The largest-scale cultivation of whole biocrust communities ever conducted in the world is taking place near Moab, according to experts.
If you’ve lived in Moab for a while, you’re familiar with the phrase “don’t bust the crust.” It’s on National Park Service stickers, Junior Ranger booklets, trailhead information signs and posters around town. The slogan refers to the craggy, dark crust that carpets unvegetated ground in the desert.
This crust goes by various names: biological, cryptogamic, microbiotic, cryptobiotic and microphytic crusts. All of these names describe the fact that the crust is made up of living organisms — bacteria, algae, mosses, lichens and fungi — in contrast to a physical, inorganic crust formed by salt or frost heave.
Though the slogan is catchy and often accompanied by cartoon illustrations, the message should be taken seriously. Damage to the biological soil crust, or biocrust, is not a trivial thing.
“Biocrusts are the keystone element of the landscape out here,” said Sue Bellagamba, regional director of The Nature Conservancy. “If we lose the biocrust, we see major impacts on the soil stability, vegetation and wildlife of the entire region.”
The crust in the Southwest has already been extensively damaged or destroyed by various human and natural impacts.
Crust is removed or covered at construction sites and resource extraction sites like oil wells. Rangeland cattle trample it. Hikers, bikers and motorized off-road vehicles can crush and/or bury the crust if they travel off-trail. Even without direct human impacts, the crust can be damaged by severe wildfires, or buried by wind-blown dusts and soils.
In recent years, climatologists have predicted hotter and drier conditions in the region, adding another threat to the health of biological soil crusts.
Biological crusts have several important functions in the desert ecosystem. One function is stabilizing the soil. Growth structures of bacteria, fungi, lichens and mosses in biological crusts bind sandy soil particles together and keep them from blowing or washing away.
Another function is water retention. The rough texture of a healthy crust keeps rainfall from quickly running off sloping ground. Organisms in the crust absorb the water, swelling up like sponges, and prevent the water from sinking too quickly through sandy soil.
Biological crusts are adapted for mutually beneficial co-existence with their neighbors, the native shrubs and grasses of the desert. Native plants growing near thriving crusts have been found to contain higher nutrient levels than shrubs with no crust nearby.
It is also thought that the crust may discourage germination of seeds from invasive exotic plants, while allowing native, adapted species to propagate.
Once the crust is harmed, the damage is not easily reversed.
A group of conservationists and scientists from several organizations is undertaking an experimental restoration effort focused on biological crust.
The Nature Conservancy, the U.S. Geological Survey, Northern Arizona University (NAU), and the non-profit Rim to Rim Restoration have partnered together and received a grant from the Wildlife Conservation Society through its Climate Adaptation Fund with support from the Doris Duke Charitable Foundation.
“Biological soil crusts are notorious for growing slowly and taking a very long time to recover from being trampled by foot traffic, cows, or being driven over,” said Dr. Colin Tucker, an ecologist at the U.S. Geological Survey.
Some elements of the crust may bounce back relatively quickly, depending on conditions — cyanobacterial and green algae components can recover in just a few years. However, the thick, craggy, physical mass of the crust can take decades to re-form, and mosses and lichens can take hundreds of years.
The experimental restoration research is based at the Canyonlands Research Center, a facility owned by The Nature Conservancy and supported by several land management and research entities.
The experiment involves transplanting crusts that are already adapted to hotter, drier regions, and using them to attempt to restore disturbed areas in the Colorado Plateau region with hearty biocrusts that can withstand the severity of predicted climate change.
“The scientific community has recently become quite good at growing biocrust quickly in a greenhouse and in test tubes,” said Dr. Sasha Reed, a USGS scientist working on the project. “But our ability to grow biocrust that survives once it’s placed at restoration sites in the real world remains poor.”
Figuring out how to transplant biocrust successfully is part of the project.
“We have run a few trials transplanting crusts from one location to another to evaluate how well it grows in different locations,” said Tucker, who is the lead scientist on the project. “We have seen mixed results: sometimes the biocrust grows really well, and sometimes it dies. We are still learning how and why this happens, which makes it a really exciting time to be working on it.”
Tucker’s team has collected crusts from areas that are soon to be disturbed, such as planned construction sites. Some of the samples are from the Colorado Plateau, and others are from the hotter, drier Mojave and Sonoran deserts to the south and west. Tucker emphasized that his team only collected biocrusts that would have been doomed.
“The biocrust we harvest would otherwise be destroyed,” he said. “We don’t harvest intact biocrust that is going to survive on its own.”
The crust must be carefully scraped from the soil while it is dry, which indicates that it’s dormant.
It is stored and transported in dark, dry conditions to a biocrust “farm” at the Mayberry Native Plant Propagation Center on River Road, where researchers nurture the samples to grow and expand them.
Once grown, the soil crusts will be moved to restorations sites in Castle Valley and Indian Creek.
This is no small task, said Dr. Anita Antoninka, research associate at the NAU School of Forestry.
“This is the largest-scale cultivation of whole biocrust communities ever conducted in the world,” Antoninka said.
Each site is about 10 acres, and both have been used for grazing and seen other human impacts in the past. The sites will be closely managed for a few years while the crust gets established.
“After that,” Tucker said, “the management will be passive: The sites will be protected from destructive land use and we will be monitoring the recovery of biocrust at these sites for decades to come.”
If the project is successful, it could lead the way in methodology for even larger-scale restoration projects.
Kara Dohrenwend is the program manager for Rim to Rim Restoration. She looks forward to the results of this project contributing to future restoration endeavors.
“We are enthusiastic about helping find methods to grow and transport biocrusts to crust restoration locations that may lead to new ideas about how to re-establish plant communities dependent on biocrust communities,” Dohrenwend said.
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“We are enthusiastic about helping find methods to grow and transport biocrusts to crust restoration locations that may lead to new ideas about how to re-establish plant communities dependent on biocrust communities.”
