USDA Forest Service

Pacific Northwest Research Station

Pacific Northwest Research Station
1220 SW 3rd Ave.
Portland, OR 97204

(503) 808-2100

US Forest Service

Land and Ecosystem Management


Forest Dynamics After Thinning and Fuel Reduction

Subtitle: A study to refine management options for restoring resiliency in ponderosa pine ecosystems



Today, many forests have characteristics that place them at greater risk of uncharacteristically severe disturbances. Recent agency initiatives and Congressional legislation have pointed to the need for large-scale and strategically located fuel reduction and restoration projects to manage landscapes within the context of ecological processes. While thinning or prescribed burning are common tools for fuel reduction and restoration in dry forests, uncertainty remains as to the ecological consequences of these treatments.

First, responses often have been assessed only over the short term and have not been established in locations such as experimental forests, where long-term studies can be pursued.

Second, treatments often have been designed to restore fuelbed conditions or forest composition and structure to historical conditions but have ignored the risks, uncertainties, and benefits of multiple environmental stresses.

A critical need remains for management options for restoring and managing forest and landscapes in anticipation of increased probability of multiple, interacting stresses that may lead to altered or new disturbance regimes with both economic and ecological consequences.

With widespread recognition by scientists and policymakers that climate change is occurring, management options are needed that recognize and accommodate uncertainty and the interaction of shifting regional climates with vegetation manipulations. Resource managers are challenged to integrate knowledge of frequent low- or mixed-severity disturbances such as wildfires and insect attacks with poorly defined shifts in regional climate, to better understand and predict forest structure and composition.



This study is located entirely within Pringle Falls Experimental Forest. Pringle Falls Experimental Forest lies within the Deschutes National Forest in central Oregon southwest of Bend, Oregon, and was established in May 1931 as a center for silviculture, forest management, and insect and disease research in ponderosa pine forests east of the Oregon Cascade Range.

Pringle Falls Experimental Forest
Pringle Falls Experimental Forest on the Deschutes National Forest.

The Lookout Mountain Unit (3,535 acres) was added to the Pringle Butte Unit in 1936. This large block of closed-canopy forest has undergone little major disturbance since about 1845 when a single stand-replacement fire resulted in the establishment of dense ponderosa pine at lower elevations and mixed conifers at higher elevations. Limited low thinning occurred about 40 years ago when the road network was established. Several long-term silvicultural studies have regional and national significance within this unit. Fire exclusion over the past 100 years has maintained high stand density, led to high basal area, and allowed high fuel accumulation. Because of stand density, average diameter, and host and fuel availability, there is a high and increasing probability that ponderosa pine across the Lookout Mountain unit will support a landscape-scale western pine bark beetle outbreak, or a wildfire will eliminate all stands. Stand replacement by fire or bark beetles will result in the discontinuation of existing high-value long-term studies and eliminate many future research opportunities.


Research Response

The study plan Forest Dynamics after Thinning and Fuels Reduction in Dry Forests outlines a set of procedures to determine short- and long-term responses of forest vegetation to thinning and fuel reduction, and to evaluate the effects of thinning and fuel reduction treatments on long-term susceptibility to fire, insects, wind, climate change, and other forest disturbances. The project will thin to five levels of density 2,554 acres of the Lookout Mountain Unit of the Pringle Falls Experimental Forest

Thinning will be followed by mowing and underburning. Long-term integrated research will use the platform of replicated treatments to address specific questions. For example,

  • What treatments best accelerate the development of large trees while reintroducing natural disturbance processes to provide greater ecosystem resiliency?
  • What is the influence of climate change interacting with treatments on vegetation dynamics and forest structure?
  • Do multi cohort stands share the same risks of multiple, interacting stresses as single-cohort stands?
Treatment assignment at Lookout Mountain
Treatment assignment at Lookout Mountain analyzed in the Final Environmental Impact Statement.

Additional studies will address the vegetation dynamics and the availability of prey species for northern spotted owls, resource allocation and use by white-headed woodpeckers, and the dynamics of ectomycorrhizal communities of dominant shrubs in fire-prone ecosystems.

The study plan was the subject of an external blind review process approved by the PNW Research Station Director March 2009, and it was analyzed as the Proposed Action in the EXF final environmental impact statement (FEIS).

Both the Station Director and Deschutes National Forest Supervisor signed the record of decision to implement the project on March 15, 2010. This decision was appealed to the Pacific Northwest Regional Forester, who upheld the decision.

League of Wilderness Defenders—Blue Mountains Biodiversity Project filed a complaint in District Court in Eugene, Oregon, on September 22, 2010. Plaintiffs alleged the FEIS failed to consider a reasonable range of alternatives, failed to ensure scientific accuracy and integrity, and failed to consider impacts of treatment effects on various wildlife species. Federal District Court ruled in favor of the Forest Service, and plaintiffs filed in 9th District Court of Appeals, May 2011. A hearing before the 9th District Court of Appeals occurred in Portland, Oregon, in March 2012. Both the District Court and Circuit Court failed to approve temporary injunctions, thus the project was initiated despite continuing court proceedings. Forest Service district wildlife biologist reported observations of northern spotted owl in the study area in July 2011, and the study plan was modified to exclude over 500 acres from treatment late in 2011. Treatment assignment at Lookout Mountain
Treatment assignment at Lookout Mountain after study modification to accommodate northern spotted owl detection.


Current Status

Pretreatment data collection began in May 2011. The first set of thinning treatments occurred in Block 4 during 2011. This first sale in Block 4 included about 17,000 CCF of live ponderosa pine, lodgepole pine, and grand fir on about 493 acres, and it was completed in late November 2011. A second sale is scheduled for summer 2012 to include about 25,000 CCF of ponderosa pine and grand fir on 733 acres in Block 2.


Associated studies

Lookout Mountain is also the site of other research that is made possible by the thinning and fuels reduction treatments. The additional research projects address the following topics:

  • Evaluating the resiliency of ponderosa pine forests to bark beetle infestations after thinning and fuel reduction treatments
  • Stand density and understory vegetation effects on tree vigor and bark beetle susceptibility
  • Forest and wildlife dynamics after thinning and fuel reduction in dry forests: studies of white-headed woodpecker and prey species of northern spotted owl
  • Collecting pretreatment data
    Collecting pretreatment data on stand structure and composition.
  • Understanding the biology and ecology of giant chinquapin
  • The combustion of large downed wood and its role in facilitating tree regeneration in ponderosa pine ecosystems
  • Multiscaled monitoring of weather and soil conditions
  • Thinning the ponderosa pine level-of-growing-stock long-term study plots at Lookout Mountain
  • Measuring change in forest structure by using remotely sensed versus field plot data

Additional Reading

Youngblood, A. 2011. Ecological lessons from long-term studies in experimental forests: ponderosa pine silviculture at Pringle Falls Experimental Forest, central Oregon. Special Issue. Forest Ecology and Management. 261(5): 937-947.

Peer, B.; Brna, P.; Jorgensen, R.; McFarland, J.; Powers, C.; Schlaich, J.; Wall, D.; Webb, B.; Youngblood, A. 2010. Final Environmental Impact Statement and Record of Decision, EXF thinning, fuels reduction, and research project. Bend Oregon. Bend/Ft. Rock Ranger District, Deschutes National Forest and PNW Station. 283. + appendices.

Logging equipment
Logging equipment working to thin block 4 during the summer 2011.



Andrew Youngblood
PNW Research Station
LaGrande Forestry Sciences Lab
Contact via email



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US Forest Service - Pacific Northwest Research Station
Last Modified: Tuesday,17June2014 at15:05:07CDT

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