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Mechanical

7.1 Brush Blades and Rakes

7.2 Front-Mounted V-Blades and V-Rakes

7.3 Rear-Mounted Plows and Rippers

7.4 Drag Scarifiers

7.5 Shear Blades, Downing Chains and Roller Drum Choppers

7.6 Patch Scarifiers

7.7 Disc Trenchers and Cone Scarifiers

7.8 Mounders

7.9 Mixing

7.10 Motormanual Scarification Attachments

7 Site Preparation Implements

A wide range of site preparation implements is available. Each implement can prepare one or more types of planting spot or seedbed. The first step in choosing the most appropriate implement is to decide what site factors should be modified to produce the optimum planting spot or seedbed for the ecosystem which must be treated. Having identified what is needed, an implement that can prepare the required planting spot can then be selected. See Appendix 3, Equipment Comparison: Costs and Productivity, for a listing of comparative costs of many implements.

7.1 Brush Blades and Rakes

Brush blades and rakes were once the most common implements for preparing scarified strips. The recent availability of more specialized implements has lead to brush blades being used primarily for the re-arrangement of slash for hazard abatement (windrowing or piling and burning), and to improve planter access where slash loading is very heavy.

Photo

Standard brush rake.

When pushing slash, care must be taken to float the blade above the ground to avoid creating excessive soil disturbance. Tilting (4- or 6-way) blades are especially useful on sloped ground. The use of retractable-toothed rakes can reduce the amount of soil disturbance associated with windrowing slash. These rakes have also been used to break up and knock down slash and create seedbed for natural regeneration. When slash loads are very heavy, brush rakes can be used to facilitate subsequent passage of more microsite-specific implements.

Photo

FMC with 6-way slash rake.

Photo

Eden rake.

Photo

Raumfix slash rake.

For additional information on blades and rakes, see Maxwell [1989] and FRDA Handbook 002 [Coates and Haeussler 1987].

Excavators equipped with wide rakes have also been used for windrowing slash. Excavators are a good choice for sensitive sites as a swath the width of the reach of the boom on either side can be prepared in one pass.

Photo

Five-tine excavator slash rake.

For additional information on excavator rakes, see FERIC Technical Note TN-180 [von der Gönna 1992].

7.2 Front-Mounted V-Blades and V-Rakes

Front-mounted V-blades and V-rakes can be used as a first-pass treatment to clear aside slash and facilitate operation of a microsite-specific implement, or to improve planter access. The advantage of V-blades compared to brush blades is that the forward movement of the prime mover need not be interrupted to unload the blade. On medium to relatively coarse-textured soils, V-blades can be used to remove competing vegetation. The resulting strips of exposed mineral soil may remain free from vegetation for some years. V-blades are also useful for the reduction of deep duff layers. V-blading has the potential to cause significant site degradation and, therefore, it should be used only with great caution, particularly on fine-textured soils.

Photo

Sanders V-blade.

7.3 Rear-Mounted Plows and Rippers

In wet areas where summer access is poor, rear-mounted plows, capable of digging deeply, can be used on frozen ground. A deep trench and roughly overturned berm are formed. On wet sites in cold climates, the trench may not provide suitable planting spots. The berm, being better drained and warmer, forms favorable planting spots unless the site has the potential of developing dense competing vegetation.

On dry sites, the trench formed by smaller rear-mounted plows can provide favorable planting spots because scarce soil water is conserved in microsites below the general ground level.

Photo

Rear-mounted ripper plow.

Agricultural breaking plows provide overturned furrow slices which have a mineral soil layer covering the inverted organic matter. Seedlings generally perform well in such planting sites. When furrow slices are laid one in contact with another, vegetation may be controlled for several years.

Photo

Triple-bottom breaking plow.

Winged subsoilers are used to break up compact subsurface horizons to improve drainage and to increase effective rooting depth. Subsoilers are limited by slash and stumps, and are generally limited to landing and skid road rehabilitation.

Photo

Winged subsoiler.

Photo

Close up - winged subsoiler.

For additional information on the winged subsoiler, see FERIC TN-146 [De Long et al. 1990] and FERIC Field Note No. Silviculture-36 [Rasmussen 1991].

7.4 Drag Scarifiers

Drag scarification is used primarily on lodgepole pine sites to create seedbed, distribute cones and provide conditions for cone opening. Serotinous cones remain closed until they are warmed sufficiently. Exposed mineral soil provides a suitable seedbed for the survival of germinants. Drag scarifiers are most suitable when slash is light and stumps are low.

