Written by Linh Nguyen/ Photos by Teresa Wicks

Malheur National Wildlife Refuge is known for its oases of wetlands, wet meadows, and homestead era stands of cottonwoods, elms, and other tall trees. One of the important, though often less focused-on habitats is the Sagebrush Steppe, covering 14,000 to 15,000 acres and shrubs are its main vegetative plants. It can be found around the fringe of the Blitzen Valley, at higher elevations, at several locations in the Double-O Unit, and along the south side of Harney Lake. This is the home for obligate shrub-steppe species like Greater sage-grouse, Brewer’s sparrow, sagebrush sparrow, and sage thrasher. This habitat also supports other animals like sagebrush lizards and mule deer. 

In arid landscapes like the uplands of Malheur National Wildlife Refuge, perennial plants are interspaced with a biological soil crusts called biocrust. This refers to the community of lichens, mosses, cyanobacteria, and fungi that live on the soil surface, work together to increase soil stability, water holding capacity, nutrient availability, elemental cycling, and seedling establishment of grasses and shrubs (Coe et al.). Lea Condon, a PhD graduate from Oregon State University, conduct her thesis on the effect of biocrust on the spread of cheatgrass, and she concluded her dissertation saying that management of biocrust “not only increase site resistance to cheatgrass but it will add to the conservation of ecosystem functions related to nutrient cycling, hydrologic cycling and soil erosion.” 

In addition, restoring biocrust might help the restoration of native plants, and the maintenance of hydrologic and nutrient cycles. Condon confirms that perennial vegetation and lichens will help resist cheatgrass and moss will promote the growth of both lichens and perennial herbaceous vegetation. The moss component of biocrust improves many functions related to Carbon, Nitrogen, and Phosphorus cycling and storage in semiarid and arid environments like the Sagebrush Steppe (Delgado-Baquerizo et al.). Delgado-Baquerizo et al. also state that the maintenance of biocrusts is important in mitigating the negative effects of climate change on high deserts. Soil respiration is heavily temperature sensitive, and the biocrust community can drive the warming effect in drylands (García-Palacios et al.). However, with the increasing effects of climate change on precipitation patterns, mosses are especially affected and decline fast, which in turn reduce crust structure and function. This can have implications for hydrology, soil stability, and nutrient cycling in dryland systems (Coe et al.). 

In conclusion, the Sagebrush Steppe is now being endangered by non-native plants, which can affect the survival of the obligate shrub-steppe species. The growth of cheatgrass can be minimized by the management of the biocrust community, mostly lichens and mosses. The moss component of the biocrust can be successfully restored without irrigation, while the lichen component is more sensitive to disturbance (Condon). Biocrust, in addition to perennial plants, restoration and conservation, is an effective method to prevent the spread of cheatgrass and other non-native noxious plants throughout the Sagebrush Steppe.

References

• Coe, Kirsten K. et al. “Precipitation-Driven Carbon Balance Controls Survivorship of Desert Biocrust Mosses”. Ecology, vol 93, no. 7, 2012, pp. 1626-1636.
• Condon, Lea A. Biological Soil Crusts of the Great Basin: An Examination of Their Distribution, Recovery From Disturbance and Restoration. : Oregon State University.
• Delgado-Baquerizo, Manuel et al. “Biocrust-Forming Mosses Mitigate the Negative Impacts of Increasing Aridity on Ecosystem Multifunctionality in Drylands”. New Phytologist, vol 209, no. 4, 2015, pp. 1540-1552.
• García-Palacios, Pablo et al. “Pathways Regulating Decreased Soil Respiration with Warming in a Biocrust-Dominated Dryland”. Global Change Biology, vol 24, no. 10, 2018, pp. 4645-4656.