United States

Department of

Agriculture

Forest Service

Alaska Region

R10-RG-170

August 2006

Lichens of the 

National Forests 

in Alaska
What is a Lichen? 

You can think of lichens as fungi that have discovered farming. Instead of parasitizing or scavenging other organisms 

for a living (such as molds, mildews, mushrooms), lichen 

fungi cultivate tiny algae and/or blue-green bacteria (called 

cyanobacteria) within the fabric of interwoven fungal threads 

that form the lichen body (or thallus). The algae and cyanobacteria produce food for the fungus by converting the sun’s 

energy into sugars through photosynthesis. Perhaps the most 

important contribution of the fungus is to provide a protective 

habitat for the algae or cyanobacteria. Thus, lichens are a 

combination of two or three organisms that live together intimately. The green or blue-green photosynthetic layer is often 

visible between two white fungal layers if a piece of lichen 

thallus is torn off.

In some cases, the fungus and the photosynthetic partner that 

together make the lichen may be found living separately in 

nature. However, many lichen-forming fungi cannot exist by 

themselves because they have become dependent on their 

photosynthetic partners for survival. But in all cases, a fungus 

looks quite different in the lichenized form compared to its 

free-living form.

How do Lichens Reproduce? 

Lichens sexually reproduce with fruiting bodies of various 

colors that can look like miniature mushrooms. These are 

called apothecia (Fig. 1) and 

contain spores that germinate 

and grow into the fungus. 

This fungus must find the 

right photosynthetic partner 

in order to become a lichen.

Lichens reproduce asexually 

in several ways. Some lichens 

have openings on the thallus 

surface called soralia (Fig. 2). 

Inside, tiny dust-like granules 

called soredia (Fig. 3) are 

Figure 1. Apothecia, fruiting 

bodies.

Figure 2. Soralia, small 

openings on thallus surface.

Figure 3. Soredia, dust-like 

granules.
produced. Soredia contain algae and fungal cells that escape 

from the parent lichen and grow into a new lichen thallus. 

Other lichens produce outgrowths that break off and grow 

into the same lichen they came from. These are called isidia

(tiny, cylindrical projections, Fig. 4) or lobules (little flaps of 

tissue, Fig. 5). These structures are often very important for 

the proper identification of lichens.

Diversity and Ecology

Lichens come in many shapes, sizes, and colors. A lichen 

thallus has one of three general growth forms: foliose, fruticose, or crustose. Foliose lichens are leaf-like with different 

upper and lower surfaces. Fruticose lichens are hair-like 

or bushy with no obvious difference between upper and 

lower surfaces. Crustose lichens are so closely attached to a 

surface, like paint spots, that the lower surface is not easily 

observable.

Lichens have specialized features enabling them to survive 

long periods of drought. In a dehydrated, inactive state 

they can resist extreme high and low temperatures and still 

function optimally whenever conditions become just right. 

Well adapted for life in marginal habitats, lichens produce 

more than 500 unique biochemical compounds that serve to 

control light exposure, repel herbivores and microbes, and 

discourage competition from plants. Among these are many 

pigments and antibiotics that are useful to humans.

Lichens are considered to be nature’s pioneers because 

they colonize newly exposed surfaces. Lichens containing 

cyanobacteria fix their own nitrogen from the air into a form 

usable by other plants. This form of nitrogen is released into 

the environment as rain washes the lichens or when lichens 

die and fall to the ground. These lichen types tend to live in 

nitrogen-poor habitats such as bare rock surfaces, the forest 

canopy, or on sandy soils. 

Figure 4. Isidia, tiny 

projections.

Figure 5. Lobules, flaps of 

tissue.
Lichens provide food for many animals including flying squirrels, black-tailed deer, and mountain goats. Many invertebrates use lichens for food or for shelter. 

The national forests in Alaska contain a myriad of habitats 

where more than 500 species of lichens thrive. A few lichens 

are generalists and can be found across many different habitats, while most are very habitat specific. 

Lichens and Air Quality Monitoring

Lichens are not protected by bark, nor do they possess an 

external waxy layer to prevent water loss like plant leaves. 

Lacking roots and other structures to transport food and 

water, lichens absorb moisture into the thallus directly from 

the humid air or rainfall, and can become quickly saturated 

like a sponge. Lichens dry out by continually losing moisture 

through evaporation when windy or dry conditions exist. 

