TAKEAWAY
Carefully selected fuels-reduction practices can lessen the impact of wildfire on Utah’s rangelands.
In Utah’s west desert, weedy Eurasian grasses such as cheatgrass and expanding pinyon-juniper woodlands are displacing native sagebrush, bunchgrasses, and wildflowers. As a result, wildfires are much more common, sometimes burning thousands of acres, threatening ranching livelihoods, rural communities, water and air quality, and recreational opportunities.
Fires are inevitable in an arid landscape with summer lightning storms and growing recreation use. As part of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP), Utah State University is helping land managers find tools to protect rangelands and people from wildfire’s worst impacts with the fewest unintended negative consequences. Student crews from USU and the U.S. Geological Survey gather data annually from a network of 21 experimental sites across the Great Basin region from Beaver, Millard, and Tooele counties to eastern Oregon and Washington. At each site, experiments were created to understand both positive and negative effects over time of proactive practices such as herbicide spraying, mowing, tree removal, and prescribed burning to reduce the fuels that feed rangeland fires.
The emerging results are complex, and the best management for a site depends on the current makeup of the vegetation, elevation, and other factors. By applying study findings to their specific circumstances, land managers can create a landscape more resistant to weed invasion and more resilient after a wildfire. Since 2006, SageSTEP scientists have informed management strategies used by the U.S. Forest Service and Bureau of Land Management in sagebrush rangelands. Research has also helped to set guidelines for selecting the right treatment at a given site and is used regularly to guide the work of organizations such as Utah’s groundbreaking Watershed Restoration Initiative.
Table 1.A.1 Remedies for pinyon and juniper tree expansion in the Great Basin
In the past 100 years, pinyon and juniper trees have expanded their historic range, partly because wildfires have been suppressed, and partly because there are fewer grasses to carry fire between trees because of grazing. These trees are using more water, out-competing other plants, and changing the ecosystem, leading to some fairly serious consequences. The following table outlines the impacts of three management remedies.
| Prescribed Fire | Cutting | Shredding |
|---|---|---|
| Prescribed fire reduces both trees and shrubs. Areas treated with prescribed fire have lower shrub cover than those treated with cutting or shredding even six years after treatment. | Clearcutting uses chainsaws to cut trees taller than half meter, and leaves them where they fall. It can reduce tree cover to less than one percent of what it was before treatment. | During mastication, live trees are shredded with a spiked, rotating drum attached to a tractor. It can be done any time the soil is dry enough to avoid excessive compaction. |
| Prescribed fire, and mechanical treatments like cutting and shredding, reduce the number of encroached trees. This increases the time that soil water is available to other plants in the spring, which increases grass and shrub growth and cover. Water and available nutrients become available to both desirable native grasses and unwanted weeds like cheatgrass. | ||
| Prescribed fire removes live trees and consumes much of the wood on the ground, allowing later wildfires to be less intense and less severe. | Cutting and shredding are more flexible, more controlled, and less risky than prescribed fire. They reduce canopy fuels and allow easier wildfire suppression, and can be done any time of year, as long as the ground is not too wet. | |
| Prescribed fire causes short-term increases in runoff and soil erosion. But this should be evaluated in the context of the big picture–avoiding more serious consequences of encroachment and wildfire. | Mechanical treatments like cutting typically double or triple the amount of small down wood that could burn during a wildfire, particularly in older woodland stands. | Shredding produces mulch that can increase water infiltration rates and reduces erosion. Shredding also aids in wildfire suppression by bringing the fire from tree tops to the ground. |
| Warm and dry sites are not wellsuited to prescribed fire, especially if native grasses are missing from the understory | The burnable mulch left after shredding and the downed wood from cutting can increase the risk of high-temperature ground fires, which may damage desirable plants and seeds by causing the fire on the ground to burn hotter and longer. | |
| Treatment of any kind increases burnable grass fuels, especially in older stands, probably because the removal of woody vegetation results in an increase in soil water during the growing season, which can be captured by grasses and flowering plants like forbs as they grow to re-claim the site. | ||
| To best maintain and increase cover, sites should be treated before the encroaching tree cover approaches 20% (to maintain shrubs) or 45% (to maintain grasses and forbs). These sites will have more surviving native plants at the onset, which will help prevent a cheatgrass invasion later. | ||
Source: sagestep.org
References
- Pyke, D.A., Chambers, J.C., Pellant, M., Miller, R.F., Beck, J.L., Doescher, P.S., Roundy, B.A., Schupp, E.W., Knick, S.T., Brunson, M., and McIver, J.D. (2018). Restoration handbook for sagebrush steppe ecosystems with emphasis on greater sage-grouse habitat—Part 3. Site level restoration decisions: U.S. Geological Survey Circular 1426, 3-2018. https://doi.org/10.3133/cir1426
- Pyke, D.A., Knick, S.T., Chambers, J.C., Pellant, M., Miller, R.F., Beck, J.L., Doescher, P.S., Schupp, E.W., Roundy, B.A., Brunson, M., and McIver, J.D. (2015). Restoration handbook for sagebrush steppe ecosystems with emphasis on greater sage-grouse habitat—Part 2. Landscape level restoration decisions: U.S. Geological Survey Circular 1418. http://dx.doi.org/10.3133/cir1418
- Pyke, D.A., Chambers, J.C., Pellant, M., Knick, S.T., Miller, R,F., Beck, J.L., Doescher, P.S., Schupp, E.W., Roundy, B.A., Brunson, M., and McIver, J.D. (2015). Restoration handbook for sagebrush steppe ecosystems with emphasis on greater sagegrouse habitat—Part 1. Concepts for understanding and applying restoration: U.S. Geological Survey Circular 1416. http://dx.doi.org/10.3133/cir1416
- Science for Sagebrush Restoration. (2023). SageSTEP Sagebrush Steppe Treatment Evaluation Project. https://sagestep.org/