At first glance, the grit crust could seem like a routine example of what researchers call a biological soil crust, or “biocrust” — a community of coexisting bacteria, fungi, algae and other microorganisms that caps the soil in coherent sheets. Around 12% of Earth’s land is covered by biocrusts. Ecologists often refer to these colonies as the planet’s “living skin.”
In 2012, Büdel and his colleagues estimated that biocrusts soak up and recycle around 7% of all the carbon and nearly half of all the nitrogen that is chemically “fixed” by terrestrial vegetation. The role of the biocrusts in procuring digestible nitrogen is particularly critical in arid deserts: Elsewhere, lightning can often convert atmospheric nitrogen to nitrates, but in the deserts, electrical storms are rare.
Half the N2! Wow, I didn’t expect that.
While traditional biocrusts drape themselves over the top layer of fine soil particles, and other kinds of organisms sprout directly on top of individual boulders, “the grit is in between — it’s a transition zone,” said Liesbeth van den Brink, an ecology researcher at the University of Tübingen who now lives just outside Pan de Azúcar with Gutiérrez Alvarado. In grit crust, the stones provide the structure, but the microbes colonize them in a coherent sheet — like a thin layer of resin grouting together a rock garden.
Jung and colleagues tested just how little water the microbes need to start photosynthesizing. The ideal serving was 0.25 millimeters of water — lower than the requirement of any other known biocrust. Once dampened, the microbes start photosynthesizing faster than any community the researchers have ever seen.
“The grit crust is setting a new threshold for conditions that make life possible,” Jung said.
Life on the edge for sure.
The crust is resilient, but it’s far from indestructible, and even human footprints can wipe out small chunks of it. That’s why the National Park Service has posted “Don’t bust the crust” signs across the western United States, urging hikers to stay on the paths to protect the breathing soil.
Once again we have a heavy foot.
TWELVE READINGS ON THE LICHEN THALLUS
I have been in contact with Trevor and Jason on the above site for years. I feed them articles like this when I see them. If they have good feedback I will add it.
Trevor made news a while back by overturning 150 years of accepted scientific wisdom.