There are two basic types of drag equipment: anchor chains with tines welded across the links, and drums with "fins" welded spirally along the surface (sharkfin barrels). These may be used separately or together to achieve certain objectives. Sharkfin barrels are heavier than the anchor chains and are used on sites where brush, slash and depth of humus render the lighter anchor chains unsatisfactory. The drums do not move as freely as the anchor chains and therefore tend to produce limited seedbed or planting sites as opposed to the random mixing and exposure achieved with the anchor chains.

Photo

Sharkfin barrels.

For additional information on drag scarification, see Appendix 4, Treatment Guide for Anchor Chains and Sharkfin Drums, FRDA Handbook 002 [Coates and Haeussler 1987] and Drag Scarification in B.C. [Glenn 1979].

7.5 Shear Blades, Downing Chains and Roller Drum Choppers

This equipment is used primarily to flatten vegetation, snags, stagnated or residual lodgepole pine and aspen. Soil disturbance is slight when the ground is frozen. If required, planting spots can be prepared by additional mechanical or motor manual treatment or by burning.

Photo

Marden chopper.

7.6 Patch Scarifiers

Patch scarifiers create three distinct microsites: a scalped, depressed patch; a low mound of inverted surface organic matter generally covered by a thin layer of mineral soil; and the level to slightly raised hinge position at the interface between the scalped patch and the mound. On dry sites with medium-textured soils, the depressed patch is the preferred planting spot because scalping increases soil temperature and improves soil water availability. The low mound has improved access to soil nutrients compared to the patch but is more prone to drought. On many sites, the slightly raised hinge position provides the optimum compromise between moisture and nutrient availability. Patch scarifiers are generally unsuitable where competing vegetation is aggressive. In B.C., patch scarification is accomplished with the Bräcke patch scarifier and the Leno, and with excavators equipped with rakes.

Photo

Two-row Bräcke patch scarifier.

For additional information on the Bräcke and Leno, see FRDA Handbook 002 [Coates and Haeussler 1987] and Maxwell [1989].

For additional information on excavators, see FERIC TN-180
[von der Gönna 1992].

7.7 Disc Trenchers and Cone Scarifiers

Disc trenchers and cone scarifiers create pairs of continuous or intermittent trenches (furrows) and berms providing a range of planting positions. The exposed mineral soil trench is preferred where moisture conservation is required. The berm, composed of irregularly overturned surface organic matter and mineral soil, is usually too loose to form a suitable microsite for planting. It does, however, act as a mulch, warming the soil below and providing a good environment for root growth. The hinge provides an intermediate planting position and is favored in most situations.

The trench profile can be adjusted by changing the disc angle, rotation speed, down-pressure, and travel speed. A disc angle more perpendicular to the direction of travel produces a wider, flatter trench, while a disc angle more parallel to the direction of travel produces a deeper, narrower trench. By increasing the down-pressure and decreasing the travel speed, a deeper trench and a well-formed berm are produced.

Photo

Silva Wadell cone scarifier.

Photo

TTS powered-disc trencher.

For more information on disc trenching, see FRDA Memo 099 [Beaudry 1989], the video Disc Trenching: A Site Preparation Technique in Review [1991] and FRDA Report 178 [von der Gönna 1992].

7.8 Mounders

Mounders prepare raised microsites for planting. For additional information on the reasons for mounding, see "3, Elevation of Prepared Planting Spots" in this chapter.

In B.C., the majority of mounding is done by excavators equipped with buckets or specialty mounding rakes. The excavator is best suited to difficult or sensitive sites and mounds can be tailored to the specific needs of the site.

Photo

Excavator mounding rake.

For additional information, see FERIC TN-180 [von der Gönna 1992] and FERIC TN-131 [Dorion 1989].

The Bräcke mounder has been used in B.C. since 1984. It is a two-row mounder having two hydraulically operated spades. The spades dig into the scalp and deposit mineral soil on the upper slope of the scalp or on the inverted surface material.

Photo

Bräcke mounder.

For additional information on the Bräcke mounder, see FRDA Handbook 002 [Coates and Haeussler 1987] and Maxwell [1989].

The Donaren 870H is a Swedish-built mounder. This mounder uses the same base assembly and hydraulics as the Donaren 180 and 280 disc trenchers. On the mounder, the traditional discs are replaced by two ripper wheels, each fitted with three toothed rippers. In 1992, the Donaren 870H was used opertionally in Alberta and was also demonstrated in B.C.

