NO. 67 Date 07/07/03
By Dennis Zachman, Supervisory Project Manager,
BLM, Colorado State Office
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 pinyonjuniper 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.
A cylindrical roller or drum, equipped with several full-length blades, is towed behind a crawler-type tractor or cat. The drum is 4.56 feet in diameter and 812 feet wide. The blades span the width of the drum
|Figure 1. A roller chopper is effective in knocking down brush and trees and chopping up the slash.|
|and extend outward 1214 inches; they are spaced 1820 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 20,00035,000 pounds. The drum will hold 8001,000 gallons of water, making the filled weight of the drum 26,50043,000 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 1320 acres per day, depending on the size of the vegetation and terrain.
A Hydro-axe, also known as a Hydro-mower, is an articulated tractor with a mowermulcher mounted on the front of the machine (Figure 2). The Hydro-axe has rubber flotation-type tires that cause little disturbance to the surface of the ground. At a width of 89 feet, the mowermulcher clips and mulches plant debris from 4 to10 inches above the ground. A single Hydro-axe can treat 616 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.
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.
|Figure 2. The Hydro-axe leaves behind a fine, protective mulch and causes little surface disturbance.|
|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.
Dennis Zachmann, Supervisory Project Manager
BLM, Colorado State Office
2850 Youngfield Street
Lakewood, CO 80215
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