Ventenata Invasion in the Blue Mountains Ecoregion

Exotic plant invasions are a growing challenge to ecosystem management, and are particularly dramatic when they alter disturbance regimes beyond the range of natural variation. A relatively new invasive annual grass, Ventenata dubia thrives at higher elevations, threatening native forest biodiversity and creating ecosystem-level changes. We are conducting landscape scale research focused on the Blue Mountain Ecoregion (BME) in the Pacific Northwest to examine the extent of ventenata invasion and associated ecosystem change.

This project will examine how fuels, fire regimes, and fire effects might shift across the region, and how these changes might affect management. This project will depict alternative scenarios of ecosystem change associated with future climate change and management actions.

The research project has four primary objectives:

Extent of Ventenata

   

Influence of Climate Change                          

Scablands

          

        Shifts in Fire Regimes                  

Ventenata Occurrence in the BME

One of our first tasks was to develop a ventenata occurrence map after compiling all known existing data combined with new spatial data collected in 2017. This is a work in progress! We will add new information as it becomes available and update the map. If you have ventenata occurrence data, please contact us!

 

Ventenata occurrence map

 

How You Can Help With Mapping Efforts

In order to map ventenata across the BME, we are seeking collaboration with weed control managers, biologists, ecologists, natural resource professionals, fire and fuel staff, students, land managers and others to collect locations of ventenata and basic site information when they visit sites as part of their normal work routines. To get started, check out our mapping tools.

Locations and site information can be collected in the field data with a mobile app (built in ESRI’s Survey123) or with a basic GPS unit and paper forms. The process should not take more than 5 minutes per location. Note that this app can be used to collect occurrence and abundance data for ANY species of interest and local units may want to use this process to collect data on other invasives or species of interest.

 
Objective 1: Extent of Ventenata Invasion
Ventenata was first reported in North America in 1952 in Washington and has since spread to six other western states (CA, OR, ID, WY, UT, MT). Ventenata is an increasing concern for both public and private land managers for a variety of reasons. Similar to other exotic invasive annual grasses it is aggressive and can dominate large areas across the landscape. The plant dries earlier in the summer than native species, but later than other exotic annual grasses, and remains highly flammable throughout the fire season creating dangerous conditions on the ground. Land managers have noted that ventenata has increased and spread over the past decade in mountain meadows and scablands of the Blue Mountain Ecoregion and yet the full extent of ventenata invasion is unknown.

We are working to assess the extent of ventenata invasion in the BME and examine how the invasion has changed through time and what environmental (climate, soil, light) and disturbance (fire and grazing) factors influence and/or exacerbate populations.

We will also develop a spatially explicit map of ventenata distribution and spread, and create a predictive model of habitat suitability in the BME. Research questions:

  • Where is ventenata increasing across the landscape?
  • What environmental factors are related to prescence?
  • What type of disturbances and management practices are exacerbating populations?

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Objective 2: Influence of Climate Change
While current ecosystem level changes due to ventenata invasion are being realized, further changes are anticipated with predicted climate change. A recent assessment of potential climate change effects on upland vegetation in the Blue Mountain Ecoregion (BME) suggested that the likelihood of forest, woodlands and shrublands being invaded by exotic annual grasses in a warmer climate will increase because of more disturbance (fire, insect and disease outbreaks, fuel treatments), effects of warming on species distributions, enhanced competitiveness of exotic plants from elevated carbon dioxide, and increased stress to native species.

Determine how different future climate change scenarios may alter the habitat suitability and potential distribution of ventenata in the BME. Research question:

  • How might climate change alter the ventenata invasion?

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Objective 3: Scablands
From monitoring plots and remotely sensed data, land managers have noted that ventenata has increased and spread over the past decade in mountain meadows and scablands of the Blue Mountain Ecoregion, outcompeting native bunchgrasses and other exotic annual grasses.

We will examine and describe ventenata dynamics in scablands and open areas and the post-fire response of ventenata to recent wildfires. Research questions:

  • Does fire exacerbate ventenata populations?

  • Is the response related to fire severity, pre-fire invasion levels, or environmental conditions?

We will also characterize ventenata populations along open areas/forested edges in invaded areas that have not burned. Research questions:

  •  What do open area/forested edges look like with respect to spread of ventenata into the forested understory?
  • Does ventenata invasion result in fuel connectivity at these edges?

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Objective 4: Shifts in Fire Regimes
One particular concern of ventenata invasion is the species’ ability to create novel landscape conditions and alter fire behavior. Forestland managers note that ventenata is a “game changer” largely because of the species’ ecosystem-level transformation potential. Several large wildfires in 2015 burned over 300,000 acres of forests and rangelands in the Blue Mountain Ecoregion (BME). Fire and fuels resource managers working these fires expressed concern regarding novel fire behavior, particularly in open meadows and scablands interspersed within the forest matrix. These open areas occur throughout the BME and are tactically used as wildland fire breaks and firefighter safety zones because fire does not traditionally carry through them due to the presence of small statured species and interspaces of shallow, gravelly/rocky soils, resulting in low fuel connectivity. The spatial arrangement of fuels across the landscape is a major driver of wildland fire behavior, and ventenata invasion has dramatically changed these areas, creating flashy fuel beds prone to fast moving fire. In the 2015 fires, firefighters witnessed rapid fire spread fueled by this dry grass.

We will estimate potential shifts in fuels and fire regimes by developing scenarios to examine how the ventenata invasion might change fuels, fire behavior, burn probabilities, fire size and fire effects across large landscapes now and into the future using several operational climate change scenarios. Research questions:

  • How might fuels, fire regimes, and fire effects shift across the region when the ventenata invasion reaches full potential (e.g. all available habitat invaded)?
  • How might fuels, fire regimes, and fire effects shift across the region under future climate change?