Predicting Burn Risk to Land Management Investments
Land management treatments in sagebrush steppe are an important opportunity to break the annual-grass fire cycle, provided they offer long-lasting resistance to annual-grass invasion and do not burn. However, for areas seeded as part of the Emergency Stabilization and Rehabilitation (ESR) program-- one of the largest programs for land management treatments-- about 1/4 have at least partially reburned over the last 30 years. USGS scientists are working to provide land managers with information that can be used to predict whether restored areas are at risk of reburning and whether reburning will lead to negative ecological impacts like cheatgrass invasion and erosion.
Background
Intact sagebrush steppe ecosystems in the western United States are dominated by patchy shrubs and perennial grasses. Bare ground between plants prevents fire from spreading too far or too quickly, and historically, healthy sagebrush landscapes didn’t burn frequently. In the last fifty years, invasion by exotic annual grasses has created conditions for larger and more severe fires. Exotic annual grasses, like cheatgrass, invade the space between native shrubs and dry out early in the year, leaving behind litter that can carry wildfires over large areas. Exotic annual grasses also quickly come back after fire, often faster than native perennial vegetation.

Land managers spray herbicides, such as imazapic, after fire to reduce initial populations of exotic annual grasses. Seeding native perennial bunchgrasses or shrubs post-fire is another common land treatment. The goal of both treatments is to give native perennials a head start on re-establishment. These land treatments can expensive, particularly because areas burned often exceed 100,000 acres, but are the best chance to break the annual grass-fire cycle. Ideally early intervention will increase landscape “resilience” --the ability to recover after disturbance-- and “resistance” --ability to resist future invasion-- and reduce the need for future repeated treatments.
Fire is becoming more frequent in the arid western United States and many areas that have burned and were treated will reburn. Reburning effects on previous treatments can vary widely. Sagebrush does not resprout after fire and can take 50-100+ years to recover, leaving a void that exotic annual grasses are likely to fill. Perennial bunchgrasses often survive burning and resprout immediately after fire. Thus, the reburning of early successful sagebrush seeding will represent a bigger loss of investment and risk of invasion than the reburning of a successful perennial bunchgrass seeding.
The Fire, Invasion, and Ecology in Sagebrush Steppe (FIREss) team is using the fire behavior model, FLAMMAP, to determine how land management treatments affect the probability of reburning and the likelihood of having a negative response to reburning. Using vegetation data from many thousands of plots that have reburned or not reburned, we are simulating past reburns to determine how treatments affect the probability of reburning. The team will then revisit some of the plots to collect data on vegetation recovery.
Goals
- Determine how herbicide and seeding treatments affect fuel types.
- Use information in step one to run FLAMMAP fire simulation models across three burn areas that have reburned. We will ask how treatments affect the probability of reburning, and look at how treatment success, proximity to areas of high wildfire risk, and different wind and fuel scenarios could impact reburn risk.
- Collect field data after reburning to assess how herbicide and seeding treatments affect the likelihood of post-fire invasion or erosion.
- Combine burn probability maps with maps displaying the likelihood of post-fire invasion or erosion to identify treatment investments that are at the greatest risk of both reburning and other negative ecological responses.
Value for Land Management
There are not enough resources to treat entire areas affected by the annual grass-fire cycle, which is a problem that is further compounded by risks of reburning. Prioritizing treatments is important and could increase the long-term return on restoration investment. This study will help managers select locations of future treatment investments to minimize their risk of reburning and subsequent invasion. The results could also help managers plan fuel break locations to protect expensive treatment investments that are likely to have a negative outcome from reburning.
USGS is partnering with the U.S. Bureau of Land Management on this project.
Land management treatments in sagebrush steppe are an important opportunity to break the annual-grass fire cycle, provided they offer long-lasting resistance to annual-grass invasion and do not burn. However, for areas seeded as part of the Emergency Stabilization and Rehabilitation (ESR) program-- one of the largest programs for land management treatments-- about 1/4 have at least partially reburned over the last 30 years. USGS scientists are working to provide land managers with information that can be used to predict whether restored areas are at risk of reburning and whether reburning will lead to negative ecological impacts like cheatgrass invasion and erosion.
Background
Intact sagebrush steppe ecosystems in the western United States are dominated by patchy shrubs and perennial grasses. Bare ground between plants prevents fire from spreading too far or too quickly, and historically, healthy sagebrush landscapes didn’t burn frequently. In the last fifty years, invasion by exotic annual grasses has created conditions for larger and more severe fires. Exotic annual grasses, like cheatgrass, invade the space between native shrubs and dry out early in the year, leaving behind litter that can carry wildfires over large areas. Exotic annual grasses also quickly come back after fire, often faster than native perennial vegetation.

Land managers spray herbicides, such as imazapic, after fire to reduce initial populations of exotic annual grasses. Seeding native perennial bunchgrasses or shrubs post-fire is another common land treatment. The goal of both treatments is to give native perennials a head start on re-establishment. These land treatments can expensive, particularly because areas burned often exceed 100,000 acres, but are the best chance to break the annual grass-fire cycle. Ideally early intervention will increase landscape “resilience” --the ability to recover after disturbance-- and “resistance” --ability to resist future invasion-- and reduce the need for future repeated treatments.
Fire is becoming more frequent in the arid western United States and many areas that have burned and were treated will reburn. Reburning effects on previous treatments can vary widely. Sagebrush does not resprout after fire and can take 50-100+ years to recover, leaving a void that exotic annual grasses are likely to fill. Perennial bunchgrasses often survive burning and resprout immediately after fire. Thus, the reburning of early successful sagebrush seeding will represent a bigger loss of investment and risk of invasion than the reburning of a successful perennial bunchgrass seeding.
The Fire, Invasion, and Ecology in Sagebrush Steppe (FIREss) team is using the fire behavior model, FLAMMAP, to determine how land management treatments affect the probability of reburning and the likelihood of having a negative response to reburning. Using vegetation data from many thousands of plots that have reburned or not reburned, we are simulating past reburns to determine how treatments affect the probability of reburning. The team will then revisit some of the plots to collect data on vegetation recovery.
Goals
- Determine how herbicide and seeding treatments affect fuel types.
- Use information in step one to run FLAMMAP fire simulation models across three burn areas that have reburned. We will ask how treatments affect the probability of reburning, and look at how treatment success, proximity to areas of high wildfire risk, and different wind and fuel scenarios could impact reburn risk.
- Collect field data after reburning to assess how herbicide and seeding treatments affect the likelihood of post-fire invasion or erosion.
- Combine burn probability maps with maps displaying the likelihood of post-fire invasion or erosion to identify treatment investments that are at the greatest risk of both reburning and other negative ecological responses.
Value for Land Management
There are not enough resources to treat entire areas affected by the annual grass-fire cycle, which is a problem that is further compounded by risks of reburning. Prioritizing treatments is important and could increase the long-term return on restoration investment. This study will help managers select locations of future treatment investments to minimize their risk of reburning and subsequent invasion. The results could also help managers plan fuel break locations to protect expensive treatment investments that are likely to have a negative outcome from reburning.
USGS is partnering with the U.S. Bureau of Land Management on this project.