What About
Cryptogamic Crust?
Background Information
What is a cryptogram?
The floor of the Columbia Basin is covered by a fragile layer: a
thin crust made up of mosses, lichens, algae, and bacteria. This
layer is called a cryptogamic crust. And the species of lichens,
algae, fungi, mosses, and cyanobacteria that share similar
habitats are collectively referred to as cryptogams. These
organisms form a biotic layer, or cryptogamic crust, over unvegetated areas
between shrubs, grasses, and flowering plants in undisturbed arid and semiarid lands of the world, including the shrub-steppe ecosystem of the
Columbia Basin. However, with the introduction of agriculture, alien plant
species, and livestock grazing, much of the cryptogamic crust in our region
has been degraded or destroyed.
Cryptogamic crust covers the surface of soil
between grasses, shrubs, and flowering plants.
Why is cryptogamic crust important to the shrub-steppe ecosystem?
Cryptogams function as soil builders. They form a spongy layer that helps protect soil from erosion, absorbs moisture, and
provides nitrogen and other nutrients for plant growth. When frozen, the cryptogamic crust uplifts and cracks. Cracks in
the layer can provide germination sites for seeds.
Why is the cryptogamic crust a fragile component of the shrub-steppe?
When large areas of the cryptogamic crust are disturbed, water and wind erode the soil. Detached pieces of crust have
little chance for reattachment. The underlying loose soil also may erode and cover the remaining, stable, crust patches.
This soil covering blocks light, preventing photosynthesis. Recovery time for cryptogamic crust varies. If the disturbance is
small, a thin layer of several cyanobacterial species may return in 5 to 7 years. If the original crust was composed of a
complex association of species and was several centimeters deep, it could take more than 100 years for the crust to recover.
How do cryptogamic organisms differ?
Fungi. Most fungi are composed of multicellular filaments called hyphae. Their cell walls are made of chitin, the same
substance that exists in the exoskeletons of insects. Fungi are the principal decomposers of organic material. They are
heterotrophic (can't make their own food) and secrete digestive enzymes onto a food source and absorb smaller molecules
that are released.
Algae. Green algae (chlorophytes) contain the photosynthetic pigments chlorophyll a, chlorophyll b, and betacarotene.
These organisms are autotrophic (can make their own food) and store food as starch.
Cyanobacteria. This group of organisms previously were known as “blue-green algae.” They are autotrophic and are
composed of prokaryotic cells that contain chlorophyll a. The cells of many species have a deeply pigmented outer
coating (sheath). This common photosynthetic, nitrogen-fixing species of the shrub-steppe are among the world’s most
self-sufficient life forms.
Lichens. Lichens are composed of two different organisms, a specific type of fungi and a green algae, or a cyanobacteria.
http://science-ed.pnnl.gov | www.midcolumbiastem.org
The components grow together in an association generally referred to as symbiotic (different organisms living together).
The thallus (lichen body) does not resemble the algae and fungi that form it. Lichens do not need an organic food
source because the alga or cyanobacteria component is photosynthetic. They can survive in extreme temperatures and
do not die when dried for extended periods. Because they absorb substances in rainwater easily and are susceptible to
airborne toxins, their occurrence is used as an index of air pollution.
Mosses. Mosses (Bryophytes) lack true roots, leaves, and transport tissues that are found in vascular plants.
Bryophytes must absorb moisture and nutrients from the air or by diffusion from nearby cells. Many have leaf-like
structures in which photosynthesis takes place.
Suggested Activities
Observe cryptogamic crust in the field
Here’s how: In areas of the Columbia Basin that contain native species such as sagebrush, bunchgrasses, and rabbitbrush,
you will find patches of ground that have a black, gray, yellow, green, or orange appearance. Also look on rock formations
and on the dead branches of native bushes. Mist the patches with water from a spray bottle and observe the cryptogams
with a magnifying glass. What do you notice happening?
Questions a scientist might ask: What types of cryptogams best protect the soil from erosion? How long does it take
for the cryptogamic crust to reform after it has been damaged by footsteps? What can be done to speed the recovery of
damaged cryptogamic crust? What cryptogams are pioneer species (first to come back after damage)? What cryptogam
species would you find in a climax community (reached a steady state over time)?
Make a cryptogamic species collection
Here’s how: After misting patches with water, cut a small section of cryptogamic crust (about 2 cm) with a metal spatula
or knife. Place the sample in a dish that contains a mixture of one part white glue and one part water. Allow the soil
component of the sample to soak up the glue mixture, being careful not to cover the
cryptogam’s surface with glue. After removing the sample from the glue, place it on a Notes
“Science is constructed of facts as a
3 x 5 card to dry. Label the card with the collection site, date, collector name,
house is of stones. But a collection of
morphological type, and (if possible) the genus and species. Observe the samples
facts is no more a science than a heap of
with a dissecting microscope or 10x magnification.
stones is a house.”
—Henri Poincare
Questions a scientist might ask: How do the cryptogamic species differ from
one soil type to another? What species are usually found growing on branches?
Which species of cryptogams are usually found growing together? How can
the growth rate of cryptogams be measured?
Keep in mind this fact sheet is intended
to be used only as background information to support your effort to encourage
inquiry-based science, which parallels the
way scientists uncover knowledge and
solve problems.
Acknowledgements
Other Resources
1. Biology, Helena Curtis, N. Sue Barnes, 1989. Worth Publishers, Inc., New York.
2. Field Key to Soil Lichens of Central and Eastern Oregon, Bruce McCune
& Roger Rosentreter, 1995. Oregon State University, Corvallis, Oregon.
3. How to Know the Lichens, Mason E. Hale, 1979. Wm. C. Brown Publishers,
Dubuque, Iowa.
Web Sites
1. Cryptobiotic Soil Crusts - http://eduscapes.com/nature/cryptsoil/index1.htm
2. Capitol Reef National Park - http://envirosci.net/111/cryptogamic.htm
3. Biological Soil Crusts - http://www.soilcrust.org/
June 2015 | Second Edition
The Shrub-Steppe Ecology Series was a
product of a public/private collaboration
led by PNNL called the Partnership for
Arid Lands Stewardship (PALS), funded
by a U.S. Dept. of Education Eisenhower
Grant. Writer Marilyn Fike; Series Editor
Georganne O’Connor; Project Manager
Karen Wieda.