SageSTEP – Sagebrush Steppe Treatment Evaluation Project

Background

The Sagebrush ecosystem of North America is one of the largest fire-prone ecosystems on the continent and is one of the most threatened ecologically by the combination of fire, plant invasions, and climate change. Removing flammable vegetation—known as fuels reduction—is a land management practice aimed at reducing the frequency and severity of wildfires. The effects of these practices have been extensively studied in forest ecosystems, but studies on the long-term ecological impacts in semiarid sagebrush steppe landscapes are needed. Sagebrush shrubs are critical for the survival of many species, including the greater sage-grouse, but these woody fuels are fire intolerant and create more intense, difficult-to-control wildfires compared to herbaceous fuels like native perennial grasses. Thinning woody fuels is thought to open up space for the spread of fire tolerant plants, improving the resilience of ecosystems to fire. Removing just enough sagebrush to lessen the severity of fires, while maintaining sufficient habitat for sage-grouse, requires finding a delicate balance.

The expansion of pinyon pine and juniper trees into sagebrush ecosystems has introduced another source of woody fuel. Pinyon and juniper can outcompete other plants for water, disrupt habitat for sagebrush-dependent wildlife, and lead to larger wildfires and more cheatgrass invasion. Land managers often remove trees using prescribed fire, cutting, or shredding. These treatment options offer different trade-offs, resulting in variable consequences for fire suppression, wildlife, and surrounding vegetation. Selecting the best option for a given treatment site is key.

To investigate the overall efficacy of fuel treatment methods, researchers conducted fuels treatments at study sites in California, Idaho, Nevada, Oregon, Utah, and Washington, and evaluated the effects on a variety of ecosystem components including plants, potential for wildfire, soils, water runoff and erosion, and birds and insects. Sites within the sagebrush/woodland network are focused on investigating the impacts of tree removal. Sites within the sagebrush/cheatgrass network are aimed at reducing woody sagebrush fuels while minimizing further exotic grass invasion.

The Experiments

Cheatgrass Network

In 2006-2008, the SageSTEP team initiated fuel reduction treatments in big sagebrush communities experiencing invasion of non-native annual grasses, primarily cheatgrass. Fuel reduction treatment methods included prescribed fire, mowing, and herbicide application.

• Prescribed fire- Firefighters initiate controlled burns to remove woody fuels (sagebrush) and invasive plants like cheatgrass. Fire kills sagebrush, which leaves openings for other species to establish.
• Mowing- Sagebrush is mowed to a height of approximately 12 inches. Mowing doesn’t kill sagebrush plants, opens space for the growth of understory species, and preserves some cover for sage-grouse.
• Herbicide application- Tebuthiuron pellets are dropped from helicopters to thin sagebrush and encourage understory growth. Another herbicide, Imazapic, is used to control the invasive annual grass cheatgrass, which can rapidly dominate landscapes after wildfire.

After the fuels treatments were completed, long-term monitoring began. Researchers conducted field surveys to look at the effects of these treatments on the magnitude and longevity of fuel reduction, greater sage-grouse habitat, and ecological resilience and resistance to invasive annual grasses.

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Woodland Network

Fuel reduction treatments within the woodland network were initiated to remove pinyon and juniper in areas where they have expanded into sagebrush ecosystems. The SageSTEP team used three different methods to remove trees.

• Prescribed fire- Controlled burning removes live trees and consumes much of the wood on the ground, resulting in less intense and severe wildfires.
• Cutting- Clearcutting uses chainsaws to cut trees taller than half a meter and leave them where they fall.
• Shredding- Also known as mastication, trees are shredded with a spiked, rotating drum attached to a tractor (this was done only at sites in Utah, a state where this approach is common).

Prescribed fire, in general, completely removes trees from the landscape. Cutting and shredding result in wood accumulation on the ground, which can act as fire fuel, but ground fires tend to be smaller and less intense than fires in the canopies of live trees.

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Future

The SageSTEP team will continue monitoring study sites for up to 25 years post-treatment. This length of time will allow researchers to begin to understand the durability of fuel treatments and the long-term impacts of fuel treatments on fire risk, as well as the influence of climate change on the plants and animals of the Great Basin.

Funding received in 2023 is allowing us to continue collecting data and analyzing results in preparation for summarizing 15 years of post-treatment sampling.

To read more about SageSTEP science and view before/after pictures of the study sites and access informational handouts and videos, visit our team's main website using this external link.