Kobziar Fire Science Lab
School of Forest Resources and Conservation

Mechanical Fuels Mastication Treatments in Mesic Flatwoods

    Jesse Kreye, PhD Candidate

    Osceola National Forest, Florida

As the wildland urban interface (WUI) area in the southeast grows, the threat to communities from wildfire becomes more widespread, while the use of prescribed fire to reduce this threat becomes more challenging.  Mechanical treatments may be employed to alter fuel complexes prior to or as an alternative to prescribed burning.  My research is currently focused on studying the effectiveness as well as the potential consequences of mechanically masticating understory shrubs and small trees in pine flatwoods of the Osceola National Forest, Florida, USA.

Mechanical mastication is a fuels treatment method that converts standing live shrubs and small trees into a dense fuelbed composed of horizontally oriented dead fragments of vegetation.  Live fuels are chopped or cut using front end or boom mounted rotating equipment containing flailing cutters that sever branches, limbs, and stems.  Important questions regarding mechanical fuels treatments are their effectiveness in reducing the threat of wildfire to communities within the WUI as well as the longevity of such effectiveness.  It is also important to understand what potential ecological effects may result from the implementation of these types of treatments across a landscape scale. 

Mechanical mastication of understory shrubs and small trees is being conducted as a fuels treatment method in Osceola National Forest in northern peninsular Florida, USA.  The sites being masticated are primarily in pine flatwoods ecosystems dominated by slash (Pinus elliottii) and longleaf pines (P. palustris) in the overstory, and by gallberry (Ilex glabra) and saw palmetto (Serenoa repens) in the understory.  Most sites have not burned in over 10 years and this fuels treatment method is being implemented to alter the fuel complex prior to  prescribed burning with the intent to reduce fire behavior.  Within these sites we have established long-term sampling plots and are monitoring both vegetation and surface fuels following treatment in order to evaluate vegetation recovery and fuel dynamics.  Monitoring vegetation recovery and the life cycles of fuelbeds over time will help us to better understand the effectiveness of these treatments to mitigating current fire hazards with the WUI. 

To fully understand the effectiveness and/or potential consequences of this treatment we are also evaluating how these resulting fuel complexes burn.  To do so we are quantifying fire behavior within these novel fuels both in the field and within constructed fuelbeds.  Following mechanical treatments we are monitoring fire behavior (rate of spread and flame heights) during prescribed burning operations and monitoring resulting fire effects (fuel consumption and tree mortality).   To better predict fire behavior in these fuels we developing and burned experimental fuelbeds constructed from material collected from treated sites.  We have burned constructed fuelbeds across 3 fuel loading treatments (10, 20, and 30 Mg/ha) at 2 fuel moisture content (FMC) treatments (9±1 and 14±2 %).  Flame heights and rate of spread were observed during burning and temperatures above and below (within the soil) these fuelbeds were recorded throughout burning with the use of thermocouples.

With continued monitoring of post-mastication vegetation and fuel dynamics and further observations of fire behavior and effects within these treatments we hope to gain a much better understanding of the effectiveness, longevity, and potential consequences of mastication in southern pine flatwoods.

Related Media, Presentations, and Papers

Fall 2011 Fire Science Lab members (Jesse Kreye, Leda Kobziar, David Godwin, Mike Camp, and Dawn McKinstry) hosted the Southern Fire Exchange workshop entitled: “Mechanical Fuels Reduction Treatments Effects on Fire Behavior, Fuel Loads, and Forest Ecology” at the Osceola National Forest.  See the handout and research summary here.