As drying occurs, elements and compounds that entered 

with moisture from the surrounding environment become 

concentrated in the lichen. During high rainfall periods, 

mobile nutrients and pollutants are leached from a lichen. In 

this way lichens serve as dynamically representative samples 

of the environmental conditions in which they are growing. 

Lichen species differ in their tolerance to air pollutants, with 

responses ranging from relatively resistant to highly sensitive. Measurements of metals, nitrogen, and sulfur content in 

lichens at different locations indicate the relative amounts of 

pollution in the air. The Forest Service uses lichens to monitor air quality on both national forests in the Alaska Region, 

primarily in wilderness areas. Lichens used for air quality 

monitoring in the Alaska Region are noted in this brochure.

The lichens featured in this brochure are arranged by the 

three general growth forms described above: foliose, fruticose, and crustose.
Foliose

Beaded tube lichen

Hypogymnia apinnata

Thallus made up of tube-like 

lobes, constricted at intervals, 

usually has a hole at the tip 

of each lobe; white upper 

surface and black underneath. 

Apothecia raised and brown. 

Occurs in forests of all types 

(conifers and hardwoods), but 

not in deep shade. Used in air 

quality monitoring. Thirteen 

species of Hypogymnia occur in 

the Alaska Region. 

Gray lungwort

Lobaria halli

Large leaf-like thallus, light 

gray when dry, dark gray when 

wet. Soralia brown to gray and 

sometimes ring-like on upper 

surface. Contains cyanobacte-

ria. Found in Sitka spruce and 

hardwood forests, but more 

common on sites with cot-

tonwood, birch, and alder. Nine 

species of Lobaria occur in the 

Alaska Region.

Cabbage lungwort

Lobaria linita 

Large leaf-like thallus, green 

or brownish-green when dry, 

bright grass-green when wet. 

Often with abundant, orange 

apothecia on upper surface. 

Contains cyanobacteria. Used 

as winter forage by mountain 

goats. It grows in shady conifer-

ous forests on lower trunks. 
Foliose

Lungwort

Lobaria pulmonaria 

Large leaf-like thallus; pale 

brown to olive brown when 

dry, bright green when wet. 

Strongly pitted upper surface 

with soralia on lobe margins. 

Contains cyanobacteria. Occurs 

in riparian Sitka spruce forests, 

hardwood forests, and maritime 

beach forests. 

Arctic kidney lichen

Nephroma arcticum

Large thallus; yellowish-green 

when dry, bright green when 

wet. Broad, flat, gray bumps on 

surface that contain cyanobac-

teria. Lower surface pale tan at 

the edge. Large orange-brown 

apothecia. In coniferous forests 

and occasionally on the forest 

floor or old logs. Nine species 

of Nephroma occur in the 

Alaska Region.

Lettuce lichen

Lobaria oregana

Large leaf-like thallus; pale 

yellowish-green on top, white 

and tan on the bottom. Lobe 

margins decorated with tiny, 

flat lobules. Contains cyano-

bacteria. Occurs in the canopy 

of old-growth forests and along 

forest edges. Also grows on 

hardwood trees. Used in air 

quality monitoring.
Foliose

Salted shield lichen

Parmelia saxatilis

Small thallus of tiny flattened 

lobes; 2–4 mm wide, pale green 

to gray. Upper surface with 

small net-like ridges and isidia, 

underside with black rhizines 

(small stiff hairs). Apothecia 

brown. In exposed and shaded 

habitats including coniferous 

and hardwood forests, and on 

rocks in upper tidal and alpine 

areas. Seven species of Parmelia

occur in the Alaska Region.

Pimpled kidney lichen

Nephroma resupinatum

Medium-sized thallus; upper 

surface brown to grayish brown, 

lobe tips with woolly appear-

ance. Lower surface pale, fuzzy 

with scattered whitish bumps. 

Contains cyanobacteria. In hu-

mid forests on hardwoods and 

conifers. 

Flaky freckle pelt

Peltigera britannica 

Large thallus; brownish-green 

when dry, grass green when 

wet. Underside has raised veins 

with tiny rhizines. Lobes have 

small granules that rub off easily 

and contain cyanobacteria. In 

humid forests on tree trunks, 

branches, and mossy soil. 

Twenty-two species of Peltigera

occur in the Alaska Region.


Foliose

Crinkled rag lichen 

Platismatia lacunosa

Medium-sized thallus; pale 

green to almost white. Upper 

surface deeply pitted and 

ridged. In coniferous forest 

canopy and on hardwoods.

