insarova et al. 1992).

Habitat

On bark or mosses over rock.In a wide variety of habitats at low elevations, but often in somewhat nutrient-enriched sites, especially in broad agricultural valleys; common on both sides of the Cascades. Widespread; throughout the PNW.

Physconia perisidiosa

PNW rating: Intermediate, Nitrophilous

General

Sensitive to Intermediate: 4-10 (Insarova et al. 1992).

Intermediate: nitrophilous (McCune & Geiser 1997).

Habitat

On bark (usually hardwood trees and shrubs), mosses over rock, rock, or thin soil over rock.In a wide variety of habitats, including steppe, alpine tundra, riparian forests, agricultural valleys, and rock outcrop areas; low to high elevations; full sun to sheltered. Widespread, throughout the PNW.

Platismatia glauca

PNW rating: Tolerant, Nitrophilous

Sulphur dioxide

Intermediate: present at 19.2-28.9 ppb (Wetmore 1983); 10-35 ppb (Peterson et al. 1992); I (Ryan 1990); (Turk & Lange 1974); moderately sensitive (Kuusinen et al. 1990); zone 5, non- nitrophilous, present on horizontal branches at 22 ppb (Hawksworth and Rose 1970).

Tolerant: 2-field, 4- fumigation (Nash & Wirth 1988).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992); (Ryan 1990).

General

Sensitive: very sensitive (Sigal & Nash 1983).

Sensitive to Tolerant: 1.7-9.2: (Insarova et al. 1992)

Tolerant: (McCune & Geiser 1997)

Habitat

On bark and wood (especially conifers), less often on rock. Moist forests, low elevations to subalpine, with broad tolerances to shade and moisture. Alaska to California, inland to Montana and Colorado; throughout the PNW.

Pseudocyphellaria anomala

PNW rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and wood, most often on deciduous trees and shrubs, occasional on conifers; rarely on rock. Low- to mid-elevation moist forests, including riparian areas, Willamette Valley hardwood forests (including oak savannas and ash swamps), and sporadically in mountain conifer forests. Alaska to California, west of the Cascade Range crest, with rare inland disjuncts to western Montana.

Pseudocyphellaria anthrapsis

PNW rating: Sensitive

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992), (Ryan 1990).

General

Sensitive: very sensitive (Sigal & Nash 1983); (McCune & Geiser 1997).

Habitat

On bark and wood, on conifers, deciduous trees, and shrubs; rarely on rock.Low- to mid-elevation moist forests, especially riparian areas; most frequent near the coast in partially open habitats. Alaska to California, with rare disjuncts inland to northern Idaho.

Pseudocyphellaria crocata

PNW rating: Sensitive

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark and wood, mainly on hardwood trees and shrubs. Low- to mid-elevation moist forests, usually in valley bottoms and foothills, often in riparian forests, ash swamps, and oak savanna. Alaska to California, west of the Cascade Range crest.

Ramalina dilacerata

PNW rating: Sensitive, Nitrophilous

Sulphur dioxide

Intermediate: present at 13.6-20.8/absent at 20.8-31.2 ppb (Wetmore 1983).

General

Sensitive: nitrophilous (McCune & Geiser 1997).

Habitat

On hardwood trees and shrubs, also frequent on conifers Most common in riparian forests and shrubs at low elevations; east of the Cascade crest mainly in areas of strongest oceanic influence. Alaska to California, west of the Cascade Range crest, inland to western Montana.

Ramalina farinacea

PNW rating: Tolerant, Nitrophilous

Sulphur dioxide

Sensitive to Intermediate: present at 22/absent at 26 ppb (Wetmore 1983); 5-35 ppb (Peterson et al. 1992); the least sensitive Ramalina, <24 ppb (Purvis et al. 1992); zone 5, tree bases, non- nitrophilous, 22 ppb (Hawksworth and Rose 1970)

Tolerant: 3-field, 2-3-fumigation (Nash & Wirth 1988).

Notes: Sensitivity increases with increasing humidity (Rao & LeBlanc 1966).

Sulphite

Tolerant: phycobiont (Marti 1983).

Nitrate

Tolerant: phycobiont (Marti 1983).

Fluoride

Sensitive: ? (Peterson et al. 1992).

Notes: Bleaching (Perkins & Millar 1987a).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992).

General

Sensitive: (Sigal & Nash 1983).

Sensitive to Intermediate: 4-9.2 (Insarova et al. 1992).

Intermediate to Tolerant: class 2 (Denison & Carpenter 1973).

Tolerant: (Ma); (McCune & Geiser 1997).

Notes: least sensitive Ramalina to inorganic fertilizers (Purvis et al. 1992); inconclusive (A10).

Habitat

On bark and wood, both conifers and hardwoods.West of the Cascade Range crest found in low to mid-elevation forests; also on trees in agricultural and urban areas; east of the Cascade crestcades mainly in low-elevation riparian habitats. Alaska to California, common west of the Cascade Range crest, uncommon to rare east of the Cascade crest, inland to western Montana.

Ramalina menziesii

PNW rating: Sensitive

Nitrate

< net photosynth, < chlorophyll content (Boonpragob & Nash 1991).

