Biocrust is important in our desert

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by Janae’ Reneaud Field

Biological soil crusts (biocrusts) is one reason the Frontera Land Alliance is building a natural trail at the Wakeem/Teschner Nature Preserve at Resler Canyon.   We are working to reduce the footprints in the canyon, keep the impact of people to designated areas for better water conservation and erosion control.

What is biocrust? It is a thin veneer of microorganisms that inhabit and bind the soil to a depth from a few millimeters to a few centimeters from the surface.

Unknown to most people, it is often thought to have little value, but that is far from the truth.

Biocrusts generally cover all soil spaces not occupied by green plants. They are key to reducing erosion, increasing water retention, and increasing soil fertility.

In most arid regions, these crusts are dominated by cyanobacteria (previously called blue-green algae), which are one of the oldest known life forms.

The biocrust allows more complex organisms like mosses and lichens to grow — and when it’s all assembled, the biocrust then holds the soil in place and prevents dust storms and erosion.

A desert landscape is highly vulnerable to destruction. And if the biocrust is disturbed enough, then not only are dust storms more likely to blow up the loose sand, but there will be less storing of carbon and the ecosystem may be reduced to what researchers call an early successional state where the site is unstable.

Recovery of a disturbed area may take up to 250 years in places of lower rainfall like our desert region, assuming the area is not again disturbed.

The organisms in crusts protect soil from erosion in a variety of ways.

Some organisms, such as cyanobacteria and microfungi, protect themselves from sharp sand grains by secreting sticky mucilage around their cells. These microbes move through the soil when moistened, leaving the mucilage behind as a trail.

These mucilage trails glue soil particles in place. Mosses and lichens cover and protect the soil surface as they grow in place, but they also have small root-like anchoring structures that penetrate into the soil surface.
Soil loss due to rainfall and water movement is increased when cyanobacterial connections are broken. This is particularly problematic when the impact is in a continuous strip, such as a vehicle or bicycle track, because channels for water flow are quickly formed, especially on slopes.

The U.S. Geological Survey states that soil crusts are important in the absorption of rainfall. This function is especially important in arid areas that experience sporadic, heavy rainfall.

When it rains, the organisms and their mucilage absorb up to ten times their volume in water and then release the water slowly into the soil once the rain ends.

To reduce disturbance of the biocrust, stay in areas designated for use such as existing tent pad camping sites whenever possible. Otherwise, set up camp in areas where living crusts do not form, such as slickrock, sandy beaches or under groves of trees.

To learn more about Resler Canyon or how you help contact Janae@FronteraLandAlliance.org.

Janae’ Reneaud Field is executive director of The Frontera Land Alliance.