Mechanical 

Treatments to Meet

Resource Needs

By Dennis Zachman, Supervisory

Project Manager, BLM, Colorado

State Office

Background

When fire is judged to be too

risky or ineffective under

acceptable prescriptions,

mechanical treatments can be

effective in meeting resource

objectives. Properly used,

mechanical treatments reduce

fire hazards, improve the proper

distribution of plant communities, increase plant diversity,

control noxious weeds, and

improve the quality and quantity

of vegetation for wildlife and livestock. Treatment increases

ground cover, which often results

in increased soil infiltration

rates and decreases in surface

runoff, soil erosion, and stream

sedimentation. Colorado

Bureau of Land Management

personnel use the following

types of mechanical treatments

to meet resource management

objectives on public lands.

Roller Chopping Treatment

Roller chopping is a mechanical

treatment that is frequently

applied to Colorado mountain

shrub types and pinyon–juniper

stands with stem diameters as

wide as 8 inches. The cost is

moderate, and the method is

extremely effective for knocking

down brush and trees and chopping up the slash (Figure 1).

Roller chopping can be done

when the soil is firm and dry

enough to support the heavy

equipment. In most instances,

the best results are achieved

when the procedure is supplemented with seeding. 

Equipment

A cylindrical roller or drum,

equipped with several full-length

blades, is towed behind a crawlertype tractor or “cat.” The drum is

4.5–6 feet in diameter and

8–12 feet wide. The blades

span the width of the drum and

extend outward 12–14 inches;

they are spaced 18–20 inches

apart around the circumference

of the drum. The drum is hollow and can be filled with water

to increase its weight. The

empty weight of the drum is

20,000–35,000 pounds. The

drum will hold 800–1,000

gallons of water, making the

filled weight of the drum

26,500–43,000 pounds. 

The roller chopper may be

pulled straight or at a diagonal

to increase the chopping action.

Two roller choppers are sometimes towed in tandem and at

slightly contrasting angles. The

cat will usually have its blade

positioned low to the ground to

push over trees and brush. A

whirlybird-type seeder can be

located at the back of the cat and

in front of the roller chopper.

The heavy weight of the roller

chopper crushes the trees and

brush, while the blades chop

them and help scratch the

ground surface. A single roller

chopper can treat 13–20 acres

per day, depending on the size

of the vegetation and terrain.

Cost

Typically, the cost of treatment

is $60 to $90 per acre, depending

on the condition of the terrain,

remoteness, contractor competition, and timing. Seed application costs $20 to $23 per acre.

Comments and Constraints

Roller chopping should not be

undertaken in extremely muddy

conditions or on rocky or steep

terrain. Roller chopping should

be avoided when snow is on the

ground and the air temperature

is near 32°F to avoid snow

packing between the blades on

the drum. However, treatment

when the air temperature is

well below 32°F is effective in

breaking up and mulching the

woody vegetation.

The increase of litter and the

blade indentations in the soil surface usually decrease the erosion

rate after roller chopping. The

roller chopper should be towed

NO. 67 DATE 07/7/03

Range

Range

Resource Note 67

page 1

Figure 1. A roller chopper is effective in knocking

down brush and trees and chopping up the slash.
up and down slopes so that the

blade indentations will retard

surface runoff and soil erosion.

For best results, seeding is done

at the time of treatment. Aerial

seeding is also an option, but is

not as effective.

Hydro-axe Treatment

The use of a Hydro-axe is a

mechanical treatment that is

frequently applied to Colorado

mountain shrub types and

pinyon–juniper stands with

stem diameters as wide as 

8 inches. This method is effective

for knocking down brush and

trees and chopping up the slash.

Equipment

A Hydro-axe, also known as a

Hydro-mower, is an articulated

tractor with a mower–mulcher

mounted on the front of the

machine (Figure 2). The

Hydro-axe has rubber flotationtype tires that cause little disturbance to the surface of the

ground. At a width of 8–9 feet,

the mower–mulcher clips and

mulches plant debris from 4

to10 inches above the ground.

A single Hydro-axe can treat

6–16 acres per day, depending

on the size of the vegetation

and the nature of the treatment. The machine can move

around trees to treat selected

areas. 

Cost

The cost of treatment is $150

to $170 per acre, depending

on the vegetative material,

condition of the terrain, and

nature of the treatment. Seed

application costs $20 to $23

per acre. 

Comments and Constraints

The litter that remains from

this treatment is much finer

than that resulting from other

types of treatments, such as

roller chopping. The Hydro-axe

allows the operator to be precise

in the areas and vegetation treated. The mulch creates a protective vegetal layer for the rubber

tire tractor to travel over, thus

reducing surface disturbance.

Large safety zones are required

when using the machine.

Contact

Dennis Zachmann, Supervisory

Project Manager

BLM, Colorado State Office

2850 Youngfield Street

Lakewood, CO 80215

Phone: 303-239-3883

E-mail:

Dennis_Zachmann@blm.gov

Range

Resource Note 67

page 2

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Figure 2. The Hydro-axe leaves behind a fine, protective

mulch and causes little surface disturbance.