Cryptogamic crust covers the surface of soil between grasses, shrubs, and flowering plants.
What is a cryptogam?
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 semi-arid 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.
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 principal decomposers of organic material. They are heterotrophic 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 and store food as starch.
Cyanobacteria. This group of organisms previously were known as "blue-green algae." They are autotrophic (make their own food) and are composed of prokaryotic cells that contain chlorophyll a. The cells of many species have a deeply pigmented outer coating (sheath). The 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. The components grow together in an association generally referred to as symbiotic. 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 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.
"Science is constructed of facts as a house is of stones. But a collection of facts is no more a science than a heap of stones is a house." Henri Poincare
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.
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.
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? What cryptogam species would you find in a climax community?
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 3 x 5 card to dry. Label the card with the collection site, date, collector name, morphological type, and (if possible) the genus and species. Observe the samples with a dissecting microscope or 10x magnification.
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?
- Biology, Helena Curtis, N. Sue Barnes, 1989. Worth Publishers, Inc., New York.
- Field Key to Soil Lichens of Central and Eastern Oregon, Bruce McCune & Roger Rosentreter, 1995. Oregon State University, Corvallis, Oregon.
- How to Know the Lichens, Mason E. Hale, 1979. Wm. C. Brown Publishers, Dubuque, Iowa.
- Cryptobiotic Soil Crusts - http://eduscapes.com/nature/cryptsoil/index1.htm
- Capitol Reef National Park - http://envirosci.net/111/cryptogamic.htm
- Biological Soil Crusts - http://www.soilcrust.org/
Initial development and printing of this fact sheet was funded by an Eisenhower Grant to the Partnership for Arid Lands Stewardship. Written by Marilyn Fike; Series Editor: Georganne O'Connor; Design: WinSome Design; Printing: Eagle Printing and Graphic Design; First Printing: December 1997; Web Development: WinSome Design.