Tree pelt lichen

Peltigera collina

Medium-sized thallus; gray 

to dark brown. Upper surface 

smooth with bluish gray soredia 

usually covering lobe margins; 

lower surface pale with small 

raised veins and tufted rhizines. 

Contains cyanobacteria. In 

humid forests on conifers and 

hardwoods. 

Varied rag lichen

Platismatia glauca

Medium-sized thallus; pale 

greenish-gray, often brown at 

the edges. Lobe margins very 

frilly with soredia and isidia. 

Lower surface shiny and brown 

with white patches. In the 

canopy of coniferous forests 

and on hardwoods. Used in air 

quality monitoring. Four species of Platismatia occur in the 

Alaska Region.


Foliose

Dimpled specklebelly lichen

Pseudocyphellaria anomala

Medium to large thallus; 

chocolate to reddish brown. 

Upper surface with a net-

work of ridges and dimples; 

ridges set off by white and gray 

soredia. Lower surface with 

conspicuous raised, white dots. 

In humid forests on conifers 

and hardwoods. Five species of 

Pseudocyphellaria occur in the 

Alaska Region. 

Orange chocolate chip 

lichen 

Solarina crocea

Medium-sized thallus; olivebrown to olive-gray on upper 

surface, lower surface bright 

orange with veins and scattered 

rhizines. Apothecia are brown 

and sunk into upper surface. 

Contains cyanobacteria. On 

soils in moist areas under late 

snow patches or seepage areas 

in cold, open habitats. Four 

species of Solarina occur in the 

Alaska Region. 

Rock tripe

Umbilicaria spp.

Thallus small, flat, and wrinkled, 

circular in shape; brownish-gray 

and brittle when dry, greenishblack and rubbery when wet. 

Attached from a single point of 

the thallus to the rock. On rock 

in open, cold habitats. Fifteen 

species of Umbilicaria occur in 

the Alaska Region. 
10

Fruticose

Witch’s hair 

Alectoria sarmentosa

Thallus long, hanging loosely, 

often twisted and somewhat 

flattened strands; pale green-

ish with small, raised white 

ridges on surface. Occasional 

brown apothecia. On conifers 

and hardwoods in all forest 

types, from sea level to alpine. 

Important winter food for blacktailed deer. Used in air quality 

monitoring. Three species of 

Alectoria occur in the Alaska 

Region.

Gray horsehair lichen

Bryoria capillaris

Thallus long; pale gray to dark 

smoky brown, hanging in 

clumps, with slender strands 

containing long narrow slits on 

the surface. In old growth forest 

habitats and forested peatlands 

on conifers and hardwoods. 

Important genus for wildlife. 

Fifteen species of Bryoria occur 

in the Alaska Region.

British soldiers 

Cladonia bellidiflora 

Small thallus made up of pale, 

yellow-green and frilly lobes. 

Contains small, erect, branchlike stems ending in cup-shaped 

tips rimmed with bright red 

apothecia. On rotting stumps 

and logs, bare soil, and among 

mosses in the open and in all 

forested habitats. Over 60 spe-

cies of Cladonia occur in the 

Alaska Region.
11

Fruticose

Gray reindeer lichen

Cladonia rangiferina

Thallus branching or tree-like 

form; white to silver gray, somewhat browned tips of branches. 

Main stems and side branches 

commonly occur in twos and 

threes, sometimes fours. On the 

ground in open, humid habitats 

among mosses and other lichens. Principal winter food for 

caribou in North America.

Devil’s matchstick

Pilophorus acicularis 

Small thallus; pale gray-green 

and granular. Erect stalks protrude from thallus and end with 

shiny, black spherical apothecia. 

Contains cyanobacteria. On 

rock surfaces in open habitats 

at all elevations. Five species of 

Pilophorus occur in the Alaska 

Region.

Smooth Cladonia

Cladonia gracilis

Small thallus of green frilly 

lobes containing variable sized, 

erect, branch-like stems. The 

smooth, pointed stems do not 

contain soredia and are greenish to olive, becoming browned 

in exposed habitats. On ground 

and rocks in exposed habitats.
12

Dotted Ramalina 

Ramalina farinacea

Thallus short and bushy; pale 

yellow to yellowish-green 

branches, narrow and flat with 

rounded soralia containing 

powdery soredia along branch 

margins. On conifers, hardwoods, and shrubs in humid 

forests. Sometimes on rocks in 

sheltered humid areas. Eight 

species of Ramalina occur in 

the Alaska Region.

