Unprecedented wildfires and environmental changes happening on a global scale.

Researchers in the Great Basin are learning how best to protect and restore these threatened places before they are permanently degraded, and unfortunately it isn’t as easy as popping a few pills.

Two concepts that help scientists understand the vulnerability of the land are: resilience and resistance. Rating a place based on resilience and resistance gives managers information about how it will respond to disturbances such as wildfire and invasive grasses like cheatgrass as well as how effective management efforts are likely to be (such as shrub/conifer cutting or prescribed fire).

Resilience

Resilient land can recover following a disturbance or management activity more easily. The resilience of land depends on the climate, the soils and the type of vegetation growing there.

In the Great Basin, resilience increases with elevation. At middle to high elevations, more precipitation and cooler temperatures combine with richer soils to create better conditions for native plant growth and reproduction, so these areas are more resilient to fire and invasive plants.

At low elevations, less precipitation and higher temperatures result in fewer resources for plants and lower resilience.

Slope, aspect and topography influence resilience because they change how much sunlight a place receives, how much water it gets, how the soil was formed and which plants are present at a given location.

Resilience of a site can be lowered by anything that kills native vegetation and prevents rapid regrowth.

This can include frequent or severe wildfires or long and severe droughts. It also can include inappropriate grazing by livestock or wild horses and burros.

Resistance

The more resistant a land is to negative events, the healthier it is. Resistance to invasive annual grasses like cheatgrass is particularly important in low- and mid-elevation sites because when invasion occurs, it can begin a cycle of wildfire that kills native plants, followed by more invasion of burnable grasses and then by more wildfires.

Resistance to invasive species depends on whether or not an area has the right soil and water for the invaders to establish, grow and reproduce, and whether or not the native plants already there can compete with the invader.

Similar to resilience, resistance to invasive plants is lowered by stressors such as natural and human-caused disturbances, especially those that decrease the ability of the native plant community to compete with the invader. Stressors include removal of sagebrush by wildfire or by insects like the Aroga moth.

They can also include inappropriate grazing or frequent and repeated fires that reduce the abundance of native perennial grasses and forbs.

Native species, especially deep-rooted perennial grasses like bluebunch wheatgrass, are key to maintaining resilience and resistance after a fire because they are the best competitors against invasive annual grasses.

Resilience and resistance in large-scale management

Understanding resilience and resistance gives landowners and land managers the ability to evaluate risks and prioritize projects across large landscapes. They can evaluate how likely an area is to recover following a fire or a restoration project and how likely it is to be invaded by annual grasses.

Because resilience to disturbance and resistance to invasive annual grasses are tightly connected to soil temperature and water availability, they can use these factors to evaluate how resilience and resistance would change with changing climate conditions.

Evaluating these factors before a juniper removal project, for example, provides information on the risk of invasion by annual grasses depending on different types of treatment (using prescribed fire versus cutting with a chainsaw).

Soil temperature and moisture data are available for most areas and can be used as the first step for evaluating resilience and resistance across project areas.

Recently, resilience and resistance levels to annual invasive grasses have been used to help land managers evaluate sage grouse habitat.

Whether or not you are concerned with the fate of the sage grouse, the overall management goal is one that anyone who relies on sage steppe rangelands can support: improved ecological conditions and better health for sagebrush lands.

Potential management activities to achieve this include fuels management, post-fire rehabilitation and habitat restoration, among others.

Using resilience and resistance in best management practices on a smaller scale

Information about the resilience and resistance of a site can be used to decide if an area would be a good candidate for specific treatments, such as conifer removal or post-fire seeding.

Determining the resilience and resistance of an area begins with knowing the ecology and looking up the ecological site descriptions (ESDs). ESDs are part of a land classification system that provides basic information about soil characteristics, such as temperature and moisture, and vegetation, such as the composition and abundance of plant species.

ESDs give information about different scenarios: what might cause a change on that site, what might happen after that change and the effects of management interventions.

Detailed information is not yet available for the entire Great Basin, but a general set of predictions has been developed that incorporates resilience and resistance and can be widely applied to the Great Basin.

Because Great Basin ecosystems occur over a broad range of environmental conditions and have varied land-use histories and ecosystems, careful evaluation of an area will always be necessary to determine the best way to support and restore it.

Generally, sites with high resilience and resistance are those that are relatively cool and moist, have deep or fine-textured soils, a high percentage of deep-rooted perennial native grasses and flowering plants, and few (or no) invasive plant species.

These types of sites typically recover well after disturbance and often do not require seeding. Sites with low resistance and resilience are those with some combination of relatively warm and dry conditions, shallow or coarse-textured soils, few deep-rooted perennial native grasses and forbs or an abundance of invasive plant species.

These sites often are slow to recover after management treatments or disturbance and are at risk of conversion to invasive annual grasses.  

For more information about ESDs, see Ecological Site Descriptions.

Jeanne C. Chambers is with the USDA Forest Service, Rocky Mountain Research Station.