Photo

Donaren 870 mounder.

For more information on the Donaren 870H, see FERIC TN-200 [Hunt 1993].

The ministry spot mounder is a prototype mounder developed by the B.C. Ministry of Forests. The digging blades of the mounder, mounted on the ripper parallelogram, are hydraulically activated and electronically controlled. The digging cycle involves forcing the digging blades into the ground, raising the blades after a predetermined period and flipping the blades to invert the mound.

Photo

Ministry of Forests spot mounder.

For additional information on the ministry spot mounder, see FERIC TN-183 [Parker 1992] and Maxwell [1989].

7.9 Mixing

Appropriately executed mixing can control competing vegetation, increase soil temperature and aeration, decrease soil bulk density, improve soil water relations, and retain nutrients stored in surface organic layers making them immediately available to crop seedlings. However, inadequate mixing can stimulate competing vegetation and introduce air pockets.

Coarse Mixing Implements

Coarse mixing is accomplished using large discing implements that heap clods of surface organic and mineral soil layers into a bed. Coarse mixing provides little control of competing vegetation, but is beneficial where low soil temperatures and/or high soil water tables inhibit seedling growth.

On sites with high competing vegetation potential, coarse mixing must be followed by planned brushing treatments.

Coarse mixing can only be undertaken on relatively clean sites so much of the forest land in B.C. is unsuitable for this treatment. The Eden bedding plow has been used as a second-pass treatment on backlog sites in north central B.C. The plow consists of six large hydraulically controlled concave discs that are arranged three to a side, each offset and with the concave side of the discs facing inward. The bedding plow creates a continuous raised bed.

Photo

Eden bedding plow.

For additional information on the Eden bedding plow, see FERIC
TN-149 [De Long 1990], and Maxwell [1989].

Fine Mixing Implements

Fine mixing is used on sites with high potential for competing vegetation, where a high rotation speed is required to chop propagating plant parts into pieces sufficiently small to prevent them from resprouting. Fine mixing requires slow travel speeds to allow sufficient time to chop up the soil and vegetation.

Fine mixing is suitable on fine-textured soils, with few cobbles or boulders. It is unsuitable on sites with the following conditions:

  • stony or bouldery soils;
  • coarse-textured soils with a thin humus layer;
  • wet sites (unless they can be subsequently bedded or mounded).

Fine mixing will result in shrubby vegetation complexes, such as willow or aspen, being replaced by herbaceous vegetation and grass. This shift in vegetation complex may not be desirable on certain ecosystems.

The Madge rotoclear is designed for high-speed mixing. The Madge is a self-powered machine pulled behind a prime mover. It drives a toothed rotor (width 2.3 m) up to 360 RPM. The rotor pulverizes and mixes the forest floor. The Madge is limited to sites that are relatively free of slash and stones.

Photo

Madge rotoclear.

For more information on the Madge rotoclear, see Maxwell [1989].

Spot Mixing Attachments

Spot mixing is prescribed for sites where mixing is biologically appropriate, but where slash, stumps, or other obstacles prohibit use of strip mixing implements. Spot mixing is also used on sites where minimal soil disturbance is required.

Spot mixing implements are usually mounted on excavators, as excavators are able to work on a wide range of sites.

Two excavator attachments, the VH mulcher and the Hytest tilling mounder, have been specifically designed for mixing. For additional information on these attachments, see:

  • FERIC Field Note 40 [von der Gönna 1992],
  • FERIC Field Note 45 [Hunt 1992], and
  • the video Excavators: Silvicultural Attachments and Treatments [1993].

Photo

Hytest tiller.

Photo

VH mulcher toolplates: the "screefer," the "nine-tooth ripper," and the "egg beater."

7.10 Motormanual Scarification Attachments

Various attachments have been developed for use with brush and chain saws. Most create small scalped patches, somewhat below the general ground level. The chain saw mounted Hawk Scarifier can make small, mixed mounds as well as scarified patches. Penetration to mineral soil with brush saw attachments may be difficult when roots are concentrated near the soil surface. For more information, see Maxwell [1989].

Photo

Hawk scarifier.


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Copyright 1999 Province of British Columbia
Forest Practices Branch
BC Ministry of Forests
This page was last updated December 1993

Comments to: Tim Ebata <Tim.Ebata@gems8.gov.bc.ca>