Fluoride

< net photosynth and < chlorophyll content (Boonpragob & Nash 1991).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992).

Tolerant: fumigation 785 ppb (Ross & Nash 1983).

General

Sensitive: very sensitive (Sigal & Nash 1983); (McCune & Geiser 1997).

Notes: Netted regions have > photosynthesis rates than strap-like regions. Large nets have < photosynthesis rates than smaller nets (Ross & Nash 1983).

Habitat

On broad-leaved trees and shrubs, occasional on conifers.Fog zone along the coast and in the Willamette-Puget trough, especially along rivers and in forested wetlands, often thickly draping whole forests or individual trees. Pacific coast from southeastern Alaska to Baja, never east of the Cascade crest.

Ramalina pollinaria

PNW rating: Sensitive, Nitrophilous

Sulphur dioxide

Sensitive: present at 13/ absent at 14.8 ppb (Wetmore 1983); zone 8, nitophilous, 13 ppb (Hawksworth and Rose 1970).

Notes: Sensitivity increases w/ increasing humidity (Rao & LeBlanc 1966).

Sulphite

Sensitive to Intermediate: phycobiont (Marti 1983).

Nitrate

Sensitive to Intermediate: phycobiont (Marti 1983).

General

Sensitive to Intermediate: (Marti 1983).

Intermediate: broadly intermediate 3-7.8 (Insarova et al. 1992).

Habitat

On bark and wood.Low-elevation swamps, often with Picea. Widespread but uncommon; in the PNW mainly between the Cascades and Rockies.

Ramalina subleptocarpha

PNW rating: Intermediate, Nitrophilous

General

Intermediate: nitrophilous (McCune & Geiser 1997).

Habitat

On bark and wood.Valley bottoms, ash swamps, and riparian hardwood forests, occasionally onto foothills, fairly frequent in urban and agricultural areas. British Columbia to California, on the coast and in the Willamette-Puget trough.

Sticta fuliginosa

PNW rating: Sensitive

Sulphur dioxide

Sensitive: genus very sensitive, <11.1 ppb (Purvis et al. 1992).

General

Sensitive: 10 (Insarova et al. 1992); (McCune & Geiser 1997).

Habitat

Usually on bark or wood or hardwoods; occasionally on conifers, rarely on rock.Fairly common in warm, moist, low-elevation forests, especially valley and foothill hardwoods such as ash swamps and oak forests. Sporadic in mountain conifer forests. Alaska to California, west of the Cascade Range crest.

Sticta limbata

PNW rating: Sensitive

Sulphur dioxide

Sensitive: 5-15 ppb (Peterson et al. 1992); genus very sensitive, <11.1 ppb (Purvis et al. 1992); zone 10, non-nitrophilous, 'pure air' (Hawksworth and Rose 1970).

Acid Rain

Sensitive: (Gilbert 1986).

General

Sensitive: 8.6-10 (Insarova et al. 1992); (McCune & Geiser 1997).

Metals

Notes: reduced C-fixation (photosynthesis) with Zn solution (Brown & Beckett 1983).

Habitat

On bark and wood, rarely rock.Fairly common in warm, moist, low-elevation forests, especially valley and foothill hardwoods such as ash swamps and oak forests. Sporadic in mountain conifer forests. Alaska to California, west of the Cascade Range crest, with rare inland disjuncts in British Columbia.

Sticta weigelii

PNW rating: Sensitive

Sulphur dioxide

Sensitive: genus very sensitive: <11.1 ppb (Purvis et al. 1992).

General

Sensitive: (McCune & Geiser 1997).

Habitat

On bark, wood, and moss mats on trees and shrubs; rarely on mossy rock.Cool, moist, old-growth conifer forests at middle elevations; uncommon. Alaska to California, west of the Cascade Range crest.

Usnea cornuta

PNW rating: Sensitive, Nitrophilous

General

Sensitve: nitrophilous (McCune & Geiser 1997).

Habitat

On bark and wood. Common on the immediate coast and coastal forests.

Usnea glabrata

PNW rating: Sensitive, Nitrophilous

General

Sensitve: nitrophilous (McCune & Geiser 1997).

Habitat

On bark and wood. Widespread but uncommon in PNW; low elevations both sides of the Cascades.

Usnea longissima

PNW rating: Sensitive

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992).

General

Sensitive: 7-10 (Insarova et al. 1992); (McCune & Geiser 1997).

Notes: Specific habitat demands and low dispersal ability make U.longissima very senstive to environmental disturbances (Esseen 1981).

Habitat

On bark and wood. In Oregon and Washington usually on riparian trees, both conifers and hardwoods, at low elevations, but not in broad open valleys; most abundant in a narrow band transitional between the mountains and foothills. Alaska to California, west of the Cascade Range crest.

Usnea subfloridana

PNW rating: Intermediate, Nitrophilous

General

Sensitve: nitrophilous (McCune & Geiser 1997).

Habitat

On trees. Washington and western Oregon. Uncommon.

Xanthoria candelaria

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Intermediate: present at 22.2/absent at 25.9 ppb (Wetmore 1983); (Ryan 1990).

