Can biological soil crust communities be restored?

CU ecologist works to stabilize soil and improve human health

By Lara Herrington Watson

Funded by a five-year grant through the Department of Defense, University of Colorado Boulder ecologist Nichole Barger is working to regenerate unique biological soil crusts that occur in the Colorado Plateau and the Western United States.

The crusts in these arid and semi-arid landscapes could be restored using a method similar to hardening off tomato plants. The landscapes may seem wide open and pristine, but they get a lot of traffic. From hikers and bikers, to off-roaders and oil and gas companies, everyone who uses the land irreversibly impacts it and its microbial soil crusts.



Biological soil crust communities, or biocrusts, consist of microbial organisms that colonize the soil in dry regions, where there is minimal plant cover.  Unlike plain dirt crusts that form on topsoil, these biocrusts are actually alive. They retain water and nutrients in the soil, fix nitrogen from the air into the soil, facilitate photosynthesis, and maintain soil integrity.

Barger and her research collaborators from Arizona State University and the U.S. Geological Survey are a few of “a little tribe of people in the U.S. and around the world who study crusts and the importance of them,” she says. “These crusts are a critically important functional component of dryland systems.”

Yet all the human activity in these fragile ecosystems disturbs these biocrusts, which take hundreds of years to form and can’t regenerate spontaneously. Once destroyed, soil surfaces become vulnerable and unstable.

“There are things that we’ve done as humans that destabilize soil surfaces, like making roads, drilling for oil and gas, and grazing cattle. All these things create dust,” Barger says.

The inadvertent impact of unstable soil includes dust storms in metropolitan areas. These storms cause traffic accidents, breathing problems and asthma, and increased hospital visits.

Now that she and her colleagues understand how vital these crusts are to the ecosystem, her current research asks, “How can we actually start restoring these biocrusts in disturbed sites?”

No one has successfully restored these sites, but Barger believes she and her collaborators will succeed.



Previous researchers have brought microorganism samples from the field to the lab and given them ideal conditions to kick-start their biomasses. The challenge is that they easily become too dependent on lab conditions.

“Now that they’re really happy in the lab, you take them out in the field. It’s almost like you put your tomato plant out too early and it just dies,” Barger says. “It’s like transplant shock.”

By exposing the biomasses to milder conditions than occur in the field, different microorganisms are promoted over others, ultimately changing the composition of the biocrust community.

When reintroduced to the field, these lab-grown biomasses would require a lot of water and nutrients to thrive, but “it’s not feasible to restore large parts of the landscape by watering a whole desert,” Barger says.

Barger’s new strategy is to put the biomasses under good conditions in the lab, but not so great that they can’t survive in their original habitats. She compares her reintroduction plan for the biomasses to hardening off tomato plants, or gradually acclimating them to harsher conditions.

“We’ll get the biomass process going, so they’re really adapted back to that environment that they came from,” Barger says.

Barger and her team conducted field experiments earlier this spring at the Hill Air Force Base in the Utah desert. A postdoctoral candidate on Barger’s research team at CU-Boulder revisited their sites in October, and the recovery so far has been promising, she said.

Once data on the site are analyzed, Barger and her team can decide what happens next. They will choose specific inoculation methods and habitat modifications for long-term experiments in the last three years of the research grant.

Barger’s lab is working on a small scale, but thinking large. Barger is confident that if her team can restore the soil crusts on military bases, with its large tanks and frequent soil disturbances, it can restore land elsewhere.

“If we could actually be successful in stabilizing areas on a larger scale, outside of these large metropolitan areas, it would be interesting to see if we could actually have declines in these dust storms,” she says.

Barger hopes ecologists can stabilize soils and “not only restore ecosystems, but at the same time have an effect on human health.”

The DoD grant funding comes through the Strategic Environmental Research and Developmental Program, DoD’s environmental science and technology program, which partners with the Environmental Protection Agency and Department of Energy.

December 2013