Fuels Planning: Science Synthesis and

Integration

Forest Structure and Fire Hazard Fact Sheet: 5

Fuel Treatment Principles for

Complex Landscapes

United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

Research Note

RMRS-RN-22-5-WWW

December 2004

Forest Structure and Fire Hazard

Team Leader

David L. Peterson

USDA Forest Service

PNW Research Station

400 N. 34th Street, Suite 201

Seattle, WA 98103

Fuels planning: Science synthesis and integration, an interagency research/management partnership to support the Ten-Year

Fire Plan, led by Russell T. Graham, RMRS,

and Sarah M. McCaffrey, NCRS.

Synthesizing

Scientific Information

for Fire and Fuels

Project Managers

Pacific Northwest

Research Station

Natural Systems, Fuels, and Fire Are Inherently Complex

Forest and shrubland ecosystems have complex patterns and biophysical processes, and the effectiveness of site-specific modification of fire hazard is directly

proportional to the quantity and quality of local data on vegetation structure and

fuels. Realistic expectations for fuel treatment plans should be based on scientific principles and data, but they must also consider the inherent complexity of

natural systems. The growing empirical database on how forest structure and

fuels affect large wildfires will inform adaptive fuel management and provide

new quantitative insights in the years ahead.

The information for this fact

sheet was provided by

David Peterson, PNW Research Station, and Sarah

McCaffrey, North Central

Research Station, USDA.

Any particular forest landscape may have a wide range of vegetation structures, fuels, and topography.

This complexity must be addressed in fire management and fuel treatments at large spatial scales.

Fire behavior modeling is reasonably accurate for surface fires, and data are available on how prescribed fires and mechanical thinning affect forest structure, fuels,

and other ecological conditions at small spatial scales. Modeling is less accurate for

crown fires and large landscapes, which make the outcomes of decisionmaking at

large scales less certain. In addition, steep slopes and extreme fire weather always

pose a challenge for fire management, and typically require higher removal of fuels

to reduce fire hazard.
The Fuels Planning fact sheets are based on preliminary findings. Information from fact sheets will be synthesized in an upcoming publication.

Forest Structure and Fire Hazard Fact

Sheets

Look for other fact sheet topics from the Forest Structure and Fire

Hazard Team with information about fire hazard, visualization, silviculture, uncertainty, and larger scale treatments.

Fuels Planning: Synthesis and Integration

This fact sheet is one in a series being produced as part of a larger project

supported by the USDA Forest Service to synthesize new knowledge

and information relevant to fire and fuels management. Fact sheets

address topics related to stand structure, environmental impacts, economics, and human responses to these factors. Information in the fact

sheets is targeted for the dry forests of the Inland West, but is often

applicable across broad regions of the country. For more information,

please visit our Web site at:

www.fs.fed.us/fire/tech_transfer/synthesis/synthesis_index

Table 1óFuel treatment principlesa.

Principle Effect Advantage Concerns

Reduce surface fuels Reduces potential Improves control, Need to keep surface

flame length reduces torching disturbance relatively low

Increase canopy base height Requires longer flame Reduces torching Opens understory,

length to start torching surface wind may increase

Decrease crown density Makes tree-to-tree Reduces potential for Surface wind may increase,

crown fire less likely crown fire surface fuels may be drier

Retain larger trees Increases proportion of Increases tree survival Removing smaller trees is

trees with thicker bark, economically less profitable

taller crowns

a

Adapted from Agee, J. K. 2002. Fire behavior and fire-resilient forests. In: Fitzgerald, S. A., ed. Fire in Oregonís forests: risks, effects, and treatment

options. Portland, OR: Oregon Forest Resources Institute: 119ñ126.

Note: The relative emphasis on these four principles may vary from stand to stand and from watershed to watershed. However, they should all be

considered in planning effective fuel treatments across complex landscapes.

One challenge is ìscaling upî our knowledge about smallscale phenomena to large, complex landscapes. Quantitative techniques for accomplishing this exist, but can

be difficult to apply. We need the expertise of local resource managers to complement the quantitative output from modeling in order to make good judgments

about potential fire hazard and fire behavior for a particular location. An interdisciplinary team of managers

and researchers is an effective approach for integrating

logistical, scientific, and regulatory issues relative to fuel

treatments.

A Focus on Basic Principles

Appropriate types of thinning and surface fuel treatments are clearly useful in reducing surface and crown

fire hazards under a wide range of fuels and topographic situations. Well-established scientific principles

(table 1) and simulation tools can be used to adjust fuel

treatments to attain specific risk levels. For example,

fire managers can reduce risk of future crown fires by

planning for fuel and forest structures that achieve a

specific fire hazard or predicted fire behavior outcome

for extreme fire weather conditions (for example, the

97th percentile worst conditions). This provides greater

resource protection and lower risk than basing fuel planning on moderate fire weather (for example, the 50th

percentile worst conditions).

In the face of this complexity, focusing on basic scientific principles can facilitate decisionmaking and guide

future data collection.