Intermediate to Tolerant: -10->30 ppb (Peterson et al. 1992); zone 5, nitophilous, 22.2 ppb (Hawksworth and Rose 1970).

Ozone/PAN

Sensitive: <20 ppb (Peterson et al. 1992); (Ryan 1990).

General

Sensitive: very sensitive (Sigal & Nash 1983); (Johnson 1979).

Sensitive to Tolerant: 2-8.9 (Insarova et al. 1992).

Habitat

On rock, also occasionally on bark.Sheltered rock faces in a wide range of macroclimates and elevations; on bark in both open and sheltered sites. Widespread, throughout the PNW.

Xanthoria elegans

PNW rating: Tolerant, Nitrophilous

Sulphur dioxide

Intermediate to Tolerant: <16-50 ppb (Vick & Bevan 1976).

Habitat

On rock, both calcareous and noncalcareous, occasionally overgrowing moss or litter over rock. Exposed to somewhat sheltered sites, often where nutrient enriched by bird or small mammal droppings. Widespread; throughout the PNW.

Xanthoria fallax

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive: present at 5.2/ absent at 5.2-10.4 ppb (Wetmore 1983).

Sensitive to Intermediate: 5-35 ppb (Peterson et al. 1992); (Ryan 1990).

Notes: reduced photosynthesis at 2.5 ppm (4) bleaching, plasmolysis of algal cells, sensitivity > w/> humidity(Rao & LeBlanc 1966).

Sulphate

Sensitive to Intermediate: phycobiont (Marti 1983).

Nitrate

Sensitive to Intermediate: phycobiont (Marti 1983); Nitrophilous (Rosentreter 1990).

Fluoride

Sensitive to Intermediate: 18 (LeBlanc et al. 1972).

Ozone/PAN

Sensitive to Tolerant: <20->65 ppb (Peterson et al. 1992).

Tolerant: (Ryan 1990).

General

Sensitive: S (Marti 1983); 9 (McCune 1988); nitrophilous (McCune & Geiser 1997).

Sensitive to Tolerant: 2-10 (Insarova et al. 1992).

Tolerant: 6.1(Hoffman 1974); (LeBlanc & Sloover 1970); (Sigal & Nash 1983); (Kershaw 1972).

Notes: Sterile in zones 1,2, zone 3-4% fertility, Zone 4-10% fertility, Zone 5-38% fertility (LeBlanc & Sloover 1970).

Habitat

On bark (especially Populus and other broad-leaved spp), occasionally on rock.Mostly open to somewhat sheltered, often nutrient-enriched sites. Widespread, common throughout the PNW.

Xanthoria parietina

PNW rating: Sensitive, Nitrophilous

Sulphur dioxide

Intermediate: present at 25.9/ absent at 25.9-33.3 ppb (Wetmore 1983).

Intermediate to Tolerant: I-T:<14.8-46.3 ppb (V3); zone 4-5: nitophilous: 25.9-22.2 ppb (Hawksworth and Rose 1970).

Tolerant: grp 1 (Eversman & Sigal 1984); tolerant to fumigation 1480 ppb/14 hrs (Turk & Lange 1974).

Notes: bleaching, plasmolysis (algal cells) > sensitivity w/> humidity (RL).

Sulphite

Tolerant: phycobiont (Marti 1983).

Nitrate

Tolerant: phycobiont (Marti 1983).

Fluoride

Sensitive to Intermediate: (Perkins & Millar 1987a).

Intermediate to Tolerant: (Perkins & Millar 1987b).

General

Sensitive: (McCune & Geiser 1997).

Sensitive to Tolerant: 1-8 (Insarova et al. 1992).

Intermediate to Tolerant: (Marti 1983); (Johnsen & Søchting 1976).

Habitat

On bark and wood, rarely on rock (e.g. gravestones).Hardwood forests in low-elevation broad valleys; scattered on Populus and other hardwoods in riparian areas in agricultural and populated areas. West of the Cascade crest; so far known in the PNW only from the Willamette-Puget trough.

Xanthoria polycarpa

PNW rating: Intermediate, Nitrophilous

Sulphur dioxide

Sensitive to Intermediate: present at 5.2-20/absent at 24 ppb (Wetmore 1983); 5-35 ppb (Peterson et al. 1992).

Intermediate: (Ryan 1990).

Fluoride

Sensitive to Intermediate: 19 (LeBlanc et al. 1972).

Ozone/PAN

Intermediate to Tolerant: (Ryan 1990).

Tolerant: >65 ppb (Peterson et al. 1992).

General

Sensitive: 14 (Hoffman 1974).

Intermediate: nitrophilous (McCune & Geiser 1997); moderately tolerant (Sigal & Nash 1983).

Tolerant: most resistant, class 1 (Denison & Carpenter 1973).

Habitat

On bark and wood; mostly on hardwoods but occasionally on conifers, often where nutrient enriched.In a wide range of habitats at low to middle elevations, but most common on hardwood twigs; also on sagebrush in steppe and in other dry open habitats. Widespread; common throughout the PNW.