The Great Basin is encrusted by a biological soil known variously as cryptogamic, microbiotic, microphytic, and cryptobiotic soil. Basically these are different names for crusty soil made by organisms (vs. crusts made of inorganic substances, like salt, or crusts that are the result of compacting the soil, like trails). The organisms within the soil release a gelatinous material that binds soil particles together in a dense matrix. Cryptogamic and microphytic refer to the fact that the crusts are formed primarily by plants that produce spores (blue-green algae, green algae and brown algae) and by bacteria, mosses, lichens and fungi. Micribiotic refers to the fact that the crusts are formed by living microorganisms. Cryptobiotic refers to a dormant or suspended state of animation that allows organisms to survive severe environmental conditions.
So any one of the names is correct--pick the one that rolls off your tongue. In the great basin, the biological soil is usually darker than the soil around it due to the density and characteristic colors of the organisms that hold the dirt together. The crusts and the surrounding flora have evolved some important survival strategies. The soil has nitrogen, phosphorus, potassium, iron, calcium, magnesium, and manganese fixing properties. The more gnarly soils trap water and increase infiltration. There are some studies that suggest the biological soils inhibit the germination of cheat grass seeds, but encourage germination of native grasses, globe mallow, blue flax and others. My own observations would support this--cheat grass is rare in biological soils. This is fortunate since cheat grass fires are hot! Biological crusts can survive low intensity fires, but are destroyed by hot fires.
Long ago, I learned that one should never walk on these soils because they take hundreds of years to form. That's not the whole truth. The cyanobacterial and green algae component can recover in as little as 1-5 years giving the appearance of a healthy crust. However, recovering crust thickness can take up to 50 years, and moss and lichen recovery may take up to 250 years. When the structures that hold the soil are crushed, the soil starts migrating from that destroyed spot and may cover neighboring biological soils deep enough to kill the organisms. The dead spots get bigger and bigger, and the dependent plats get fewer and fewer.
To me, what is remarkable is that the crusts represent a living organic community. I've heard reference to the lifeless, barren desert. By some estimates, these soil crusts cover as much as 70% of the open ground in the Great Basin.
To me, what is remarkable is that the crusts represent a living organic community. I've heard reference to the lifeless, barren desert. By some estimates, these soil crusts cover as much as 70% of the open ground in the Great Basin.
Lifeless? Hardly!
Fore more information and some really cool microscopic pictures follow this link
http://geochange.er.usgs.gov/sw/impacts/biology/crypto/
