“We call that very thin layer on the surface of the soil ‘biological crust,’ or ‘biocrust’ for short,” explained Northern Arizona University School of Forestry Assistant Professor Matt Bowker, Ph.D. “It’s held together by living organisms, mostly cyanobacteria and fungi, that weave through the soil. They make a platform that other organisms, like mosses and lichens, can then colonize.”
The biocrust is hard to the touch. Its dark color is the result of organisms producing a sunscreen to protect them from the Southwest’s harsh ultraviolet rays. It also repels raindrops and shelters loose sand from wind. But it can be easily crushed when trampled on or driven over; and thus, it has been destroyed in some places. Scientists are concerned about the loss of biocrusts in the desert Southwest, particularly in the face of a warming, drying climate.
“Climate change is going to hit them hard because a lot of these organisms are right at their thermal edge, or their temperature edge,” said pioneering biocrust scientist Jayne Belnap, a research ecologist with the U.S. Geological Survey Southwest Biological Science Center. “They can’t stand it any hotter. And when you lose that soil stability, the things that blow away when you see a dust storm for instance, or you see sediment in water, you’re seeing the fertility of that site leaving that site.”
In Bowker’s School of Forestry laboratory, he is growing living biocrust.
“We’re trying to find a way to fix crusts – basically re-grow the living skin,” said Bowker. “One of the interesting and surprising things we found is counterintuitive. First of all, if you disturb these crusts, it could take decades for them to naturally re-grow. That would lead you to believe that they grow really slowly. But what we found is that’s not actually true. That’s not hardwired. What we think instead is that disturbance and a harsh environment, a harsh climate, is what constrains them. So if we take these organisms into the lab, give them everything that they need, give them water, give them nutrients, they can grow fast. we can grow crusts in weeks to months, rather than years to decades. So that’s the exciting front that we’re trying to push.”
Bowker’s artificially-grown biocrust was planted in a remote soil garden in the Canyonlands Research Center of southern Utah last April. Other experiments there include soil samples transplanted from different elevations.
“We know the communities are very similar. But are they adapted to live in that one particular climate environment, or can they live somewhere else? So [in these experiments], they’re either in their home, 500 feet lower, or 500 feet higher. There are some species that are not doing well, some that are doing better, but this is very early data,” said NAU School of Forestry Research Associate Anita Antoninka, Ph.D. “The goal here is to understand if they can adapt to climate change and also to be able to target species for site restoration. Understanding which groups do well together or alone, and where they might do best, will help us to figure out what we can in terms of restoration for the future.”
NAU’s greenhouse-grown soil also is being tested in the pinyon-juniper woodlands of New Mexico’s Bandelier National Monument. Forestry graduate student Kristina Young says a combination of land use and history, including past overgrazing and periodic droughts, have caused much of the bare soil to erode.
“We collected biological soil from the area, grew it here and are putting it back out there,” said Young. “The New Mexico monsoon season brings intense rain all at one time. There’s so much water pouring over the landscape really quickly that the soil can’t absorb it and without vegetation on the ground anymore in some places, it can’t hold onto the water.”
One of the big concerns about soil erosion at the monument is the loss of archaeological resources, she says. “Those are being damaged. You can see where pot sherds are being moved far distances as the soil is washed away.”
Meanwhile, NAU soil ecology doctoral student Henry Grover is cultivating “fire mosses,” a group of biocrust organisms that grow after a high-severity wildfire burns through the forest. He’s hoping to develop moss-heavy biocrusts that can be used along with re-seeding and mulching efforts on post-fire landscapes to restore and stabilize the soil and prevent flooding, as in the case of the Schultz fire.
“We’re looking at ways to stimulate the mosses and improve that growth rate,” he said. “We’ve found we can take a sample with 20 percent moss cover and bring it to 100 percent cover in nine weeks in the greenhouse.”
NAU scientists hope their experiments will advance the understanding and development of healthy surface soil.
“Growing crusts in the lab and then reintroducing them to damaged landscapes might be a tool that we can use to keep dust from getting into the air and keep fertility in the soil where it belongs so we can have productive plant communities and support animals that rely on plants, as well,” he said.
Bowker and his team continue to look for the most resilient mosses, lichens, bacteria and combinations of organisms to create the best recipe for boosting biocrust in the Southwest. FBN
By Bonnie Stevens, FBN
Photo by Bonnie Stevens