Fuels Planning: Science Synthesis and

Integration

Economic Uses Fact Sheet: 1

Mastication Treatments and Costs

United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

Research Note

RMRS-RN-20-1-WWW

September 2004

Mastication Fuel Treatments

Mastication, or mulching, is a mechanical fuel treatment that changes the structure and size of fuels in the stand. Trees

and understory vegetation are chopped,

ground, or chipped, and the resulting

material is left on the soil surface. Converting 20 tons per acre of understory

biomass into small pieces would produce

a uniform layer about 1 inch deep across

the stand. From a fuels perspective, the

total fuel loading is not immediately affected. However, the vertical height of the fuels is lowered, and more fuel volume

is shifted into 1- and 10-hour size classes. Ongoing studies will determine the

effect of mastication on subsequent fire behavior and nutrient cycling.

Mastication Equipment

A wide variety of mastication equipment provides tools to match the requirements of nearly any treatment. Some machines have tracks; some have wheels;

some have the cutting head mounted on a boom. Windell and Bradshaw (2000)

provide a catalog illustrating many of the current equipment designs. A primary

design variation is the type of cutterheadóvertical shaft or horizontal shaft. Vertical shaft cutters are essentially giant lawnmowers. They tend to be less expensive

to operate but are more limited in the diameter of material that can be treated, and

they tend to produce a coarser chunk. Horizontal shaft cutterheads, in contrast,

produce smaller chips and can treat larger stems but tend to cost more to operate.

Another key design variation is the type of base machine on which the cutterhead

is attached. The type of base machine is a critical factor that affects the amount of

soil disturbance, operational slope limitations, and operating cost. Each has plusses

and minuses that should be considered in specific management applications. There

are some specialized, very low ground pressure tracked machines that can be used

on sensitive or soft soils to minimize soil disturbance. For steep slopes, there are

self-leveling tracked machines and modified walking excavators. There are small

tracked or wheeled machines that can operate in tight spaces. Boom-type machines can significantly reduce the amount of area disturbed and can also operate

the cutter in tight spacing. Wheeled machines are generally faster and less expensive to operate.

Where Is Mastication Used?

Mastication is more than simply mowing. It is a fuel and silvicultural treatment that

should be designed to achieve desired ecological conditions. It can be used as either

Economics Team Co-Leads:

Roger Fight

Jamie Barbour

USDA Forest Service

Pacific Northwest Research Station

620 SW Main Street, Suite 400

Portland, OR 97205

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

The information for this

fact sheet was provided by

Bob Rummer at the USFS

Forest Operations Research

Lab, Auburn, Alabama.
The Fuels Planning fact sheets are based on preliminary findings. Information from fact sheets will be synthesized in an upcoming publication.

a surrogate for fire or as a pretreatment for reintroducing

fire in overstocked stands. There are many situations

where the use of fire as a stand management tool is not

desirable. Some examples may be around structures in

the wildland-urban interface, along rights-of-way for utilities or transportation, or in areas where air quality constraints limit burning. As a fire surrogate, mastication may

become a recurring treatment (like a fire return cycle) to

control vegetation, particularly with hardwoods that coppice vigorously. It may be necessary to cut and grind some

larger diameter stems in the initial entry. Generally, fire

surrogate prescriptions would specify a smaller residual

fuel size in order to speed decomposition.

In contrast, mastication as a pretreatment for reintroducing fire should be designed to get the stand in a condition that allows larger burning windows and/or shifts

the expected fire behavior toward more controllable conditions. Where mastication will be followed by fire, it is

not necessary to reduce everything to small pieces. Some

of the stand can be treated with fire. For example, isolated patches of understory that are difficult to masticate

may be left. Vertical shaft cutterheads may be a better

match in these conditions.

Treatment Factors Affecting Cost

Actual costs have ranged from hundreds to thousands

of dollars per acre. Some areas, such as steep slopes, can

be expensive to treat. However, many factors that affect

costs can be controlled by the prescription. Some key

things to consider:

Minimize the amount of volume treated

ï Leaving 3 inches and larger stems provides course

woody debris and helps to optimize efficiency.

ï Donít use masticators as feller-bunchers.

ï For big machines, mastication is typically inefficient at 25 tons per acre or greater.

ï Specify the largest acceptable resulting fuel sizes.

Minimize constraints on travel

ï Avoid treatment areas narrower than a chain

lengthó66 feet wide.

ï Try to avoid operating in dense residual stands

greater than 100 trees per acre.

ï Minimize areas of steep slope (20 percent or

greater) or broken terrain.

ï Donít apply soil disturbance constraints unless

necessary.

Provide adequate access for service

ï Equipment requires road access for fueling and

maintenance.

Reference

Windell, Keith; Bradshaw, Sunni. 2000. Understory biomass reduction methods and equipment catalog. Tech.

Rep. 0051-2826-MTDC. Missoula, MT: U.S Department

of Agriculture, Forest Service, Missoula Technology and

Development Center. 156 p. Online at: www.fs.fed.us/fmsc/

sdu/technology/mtdc-catalog/index.php [July 2003].

Economics Team Fact Sheets

Look for fact sheet topics from the Economics Team including prescribed

fire costs, harvesting, log hauling, NEPA and other regulations, wood utilization, economic impacts on communities, markets for wood, and harvest equipment requirements.

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