Explore how fire and people’s relationship with it have shaped diverse ecosystems across Oregon.
How fire historically shaped the Northern Great Basin Rangelands
Shrubs like Wyoming big sagebrush were relatively spread out and interspersed with native perennial bunchgrasses. When dry, these grasses were especially receptive to ignitions. While bunchgrasses provided fine fuels that carried fire between shrubs, the bare interspaces between shrubs and grass “bunches” moderated the rate of fire spread. Sagebrush plants burn for long periods, concentrating a lot of heat in their immediate vicinity, meaning higher burn severity was mostly limited to the area surrounding them.
This relatively low fuel continuity and varying levels of burn severity meant that wildfire created smaller, interspersed burned patches that provided a mix of wildlife habitat and successional states. Bunchgrasses readily recovered from their underground root structures while sagebrush grew from seed over 30 years.
Changes to the northern Great Basin Rangelands fire patterns
Over time, a combination of fire suppression and the introduction of invasive annual grasses has led to higher fuel loads and larger, more frequent wildfires. Invasive annual grasses readily colonize disturbed areas, such as those that have been improperly grazed or experienced severe fire.
As a result, invasive annual grasses have become more abundant, increasing the likelihood of ignition and fire propagation. Fires spread more rapidly, leading to larger burned areas, which are further vulnerable to invasion by annual grasses, especially at lower elevations and drier sites.
How fire shapes the Northern Great Basin Rangelands today
Sites colonized by annual grasses further increase the likelihood of fire and rapid fire spread. Frequent burns across large areas make it difficult for slow-growing shrubs such as sagebrush to establish and for perennial grasses to compete with annual grasses.
Not all flame’s the same
Fire has played a significant role in shaping landscapes throughout history, sparked by both lightning and the intentional use of fire by Indigenous peoples. Fire enabled people to manage and adapt to their local ecosystems, helping them produce food, tools, materials and medicines, as well as maintain prairies, clearings and travel routes. It also helped reduce the risk of larger, more destructive fires by preventing the accumulation of excess fuel. Beyond human use, fire serves vital ecological functions, such as clearing dead vegetation, recycling nutrients, creating habitats for plants and animals, promoting germination and new growth and controlling insects and diseases.
Oregon is a very diverse state from the coast to the Cascade Mountains and the Great Basin. Because of this, it makes sense that the way fire behaves also varies across the state. In other words, fire happens in different patterns and has different effects. This resource explains the role of fire in seven ecoregions of Oregon.
Ready to learn more? https://beav.es/NAFTS.
This publication was made possible with funding from the Oregon Forest Resources Institute in cooperation with the Forestry and Natural Resources Extension Program at Oregon State University.
About the authors
