Mastication Treatments in Southwestern Forests

Mastication Overview

• Definition: Mastication involves reducing vegetation by grinding, shredding, or chomping, aimed at altering fuel load and fire risk.

• Benefits: Proper mastication treatments can reduce fire risk and severity by rearranging canopy, ladder, and surface fuels.

• Note: Biomass typically remains on-site during treatments, meaning fuel loading is reconfigured rather than reduced.

Equipment Types

• Types of Mastication Equipment:

  • Horizontal Shaft Masticators (Drum Masticators)

  • Vertical Shaft Masticators (Rotary Disc Masticators)

• Application: Can be mounted on various vehicles such as tracked vehicles (feller bunchers) and rubber-tired loading vehicles (skidders).

Mastication in the Southwest

• Target Areas:

  • Used primarily in urban interface areas to create buffer zones against fire risk.

  • Effective where smoke concerns exist, particularly near residential areas.

• Impact on Fuel Condition:

  • Rearranges fuel profile to lessen hazard without reducing fuel loading.

  • Helps retain moisture in the ground and fosters beneficial soil organisms by preventing direct sunlight exposure.

Case Study: Acid Canyon

• Location: Near Los Alamos, located in open space surrounded by neighborhoods.

• Harvesting Details:

  • Targeted trees up to four inches in diameter, with smaller trees masticated after limbing.

• Desired Outcomes:

  • Minimal residual masticated material observed leading to proliferation of grasses, indicating effective treatment.

Impact on Fire Behavior

• Key Metrics: The effectiveness of mastication evaluated based on its ability to influence:

  • Rate of fire spread.

  • Probability of crown fire occurrence.

  • Overall fire severity.

• Positive Influence: Regional land managers report that mastication has moderated fire behavior under certain conditions.

• 2011 Donaldson Fire Example:

  • Fire burned over previously masticated areas, demonstrating positive impacts on control efforts.

  • Easier to manage with hand crews, engines, and dozers due to lower chances of crown fire.

Challenges and Limitations

• Adverse Conditions: Extreme burning conditions in recent years raised questions regarding mastication's reliability.

• Horseshoe Two Fire Experience:

  • Intense fire behavior observed, comparable to piñon-juniper crown fires, despite mastication treatment.

  • Indicated the limits of direct attack strategies in such scenarios.

• Post-Cerro Grande Fire Treatments:

  • Implemented in Los Alamos area post-2007 fire; selective thinning led to different fire behaviors.

  • Masticated areas exhibited high fire intensity and mortality rates during Las Conchas fire.

Unintended Consequences of Mastication

• Soil Impact:

  • High masticated material depth may lead to soil sterilization and root damage.

  • Longer heat exposure during a fire can negatively affect soil quality.

• Invasive Species Promotion:

  • Layered biomass can hinder native species' recovery, favoring exotic species like bull thistle.

Ecological Considerations

• Management Trade-offs:

  • Decisions in fuels management involve balancing positive and negative ecological impacts.

  • Mastication may moderate fire behavior but does not universally reduce tree mortality.

• Implementation Caution:

  • Mastication should be tailored to specific site conditions, emphasizing close communication with resource specialists.

Future Directions

• Research Findings:

  • Mastication shows potential for moderating fire behavior more than reducing tree mortality.

  • Prescribed fire treatments alongside mastication may enhance ecological resilience.

• For further resources on mastication treatments, refer to the Southwest Fire Science Consortium publications.