Coproduced Research Helps Managers Assess Fuel Maintenance Treatment Effectiveness in Fire-Prone Central Oregon

Photo Credit

USDA Forest Service

A firefighter ignites a prescribed burn on the Deschutes National Forest.

To ensure the success of the agency’s 2022 10-year Wildfire Crisis Strategy, Forest Service researchers are working with land managers to address fundamental questions about the effects and longevity of fuel treatments on the Central Oregon Wildfire Crisis Strategy priority landscape.

Historically, the ponderosa pine and mixed-conifer forests in this part of central Oregon burned frequently, with low- to mixed-severity fires. Long periods of fire exclusion have left these forests more vulnerable to drought and insect infestations and created fuel conditions more conducive to extreme fire behavior. Central Oregon’s risk for extreme wildfire led to its early selection as a focal landscape identified for targeted investments under the Wildfire Crisis Strategy.

Fuel treatments that reduce vegetation, such as thinning and prescribed fire, are critical for promoting resilience and reducing fire risk in these forests. However, the benefits stemming from fuel reduction treatments in these forest types only last about 10 to 20 years.

Harold Zald, a research ecologist with the Pacific Northwest Research Station, is leading a study along with Chris Fettig, a research entomologist with the Pacific Southwest Research Station, to fill in information gaps about the long-term effects of fuels reduction in these forests.

“The Wildfire Crisis Strategy is about increasing the pace and scale of fuel treatments. However, the treatments themselves need to be maintained, and we don’t have a great understanding of what that means. How do we make these treatments effective over the long term?” Zald explained.

Zald’s study will take place on Lookout Mountain in the Pringle Falls Experimental Forest, which is within the Deschutes National Forest and Central Oregon Wildfire Crisis Strategy priority landscape. The project builds on a 2,520-acre operational-scale experiment known as the Lookout Mountain Study that began a decade ago. Study treatments include four levels of overstory thinning (implemented in 2011 through 2013), mastication and mowing (implemented in 2012 through 2014), and prescribed burning (2013 through 2015). Randomly assigned units were left untreated as a reference.

The project, which was conceived jointly with managers from the Deschutes National Forest, is one of the few silviculture experiments being conducted at the same broad scale as the fuel treatment implementation goals envisioned by the Wildfire Crisis Strategy. The broad scope of the project, along with its collaborative approach, will help the agency work toward its ambitious goals of restoring fire-adapted ecosystems on a landscape scale.

Objectives

• Quantify long-term (~10 year) effects of operational-scale overstory thinning coupled with understory fuels reduction in ponderosa pine and mixed-conifer forests in the Lookout Mountain study at Pringle Falls Experimental Forest. 
• Provide management-relevant science to inform implementation of planned fuels maintenance treatments in the Lookout Mountain Study, Deschutes National Forest fuels maintenance project, and Central Oregon Wildfire Crisis Strategy Landscape. 
• Continue long-term data collection within the Lookout Mountain study area to determine effects of treatments on tree mortality and its causal agents, overstory tree composition and structure, understory vegetation composition and abundance, and large down woody debris. 
• Develop mapping methods with remotely sensed data to quantify shrub cover relation to overstory thinning and understory fuels reduction. 
• Quantify current surface fuels in relation to overstory thinning and understory fuels reduction.

Expected Products 

• A model integrating field data and remotely-sensed data to map current shrub cover and how it varies within and between treatments. 
• A field workshop for managers that synthesizes long-term effects of initial treatments to inform implementation of fuels maintenance treatments in the Lookout Mountain Study, Deschutes National Forest fuels maintenance project, and Central Oregon Wildfire Crisis Strategy Landscape. 
• Peer-reviewed publications on the long-term (~10 year) effects of operational-scale overstory thinning and understory fuels reduction on tree mortality, forest composition and structure, and surface fuels.

Expected Outcomes 

The Lookout Mountain study will as serve a focal point for knowledge sharing among a diverse set of researchers, forest managers, and fuel managers in the Central Oregon Wildfire Crisis Strategy priority landscape.

Information from this project will be used to inform operational-scale fuels maintenance treatments.

This project will also lead to better understanding about the following: 

• The extent to which tree mortality following initial thinning and burning needs to be incorporated into treatment guidelines to achieve long-term objectives. 
• The effect of repeated fuels maintenance treatments on tree mortality over the subsequent decade. 
• The influence of fuel loads and live fuels on fuels maintenance treatments. 
  • Potential treatment options to mitigate the effects of fuel loads and live fuel, and how these options may differ based on plant associations, stand densities, and dominant understory shrub species

Metrics of Success

Project findings will continue to inform management of forest composition and structure to reduce the flammability of ponderosa pine and mixed-confer forests in the Central Oregon Wildfire Crisis Strategy priority landscape. Findings will help managers assess the effectiveness of fuel maintenance treatments in reducing fuels while enhancing forest resistance and resilience to disturbance.

Geographies 

Deschutes National Forest and Central Oregon Wildfire Crisis priority landscape

Keywords: Fuel treatments, silviculture, remote sensing, wildfire risk reduction, forest restoration, coproduction