Home | Vegetation | Plant Species | Non-Vacular Plants
Biological Soil Crusts
Non-Vacular Plants, Vegetation Around Las Vegas
Biological Soil Crust

Biological soil crusts, also called cryptogamic crusts or cryptobiotic crusts, are complex associations of cyanobacteria, green and brown algae, lichens, mosses, microfungi, and other kinds of bacteria that grow in and on the soil in the open spaces between plants.

These organisms pioneer barren, open areas where nothing else can grow. The cyanobacteria and microfungi weave a network of filaments through the top few inches of soil. The filaments exude a mucilaginous sheath that binds loose sand and soil particles together, thereby stabilizing and protecting the soil surface from wind and water erosion.

Biological Soil Crust

In addition to stabilizing the soil, the microbial community is important in the development of desert vegetation communities. As the microbes grow and die over time, they add organic matter to the soil, which aids in water retention and provides nutrients for desert plants. The cyanobacteria also convert atmospheric nitrogen to a form that plants can use. The addition of nitrogen is important in desert ecosystems because nitrogen levels typically are low and often restrict the growth of plants.

Biological Soil Crust

Over time, the bacterial community grows and produces a roughened soil surface with little humps and peaks. These raised sites provide places where bits of lichens and mosses can grow. The peaks grow at a rate of about 1/4-inch per 100 years, so after a few centuries, the little peaks can grow to over 1-inch high. Some years ago, I found an old fire pit with charcoal in southeastern Utah with 1-1/4 inch high peaks growing inside the fire ring; Park Rangers estimated the fire pit to have been at least 500-years old!

Biological Soil Crust
Biological soil crust "in bloom."

Because of their importance in stabilizing the soil and in aiding the growth of plants, we should avoid walking on or otherwise damaging (biking, driving, pitching tents) the biological soil crusts. Mature crusts can be recognized as being darker and rougher than the surrounding bare soil, so when you see biological crusts, stay on trails, walk in washes, walk on bare rock, or just walk around them to the extent that we can. If a group of hikers must walk across crusted surfaces, spread apart and walk different paths so as not to create a rut where wind and water erosion can further damage the biological community.

Biological Soil Crust
Biological soil crusts on gypsum soil
Biological Soil Crust
Biological soil crusts on gypsum soil
Biological Soil Crust
Biological soil crusts on gypsum soil
Biological soil crust
Biological soil crusts on gypsum soil
Biological Soil Crust
Biological soil crust "in bloom"
Biological Soil Crust
Biological soil crust "in bloom"
Biological Soil Crust
Remarkable covering of Biological Soil Crust
Biological Soil Crust
Biological Soil Crust on shady, north-facing mud slope
Biological Soil Crust
Biological Soil Crust on shady, north-facing mud slope
Biological Soil Crust
Biological Soil Crust on shady, north-facing mud slope
Biological Soil Crusts
Tire-track damaged crypto soil
Biological Soil Crusts
Tire track zoom: the crust died except for groves in the tread
Biological Soil Crust
Tire tracks last a long time on Biological Soil Crusts
More to come
More to come ...

Note: All distances, elevations, and other facts are approximate. Names generally follow the USDA database.
copyright; Last updated 170826

All Non-Vascular Plant Species Index Glossary Copyright, Conditions, Disclaimer Home

 

Google Ads