Waterfingers 

Siphula ceratites

Thallus made up of white, dented stalks, mostly unbranched, 

in dense clumps. On soil or 

mud in sun-exposed seeps. 

Sometimes submerged in water. 

One species of Siphula occurs 

in the Alaska Region.

Fruticose

Coral lichen

Sphaerophorus globosus 

Thallus short and shrubby, 

variable in form and color 

from pale, greenish-white in 

shady sites to copper-brown in 

exposed habitats. Branchlets 

often ending with spherical 

apothecia that are slit open and 

have sooty-black spores. In all 

forested habitats on conifers 

and hardwoods and in alpine 

areas on rocks and soil. Two 

species of Sphaerophorus occur 

in the Alaska Region.
13

Foam lichen 

Stereocaulon spp.

Thallus medium-sized; pale gray 

to white branch-like stalks with 

tiny, frilly lobules and pink or 

brown wart-like structures that 

contain cyanobacteria. Stalks 

of some species may be tipped 

with black or brown apothecia. 

On soil and rocks in open 

habitats. Twenty-eight species 

of Stereocaulon occur in the 

Alaska Region.

Fruticose

Tundra spaghetti 

Thamnolia spp.

Thallus occasionally forming 

upright, white to creamy, stringy 

turfs but usually prostrate or 

sprawling. Thallus strings are 

roundish in cross section with 

tapering ends and have simple 

branching. On soil in sub-alpine 

to alpine areas. Two species of 

Thamnolia occur in the Alaska 

Region.

Methuselah’s beard 

Usnea longissima

Thallus often long (up to2 m 

or more); pale greenish. 

Hanging freely, with one long 

main branch and many short, 

perpendicular side branches, 

all cylindrical. Surface often 

with circular cracks and white 

patches. On conifers and hard-

woods in humid and open for-

est habitats within a few miles 

of salt water. Very sensitive to 

air pollution, especially sulfur 

dioxide and acid rain. Fourteen 

species of Usnea occur in the 

Alaska Region. 
14

Crustose

Fairy barf 

Icmadophila ericetorum

Thallus pale to grey-green 

with pink to brown apothecia. 

On old stumps and logs in 

shady habitats. One species 

of Icmadophila occurs in the 

Alaska Region.

Yellow map lichen 

Rhizocarpon geographicum

Thallus of yellow bumps 

with black apothecia tucked 

between the bumps. On rock 

surfaces in open, cold alpine 

habitats and near glaciers. Used 

in estimating the ages of recent 

geomorphic exposures, particularly glacial moraines. Eleven 

species of Rhizocarpon occur in 

the Alaska Region. 

Bull’s–eye lichen

Placopsis sp. 

Thallus pinkish white to pinkish to yellowish brown, often 

turning greenish when wet at 

the edges; large brownish spots 

containing the cyanobacteria 

are almost always present near 

the center of the round thallus. 

Scattered apothecia are pink to 

brown disks with a white rim. 

On most rock types in open 

areas. Often a primary invader 

of newly exposed rock surfaces. 

Three species of Placopsis occur 

in the Alaska Region.
15

Nitrogen-tolerant lichens on rocks frequented by birds and 

mammals.

Lichens used in air quality monitoring in the Alaska Region.
16

Lichens of the National Forests in Alaska highlights 30 of 

the more conspicuous lichens found in the Alaska Region of 

the USDA Forest Service. This Region includes the Tongass 

National Forest; the nation’s largest at 17 million acres, and 

the 5-million acre Chugach National Forest. The Tongass 

encompasses most of southeastern Alaska, and the Chugach 

roughly surrounds Prince William Sound. 

This brochure was developed by the Alaska Region Air, 

Botany and Ecology programs with funding provided by the 

Alaska Region Air program.

Photographs were provided by: Karen L. Dillman, Linda 

H. Geiser, Steve and Sylvia Sharnoff and Rick L. Turner. 

Drawings by Alexander Mikulin.

The USDA Forest Service maintains a website on air quality 

for the Pacific Northwest region that includes the Alaska 

region (http://www.nacse.org/lichenair) which includes more 

information on lichens.

Cover photograph: Methuselah’s beard lichen (described inside) and devil’s club growing at the edge of a maritime beach 

forest on the Tongass National Forest. 

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